US3816744A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fast response automatic brightness control circuit for second generation image intensifier tube
Assignee: United States Department of the Army
•
Filing: 1973-10-05
•
Granted: 1974-06-11
•
Expires: 1993-10-05
Abstract
Abstract A fast response automatic bright source protection circuit for an image intensifier tube in which the amount of screen current, which is produced according to the light intensity of a target source, is sensed at the gate electrode of a junction FET. The gate electrode of the junction FET is connected between a resistor and a low junction capacitance diode that are serially connected in the path of the screen current. Since the diode has a very low junction capacitance, any fluctuation in the screen current has a very short transient time at the gate electrode of the junction FET. The drain electrode of the FET controls the drive of voltage regulated oscillators. The voltage regulated oscillator outputs are transformer coupled to voltage multipliers whose outputs produce large direct current bias voltages that are applied to the cathode, to the input and the output electrodes of a microchannel plate, and to the screen. These bias voltages applied to the input and output electrodes change inversely with any change of the screen current. Therefore, with the microchannel plate bias voltages varying inversely with the screen current, the brightness of the target source being viewed through the image intensifier remains constant at the output of the image intensifier tube.
Inventors
- 👤 S Chow
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 13:45
CPC Classifications
H; H01; H01J; H01J29/00; H01J29/98
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
336 words
An improved fast response automatic brightness control circuit for an image intensifier comprising a direct current voltage source and first and second oscillator and constant current source means for amplifying and converting said direct current voltage source into a first and a second train of positive pulses, a first, a second, and a third voltage multiplier means wherein said second voltage multiplier means amplifies said first train of positive pulses into a much larger direct current voltage and said first and third voltage multiplier means amplifies said second train of positive pulses into much larger positive direct current voltages with the output from said first voltage multiplier means applied to a cathode and the output of said second voltage multiplier means applied across the input and output electrodes of a microchannel plate and the output of said third voltage multiplier means applied to a screen, and a clamping circuit connected between said cathode and said input electrode to clamp the cathode voltage into its stable region, the improvement being in an automatic brightness control circuit that comprises: a screen current sensing resistor and diode serially connected in the screen current path; an N-P-N transistor amplifier having base, collector, and emitter electrodes wherein the emitter electrode is connecteD to ground and the collector electrode is connected to said first oscillator and constant current source means for controlling the amplitude of the train of positive pulse therefrom; a junction FET having a base electrode connected between said sensing resistor and said diode, a source electrode connected to ground, and a drain electrode connected to the base electrode of said N-P-N transistor amplifier wherein any change in screen current biases the base electrode of said junction FET to inversely change the amplitude of said train of positive pulses at the output of said first oscillator and constant current source means that are applied to the input to said second voltage multiplier means and to the input and output electrodes of said microchannel plate for automatically stabilizing the screen current.
Claim 2
Dependent Claim
336 words
An improved fast response automatic brightness control circuit for an image intensifier comprising a direct current voltage source and first and second oscillator and constant current source means for amplifying and converting said direct current voltage source into a first and a second train of positive pulses, a first, a second, and a third voltage multiplier means wherein said second voltage multiplier means amplifies said first train of positive pulses into a much larger direct current voltage and said first and third voltage multiplier means amplifies said second train of positive pulses into much larger positive direct current voltages with the output from said first voltage multiplier means applied to a cathode and the output of said second voltage multiplier means applied across the input and output electrodes of a microchannel plate and the output of said third voltage multiplier means applied to a screen, and a clamping circuit connected between said cathode and said input electrode to clamp the cathode voltage into its stable region, the improvement being in an automatic brightness control circuit that comprises: a screen current sensing resistor and diode serially connected in the screen current path; an N-P-N transistor amplifier having base, collector, and emitter electrodes wherein the emitter electrode is connecteD to ground and the collector electrode is connected to said first oscillator and constant current source means for controlling the amplitude of the train of positive pulse therefrom; a junction FET having a base electrode connected between said sensing resistor and said diode, a source electrode connected to ground, and a drain electrode connected to the base electrode of said N-P-N transistor amplifier wherein any change in screen current biases the base electrode of said junction FET to inversely change the amplitude of said train of positive pulses at the output of said first oscillator and constant current source means that are applied to the input to said second voltage multiplier means and to the input and output electrodes of said microchannel plate for automatically stabilizing the screen current.
Claim 3
Dependent Claim
23 words
An improved fast response automatic brightness control circuit as set forth in claim 1 wherein said diode is a low junction capacitance diode.
Claim 4
Dependent Claim
22 words
An improved fast response automatic brightness control circuit as set forth in claim 2 wherein said diode is a LVMB type diode.
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) | 1977-06-10 | 1977-12-10 | 1978-06-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-10 | 1981-12-10 | 1982-06-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-10 | 1985-12-10 | 1986-06-11 | $7700.00 | Window Closed / Lapsed |