US3881054A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and circuit arrangement for independently controlling the contrast and brightness adjustment of an image receiver, more particularly in videotelephone subscriber stations
Assignee: Siemens AG
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Filing: 1973-06-26
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Granted: 1975-04-29
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Expires: 1993-06-26
Abstract
Abstract A method is disclosed which is particularly useful in videotelephone subscriber stations where the contrast and brightness controls comprising potentiometers are located at a point outside the image receiver for independently controlling the contrast and brightness adjustment of the receiver whereon a picture is projected line by line. The method comprises adding a ''''white'''' pulse to the picture signal for each line, the amplitude of this pulse corresponding to the maximum effective voltage for white, so that the portion of the picture to be reproduced at the desired maximum luminance is clamped to a value (or white level) adjustable relative to the maximum value of the white pulse; shifting the porch of the white pulse by varying the gain of an amplifier to which the picture signal including the added white pulse is applied by means of a contrast control, the difference between the white level and the maximum value of the white pulse being left unchanged; and adjusting the distance between the maximum value for white and the white pulse while maintaining said porch substantially constant by varying the gain of said amplifier using said brightness control.
Inventors
- 👤 Klaus Walla
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 21:28
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/44; H04N5/57
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
204 words
A method of independently adjusting the contrast and brightness of an image receiver whereon a picture is projected line by line, particularly in video-telephone subscriber stations, said contrast and brightness controls comprising potentiometers located at a point outside the apparatus; comprising: adding a white pulse to the picture signal during the line blanking interval for each of said lines, the amplitude of said pulse corresponding to the maximum effective voltage for white, shifting the porch of the white pulse by varying the gain of an amplifier to which the picture signal including said added white pulse is applied by regulating the dc bias thereof by means of said contrast control, the difference between the white-level and the amplitude of the white pulse being left unchanges, and adjusting the distance between the white level and the amplitude of the white pulse while maintaining said porch substantially constant by varying the gain of said amplifier by regulating the dc bias thereof using said brightness control the desired maximum white level of the picture being clamped to a level which is an adjustable distance from the amplitude of the inserted white pulse, the porch remaining at substantially the same unclamped value during adjustment of said brightness control.
Claim 2
Independent Claim
204 words
A method of independently adjusting the contrast and brightness of an image receiver whereon a picture is projected line by line, particularly in video-telephone subscriber stations, said contrast and brightness controls comprising potentiometers located at a point outside the apparatus; comprising: adding a white pulse to the picture signal during the line blanking interval for each of said lines, the amplitude of said pulse corresponding to the maximum effective voltage for white, shifting the porch of the white pulse by varying the gain of an amplifier to which the picture signal including said added white pulse is applied by regulating the dc bias thereof by means of said contrast control, the difference between the white-level and the amplitude of the white pulse being left unchanges, and adjusting the distance between the white level and the amplitude of the white pulse while maintaining said porch substantially constant by varying the gain of said amplifier by regulating the dc bias thereof using said brightness control the desired maximum white level of the picture being clamped to a level which is an adjustable distance from the amplitude of the inserted white pulse, the porch remaining at substantially the same unclamped value during adjustment of said brightness control.
Claim 3
Dependent Claim
41 words
The method as set forth in claim 1, including the step of initially adjusting the picture signal in a variable-gain amplifier (KV) to a constant amplitude at the time of occurrence of a synchronizing pulse (si) transmitted in said picture signal.
Claim 4
Dependent Claim
38 words
The method as set forth in claim 1, including the step of suppressing said white pulse at the output of said amplifier by the addition of a synchronous pulse of equal amplitude via another input of said amplifier.
Claim 5
Dependent Claim
207 words
A circuit arrangement including brightness and contrast control means including potentiometers for adjustment of an image receiver wherein a picture is projected line by line, particularly in video-telephone subscriber stations, and including amplifier means for receiving and controllably amplifying said picture signal means in said amplifier means for adding a white pulse to the line blanking interval of the picture signal for each line, the amplitude of said pulse corresponding to the maximum effective voltage for white, said amplifier including means for clamping the white value picture signal to be reproduced to a value relative to said maximum value of said white pulse, said contrast control means being coupled to said amplifier to control by controlling the dc bias thereof the gain applied to said picture signal carrying said white pulse, the porch of the white pulse thereby being shifted, the distance between the white level of the picture signal and the aMplitude of the white pulse being unchanged, said brightness control being coupled to said amplifier to vary the gain thereof by controlling the dc bias thereof to adjust the distance between the maximum value for said picture signal and the amplitude of the white pulse, the value of the unclamped porch remaining substantially the same.
Claim 6
Dependent Claim
207 words
A circuit arrangement including brightness and contrast control means including potentiometers for adjustment of an image receiver wherein a picture is projected line by line, particularly in video-telephone subscriber stations, and including amplifier means for receiving and controllably amplifying said picture signal means in said amplifier means for adding a white pulse to the line blanking interval of the picture signal for each line, the amplitude of said pulse corresponding to the maximum effective voltage for white, said amplifier including means for clamping the white value picture signal to be reproduced to a value relative to said maximum value of said white pulse, said contrast control means being coupled to said amplifier to control by controlling the dc bias thereof the gain applied to said picture signal carrying said white pulse, the porch of the white pulse thereby being shifted, the distance between the white level of the picture signal and the aMplitude of the white pulse being unchanged, said brightness control being coupled to said amplifier to vary the gain thereof by controlling the dc bias thereof to adjust the distance between the maximum value for said picture signal and the amplitude of the white pulse, the value of the unclamped porch remaining substantially the same.
Claim 7
Dependent Claim
39 words
The circuit arrangement as claimed in claim 4, wherein the tap of said brightness potentiometer is connected to the base input of said clamping means the ends of said potentiometer being connected between said amplifier supply and said ground.
Claim 8
Dependent Claim
34 words
The apparatus of claim 4 including a variable gain amplifier means in said picture input for setting said line signal to constant amplitude at the time of occurrence of a constant amplitude synchronizing pulse.
Claim 9
Dependent Claim
54 words
The apparatus of claim 6, wherein said amplifier includes first and second pulse inputs receiving pulses of substantially equal amplitude and of opposite polarity, one of said pulses comprising said line pulse, and said amplifier including means coupled to said first and second inputs for combining said pulses and thereby suppressing said white pulse.
Claim 10
Dependent Claim
50 words
The circuit arrangement as claimed in claim 4, wherein said contrast control potentiometer is connected with one end directly to the supply potential of said amplifier means the tap of said contrast potentiometer being connected to a first transistor of said amplifier means for controlling amplification of said picture signal.
Claim 11
Dependent Claim
25 words
The circuit arrangement as claimed in claim 8, wherein the tap of said brightness potentiometer is connected to the base input of said clamping means.
Claim 12
Dependent Claim
49 words
The circuit arrangement as claimed in claim 8, wherein the other end of said contrast control potentiometer is connected to the base of a second transistor and thereby to said clamping means, the tap of said brightness control being coupled to said other end of said contrast control potentiometer.
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) | 1978-04-28 | 1978-10-28 | 1979-04-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-28 | 1982-10-28 | 1983-04-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-28 | 1986-10-28 | 1987-04-29 | $7700.00 | Window Closed / Lapsed |