Photographic camera with electronic flash sneak charge

A photographic camera system for use with film units of the self-developing type including control means for providing a sneak charge of the electronic flash between the exposure interval and the film transport interval in order to reduce the apparent flash charge time subsequent to the transport of the film unit from the camera even though the overall charge time for the electronic flash remains unchanged.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a photographic camera system with an electronic 
flash sneak charge and, more particularly, to a photographic camera system 
with an electronic flash for which the apparent charging time subsequent 
to an exposure cycle is reduced by a sneak charge. 
2. Description of the Prior Art 
Fully automatic cameras most recently sold by Polaroid Corporation, of 
Cambridge, Mass., U.S.A., are intended to be used with well-known instant 
developing film cassettes which include an integral power supply. The 
power supply forming an integral part of the cassette is a battery which 
supplies electrical energy for the operation of components of the camera 
in which the film units are exposed and processed. The cameras include 
various subsystems which, for instance, may be an exposure control system, 
a film transport system, a dark slide removal system, a motor powered 
mechanism for transporting and processing an exposed film unit, and 
electronic logic circuits that provide a sequence control of functions. In 
addition, it is highly desirable that such cameras be adapted for use with 
an electronic flash and that the electronic flash be powered from the film 
cassette battery as is described in U.S. Pat. No. 4,074,295, entitled 
"Compact Accessory Strobe for Cameras with Battery Enclosed Film Pack", by 
Richard C. Kee, issued Feb. 14, 1978, in common assignment herewith, or 
U.S. Pat. No. 4,231,645, entitled "Camera with Telescoping Dual 
Actuators", by Carl W. Davis et al., issued Nov. 4, 1980, in common 
assignment herewith. However, powering both the film transport motor as 
well as the electronic flash presents a high power drain to the battery 
which could potentially result in a battery failure prior to the exposure 
of all the film units in the film cassette. Such a battery failure would 
become likely if the user should turn on the flash and leave it to operate 
in a continuous charging mode over an extended period of time. 
Thus, it has been recognized that the operation of the film transport motor 
and the charging of the electronic flash must be sequentially timed so as 
not to occur simultaneously as fully described in U.S. Pat. No. 3,846,812, 
entitled "Automatic Electronic Flash Camera", by Conrad H. Biber, issued 
Nov. 5, 1974, in common assignment herewith and now incorporated by 
reference herein. In the aforementioned camera, once the exposed film unit 
has been transported and ejected from the camera, the electronic flash is 
sequenced to charge in readiness for the next succeeding photographic 
exposure operation. Thus, a photographer perceives the termination of the 
first photographic exposure cycle when the exposed film unit is ejected 
from the camera whereupon he must thereafter wait for the electronic flash 
to become fully charged before implementing the next succeeding 
photographic exposure cycle. Since the photographer readily perceives the 
ejection of the exposed film unit as the final act in the exposure cycle, 
the subsequent time required to charge the electronic flash before the 
next succeeding photographic exposure cycle can be initiated is readily 
apparent to him and may appear to be exceedingly long even if in fact it 
is only a matter of seconds, particularly if the photographer is anxious 
to implement the next succeeding photographic exposure cycle. However, as 
previously discussed, the charging of the electronic flash cannot be 
accomplished during the operation of the film transport motor because of 
an excessive drain upon the film cassette battery. 
Therefore, it is a primary object of this invention to provide a 
photographic camera system wherein the apparent charging time for an 
electronic flash subsequent to the ejection and transfer of an exposed 
film unit from the camera is shortened by a predetermined charge interval 
sneaked in prior to the operation of the film transport motor. 
Other objects of the invention will in part be obvious and will in part 
appear hereinafter. The invention accordingly comprises the mechanism and 
system possessing the construction, the combination of elements and the 
arrangement of parts which are exemplified in the following detailed 
disclosure. 
SUMMARY OF THE INVENTION 
In a photographic camera system for use with film units of the 
self-developing type wherein the camera system includes an exposure 
control system for controlling the exposure interval, motor driven film 
transport means for automatically transporting exposed film units from the 
camera system subsequent to exposure and an electronic flash for providing 
artificial illumination during the exposure interval there is provided an 
improved control means for enabling the electronic flash to operate in a 
charging mode for a predetermined interval immediately subsequent to the 
exposure interval while simultaneously disabling the film transport motor 
from operating. Subsequent to the predetermined time interval the control 
means of this invention operates to disable the electronic flash from 
operating in its charging mode while simultaneously enabling the film 
transport motor to operate to transport the exposed film unit from the 
camera so as to provide a sneak charge during the predetermined interval 
in order to reduce the apparent charge time subsequent to the film unit 
being transported from the camera system without reducing the overall 
charge time required. The camera system may additionally include a 
manually actuatable photographic exposure initiation switch connected so 
that the actuation thereof operates to enable the exposure control system 
to commence an exposure interval. The aforementioned control means 
includes means responsive to the manual actuation of the photographic 
exposure initiation switch subsequent to the exposure interval for 
enabling the electronic flash to operate in its charging mode for the 
duration of the time that the photographic exposure initiation switch 
remains actuated while simultaneously disabling the film transport motor 
from operating.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawing there is shown at 10 a block diagram for a 
photographic camera system embodying the features of this invention. A 
photographic exposure cycle may be commenced in the usual manner by 
manually closing a photographic exposure initiation switch 12 so as to 
connect a power supply from the terminal V.sub.0 to an exposure control as 
shown generally at 14. The exposure control 14 may be of any well-known 
type such as those embodying scanning shutter blade elements which operate 
to vary exposure aperture areas with time during the exposure interval as 
taught by U.S. Pat. No. 3,942,183, entitled "Camera with Pivoting Blades", 
by George D. Whiteside, issued Mar. 2, 1976, in common assignment herewith 
and now incorporated by reference herein. Such scanning shutter blade 
mechanisms generally include a pair of counter-reciprocating shutter blade 
elements each having a primary aperture that traverses the optical axis of 
the camera during the exposure interval. The primary apertures are shaped 
so that upon overlying one another during countermovement of the blades, 
there is defined an effective exposure aperture value which increases to a 
maximum value in a determinate period of time. 
Exposure control is provided in a well-known manner by a pair of secondary 
photocell apertures in respective shutter blade elements which admit scene 
light to a photoresponsive element in correspondence with the scene light 
admitted to the focal plane during shutter blade movement through an 
exposure cycle. The output from the photoresponsive element is directed to 
an integrator circuit which triggers upon reaching an integration level 
corresponding to a desired exposure value to terminate the exposure 
interval by returning the shutter blade elements back to their initial 
scene light blocking position as fully described in U.S. Pat. No. 
3,942,183, supra. 
The exposure control 14 also includes an objective lens assembly or 
arrangement which may be either of the fixed or variable focus type for 
focusing image forming light rays in a well-known manner at the focal 
plane in the camera. 
The exposure control 14 is also arranged to operate in synchronism with an 
electronic flash as shown generally at 16 in any conventional manner. In 
one such embodiment the shutter blade mechanism of the exposure control 14 
and the electronic flash 16 are arranged to operate in either a high 
ambient scene light intensity mode of operation where no artificial 
illumination is provided or a low ambient scene light intensity mode of 
operation where the electronic flash is fired to provide a source of 
artificial illumination. Under conditions of low ambient scene light 
intensity where the electronic flash 16 is expected to be fired, the 
scanning shutter blade mechanism of the exposure control 14 may be stopped 
at an aperture value corresponding to the camera-to-subject distance as 
determined by focusing the objective lens. Systems of the aforementioned 
type are generally referred to as "follow-focus" systems and the maximum 
aperture to which the scanning shutter blade elements are allowed to open 
is controlled by a rangefinding or focusing system of the camera in a 
manner as is fully disclosed in U.S. Pat. No. 3,977,014, entitled 
"Follow-Focus Exposure Control System with Improved Uniform Trim Control" 
, by Philip R. Norris, issued Aug. 24, 1976, in common assignment herewith 
and now incorporated by reference herein. 
In another alternative embodiment, the exposure control 14 need not operate 
to actually stop the opening shutter blade movement at a maximum effective 
exposure aperture as determined by the rangefinding or focusing system of 
the camera 10, but may instead vary the time at which the flash light is 
fired during the opening shutter blade movement as determined in 
correspondence with the rangefinding or focusing system of the camera 10. 
Since the duration of the flash light is short in comparison to the time 
required for the shutter blade mechanism to scan from its scene light 
blocking position to its maximum exposure aperture defining position, the 
aperture defined by the shutter blade elements at the instant of 
electronic flash firing for practical purposes constitutes the effective 
aperture by which the exposure occurs. Such a system is more fully 
described in U.S. Pat. No. 3,478,660, entitled "Photographic Apparatus 
with Flash Exposure Control System", by Edwin H. Land, issued Nov. 18, 
1969, in common assignment herewith and now incorporated by reference 
herein. This range responsive flash fire system can also be utilized in 
conjunction with a sonar rangefinding device as is more fully described in 
U.S. Pat. No. 4,188,103, entitled "Range Synchronized Flash Photographic 
Apparatus and Method for Achieving Optimum Exposure", by Conrad H. Biber 
et al., issued Feb. 12, 1980, in common assignment herewith and now 
incorporated by reference herein. 
Exposure control 14 may alternatively be of a type which provides 
artificial illumination to fill in the photographic subjects against a 
brightly backlit scene as is more fully disclosed in U.S. Pat. No. 
4,023,187, entitled "Exposure Control System with Fill Flash Race 
Condition", by Edwin K. Shenk, issued May 10, 1977, in common assignment 
herewith and now incorporated by reference herein. In this embodiment the 
exposure control 14 operates under conditions of low ambient scene light 
intensity to fire the electronic flash 16 at a predetermined time period 
subsequent to the initiation of the exposure interval. Under conditions of 
high ambient scene light intensity the exposure control 14 operates to 
fire the electronic flash 16 as a consequence of the time integration of 
the scene light intensity incident to the photoresponsive element reaching 
a predetermined value. In still another alternative arrangement, exposure 
control 14 may be of a type which provides sonar rangefinder controlled 
focusing and flash firing in a manner as is more fully described in U.S. 
Pat. No. 4,315,676, entitled "Camera with Autoranging Focusing and Flash 
Fire Control", by Arthur G. LaRocque et al., issued Feb. 16, 1982, in 
common assignment herewith and now incorporated by reference herein. 
Referring more specifically now to the electronic flash 16 it can be seen 
to comprise a main storage capacitor 22 which may be charged up to an 
operating voltage by a conventional voltage converter circuit as shown 
generally at 24. The voltage converter 24 operates in a conventional 
manner to convert a DC voltage as may be derived from the power supply 
connected to the terminal V.sub.0 which may be in the order of 6 volts to 
a suitable flash operating voltage such as 350 volts. A flashtube 26 is 
connected in parallel relation with respect to the storage capacitor 22 
and may be ignited by a trigger circuit 28 of any conventional form which 
is set in operation by the closing of conventional synchronous contacts of 
the exposure control 14 in the usual manner. As will be readily 
understood, the electronic flash 16 may be formed as an integral part of 
the camera system 10 or, alternatively, may be made as a detachable 
accessory, if so desired. 
The photographic system 10 is designed for use with film units of the 
self-developing type similar to that described in U.S. Pat. No. 3,415,644, 
issued to Edwin H. Land on Dec. 10, 1968, in common assignment herewith 
and now incorporated by reference herein. The film units are packaged in 
well-known instant developing film cassettes similar to that disclosed in 
U.S. Pat. No. 3,874,875, issued to Edwin H. Land on Apr. 1, 1975, in 
common assignment herewith and now incorporated by reference herein. These 
well-known instant developing cassettes include an integral power supply 
which connects to the V.sub.0 power terminal in a well-known manner. The 
power supply which forms an integral part of the cassette is preferably a 
6 volt battery which supplies electrical energy for the operation of the 
exposure control 14, electronic flash 16 and a film transport motor 20 for 
transporting an exposed film unit in a well-known manner as more fully 
described in U.S. Pat. No. 4,040,072, entitled "Shutter Latch Arrangement 
Releasable Through Shutter Blade Actuation and Resettable Through Film 
Advancement", by Bruce K. Johnson et al., issued Aug. 2, 1977, in common 
assignment herewith and now incorporated by reference herein. The motor 20 
is controlled by a motor drive circuit 18 which receives an enabling input 
signal from the collector terminal of an NPN transistor 34. The voltage 
converter 24 of the electronic flash 16 is also enabled in like manner by 
an input signal received from the collector terminal of another NPN 
transistor 36 having a base terminal connected in common with the base 
terminal of the transistor 34. The transistors 34 and 36 receive output 
base control signals simultaneously from an OR gate 32. One input terminal 
of the OR gate 32 connects directly to the power supply terminal V.sub.0 
by way of the exposure initiation switch 12, and the other input terminal 
to the OR gate 32 connects to the output of a timer 30 which preferably 
comprises a monostable multivibrator triggered in the manner of this 
invention from an output signal from the exposure control 14 upon the 
termination of the exposure interval. 
Since the camera system 10 is powered from a single 6 volt battery 
manufactured as an integral part of the film cassette in the 
aforementioned manner, there would be presented a high power drain to the 
battery which could potentially result in battery failure prior to the 
exposure of all the film units in the film cassette if the film transport 
motor 20 is driven at the same time the voltage converter 24 is turned on 
to charge the main storage capacitor 22. This difficulty was recognized in 
U.S. Pat. No. 3,846,812, supra, which provided for a controlled sequence 
in which subsequent to the termination of the exposure interval the film 
transport motor was operated to eject the film unit while the electronic 
flash was prohibited from charging until the film unit was completely 
ejected. Thus, the film transport and electronic flash charging operations 
occurred sequentially and not simultaneously in order to conserve the 
energy of the film cassette battery. 
The photographic camera system of this invention, however, while also 
operating not to simultaneously energize the film transport motor 20 
during the time that the voltage converter 24 operates to charge the 
storage capacitor 22, additionally provides for a sneak charge interval 
during which the storage capacitor 22 is partially charged prior to the 
operation of the film transport motor 20 so as to reduce the apparent 
strobe charge time subsequent to when the film unit is finally ejected 
from the camera without changing the overall charge time required to 
charge the electronic flash 16. The sneak charge of this invention for the 
electronic flash 16 which effectively reduces the apparent charge time 
subsequent to the ejection of the film unit is provided in the following 
manner. 
Subsequent to the termination of the exposure interval as implemented in 
the aforementioned manner by the exposure control 14, there is provided in 
a well-known manner a trigger signal to the timer 30. The timer 30 which 
as previously discussed preferably comprises a monostable multivibrator, 
in turn, responds to the trigger signal from the exposure control 14 by 
providing an affirmative (binary logic 1) signal level for a predetermined 
time interval, i.e., timing pulse, so as to switch the output from the OR 
gate 32 to an affirmative (binary logic 1) signal level and thereby drive 
the transistors 34 and 36 into saturation. Turning on the transistors 34 
and 36 in this manner disables the motor drive control circuit 18 from 
energizing the film transport motor 20 while simultaneously enabling the 
voltage converter 24 to charge the capacitor 22 for the duration of the 
pulse provided by the timer 30. 
The timing pulse provided by the timer 30 may be in the order of 1 second 
thereby enabling the voltage converter 24 to sneak in a 1 second charge 
cycle prior to the operation of the film transport motor 20. Subsequent to 
the expiration of the timing pulse from the timer 30, the affirmative 
(binary logic 1) signal level changes to a low (binary logic 0) signal 
level so as to switch the output from the OR gate 32 to a low (binary 
logic 0) signal level and thereby turn off transistors 34 and 36. This, in 
turn, disables the voltage converter 24 from further charging the storage 
capacitor 22 while simultaneously enabling the motor drive circuit 18 to 
energize the motor 20 and thereby transport the exposed film unit through 
the processing rolls from the camera. The exposure control 14 may 
thereafter operate in the usual manner to provide the appropriate control 
signals to the motor drive circuit 18 so as to deenergize the film 
transport motor 20 upon the complete ejection of a film unit and 
simultaneously enable the voltage converter 24 to again charge the storage 
capacitor 22 in a manner as is fully described in U.S. Pat. No. 3,846,812, 
supra. 
Should the photographer continue to manually actuate the photographic 
exposure initiation switch 12 subsequent to the expiration of the exposure 
interval, there will be provided an affirmative (binary logic 1) signal 
level to the OR gate 32 so as to turn on the transistors 34 and 36 
regardless of the state of the output signal from the timer 30. Thus, the 
photographer by not releasing the exposure initiation switch 12 can delay 
the energization of the film transport motor 20 while simultaneously 
extending the electronic flash charge time particularly in situations 
where the noise from the film transport motor 20 may be socially 
undesirable. As is readily apparent, should the photographer release the 
exposure initiation switch 12 subsequent to the expiration of the 
predetermined timing pulse provided by the timer 30, then the output 
signal from the OR gate 32 will switch to a low (binary logic 0) signal 
level to turn off the transistors 34 and 36 so as to enable the motor 
drive control circuit 18 to energize the transport motor 20 while 
simultaneously disabling the voltage converter 24 from further charging 
the storage capacitor 22. 
As will be readily understood the electronic flash 16 may be of the 
regulated type and may also be utilized in a camera system of a type as 
described in U.S. Pat. No. 4,348,087, entitled "Photographic System for 
Automatic Recharging Electronic Flash", by Seymour Ellin, issued Sept. 7, 
1982, in common assignment herewith and now incorporated by reference 
herein. Therefore, the electronic flash 16 may be charged subsequent to 
the transport of the exposed film unit from the camera to a full charge 
condition after which the converter 24 is turned off until the 
photographer initiates a subsequent exposure cycle. Thus, in this manner 
there is provided a sneak charge between the exposure interval and the 
film transport interval which operates to reduce the apparent charge time 
subsequent to transport of the exposed film unit from the camera even 
though the overall flash charge time remains unchanged. Since the 
photographer only perceives the flash charge time subsequent to the 
transport of the exposed film unit from the camera, the sense provided is 
one of a substantially shortened charge time for the electronic flash 16. 
Since certain changes may be made in the above-described system and 
apparatus without departing from the scope of the invention herein 
involved, it is intended that all matter contained in the description 
thereof or shown in the accompanying drawing be interpreted as 
illustrative and not in a limiting sense.