Photographic exposure apparatus for providing small apertures

An exposure control system for photographic apparatus having a shutter-diaphragm mechanism for regulating the exposure aperture and the exposure interval under both ambient and flash illumination conditions having a blade arrangement which when driven in an opening direction provides enlarging aperture values in a tracking relation defining both a taking aperture and a photocell aperture. The latter being specially configured to initially provide relatively small aperture values necessary for proper flash exposure at near subject distances includes a pair of blade openings wherein the leading portion of one opening is a segment of short length as measured along the axis of diaphragm movement so that, when it is in overlapping arrangement to the leading edge of the other opening, very small aperture values result.

BACKGROUND OF THE INVENTION 
This invention relates generally to photographic exposure control systems 
and, more particularly, to an exposure control system which is responsive 
to scene lighting in both ambient and flash modes of operation. 
In U.S. Pat. No. 3,896,458, an automatic exposure control system responsive 
solely to scene light in ambient operation and additionally responsive to 
a subject distance in flash operation is described. In that arrangement, a 
shutter-diaphragm mechanism having a pair of reciprocally moving blade 
members simultaneously defines two correlated aperture values respectively 
controlling the scene light emitted to both the film plane and the camera 
photocell. 
In the above-noted system, the shutter-diaphragm is driven from a closed 
position through enlarging aperture values with the photocell aperture, 
while small in comparison to the taking aperture, in a leading arrangement 
to the taking aperture so as to provide suitable anticipation of the final 
exposure value when the optical path is again blocked in accordance with a 
termination signal from the photocell network. In flash operation, the 
shutter-diaphragm is halted at predetermined positions in accordance with 
subject distance to select an operational aperture value for both the 
taking aperture and the photocell aperture. Compatible operation of the 
photoresponse is required for both modes of operation, but, additionally, 
because of the high light intensity reflected from the scene at near 
distances with flash exposure, it is important to provide very small 
photocell aperture values during initial stages of the blade opening. The 
latter requirement is complicated by factors inherent in forming small 
blade openings and in maintaining such openings in alignment during blade 
movement. 
Consequently, it is an important object of this invention to provide a 
photographic exposure control system having improved photoresponsiveness. 
It is another primary object of this invention to provide an improved 
automatic exposure control system suitable for both flash and ambient 
illumination at near subject distances. 
Still another object of this invention is to provide a photographic 
diaphragm system having novel blade openings configured for providing 
relatively small, initial aperture values. 
SUMMARY OF THE INVENTION 
In accordance with the general concept of the invention, the exposure 
control system includes a diaphragm mechanism comprising a pair of 
reciprocally mounted blades which under actuation define changing values 
of both a taking aperture and a photocell aperture. The blades include a 
pair of secondary openings for defining photocell aperture values with one 
of the pair of secondary openings having a small leading edge portion 
followed by a portion of still further reduced size so that when the one 
secondary opening is initially brought into overlying relation with the 
leading edge of the other secondary opening, only the small leading edge 
portion of the one opening contributes to the photocell aperture value. 
In the illustrated embodiment, the one opening is segmented and includes a 
first aperture of short length followed by an opaque blade portion and 
ultimately a second aperture forming the main body of the one opening.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIG. 1, it can be seen that the exposure control system 
includes a housing 10 which comprises a rear casting 12 for supporting the 
components of the system. Surrounding the front and top of the casting 12 
is a cover 14 which is structured as shown at 16 to support a packaged 
flashlamp array and related components, and which includes openings (not 
shown) through which protrude manually adjustable trim and focus wheels 
partially shown in dotted outline at 18 and 20, respectively. Centrally 
disposed within the back wall of the casting 12 is an exposure or 
light-entering opening 22 which defines the maximum available exposure 
aperture for the system. 
Mounted on the casting 12 is a shutter-diaphragm mechanism 15 formed of a 
pair of elongated blades 24 and 26 which cooperate with an interconnecting 
actuator or walking beam 28. The blades 24 and 26 are slideably mounted on 
casting 12 by means of a bracket 30 which also serves to support a 
variable focus lens assembly illustrated at 32. Connection between the 
lens assembly 32 and the focus wheel 20 is provided by an idler gear shown 
at 34 such that rotation of the focus wheel 20 provides displacement of 
the lens assembly 32 normal to the mechanism 15 for focusing of 
image-carrying rays passing through the aperture opening 22 (when the 
blades 24 and 26 are in an open orientation as in FIG. 2) to a rearwardly 
positioned film plane (not shown) when the system of FIG. 1 is employed in 
conjunction with a suitable film exposure chamber. 
A pair of primary openings 36 and 38 formed in the blades 24 and 26 provide 
variable aperture openings in accordance with longitudinal displacement of 
the blades with respect to each other responsive to movement of the 
walking beam 28. In this respect, it can be seen that the walking beam 28 
is journaled for rotation around a stud 40 extending from the rear casting 
12. Elongate slots 42 and 44 formed in the distal ends of the walking beam 
28 provide coupling with pins 46 and 48 fixed to and extending 
respectively from blades 24 and 26. Thus interconnected, the blades 24 and 
26 move simultaneously with each other to define a main aperture opening 
of progressively varying value over the light entrance opening 22. 
The blades 24 and 26 include end portions shown respectively at 50 and 52 
which extend through a light detecting station 54. These end portions 50 
and 52 overlie a photocell 62 of a light integrating unit (not shown) such 
that the openings 56 and 58 define a secondary or photocell aperture of 
progressively varying value in accordance with movement of the blades 24 
and 26 and in synchronism or tracking relation with particular aperture 
values provided by the openings 36 and 38. As later explained in detail 
with regard to FIG. 7, the openings 56 and 58 are specially constructed to 
provide very small apertures upon initial movement of the blades. 
A tractive electromagnetic device in the form of a solenoid 70 is employed 
to displace the blades 24 and 26 with respect to each other and the 
casting 12. As illustrated in FIG. 1 of the drawings, the solenoid plunger 
72 is affixed to the walking beam 28 by means of a pin or stud 74 such 
that displacement of the plunger 72 will rotate the walking beam 28 around 
its pivot pin 40 and appropriately displace the shutter blades 26 and 28. 
A spring member 76 surrounds the solenoid plunger 72 and biases it in a 
direction tending to open the blades so that the exposure system is 
particularly useful in a reflex camera in which a normally open shutter 
condition facilitates viewing and focusing procedures. Consequently, in 
the present arrangement, the blades 24 and 26 are drawn to their closed 
position (as shown in FIG. 1) only while the solenoid 70 is energized; 
with subsequent de-energization of the solenoid 70 permitting the blades 
24 and 26 to move toward their maximum aperture opening under the urging 
of the spring 76. This deriving arrangement for the exposure control 
mechanism is described in more detail in the U.S. Pat. No. 3,868,712 
issued to Conrad H. Biber on Feb. 25, 1975. It should be understood, 
however, that the exposure control system of the invention is equally 
applicable to photographic systems where the blades are held in a normally 
closed position. 
In operation of the system, blades 24 and 26 are displaced from their 
terminal blocking position shown in FIG. 1 to provide enlarging aperture 
values, for example, as shown in FIG. 2, by de-energizing the solenoid 70 
which permits the spring 76 to drive plunger 72 outwardly of the solenoid 
and, in turn, rotate walking beam 28 in a counter-clockwise direction (as 
viewed in FIG. 1) to force the aperture forming openings 36 and 38 and 56 
and 58 into increasing coincidence as shown in FIGS. 2 and 4. The exposure 
interval is then terminated by again energizing the solenoid 70 so as to 
retract the plunger 72 against the spring 76. 
As explained in detail in the above-noted U.S. Pat. No. 3,896,458, for 
flash operations a follow-focus mechanism 80 (shown in detail in FIGS. 4 
and 5) is employed in conjunction with the light detecting station 54. As 
shown in FIGS. 4 and 5, the focus wheel 20 carries on its underside a cam 
track 82 within which a cam follower 85 is located. The cam follower 85 
extends from beneath the focus wheel 20 to a point where it may be 
utilized to engage and stop the travel of the walking beam 28 at selected 
points in the beam path. This follow-focus mechanism 80 is made effective, 
when a flash unit 17 is mounted on the mechanism 14 as shown in FIG. 3, by 
means of a solenoid designated at 84 which, in effect, provides mechanical 
coupling between the focusing wheel 20 and the walking beam 28. 
Referring now to FIG. 5 wherein the follow-focus mechanism 80 is shown in 
elevation with the focusing wheel 20 placed at the bottom of the view, it 
can be seen that the cam follower comprises an arm member 86 which extends 
across the focus wheel 20 and carries at one end a stud 88 which is 
positioned within the cam track 82. Carried at the other end 87 of the arm 
86 opposite from the stud 88 is an interceptor element 90 which is 
pivotally mounted to the arm 86 by a shaft 92 and is operable in 
accordance with energization of the follow-focus solenoid 84 to intercept 
a depending stud 94 of the walking beam 28. This interception is 
accomplished by means of an arm member 96 which couples the solenoid 84 to 
the interceptor member 90. A spring member 98 is employed to urge the 
solenoid arm 96 downwardly so as to hold the interceptor 90 in a normally 
inoperative position. 
Upon insertion of a flash array 17 (shown in FIG. 3), the exposure control 
system is automatically programmed for flash mode operation and includes 
automatic energization of solenoid 84 and, hence, operation of the 
follow-focus mechanism 80, responsive to initiation of an exposure 
interval. That is, following closing of the blades 24 and 26 and just 
prior to exposure, the solenoid 84 is energized to draw the extended arm 
96 in a direction away from the focus wheel 20 and thereby pivots the 
interceptor 90 into the path of the walking beam stud 94 which arrests 
movement of the beam at a given point and thereby selects the final 
aperture values to be employed during that flash exposure. 
Prior to completing the description of the hybrid flash control, the 
ambient mode operation will be explained. In the operation of the exposure 
control system, the follow-focus mechanism is disabled during ambient mode 
operation and once the viewing mode has been completed and the exposure 
chamber (not shown) prepared for exposure, with the blades 24 and 26 in 
their closed position shown in FIG. 1, the exposure interval is initiated 
by de-energizing the solenoid 70 to thereby release the blades which 
subsequently determine progressively enlarging apertures over both the 
exposure opening 22 and the photocell 62. During this exposure interval, 
the photocell 62 receives increasing amounts of scene light due to its 
progressively enlarging aperture value until it receives a total amount of 
light equal to a previously programmed value which initiates termination 
of the exposure interval. This termination is brought about by a signal 
which again energizes solenoid 70 to reclose the blades 24 and 26. 
In the ambient mode, since the interceptor 90 is not positioned for 
interception, both the size of the main aperture and the photocell 
aperture are progressively enlarged as depicted in FIG. 6. The secondary 
or photocell aperture values defined by openings 56 and 58 produce a curve 
as approximately depicted at 130 when the blades 24 and 26 are driven from 
a fully closed position shown in FIG. 1 to a full open position shown in 
FIG. 2. Likewise, the primary or main exposure aperture also follows a 
curve approximately as depicted at 132 during this blade movement. 
It should be understood that generally the photocell aperture area or value 
is much smaller than the area of the corresponding taking aperture. 
However, in FIG. 8, the curves are normalized; a normalized photocell area 
being defined as one which provides a correct exposure interval for a 
scene brightness where a long exposure time is employed such that opening 
and closing times become negligible. The final photocell aperture value 
depicted in this figure at 144 represents this normalized area. 
As can be seen, the photocell aperture leads the main aperture or, that is, 
opens at a faster rate relative to its full open position than does the 
main aperture. This leading initially occurs because the openings 56 and 
58 of the blades are closer together and begin to overlap sooner than the 
main openings 36 and 38 when the blades are displaced relative to each 
other in an opening direction. This lead time is employed so that the 
light detecting station 54 can provide an adequate anticipation of, or 
brightness sample related to, the total amount of light passing through 
the main aperture by the time the blades are closed, and thus take into 
account solenoid reaction time and the blade closing time. 
Turning now to the flash mode, it should be first noted that under flash 
conditions the exposure control system operates as a hybrid system which 
regulates the exposure with regard to both subject distance and scene 
lighting. That is, correlated taking an photocell aperture values are 
selected by the follow-focus mechanism while the exposure interval is 
determined by the light integrating arrangement. 
As in the ambient mode, once the camera exposure chamber is prepared for an 
exposure cycle, the exposure control system is automatically triggered to 
operate through an exposure phase. For flash, however, the exposure phase 
additionally includes a first timing signal for energizing the 
follow-focus mechanism 80, and after a suitable delay to permit the blades 
24 and 26 to reach their selected aperture, a second timing signal for 
firing a flash bulb. As in ambient, the light detecting station 54 is 
operative such that upon receiving a sufficient total amount of light, it 
energizes solenoid 70 to again close the blades 24 and 26. 
The described exposure system is designed for use from near subject 
distances of 10 inches to infinity in ambient and to 20 feet in flash such 
that to accommodate the high intensity of the reflected flash light at 
near distances, the photocell aperture values initially formed during 
movement of the blade mechanism must be relatively small. This follows 
from the fact that the photocell aperture values must be correlated to the 
taking aperture, and the maximum photocell aperture value is limited by 
available photocell area and packaging considerations. These constraints 
result in very small photocell aperture values (i.e., ranging upward from 
0.0017 square inch) being required for correlation to the small taking 
aperture values which are employed under high intensity ambient and at 
near focal distances in flash exposure. 
These very small aperture values are achieved in the illustrated embodiment 
by uniquely formed photocell or secondary openings 56 and 58 which will 
now be described with regard to FIG. 7. 
Each of the openings 56 and 58 comprise small leading portions as defined 
with respect to the opening movement of the blades along the longitudinal 
blade axis 100 in a direction which tends to displace the openings 56 and 
58 toward each other into increasing coincidence. As can be seen from FIG. 
7, opening 58 comprises a first aperture 102 formed as a narrow slit 
oriented with its longitudinal axis (not shown) inclined to, and 
preferably perpendicular to, the blade axis 100, followed by a relative 
large second aperture 104 which forms the main body of the opening 58. 
Since the main body 104 of the opening 58 is similar to that of the opening 
56, it will be described with the latter. Turning now to the opening 56, 
it can be seen that it comprises a leading section 106 formed as a narrow 
elongated slit having its longitudinal axis aligned with the blade axis 
100. This leading section 106 cooperates with the upright slit 102 of 
opening 58 to form an initial photocell aperture value of relatively small 
size, as later explained with regard to FIG. 8. 
Following each of these leading slits 102 and 104, the openings 56 and 58 
respectively include wider portions 108 and 110 which then give way to 
still wider identical portions in each opening. Hence, proceeding further 
along both openings 56 and 58, from the sections 108 and 110, are tapered 
portions 112 and 114, step portions 116 and 118, the widest portions 120 
and 122 and trailing portions 124 and 126 which are narrower than the step 
portions 116 and provide a slight reduction in photocell aperture value 
when the taking aperture passes through its maximum in ambient operation. 
Exemplary dimension of pertinent parts of the openings 56 and 58 follow so 
as to aid in the description of the openings and to provide an 
appreciation of the relatively small initial aperture values achieved. 
Referring first to the opening 58, the slit 102 is preferably 0.080 inche 
high and 0.012 inche long as measured along the axis 100, the latter 
dimension being defined as the length since it lies along the blade axis 
100. The section 110 trails the upright section 102 by 0.068 inche so as 
to be 0.080 inche behind the leading edge of the section 102 and is 0.033 
inche wide and 0.080 inche long. The section 114 tapers from 0.054 inch 
wide to 0.082 inch, while step 118 is 0.120 inch wide and 0.045 inch long 
and the maximum step 122 is 0.160 inch wide and 0.065 inch long. 
Turning now to the opening 56, the leading slit 106 is made 0.014 inch wide 
and 0.080 inch long, followed by the section 108 which diverges from 0.025 
inch to 0.033 inch over a length of 0.080 inch. The remaining sections 
112, 116, 120 and 124 are substantially identical to their counterparts 
114, 118 and 122 respectively of the opening 58. 
The operation of the openings 56 and 58 will now be explained. As the 
blades 24 and 26 are displaced from a blocking position shown in FIG. 1 in 
a direction to bring the main openings 36 and 38 into coincidence, the 
photocell openings 56 and 58 begin to overlap as the leading end of the 
section 106 passes into coincidence with the slit 102 and provides a very 
small aperture value (e.g., 0.0017 square inches) defined by the 
intersecting slits as shown in FIG. 8. This value of the photocell 
aperture then remains substantially constant with blade movement until the 
slit 106 reaches the section 110 and the slit 102 reaches the section 108 
as shown in FIG. 9. As the latter occurs, the small initial aperture value 
begins to gradually increase. 
In the illustrated embodiment, the length of the slit 106 is equal to the 
distance the body 104 of the opening 58 trails the leading edge of the 
slit 102 so that the section 108 starts to coincide with the slit 102 as 
the latter starts to coincide with the main body 104 and specifically with 
the section 110 thereof. However, it is important to note that by varying 
the length of the slit 106 or the spacing between the slit 102 and its 
main body 104, the further enlargement in aperture value can be 
advantageously controlled. 
Preferably both slits 102 and 106 are as narrow as practical so as to 
permit economical forming and, hence, have approximately the same 
transverse dimension which essentially determines the minimum photocell 
aperture value since one slit is perpendicular to the other. Additionally, 
the upright slit 102 should be separated from the next larger section 
(section 110) of its opening by a spacing which preferably is several 
times larger than the dimension of the upright section as measured along 
the blade axis 100 so that the small value formed by the crossed slit is 
retained during some further movement of the blades. That is, once the 
leading sections fully intersect, slight further movement only changes the 
aperture value in accordance with any change in the width of the 
longitudinal slit 106 since its tip is then in coincidence with the opaque 
blade portion lying between slit 102 and the body portion 104 and, hence, 
does not add to the aperture value as in the conventional aperture 
arrangement. Stated otherwise, during slight further movement of the 
blades, the tip of the slit 106 passes out of coincidence with any portion 
of the other opening and only a previously unused portion of the slit 106 
is in coincidence with the slit 102. 
In an alternate embodiment, very small aperture values are achieved by 
uniquely formed photocell or secondary openings 56 and 58 which will now 
be described with regard to FIG. 10. 
In this arrangement, each of the photocell openings designated 136 and 138 
comprise main body sections 142 and 144 (which are symmetrical about the 
blade path or axis 100 which passes through the center of the photocell 
62) and pointed leading portions 146 and 148, respectively, which extend 
toward each other at an oblique angle to the blade axis. 
The leading portions 146 and 148 are each brought to a point so that a very 
small aperture value is formed as these points intersect as shown at 150 
in FIG. 11 during initial blade movement toward each other. Then as blade 
movement continues, ever widening portions of the leading members 146 and 
148 come into coincidence to provide a smoothly increasing aperture value 
whose precise value is at any given time essentially defined primarily by 
the transverse dimension of the leading section as measured parallel to 
the axis 100. This follows from the fact that, similar to the preferred 
embodiment, once the leading sections intersect, slight further movement 
brings previously unused portions of the leading sections into coincidence 
(as shown in FIG. 12) while preceding leading sections designated at 154 
and 156 pass over each other and hence do not contribute to the aperture 
value designated at 158. 
Hence, the use of tapered, diverging leading portions located at an oblique 
angle to the blade path provide a very controlled aperture change which 
ranges between a relatively small photocell value to a relatively large 
value. 
It should be understood that this invention may be practiced or embodied in 
still other ways without departing from the spirit or essential character 
thereof. Hence, the illustrated embodiment herein is illustrative and not 
restrictive, the scope of the invention being indicated by the appended 
claims and all variations which come within the meaning of the claims are 
intended to be embraced therein.