Note: Descriptions are shown in the official language in which they were submitted.
~11957~3
The invention is in the field of photoflash
lamp units, such as multiple flash arrays having flash
lamps enclosed in a housing provided with a transparent
front cover through which light passes from a lamp when
flashed.
Various reflector designs have been devised to
direct the light from a flashing lamp toward the scene
being photographed, so as to utilize the light more
effectively than would be the case with a bare lamp emitting
its light in all directions. Concave reflectors are
customarily positioned behind the flash lamps so as to
reflect and concentrate the light of the flashing lamp
toward the scene being photographed. For example, U.S.
Patent No. 3,609,332 - dated September 28, 1971 to
Donald R. Schindler discloses a flash lamp unit having
elongated concave quasi-cylindrical reflectors positioned
behind and axially aligned with elongated tubular flash
lamps. These reflectors, the side portions of which extend
laterally sideways of and flank the lamps, have a parabolic
curvature so as to effectively reflect a maximum of light
from a flashing lamp in a frontward direction to illuminate
the scene being photographed. U.S. Patent No. 3,993,896 -
dated November 23, 1976 to Alfred Wacker discloses a flash
lamp unit having elongated concave quasi-cylindrical
reflectors of which the side portions which extend laterally
sideways of and flank the lamps are flat instead of having
parabolic curvatures as in the Schindler patent, and there-
fore reflect light more laterally than required to
illuminate the scene to be photographed, whereby some of the
3Q light would ~e wasted. To usefully recover some of this
light that would be wasted, the transparent ~ront coyer is
proyided with groups of prisms in front of the side portions
7V
of the reflectors, which prisms direct the reflected light
more frontwardly toward the scene to be photographed.
The primary object of the invention is to provide
an improved photoflash unit having improved illumination
efficiency and which projects increased illumination onto a
scene being photographed.
The invention comprises, briefly and in a
preferred embodiment, a photoflash unit having one or more
elongated flash lamps, and a light-transmissive cover in
front of the flash lamps which is provided with a group of
one or more elongated light-refractive elements or prism
means at a region directly in front of each flash lamp and
parallel to the lamp axis so as to refract some of the light
from the lamp when flashed in a more frontward direction.
Preferably, an additional group of elongated prism means is
provided in front of and perpendicular to the axis of each
lamp, to further increase the useful frontwardly directed
light from the unit, and may be incorporated in a cover of
the array. One group of prisms can be on one surface (for
example, the front) of the cover and the other group of
prisms can be on the other surface (for example, the rear)
of the cover. The two groups of refractive elements may be
combined at a single surface, in the form of sections or
facets having oblique angles so as to provide a refractive
system which is the optical equivalent of discrete
horizontal and vertical prisms. In a flash unit having an
elongated flash lamp axially aligned in combination with an
elongated quasi-cylindrical reflector, the prisms of the
cover perpendicular to the axes of the lamp and reflector
may additionally function to refract frontwardly light that
1~95~(~
.
is divergently reflected by the reflector with longitudinal
components in planes parallel to said axes.
Figure 1 is a perspective view of a multiple
flash lamp array in accordance with a preferred embodiment
of the invention.
Figure 2 is a partial sectional view of Figure 1
taken on the line 2-2 thereof.
Figure 3 is a partial sectional view of Figure 1
taken on the line 3-3 thereof.
Figure 4 is an exploded view of the array of
Figure 1 showing the internal parts.
A multiple flash lamp unit 17 of the FlipFlash
planar array type and containing a plurality of electrically
fired flash lamps is provided with a plug-in connector tab
18 at the lower side or end thereof, adapted to fit into a
socket of a camera or flash adapter. The lamp array 17 is
provided with a second plug-in connector tab 18' at the top
side or end thereof, whereby the array 17 is adapted to be
attached to the camera socket in either of two orientations,
i.e., with either the tab 18 or the tab 18' plugged into the
socket. The array 17 is provided with an upper group 21 of
flash lamps 22r 23, 24, and 25, and a lower group 26 of
flash lamps 27, 28, 29, and 30, the lamps being arranged in
a planar configuration. Reflectors 22', etc., are disposed
behind and laterally sideways of the respective flash lamps,
so that as each lamp is flashed, its light is projected
forwardly of the array 17. The lamps are arranged and con-
nected so that when the array is connected to a camera by
the connector 18, only the upper group 21 of lamps will be
flashed, and when the array is turned end for end and con-
nected to the camera by the other connector 18~, only the
then upper group 26 of lamps wil be flashed. By this
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arrangement, only lamps relatively far from the lens axis
are flashable, thus reducing the undesirable red-eye effect.
The construction of the array comprises front and
back housing members 36 and 37, which preferably are made of
plastic and are provided with interlocking members 38 which
can be molded integrally with the housing members and which
lock the housing members together in final assembly to form
a unitary flash array structure. In the preferred embodi-
ment shown, the front housing member 36 is a rectangular
concavity and the back housing member 37 is substantially
flat and includes integral extensions 39 and 39' at the ends
thereof which partly surround and protect the connector tabs
18 and 18' and also function to facilitate mechanical attach-
ment to the camera socket. Sandwiched between the front and
back housing members 36 and 37, in the order named/ are the
flash lamps 22, etc., a unitary reflector member 41 (prefer-
ably of aluminum-coated plastic) shaped to provide the
individual reflectors 22', etc., a printed circuit board 42
provided with integral connector tabs 18 and 18', and an
indicia sheet 43 which may be provided with instructions
and other indicia such as flash indicators located behind
the respective lamps and which change color or appearance
due to heat and/or light radiation from a flashing lamp,
thus indicating at a glance which of the lamps have been
flashed and not flashed.
The indicia sheet 43 may be of paper or thin card-
board and provided with openings where the flash indicators
are desired, the openings being covered with flash indicator
material 48, such as a sheet-like heat-sensitive plastic
material, for example biaxially oriented polypropylene,
which shrinks or melts when subjected to heat or radiant
energy from an adjacent flashing lamp thus effectively
changing the color of the openings in the indicia sheet 43.
Openings 51 are provided through the reflector unit 41 and
the circuit board 42 to facilitate radiation from flashing
lamps reaching the flash indicator sheet 48. The rear
housing member 37 is transparent (either of clear material
or provided with window openings) to permit viewing of the
indicla on the indicia sheet 43. The front housing member
36 is transparent at least in front of the lamps 22, etc.,
to permit light from flashing lamps to emerge frontwardly
of the array, and may be tinted to alter the color of light
from the flash lamps.
The height and width of the rectangular array are
substantially greater than its thickness, and the heights
and widths of the reflector member 41 and circuit board 42
are substantially the same as the interior height and width
of the housing member 36, to facilitate holding the parts in
place.
The tab 18, which is integral with the circuit
board 42, is provided with a pair of electrical terminals
31 and 32, and similarly the tab 18' is provided with a pair
of terminals 31' and 32', for contacting terminals of a
camera socket for applying firing voltage pulses to the
array. Each tab is provided with a third terminal 33 and
33', respectively, which functions to electrically short the
circuitry of the inactive lower group of lamps, when the
array is plugged into a socket. The terminals 31 and 31'
are shown as having a lateral "T-bar" configuration for
temporarily shorting the socket terminals while the array
is being plugged in, to discharge any residual voltage charge
in the firing pulse source and also to reduce the likelihood
of lamps being accidentally flashed by electrostatic voltage
when the array is handled.
0
The circuit board 42 has a "printed circuit"
thereon, as will be described, for causing sequential flashing
of the lamps by firing voltage pulses applied to the terminals
31, 32 or 31', 32'. The top and bottom halves of the printed
circuitry preferably are reverse mirror images of each other.
The lead wires 22a, 22b, etc., of the lamps 22, etc., may be
attached to the circuit board 42 in various ways, such as by
means of metal eyelets 22a', 22b', etc., placed through open-
ings in the board. The lead wires 22a, 22b, etc., pass
through openings 52 in the reflector member 41 and into or
through the respective pairs of eyelets 22a', 22b', etc.,
and the ends of the eyelets are crimped or bent to hold the
lead wires and make electrical contact thereto and also to
hold the eyelets in place with their heads in electrical
contact with the circuit of the circuit board.
A metal clip 56 is clipped onto the reflector
member 41, which reflector preferably is made of metal-coated
plastic, and the rear of the clip 56 rests in touching
contact against an area 57 of an electrical ground circuit
run 58 on the board and which includes the terminals 31 and
31' and which makes contact with one of the connector eyelets
22a' or 22b', etc., for each of the lamps 22, etc., whereby
the reflector unit 41 additionally functions as an electrically
grounded shield, in the particular embodiment described.
Areas 59 on the transparent front housing member
36 may be made opaque or partly opaque, such as by making
the surface roughened at these areas, to fully or partly
conceal the lamp lead-in wires 22a, 22b, etc., and/or the
lower portions of the lamps, for improved appearance of the
array.
The circuit board terminal 32 is part of a con-
ductor run that is electrically connected to lead-in wire
24a of lamp 24 at the eyelet 24a' and terminates at radiation
switches 61, 62, and 63 respectively positioned near lamps
24, 25, and 23. A circuit board conductor run 64 is connected
electrically to the remaining lead wire of flash lamp 25 at
eyelet 25a' and terminates at the radiation switch 61. A
circuit board conductor run 65 is connected to the remaining
lead-in wire of flash lamp 23 at eyelet 23a' and terminates
at the radiation switch 62. Similarly, a circuit board
conductor run 66 is connected to the remaining lead-in wire
of flash lamp 22 at eyelet 22b'~ and terminates at radiation
switch 63.
The radiation switches 61, 62, and 63 are respec-
tively in contact with and bridge across the circuit runs
that are connected to them. The material for the radiation
switches may be suitable material initially having an open
circuit or high resistance, the resistance thereof becoming
zero or a low value when the material receives radiation in
the form of heat and/or light from a respective adjacent
lamp, upon the lamp being flashed. For this purpose, each
of the radiation switches is respectively positioned behind
and near to a flash lamp 24, 25, 23. Windows in the form
of transparent sections or openings 69 may be provided in
the reflectors in front of the switches as shown in Fig. 4
to facilitate radiation transfer. A suitable material for
the radiation switches is silver oxide or carbonate dispersed
in a binder such as polyvinyl resin. Each of these radiation
switches, upon receiving heat and/or light radiation from
the adjacent lamp when it is flashed, changes from an open
circuit or high resistance to a closed circuit or low
resistance between its switch terminals on the circuit board.
As has been explained, the lower portion of the
circuit board contains a substantially reverse mirror image
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570
of the same circuit shown in the upper part of the circuit
board, and therefore will not be described in detail. It
will be noted that the circuit runs from the plugged-in
terminals 31 and 32 at the lower part of the circuit board
extend upwardly so as to activate the circuitry in the upper
half of the circuit board, Similarly, when the unit is
turned around and tab 18' is plugged into a socket, the
circuit board terminals 31' and 32' will be connected to and
activate the lamps which then will be in the upper half of
the circuit board, and hence in the upper half of the flash
unit 17. This accomplishes, as has been stated, the
desirable characteristic whereby only the group of lamps
relatively farthest away from the lens axis will be flashed,
thereby reducing or eliminating the undesirable red-eye
effect.
Further details of the above-described construction are dis-
closed in U.S. Patent 3,935,442 to James Hanson.
The circuit on the circuit board 42 functions as
follows. Assuming that none of the four lamps in the upper
half of the unit 17 have been flashed, upon occurrence of
a first firing pulse applied across the terminals 31, 32,
this pulse will be directly applied to the lead-in wires
of the first-connected flash lamp 24, whereupon the lamp 24
flashes and becomes an open circuit between its lead-in
wires. Heat and/or light radiation from the flashing first
lamp 24 causes the adjacent radiation switch 61 to become
a closed circuit (or a low value of resistance), thereby
connecting the circuit board terminal 32 electrically to
the lead-in wire of the second lamp 25 at eyelet 25a'. sy
the time this occurs, the firing pulse has diminished to a
value insufficient to cause the second lamp 25 to flash.
When the next firing pulse occurs, it is applied to the
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111~5 70
lead-in wires of the second lamp 25, via the now closed
radiation switch 61, whereupon the second lamp 25 flashes,
thereby causing radiation switch 62 to assume zero or low
resistance, and the second lamp 25 now has an open circuit
or high resistance between its lead-in wires. When the
next firing pulse occurs, it is applied via now closed radi-
ation switch 62 to the third lamp 23, thereby firing the
lamp which becomes an open circuit, and the radiation from
it causes the radiation switch 63 to become essentially a
closed circuit across its terminals. Thus, the next firing
pulse will be applied, via now closed radiation switch 63,
to the lead-in wires of the fourth flash lamp 22, thereupon
causing the lamp to flash. Since this lamp is the last lamp
in the active circuit, it does not matter whether its lead-
in wires are an open or closed circuit after flashing.
Additional ~lash lamps, radiation switches, and electrical
conductors can be employed, if desired, using the just de-
scribed principles. When the flash unit is turned around
the other connector tab 18' attached to the camera socket,
the group of lamps that then become uppermost and relatively
farthest away from the lens axis will be in an active circuit
and will be flashed in the same manner as has been described.
In a preferred embodiment, the lamps 22, etc., are high
voltage types, requiring about 1000 volts for example, at
low current, for flashing, and this voltage can be provided
by impacting or stressing a piezoelectric element in the
camera.
The flash lamps 22-25 and 27-30 have the well-known
elongated cylindrical configuration as best shown in Figure
4, and the individual reflectors 22'-25' and 27'-30' are in
the form of elongated concave quasi-cylinders having para-
bolic curvatures as viewed in Figure 3, and are further de-
i7Q
scribed in the above-referenced Schindler patent. The re-
flectors reflect light from a flashing lamp substantially
frontwardly of the array and in a horizontally divergent
pattern as indicated by a bundle 71 of light-ray lines
(Fig.3) emanating from various points within the flash lamp
30 and being reflected by a side portion 72 of the reflector
30' into a divergent pattern. The sum of all such divergent
light patterns, reflected by the area of the reflector from
the flash lamp, is a horizontally divergent flash of re-
flected light which substantially fills and illuminates a
scene being photographed. Stated another way, the angle of
divergence horizontally of the light reflected frontwardly
by the reflector is about the same as that of the picture-
viewing angle of a typical camera lens, i.e., about 40.
The words "horizontal" and "vertical" as used herein regard-
ing the shape and/or directional spread of light from a
flashing lamp are relative terms and are interchangeable
if the array is turned 90. In the embodiment shown and
described, the axes of the elongated flash lamps and re-
flectors are vertical as is their usual orientation when
pictures are taken using presently available FlipFlash
arrays. A vertical spread or divergence of light reflected
by each reflector is caused in part by the elongated
configurations of the flash lamps and their reflectors.
Since the light radiated from every point in the flashbulb
emanates in the form of a widely divergent beam, sub-
stantially in all directions of a sphere having its center
at the point in the flash lamp under consideration, light
rays from that point which are in a horizontal plane will be
reflected by the reflector horizontally ahead; and the light
rays having a sufficient vertical component (up or down)
will be reflected by the reflector frontwardly and with a
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lll9S ~ O
vertical component (up or down), such as the light ray 73
(Fig.2) originating from a point 74 of the flash lamp 23
and reflected at a point 74' on the surface of the
reflector 23', will be reflected outside of the scene being
photographed.
Light emanating from the array directly from a
flash lamp (and not reflected by the reflector) is divergent
over an angle considerably greater than required for covering
the scene to be photographed, and therefore the portion of
this light falling outside the boundaries of the scene being
photographed is wasted.
In accordance with the invention, one or more
elongated light-refractive prism means are provided substan-
tially directly in front of and parallel to the axis of each
flash lamp so as to refract some of the light therefrom when
flashed in a more frontward direction, thus increasing the
efficiency and useful light output of the array. These
prism means may be bevel-shaped prisms at either or both of
the front and rear surfaces of the front wall of the front
cover 36. For example, a pair of elongated prisms 75 and
76, shown most clearly in Figs. 2 and 3, extend vertically
in front of one column of vertically oriented lamps 23, 25,
28, and 30, and another similar pair of prisms 75' and 76'
extend vertically in front of the other column of vertically
oriented lamps 22, 24, 27, and 29. Thus, the prisms are
parallel to the lamp axes. These pairs of prisms preferably
are molded on the rear surface 77 of the front part of the
cover 36, and have rearwardly extending spaced apart steps
or edges 75a and 76a which are symmetrical with respect to
the lamp axes, the working surfaces 75b and 76b (which may
be flat or curved, as desired) of these prisms being beveled
so as to taper mutually outwardly and to the rear surface 77
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of the cover. The prism steps 75a and 76a can be made
shallower, or non-existent, by filling some or all of the
space between them with the molded cover material. The
portions 77a and 77a' of the rear of the front cover respec-
tively between the prism inside edges 75a, 76a and 75a', 76a'
are shown flat so as to permit light transmission in normal
manner from the central sector of the flashing lamp. In
cèrtain arrays, such as those containing large diameter lamps,
it may be advantageous to provide one or more additional
elongated prisms in these portions 77a and 77a'. The prisms
75 and 76 can extend continuously the entire height of the
array, or can be discontinuous at intervals 78 where not
needed, as shown in Figure 2. As shown in Figure 3, an
exemplary light ray 81 emanating from the flashing lamp 29
and which is in a direction sufficiently sideways so as to
fall outside of the area of the scene being photographed is
refracted somewhat frontwardly by the prism 75', as
indicated at 81', so as to contribute to the useful
illumination of the scene. Similarly, another exemplary
light ray 82 emanating from the lamp sufficiently sideways
in the opposite direction so as to fall outside of the area
of the scene being photographed is refracted somewhat
frontwardly by the prism 76', as indicated at 82', so as
to contribute to the useful illumination of the scene.
Although only two exemplary refracted light rays 81' and 82'
are shown, there are virtually an infinite number of individual
light rays emanating from areas of the flash lamp and which
are refracted somewhat frontwardly by the prisms 75' and 76'
(and also 75 and 76) in front of each lamp, with differing
degrees of forward vector component (i.e., light rays
emanating from different points of the lamp will have
differing refracted frontward directions, similar to the
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reflected bundle 71 of light rays) so that light directly
from the lamp which would otherwise fall uselessly outside
the picture area is refracted into the picture area with
fairly good brightness uniformity over the area. Many of
these refracted light rays will have vertical components
of direction (up or down), further contributing to uniformity
of brightness of the refracted light over the picture scene
area. The foregoing improvements apply mainly to light
emanating from the front portion of the lamp. A plurality
of parallel prisms can be substituted for the individual
prisms 75, 76, etc., in a Fresnel manner. Adding further
prisms outwardly from those shown, and in front of the
reflector sides 72, would not contribute significantly to
the desired effect just described, and would be detrimental
to the desirable pattern of reflected light achieved by the
parabolic reflectors. However, if the reflectors are not
parabolic, or are non-specular, it may be desirable to
provide vertical prisms in front of the reflector sides to
improve the distribution of light. Optimum size and shape
of the prisms can be determined experimentally and by
optical design principles. The essence of the invention is
that at least a portion of the prisms 75 and 76,etc., be
directly in front of, and preferably close to, the respective
lamps, as best shown in Figure 3.
One or more prisms may be provided in front of
each lamp in a horizontal orientation and crosswise with
respect to the vertical prisms 75, 76, etc. Groups 86 and
87 of horizontal and mutually parallel Fresnel-arranged
prisms can be molded in a surface of the plastic cover 36,
preferably at the front or opposite surface from where the
vertical prisms 75, 76, etc., are provided. The horizontal
prisms of the group 87 are positioned in front of the lower
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o
side region of each elongated flash lamp 23, etc., and are
shaped to refract light rays somewhat upwardly (the array
being assumed to be in its normal intended position for use,
as shown in the drawing). For example, a light ray 88
emanating directly from a point 89 in the lamp 23 when
flashed and having a sufficient downward vector component
so that it would fall outside of the picture scene area as
covered by the camera lens, is refracted more frontwardly,
as indicated at 88', by one of the prisms of group 87 so as
to usefully fall in the picture area. Many light rays, such
as rays 91, 92, and 93 which emanate from the flashing lamp
and which would illuminate the picture area, will be
refracted as indicated at 91', 92', and 93' and will still
usefully illuminate the picture area. The other group 86
of prisms, positioned in front of the upper side region of
the lamp, functions similarly, by refracting some of the
light from the flash lamps, having upward components, somewhat
downwardly and hence more frontwardly and onto the picture
area.
Preferably, the groups 86 and 87 of horizontal
prisms extend entirely across the widths of the reflectors
22', etc., and additionally perform a useful function of
refracting somewhat frontwardly some of the reflected light
from a flashing lamp having a sufficient vertical vector
component so that after reflection by the reflector 23',
etc., it would fall outside of the area of the scene being
photographed. For example, the reflected light ray 73
(Figure 2), described above as having a sufficient vertical
vector component so as to fall uselessly outside of the
picture srea as seen by the camera lens, is refracted some-
what frontwardly by the group 86 of prisms, as indicated at
73', so as to contribute to the illumination of the picture
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~9570
area. Other light rays which would illuminate the picture
area are refracted toward different parts of the picture
area, and some light rays that would illuminate the picture
area are refracted outside the picture area. It has been
found that the amount of light refracted into the picture
area by the horizontal groups 86, 87 of prisms is considerably
greater than the amount of light refracted out of the
picture area by these prisms. This is believed to be due to
the elongated shapes of the lamps and reflectors, and the
placements of the groups 86 and 87 of prisms across the
upper and lower portions of each lamp and reflector, so that
a greater amount of light from the central lengthwise region
of a lamp is usefully refracted into the picture area than
the amount of light from near the ends of a lamp that becomes
refracted out of the picture area.
The above-described crisscross arrangement of
prisms, applied to a regular FlipFlash array, provides an
increase of about 12~ in total zonal lumen seconds of
illumination directed from a flashing lamp onto the picture
scene area as is "seen" by a normal camera lens having a 40
angle of view, the flash array being attached to the camera
in the normal way. About half of this gain is contributed
by the vertical groups o~ prisms 75, 76, etc., and the other
half by the horizontal groups 86, 87 of prisms. Preferably,
the criss-cross groups of prisms are molded into the front
cover 36 of the array, as shown, and preferably the vertical
groups 75, 76 and 75', 76' of prisms are at the rear surface,
and the horizontal groups 86, 87 of prisms are at the front
surface, of the front cover 36.
For simplicity in the drawing, the illustrative
light rays 73, 93, 81', etc., passing through the front
cover are shown as being refracted at only one surface, whereas
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in reality there will be some refraction at each surface
as is the case of any light ray passing obliquely through
boundaries of two mediums, such as air and plastic, having
different optical indices of refraction.
The principles of the invention can be applied to
flash arrays in which the elongated lamps are horizontal
when the array is in its normal intended position for flash-
ing, in which event the above-used terms "vertical" and
"horizontal", as applied to the lamps and prisms, would be
interchanged.
The prism means can comprise various embodiments,
such as elongated prisms as described above, or they can be
segmented into individual aligned elements, or other refrac-
tive configurations. Thus, the term "prism means" is used
herein in a broad sense so as to include various suitable
refractive means and arrangements.
While preferred embodiments of the invention have
been shown and described, various other embodiments and
modifications thereof will become apparent to persons skilled
in the art and will fall within the scope of the invention
as defined in the following claims. The principles of the
invention can be applied to flashcubes and other types of
flash units.
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