JP6632339B2 - Image processing device, imaging device, image processing method, program, storage medium - Google Patents

Description

  The present invention relates to an image processing apparatus, and more particularly, to an image processing apparatus that corrects chromatic aberration of magnification of an image captured via an optical system.

  An image obtained by imaging with an imaging device such as a digital camera is affected by chromatic aberration of magnification of an optical system such as an imaging lens. As a method of correcting the color shift, there is a method of storing in advance a color shift amount according to the state of the lens (for example, see Patent Document 1).

  Since the amount of color shift is a value that changes continuously, it is necessary to correct the amount of color shift of less than one pixel in order to correct the amount of color shift on an image. As a method of correcting such a color shift amount of a unit less than one pixel, an interpolation algorithm such as bilinear interpolation or bicubic interpolation has been proposed. In the case of the known Bayer arrangement, it is general to correct the color shift amount of the R pixel or the B pixel with reference to the G pixel.

JP-A-8-205181

  However, since interpolation is not performed on G pixels, if bilinear interpolation is performed only on B pixels, there is a problem that the band of B pixels disappears on G pixels. FIG. 4A shows an example of a frequency characteristic of bicubic interpolation, and FIG. 4B shows an example of a frequency characteristic of bilinear interpolation. By performing a correction having a steep frequency characteristic as shown in FIG. 4A, a highly accurate band correction can be performed. However, there is a problem that undershoot and overshoot are strongly generated.

  In view of the above problems, an object of the present invention is to provide an image processing device, an imaging device, an image processing method, a program, and a storage medium that are advantageous for correcting lateral chromatic aberration.

An image processing apparatus as one aspect of the present invention is an image processing apparatus that corrects a color shift amount of a second color light with respect to a first color light due to chromatic aberration of magnification of an image captured via an optical system, A first correction unit that has a first frequency characteristic and corrects the color shift amount by using a first interpolation process of interpolating a signal component between pixels for the second color component of the image; depending on No. color Sashin obtained by subtracting the first color signal from the second color signal after the first interpolation processing, and the first interpolation process, slower than the first frequency characteristic A second interpolation process having a suitable second frequency characteristic, and a second correction unit that corrects the color shift amount using the second interpolation process.

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

  According to the present invention, it is possible to provide an image processing device, an imaging device, an image processing method, a program, and a storage medium that are advantageous for correcting lateral chromatic aberration.

FIG. 1 is a diagram for describing a configuration of an imaging device according to an embodiment of the present invention. FIG. 4 is a diagram for explaining a configuration of a chromatic aberration-of-magnification correcting unit according to the embodiment of the present invention. 5 is a flowchart illustrating an operation of a color difference determination unit according to the embodiment of the present invention. FIG. 4 is a diagram for explaining frequency characteristics of bicubic interpolation and bilinear interpolation according to the embodiment of the present invention. FIG. 4 is a diagram for explaining a line profile after bicubic magnification correction and after bilinear magnification correction according to the embodiment of the present invention. FIG. 5 is a diagram for explaining a line profile of a color difference signal after bicubic magnification correction and bilinear magnification correction according to the embodiment of the present invention. 6 is a flowchart illustrating an operation of a contrast determination unit according to the embodiment of the present invention. 5 is a flowchart for explaining operations of a combining unit and a combining ratio calculating unit according to the first embodiment of the present invention. FIG. 7 is a diagram for explaining a relationship between a color difference difference signal and a determination value Val according to the embodiment of the present invention. FIG. 4 is a diagram for explaining a relationship between a contrast value and a determination value Val according to the embodiment of the present invention. FIG. 7 is a diagram for explaining a relationship between a combination ratio and a determination value Val according to the embodiment of the present invention. FIG. 4 is a diagram for explaining contrast determination of a pixel of interest according to the embodiment of the present invention. It is a flowchart for demonstrating the operation | movement of the combination part and the combination ratio calculation part concerning 2nd Embodiment of this invention. FIG. 7 is a diagram for explaining an operation of the color interpolation unit according to the embodiment of the present invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. The embodiment described below is an example as a means for realizing the present invention, and should be appropriately modified or changed depending on the configuration of the apparatus to which the present invention is applied and various conditions. However, the present invention is not limited to the embodiment.

  FIG. 1 is a configuration diagram illustrating the entire imaging apparatus. In FIG. 1, an imaging unit 101 includes a photographic lens (optical system) (not shown), an imaging element that captures an image formed by the photographic lens, and a driving circuit for driving the optical image formed by the photographic lens. Convert to a signal. An analog signal output from the imaging unit 101 is converted into a digital signal by the A / D conversion unit 102. The image signal converted into a digital signal by the A / D conversion unit 102 is input to the image processing unit 103. In other words, the image processing unit 103 acquires a captured image (image signal) output from the image sensor. The image processing unit 103 includes a WB processing unit 104, a color interpolation unit 105, a chromatic aberration of magnification correction unit 106, and a signal processing unit 107, and is controlled by a system controller 108. In the WB processing unit 104, a known white balance (WB) process is performed, and the image signal on which the WB process has been performed is input to the color interpolation unit 105. In this embodiment, the lens-integrated imaging device is taken as an example. However, the present invention is not limited to this, and can be applied to an imaging device of a lens interchangeable type, that is, an imaging device of a so-called interchangeable lens system.

  Here, the operation of the color interpolation unit 105 will be described with reference to FIG. The known Bayer array shown in FIG. 14A is separated into R, G, and B components. For a pixel position that has not been separated, 0 is inserted (FIG. 14B). A known color interpolation process is performed on each plane image generated in FIG. 14B for each component (FIG. 14C).

  Referring back to FIG. 1, the image signal on which the known color interpolation has been performed by the color interpolation unit 105 is input to the magnification chromatic aberration correction unit 106. Although the details will be described later, the image signal after the magnification chromatic aberration correction corrected by the magnification chromatic aberration correction unit 106 is input to the signal processing unit 107, and known luminance signal processing, chrominance signal processing, and the like are performed. The signal that has been subjected to predetermined processing by the image processing unit 103 is output from the image processing unit 103 and stored in an image recording medium such as a semiconductor memory (not shown) in a predetermined format. Further, the signal output from the image processing unit 103 may be displayed on a display (display unit) not shown. The operation of the image processing unit 103 is controlled by the system controller 108 (control unit). The system controller 108 controls the entire image pickup apparatus as a whole. In the present embodiment, the image processing unit 103 (the chromatic aberration of magnification correcting unit 106) and the system controller 108 constitute an image processing apparatus that corrects the chromatic aberration of magnification of an image (captured image) captured via the optical system. Note that the image processing device of the present invention is not limited to the one mounted on the imaging device, and may be provided outside the imaging device. For example, it may be configured from a server connected to the imaging device via the Internet (cloud computing). Of course, the image processing apparatus may be connected via a network to another personal computer (PC) storing image information, a mobile phone, a dedicated terminal such as a PDA or a game machine, or the like.

  Next, the operation of the magnification chromatic aberration corrector 106 will be described with reference to FIG. FIG. 2 is a configuration diagram showing details of the chromatic aberration of magnification correction unit 106. Here, a case will be described as an example where the chromatic aberration of magnification of the B pixel with respect to the G pixel is corrected. Reference numeral 201 denotes a B signal color-interpolated by the color interpolation unit 105, and 202 denotes a G signal color-interpolated by the color interpolation unit 105. The B signal 201 is input to a bilinear interpolation unit 203 and a bicubic interpolation unit 204, respectively. The bilinear interpolation unit (third correction unit) 203 performs known bilinear interpolation (second interpolation processing) using surrounding B pixels, and is input to the synthesis unit 205. The bilinear interpolation unit 203 performs a bilinear interpolation process to correct a color shift amount of a unit of less than one pixel of the second color light (B light) with respect to the first color light (G light) caused by the chromatic aberration of magnification. To correct lateral chromatic aberration. That is, the color shift amount is corrected using a bilinear interpolation process (second interpolation process) for interpolating a signal component between pixels for the B light component of the captured image. The bicubic interpolation unit (first correction unit) 204 performs known bicubic interpolation (first interpolation processing) using surrounding B pixels, and sends the result to the synthesis unit 205, the contrast determination unit 206, and the color difference determination unit 207. Is entered. The bicubic interpolation unit 204 performs a bicubic interpolation process to correct a color shift amount of a unit of less than one pixel of the second color light (B light) with respect to the first color light (G light) caused by the chromatic aberration of magnification. To correct lateral chromatic aberration. That is, the color misregistration amount is corrected by using a bicubic interpolation process (first interpolation process) for interpolating a signal component between pixels for the B light component of the captured image. A first correction unit contrast determination unit (second determination unit) 206 acquires a contrast value (contrast information) from the G signal or the B signal, and details of which will be described later, but the B signal or the G signal after bicubic interpolation. It is determined whether or not it is a high contrast edge. Then, the determination result is input to the combination ratio calculation unit 208. The color difference determination unit (first determination unit) 207 acquires a color difference signal (color difference information) of the first color signal (G signal) and the second color signal (B signal), and the details will be described later. Undershoot is determined from the color difference signals before and after the cubic interpolation. Then, the determination result is input to the combination ratio calculation unit 208. The combining unit 205 converts the data (first data) output from the bicubic interpolation unit 204 and the data (second data) output from the bilinear interpolation unit 203 based on the output of the combining ratio calculation unit 208. Combine. That is, the combining ratio calculating unit 208 and the combining unit 205 function as a combining unit that combines the first data and the second data based on at least one of the contrast information or the color difference information regarding the captured image.

  The bilinear interpolation and the bicubic interpolation will be described with reference to FIGS. FIGS. 4A and 4B show frequency responses of bicubic interpolation and bilinear interpolation, respectively. The horizontal axis indicates frequency, and the vertical axis indicates amplitude. The bilinear interpolation has a feature that a frequency response characteristic is gradual and a blurred image with low reproduction accuracy is obtained, but no undershoot or overshoot occurs. On the other hand, the bicubic interpolation has a characteristic that the frequency response characteristic is steeper and the reproduction accuracy is higher, but undershoot / overshoot occurs. As shown in FIG. 4, the bilinear interpolation processing has a gentler frequency characteristic (second frequency characteristic) than the bicubic interpolation processing when compared at the maximum slope of the frequency response. Further, the bicubic interpolation processing has a steeper frequency characteristic (first frequency characteristic) than the bilinear interpolation processing when compared at the maximum slope of the frequency response. As described above, the bicubic interpolation unit 204 functions as a first interpolation unit that performs the first interpolation process having the first frequency characteristic on the captured image and outputs the first data. The bilinear interpolation unit 203 performs a second interpolation process on the captured image having a second frequency characteristic that is gentler than the first frequency characteristic, and outputs second data. Function as

  FIG. 5 shows a line profile of a subject having an edge after correcting the chromatic aberration of magnification. The horizontal axis shows the pixel position, and the vertical axis shows the pixel value when the pixel position on the horizontal axis is normalized to 1. Reference numeral 503 denotes a G pixel line profile, 501 denotes a B pixel line profile when bilinear interpolation is performed, and 502 denotes a B pixel line profile when bicubic interpolation is performed. B pixels are corrected in sub-pixel units (for example, 0.5 pixels). The B signal subjected to the bilinear interpolation of 501 does not cause undershoot or overshoot, but becomes a signal blurred from the G signal due to the influence of the interpolation. On the other hand, the B signal subjected to the bicubic interpolation of 502 becomes a signal having the same edge as the G signal (region 2), but overshoot occurs in region 1 and undershoot occurs in region 3. Due to the effect of the undershoot, the luminance signal appears to sink below the surroundings or coloring occurs. In the following description, description will be continued focusing on undershoot.

  FIG. 6 shows a line profile of a color difference signal (BG) in a subject having this edge. Reference numeral 601 denotes a difference signal between the B signal and the G signal after bilinear interpolation, and 602 denotes a difference signal between the B signal and the G signal after bicubic interpolation. It can be seen from the line profile 602 that undershoot has occurred in region 3. In the present invention, an area in which an undershoot has occurred, such as area 3 in 602, is detected, and the occurrence of undershoot is suppressed by increasing the weight of bilinear correction (performing weighting processing) in the undershoot area. .

  The operation of the color difference determination unit of the present invention will be described with reference to the flowchart of FIG. In step S301, a color difference signal Cb before correction is obtained (calculated) from the B signal and the G signal before magnification correction. Next, in step S302, the corrected color difference signal Cb 'is obtained (calculated) from the B signal and the G signal after the bicubic magnification correction. Next, the process proceeds to step S303, and if Cb 'is a negative value, it is determined that there is a possibility of undershoot, and the process proceeds to step S304. On the other hand, if Cb 'is not a negative value in step S303, it is determined that there is no possibility of undershoot, and the flow advances to step S309. Next, in step S304, a color difference difference signal SubCb before and after the magnification correction is obtained. In the area where the undershoot occurs in FIG. 6 (area 3), the color difference difference signal SubCb has a large value. Therefore, when the color difference difference signal SubCb is equal to or larger than a predetermined value, it is determined that an undershoot has occurred. Next, the process proceeds to step S305, and when SubCb is smaller than the threshold value Thres1, the process proceeds to step S309, and the determination value Val1 is set to 0. On the other hand, if SubCb is larger than the threshold value Thres1 in step S305, the process proceeds to step S306. In step S306, when SubCb is larger than the threshold value Thres2, the process proceeds to step S308, and the determination value Val1 is set to 1. On the other hand, when SubCb is smaller than the threshold value Thres2 in step S306, the process proceeds to step S307, and the determination value Val1 is obtained by linear interpolation. As described above, the color difference determination unit (first determination unit) 207 acquires the color difference signals of the G signal and the B signal, and according to the color difference signals, the color difference signal of a predetermined numerical range (0 to 1 in the present embodiment). Set a numerical value from the middle. Specifically, the color difference determination unit 207 subtracts the G signal from the first color difference signal obtained by subtracting the G signal from the B signal before performing the bicubic interpolation, and the G signal from the B signal obtained after performing the bicubic interpolation. Obtain a second color difference signal. Further, a difference signal obtained by subtracting the second color difference signal from the first color difference signal is obtained. Thereafter, when the second color difference signal is a value equal to or greater than 0 (positive value), the color difference determination unit 207 sets the smallest numerical value (that is, 0) from a predetermined numerical range 0 to 1. When the second color difference signal has a negative value, a numerical value is set from a predetermined numerical range 0 to 1 so that the numerical value to be set increases when the differential signal increases. FIG. 9 illustrates the relationship among SubCb, threshold values Thres1, Thres2, and determination value Val1 in the above processing. In FIG. 9, when SubCb is smaller than Thres1, the judgment value Val1 outputs 0, and when SubCb is larger than Thres2, the judgment value Val1 outputs 1. When SubCb is between the thresholds Thres1 and Thres2,

Becomes

  As described above, when the color difference difference signal is large, the value of the determination value Val1 increases, and it is determined that an undershoot occurs.

  Next, the operation of the contrast determination unit of the present invention will be described with reference to the flowchart of FIG. In step S701, a contrast value around the target pixel is obtained. An example of the contrast determination will be described with reference to FIG. Assuming that the difference between the maximum value and the minimum value of the surrounding pixels is G11 and the contrast value is Cont,

Becomes

  Next, the process proceeds to step S702, and if the contrast value Cont is smaller than the threshold value Thres3, the process proceeds to step S706 to set the determination value Val2 to 0. On the other hand, if the contrast value Cont is larger than the threshold value Thres3 in step S702, the process proceeds to step S703. If the contrast value Cont is larger than the threshold value Thres4 in step S703, the process proceeds to step S705, and the determination value Val2 is set to 1. On the other hand, if the contrast value Cont is smaller than the threshold value Thres4 in step S703, the process proceeds to step S704 to determine the determination value Val2 by linear interpolation. As described above, the contrast determination unit (second determination unit) 206 acquires the contrast value around the pixel of interest, and according to the contrast value, from within a predetermined numerical range (0 to 1 in the present embodiment). Set a numerical value. Specifically, the contrast determination unit 206 obtains a contrast value around the pixel of interest of the G signal, and from the predetermined numerical value range 0 to 1 so that when the contrast value increases, the numerical value to be set increases. Set a numerical value. FIG. 10 illustrates the relationship between the contrast value Cont, the threshold values Thres3 and Thres4, and the determination value Val2 in the above processing. In FIG. 10, when Cont is smaller than Thres3, the judgment value Val2 outputs 0, and when Cont is larger than Thres3, the judgment value Val2 outputs 1. When Cont is between the thresholds Thres3 and Thres4,

Becomes

  Here, the G pixel is used for determining the contrast, but a B pixel or a Y pixel synthesized at a known ratio of Y = 0.3R + 0.6G + 0.1B may be used. In addition, the detection is performed in a 3 × 3 area, but the present invention is not limited to this.

  Next, the operation of the combining unit 205 and the combining ratio calculating unit 208 of FIG. 2 of the present invention will be described with reference to the flowchart of FIG. In step S801, a result Val obtained by multiplying the result of the determination value Val2 of the contrast determination by the result of the determination value Val1 of the color difference determination is obtained. Next, the process proceeds to step S802, and is compared with the threshold value Thres5. If the determination value val is small, the process proceeds to step S806 to set the combination ratio MIX to min_thres. On the other hand, if the determination value val is larger than the threshold Thres5 in step S802, the process proceeds to step S803. If the determination value val is larger than the threshold value Thers6 in step S803, the process advances to step S805 to set the combination ratio MIX to max_thres. On the other hand, if the determination value Val is smaller than the threshold value Thres6 in step S803, the process proceeds to step S806, and the combination ratio MIX is obtained by linear interpolation. FIG. 11 illustrates the relationship between the determination value Val and the combination ratio MIX. In FIG. 11, when the determination value Val is smaller than Thres5, the combination ratio MIX outputs min_thres, and when the determination value Val is greater than Thres6, the combination ratio MIX outputs max_thres. When the determination value Val is between the threshold value Thres5 and the threshold value Thres6,

Becomes

  Returning to the flowchart of FIG. 8 again, when the combination ratio MIX is determined in step S804, step S805, or step S806, the process proceeds to step S807. Combine the values.

  Referring back to FIG. 2, the combination ratio calculation unit 208 obtains a combination ratio from the determination output of the contrast determination unit (edge determination unit) 206 and the determination output of the color difference determination unit 207, and inputs it to the combination unit 205. The synthesizing unit 205 determines the synthesizing ratio between the outputs of the bilinear interpolation and the bicubic interpolation based on the output of the synthesizing ratio calculating unit 208. As described above, in the present embodiment, the combining ratio calculation unit 208 and the combining unit 205 use the bicubic interpolation processing (first interpolation processing) and the bilinear interpolation processing (second interpolation processing) to perform magnification chromatic aberration ( It functions as a second correction unit for correcting the (color shift amount). The second correction unit corrects the result (output value) of the first interpolation process using the first interpolation process and the second interpolation process. Specifically, in accordance with at least one (here, both) of the result of the color difference determination unit 207 and the result of the contrast determination unit 206, the result of the first interpolation process is determined using the second interpolation process. The correction is performed based on the result of interpolating the signal components between pixels. More specifically, according to the color difference signal obtained by subtracting the G signal from the B signal after the first interpolation processing and the contrast of the captured image, the result (output value) of the first interpolation processing and the second The result (output value) of the interpolation processing is synthesized based on the calculated synthesis ratio. In the present embodiment, the result (output value) of the first interpolation process and the second interpolation process are performed in accordance with the color difference signal obtained by subtracting the G signal from the B signal after the first interpolation process and the contrast of the captured image. Change the synthesis ratio of the processing result (output value). Specifically, as the numerical value obtained by multiplying the numerical value set by the color difference determining unit 207 and the numerical value set by the contrast determining unit 206 increases, the ratio of the result of the second interpolation processing to the result of the first interpolation processing increases Is changed so that is larger. Assuming that the pixel value B_lin after the bilinear interpolation and the pixel value B_cub after the bicubic interpolation are the combination ratio MIX (0 to 1), the pixel value B_out after the combination is

Becomes

  As described above, when it is detected that the color difference difference signal obtained from the B signal and the G signal before and after the magnification chromatic aberration correction in which the bicubic interpolation is performed and the contrast is large, the combining ratio after the bilinear interpolation is determined. Set higher (perform weighting processing). In other words, the frequency response characteristic of the interpolation function is changed to a gentle setting. By doing so, it is possible to suppress a decrease in image quality due to the effect of undershoot while maintaining the contrast in the normal region.

  Further, in the present embodiment, the correction of the B pixel has been described, but the same applies to the correction of the R pixel, and a description thereof will be omitted.

  According to the present embodiment, it is possible to suppress the occurrence of undershoot and overshoot while eliminating the loss of the band due to the interpolation of the B pixels, and it is possible to perform highly accurate correction of the chromatic aberration of magnification. Therefore, it is possible to provide an image processing device, an imaging device, and an image processing method that are advantageous for correcting magnification chromatic aberration.

  Hereinafter, a second embodiment of the present invention will be described with reference to the flowchart of FIG. The second embodiment differs from the first embodiment only in the operation of the combination ratio calculation unit in FIG. 2, and the description of the other parts will be omitted. In step S1301 of FIG. 13, Val is acquired using the MAX value of the result of the determination value Val2 of the contrast determination and the determination value Val1 of the color difference determination as the determination value. Hereinafter, steps S1302 and subsequent steps are the same as those described with reference to FIG. 8 in the first embodiment, and thus detailed description will be omitted. That is, also in the present embodiment, the combining ratio calculation unit 208 and the combining unit 205 use the bicubic interpolation process (first interpolation process) and the bilinear interpolation process (second interpolation process) to perform chromatic aberration of magnification (chromaticity). It functions as second correction means for correcting the amount of deviation. The second correction unit corrects the result (output value) of the first interpolation process using the first interpolation process and the second interpolation process. Specifically, according to at least one of the results of the color difference determination unit 207 and the result of the contrast determination unit 206 (here, whichever is greater), the result of the first interpolation Are corrected using the result of interpolating the signal components between pixels. More specifically, the result (output value) of the first interpolation processing and the second interpolation processing are performed in accordance with the color difference signal obtained by subtracting the G signal from the B signal after the first interpolation processing or the contrast of the captured image. The result (output value) of the interpolation processing is synthesized based on the calculated synthesis ratio. In the present embodiment, the result (output value) of the first interpolation processing and the second interpolation processing are performed in accordance with the color difference signal obtained by subtracting the G signal from the B signal after performing the first interpolation processing or the contrast of the captured image. Change the synthesis ratio of the processing result (output value). Specifically, the larger the numerical value set by the color difference determining unit 207 and the numerical value set by the contrast determining unit 206, the larger the numerical value of the first interpolation processing is compared with the result of the second interpolation processing. Is changed to increase the ratio of

  As described above, when it is detected that the color difference difference signal obtained from the B signal and the G signal before and after the magnification chromatic aberration correction in which the bicubic interpolation is performed is large or the contrast is large, the synthesis ratio after the bilinear interpolation is determined. Set higher (perform weighting processing). In other words, the frequency response characteristic of the interpolation function is changed to a gentle setting. By doing so, it is possible to suppress a decrease in image quality due to the effect of undershoot while maintaining the contrast in the normal region.

  As described above, according to the present embodiment, it is possible to suppress the occurrence of undershoot and overshoot while eliminating the disappearance of the band due to the interpolation of the B pixels, and it is possible to perform highly accurate correction of the chromatic aberration of magnification. . Therefore, it is possible to provide an image processing device, an imaging device, and an image processing method that are advantageous for correcting magnification chromatic aberration.

  As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

  For example, a case in which a software program that realizes the functions of the above-described embodiments is supplied to a system or an apparatus having a computer that can execute the program directly from a recording medium or using wired / wireless communication and the program is executed Is also included in the present invention.

  Therefore, the program code itself supplied and installed in the computer to implement the functional processing of the present invention by the computer also implements the present invention. That is, the present invention also includes a computer program in which a procedure for implementing the functional processing of the present invention is described.

  In this case, any form of the program, such as an object code, a program executed by an interpreter, and script data to be supplied to the OS, may be used as long as the program has a function. As a recording medium for supplying the program, for example, a magnetic recording medium such as a hard disk or a magnetic tape, an optical / magneto-optical storage medium, or a nonvolatile semiconductor memory may be used.

  As a method of supplying the program, a method in which a computer program forming the present invention is stored in a server on a computer network, and a connected client computer downloads and programs the computer program is also conceivable.

  INDUSTRIAL APPLICATION This invention can be utilized suitably for imaging devices, such as a compact digital camera, a single-lens reflex camera, and a video camera.

204 Bicubic interpolation unit 205 Synthesis unit 208 Synthesis ratio calculation unit

Claims (16)

An image processing apparatus that corrects a color shift amount of a second color light with respect to a first color light due to chromatic aberration of magnification of an image captured via an optical system,
A first correction unit that has a first frequency characteristic and corrects the color shift amount using a first interpolation process that interpolates a signal component between pixels for the second color component of the image;
The first in accordance with the No. color Sashin obtained by subtracting the first color signal from the second color signal after the interpolation processing, and the first interpolation process, than the first frequency characteristic A second interpolating process having a gradual second frequency characteristic, and a second correcting unit configured to correct the color shift amount using a second interpolating process;
An image processing apparatus comprising: Said second correction means, the first in accordance with the No. color Sashin obtained by subtracting the first color signal from the second color signal after the interpolation processing, the result of the first interpolation processing 2. The image processing apparatus according to claim 1, wherein the correction is performed using a result obtained by interpolating the signal components between the pixels using the second interpolation processing.   The image processing apparatus according to claim 1, wherein the second correction unit combines a result of the first interpolation processing and a result of the second interpolation processing. Said second correction means, the first in accordance with the No. color Sashin obtained by subtracting the first color signal from the second color signal after the interpolation processing, the result of the first interpolation processing The image processing apparatus according to claim 3, wherein a synthesis ratio of a result of the second interpolation processing is changed. The second correction unit is configured to perform the synthesis based on a color difference signal obtained by subtracting the signal of the first color from the signal of the second color after the first interpolation processing, and a contrast of the image. The image processing apparatus according to claim 4, wherein the ratio is changed. A first determination unit that acquires the color difference signal and sets a numerical value from a predetermined numerical range according to the color difference signal;
A second determination unit configured to obtain a contrast value of the signal of the first color or the signal of the second color and set a numerical value from the predetermined numerical value range according to the contrast value;
The second correction means may determine that the larger the value obtained by multiplying the value set by the first determination means and the value set by the second determination means, the larger the value of the second interpolation The image processing apparatus according to claim 5 , wherein the synthesis ratio is changed so that a ratio of a result of the interpolation processing is increased. A first determination unit that acquires the color difference signal and sets a numerical value from a predetermined numerical range according to the color difference signal;
A second determination unit configured to obtain a contrast value of the signal of the first color or the signal of the second color and set a numerical value from the predetermined numerical value range according to the contrast value;
The second correction unit is configured such that the larger the larger of the numerical value set by the first determining unit and the numerical value set by the second determining unit, the larger the value of the first interpolation process is, The image processing apparatus according to claim 5 , wherein the combining ratio is changed so that a ratio of a result of the second interpolation processing increases. The first determination unit may include a first color difference signal obtained by subtracting the first color signal from a second color signal before performing the first interpolation process, and a first color difference signal after performing the first interpolation process. A second color difference signal obtained by subtracting the first color signal from the second color signal, and a difference signal obtained by subtracting the second color difference signal from the first color difference signal.
Wherein the difference signal is large, as numerical values the setting increases, the image processing apparatus according to claim 6 or 7, characterized in that to set the numerical value from the predetermined value range. The first determination unit may include a first color difference signal obtained by subtracting the first color signal from a second color signal before performing the first interpolation process, and a first color difference signal after performing the first interpolation process. A second color difference signal obtained by subtracting the first color signal from the second color signal, and a difference signal obtained by subtracting the second color difference signal from the first color difference signal.
If the second color difference signal is a positive value, the image processing apparatus according to claim 6 or 7, characterized in that setting the smallest number from among the predetermined numerical range. The second determination unit acquires a contrast value around the pixel of interest of the first color signal or the second color signal,
If the contrast value is larger, the so Numeric values increases, the image processing apparatus according to any one of claims 6 to 9, characterized in that to set the numerical value from the predetermined value range . It said first interpolation processing is bicubic interpolation, the image processing apparatus according to any one of claims 1 to 10, wherein the second interpolation process is bilinear interpolation. The image processing apparatus according to any one of claims 1 to 11, wherein a third correction means for correcting the color shift amount using the second interpolation process. An image sensor that captures an image formed by the optical system;
An image processing apparatus comprising: the image processing apparatus according to claim 1, wherein magnification chromatic aberration of an image output from the image sensor is corrected. An image processing method for correcting a color shift amount of a second color light with respect to a first color light due to a chromatic aberration of magnification of an image captured via an optical system,
A first correction step that has a first frequency characteristic and corrects the color shift amount using a first interpolation process that interpolates a signal component between pixels for the second color component of the image;
The first in accordance with the No. color Sashin obtained by subtracting the first color signal from the second color signal after the interpolation processing, and the first interpolation process, than the first frequency characteristic A second correction step of correcting the color shift amount using a second interpolation process having a gradual second frequency characteristic;
An image processing method comprising:   A computer-executable program in which each step of the image processing method according to claim 14 is described.   A computer-readable storage medium storing a program for causing a computer to execute each step of the image processing method according to claim 14.