1. Field of the Invention This invention relates generally to a photographic camera apparatus for use with a source of artificial illumination having a controlled maximum exposure time out period and, more particularly, to a photographic camera apparatus for use with a source of artificial illumination and including control means for providing either a shortened or extended maximum exposure interval time out period dependent upon camera-to-subject distance as determined either directly by means of sonic ranging or indirectly by sampling reflected scene light immediately subsequent to the firing of a source of artificial illumination.

2. Description of the Prior Art Exposure control systems embodying scanning shutter blade elements which operate to vary the exposure aperture areas with time during the exposure interval are well known as indicated by U. S. Patent No. 3,942,183. 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 determined period of time.

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Exposure control is provided by a pair of secondary photocell apertures in the respective shutter blade elements which admit scene light to a photorespon- sive element in correspondence wi.th the scene light admitted to the focal plane during shutter blade movement through an exposure cycle. The output from the photo- responsive element is directed to an integration 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.

Such exposure control systems may be utilized with a source of flash illumination not only during conditions of low ambient scene light intensity but also under conditions of high ambient scene light intensity where it becomes desirable to provide the artificial illumination to fill in the photographic subject against a brightly back lit scene as disclosed in U. S . Patent No. 4,023,187. The artificial illumination control system operates under conditions of low ambient scene light intensity to fire the source of artificial illumination at a predetermined time subsequent to the initiation of the exposure interval. Under conditions where the photographic subject is within the effective range of the flash and provides average scene light reflection, the light integration circuit will integrate the reflected scene light until reaching an integration level corresponding to a desired exposure value to terminate the exposure interval by returning the shutter blade elements to their light blocking position.

However, under conditions where the photographic subject provides for a low degree of artificial scene light reflection or is located eyond the effective range of the flash, there may be insufficient reflected scene light for the integration circuit to reach the integration level corresponding to the desired exposure value. Thus

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it is known "O provide an exposure interval time out circuit for limiting the maximum time that the shutter blade elements remain in the scene light unblocking position. Such time out circuits provide either an extended maximum exposure interval time out period in the order of 1-2C seconds when the source of artificial illumination is disconnected from the camera or a shortened maximum exposure interval time out period in the order of 65 milliseconds when the source of artificial illumination is connected to the camera. Such a shortened maximum exposure interval time out period can provide generally satisfactory results in situations where the photographic subject is located within the effective range of the flash and has a low scene light reflectance characteristic or where the subject is located just beyond the effective range of the flash and where there is still substantial reflected scene light albeit insufficient to cause the integration circuit to reach the required integration level corresponding to the desired exposure value within the shortened maximum exposure interval time out period. Under the aforemen¬ tioned conditions, the photographic film may be slightly underexposed but may nevertheless provide a generally satisfactory photograph which is not blurred. The above-mentioned extended maximum exposure time out interval is suitable for use under conditions where the photographic subject may be so far removed from the effective range of the flash that there is little or no reflected flash light. Under these conditions, it is desirable to extend the maximum time out period for the exposure interval far beyond the maximum allowable time to which an exposure interval may be extended without incurring the adverse blurring effects from the normally expected hand motion of a handheld camera. Under these conditions, it is preferable to utilize a tripod or some other stable means for mounting the camera so as not to incur adverse blurring effects. Thus, with

such an extended maximum exposure interval time out period, it iϊ. possible for the photographic film to record all available ambient scene light such as starlight, street light. or building lights. Heretofore, whether the camera provided the photographer with an extended or shortened maximum exposure interval time out period depended upon whether the photographer connected the source of artificial illumination to the camera or not. Thus, the photographer had to evaluate the camera-to- subject range as well as the probable flash light reflectivity of the subject in order to decide whether the best results could be achieved by either using the artificial illumination with a shortened maximum exposure interval time out period or by not using the artificial illumination and relying solely on the extended maximum exposure interval time out period to record all available scene light.

Therefore, it is a primary object, of this invention to provide a photographic camera apparatus with a fully automatic exposure control system for selectively differentiating between conditions where the photographic subject is located close enough to the camera that there is likely to be substantial but insufficient reflected flash light to effect the termina- tion of exposure solely as a function of scene light integration and it is desirable to provide a shortened maximum exposure interval time out period, and conditions where the photographic subject is located far enough from the camera that there is likely to be little or no reflected flash light and it is desirable to provide an extended maximum exposure interval time out period.

It is a further object of this invention to provide a photographic camera apparatus with a fully automatic exposure control system for determining the camera-to-subject distance either directly by sonic ranging or i directly by sampling the reflected flash light iramediaf.ly subsequent to the firing of a source of

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artificial illumination and for automatically responding to either the sonically determined subject distance or the sampled scene light to provide either a shortened maximum exposure interval time out period where the subject is located close enough to the camera that it is likely to be substantial but insufficient reflected flash light .o effect the termination of exposure solely as a function of scene light integration or an extended maximum exposure interval time out period under conditions where the subject is located far enough from the camera that there is likely to be virtually no reflected flash light.

Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises a mechanism and system possessing a construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.

Summary of the Invention A photographic camera apparatus of the type including means for defining a film plane, means for transmitting light from a scene along an optical path to expose photosensitive film located in the film plane, an exposure control system for allowing the passage of scene light along the optical path to the film plane to define an exposure interval further includes the improvement comprising range means for providing an output response related to the camera-to-subject distance. Control means are provided for imposing one maximum time limit to the duration of the exposure interval provided by the exposure control system in response to the output which the range means is expected to provide when the camera-to-subject distance is within one select range of camera-to-subject distances. The control means also operates to provide a longer maximum time limit to the duration of the exposure interval provided by the exposure control system in response to the output which

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the range means is expected to provide when the camera-to- subject distance is within another select range of camera- to-subject distances.

Description of the Drawings The novel features that are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with other objects and advantages thereof will be best understood from the following description of the illustrated embodiment when read in connection with the accompanying drawings wherein:

FIG. 1 is a front elevational view of the shutter blade mechanism of this invention; FIG. 2 is a front elevational view of the shutter blade mechanism of FIG. 1 in a different position from that of FIG. 1;

FIG. 3 is a front elevational view of the shutter blade mechanism of FIG. 1 in still another position from chat of FIGS. 1 and 2;

FIG. 4 is an electrical schematic view of one preferred embodiment for the control system of this invention; and

FIG. 5 is an electrical schematic view of another preferred embodiment for the control system of this inventio .

Description of the Preferred Embodiments In FIG. 1, there is shown a photographic exposure control apparatus 10 disposed about a baseblock casting 12. Within the baseblock casting 12, there is provided an exposure opening 14 which defines the maximum available exposure aperture for the system. An objective or taking lens 16 is provided in overlying - relation to the light entry opening 14 wherein the objective lens 16 may comprise a lens mount which may be adapted to provide translational movement of the lens 16 along a central optical axis 18 for focusing of

carrying rays. The image carrying rays are directed to a film plane (not shown) by way of a reflecting mirror (also not shown) all of which are stationed within an exposure chamber (also not shown) as described in U. S. Patent No. 4,040,072.

Intermediate the objective lens 16 and light entry exposure opening 14, there is provided a shutter blade mechanism comprising two overlapping shutter blade elements 20 and 21 of the so-called "scanning type". A pair of scene light admitting primary apertures 22 and 24 are provided respectively in the blade elements 20 and 21 to cooperatively define a progressive variation of effective aperture openings in accordance with simultaneous longitudinal and lateral displacement of one blade element with respect to the other as described in U. S. Patent No. 3,942,183. The apertures 22 and 24 are selectively shaped so as to overlap the light entry exposure opening 14 thereby defining a gradually varying effective ape-rture size as a function of the position of the blade elements 20 and 21.

Each of the blades 20 and 21 may additionally be configured to have corresponding photocell sweep secondary apertures 26 and 28. Photocell sweep secondary apertures 26 a 28 may be configured to track in a predetermined corresponding relationship with respect to the scene light admitting primary apertures 22 and 24. The photocell sweep secondary apertures 26 and 28 move in the same manner as the primary apertures 22 and 24 to define a secondary aperture for admitting scene light to a photoresponsive element 30. The blades 20 and 21 also include respectively a third pair of ^" apertures 26A and 28A.

Projecting from the baseblock casting 12 at a location spaced laterally apart from the light entry exposure opening 14 is a pivot pin or stud 32 which pivotally and translatably engages elongate slots 34 and 36 formed in respective shutter blade elements 20 and 21.

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Pin 32 may be integrally formed with the baseblock casting 12 and blade elements 20 and 21 may be retained in engaging relation with respect to the pin 32 by any suitable means such as peening over the outside end of pin 32.

The opposite ends of the blade elements 20 and 21 respectively include extended portions which pivotally connect to a walking beam 38. The walking beam 38 is disposed for rotation relative to the baseblock 12 by pivotal connection to a pin 40. The walking beam 38 is pivotally connected at its distal ends to the shutter blade elements 20 and 21 by respective pin members 42 and 44.

A solenoid 46 is provided to displace the shutter blades 20 and 21 with respect to each other and the baseblock casting 12. The solenoid 46 includes a cylindrical plunger 48 which retracts inwardly into the body of the solenoid upon energization of the solenoid winding. The solenoid plunger 48 includes an end cap 50 at the outsicie end thereof together with a vertical slot or groove 52 within the end cap 50 for loosely engaging a pin 54 extending outwardly from the walking beam 38. In this manner longitudinal displacement of the plunger 48 operates to rotate the walking beam about the pivot pin 40 to displace the shutter blades 20 and 21. The drive means may include a helical compression spring 56 around the plunger 48 so as to continuously urge the end cap 50 outward of the solenoid 46 , thereby also continuously urging the blade elements 20 and 21 into positions defining the largest effective primary aperture over the light entry exposure opening 14. In some arrangements it may be preferable to utilize a tension spring in place of compression spring 56. The exposure control system of this invention is biased to continuously urge the shutter blade elements 20 and 21 into scene light unblocking orientation.

The shutter blades, 20 and 21 are drawn from their scene light unblocking arrangement (FIG. 3) to their scene light blocking arrangement (FIGS. 1 and 2) when the solenoid 46 is energized. It should be understood that the exposure control system of this invention would be equally applicable to photographic systems where the blades 20 and 21 are biased to a normally closed position. Since in the preferred embodiment the shutter blade elements 20 and 21 are spring biased to their light unblocking arrangement, continued energization of the solenoid 46 to hold the shutter blade elements 20 and 21 in their blocking arrangement would present an intolerable power drain on the camera battery. In order to avoid this continued energization of the solenoid 46, there is provided a latch mechanism (not shown) which operates normally to latch the shutter blade mechanism in its blocking arrangement (FIG. 1) , and which unlatches the shutter blade mechanism to permit the shutter blade elements 20 and 21 to be moved to their unblocking arrangement (FIG. 3) to commence a photographic exposure cycle and which responds at the termination of an exposure cycle to relatch the shutter blade elements 20 and 21 in their light blocking arrangement to permit the deenergization of the solenoid 46. FIG. 4 shows a wiring diagram for one preferred embodiment for the control means of this invention for providing either the shortened or extended maximum exposure interval time out period by means of sonic ranging. An electronic flash 60 is cooperatively associated with the apparatus to provide transient artificial illumination to expose the film. The electronic flash apparatus 60 comprises a main storage capacitor 62 wnich may be charged up to an operating ' voltage by any conventional voltage converter circuit 64. The voltage converter 64 operates to convert a DC voltage, as may be derived from the camera battery (not shown) which can be in the order of 6 volts, to a suitab

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strobe operating voltage such as 350 volts. A flash tube 66 is connected in parallel to the storage capacitor 62. The flash tube 66 can be ignited by a trigger circuit 70 set in operation by a flash fire signal. A scene light detecting ard integrating control circuit 72 is provided and comprises the photoresponsive element 30 connected across the input terminals 74 and 76 of an operational amplifier 78. The amplifier 78 being a differential amplifier, has an infinite gain and an infinite input impedance and a zero output impedance. The input circuitry of the amplifier 78 is such that the apparent input impedance for the photoresponsive element 30 is substantially zero which permits the photorespon¬ sive element 30 to operate in a current mode. Consequently, the current generated by the photorespon¬ sive element 30 is limited substantially by its own internal impedance. To accomplish this effect, a feedback capacitor 80 is connected between one input terminal 74 of the operational amplifier 78 and an output terminal 82 from the operational amplifier 78.

Any difference in potential supplied by the photoresponsive element 30 across input terminals 74 and 76 operates to cause a current of opposite polarity to be produced through feedback capacitor 80. As a consequence, the feedback capacitor 80 provides a substantially instantaneous feedback signal of opposite polarity which serves to counteract any differential signal voltage impressed by the photoresponsive element 30 across the input terminals 74 and 76. Thus, although the amplifiei 78 has a very high input impedance, the photoresponsive element 30, when connected in the aforementioned manner, experiences only .a very low input impedance to the amplifier 78. Therefore, the current output of the photoresponsive element 30 is directed into the feedback circuit 78. In this manner, the photoresponsive element 30 operates in a constant current mode to provide a substantially linear output response

at output terminal 82 as described in ϋ. S. Patent No. 3,620,143.

The strobe and exposure control circuitry preferably derive charging power from a battery provided with a film cassette. The battery preferably powers the circuitry of FIG. 4 by way of three switches S ₁ , S ₂ , and S ₃ as described in U. S. Patent No. 4,040,072. The exposure control circuitry of this invention also includes a motor and solenoid control circuit 124 which operates in a manner described in U. S. Patent No.

4,040,072. The circuit 124 controls the current delivered to the solenoid 46 and to a motor 126. The film units for use with the camera are preferably of the self- developing type, and the motor 126 is provided to advance and process the film units in a well-known manner. There is also provided a sonic rangefinder 132 as described in U. S. Patents No. 4,199,246, and 4,167,316. The sonic rangefinder 132 includes a range signal transmitting circuit 134 which may be actuated to issue a transmit commence signal to a sonic transducer 136 to cause transmission of a sonar ranging signal comprising a burst of sonic energy. The transducer 136 thereafter operates to detect an echo signal reflected from the photographic subject at an elapsed time interval after the transmission of the ranging signal. An echo detector circuit 138 then provides a signal indicative of this elapsed time which corresponds to the distance between the camera and the subject to be photographed. When the electronic flash 60 is fully charged after closure of a manually actuatable on/off switch S4 in readiness for a photographic exposure cycle, a photographic exposure cycle may be initiated by manually actuating a button A to close the switch S.. Closure of the switch S. , in turn, activates the motor and solenoid control circuit 124 to energize the solenoid 46 and retract the plunger 48 inwardly to rotate the walking

beam 38 from its position shown in FIG. 1 to its position shown in FIG. 2. This limited counterclockwise movement of the walking beam 38 releases a latch mechanism (not shown) and effects closing of the switches S- and S,.

Closure of the switch S ₃ provides a logic signal by way of the circuit 124 to power down the solenoid 46 from an initial high current energization condition to a lower circuit energization sufficient temporarily to hold the plunger in its retracted position (FIG. 2) .

Closure of the switch S ₃ also actuates the sonar rangefinder 132 to transmit the sonar ranging signal, by providing the requisite logic signal to a transmit control circuit 130 for transmission of clock pulses from a clock circuit 128 to the range signal transmitting circuit 134. Before closure of the switch S ₃ there is provided a low (binary logic 0) output signal level at one input of an AND gate 140 which, in turn, provides a low (binary logic 0) input to an OR gate 144. The other input terminal of the OR gate 144 is also at a low (binary logic 0) level from an AND gate 150 which, in turn, receives one input from the echo detector circuit 138 which assumes a low (binary logic 0) output signal level until the receipt of the echo signal by the transducer 36. The output signal from the OR gate 144, in turn, is directed to enable an up/down counter 146. The up/down counter 146 is in a disabled state before closure of the switch S,. Closure of the switch S, provides an assertive (binary logic 1) output signal level to one input terminal of the AND gate 140 which switches the AND gate 140 to provide an assertive (binary logic 1) output signal level since the other input to the AND gate 140 is already at an assertive (binary logic 1) output signal level by virtue of the low (binary logic 0) output signal level from the echo detector circuit 138 being inverted by an inverted gate 142. The OR gate 144

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switches in synchronism with the closure of the switch S, to provide an assertive (binary logic 1) output signal level to enable the up/down counter 146. The up/down status of the counter 146 is controlled by the output signal of the echo detector circuit 138, and prior to receipt of an echo signal by the transducer 136, the counter 146 is set for an up count mode of operation by virtue of the low (binary logic 0) output signal level from the echo detector circuit 138. Ihmi initial condition of the up/down counter

146 is empty and a counter status circuit 148 senses the terminal count, of the counter 146 and provides an assertive (binary logic 1) output signal level as an indication that the up/down counter 146 is empty. The output from the circuit 148 is directed to an inverter gate 151 to provide a high (binary logic 1) signal to the AND gate 150 immediately after the up/down counter 146 starts to count up, and the output cf the circuit 148 switches to a low (binary logic 0) output signal level. The count is provided to the up/down counter

146 from the clock 128 by way of a frequency divide circuit 154 which inputs a pair of AND gates 156 and 158. A second input terminal to the AND gate 156 receives the inverted output signal from the echo detector circuit 138 and is thus enabled by an assertive (binary logic 1) output signal level prior to detection of the echo signal by the echo detect circuit 138. A third input terminal to the AND gate 156 receives an assertive (binary logic 1) signal upon closure of the switch S,. A second input terminal to the AND gate 158 receives a signal inverted by an inverter 162 from a brightness level detect circuit 120. A third input terminal to the AND gate 158 receives the output signal of a level detect circuit 122. The output signals from the AND gates 156 and 158 are directed to an OR gate 164, which operates to input the clock pulse to the up/down counter 146.

The aforementioned movement of the shutter blades from their position shown in FIG. 1 to their position shown in FIG. 2 operates to move the photocell apertures 26A and 28A to overlap with respect to each other to admit scene light to the photoresponsive element 30. Element 30 responds to incident scene light and provides an output signal to the brightness level detect circuit 120 which, in turn, provides a low (binary logic 0) output signal if the intensity of detected scene light is below a select level, and a high (binary logic 1) output signal if the intensity of detected scene light is above the selected level, as described in U. S. Patent No. 4,192,587. The selected levels at which the circuit 120 provides a high (binary logic 1) output signal and at which it provides a low (binary logic 0) signal may,

2 for example, be in the order of lOOc/ . The circuit herein described operates to provide the selected exposure interval time out period only under conditions where the ambient scene light intensity is less than the

2 selected 100 c/m , and where the brightness level detect circuit 120 provides the low (binary logic 0) output signal. The camera and flash apparεtus herein described can provide a proportional fill-in flash under conditions

2 of high ambient scene light intensity above 100 c/m where the brightness level detect circuit 120 provides a high (binary logic 1) output signal as described in U. S. Patent No. 4,192,587. However, since the means for selecting the exposure interval time out period of this invention preferably does not operate in the proportional fill-in flash mode, it will not be further described.

Receipt of the echo signal by the transducer 136 signals the echo detector circuit 138 to provide an assertive (binary logic 1) output signal level to the inverter 142, the up/down status input terminal to the up/down counter 146, the AND gate 150, and the motor and solenoid control circuit 124. The latter responds by

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deenergizing the solenoid 46 to release the shutter blade elements 20 and 21 to commence an exposure cycle. The low (binary logic 0) output signal from the inverter 142, in turn, disables the AND gate 140 to provide a low (binary logic 0) output signal to the OR gate 144 which then switches to a low (binary logic 0) output signal to disable the up/down counter 146. In addition, the assertive (binary logic 1) output signal from the echo detector circuit 138 operates to change the mode of operation of the counter 146 from an up count mode of operation to a down count mode of operation. The low (binary logic 0) output signal level from the inverter 142 also operates to disable the AND gate 156 from transmitting the clock pulses for the remainder of the exposure cycle.

The shutter time out circuit of this invention is shown at 173 and comprises a binary counter 174 which receives the clock pulse from the clock 128 by way of a frequency divide circuit 178 and an AND gate 176; The output from the binary counter 174 is decoded at line 182 to provide a shortened maximum exposure time out signal which is directed to an AND gate 170, the output of which is directed to an OR gate 180. The binary counter 174 is also decoded at line 184 to provide an extended maximum exposure interval time out signal to an AND gate 172, the output from which is directed to an OR gate 180. The AND gate 170 and 172 receive additional input signals from a latching flip-flop circuit 166 which receives a decode output signal from the up/down counter 146 when the up count surpasses a number of pulses corresponding to a selected camera-to-subject range. The output from the OR gate 180 is thereafter directed to the motor and solenoid control circuit 124 to control the reenergiza- tion of the solenoid 46 and the termination of the exposure interval.

The up/down counter 146 initially counts up the clock pulse in synchronism with the transmission of

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the ranging signal by the sonic rangefinder 132 so that the number of clock pulses counted by the counter 146 corresponds directly to the camera-to-subject range. During the up count operation of the counter 146, a decode signal is provided to the flip-flop 166 to switch its output signal to an assertive (binary logic 1) output signal in the event the subject is located far beyond the effective range of the flash and virtually no reflected flash light can be expected to reach the photoresponsive element 30. If, however, the subject is located only slightly beyond the effective range of the flash, from where sufficient flash light may be reflected to provide an acceptable photograph, the decode signal is not provided to the flip-flop 166, and its output remains at a low (binary logic 0) signal level.

The photographic exposure cycle starts upon the deenergization of the solenoid 46 which releases the shutter blade elements 20 and 21 for movement from the light blockirg arrangement of FIG. 2 to the light unblocking arrangement of FIG. 3. The shutter blade elements 20 and 21 are moved by the compression spring 56 to progressively enlarge the exposure aperture defined by the overlapping apertures 22 and 24 over the light entry exposure opening 14. At the same time, the photocell sweep secondary apertures 26 and 28 define a progressively enlarging aperture over the photoresponsive element 30.

An LED (not shown) is aligned coaxially to the photoresponsive element 30 on the opposite side of the shutter blade elements 20 and 21 to provide illumination detectable by the photoresponsive element 30, when the secondary apertures 26 and 28 first overlap, without interfering with the transmission of scene light through the apertures 26 and 28. Alternatively, separate apertures (not shown) may be provided to admit the light from the LED to the photocell .30 in synchronism with the commencement of the exposure interval as described in fTURt

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U. S. Patents No. 3,628,437 and 4,192,587. The LED is energized to provide illumination for a set period after release of the shutter blade elements 20 and 21 so that regardless of any actual low ambient scene light intensity, an indication may be provided as to the instant at which the primary apertures 44 and 46 overlap to admit scene light to the focal plane since the light from the LED is admitted to the photocell 30 at the very instant the secondary apertures 22 and 24 first overlap. The photocell 30 responds to the light emitted by the LED the instant the secondary apertures 22 and 24 overlap to provide an output signal to the integrator 72 which, in turn, triggers the level detector 122 at a normalized trigger voltage of approximately 0.1 volt to provide an assertive (binary logic 1) output signal which is directed to one input terminal of the AND gate

150 and operates to switch the AND gate 150 to an assertive (binary logic 1) output signal to switch the OR gate 144 to an assertive (binary logic 1) output- signal level thereby enabling the up/down counter 146 to count down from the count stored during the sonar ranging opera-io . The assertive (binary logic 1) output signal level from the level detector 122 is also directed to one input terminal of the AND gate 158 to enable the AND gate 158 to transmit the clock pulses received from the clock 128 by way of the frequency divide circuit 154.

The clock pulses are thereafter gated by the OR gate 164 to the up/down counter 146. The up/down counter 146 operates in its down count mode of operation by virtue of the assertive (binary logic 1) output signal level received from the echo detector circuit 138 upon receipt of the ranging signal.

Deenergization of the solenoid 46 to commence the exposure interval also provides a high (binary logic 1) output signal level to enable the AND gate 176 to gate the clock pulses received from the clock 128 by way of the frequency divide circuit 178. In this manner,

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deenergizaticn of the solenoid 46 starts the counter 174 counting to provide either the shortened or extended maximum exposure interval time out period in the following manner. Under conditions of low ambient scene light intensity, the counter 146 will empty and the output from the counter status circuit 148 will switch from a low (binary logic 0) output signal level to an assertive (binary logic 1) output signal level to switch an AND gate 186 and thereby provide an assertive (binary logic 1) output signal level to trigger the flash trigger circuit 70 to fire the flash tube 66. The AND gate 186 enabled by an assertive (binary logic 1) output signal received from the level detector 122, operates to inhibit premature firing of the flash 60 when the counter 46 starts to count up from zero. The down count of the counter 146 provides a range responsive time signal commencing with the initiation of the exposure interval and terminating at a subsequent time corresponding to the distance between the camera and the subject to be photographed, thereby firing the flash when the aperture has obtained a size related to the camera-to-subject distance described in ϋ. S. Patents No. 4,188,103 and 4,192,587. The assertive (binary logic 1) output signal level from the counter status circuit 148 is also inverted by the inverter 151 to disable the AND gate 150 and to provide a low (binary logic 0) output signal level by way of the OR gate 144 to disable the counter 146.

If the photographic subject is within the effective range of the flash and displays an average scene light reflectance characteristic, there will be provided an immediate and substantial increase in the reflected scene light directed to the photoresponsive element 30. The photoresponsive element 30 and its associated light integrating circuit 72 respond immediately to this increased reflected scene light to provide the required voltage to trigger another level detector 88. For

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purposes of illustration, the level detector 88 is configured to trigger upon the input reaching 1 volt which is a normalized value representative of an optimum or select film exposure value for a predetermined film speed. The level detector 88 provides an assertive (binary logic 1) output signal level to the OR gate 180 so as to switch the OR gate 180 and provide an assertive (binary logic 1) output signal level back to the motor and solenoid control circuit to effect the reenergization of the solenoid 46 in order to terminate the exposure interval.

However, in the event the photographic subject is either within the effective range of the flash and has low light reflectance, or is just beyond the effective range of the flash, there will likely not be a sufficient increase in reflected flash light incident on the photoresponsive element 30 for the light integrat¬ ing circuit 72 to reach the required voltage (1.0 volt) to trigger the level detector 88. However, in these situations, there may nevertheless still be sufficient reflected flash light to provide for an acceptable photograph. Thus, it becomes desirable to limit the exposure interval time out period to the maximum allowable time to which an exposure interval may be extended without incurring the adverse blurring effects from the normally expected hand motion of a handheld camera. Toward this end, the binary counter 174 and AND gates 170 and 172 operate to provide maximum exposure time out periods in the following manner. If the photographic subject is located within the effective range of the flash or just beyond the effective rarge of the flash, the up/down counter 146 will not ccur.t up a sufficiently high number of pulses during the ir.itial sonar ranging operation to provide a decode signal to switch the flip-flop 166 which will thereby continue to provide a low (binary logic 0) output signal level to the AND gate 172. The low (binary logic

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0) output signal level from the flip-flop 166 will be inverted by the inverter 168 to enable the AND gate 170 to switch upon receiving a decode output signal from the binary counter 174 along line 182 while simultaneously disabling the AND gate 172. The AND gate 170, in turn, provides an assertive (binary logic 1) output signal level to the OR gate 180 so as to switch the OR gate 180 to provide an assertive (binary logic 1) output signal level to the motor and solenoid control circuit 124 so as to, in turn, energize the solenoid 46 and terminate the exposure interval in a well-known manner. In this manner, the binary counter 174 provides a decode output signal to impose a shortened maximum exposure level time out period in the event that there is insufficient scene light for the photocell 30 and light integrator 72 to trigger the level detector 88. The shortened maximum exposure time out interval provided by the shutter time out circuit 94 generally coincides with the maximum time allowable to which an exposure interval may be extended without incurring any adverse blurring effects from the motion of a handheld photographic apparatus.

Therefore, in the event that there is neither sufficient available ambient scene light and/or reflected artificial light for the output signal from the light integrator circuit to reach 1 volt, the shutter time out circuit 173, which commences timing in synchronism with the deenergization of the solenoid 46 and release of the shutter blade elements 20 and 21, will operate to provide an assertive (binary logic 1) output signal level and a shortened maximum exposure interval time out period which, for example, may be in the order of 54 milliseconds as controlled by the assertive (binary logic 1) output signal level received from the decode signal along line 182 from the binary counter 174. Such an exposure interval may not be sufficient to provide the optimum film exposure; however, the resultant photograph may still be of generally acceptable quality to the photographer which

would otherwise have been entirely lost.

Under conditions of low ambient scene light intensity where the photographic subject is located far beyond the effective range of the flash so that no reflected flash light can be expected to reach the photo¬ responsive element, the up/down counter 146 will count up by a sufficient number of pulses during the sonar ranging operation to provide a decode signal to the flip-flop 166 to switch its output therefrom to an assertive (binary logic 1) output signal level and enable the AND gate 172. The AND gate 170 is disabled by the inverter 168. Under these conditions, the decode signal from binary counter 174 gates the AND gate 172 to an assertive (binary logic 1) signal and switches the OR gate 180 to provide an assertive (binary logic 1) output signal level to the motor and solenoid control circuit to energize the solenoid 46 and terminate the exposure.

The decode signal provided at line 184 operates to extend the maximum exposure time out period to a greater time than the time to which an exposure interval may be extended without incurring the adverse blurring effects from the motion of a handheld camera. This extended maximum exposure time out ^' period may be in the order of 350 milliseconds and would provide a true time photograph under conditions where the camera is preferably held on a tripod or some other stable mount. Since under these conditions little or no transient light provided by the flash is reflected from the scene, a shutter maximum exposure interval time out period allows the photographic film to record all the existent ambient scene light such as starlight, street light, window lights, etc.

FIG. 5 shows a schematic wiring diagram for- an alternate embodiment of this invention for providing either the shortened or extended maximum exposure interval time out period by sampling the reflected strobe light immediately subsequent to firing the strobe 60.

The output signal from the light integrator circuit 72 is directed to three level detector circuits 84, 86, and 88, which may be well-known Schmidt triggers. The output signal from the level detector 84 is directed 5 to a latch circuit 90 which may function in the manner of a D flip-flop. The output signal from the level detector 86 is directed to an OR gate 98 which, in turn, provides an output signal along line 100 to control the flash fire trigger circuit 70. The output signal from

ICC previously described level detector 88, in turn, is now directed to an OR gate 96 which provides an output signal to control the energization of the solenoid 46. For purposes of illustration, level detector 88 is again configured to trigger at 1 volt, which as previously

15 discussed is the normalized value representative of the select or optimum film exposure value for a predetermined film speed. Level detectors 86 and 84 are, respectively, set to trigger at 0.75 volts and 0.50 volts. Again, the 0.75 volt and 0.50 volt trigger levels represent

20 normalized values.

A flash delay circuit 92 receives an input signal by way of a line 91 upon the deenergization of the solenoid 46 to provide a time delayed output signal which is inverted by an inverter 97 and which is directed to

25 the other input terminal of the OR gate 98. The time delay provided by the circuit 92 is preferably in the order of about 65 milliseconds. In like manner, a shutter time out circuit 94 receives an input signal upon the deenergization of the solenoid 46 to provide a time

30 delayed output signal which is directed to the other input terminal of the OR gate 96. The shutter time out circuit 94 operates in the manner of this invention to impose either the shortened maximum exposure interval time out period in case there is some reflected scene light from

35 the photographic subject albeit insufficient to provide for an optimum film exposure or the extended maximum exposure interval time out period where there is little

or no reflected scene light.

The latch circuit 90 operates to transmit the output signal from the level detector 84 to the shutter time out circuit 94 by way of line 116 for a select period of time as determined by the output pulse width from a onostable multivibrator (one shot) 114. The output pulse width from the multivibrator 114 is selected to generally overlap the period of illumination of the flash tube 66 and may be in the order of 2 milliseconds. The latch circuit 90 receives the output signal from the level detector 84 and inverts the output signal by way of an inverter gate 102, the output of which is directed to an AND gate 104. A non-inverted output signal from the level detector 84 is directed to another AND gate 106. The output signal from the AND gates 104 and 106 are directed, respectively, to the input terminals of a pair of NOR gates 110 and 112. The NOR gates 110 and 112 are connected to provide an RS latch circuit 108. The other input terminals to the AND gates 104. and 106 are in common connection and receive the output signal from the mono¬ stable multivibrator 114. The output from the RS latch circuit 108 is directed by way of line 116 to control the shutter time out circuit 94.

Assuming that the electronic flash 60 has been fully charged, a photographic exposure cycle may be commenced by actuating the button A which operates, in turn, to energize the solenoid 46 and release the shutter blade latch mechanism (not shown)- as described in U. S. Patent No. 4,040,062. The photographic exposure cycle is subsequently commenced upon the opening of switch S. deenergizing the solenoid 46 to release the shutter blade elements 20 and 21 for movement to the scene light unblocking arrangement. The shutter blade elements 20 and 21 are moved in the aforementioned manner. Under conditions of low ambient scene light intensity where a source of artificial illumination such as the flash 60 is normally expected to be used, the

light integrator circuit 72 will generally not reach the 0.75 volt output response before the expiration of the 65 millisecond flash time delay. Instead, the 0 volt signal level at line 91 resulting from the deenergization of the solenoid 46 is transmitted by the flash delay circuit 92 at the.expiration of the 65 millisecond time delay and inverted by the inverter 97 to provide an assertive (binary logic 1) output signal level to the OR gate 98. OR gate 98, in turn, provides an assertive (binary logic 1) output signal to trigger the flash trigger circuit 70 and thereby fire the flash tube 66.

If the photographic subject is within the effective range of the flash and displays an average flash light reflectance characteristic, there will be provided an immediate substantial increase in the reflected scene light directed to the photoresponsive element 30. The photoresponsive element 30 and its associated light integrating circuit 72 respond immediately to provide the voltage required to trigger the level detector 88. The level detector 88, in turn, provides an assertive (binary logic 1) output signal level to the OR gate 96 to switch the OR gate 96 to effect the reenergiza- tion of the solenoid 46 in order to terminate the exposure interval. In the event that the photographic subject is either within the effective range of the flash and has a low degree of flash light reflectance or is just beyond the effective range of the flash, there will likely not be provided the required increase in the reflected scene light incident to the photoresponsive element 30 for the light integrating circuit 72 to reach the required voltage (1.0 v) to trigger the level detector 88. As previously discussed, in the situations where the photographic subject is within the effective range of the flash and has a low degree of scene light reflectance or is only slightly beyond the effective range of the flash, there still may be sufficient reflected scene

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light to provide for an acceptable photograph. Under these conditions, it is desirable to limit the exposure interval time out period to the maximum allowable time to which an exposure interval may be extended without incurring the adverse blurring effects from the motion of a handheld camera. Toward this end, the level detector 84 and latch circuit 90 operate to provide a control signal to the shutter time out circuit 94 to select a shortened maximum exposure interval time out period so as not to incur the adverse blurring effects resulting from the motion of the photographer.

Thus, if the scene light integration signal immediately following the firing of the flash tube 66 reaches 0.50 volts, the level detector 84 is triggered to provide an assertive (binary logic 1) output signal level to the latch 90. The assertive output signal from the level detector 84, in turn, is inverted by the inverter 102 and directed to one input terminal of the AND gate 104. The assertive output- signal from the level detector 84 is also simultaneously directed to an input terminal of the AND gate 106. The AND gates 104 and 106 are gated by the output pulse from the monostable multi¬ vibrator 114 which as previously discussed provides an assertive (binary logic 1) output signal level for a time period of preferably 2 milliseconds immediately following the firing of the flash. The 2 millisecond pulse width output from the monostable multivibrator 114 is sufficient to overlap the period of illumination of the flash 60. Thus, the aforementioned scene light integration which occurs during the 2 millisecond multivibrator 114 output pulse provides an indication of camera-to-subject range adjusted to account for variations in scene reflectivity characteristics not previously accounted for in the aforementioned sonic ranging system. During this time period, the AND gate 104 responds to the nonassertive (binary logic 0) input signal level from the inverter 102 and the assertive

(binary logic 1) output signal level from the monostable multivibrator 114 to provide a nonassertive (binary logic

0) output signal level to the corresponding input terminal of the NOR gate 110. The AND gate 106, in turn, responds to the assertive (binary logic 1) output signal level from the level detector 84 and the assertive (binary logic 1) output signal level from the multivibrator 114 to provide an assertive (binary logic 1) output signal level to the corresponding input terminal of the NOR gate 112. Under these input conditions the NOR gates 110 and 112 cooperate to provide an assertive (binary logic 1) output signal level to the shutter time out circuit 94 by way of line 116. The shutter time out circuit 94, in turn, responds to the assertive (binary logic 1) input signal level from line 116 to impose a shortened maximum exposure interval time out period. The shortened maximum exposure time out interval provided by the shutter time out circuit 94 generally coincides with the maximum time allowable to prevent any adverse blurring effects from the motion of a handheld photographic camera apparatus. In the aforementioned example, the minimum shutter time out period has been selected to be in the order of 50 milli¬ seconds.

Thus, in the event that there is neither sufficient available ambient scene light and/or reflected artificial scene light for the output signal from the light integrator circuit 72 to reach 1 volt, the shutter time out circuit 94, which commenced timing in synchronism with the deenergization of the solenoid 46 and release of the shutter blade elements 20 and 21, operates to provide an assertive (binary logic 1) output signal level in a shortened maximum exposure interval time out period of 108 milliseconds as controlled by the assertive (binary logic

1) output signal level received from the latch 90 by way of line 116. The assertive (binary logic 1) output signal level from the shutter time out circuit 94, in turn, operates to switch the OR gate 96 to energize the solenoid! f OM

46 and thereby close the shutter blade elements. This exposure interval may not be sufficient to provide the optimum film exposure; however, it may result in a photograph of generally acceptable quality. Under conditions of low ambient scene light intensity where the photographic subject is located far beyond the effective range of the flash so that virtually no reflected flash light can be expected to reach the photoresponsive element 30, the level detector 84 will not provide the assertive (binary logic 1) output signal level during the time period of the multivibrator 114 output pulse. The scene light integration which occurs during the period of the multivibrator 114 output pulse again provides an indication of camera-to-subject range adjusted to account for variations in scene reflectivity characteristics. Under these conditions, the inverter 102 operates to invert the nonassertive (binary logic 0) output signal level from the level detector 84 to provide an assertive (binary logic 1) output signal level to the AND gate 104. The assertive (binary logic 1) output signal level from the multivibrator 114 to the other input terminal of the AND gate 104, in turn, operates to provide an assertive (binary logic 1) output signal level from the AND gate 104 to the NOR gate 110. In like manner, the nonassertive (binary logic 0) output signal level from the level detector 84 to the AND gate 106, and the assertive (binary logic 1) output signal level from the multivibrator 114 to the other input terminal of the AND gate 106 operate to provide a nonassertive (binary logic 0) output signal level to the input terminal of the NOR gate 112. Under these conditions, the NOR gates 110 and 112 cooperate to provide a nonassertive (binary logic 0) output signal level to the shutter time out - circuit 94 by way of the interconnecting line 116. The nonassertive (binary logic 0) input signal level to the shutter time out circuit 94 operates to provide an extended maximum exposure interval time out period which

is greater than the maximum allowable time to which an exposure interval may be extended without incurring the adverse blurring effects from the normally expected hand motion of a handheld camera. This extended maximum shutter time out period may be in the order of 350 milli¬ seconds and would provide a true time photograph under conditions where the camera is preferably held on a tripod or some other stable mount. Since under these conditions little or none of the artificially provided light by the flash is reflected from the scene, the extended maximum exposure interval time out period allows the photographic film to record all the existent ambient scene light such as starlight, street lights, window lights, etc.

Under conditions of high ambient scene light intensity, the flash 60 may be fired by way of the level detector 96 and OR gate 98 in a manner described in U. S. Patent No. 4,023,187 to provide a fill-in flash capability. Under conditions of high ambient scene light intensity, the light integrator circuit 72 provides a sufficient output signal to trigger the level detector 88 and terminate the exposure interval prior to the expiration of either the shortened or extended maximum exposure interval time out periods. In additon, it should be readily understood that the invention herein described would be equally applicable to a quench strobe.

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