US3581098A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic brightness control
Assignee: TDK Micronas GmbH
•
Filing: 1969-02-24
•
Granted: 1971-05-25
•
Expires: 1989-02-24
Abstract
Abstract The brightness of a phosphor display screen of an image intensifier tube is automatically controlled by a currentlimiting device connected between a direct current source and an oscillator which supplies an alternating voltage to a voltage multiplier, the latter in turn applying a direct accelerating voltage between the input photocathode and output display screen of the tube. The current-limiting device acts to provide a relatively constant current when the input light intensity and corresponding output current of the display screen increase to a predetermined level.
Inventors
- 👤 Alan W Hoover
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 17:38
CPC Classifications
H; H01; H01J; H01J31/00; H01J31/08; H01J31/50; H02; H02M; H02M3/00; H02M3/22; H02M3/24; H02M3/28; H02M3/325; H02M3/335; H02M3/338; H02M3/3381; Y; Y10; Y10S; Y10S315/00; Y10S315/07
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
135 words
An image brightness control system comprising: an image intensifier tube having a photocathode input electrode emitting electrons in response to the intensity of light applied thereto and a phosphor display screen output electrode providing an image display in accordance with said electrons impinging thereon, a voltage multiplier applying a direct voltage between said input and output electrodes for accelerating said electrons and directing said accelerated electrons to said diSplay screen for increasing the brightness of said image, an oscillator circuit applying an alternating voltage to said voltage multiplier, a direct current source, and direct current-limiting means connected between said direct current source and said oscillator to limit the direct current supplied to said oscillator from said direct current source to a predetermined current level for limiting the brightness of said image displayed on said screen.
Claim 2
Dependent Claim
135 words
An image brightness control system comprising: an image intensifier tube having a photocathode input electrode emitting electrons in response to the intensity of light applied thereto and a phosphor display screen output electrode providing an image display in accordance with said electrons impinging thereon, a voltage multiplier applying a direct voltage between said input and output electrodes for accelerating said electrons and directing said accelerated electrons to said diSplay screen for increasing the brightness of said image, an oscillator circuit applying an alternating voltage to said voltage multiplier, a direct current source, and direct current-limiting means connected between said direct current source and said oscillator to limit the direct current supplied to said oscillator from said direct current source to a predetermined current level for limiting the brightness of said image displayed on said screen.
Claim 3
Dependent Claim
31 words
The system of claim 1 wherein the input light intensity and the direct current and the display brightness response characteristics are relatively linear in the range below said predetermined current level.
Claim 4
Dependent Claim
92 words
The system of claim 1 wherein said tube includes three cascaded image intensifier stages and stepped connections between said voltage multiplier and said stages, each stage including a photocathode input electrode and phosphor screen output electrode, and first and second fiber optic means coupling light from the first and second stage phosphor screens to the second and third stage photocathodes respectively, each said fiber optic means including a phosphor screen and photocathode coatings on opposite sides thereof, each of said coatings on opposite sides having a common stepped connection to said multiplier.
Claim 5
Dependent Claim
45 words
The system of claim 2 wherein the input impedance of said oscillator decreases with increasing current therethrough and the input impedance of said limiter operating above said predetermined current level increases with increasing current therethrough to provide a relatively constant total impedance above said level.
Claim 6
Dependent Claim
17 words
The system of claim 3 including a focusing anode extending from each phosphor screen toward each photocathode.
Claim 7
Dependent Claim
102 words
The system of claim 4 wherein said limiting means includes a common base connected transistor having an emitter electrode and emitter resistor connected in series with one terminal of said direct current supply means and a collector electrode connected to a terminal of said oscillator, a Zener diode connected between said one terminal and the base electrode to establish a reference voltage for said predetermined level, and a resistor having one end connected to said base electrode, the other terminal of said direct current supply means being connected to the other end of said resistor and the other terminal of said oscillator.
Claim 8
Dependent Claim
21 words
The system of claim 6 including a bypass capacitor connected across said current limiter providing a low impedance for said oscillator.
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) | 1974-05-24 | 1974-11-23 | 1975-05-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-05-24 | 1978-11-23 | 1979-05-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-05-24 | 1982-11-23 | 1983-05-25 | $7700.00 | Window Closed / Lapsed |