US3673415A - Shutter operating circuit having means to close shutter when light is insufficient - Google Patents
Shutter operating circuit having means to close shutter when light is insufficient Download PDFInfo
- Publication number
- US3673415A US3673415A US86653A US3673415DA US3673415A US 3673415 A US3673415 A US 3673415A US 86653 A US86653 A US 86653A US 3673415D A US3673415D A US 3673415DA US 3673415 A US3673415 A US 3673415A
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- United States
- Prior art keywords
- shutter
- circuit
- resistor
- capacitor
- time determining
- Prior art date
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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
- G03B7/00—Control of exposure by setting shutters, diaphragms or filters, separately or conjointly
- G03B7/08—Control effected solely on the basis of the response, to the intensity of the light received by the camera, of a built-in light-sensitive device
- G03B7/081—Analogue circuits
- G03B7/083—Analogue circuits for control of exposure time
Definitions
- An electric shutter operating circuit functions to determine a proper shutter time in accordance with the brightness of an object to be photographed, but the prior shutter. operating circuit is defective in that it operates to continuously maintain the shutter in the opened condition when the object is very dark.
- a high resistance resistor is connected in parallel with the photoconductive element so as to establish a definite time constant by a capacitor and the resistance valve of the resistor m manifested thereby when the photoconductive element manifests an extremely high resistance whereby to close the shutter after it has been opened for a definite interval of time.
- the photoconductive element or the time constant determining element is a passive element
- the high resistance element connected in parallel therewith operates as desired whereas when the time constant determining element comprises a photo-electromotive element it is impossible to close the shutter with the prior shutter operating circuit utilizing a parallel connected high resistance element.
- FIG. 1 the accompanying drawing blocks A and B show a conventional shutter operating circuit utilizing a photo-electromotive element.
- A represents a shutter time determining-circuit while block B a well known shutter control circuit. Since the construction of the shutter control circuit contained in block B is well known in the art, the detail thereof has been omitted fromthe drawing a source E is connected to the shutter operating circuit through a switch 8,.
- the shutter time determining circuit A comprises a photoelectromotive element P which generates an electromotive force when it is irradiated with light andcooperates with a capacitor C to form a serially connected time constant circuit.
- a switch S connected in parallel with capacitor C is arranged to be opened concurrently with the operation of a shutter release.
- a semiconductor element TR-l a field efiect transistor for example, having a high input impedance characteristic.
- the source electrode of the field effect transistor TR-l is connected to the negative pole of the source E through a variable resistor VRwhereas the drain electrode to the positive pole of the source through a variable resistor R,
- a bleeder circuit comprising a resistor R and a variable resistor R is connected between the positive pole of the source E and the source electrode, and the juncture between these resistors is connected to one side of the photoelectromotive element P.
- the gate electrode of the field effect transistor TR-l is connected to the juncture between the element P and capacitor C
- the negative bias impressed upon the photo-electromotive element P for example a solar cell
- the presently available solar cell having a high signal-to-noise ratio has a very small output, moreover there is a limit for the signal-to-noise ratio and the internal resistance of the solar cell is very high, for example more than several thousand megohms. It is impossible to prevent permanent opening of the shutter even when a high resistance resistor is connected in parallel with the photo-electromotive element.
- More specific object of this invention is to provide a novel shutter operating circuit which can positively close the shutter of a camera even when the brightness of an object is not sufficiently high.
- a shutter operating circuit comprising a shutter time determining circuit including a photo-electromotive element and a high input impedance transistor; means to initiate the operation of the shutter time determining circuit; a shutter control circuit. controlled by the shutter time determining circuit; and a source of supply connected to two circuits described above, there are provided a series circuit including a resistor and a capacitor which is connected across the source and a switching transistor with its base electrode connected to the juncture between the resistor and the capacitor, the series circuit acting to trigger the switching transistor to operate the shutter control circuit when the shutter time determining circuit fails to operate after elapse of a predetermined interval after the operation of the initiating means.
- FIGURE shows a block diagram of one example of the shutter operating circuit embodying this invention.
- a series circuit including a resistor R and a capacitor C is connected across E source through switch S and the juncture between resistor R and capacitor C is connected to the base electrode a switching transistor TR-2.
- the emitter electrode of this transistor is connected to the negative pole of source E through a potentiometer resistor R whereas the collector electrode of transistor TR-2 is connected to the drain electrode of the field effect transistor TR-l.
- Resistor R and capacitor C comprises a time constant circuit that determines an instant at which switching transistor TR-2 becomes conductive, the time constant being determined by a preset interval between the opening of the shutter caused by a release button and an instant at which the shutter should be closed.
- the time constant is determined by the product of the resistance of resistor R and the capacitance of capacitor C In operation, switch S is closed. Concurrently with the operation of the shutter release, short circuiting switch S is opened.
- the output current from the photo-electromotive element P commences to charge capacitor C Where the light impinging upon the photo-electromotive element P is extremely weak so that the voltage across capacitor C does not build up to a valve suflicient to turn ON transistor TR-l, this transistor will not be rendered conductive by the capacitor voltage so that the shutter will be maintained in the opened state.
- capacitor C is charged by source E through switch S, and resistor R to a voltage sufficient to render conductive transistor TR-2 during the predetermined interval.
- transistor TR-2 controls the shutter control circuit B as if the field effect transistor TR-1 were rendered conductive, thus closing the shutter.
- the interval which is determined by the resistor R and the capacitor C can be made variable.
- An example of this construction is provided, as shown in the drawing by connecting another resistor R through a switch S across the resistor R When the switch S, is closed, the time constant obtained by the resultant resistance of the resistor parallel circuit and the capacitor C becomes decreased and therefore said interval becomes short.
- Such a shutter operating circuit as this embodiment is useful for an automatic shutter camera for use with photoflash device.
- this invention provides a new and improved shutter control circuit which assures desired shutter opening period under adverse light conditions.
- a shutter operating circuit comprising a shutter time determining circuit including a photo-electromotive element and a high input impedance transistor; means to initiate the operation of said shutter time determining circuit; a shutter control circuit controlled by said shutter time determining circuit; and a source of supply connected to said two circuits, the improvement which comprises a series circuit connected across said source and including serially connected a first resistor and capacitor and a switching transistor with its base electrode connected to the juncture between said resistor and capacitor, said series circuit acting to trigger said switching transistor to operate said shutter control circuit when said shutter time determining circuit fails to operate after elapse of a predetermined interval after the operation of said initiating means.
- the shutter operating circuit according to claim 1 is further provided with the second resistor connectable across said first resistor of said series circuit and a switch adapted to connect said second resistor in parallel with said first resistor.
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Transforming Light Signals Into Electric Signals (AREA)
Abstract
In a shutter operating circuit comprising a shutter time determining circuit including a photo-electromotive element, and a high input impedance transistor; means to initiate the operation of the shutter time determining circuit; a shutter control circuit controlled by the shutter time determining circuit; and a source of supply connected to said two circuits, there are provided a series circuit connected across the source and including serially connected resistor and capacitor, and a switching transistor with its base electrode connected to the juncture between the resistor and the capacitor, the series circuit acting to trigger the switching transistor to operate the shutter control circuit when the shutter time determining circuit fails to operate after elapse of a predetermined interval after the operation of the initiating means.
Description
United States Patent Yoshimura et a].
[ 1 June 27, 1972 l/l969 Mori et al. ..95/l0CT 12/1969 Fuwa et a1 ..250/2l2 X Primary Examiner-James W. Lawrence [72] inventors: Hirof'umi Yoshimura, Okaya; Hisatoshi Ass[s,ammmine, 1- Grigsby fakaham, shlmosuwa'Mach" both of AttameyChittick, Pfund, Birch, Samuels & Gauthier apan I [73] Assignee: Yashica Company Limited, Tokyo, Japan [57] ABSTRACT [22 Fil d; No 4 1970 in a shutter operating circuit comprising a shutter time determining circuit including a photo-electromotive element, and a [2n Appl' 86653 high input impedance transistor; means to initiate the operation of the shutter time determining circuit; a shutter control 30 F i Application priority Data circuit controlled by the shutter time determining circuit; and a source of supply connected to said two circuits, there are NOV. 8, 1969 Japan ..44/105631 p i a Series circuit Connected across the Source and cluding serially connected resistor and capacitor, and a if zs switching transistor with its base electrode connected to the E g 0 juncture between the resistor and the capacitor, the series ciro arc cuit acting to trigger the switching transistor to operate the shutter control circuit when the shutter time determining cir- [56] References Cited cuit fails to operate after elapse of a predetermined interval U D STATES PATENTS after the operation of the initiating means.
3,326,103 6/1967 Topaz ..95/l0 CT 4 Claims, 1 Drawing Figure --L SHUTTER TIME DETERMINING CIRCUIT I 6? 8 RI}? EH3? 4 P O SHUTTER Y CONTROL S2 l CIRCUIT TR-2 TR-l R2 E 2R5 Cl VR I PKTENTEDJUHZT I972 3673.415
A B SHUTTER TIME DETERMINING CIRCUIT Mr RI gm? SHUTTER L CONTROL {S2 CIRCUIT INVENTOR S HIROFUM I YOSHIMURA HISA'IOSHI TAKAHATA SHUTTER OPERATING CIRCUIT HAVING MEANS TO CLOSE SHU'I'IER WHEN LIGHT IS INSUI FICIENT BACKGROUND OF THE INVENTION This invention relates to a shutter operating circuit for cameras, and more particularly to a shutter operating circuit employing a photo-electromotive element.
1 An electric shutter operating circuit functions to determine a proper shutter time in accordance with the brightness of an object to be photographed, but the prior shutter. operating circuit is defective in that it operates to continuously maintain the shutter in the opened condition when the object is very dark. In the prior art shutter operating circuit utilizing a photoconductive element as means for determining the shutter time, for the purpose of eliminating this difirculty, a high resistance resistor is connected in parallel with the photoconductive element so as to establish a definite time constant by a capacitor and the resistance valve of the resistor m manifested thereby when the photoconductive element manifests an extremely high resistance whereby to close the shutter after it has been opened for a definite interval of time. Such idea has been disclosed in, for example, specifications of the US. Pat. Nos. 3,326,103 and 3,422,738.
When the photoconductive element or the time constant determining element is a passive element, the high resistance element connected in parallel therewith operates as desired whereas when the time constant determining element comprises a photo-electromotive element it is impossible to close the shutter with the prior shutter operating circuit utilizing a parallel connected high resistance element.
In. the accompanying drawing blocks A and B show a conventional shutter operating circuit utilizing a photo-electromotive element. 'More particularly, A represents a shutter time determining-circuit while block B a well known shutter control circuit. Since the construction of the shutter control circuit contained in block B is well known in the art, the detail thereof has been omitted fromthe drawing a source E is connected to the shutter operating circuit through a switch 8,. The shutter time determining circuit A comprises a photoelectromotive element P which generates an electromotive force when it is irradiated with light andcooperates with a capacitor C to form a serially connected time constant circuit. A switch S connected in parallel with capacitor C is arranged to be opened concurrently with the operation of a shutter release. There is'provided a semiconductor element TR-l a field efiect transistor for example, having a high input impedance characteristic. The source electrode of the field effect transistor TR-l is connected to the negative pole of the source E through a variable resistor VRwhereas the drain electrode to the positive pole of the source through a variable resistor R,, a bleeder circuit comprising a resistor R and a variable resistor R is connected between the positive pole of the source E and the source electrode, and the juncture between these resistors is connected to one side of the photoelectromotive element P. The gate electrode of the field effect transistor TR-l is connected to the juncture between the element P and capacitor C In the circuit constructed as above described, in order to eliminate the effect of the dark current upon the switching time it is necessary to decrease the negative bias impressed upon the photo-electromotive element P, for example a solar cell, thus decreasing the dark current. The presently available solar cell having a high signal-to-noise ratio has a very small output, moreover there is a limit for the signal-to-noise ratio and the internal resistance of the solar cell is very high, for example more than several thousand megohms. It is impossible to prevent permanent opening of the shutter even when a high resistance resistor is connected in parallel with the photo-electromotive element.
SUMMARY OF THE INVENTION It is the principal object of this invention to obviate aforementioned defects.
More specific object of this invention is to provide a novel shutter operating circuit which can positively close the shutter of a camera even when the brightness of an object is not sufficiently high.
According to this invention, in a shutter operating circuit comprising a shutter time determining circuit including a photo-electromotive element and a high input impedance transistor; means to initiate the operation of the shutter time determining circuit; a shutter control circuit. controlled by the shutter time determining circuit; and a source of supply connected to two circuits described above, there are provided a series circuit including a resistor and a capacitor which is connected across the source and a switching transistor with its base electrode connected to the juncture between the resistor and the capacitor, the series circuit acting to trigger the switching transistor to operate the shutter control circuit when the shutter time determining circuit fails to operate after elapse of a predetermined interval after the operation of the initiating means.
BRIEF DESCRIPTION OF THE DRAWING The invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawing in which a single FIGURE shows a block diagram of one example of the shutter operating circuit embodying this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT According to this invention, a series circuit including a resistor R and a capacitor C is connected across E source through switch S and the juncture between resistor R and capacitor C is connected to the base electrode a switching transistor TR-2. The emitter electrode of this transistor is connected to the negative pole of source E through a potentiometer resistor R whereas the collector electrode of transistor TR-2 is connected to the drain electrode of the field effect transistor TR-l.
Resistor R and capacitor C comprises a time constant circuit that determines an instant at which switching transistor TR-2 becomes conductive, the time constant being determined by a preset interval between the opening of the shutter caused by a release button and an instant at which the shutter should be closed. The time constant is determined by the product of the resistance of resistor R and the capacitance of capacitor C In operation, switch S is closed. Concurrently with the operation of the shutter release, short circuiting switch S is opened. The output current from the photo-electromotive element P commences to charge capacitor C Where the light impinging upon the photo-electromotive element P is extremely weak so that the voltage across capacitor C does not build up to a valve suflicient to turn ON transistor TR-l, this transistor will not be rendered conductive by the capacitor voltage so that the shutter will be maintained in the opened state. However, according to this invention, capacitor C is charged by source E through switch S, and resistor R to a voltage sufficient to render conductive transistor TR-2 during the predetermined interval. As a result, transistor TR-2 controls the shutter control circuit B as if the field effect transistor TR-1 were rendered conductive, thus closing the shutter.
In accordance with another embodiment of this invention, the interval which is determined by the resistor R and the capacitor C, can be made variable. An example of this construction is provided, as shown in the drawing by connecting another resistor R through a switch S across the resistor R When the switch S, is closed, the time constant obtained by the resultant resistance of the resistor parallel circuit and the capacitor C becomes decreased and therefore said interval becomes short. Such a shutter operating circuit as this embodiment is useful for an automatic shutter camera for use with photoflash device.
Thus, this invention provides a new and improved shutter control circuit which assures desired shutter opening period under adverse light conditions.
It will be clear that the invention is not limited to the particular embodiment illustrated and that many changes and modifications will occur to one skilled in the art within the true scope and spirit of the invention as defined in the ap pended claims.
What is claimed is:
1. In a shutter operating circuit comprising a shutter time determining circuit including a photo-electromotive element and a high input impedance transistor; means to initiate the operation of said shutter time determining circuit; a shutter control circuit controlled by said shutter time determining circuit; and a source of supply connected to said two circuits, the improvement which comprises a series circuit connected across said source and including serially connected a first resistor and capacitor and a switching transistor with its base electrode connected to the juncture between said resistor and capacitor, said series circuit acting to trigger said switching transistor to operate said shutter control circuit when said shutter time determining circuit fails to operate after elapse of a predetermined interval after the operation of said initiating means.
2. The shutter operating circuit according to claim 1 wherein said photo-electromotive circuit is connected in series with a capacitor which is normally short circuit by a switch which is opened when a shutter release is operated so that when an object to be photographed has sufficient light, said photo-electromotive element charges said capacitor within a predetermined interval to trigger said high input impedance transistor.
3. The shutter operating circuit according to claim 1 wherein said first resistor is a variable resistor.
4. The shutter operating circuit according to claim 1 is further provided with the second resistor connectable across said first resistor of said series circuit and a switch adapted to connect said second resistor in parallel with said first resistor.
Claims (4)
1. In a shutter operating circuit comprising a shutter time determining circuit including a photo-electromotive element and a high input impedance transistor; means to initiate the operation of said shutter time determining circuit; a shutter control circuit controlled by said shutter time determining circuit; and a source of supply connected to said two circuits, the improvement which comprises a series circuit connected across said source and including serially connected a first resistor and capacitor and a switching transistor with its base electrode connected to the juncture between said resistor and capacitor, said series circuit acting to trigger said switching transistor to operate said shutter control circuit when said shutter time determining circuit fails to operate after elapse of a predetermined interval after the operation of said initiating means.
2. The shutter operating circuit according to claim 1 wherein said photo-electromotive circuit is connected in series with a capacitor which is normally short circuit by a switch which is opened when a shutter release is operated so that when an object to be photographed has sufficient light, said photo-electromotive element charges said capacitor within a predetermined interval to trigger said high input impedance transistor.
3. The shutter operating circuit according to claim 1 wherein said first resistor is a variable resistor.
4. The shutter operating circuit according to claim 1 is further provided with the second resistor connectable across said first resistor of said series circuit and a switch adapted to connect said second resistor in parallel with said first resistor.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10563169 | 1969-11-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3673415A true US3673415A (en) | 1972-06-27 |
Family
ID=14412804
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US86653A Expired - Lifetime US3673415A (en) | 1969-11-08 | 1970-11-04 | Shutter operating circuit having means to close shutter when light is insufficient |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US3673415A (en) |
| DE (1) | DE2054751A1 (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3769886A (en) * | 1971-08-06 | 1973-11-06 | Asahi Optical Co Ltd | Shutter operating mechanism having an automatic exposure time control means for photographic camera |
| US3849786A (en) * | 1971-12-10 | 1974-11-19 | Minolta Camera Kk | Light integrating type light detector circuit with photovoltaic cell |
| US3864565A (en) * | 1972-09-21 | 1975-02-04 | Asahi Optical Co Ltd | Light amount integration means |
| US4037237A (en) * | 1975-11-12 | 1977-07-19 | Eastman Kodak Company | Exposure control apparatus |
| US4052726A (en) * | 1973-06-14 | 1977-10-04 | Eastman Kodak Company | Exposure control apparatus |
| US4190335A (en) * | 1976-10-16 | 1980-02-26 | Olympus Optical Company, Ltd. | Shutter controlling aid means for use with camera |
| US4214825A (en) * | 1976-12-03 | 1980-07-29 | Olympus Optical Co., Ltd. | Shutter control means with auto strobo for electrical shutter camera |
| US5175484A (en) * | 1988-09-26 | 1992-12-29 | Power Beat International, Ltd. | Electrical power distribution |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3326103A (en) * | 1964-12-09 | 1967-06-20 | Polaroid Corp | Auxiliary shutter timing mechanism |
| US3422738A (en) * | 1964-07-24 | 1969-01-21 | Citizen Watch Co Ltd | Automatic exposure flash camera |
| US3485152A (en) * | 1966-03-05 | 1969-12-23 | Ricoh Kk | Photographic camera incorporating a battery charger |
-
1970
- 1970-11-04 US US86653A patent/US3673415A/en not_active Expired - Lifetime
- 1970-11-06 DE DE19702054751 patent/DE2054751A1/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3422738A (en) * | 1964-07-24 | 1969-01-21 | Citizen Watch Co Ltd | Automatic exposure flash camera |
| US3326103A (en) * | 1964-12-09 | 1967-06-20 | Polaroid Corp | Auxiliary shutter timing mechanism |
| US3485152A (en) * | 1966-03-05 | 1969-12-23 | Ricoh Kk | Photographic camera incorporating a battery charger |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3769886A (en) * | 1971-08-06 | 1973-11-06 | Asahi Optical Co Ltd | Shutter operating mechanism having an automatic exposure time control means for photographic camera |
| US3849786A (en) * | 1971-12-10 | 1974-11-19 | Minolta Camera Kk | Light integrating type light detector circuit with photovoltaic cell |
| US3864565A (en) * | 1972-09-21 | 1975-02-04 | Asahi Optical Co Ltd | Light amount integration means |
| US4052726A (en) * | 1973-06-14 | 1977-10-04 | Eastman Kodak Company | Exposure control apparatus |
| US4037237A (en) * | 1975-11-12 | 1977-07-19 | Eastman Kodak Company | Exposure control apparatus |
| US4190335A (en) * | 1976-10-16 | 1980-02-26 | Olympus Optical Company, Ltd. | Shutter controlling aid means for use with camera |
| US4214825A (en) * | 1976-12-03 | 1980-07-29 | Olympus Optical Co., Ltd. | Shutter control means with auto strobo for electrical shutter camera |
| US5175484A (en) * | 1988-09-26 | 1992-12-29 | Power Beat International, Ltd. | Electrical power distribution |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2054751A1 (en) | 1971-05-27 |
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