Patent US3130361A successfully refreshed from Google Patents.
US3752905A
Expired / Lapsed
US
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Gamma control in the luminance channel of a color television transmitter
Assignee: Individual
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Filing: 1971-12-15
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Granted: 1973-08-14
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Expires: 1991-12-15
Abstract
Abstract The invention relates to a method and apparatus for transmitting a television picture signal having a high contrast range. The method involves integrating at least a portion of the television picture signal to obtain a test signal. The test signal is sensed by a threshold circuit which generates a control signal when the test signal approaches or exceeds a threshold level. The television picture signal is also simultaneously transmitted through two parallel channels, one channel including a linear amplifier and the other channel including a gamma amplifier having a changeable gain characteristic. The control signal, generated in response to the test signal exceeding the threshold level, modifies the gain characteristic of the gamma amplifier to increase the amplification of the signal corresponding to the picture in the shaded areas and reducing the amplification of the signal corresponding to the picture in the light areas. The output of the two channels are then combined in a mixer prior to transmission. An apparatus is disclosed for carrying out the method.
Inventors
- 👤 H Schneider
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 14:00
CPC Classifications
H; H04; H04N; H04N9/00; H04N9/64; H04N9/68; H04N9/69
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
133 words
A method for transmitting a color television picture signal having a high contrast range and having a luminance signal transmitted over a luminance channel and chrominance signals transmitted over chrominance channels, comprising, in combination, the steps of processing at least a portion of said luminance signal to obtain a test signal; furnishing a threshold signal; comparing said test signal to said threshold signal and generating a control signal when said test signal exceeds said threshold signal; and increasing the amplification of a portion of the luminance signal corresponding to the picture in the shaded areas and reducing the amplification of the portion of the luminance signal corresponding to the picture in the light areas in dependence on said control signal, while maintaining the amplification in said chrominance channels independent of said control signal.
Claim 2
Independent Claim
133 words
A method for transmitting a color television picture signal having a high contrast range and having a luminance signal transmitted over a luminance channel and chrominance signals transmitted over chrominance channels, comprising, in combination, the steps of processing at least a portion of said luminance signal to obtain a test signal; furnishing a threshold signal; comparing said test signal to said threshold signal and generating a control signal when said test signal exceeds said threshold signal; and increasing the amplification of a portion of the luminance signal corresponding to the picture in the shaded areas and reducing the amplification of the portion of the luminance signal corresponding to the picture in the light areas in dependence on said control signal, while maintaining the amplification in said chrominance channels independent of said control signal.
Claim 3
Dependent Claim
23 words
A method as defined in claim 1, wherein processing comprises integrating said luminance signal over a predetermined time to obtain its mean value.
Claim 4
Dependent Claim
51 words
A method as defined in claim 1, wherein increasing the amplification of the luminance signal corresponding to the shaded areas and reducing the amplification of the luminance signal corresponding to the picture in the light areas respectively comprises controlling, with said control voltage, the correction function of the transmitter gamma stage.
Claim 5
Dependent Claim
21 words
A method as defined in claim 1, wherein processing comprises integrating said luminance signal portion over a plurality of picture frames.
Claim 6
Dependent Claim
51 words
A method as defined in claim 1, wherein the steps of increasing and reducing the amplification of luminance signal comprises splitting the latter for amplification in two parallel paths, said amplification being linear in one path and non-linear in the other path, and controlling said non-linear amplification with said control signal.
Claim 7
Dependent Claim
52 words
A method as defined in claim 5, further including the step of combining the amplified outputs from said parallel paths, and adjusting the relative proportion in which the outputs are combined to thereby vary the amount of amplification of the luminance signal corresponding to the shaded areas and to the light areas.
Claim 8
Dependent Claim
157 words
Apparatus for transmitting a color television picture signal having a high contrast range and having a luminance signal transmitted over a luminance channel and chrominance signals transmitted over chrominance channels, comprising, in combination, processing means for processing at least a portion of said luminance signal to obtain a test signal; threshold circuit means connected to said procesSing means for furnishing a control signal when said test signal exceeds a predetermined threshold signal; amplification means in said luminance channel, said amplification means having a predetermined characteristic curve; varying means in said amplification means for increasing the amplification of said luminance signal corresponding to the picture in the shaded areas and reducing the amplification of said luminance signal corresponding to the picture in the light area in dependence upon said control signal; and amplification means in said chrominance channel, operative for processing said chrominance signals in accordance with predetermined characteristic curves independent of the contrast range in said picture.
Claim 9
Dependent Claim
157 words
Apparatus for transmitting a color television picture signal having a high contrast range and having a luminance signal transmitted over a luminance channel and chrominance signals transmitted over chrominance channels, comprising, in combination, processing means for processing at least a portion of said luminance signal to obtain a test signal; threshold circuit means connected to said procesSing means for furnishing a control signal when said test signal exceeds a predetermined threshold signal; amplification means in said luminance channel, said amplification means having a predetermined characteristic curve; varying means in said amplification means for increasing the amplification of said luminance signal corresponding to the picture in the shaded areas and reducing the amplification of said luminance signal corresponding to the picture in the light area in dependence upon said control signal; and amplification means in said chrominance channel, operative for processing said chrominance signals in accordance with predetermined characteristic curves independent of the contrast range in said picture.
Claim 10
Dependent Claim
51 words
Apparatus as defined in claim 7, further comprising signal mixing means; and wherein said amplification means in said luminance channel comprises two parallel channels for supplying said luminance signal to said signal mixing means, one of said channels including linear amplification means, the other of said channels including non-linear amplification means.
Claim 11
Dependent Claim
33 words
Apparatus as defined in claim 8, wherein said processing means comprises a third parallel channel including integrating means for generating a mean value of said luminance signal portion which comprises said test signal.
Claim 12
Dependent Claim
55 words
Apparatus as defined in claim 9, wherein said signal mixing means is adjustable; and wherein said threshold circuit means responds to a predetermined threshold voltage at the output of said integrating means for changing the ratio of the signals transmitted by way of each of said two channels, respectively, having linear and non-linear amplification characteristics.
Claim 13
Dependent Claim
62 words
An apparatus as defined in claim 9, wherein said non-linear amplification means comprises a gamma stage having a variable characteristic curve, said threshold value being selected so that when said mean value of said luminance signal portion corresponds to a corresponding value for ''''white,'''' said characteristic curve is changed to increase the number of distinguishable degrees of luminosity in the light areas.
Claim 14
Dependent Claim
62 words
An apparatus as defined in claim 9, wherein said non-linear amplification means comprises a gamma stage having a variable characteristic curve, said threshold value being selected so that when said mean value of said television signal portion corresponds to a corresponding value for ''''black,'''' said characteristic curve is changed to increase the number of distinguishable degrees of luminosity in the shaded areas.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-08-13 | 1977-02-12 | 1977-08-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-13 | 1981-02-12 | 1981-08-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-13 | 1985-02-12 | 1985-08-14 | $7700.00 | Window Closed / Lapsed |