Automatic exposure control with regard to backlight

Claim 2

The automatic exposure control apparatus according to claim 1, wherein said select region luminance calculation means selects the predetermined number of regions having low average luminances of said plurality of regions.

Claim 3

The automatic exposure control apparatus according to claim 1, wherein said value representing said backlight degree is calculated by u = k*(c1 - V) , where u, k, cl and V represent said value, a gain, a constant and said average luminance obtained by said select region luminance calculation means, respectively, and if cl - V < 0 then u = 0.

Claim 4

The automatic exposure control apparatus according to claim 1, wherein said select region luminance calculation means arranges said average luminances obtained by said region luminance calculation means in the luminance order, groups said plurality of regions into a plurality of sets according to said luminance order, and calculates an average luminance of each set of said plurality of sets; said backlight degree calculation means calculates a value representing a backlight degree based on said average luminance of each set of said plurality of sets.

Claim 5

The automatic exposure control apparatus according to claim 1, wherein said value representing said backlight degree is calculated according to the rules of the fuzzy inference.

Claim 6

The automatic exposure control apparatus according to claim 1, wherein said value representing said backlight degree is calculated according to a linear multiple function.

Claim 7

An automatic exposure control apparatus comprising: state judgment means for judging whether an image frame is in a backlight state or in an excessive frontlight state; image frame luminance calculation means for calculating an average luminance of said image frame; region luminance calculation means for calculating average luminances of a plurality of regions, said plurality of regions constituting said image frame; first select region luminance calculation means for arranging said average luminances obtained by said region luminance calculation means in the luminance order, for selecting at least one of said plurality of regions according to said luminance order, and for calculating an average luminance of said selected regions; second select region luminance calculation means for arranging said average luminances obtained by said region luminance calculation means in the luminance order, for selecting at least another one of said plurality of regions according to said luminance order, and for calculating an average luminance of said selected regions; backlight degree calculation means for calculating a first value representing a backlight degree based on said average luminance obtained by said first select region luminance calculation means; excessive frontlight degree calculation means for calculating a second value representing an excessive frontlight degree based on said average luminance obtained by said second select region luminance calculation means; correction amount determination means for determining a correction amount based on the judgment result by said state judgment means, said first value and said second value; target luminance calculation means for calculating a target average luminance for an exposure correction based on said correction amount; and exposure correction means for correcting an exposure so that said average luminance obtained by said image frame luminance calculation means is kept substantially equal to said target average luminance.

Claim 8

The automatic exposure control apparatus according to claim 7, wherein said image frame includes an upper region and a lower region, said state judgment means compares an average luminance of said upper region with an average luminance of said lower region, and judges whether said image frame is in a backlight state or in an excessive frontlight state based on the result of comparison.

Claim 9

The automatic exposure control apparatus according to claim 7, wherein said first select region luminance calculation means selects the predetermined number of regions having low average luminances of said plurality of regions.

Claim 10

The automatic exposure control apparatus according to claim 7, wherein said second select region luminance calculation means selects the predetermined number of regions having high average luminances of said plurality of regions.

Claim 11

The automatic exposure control apparatus according to claim 7, wherein said second select region luminance calculation means selects the predetermined number of regions having low average luminances of said plurality of regions.

Claim 12

The automatic exposure control apparatus according to claim 7, wherein said image frame includes a lower central region, an upper region, a left region and a right region; said state judgment means compares an average luminance of a first region with an average luminance of a second region and judges whether said image frame is in a backlight state or in an excessive frontlight state based on the result of comparison; where, said first region is a combination of said upper region with one of said left region and said right region, which has a lower average luminance than the other, and said second region is a combination of said lower central region with one of said left region and said right region, which has a higher average luminance than the other.

Claim 13

The automatic exposure control apparatus according to claim 12, wherein the sum of the vertical length of said left region and the vertical length of said upper region is smaller than the vertical length of said image frame, and the sum of a vertical length of said right region and said vertical length of said upper region is smaller than said vertical length of said image frame.

Claim 14

The automatic exposure control apparatus according to claim 7, wherein said image frame includes a first upper region and a lower region; said image frame also includes a lower central region, a second upper region, a left region and a right region; said state judgment means includes: (a) first/second region comparison means for comparing an average luminance of a first region with an average luminance of a second region and for generating a first judgment value indicating the result of comparison, (b) upper/lower region comparison means for comparing an average luminance of said first upper region with an average luminance of said lower region and for generating a second judgment value indicating the result of comparison, and (c) judgment means for judging whether said image frame is in a backlight state or in an excessive frontlight state based on said first judgment value and said second judgment value; where, said first region is a combination of said second upper region with one of said left region and said right region, which has a lower average luminance than the other, and said second region is a combination of said lower central region with one of said left region and said right region, which has a higher average luminance than the other.

Claim 15

The automatic exposure control apparatus according to claim 7, wherein said image frame includes a lower central region, an upper region, a left region and a right region; said state judgment means includes: (a) first/second region comparison means for comparing an average luminance of a first region with an average luminance of a second region and for generating a judgment value indicating the result of comparison, (b) correlation calculation means for calculating a correlation value representing a correlation relationship between the distribution of said average luminances obtained by region luminance calculation means and a predetermined distribution of luminances, and (c) judgment means for judging whether said image frame is in a backlight state or in an excessive frontlight state based on said judgment value and said correlation value; where, said first region is a combination of said upper region with one of said left region and said right region, which has a higher average luminance than the other, and said second region is a combination of said lower central region with one of said left region and said right region, which has a lower average luminance than the other.

Claim 16

The automatic exposure control apparatus according to claim 7, wherein said image frame includes a central region and a peripheral region; said image frame also includes a lower central region, an upper region, a left region and a right region; said state judgment means includes: (a) first/second region comparison means for comparing an average luminance of a first region with an average luminance of a second region and for generating a first judgment value indicating the result of comparison, (b) central region comparison means for comparing an average luminance of said central region with an average luminance of said image frame and for generating a second judgment value indicating the result of comparison, (c) correction means for correcting said first judgment value based on said second judgment value, and (d) judgment means for judging whether said image frame is in a backlight state or in an excessive frontlight state based on said corrected first judgment value; where, said first region is a combination of said upper region with one of said left region and said right region, which has a higher average luminance than the other, and said second region is a combination of said lower central region with one of said left region and said right region, which has a lower average luminance than the other.

Claim 17

The automatic exposure control apparatus according to claim 7, wherein said image frame includes a first upper region and a lower region; said image frame also includes a lower central region, a second upper region, a left region and a right region; said automatic exposure control apparatus further includes indoor/outdoor judgment means for judging whether indoors or outdoors; said state judgment means includes: (a) first/second region comparison means for comparing an average luminance of a first region with an average luminance of a second region and for generating a first judgment value indicating the result of comparison, (b) upper/lower region comparison means for comparing an average luminance of said first upper region with an average luminance of said lower region and for generating a second judgment value indicating the result of comparison, (c) select means for selecting one of said first judgment value and said second judgment value according to the result of judgment by said indoor/outdoor judgment means, and (d) judgment means for judging whether said image frame is in a backlight state or in an excessive frontlight state based on said selected judgment value; where, said first region is a combination of said second upper region with one of said left region and said right region, which has a higher average luminance than the other, and said second region is a combination of said lower central region with one of said left region and said right region, which has a lower average luminance than the other.

Claim 18

The automatic exposure control apparatus according to claim 17, wherein said indoor/outdoor judgment means includes: (a) detecting means for detecting infrared rays, (b) conversion means for converting said detected infrared rays into an electric signal, and (c) judgment means for judging whether indoors or outdoors based on said electric signal.

Claim 19

The automatic exposure control apparatus according to claim 17, wherein said indoor/outdoor judgment means includes: (a) dividing means for dividing said average luminance obtained by said image frame luminance calculation means by a diaphragm value, (b) judgment means for judging whether indoors or outdoors based on the result of division by said dividing means.

Claim 20

The automatic exposure control apparatus according to claim 17, wherein said indoor/outdoor judgment means includes: (a) detecting means for detecting a color temperature, (b) conversion means for converting said color temperature into an electric signal, and (c) judgment means for judging whether indoors or outdoors based on said electric signal.

Claim 21

The automatic exposure control apparatus according to claim 17, wherein said indoor/outdoor judgment means includes: (a) first calculation means for calculating an average of a color difference of said image frame, (b) second calculation means for calculating a color temperature based on said average of said color difference, (c) conversion means for converting said color temperature into an electric signal, and (d) judgment means for judging whether indoors or outdoors based on said electric signal.

Claim 22

The automatic exposure control apparatus according to claim 1, wherein said backlight degree calculation means includes: (a) normalization means for normalizing said average luminance obtained by said select region luminance calculation means, and (b) calculation means for calculating said value representing said backlight degree based on said normalized average luminance.

Claim 23

The automatic exposure control apparatus according to claim 7, wherein said backlight degree calculation means includes: (a) normalization means for normalizing said average luminance obtained by said first select region luminance calculation means, and (b) calculation means for calculating said first value representing said backlight degree based on said normalized average luminance; said excessive frontlight degree calculation means includes: (a) normalization means for normalizing said average luminance obtained by said second select region luminance calculation means, and (b) calculation means for calculating said second value representing said excessive frontlight degree based on said normalized average luminance.

Claim 24

The automatic exposure control apparatus according to claim 7, wherein said select region luminance calculation means arranges said average luminances obtained by said region luminance calculation means in the luminance order, groups said plurality of regions into a plurality of sets according to said luminance order, and calculates an average luminance of each set of said plurality of sets; said backlight degree calculation means calculates a value representing a backlight degree based on said average luminance of each set of said plurality of sets.

Claim 25

The automatic exposure control apparatus according to claim 7, wherein said value representing said backlight degree is calculated according to the rules of the fuzzy inference.

Claim 26

The automatic exposure control apparatus according to claim 7, wherein said value representing said backlight degree is calculated according to a linear multiple function.