EP0106368A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Noise reduction circuit arrangement of solid-state video camera
Assignee: Hitachi Ltd
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Filing: 1983-10-19
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Granted: —
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Expires: 2003-10-19
Abstract
Abstract A noise reduction circuit arrangement for video signals under low brightness condition has a high-pass filter (3A, 3B) which detects the level of a video signal to switch the amount of passage of a high-frequency band component in accordance with a magnitude of the level. The video signal, produced from an image pickup element, is supplied to a low-pass filter (2) and the high-pass filter. The high-frequency band component produced from the high-pass filter and changed in amplitude in accordance with the level of the video signal and a low-frequency band component produced from the low-pass filter are added at an adder (10) so as to effect aperture correction in principle. The high-frequency band to be added is so controlled. as to more decrease when the brightness of the video signal is low than when the brightness is not low.
Inventors
- 👤 Hiroshi Kudo
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 23:38
CPC Classifications
H; H04; H04N; H04N25/00; H04N25/60
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
191 words
A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means (2) supplied with a video signal produced from an image pickup element, for passing a low-frequency band component of the video signal; high-pass filter means (3A, 3B) supplied with the video signal produced from the image pickup element, for passing a high-frequency band component of the video signal; level detector means- (5, 5a, 6) detecting the level of the video signal, for producing a control signal in accordance with a degree of brightness of the video signal; correcting means (7, 7A) responsive to the control signal produced from said level detector means, for controlling frequency characteristics of the high-frequency band component of the video signal passed . through and produced from said high-pass filter means such that the amount of the high-frequency band component is more decreased when brightness of the video signal is low than when the brightness is not low; and adder means (10) for adding the low-frequency band component from said low-pass filter means and the high-frequency band component produced from said high-pass filter means and controlled by said correcting means.
Claim 2
Dependent Claim
191 words
A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means (2) supplied with a video signal produced from an image pickup element, for passing a low-frequency band component of the video signal; high-pass filter means (3A, 3B) supplied with the video signal produced from the image pickup element, for passing a high-frequency band component of the video signal; level detector means- (5, 5a, 6) detecting the level of the video signal, for producing a control signal in accordance with a degree of brightness of the video signal; correcting means (7, 7A) responsive to the control signal produced from said level detector means, for controlling frequency characteristics of the high-frequency band component of the video signal passed . through and produced from said high-pass filter means such that the amount of the high-frequency band component is more decreased when brightness of the video signal is low than when the brightness is not low; and adder means (10) for adding the low-frequency band component from said low-pass filter means and the high-frequency band component produced from said high-pass filter means and controlled by said correcting means.
Claim 3
Dependent Claim
50 words
A noise reduction circuit arrangement according to Claim 1 wherein said correcting means comprises variable gain amplifier means (15, 16, 17) which increases gain for the high-frequency band component by receiving the control signal produced from said level detector means when the brightness of the video signal is not low.
Claim 4
Dependent Claim
49 words
A noise reduction circuit arrangement according to Claim 1 wherein said correcting means comprises means (7A; 7a, 7b, 7c) for decreasing a cut-off frequency of said high-pass filter means by receiving the control signal produced from said level detector means when the brightness of the video signal is low.
Claim 5
Dependent Claim
45 words
A noise reduction circuit arrangement according to Claim 2 wherein said variable gain amplifier means includes a transistor amplifier (17) responsive to said control signal to switch connection and disconnection of a capacitor (15) in parallel with an emitter resistor (16) of the transistor amplifier.
Claim 6
Dependent Claim
48 words
A noise reduction circuit arrangement according to Claim 3 wherein said cut-off frequency decreasing means includes a capacitor (7C) for bypassing the high-frequency band component produced from said high-pass filter means, and means (7a, 7b) responsive to said control signal to effect connection and disconnection of the capacitor.
Claim 7
Dependent Claim
43 words
A noise reduction circuit arrangement according to any of Claims 1 to 5 wherein said video signal level detector means comprises means .(5) for integrating the video signal, and level comparator means (6) for comparing an integrated output signal with a reference level.
Claim 8
Dependent Claim
47 words
A noise reduction circuit arrangement according to any of Claims 1 to 5 wherein said video signal level detector means comprises rectifier means (5a) for rectifying the video signal, and level comparator means (6) for comparing the level of a rectified output signal with a reference level.
References Cited (Backward Citations)
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