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US3712190A Expired / Lapsed US ⏱️ 0.0 years remaining

Automatic exposure controls for cameras

Assignee: Pentax Corp
•
Filing: 1971-11-24
•
Granted: 1973-01-23
•
Expires: 1991-11-24
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Abstract

Abstract A camera having circuitry for automatically determining exposure of film in the camera. The circuitry includes a photosensitive element for receiving light from the object to be photographed and for converting the light into a corresponding electrical signal which varies according to a geometric progression. The signal is stored by a capacitor in the form of a voltage which varies according to an arithmetic progression. A logarithmically operating structure which includes at least one diode is electrically connected between the photosensitive element and the capacitor for converting the geometrically varying signal from the photosensitive element into the arithmetically varying signal stored as a voltage by the capacitor and for reconverting the signal stored at the capacitor into a geometrically varying signal which corresponds precisely to that of the photosensitive element, this logarithmetically operating structure functioning to convert the signal stored at the capacitor into the geometrically varying signal in precisely the same way that the signal was initially converted from the geometrically varying signal of the photosensitive element into the arithmetically varying signal stored as a voltage by the capacitor. An oscillating circuit receives the signal from the capacitor after it has been converted back into a signal varying according to a geometric progression by the logarithmetically operating structure, and this oscillating circuit drives shutter-operating structure which operates to open and close the shutter in accordance with the frequency of pulses of the oscillating circuit, this latter frequency being determined by the signal derived from the capacitor.

Inventors

  • 👤 T Nobusawa

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-28 08:31
CPC Classifications
G; G03; G03B; G03B7/00; G03B7/08; G03B7/081; G03B7/083

Claims Analysis

Total Claims: 8
Claim 1
Independent Claim 278 words
In a camera, photosensitive means for receiving the light from an object which is to be photographed and for converting the received light into a corresponding electrical signal which varies according to a geometric progression, storing means for storing the latter signal as a voltage which varies according to an arithmetic progression, logarithmic means electrically connected with said photosensitive means and storing means for converting the signal from said photosensitive means which varies according to a geometric progression into a signal which varies according to an arithmetic progression and which is stored as said voltage by said storing means and for reconverting the stored signal at said storing means back into a signal which varies according to a geometric progression, said logarithmic means coacting with said photosensitive means and with said storing means for converting the signal stored at the latter back into a signal varying according to a geometric progression in precisely the same way that the signal was initially converted when transmitted by said logarithmic means from said photosensitive means to said storing means, so that the signal taken from the storing means corresponds precisely to the signal produced by said photosensitive means with the light received thereby, oscillating circuit means electrically connected with said logarithmic means to be operated by the latter for providing pulses at a frequency determined by the signal derived from said storing means by said logarithmic means, and shutter-operating means electrically connected to said oscillating circuit means to be driven thereby for first opening and then closing a shutter in accordance with the operation of said oscillating circuit means by said logarithmic means with the signal derived from said storing means.
Claim 2
Dependent Claim 278 words
In a camera, photosensitive means for receiving the light from an object which is to be photographed and for converting the received light into a corresponding electrical signal which varies according to a geometric progression, storing means for storing the latter signal as a voltage which varies according to an arithmetic progression, logarithmic means electrically connected with said photosensitive means and storing means for converting the signal from said photosensitive means which varies according to a geometric progression into a signal which varies according to an arithmetic progression and which is stored as said voltage by said storing means and for reconverting the stored signal at said storing means back into a signal which varies according to a geometric progression, said logarithmic means coacting with said photosensitive means and with said storing means for converting the signal stored at the latter back into a signal varying according to a geometric progression in precisely the same way that the signal was initially converted when transmitted by said logarithmic means from said photosensitive means to said storing means, so that the signal taken from the storing means corresponds precisely to the signal produced by said photosensitive means with the light received thereby, oscillating circuit means electrically connected with said logarithmic means to be operated by the latter for providing pulses at a frequency determined by the signal derived from said storing means by said logarithmic means, and shutter-operating means electrically connected to said oscillating circuit means to be driven thereby for first opening and then closing a shutter in accordance with the operation of said oscillating circuit means by said logarithmic means with the signal derived from said storing means.
Claim 3
Dependent Claim 13 words
The combination of claim 1 and wherein said storing means is a capacitor.
Claim 4
Dependent Claim 54 words
The combination of claim 1 and wherein said logarithmic means includes a pair of diodes one of which is electrically connected between said photosensitive means and said storing means and the other of which is electrically connected between said storing means and said oscillating circuit means, said pair of diodes having the same characteristics.
Claim 5
Dependent Claim 44 words
The combination of claim 1 and wherein said logarithmic means includes a single diode and a switch Means electrically connected therewith for connecting said single diode first between said photosensitive means and storing means and then between said storing means and oscillating circuit means.
Claim 6
Dependent Claim 86 words
The combination of claim 1 and wherein said shutter-operating means includes a pair of relays for respectively opening and closing a shutter, a pair of thyristors electrically connected with said relays for respectively actuating the latter, and electrical means electrically interconnecting said oscillating circuit means and said pair of thyristors for respectively firing the latter with an interval between the firing thereof determined by the operation of said oscillating circuit means with the signal transmitted to the latter from said storing means by said logarithmic means.
Claim 7
Dependent Claim 15 words
The combination of claim 5 and wherein said oscillating circuit means includes a unijunction transistor.
Claim 8
Dependent Claim 14 words
The combination of claim 5 and wherein said oscillating circuit means includes a multivibrator.

References Cited (Backward Citations)

DE2062606A1 Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1976-01-23 1976-07-24 1977-01-23 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1980-01-23 1980-07-24 1981-01-23 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1984-01-23 1984-07-24 1985-01-23 $7700.00 Window Closed / Lapsed

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