US5416533A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for correcting a black level of a video signal
Assignee: Panasonic Holdings Corp
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Filing: 1992-06-15
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Granted: 1995-05-16
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Expires: 2012-06-15
Abstract
Abstract A pedestal clamping device clamps a pedestal level of an input video signal in response to a predetermined pedestal voltage, and converts the input video signal into a clamped video signal. A black-level expanding device expands a tone of a black portion of the clamped video signal, and converts the clamped video signal into a black-level expanded video signal. A color greatest detecting device detects a greatest of color signals of the input video signal. A adding device adds an output signal from the color greatest detecting device and the pedestal voltage. A black-level comparing device detects a blackest portion of the black-level expanded video signal; compares the detected blackest portion of the black-level expanded video signal with the output signal from the adding device; and controls a degree of expanding the black tone by the black-level expanding device in response to a difference between the detected blackest portion of the black-level expanded video signal and the output signal from the adding device.
Inventors
- 👤 Atsuhisa Kageyama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 19:35
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/14; H04N5/16; H04N5/18; H04N5/185; H04N9/00; H04N9/64; H04N9/72; H04N9/67; H04N9/68
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
214 words
An apparatus for correcting a black level of a video signal, comprising: a pedestal clamp circuit for clamping a pedestal level of an input luminance signal in response to a predetermined pedestal voltage, and converting the input luminance signal into a clamped luminance signal; a black-level expanding circuit for expanding a tone of a black portion of the clamped luminance signal, and converting the clamped luminance signal into a black-level expanded luminance signal; a color detection matrix circuit for detecting a predetermined-color portion in response to an input color difference signal; a gain control circuit for controlling an amplitude of an output signal from the color detection matrix circuit; an adding circuit for adding an output signal from the gain control circuit and the pedestal voltage; and a black-level comparing circuit, responsive to the black-level expanded luminance signal and an output signal from the adding circuit, for detecting a blackest portion of the black-level expanded luminance signal, comparing the detected blackest portion of the black-level expanded luminance signal with the output signal from the adding circuit, and controlling a degree of expanding the black tone by the black-level expanding circuit in response to a difference between the detected blackest portion of the black-level expanded luminance signal and the output signal from the adding circuit.
Claim 2
Independent Claim
214 words
An apparatus for correcting a black level of a video signal, comprising: a pedestal clamp circuit for clamping a pedestal level of an input luminance signal in response to a predetermined pedestal voltage, and converting the input luminance signal into a clamped luminance signal; a black-level expanding circuit for expanding a tone of a black portion of the clamped luminance signal, and converting the clamped luminance signal into a black-level expanded luminance signal; a color detection matrix circuit for detecting a predetermined-color portion in response to an input color difference signal; a gain control circuit for controlling an amplitude of an output signal from the color detection matrix circuit; an adding circuit for adding an output signal from the gain control circuit and the pedestal voltage; and a black-level comparing circuit, responsive to the black-level expanded luminance signal and an output signal from the adding circuit, for detecting a blackest portion of the black-level expanded luminance signal, comparing the detected blackest portion of the black-level expanded luminance signal with the output signal from the adding circuit, and controlling a degree of expanding the black tone by the black-level expanding circuit in response to a difference between the detected blackest portion of the black-level expanded luminance signal and the output signal from the adding circuit.
Claim 3
Independent Claim
214 words
An apparatus for correcting a black level of a video signal, comprising: a pedestal clamp circuit for clamping a pedestal level of an input luminance signal in response to a predetermined pedestal voltage, and converting the input luminance signal into a clamped luminance signal; a black-level expanding circuit for expanding a tone of a black portion of the clamped luminance signal, and converting the clamped luminance signal into a black-level expanded luminance signal; a color detection matrix circuit for detecting a predetermined-color portion in response to an input color demodulation signal; a gain control circuit for controlling an amplitude of an output signal from the color detection matrix circuit; an adding circuit for adding an output signal from the gain control circuit and the pedestal voltage; and a black-level comparing circuit, responsive to the black-level expanded luminance signal and an output signal from the adding circuit, for detecting a blackest portion of the black-level expanded luminance signal, comparing the detected blackest portion of the black-level expanded luminance signal with the output signal from the adding circuit, and controlling a degree of expanding the black tone by tile black-level expanding circuit in response to a difference between the detected blackest portion of the black-level expanded luminance signal and the output signal from the adding circuit.
Claim 4
Independent Claim
214 words
An apparatus for correcting a black level of a video signal, comprising: a pedestal clamp circuit for clamping a pedestal level of an input luminance signal in response to a predetermined pedestal voltage, and converting the input luminance signal into a clamped luminance signal; a black-level expanding circuit for expanding a tone of a black portion of the clamped luminance signal, and converting the clamped luminance signal into a black-level expanded luminance signal; a color detection matrix circuit for detecting a predetermined-color portion in response to an input color demodulation signal; a gain control circuit for controlling an amplitude of an output signal from the color detection matrix circuit; an adding circuit for adding an output signal from the gain control circuit and the pedestal voltage; and a black-level comparing circuit, responsive to the black-level expanded luminance signal and an output signal from the adding circuit, for detecting a blackest portion of the black-level expanded luminance signal, comparing the detected blackest portion of the black-level expanded luminance signal with the output signal from the adding circuit, and controlling a degree of expanding the black tone by tile black-level expanding circuit in response to a difference between the detected blackest portion of the black-level expanded luminance signal and the output signal from the adding circuit.
Claim 5
Dependent Claim
72 words
In an apparatus for controlling a black level of luminance components of a video signal with respect to a reference level in a closed-loop control, the improvement comprising: means for detecting whether or not an image represented by the video signal has a color different from a gray between black and white, and outputting a detection signal representative thereof; and means for varying the reference level in response to the detection signal.
Claim 6
Dependent Claim
72 words
In an apparatus for controlling a black level of luminance components of a video signal with respect to a reference level in a closed-loop control, the improvement comprising: means for detecting whether or not an image represented by the video signal has a color different from a gray between black and white, and outputting a detection signal representative thereof; and means for varying the reference level in response to the detection signal.
Claim 7
Dependent Claim
71 words
In an apparatus for controlling a black level of luminance components of a video signal with respect to a reference level in a closed-loop control, the improvement comprising: means for detecting a component of the video signal which corresponds to a predetermined color different from a gray between black and white, and outputting a detection signal representative thereof; and means for varying the reference level in response to the detection signal.
Claim 8
Dependent Claim
71 words
In an apparatus for controlling a black level of luminance components of a video signal with respect to a reference level in a closed-loop control, the improvement comprising: means for detecting a component of the video signal which corresponds to a predetermined color different from a gray between black and white, and outputting a detection signal representative thereof; and means for varying the reference level in response to the detection signal.
Claim 9
Dependent Claim
83 words
An apparatus as recited in claim 3, wherein said means for detecting comprises greatest-detecting means for detecting a greatest color difference signal and generating a first signal representing a greatest color difference signal component of the video signal, said means for varying responsive to said first signal for decreasing expansion of the black level of the video signal when said first signal exceeds a predetermined level representing a portion of the image being different from gray, thereby preventing undesirable darkening of non-gray colors.
Claim 10
Dependent Claim
40 words
An apparatus as recited in claim 5, further comprising means for clipping and limiting said first signal and providing a confined signal for controlling said means for varying to decrease said expansion of the black level of said video signal.
Claim 11
Dependent Claim
83 words
An apparatus as recited in claim 4, wherein said means for detecting comprises greatest-detecting means for detecting a greatest color difference signal and generating a first signal representing a greatest color difference signal component of the video signal, said means for varying responsive to said first signal for decreasing expansion of the black level of the video signal when said first signal exceeds a predetermined level representing a portion of the image being different from gray, thereby preventing undesirable darkening of non-gray colors.
Claim 12
Dependent Claim
40 words
An apparatus as recited in claim 7, further comprising means for clipping and limiting said first signal and providing a confined signal for controlling said means for varying to decrease said expansion of the black level of said video signal.
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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) | 1998-05-15 | 1998-11-14 | 1999-05-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-05-15 | 2002-11-14 | 2003-05-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-05-15 | 2006-11-14 | 2007-05-16 | $7700.00 | Window Closed / Lapsed |