Patent US3582220A successfully refreshed from Google Patents.
US3582220A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Light contrast meter for measuring the difference between maximum light intensity and immediately incident light intensity or other intensity
Assignee: Pentax Corp
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Filing: 1969-02-18
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Granted: 1971-06-01
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Expires: 1989-02-18
Abstract
Abstract A light contrast meter successively exposable to different light intensities provides a visual indication of the light intensity extremes or the difference between the light intensity extreme and the immediate incident light. In one form a capacitor is charged through a diode to a voltage corresponding to maximum incident light and is connected in series with an impedance the voltage across which varies with the incident light and a meter measures the difference of this voltage and that across the capacitor. In another form a pair of photoconductors are connected in series with respective resistors one capacitor being connected through a diode across the first resistor and another capacitor being connected through a diode across the second photoconductor and meters measure the capacitor voltages.
Inventors
- 👤 Tsukumo Nobusawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 08:27
CPC Classifications
G; G01; G01J; G01J1/00; G01J1/42; G01J1/44
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
65 words
A light measuring device comprising a photocell successively exposable to light of different intensities, a capacitor, first means responsive to the light intensity incident on said photocell for charging said capacitor to a predetermined voltage corresponding to an extreme intensity of the light incident on said photocell and second means responsive to a function of the light incident on said photocell and said predetermined voltage.
Claim 2
Dependent Claim
65 words
A light measuring device comprising a photocell successively exposable to light of different intensities, a capacitor, first means responsive to the light intensity incident on said photocell for charging said capacitor to a predetermined voltage corresponding to an extreme intensity of the light incident on said photocell and second means responsive to a function of the light incident on said photocell and said predetermined voltage.
Claim 3
Dependent Claim
72 words
The light measuring device of claim 1 wherein said photocell comprises a photoconductor and said charging means comprises a voltage source, a voltage divider including said photoconductor and an impedance as legs thereof, means connecting said voltage divider across said voltage source, and means including a diode connecting said capacitor across one of said voltage divider legs for charging said capacitor to the maximum voltage across said one of said divider legs.
Claim 4
Dependent Claim
49 words
The light measuring device of claim 2 wherein said second means comprises an amplifier including an output and a high impedance input and means for connecting said capacitor in series with one of said voltage divider legs to said amplifier input, and a meter connected to said amplifier output.
Claim 5
Dependent Claim
21 words
The light measuring device of claim 2 including a switch connected across said capacitor and movable between open and closed positions.
Claim 6
Dependent Claim
15 words
The light measuring device of claim 2 wherein said impedance comprises a logarithmically responsive diode.
Claim 7
Dependent Claim
55 words
The light measuring device of claim 2 wherein said capacitor is connected in series with said diode across said impedance, and said second means comprises an amplifier having an output and a high impedance input and a meter connected to said output, said capacitor and said impedance being connected in series across said amplifier input.
Claim 8
Dependent Claim
61 words
A light measuring device comprising light sensitive means successively exposable to light varying between maximum and minimum intensities, first and second capacitors, means responsive to said light sensitive means for charging said first and second capacitors to voltages corresponding respectively to said incident light of maximum and minimum intensities, and means for providing visual indications of the voltages across said capacitors.
Claim 9
Dependent Claim
61 words
A light measuring device comprising light sensitive means successively exposable to light varying between maximum and minimum intensities, first and second capacitors, means responsive to said light sensitive means for charging said first and second capacitors to voltages corresponding respectively to said incident light of maximum and minimum intensities, and means for providing visual indications of the voltages across said capacitors.
Claim 10
Dependent Claim
81 words
The light measuring device of claim 7 wherein said light sensitive means comprises first and second photoconductors, said capacitor charging means comprises a voltage source, a first impedance connected in series with said first photoconductor across said voltage source and means including a first diode connecting said first capacitor across said first photoconductor, a second impedance connected in series with said second photoconductor across said voltage source, and means including a second diode connecting said second capacitor across said second impedance.
Claim 11
Dependent Claim
41 words
The light measuring device of claim 8 wherein said visual indicating means includes a pair of amplifiers having outputs and high impedance inputs connected to respective of said capacitors, and a meter connected to the output of each of said amplifiers.
Claim 12
Dependent Claim
77 words
A light measuring device comprising light sensitive means successively exposable to light of different intensities, a capacitor, means including a diode connected in series with said capacitor responsive to said light sensitive means for charging said capacitor to a voltage corresponding to one extreme of said light intensities, and means for providing an indication of the relationship of the light intensity corresponding to said voltage and a light of different intensity incident on said light sensitive means.
Claim 13
Dependent Claim
77 words
A light measuring device comprising light sensitive means successively exposable to light of different intensities, a capacitor, means including a diode connected in series with said capacitor responsive to said light sensitive means for charging said capacitor to a voltage corresponding to one extreme of said light intensities, and means for providing an indication of the relationship of the light intensity corresponding to said voltage and a light of different intensity incident on said light sensitive means.
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) | 1974-05-31 | 1974-11-30 | 1975-06-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-05-31 | 1978-11-30 | 1979-06-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-05-31 | 1982-11-30 | 1983-06-01 | $7700.00 | Window Closed / Lapsed |