Patent US3574443A successfully refreshed from Google Patents.
US3574443A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for determining the quantity of time-integrated light
Assignee: Minolta Co Ltd
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Filing: 1969-02-07
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Granted: 1971-04-13
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Expires: 1989-02-07
Abstract
Abstract The present invention concerns an apparatus using a transistor circuit including a photocell for determining the quantity of time-integrated light and it specifically concerns a flash exposure meter which determines the time-integrated value of the light reflected from the object illuminated by the flash light or the incident light on the object.
Inventors
- 👤 Yasuhiro Nanba
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 16:25
CPC Classifications
G; G01; G01J; G01J1/00; G01J1/42; G01J1/4209; G01J1/4214; G01J1/44; G01J1/46
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
137 words
Light integrating switching apparatus, comprising: a constant DC power source, photoconductive means for producing photoelectric current in response to light incident thereon, means for amplifying said electric current to produce a linear current output, means for integrating said linear current output, said means including an integrating condenser serially connected to a first diode and a second diode parallelly connected with said condenser and said first diode, said first and second diodes each having a terminal voltage proportional to the logarithm of current through the diode so that said condenser integrates said linear current output to provide a voltage proportional to the logarithm of said photoelectric current, timing control means including an RC delay circuit for controlling the charging time of said means for integrating, means for detecting said integrated voltage, and means for indicating said detected voltage.
Claim 2
Dependent Claim
137 words
Light integrating switching apparatus, comprising: a constant DC power source, photoconductive means for producing photoelectric current in response to light incident thereon, means for amplifying said electric current to produce a linear current output, means for integrating said linear current output, said means including an integrating condenser serially connected to a first diode and a second diode parallelly connected with said condenser and said first diode, said first and second diodes each having a terminal voltage proportional to the logarithm of current through the diode so that said condenser integrates said linear current output to provide a voltage proportional to the logarithm of said photoelectric current, timing control means including an RC delay circuit for controlling the charging time of said means for integrating, means for detecting said integrated voltage, and means for indicating said detected voltage.
Claim 3
Dependent Claim
76 words
Light integrating apparatus as in claim 1 further comprising a power source switch connected in series with said DC power source: a discharge switch for discharging said condenser, means for providing a flash light output, said means including a flash trigger switch sErially connected therewith, and said switches are constructed so that when said discharge switch is ''''off'''' said power source switch is ''''on'''' and said flash trigger switch is ''''on'''' after a predetermined time delay.
Claim 4
Dependent Claim
22 words
Light integrating apparatus as in claim 1 wherein the resistance in said timing control means is variable for varying the delay time.
Claim 5
Dependent Claim
79 words
Light integrating apparatus as in claim 1 wherein said means for amplifying includes feedback means for maintaining the terminal voltage of said photoconductive means constant and means for establishing the operating point of said photoconductive means to provide a photoelectric current output therefrom proportional to the intensity of light incident thereon, said means for amplifying further includes a differential amplifier composed of field effect transistors and said photoconductive means is connected between the gates of said field effect transistors.
Claim 6
Dependent Claim
50 words
Light integrating apparatus as in claim 4 wherein said means for indicating includes a scale band movable in accordance with the sensitivity of a film and having scale spacings in accordance with exposure values of said film whereby a required exposure is automatically obtained corresponding to a given film sensitivity.
Claim 7
Dependent Claim
35 words
Light integrating apparatus as in claim 5 wherein said means for detecting includes another differential amplifier including additional field effect transistors, said integrating condenser is connected between the gates of said additional field effect transistors.
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) | 1974-04-12 | 1974-10-12 | 1975-04-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-04-12 | 1978-10-12 | 1979-04-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-04-12 | 1982-10-12 | 1983-04-13 | $7700.00 | Window Closed / Lapsed |