JP2015002400A - Shading correction apparatus, focus detection apparatus, imaging apparatus, shading correction method, program, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform appropriate shading correction while suppressing a correction data amount to hold, when performing shading correction on an output signal from an imaging sensor comprising plural photoelectric converters in each pixel.SOLUTION: The shading correction apparatus comprises: input means 800 which receives a first output signal and a second output signal obtained by independently reading signals of the plural photoelectric converters and a third output signal obtained by adding and reading the signals of the plural photoelectric converters; storage means 106 which stores two of a first correction value, a second correction value, and a third correction value for respective shading correction of the first to third output signals; operation means 805 which operates a remaining correction value other than the two correction values among the first to third correction values; and correction means 806 which performs the shading correction on the basis of the first correction value, the second correction value, and the third correction value.

Description

  The present invention relates to a shading correction apparatus.

  Patent Document 1 discloses an imaging device in which a first photodiode and a second photodiode are provided in each pixel (under one microlens). Patent Document 1 includes a first mode in which signals from the first photodiode and the second photodiode are independently output to perform focus detection by a phase difference detection method using an image sensor. It is disclosed. Further, it is disclosed that a second mode for generating a captured image by adding and outputting signals from the first photodiode and the second photodiode is disclosed.

  Japanese Patent Application Laid-Open No. 2004-228561 is an image pickup device including an image pickup pixel and a focus detection pixel provided separately from the image pickup pixel, and performing shading correction on signals from the image pickup pixel and the focus detection pixel. It is disclosed. Patent Document 2 discloses that shading correction is performed on an output signal from an imaging pixel using shading correction data for the imaging pixel stored in a storage unit. Further, it is disclosed that shading correction is performed on the output signal from the focus detection pixel using the shading correction data for A pixel and the shading correction data for B pixel stored in the storage means.

JP 2001-083407 A JP 2009-244858 A

  In order to accurately perform the shading correction, it is necessary to provide correction data of a total of three patterns including a focus detection correction value (for A image and B image) and an imaging correction value.

  In Patent Document 2, the image sensor is provided with a so-called dedicated pixel that does not share an imaging pixel and a focus detection pixel, that is, specialized for each application. Therefore, each pixel has independent characteristics, and it is necessary to individually provide correction data for imaging and focus detection (for A image and B image). Therefore, Patent Document 2 has a problem that the memory capacity for holding correction data increases.

  The present invention can perform appropriate shading correction while suppressing the amount of correction data to be held when performing shading correction on an output signal from an image sensor having a plurality of photoelectric conversion units in each pixel. It is an exemplary object to provide a shading correction apparatus.

  A shading correction apparatus according to one aspect of the present invention is a shading correction apparatus that performs shading correction on an output signal from an image sensor having a plurality of photoelectric conversion units in each pixel, and independently outputs signals from the plurality of photoelectric conversion units. Input means for inputting at least two output signals among the read first output signal and second output signal, and the third output signal read by adding the signals of the plurality of photoelectric conversion units. A first correction value for correcting shading of the first output signal, a second correction value for correcting shading of the second output signal, and a shading correction of the third output signal. Storage means for storing two of the third correction values, and the two of the first correction value, the second correction value, and the third correction value. Computation means for computing a remaining correction value other than a positive value, and correction means for performing shading correction based on the first correction value, the second correction value, and the third correction value It is characterized by that.

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

  According to the present invention, when shading correction is performed on an output signal from an image sensor having a plurality of photoelectric conversion units in each pixel, appropriate shading correction can be performed while suppressing the amount of correction data to be held. it can.

1 is an overall block diagram of an imaging apparatus according to an embodiment of the present invention. It is a schematic block diagram of the image sensor in the Example of this invention. It is a block diagram of the pixel array of the image pick-up element in the Example of this invention. It is a light-receiving state explanatory drawing in the screen center area | region in the image pick-up element in the Example of this invention. It is light reception state explanatory drawing in the screen edge area | region in the image pick-up element in the Example of this invention. It is an example of the image which image | photographed the uniform light in the Example of this invention. It is an example of the shading data in the Example of this invention. 1 is a schematic block diagram of a shading correction apparatus according to a first embodiment of the present invention. It is an example of the outline | summary of correction | amendment data and correction | amendment data generation in 1st Example of this invention. It is a schematic block diagram of the shading correction apparatus in the 2nd Example of this invention.

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

  FIG. 1 is a block diagram illustrating a configuration example of an imaging apparatus according to the present invention. Reference numeral 100 denotes an imaging apparatus (main body). Reference numeral 101 denotes an image sensor such as a CMOS sensor. Reference numeral 102 denotes an A / D converter that performs analog-digital conversion on a signal supplied from the image sensor 101.

  Reference numeral 103 denotes a DSP (Digital Signal Processor) that performs various correction processes and development processes on the data supplied from the A / D converter 102. The DSP 103 also controls various memories such as the ROM 106 and the RAM 107 and writes image data to the recording medium 108.

  A timing generation circuit 104 supplies control signals to the image sensor 101, A / D converter 102, and DSP 103, and is controlled by the CPU 105.

  Reference numeral 105 denotes a CPU as control means for controlling the entire imaging apparatus 100. The CPU 105 controls the DSP 103, the timing generation circuit 104, and the camera function using each unit (not shown). The switches 109 to 111, the mode dial 112, etc. are connected, and processing corresponding to each state is performed. Execute. Further, the CPU 105 also has a function as a focus detection unit of a phase difference detection method for obtaining a phase difference between a pair of image signals based on an output from the DSP 103 using a correlation calculation. As described above, the CPU 105 functions as a part of a focus detection device that performs focus detection of a shooting lens (shooting optical system) (not shown).

  Reference numeral 106 denotes a ROM as a storage unit that stores a control program of the imaging apparatus and various correction data. Reference numeral 107 denotes a RAM that temporarily stores image data and correction data processed by the DSP 103.

  Various correction data (for example, shading correction data) acquired in each step is stored in the ROM 106, and is developed in the RAM 107 at the time of shooting and used for correction.

  Reference numeral 108 denotes a recording medium that stores a photographed image, and is connected to the imaging apparatus 100 via a connector (not shown). Reference numeral 109 denotes a power switch (power SW) for activating the imaging apparatus 100. Reference numeral 110 denotes a first shutter switch (SW1) for instructing start of imaging preparation operations such as AF (autofocus) processing, AE (automatic exposure) processing, flash light control processing, and the like.

  Reference numeral 111 denotes a second shutter switch (SW2) that instructs the start of a series of operations (imaging operations) until a signal read from the image sensor 101 is written to the recording medium 108 via the A / D converter 102 and the DSP 103. . Reference numeral 112 denotes a mode dial for selecting an operation mode of the imaging apparatus 100.

  The imaging apparatus 100 of the present invention is connected to a photographing lens (not shown), and can perform a focus detection operation and the like by exchanging communication with the photographing lens. In the present embodiment, the lens interchangeable imaging device (imaging system, camera system) (having an unillustrated interchangeable lens) has been described with reference to FIG. 1, but the present invention is also applicable to a lens integrated imaging device. It is possible to apply.

FIG. 2 is a diagram showing an outline of the image sensor 101 of the present invention. In FIG. 2, the image sensor 101 includes a pixel array (pixel unit) 1001, a vertical selection circuit 1002 that selects a row in the pixel array 1001, and a horizontal selection circuit 1004 that selects a column in the pixel array 1001. In addition, the pixel array 1001 includes a read circuit 1003 that reads a signal of a pixel selected by the vertical selection circuit 1002 and a serial interface (SI) 1005 for determining an operation mode of each circuit from the outside. The reading circuit 1003 includes a memory for storing signals, a gain amplifier, and the like for each column. The image sensor 101 includes, for example, control circuits such as a vertical selection circuit 1002, a horizontal selection circuit 1004, and a readout circuit 1003 in addition to the illustrated components.

Typically, the vertical selection circuit 1002 sequentially selects a plurality of rows of the pixel array 1001 and reads them out to the reading circuit 1003. The horizontal selection circuit 1004 sequentially selects a plurality of pixel signals read by the reading circuit 1003 for each column. FIG. 3 is a diagram showing a pixel array 1001 of the image sensor 101 of the present invention. The pixel array 1001 is configured by arranging a plurality of two-dimensional arrays in order to provide a two-dimensional image. Reference numerals 301, 302, 303, and 304 denote unit pixels. Each unit pixel has one microlens. The unit pixel has a left (first) photodiode such as 301L, 302L, 303L, and 304L and a right (second) photodiode such as 301R, 302R, 303R, and 304R under one microlens. I have. In other words, the image sensor 101 of the present invention has a plurality of photodiodes (photoelectric conversion units) in each pixel.

  FIG. 3 shows a structure in which two photodiodes are provided in one pixel, such as the left photodiodes 301L, 302L, 303L, 304L..., The right photodiodes 301R, 302R, 303R, 304R. . However, the present invention is not limited to this. For example, the number of photodiodes (PD) included in one pixel may be any number as long as it is two or more, for example, four PDs, nine PDs, and the like.

  FIG. 4 is a diagram showing a state of light reception in the image sensor 101 having the pixel configuration shown in FIG.

  FIG. 4 is a conceptual diagram in which the light beam emitted from the exit pupil of the photographing lens enters the image sensor 101.

  Reference numeral 401 denotes a cross section of the pixel array. Reference numeral 402 denotes a microlens (ML), and reference numeral 403 denotes a color filter (CF). Here, the image sensor 101 of this embodiment employs a pixel configuration called a primary color Bayer array. Specifically, a two-dimensional single-plate CMOS color image sensor in which primary color filters of R (Red), G (Green), and B (Blue) are arranged in a Bayer array is used. Reference numerals 404 and 405 denote a pair of photodiodes arranged corresponding to one microlens 402. The pair of photodiodes 404 and 405 corresponds to, for example, 301L and 301R in FIG. Reference numeral 406 denotes an exit pupil of the photographing lens.

  Here, for the pixel having the microlens 402 (that is, the pixel including the pair of photodiodes 404 and 405), the center of the light beam emitted from the exit pupil is defined as the optical axis 409. Light emitted from the exit pupil enters the image sensor 101 with the optical axis 409 as the center. Reference numerals 407 and 408 denote partial areas of the exit pupil of the photographing lens. The exit pupil partial area 407 and the exit pupil partial area 408 are different from each other. In FIG. 4, the outermost rays of light passing through the partial area 407 of the exit pupil are indicated by 410 and 411, and the outermost rays of light passing through the partial area 408 of the exit pupil are indicated by 412 and 413. ing. As can be seen from this figure, among the light beams emitted from the exit pupil, the upper light beam is incident on the photodiode 405 and the lower light beam is incident on the photodiode 404 with the optical axis 409 as a boundary. That is, each of the photodiode 404 and the photodiode 405 receives light from another region (different region) of the exit pupil of the photographing lens.

  Taking advantage of this characteristic, the phase difference is detected. The phase difference detection method is known, but will be briefly described below. In the area within the pixel, the phase is detected if the data obtained from the multiple left photodiodes is used as the first line and the data obtained from the multiple right photodiodes is used as the second line to obtain correlation data between the lines. it can. Specifically, for example, in the pixel array shown in FIG. 3, the output of the photodiode located on the left side of the row 305 such as the photodiodes 301L, 302L, 303L, and 304L is defined as the first line. Further, for example, in the pixel array shown in FIG. 3, the output of the photodiode located on the right side of the row 305 such as the photodiodes 301R, 302R, 303R, 304R is the second line. In addition, data added in the row direction such as row 305 and row 306 or row 307 may be used as the first line and the second line.

  An image obtained by collecting the first lines is referred to as a first output signal (A image), and an image obtained by collecting the second lines is referred to as a second output signal (B image).

  FIG. 5 is also a conceptual diagram in which the light beam emitted from the exit pupil of the photographing lens similar to that in FIG. 4 enters the image sensor 101, but the pixel of interest is the screen center region of FIG. 3 in FIG. On the other hand, FIG. 5 illustrates the pixels in the screen edge region. The number of each part is the same as in FIG.

  Here, for the pixel having the microlens 502 (that is, the pixel including the pair of photodiodes 504 and 505), the center of the light beam emitted from the exit pupil is defined as the optical axis 509. The light emitted from the exit pupil enters the image sensor 101 with the optical axis 509 as the center. Reference numerals 507 and 508 denote partial areas of the exit pupil of the photographing lens. The exit pupil partial region 507 and the exit pupil partial region 508 are different from each other. In FIG. 5, the outermost rays of light passing through the partial area 507 of the exit pupil are indicated by 510 and 511, and the outermost rays of light passing through the partial area 508 of the exit pupil are indicated by 512 and 513. ing. At this time, the light quantity obtained from the photodiode 504 out of the pair of photodiodes 504 and 505 is smaller than the light quantity obtained from the photodiode 404 in the center area of the screen in FIG. Further, the amount of light obtained from the photodiode 505 is larger than the amount of light obtained from the photodiode 405 in the center area of the screen in FIG.

  This is due to the ray angle. At the screen end opposite to the screen end shown in FIG. 5, the amount of light obtained by the photodiode 504 is greater than the amount of light obtained by the photodiode 404 in the screen center region in FIG. Become more. Further, the amount of light obtained by the photodiode 505 is smaller than the amount of light obtained by the photodiode 405 in the screen center region in FIG.

  For example, although the outputs of the two sets of photodiodes 504 and 505 located at the left and right ends of the screen (arranged symmetrically with respect to the optical axis 509) are different due to the influence of the ray angle, the photodiodes 504 and 505 are different. As a result, the output is almost the same.

  Examples of the output of the photodiode 404 (A image = first output signal) and the output of the photodiode 405 (B image = second output signal) described in FIGS. 4 to 5 are shown in FIGS. In the present invention, the first output signal and the second output signal are obtained by independently reading signals from a plurality of photoelectric conversion units (for example, a pair of photodiodes 404 and 405). Further, examples of outputs (A + B image = third output signal) in which the photodiode 404 and the photodiode 405 are combined, which are different from the first and second output signals, are shown in FIGS. Show. Note that in the present invention, the third output signal is obtained by adding signals from a plurality of photoelectric conversion units (for example, a pair of photodiodes 404 and 405) and reading them out.

  Note that the imaging device 101 of the present invention can share the same pixel for focus detection and imaging by reading out a plurality of photoelectric conversion units independently or by adding them. That is, the first output signal and the second output signal can be used for focus detection, and the third output signal can be used as an image output.

  FIG. 6 is an image obtained by photographing uniform light according to the present invention, and FIG. 7 is a shading obtained by averaging the output of a specific color (for example, a pixel having a green color filter) in the vertical direction. Shown as data.

  When using a general photographic optical system, the A image changes (shading) as shown in Fig. 6 (a): screen left> screen center> screen right, and B image as shown in Fig. 6 (b). Change (shading) of screen left <screen center <screen right. Naturally, in the A + B image that is the image output, an output peak appears in the center of the screen as shown in FIG. 6C, and the output decreases as it goes to the periphery, so that the shading is a so-called peripheral light amount drop.

  The shading as shown in FIG. 6 to FIG. 7 causes the output difference between the A image and the B image, so that the distance measurement performance is deteriorated. It is necessary to accurately perform the corresponding shading correction.

  This shading correction will be described in detail with reference to FIGS.

  FIG. 8 is a diagram mainly showing a part of the DSP 103 described in FIG. 1 as a configuration (shading correction device) for performing shading correction, and FIG. 9 is an image diagram showing generation of correction data.

  In FIG. 8, the DSP 103 is provided with an input unit (input unit) 800 that receives an output signal (image output) from the image sensor 101 via the A / D converter 102. A memory area 801 is provided for temporarily storing a signal input from the input means. The memory area 801 is divided into areas 802, 803, and 804 for storing a plurality of image outputs. Reference numeral 802 denotes a first area in which the output of only the A image of the image sensor 101 (image output obtained only from the left photodiode) is stored. Reference numeral 803 denotes a second area for storing the output of only the B image (image output obtained only by the right photodiode). Reference numeral 804 denotes a third area for storing an output of an A + B image (an image output obtained by combining left and right photodiode outputs) obtained by adding the A image and the B image.

  Reference numeral 805 denotes second correction data (second correction value) based on first correction data (first correction value) and third correction data (third correction value) sent from the RAM 107 described later. ). Here, the first correction value is a correction value for correcting the shading of the first output signal, and the second correction value is a correction value for correcting the shading of the second output signal. The third correction value is a correction value for correcting the shading of the third output signal. Reference numeral 806 denotes a correction unit that performs shading correction on the A image, the B image, and the A + B image using the first to third correction data, respectively.

  In addition, the ROM 106 and the RAM 107 are each provided with two correction data areas as areas for handling shading correction data. For example, A-image correction data (first correction value) is stored in the first correction data area 1061 of the ROM 106, and A + B image correction data (third) is stored in the second correction data area 1062 of the ROM 106. Correction value) is stored. The correction data for the A image and the correction data for the A + B image are transferred to the third correction data area 1071 and the fourth correction data area 1072 of the RAM 107 when the imaging apparatus 100 is activated, and are used for correction. The Here, as shown in FIG. 8, the correction data for the A image stored in the first correction data area 1061 of the ROM 106 is transferred to the third correction data area 1071 of the RAM 107. Further, the correction data for A + B image stored in the second correction data area 1062 of the ROM 106 is transferred to the fourth correction data area 1072 of the RAM 107.

  The ROM 106 and the RAM 107 are provided corresponding to an area 1063 for holding an output value of a standardization point of each image (an output value at the center position (fourth correction value) and the like), which will be described later, and the area 1063. A region 1073 is also provided. Similarly, this data is transferred from the area 1063 of the ROM 106 to the area 1073 of the RAM 107 when the image pickup apparatus 100 is activated, and is used for correction.

  After the shading correction by the correction means 806, the corrected images (A image, B image, A + B image) are temporarily stored in the areas 808 to 810 in the memory area 807 for temporary storage. Here, the output of the corrected A image is temporarily stored in the area 808, the output of the corrected B image is temporarily stored in the area 809, and the output of the corrected A + B image is temporarily stored in the area 810. Thereafter, the output is shifted to a block that performs correction at another correction stage. Detailed description of the subsequent correction is omitted.

  In the present embodiment, the memory areas 801 and 807 are individually described for convenience of explanation, but actually, they can be shared by using them in time series.

  Next, an example of correction data and an example of correction data generation will be described with reference to FIG.

  FIGS. 9A to 9C are diagrams illustrating horizontal shading of each image output before correction (that is, output of A image, B image, and A + B image).

  FIGS. 9D to 9F show correction data (plotting correction coefficients for each column) for each image (that is, each of A image, B image, and A + B image).

  FIGS. 9 (g) to 9 (i) are diagrams showing horizontal shading of each image output after correction (that is, output of corrected A image, corrected B image, corrected A + B image). It is.

  The center position outputs Lca, Lcab, and Lcb of each of the A, A + B, and B images shown in FIGS. 9A to 9C are areas of the ROM 106 as calculation data (standardization points). 1063. This data is transferred from the area 1063 to the area 1073 of the RAM 107 and used when the imaging apparatus 100 is activated.

  Also, the coefficients Ka and Kab (for each column) to be multiplied are obtained in advance so as to be the screen center level of the horizontal shading of the A image and the A + B image described in FIGS. 9D to 9E. Are stored in areas 1061 to 1062 of the ROM 106. This data is transferred from the areas 1061 to 1062 to the areas 1071 to 1072 of the RAM 107 and used when the imaging apparatus 100 is activated.

  In the present embodiment, the coefficient Kb (for each column) (second correction data) to be multiplied is stored in the ROM 106 so as to be at the screen center level of the horizontal shading of the B image shown in FIG. Absent. More specifically, the imaging apparatus 100 of the present invention does not have the second correction data (B image correction data). Therefore, in this embodiment, the second correction data (B image correction data) Kb shown in FIG. 9F is the first correction data: Ka, the third correction data: Kab, and the center position output. It is generated from the Lca, Lcab, and Lcb by the calculation means 805. In other words, in this embodiment, the remaining correction values other than the two correction values stored in the ROM 106 among the first correction value, the second correction value, and the third correction value are calculated. Generate by.

  Specifically, the second correction data: Kb is calculated as follows for each column of data from the above data.

Kb (n) = (Kab (n) −Lca) / {(Lcab / Kab (n)) − (Lca / Ka (n))}
Kb (n): Correction coefficient for a predetermined row of the B image
Ka (n): Correction coefficient for a predetermined row of the A image
Kab (n): Correction coefficient for a predetermined row of A + B image
Lca: Center position output of A image (normalization point)
Lcab: A + B center position output (standardized point)
The correction data for the A image, A + B image, and B image described here, and the output are data for each type of color separation as an image sensor (eg, for each Bayer separation of a green filter, a red filter, and a blue filter). By holding it, it is possible to perform highly accurate correction.

  Of course, it may be implemented as a luminance correction common to all colors. In that case, the calculation is performed after performing a predetermined calculation for obtaining the luminance value Y based on the data of each color.

  9 (g) to 9 (i) show the results of correcting the image output of FIGS. 9 (a) to 9 (c) with the correction data of FIGS. 9 (d) to 9 (f). Image output shading. FIGS. 9 (g) to 9 (i) show that the output is normalized to the normalized point (center output value) in FIGS. 9 (a) to 9 (c).

  As described above, in the first embodiment of the present invention, two types of correction data (A image and A + B image in this embodiment) are used for three types of images, A image, B image, and A + B image. The third type of correction data is obtained by calculation. By doing so, it is possible to obtain a desired performance by preventing an increase in distance measurement performance and deterioration of peripheral image quality due to shading by performing appropriate shading correction while suppressing an increase in necessary memory.

  In this embodiment, the capacity is controlled by both the ROM 106 and the RAM 107. For example, two types of data are stored in the ROM 106 as initial data, and the RAM 107 has three types of data areas. It may be. In that case, the correction data is stored in the RAM 107 after the above calculation is performed when the imaging apparatus 100 is activated. The shading correction apparatus configured as described above is also in accordance with the memory capacity reduction (reduction in the capacity of the ROM 106), which is an object of the present invention.

  In this embodiment, it is described that the image sensor 101 generates an output of an A image, a B image, and an A + B image and inputs and stores the output in the DSP 103. However, the present invention is limited to the operation. It is not a thing. Since the output of the image sensor with this configuration is A image + B image≈ (A + B image), it is also possible to obtain the third output from the desired two outputs among the A image, B image, and A + B image by calculation. It is.

  Specifically, the output of the A image and the B image is obtained, the addition operation of the A image and the B image is performed to obtain an A + B image, or the A image (or B image) and the A + B image are obtained, and the A + B image is obtained. There is no problem even if a method of obtaining the output of the B image (or A image) by calculating the difference between the A image (or B image) is obtained.

  In the second embodiment of the present invention, three types of corrected images are obtained by using two types of correction data by changing the order of arithmetic processing.

  FIG. 10 is a diagram showing a part of the details of the DSP 103 in the second embodiment of the present invention as a configuration for performing shading correction (shading correction apparatus), and the outline is the same as that described in FIG. Here, only the description of the different parts will be described.

  In FIG. 10, only the first area 802 and the third area 804 are provided in the memory area 801 for temporary storage, and the second area 803 is not provided. That is, in this embodiment, only the A image output and the A + B image output are stored, and the B image output is not stored. More specifically, in this embodiment, the B image is not accurately acquired as the imaging operation.

  The correction unit 806 corrects the A image and the A + B image using the first and third correction data stored in the areas 1071 to 1072 of the RAM 107. Thereafter, the corrected A image output and A + B image output are transferred to the areas 808 and 810 in the memory area 807 and sent to the computing means 1000.

  The arithmetic unit 1000 obtains an output equivalent to the corrected B image output by performing a difference process between the corrected A + B image output and the corrected A image output. The result of the calculation means is transferred as a B image correction output to the area 809 (corrected B image storage area) in the memory area 807. As for the subsequent correction, the detailed description is omitted as in the first embodiment.

  Note that the memory areas 801 and 807 are individually shown for convenience of explanation, but actually, they can be shared by using them in time series.

  In this embodiment, the image sensor 101 performs an operation after correcting the output of the A image and the A + B image to generate a B image after the shading correction. However, the present invention is limited to the operation. It is not something. Since the output of the image sensor with this configuration is A image + B image≈ (A + B image), it is also possible to obtain the third output from the desired two outputs by calculation.

  Specifically, there is no problem even if a method of adding the outputs of the A image and the B image after shading correction to obtain a corresponding A + B image after the shading correction is used. In addition, there is no problem even if a method of subtracting the B image from the A + B image after shading correction to obtain the corresponding A image output after the shading correction is used for the output of the B image and the A + B image.

  As described above, by correcting the first and second images and then subtracting or adding them to obtain the third image output, it is possible to obtain a third image equivalent to the corrected one. Therefore, an appropriate image can be obtained without increasing the memory area.

  In the first embodiment and the second embodiment of the present invention, only the example in which two photodiodes (photoelectric conversion elements) are arranged under one microlens has been described. It is not limited. For example, the present invention can be applied to the case where four photodiodes are provided under one microlens. In this case, the output of each of the four photodiodes may be used, or the four photodiodes may be divided into two parts, for example, left and right parts, and the two parts may be added and used. Good. Even when such a configuration is adopted, shading correction data is provided in a division suitable for the photodiode to be used, and by calculating shading correction data that is not held by calculation, it is possible to prevent the memory area from increasing. can do. Further, as in the second embodiment, not all of the necessary images may be acquired, and a part of the images may be handled by calculating the corrected image.

In the first embodiment and the second embodiment of the present invention, an example in which signals of all photodiodes are used as signals used in an image is described, but the present invention is not limited to this. For example, the present invention can be applied to a case where five photodiodes are disposed in one pixel and only four photodiodes are used for an image. In this case, it is assumed that a photodiode with a different configuration (including those with different addition states) from the data for information collection (for focus detection) is used for images, and appropriate correction is made by using different correction data. You can
(Other embodiments)
The object of the present invention can also be achieved as follows. That is, a storage medium in which a program code of software describing a procedure for realizing the functions of the above-described embodiments is recorded is supplied to an apparatus (for example, an imaging apparatus). The computer (or CPU, MPU, etc.) of the device reads out and executes the program code stored in the storage medium.

  In this case, the program code itself read from the storage medium realizes the novel function of the present invention, and the storage medium and program storing the program code constitute the present invention.

  Examples of the storage medium for supplying the program code include a flexible disk, a hard disk, an optical disk, and a magneto-optical disk. Further, a CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD-R, magnetic tape, nonvolatile memory card, ROM, or the like can also be used.

  Moreover, the function of the above-described embodiment is realized by making the program code read by the computer executable. Further, based on the instruction of the program code, an OS (operating system) or the like running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments may be realized by the processing. included.

  Furthermore, the following cases are also included. First, the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing.

  The present invention can be suitably used for camera systems such as compact digital cameras, single-lens reflex cameras, and video cameras.

301L, 301R, 404, 405, 504, 505: Photodiode 103: DSP
106: ROM
107: RAM
1061, 1071: First correction data 1062, 1072: Third correction data 805, 1000: Calculation means 806: Correction means

Claims (15)

A shading correction device that performs shading correction on an output signal from an image sensor having a plurality of photoelectric conversion units in each pixel,
At least one of a first output signal and a second output signal obtained by independently reading the signals of the plurality of photoelectric conversion units, and a third output signal read by adding the signals of the plurality of photoelectric conversion units. Input means for receiving two output signals;
A first correction value for shading correction of the first output signal, a second correction value for shading correction of the second output signal, and a first correction value for shading correction of the third output signal. Storage means for storing two of the three correction values,
An arithmetic means for calculating a remaining correction value other than the two correction values among the first correction value, the second correction value, and the third correction value;
Correction means for performing shading correction based on the first correction value, the second correction value, and the third correction value;
A shading correction apparatus comprising:   The storage means stores a fourth correction value that normalizes the output value at the center position of each of the first output signal, the second output signal, and the third output signal. The shading correction apparatus according to claim 1, wherein   The shading correction apparatus according to claim 2, wherein the calculation unit calculates the remaining correction value using the two correction values and the fourth correction value. The two correction values are the first correction value and the third correction value,
The shading correction apparatus according to claim 3, wherein the calculation unit calculates the second correction value which is the remaining correction value as follows.
Kb (n) = (Kab (n) −Lca) / {(Lcab / Kab (n)) − (Lca / Ka (n))}
Here, Kb (n) is the correction coefficient of the predetermined column of the second correction value, Ka (n) is the correction coefficient of the predetermined column of the first correction value, and Kab (n) is the third correction value. , Lca is an output value at the center position of the first correction value, and Lcab is an output value at the center position of the third correction value. A shading correction device that performs shading correction on an output signal from an image sensor having a plurality of photoelectric conversion units in each pixel,
At least one of a first output signal and a second output signal obtained by independently reading the signals of the plurality of photoelectric conversion units, and a third output signal read by adding the signals of the plurality of photoelectric conversion units. Input means for receiving two output signals;
A first correction value for shading correction of the first output signal, a second correction value for shading correction of the second output signal, and a first correction value for shading correction of the third output signal. Storage means for storing two of the three correction values,
Correction means for performing shading correction of two output signals among the first output signal, the second output signal, and the third output signal based on the two correction values;
Based on the two output signals corrected by the correction means, calculation means for calculating the corrected remaining output signal;
A shading correction apparatus comprising:   6. The shading correction apparatus according to claim 5, wherein the calculation means calculates the corrected remaining output signal by adding or subtracting the two corrected output signals.   7. The correction value stored in the storage unit holds a correction value for each type of color filter provided in the image sensor. The shading correction apparatus as described.   The shading correction apparatus according to claim 1, wherein the imaging element includes one microlens and the plurality of photoelectric conversion units in each pixel.   The said 1st output signal and said 2nd output signal are used for focus detection, and said 3rd output signal is used as an image output, The any one of Claims 1-8 characterized by the above-mentioned. Shading correction device. A shading correction apparatus according to any one of claims 1 to 9,
Focus detection means for performing focus detection based on the first output signal and the second output signal corrected by the shading correction device;
A focus detection apparatus comprising: An image sensor having a plurality of photoelectric conversion units in each pixel;
A shading correction apparatus according to any one of claims 1 to 9,
An imaging apparatus comprising: A shading correction method for shading correction of an output signal from an image sensor having a plurality of photoelectric conversion units in each pixel,
At least one of a first output signal and a second output signal obtained by independently reading the signals of the plurality of photoelectric conversion units, and a third output signal read by adding the signals of the plurality of photoelectric conversion units. An input step in which two output signals are input;
A first correction value for shading correction of the first output signal, a second correction value for shading correction of the second output signal, and a first correction value for shading correction of the third output signal. A storage step of storing two of the three correction values,
A calculation step of calculating a remaining correction value other than the two correction values among the first correction value, the second correction value, and the third correction value;
A correction step of performing shading correction based on the first correction value, the second correction value, and the third correction value;
A shading correction method comprising: A shading correction method for shading correction of an output signal from an image sensor having a plurality of photoelectric conversion units in each pixel,
At least one of a first output signal and a second output signal obtained by independently reading the signals of the plurality of photoelectric conversion units, and a third output signal read by adding the signals of the plurality of photoelectric conversion units. An input step in which two output signals are input;
A first correction value for shading correction of the first output signal, a second correction value for shading correction of the second output signal, and a first correction value for shading correction of the third output signal. A storage step of storing two of the three correction values,
A correction step for performing shading correction of two output signals of the first output signal, the second output signal, and the third output signal based on the two correction values;
A calculation step of calculating the corrected output signal based on the two output signals corrected by the correction step;
A shading correction method comprising:   A computer-executable program in which a procedure of the shading correction method according to claim 12 is described. A computer-readable storage medium storing a program for causing a computer to execute the steps of the shading correction method according to claim 12 or 13.