US4498753A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Photometric apparatus for cameras
Assignee: Olympus Corp
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Filing: 1983-09-16
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Granted: 1985-02-12
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Expires: 2003-09-16
Abstract
Abstract A photometric apparatus for a camera comprises a reference voltage circuit; an operational amplifier including a photoelectromotive element for photometry, an output terminal of said reference voltage circuit and an input terminal of said amplifier being connected through an impedeance element to a voltage divider tap of a battery; and a switching circuit for switching said reference voltage circuit to an operable condition as well as for changing set resistors which apply a bias current to said operational amplifier, in synchronism with a shutter releasing operation.
Inventors
- 👤 Kazunori Mizokami
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 11:19
CPC Classifications
G; G03; G03B; G03B7/00; G03B7/08; G03B7/10
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
191 words
A photometric apparatus for a camera, comprising: a power source for supplying power to a camera; an impedance element connected to a voltage divider terminal of said power source; a reference voltage circuit whose output terminal is connected to said voltage divider terminal through said impedance element, the circuit producing a reference voltage of a low impedance at said output terminal during its operable condition; an operational amplifier which has an input terminal to which a voltage at the output terminal of said reference voltage circuit is constantly applied and which is constantly in an operable condition with a bias current of an extremely low power consumption, the amplifier producing a logarithmically converted voltage of a photocurrent flowing through a photoelectromotive element for photometry which is connected between both input terminals of said amplifier with a zero bias; and a switching circuit for switching said reference voltage circuit from its inoperable condition and switches said operational amplifier from a condition that a bias current of an extremely low power consumption is supplied to a normal operable condition that a normal bias current is supplied, in synchronism with a photometry initiation signal.
Claim 2
Dependent Claim
191 words
A photometric apparatus for a camera, comprising: a power source for supplying power to a camera; an impedance element connected to a voltage divider terminal of said power source; a reference voltage circuit whose output terminal is connected to said voltage divider terminal through said impedance element, the circuit producing a reference voltage of a low impedance at said output terminal during its operable condition; an operational amplifier which has an input terminal to which a voltage at the output terminal of said reference voltage circuit is constantly applied and which is constantly in an operable condition with a bias current of an extremely low power consumption, the amplifier producing a logarithmically converted voltage of a photocurrent flowing through a photoelectromotive element for photometry which is connected between both input terminals of said amplifier with a zero bias; and a switching circuit for switching said reference voltage circuit from its inoperable condition and switches said operational amplifier from a condition that a bias current of an extremely low power consumption is supplied to a normal operable condition that a normal bias current is supplied, in synchronism with a photometry initiation signal.
Claim 3
Dependent Claim
20 words
A photometric apparatus according to claim 1, in which said impedance element is a resistor of high impedance (high resistance).
Claim 4
Dependent Claim
51 words
A photometric apparatus according to claim 1, in which said reference voltage circuit comprises a transistor circuit which becomes operable by the switching action which is in synchronism with said switching circuit and a variable resistor for presetting a reference voltage at its output terminal while said transistor circuit is operable.
Claim 5
Dependent Claim
110 words
A photometric apparatus according to claim 1, in which said operational amplifier comprises a first set resistor for supplying a bias current sufficient to allow said amplifier to perform a predetermined photometric operation and a second set resistor of high resistance for supplying said amplifier with a bias current under an extremely low power consumption, whereby a bias current is applied through at least said first set resistor to said amplifier by a switching action of said switching circuit in synchronism with a photometry initiation signal and a bias current is applied only by said second set resistor to said amplifier while said switching circuit is in an inoperable condition.
Claim 6
Dependent Claim
89 words
A photometric apparatus according to claim 1, in which said switching circuit comprises a first switching transistor for switching said reference voltage circuit from its inoperable condition to its operable condition by turning said switching circuit on in synchronism with a photometry initiation signal and a second switching transistor for switching said operational amplifier from a condition that a bias current of an extremely low power consumption is supplied to another condition that a normal bias current is supplied concurrently with the switching action of said first switching transistor.
Claim 7
Dependent Claim
169 words
A photometric apparatus for a camera comprising an operational amplifier having first and second input terminals and an output terminal; a photoelectromotive element for photometry coupled across said input terminals; semi-conductor means for producing a logarithmically converted voltage of a photocurrent flowing through the photoelectromotive element coupled between said output terminal and one of said input terminals of said operational amplifier; a power source; a reference voltage circuit having an output coupled to one input of said operational amplifier; coupling means including a voltage divider and impedance means coupled between said power source and one input of said operational amplifier; a switching circuit responsive to a photometry initiated signal for turning on the normally disabled reference voltage circuit, whereby a low voltage reference level is applied to said operational amplifier by said impedence means when said reference voltage circuit is disabled and a voltage reference level of greater voltage value is applied to said operational amplifier by said reference voltage circuit upon the occurrence of said photometry initiate signal.
Claim 8
Dependent Claim
169 words
A photometric apparatus for a camera comprising an operational amplifier having first and second input terminals and an output terminal; a photoelectromotive element for photometry coupled across said input terminals; semi-conductor means for producing a logarithmically converted voltage of a photocurrent flowing through the photoelectromotive element coupled between said output terminal and one of said input terminals of said operational amplifier; a power source; a reference voltage circuit having an output coupled to one input of said operational amplifier; coupling means including a voltage divider and impedance means coupled between said power source and one input of said operational amplifier; a switching circuit responsive to a photometry initiated signal for turning on the normally disabled reference voltage circuit, whereby a low voltage reference level is applied to said operational amplifier by said impedence means when said reference voltage circuit is disabled and a voltage reference level of greater voltage value is applied to said operational amplifier by said reference voltage circuit upon the occurrence of said photometry initiate signal.
Claim 9
Dependent Claim
50 words
The photometric apparatus of claim 6 further comprising a second switching circuit for providing a low bias current to said operational amplifier in the absence of a photometry initiate signal, and for abruptly increasing the bias current provided to said operational amplifier upon the occurrence of said photometry initiate signal.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-02-12 | 1988-08-13 | 1989-02-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-02-12 | 1992-08-13 | 1993-02-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-02-12 | 1996-08-13 | 1997-02-12 | $7700.00 | Window Closed / Lapsed |