US4229767A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Beam control circuit for diode-gun type camera tubes
Assignee: Ampex Corp
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Filing: 1979-03-23
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Granted: 1980-10-21
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Expires: 1999-03-23
Abstract
Abstract A beam control circuit which instantaneously increases beam current just sufficiently to discharge a highlight, utilizes the fact that a substantially linear relationship exists between the grid current and the available beam current of a diode-gun camera tube. A tube grid control circuit provides means for calibrating the relationship between the incoming signal current and the available beam current. A highlight enable circuit coupled to the grid control circuit is pre-biased whereby the beam current of the tube is maintained at a constant value as long as the video signal current remains within its normal operating range, i.e., there are no highlights in the viewed scene. However, when the video signal current increases above the pre-bias level, as in the presence of a highlight, the highlight enable circuit conducts to cause a corresponding increase in the beam current of the tube, wherein the beam current maintains a pre-calibrated, substantially constant margin above the video signal current which is just sufficient to discharge the highlight.
Inventors
- 👤 John O. Ryan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 18:51
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/40; H04N23/41
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
125 words
In a camera pickup tube having a substantially linear relationship between the grid current and the beam current thereof, a control circuit for controlling the beam current with respect to a video signal current, comprising the combination of; highlight enable means coupled to the video signal current and pre-biased to a given upper limit of a normal video signal current operating range; tube grid control means coupled to the grid and including means for pre-calibrating a relationship between the video signal current and any change in the beam current caused thereby; and said tube grid control means is responsive to the highlight enable means in the presence of highlights, to generate increases in beam current which maintain a selected margin corresponding to the pre-calibrated relationship.
Claim 2
Dependent Claim
125 words
In a camera pickup tube having a substantially linear relationship between the grid current and the beam current thereof, a control circuit for controlling the beam current with respect to a video signal current, comprising the combination of; highlight enable means coupled to the video signal current and pre-biased to a given upper limit of a normal video signal current operating range; tube grid control means coupled to the grid and including means for pre-calibrating a relationship between the video signal current and any change in the beam current caused thereby; and said tube grid control means is responsive to the highlight enable means in the presence of highlights, to generate increases in beam current which maintain a selected margin corresponding to the pre-calibrated relationship.
Claim 3
Dependent Claim
36 words
The control circuit of claim 1 wherein the highlight enable means includes; transistor means pre-biased to said given upper limit and responsive to video signal currents exceeding the limit to enable the tube grid control means.
Claim 4
Dependent Claim
37 words
The control circuit of claim 2 wherein the pre-calibrating means includes; adjustable resistance means for providing a selected beam current given a selected video signal current commensurate with the pre-biased upper limit of the highlight enable means.
Claim 5
Dependent Claim
75 words
The control circuit of claim 3 wherein; said transistor means includes a selected pre-bias resistance and generates an enable signal only when the video signal current exceeds the given upper limit due to the presence of a highlight; and said pre-calibrating means maintains a corresponding increase in the beam current commensurate with the selected margin relationship between the beam current and the video signal current as the video signal current exceeds the given upper limit.
Claim 6
Dependent Claim
92 words
The control circuit of claim 4 wherein; the transistor means includes a dual transistor, wherein the first stage is coupled to the video signal current and provides temperature compensation, the second stage is coupled to the first stage and provides an output junction therefrom, said second stage being pre-biased to said given upper limit; the control circuit including a current source coupled to the second stage output junction; and the tube grid control means including a pair of transistors coupled to define a multiplying current mirror circuit including said adjustable resistance means.
Claim 7
Dependent Claim
38 words
The control circuit of claim 5 further including; means for supplying a blanking signal; and a transistor switch coupled to the grid and disposed to shut off the tube in response to the presence of the blanking signal.
Claim 8
Dependent Claim
112 words
A control circuit for controlling the beam current in a diode-gun camera tube having a control grid, the circuit being coupled to receive a video signal current which has a normal operating range in the absence of highlights which range corresponds to a normal beam current operating range, the combination comprising; circuit means coupled directly to the tube control grid from the video signal current to enable the tube to generate highlight suppressing beam currents exceeding the upper limit of the normal operating range thereof upon the occurrence of highlights, and including grid control means for increasing the highlight suppressing beam currents at a substantially constant preselected margin above the signal current.
Claim 9
Dependent Claim
112 words
A control circuit for controlling the beam current in a diode-gun camera tube having a control grid, the circuit being coupled to receive a video signal current which has a normal operating range in the absence of highlights which range corresponds to a normal beam current operating range, the combination comprising; circuit means coupled directly to the tube control grid from the video signal current to enable the tube to generate highlight suppressing beam currents exceeding the upper limit of the normal operating range thereof upon the occurrence of highlights, and including grid control means for increasing the highlight suppressing beam currents at a substantially constant preselected margin above the signal current.
Claim 10
Dependent Claim
74 words
The circuit of claim 7 wherein the circuit means further includes; pre-biased switch means for precluding an increase in the video signal current supplied to the grid control means as long as the video signal current remains within its normal operating range; and wherein the switch means supplies an enable signal current to the grid via the grid control means when the video signal current exceeds the upper limit of its normal operating range.
Claim 11
Dependent Claim
45 words
The circuit of claim 8 wherein the grid control means includes pre-calibrating means for establishing the substantially constant preselected margin, and for maintaining the margin between the beam current and the video signal current with increases in the latter caused by the occurrence of highlights.
Claim 12
Independent Claim
112 words
A method for suppressing highlights which appear as large increases in the video signal current of a video camera, by controlling the beam current in the camera pickup tube thereof, the tube having a control grid and a substantially linear relationship between the control grid current and the beam current, comprising the steps of; establishing a preselected current margin between the beam current and the video signal current; pre-biasing the video signal current to define a normal operating range in the absence of highlights; and maintaining the preselected current margin between the beam current and the video signal current when the latter exceeds its normal operating range in the presence of highlights.
Claim 13
Independent Claim
112 words
A method for suppressing highlights which appear as large increases in the video signal current of a video camera, by controlling the beam current in the camera pickup tube thereof, the tube having a control grid and a substantially linear relationship between the control grid current and the beam current, comprising the steps of; establishing a preselected current margin between the beam current and the video signal current; pre-biasing the video signal current to define a normal operating range in the absence of highlights; and maintaining the preselected current margin between the beam current and the video signal current when the latter exceeds its normal operating range in the presence of highlights.
Claim 14
Dependent Claim
51 words
The method of claim 10 wherein the step of establishing includes; applying a selected current signal level commensurate with the upper limit of the normal operating range of the video signal current; pre-calibrating the control grid current in response to said selected current signal level to establish the preselected current margin.
Claim 15
Dependent Claim
78 words
The method of claim 11 wherein the step of pre-biasing includes; preventing any increase in the selected current signal level in the absence of highlights while the video signal level in the video signal current remains within its normal operating range; and increasing the selected current signal level when the video signal current exceeds the normal operating range in the presence of highlights while maintaining the preselected current margin between the beam current and the video signal current.
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) | 1983-10-21 | 1984-04-21 | 1984-10-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-10-21 | 1988-04-21 | 1988-10-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-10-21 | 1992-04-21 | 1992-10-21 | $7700.00 | Window Closed / Lapsed |