Auto iris/gamma correction apparatus for making automatic exposure adjustment and/or automatic gamma correction in response to video signal and image sensing apparatus comprising such auto iris/gamma correction apparatus

Claim 2

A gamma correction apparatus responsive to a video signal obtained from image sensing means (1, 3, 4) for automatically performing gamma correction of the video signal, comprising means (43), having a plurality of gamma correction values, for performing gamma correction of said video signal according to a particular gamma correction value selected from said plurality of gamma correction values, means (7, 8, 9), responsive to said video signal, for providing in a time-divisional manner a plurality of sampling areas of a sensed image in said video signal, evaluating value detecting means (6, 10a, 10b, 10c, 10d, 10e, 10f), responsive to said plurality of sampling areas, for detecting a level of a luminance signal in the video signal in each of said plurality of sampling areas and for supplying the level as a first evaluating value for the corresponding sampling area so as to form a plurality of first evaluating values, means (40a, 40b, 40c, 40d, 40e, 40f, 41, 44), operative in response to said plurality of first evaluating values, for computing a contrast value indicative of contrast of the sensed image, and means (44), connected to said gamma correction performing means and responsive to said contrast value, for determining the particular one of said plurality of gamma correction values to be used by said gamma correction performing means in performing gamma correction of said video signal.

Claim 3

The gamma correction apparatus according to claim 1, wherein said contrast value computing means comprises means for selecting a maximum value A and a minimum value B of the first evaluating values and computing a ratio (A/B) of the maximum value A to the minimum value B, said ratio being indicative of the contrast of said image, and said particular one gamma correction value determining means comprises means for determining a gamma correction value γ corresponding to said ratio (A/B) based on the following relation: γ=a LOG (A/B)+b where: a and b are respectively negative and positive constants.

Claim 4

The gamma correction apparatus according to claim 1, wherein said plurality of the sampling areas are set such that all the sampling areas encompass corresponding image areas of substantially the same size.

Claim 5

The gamma correction apparatus according to claim 1, wherein said plurality of the sampling areas are set such that at least one of the sampling areas encompasses a corresponding image area having a different size from the size of corresponding image areas encompassed by other one of said sampling area.

Claim 6

An auto iris-gamma correction apparatus responsive to a video signal obtained from image sensing means (1, 3, 4) for automatically adjusting exposure to an object and automatically performing gamma correction of the video signal, comprising: means (2, 5, 19) for changing exposure to said object, means (43), having a plurality of gamma correction values, for performing gamma correction of said video signal according to a particular gamma correction value selected from said plurality of gamma correction values, means (7, 8, 9), responsive to said video signal, for providing in a time-divisional manner a plurality of sampling areas of a sensed image in said video signal, evaluating value detecting means (6, 10a, 10b, 10c, 10d, 10e, 10f), responsive to said plurality of sampling areas, for detecting a level of a luminance signal in the video signal in each of said plurality of sampling areas and for supplying the level as a first evaluating value for the corresponding sampling area so as to form a plurality of first evaluating values, first means (12), responsive to said plurality of first evaluating values, for computing a second evaluating value representing the sensed image, exposure control means (17, 18), operative in response to said second evaluating value and a predetermined value, for controlling said exposure changing means such that said second evaluating value coincides with the predetermined desired value, second means (40a, 40b, 40c, 40d, 40e, 40f, 41, 44), operative in response to said plurality of first evaluating values, for computing a contrast value indicative of contrast of the image, and means (44), connected to said gamma correction performing means and responsive to said contrast value, for determining the particular one of said plurality of gamma correction values to be used by said gamma correction performing means in performing gamma correction of said video signal.

Claim 7

An auto iris-gamma correction apparatus responsive to a video signal obtained from image sensing means (1, 3, 4) for automatically adjusting exposure to an object and automatically performing gamma correction of the video signal, comprising: means (2, 5, 19) for changing exposure to said object, means (43), having a plurality of gamma correction values, for performing gamma correction of said video signal according to a particular gamma correction value selected from said plurality of gamma correction values, means (7, 8, 9), responsive to said video signal, for providing in a time-divisional manner a plurality of sampling areas of a sensed image in said video signal, evaluating value detecting means (6, 10a, 10b, 10c, 10d, 10e, 10f), responsive to said plurality of sampling areas, for detecting a level of a luminance signal in the video signal in each of said plurality of sampling areas and for supplying the level as a first evaluating value for the corresponding sampling area so as to form a plurality of first evaluating values, first means (12), responsive to said plurality of first evaluating values, for computing a second evaluating value representing the sensed image, exposure control means (17, 18), operative in response to said second evaluating value and a predetermined value, for controlling said exposure changing means such that said second evaluating value coincides with the predetermined desired value, second means (40a, 40b, 40c, 40d, 40e, 40f, 41, 44), operative in response to said plurality of first evaluating values, for computing a contrast value indicative of contrast of the image, and means (44), connected to said gamma correction performing means and responsive to said contrast value, for determining the particular one of said plurality of gamma correction values to be used by said gamma correction performing means in performing gamma correction of said video signal.

Claim 8

The auto iris-gamma correction apparatus according to claim 5, wherein, said first computing means comprises: means for weighting each of said first evaluating values with a predetermined weight, and means for decreasing the weighting of any one of the first evaluating values in computing said second evaluating value whenever the one of the first evaluating values exceeds a predetermined allowable range with respect to a reference value.

Claim 9

An image sensing apparatus for automatically performing gamma correction of a video signal, comprising: image sensing means (1, 3, 4) having a lens and an image sensor for generating a video signal in response to incident light from an object, means (43), having a plurality of gamma correction values, for performing gamma correction of said video signal according to a particular gamma correction value selected from said plurality of gamma correction values, means (7, 8, 9), responsive to said video signal, for providing in a time-divisional manner a plurality of sampling areas of a sensed image in said video signal, evaluating value detecting means (6, 10a, 10b, 10c, 10d, 10e, 10f), responsive to said plurality of sampling areas, for detecting a level of a luminance signal in the video signal in each of said plurality of sampling areas and for supplying the level as a first evaluating value for the corresponding sampling area so as to form a plurality of first evaluating values, means (40a, 40b, 40c, 40d, 40e, 40f, 41, 44), operative in response to said plurality of first evaluating values, for computing a contrast value indicative of contrast of the sensed image, and means (44), connected to said gamma correction performing means and responsive to said contrast value, for determining the particular one of said plurality of gamma correction values to be used by said gamma correction performing means in performing gamma correction of said video signal.

Claim 10

An image sensing apparatus for automatically performing gamma correction of a video signal, comprising: image sensing means (1, 3, 4) having a lens and an image sensor for generating a video signal in response to incident light from an object, means (43), having a plurality of gamma correction values, for performing gamma correction of said video signal according to a particular gamma correction value selected from said plurality of gamma correction values, means (7, 8, 9), responsive to said video signal, for providing in a time-divisional manner a plurality of sampling areas of a sensed image in said video signal, evaluating value detecting means (6, 10a, 10b, 10c, 10d, 10e, 10f), responsive to said plurality of sampling areas, for detecting a level of a luminance signal in the video signal in each of said plurality of sampling areas and for supplying the level as a first evaluating value for the corresponding sampling area so as to form a plurality of first evaluating values, means (40a, 40b, 40c, 40d, 40e, 40f, 41, 44), operative in response to said plurality of first evaluating values, for computing a contrast value indicative of contrast of the sensed image, and means (44), connected to said gamma correction performing means and responsive to said contrast value, for determining the particular one of said plurality of gamma correction values to be used by said gamma correction performing means in performing gamma correction of said video signal.

Claim 11

The image sensing apparatus according to claim 7, wherein said contrast value computing means comprises means for selecting a maximum value A and a minimum value B of the first evaluating values and computing a ratio (A/B) of the maximum value A to the minimum value B, said ratio being indicative of the contrast of said image, and said particular one gamma correction value determining means comprises means for determining a gamma correction value γ corresponding to said ratio (A/B) based on the following relation: γ=a LOG (A/B)+b where: a and b are respectively negative and positive constants.

Claim 12

The image sensing apparatus according to claim 7, wherein said plurality of the sampling areas are set such that all the sampling areas encompass corresponding image areas of substantially the same size.

Claim 13

The image sensing apparatus according to claim 7, wherein said plurality of the sampling areas are set such that at least one of the sampling areas encompasses a corresponding image area having a different size from the size of corresponding image areas encompassed by other one of said sampling areas.

Claim 14

An image sensing apparatus for automatically adjusting exposure to an object and automatically performing gamma correction of a video signal, comprising: image sensing means (1, 3, 4) having a lens and an image sensor for generating a video signal in response to incident light from an object, means (2, 5, 19) for changing exposure to said object, means (43), having a plurality of gamma correction values, for performing gamma correction of said video signal according to a particular gamma correction value selected from said plurality of gamma correction values, means (7, 8, 9), responsive to said video signal, for providing in a time-divisional manner a plurality of sampling areas of a sensed image in said video signal, evaluating value detecting means (6, 10a, 10b, 10c, 10d, 10e, 10f), responsive to said plurality of sampling areas, for detecting a level of a luminance signal in the video signal in each of said plurality of sampling areas and for supplying the level as a first evaluating value for the corresponding sampling area so as to form a plurality of first evaluating values, first means (12), responsive to said plurality of first evaluating values, for computing a second evaluating value representing the sensed image, exposure control means (17, 18), operative in response to said second evaluating value and a predetermined value, for controlling said exposure changing means such that said second evaluating value coincides with the predetermined desired value, second means (40a, 40b, 40c, 40d, 40e, 40f, 41, 44), operative in response to said plurality of first evaluating values, for computing a contrast value indicative of contrast of the image, and means (44), connected to said gamma correction performing means and responsive to said contrast value, for determining the particular one of said plurality of gamma correction values to be used by said gamma correction performing means in performing gamma correction of said video signal.

Claim 15

An image sensing apparatus for automatically adjusting exposure to an object and automatically performing gamma correction of a video signal, comprising: image sensing means (1, 3, 4) having a lens and an image sensor for generating a video signal in response to incident light from an object, means (2, 5, 19) for changing exposure to said object, means (43), having a plurality of gamma correction values, for performing gamma correction of said video signal according to a particular gamma correction value selected from said plurality of gamma correction values, means (7, 8, 9), responsive to said video signal, for providing in a time-divisional manner a plurality of sampling areas of a sensed image in said video signal, evaluating value detecting means (6, 10a, 10b, 10c, 10d, 10e, 10f), responsive to said plurality of sampling areas, for detecting a level of a luminance signal in the video signal in each of said plurality of sampling areas and for supplying the level as a first evaluating value for the corresponding sampling area so as to form a plurality of first evaluating values, first means (12), responsive to said plurality of first evaluating values, for computing a second evaluating value representing the sensed image, exposure control means (17, 18), operative in response to said second evaluating value and a predetermined value, for controlling said exposure changing means such that said second evaluating value coincides with the predetermined desired value, second means (40a, 40b, 40c, 40d, 40e, 40f, 41, 44), operative in response to said plurality of first evaluating values, for computing a contrast value indicative of contrast of the image, and means (44), connected to said gamma correction performing means and responsive to said contrast value, for determining the particular one of said plurality of gamma correction values to be used by said gamma correction performing means in performing gamma correction of said video signal.

Claim 16

The image sensing apparatus according to claim 11, wherein, said first computing means comprises: means for weighting each of said first evaluating values with a predetermined weight, and means for decreasing the weighting of any one of the first evaluating values in computing said second evaluating value whenever the one of the first evaluating values exceeds a predetermined allowable range with respect to a reference value.