US4731529A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Light measuring circuit having circuitry for bypassing a low frequency component in the output of a photoelectric conversion element
Assignee: Canon Inc
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Filing: 1986-04-02
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Granted: 1988-03-15
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Expires: 2006-04-02
Abstract
Abstract A light measuring circuit, consisting of an amplifying circuit amplifying the output of a photoelectric conversion element, is arranged to detect the occurrence of a low frequency component in the output of the photoelectric conversion element that comes to exceed a given level and, upon detection of that, to bypass the output of the photoelectric conversion element to prevent the output of the amplifying circuit from being saturated by a DC light (external or ambient light).
Inventors
- 👤 Toshifumi Ohsawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 05:35
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3084; H04; H04B; H04B10/00; H04B10/60
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
110 words
A DC signal suppression circuit for a photo-signal amplifying circuit using an operational amplifier, comprising: (a) photoelectric conversion means; (b) a parallel circuit consisting of an operational amplifier having an input terminal connected to said photoelectric conversion means, a T type low-pass filter disposed in a negative feedback loop of said operational amplifier, and a resistor; and (c) bypass switching means connected to a contact point between a resistor and a capacitor of said T type low-pass filter, said bypass switching means turning on to bypass a photocurrent from the photoelectric conversion means when a value of a current flowing through the contact point becomes higher than a predetermined value.
Claim 2
Dependent Claim
110 words
A DC signal suppression circuit for a photo-signal amplifying circuit using an operational amplifier, comprising: (a) photoelectric conversion means; (b) a parallel circuit consisting of an operational amplifier having an input terminal connected to said photoelectric conversion means, a T type low-pass filter disposed in a negative feedback loop of said operational amplifier, and a resistor; and (c) bypass switching means connected to a contact point between a resistor and a capacitor of said T type low-pass filter, said bypass switching means turning on to bypass a photocurrent from the photoelectric conversion means when a value of a current flowing through the contact point becomes higher than a predetermined value.
Claim 3
Dependent Claim
35 words
A circuit according to claim 1, wherein said bypass switching means is composed of a transistor, which has a base thereof connected to a voltage dividing point between resistors forming said T type low-pass filter.
Claim 4
Dependent Claim
104 words
A DC signal suppression circuit for a photo-signal amplifying circuit using an operational amplifier, comprising: (a) an operational amplifier; (b) a light receiving element connected between inputs of said operational amplifier; (c) a low-pass filter circuit, composed of a resistor and a capacitor, connected in a feedback path of said operational amplifier; (d) a resistor connected in parallel to said low-pass filter circuit; and (e) a bypass circuit which turns on to bypass a photoelectric current generated in said light receiving element when a value of a photoelectric current flowing through the resistor of said low-pass filter circuit becomes higher than a predetermined value.
Claim 5
Dependent Claim
104 words
A DC signal suppression circuit for a photo-signal amplifying circuit using an operational amplifier, comprising: (a) an operational amplifier; (b) a light receiving element connected between inputs of said operational amplifier; (c) a low-pass filter circuit, composed of a resistor and a capacitor, connected in a feedback path of said operational amplifier; (d) a resistor connected in parallel to said low-pass filter circuit; and (e) a bypass circuit which turns on to bypass a photoelectric current generated in said light receiving element when a value of a photoelectric current flowing through the resistor of said low-pass filter circuit becomes higher than a predetermined value.
Claim 6
Dependent Claim
20 words
A DC signal suppression circuit according to claim 3, wherein said low-pass filter circuit is a T type low-pass filter.
Claim 7
Dependent Claim
18 words
A DC signal suppression circuit according to claim 3, wherein said bypass circuit is composed of a transistor.
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) | 1991-03-15 | 1991-09-14 | 1992-03-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-03-15 | 1995-09-14 | 1996-03-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-03-15 | 1999-09-14 | 2000-03-15 | $7700.00 | Window Closed / Lapsed |