Video camera apparatus having an exposure control device

Claim 2

A video camera apparatus, comprising: (A) an image sensor for converting an image formed on an image sensing plane to an image signal; (B) an image processing circuit for performing a predetermined camera process on the image signal output from said image sensor and outputting a video signal based on a predetermined format; (C) an iris control circuit for controlling an iris by a feed-back loop for controlling an amount of incident light; (D) a gain control circuit for controlling a gain for amplifying the image signal by a feed-back loop serially connected to said iris control circuit; (E) a detecting circuit for extracting, between said image sensor and said image processing circuit, a predetermined signal from the image signal in each of a plurality of areas set in an image frame and detecting levels of the predetermined signals and distribution of the levels of the predetermined signals, said detecting circuit discriminating an exposure condition on the basis of the distribution; and (F) an exposure control circuit for selecting said areas and controlling said iris control circuit and said gain control circuit and correction responding speeds of said iris control circuit and said gain control circuit on the basis of the levels of the predetermined signals and the exposure condition.

Claim 3

An apparatus according to claim 1 , wherein said exposure control circuit is arranged to output a correcting signal to correct a change of the predetermined signal, depending on a detection value of the predetermined signal level corresponding to each of said plurality of areas detected by said detecting circuit and to correct said change of the predetermined signal level on the basis of the correcting signal, and said exposure control circuit is so arranged that a correction responding speed to the detection value of a smaller area is slower than that of a larger area.

Claim 4

An apparatus according to claim 2 , wherein said exposure control circuit is arranged to vary a time constant at the time of applying the correcting signal, in accordance with a size of each of said plurality of areas.

Claim 5

An apparatus according to claim 1 , wherein said detecting circuit is arranged to detect a level of a luminance signal of the image in each of said plurality of areas and to detect a change of the luminance level as a change of said predetermined signal level.

Claim 6

An apparatus according to claim 3 , wherein said exposure control circuit includes light amount limiting means for limiting an amount of incident light to said image sensing plane and the gain control circuit for varying a gain of said predetermined signal.

Claim 7

A video camera apparatus, comprising: (A) an image sensor for converting an image formed on an image sensing plane to an image signal; (B) an image processing circuit for performing a predetermined process on the image signal output from said image sensor and outputting an image signal based on a predetermined format; (C) an iris control circuit for controlling an iris by a feed-back loop for controlling an amount of incident light; (D) a gain control circuit for controlling a gain for amplifying the image signal by a feed-back loop serially connected to said iris control circuit and independently operable to the feed-back loop of said iris control circuit; (E) a detecting circuit for extracting, between said image sensor and said image processing circuit, a predetermined signal from the image signal in each of a plurality of areas set in an image frame corresponding to said image sensing plane and detecting levels of the predetermined signals and a distribution of the levels of the predetermined signals; and (F) an exposure control circuit for selecting said plurality of areas and controlling said iris control circuit and said gain control circuit and correction responding speeds of at least one of said iris control circuit and said gain control circuit on the basis of the levels of the predetermined signals and the distribution.

Claim 8

A video camera apparatus, comprising: (A) an image sensor for converting an image formed on an image sensing plane to an image signal; (B) an image processing circuit for performing a predetermined process on the image signal output from said image sensor and outputting an image signal based on a predetermined format; (C) an iris control circuit for controlling an iris by a feed-back loop for controlling an amount of incident light; (D) a gain control circuit for controlling a gain for amplifying the image signal by a feed-back loop serially connected to said iris control circuit and independently operable to the feed-back loop of said iris control circuit; (E) a detecting circuit for extracting, between said image sensor and said image processing circuit, a predetermined signal from the image signal in each of a plurality of areas set in an image frame corresponding to said image sensing plane and detecting levels of the predetermined signals and a distribution of the levels of the predetermined signals; and (F) an exposure control circuit for selecting said plurality of areas and controlling said iris control circuit and said gain control circuit and correction responding speeds of at least one of said iris control circuit and said gain control circuit on the basis of the levels of the predetermined signals and the distribution.

Claim 9

An apparatus according to claim 6 , wherein said detecting circuit is arranged to detect a level of luminance signal of the image in each of said plurality of areas and to detect a change of the luminance level as a change of said predetermined signal level.

Claim 10

An apparatus according to claim 6 , wherein said image sensor is arranged to set detection areas at a central portion and a portion around said central portion on said image sensing plane.

Claim 11

An apparatus according to claim 8 , wherein said exposure control circuit is arranged to output a correction signal for correcting a change of the predetermined signal, depending on a detection value of the predetermined signal level corresponding to each of said plurality of areas detected by said detecting circuit and to correct the change of the predetermined signal level according to output of the correction signal, and said exposure control circuit is so arranged that a responding speed of a correcting operation based on the correction signal corresponding to the detection area set at said central portion is slower than that of the correcting operation based on the correction signal corresponding to the detection area set around said central portion.

Claim 12

An apparatus according to claim 9 , wherein said exposure control circuit is arranged to vary a time constant at the time of applying the correction signal, in accordance with a size of each of said plurality of areas.

Claim 13

An apparatus according to claim 9 , wherein said exposure control circuit includes light amount limiting means for limiting an amount of incident light to said image sensing plane and the gain control circuit for varying a gain of said predetermined signal.

Claim 14

A video camera apparatus, comprising: (A) an image sensor for converting an image formed on an image sensing plane to an image signal; (B) an image processing circuit for performing a predetermined process on the image signal output from said image sensor and outputting an image signal based on a predetermined format; (C) an iris control circuit for controlling an iris by a feed-back loop for controlling an amount of incident light; (D) a gain control circuit for controlling a gain for amplifying the image signal by a feed-back loop serially connected to said iris control circuit; (E) a detecting circuit for extracting, between said image sensor and said image processing circuit, a predetermined signal from the image signal in each of a plurality of patterns set in an image frame and detecting levels of the predetermined signals and a pattern of the levels of the predetermined signals, said detecting circuit discriminating an exposure condition on the basis of the distribution; and (F) an exposure control circuit for selecting said areas and controlling said iris control circuit and said gain control circuit and correction responding speeds of at least one of said iris control circuit and said gain control circuit on the basis of the levels of the predetermined signals and the distribution.

Claim 15

A video camera apparatus, comprising: (A) an image sensor for converting an image formed on an image sensing plane to an image signal; (B) an image processing circuit for performing a predetermined process on the image signal output from said image sensor and outputting an image signal based on a predetermined format; (C) an iris control circuit for controlling an iris by a feed-back loop for controlling an amount of incident light; (D) a gain control circuit for controlling a gain for amplifying the image signal by a feed-back loop serially connected to said iris control circuit; (E) a detecting circuit for extracting, between said image sensor and said image processing circuit, a predetermined signal from the image signal in each of a plurality of patterns set in an image frame and detecting levels of the predetermined signals and a pattern of the levels of the predetermined signals, said detecting circuit discriminating an exposure condition on the basis of the distribution; and (F) an exposure control circuit for selecting said areas and controlling said iris control circuit and said gain control circuit and correction responding speeds of at least one of said iris control circuit and said gain control circuit on the basis of the levels of the predetermined signals and the distribution.

Claim 16

An apparatus according to claim 12 , wherein said exposure control circuit is arranged to output a correcting signal to correct a change of the predetermined signal, depending on a detection value of the predetermined signal level corresponding to each of said plurality of patterns detected by said detecting circuit and to correct a change of the predetermined signal level on the basis of the output of the correcting signal, and said exposure control circuit is so arranged that a correction responding speed to the detection value of a smaller area is slower than that of a larger size.

Claim 17

An apparatus according to claim 13 , wherein said smaller area is formed in a central portion of said image sensing plane and said larger area is equal to the whole image sensing plane.

Claim 18

An apparatus according to claim 12 , wherein said exposure control circuit is arranged to vary a time constant at the time of an exposure controlling operation in accordance with the size of areas.

Claim 19

An apparatus according to claim 12 , wherein said predetermined signal is a brightness level in said image signal.

Claim 20

An apparatus according to claim 12 , wherein said exposure control circuit controls a diaphragm which restricts an amount of incident light on image pick-up means and a gain of said image signal.

Claim 21

An apparatus according to claim 12 , wherein said exposure control circuit discriminates conditions of the image from a detection result of said detecting circuit and controls said plurality of patterns according to the discrimination so as to change over a light measuring pattern.

Claim 22

An exposure control method, comprising: (A) a step of performing a predetermined process on an image signal output from an image sensor and outputting an image signal based on a predetermined format; (B) a step of controlling an amount of incident light by controlling an iris with a first feed-back loop; (C) a step of controlling a gain for amplifying the image signal by using a second feed-back loop; (D) a step of extracting a predetermined signal from the image signal in each of a plurality of areas defined in an image frame, detecting levels of the predetermined signals and distribution of the levels of the predetermined signals and discriminating an exposure condition on the basis of the distribution; and (E) a step of controlling an exposure by selecting the areas and controlling the iris and the gain and correction responding speeds of the iris and the gain on the basis of the levels of the predetermined signals and the exposure condition.

Claim 23

An exposure control method, comprising: (A) a step of performing a predetermined process on an image signal output from an image sensor and outputting an image signal based on a predetermined format; (B) a step of controlling an amount of incident light by controlling an iris with a first feed-back loop; (C) a step of controlling a gain for amplifying the image signal by using a second feed-back loop; (D) a step of extracting a predetermined signal from the image signal in each of a plurality of areas defined in an image frame, detecting levels of the predetermined signals and distribution of the levels of the predetermined signals and discriminating an exposure condition on the basis of the distribution; and (E) a step of controlling an exposure by selecting the areas and controlling the iris and the gain and correction responding speeds of the iris and the gain on the basis of the levels of the predetermined signals and the exposure condition.

Claim 24

A method according to claim 19 , wherein said exposure controlling step outputs a correcting signal to correct a change of the predetermined signal depending on a detection value of the predetermined signal level corresponding to each of said plurality of areas and to correct the change of the predetermined signal level on the basis of the correcting signal, and in said exposure controlling step a correction responding speed to the detection value of a smaller area is slower than that of a larger area.

Claim 25

A method according to claim 20 , wherein in said exposure controlling step a time constant at the time of applying the correcting signal is varied in accordance with a size of each of said plurality of areas.

Claim 26

A method according to claim 19 , wherein in said extracting step a level of a luminance signal of the image in each of said plurality of areas is detected as a change of said predetermined signal level.

Claim 27

A method according to claim 21 , wherein said exposure controlling step includes a light amount limiting step of limiting an amount of incident light to said image sensor and the gain controlling step of varying a gain of said predetermined signal.