JP2015139141A5 - - Google Patents

Description

The image processing apparatus according to the present invention provides a signal of a color that is missing in each pixel of the plurality of pixels with respect to a color mosaic image signal obtained by photoelectrically converting an optical image of a subject with the plurality of pixels. An image processing apparatus including an interpolation unit that performs an interpolation process using image signals of surrounding pixels of the pixel, wherein the interpolation unit generates a color image signal by performing the interpolation process in each of a plurality of specified directions. A direction-by-direction interpolation unit, a degree-of-dispersion calculation unit that calculates a degree of dispersion of a color signal obtained from a color image signal output from each of the plurality of direction-by-direction interpolation units, and the plurality of degrees calculated by the degree of dispersion calculation unit and noise characteristic calculation means for calculating a weighting coefficient based on the noise amount of the color signal for each of the plurality of picture element using each direction of dispersion of the prescribed direction, heavy said noise characteristic calculation means has calculated Based on the coefficients, evaluation means for calculating the color image signal output from each of the plurality of direction-specific interpolation means for each of the plurality of prescribed directions for each pixel, and the evaluation calculated by the evaluation means And generating means for generating color interpolated image data by selecting or weighted adding the color image signals interpolated by the plurality of interpolating means for each direction based on the value for each pixel.

FIG. 8 is a flowchart of the interpolation image generation processing by the image generation unit 309. In step S801, the image generation unit 309, for each pixel, or by comparing the evaluation value _{C VARV} for evaluation value _{C VARH} and V directions of the interpolation with respect to the H direction of interpolation, an evaluation value _{C VARH} <evaluation value _{C VARV} whether Determine whether. In FIG. 8, the evaluation value _Cvarh is abbreviated as Ch and is abbreviated as the evaluation value Cv . Images generation unit 309, (YES at S801) when the evaluation value _{C VARH} <evaluation value _{C VARV,} the process proceeds to step S802, the case where the evaluation value _{C VARH} ≧ evaluation value _{C VARV} (NO in S801), The process proceeds to step S803.

In general, the blur width of lateral chromatic aberration is significantly smaller than the blur width of axial chromatic aberration, and depending on the shooting conditions such as aperture value, focal length, and subject distance, extremely thin lateral chromatic aberration is caused by the interpolation direction. It may appear differently. In that case, there is a concern that lateral chromatic aberration may have an adverse effect in the evaluation value calculation process based on the degree of dispersion of the demosaicing unit 105. Accordingly, magnification chromatic aberration correction unit 1402 performs correction processing of chromatic aberration of magnification ahead demosaicing process.

102 color image sensor
103 A / D conversion unit 105 Demosaicing unit 111 Control unit 302 H direction interpolation unit 303 V direction interpolation unit 304 H direction dispersion degree calculation unit 305 V direction dispersion degree calculation unit 306 H direction noise characteristic calculation unit 307 V direction noise characteristic calculation Unit 308 evaluation value calculation unit 309 image generation unit 901 noise characteristic calculation unit 1301 preprocessing unit 1401 scratch correction unit 1402 magnification chromatic aberration correction unit

Claims (14)

A color mosaic image signal obtained by photoelectrically converting an optical image of a subject with a plurality of pixels is used as a signal of a color missing in each pixel of the plurality of pixels, using an image signal of a pixel around each pixel. An image processing apparatus comprising an interpolation means for performing interpolation processing,
The interpolation means includes
A plurality of direction-specific interpolation means for generating a color image signal by performing the interpolation processing in each of a plurality of prescribed directions;
A degree-of-dispersion calculating means for calculating the degree of dispersion of color signals obtained from the color image signals output from the plurality of direction-specific interpolation means;
Noise characteristic calculation means for calculating a weighting factor based on a noise amount of the color signal for each pixel of the plurality of pixels using the degree of dispersion in each direction of the plurality of prescribed directions calculated by the dispersion degree calculation means;
Evaluation means for calculating an evaluation value of a color image signal output from each of the plurality of direction-specific interpolation means for each direction in the plurality of specified directions based on the weighting factor calculated by the noise characteristic calculation means. When,
Generating means for generating color interpolated image data by selecting or weighted adding color image signals interpolated by the plurality of direction-specific interpolation means for each pixel based on the evaluation value calculated by the evaluation means; An image processing apparatus.   The image processing apparatus according to claim 1, wherein the noise characteristic calculating unit decreases the weighting factor as the degree of dispersion calculated by the degree of dispersion calculating unit increases.   3. The image according to claim 1, wherein the generation unit selects a signal that has been subjected to the interpolation processing in a prescribed direction having a small evaluation value calculated by the evaluation unit, out of the plurality of prescribed directions. Processing equipment. The weighting factor calculated by the noise characteristic calculating unit is based on the magnitude of noise of each color component in Bayer image data obtained by performing white balance processing on the color mosaic image signal. The image processing apparatus according to any one of 1 to 3. 4. The weighting factor calculated by the noise characteristic calculating unit is based on a noise magnitude of the color mosaic image signal or a color image signal in each prescribed direction subjected to the interpolation processing. The image processing apparatus according to any one of the above. Storage means for storing the weighting factor as a lookup table;
4. The image processing apparatus according to claim 1, wherein the noise characteristic calculation unit calculates the weighting factor using the lookup table. 5.   The image processing apparatus according to claim 1, wherein the degree of dispersion calculating unit calculates the degree of dispersion using a color difference in a G, RG, and BG color space. . The image processing apparatus according to claim 1, wherein the dispersity calculating unit calculates the dispersity using a color difference signal in an L ^* a ^* b ^* uniform color space.   The generation unit generates a two-dimensional plane composed of evaluation values calculated for each pixel in each of the plurality of prescribed directions by the evaluation unit, and applies a low-pass filter to the two-dimensional plane. The image processing apparatus according to claim 1. Before performing the interpolation processing on the color mosaic image signal, pre-processing means for performing predetermined pre-processing on the color mosaic image signal,
The said interpolation means performs the said interpolation process with respect to the color mosaic image signal by which the said predetermined pre-processing was performed by the said pre-processing means, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. Image processing device.   The preprocessing means performs at least one of color image signal correction processing, white balance processing, and magnification chromatic aberration correction processing related to flaw pixels included in the plurality of pixels as the preprocessing. The image processing apparatus according to claim 10. A color mosaic image signal obtained by photoelectrically converting an optical image of a subject with a plurality of pixels is used as a signal of a color missing in each pixel of the plurality of pixels, using an image signal of a pixel around each pixel. An image processing method having an interpolation step for performing interpolation processing,
The interpolation step includes
A direction-specific interpolation step for generating a color image signal by performing the interpolation processing in each of a plurality of prescribed directions;
A degree-of-dispersion calculation step of calculating a degree of dispersion of a color signal obtained from the color image signal generated in the direction-specific interpolation step;
A noise characteristic calculating step of calculating a weighting factor based on a noise amount of the color signal for each pixel of the plurality of pixels using the degree of dispersion of each of the plurality of prescribed directions calculated in the degree of dispersion calculating step;
Based on the weighting factor calculated in the noise characteristic calculation step, an evaluation step for calculating the evaluation value of the color image signal obtained in the direction-specific interpolation step for each pixel in each direction of the plurality of specified directions;
And a generation step of generating color interpolation image data by selecting or weighting and adding the color image signal interpolated in the direction-specific interpolation step for each pixel based on the evaluation value calculated in the evaluation step. An image processing method. Before performing the interpolation step, as the predetermined pre-processing for the color mosaic image signal, at least one of a color image signal correction process, a white balance process, and a magnification chromatic aberration correction process related to a scratch pixel included in the plurality of pixels. A pre-processing step for
The image processing method according to claim 12, wherein the interpolation step performs the interpolation processing on the color mosaic image signal on which the predetermined preprocessing has been performed in the preprocessing step. A program causing a computer to execute the image processing method according to claim 12 or 13.