JP2015222870A - Image processing method, image processing apparatus, imaging apparatus, image processing program and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing method capable of effectively reducing a color blur in a color image.SOLUTION: The image processing method includes the steps of: correcting the chromatic aberration of magnification of an imaged image; detecting a first region having a monotonous increase or a monotonous decrease in the level of a color signal or a luminous signal of the imaged image, on which the chromatic aberration of magnification is corrected, to a first direction in a predetermined section; judging a second region in which the color blur occurs, on the basis of optical information of the color blur in the imaging optical system and the information related to the first region; and correcting the imaged image, on which the chromatic aberration of magnification is corrected, in a manner to reduce the color blur.

Description

  The present invention relates to an image processing method for reducing color bleeding in a color image.

  Conventionally, a color that does not originally exist around a bright portion of a color image may occur as a color blur due to chromatic aberration of the photographing optical system. The chromatic aberration of the photographing optical system can be optically reduced to some extent by combining a plurality of lenses made of materials having different dispersions. However, in recent years, the size of image pickup apparatuses has been reduced, and it has been required to increase the resolution of sensors used in image pickup elements and to reduce the size of imaging optical systems. It is difficult to sufficiently suppress chromatic aberration by the configuration of the imaging optical system. .

  Chromatic aberration is roughly classified into lateral chromatic aberration (magnification chromatic aberration) and longitudinal chromatic aberration (axial chromatic aberration). Lateral chromatic aberration is a phenomenon in which the image formation position shifts in the direction along the image plane depending on the wavelength. Longitudinal chromatic aberration is a phenomenon in which the imaging position shifts in the direction along the optical axis depending on the wavelength. As disclosed in Patent Document 1, lateral chromatic aberration can be corrected by geometric transformation that adds different distortions to each of the R (red), G (green), and B (blue) color planes. On the other hand, longitudinal chromatic aberration cannot be corrected by the geometric transformation.

  In Patent Document 2, a region in which a G (green) plane is saturated is searched using a characteristic in which color blur is mainly generated in the vicinity of a whiteout (a saturated region of a preset signal), and a region around the region is searched. A method of calculating a correction amount by integrating the pixels is disclosed. Patent Document 3 discloses a method of determining a region where a color plane pixel value in a color image monotonously increases or decreases as a color blur generation region and removing the color blur.

US Pat. No. 6,724,702 JP 2007-133582 A JP 2009-268033 A

  However, in the method disclosed in Patent Document 2, color blur that causes discomfort to the observer also occurs in a region that is not overexposed, and thus correction of color blur is insufficient. Further, according to the method disclosed in Patent Document 3, it is possible to correct the color blur of the region that is not overexposed. However, since color blur occurs due to aberrations in the photographing optical system, there are directions in which color blur occurs and does not occur in a subject in a photographing optical system having asymmetric aberrations such as coma aberration. When the color of the subject is similar to the color blur, there is a possibility that the subject color is erroneously determined as a color blur even in a direction where the color blur does not occur, and the original color of the subject is removed.

  In order to reduce color blur more effectively, it is necessary to consider lateral chromatic aberration due to the influence of manufacturing variations of the optical system and eccentricity adjustment.

  Accordingly, the present invention provides an image processing method, an image processing apparatus, an imaging apparatus, an image processing program, and a storage medium that can effectively reduce color bleeding in a color image.

  An image processing method according to one aspect of the present invention includes a step of correcting a magnification chromatic aberration of a captured image, and a level of a color signal or a luminance signal of the captured image in which the magnification chromatic aberration is corrected monotonously in a first direction in a predetermined section. A step of detecting a first area increasing or monotonously decreasing, and a second area in which the color blur is generated based on the optical information on the color blur of the photographing optical system and the information on the first area And a step of correcting the captured image in which the lateral chromatic aberration is corrected so as to reduce the color blur.

  An image processing apparatus according to another aspect of the present invention includes a correction unit that corrects magnification chromatic aberration of a captured image, and a first direction in which a level of a color signal or a luminance signal of the captured image in which the magnification chromatic aberration is corrected is a predetermined interval. Based on the detection means for detecting the first area monotonically increasing or decreasing monotonically, the optical information regarding the color blur of the photographing optical system, and the information regarding the first area, the color blur is generated. Determination means for determining the second area, and correction means for correcting the captured image in which the lateral chromatic aberration is corrected so as to reduce the color blur.

  An imaging apparatus according to another aspect of the present invention includes an imaging device that photoelectrically converts an optical image and outputs a captured image, a correction unit that corrects lateral chromatic aberration of the captured image, and a captured image that has corrected the lateral chromatic aberration. Detecting means for detecting a first region in which the level of the color signal or the luminance signal monotonously increases or decreases monotonously in the first direction in a predetermined section; optical information relating to color blur of the photographing optical system; and the first information A determination unit that determines a second region in which the color blur occurs based on information about the region; a correction unit that corrects the captured image in which the lateral chromatic aberration is corrected so as to reduce the color blur; and Have

  An image processing program according to another aspect of the present invention includes a step of correcting magnification chromatic aberration of a photographed image, and a level of a color signal or a luminance signal of the photographed image corrected for the magnification chromatic aberration in a first direction in a predetermined section. Detecting a first region that is monotonously increasing or monotonically decreasing; and second information in which the color blur is generated based on optical information relating to color blur of the photographing optical system and information relating to the first region. The computer is configured to execute a step of determining an area and a step of correcting a captured image in which the magnification chromatic aberration is corrected so as to reduce the color blur.

  A storage medium according to another aspect of the present invention stores the image processing program.

  Other objects and features of the invention are described in the following embodiments.

  According to the present invention, it is possible to provide an image processing method, an image processing apparatus, an imaging apparatus, an image processing program, and a storage medium that can effectively reduce color bleeding in a color image.

It is a block diagram of the image processing apparatus in this embodiment. It is a flowchart which shows the image processing method in this embodiment. It is a flowchart which shows the monotonous increase / decrease determination process in this embodiment. In this embodiment, it is a figure which shows an example in case the pixel area of the monotonous increase / decrease determination object has a monotonous increase / decrease characteristic. In this embodiment, it is a figure which shows an example in case the pixel area of the monotonous increase / decrease determination object does not have a monotonous increase / decrease characteristic. In this embodiment, it is a figure which shows the pixel area for the monotone increase / decrease determination centering on an attention pixel. In this embodiment, it is a figure which shows the pixel area for the monotone increase / decrease determination which used the attention pixel as the end point. In this embodiment, it is a figure which shows the area | region of 3x3 pixel in an image. In this embodiment, it is a figure which shows the result of having applied the low-pass filter with respect to each pixel of the area | region of 3x3 pixel in an image. In this embodiment, it is a figure which shows the example of the change of an input signal at the time of applying a low-pass filter with respect to each pixel. In this embodiment, it is a figure which shows the example of the monotone increase / decrease detection of the imaging optical system which has a symmetrical aberration. In this embodiment, it is a figure which shows the example of the monotone increase / decrease detection of the imaging optical system which has an asymmetrical aberration. It is explanatory drawing of the optical information in this embodiment. In this embodiment, it is a figure which shows the example which determines a color bleeding area | region based on optical information and a monotonous increase / decrease detection result. It is explanatory drawing of the two-dimensional optical information in this embodiment. In this embodiment, it is a figure which shows the color blur determination process using optical information. It is explanatory drawing of the calculation method of the optical information in this embodiment. In this embodiment, it is a figure which shows the typical pixel value change of a blue blur. In this embodiment, it is a characteristic view of the nonlinear conversion with respect to the pixel value of B plane. It is a figure which shows the chromaticity coordinate ab surface in this embodiment. In this embodiment, it is a figure which shows the area | region of 3 * 3 pixel in B plane by a monotone increase / decrease determination result. 1 is a configuration diagram of an imaging apparatus in Embodiments 1 and 3. FIG. FIG. 6 is a configuration diagram of an image processing system in Embodiment 2. It is a flowchart which shows the correction process (1st correction process) of the magnification chromatic aberration (1st magnification chromatic aberration) in this embodiment. It is explanatory drawing of the correction process of the magnification chromatic aberration in this embodiment. It is a flowchart which shows the correction process (2nd correction process) of the asymmetric magnification chromatic aberration (2nd magnification chromatic aberration) in this embodiment. It is explanatory drawing of the correction process of the asymmetric magnification chromatic aberration (2nd magnification chromatic aberration) in this embodiment. It is explanatory drawing of the lateral chromatic aberration (1st lateral chromatic aberration) in this embodiment. It is explanatory drawing of the asymmetric lateral chromatic aberration (2nd lateral chromatic aberration) in this embodiment. It is explanatory drawing of the correction process of lateral chromatic aberration and asymmetric lateral chromatic aberration in this embodiment. 10 is a flowchart illustrating an image processing method according to the third exemplary embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, an image processing apparatus and an image processing method in this embodiment will be described with reference to FIGS. 1A and 1B. FIG. 1A is a block diagram of an image processing apparatus 100 in the present embodiment. FIG. 1B is a flowchart of an image processing method (image processing program) in the present embodiment. Each step in FIG. 1B is executed based on a command from the image processing apparatus 100, that is, by each unit of the image processing apparatus 100.

  As shown in FIG. 1A, an image processing apparatus 100 includes an input unit 101, a correction unit 102 (magnification chromatic aberration correction unit), a detection unit 103, a determination unit 104, a correction unit 105 (color blur correction unit), an output unit 106, The storage unit 107 is provided. First, in step S1 of FIG. 1B, the image processing apparatus 100 (input unit 101) acquires a captured image as an input image. The input image is a digital image (captured image) obtained by receiving light with an image sensor via a photographic optical system, and is deteriorated due to aberration of the photographic optical system including a lens and various optical filters. The photographing optical system can be configured using not only a lens but also a mirror (reflection surface) having a curvature.

  The color component of the input image has information on RGB color components, for example. As the color component, other commonly used color spaces such as brightness, hue, and saturation expressed in LCH, luminance expressed in YCbCr, and color difference signals can be selected and used. As other color spaces, XYZ, Lab, Yuv, and JCh can be used. Color temperature may also be used. The captured image can be acquired by connecting the imaging device and the image processing device by wire or wirelessly. The captured image can also be acquired via a storage medium.

  Subsequently, in step S2, the image processing apparatus 100 (correction unit 102) corrects the lateral chromatic aberration (color shift) of the input image (captured image) acquired via the input unit 101 (a lateral chromatic aberration correction step). In the present embodiment, the correction unit 102 executes two processes (a first correction process and a second correction process) as the correction process for the lateral chromatic aberration. The first correction process is a process for correcting a difference in magnification (image size) for each color of the photographing optical system, and a process for correcting the lateral chromatic aberration (first lateral chromatic aberration) remaining on the design value. It is. In the present embodiment, when simply referred to as lateral chromatic aberration, it means the first lateral chromatic aberration. The second correction process is a process for correcting an aberration (second lateral chromatic aberration) corresponding to a deviation from a design value generated in the manufacturing process of the photographing optical system. In the present embodiment, the second lateral chromatic aberration is referred to as asymmetric lateral chromatic aberration for convenience.

(Detection and correction of lateral chromatic aberration)
First, correction of lateral chromatic aberration (first lateral chromatic aberration) remaining on the design value will be described with reference to FIG. FIG. 27 is an explanatory diagram of the first lateral chromatic aberration. FIG. 27A is a simulated view of an input image in which lateral chromatic aberration remains, and FIG. 27B is a cross-sectional view along the horizontal direction (x direction) of FIG. In FIG. 27A, the x-axis indicates the horizontal position, the y-axis indicates the vertical position, and the intersection of the x-axis and the y-axis indicates the center of the image (input image). In FIGS. 27A and 27B, the solid line represents the G plane, the dotted line represents the R plane, and the alternate long and short dash line represents the B plane.

  In FIGS. 27A and 27B, the optical system is a coaxial system, and aberrations other than lateral chromatic aberration are corrected, and the shape of the intensity of the original image matches in RGB and is shifted by the amount of lateral chromatic aberration. And In this case, as shown in FIG. 27B, the pixel value of the B plane is higher than that of the R plane and the G plane on the low image height side (the intersection side of the x axis and the y axis). For this reason, in the region on the low image height side, the image appears to blur blue (color blur appears to occur). On the other hand, on the high image height side (on the opposite side of the intersection of the x axis and the y axis), the pixel value of the R plane is higher than that of the G plane or B plane. For this reason, in the region on the high image height side, the image appears to blur in red (color blur appears to occur).

  When color blur correction is performed in such a state, color blur occurs even when the planes of the respective colors are shifted due to the influence of lateral chromatic aberration as shown in FIGS. 27 (a) and 27 (b). It will be processed as a thing. For this reason, color blur correction cannot be performed correctly, and there is a possibility that the color of the input image cannot be restored (corrected) to the original color. For example, in the case of FIGS. 27A and 27B, if the color blur correction is performed until the RGB shapes match, the portion where RGB overlaps is a part of the inner side, so that it is more than the shape of the original image. The edge part may be cut off. Alternatively, when trying to match the RGB shape to the G plane so that the edge portion is not scraped, the pixel value of the R plane is low on the low image height side, while the pixel value of the B plane is low on the high image height side. . As a result, problems such as color loss may occur. Therefore, in the present embodiment, a color blur correction process described later is performed after the correction process of the lateral chromatic aberration. Thereby, it is possible to correct the color blur of the subject generated by the optical system with high accuracy and appropriately.

  Next, a method for detecting and correcting lateral chromatic aberration from an input image will be described with reference to FIGS. FIG. 23 is a flowchart showing a correction process (first correction process) of lateral chromatic aberration (first lateral chromatic aberration). Each step in FIG. 23 constitutes part of step S2 in FIG. 1B. FIG. 24 is an explanatory diagram of magnification chromatic aberration correction processing.

  First, in step S <b> 11 of FIG. 23, the image processing apparatus 100 (correction unit 102) detects an edge (edge region) in which a color shift due to lateral chromatic aberration appears significantly from the input image. In the present embodiment, the correction unit 102 detects an edge using a Y (luminance) plane. Preferably, the detection target edge is limited to an edge whose pixel value changes greatly in the radial direction from the optical center. Thereby, it is possible to acquire a highly accurate color misregistration amount. In the Y plane, the color shift due to the chromatic aberration of magnification appears mixed together. For this reason, it is preferable to select an edge having a certain width such that the pixel value monotonously increases or monotonously decreases for a plurality of pixels.

  Subsequently, in step S12, the correction unit 102 acquires the color misregistration amount at each edge (edge region) detected in step S11. Here, depending on the positional relationship between the optical center and each edge, the color misregistration direction is any one of up / down direction, left / right direction, upper right / lower left direction, upper left / lower right direction. By applying, the processing can be simplified.

  Correlation between color components is used to obtain the amount of color shift at each edge. For example, the amount of color misregistration can be acquired by determining the sum of absolute differences between color components. While the R plane (or B plane) is moved in the color shift direction with respect to the G plane, a search is made for a place where the sum of absolute differences between color components is minimized in pixels near the detected edge. From the position where the sum of absolute differences detected here is minimized, it is possible to obtain the color shift amount of the R plane (or B plane) with respect to the G plane. The sign of the amount of color shift obtained in step S12 is negative when the R plane (or B plane) is shifted toward the optical center with respect to the G plane, and the R plane (or B plane) with respect to the G plane. Is positive if it is displaced in the direction opposite to the optical center.

  Subsequently, in step S13, the correction unit 102 determines the image height and the color shift amount based on the image height of each edge detected in step S11 and the color shift amount of each edge acquired in step S12. The correction data is created. Here, the image height is a distance from a pixel (optical center) corresponding to the optical center. The correction data is created by the following procedure.

  First, assuming that the image height of the edge detected in step S11 is L and the color shift amount acquired in step S13 is D, the color shift with respect to the image height L is expressed by the following equation (1). A rate M is determined.

M = L / (L + D) (1)
Subsequently, as illustrated in FIG. 24A, the correcting unit 102 divides the input image into eight regions (h1 to h8) for each image height, and determines a region to which the detected edge belongs. Then, the correction unit 102 calculates the color misregistration rate M and determines a region to which the edge belongs for a plurality of edges detected in the input image. Further, the correction unit 102 totals the color misregistration rates M for each of the eight regions divided for each image height, obtains an average value of the color misregistration rates M for each region, and determines the color misregistration rate for each region.

  Subsequently, as shown in FIG. 26B, the correcting means 102 is based on the image height and the obtained color misregistration rate, and a higher-order polynomial approximate expression F () representing the relationship between the image height and the color misregistration rate. L) is obtained and used as correction data. FIG. 26B shows an example in which correction data is calculated using a cubic polynomial.

  Note that edge detection and color misregistration amount acquisition may be performed for all edges in the screen. However, in the eight regions divided for each image height, the detection of edges and the acquisition of the color misregistration amount are completed at the stage where the number of color misregistration ratios equal to or greater than a predetermined threshold is aggregated, thereby maintaining reliability. Processing efficiency can be improved. In addition, among the eight regions divided for each image height, only the region where the corresponding edge is found is used for calculation of the higher-order polynomial approximation, so that even if there is a region where the corresponding edge is not found, correction is performed. Data can be created.

  Subsequently, in step S14 of FIG. 23, the correcting unit 102 corrects the color shift (magnification chromatic aberration) using the correction data created in step S13. First, the correction unit 102 calculates the pixel height (X, Y) from the image height L of the pixel (X, Y) in the pixel (X, Y) of the correction target plane (R plane, B plane) as represented by the following expression (2). A color misregistration rate M is obtained. Here, it is assumed that the optical center is a coordinate system of (0, 0).

M = F (L) (2)
Subsequently, the correcting unit 102 obtains the coordinates (X1, Y1) of the pixel generated by the color misregistration correction as represented by the following equations (3-1) and (3-2).

X1 = M × X (3-1)
Y1 = M × Y (3-2)
The correction unit 102 generates a pixel value corresponding to the coordinates (X1, Y1) in the correction target plane by a general interpolation process, and sets it as the pixel value of the pixel (X, Y). By performing these processes for all pixels, color misregistration correction is performed. In step S15, the correction unit 102 outputs a corrected image.

(Detection and correction of asymmetric lateral chromatic aberration)
Next, with reference to FIG. 28, correction of asymmetric lateral chromatic aberration (second lateral chromatic aberration) that occurs in the manufacturing process of the photographing optical system will be described. FIG. 28 is an explanatory diagram of asymmetric lateral chromatic aberration (second lateral chromatic aberration) in the present embodiment. FIG. 28A is a simulated view of an input image in which asymmetric lateral chromatic aberration remains, and FIG. 28B is a cross-sectional view along the horizontal direction (x direction) of FIG. In FIG. 28A, the x-axis indicates the horizontal position, the y-axis indicates the vertical position, and the intersection of the x-axis and the y-axis indicates the center of the image (input image). In FIGS. 28A and 28B, the solid line represents the G plane, the dotted line represents the R plane, and the alternate long and short dash line represents the B plane.

  In FIGS. 28A and 28B, it is assumed that the optical system is broken from a completely rotationally symmetric system due to a shape error at the time of manufacture or an influence of a tilt or shift of the lens. As in FIGS. 27 (a) and 27 (b), aberrations other than lateral chromatic aberration have been corrected, and the shape of the intensity of the original image is the same between RGB and shifted by the amount of lateral chromatic aberration. It shall be. When affected by asymmetric chromatic aberration of magnification as shown in FIG. 28, the color intensity is symmetric with respect to the center of the image, unlike the case of FIG. And even if there is an object of the same color, the color bleeding is different.

  In FIGS. 28A and 28B, the object on the left side with respect to the y-axis has a higher pixel value of the B plane than the R plane and the G plane on the low image height side, and the G plane and B on the high image height side. The pixel value of the R plane is higher than that of the plane. Conversely, the object on the right side of the y-axis has a higher pixel value of the R plane than the G plane or B plane on the low image height side, and a pixel value of the B plane higher than the R plane or G plane on the high image height side. Is expensive. In this way, when color blur occurs asymmetrically with respect to the center of the image due to asymmetric chromatic aberration of magnification, only the above-described correction processing (first correction processing) described with reference to FIG. It is not possible to correct the color blur. In addition, if color blur correction described later is performed in such a state, a color shift due to asymmetric lateral chromatic aberration is processed as a color blur occurring, and correction cannot be performed correctly, and the original color can be restored. It can happen that you can't.

  In the case as shown in FIG. 28, if correction is made until the RGB shapes match, the portion where RGB overlaps is a part of the inner side, and therefore the edge portion is cut away from the shape of the original image. Or, in the case of FIG. 28, when trying to align with the G plane so that the edge portion is not scraped, the pixel value of the R plane on the low image height side and the B plane pixel on the high image height side of the object on the left side with respect to the y axis. It becomes lower than the pixel value of the G plane, and color loss may occur. On the other hand, in the case of FIG. 28, the pixel value of the B plane is lower on the low image height side and the pixel value of the R plane is lower than the pixel value of the G plane on the high image height side. For this reason, even if there is an object of the same intensity and the same color at a position symmetrical to the left side with respect to the y-axis as described above, the color bleeding and color loss are different from the left side. Also, depending on how asymmetric chromatic aberration of magnification occurs, even if one side is properly corrected with respect to the y-axis, the opposite side may be undercorrected or overcorrected.

  Therefore, in the present embodiment, after correcting the lateral chromatic aberration (first lateral chromatic aberration) and the asymmetric lateral chromatic aberration (second lateral chromatic aberration) remaining on the design value, a color blur correction process described later is performed. . Accordingly, it is possible to correct the color blur of the subject generated by the optical system with high accuracy and appropriately.

  Next, a method for detecting and correcting asymmetric chromatic aberration of magnification from an input image will be described with reference to FIGS. FIG. 25 is a flowchart showing a correction process (second correction process) for asymmetric lateral chromatic aberration (second lateral chromatic aberration). Each step in FIG. 25 constitutes part of step S2 in FIG. 1B. FIG. 26 is an explanatory diagram of an asymmetric magnification chromatic aberration correction process.

  First, in step S21 of FIG. 25, the image processing apparatus 100 (correction unit 102) detects an edge (edge region) in which a color shift due to lateral chromatic aberration appears significantly from the input image. A Y (luminance) plane is used for edge detection.

  Subsequently, in step S22, the correction unit 102 acquires a color misregistration amount for each edge (edge region) detected in step S21, and calculates a correction amount (a correction amount for each of a plurality of divided regions of the captured image). To do. Here, depending on the positional relationship between the optical center and each edge, the color misregistration direction is any one of up / down direction, left / right direction, upper right / lower left direction, upper left / lower right direction. To simplify the process. Since the acquisition of the color misregistration amount at each edge is as described above, the description thereof is omitted. In step S23, the correction unit 102 corrects the asymmetric lateral chromatic aberration (asymmetrical lateral chromatic aberration) using the correction amount calculated in step S22. The correction data creation procedure and correction flow in steps S22 and S23 will be specifically described below.

  First, in step S22, the correction unit 102 divides the image into four regions (A to D) in the circumferential direction as shown in FIG. 26, and determines the region to which the aforementioned edge belongs. Then, the correcting unit 102 aggregates the color misregistration amount D for each of the regions divided with respect to the plurality of edges detected in the image, obtains an average value of the color misregistration amounts D for each region, and calculates the color misregistration amount of each region. decide. Subsequently, the correction unit 102 compares the calculated color misregistration amount D for each region, and determines the correction amount of the correction target plane (R plane, B plane).

  Assuming that the correction amounts (first correction amounts) of the areas A, B, C, and D are Da, Db, Dc, and Dd, respectively, the horizontal correction amount DH and the vertical correction amount DV (second correction amount) (Correction amount) is expressed by the following equations (4-1) and (4-2), respectively.

DH = (Dc−Da) / 2 (4-1)
DV = (Db−Dd) / 2 (4-2)
In the present embodiment, the horizontal correction amount DH is calculated from the color misregistration amounts of the regions A and C, and the vertical correction amount DV is calculated from the color misregistration amounts of the regions B and D. In this embodiment, the image is divided in the circumferential direction, but by dividing the image in the image height direction, it is possible to change the correction amount for each image height and shift the correction target plane nonlinearly. Become.

  When the photographing optical system 201 is completely rotationally symmetric, lateral chromatic aberration also occurs rotationally symmetrically with respect to the center of the screen, so that DH = 0 and DV = 0. On the other hand, when the symmetry of the photographing optical system 201 is lost due to the influence of a manufacturing error or the like, the lateral chromatic aberration is also rotationally asymmetric, and when Dc> Da (DH> 0), the correction target plane is shifted to the region C side. Make corrections. On the other hand, when Dc <Da (DH <0), correction is performed by shifting to the region A side. Similarly, in the vertical direction, when Db> Dd (DV> 0), correction is performed by shifting the plane to be corrected to the region B side. When Dc <Dd (DH <0), the region A side is corrected. Correction is performed by shifting.

  Subsequently, in step S23, the correction unit 102 uses the horizontal correction amount DH and the vertical correction amount DV as correction data for asymmetric chromatic aberration of magnification caused by a manufacturing error or the like to correct the color shift. Here, the pixel of the plane to be corrected (R plane, B plane) is defined as pixel (X, Y). At this time, using the horizontal correction amount DH and the vertical correction amount DV, the coordinates (X2, Y2) of the pixel generated by the color misregistration correction are expressed by the following equations (5-1) and (5). -2).

X2 = X + DH (5-1)
Y2 = Y + DV (5-2)
Expressions (5-1) and (5-2) are coordinate systems whose optical center is (0, 0).

  The correcting unit 102 generates a pixel value corresponding to the coordinates (X2, Y2) in the correction target plane by a general interpolation process, and sets the pixel value of the pixel (X, Y). By performing these processes for all pixels, color misregistration correction is performed. In this embodiment, the correction amount is calculated by dividing the image into four as shown in FIG. 26. However, the amount of color misregistration for each region is obtained by dividing the image into eight, and the correction amount is calculated from the amount of color misregistration. May be calculated and correction processing may be performed. As described above, in step S23, a correction amount (second correction amount) in a direction different from the radial direction with respect to the center of the captured image (optical axis center, correction center) calculated based on the correction amount in step S22 is used. Thus, the second lateral chromatic aberration is corrected. More preferably, the second lateral chromatic aberration is corrected using the correction amount in the horizontal direction and the correction amount in the vertical direction of the captured image as the correction amount in a direction different from the radial direction. In the present embodiment, the first correction amount and the second correction amount are different from each other between the first position and the second position that are symmetrical with respect to the center of the captured image.

  The method for detecting and correcting lateral chromatic aberration (first lateral chromatic aberration) and asymmetric lateral chromatic aberration (second lateral chromatic aberration) from the image is as described above. Correction processing may be performed in combination. By utilizing the information of the design value, it is possible to handle the lateral chromatic aberration as a reduction in erroneous detection or as an amount of deviation from the design value based on the design value.

  Subsequently, in step S <b> 3, the image processing apparatus 100 (detection unit 103) is a region where the pixel value (signal level) of any one of the color planes constituting the color image is monotonously increasing or monotonically decreasing. Is detected. Then, the detection means 103 tentatively determines the detected area as a color blur generation area (monotonic increase / decrease detection step). Several methods are conceivable as a method of determining the color blur generation region in the monotonous increase / decrease detection step. In the present embodiment, the determination is made based on the change characteristic of the pixel value that blurs in a certain pixel section (predetermined section).

  Since color blur occurs when the imaging position shifts in the direction along the optical axis depending on the wavelength, for example, in the case of blue blur, the blue plane (B plane) is out of focus (out of focus). . The color blur due to the defocusing exists over a certain pixel section, and the pixel value change of the color blur at that time has a characteristic of gradually decreasing from the highlight portion to the shadow portion of the image. Therefore, when the pixel value change of color blur in a certain pixel section has a monotonous increase or monotonic decrease characteristic, there is a possibility that color blur has occurred, so that it is temporarily determined as a color blur generation region.

  As described above, in the present embodiment, the image sensor includes a plurality of color filters. The detecting unit 103 monotonously increases the signal level (pixel value) of the color plane corresponding to at least one color filter of the image obtained from the image sensor in any direction (first direction) in a predetermined section. Alternatively, a monotonically decreasing area (first area) is detected. However, the present embodiment is not limited to this, and instead of the signal level of the color plane, for example, the signal level of the luminance plane (Y plane) generated from the image obtained from the image sensor increases monotonously or monotonically. You may comprise so that the area | region which is reducing may be detected. That is, the detection unit 103 monotonously increases or monotonously increases the level of the color signal or the luminance signal (the signal level of the color plane or the luminance plane) of the captured image (aberration corrected image) corrected for the chromatic aberration of magnification in the first direction in a predetermined section. A decreasing first region is detected.

  Actually, when the photographing optical system has asymmetrical aberrations such as coma aberration, there is a direction in which the color blur generated by the photographing optical system is generated with respect to the subject and a direction in which it does not occur. For this reason, if the color blur generation area is determined only from monotonous increase / decrease, if the subject has a color similar to the color blur, the subject color may be erroneously determined to be color blur. Accordingly, it is not possible to correctly determine the color blur generation area only by monotonic increase / decrease detection.

  In the present embodiment, the region for detecting monotonic increase or monotonic decrease is a horizontal, vertical or diagonal pixel section centered on the target pixel of the color image, a horizontal direction with the target pixel as an end point, It includes either a vertical or diagonal pixel section.

  Detection of monotonic increase / decrease is performed by first calculating the pixel value gradient of the color plane. When the input image is composed of, for example, three color planes of the G plane, the B plane, and the R plane, the B plane is set as a color blur removal target, and the G plane is used as a reference plane. The respective luminance gradients Blea and Glea with respect to the B plane and the G plane are calculated as expressed by the following equation (6).

  In Expression (6), G (x + 1, y) and B (x + 1, y) are pixel values on the right side of the target pixel in the G plane and B plane, respectively. G (x−1, y) and B (x−1, y) are pixel values on the left side of the target pixel in the G plane and the B plane, respectively. G (x, y + 1) and B (x, y + 1) are pixel values below the pixel of interest in the G plane and B plane, respectively. G (x, y-1) and B (x, y-1) are pixel values above and below the pixel of interest in the G plane and B plane, respectively. Although this embodiment will be described with three color planes, processing can be performed with any color plane depending on the number of color planes constituting the image.

  Next, with reference to FIGS. 2 to 4, a method for determining a color blur occurrence area in the monotonous increase / decrease detection process will be described. FIG. 2 is a flowchart showing a monotonous increase / decrease determination process (monotonic increase / decrease detection step: step S3) in the present embodiment. Each step in FIG. 2 is mainly executed by the image processing apparatus 100 (detection unit 103). First, in step S1520, the image processing apparatus 100 determines whether the ISO sensitivity is high (whether the ISO sensitivity is higher than a predetermined sensitivity). If the ISO sensitivity is high, the process proceeds to step S1521. On the other hand, if the ISO sensitivity is not high, the process proceeds to step S1522.

  In step S1522, the image processing apparatus 100 analyzes a change in the pixel value of the input signal with respect to vertical, horizontal, and diagonal pixel sections (predetermined sections) when the pixel of interest of the input image is the center. In step S1523, the image processing apparatus 100 determines (detects) whether or not the change in the pixel value of the input signal in the pixel section has a monotonous increase / decrease characteristic. As a result of the determination, if the change in the pixel value of the input signal in the pixel section does not have a monotonous increase / decrease characteristic, in step S1524, the image processing apparatus 100 displays the vertical / horizontal when the target pixel is the end point.・ A pixel value change of an input signal is analyzed for an oblique pixel section. In step S1525, the image processing apparatus 100 determines whether the change in the pixel value of the input signal in the pixel section has a monotonous increase / decrease characteristic.

  FIG. 3 is a diagram illustrating an example of a case where a pixel section subject to monotonous increase / decrease determination has a monotonous increase / decrease characteristic, where the vertical axis indicates the pixel value and the horizontal axis indicates the distance. FIG. 4 is a diagram illustrating an example of a case where a pixel section for which monotonous increase / decrease is determined does not have a monotonous increase / decrease characteristic, where the vertical axis indicates the pixel value and the horizontal axis indicates the distance. The image processing apparatus 100 performs monotonous increase / decrease determination on an input signal having a change in pixel value as shown in FIGS. The white squares shown in FIGS. 3 and 4 are the target pixels.

  As shown in FIG. 3, an image in which a change in the pixel value of the input signal has a monotonous increase / decrease characteristic has a monotonous increase / decrease characteristic in a pixel section where the monotonous increase / decrease determination is performed. Therefore, as a result of the analysis in step S1522 or S1524, in step S1523 or S1525, the image processing apparatus 100 determines that the pixel section has a monotonous increase / decrease characteristic. On the other hand, it is determined that the image having the change characteristic of the pixel value of the input signal as shown in FIG. 4 does not have the monotonous increase / decrease characteristic.

  If the change in the pixel value of the input signal in the pixel section has a monotonous increase / decrease characteristic (monotonic increase characteristic or monotonic decrease characteristic), the image processing apparatus 100 sets a monotonous increase / decrease flag in step S1527. On the other hand, if the change in the pixel value of the input signal in the pixel section does not have a monotonous increase / decrease characteristic (monotonic increase characteristic or monotonic decrease characteristic), the image processing apparatus 100 sets a monotonous increase / decrease flag in step S1526. Absent.

  The monotonous increase / decrease determination described above is applied to each pixel of the B plane. As a result, each pixel is associated with “1” if the monotonous increase / decrease flag is set, and “0” if the monotone increase / decrease flag is not set, and is generated and held as a monotone increase / decrease determination result plane. This is used for determination (step S4 in FIG. 1). Details of the method of using the monotonous increase / decrease determination result plane will be described later.

  Next, with reference to FIG. 5 and FIG. 6, a method for setting a pixel section for performing monotonous increase / decrease determination on the target pixel will be described. FIGS. 5A to 5D are diagrams illustrating a monotonic increase / decrease pixel section centered on a target pixel. FIGS. 6A to 6H are diagrams showing a monotone increase / decrease pixel section with the target pixel as an end point. Of the method of setting the pixel section centered on the target pixel and the method of setting the pixel section centered on the target pixel, the method of setting the pixel section centered on the target pixel is shown in FIGS. A method of setting the horizontal direction and the vertical direction around the target pixel as in FIG.

  Further, as a method for setting a pixel section centered on the target pixel, a method of setting the target pixel in an oblique direction as shown in FIGS. 5C and 5D can be considered. In other words, the isotropic property can be imparted to the diagonal direction by setting a pixel section having a distance similar to that in the horizontal direction or the vertical direction. In this case, the angle in the oblique direction is limited to a setting of 45 degrees with respect to the horizontal direction or the vertical direction as shown in FIGS. However, the present embodiment is not limited to this, and an arbitrary angle other than 45 degrees can be set. The distance d of the pixel section at that time is calculated using the following equation (7).

In Expression (7), x represents a horizontal direction, and θ represents an angle from the horizontal.

  On the other hand, the color blur around the highlight area and the color blur around the shadow area in the image are affected by saturation and noise, respectively. There is a case where it cannot be judged correctly because it does not have an increase / decrease characteristic. In that case, as shown in FIG. 6, a method of setting a pixel section with the target pixel as an end point is effective. When the monotonous increase / decrease determination is performed by the method as described above and there is a pixel section having the monotonous increase / decrease characteristic in any one of the pixel sections shown in FIG. 5 and FIG. It is determined to be a pixel.

  In the present embodiment, the pixel value of the input signal is used as a target for monotonic increase / decrease determination, but luminance gradient may be used. In that case, it is preferable to determine that the color blur is in a case where the change in the luminance gradient is reversed only once in a certain pixel section. It is effective to set the appropriate value of the number of pixels in the pixel section to the minimum color blur width among the color blurs generated under certain shooting conditions of the imaging apparatus.

  The color blur width varies depending on the shooting conditions (aperture value, focal length, focusing accuracy, focus position in the image plane, coordinates on the image sensor, etc.) of the imaging apparatus. Therefore, it is possible to detect the color blur of the minimum width by matching the appropriate value of the number of pixels in the pixel section with the color blur of the minimum width of various color blurs generated according to various photographing conditions. The maximum width color blur can be detected even by using a pixel section adapted for the minimum width color blur.

  By performing monotonous increase / decrease determination as described above, it is possible to extract a color blur to be detected. However, depending on the shooting conditions such as high ISO sensitivity, the S / N ratio may decrease due to noise included in the input signal, and as a result, the color blur may not have a monotonous increase / decrease characteristic. In that case, it is effective to perform a filtering process with a digital filter on the input signal in step S1521 in FIG. In the present embodiment, a case where the digital filter is a low-pass filter will be described, but the present invention is not limited to this.

  There are several methods for applying a low-pass filter to the input signal. For example, a case will be described in which a [1 2 1] low-pass filter in which the weighting coefficient of the pixel of interest is twice as large as that of adjacent pixels is applied. FIG. 7 is a diagram showing an area of 3 × 3 pixels in an image. As shown in FIG. 7, when p is a target pixel in a certain region of 3 × 3 pixels in an image, first, a low-pass filter of [1 2 1] is applied in the horizontal direction. At this time, the target pixel is expressed as the following Expression (8).

P = (d · 1 + p · 2 + e · 1) / 4 (8)
When the adjacent pixels are calculated in the same manner, they are as shown in FIG. FIG. 8 is a diagram illustrating a result of applying a low-pass filter to each pixel in a 3 × 3 pixel region in an image. Subsequently, when the low-pass filter of [1 2 1] is applied in the vertical direction, the target pixel is expressed as the following Expression (9).

PP = (B · 1 + P · 2 + G · 1) / 4 (9)
With reference to FIG. 9, an example of a change in the input signal when the low-pass filter is applied will be described. FIG. 9 is a diagram illustrating an example of a change in an input signal when a low pass filter is applied to each pixel. In FIG. 9, the horizontal axis indicates the distance (cross section on the image, that is, the pixel section from the target pixel), and the vertical axis indicates the pixel value of the plane.

  The solid line in FIG. 9 indicates the case where the low-pass filter is not applied, the fine broken line indicates the case where the low-pass filter [1 2 1] is applied, and the coarse broken line indicates the case where the low-pass filter [1 4 6 4 1] is applied. Yes. Here, [1 4 6 4 1] means that a low-pass filter is applied by applying a weighting factor to a pixel adjacent to the target pixel and a pixel separated by another pixel. By smoothing the input signal by applying the low-pass filter in this way, it is possible to highlight the monotonous increase / decrease characteristics inherent in color fringing. In this embodiment, the low-pass filter is applied in the order of the horizontal direction and the vertical direction, but the present invention is not limited to this. The low-pass filter may be applied in the reverse order, that is, in the order of the vertical direction and the horizontal direction. It is also possible to calculate a two-dimensional low-pass filter coefficient and apply the low-pass filter simultaneously in the horizontal direction and the vertical direction.

  Returning to FIG. 1B, in step S4, the image processing apparatus 100 (determination unit 104) determines that the region (first region) temporarily determined as the color blur generation region by the detection unit 103 in step S3 is the color blur generation region. It is determined whether or not (second region) (color blur determination step). That is, the determination unit 104 determines an area (second area) where color blur is generated based on optical information related to color blur of the photographing optical system and information related to the first area. The optical information is, for example, information related to the second direction in which color blur occurs in the photographing optical system (optical information in the color blur generation direction). In the present embodiment, the color blur generation area is determined using optical information of the color blur generation direction of the photographing optical system that captured the input image.

  As described above, the determination unit 104 compares the first direction (the direction in which the signal level monotonously increases or decreases monotonously) with the second direction (the direction in which the color blur of the photographing optical system occurs). Determine the area. For example, when the first direction and the second direction match each other, the determination unit 104 determines that the first region (the region detected in step S3) is the second region (the region where the color blur is generated). ).

  Here, with reference to FIG. 10 and FIG. 11, an adverse effect when the color blur area is determined only from the monotonous increase / decrease detection process will be described. An image obtained by imaging a subject with an imaging device such as a digital camera includes a blur component as an image degradation component caused by spherical aberration, coma aberration, field curvature, astigmatism, etc. of the photographing optical system. . Such a blur component is generated when a light beam emitted from one point of a subject to be collected again at one point on the imaging surface when an aberration is not caused and there is no influence of diffraction is formed by forming an image with a certain spread.

  The blur component is optically represented by a point spread function (PSF), and is different from blur due to a focus shift. In addition, color bleeding in a color image can also be said to be a difference in blurring for each wavelength of light with respect to axial chromatic aberration, chromatic spherical aberration, and chromatic coma aberration of the optical system. Further, the lateral color misregistration can be said to be a positional misalignment or a phase misalignment due to a difference in imaging magnification for each wavelength of light when the lateral chromatic aberration is caused by the optical system.

  An optical transfer function (OTF) obtained by Fourier-transforming the point spread function (PSF) is frequency component information of aberration and is represented by a complex number. The absolute value of the optical transfer function (OTF), that is, the amplitude component, is referred to as MTF (Modulation Transfer Function), and the phase component is referred to as PTF (Phase Transfer Function). MTF and PTF are frequency characteristics of an amplitude component and a phase component of image degradation due to aberration, respectively. Here, the phase component is expressed as the following formula (10) with the phase angle as the phase angle.

PTF = tan ⁻¹ (Im (OTF) / Re (OTF)) (10)
In formula (10), Re (OTF) and Im (OTF) are the real part and the imaginary part of OTF, respectively.

  As described above, since the optical transfer function (OTF) of the optical system deteriorates the amplitude component and the phase component of the image, each point of the subject becomes asymmetrically blurred like coma aberration in the deteriorated image. .

  FIG. 10 is a diagram illustrating a case where monotonous increase / decrease detection is performed on an image captured with optical characteristics in which each point of a subject is symmetrically blurred such as spherical aberration. 10A shows a pixel value section of the subject, FIG. 10B shows a PSF section of the photographing optical system, and FIG. 10C shows a pixel value section of the subject photographed by the photographing optical system. As shown in FIG. 10B, when the photographing optical system has symmetrical aberration characteristics and the PSF is symmetrical, the edge cross sections on both sides of the subject are both degraded images as a solid line in FIG. It is photographed like this. In FIG. 10C, for comparison, the luminance cross section of the subject shown in FIG. If the white square in FIG. 10C is used as the target pixel and the monotone increase / decrease determination is performed, both edges are determined as the monotone increase / decrease area. Further, since color blur actually occurs, the color blur generation region is correctly determined.

  FIG. 11 is a diagram illustrating a case where monotonous increase / decrease detection is performed on an image captured in a state in which each point of a subject is asymmetrically blurred such as coma. 11A is a pixel value cross section of the subject, FIG. 11B is a PSF cross section of the photographing optical system, and FIG. 11C is a pixel cross section of the subject photographed by the photographing optical system. As shown in FIG. 11B, when the photographing optical system has an asymmetric aberration characteristic and the PSF is asymmetric, the edge cross section of the subject is large only on one side, particularly in the optical characteristic that greatly deteriorates only on one side edge. A deteriorated image is taken as shown by the solid line in FIG. When monotonous increase / decrease detection is performed on such a photographed image, both edges are determined as monotonous increase / decrease areas, but since the color blur actually generated by the photographing optical system is only on one side, the original color of the subject is blurred. As a result, an adverse effect occurs. If the color blur correction is performed only by monotonous increase / decrease, the original color of the subject is removed, which may result in an unnatural image. If you try to avoid this, the correction will be weak.

  Therefore, in the present embodiment, the image processing apparatus 100 holds or acquires optical information regarding the direction of occurrence of color blur of the photographing optical system as shown in FIGS. 10B and 11B. When the monotonous increase / decrease direction of the monotonic increase / decrease detection matches the color blur generation direction, the image processing apparatus 100 determines that the color blur generation region is present. Here, the term “matching” means not only the case of exact matching but also the case of substantial matching.

  The optical information will be described with reference to FIG. FIG. 12 is an explanatory diagram of optical information in the present embodiment, and shows a PSF cross section and optical information of the photographing optical system. FIG. 12A shows optical information when the PSF of the photographing optical system shown in FIG. 10B is symmetric. FIG. 12B shows optical information when the PSF of the photographing optical system shown in FIG. 11B is asymmetric. For example, it has 1 in the direction in which color blur occurs due to the aberration of the photographing optical system, and 0 if it does not occur. In FIG. 12A, since the color blur occurs symmetrically on both sides, the optical information has a value of 1 on both sides. In FIG. 12B, color blur is generated asymmetrically, and no color blur is generated at the left edge, and a value of 1 is generated because color blur is generated at the right edge.

  FIG. 13 is a diagram illustrating an example of determining a color blur area based on optical information and a monotonous increase / decrease detection result. As shown in FIG. 13 (a), for example, when monotonic decrease is detected by monotone increase / decrease detection, the optical information in the monotonic decrease direction is referred to. To do. Further, as shown in FIG. 13B, the optical information in the monotonously decreasing direction is referred to, and if it has 0, it is determined that the color of the subject. As described above, by having information on the direction in which chromatic aberration occurs and the direction in which chromatic aberration does not occur as the aberration of the photographing optical system, it is possible to correctly determine the color and color blur of the subject, thereby improving the accuracy of color blur correction. It becomes possible. Although the direction of occurrence of color blur is 1 and the direction of non-occurrence is 0, it is only necessary to know the direction of occurrence, and it is not necessary to be 0 and 1. Since the aberration of the photographic optical system changes depending on the image height, it is possible to correct with high accuracy by having optical information at a plurality of image heights. For image heights that do not have correction values, interpolation may be generated from nearby correction values. In addition, since the aberration of the photographic optical system changes depending on the photographic conditions (focal length of the photographic optical system, subject distance, aperture value (Fno)), the optical information is stored or acquired for each photographic condition, thereby achieving high accuracy. Correction can be performed.

  10 and 11, the optical information has been described as one-dimensional information. However, when the captured image is two-dimensional array data, the optical information may be held as two-dimensional data. FIG. 14 is an explanatory diagram when the optical information is two-dimensional. FIG. 14C shows an example in which optical information is held as data in eight directions of up / down / left / right, 45 degrees oblique and 135 degrees on the screen. In FIG. 14, color coma in the photographing optical system is generated in the upward direction of the screen, and 1 optical information is held in the generation direction. 0 is maintained in the direction where no color blur occurs. Monotonic increase / decrease detection is performed in the above eight directions, and it is determined that the color is blurred when 1 of the optical information is held in the direction in which the monotonic decrease is detected. Even if a monotonic decrease is detected, if the optical information 1 is not held in the detected direction, it is determined as the color of the subject.

  As described above, the image processing apparatus 100 holds or acquires the optical information regarding the direction in which the color blur of the photographing optical system occurs. Preferably, the image processing apparatus 100 includes a storage unit 107 that stores optical information. More preferably, the storage unit 107 stores optical information for each shooting condition. The photographing condition includes at least one of a focal length, a subject distance, and an aperture value of the photographing optical system. Note that the storage unit 107 may be provided outside the image processing apparatus 100.

  The image processing apparatus 100 can determine the color blur area with high accuracy by referring to the detection direction and the optical information when detecting monotonous increase / decrease. Although the monotone increase / decrease determination has been described in the monotone decrease direction, the color blur determination may be performed using the monotone increase direction. In addition, the monotonous increase / decrease determination and the correction value of the optical information have been described in eight directions, but are not limited to eight directions. In order to improve accuracy, the number of detection directions may be increased. Alternatively, the number of detection directions may be reduced in order to reduce the amount of data related to optical information.

  Further, the image processing apparatus 100 may be configured to hold or acquire information regarding the color blur intensity (color blur intensity information) as optical information in addition to the color blur generation direction. In this case, correction can be performed with higher accuracy. As shown in FIG. 14B, in general, the amount of color blur due to the aberration of the photographing optical system differs depending on the direction. Therefore, as shown in FIG. 14D, color blur intensity information regarding the amount of color blur may be added in the direction in which color blur occurs.

  Next, with reference to FIG. 15, the color blur determination when the color blur intensity information is used will be described. FIG. 15 is a diagram illustrating a color blur determination process using optical information, and illustrates an example in which the optical information has only the color blur generation direction. When determining the color blur generation region for the pixel of interest 1 surrounded by the square in the figure, first, monotonic decrease determination is performed in eight directions, up and down, left and right, 45 degrees oblique, and 135 degrees oblique, with the pixel of interest at the center. In the case of FIG. 15A, since the high-luminance subject is located below the target pixel, the upper, upper right, and upper left are determined as the directions in which the monotonic decrease of the target pixel 1 is detected. Since the optical information in the three directions is “1” indicating the color blur generation direction, the target pixel 1 is determined to be a color blur generation region. Similarly, if the pixel of interest 2 is also detected, the monotone decreasing direction is determined to be upper, upper right, right, and lower right. However, since the color blur occurrence direction of the optical information holds “0” indicating a direction that does not occur in the lower right, the final color blur detection direction of the target pixel 2 is monotonically decreased and the optical information is higher than the optical information. , Upper right and right. Although the noticeable pixel 1 and the noticeable pixel 2 are determined to have no color blur, as shown in FIG. 14B, the amount of color blur in the photographing optical system varies depending on the direction. In No. 2, the amount of color bleeding is different. If the optical information does not have intensity information, the amount of color blur cannot be determined, so that correction cannot be performed by changing the intensity of correction in the subsequent color blur correction process. Therefore, if the color blur correction is increased in accordance with the target pixel 1, the target pixel 2 is overcorrected, and if the color blur correction is decreased in accordance with the target pixel 2, the target pixel 1 is insufficiently corrected.

  Therefore, as shown in FIG. 14D, it is preferable to add the color blur generation direction and the color blur intensity information in the direction to the optical information. FIGS. 15A and 15B show a method for determining a color blur area when color blur intensity information is also added to the optical information. In the target pixel 3 in FIG. 15B, the three directions of upper, upper left, and upper right are determined by monotonic decrease determination, but the color blur intensity of the optical information is also detected as strong color blur intensity of 2, 3, and 2, respectively. can do. In the target pixel 4 in FIG. 15C, the three directions of upper, upper right, and lower left are determined, but the color blur intensity of the optical information in that direction is 3, 2, 1 and weaker than the target pixel 3, respectively. A color blur intensity is detected. Therefore, for example, by changing the intensity of correction (image correction intensity) of the subsequent color blur correction process according to the average value of the color blur intensity in the detected direction, Even when different, more accurate correction is possible.

  The target pixel 3 has an average color blur intensity value of about 2.3, and the target pixel 4 has an average color blur intensity value of 2.0, which can be used to change the correction strength. It becomes. Although the description has been made using the average value of the color blur intensity, the present invention is not limited to this. For example, the color blur correction coefficient may be changed using the color blur intensity value in the centroid direction of a plurality of detected directions as the color blur direction. At the target pixel 3, the direction of the center of gravity is upward, so the color blur intensity is 3, and at the target pixel 4, the direction of the center of gravity is upper right, so the color blur intensity is 2, and this value can be used to change the correction strength. Become. When the center of gravity direction is adopted, for example, when the center of gravity in the four directions of upper, upper right, right, and lower right is calculated, the direction closest to the center of gravity direction may be the two directions of upper right and right. In this case, it is conceivable to use an average value in two directions, a color blur intensity of the larger one of the two directions, or a color blur intensity of the smaller of the two directions. In the present embodiment, the use of the average value and the direction of the center of gravity has been described. However, the color blur intensity information of the optical information may be arbitrarily calculated to change the correction strength at the time of color blur correction.

  Thus, preferably, when the first direction and the second direction match each other in a plurality of directions, the image processing apparatus 100 (correction unit 105) calculates information on the intensity of color blur in the plurality of directions. And correct the image. More preferably, when the first direction and the second direction coincide with each other in a plurality of directions, the correction unit 105 uses the information or the average value regarding the intensity of color blur in the centroid direction of the plurality of directions. Correct it.

  Next, a method for calculating optical information will be described with reference to FIG. FIG. 16 is an explanatory diagram of a method for calculating optical information, and shows a PSF cross section (solid line) of the G plane of the photographing optical system and a PSF cross section (dotted line) of the B plane in an arbitrary direction held as optical information. Yes. Here, a method for calculating the optical information regarding the color blur of the B plane using the G plane as a reference plane will be described.

  Due to the chromatic aberration of the photographing optical system, the G plane and the B plane have different PSF shapes depending on the aberration in each wavelength band. Further, since the G plane and the B plane are imaged at shifted positions due to lateral chromatic aberration, the peak positions of the respective PSFs are also calculated at shifted positions as shown in FIG. The displacement of each color plane due to lateral chromatic aberration can be corrected by a conventional geometric transformation that applies different distortions to each color plane. Therefore, as shown in FIG. 16B, the PSF peak positions of the G plane and the B plane are made to coincide with each other, and the difference between the PSF areas of the G plane and the B plane, which are the hatched portions in the figure, is blurred. A method of adopting the strength can be considered.

  In FIG. 16B, the area difference of the right edge is larger than the area difference of the left edge than the peak, so that it can be seen that the color blur is greatly generated at the right edge. If this area is small, the color blur is inconspicuous, and therefore, when the area is small, the direction in which the color blur does not occur can be set. Further, the color blur intensity can be determined from the area ratio. As described above, the direction in which color blur occurs in the optical information and the color blur intensity can be calculated, but the calculation method is not limited to the method using the area difference of the PSF. For example, in FIG. 16B, a method of using the difference in inclination between the edges of the G plane and the B plane can be considered. When color blurring occurs, the inclination of the edge tends to be gentle, and thus optical information may be determined by using a difference in inclination.

  In this embodiment, the method of matching the peak values when calculating the color blur intensity is described. However, the color blur intensity may be calculated by matching the centroids of the PSFs instead of the peak values. As described above, according to the present embodiment, it is possible to calculate the color blur generation direction and the color blur intensity information of the optical information.

  Referring back to FIG. 1B, in step S5, the image processing apparatus 100 (correction unit 105) corrects color blur for the region (second region) determined as the color blur region by the determination unit 104 in step S4. Processing (processing for correcting an image) is performed (color blur correction step). That is, the correcting unit 105 corrects the captured image in which the lateral chromatic aberration is corrected so as to reduce color blur.

  FIG. 17 is a diagram illustrating a typical pixel value change of blue blur. In FIG. 17, the horizontal axis is the distance (cross section on the image), and the vertical axis is the pixel value of the B plane and the G plane. In FIG. 17, it is assumed that there is a high brightness subject exceeding the saturation brightness at the left end. Further, the tail of the pixel value change exponentially spreads around the light source, which is originally not bright, due to light that oozes from the light source due to aberration or flare.

  The G plane which is the reference plane is not free from bleeding, but has a certain extent. However, it is smaller than the B-plane that is subject to color blur removal. Further, the image sensor cannot measure pixel values above a certain saturation level. In such a pixel value change, if the intensity of the B-plane to be subjected to color bleeding removal exceeds the intensity of the G-plane that is the reference plane, blue bleeding occurs.

  In the present embodiment, the image processing apparatus 100 estimates the amount of blurring of the B plane based on the slope of the change in pixel value of the B plane that is subject to color blur removal. Therefore, by multiplying the absolute value of the brightness gradient Blea of the B plane by the coefficient k1, the first estimated blur amount E1 is obtained as expressed by the following equation (11).

E1 = k1 | Blea | (11)
In Expression (11), k1 is a positive value. However, in the area A1 where the B plane is saturated, the pixel value gradient becomes 0, and the luminance gradient before saturation cannot be obtained.

  Therefore, the estimated bleeding amount E2 for the region A1 where the B plane is saturated is estimated based on the luminance gradient Glea of the pixel value change of the G plane, as shown in the following equation (12).

E2 = k2 | Glea | (12)
In Expression (12), k2 is a positive value.

  Next, nonlinear conversion is performed on the pixel values of the B plane to generate the saturation S. This non-linear transformation indicates whether or not the B plane is saturated. In the region where the intensity of the B plane is saturated, the saturation S is 1, and in the region where the intensity of the B plane is low, the saturation S is 0. Although the saturation S may be a binary value of 0 or 1, the saturation S may be a value that continuously varies from 0 to 1 as shown in FIG. FIG. 18 is a characteristic diagram of nonlinear conversion with respect to the pixel value of the B plane.

Based on the generated saturation S, the estimated blur amount E1 or the estimated blur amount E2 calculated as described above is selected. That is, if the saturation S is a binary value of 0 and 1, a new estimated bleeding amount E is obtained.
E = E1 (when S = 0)
E = E2 (when S = 1)
And If the saturation S is a value that continuously changes from 0 to 1, a new estimated bleeding amount E is
E = (1-S) E1 + SE2
And

  Next, the estimated blur amount E is corrected to determine the amount E ′ to be actually removed. The estimated bleeding amount (removal amount) is in line with a certain model and does not necessarily match the actual bleeding amount. For example, even in the case of light detected on the same B plane, the blurring method varies between light having a wavelength of 450 nm and light having a wavelength of 400 nm, but this is not considered in step S4 (color blur determination step). When the estimated amount of blurring (removal amount) is too small, a slight amount of blueness remains after the removal of blue blurring. On the other hand, if the estimated blurring amount (removal amount) is excessive, the B plane may be excessively reduced with respect to the gray background, resulting in a yellowish green color.

  In particular, the latter (when it becomes yellowish green) is unnatural and gives the viewer a great sense of discomfort. Therefore, in step S5 (color blur correction process), the blur removal is limited to operate only within a certain hue range. For this reason, first, in step S5, the chromaticity of the pixel is calculated. The following formula (13) is established for the strengths of the R, G, and B planes.

  FIG. 19 is a chromaticity coordinate ab plane with a in the equation (13) as the horizontal axis and b as the vertical axis. As shown in FIG. 19, blue is in the fourth quadrant indicated by the diagonal lines on the chromaticity coordinate ab plane (note that red, yellow and purple are the first quadrant, green and white are the second quadrant, and blue-green is the third quadrant. In the quadrant). When the estimated blur amount E is removed from the intensity of the B plane, B = B−E, and the chromaticity coordinate ab plane moves in the upper left direction as indicated by a dotted arrow. The starting point of the arrow is the chromaticity before the estimated blur amount E is removed, and the end point is the chromaticity after the estimated blur amount E is removed. From this, when the working hue range is limited to a> 0 and b <0, the following expression (14) is established.

B> 0.22R + 0.68G and B> −1.84R + 3.30G (14)
For this reason, the pixel E that does not satisfy Expression (14) is set to a removal amount E ′ = 0 that is actually removed, and is excluded from the color blur removal target. As a result, the pixel value of the pixel that does not satisfy Expression (14) is not affected. In FIG. 19, only the region in the fourth quadrant indicated by diagonal lines is the removal target.

  Further, the removal amount E ′ is set so as to satisfy the following expression (15) even for a pixel satisfying the expression (14).

E ′ = min (E, B− (0.22R + 0.68G), B − (− 1.84R + 3.30G)) (15)
As a result, the change in chromaticity due to the removal of the removal amount E ′ remains in the fourth quadrant as indicated by the solid line arrow in FIG.

  In the present embodiment, the restriction is made in the fourth quadrant of the chromaticity coordinate ab plane. However, the present invention is not limited to this, and the restriction may be made at an arbitrary angle. At this time, it is necessary to satisfy the following expression (16).

B> r1 · G + r2 · R and B> r3 · G + r4 · R (16)
In the equation (16), r1 to r4 are calculated as the following equation (17) using the limit angle θ. The hue limit is defined by two straight lines passing through the origin of the chromaticity coordinate ab plane, and θ1 and θ2 are angles representing the two straight lines.

  As a result, it is possible to prevent the B plane from decreasing beyond the hue limit range. The color plane removal amount E ′ calculated as described above is retained as the removal amount plane, and color blur correction processing is performed. The above-described low-pass filter is applied to the removal amount plane. In this embodiment, a simple a * b * plane is used for hue restriction. However, the present invention is not limited to this, and hue restriction processing is performed on the uv plane using a 3 × 3 RGB → YUV matrix. You may do.

A new B plane is created by subtracting the removal amount E ′ from the strength of the B plane. Only the pixels that have been determined as the color blur area in the color blur determination step S4 are to be removed from the color blur. Therefore, the strength of the new B plane is as follows:
B = BE '
If the monotonous increase / decrease flag is “0”,
B = B
It becomes. As described above, in step S6 of FIG. 1, the image processing apparatus 100 (output unit 106) outputs a color image obtained by correcting the B plane as an output image.

  Here, let us consider a case where the monotonous increase / decrease determination result in a certain region of 3 × 3 pixels in the image shown in FIG. 7 switches the value of the monotonous increase / decrease determination flag in adjacent pixels as shown in FIG. In such a case, the removal amount fluctuates in the boundary portion of the pixel (a case where the pixel is removed by a neighboring pixel and a case where the pixel is not removed is mixed), and the change of the pixel value becomes steep, unnatural and uncomfortable to the observer. May give. Therefore, a method of applying a low-pass filter to the generated removal amount plane is effective.

  Also, the following equation (18) calculates the gain of each pixel of the color plane using the monotonic increase / decrease determination result plane, and multiplies the removal amount to perform smoothing processing on the boundary portion (monotone increase / decrease determination result plane). You may go.

  In the example illustrated in FIG. 20, the removal amount E ″ of the pixel p is expressed as the following Expression (19).

  With the above method, it is possible to remove only the color blur without a sense of incongruity.

  Next, with reference to FIG. 21, an imaging apparatus according to Embodiment 1 of the present invention will be described. FIG. 21 is a configuration diagram of the imaging apparatus 200 in the present embodiment. The imaging apparatus 200 is installed with an image processing program for performing color blur correction processing (the above-described image processing method) of a captured image. This color blur correction processing is performed by an image processing unit 204 (image processing) in the imaging apparatus 200. Device).

  The imaging device 200 includes a photographing optical system 201 (lens) and an imaging device main body (camera main body). The photographing optical system 201 includes a diaphragm 201a and a focus lens 201b, and is configured integrally with an imaging apparatus main body (camera main body). However, the present embodiment is not limited to this, and can also be applied to an imaging apparatus in which the imaging optical system 201 is replaceably attached to the imaging apparatus main body.

  The image sensor 202 photoelectrically converts a subject image (optical image) obtained via the photographing optical system 201 to obtain an image (captured image). That is, the subject image is photoelectrically converted by the image sensor 202 and converted into an analog signal (electric signal). The analog signal is converted into a digital signal by the A / D converter 203, and the digital signal is input to the image processing unit 204.

  An image processing unit 204 (corresponding to the image processing apparatus 100) performs predetermined processing on the digital signal and performs the above-described color blur correction processing. First, the image processing unit 204 (imaging condition acquisition unit) acquires imaging condition information of the imaging apparatus from the state detection unit 207. The imaging condition information is information related to an aperture, a shooting distance, a focal length of a zoom lens, and the like. The state detection unit 207 can acquire the imaging condition information directly from the system controller 210, but is not limited to this. For example, the imaging condition information regarding the imaging optical system 201 can be acquired from the imaging optical system control unit 206. Note that the color blur correction process (image processing method) of this embodiment is as described with reference to FIG. 1B.

  In step S2 of FIG. 1B, the correction unit 102 executes correction processing for two lateral chromatic aberrations. As described above, the correction unit 102 corrects the lateral chromatic aberration (first lateral chromatic aberration) remaining at the design stage and the asymmetric lateral chromatic aberration (second lateral chromatic aberration). As described above, in this embodiment, both lateral chromatic aberration corrections (first correction process and second correction process) are executed, but the lateral chromatic aberration remaining in the design stage after correcting the asymmetric lateral chromatic aberration. Any one of the two correction processes may be performed first.

  Alternatively, the two correction processes can be executed in parallel (simultaneously or within the same period). As a method of executing the two correction processes in parallel, for example, as shown in FIG. 29, an image area is divided into a circumferential direction and an image height direction, and each correction amount is determined based on the color shift amount of each area. Can be calculated. Alternatively, in step S2 of FIG. 1, only correction for the asymmetric lateral chromatic aberration (second correction process) is executed, and correction of the lateral chromatic aberration remaining in the design stage (first correction process) is the color blur in step S5. It may be performed at the time of correction. In this case, in step S5, the color blur correction process is executed in consideration of the color shift due to the chromatic aberration of magnification.

  Optical information regarding the color blur generation direction of the photographing optical system 201 is held in the storage unit 208. The image processing unit 204 acquires optical information corresponding to the shooting conditions from the storage unit 208 and performs color blur correction processing, and the output image is stored in the image recording medium 209 in a predetermined format. The display unit 205 displays an image obtained by performing a predetermined display process on the image subjected to the color blur correction process of the present embodiment. However, the present embodiment is not limited to this, and an image subjected to simple processing for high-speed display may be displayed on the display unit 205.

  In the present embodiment, a series of control is performed by the system controller 210, and mechanical driving of the photographing optical system 201 is performed by the photographing optical system control unit 206 based on an instruction from the system controller 210. The photographing optical system control unit 206 controls the aperture diameter of the aperture 201a as the F number photographing state setting. The photographing optical system control unit 206 controls the position of the focus lens 201b by an unillustrated autofocus (AF) mechanism or manual manual focus mechanism in order to adjust the focus according to the subject distance. Note that functions such as aperture diameter control and manual focus of the aperture 201a may not be executed according to the specifications of the imaging apparatus 200. The photographing optical system 201 can be provided with optical elements such as a low-pass filter and an infrared cut filter.

  Next, an image processing system according to the second embodiment of the present invention will be described with reference to FIG. FIG. 22 is a configuration diagram of an image processing system 300 in the present embodiment. Note that the color blur correction process (image processing method) of this embodiment is as described with reference to FIG.

  In FIG. 22, an image processing apparatus 301 (corresponding to the image processing apparatus 100 in FIG. 1A) is a computer device equipped with image processing software 306 for causing a computer to execute the image processing method of this embodiment. The imaging device 302 is an imaging device such as a camera, a microscope, an endoscope, or a scanner. The storage medium 303 is a storage unit that stores captured images, such as a semiconductor memory, a hard disk, or a server on a network.

  The image processing apparatus 301 acquires captured image data from the imaging device 302 or the storage medium 303, and outputs the image data subjected to predetermined image processing to one or more of the output device 305, the imaging device 302, and the storage medium 303. Output. Further, the output destination can be stored in a storage unit built in the image processing apparatus 301. The output device 305 is a printer, for example. Further, the image processing software 306 can be installed in the image processing apparatus 301 from a network or a storage medium such as a CD-ROM 307.

  A display device 304 that is a monitor is connected to the image processing apparatus 301. Therefore, the user can perform the image processing work through the display device 304 and evaluate the corrected image. The image processing software 306 performs color blur correction processing (image processing method) of the present embodiment, and performs development and other image processing as necessary.

  It should be noted that information (correction information) related to the contents of data for image processing and the transfer between devices in this embodiment is preferably attached to individual image data. By adding necessary correction information to the image data, the correction processing of the present embodiment can be appropriately performed as long as the device is equipped with the image processing apparatus of the present embodiment. Further, the optical information regarding the color blur generation direction of the photographing optical system may be acquired through a network as well as a method of reading from a recording unit of a device equipped with the image processing apparatus of the present embodiment, or a PC, Information can be acquired from a camera, a lens, or the like.

  Next, an image pickup apparatus according to Embodiment 3 of the present invention will be described. The imaging apparatus according to the present embodiment is different from the correction method according to the first embodiment in the method for correcting the lateral chromatic aberration. Specifically, in the first embodiment, the image processing unit 204 calculates a correction amount from the acquired image (input image), whereas in the present embodiment, information on the correction amount is stored in a storage unit (storage unit) or the like. Are stored in advance, and the information is read out at the time of correction and corrected. The other configuration of the imaging apparatus in the present embodiment is the same as that of the imaging apparatus 200 of Embodiment 1 described with reference to FIG.

  With reference to FIG. 30, an image processing method (image processing program) in the present embodiment will be described. Each step of FIG. 30 is executed based on a command from the image processing apparatus 100 (image processing unit 204), that is, by each unit of the image processing apparatus 100. Note that steps S31 and S33 to S37 of FIG. 30 are the same as steps S1 to S6 of FIG.

  First, in step S31, the image processing apparatus 100 (input unit 101) acquires a captured image (input image). Subsequently, in step S32, the image processing apparatus 100 (correction unit 102) obtains information (magnification chromatic aberration correction information) related to the correction amount of the chromatic aberration of magnification stored in the storage unit (storage unit 107). The information regarding the correction amount stored in the storage unit 107 is information measured in advance using a chart or the like, and is a difference value (deviation amount) from the amount of lateral chromatic aberration of the design value. Further, the information on the correction amount may be a measured difference value, or an approximate value calculated based on the difference value or a value processed to facilitate correction at the time of correction may be used. Good. In the present embodiment, the difference value from the amount of chromatic aberration of magnification of the design value is used as the correction amount. However, the present invention is not limited to this, and information on both the chromatic aberration of magnification and the asymmetric magnification chromatic aberration is corrected. It may be used as

  Subsequently, in step S33, the correction unit 102 corrects the chromatic aberration of magnification using information (magnification chromatic aberration correction information) related to the correction amount acquired in step S32. Since the information on the acquired correction amount includes information on the asymmetric magnification chromatic aberration generated in the manufacturing process, the asymmetry can be reduced by performing the correction processing described in the first embodiment based on the information. Can be reduced. Subsequent steps S34 to S37 are the same as steps S3 to S6 of the first embodiment, respectively, and thus description thereof is omitted.

  As described above, in this embodiment, it is necessary to measure information on the correction amount in advance. However, if information on correction of lateral chromatic aberration is held in advance, the amount of calculation for the acquired image can be reduced. For this reason, according to the configuration of the present embodiment, it is possible to increase the processing speed and reduce the processing load. In this embodiment, the correction unit 102 acquires the difference value from the design value as correction information for the lateral chromatic aberration in step S32, but the present invention is not limited to this. Instead of the difference value, the chromatic aberration of magnification itself may be measured and information regarding the chromatic aberration of magnification may be stored in the storage unit (storage unit 107), and the information may be used as correction information for the chromatic aberration of magnification.

  Preferably, in the step of correcting the lateral chromatic aberration of each embodiment, the lateral chromatic aberration is detected from the captured image, and the correction amount of the lateral chromatic aberration is determined based on the detected lateral chromatic aberration. Alternatively, preferably, in the step of correcting the chromatic aberration of magnification of each embodiment, the correction amount of the chromatic aberration of magnification is determined based on correction information of the chromatic aberration of magnification stored in advance.

  Preferably, in the step of correcting the lateral chromatic aberration, the first lateral chromatic aberration included as a design value of the photographing optical system is corrected. Preferably, in the step of correcting the lateral chromatic aberration, the second lateral chromatic aberration corresponding to a deviation from the design value of the photographing optical system is corrected.

  Each embodiment is also realized by executing the following processing. That is, software (program) that realizes the above functions is supplied to a system or apparatus via various storage media such as a network or a CD-ROM, and a computer (CPU, MPU, etc.) of the system or apparatus executes the program. It is a process to read and execute.

  According to each embodiment, for the image after correcting the chromatic aberration of magnification, correcting the color blur using the monotonic increase or decrease determination of the pixel value of each color plane and the information on the color blur generation direction of the imaging optical system. Accordingly, it is possible to effectively correct the color blur of the color image. Therefore, according to each embodiment, it is possible to provide an image processing method, an image processing apparatus, an imaging apparatus, an image processing program, and a storage medium that can effectively reduce color bleeding in a color image.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

100 Image processing apparatus 102 Correction unit 103 Detection unit 104 Determination unit 105 Correction unit

Claims (23)

Correcting the chromatic aberration of magnification of the captured image;
Detecting a first region in which a level of a color signal or a luminance signal of a captured image in which the lateral chromatic aberration is corrected monotonously increases or decreases in a first direction in a predetermined section;
Determining a second area in which the color blur is generated based on optical information on the color blur of the photographing optical system and information on the first area;
An image processing method comprising: correcting a captured image in which the lateral chromatic aberration is corrected so as to reduce the color blur. In the step of correcting the lateral chromatic aberration,
Detecting the lateral chromatic aberration from the captured image;
2. The image processing method according to claim 1, wherein a correction amount of the lateral chromatic aberration is determined based on the detected lateral chromatic aberration.   The image processing method according to claim 1, wherein in the step of correcting the lateral chromatic aberration, a correction amount of the lateral chromatic aberration is determined based on previously stored correction information of the lateral chromatic aberration.   4. The image processing method according to claim 1, wherein in the step of correcting the lateral chromatic aberration, the first lateral chromatic aberration included as a design value of the photographing optical system is corrected. 5. The step of correcting the chromatic aberration of magnification includes
Detecting an edge region of the captured image;
Obtaining a color misregistration amount in the edge region;
Creating correction data based on the image height of the edge region and the color shift amount;
The image processing method according to claim 4, further comprising: correcting the first lateral chromatic aberration using the correction data.   6. The image processing according to claim 1, wherein in the step of correcting the lateral chromatic aberration, the second lateral chromatic aberration corresponding to a deviation from a design value of the photographing optical system is corrected. Method. The step of correcting the chromatic aberration of magnification includes
Detecting an edge region of the captured image;
Calculating a first correction amount for each of the plurality of divided regions of the captured image based on the color shift amount of the edge region;
Correcting the second lateral chromatic aberration using a second correction amount calculated based on the first correction amount and having a direction different from the radial direction with respect to the center of the captured image. The image processing method according to claim 6.   In the step of correcting the second lateral chromatic aberration, the second lateral chromatic aberration is calculated using the second correction amount in the horizontal direction and the vertical direction of the photographed image calculated based on the first correction amount. The image processing method according to claim 7, wherein the correction is performed.   The image processing method according to claim 7, wherein the first correction amount is different between a first position and a second position that are symmetrical with respect to a center of the captured image.   The image processing method according to claim 1, wherein the optical information is information related to a second direction in which color blur of the photographing optical system occurs.   The image processing method according to claim 10, wherein in the step of determining the second area, the second area is determined by comparing the first direction with the second direction. .   In the step of determining the second area, it is determined that the first area is the second area when the first direction and the second direction coincide with each other. The image processing method according to claim 10 or 11.   The image processing method according to claim 1, wherein the optical information is information relating to a color blur intensity of the photographing optical system.   The image processing method according to claim 13, wherein in the step of correcting the captured image in which the chromatic aberration of magnification is corrected, the intensity for correcting the captured image is changed based on information on the intensity of the color blur.   In the step of correcting the photographed image in which the lateral chromatic aberration is corrected, when the first direction and the second direction coincide with each other in a plurality of directions, information on the intensity of color blur in the plurality of directions is calculated. The image processing method according to claim 12, wherein the captured image is corrected.   In the step of correcting the captured image in which the lateral chromatic aberration is corrected, when the first direction and the second direction coincide with each other in a plurality of directions, information on the color blur intensity in the centroid direction of the plurality of directions The image processing method according to claim 15, wherein the photographed image is corrected by using.   The step of determining the second area determines the second area based on the optical information stored for each photographing condition. Image processing method.   The image processing method according to claim 17, wherein the photographing condition includes at least one of a focal length, a subject distance, and an aperture value of the photographing optical system.   In the step of detecting the first region, a signal level of a color plane corresponding to at least one color filter of the photographed image obtained from an image sensor having a plurality of color filters, or generated from the photographed image. The first area in which the signal level of a luminance plane is monotonously increasing or monotonically decreasing in the first direction in the predetermined section is detected. An image processing method described in 1. Correction means for correcting the lateral chromatic aberration of the captured image;
Detecting means for detecting a first region in which a level of a color signal or a luminance signal of a captured image in which the magnification chromatic aberration is corrected monotonously increases or decreases in a first direction in a predetermined section;
Determination means for determining a second area where the color blur is generated based on optical information regarding color blur of the photographing optical system and information regarding the first area;
An image processing apparatus comprising: correction means for correcting a captured image in which the chromatic aberration of magnification is corrected so as to reduce the color blur. An image sensor that photoelectrically converts an optical image and outputs a captured image;
Correction means for correcting lateral chromatic aberration of the captured image;
Detecting means for detecting a first region in which a level of a color signal or a luminance signal of a captured image in which the magnification chromatic aberration is corrected monotonously increases or decreases in a first direction in a predetermined section;
Determination means for determining a second area where the color blur is generated based on optical information regarding color blur of the photographing optical system and information regarding the first area;
An image pickup apparatus comprising: correction means for correcting a captured image in which the chromatic aberration of magnification is corrected so as to reduce the color blur. Correcting the chromatic aberration of magnification of the captured image;
Detecting a first region in which a level of a color signal or a luminance signal of a captured image in which the lateral chromatic aberration is corrected monotonously increases or decreases in a first direction in a predetermined section;
Determining a second area in which the color blur is generated based on optical information on the color blur of the photographing optical system and information on the first area;
An image processing program configured to cause a computer to execute a step of correcting a captured image in which the magnification chromatic aberration is corrected so as to reduce the color blur.   A storage medium storing the image processing program according to claim 22.