US3864701A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic exposure control circuit
Assignee: Siemens AG
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Filing: 1973-03-02
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Granted: 1975-02-04
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Expires: 1993-03-02
Abstract
Abstract An automatic exposure control circuit for a camera employs a photo-responsive semiconductor device disposed in position to receive light emitted from a scene to be photographed through a filter wheel which is, when exposure is initiated, rotated to vary the density of the filter interposed between the photoresponsive semi-conductor and the scene to be photographed. the rising current characteristic produced by the photo-responsive semiconductor is amplified by a differential amplifier having a negative feed-back network including a low pass filter, and a positive feed-back network establishing a predetermined threshold voltage for the output of the differential amplifier. The time at which the threshold of the positive feed-back circuit is reached is dependent upon the density of light received from the scene to be photographed, and the differential amplifier produces an output pulse which is encoded in time position in correspondence to the intensity of the illumination in the scene to be photographed.
Inventors
- 👤 Gerhard Krause
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 18:29
CPC Classifications
G; G03; G03B; G03B7/00; G03B7/08; G03B7/081; G03B7/083
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
105 words
In a camera having a shutter and a device, means for exposing said photoresponsive device to light from a scene to be photographed, and means for varying the amount of such exposure during the open period of said camera shutter the combination comprising an amplifier with high pass characteristic, means for connecting an input of said amplifier with said photoresponsive device, and a threshold value detector connected with the output of said amplifier and adapted to respond to the signal produced at the output of said amplifier to produce a control signal adapted for use in effecting the setting of the exposure of the camera.
Claim 2
Dependent Claim
105 words
In a camera having a shutter and a device, means for exposing said photoresponsive device to light from a scene to be photographed, and means for varying the amount of such exposure during the open period of said camera shutter the combination comprising an amplifier with high pass characteristic, means for connecting an input of said amplifier with said photoresponsive device, and a threshold value detector connected with the output of said amplifier and adapted to respond to the signal produced at the output of said amplifier to produce a control signal adapted for use in effecting the setting of the exposure of the camera.
Claim 3
Dependent Claim
47 words
Apparatus according to claim 1 wherein said amplifier is an operational amplifier having inverting and non-inverting inputs, said inverting input being connected with said photo-responsive device, and including a negative feed-back network having a low-pass characteristic interconnected between the output of said amplifier and said inverting input.
Claim 4
Dependent Claim
24 words
Apparatus according to claim 2, wherein said threshold value detector produces said control signal when the output of said amplifier exceeds said threshold value.
Claim 5
Dependent Claim
19 words
Apparatus according to claim 3, including positive feedback means interconnecting the output of said amplifier to said non-inverting input.
Claim 6
Dependent Claim
51 words
Apparatus according to claim 4 wherein said positive feedback means includes an element having a nonlinear current-voltage characteristic in which the rate of change in current flowing through such element as a result of a unit change in voltage drop across said element increases for increasing values of said voltage drop.
Claim 7
Dependent Claim
12 words
Apparatus according to claim 5, wherein said feed-back element is a diode.
Claim 8
Dependent Claim
61 words
Apparatus according to claim 1, including a resistor connected between the output of said amplifier and an inverting input of said amplifier to furnish negative feedback to said inverting input, and a switch interconnected in parallel with said resistor, said switch being adapted to be opened at a predetermined instant after actuation of the camera release to initiate an exposure interval.
Claim 9
Dependent Claim
28 words
Apparatus according to claim 1, including an operating voltage source, and means for connecting said operational amplifier with said voltage source at the beginning of said exposure interval.
Claim 10
Dependent Claim
110 words
An electronic shutter control for a shutter, said control comprising a photoresponsive device, means for exposing said photoresponsive device to light from a scene to be photographed during the open period of said shutter, means for varying the amount of such exposure during an exposure period, an amplifier connected with said photoresponsive device for amplifying an electrical signal produced thereby in response to the light to which it is exposed, and means for selectively applying positive feedback to said amplifier when said electrical signal reaches a predetermined value, whereby said amplifier produces a pulse for controlling a shutter at a time coincident with said electrical signal reaching said predetermined value.
Claim 11
Dependent Claim
110 words
An electronic shutter control for a shutter, said control comprising a photoresponsive device, means for exposing said photoresponsive device to light from a scene to be photographed during the open period of said shutter, means for varying the amount of such exposure during an exposure period, an amplifier connected with said photoresponsive device for amplifying an electrical signal produced thereby in response to the light to which it is exposed, and means for selectively applying positive feedback to said amplifier when said electrical signal reaches a predetermined value, whereby said amplifier produces a pulse for controlling a shutter at a time coincident with said electrical signal reaching said predetermined value.
Claim 12
Dependent Claim
33 words
Apparatus according to claim 9, wherein said means for selectively applying positive feedback to said amplifier comprises a diode connected between the output of said amplifier and a non-inverting input of said amplifier.
Claim 13
Dependent Claim
175 words
In a camera having a photo-responsive device, means for exposing said photo-responsive device to light from a scene to be photographed, and means for varying the amount of such exposure during the exposure period of said camera, the combination comprising an operational amplifier with a high-pass characteristic, said amplifier having inverting and non-inverting inputs, means for connecting said inverting input of said amplifier with said photo-responsive device, a threshold value detector connected with the output of said amplifier and adapted to respond to the signal produced at the output of said amplifier to produce a control signal adapted for use in effecting the setting of the exposure of the camera, and a negative feedback network having a low-pass characteristic interconnected between the output of said amplifier and said inverting input, said negative feedback network comprising a pair of resistors interconnected in series between the output of said amplifier and said inverting input, and a series circuit including a resistor and a capacitor connected between the junction of said pair of resistors and a reference potential.
Claim 14
Dependent Claim
175 words
In a camera having a photo-responsive device, means for exposing said photo-responsive device to light from a scene to be photographed, and means for varying the amount of such exposure during the exposure period of said camera, the combination comprising an operational amplifier with a high-pass characteristic, said amplifier having inverting and non-inverting inputs, means for connecting said inverting input of said amplifier with said photo-responsive device, a threshold value detector connected with the output of said amplifier and adapted to respond to the signal produced at the output of said amplifier to produce a control signal adapted for use in effecting the setting of the exposure of the camera, and a negative feedback network having a low-pass characteristic interconnected between the output of said amplifier and said inverting input, said negative feedback network comprising a pair of resistors interconnected in series between the output of said amplifier and said inverting input, and a series circuit including a resistor and a capacitor connected between the junction of said pair of resistors and a reference potential.
Claim 15
Dependent Claim
134 words
An electronic shutter control comprising a photo-responsive device, means for exposing said photo-responsive device to light from a scene to be photogaphed, means for varying the amount of such exposure during an exposure period, an amplifier connected with said photo-responsive device for amplifying an electrical signal produced thereby in response to the light to which it is exposed, a diode connected between the output of said amplifier and a non-inverting input of said amplifier for selectively applying positive feedback to said amplifier when said electrical signal reaches a predetermined value, whereby said amplifier produces a pulse for controlling a shutter at a time coincident with said electrical signal reaching said predetermined value, and a low-pass filter means for applying negative feedback to said amplifier for re-establishing a quiescent condition of operation following said pulse.
Claim 16
Dependent Claim
134 words
An electronic shutter control comprising a photo-responsive device, means for exposing said photo-responsive device to light from a scene to be photogaphed, means for varying the amount of such exposure during an exposure period, an amplifier connected with said photo-responsive device for amplifying an electrical signal produced thereby in response to the light to which it is exposed, a diode connected between the output of said amplifier and a non-inverting input of said amplifier for selectively applying positive feedback to said amplifier when said electrical signal reaches a predetermined value, whereby said amplifier produces a pulse for controlling a shutter at a time coincident with said electrical signal reaching said predetermined value, and a low-pass filter means for applying negative feedback to said amplifier for re-establishing a quiescent condition of operation following said pulse.
References Cited (Backward Citations)
US3426357A
Cited
US3679905A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-02-03 | 1978-08-05 | 1979-02-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-03 | 1982-08-05 | 1983-02-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-03 | 1986-08-05 | 1987-02-04 | $7700.00 | Window Closed / Lapsed |