Noise reduction circuit arrangement of solid-state video camera

Claim 2

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 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 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 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 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; said correcting means comprising variable gain amplifier means 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, said variable gain amplifier means including a transistor amplifier responsive to said control signal to switch connection and disconnection of a capacitor in parallel with an emitter resistor of the transistor amplifier.

Claim 3

A noise reduction circuit arrangement according to claim 1 wherein said video signal level detector means comprises means for integrating the video signal, and level comparator means for comparing an integrated output signal with a reference level.

Claim 4

A noise reduction circuit arrangement according to claim 1 wherein said video signal level detector means comprises rectifier means for rectifying the video signal, and level comparator means for comparing the level of a rectified output signal with a reference level.

Claim 5

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 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 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 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 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; said correcting means comprising means 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, said cut-off frequency decreasing means including a capacitor for bypassing the high-frequency band component produced from said high-pass filter means, and means responsive to said control signal to effect connection and disconnection of the capacitor.

Claim 6

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 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 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 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 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; said correcting means comprising means 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, said cut-off frequency decreasing means including a capacitor for bypassing the high-frequency band component produced from said high-pass filter means, and means responsive to said control signal to effect connection and disconnection of the capacitor.

Claim 7

A noise reduction circuit arrangement according to claim 4 wherein said video signal level detector means comprises means for integrating the video signal, and level comparator means for comparing an integrated output signal with a reference level.

Claim 8

A noise reduction circuit arrangement according to claim 4 wherein said video signal level detector means comprises rectifier means for rectifying the video signal, and level comparator means for comparing the level of a rectified output signal with a reference level.

Claim 9

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 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 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 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 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; said video signal level detector means including means for integrating the video signal, and level comparator means for comparing an integrated output signal with a reference level.

Claim 10

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 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 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 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 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; said video signal level detector means including means for integrating the video signal, and level comparator means for comparing an integrated output signal with a reference level.

Claim 11

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 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 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 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 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; said video signal level detector means including rectifier means for rectifying the video signal, and level comparator means for comparing the level of a rectified output signal with a reference level.

Claim 12

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 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 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 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 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; said video signal level detector means including rectifier means for rectifying the video signal, and level comparator means for comparing the level of a rectified output signal with a reference level.

Claim 13

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 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 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 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 fitler 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 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; said correcting means including variable gain amplifier means 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; and said video signal level detector means including means for integrating the video signal, and level comparator means for comparing an integrated output signal with a reference level.

Claim 14

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 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 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 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 fitler 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 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; said correcting means including variable gain amplifier means 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; and said video signal level detector means including means for integrating the video signal, and level comparator means for comparing an integrated output signal with a reference level.

Claim 15

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 supplied with the video signal produced fromt he image pickup element, for passing a high-frequency band component of the video signal; level detector means 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 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 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; said correcting means including variable gain amplifier means 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; and said video signal level detector means including rectifier means for rectifying the video signal, and level comparator means for comparing the level of a rectified output signal with a reference level.

Claim 16

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 supplied with the video signal produced fromt he image pickup element, for passing a high-frequency band component of the video signal; level detector means 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 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 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; said correcting means including variable gain amplifier means 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; and said video signal level detector means including rectifier means for rectifying the video signal, and level comparator means for comparing the level of a rectified output signal with a reference level.

Claim 17

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 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 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 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 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; said correcting means including means 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; and said video signal level detector means including means for integrating the video signal, and level comparator means for comparing an integrated output signal with a reference level.

Claim 18

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 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 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 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 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; said correcting means including means 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; and said video signal level detector means including means for integrating the video signal, and level comparator means for comparing an integrated output signal with a reference level.

Claim 19

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 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 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 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 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; said correcting means including means 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; and said video signal level detector means including rectifier means for rectifying the video signal, and level comparator means for comparing the level of a rectified output signal with a reference level.

Claim 20

A noise reduction circuit arrangement under low brightness operation of a video camera comprising: low-pass filter means 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 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 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 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 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; said correcting means including means 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; and said video signal level detector means including rectifier means for rectifying the video signal, and level comparator means for comparing the level of a rectified output signal with a reference level.