US4839569A
Expired / Lapsed
US
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Method and apparatus for providing gain control for an image intensifier tube
Assignee: Varo Inc
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Filing: 1987-12-08
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Granted: 1989-06-13
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Expires: 2007-12-08
Abstract
Abstract A photocathode current sensing circuit (58) is provided to adjust the electron accelerating voltage to a cone (32) and a phosphor screen (34) on an image intensifier tube (26). The voltage is adjusted by an anode power supply (60) which is responsive to the photocathode current sensing circuit (58). As light strikes the photocathode (28), a current (56) is generated. The current (56) is directly proportional to the intensity of light striking the photocathode (28). As the light and the current (56) decrease, the sensing circuit (58) controls the power supply (60) to provide a higher voltage to the cone (32) and the screen (34). By increasing the voltage to the cone (32) and the screen (34) the electrons are provided with more acceleration and, therefore, are intensified for viewing on the screen (34). An increase in light operates oppositely and decreases the intensity on the screen (34).
Inventors
- 👤 II William M. Dallin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 19:35
CPC Classifications
H; H01; H01J; H01J31/00; H01J31/08; H01J31/50; H01J2231/00; H01J2231/50; H01J2231/50005; H01J2231/5001; H01J2231/50015; H01J2231/50057; H01J2231/50063
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
121 words
An improved apparatus for viewing objects under low light conditions, comprising: a photocathode for emitting electrons when the low level light rays strike the photocathode; a screen for receiving the electrons; an anode cone for directing the electrons onto said screen; a housing for supporting said photocathode, said anode cone and said screen; an adjustable power supply voltage for accelerating the electrons from said photocathode to said screen; a guard conductor in said housing proximate said photocathode and electrically isolated from said screen and said photocathode, said guard conductor utilized for removing tray current; and means for sensing a current generated by the light striking said photocathode and for adjusting the accelerating voltage in response to changes in the photocathode current.
Claim 2
Dependent Claim
121 words
An improved apparatus for viewing objects under low light conditions, comprising: a photocathode for emitting electrons when the low level light rays strike the photocathode; a screen for receiving the electrons; an anode cone for directing the electrons onto said screen; a housing for supporting said photocathode, said anode cone and said screen; an adjustable power supply voltage for accelerating the electrons from said photocathode to said screen; a guard conductor in said housing proximate said photocathode and electrically isolated from said screen and said photocathode, said guard conductor utilized for removing tray current; and means for sensing a current generated by the light striking said photocathode and for adjusting the accelerating voltage in response to changes in the photocathode current.
Claim 3
Dependent Claim
21 words
The apparatus of claim 1, wherein said guard conductor further includes means for connecting said guard conductor to a ground potential.
Claim 4
Dependent Claim
35 words
The improved apparatus of claim 1, wherein said guard conductor comprises: a first insulator proximates the photocathode; a grounded insert portion attached to said first insulator; and a second insulator attached to said grounded insert.
Claim 5
Dependent Claim
15 words
The apparatus of claim 3, wherein said first and second insulators comprise a ceramic material.
Claim 6
Dependent Claim
12 words
The apparatus of claim 3, wherein said insert portion comprises stainless steel.
Claim 7
Dependent Claim
22 words
The improved apparatus of claim 1, wherein said means for sensing a photocathode current comprises a circuit for generating a piecewise voltage.
Claim 8
Dependent Claim
20 words
The apparatus of claim 6, wherein said circuit is responsive to increasing photocathode currents for producing correspondingly lower linear voltages.
Claim 9
Dependent Claim
32 words
The improved apparatus of claim 6, wherein said circuit includes an amplifier for amplifying said piecewise linear voltage, said amplifier producing a corresponding output voltage for use in generating said accelerating voltage.
Claim 10
Independent Claim
86 words
A method for removing stray current generated within an image intensifier tube of the type having a photocathode emitting electrons which are accelerated by a voltage toward a screen, comprising the steps of: separating a current generated by such photocathode from the stray current by insulating said photocathode from said screen with a guard conductor located proximate said photocathode; removing said stray current such that it does not affect the operation of said tube; and generating an electron accelerating voltage in response to said photocathode current.
Claim 11
Independent Claim
86 words
A method for removing stray current generated within an image intensifier tube of the type having a photocathode emitting electrons which are accelerated by a voltage toward a screen, comprising the steps of: separating a current generated by such photocathode from the stray current by insulating said photocathode from said screen with a guard conductor located proximate said photocathode; removing said stray current such that it does not affect the operation of said tube; and generating an electron accelerating voltage in response to said photocathode current.
Claim 12
Dependent Claim
23 words
The method of claim 9, wherein said separating step further comprises grounding the guard conductor to draw off and remove said stray current.
Claim 13
Dependent Claim
21 words
The method of claim 9, further including generating said accelerating voltage in a nonlinear manner in response to said photocathode current.
Claim 14
Independent Claim
82 words
A method for automatically controlling gain in an image intensifier tube of the type having a photocathode emitting electrons which are accelerated toward a screen by a voltage, comprising the steps of: sensing a current generated by said photocathode; varying said voltage for accelerating the electrons in response to said sensed photocathode current; and isolating said photocathode from said screen with an insulated guard conductor proximate said screen to prevent leakage current generated by said voltage from mixing with said photocathode current.
Claim 15
Independent Claim
82 words
A method for automatically controlling gain in an image intensifier tube of the type having a photocathode emitting electrons which are accelerated toward a screen by a voltage, comprising the steps of: sensing a current generated by said photocathode; varying said voltage for accelerating the electrons in response to said sensed photocathode current; and isolating said photocathode from said screen with an insulated guard conductor proximate said screen to prevent leakage current generated by said voltage from mixing with said photocathode current.
Claim 16
Dependent Claim
19 words
The method of claim 12, wherein the step of sensing a photocathode includes amplifying representations of said photocathode current.
Claim 17
Dependent Claim
21 words
The method of claim 12, wherein the step of isolating the photocathode from the screen further includes grounding said guard conductor.
Claim 18
Dependent Claim
74 words
Apparatus for automatically controlling gain in an image intensifier tube of the type having a photocathode emitting electrons which are accelerated toward a screen, comprising: means for sensing a current generated by the photocathode; means for adjusting a voltage for accelerating the electrons in response to said sensed photocathode current; and means for isolating the photocathode from the screen to prevent a leakage current generated by said voltage from mixing with said photocathode current.
Claim 19
Dependent Claim
74 words
Apparatus for automatically controlling gain in an image intensifier tube of the type having a photocathode emitting electrons which are accelerated toward a screen, comprising: means for sensing a current generated by the photocathode; means for adjusting a voltage for accelerating the electrons in response to said sensed photocathode current; and means for isolating the photocathode from the screen to prevent a leakage current generated by said voltage from mixing with said photocathode current.
Claim 20
Dependent Claim
23 words
The apparatus of claim 15 wherein said means for sensing a photocathode current includes an amplifier for amplifying representations of said photocathode current.
Claim 21
Dependent Claim
25 words
The apparatus of claim 16, wherein the means for sensing further includes a circuit for generating a piecewise linear voltage for input to said amplifier.
Claim 22
Dependent Claim
17 words
The apparatus of claim 17 wherein said piecewise linear circuit includes at least one threshold responsive device.
Claim 23
Dependent Claim
24 words
The apparatus of claim 18, wherein said circuit is operable to generate a characteristic curve having a break point for each said threshold device.
Claim 24
Dependent Claim
36 words
The apparatus of claim 15, wherein said means for adjusting a voltage includes a variable voltage supply responsive to the output of said means for sensing for providing changes in the voltage for accelerating the electrons.
Claim 25
Dependent Claim
59 words
The apparatus of claim 15, wherein said means for isolating the photocathode from the screen comprises: an insert portion; a first insulator separating said insert portion from said photocathode; a second insulator separating said insert portion from the screen; and a ground connected to said insert portion such that said leakage current is drawn off prior to the photocathode.
Claim 26
Dependent Claim
14 words
The apparatus of claim 21, wherein said insert portion is positioned proximate the photocathode.
References Cited (Backward Citations)
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1992-06-12 | 1992-12-12 | 1993-06-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-06-12 | 1996-12-12 | 1997-06-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-06-12 | 2000-12-12 | 2001-06-13 | $7700.00 | Window Closed / Lapsed |