Image acquisition apparatus, image obtaining method, image obtaining program, and storage medium
An image acquisition apparatus includes: an image acquisition device that includes normal image-acquisition pixels and a phase-difference detection pixel; a shift unit that shifts the image acquisition device; a phase-difference-pixel correcting unit that corrects a pixel value obtained by the phase-difference detection pixel to a value equivalent to values obtained by the normal image-acquisition pixels; a pixel storage unit that arranges and stores the pixel values after the correction at storage areas; and a high-resolution-image compositing unit that composites the stored pixel values to generate a high-resolution image. The shift unit shifts the image acquisition device such that pixel values that correspond to a specific color and that include the pixel value of a normal image-acquisition pixel exist at the same pixel position as the phase-difference detection pixel in the high-resolution image. The high-resolution-image compositing unit composites the pixel values corresponding to the specific color at a predetermined compositing ratio.
1. An image acquisition apparatus comprising:
an image acquisition device that includes normal image-acquisition pixels periodically provided with color filters having a plurality of colors, and a phase-difference detection pixel used for focus detection;
a shift mechanism that is configured to shift the image acquisition device; and
a hardware processor that, under control of a program stored in a memory, performs:
shifting, by controlling the shift mechanism, the image acquisition device in a predetermined shift direction by a shift amount in units of subpixels;
correcting, through interpolation, a pixel value obtained by the phase-difference detection pixel to a value equivalent to values obtained by the normal image-acquisition pixels;
arranging and storing the pixel value of each of the pixels of the image acquisition device corrected in the correcting at a storage area corresponding to the shift direction and shift amount of the image acquisition device shifted in the shifting; and
compositing the pixel values of the plurality of pixels stored in the storing, thereby generating a high-resolution image having a higher resolution than a resolution of the image acquisition device,
wherein:
in the shifting, the image acquisition device is shifted such that a plurality of pixel values that correspond to a specific color of at least one type of the color filters provided for the normal image-acquisition pixels and that include the pixel value of at least one of the normal image-acquisition pixels exist at a same pixel position as the phase-difference detection pixel in the high-resolution image,
in the compositing, the plurality of pixel values corresponding to the specific color are composited at a predetermined compositing ratio, and
in the compositing, the compositing ratio is controlled based on a contrast at a position corresponding to at least the phase-difference detection pixel in the high-resolution image.
2. The image acquisition apparatus according to claim 1 , wherein the hardware processor, under control of the program stored in the memory, further performs:
detecting a moving-object degree at a position of a pixel at which a plurality of pixel values corresponding to a same color exist, from the pixel values at the pixel, and
wherein, in the compositing, the compositing ratio is further controlled based on the detected moving-object degree.
3. The image acquisition apparatus according to claim 2 , wherein the corrected pixel value of the phase-difference detection pixel is not used to detect the moving-object degree.
4. An image obtaining method comprising:
shifting an image acquisition device that includes normal image-acquisition pixels periodically provided with color filters having a plurality of colors and a phase-difference detection pixel used for focus detection, in a predetermined shift direction by a shift amount in units of subpixels;
correcting, through interpolation, a pixel value obtained by the phase-difference detection pixel to a value equivalent to values obtained by the normal image-acquisition pixels;
arranging and storing the pixel value of each of the pixels of the image acquisition device corrected in the correcting at a storage area corresponding to the shift direction and shift amount of the image acquisition device shifted in the shifting; and
compositing the pixel values of the plurality of pixels stored in the storing, thereby generating a high-resolution image having a higher resolution than a resolution of the image acquisition device,
wherein:
in the shifting, the image acquisition device is shifted such that a plurality of pixel values that correspond to a specific color of at least one type of the color filters provided for the normal image-acquisition pixels and that include the pixel value of at least one of the normal image-acquisition pixels exist at a same pixel position as the phase-difference detection pixel in the high-resolution image,
in the compositing, the plurality of pixel values corresponding to the specific color are composited at a predetermined compositing ratio, and
in the compositing, the compositing ratio is controlled based on a contrast at a position corresponding to at least the phase-difference detection pixel in the high-resolution image.
5. A non-transitory computer-readable storage medium having an image obtaining program stored thereon, the image obtaining program being executable by a hardware processor to control the hardware processor to perform:
shifting an image acquisition device that includes normal image-acquisition pixels periodically provided with color filters having a plurality of colors and a phase-difference detection pixel used for focus detection, in a predetermined shift direction by a shift amount in units of subpixels;
correcting, through interpolation, a pixel value obtained by the phase-difference detection pixel to a value equivalent to values obtained by the normal image-acquisition pixels;
arranging and storing the pixel value of each of the pixels of the image acquisition device corrected in the correcting at a storage area corresponding to the shift direction and shift amount of the image acquisition device shifted in the shifting; and
compositing the pixel values of the plurality of pixels stored in the storing, thereby generating a high-resolution image having a higher resolution than a resolution of the image acquisition device,
wherein:
in the shifting, the image acquisition device is shifted such that a plurality of pixel values that correspond to a specific color of at least one type of the color filters provided for the normal image-acquisition pixels and that include the pixel value of at least one of the normal image-acquisition pixels exist at a same pixel position as the phase-difference detection pixel in the high-resolution image,
in the compositing, the plurality of pixel values corresponding to the specific color are composited at a predetermined compositing ratio, and
in the compositing, the compositing ratio is controlled based on a contrast at a position corresponding to at least the phase-difference detection pixel in the high-resolution image.