Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
" ~31970
BACKGROUND OF~THE INVENTION
This invention relates to an automatic focusing camera
which, without a prior knowledge of the distance of a subject
to the camera, is capable of bringing the subject into focus in
response to initiation of a camera cycle.
Cameras have become known in which initiation of a
camera cycle causes the lens mount of an adjustable lens assembly
to be driven from a park position to a focus position dependent
on subject distance as determined by a range finder system that
generates a range parameter related to subject distance. When
an exposure cycle in such a camera is initiated, the range
finder system beams a burst of ultrasonic energy toward the
subject. The interval of time between transmission of the burst
and receipt of an echo is a parameter linearly related to subject
distance by a fixed scale factor which defines a parametric
relationship between time and the lens/subject function of the
camera.
As is well known, the lens/subject function establishes
the relationship between the distance of a subject and the
position of the lens mount on the camera at which an image of
; the subject at that distance is in focus on the focal plane of
the camera. Such function also establishes the range of distances
over which subjects can be brought into focus by movin~ the lens
mount.
Once the range parameter is generated, a motor moves
the lens mount from a park position to a focus position
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depending on subject distance as determined by the range
parameter, the shutter mechanism of the camera then being
actuated to effect exposure of film located in a focal plane
at a recording station behind the shutter mechanism. Sensing
of the termination of exposure causes the motor to drive the
lens mount back to its park position thereby terminating the
exposure cycle.
When a photoelectrically controlled shutter mechanism
is incorporated into a camera of the type described, it would
appear that proper exposure as well as focus will be obtained
each time an exposure cycle is initiated without a-priori
knowledge of either light conditions of the scene being
photographed or subject distance. This is not the case,
however, when an attempt is made to photograph a subject
located closer to the camera than the minimum distance designed
into the optical system of the lens mount, or when an attempt
is made to photograph a subject under flash illumination
conditions and the subject is outside a predetermined range
of distances dependent on the range of exposure values of
the shutter mechani~m and the light output of the flash unit.
Under ambient lighting conditions, a poorly fccused photograph
~.
will result when a subject is closer than a minimum distance.
- Under flash illumination conditions, an overexposed photograph
will result when a subject is closer than the minimum pre-
determined range, and an underexposed photograph will result
when the subject is further than the maximum predetermined
range.
It is therefore an object of the present invention
to provide a new and improved camera for controlling camera
operation in accordance with subject distance.
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A further object is to provide a camera capable of
indication of operable limits of the camera versus subject
distance under both ambient and flash mode conditions.
` BRIEF DESCRIPTION OF THE INVENTION
In accordance with the present invention, an indicator
associated with an automatic focusing camera is responsive to
initiation of a camera cycle for producing an indication and
for inhibiting further camera operation if the subject is too
near the camera to be in focus or too near or too far for proper
flash exposure. Under the above conditions, a camera inhibit
signal is produced which is effective to terminate the camera
cycle without actuating the shutter mechanism. When the camera
is operated in its flash mode, and the subject is outside a
predetermined range within which the shutter mechanism is capable
of producing a properly exposed photograph, the indicator pro-
vides an indication that the subject is either too near or too
far from the camera for proper flash exposure to be achieved.
In this case, a camera inhibit signal is also produced, such
signal terminating camera operation without permitting the
shutter mechanism to be actuated.
More specifically, the invention is a camera operable
to record an image of a subject located within a given range of
; subject distance having a rangefinder which, in response to
camera actuation, generates an electric signal representative of
the distance to the subject, the given range of subject distances
being represented by a given range of rangefinder signal values,
and additionally comprising meanæ operative in response to a
rangefinder signal having a value lying outside the said given
range of values to provide an indication that the subject is
outside the said range or to inhibit operation of a shutter
arrangement within the camera to prevent recording of an image
of the subject.
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In one embodiment of the invention, the indication and
inhibit signal are provided in response to movement of the lens
mount toward or to a focus position, as determined b~ a range
parameter, which is outside the lens position permitted under the
described conditions. Then the inhibit signal causes the lens
mount to be returned to its start position without actuating
the shutter thereby terminating the camera cycle.
In another embodiment of the invention, digital or
analog logic is utilized in connection with generation of
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the range parameter to provide indication and inhibit signals.
This arrangement permits the camera cycle to be terminated
without moving the lens mount from its park position.
BRIEF DESCRIPTION OF THE D~AWINGS
S Embodiments of the present invention are disclosed
in the accompanying drawings wherein:
Fig. 1 is a schematic block diagram of an autofocus
camera of the type desc~ibed showing the various positions of
its lens mount in relation to the too-close and too-far
positions of a subject;
Fig. 2 is a block diagram of- the camera of Fig. 1
illustrating its ranging and focusing arrangement in accor-
dance with the present invention;
Fig. 2A is a timing diagram associated with the
block diagram o Fig. 2;
Fig. 3 is a block diagram of the second embodiment
of the present invention;
Fig. 4 is a schematic showing of the range counter
and decoder shown in Fig. 3;
Fig. 5 is a chart showing the relationship between
the stored count of the range counter and the distance of the
subject to the camera;
Fig. 6 i8 a detailed logic diagram o the indicator
and inhibitor arrangements of Fig. 3;
Fig. 7 shows timing diagrams associated with an
- analog embodiment of the indicating and inhibiting arrange-
ment of Fig. 3;
Fig. 8 is a typical block diagram for generating
the analog voltages shown in Fig. 7; and
Fig. 9 is a logic diagram for producing too-near
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and too-far indications as well as the camera inhibit signal -
from the analog system of Fig. 8.
DETAILED DESCRIPTION
Referring now to Fig. 1, reference numeral 10
pertains to an automatic focus camera of the type disclosed
in the application identified above and comprises a housing 11
containing a focal plane 12 defining a recording station
located behind a shutter mechanism 13 which may be ass~ciated
with a photodetector (not shown) for sensing the amount o
light passing the shutter mechanism when the latter is actuated.
A sheet of photosensitive material (not shown) is located in
the focal plane for receiving light from a scene being photo-
graphed when the shutter mechanism is actuated. A lens 14
is carried on one axial end of an adjustable lens mount 15
having a sleeve member 16 carrying on its opposite axial end
internal threads that engage a threaded tube 17 on the camera
housing permitting rotation of the lens mount to impart
axial displacement of the lens 14.
Given the type of lens, its focal length, and other
parameters of the optical system, the lens mount will have a
given lens/subject function which relates the axial position
of a lens unt at which a sub~ect 18 is in focus to the
distance of the subject to the focal plane. In order to
- adj~ust the axial position of the lens mount, pinion 19 is
provided. The teeth of this pinion engage the toothed
periphery of lens mount 15 so that rotation of pinion 19
by a drive means 20, i.e., an electric motor and forward
and backward controls, imparts rotation to the lens mount.
Rotation of the pinion in one direction (i.e., clockwise)
rotates the lens mount couterclockwise and moves it to the
1131~370
right as seen in Fig. 1, from its park position closest to
the housing to a close-up position. In the park position
of the lens mount 15, the front face 21 will occupy the
position shown by line 21A. Line 21B shows the position
of face 21 when the lens mount is in its close-up position.
If desired, movement of the lens mount can be
limited in the one direction to its close-up position. In
such case, a stop would`be formed by the closed end (shown
dotted) of slot 22 in the inner surface of sleeve 17 which
cooperates with a fixed pin 23, fixed to tube 17 and pro-
jecting into the slot. Rotation of the pinion in the opposite
directi~n (i.e., counterclockwise) would move the lens mount
in the opposite direction and return it to its park position
where it abuts housing 11 which limits further travel in the
opposite direction.
When the lensmount is in close-up position 21B,
suhject 18 will be in focus when it is located in close-up
plane 24 at some minimum distance, the absolute value of
which is dePendent on the lens/subject function as well as
the mechanics of the lens mount selected by the camera
designer. With the lens mount at the hyper~ocal position 21C,
subiect 18 will be in focus when it is located in the hyper-
focal plane 25 or beyond. Thus, an image of a subject
located within the subject range defined between planes 24,
25 shown in Fig. 1 can be focused on the focal plane of the
camera by selecting the position of the lens mount as pre-
scribed by the lens/subject function within the limits of
the close-up and hyperfocal positions of the lens mount.
A subject closer to the camera than the minimum distance
cannot be brought into focus since the lens mount cannot be
1131970
moved beyond its close-up position to the position indicated
at 21D.
Camera 10 also includes a range finder means 26
having an acoustic ranging device 36 and a jam sensor 27
actuated by an actuator button 28. On manual depression of
the actuator button, a switch (not shown) is closed and a
cycle of the camera is initiated whereby range finder means
26 generates a range parameter directly related to ubject
distance and computes, from such parameter, a number repre-
senting the focus position of the lens mount in accordance
with the lens/subject function. Such number also represents
the distance of the subject from the camera.
Drive means 20 is responsive to the number computed
by the range finder means, and drives the lens mount 15 from
its park position to its focus position by suitable rotation
of pinion 19. Upon arrival of the lens mount at its focus
position, a shutter mechanism 13 is actuated to effect
exposure of a photosensitive sheet ~not shown) lying in the
film plane 12. The shutter mechanism 13 then signals
completion of exposure, and the drive means responds by
driving the lens mount 15 back to its park position thereby
~erminating the camera cycle~
~he above-described operation of camera 10 permits
photographing Of a subject without a-priori knowledge of
subject distance by reason of the focusing arrangement
described above. Only when the subject being photographed
is closer to the camera than the minimum distance associated
with the camera will an improperly focused picture be obtained.
Where ambient scene lighting conditions are low
such that improper exposure will result unless a time exposure
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is made, the camera can be switched from an ambient mode of
operation to a flash mode of operation. Such switching can
be accomplished by the attachment of a flash accessory;
however, for simplicity of the present description, the camera
S 10 is illustrated herein with an affixed flash assembly or
flash unit 29 for the purpose of illuminating subject 18
with the output of a flash lamp or strobe 30 when switch 31
is moved from an ambien~ to a flash position; the lat~er
being indicated by broken lines 31A. Lead 45 interconnecting
the flash unit 29 with the camera provides for synchronization
of the flash energization with the movement of shutter
mechanism 13 in a conventional manner.
Since camera exposure systems do not provide an
unlimited range of exposure values (available combinations
of diaphragm size and exposure intervals) there is a minimum
and a maximum exposure value associated therewith which are
important considerations for flash photography where the
flash energy is fixed. Consequently, proper flash exposure
can be achieved only with a limited range of subject distances.
For instance, if the minimum exposure value is designed to
produce a proper exposure when the subject is loaated at the
plane 24, an exposure of a ~ubject located at still nearer
the camera, i.e., in plane 33, will be overexposed while
subjects at far distances will be underexposed. Although
they are often different, the close-up distance (plane 24)
which defines the minimum distance of a subject at which
focus can be achieved is treated herein as the same
minimum distance at which flash illumination will properly
expose the subject. Additionally, for reference purposes,
plane 34 has herein been selected to designate the maximum
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distance of a subject under flash illumination at which the
subject will be properly exposed. Thus, the distance between
planes 24 and 34 represents the flash illumination range
within which the subject will be properly exposed. Therefore,
S utilization of camera 10 in its flash mode of operation
without a-priori knowledge of the distance of the subject
will result in proper exposure only for subjects located
between planes 24 and 3~.
In order to obtain properly focused photographs
under ambient lighting conditions, independently o~ the
distance of the subject to the cam~ra, and in order to obtain
properly exposed photographs under flash illumination con-
ditions without a-priori knowledge of the subject distance,
the present invention incorporates into an automatic focusing
camera an indicator and/or camera inhibitor operative if the
subject is too close for proper focusing or outside the range
for proper exposure under flash illumination conditions, so
as to warn the operator of the existence of these situations
and prevent further camera operation.
In the embodiment shown in Figs. 1 and 2, indicator
35 operates in respon$e to mechanically sensing the position
of the lens mount after it is driven to its focus position
by the range finder means while in the embodiment of Fig. 3,
indicator 35A operates in response to the output of the range
finder system before movement of the lens mount occurs. In
both embodiments, the indicator is responsive to initiation
of a camera cycle for producing an indication when the subject
is too near for proper focusing or outside the range (too near
or too far) for proper exposure if the camera is operated in
its flash mode. An inhibit signal is also produced, and is
113~970
effective to terminate the camera cycle without actuating the
shutter mechanism.
The camera apparatus illustrated herein are described
with respect to a single camera cycle including ranging, focus-
ing and exposure; however, it should be noted that it is often
preferable to provide means for cycling the camera only through
ranging and focusing. In the latter case, however, the novel
indicating arrangements will still operate in the manner to be
described.
The operation of the block diagram in Fig. 2 is
described below in connection with two situations:
(1) ambient light operation with the subject located
at a distance greater than the minimum distance, or flash
illumination operation where the subject is located within a
predetermined subject range that provides proper exposure under
flash illumination; and
(2) ambient light operation when the subject is
located at a distance less than the minimum distance, and flash
illumination operation when the subject is located outside the
predetermined range that provides proper exposure.
A camera cycle is initiated by manual actuation of
the camera cycle button 28 (shown ~chematically in Fig. 2)
which powers the camera from an electrical source or supply 44
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1131~70
and actuates the range finder 26 by establishing a step
function whose leading edge is detected at 47 and used to
key acoustic ranging device 36, as well as to start the
operation of a clock 58. Ranging device 36 transmits a
burst of ultrasonic energy 60 which is beamed at subject 18.
Energy reflected from the subject will be received by the
acoustic ranging device 36 and cause the latter to produce
a RECEIVE or range pulsè 48 at a time ~ following trans-
mission (see Fig. 2A). During this interval, c.lock 58
produces a periodic train of pulses which increment a counter
60 while a decoder 62 serves to decode the contents of
counter 60 to produce the break points of an approximation
of the lens/subject function as described in the above-
identified patent application. A programmed divider 63,
responsive to the output of decoder 62, functions as a
scaled clock whose pulse repetition frequency varies in
accordance with the approximation of the lens/subject
function which, itself is parametrically related to time
in accordance with the relationship between the interval~C
: 20 and subject distance. The output of divider 63 is applied
through an AND gate 40 andan OR gate 42 to a range counter 41.
A latch 64, initially set by the transmit signal~
is reset upon receipt of pulse 48. Thus, the output of latch
64 is a pulse of duration ~C and hence, gate 40 is enabled by
latch 64 only during the time between the start of transmission
from acoustic ranging device 36 and receipt of an echo by this
device.
At the instant transmission of an ultrasonic burst
occurs,the scaled clock isgated into a range counter 41. In the
interval of time between start of transmission and the earliest
113~9~)
time the receiver is capable of detecting an echo (taking
into account the transmission time of the burst and the
blanking time of the receiver to prepare it for reciept of
an echo), the scaled clock will have produced Pl pulses
where ~1 is a number representing both the close-up position
of the lens mount and the minimum distance of the camera
(see Fig. 1). ThP scaled clock continues to run producing
pulses at a rate determlned by the program of divider 63 so
that when echo pulse 48 occurs and gate 40 closes, the
contents of counter 41 will be ~, where ~ is a number
representing both the focus positiQn of the lens mount an~
the distance of the subject from the camera. As explained
below, the maximum number that can be inserted into counter
41 by the scaled clock is ~2~ where ~2~ and ~2 is
a number representing the hyperfocal position of the lens
mount.
Initially, the lens mount is located at its park
position with which the number ~3 is associated, where ~3
~ P2. To reach its focus position represented by the number
~ (stored in the range counter 41) the lens mount must ~e
displaced a distance proportional to P3 - ~. This result is
achieved by a decoder 43 which produces a focus control
signal when the contents of the range counter 41 reaches the
number ~3, the range counter being incremented from its value
~ by displacement of the lens mount as described below.
In addition to closing gate 40 and terminating the
incrementing of counter 41 by the scaled clock, echo pulse 48
also sets trailing edge latch 65 which enables AND gate 68 and
AND gate 66. Enablement of gate 66 applies power to motor 32
of drive means 20 through forward motor control 67 while
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gate 68 permits conduction to gate 42 and range counter 41
of lens position pulses. Power from supply 44 is thus
applied to forward motor control 67 which is effective to
energize motor 32 operatively connected to lens mount 15
through pinion 19. Motor 32 moves the lens mount and thereby
operates auxiliary pulse generator 35 whose details are shown
in the above-identified application. Auxiliary pulse generator
37 thus produces pulses only when motor 32 moves the lens
mount, the rate at which pulses are produced being dependent
upon the rate at which the motor moves the lens mount; the
accumulated number of pulses created thereby being propor-
tional to the distance moved by the lens mount. These pulses
are applied to counter 41 through gate 68 (which is enabled
by the setting of latch 65 upon receipt of echo pulse 48)
and OR gate 42.
Thus, the contents of counter 41 increases from ~
(a number representing the focus position of the lens mount)
towards a full-up condition, i.e., the number p3. When the
contents of counter 41 reaches ~3, decoder 43 produces a
focus control signal which resets the latch 65 thereby
opening gate 66 so as to disable forward motor control 67,
therebY deenergizing motor 32 and further lens movement. In
addition, the focus control signal produced by decoder 43 is
applied via delay 38 and normally open gate 39, to shutter
actuator 69 which actuates shutter mechanism 13 thereby
exposing the film located at focal plane 12 of the camera.
A jam sensor 27 comprising a clock 80, a jam counter 74 and
a decoder 82, operate to fill up the range counter 41 and
hence force a focus control signal when a mechanical jam
occurs.
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If the camera is being operated in its ambient
illumination mode, switch 31 will have the position shown
in solid lines in Fig. 1 and operation of flash unit 29 will
be suppressed. If the camera is being operated in its flash
illumination mode, switch 31 will be in position 31A thereby
synchronizing the triggering of flash device 30 with shutter
actuation in a conventional manner. In either case, exposure
will be controlled by a photocell (not shown) which, in a
conventional manner, integrates the light incident on the
film due to actuation of the shutter mechanism, and terminates
exposure when a predetermined amount of light has been
received by the film.
Completion of exposure is detected at 49 thereby
triggering one shot multivibrator 70 which produces a voltage
for a predetermined period of time enabling gate 71 for this
period and permitting power from supply 44 to be applied to
backward motor control 72 which is effective to power motor
32 in the direction opposite to the direction in which
control 67 powered the motor; and the motor will thus drive
lens mount 15 from its focus position back to its park
position. A clutch (not shown) prevents burn out of the
motor when the lens reaches its park position prior to end
of the time period set by the muItivibrator 70. Alternatively,
a lens switch (not shQwn) may be employed to shed the power
load when the lens reaches this position.
~ camera cycle has thus been completed, such cycle
starting with manual actuation of the camera button when the
lens ~ount is in its park position, and including movement
of the lens mount to its focus position, completion of exposure,
and movement of the lens mount back again to its park position.
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When the camera is operated in its amhient illumi-
nation mode, and the subject is located at a distance from
the lens mount greater than the hyperfocal distance, the
scaled clock will reach the number ~2' corresponding to the
hyperfocal distance (approximately 7 meters), before range
pulse 48 occurs and before it can reset latch 64. As a
consequence, when the count of divider 63 reaches the hyper-
focal distance before pùlse 48 occurs, the divider produces
a signal in line 63A which is applied to latch 64 resetting
the same. In such case, range counter 41 will contain the
number ~2 corresponding to the hyperfocal position of the
lens mount; and the setting of latch 65 is effective to
enable motor 32 which operates to drive the lens mount from
its park position to the hyperfocal position. It can be seen,
therefore, that a subject at a distance in excess of the
hyperfocal distance of the camera will be in focus because
the lens mount will move to its hyperfocal position.
Indicator 35 becomes effective when the second
situation outlined above occurs, namely, when camera operation
is set for ambient light and the subject is located at a
distance~less than the minimum distance, as well as when the
camera is set for flash illumination operation and the subject
is located outside the range of flash. Assume first that a
camera cycle is initiated when the camera is set for ambient
light operation and the subject lies in plane 33 (i.e., too
close for focusing). In such case, motor 32 is ef~ective to
drive lens mount 15 from its park position to the position
shown at 21D in Fig. 1 wherein the lens mount closes normally
open switch 50 located in the recess within which the lens
mount is slidable. The closure oi this switch occurs as soon
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as the lens mount passes its position 21B, and in any event
prior to the time that the focus control signal is applied
to the shutter actuator 69, a delay 38 insures this situation.
The closure of switch 50 powers indicator lamp 84
and sends a signal through OR gate 85 to AND gate 86. Simul-
taneously present at the other input to AND gate 86 is the
"focus control signal" which causes the AND gate to produce
an output signal that disables gate 39 and triggers one-shot
multivibrator 70. The disabling of gate 39 prevents the
focus control signal, after it has been delayed at 38, from
passing to shutter actuator 69. Thus, it can be seen that
the movement of the lens mount beyond position 21B (Fig. 1)
in accordance with the operation of range finder means 26
will inhibit actuation of the shutter mechanism, and at the
same time enable multivibrator 70 which will drive the lens
mount back to its park position to terminate the exposure
cycle. Furthermore, the user is advised of this "too close"
condition by reason of the illumination of lamp 84 which may
be in the form of a light emitting diode 84 positioned in
2D viewfinder 87 of the camera, a9 9hown in Fig. 1. Thus, when
an attempt i8 made to photograph a subject under ambient
light where the subject is located closer to the camera than
the minimum distance for which the optical system of the
camera has been designed,indicator 35 provides an indication
of this situation and also provides an inhibit signal that
terminates the exposure cycle without allowing the shutter
mechanism to be actuated. In addition, the inhibit signal
causes the lens mount to be driven back to its park position.
In the event that the camera is operated in its
flash mode (i.e., switch 31 is in position 31A) and the sub~ect
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1~31~70
is located at, say plane 33 (i.e., too close for proper
exposure under flash illumination), indicator 35 is also
effective to inhibit exposure. As described above, the
initiation of a camera cycle will cause motor 32 to drive
the lens mount from its park position to position 21D (Fig.l~,
thereby again closing switch 50. Indicator 35 reacts in
exactly the same wa~ as described above to inhibit exposure
and terminate the exposure cycle.
In the event that the camera is operated in its
flash mode and the subject is located beyond plane 34 (i.e.,
too far for proper exposure under flash conditions), initia-
tion of an exposure cycle will cause motor 32 to drive the
lens mount from its park position to its position shown in
full lines in Fig. 1. In such position, the lens mount will
clear and thereby release the normally closed switch 51
located in housing 11 and engageable by the lens mount only
when the latter is in a focus position for subjects located
closer to the camera than the maximum distance for flash
illumination represented by plane 34. Therefore, for a
subjcct located beyond plane 34, the lens mount will be
clear of switch 51 which becomes closed once the lens mount
has been driven to its too far position.
Re~erring to Fig. 2, it can be seen that when the
focus control signal occurs, all of the inputs to AND gate 87
will exist simultaneously and this gate will have an output
produced by decoder 43. The output of AND gate 87 will
illuminate lamp 88 (also positioned in viewfinder 87)
indicating that the subject is beyond the maximum distance
for which a flash picture can be taken. In addition, the
output of AND gate 87 will pass through OR gate 85 and be
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applied to AND gate 86 which will produce an inhibit signal
that will disable gate 39 and prevent the delayed focus
control signal from operating actuator 69. In addition, the
inhibit signal will be applied to multivibrator 70 for the
purpose of causing motor 32 to drive the lens mount back to
its park position thereby terminating the exposure cycle
without allowing the shutter mechanism to be actuated.
Indicator 35 shown in Fig. 2 is thus effective
only after the lens mount has been moved from its park to
its focus position. The decision to terminate the exposure
cycle without effecting shutter actuation is made on the
basis of the focus position of the lens mount. Switching
arrangements other than that shown in the drawing can be
utilized for sensing the focus position of the lens mount
and producing the indications and inhibit signals described
above. Regardless of the switching arrangement utili~ed,
however, indicator 35 is effective to provide an indication
whenever the subject is closer than the minimum distance for
which the optical system of the camera has been designed as
well as whenever the subject is outside the range for which
flash illumination will be proper when the camera is operated
in its flash mode. Whenever an indication is provided, an
inhibit signal is also provided for the purpose of preventing
actuation of the shutter and for terminating the camera cycle.
Fig. 3 discloses another embodiment wherein the lens
actuated too-close, too-far system is replaced by an indicator
35A, whose operation relies upon the contents of range counter
41 and does not depend upon physical movement of the lens
mount. The camera of Fig. 3 is similar to that of Fig. 2
except for the modifications required to accommodate the
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indicator 35A. Advantageously, it should be noted that
(as explained below) since lens movement is unnecessary in
the second and third embodiments for indicating subject
distance and/or inhibiting exposure etc., thes~ embodiments
(in contrast to the embodiment of Fig. 2) are suitable for
flash subject distance in a fixed lens or so-called ixed
focus cameras. Counter 41 is a typical binary counter, and
for discussion purposes; the counter is shown in Fig. 4 as
a 4-bit binary counter. It should be understood that in an
actual camera, more bits would be used for the purpose of
increasing the number of divisions into which the range of
a subject can be divided. However, the principal of opera-
tion is the same.
Counter 41 is incremented by the output of scaled
clock 63 in the manner described above. The states of counter
41 as a function of time and the output of the scaled clock
are shown in Fig.~5. Associated with each state is both a
position of the lens mount as described above as well as the
range of a subject. That is to say, if counter 41 has the
state 0011 when RECEIVE pulse 48 occurs, then the distance
of the subject causing this pulse will be three feet (using
the typical figures ghown in Fig. 5). If it is assumed that
the minimum distance f~r which the optical system of the
camera is designed is four feet, then the state of counter
41 for a subject located less than the minimum distance from
the camera can be any one of the four states contained within
the legend "too near for flash with focus". Minimization of
these states is the logical quantity Q3 Q4, which is the
logical operation carried out by an AND gate 90 (Fig. 6).
This gate will have an output during the first three increments
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of counter 41. If a RECEIVE pulse 48 occurs during this time,
then the conclusion is that the subject is closer to the
camera than the minimum distance defined by plane 24 (Fig. 1).
As shown in Fig. 6, a latch 91 is set under these
conditions causing illumination of lamp 84A indicating that
the subject is too near for achieving focus under ambient
lighting conditions, or too near for achieving proper exposure
under flash illumination. The output of latch 91 passes
- through an OR gate 92 to produce a camera inhibit signal
which disables gate 93 and prevents the delayed output of
latch 65 from enabling gate 66 to operate the lens motor 32.
In other words, the inhibit signal appears, in time, before
the delayed output of latch 65 thereby preventing the motor
32 from being energized. As a consequence, the lens mount
remains at its park position. In addition, the camera inhibit
signal produced by OR gate 92 disables gate 39 to prevent the
application of an input to the shutter actuator 69 and also
actuates the multivibrator 70 to terminate the camera cycle.
From the above, it can be seen that the camera cycle is
terminated without any movement of the lens mount and without
shutter actuation.
If the camera is in its flash mode of operation,
and the subject is located at a distance greater than the
maximum distance as given b~ plane 34 (Fig. 1), initiation
of a camera cycle will cause the range counter 41 to have
one of the five states inc}uded within the legend "too far
for flash" shown in Fig. 5. Minimization of these states
produces the logical quantity Q4 (Ql Q2 + Q3). This logic
is carried out by indicator 35A as shown in Fig. 6. Speci-
fically, the output of AWD gate 95 will be indicative of a
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subject being located beyond plane 34. If AND gate 95 has
an output when a RECEIVE pulse occurs, and the camera is in
its flash mode, AND gate 96 would have an output which sets
latch 97 illuminating lamp 88A. This lamp provides an
indication that the subject is too far for achieving a
proper exposure under flash illumination. Latch 97 also
provides a camera inhibit signal as a consequence of OR
gate 92, the inhibit signal serving to inhibit the enabling
of gates 66 and 39 and to terminate the camera operation as
described above.
The division of the output into the steps shown
in Fig. 5 is entirely arbitrary. For example, the "usable
range for ambient" could be larger or smaller than that shown
and will depend upon the camera design. The size of the
range "too near for flash" could be different from the range
"too near for focus", this too being dependent on camera
design, and the logic required for such other ranges will
depend directly on the ranges actually used.
Alternative to indicator 35A, which operates on
the output of range counter 41, an indicator according to
the present invention can take the form shown at 35~ in Fig~ 9.
In this embodiment, the operation of the indicator is based on
a recognition that the time required for the output of the
scaled clock to reach a number representative of the distance
of the subject is dependent on the scale factor of the scale
clock. Thus, timing independent of the scaled clock can be
used for an indicator if the timing is synchronized with the
scaled clock. A stable reference with respect to the opera-
tion of the scaled clock is a suitable starting point for
timing. Such stable reference could be the depression of
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shutter release button 28 which is "start" as indicated in
the timing diagram of Fig. 7. In such case, circuitry 100
shown in Fig. 8 will provide the necessary logical inputs to
indicator 35B shown in Fig. 9.
Circuitry 100 comprises integration circuit 101
with a time constant of (R,Cl), and integration circuit 102
with a time constant of (R,C2) which is larger than the time
constant of circuit 101: The time rate of change of the
output of these two integrators is illustrated in Fig. 7.
After depression of shutter release button 28 which closes
a start switch 103, the output of integrator 101 (shown at
TC #l) will reach a trigger level at a time tN which will be
prior to the time tF that the output of integrator 102 (shown
at TC #2) reaches its trigger level. Each of the integrator
circuits 101 and 102 include inverters, with circuit 101
having a single inverter 104 (whose output changes from N
to N at the end of the interval between the closing of start
switch 103 and tN) with circuit 102 having a pair of inverters
104 and 105; the output of the latter changing from F to F at
the end of the interval between switch closing and tF.
By a suitable selection of the time c~nstants for
integrators 101 and 102, the time tN will correspond to the
time required for the range counter 41 to accumulate pulses
from the scaled clock indicative for a subject located at the
minimum distance from the camera. Similarly, the time tF
will be the time required for range counter 41 to accumulate
pulses from the scaled clock corresponding to a subject
located at the maximum distance from the camera.
Indicator 35B shown in Fig. 9 utilizes the logic
signals developed by the circuitry shown in Fig. 8 as well as
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the logic signals representing the RECEIVE pulse 48 and the
position of flash switch 31. Thus, if the RECEIVE pulse
occurs before tN (corresponding to the too-close position),
an AND gate 107 is enabled by the receive signal and N output
of inverter 104. Hence, under these conditions, the gate 1~7
will have an output that will set a latch 108 illuminating an
indicator lamp 84B and thereby providing an indication that
the subject is too closè to the camera fox focusing or for
achieving proper exposure under flash illumination. Similarly,
in the flash mode (signalled by switch 31) if RECEIVE pulse 48
has not occured (REC) before tF (corresponding to the too-far
position), an AND gate 109 is enabled by the NOT receive
signal, the flash mode signal, and the F output of inverter
106. Hence, under these conditions, the gate 109 will have
an output that will set a latch 110 thereby illuminating a
lamp 88B and providing an indication that the subject is
beyond the maximum distance for proper exposure under flash
illumination conditions.
As is the case of indicator 35A, indicator 35B
produces an inhibit signal by means of an OR gate 111 whenever
either of latches 108 or 110 is set. Such inhibit signal is
used to disable gates 93 and 39 (Fig. 3) and to actuate the
multivibrator 70.
Hence, the latch 108 is set, producing an indication
and an inhibit condition if the RECIEVE signal 48 occurs before
the N output of inverter 104 (before time tN)~ while the latch
107 is set if the RECEIVE signal has not occurred before the
output of inverter 106 has changed to F (after time t ).
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It is believed that the advantages in and improved
results furnished by the method and apparatus of the present
invention are apparent from the foregoing description of the
various embodiments of the invention. Changes and modifica-
tions can be made without departing from the spirit and scopeof the invention a~ sought to be defined in the claims that
ollow.
