Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1991-07-18
1993-11-16
Kostak, Victor R.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358169, H04N 557
Patent
active
052628620
ABSTRACT:
A black compensation circuit for compensating a luminance signal which is subjected to edge enhancement, comprises: a black-level expanding circuit responsive to a control signal including an edge enhancement component and the luminance signal for performing expansion of a tone of a black portion of the luminance signal and for performing conversion of the luminance signal into a black-level expanded signal in the absence of the control signal; a low-pass filter circuit for low-pass filtering the luminance signal to remove the edge enhancement component; a detection circuit responsive to an output of the low-pass filter circuit for detecting the blackest level for a given interval; and a comparing circuit for comparing the blackest level with a given level to produce the control signal, the black-level expanding circuit stopping the expansion and the conversion in the presence of the control signal. The blackest level does not change with sharpness because after the luminance signal subjected to edge enhancement is passed through the low-pass filter, it is sent to the detection circuit. An input signal of the low-pass filter may be supplied from the black-level expanding circuit.
REFERENCES:
patent: 4204229 (1980-05-01), Heuze
patent: 4631589 (1986-12-01), Hongu et al.
patent: 4937671 (1990-06-01), Engel
patent: 4975773 (1990-12-01), Rabii
patent: 5087967 (1992-02-01), Matsumoto et al.
Kageyama Atsuhisa
Sadamatsu Hideaki
Kostak Victor R.
Matsushita Electric - Industrial Co., Ltd.
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