Note: Descriptions are shown in the official language in which they were submitted.
CA 02458930 2004-02-26
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A T~LT INDICATOR FOR FIREARMS
Technical Field of the Invention
The present invention relates to the general art of firearms, and to the
particular
field of controlling and aiming the firearm during use.
Background of the Invention
The sport of target shooting has become very popular in recent years. This
sport
has taken several forms, including the use of rifles, hand guns, air guns and
the like.
Furthermore, many overall competitions, such as modern pentathlon, include a
section of target
shooting of some sort. Obviously, accuracy is of prime importance in such
competitions.
Modern competitions have become so close that unaided aiming of a firearm may
be
insufficient.
While accuracy and precision are extremely important to target shooters, such
considerations are also important to other applications, including but not
limited to, hunting and
military applications. Accordingly, while the present disclosure specifies
target shooting, it is
understood that it is equally applicable to other applications.
There have been many improvements to the standard firearm intended to
increase the marksman's accuracy and ability to hit a target. The development
of telescopic
sights, also known as scopes, is one of the earliest improvements in this
area. Scopes are used
to improve viewing of the target such as via optical magnification, to
determine where the
projectile will land.
The way a firearm is held by the user can have an impact on the firearm
accuracy which is far from insignificant. Side to side tilt of the firearm is
one significant source
of inaccuracy. This "tilt" is often referred to as "canting" of the firearm.
Many hunters and
marksmen rely on their inner sense of balance to ensure that the firearm is
not canted. This
attitude presupposes that the shooter has a fully functional, unimpaired sense
of balance and
that this sense of balance can somehow be translated over into the handling of
the firearm.
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Studies of airplane pilots reveal that the human sense of balance is easily
confused by a number of influences and that the pilot should disregard his or
her feelings and
trust the plane's instruments. The human sense of balance is likewise subject
to a number of
disorienting influences including rifle recoil, the loud sounds associated
with shooting, the
repeated focusing on distant targets as viewed through one eye, and prolonged
periods of
standing. A hunter is subjected to even more disorienting influences,
including the elements
(heat, cold, wind, rain, etc.) and rough and uneven terrain. In addition,
hunters may spend
hours of hiking through rough and uneven terrain before firing a shot. The
human sense of
balance can be confused under such circumstances.
Many different kinds of sights have evolved to meet the demands of the market
over the past few years with the recent trend being toward higher
magnifications. Some scopes
approach forty power magnification. Scope builders are challenged to provide a
clear and bright
image to the eye even at high magnifications. There is more light loss in the
scope as
magnification increases which results in a dimmer view of the target. Scope
makers have made
larger objective lenses in order to counter this loss of image brightness. The
manufacturers
have tended to design larger objective lenses which allow more light into the
erector tube,
ocular assemblies and, ultimately, the shooter's eye.
While accuracy of such larger scopes has increased, they have created
problems.
The objective diameter of the scope is so large that the scope must be mounted
high off the
barrel of the firearm in order to gain clearance between the barrel and the
objective housing. At
first blush this seems to be only a problem of mounting the scope. The large
scope requires
taller scope rings in order to mount the centerline of the scope high enough
to obtain the
necessary clearance. Practically, however, as the scope is mounted higher and
higher from the
central bore of the firearm, the sighting system becomes more sensitive to
inaccuracies due to
errors in repeatability. Therefore, various level indicators have been
proposed to assist a shooter
in maintaining the firearm level and correct one source of shooting error.
The ability of a shooter to maintain his head in an upright shooting position
and
simultaneously focus on both the aiming indicator and the target greatly
affect the ability of the
marksman to accurately hit a target. Furthermore, in target shooting,
competitions have
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become so close that anything that detracts from the shooter's accuracy can be
extremely
detrimental. Windage, perspective, and even atmospheric aberrations must be
accounted for by
a skilled marksman. Stance, instability, physical fatigue, mental fatigue, eye
strain and eye
fatigue can adversely affect the marksman. The marksman must even control his
breathing. In
extremely skilled competitions, competitors are further concerned with the
effects of their pulse
on the accuracy and precision of their shooting.
To accurately account for all of these variables while still keeping the
firearm
locked on target, the shooter must be able to "compartmentalize" the
variables. That is, he
must maintain his primary concentration on the target while unconsciously
accounting for the
other factors. This is where his training and practice are important. Through
training and
practice, a marksman can learn to subconsciously adjust his stance, etc.,
while concentrating on
the target. Anything that interferes with the shooter's single primary
concentration on the
target may be detrimental to his accuracy. Thus, it is most desirable to set
up a firearm so the
shooter can maintain his primary concentration on the target and shift all
other factors to his
secondary concentration. That is, the shooter's primary concentration will be
a conscious
concentration on the target while his secondary concentration will be a
subconscious
"awareness" of the other factors. In fact, the shooter may not even be
consciously aware at all
of some of the secondary concentration factors.
For purposes of this disclosure, the term "primary concentration" will refer
to the
concentration which the shooter is consciously aware of; whereas the term
"secondary
concentration" will refer to the more or less unconscious state of which the
shooter may not
even be aware. For example, the target will be a subject of the shooter's
primary concentration
while the shooter's balance will be a subject of the shooter's secondary
concentration.
There have been several prior sighting systems that attempt to provide level
indication on firearms in order to help the shooter hold the firearm level
during use and to keep
the same roll orientation during sighting in and during shooting to help avoid
errors due to
variables such as those discussed above. Some of these designs have included
bubble levels
that are placed in various locations such as on the receiver at the rear of
the firearm, or in front
of the sight. There are various different mounting schemes such as the use of
clamps around a
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scope body or in front of an iron site and even bubble levels incorporated
into the erector
assembly inside the scope. All of these designs have been proposed in order to
give the shooter
an indication of when the firearm is level so repeatable impacts can be made
at the target.
The level indicators mentioned above do not approach the above-mentioned
division of concentrations and do not recognize that there is a difference
between primary and
secondary concentrations. Prior level indicators require a shift in visual
focus and primary
concentration to accomplish objectives other than simply sighting a target,
such as leveling the
firearm. Thus, these designs are not as successful as possible. As discussed
above, in highly
competitive shooting the shooter must concentrate on the alignment of the
sighting system with
9 0 the target and on nothing else. Distractions to this concentration such as
moving the eye to a
bubble level either inside the scope or out of the shooter's field of vision
are extremely
undesirable and cannot be done simultaneously with sighting the target. As
discussed above,
these distractions take the shooter's primary concentration away from the
target and thus are
undesirable.
Some sighting units provide information, such as leveling information, in
addition
to target sighting assistance. However, since these prior sighting units do
not recognize that
there is a difference between primary concentration and secondary
concentration, these sighting
units actually detract from the shooter's primary concentration when providing
additional
information because this additional information is presented in such a manner
as to require the
shooter to focus his primary concentration on that additional information.
This somewhat
vitiates or reduces, the advantages of the additional information. The user of
a prior level
indicator is required to consciously shift his primary concentration from one
information
providing element to another during the targeting process. The factors may
change during the
time it takes to shift primary concentration and the shooter will then be
required to again
consciously shift his concentration back to the first information providing
element. While
making these shifts, the shooter must still be subconsciously accounting for
the other factors,
such as stance, balance and the like.
Psychological studies have shown that a person is able to focus his primary
concentration on only one thing at a time. These studies have shown that it
can take as much
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as one full second to fully focus primary concentration on a second item after
focusing the
primary concentration on a first item. For example, these studies have thus
found that cellular
telephone use by an automobile driver can be dangerous because the person's
primary
concentration is not fully focused on his driving, and an accident can occur
in the time it takes
to shift his concentration from a conversation on the cellular telephone back
to his driving. This
analogy illustrates the inability of one to actively focus not only one's
conscious visual activity
but also his concentration on many inputs simultaneously. Therefore, there is
a need for a
firearm targeting device that can help a shooter accurately aim the firearm
without interfering
with his primary concentration.
Firearm targeting devices of the past, especially those using a bubble level,
generally require the user to align two objects, such as the bubble and
reference marks, or the
target reticle and the bubble. Aligning two objects in this manner generally
requires the user to
focus his primary concentration on the objects being aligned. This requires a
shift of primary
concentration and has the above-discussed disadvantages. For this reason, any
level indicator
that requires the user to align two elements will require the user to change
the focus of his
primary concentration, no matter where the level indicating elements are
located, thereby
creating the above-discussed problems and disadvantages.
Furthermore, in many situations, a firearm does not need to be perfectly
level,
and sufficient accuracy and precision can be achieved with a firearm that is
not as level as in
other situations. For example, a tilt of several degrees may be acceptable in
one situation, but
not in another. Accordingly, it would be desirable to have a firearm level
indicator that permits
the user to account for leveling tolerances without requiring the user to use
his primary
concentration to account for the tolerances. Therefore, there is a need for a
firearm leveling
system that can be utilized while maintaining primary concentration on lining
up the sighting
system with the target.
While scope type sighting systems have been discussed, it is noted that other
sighting systems, such as iron sights, also are subject to the above-discussed
leveling problems.
Accordingly, the present disclosure is intended to include iron sights as
well.
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Summary of the Invention
Various advantages are achieved by a level indicating system of this invention
that provides information regarding whether the firearm is level in a manner
which is absorbed
by the shooter without interfering with his primary concentration on the
target. More
specifically, a tilt indicator of the present invention provides a shooter
with information which he
absorbs using his secondary concentration. In this manner, the tilt of the
firearm is relegated to
the same concentration area as variables such as sway or balance, breathing,
etc., and the
shooter can therefore maintain his conscious and primary concentration on the
target.
The preferred tilt indicator of the present invention includes a visual
indicator
that is activated when the firearm is level and is not active when the firearm
is not level. The
indicator is thus binary, that is, it has two conditions, on or off, one of
which excludes the
other. The tilt indicator can also include other binary visual indicators that
are activated when
the firearm is not level and are de-activated when the firearm is level. The
individual signals of
the tilt indicator of the present invention are thus binary, that is, the
signals have only two
mutually exclusive states as opposed to analog which has an infinite number of
states.
Several binary signals can be provided to produce a level indication that
changes
as the amount of tilt changes. This provides the user with a range of
acceptable tilt in which to
work whereby if a tilt is acceptable in one situation but not in another, the
user can be aware of
this and account for it.
One specific embodiment of the level indicating system includes a pendulum-
type
element having a single pivot access, a weight to keep the pendulum suspended
and a series of
apertures in the pendulum whereby the pendulum acts as a mask for a set of
light emitting/light
receiving elements. The pendulum can be damped using magnets or spring-like
elements so
effects of quick movements of the firearm, including recoil, do not adversely
affect the tilt
sensor system. Still further, stops can be used to further protect the
pendulum from undue
movement. One form of the embodiment includes infrared detectors and infrared
LED emitters.
Each emitter is spaced from its corresponding detector with a plumb line
located between them.
The mask blocks light when the mask is located between the emitters and the
receivers, and permits light to pass when apertures are located between the
light emitters and
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the light receivers. A circuit interprets which emitter/receiver pairs are
blocked and which pairs
are coupled. Signals are connected to the circuit to be activated according to
which pair is
coupled and which pairs are blocked. Firearm tilt is thus interpreted. The
intensity of the signal
can change according to the degree of tilt, or a flashing signal can have its
frequency change as
the degree of tilt changes.
The apertures can be teardrop shaped or arranged in order of size so the
amount
of light passing through an aperture will change according to the position of
the aperture with
respect to the emitter/receiver pair. The binary signals can thus be used to
produce analog-like
information.
In addition to the pendulum, other elements can be used, including Hall-effect
magnets as well as other similar elements.
Other forms of tilt sensors can be used, including a rolling electrically
conductive
element, such as a ball. The ball can be used in conjunction with a printed
circuit board which
defines the exact contacts which are connected by the ball as it rolls along a
curved track. One
set of contacts indicates level while other contact sets indicate tilted
conditions. This is a
simple system in which recoil effects are minimized.
In a form of the sensing system which includes coils and an electrically
conductive ball that rolls through the coils to alter their impedance, the
ball rolls in response to
firearm tilt, and the coils are connected to a bridge circuit that sends
signals according to the
impedance of the coils, and hence in accordance with the degree of firearm
tilt. Various
elements, such as potentiometers or the like can be included in the bridge
circuit to adjust the
sensitivity of the circuit. The ball can be located in a tube that is either
under vacuum or can
contain a fluid to control movement of the ball. The ball rides on a curved
track in one form of
the invention. Bubbles or the like can be used to act as masks in the case of
an optical system.
The ball can also be located on a track defined in the circuit board. When the
printed circuit board is cut, it is cut so that traces on either side of the
circuit board are opposite
to each other. When the ball lines up and connects the circuit board traces on
either side of the
circuit board and across the edge of the board, the circuit is completed.
Plating can also
enhance the height and shape of the edge of the traces as they appear at the
cut edge of the
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circuit board. This enhancement makes it easier for the ball to contact both
electrical traces.
Since the ball is spherical and not flat, there is a slight rise in the edge
of the traces in order to
ensure a complete circuit when the traces contact across the arc of the ball.
Through electronic circuitry in combination with the ball and track form of
sensor, various visual indications can be provided which distinguish the
degree of tilt. For
example, a first set of traces on either side of the centerline can be
indicated as an
uninterrupted signal and moving further on traces farther from the centerline
can be associated
with a cycling signal. The rate of cycle can be used to indicate the degree of
tilt.
Other types of electrical circuits can also be used in which the track on
which
the ball rolls can include a wire wound coil which would make a variable
impedance. This
system requires calibration so that as the ball moves along a single hot trace
and completes the
circuit to the opposite side of the track, the circuit converts the impedance
into a signal.
The invention can alternatively include LED indicators which are accessed with
the ends of fiber optic cables. Several cables can be used, with one cable,
such as a central
cable, indicating a level orientation for the firearm while other cables
indicate tilted conditions.
The fiber optic cables are brought from the level indicator LEDs to an optical
interface in front of
a sighting system. The sighting system can include a rubber annular ring which
surrounds the
ocular lens of a scope, or an iron sight or other such target sighting element
used on a firearm.
The sighting system can include several, such as three, small holes connected
to the fiber optic
cables. The rubber ring can be incorporated into the sighting system eyepiece
which a user
uses to block extraneous light from entering his field of vision.
Alternatively, the level indicator
system can provide an output for wires and a single electrical cable can be
brought up to the
sighting system. Separate indicators, such as incandescent lamps or LEDs or
the like, can be
placed remotely at the sighting interface in a manner similar to that
described above.
Such separate indicators may reflect orientation as measured by an
accelerometer. In such an embodiment, a controller may initiate activation of
a particular signal
indicator in response to the accelerometer sensing an angular orientation or a
specified range of
angular orientation. As such, the controller generates and conveys a signal
indicative of firearm
tilt to the indicator in such a manner as to not obstruct visual acquisition
of the image.
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The level indicating system of the present invention can be used in connection
with any firearm and sighting system combination. The signal indicators are
housed in the
eyepiece and can be placed on any sighting system eyepiece.
Brief Description of the Drawin4 FiQUres
Figure 1 is a schematic illustrating a sight line through a scope in relation
to a
trajectory of a projectile from a firearm.
Figures 2 and 3 are schematics illustrating how cant affects a projectile
between
the time it leaves the firearm and impact.
Figure 4A is a rear and top perspective view of a scope mounted on a firearm.
Figure 4B is a rear and top perspective view of an iron sight mounted on a
firearm.
Figures 5 and 5A are sectional views of an eye with the macula lutea indicated
and an indication of both the central vision and the peripheral vision
associated with the eye.
Figure 6A illustrates a telescopic sight.
Figure 6B illustrates a peep sight.
Figure 7 is a perspective view of an overall unit incorporating the present
invention.
Figure 8A is a schematic of a bridge circuit used in connection with the
sensor
and signal elements of the firearm tilt indicator of the present invention.
Figure 8B is a schematic of a bridge circuit used in connection with coils and
a
"slug tuned' circuit.
Figure 9 is a schematic of an optical circuit used in connection with the
sensor
and signal elements of the firearm tilt indicator of the present invention.
Figure 10 is a schematic of a simple switch-type circuit used in connection
with
the sensor and signal elements of the firearm tilt indicator of the present
invention.
Figure 11 A is a sketch illustrating the use of a ball or bubble used in
connection
with optical sensors to indicate the tilt of a firearm.
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Figure 1 1 B is a sketch illustrating another form for the use of a ball or
bubble
used in connection with optical sensors to indicate the tilt of a firearm.
Figure 12A is a sketch of a ball and track arrangement for a coil/ball form of
the
system used to sense firearm tilt.
Figure 12B is a schematic of a resistance bridge circuit used in connection
with
the sensor and signal elements of the firearm tilt indicator of the present
invention.
Figure 13 is a schematic of a circuit using optical output to activate signals
concerning the tilt of a firearm.
Figure 14 is a schematic of a simple circuit which uses bridge circuits in
conjunction with each light receiver element and which is used in connection
with the sensor
and signal elements of the firearm tilt indicator of the present invention.
Figure 15 is a perspective view of a mask used to control an optical sensor
form
of the tilt sensor of the present invention.
Figure 16 is a top plan view of the sensor shown in Figure 15.
Figure 17 is another form of the mask used in the tilt sensor system of the
present invention.
Figure 18 is yet another form of the mask used in the tilt sensor system of
the
present invention.
Figure 19 is a ball and track form of the firearm tilt sensor system used in
the
present invention.
Figure 20 is a top plan view of the sensor shown in Figure 19.
Figure 21 shows a ball in a viscous fluid in one form of the firearm tilt
sensor of
the present invention.
Figure 22 illustrates the ball/viscous fluid form of the invention in
combination
with optical sensors.
Figure 23 illustrates a coil form of the firearm tilt sensor of the present
invention.
Figure 24 is an exploded perspective view of the coil form of the sensor shown
in Figure 23.
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Figure 25 shows a sensor array similar to that shown in Figure 19 in a
mountable
form.
Figure 26 is a schematic of a bridge circuit and is another form of the
circuit
shown in Figure 8 and which includes an amplifier.
Figure 27 is an exploded perspective view of a level sensor in combination
with a
scope and a housing.
Fig. 28 is a perspective view of a tilt indicator coupled to the scope of a
rifle.
Fig. 29 is an end view of the tilt indicator shown in Fig. 28 and taken along
line
29-29.
Fig. 30 is block diagram generally showing a hardware circuit suited to
execute
processes associated with the tilt indicator of Fig. 29.
Fig. 31 is a flow chart illustrating sequence steps suited to configure and
utilize
the tilt indicator of Fig. 29.
Detailed Description of the Preferred Embodiment of the Invention
For initial discussion purposes, it is helpful to illustrate basic shooting
difficulties
addressed by the invention. The firearm must be held in exactly the same
position for each shot
or errors are magnified, especially by taller scopes. This sensitivity is
acutely important when
considering the uprightness with which the firearm is held. This is commonly
called holding the
firearm level. That is, the firearm is held so the sighting of the target is
carried out with the
firearm in exactly the same vertical plane as it was when the firearm was
sighted in. Rolling the
firearm about its central axis with respect to the orientation of the firearm
when it is initially
sighted in will have detrimental effects on the accuracy of the shot. This
will be referred to
herein as being out of level and the roll will also be referred to as cant or
tilt. This is a common
problem that has been addressed in many ways, none of which solve the problems
inherent in
the human psyche.
There are two compounding problems. The first problem is that when sighting
through a scope or iron sight, the eye sees the target through the central
axis of the sighting
system which may be offset from the bore central axis of the firearm. The
second problem is
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that the actual bore or central axis of the barrel is at an angle to the
central axis of the scope.
In essence, there are two converging lines, the central axis (sight line) of
the scope and the
central axis (bore) of the barrel. In theory, if the projectile had no
trajectory, the point of impact
would be where those two lines intersect. However, since a projectile always
drops from the
moment it leaves the muzzle, compensation must be made in order to enable the
projectile to
accurately hit the intended target.
Determination of the necessary compensation for a given target range is termed
as "sighting in" a firearm or a scope so impact of the projectile will match
the optical center of
the target at a given distance. For example, if a firearm is sighted in with a
100 yard zero, the
impact point of the projectile will be where the optical system is centered at
100 yards. If
shooting is at a target 50 yards out, normally the shooter compensates for
elevation (trajectory)
in estimating where the projectile will impact a 50 yard target based on a 100
yard zero point.
In such a case, if the scope is rotated about the scope's central axis (i.e.,
out of level) not only
will the point of impact be elevationally incorrect, but will also be windage
incorrect due to the
error between the point of impact and the closer or farther away target.
This effect can be understood from the following discussion with reference to
Figures 1-3.
As shown in Figure 1, sights on a firearm are placed at an angle to the bore
to
make up for the forces that act on the projectile during flight. The most
important of these are
gravity and air movement or wind. Gravity acts in the vertical direction and
its effect is
proportional to time of flight. As a result, the sight is adjusted as
indicated in Figure 1. Figures
2 and 3 show a graphic depiction of a typical projectile trajectory showing a
sight axis SA
versus the bore axis of a standard trajectory (exaggerated for clarity) for an
air gun (see plane
1 ). The projectile path trajectory is shaded to show the area under and above
the central site
axis. Because the shooter's eye is the point of reference when a firearm is
canted, the sighting
axis SA becomes the axis of rotation. This in turn rotates the barrel directly
under the sighting
axis. Therefore, the illustrations show the sighting axis always as the center
of rotation. Cant
may happen in either a clockwise or a counterclockwise direction about a
point.
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Plane 2 shows a firearm which is canted 90 degrees counter-clockwise. The
angle between the bore and the sight line is indicated as angle A. Since the
relationship
between the scope and the barrel does not change when the firearm is canted,
an identical
plane is shown rotated counter-clockwise 90 degrees. Although it would be hard
to cant a rifle
90 degrees, it is shown this way to allow the illustrations to be clear. The
second plane still
maintains the central sight axis SA at the target, however, the projectile has
been directed to
the left.
The trajectory path shown in Plane 2 is imaginary, a result of gravity from
Plane
1 sighting settings. The gravity that once pulled the projectile back onto the
target still pulls
down on the projectile; however, some of the elevation offset "e" is lost.
This accounts for the
elevation error or in effect the "drop" in projectile impact. In addition, the
elevation angle A that
was used in the Plane 1 to counteract gravity has now become a windage angle B
directing the
barrel off to the left.
Therefore, two errors have been introduced: the first error being that of the
barrel pointing off to the left and the second error of no longer having
gravity normal to the
elevation plane. These two errors combine to cause a projectile to hit low and
to the right of a
target when the firearm is canted or rolled about its central axis from the
sighting in orientation.
The new projectile path is shown to hit at a point of impact "y". This actual
point of impact "y"
therefore accounts for both windage and gravity effects.
Therefore, when a marksman needs to accurately hit a target, it is highly
desirable to have a telescopically equipped firearm that is kept perfectly and
repeatably level
during sighting in and during all shooting.
Shown in Figure 4A is a firearm 10 having a central axis 11 and having a scope
12 mounted thereon. Scope 12 has an objective section 14 on one end thereof
and an ocular
section 16 on another end thereof. As discussed above, and indicated in Figure
1, scope 12 is
mounted at an angle O to bore centerline C in order to compensate for the
effect of gravity on a
projectile fired from bore 20 of firearm 10. The trajectory 22 of the
projectile is indicated in
Figure 1 and sight line 24 from scope 12 is also shown. Since scope 12 is
mounted at an angle
with respect to trajectory 22, sight line 24 will intersect trajectory at
point P. As discussed
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above, point P is set when the firearm is sighted in. As shown in Figure 6A,
scope 12 includes
a targeting reticle 30 which includes a vertical crosshair 32 and a horizontal
crosshair 34 which
intersect at intersection 36 which can correspond the point P of impact in
Figure 1 for a sighted
in distance.
Shown in Figure 4B is a firearm 10' which includes an iron sight 12'. Iron
sighted firearm 10' is subject to the above-discussed sighting-in and leveling
problems.
Accordingly, firearm 10' will not be discussed in detail as the description
presented will be
applicable to this firearm as well.
In using scope 12, a marksman concentrates his primary concentration on
placing his target in the proper position on reticle 30 to accurately hit the
target. The marksman
is consciously concentrating on this placement while unconsciously accounting
for his body
sway, tilt, and other such factors in his secondary concentration. As
discussed above, it is
most desirable that the marksman be able to maintain his primary concentration
on targeting
while relegating the other elements to his secondary concentration. As was
also discussed
above, tilt of the firearm is a factor in accurately hitting a target. That
is, if the firearm is rolled
about its central axis 11 from its orientation during initial sighting in, the
precision of the firearm
and its targeting system will be affected and hence the accuracy of the shot
will be affected.
Heretofore, firearm tilt indicators have required the shooter to focus his
primary concentration
on them, thereby taking his primary focus off of the central task of aligning
the target with the
sighting device. As discussed above, this vitiates the effectiveness of the
entire firearm
targeting system.
A peep sight 12", such as shown in Figure 6B, is used in conjunction with
firearm 10'. In using sight 12", a marksman focuses his primary concentration
on placing his
target in proper position in peep aperture 36'. The primary concentration will
be focused on
targeting, while the other elements should be placed in the secondary
concentration. As
discussed above, it is the primary object of the present invention to place
firearm level and/or tilt
information into the secondary concentration of the marksman.
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The present invention positions the firearm tilt indicating system so
information
from this tilt indicating system is absorbed by the shooter via his secondary
concentration so his
primary concentration on the target is uninterrupted.
Referring to Figure 5, it can be seen that a person's eye has a portion ML
known
as the macula lutea. The macula lutes is defined in references such as Taber's
Cyclopedic
Medical Dictionary edited by Clarence W. Taber and published in 1963 by F.A.
Davis Company
of Philadelphia as "the yellow spot on the retina about 2.08 mm to the outer
side of the optic
nerve exit...which functions as the area of most acute vision (central
visionl," and peripheral
vision is defined by the McGraw-Hill Dictionary of Scientific and Technical
Terms edited by
Daniel N. Lapedes and published by McGraw-Hill Book Company in 1974 as "the
act of seeing
images that fall upon parts of the retina outside the macula lutes. Also known
as indirect
vision." The area of a person's central vision is indicated in Figure 5 as CV
and the area of a
person's peripheral vision is indicated in Figure 5 at PV. The peripheral
vision area extends to
the outer limit of the perimeter subtended by a cone OV which represents the
total field of
vision for an eye without moving the eye from a focal point. The area of
central vision is defined
by drawing lines from the outside of the macula lutes, which is located around
the optic nerve
with a radius of 2.08 mm, through the eye lens. The cone thus defined will be
the area on
which the person's central vision is focused; whereas, the area outside of
such cone, but still
within the area defined by the intersection of cone OV and retina R, will be
the area of the
person's peripheral vision. The central vision cone will thus have a planar
"base" area at a
particular location defined by the radius of the cone at that location. The
limits of the central
vision and the peripheral vision will be more specifically discussed below
with regard to Figure
5A. For the sake of reference, as shown in Figure 5, the eye includes optic
nerve ON, lens LS,
iris IS and pupil PS. As shown in Figure 5, the focal point F is outside the
macula luta and just
at the perimeter of cone OV so the focal point will be seen, but in peripheral
vision and very
fuzzy.
Referring to Figure 5A, it can be seen that dimension L represents the linear
dimension of the area that will be viewed by a viewer's central vision at a
distance X from the
viewer's eye since the limits of dimension L fall on the limits of the macula
lutes of the viewer's
CA 02458930 2004-02-26
-16-
eye; whereas dimension L' represents the linear dimension of the area that
will be within the
outer limits of sight at distance X from the user's eye because the limits of
dimension L' fall on
the area defined by cone OV without moving the viewer's eye. Accordingly,
dimension oL
represents linear dimension of the area that will be viewed by the viewer's
peripheral vision
when that viewer is focusing on object L at distance X from the eye. Thus, any
object in the
annular area having a dimension oL and extending from the limits of dimension
L to the limits of
dimension L' will be viewed by the viewer's secondary concentration while his
primary
concentration is on objects in the area represented by dimension L. By
geometric construction,
it can be concluded that L = M~ (X/E) where M~ is the diameter of the macula
lutea; X is the
distance between the plane containing cornea C of the viewer's eye and the
plane containing
the object being viewed; and E is the distance between the plane containing
the viewer's retina
and the plane containing the cornea of the viewer's eye. Further, L' = 0"
(X/E) where O~ is the
linear distance defined by the intersection of cone OV and the viewer's retina
and is the outer
limit of the area that can be viewed by a viewer's peripheral vision without
moving his eye from
a given position. Thus, in accordance with the teaching of the present
invention, the tilt signals
are located in annular area represented by dimension nL which is outside the
circle having a
diameter L (the area of primary concentration) and inside a circle having a
diameter L' (the area
of secondary concentration).
People naturally focus their primary concentration on the items in their
central
vision and relegate items in their peripheral vision to their secondary
concentration.
Accordingly, the tilt indicator of the present invention has its signal output
located to be in the
peripheral vision of the shooter while he focuses his central vision on the
target. Therefore,
referring to Figure 6A, tilt or level indicating signal 40 of the present
invention is located on the
firearm target viewing element to be outside the area CV when area CV is
focused on reticle 30
(with area CV having a dimension L as discussed above), and hence in area eL.
Target reticle
includes intersection 36 at or near which the shooter will place the target.
Thus, his central
vision will extend to an outer periphery indicated by circle CP which
represents the intersection
of the central vision cone with the plane containing the reticle 30 (with
dimension L). All items
located outside perimeter CP (but within perimeter CP' which corresponds to
dimension L'
CA 02458930 2004-02-26
_ 17 _
discussed above) will be viewed by the shooter's peripheral vision, with
perimeter CP being
sized by the above-discussed construction from the outer periphery of the
macula lutea via the
central area of the lens of the eye. Accordingly, firearm level indicating
signal 40 of the present
invention is located beyond the area circumscribed by perimeter CP but within
perimeter CP' and
hence in position to be viewed by the user's secondary concentration.
In other words, if the area containing the level indicator signal is AreaP~
(i.e., the
area corresponding to the peripheral vision of the shooter when he is focusing
on the targetl,
and the area contained in the central vision cone is Areaop (which is equal to
Area~P), the area
circumscribed by the intersection of the central vision cone and the plane
containing the reticle,
then AreaP" surrounds Area~P (i.e., the peripheral vision area surrounds the
central vision area).
As shown in Figures 6A and 6B, there is a space S and S' between perimeter
line CP and CP'
(which corresponds to the annular area having a linear dimension eL discussed
above) and the
location of the firearm level indicator signal to ensure that the signal is
viewed by the user's
peripheral vision and to ensure that the information associated with the level
indicator signal
does not interfere with the shooter's primary concentration.
Referring to Figure 6B, tilt or level indicating signal 40' is located on
firearm
target viewing element 12" to be outside area CP" when area CP" (representing
the central
vision) is focused on peephole 36'. As shown in this illustrative example,
target viewing
element 12" is on an iron sight equipped firearm as, for example, shown in
Fig. 4B. The
marksman's central vision extends to an outer periphery on element 12"
indicated by circle CP"
which represents the intersection of the central vision cone with the
peepsight 12". All items
located outside perimeter CP" (but within the above-discussed outer vision
cone represented in
Figure 6B as perimeter CP"') will be viewed by the marksman's peripheral
vision, with perimeter
CP" being sized by the above-discussed construction from the outer periphery
of the macula
lutea via the center of the lens of the eye. Signals from level indicator 40'
are located outside
the area circumscribed by the central vision circle CP" and hence will be in
position to be
viewed by the user's secondary concentration while the viewer's primary
concentration on the
target via the targeting display is uninterrupted and non-distracted by the
firearm level indicating
system.
CA 02458930 2004-02-26
-18-
The level indicating system of the present invention can take several forms,
just
so the signal thereof is located to be outside the area of the shooter's
primary concentration and
in the area which is viewed by the shooter's secondary concentration when he
is focusing his
primary concentration on the target with no shifting back and forth between
primary objects and
other signals.
The overall system used for the level indicating system is shown in Figure 7
and
a basic circuit is indicated in Figure 8A. As shown in Figure 7, the system
includes a sensor
unit SU which is mounted on a firearm for movement therewith, cables, such as
fiber optic
cables FOC connected at one end thereof to light sources in unit SU and at the
other end to
indicators Y, Y' and G mounted in a mount M that is attached to eyepiece EU of
a sighting
system. Indicators Y, Y' and G will be discussed below and indicate the tilt
of the firearm as
sensed by sensors in unit SU and as interpreted by circuitry associated with
the sensors in unit
SU.
Figure 8A is a block diagram which shows two sensor inputs 50 and 52 driving
indicators 54 and 56 respectively and logic circuitry 58 required to have a
third indicator 60
show "on" when the indicators 54 and 56 are "off". Indicators 54 and 56 are
driven by the
input from sensors 50 and 52 respectively. The sensor signals are conditioned
appropriately
(shown in the block diagram as adjustable gain, though the conditioning could
result from a
fixed design) in order to drive the indicators. These indicators can respond
to the conditioned
sensor signal with increasing brightness as the sensor signal increases,
changing in a flashing
rate as the signals increases, or the like as appropriate for the user.
The sensor signals are also conditioned appropriately to drive logic circuit
58
shown as including Schmitt trigger input inverters, to form a logical NAND so
that if both
sensors 50 and 52 signals are below the logic threshold (from the Schmitt
trigger inverters),
then indicator 60 is "on." Any other condition results in indicator 60 being
off.
Inductance Circuits
The sensor inputs can be realized from a plurality of technologies. For
example,
as will be discussed below, the level indicator could be constructed so that a
ball rolls in and out
of inductive coils. The ball is of a material that substantially changes the
inductance of the
CA 02458930 2004-02-26
-19-
coils. Such "slug-tuned" indicators, commonly found in radio frequency
circuits, are well known
though the adjustment method is quite different. The coils are located at
either end of the level
so the ball can roll thereby exhibiting the largest change in inductance. The
cores are chosen
for their properties of reluctance and frequency response. Additionally, "air
core" inductors are
widely used though their inductance per volume is much lower than coils with a
ferromagnetic
core. The slug tuned coils are attractive since the "free space" does not, for
practical purposes,
magnetically saturate or suffer from the frequency response limitations of
core materials.
If a leveling tube has coils wrapped around the outside of a leveling element,
the
inductance of the coils will be largely unaffected by glass, plastic,
dampening fluid or other
materials of the tube. Allowing a ball made of steel or other ferromagnetic
material to roll
constrained within this leveling tube would change the inductance of the coils
as it moves in
and out.
One method of sensing the change in inductance is shown in Figure 8B and
includes a balanced bridge 70. Bridge 70 is driven with an a-c source 72 at an
appropriate
frequency so the changes in inductance are optimally detectable. The change in
inductance
from coil 74 or coil 76 is sensed as the bridge is unbalanced due to one or
the other inductors
changing impedance as the ball or slug is introduced into the center.
Resistors 78 and 80 serve
to construct the bridge and are also adjusted to account for differences in
the coils. The resistor
values are selected to balance power consumption and detection of inductance
changes.
The voltage detectors and filters 82 and 84 shown in Figure 8 can utilize
nearly
any RF detection technique, including simple diode and filter circuits well
known as envelope
detectors. The values of the capacitors and resistors are chosen to balance
the needs of power
consumption, rate of change for the user interface and other considerations
known to those
skilled in the art based on the teaching of this disclosure.
Optical
Alternatively, a specific embodiment of an optical approach is shown in Figure
9.
Figure 9 shows all electrical elements of a circuit 88. Left and right sensors
90 and 92 have
their sensitivities adjusted by resistors 94 and 96 respectively. With
properly chosen emitter
resistors for the LEDs, a balance of the indicator threshold and logic
threshold can be obtained.
CA 02458930 2004-02-26
-20-
This will allow the left and right LEDs 94 and 96 respectively to begin to
come on while the
center LED 98 is still lit. This design has an "off/on" condition for center
LED 98 while left and
right LEDs 90 and 92 have variable brightness depending on the degree of tilt.
A calibration approach for this design includes blocking the left sensor and
adjusting RF so left LED just starts to fade, then returning the adjustment so
that the LED is on
fully. The design allows for the voltage at "A" to go below the digital
threshold when the left
LED is nearly on fully (as sensed by the emitter resistor).
Yet another approach to translating firearm tilt into signals includes a
circuit such
as circuit 100 shown in Figure 10 in which a ball 102 rolls in a cylinder 104
mounted on the
firearm. Ball 102 rolls left or right according to the tilt of the firearm.
Light activated circuits
106Y, 1066 and 106Y' are each arranged to provide a circuit between an emitter
108Y, 1086
and 108Y~ and a receiver 1 10Y, 1106 and 110Y' respectively when light from
the emitter is
received by its corresponding receiver. Ball 102 is opaque and thus prevents
light from reaching
a receiver when the ball is interposed between the emitter and the
corresponding receiver.
Circuit 100 is arranged whereby power from source 112Y is short circuited and
hence not
applied to LED Y' when light from emitter 108Y is received by receiver 100Y
and so forth.
However, when ball 102 is interposed between an emitter and its corresponding
receiver, the
circuit is open at that point whereby current flows to the LED. Thus, as shown
in Figure 10,
with ball 102 interposed between emitter 1086 and receiver 1066, lights Y and
Y' are dark as
their power sources are shorted, but light G is active as its power source
applies power to LED
G. Thus, the circuit 100 is really a simple switch circuit.
The position of a ball BA or bubble in the level sensor of the present
invention
can also be determined by optical sensors "A" and "B" as indicated in Figure 1
1 A. More
specifically, the reflectance of the ball or bubble can be sensed by emitter
and detector pairs
that measure and respond to reflected light from the bubble or ball as
indicated in Figure 11 A.
Another system is shown in Figure 1 1 B and allows the bubble or ball to
obstruct
the light in communication between an emitter and detector pair. The emitter
and detector pairs
can be arranged advantageously to avoid interference or "cross talk" between
them. In either
system shown in Figures 1 1 A and 11 B, determining the position of the ball
or bubble can be
CA 02458930 2004-02-26
-21
accomplished by detecting its presence in a given region. Rather than placing
an emitter-
detector pair in the "middle" to detect level, the circuit shown in Figure 13
shows a lack of
presence yielding information.
The schematic shown in Figure 13 illustrates an embodiment that uses light
emitting diodes as the emitters and phototransistors as the detectors. Power
is supplied to the
emitters and is regulated as shown to allow operation within the
recommendations of the
manufacturer. The optical signal is received by photoresistors connected so
that the low
impedance emitter node drives the circuit. The variable resistors RA and RB
are shown as one
way to calibrate the circuit. Appropriate values for these variable resistors
can be chosen to
account for the fixed and variable optical properties of the level tube
materials and the variations
of the current transfer ratio of the emitter-detector pair. This allows
calibration.
The output of the photoresistors is received by a Schmitt trigger input
digital
device to allow for noise margin. The logic that follows lights the "A"
indicator when the ball or
bubble is within the "A" region. It also lights the "B" indicator when the
ball is within the "B"
region. An illustrative feature of this logic lights the "level" indicator
when the ball or bubble is
not detected within either the "A" or the "B" region. This schematic can be
expanded for any
number of emitter-detector pairs and combinations. The logic can be expanded
to accommodate
the required functions.
Shown in Figure 14 is yet another circuit 120 which is a resistance sensor and
which uses a change in resistance of a light sensitive element to directly
unbalance a resistance
bridge to change the intensity of a signal element. For example, as shown in
Figure 14, when
light from emitter 122Y falls on receiver 124Y, the resistance of a resistor
associated with
receiver 124Y changes unbalancing bridge circuit 126 and changing the
intensity of LED signal
128Y. Similar bridge circuits are associated with signals G and Y'. A ball
102' located in
chamber 104' mounted on the firearm rolls to affect the light transmitted and
received by the
receivers 124Y, 1246 and 124Y'.
Resistance
Changing values of resistance can also be used to determine the amount of tilt
of a firearm. Systems incorporating resistance in this manner are shown in
Figures 12A and
CA 02458930 2004-02-26
-22-
12B. Referring to Figures 12A and 12B, it is seen that the position of a ball
11 1 on a track 112
can be sensed by measuring the value of resistance of the electrical path
formed by the ball and
the track. Measuring the resistance can be done using a bridge circuit such as
bridge circuit
113. Determining the position of ball 111 on track 112 is made by knowing the
relationship of
resistance to position of ball 111 on track 112. Bridge circuit 113 has a
voltage that is
proportional to the resistance of the track. The values of R"3 and R"3, are
chosen to
accommodate the requirements of precision, power consumptions, and other
practical trade-offs
normally encountered in circuit design.
Calibration of "level" can be obtained in several ways. One way is to
mechanically level the system and then establish that resistance as "level".
Then values of
resistance less than "level" would indicate out of level in the other
direction. Another way is to
mechanically level the system then adjust R"3-and the gain of the associated
amplifier A"3to
accommodate comparisons of position, displays or other indicators.
Various elements can be used to control the amount of light received by a
receiver based on the tilt of the firearm. Several examples of such elements
are disclosed in
Figures 15 through 18. However, these embodiments are intended to be examples
only and are
not intended to be limiting, as other forms of such elements will occur to
those skilled in the art
based on the teaching of this disclosure. These elements are also intended to
be included within
the scope of this invention as well.
Masks
Shown in Figures 15 and 16 is a system 140 which includes two light emitter
elements, such as element 142 which can be an incandescent light source if
suitable, and two
light receiving elements such as element 144 which can correspond to elements
90 and 92
shown in Figure 9 for circuit 88. Light transmission to receiver 144 is
controlled by mask
element 146 which is pivotally mounted on base 148 to swing in directions 150
and 150' about
pivot pin 152. Base 148 is fixed to the firearm and oriented so mask 146
pivots in directions
150 and 150' as the firearm is tilted about its longitudinal axis as discussed
above. A magnet
160 is located in base 148 and mask 146 is metallic so pivotal movement of
mask 146 is
damped by magnet 160. This prevents undesired movement of mask 146 or
undesired impact
CA 02458930 2004-02-26
-23-
between mask 146 and stops associated with projections 154 and 154' if the
firearm is tilted
too rapidly or too much. A lens, such as lens 156, focuses light onto each
light receiving
element.
Mask 146 includes teardrop shaped holes 160 and 162 through which light
passes when the holes are aligned with the light emitters. The teardrop shape
of holes 160 and
162 causes light amounts to increase or decrease according to the position of
the hole with
respect to the light source. In this manner, the light intensity associated
with the signals, such
as signals 94 and 96 in Figure 9, will vary according to the amount of firearm
tilt. As discussed
above in regard to circuit 88, when mask 146 is in an upright orientation,
that is when vertical
centerline 166 is vertical with respect to the ground, no light will pass mask
146 and center
signal 98 will be activated. The same condition can be effected using circuit
100 or circuit 120
with mask 146 substituted for ball 102.
Another form of mask is shown in Figure 17 as mask 146'. Mask 146' has a
light emitter element and its corresponding light receiving element both
mounted on a single
element, such as elements 170 and 172 which span mask 146'. Elements 170 and
172 as well
as base 148' are all mounted on a bracket 174 which is mounted on the firearm.
Yet another form of mask is shown in Figure 18 as mask 146". Mask 146" is
generally similar to mask 146' and operates in a manner generally similar
thereto. Mask 146"
includes a T-shaped body 180 having a central portion 182 and a curved top
portion 188 on the
end of central portion 182 opposite to a bottom wall 184. A curved top plate
190 having light
transmitting-holes 192 defined therethrough is located on top portion 188.
Light sensor arrays
200 and 202 are fixedly mounted on wall 204 of base 206 and light is
transmitted from one
portion of each array and is received by another corresponding portion of the
same array. Plate
190 is interposed between each light source and its corresponding light
receiver of each array to
permit the light transmission/receipt function of each array when a hole 192
is located between
a light transmission element and its corresponding light receiving element of
an array, and to
interrupt the light transmission and receipt operation when the holes are not
so positioned.
Base 180 moves in directions 210 and 212 generally about an imaginary pivot
due to the bending of thin, flexible plates 214, 216 which connect top portion
188 to bottom
CA 02458930 2004-02-26
- 24 -
218 of base 206. This will open or occlude the light transmission paths
associated with arrays
200 and 202. Mask 146" is mounted on a firearm to cause the just-mentioned
pivoting when
the firearm is tilted out of a.desired upright orientation so the above-
discussed accuracy and
repeatability are achievable by the user. A magnet 220 is attached to bottom
184 of central
portion 182 and is attracted to a lower, metallic plate 221 to dampen the side-
to-side motion.
The sensor arrays 200 and 202 are connected to the signal circuits as
discussed above.
Switches
Yet another form of a system for controlling the signals discussed above is
shown in Figures 19 and 20. Control unit 220 includes a multiplicity of spaced
apart switches,
such as switch 222, that are normally open and are closed by a moving element,
such as
electrically conductive ball 224, that moves in accordance with tilting
movement of the firearm.
The switches are part of circuits that connect the signal lights to a power
source when closed.
Switches on one side or the other of a centerline will activate one signal
light while switches at
or near the centerline will activate another signal light as discussed above.
As can be seen in
Figures 19 and 20, each switch includes two electrically conductive contacts,
such as contacts
225 and 226, separated by an electrical insulator 228. A housing 230 has a
bore 232 defined
therethrough in which ball 224 moves in directions 234 or 236 depending on the
tilt of a firearm
on which housing 220 is mounted. Housing 220 is mounted on the firearm to
cause ball 224 to
move when the firearm is tilted as above discussed.
Bore 232 can be under vacuum conditions to facilitate movement of ball 224, or
can contain a fluid which will control movement of ball 224 in bore 232. A
viscous fluid 240,
such as light oil or the like, is shown in Figure 21. The fluid will damp, or
control movement of
ball 224.
As indicated in Figures 22 and 25, a ball 224' can serve the same purpose as
masks 146, 146' and 146" and is positioned to move in directions 242 and 244
along a path
that is interposed between a light transmitter and a light receiver, such as
optical sensors 246
and light generators 247. Ball 224' is contained in an optically transparent
container, such as
tube 250, which is either under a vacuum or contains a viscous fluid 252 to
control movement
of ball 224'. Tube 250 is mounted by a base unit 251 and braces BR to cause
ball 224' to
CA 02458930 2004-02-26
-25-
move in response to tilting of the firearm while light associated with
sensor/transmitter arrays
that are located on tube 250 activate signals as discussed above to indicate
to a user when the
firearm is properly oriented or is tilted in an undesired manner.
Inductance Systems
As discussed above, many methods can be used to sense tilt of the firearm and
translate that sensing to signals that are displayed to a user in his
secondary concentration. One
of these methods includes inductance and the change in inductance as the
firearm is tilted.
A means for sensing firearm tilt is shown in Figures 23 and 24 as impedance
means 253. Means 253 includes a hollow tube 254 which is mounted on a firearm
to tilt about
a tube transverse axis when the firearm is tilted as discussed above. Means
253 utilizes the coil
concept discussed above and a movable electrically conductive element, such as
metal ball 255,
is movably located inside tube 254 to move along a longitudinal centerline of
that tube in
directions 256 and 258 as the firearm is tilted. Coils, such as coils 260 and
262, are mounted
on tube 254 at locations that are spaced apart along the longitudinal
centerline. The coils are
part of circuits, such as the bridge circuit shown in Figure 26 and discussed
below, that are
altered when an electrically conductive element, such as ball 255, passes
through the coil. The
circuits are connected to the indicators discussed above so when the firearm
is in a desired
orientation, one signal is activated, and another signal is activated when the
ball is moved by
the firearm being in an undesired orientation. Ball 255 moves along a track
266 which can be
curved if desired, and spacer elements, such as element 268, separate adjacent
coils so
adjacent coils do not interfere with each other, or the circuits associated
therewith.
Alternative Inductance Bridge Circuit
As discussed above, measurement of the inductance associated with the
systems using coils to sense tilt can be carried out in various ways,
including bridge circuits
such as illustrated above in Figure 8B. Another bridge circuit 270 is shown in
Figure 26
connects coils 260 and 262 and is stimulated with a frequency source 271 to
detect and
amplify the voltage in the bridge. This voltage, if in balance (i.e. zero)
would indicate "level".
As the ball moves toward a given coil, the inductance increases and more
current is shunted
through it. This would be observed in the bridge as an imbalance. This
imbalance is detected
CA 02458930 2004-02-26
-26-
(via a diode detector or other method) and, if necessary, amplified via
amplifier 272. The sign
and magnitude of the detected voltages indicate the position of the ball
within the tube. As
discussed above, filter circuits can also be included and the filters could be
stimulated and the
responses compared. The stimulus could include impulse or step functions and
the harmonic
content compared.
Overall Svstem
An overall arrangement for the tilt sensor which is the subject of this
disclosure
is shown in Figures 7 and 27 as unit SU. Unit SU includes a housing having a
top cover 302 and
a base element 304 which is mounted on a firearm to tilt therewith. Base
element 304 is
mounted on a firearm by a clamp element 306 which includes threaded fasteners,
such as bolts
308 for attaching the clamp to the base unit and on the firearm. Fiber optic
cables FOC extend
into the housing to receive appropriate input from a light generating element,
such as an LED
312, an incandescent lamp or the like, via control circuits such as discussed
above and to
transmit such light to the indicators such as the indicators discussed above.
An adjustment unit
AU is also located in housing 300.
Accelerometer Embodiment
Referring to Figs. 28-31, another embodiment interfaces an accelerometer 512
with a controller 514 and signal indicators 402-410 to unobtrusively
communicate tilt
information to a user of a scope 600 or other sighting device. Generally, the
ocular housing of
the tilt indicator 400 illustrated in Fig. 29 employs the accelerometer 512
and other tilt sensing
circuitry to convey orientation information to the user via at least one
signal indicator. As
shown in Fig. 29, the peripheral positioning of the signal indicators) 402-410
ensures they do
not obstruct visual target acquisition when removably attached to a rifle
scope 600, as shown
in Fig. 28. As may be appreciated, the battery operated tilt indicator 400 is
configured to
mount onto a scope housing 600 of Fig. 28 with the signal indicators 402-410
(Fig. 29)
recessed on an annular ring 411 and oriented in any suitable fashion. Tilt
indicator 400 is
preferably positioned behind all optical elements or optics 602 of housing 600
as shown in Fig.
28. This helps ensure that only the shooter's peripheral vision is used to
view signal indicators
402-410.
CA 02458930 2004-02-26
-27-
During targeting, a controller 514 shown housed within the tilt indicator 400
of
Figs. 29 and 30 may electronically activate one or more signal indicators 402-
410, such as a
bank of light emitting diodes (LEDs) as illustrated particularly in Fig. 29.
Other embodiments
may incorporate liquid crystal technology or other visual indication
technology. In any case, the
signal indicators 402-410 may communicate to the user an approximate degree of
tilt relative to
a zero reference point. As such, a program executed by the controller 514, or
suitable
microprocessor, of Fig. 30 may initiate activation of a particular signal
indicator 402-410 in
response to circuitry sensing an angular orientation or a specified range of
angular orientation.
For instance, one signal indicator 402 shown in Fig. 29 may illuminate when
the tilt indicator
400 is oriented within 1 ° of the reference point. The signal
indicators 402-410 may further
convey the direction of tilt in one axis relative to the zero reference point.
The user may also adjust settings of the tilt indicator 400 to include a
desired
zero reference point, which may or may not reflect a true horizontal
orientation. Other
configurable parameters accessible via an interface of the tilt indicator 400
include the reported
tolerance of tilt, or resolution mode. As discussed below, the resolution mode
of tilt indicator
400 refers to a scale or range of tilt measurements that define the activation
of signal indicators
402-410. The resolution mode feature accommodates different applications and
user
preferences by allowing adjustment between different tilt measurements.
Consequently, the
user may select resolution modes having smaller or larger range tolerances for
tilt measurements
depending on whether the user demands more or less precision, respectively.
Additionally, the
user may operate switches or buttons 412, 414 (Fig. 29) to manipulate the
brightness of the
signal indicators 402-410 to account for different environments and user
preferences.
Each button 412, 414 is configured to receive user input regarding parameter
preferences. As such, an operator may adjust settings to account for different
circumstances,
such as lighting, application and preference. For convenience and space
considerations, a user
may manipulate multiple parameters using a single button. For example, the
duration for which
the user depresses a button may prompt different display options.
More particularly, a first button 412 may initiate procedures within the
controller
514 shown in Fig. 30 that shutdown/power-up and reinitialize memory 517 and
other processes.
CA 02458930 2004-02-26
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The first button 412 of Fig. 29 may additionally actuate a switch that
controls signal indicator
402-410 brightness. Using the button 412 as discussed below in detail, the
user may toggle
through a sequence of brightness levels until settling on one that accounts
for environmental
conditions and user preference.
A second button 414 of Fig. 29 allows the user to sequence through different
resolution modes. Resolution modes may correspond to a level of tilt
measurement precision
required by a specific application. For instance, a center, green signal
indicator 402 may flash
during setup to indicate the most sensitive or precise resolution setting.
Such a mode may be
appropriate for bench rest applications in that it allows only 2.5° of
imprecision in either
direction relative to the zero reference point.
Similarly, two yellow signal indicators 404, 406 may flash during setup to
indicate an intermediate resolution mode appropriate for field shooting. Field
shooting may
generally tolerate 2° - 5° of tilt in each direction relative to
the zero reference point, a range
registered by the intermediate mode. Blinking red lights 408, 410 communicate
the least
precise resolution mode. This mode may allow a free-hand shooter to utilize
the embodiment by
tolerating nearly 10° of tilt in either direction. As discussed below,
a user may select and recall
a resolution mode using the mode button 414 after experimenting with different
modes to
determine personal preferences for different applications.
Resolution mode selection dictates the level or degree of imprecision
communicated to a shooter via the signal indicators 402-410. That is, in
addition to
communicating the current mode setting to a user during initialization, the
signal indicators 402-
410 of the embodiment communicate or convey the relative degree and direction
of tilt while
aiming and firing the firearm. For example, when operating in any of the above
three resolution
modes, a single signal indicator 402-410 may illuminate to indicate the
direction of tilt relative
to the zero reference point. The illumination of only one indicator 402-410 at
any given time
further serves to conserve battery longevity and limit shooter distraction.
More particularly, the green signal indicator 402 will light when the tilt
indicator
400 is within a specified angular range of the zero reference point
corresponding to a given
resolution mode. As discussed herein, the angular range is specified according
to the operating
CA 02458930 2004-02-26
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resolution mode. Generally, however, illumination of the green signal
indicator 402 conveys to
the user that the scope is within the most precise, or narrow, angular range
of the selected
resolution mode. A yellow signal indicator 404, 406 may illuminate in response
to the measured
tilt falling outside of the specified angular range, but still within some
intermediate angular
range.
Further, a yellow signal indicator 404 or 406 will illuminate depending on the
direction of measured tilt. In this manner, the feature facilitates correction
of a tilt scenario at
the same moment it signals the error. Should the measured tilt register
outside of the
intermediate range, a red signal indicator 408 or 410 in the direction of the
recorded tilt will
illuminate. Preferably, signal indicators 402-410 will not illuminate whenever
the tilt of the
scope exceeds the range prescribed by the least precise mode.
As discussed above, the tolerated ranges of the described signal indicator
applications will vary according to the resolution mode in which the tilt
indicator 400 operates.
For instance, high precision mode will enable the green signal indicator 402
so long as the level
indicator 400 remains oriented within 2.5° in either direction of the
zero reference point.
Alternatively, intermediate resolution mode may expand this range by a degree
so that the green
signal indicator 402 lights while the scope is within 3.5° of the
reference point in either
direction. Finally, the least precise resolution mode allows for four degrees
of variation in any
direction of the zero reference point, while still illuminating the green
signal indicator 402. As
such, each of the three resolution modes have different, scaled tolerances
that the controller
may convey via illuminated signal indicators 402-410.
The mode selection button 414 additionally enables the user to set the zero
reference point used to calculate tilt. This feature capitalizes on
programming within
conventional accelerometers to accommodate shooting scenarios where a user
requires an
orientation other than true zero, i.e., a true horizontal orientation. As
such, both buttons 412,
414 may act in tandem to control the power, brightness, level setting and
other parameters of
the tilt indicator 400.
The block diagram of Fig. 30 shows an exemplary circuit layout configured to
execute process steps associated with the tilt indicator 400 of Fig. 29.
Generally, a power
CA 02458930 2004-02-26
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supply 510, which may include two lithium-ion batteries, supports a circuit
that additionally
includes a voltage regulator 511, an accelerometer 512 , controller 514,
switches 412, 414 and
a bank of signal indicators 402-410. To initiate a given shooting session, a
user may actuate a
switch 412 or 414 via a button or other suitable interface component of the
tilt indicator 400.
The activated switch 412 or 414 completes a circuit to the controller 514. Of
note, a suitable
controller 514 may embody a microprocessor or CPU, preferably one having an
associated
memory 517.
The resultant signal transmitted to the controller 514 of Fig. 30 may cause it
to
retrieve stored settings and coefficients from its memory 517. As part of, or
immediately
following such initialization processes, the controller 514 may provoke the
illumination of the
signal indicators 402-410. For instance, select indicators may flash in such a
manner as to
indicate a current operating mode of the tilt indicator 400.
The controller 514 may subsequently transmit a command to the accelerometer
512 instructing it to sample the orientation of the tilt indicator 400
relative to a specified, zero
reference point. In response, the exemplary accelerometer 512 may output
signals having duty
cycles comprising a ratio of pulse width to period. As such, the duty cycles
are proportional to
acceleration and formatted to be immediately processed by the controller 514.
The controller
514 may repetitively average and record accelerometer 512 output in memory 517
to improve
noise margins. As discussed above in detail, an exemplary accelerometer 512
includes an offset
feature that the embodiment exploits to allow a user to adjust zero reference.
The controller 514 executes program code 519 to process the accelerometer
512 output according to an algorithm discussed below in detail. The controller
514 of Fig. 30
further converts the degree of tilt gleaned from the algorithm into a signal
operable to selectively
activate signal indicators 402-410. For instance, the signal may illuminate an
indicator
appropriate to communicate a degree and direction of tilt to a user for a
given resolution mode.
As discussed herein, a user may activate a switch 412 or 414 to configure
parameters of the tilt indicator 400. The controller 514 of Fig. 30 identifies
the origin and
duration of the switch 412 or 414 initiated signal to adjust brightness,
power, mode and
reference settings. The program 519 of the embodiment may communicate such
parameters to
CA 02458930 2004-02-26
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the user via the bank of signal indicators 402-410. Further, the controller
514 may store
applicable settings and coefficients in anticipation of a next session.
The flowchart of Fig. 31 shows sequence steps associated with such a session.
More specifically, the flowchart illustrates an exemplary processing cycle for
setting and
displaying parameters of the tilt indicator 400 (Fig. 29) in such a manner as
to unobtrusively
convey tilt angle. Turning more particularly to block 420 of Fig. 31, the user
may depress the
first, on/off, button 412 (Fig. 29) of the tilt indicator 400. As discussed in
the text
accompanying Fig. 30, the button may activate a switch 412 that, in turn,
initializes a controller
514 and associated memory 517 contained within the circuitry of the apparatus.
Such
initialization processes include preparing the controller 514 to receive
stored coefficients from
memory 517. Exemplary coefficients may relate to saved reference points,
modes, brightness
levels and other preferences. A user may depress the button at block 420 of
Fig. 31 when
initially turning the apparatus on, beginning a new cycle, or powering down.
At block 422 of Fig. 31, the controller 514 of Fig. 30 may initiate self-test
procedures to ensure proper configuration and operation. In one instance, the
embodiment may
rely on the generation and evaluation of checksum values. For example, the
memory
component of the controller may retrieve a unique sequence of numbers for
verification
purposes. The controller may initiate such evaluation and relate proper
operation to the user by
illuminating signal indicators in a unique, start-up sequence.
An exemplary sequence may involve the signal indicators flashing at block 422
to remind the user of the current resolution mode setting. The current mode
setting may
correspond to the last mode setting specified by the user. For example, if a
user last operated
the tilt indicator while in high precision resolution mode, then the green
signal indicator 402 of
Fig. 29 may flash. While such a default is convenient for users who
demonstrate a consistent
mode preference, the embodiment presents a user with the opportunity to switch
modes as
discussed below at block 440 of Fig. 31.
Following setup at block 424, the tilt circuitry contained within the ocular
housing may sample the relative orientation of the tilt indicator. Namely, the
controller sends a
command to the accelerometer circuitry causing it to sample the orientation of
the scope at
CA 02458930 2004-02-26
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block 424. Of note, the tilt measurement is conducted relative to the zero
reference point
retrieved from memory at block 420. As discussed below, the accelerometer
responds by
outputting duty cycle data to the controller. The controller repetitively
samples and averages
such data to ensure application timing requirements and improve noise margins.
The controller
may further record the accelerometer output at block 424.
Of note, the output from the accelerometer may incorporate an offset factor.
Such an offset may allow the user to set or orient an independent zero
reference point for the
accelerometer, independent of gravitational orientation. The present
embodiment exploits this
feature to accommodate shooter preferences or requirements that mandate that
the scope not
be oriented at true zero, that is, aligned with gravity. At some point during
installation, the user
may determine what offset, if any, they require. In this manner, the
accelerometer may adjust
readings using the offset to reflect the user specified zero reference point.
As such, level measurements reported by the signal indicators will reflect the
offset value. For instance, the user may wish to orient the indicator
5° off of true zero for a
specific application. As such, if the accelerometer of the scope has an offset
of minus 5°, then
5° will be subtracted from a recorded, true tilt measurement. The
controller then records the
resultant tilt reading at block 424 and uses it to determine a level
measurement at block 426.
More particularly, the controller may execute program code at block 426
embodying the following algorithm: ARCSINf/t,/t2 - 0.51/0.1251. In the
equation, t, and t2 are
duty cycles of the accelerometer. The subtracted 0.5 value embodies a
normalizing factor of
the accelerometer, while the 12.5% in the denominator of the equation is a
preferred scaling
factor. The accelerometer outputs both duty cycles, t, and t2 (ratios of pulse
width to period),
as analog signals. A counter of the controller interprets and manipulates the
output according
to the above equation.
Of note, the function of the arcsin embodies the acceleration of the
accelerometer, which the ARCSIN function converts into a tilt measurement
reported in degrees.
As tilt is nonlinear with acceleration, the embodiment uses the equation to
reasonably
approximate tilt. As can be appreciated, a preferred embodiment may store and
recall tilt
CA 02458930 2004-02-26
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measurements in a lookup table accessible by the controller. Such a
configuration requires
fewer processing cycles of the controller.
Having calculated the measurement level at block 426, the embodiment may
update the user display at block 428. Namely, the controller may translate the
degree of the tilt
calculated at block 426 into signal indicator responses digestible by the
user. For instance, the
processor may associate the tilt measurement with a signal configured to
prompt the
illumination of an appropriate signal indicator. If operating in high
precision mode, for example,
the embodiment may illuminate the center, green signal indicator so long as
the shooter
maintains an attitude within 2.5° of zero reference in either
direction. Should the level
measurement stray outside of this range, but still remain within five degrees
of the reference
point, the controller may generate another signal configured to light a yellow
signal indicator.
The controller may further select the signal indicator on the side of the
display
corresponding to the angle of tilt. In this manner, the tilt indicator not
only transparently relates
a relative measurement of tilt, but also the direction of the imprecision. If
the calculated tilt
measurement exceeds 5° in either direction of zero reference while
still operating in precision
mode, then the controller may cause a red signal indicator to light. As above,
the selected
signal indicator may reflect the direction of the tilt.
Additionally, the degree of imprecision tolerated by the tilt indicator will
vary
according to the operating mode of the user. For instance, the indicator may
display a yellow
signal indicator for a shooter within 8° of zero while in off-hand, or
the least precise resolution
mode. When operating in intermediate, or field resolution mode, the same
8° of imprecision may
instead illuminate a red signal indicator.
After or prior to an initial use, the user may wish to adjust parameters of
the
display at blocks 430 and/or 438. As discussed in the text accompanying block
420, brightness
and resolution parameters retrieved from memory may serve initially as default
settings. As
such, the settings may reflect the setting used in a last application. They
may alternatively
include factory default values. The present embodiment nonetheless enables the
user to adjust
these settings to account for different circumstances, such as lighting,
application and mood.
For convenience and space considerations, a user may manipulate multiple
parameters using a
CA 02458930 2004-02-26
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single button. In a preferred embodiment, the duration for which the user
keeps the button
depressed may prompt different display options.
More particularly, a user may depress the first button for some interval
between
one half and two seconds to select a brightness level at block 430. As
discussed above,
brightness refers to the light intensity of the signal indicators. Optimal
intensity may vary as a
product of both environmental conditions, such as sun position, as well as
user preference. The
controller may register the duration that the button is depressed and generate
a toggle
command, accordingly.
In response to receiving the command, the controller may cause the signal
indicators to sequence through four different brightness levels at block 432
until the user selects
one by repressing the button. Of note, the command may activate different
combinations of
resisters in series with the bank of signal indicators in order to achieve
varying levels of
brightness. The controller may then store the selected brightness level within
its memory. As
discussed above, the tilt indicator may default to the stored brightness level
when reset at block
420.
Should the user hold the on/off button down for more than five seconds at
block
430, then the controller may power-down the tilt indicator at block 436. More
particularly, the
button may release a switch and initiate shutdown procedures within the
controller. For
convenience, a hysterisis loop in the level display circuitry may prevent the
brightness from
toggling if the on/off button is continuously depressed for over two seconds.
Should the on/off button be ignored altogether, or depressed for less than
half of
a second at block 430, then the embodiment may allow the user to proceed
directly to
configuring resolution mode. As such, the embodiment allows users to bypass
brightness
configuration. In this manner, the user proceeds directly to mode selection at
block 438. Of
note, the half of a second tolerance may be built-in to account for an
inadvertent bumps, so
that accidental contact does not disrupt a shooting sequence. That is,
accidental contact with
the button that results in it being depressed less than a half a second will
not initiate brightness
or shutdown operations.
CA 02458930 2004-02-26
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A user may similarly adjust the mode in which the tilt indicator operates at
block
438. As discussed above, resolution mode refers to the range of tilt tolerated
for a specific
application. For instance, an off-hand shooter may consider a gun tilt of
seven degrees
acceptable, while a bench shooter using a sandbag for stability may consider
only one degree of
variation appropriate. To adjust mode accordingly, the user may depress the
mode button 414
shown in Fig. 29. As with the above discussed brightness selection, the
duration of time the
user holds down the button may cause the circuitry to offer different
configuration options.
More particularly, the user may manipulate operating mode by depressing the
mode button at block 438 for at least some minimum interval, such as a half a
second. As
such, the embodiment will sequence through mode settings at block 440 until
the user presses
the button again to indicate a selection. For instance, the green signal
indicator may flash to
communicate the availability of high precision mode. Should the user not
desire such resolution,
they may wait for both yellow lights of the tilt indicator to simultaneously
flash for five times
(for 0.25 seconds each) to indicate intermediate precision mode.
The user could repress and release the mode button to select intermediate
resolution mode, should the shooting application call for field-level
accuracy. Otherwise, the tilt
indicator may next flash the red signal indicators to signify a least precise
mode. The user may
select this mode as before, or wait for the embodiment to toggle back to the
green signal
indicator, which corresponds to high precision mode. In a preferred
embodiment, each set of
signal indicators may flash five times before sequencing to the next mode. As
before, the
embodiment may incorporate the minimum, half-second interval that the user
must hold down
the mode button to account for jarring and inadvertent bumps.
Should the user depress the mode button for longer than five seconds at block
438, then the tilt indicator apparatus may acquire and set a new zero
reference point at block
444. This feature allows the user to tailor the orientation of their gun from
conventional, true
zero to accommodate different shooting requirements. The embodiment may
further store the
updated zero reference point within controller memory. As such, the controller
will recall the
zero value when calculating tilt at block 426. As with the on/off button, the
user may elect to
bypass the mode reconfiguration and/or zero reset functions altogether, by not
depressing the
CA 02458930 2004-02-26
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mode button. Also as above, a hysterisis loop in the level display circuitry
may prevent the
signal indicators from toggling through resolution modes if the button is
continuously depressed
for over two seconds.
In either case, the embodiment may cycle through a run-time counter at block
448. The counter, which may embody a conventional clock or other timing
mechanism,
registers quantities of time passing in between activation of switches via the
on/off or mode
buttons. For instance, block 450 may determine that the user has not adjusted
the brightness,
mode or zero value for a period exceeding thirty minutes. In response, the
counter may send a
signal to the controller, which in turn, initiates shutdown procedures at
block 436.
Of note, the exemplary thirty minute period may be adjusted by the user and/or
reflect some factory setting. Such a counter feature serves to preserve
battery life in the event
that the user neglects to turn the tilt indicator off in between applications.
Where the period of
inactivity does not exceed thirty minutes, the embodiment cycles back to block
424, where the
level of tilt is recalculated and the user display is updated for the user.
While the present invention has been illustrated by a description of various
embodiments and while these embodiments have been described in considerable
detail, it is not
the intention of the applicants to restrict or in any way limit the scope of
the appended claims
to such detail. Additional advantages and modifications will readily appear to
those skilled in
the art. The invention in its broader aspects is therefore not limited to the
specific details,
representative apparatus and method, and illustrative example shown and
described.
Accordingly, departures may be made from such details without departing from
the spirit or
scope of Applicant's general inventive concept.
What is claimed is:
