JP2014072676A - Image processing circuit, image processing method, and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing circuit which can approximate a color of image data to a color of incident light made incident to a lens.SOLUTION: An image processing section 30 has: a signal processing part 31 for applying prescribed signal processing to data outputted by an image sensor 14 and generating image data PD; and a chromatic aberration extraction circuit 41 for extracting chromatic aberration from the image data PD. The image processing section 30 has: a color data calculation circuit 42 which calculates color data D4 corresponding to a color of incident light made incident to a lens 12 which forms an image to an image sensor 14 on the basis of the chromatic aberration; and a differential circuit 43 which calculates a differential value D5 between color data at a position where the chromatic aberration of the image data PD has been extracted and the color data D4. The image processing section 30 has a correction circuit 46 which corrects the image data PD in accordance with a correction value D7 after weighing the differential value D5 with the weighed value D6.

Description

  The present invention relates to an image processing circuit, an image processing method, and an imaging apparatus.

  In an imaging apparatus equipped with an image sensor such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), predetermined signal processing is performed on a signal read from the image sensor to generate image data for output. (For example, see Patent Documents 1 and 2). As signal processing in this imaging apparatus, for example, white balance adjustment, gain adjustment, defect signal correction, camera shake correction processing, and the like are executed. Image data with excellent image quality can be obtained by such various signal processing.

JP 2001-186533 A JP 2000-003437 A

  By the way, in the said imaging device, the intensity | strength of each R (red), G (green), and B (blue) light which injects into the said imaging device is detected using an image sensor, and the intensity of the light is detected. Judging the color of the subject. Then, the signal read from the image sensor is subjected to the various signal processes described above to generate image data for output. However, due to signal processing such as white balance adjustment, noise, and the like, an error occurs between the color data of the image data and the color of light actually incident on the imaging device. For this reason, the color data of the image data after performing signal processing such as white balance adjustment differs from the actual color of the subject. Then, for example, when the imaging apparatus is used at a medical site, there is a possibility that it may adversely affect lesion diagnosis.

  According to an aspect of the present invention, a chromatic aberration extraction circuit that extracts chromatic aberration from image data generated by performing predetermined signal processing on data output from an image sensor, and the imaging based on the chromatic aberration A color data calculation circuit that calculates color data corresponding to the color of incident light incident on a lens that forms an image on the element, and a difference value between the color data and color data at a position where the chromatic aberration of the image data is extracted And a correction circuit for correcting the image data in accordance with the difference value.

  According to one aspect of the present invention, there is an effect that the color of image data can be made close to the color of incident light incident on a lens.

1 is a block diagram illustrating an imaging apparatus according to an embodiment. (A)-(c) is explanatory drawing which shows a chromatic aberration. Explanatory drawing which shows the calculation table of one Embodiment. Explanatory drawing which shows the position on an image sensor. The flowchart which shows the image correction method. (A), (b) is explanatory drawing which shows the conditions which are easy to detect a chromatic aberration. Explanatory drawing which shows the calculation table of a modification.

(First embodiment)
Hereinafter, a first embodiment will be described with reference to FIGS.
An imaging apparatus 1 illustrated in FIG. 1 is a digital still camera, for example. The imaging apparatus 1 includes an imaging unit 10, an analog front end (AFE) 20, an image processing unit 30, and a memory 50.

  The imaging unit 10 includes an imaging optical system (optical system) 11 and an image sensor 14. The optical system 11 includes a lens 12 that collects light from the subject and a diaphragm 13. The lens 12 is a zoom lens that can change (magnify) the focal length, for example. For example, the lens 12 includes a zoom lens group and a focus lens. The lens 12 forms a subject image for photographing the subject on the light receiving surface of the image sensor 14. In the lens 12, for example, the zoom lens group is moved along the optical axis direction under the control of an autofocus (AF) control unit 32 in the image processing unit 30. Thereby, the zoom magnification (magnification) of the lens 12 is adjusted. In the lens 12, for example, the focus lens is moved along the optical axis direction by the control of the AF control unit 32. As a result, the focus of the subject image on the light receiving surface of the image sensor 14 is adjusted.

  The diaphragm 13 adjusts the amount of light transmitted through the lens 12 according to the subject illuminance. The image sensor 14 includes, for example, a Bayer array color filter and an image sensor including a plurality of pixels including a photoelectric conversion unit. As the image sensor, a CCD (Charge Coupled Device) image sensor, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, or the like is used. The image sensor 14 photoelectrically converts the subject image to generate an imaging signal (analog signal).

  The AFE 20 includes, for example, a preamplifier and an analog-digital conversion circuit (ADC). The AFE 20 converts the imaging signal output from the image sensor 14 into a digital signal, and outputs the digital signal to the image processing unit 30 as image data (Bayer data).

  The image processing unit 30 includes a signal processing unit 31, an AF control unit 32, and an image correction unit 40. The signal processing unit 31 performs various types of image processing on the RGB format image data (input image data) input from the AFE 20, and outputs the processed image data PD to the image correction unit 40. Various types of image processing include, for example, preprocessing such as white balance adjustment, gain adjustment, and defect signal correction, and camera shake correction processing that corrects a shift between continuously captured pixels. Here, the above-mentioned camera shake correction is a technique for correcting camera shake by image processing. For example, a plurality of images are calculated so that a shift amount is calculated for a plurality of images continuously shot with a short exposure time and the shift is corrected. This is a technique for correcting camera shake by aligning and composing images. Then, the signal processing unit 31 outputs camera shake data D1 indicating the amount of camera shake (the amount of shift between the pixels) obtained by the camera shake correction to the image correction unit 40.

  In addition, the signal processing unit 31 calculates an AF evaluation value indicating the focus state based on the input image data, and outputs the AF evaluation value to the AF control unit 32. Specifically, after extracting the luminance signal from the input image data, the signal processing unit 31 calculates an AF evaluation value indicating the contrast intensity of the input image data by integrating high-frequency components in the screen of the luminance signal. The AF evaluation value is output to the AF control unit 32. Here, the AF control unit 32 executes AF control for bringing the subject into focus based on the AF evaluation value. That is, the AF control unit 32 detects a focus position (AF position) based on the AF evaluation value, and controls to move the focus lens of the lens 12 to the focus position. As the AF control, for example, a well-known hill-climbing AF control can be used.

  Further, the signal processing unit 31 detects the AF position (focus position) in the input image data based on the input image data and the like, and supplies the AF data D2 including the position information of the AF position to the image correction unit 40. Output.

  The image correction unit 40 receives the image data PD from the signal processing unit 31, and the shooting conditions (specifically, the conditions of the optical system 11) when shooting the image data PD are the AF control unit 32 and the like. It is input from. The image correction unit 40 corrects the color data of the image data PD obtained by performing various signal processes on the input image data using chromatic aberration. Specifically, the image correction unit 40 corrects the color data of the image data PD so as to approach the color of incident light incident on the lens 12 using chromatic aberration. Then, the image correction unit 40 stores the corrected image data PD1 after correction in the memory 50.

  Here, an image correction method (image processing method) in the image correction unit 40 will be briefly described. First, the color data of the image data PD subjected to signal processing such as white balance adjustment in the signal processing unit 31 is incident light L1 incident on the lens 12 due to the signal processing or the like (see FIG. 2A). As described above, it is different from the actual color of the subject. On the other hand, in the imaging device 1 using the lens 12, an imaging error called chromatic aberration occurs. As shown in FIG. 2A, this chromatic aberration is when the incident light L1 is incident on the lens 12 and passes through the lens 12 with the wavelength of the light waves LR, LG, LB of the incident light L1. This aberration is caused by the difference in refractive index. Due to such chromatic aberration, for example, an imaging position (edge) where a light wave LR having a red (R) wavelength component forms an image on the light receiving surface of the image sensor 14 and an imaging of a light wave LG having a green (G) wavelength component. The position and the imaging position of the light wave LB having the blue (B) wavelength component are different from each other. In other words, the difference between the imaging positions (edges) at which the light waves LR, LG, and LB having wavelength components of RGB colors are imaged is chromatic aberration. In this specification, as shown in FIGS. 2B and 2C, the difference (number of pixels) between the imaging position of the green light wave LG and the imaging position of the red light wave LR is expressed as “between green and red. The difference (number of pixels) between the image formation position of the blue light wave LB and the image formation position of the green light wave LG is referred to as “chromatic aberration”. Such chromatic aberration is a value uniquely determined by the color of the subject 60 (here, wood) and the characteristic data of the optical system 11 (the refractive index, magnification, aperture, etc. of the lens 12). For example, a case where the color at an arbitrary point 61 of the subject 60 is light green (see FIG. 2B) and a case where the color is dark green (see FIG. 2C) will be described. For simplification of description, a case where the red and blue components at the point 61 of the subject 60 are the same and only green is different will be described. First, since the frequency of light is higher in darker green than in light green, the refractive index is higher. Therefore, when the subject 60 is dark green (see FIG. 2C), in the image sensor 14, the image formation position of the green light wave LG is when the subject 60 is light green (see FIG. 2B). ) Is detected at a position closer to the imaging position of the blue light wave LB. That is, when the subject 60 is dark green, the chromatic aberration between blue-green is reduced while the chromatic aberration between green and red is increased compared to the case of light green. As described above, depending on the color of the subject 60, the imaging positions of the RGB light waves LR, LG, and LB in the image sensor 14 are different, and the chromatic aberration between blue-green and green-red is different. For this reason, by detecting such chromatic aberration (specifically, chromatic aberration between blue-green and green-red), the color of the incident light L1 incident on the lens 12 can be determined. It can be said that the color can be judged. Therefore, the image correction unit 40 detects chromatic aberration and uses the chromatic aberration to correct the color data of the image data PD so as to approach the color of the incident light L1 incident on the lens 12 (the color of the subject 60). .

Next, an example of the internal configuration of the image correction unit 40 will be described.
As shown in FIG. 1, the image correction unit 40 includes a chromatic aberration extraction circuit 41, a color data calculation circuit 42, a difference circuit 43, a weighting circuit 44, a multiplication circuit 45, and a correction circuit 46. .

  Image data PD and AF data D <b> 2 are input from the signal processing unit 31 to the chromatic aberration extraction circuit 41. The chromatic aberration extraction circuit 41 extracts chromatic aberration at a predetermined position (chromatic aberration extraction position) of the image data PD based on the image data PD and the AF data D2. Then, the chromatic aberration extraction circuit 41 outputs the extracted chromatic aberration and position information indicating the detection position of the chromatic aberration on the image sensor 14 to the color data calculation circuit 42, and weights the position data D3 indicating the chromatic aberration extraction position. 44.

  The color data calculation circuit 42 performs RGB based on the extracted chromatic aberration, the detection position of the chromatic aberration on the image sensor 14, and the shooting condition when shooting the image data PD (condition of the optical system 11). Color data D4 including color information (light intensity) of each color is calculated. Specifically, the color data calculation circuit 42 has a calculation table 42A for calculating color data D4 corresponding to the color of the incident light L1 incident on the lens 12 from the extracted chromatic aberration. As shown in FIG. 3, the calculation table 42A includes characteristics data of the optical system 11 such as the zoom magnification (magnification) of the lens 12 and the aperture, the position on the image sensor 14 from which chromatic aberration is extracted, chromatic aberration between green and green, and green It is a table | surface which shows the relationship between the chromatic aberration between red, and the color data D4 containing the color information of each color of RGB. Specifically, in the calculation table 42A, the magnification of the lens 12 (1 to h times), the diaphragm (1.0 to j), the detection position on the image sensor 14 (1 to k: see FIG. 4), blue green One color data D4 is associated with each combination of numerical values of the chromatic aberration (1 pixel to m pixel) between and the chromatic aberration between green and red (1 pixel to n pixel). That is, when input parameters including the magnification of the lens 12 and the photographing condition of the optical system 11 of the aperture, the detection position on the image sensor 14, and chromatic aberration (chromatic aberration between blue-green and green-red) are determined, the calculation table 42A includes Based on this, color information for each color of RGB is uniquely determined, and color data D4 is calculated.

  Here, as described above, the chromatic aberration is a value uniquely determined by the color of the subject (the color of the incident light L1) and the characteristic data of the optical system 11 (the refractive index, magnification, aperture, etc. of the lens 12). In other words, the color of the subject (the color of the incident light L1) can be uniquely determined from the chromatic aberration and the characteristic data of the optical system 11. Therefore, in the color data calculation circuit 42, calculation corresponding to the optical system 11 (lens 12) is performed based on the characteristic data of the optical system 11 acquired at the time of evaluating the performance of the optical system 11 (lens 12 and aperture 13). A table 42A is prepared in advance, and color data D4 indicating the color of the incident light L1 is calculated from chromatic aberration using the calculation table 42A. Since the refractive index is a characteristic value unique to the lens 12 and is a fixed value, it is not included in the input parameter. However, the relationship between the color data D4 (color of the incident light L1) and chromatic aberration according to the refractive index. Therefore, the refractive index of the lens 12 is reflected in the calculation table 42A. In other words, in the calculation table 42A, based on the refractive index of the lens 12, the characteristic data of the optical system 11 that is a photographing condition, the chromatic aberration, and the color data D4 are associated with each other. That is, the calculation table 42A includes “the chromatic aberration inherent to the lens 12” determined based on the refractive index inherent to the lens 12 and “characteristic data of the optical system 11” serving as a photographing condition, and the incident light L1 incident on the lens 12. It is generated so as to show a relationship with “color data D4” indicating a color.

  The detection position on the image sensor 14 in the input parameter is represented by a number assigned to each pixel of the image sensor 14 (imaging device). In this example, as shown in FIG. 4, for example, “1” is assigned to the upper left pixel of the image sensor 14, that is, the pixel in the first row and the first column, and the pixels in the first row are sequentially added from the left. Are given numbers (here, “2” to “15”). Subsequently, the next number (here, “16”) is assigned to the pixel in the second row and the first column of the image sensor 14, and the number is assigned to the pixels in the second row in order from the left. . Similarly, all pixels of the image sensor 14 are numbered, and the number of the lower right pixel of the image sensor 14 is “k”. Further, in FIG. 3, for simplification of the drawing, the color information of each RGB color in the color data D4 is shown as “XXX”, but actually, the color information of each RGB color is represented by a decimal number, for example, It is represented by a value from “0” to “255”.

  The difference circuit 43 receives the color data D4 calculated by the color data calculation circuit 42 and the image data PD output from the signal processing unit 31. The difference circuit 43 calculates a difference value D5 between the color data of the image data PD and the color data D4 at the chromatic aberration detection position, and outputs the difference value to the multiplication circuit 45.

  The weighting circuit 44 receives camera shake data D1 and AF data D2 from the signal processing unit 31, and position data D3 from the chromatic aberration extraction circuit 41. The weighting circuit 44 calculates a weight value D6 indicating the accuracy (reliability) of the chromatic aberration extracted by the chromatic aberration extraction circuit 41 based on the camera shake data D1, the AF data D2, and the position data D3. Then, the weighting circuit 44 outputs the calculated weight value D6 to the multiplication circuit 45.

The multiplication circuit 45 calculates a multiplication value of the difference value D5 from the difference circuit 43 and the weight value D6 from the weighting circuit 44, and outputs the multiplication value as the correction value D7 to the correction circuit 46.
The correction circuit 46 generates corrected image data PD1 obtained by correcting the color data of the entire image data PD based on the correction value D7 from the multiplication circuit 45. Then, the correction circuit 46 outputs the corrected image data PD1 and the correction value D7 to the memory 50.

In the present embodiment, the weighting circuit 44 and the multiplication circuit 45 are examples of a correction value generation circuit.
Next, the operation (image correction method) of the image correction unit 40 will be described in detail.

  In step S1 and step S2 shown in FIG. 5, the chromatic aberration extraction circuit 41 selects a position where chromatic aberration is easily detected (extracted) as a chromatic aberration detection position for extracting chromatic aberration from the image data PD input from the signal processing unit 31. . Here, conditions for easily detecting chromatic aberration will be described. More specifically, as shown in FIG. 6A, the chromatic aberration becomes more prominent as the distance from the center of the image data PD (image sensor 13), that is, the closer to the outer edge of the image. For this reason, it is easier to detect chromatic aberration as the distance from the center of the image increases. Further, as shown in FIG. 6B, since the edge (boundary) of the image is strong at the in-focus position (AF position) that is in focus, it is easier to detect chromatic aberration as it approaches the AF position. Furthermore, since the edge of an image is easier to detect when there is less camera shake, the smaller the camera shake, the easier it is to detect chromatic aberration. In FIG. 6B, the solid line frame is the AF position (focus position), and the broken line frame is the AF position candidate.

  Therefore, in step S1 shown in FIG. 5, first, a plurality of chromatic aberration extraction position candidates close to the AF position are selected. That is, a plurality of AF positions or positions close to the AF position are selected as chromatic aberration extraction position candidates. Subsequently, in step S2, a candidate far from the center of the image is selected as a chromatic aberration extraction position from among the plurality of selected candidates. Specifically, the candidate of the position farthest from the center of the image data PD (image sensor 13) is selected as the chromatic aberration extraction position from among the plurality of selected chromatic aberration extraction position candidates. Thereby, a position where chromatic aberration is easily detected (specifically, a position close to the AF position and away from the center of the image) is selected as the chromatic aberration extraction position.

  Next, in step S3, the chromatic aberration extraction circuit 41 extracts chromatic aberration at the selected chromatic aberration extraction position. Specifically, the chromatic aberration extraction circuit 41 detects the imaging positions (edges) of the light waves LR, LG, and LB (see FIG. 2) of each RGB color at the chromatic aberration extraction position, and extracts chromatic aberration from the difference value of these edges. (calculate. More specifically, the chromatic aberration extraction circuit 41 calculates chromatic aberration between blue and green from the difference value between the edge of the blue light wave LB and the edge of the green light wave LG, and the edge of the green light wave LG and the red light wave. Chromatic aberration between green and red is calculated from the difference value from the edge of LR.

  Next, in step S4, the color data calculation circuit 42 obtains color data D4 corresponding to the color of the incident light L1 incident on the lens 12 from the chromatic aberration extracted at the chromatic aberration extraction position based on the calculation table 42A. calculate. Specifically, the extracted chromatic aberration, the detection position of the chromatic aberration on the image sensor 14, and the conditions of the optical system 11 when the image data PD is captured (specifically, the magnification and aperture of the lens 12) ) As input parameters, the color data D4 is calculated from the calculation table 42A. Thereby, the color data D4 corresponding to the color of the incident light L1 incident on the lens 12 can be calculated from the chromatic aberration inherent to the lens 12 and the condition of the optical system 11.

  Subsequently, in step S5, the difference circuit 43 calculates a difference value D5 between the color data of the image data PD at the chromatic aberration extraction position and the color data D4 calculated in the previous step S4. Based on the difference value D5, an error between the color of the image data PD and the color of the incident light L1 can be determined.

  Next, in step S6, the weighting circuit 44 generates a weight value D6 indicating whether or not the chromatic aberration calculated in the previous step S3 is an accurate value. Specifically, the weighting circuit 44 weights the difference value D5 according to whether or not the chromatic aberration extracted in the previous step S3 is a highly reliable chromatic aberration detected under conditions that allow easy detection. A weight value D6 is generated. More specifically, the weighting circuit 44 calculates the distance between the chromatic aberration extraction position selected in the previous step S2 and the center position of the image data PD based on the position data D3 from the chromatic aberration extraction circuit 41, and A first value A1 is generated according to the distance. The first value A1 is, for example, a value from “0” to “1”, and is a value that approaches “1” as the chromatic aberration extraction position is further away from the center position of the image data PD. The weighting circuit 44 calculates a distance between the chromatic aberration extraction position and the AF position (focus position) based on the AF data D2 from the signal processing unit 31 and the position data D3, and sets the distance to the distance. In response, the second value A2 is generated. The second value A2 is, for example, a value from “0” to “1”, and is a value that approaches “1” as the chromatic aberration extraction position approaches the AF position (focus position). Further, the weighting circuit 44 generates the third value A3 based on the camera shake data D1 from the signal processing unit 31. The third value A3 is, for example, a value from “0” to “1”, and is a value that approaches “1” as the camera shake amount decreases. Then, the weighting circuit 44 calculates a value obtained by multiplying the first value A1, the second value A2, and the third value A3 as a weight value D6 (= A1 × A2 × A3). This weight value D6 is a condition that the chromatic aberration is easily detected in the previous step S3 (a condition that the chromatic aberration extraction position is far from the center of the image and close to the AF position, and there is little camera shake). The closer to "1".

  Next, in step S7, the multiplication circuit 45 multiplies the difference value D5 and the weight value D6 to calculate a correction value D7. That is, the multiplication circuit 45 generates a correction value D7 obtained by weighting (correcting) the difference value D5 with the weight value D6. Here, the reason why the difference value D5 is weighted by the weight value D6 will be described. If chromatic aberration can be accurately extracted in step S3, the color of the incident light L1 can be uniquely determined based on the chromatic aberration and the conditions of the optical system 11. However, chromatic aberration cannot always be accurately detected, and the accuracy (reliability) decreases depending on the detection conditions. Therefore, a weight value D6 that approaches “1” is generated as the chromatic aberration is detected under conditions that facilitate the detection of chromatic aberration, that is, the accuracy (reliability) of the chromatic aberration detected in step S3 is higher, and the weight value D6 is generated. Thus, the difference value D5 is weighted. Thus, the higher the accuracy of the detected chromatic aberration, the closer the correction value D7 is to the difference value D5. On the other hand, the lower the accuracy of the detected chromatic aberration, the closer the correction value D7 is to “0”.

  Subsequently, in step S8, the correction circuit 46 corrects the color data of the entire image data PD using the correction value D7 to generate corrected image data PD1. Specifically, the correction circuit 46 adds the correction value D7 to the color data of each pixel of the image data PD, thereby correcting the color data of the entire image data PD to generate corrected image data PD1. Here, the correction value D7 is closer to the difference value D5 as the accuracy of the chromatic aberration detected in step S3 is higher. For this reason, when chromatic aberration is detected under easy-to-detect conditions, the color of the entire image data PD is determined by the correction value D7 close to the difference value D5 between the color data D4 calculated from the chromatic aberration and the color data of the image data PD. Data is corrected. Thereby, the color of the corrected image data PD1 after correction can be brought close to the color of the incident light L1, and as a result, the color of the corrected image data PD1 can be brought close to the color of the subject. The correction value D7 (and difference value D5) used in the correction process is generated based on the chromatic aberration extracted from one chromatic aberration extraction position. However, the error between the color data of the image data PD and the color of the incident light L1 is substantially the same for the entire image data PD. Therefore, by correcting the color data of the entire image data PD using the correction value D7, the color of the entire corrected image data PD1 can be brought close to the color of the subject.

  Then, the corrected image data PD1 is stored in the memory 50, and the correction value D7 is stored in the memory 50. By storing the correction value D7 in the memory 50 in this way, when the next image data PD is generated, the correction value D7 read from the memory 50 is used without generating a new correction value D7. The next image data PD can be corrected. Note that the correction value D7 may be calculated every time, for example, at the time of shooting by the imaging device 1 (when the image data PD is generated), or only at the first shooting after the imaging device 1 is activated. May be.

According to this embodiment described above, the following effects can be obtained.
(1) Chromatic aberration is extracted from the image data PD, color data D4 corresponding to the color of the incident light L1 is calculated from the chromatic aberration, and an image is displayed according to the difference value D5 between the color data D4 and the color data of the image data PD. The data PD was corrected. Accordingly, the color of the incident light L1 can be determined based on the chromatic aberration inherent in the lens 12 included in the imaging device 1, and the image data PD can be corrected so as to approach the color of the incident light L1.

  (2) A correction value D7 that is closer to the difference value D5 as the accuracy (reliability) of the extracted chromatic aberration is higher is generated, and the image data PD is corrected with the correction value D7. As a result, the difference value D5 is corrected according to the accuracy of chromatic aberration, that is, whether or not chromatic aberration is extracted under conditions that are easy to detect, so that the correction accuracy for the image data PD can be improved. That is, by correcting the image data PD with the correction value D7, the color of the corrected image data PD1 after the correction can be made closer to the color of the incident light L1.

  (3) Chromatic aberration based on the distance between the chromatic aberration extraction position and the center position of the image data PD, the distance between the chromatic aberration extraction position and the focus position (AF position), and the amount of camera shake in the image data PD. The weight value D6 indicating the accuracy of the correction is generated, and the correction value D7 is generated by correcting the difference value D5 with the weight value D6. As a result, the accuracy of chromatic aberration can be determined using a plurality of parameters (two distance information and the amount of camera shake), so that the determination accuracy can be improved.

  (4) The color data calculation circuit 42 corresponds to the characteristic data of the optical system 11 (magnification and aperture of the lens 12) and chromatic aberration, which are imaging conditions, and the color of the incident light L1, based on the refractive index of the lens 12. A calculation table 42A associated with the color data D4 is prepared. As a result, the color data D4 is uniquely determined as long as the chromatic aberration and the photographing condition of the optical system 11 are determined, so that the color data D4 can be easily calculated from the chromatic aberration.

(Other embodiments)
In addition, the said embodiment can also be implemented in the following aspects which changed this suitably.
In the above embodiment, all of the plurality of parameters (the magnification of the lens 12, the aperture, the detection position on the image sensor 14, the chromatic aberration between blue and green, and the chromatic aberration between green and red) that are input parameters when calculating the color data D4. Was a variable. For example, the subject is photographed with the magnification of the lens 12, the aperture, and the detection position on the image sensor 14 being fixed, and the correction value is calculated from the image data PD generated at that time. D7 may be generated. By performing such calibration, the amount of data in the calculation table 42A for calculating the color data D4 from the chromatic aberration can be reduced as shown in FIG. In the calculation table 42A shown in FIG. 7, the magnification of the lens 12, the diaphragm, and the detection position on the image sensor 14 are also shown in order to clarify the difference from the calculation table 42A shown in FIG. Actually, these pieces of information can be omitted from the calculation table 42A. That is, in the calculation table 42A in this case, the chromatic aberration and the color data D4 are associated with each other based on the refractive index of the lens 12. Then, the color data calculation circuit 42 calculates the color data D4 using only the chromatic aberration extracted by the chromatic aberration extraction circuit 41 as an input parameter based on the calculation table 42A shown in FIG. The correction value D7 generated at the time of shooting with the shooting conditions of the optical system 11 fixed in this way can be used for correction of the image data PD obtained by normal shooting thereafter.

  Alternatively, at the time of the calibration, an object having a preset “reference color” may be photographed, and the correction value D7 may be generated from the image data PD generated at that time. According to this, since the color of the incident light L1 incident on the lens 12 is limited, the color data D4 corresponding to the color of the incident light L1 is also limited. For this reason, the data amount of the calculation table 42A for calculating the color data D4 from the chromatic aberration can be further reduced.

  In the weighting circuit 44 of the above embodiment, the weight value D6 is calculated using the amount of camera shake obtained from electronic camera shake correction (camera shake correction by image processing). For example, the weight value D6 may be calculated using an amount of camera shake obtained from optical camera shake correction or image sensor shift type camera shake correction.

In the above embodiment, the camera shake data D1 and the third value A3 may be omitted. In this case, the weight value D6 is generated only from the first value A1 and the second value A2.
In the above embodiment, the second value A2 is generated according to the distance between the chromatic aberration extraction position and the AF position. For example, the second value A2 may be generated according to the distance between the focus position where the user manually focuses the subject and the chromatic aberration extraction position. That is, not only the AF position but the in-focus position, the second value A2 may be generated according to the distance between the in-focus position and the chromatic aberration extraction position.

  In the above embodiment, the weight value D6 may be omitted, that is, the weighting (correction) of the difference value D5 by the weight value D6 may be omitted. In this case, the image data PD is corrected with the difference value D5 calculated by the difference circuit 43.

  In the above embodiment, one chromatic aberration extraction position is selected, color data D4 is calculated based on the chromatic aberration extracted at the selected chromatic aberration extraction position, and a difference value D5 and a weight value D6 based on the color data D4 are calculated. From this, the correction value D7 is generated. Not limited to this, for example, a plurality of chromatic aberration extraction positions are selected, color data D4 is calculated based on the chromatic aberration extracted at each of the selected chromatic aberration extraction positions, and a difference value based on each of the plurality of color data D4 is calculated. D5 is calculated. Then, a plurality of weight values D6 indicating the accuracy of the plurality of extracted chromatic aberrations are calculated, and a plurality of correction values D7 are generated by weighting the difference value D5 with a corresponding weight value D6. May be. In this case, for example, the image data PD may be corrected with an average value of a plurality of correction values D7.

The imaging device 1 of the above embodiment may be embodied in a digital video camera or the like having a still image shooting function.
In the above embodiment, the process for executing the image correction process is divided into blocks and shown in FIG. That is, the image correction process is executed by a chromatic aberration extraction circuit 41, a color data calculation circuit 42, a difference circuit 43, a weighting circuit 44, a multiplication circuit 45, and a correction circuit 46, as shown in FIG. . Note that these units shown in FIG. 1 are shown separately to explain the processing executed in the image correction unit 40, and it is not necessary to have hardware for executing these processings. Any configuration that can be executed according to a program may be used.

DESCRIPTION OF SYMBOLS 1 Imaging device 11 Optical system 12 Lens 13 Aperture 14 Image sensor (imaging element)
30 Image processing unit (image processing circuit)
31 Signal Processing Unit 40 Image Correction Unit 41 Chromatic Aberration Extraction Circuit 42 Color Data Calculation Circuit 42A Calculation Table 43 Difference Circuit 44 Weighting Circuit 45 Multiplication Circuit 46 Correction Circuit 60 Subject PD Image Data D5 Difference Value D6 Weight Value D7 Correction Value L1 Incident Light

Claims (8)

A chromatic aberration extraction circuit that extracts chromatic aberration from image data generated by performing predetermined signal processing on data output from the image sensor;
A color data calculation circuit that calculates color data corresponding to the color of incident light incident on the lens that forms an image on the imaging device, based on the chromatic aberration;
A difference circuit that calculates a difference value between the color data and color data at a position where the chromatic aberration of the image data is extracted;
A correction circuit for correcting the image data according to the difference value;
An image processing circuit. A correction value generating circuit for generating a correction value from the difference value;
The correction value generation circuit generates the correction value that is closer to the difference value as the reliability of the chromatic aberration is higher,
The image processing circuit according to claim 1, wherein the correction circuit corrects the image data based on the correction value.   The correction value generation circuit corrects the difference value according to a distance between an extraction position where the chromatic aberration is extracted and a center position of the image data, and a distance between the extraction position and a focus position. The image processing circuit according to claim 2, wherein the correction value is generated.   The image processing circuit according to claim 3, wherein the correction value generation circuit generates the correction value by correcting the difference value according to a camera shake amount in the image data. The color data calculation circuit includes:
A calculation table in which the chromatic aberration and the color data are associated with each other based on the refractive index of the lens;
The image processing circuit according to claim 1, wherein the color data is calculated from the chromatic aberration based on the calculation table. The color data calculation circuit includes:
Based on the refractive index of the lens, it has a calculation table in which the characteristic data as the photographing condition of the optical system including the lens and the chromatic aberration and the color data are associated
5. The image processing circuit according to claim 1, wherein the color data is calculated from the chromatic aberration and an imaging condition of the optical system based on the calculation table. Chromatic aberration is extracted from image data generated by performing predetermined signal processing on the data output from the image sensor,
Based on the chromatic aberration, calculate color data corresponding to the color of incident light incident on the lens that forms an image on the imaging device;
Calculating a difference value between the color data and the color data at the position where the chromatic aberration of the image data is extracted;
Correcting the image data according to the difference value;
An image processing method. An image sensor;
An optical system including a lens that forms an image of a subject on the image sensor;
A signal processing unit that performs predetermined signal processing on data output from the image sensor to generate image data;
A chromatic aberration extraction circuit for extracting chromatic aberration from the image data;
A color data calculation circuit that calculates color data corresponding to the color of incident light incident on the lens based on the chromatic aberration;
A difference circuit that calculates a difference value between the color data and color data at a position where the chromatic aberration of the image data is extracted;
A correction circuit for correcting the image data according to the difference value;
An imaging device comprising: