Exposing apparatus for performing exposure control corresponding to the luminance level of an object

A video camera having an exposing apparatus, comprising:

• a lens group for fetching a light from an object;
• an iris for adjusting an amount of light from said lens group;
• an image pickup device for converting the light which passed through said iris into an electric signal;
• an AGC circuit for setting a signal level of an output signal from said image pickup device into a predetermined level;
• a detecting circuit for detecting a luminance signal level from an output signal from said AGC circuit;
• a reference level signal setting circuit for supplying an exposure control reference value;
• a control circuit for producing control signals based upon said luminance signal level when an output level of said detecting circuit is larger than a reference level modulation value, said control signals being utilized to control said iris, said image pickup device and said AGC circuit;
• and
• an exposure control reference value modulating circuit for modulating said exposure control reference value in accordance with a reference level modulation coefficient to produce said reference level modulation value, said exposure control reference value modulating circuit including means for receiving said control signals, means for setting a start and an end luminance levels and means for calculating said reference level modulation coefficient in accordance with said start and end luminance levels.

An exposing apparatus in a video camera, comprising:

• a lens group for fetching a light from an object;
• an iris for adjusting an amount of light from said lens group;
• an image pickup device for converting the light which passed through said iris into an electric signal;
• an AGC circuit for setting a signal level of an output signal from said image pickup device into a predetermined level;
• a detecting circuit for detecting a luminance signal level from an output signal from said AGC circuit;
• a reference level signal setting circuit for setting an exposure control reference value to control the iris in which said exposure control reference value can be arbitrarily set and in which said iris is controlled so as to be opened a relatively small amount in a high luminance state by increasing said exposure control reference value;
• a control circuit for producing a control signal in correspondence to said luminance signal level when an output level of said detecting circuit is larger than a reference level modulation value;
• and
• an exposure control reference value modulating circuit receiving said control signal for modulating said exposure control reference value so as to form said reference level modulation value when the iris is controlled, said exposure control reference value modulating circuit comprises a luminance level operating circuit to which a gain of said iris and a gain amount of said AGC circuit are supplied, a high luminance judging circuit to which an output signal of said luminance level operating circuit is input and into which a start luminance level and an end luminance level of the reference level modulation are set, a modulation start/end setting circuit for setting the start luminance level and the end luminance level of the modulation of said luminance signal, a modulation coefficient calculating circuit to which a modulation coefficient calculation level is input on the basis of set values of said start and end luminance levels, and a modulation degree setting circuit to set the maximum modulation degree of said modulation coefficient calculating circuit.

A video camera having an exposing apparatus, comprising:

• a lens group for fetching a light from an object;
• an iris for adjusting an amount of light from said lens group;
• an image pickup device for converting the light which passed through said iris into an electric signal;
• an AGC circuit for setting a signal level of an output signal from said image pickup device into a predetermined level;
• a detecting circuit for detecting a luminance signal level from an output signal from said AGC circuit;
• a reference level signal setting circuit for setting an exposure control reference value to control the iris in which said exposure control reference value can be arbitrarily set and in which said iris is controlled so as to be opened a relatively small amount in a high luminance state by increasing said exposure control reference value;
• a control circuit for producing a control signal in correspondence to said luminance signal level when an output level of said detecting circuit is larger than a reference level modulation value;
• and
• an exposure control reference value modulating circuit receiving said control signal for modulating said exposure control reference value so as to form said reference level modulation value when the iris is controlled, said exposure control reference value modulating circuit comprises a luminance level operating circuit to which a gain of said iris and a gain amount of said AGC circuit are supplied, a high luminance judging circuit to which an output signal of said luminance level operating circuit is input and into which a start luminance level and an end luminance level of the reference level modulation are set, a modulation start/end setting circuit for setting the start luminance level and the end luminance level of the modulation of said luminance signal, a modulation coefficient calculating circuit to which a modulation coefficient calculation level is input on the basis of set values of said start and end luminance levels, and a modulation degree setting circuit to set the maximum modulation degree of said modulation coefficient calculating circuit.