US3205795A - Automatic exposure control device - Google Patents

Automatic exposure control device Download PDF

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Publication number
US3205795A
US3205795A US150228A US15022861A US3205795A US 3205795 A US3205795 A US 3205795A US 150228 A US150228 A US 150228A US 15022861 A US15022861 A US 15022861A US 3205795 A US3205795 A US 3205795A
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Prior art keywords
exposure
blade
shutter
aperture
spring
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US150228A
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English (en)
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David S Grey
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Polaroid Corp
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Polaroid Corp
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Priority to US150228A priority Critical patent/US3205795A/en
Priority to GB40813/62A priority patent/GB1019932A/en
Priority to CH1290262A priority patent/CH429433A/fr
Priority to BE624439A priority patent/BE624439A/fr
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Publication of US3205795A publication Critical patent/US3205795A/en
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B9/00—Exposure-making shutters; Diaphragms
    • G03B9/08—Shutters
    • G03B9/36—Sliding rigid plate
    • G03B9/40—Double plate
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B9/00—Exposure-making shutters; Diaphragms
    • G03B9/58—Means for varying duration of "open" period of shutter
    • G03B9/62—Means for varying duration of "open" period of shutter by varying interval of time between end of opening movement and beginning of closing movement

Definitions

  • Another object of the invention is to provide a photoelectrically responsive exposure control mechanism in which proper exposure is determined by the action of solenoid devices which in turn are responsive to the action of an electronic trigger circuit.
  • the present invention therefore contemplates a photoelectrically responsive exposure control mechanism in which galvanometers have been replaced by electronic trigger circuits and associated solenoid devices which not only provide extremely fast shutter action when required, but also perform a timing function during exposure so that the exposure control device will accurately respond to changes in ambient illumination when the camera shutter is open.
  • the invention accordingly comprises the apparatus possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.
  • FIG. 2 is a schematic, front-elevational view of the embodiment of FIGURE 1 showing the parts thereof during exposure operation of the invention
  • FIG. 3 is a schematic of one embodiment of an electrical circuit employed for controlling exposure values of the mechanism of FIG. 1;
  • FIG 5 is a front-elevational, schematic view of the embodiment of FIG. 4 showing the parts thereof during exposure;
  • FIG. 6 is a front-elevational, schematic view of the embodiment of FIG. 4 showing the parts thereof immediately after termination of exposure and before the parts are reset;
  • FIG. 7 is a schematic diagram of an electronic circuit for controlling the exposure values of the device of FIG. 4;
  • FIG. 8 is an exploded, perspective, partly fragmentary view of yet another embodiment of the invention showing the parts thereof in rest position;
  • FIG. 10 is a circuit schematic of an electronic device for controlling the exposure values of the embodiment of FIG. 9;
  • FIG. 12 is a schematic diagram of an electronic circuit for controlling the exposure intervals of the arrangement shown in FIG. 11.
  • the novel control means is employed to actuate a modification of a shutter mechanism of the. essentially freemoving type such as is described in US. Patent No. 2,752,834 issued July 3, 1956, to M. N. Fairbank.
  • a shutter blade normally mounted upon a housing in a covering relation to an exposure aperture.
  • an impulse member or kicker As a means for imparting an aperature-uncovering movement to the blade, there is provided an impulse member or kicker.
  • the kicker is normally held by a latch means in a stationary position against the biasing action of resilient means used for moving the kicker when desired.
  • the versatility of the present invention is exhibited in another or alternative embodiment wherein the novel control means is employed with a two bladed shutter mechanism.
  • the shutter mechanism includes a pair of shutter blades, one of which is normally mounted in covering position relative to an exposure aperture while the other is normally mounted in uncovering position relative to the aperture. Both blades are biased for sequential movement out of their respec tive normal positions such that the one blade normally in covering position is movable to uncovering position to initiate an exposure, and after a predetermined time interval, the other blade is movable to covering position to terminate the exposure.
  • This variable electrical parameter is compared by an appropriate circuit against a fixed voltage provided, for instance, by a voltage-dividing network.
  • a fixed voltage provided, for instance, by a voltage-dividing network.
  • the positive. feedback of the trigger circuit insures that the circuit abruptly delivers an amplified electrical signal which actuates an electromechanical transducer, such as a solenoid, the latter in turn initiating movement of the other shutter blade to terminate exposure.
  • an electromechanical transducer such as a solenoid
  • FIGURES 1 through 3 the embodiment first described above is shown therein and comprises a shutter-and-diaphragm assembly indicated generally by the reference numeral 26
  • Assembly 20 includes a housing portion 22 shown in fragment only for supporting the various elements of the embodiment.
  • a conventional camera lens system represented in cross-section by exposure aperture 24.
  • a diaphragm means 26 Disposed for movement across the optical axis of the lens system and mounted upon housing portion 22 is a diaphragm means 26 and a movable shutter member such as shutter blade 28.
  • bounce spring 36 comprises at least a resilient portion positioned to engage lug 34 of the shutter blade during rotation of the latter, and is therefore adapted to absorb energy from the shutter blade upon engagement therewith and to transmit a substantial portion of the absorbed energy back to the blade for providing the impetus which returns the blade to its rest position.
  • Spring 36 is therefore preferably formed of a resilient substance such as Phosphor bronze or spring steel.
  • Means are provided for mounting the bounce spring for movement along the path of rotation of lug 34 so as to vary the travel of the blade and, therefore, vary the exposure time interval afforded by movement of the latter.
  • Such a means is provided by a substantially circular element, such as wheel 50, upon a peripheral portion of which spring 36 is fixedly mounted. Wheel 50 is mounted for rotation about a pivotal axis which is substantially colinear to the axis of rotation of the shutter blade, and the plane of rotation of the wheel is therefore substantially parallel to the plane of movement of the shutter blade.
  • the linkage comprises an elongated connecting rod or link 84 which is pivotally mounted adjacent its extremities respectively upon a portion of leaf '72 and upon arm 86, the latter constituting a member which is rigidly connected to and projects from lever 56 intermediate its extremities.
  • link 84 By coupling leaf 72 to leaf 70 through another elongated connecting rod 88 pivotally mounted adjacent its extremities respectively upon portions of each of the leaves, the rotation of leaf 72 is accompanied by a similar rotation of leaf 7 in an opposite direction.
  • the electrical parameter established by potentiometer 92 is intended to vary as a function of a mechanical displacement, i.e., the angular displacement of lever 56 or lever 66 which angular displacement also determines the values of the effective exposure aperture and the exposure time interval and, therefore, the exposure value. Consequently, lever 56, or some element movable in fixed relation thereto, can be employed for varying the potentiometer setting.
  • actuating lever 66 is adapted to perform this function by inclusion therewith of arm 96, extending radially outward from the axis of rotation of and forming an integral part of the actuating lever.
  • the potentiometer 92 sweeps from a minimum to a maximum resistance as the exposure aperture and exposure interval change from minimum to maximum openings and times, respectively. This action corresponds to the response of the photo-electric cell 90, which has its maximum value of resistance at the low levels of ambient illumination, at which condition the exposure aperture and exposure interval must be at their maximum settings. With appropriate changes in circuitry and mode of operation, the potentiometer 92 could be arranged to sweep from a maximum to a minimum resistance. Such action would eliminate the possibility of any false exposure initiation that may occur with the arrangement shown in FIGURE 1 should the potentiometer 92-have any open spots which momentarily increase its elfective resistance to infinity.
  • diaphragm means for varying the etfective magnitude of exposure aperture 124 have been omitted, but it is understood that a diaphragm may be employed with this embodiment either in coupled or uncoupled relation to the other elements thereof.
  • Blade 126 is provided with a similarly dimensioned covering portion 138 at one extremity thereof and is mounted for movement, as by rotation about pivot 140, adjacent its opposite end. Blade 126 is movable about pivot 140 from an uncovering position wherein portion 138 is wholly to one side of opening 124 to a closed position wherein covering portion 138 is aligned with and occludes opening 124. Both blades are mounted so that the covering portions are movable in their own planes closely adjacent and parallel to one another thereby minimizing light leakage between the blades.
  • element 144 includes a latch portion or notch 148 which is normally in engagement with the extremity of second arm 134 when blade 128 is in its covering position.
  • Resilient means such as spring 150 mounted on housing 122, are provided in engagement with element 144 for rotating the latter about its pivot point so that notch 148 is retained in engagement with arm 134.
  • Blade 126 includes, adjacent pivot 140, a V-shaped lever or rocker 162 firmly affixed to the blade and movable therewith, the apex of the V-shape being approximately located at pivot 140.
  • Rocker 162 is so shaped and disposed relative to blade 126 that when covering portion 138 of the latter is in its uncovering position, one
  • rocker 162 is formed of a magnetizable material such as iron which is subject to attraction by magnetic force.
  • the other arm of rocker 162 is adapted to contact and be retained by the larger field of other arm of device 152 when blade 126 is in its covering position relative to opening 124.
  • Bell crank 164 comprises an element mounted for rotation about appropriate bearing means such as pivot 166 disposed on housing portion 122, and includes a first arm 168 extending radially from pivot 166 outwardly of the confines of housing portion 122 so that the radial extremity of arm 168 may be grasped by an operator of the device for rotating the bell crank.
  • Bell crank 164 also includes a second arm 170 which also extends radi ally from pivot 166 and at an angle to arm 168, both arms lying substantially in the plane of rotation of the bell crank.
  • Arm 170 is so dimensioned that the path of movement of the radial extremity thereof intersects the position of shutter latch 144, the radial extremity of arm 170 being therefore engageable with the shutter latch.
  • Resilient means such as spring 172 are provided for biasing the bell crank for rotation such that the radial extremity of arm 170 is biased away from engagement with shutter latch 144.
  • Means such as pin 174 mounted upon housing portion 122 are provided in the path of movement of arm 168 for limiting the rotation of the bell crank under the bias of spring 172.
  • the radial extremity of arm 168 is grasped by an operator and pressure is exerted thereagainst to rotate bell crank 164 against the bias of spring 172.
  • the rotation of the bell crank in the clockwise direction against the bias of spring 172 causes the radial extremity of arm 170 to engage shutter latch 144 and rotate the latter about its pivotal axis at 146 and against the bias of spring 150.
  • the rotation of the shutter latch causes notch 148 to disengage second arm 134 of shutter blade 128; this frees the latter for movement from its covering position to an uncovering position under the impetus provided by spring 142, thereby initiating exposure through opening 124 as shown in FIG. 5.
  • Shutter blade 128 is provided on first arm 132 with an abutment or pin 176.
  • pin 176 is in engagement with spring contact 178 of switch 180, for retaining the spring contact out of engagement with relatively fixed contact 182 of the switch.
  • pin 178 is rotated and permits spring contact 178 to close under its own resiliency and engage fixed contact 182, thereby closing a circuit substantially simultaneously with the initiation of exposure.
  • This embodiment of the invention includes means for controlling or determining the exposure value, particularly the exposure time interval, of the mechanism, and comprises an electrical circuit such as shown in detail in FIG. 7, being shown schematically in FIGS. 4-6.
  • This circuit includes means such as photoelectric cell and capacitor 192 for establishing a relatively variable electrical parameter, which in this embodiment, is a voltage.
  • Means such as voltage divider 194 are also included for establishing a relatively fixed or constant electrical parameter or voltage.
  • the circuit includes another form of electronic trigger circuit indicated generally at 196 for comparing the two voltages and for actuating solenoid 156 only when the two voltages have attained a predetermined relationship to one another.
  • Voltage divider 194 is preferably in the form of an electrically resistive winding having a variable tap intermediate its extremities.
  • the electrical parameter established by the series combination of cell 190 and capacitor 192 is intended to vary as a function of time and is determined by the product of the value R of the cell and the value C of the capacitor, the product RC being the well-known time constant of charging. It is apparent that the product RC varies in accordance with the intensity of light incident upon cell 190 which determines the resistive value of the latter when, as in this embodiment, the cell employed is a photoconductive element.
  • the intermediate tap of voltage divider 194 can be predeterminedly set to establish a desired voltage drop.
  • Comparator means 196 which acts as an electronic switch, as shown in FIG. 7, comprises a pair of transistors 198 and 200.
  • transistor 198 is an NPN transistor while transistor 200 is a PNP transistor.
  • the circuit includes solenoid 156, one end of which is grounded and the opposite end of which is connected to both the collector of transistor 21M) and one side of capacitor 192.
  • the base of transistor 200 is connected to the collector of transistor 198.
  • One terminal of cell 190 is coupled in series to the other side of capacitor 192 and the base of transistor 19?: is connected to a point between the capacitor and the cell.
  • the emitter of transistor 200 is electrically connected to the other terminal of cell 190, to one contact of switch 180 and also led to ground through the total resistance of voltage divider 194.
  • the emitter of transistor 198 is connected to the intermediate tap of the voltage divider and thence to ground through at least a portion of the latter.
  • a power supply in the form of battery 202 is provided, the negative terminal of the battery being grounded and the positive terminal being connected to the other contact of switch 180.
  • transistor 198 When the voltage at the base of transistor 198 reaches a level which is more positive than the emitter potential, the transistor will conduct drawing a small current and driving the base of transistor 209 negative with respect to its emitter, causing initiation of electronic flow through the collector of transistor 200 to its emitter.
  • the present embodiment also preferably includes a shunt resistor 206 across the solenoid to prevent circuit oscillation following closure of the switch 180.
  • a shunt resistor 206 across the solenoid to prevent circuit oscillation following closure of the switch 180.
  • manual means may be provided for adjusting the position of the intermediate tap of voltage divider 194.
  • the rocker rapidly rotates until the other arm thereof engages with and is retained by arm 169 of device 152.
  • the rotation of the rocker is, of course, accompanied by the rotation of blade 126, thus resulting in closure of opening 124 and termination of exposure as shown in FIG. 6.
  • the exposure time interval therefore established respectively by the sequence of uncovering movement of blade 128 and the closing movement of blade 126 is determined by the time constant of comparator means 196, the latter in turn being a function of the intensity of illumination incident upon photocell 190.
  • the circuit shown in FIG. 7 may be employed in conjunction with a unitary blade shutter and diaphragm mechanism similar to that illustrated in FIG. 1.
  • the third modification is shown particularly in FIG. 8 and comprises shutter blade 228 formed, mounted, and retained similarly to shutter blade 28 theretofore described.
  • the third embodiment also includes diaphragm means indicated generally at 226 comprising a multiple leaved element substantially similar to diaphragm means 26 hereinbefore described.
  • means are provided for variably limiting the travel of shutter blade 228 from its covering position wherein it is retained by magnet 232.
  • the means for limiting the blade travel comprises a reversing means such as bounce spring 236 which is positionable in the path of travel of lug 234, the latter forming a portion of the shutter blade.
  • impact means such as kicker 240 shaped, positioned, mounted and resiliently biased as by kicker spring 242 in a manner similar to that described in connection with kicker 40.
  • Latch means 246 are provided for releasably restraining the kicker from movement, latch means 246 being also similar in shape and construction to lever 46.
  • Element 253 is so mounted that the gear teeth of segment 254 are in meshing engagment with gear 252 so that rotation of the element rotates wheel 250 thereby changing the position of the bounce spring relative to the position of closure of shutter blade 228.
  • resilient means such as elongated driving spring 256, one end of which is anchored adjacent the radial extremity of second arm 258 of element 253, and the other end of which is anchored upon the support (not shown) for the elements of the shutter mechanism.
  • Spring 256 is preferably disposed for urging element 253 in a rotational direction which, when transmitted to wheel 250, tends to move bounce spring 236 away from the covering position of blade 228, thereby increasing the total arcuate travel of the latter.
  • the circuit closed by switch 180 and employed with this embodiment of the invention is substantially the same circuit shown and described hereto-fore in connection with FIG. 7 and comprising a photoelectric cell 190, capacitor 192, an electromechanical transducer or solenoid 156 and trigger circuit 196, these elements being shown only diagrammatically in FIG. 8.
  • the operation of the circuit is also substantially the same as the opiiration heretofore described regarding the circuit of FIG. 7 and results in actuation of solenoid 156.
  • the actuation of the solenoid then causes, after a time interval predetermined by the value of the resistance of the photoelectric cell and the value of the capacitor, latch means 246 to rotate in a clockwise direction.
  • latch means 246 includes latching element or pawl 278 movable therewith. Because wheel 250 is provided about its external periphery with a con tinuous plurality of teeth, the rotation of latch means 246 in a clockwise direction moves pawl 278 into engagement with the teeth, thereby locking both the bounce spring and diaphragm in fixed positions almost immediately as exposure is initiated. This provides for the shutter mechanism an exposure value determined by both the distance the bounce spring has moved and the extent that the diaphragm means has opened during the time interval between.
  • the bounce spring is returned to its initial position adjacent lug 234 and the diaphragm means is correspondingly returned to a position wherein it provides a minimum or no opening, as the case may be, simply by rotation by the operator of third arm 260 in a counterclockwise direction.
  • the rotation of arm 260 continues until pin 27d reen-gages spring contact 272 and moves the latter out of engagement wit-h the fixed contact thereby opening the switch.
  • the spring loading on element 266 causes the latter to reengage the extremity of second arm 258 locking the latter in position.
  • the rotation of element 253 in the counterclockwise direction stresses spring 256.
  • the solenoid operated actuated mechanisms function when passage of current through the solenoids is initiated.
  • These embodiments can also, with appropriate mechanical modifications, be actuated or made to operate on the basis of solenoid operated actuated mechanisms which function when passage of current through the solenoids is terminated. For instance, in the embodiment of FIG. 7, simply by interchanging the position of the capacitor and the photoelectric cell in the circuit, reverse action occurs.
  • Yet another embodiment of the present invention operates basically upon the principle of solenoid operation by turning off the current therethrough and is illustrated in the circuit of FIG. 10.
  • This circuit is particularly well adapted for use with a two-bladed shutter mechanism, such as that shown in FIG. 9, wherein the sequential release of the blades determines the exposure time interval.
  • Each blade is preferably solenoid actuated and the circuit uses the inductive kick derived from the opening of one solenoid in order to provide a large voltage for charging a capacitor.
  • the discharge rate of the capacitor in terms of RC, where R is a photoelectric cell resistance and C the capacitance of the capacitor, determines the desired exposure time interval.
  • means such as photoelectric cell 300 for establishing a relatively fixed or constant electrical parameter or voltage dependent upon the intensities of radiation incident thereon, and capacitor 302 for establishing a relatively variable electrical parameter.
  • the circuit also includes another form of electronic trigger circuit 304, characterized in having positive feedback, and provided for comparing, in a sense, the electrical parameters provided respectively by the photoelectric cell and capacitor.
  • the circuit comprises a pair of transistors 306 and 308 which, in the form shown, are respectively of the NPN and PNP types.
  • the transistors are connected so that the collector of transistor 306 is coupled to the base of transistor 308, the emitter of transistor 3% being grounded.
  • One side of cell 300 is in series with the base of transistor 306, while the other side of the cell is conl nected in series through capacitor 332 to the col ector of transistor 308.
  • the emitter of transistor 308 is connected to a point intermediate diodes 313 and 320, means being provided for connecting the latter point to lead 322, and therefore to the collector circuit of transistor 308, through respectively another electrical valve, or diode 324, and a switch means, such as switch 326, in series with one another.
  • a point intermediate diode 324 and switch 326 is connected to one terminal, such as the positive side of a DC. power source, or battery 32%, the other side of the battery being grounded.
  • a point intermediate switch 314 and solenoid 312 is also tapped to ground.
  • Diode 324 is placed in the circuit in known manner so that current can only flow therethrough into the emitter of transistor 308 while diodes 318 and 320 respectively are placed in the circuit so that current can only flow in the same direction through both and away from switch 314.
  • locker elements 334 and 336 have respectively connected thereto means, such as springs 338 and 340, for moving them in predetermined directions of rotation; rocker elements 334 and 336 having respectively attached thereto and movable therewith substantially planar shutter blades 342 and 344 which are made and disposed similarly to the shutter blades of FIG. 4.
  • Rocker element 336 is normally disposed so that blade 344 is in uncovering position to exposure aperture 346, while rocker element 334 is normally disposed such that blade 342 is in covering position with respect to the exposure aperture, both springs 338 and 340 exerting biases tending to move the rocker elements out of normal disposition.
  • Both rocker elements are formed of a magnetizable metal, such as soft iron.
  • the electromagnetic transducers of this embodiment differ primarily from those shown in FIG. 4 in that the rocker elements of the former, when in their normal position, are in contact with the soft iron cores of the solenoids.
  • FIG. 9 also includes a timing device comprising a fly-wheel 354 biased for rotation by spring 356 and held in a predetermined position against the bias of spring 356 by engagement of a portion of the fiy-wheel with portion 358 of element 350 when the latter is in engagement with the rocker elements.
  • Switches 314 and 326 are respectively operable in sequence following the release of fly-wheel 354 inasmuch as switch 314 comprises a pair of switch contacts, at least one of which is normally held in contact with the other (to provide a closed circuit) by engagement with portion 360 of the Elly-wheel when the latter is in its predetermined position; the one contact is preferably resiliently biased to open switch 314 when released from engagement with the flywheel.
  • Switch 316 in turn comprises a pair of contacts normally in contact with one another, and at least one of which is in the path of movement of portion 360 of flywheel 354 such that the switch contacts are forced out of engagement with one another when the one contact is engaged by portion 360 during its movement.
  • the one contact of switch 326 is preferably biased to close the switch when released from engagement with the fiy-wheel.
  • Stop means such as pin 362 are provided in the path of movement of portion 358 of the fly-wheel in order to limit its rotation under the bias of spring 356.
  • the inductive kick charges capacitor 302 to a much higher voltage than that of the battery.
  • capacitor 302 is a 0.2. mfd. condenser and solenoid 310 is a 1,000 turn, No. 30 wire, 10 ohm solenoid with a transformer iron core
  • the capacitor can be charged to approximately 40 to 50 volts from the inductive kick.
  • the charge on the capacitor is a function of the resistance of photoelectric cell 300 inasmuch as the capacitor is shunted by transistor 308.
  • transistors 306 and 308 will conduct, the base current of transistor 308 being controlled by the collector current of transistor 306, which in turn is controlled by its base current according to the value of the resistance of cell 300.
  • the capacitor starts discharging approximately as soon as it is charged up.
  • the charging time is quite short and fiy-wheel 354 is adapted to open switch 326 substantially at the same time as the charge on the capacitor reaches peak value.
  • the discharge rate of capacitor 302 is linearly proportional to the resistance of cell 300, i.e., the discharge current is equal to the product of capacitor voltage times cell conductance (E P).
  • E P falls below a value predetermined by the trigger circuit, transistors 306 and 308 are no longer in saturation. The transistors are considered in saturation when current through the photocell is sufficient such that the battery current through solenoid 312 is limited by the resistance of the latter.
  • diode 324 provides means which prevents the inductive kick from solenoid 310 from traversing battery 328.
  • Diode 318 is provided in the circuit in order to prevent a short circuit of battery 328 when switch 314 is in its closed position. It should be noted that when switch 326 is opened, the battery bias upon the base of transistor 306 is reduced, but due to the charge on capacitor 302 the base of the transistor remains biased until the capacitor discharge drops the base ,current below its critical value.
  • Afiixed to the other end of blade 406 is a magnetic keeper element 432 located adjacent to solenoid 434 and held thereby when the solenoid is energized.
  • a switch S2 having a pair of resilient conducting members 436, 438 is normally closed when the parts are in the rest position by means of a conducting member 440 aflixed to the end of blade 404, insulated therefrom, and arranged to bridge the members 436, 438 when proximate thereto.
  • a second switch S1 has a pair of resilient members 442, 444 which are normally open when the parts are in the rest position but arranged to close when the release button 426 is depressed.
  • resilient member 444 is mounted in a fixed position and element 442 is mounted on the shaft 424, suitably insulated therefrom, such that movement of the shaft causes the elements to come together and close the switch. The switch will remain closed so long as the button is held by the camera operator.
  • a suitable cocking member in the form of a pivotally mounted bellcrank 446 is arranged in the shutter housing having arms 448, 450.
  • Arm 448 is normally adjacent the ends of the blades 404, 406 following completion of exposure and arm 450 is arranged to project from the shutter housing and has affixed to its outer end a cocking button 452 which may be manipulated by the camera operator to move the cocking member in a counterclockwise direction to effect return of the shutter blades to the rest position.
  • the cocking button 452 will be moved in a counterclockwise direction, and this will cause arm 448 to engage rod 430 and move the two shutter blades back together to the rest position at which the latch portion 420 will ride up over pin 422 and then drop down behind it to hold the parts at the rest position.
  • a spring 454 atfixed to arm 448 allows the cocking button to return to its normal position.
  • Cell 460 is a suitable photoconductive member whose resistance varies inversely as a function of changes in ambient light.
  • the transistors, 456, 458 may be either PNP or NPN depending upon the polarity of the source.
  • a suitable source of electric energy in the form of battery 461, one terminal of which is grounded and connected by means of lead 462 to one side of photoelectric cell 460 through switch S2, the other terminal of which is connected by means of lead 464 to the other side of photoelectric cell 460 through switch S1.
  • the base of transistor 456 is connected between cell 460 and switch S2 by means of lead 466 and the base of transistor 458 is connected to the collector electrode of transistor 456.
  • a capacitor 468 is connected across cell 460 between leads 464 and 466.
  • a resistor 470 is connected from lead 464 to the collector of transistor 456.
  • Solenoid 434 is connected to the collector of transistor 458 from lead 464.
  • a capacitor is connected across the solenoid to protect the transistors against fly-back surges during collapse of the solenoids magnetic field; the capacitor also minimizes the release time of the solenoid and holds this time within tolerable limits from unit to unit.
  • the emitter of transistor 456 is connected by means of a tap 472 to a resistor 480 connected between lead 462 and the emitter of transistor 458.
  • a compensating resistor 432 is connected between switch S2 and lead 466.
  • switch S2 When the shutter is in the rest position, switch S2 is closed, and upon actuation of shutter release button 426, switch S1 is closed.
  • switch S1 closes, capacitor 468 immediately becomes charged to almost the potential of battery 461 and the circuit parameters are selected so that transistor 458 is on, or conducting, and transistor 456 is off, or nonconducting. This allows solenoid 434 to be energized and hold the blade 406 in the rest position.
  • switch S2 Shortly after switch S1 is closed, continued movement of the release button 426 will raise the latch portion 420 from pin 422 and allow shutter blade 404 to move and thus open switch S2.
  • capacitor 468 discharges across the cell 460, and its rate of discharge will be determined by the magnitude of resistance assumed by the cell at that particular instant.
  • the capacitor voltage reaches a level at which the base of transistor 456 is properly biased, it will be switched on and thus become conducting, which will have the effect of switching off transistor 458 and cause it to be non-conducting, which in turn deenergizes solenoid 434.
  • shutter blade 406 is released and is moved by its spring to terminate exposure.
  • the two transistors operate as a conventional trigger circuit and provide instantaneous switching when required to terminate exposure in accordance with the proper exposure interval, as determined by the magnitude of resistance of photoelectric cell 460 and the capacity of capacitor 468.
  • the exposure aperture 400 could be varied through an appropriate range, or a filter could be placed in front of the photoelectric cell, to have the circuit function properly through the range of film speeds used.
  • the aperture 400 may be f8.8 to provide suitable exposure for a range in film speeds between ASA 50 and ASA 3000. For this range, two selectively usable capacitors may be provided.
  • the resistor 482 is a compensating resistor having a low value of resistance, and this is used because the photoelectric cell does not have a truly linear characteristic, particularly at high light levels, when its resistance becomes too low for proper action in the circuit arrangement of FIG. 12.
  • the value of resistance of resistor 482 is selected to compensate for the action of the photoelectric cell at high light levels; that is, at such high light levels, the voltage drop across resistor 482 during charging of capacitor 468 is a significant amount compared to the voltage drop across cell 460 and has the effect of reducing the charge on the capacitor. The effect is to speed up the action of the capacitor at high light levels, for its voltage has been reduced prior to initiation of discharge, thus permitting it to reach the desired trigger value within the proper control interval.
  • the resistance of cell 460 is so much higher than that of resistor 482 that the latter has no significant efiect on the level of voltage to which the capacitor is charged.
  • the various components of the circuit of FIG. 12 will have slight variations in value within specified tolerances; and in order to compensate for such variations and calibrate the circuit for proper triggering action, the tap 472 and associated resistor 480 are provided.
  • the blades have been designed to come to rest after release in a period of 2 milliseconds.
  • the capacitor 468 is charged in less than 1 millisecond and is ready to discharge substantially coincident with release of blade 404.
  • the two blades will be moving together during exposure; that is, approximately 1 millisecond after release of blade 404, blade 406 will be (released and the apertures 408, 410 will be moving together somewhat like a curtain shutter with respect to exposure aperture 400.
  • Photoelectric cell 460 responds very rapidly to changes in ambient light (about 1-5 milliseconds time delay between high and low levels of light), and this dynamic response enables the shutter mechanism to respond dynamically to changing light levels and still function properly to automatically control exposure.
  • the exposure control mechanism of FIGS. 11 and 12 will function to automatically control exposures for flash photography when the object being photographed is between 3-4 feet and 10-15 feet from the camera. Such exposures will be of short enough duration to allow the camera to be hand-held during exposure.
  • Automatic photographic exposure control means adapted to establish an exposure parameter in accordance with the intensity of light from a scene being photographed, said exposure control means comprising, in combination:
  • photoelectric means arranged to receive light from said scene and having an electrical property which varies functionally with variations in intensity of said light
  • said elements comprise a pair of shutter blades movable in sequence to uncover and cover an exposure aperture, said time period running from initiation of movement of the first of said blades to uncover said aperture to termination of movement of the second of said blades to cover said aperture.
  • first shutter operator means selectively operable to permit movement of said blades to said unblocking position, thereby initiating an exposure
  • timing network including a photoconductor exposed to light from said scene and having a resistance which varies functionally with variations in the level of scene brightness;
  • said voltage sensitive trigger circuit being responsive to the resistance of said photoconductor for operating said second shutter operator means and terminating exposure
  • timing network being constructed and ar-

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Shutters For Cameras (AREA)
US150228A 1961-11-06 1961-11-06 Automatic exposure control device Expired - Lifetime US3205795A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US150228A US3205795A (en) 1961-11-06 1961-11-06 Automatic exposure control device
GB40813/62A GB1019932A (en) 1961-11-06 1962-10-29 Automatic exposure control device for photographic purposes
CH1290262A CH429433A (fr) 1961-11-06 1962-11-05 Dispositif automatique de réglage et de commande d'exposition d'un appareil de prise de vues
BE624439A BE624439A (fr) 1961-11-06 1962-11-05 Dispositif automatique pour régler des expositions photographiques

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US150228A US3205795A (en) 1961-11-06 1961-11-06 Automatic exposure control device

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US3205795A true US3205795A (en) 1965-09-14

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BE (1) BE624439A (fr)
CH (1) CH429433A (fr)
GB (1) GB1019932A (fr)

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3257919A (en) * 1962-04-09 1966-06-28 Copal Co Ltd Photographic shutter with automatic control means for exposure time
US3314347A (en) * 1964-10-20 1967-04-18 Agfa Ag Camera shutters
US3393619A (en) * 1964-05-15 1968-07-23 Agfa Ag Automatic exposure control for photographic cameras
US3411421A (en) * 1964-08-27 1968-11-19 Agfa Gevaert Ag Automatic shutter and diaphragm setting device
US3435745A (en) * 1966-11-15 1969-04-01 Ricoh Kk Electric shutter for use in photographic cameras
US3442190A (en) * 1965-07-21 1969-05-06 Honeywell Inc Photographic apparatus
US3482497A (en) * 1967-03-15 1969-12-09 Eastman Kodak Co Automatic exposure control for cameras
US3511145A (en) * 1967-05-30 1970-05-12 Eastman Kodak Co Photographic camera with an exposure control device
US3518928A (en) * 1967-06-30 1970-07-07 Agfa Gevaert Ag Exposure control for photographic cameras
US3611895A (en) * 1968-10-31 1971-10-12 Agfa Gevaert Ag Photographic camera for use in daylight and artificial light
FR2189768A1 (fr) * 1972-05-26 1974-01-25 Seiko Koki Kk
US3810204A (en) * 1971-11-29 1974-05-07 Agfa Gevaert Ag Photographic camera with automatic exposure control arrangement
US3898675A (en) * 1969-10-28 1975-08-05 Nippon Kogaku Kk Camera provided with electronic shutter of the type automatically controlling exposure time
US4209243A (en) * 1978-12-01 1980-06-24 Polaroid Corporation Shutter and trim apparatus
DE3502726A1 (de) * 1984-02-22 1985-08-22 Veb Pentacon Dresden Kamera- Und Kinowerke, Ddr 8021 Dresden Fotografischer verschluss mit elektromagnetischer steuerung

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US1939243A (en) * 1930-01-25 1933-12-12 Eastman Kodak Co Photographic printing apparatus
US1973468A (en) * 1931-05-08 1934-09-11 Eastman Kodak Co Method and means for photographic printing
US2179718A (en) * 1938-06-09 1939-11-14 Nicholas V Fedotoff Automatic camera shutter device
US2179717A (en) * 1939-11-14 Automatic photographic shutter
US2346079A (en) * 1942-09-17 1944-04-04 Honeywell Regulator Co Electrical timing apparatus
US2484299A (en) * 1947-10-20 1949-10-11 Ervin D Labrum System for timing exposure interval of photographic prints
US2572229A (en) * 1947-09-16 1951-10-23 Gen Aniline & Film Corp Electrically operated photographic shutter
US2577774A (en) * 1946-10-09 1951-12-11 Micro Recording Company Automatic exposure timer for cameras
US2856831A (en) * 1953-09-16 1958-10-21 Robert C Gipe High speed light beam shutter mechanism
US2965814A (en) * 1957-05-21 1960-12-20 Zindler Lumoprint Kg Method of and circuit arrangement for timing photographic and other processes
US2978970A (en) * 1956-08-23 1961-04-11 Compur Werk Friedrich Deckel Photographic shutter construction
US2990757A (en) * 1955-04-21 1961-07-04 Cartonnages D Echantillonnage Photographic or cinematographic apparatus and the like
US3020816A (en) * 1959-02-28 1962-02-13 Ernst Leitz Ges Mit Beschrankt Shutter for photographic apparatus
US3027818A (en) * 1959-07-17 1962-04-03 Eastman Kodak Co Automatic exposure control for photographic cameras
US3056332A (en) * 1960-03-18 1962-10-02 Beregowitz Louis Photoelectrically controlled switching circuit
US3063354A (en) * 1959-05-23 1962-11-13 Meopta Narodni Podnik Device for automatically controlling the exposure time for photographic purposes
US3082673A (en) * 1958-04-23 1963-03-26 Yashica Co Ltd Shutter for photographic cameras
US3106666A (en) * 1959-09-23 1963-10-08 Kuckens Electrical time switching apparatus
US3134053A (en) * 1959-02-28 1964-05-19 Firm Gebruder Netzsch Non-constant controls with photoelectric switches

Patent Citations (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2179717A (en) * 1939-11-14 Automatic photographic shutter
US1939243A (en) * 1930-01-25 1933-12-12 Eastman Kodak Co Photographic printing apparatus
US1973468A (en) * 1931-05-08 1934-09-11 Eastman Kodak Co Method and means for photographic printing
US2179718A (en) * 1938-06-09 1939-11-14 Nicholas V Fedotoff Automatic camera shutter device
US2346079A (en) * 1942-09-17 1944-04-04 Honeywell Regulator Co Electrical timing apparatus
US2577774A (en) * 1946-10-09 1951-12-11 Micro Recording Company Automatic exposure timer for cameras
US2572229A (en) * 1947-09-16 1951-10-23 Gen Aniline & Film Corp Electrically operated photographic shutter
US2484299A (en) * 1947-10-20 1949-10-11 Ervin D Labrum System for timing exposure interval of photographic prints
US2856831A (en) * 1953-09-16 1958-10-21 Robert C Gipe High speed light beam shutter mechanism
US2990757A (en) * 1955-04-21 1961-07-04 Cartonnages D Echantillonnage Photographic or cinematographic apparatus and the like
US2978970A (en) * 1956-08-23 1961-04-11 Compur Werk Friedrich Deckel Photographic shutter construction
US2965814A (en) * 1957-05-21 1960-12-20 Zindler Lumoprint Kg Method of and circuit arrangement for timing photographic and other processes
US3082673A (en) * 1958-04-23 1963-03-26 Yashica Co Ltd Shutter for photographic cameras
US3020816A (en) * 1959-02-28 1962-02-13 Ernst Leitz Ges Mit Beschrankt Shutter for photographic apparatus
US3134053A (en) * 1959-02-28 1964-05-19 Firm Gebruder Netzsch Non-constant controls with photoelectric switches
US3063354A (en) * 1959-05-23 1962-11-13 Meopta Narodni Podnik Device for automatically controlling the exposure time for photographic purposes
US3027818A (en) * 1959-07-17 1962-04-03 Eastman Kodak Co Automatic exposure control for photographic cameras
US3106666A (en) * 1959-09-23 1963-10-08 Kuckens Electrical time switching apparatus
US3056332A (en) * 1960-03-18 1962-10-02 Beregowitz Louis Photoelectrically controlled switching circuit

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3257919A (en) * 1962-04-09 1966-06-28 Copal Co Ltd Photographic shutter with automatic control means for exposure time
US3393619A (en) * 1964-05-15 1968-07-23 Agfa Ag Automatic exposure control for photographic cameras
US3411421A (en) * 1964-08-27 1968-11-19 Agfa Gevaert Ag Automatic shutter and diaphragm setting device
US3314347A (en) * 1964-10-20 1967-04-18 Agfa Ag Camera shutters
US3442190A (en) * 1965-07-21 1969-05-06 Honeywell Inc Photographic apparatus
US3435745A (en) * 1966-11-15 1969-04-01 Ricoh Kk Electric shutter for use in photographic cameras
US3482497A (en) * 1967-03-15 1969-12-09 Eastman Kodak Co Automatic exposure control for cameras
US3511145A (en) * 1967-05-30 1970-05-12 Eastman Kodak Co Photographic camera with an exposure control device
US3518928A (en) * 1967-06-30 1970-07-07 Agfa Gevaert Ag Exposure control for photographic cameras
US3611895A (en) * 1968-10-31 1971-10-12 Agfa Gevaert Ag Photographic camera for use in daylight and artificial light
US3898675A (en) * 1969-10-28 1975-08-05 Nippon Kogaku Kk Camera provided with electronic shutter of the type automatically controlling exposure time
US3810204A (en) * 1971-11-29 1974-05-07 Agfa Gevaert Ag Photographic camera with automatic exposure control arrangement
FR2189768A1 (fr) * 1972-05-26 1974-01-25 Seiko Koki Kk
US4209243A (en) * 1978-12-01 1980-06-24 Polaroid Corporation Shutter and trim apparatus
DE3502726A1 (de) * 1984-02-22 1985-08-22 Veb Pentacon Dresden Kamera- Und Kinowerke, Ddr 8021 Dresden Fotografischer verschluss mit elektromagnetischer steuerung

Also Published As

Publication number Publication date
GB1019932A (en) 1966-02-09
BE624439A (fr) 1963-05-06
CH429433A (fr) 1967-01-31

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