Television camera equipped with continuously-variable-speed electronic shutter function
First Claim
1. 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.
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Abstract
A television camera equipped with a continuously-variable-speed electronic shutter function which can control the charge-storing time of a solid-state image sensor and an amplifier so that a video signal follows the optimum light amount for a subject at high speed and with high accuracy. A shutter-equipped image sensor which is controlled by a shutter pulse generating unit, converts light incident on an optical lens into an electric signal. The electric signal, after being passed through an amplifier and a signal processing unit, is detected by a video level detecting unit as a video level. A shutter control unit holds the shutter amount corresponding to the video level for each field to immediately calculate an estimated shutter amount by using a predetermined equation, and supplies the calculated shutter amount to the shutter pulse generating unit for each field. A control mode decision unit exclusively controls a gain control unit serving as an AGC and the shutter control unit.
31 Citations
6 Claims
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1. A video camera comprising:
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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. - View Dependent Claims (2, 3)
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4. A video camera comprising:
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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. - View Dependent Claims (5, 6)
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Specification