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US 7,024,108 B2Granted
Image pickup apparatus with precise exposure value, exposure decision method, program, and storage medium
AssigneeCanon Kabushiki Kaisha
InventorKenji Takahashi
Life of this patent
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Abstract
The object of this invention is to increase the precision of an exposure value in a scan AE scheme. To achieve this object, an image is picked at a plurality of exposure values. Screen-split brightness values and exposure value differences are obtained for the respective exposure values. Two screen-split brightness values and exposure value differences are selected from the relationship between the exposure value differences. A brightness value is calculated from the selected values to decide an exposure value in actual exposure.
Claims8
An image pickup apparatus comprising:
- an image pickup device that picks up an object;
- and
- a processing device having
- a brightness value calculation unit that obtains a plurality of brightness values at respective exposure values from a plurality of image data obtained by picking up an image of the object by said image pickup device at a plurality of different exposure values,
- an exposure difference value calculation unit that calculates a plurality of exposure difference values representing differences between the brightness values and a preset target brightness value in actual exposure, and
- an exposure value calculation unit configured to calculate an exposure value in actual exposure on the basis of at least two image data of the plurality of image data in accordance with calculation results of said exposure difference value calculation unit,
- wherein said exposure difference calculation unit calculates the exposure difference values with respect to said at least two image data, and said exposure value calculation unit calculates the exposure value in actual exposure using a ratio of the exposure difference values.
4 more elements
An exposure decision method comprising:
- a brightness value calculation step of obtaining brightness values of an image at respective exposure values from a plurality of image data obtained by picking up an image at a plurality of different exposure values;
- an exposure difference value calculation step of calculating exposure difference values representing differences between the brightness values and a preset target brightness value in actual exposure;
- and
- an exposure value calculation step of calculating an exposure value in actual exposure on the basis of at least two image data of the plurality of image data, and using different formulas in accordance with calculation results in the exposure difference value calculation steps,
- wherein said exposure difference value calculation step calculates the exposure difference values with respect to said at least two image data, and said exposure value calculation step calculates the exposure value in actual exposure by using a ratio of the exposure difference values.
2 more elements
Dependencies are inferred from the claim text.