Television camera equipped with continuously-variable-speed electronic shutter function

Claim 2

A video camera comprising: an image sensor, including a continuously-variable-speed electronic shutter, for converting an optical signal into an electrical signal and outputting a video signal; a lens for focusing an image of a subject on said image sensor; an amplifier for amplifying said video signal and outputting an amplified signal; signal processing means for processing said amplified signal and outputting a processed video signal; video level detecting means for detecting a level of said processed video signal for each field and outputting a signal representing a detected video signal level; gain control means for controlling a gain of said amplifier so as to maintain the signal representing the detected video signal level at a fixed value in an AGC mode; shutter control means for calculating an estimated shutter amount, in a shutter mode, said shutter control means comprising means for (i) subtracting a target value of the video level from the detected video signal level to obtain a difference, (ii) multiplying the difference by a coefficient and a current shutter amount, corresponding to a preceding estimated shutter amount, to obtain a correction shutter amount, and (iii) adding said correction shutter amount to the current shutter amount to obtain said estimated shutter amount; shutter pulse generating means for supplying a shutter pulse to said image sensor in accordance with said estimated shutter amount; and control mode decision means for automatically placing said gain control means and the image sensor in said AGC mode or said shutter mode, in accordance with (i) said signal representing the detected video signal level, (ii) said estimated shutter amount, and (iii) said gain of said amplifier, said control mode decision means operating independently of whether an amount of light of the optical signal is constant.

Claim 3

A video camera according to claim 1, wherein said signal processing means divides the signal supplied from said amplifier on a field-by-field basis to process the signal.

Claim 4

A video camera according to claim 1, wherein said video level detecting means selects a part of the field area corresponding to the signal supplied from said signal processing means.

Claim 5

A video camera comprising: an image sensor, including a continuously-variable-speed electronic shutter, for converting an optical signal into an electrical signal and outputting a video signal; a lens for focusing an image of a subject on said image sensor; an amplifier for amplifying said video signal and outputting an amplified signal; signal processing means for processing said amplified signal and outputting a processed video signal; video level detecting means for detecting a level of said processed video signal for each field and outputting a signal representing a detected video signal level; gain control means for controlling a gain of said amplifier so as to maintain the signal representing the detected video signal level at a fixed value in an AGC mode and controlling the gain of said modifier in accordance with shutter control in a shutter mode; shutter control means for calculating an estimated shutter amount and a minute shutter amount, in the shutter mode, said shutter control means comprising means for (i) subtracting a target value of the video level from the detected video signal level to obtain a difference, (ii) multiplying the difference by a coefficient and a current shutter amount, corresponding to a preceding estimated shutter amount, to obtain a correction shutter amount, (iii) adding said correction shutter amount to the current shutter amount to obtain an imaginal estimated shutter amount, (iv) subtracting a minute shutter amount from the imaginal estimated shutter amount to obtain the estimated shutter amount, and (v) subtracting an optimized correction shutter amount from the correction shutter amount to obtain the minute shutter amount; shutter pulse generating means for supplying a shutter pulse to said image sensor, during a vertical or a horizontal blanking period, in accordance with said estimated shutter amount; shutter amount conversion means for (i) converting the minute shutter amount to a correction amount by dividing the minute shutter amount by the current shutter amount and multiplying by a coefficient so as to obtain the correction gain amount, and (ii) supplying said correction gain amount to said gain control means; and control mode decision means for automatically placing said gain control means and the image sensor in said AGC mode or said shutter mode, in accordance with (i) said signal representing the detected video signal level, (ii) said imaginal estimated shutter amount, and (iii) said gain of said amplifier, said control mode decision means operating independently of whether an amount of light of the optical signal is constant.

Claim 6

A video camera comprising: an image sensor, including a continuously-variable-speed electronic shutter, for converting an optical signal into an electrical signal and outputting a video signal; a lens for focusing an image of a subject on said image sensor; an amplifier for amplifying said video signal and outputting an amplified signal; signal processing means for processing said amplified signal and outputting a processed video signal; video level detecting means for detecting a level of said processed video signal for each field and outputting a signal representing a detected video signal level; gain control means for controlling a gain of said amplifier so as to maintain the signal representing the detected video signal level at a fixed value in an AGC mode and controlling the gain of said modifier in accordance with shutter control in a shutter mode; shutter control means for calculating an estimated shutter amount and a minute shutter amount, in the shutter mode, said shutter control means comprising means for (i) subtracting a target value of the video level from the detected video signal level to obtain a difference, (ii) multiplying the difference by a coefficient and a current shutter amount, corresponding to a preceding estimated shutter amount, to obtain a correction shutter amount, (iii) adding said correction shutter amount to the current shutter amount to obtain an imaginal estimated shutter amount, (iv) subtracting a minute shutter amount from the imaginal estimated shutter amount to obtain the estimated shutter amount, and (v) subtracting an optimized correction shutter amount from the correction shutter amount to obtain the minute shutter amount; shutter pulse generating means for supplying a shutter pulse to said image sensor, during a vertical or a horizontal blanking period, in accordance with said estimated shutter amount; shutter amount conversion means for (i) converting the minute shutter amount to a correction amount by dividing the minute shutter amount by the current shutter amount and multiplying by a coefficient so as to obtain the correction gain amount, and (ii) supplying said correction gain amount to said gain control means; and control mode decision means for automatically placing said gain control means and the image sensor in said AGC mode or said shutter mode, in accordance with (i) said signal representing the detected video signal level, (ii) said imaginal estimated shutter amount, and (iii) said gain of said amplifier, said control mode decision means operating independently of whether an amount of light of the optical signal is constant.

Claim 7

A video camera according to claim 4, wherein said signal processing means divides the signal supplied from said amplifier on a field-by-field basis to process the signal.

Claim 8

A video camera according to claim 4, wherein said video level detecting unit selects a part of the field area corresponding to the signal supplied from said signal processing means.