JP2002185971A - Irregular color correcting device and electronic camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an irregular color correcting device and an electronic camera capable of perfectly removing irregular colors caused by optical aberration or the temperature distribution of an imaging device without making the device complicated and expensive. SOLUTION: A gain table 28 stores a gain for correcting the irregular colors of an imaging signal occurring corresponding to the optical characteristic of a lens system 10 as a function or the several pixels of the imaging device 14 as a unit. An offset table 22 stores an offset for correcting the irregular colors of the imaging signal occurring corresponding to the electrical characteristic of the device 14 as a function or the several pixels of the imaging device 14 as a unit. A gain calculation part 30 reads a gain from the gain table 28 to calculate a required correcting quantity and an offset calculation part 24 reads offset from the table 24 to calculate the required correcting quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for correcting color unevenness and an electronic camera, and more particularly, to a method for generating an optical image via an optical system by photoelectric conversion by an image sensor according to the characteristics of the optical system or the image sensor. The present invention relates to a color unevenness correction device for correcting color unevenness and an electronic camera.

[0002]

2. Description of the Related Art As a conventional apparatus for recording an image signal, for example, a video camera is cited.
Generally, an analog image signal output from an image sensor such as a CD (Charge Coupled Device) is magnetically recorded on a video tape. In a conventional apparatus for recording an analog image signal, when color unevenness (shading) occurs in an analog image signal output from an image sensor, the color unevenness is normally corrected by the following two methods.

In a first correction method, an R (red) signal and a G (green) signal included in an image signal are adjusted for the purpose of adjusting white balance.
This is a method of multiplying each of the (green) signal and the B (blue) signal by a constant gain. This method uses the R, G, B of the image sensor.
When there is a difference between the sensitivity characteristics for R, G, and B, the sensitivity is used to adjust the sensitivity of the image sensor for R, G, and B.
If there is a difference between the sensitivity characteristics of the image sensor for R, G, and B, for example, when a white optical image is captured, a greenish-white image signal is obtained. In this method, color unevenness is corrected by using, as a unit, an element group for imaging an R signal, an element group for imaging a G signal, and an element group for imaging a B signal provided in the imaging element.

The second correction method is for correcting an offset due to a dark current generated in an image sensor, and a dark current that does not occur or is negligible for each of R, G, and B signals. The dark current generated outside the effective area where the current is generated is measured, and this value is subtracted from the pixel signal output from each pixel to correct the offset. Also in this correction method, color unevenness is corrected for each element group that captures an R signal, a G signal, and a B signal.

[0005]

By the way, in the conventional apparatus, the sensitivity unevenness of the image pickup device can be corrected by the above-described white balance adjustment or the like. However, spherical aberration, astigmatism, chromatic aberration,
If other aberrations occur, the intensity of the optical image formed on the imaging surface of the imaging device via the optical system changes according to the position of the imaging surface. Further, the offset due to the dark current generated in the image sensor changes according to the temperature distribution of the image sensor, and the dark current changes according to the position of the image surface because the temperature distribution is not constant on the image sensing surface of the image sensor. There is a problem that such color unevenness caused by the aberration of the optical system and the temperature distribution of the image sensor cannot be completely corrected by the above-described method.

In recent years, the processing capability of semiconductor integrated circuits has been improved, and electronic cameras, scanners, digital video cameras, and the like, which obtain digital images by capturing an optical image via an optical system using an image sensor such as a CCD. Is frequently used. Even in an apparatus for obtaining such a digitized image signal, color unevenness occurs due to aberration of an optical system and temperature distribution of an image sensor. 2. Description of the Related Art In an electronic camera, there is a technique for correcting shading based on an inclination of mounting of an image sensor or a lack of peripheral light amount of an optical system.

According to this technique, a horizontal direction (H direction) and a vertical direction (V direction) of a pixel group provided in an image sensor are divided into blocks each including a predetermined number of pixels, and each block at a central position in the vertical direction is formed. The shading correction coefficient is calculated in advance and stored only for. Then, at the time of imaging, the shading correction coefficient is read from the storage device, and shading correction is performed with a simple configuration by shading the captured image signal.

By the way, when the electronic camera was commercialized, the number of pixels was, for example, about 600 pixels in the horizontal direction and about 480 pixels in the vertical direction. However, in recent years, high definition has been required. An electronic camera having about 1024 pixels in the vertical direction is being realized. Since electronic cameras with a total number of pixels exceeding 1 million pixels are positioned as professional or high-end equipment, it is necessary to almost completely eliminate color unevenness caused by aberrations in the optical system and temperature distribution of the image sensor. Is required.

[0009] Eliminating the color unevenness caused by the aberration of the optical system and the temperature distribution of the image pickup element cannot be achieved almost completely by this technique. Therefore, correction coefficients (gain and offset) for correcting the aberration of the optical system and the temperature distribution of the image sensor are stored in advance for each pixel,
It is considered that by reading out the correction coefficient stored at the time of imaging and correcting the imaging signal, it is possible to almost completely eliminate color unevenness caused by aberration of the optical system and temperature distribution of the imaging device.

[0010] However, storing a correction coefficient consisting of a gain and an offset for each pixel for an image sensor having a number of pixels exceeding 1 million pixels requires an enormous storage capacity, complicating the apparatus and increasing the cost. There is a problem that leads to the conversion. Although the problem in correcting color unevenness has been described above by taking an electronic camera as an example, such a problem is caused by a device such as a scanner or a digital video camera that captures an optical image via an optical system with an image sensor. The same applies to.

The present invention has been made in view of the above circumstances, and almost completely eliminates color unevenness caused by aberrations of an optical system and a temperature distribution of an image pickup element without inviting a complicated apparatus and a high price. It is an object of the present invention to provide a color nonuniformity correction device and an electronic camera that can be removed at a time.

[0012]

In the following, in the examples shown in this section, for ease of understanding, specific items of the present invention will be described with reference numerals shown in the drawings of the embodiments. ,
The configuration of the present invention or the specific matters of the present invention are not limited to those restricted by these reference numerals. In order to solve the above problem, a color unevenness correction apparatus according to a first aspect of the present invention includes: an image sensor (14) that photoelectrically converts an optical image via an optical system (10) to output an image signal; Optical system (1
0) a first correction function storage unit (28) for storing a first correction function for correcting color unevenness of the imaging signal generated according to the optical characteristic, and a first correction function storage unit (28). A first correction unit (30, 32) for correcting color unevenness of the imaging signal based on a first correction function. According to the present invention, the first correction function for correcting the color unevenness of the imaging signal generated according to the optical characteristics of the optical system is stored in advance in the first correction function storage means,
Since the correction means reads out the first correction function from the first correction function storage means at the time of imaging and corrects the color unevenness of the image signal, it is possible to remove the color unevenness caused by the aberration of the optical system. Further, since the function for correcting the color unevenness is stored, the cost of the apparatus does not increase. The color non-uniformity correcting apparatus according to a second aspect of the present invention is the color non-uniformity correcting apparatus according to the first aspect, wherein the color non-uniformity correcting apparatus according to the first aspect corrects color non-uniformity of the image pickup signal generated according to electrical characteristics of the image sensor (10). A second correction function storage means (22) for storing the second correction function; and a second correction function storage means (2) for storing the second correction function.
A second correction unit (24, 26) for correcting color unevenness of the imaging signal based on the second correction function stored in 2). According to the present invention, the second correction function for correcting the color unevenness of the imaging signal generated according to the electrical characteristics of the imaging device is stored in advance in the second correction function storage unit, and the second correction unit stores the second correction function during the imaging. Since the second correction function is read from the correction function storage means to correct the color unevenness of the imaging signal, it is possible to remove the color unevenness caused by the electric characteristics of the image sensor. Here, since the color unevenness caused by the temperature distribution of the image sensor can be removed in addition to the color unevenness caused by the aberration of the optical system described above, the color unevenness of the image signal is almost completely removed. be able to. Further, since the function for correcting the color unevenness is stored, the cost of the apparatus does not increase. Further, the color non-uniformity correction apparatus according to the third aspect of the present invention includes the first
In the color unevenness correction apparatus according to the second aspect or the second aspect,
The first correction function is a position in a first direction (X-axis direction) set in an imaging plane of the image sensor (14) and a second direction orthogonal to the first direction (X-axis direction). A function defining a gain corresponding to a position in the (Y-axis direction), wherein the first correction means (30, 32) multiplies the imaging signal by a gain defined by the first correction function. And Further, in the color shading correction apparatus according to a fourth aspect of the present invention, in the color shading correcting apparatus according to the third aspect, the second correction function includes: a position in the first direction (X-axis direction); Is a function that defines an offset corresponding to the position in the direction (Y-axis direction) of the second correction unit (24,
26) is characterized in that an offset defined by the second correction function is added to the imaging signal. Also,
The color shading correction apparatus according to a fifth aspect of the present invention is the color shading correcting apparatus according to the third or fourth aspect, wherein the first correction function storage means (28) stores the first correction function in the first correction function. The discrete value is stored as a discrete value that varies in accordance with the position in the first direction (X-axis direction) and the position in the second direction (Y-axis direction). It is characterized by including a gain calculating means (30) for calculating an approximate value of the specified gain. According to the present invention, the first correction function is stored in advance as a discrete value whose discrete value changes, and an approximate value of the gain defined by the first correction function is obtained by interpolating the discrete value stored at the time of imaging. Since the color unevenness is corrected by using this method, it is possible to almost completely eliminate the color unevenness caused by the aberration of the optical system and the temperature distribution of the image sensor without causing the apparatus to be complicated and expensive. Further, the color unevenness correction apparatus according to a sixth aspect of the present invention is the color unevenness correction apparatus according to the fifth aspect, wherein the second correction function storage means (22) stores the second correction function in the first direction. The discrete value is stored as a discrete value that varies according to the position in the (X-axis direction) and the position in the second direction (Y-axis direction), and the discrete value is interpolated and defined by the second correction function. An offset calculating means (24) for calculating an approximate value of the offset is provided. According to this invention, the approximate value of the offset defined by the second correction function is obtained by previously storing the second correction function as a discrete value whose discrete value changes, and interpolating the discrete value stored during imaging. Since the color unevenness is corrected by using this method, it is possible to almost completely eliminate the color unevenness caused by the aberration of the optical system and the temperature distribution of the image sensor without causing the apparatus to be complicated and expensive. The color non-uniformity correcting apparatus according to a seventh aspect of the present invention is the color non-uniformity correcting apparatus according to the fifth or sixth aspect, wherein the discrete value of the discrete value is the first degree.
The direction (X-axis direction) and the second direction (Y-axis direction) are set in accordance with the amount of change in the color unevenness of the imaging signal. According to the present invention, the above-described discrete values are set in accordance with the amount of change in the color unevenness of the imaging signal. For example, the discreteness is reduced for a portion where the amount of change in the color unevenness is large, and for a portion where the amount of change is small. By increasing the degree of discreteness, an approximate value of the first correction function or the second correction function can be obtained more accurately, so that color unevenness is almost completely eliminated without incurring complexity and high cost of the apparatus. Preferred above. According to an eighth aspect of the present invention, there is provided the color non-uniformity correcting apparatus according to any one of the first to seventh aspects, wherein an image signal output from the image sensor (14) is output for a predetermined time. It is characterized by comprising an integrating means (20) for integrating. According to the present invention, even when the light intensity of the optical image formed on the imaging device via the optical system is low, the integration means integrates the imaging signal output from the imaging device for a predetermined time, thereby obtaining the imaging signal. Has increased the strength. When the imaging signals are integrated, color irregularities caused by the aberration of the optical system and the temperature distribution of the image sensor are also integrated. Is corrected using the first correction function, and the color unevenness caused by the temperature distribution of the image sensor is corrected using the second correction function. Color unevenness can be corrected. Further, according to a color unevenness correction apparatus according to a ninth aspect of the present invention, in the color unevenness correction apparatus according to the third aspect or the fourth aspect, the imaging signal is orthogonal to an imaging surface of the imaging element (14). Imaging signals obtained by imaging at a plurality of different positions in a third direction (Z-axis direction), wherein the first correction function is based on the first direction (X-axis direction) and the second direction (X-axis direction). It is a function that defines a gain according to the position in the Y-axis direction) and the position in the third direction (Z-axis direction). Further, the color non-uniformity correcting apparatus according to a tenth aspect of the present invention is the color non-uniformity correcting apparatus according to the ninth aspect, wherein the second correction function includes the first direction (X-axis direction) and the second direction ( It is a function that defines an offset according to the position in the third direction (Y-axis direction) and the third direction (Z-axis direction). According to the inventions according to the ninth and tenth aspects, even when a three-dimensional optical image consisting of the first direction, the second direction, and the third direction is captured, each direction is taken. Can correct the color unevenness caused by the aberration of the optical system and the temperature distribution of the image sensor. The color non-uniformity correction apparatus according to the eleventh aspect of the present invention is the color non-uniformity correction apparatus according to the ninth or tenth aspect, wherein the first correction function storage means (2
8) changing the first correction function according to the position in the first direction (X-axis direction), the position in the second direction (Y-axis direction), and the position in the third direction (Z-axis direction). The discrete value is stored as a discrete value having a variable discrete degree, and interpolation processing is performed using discrete values of six or more adjacent points stored in the first correction function storage means (28), and defined by the first correction function. And a gain calculating means (30) for calculating an approximate value of the gain to be obtained. Further, the color unevenness correction apparatus according to a twelfth aspect of the present invention is the color unevenness correction apparatus according to the eleventh aspect, wherein the second correction function storage means stores the second correction function in the first direction (X-axis direction). Direction), the position in the second direction (Y-axis direction) and the position in the third direction (Z-axis direction) are stored as discrete values that vary with the degree of discreteness, and the second correction function is stored. And an offset calculating means (24) for performing an interpolation process using discrete values of six or more adjacent points stored in the means and calculating an approximate value of the offset defined by the second correction function. And According to the inventions according to the eleventh and twelfth aspects, when capturing a three-dimensional optical image, it is necessary to handle more pixels, and the process of correcting color unevenness increases. The first correction function or the second correction function is stored in advance as a discrete value whose discrete value changes, and an approximate value of the gain defined by the first correction function or the second correction is obtained by interpolating the discrete value stored during imaging. Since the color unevenness is corrected by obtaining an approximate value of the offset defined by the function, the color unevenness caused by the aberration of the optical system and the temperature distribution of the image sensor without complicating the apparatus and increasing the price. Can be almost completely removed. Further, an electronic camera according to the present invention includes the color non-uniformity correction device according to any of the first to twelfth aspects, and storage means for storing an image signal corrected by the color non-uniformity correction device. And According to the present invention, there is provided a color non-uniformity correction apparatus capable of almost completely removing color non-uniformity caused by aberrations of an optical system and temperature distribution of an image sensor without inviting an increase in complexity and cost of the apparatus. With this arrangement, a high-definition electronic camera capable of correcting color unevenness caused by aberration of the optical system and temperature distribution of the image sensor can be provided at low cost.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a color unevenness correcting apparatus and an electronic camera according to an embodiment of the present invention. FIG. 1 is a functional block diagram illustrating a configuration of a color non-uniformity correction device according to an embodiment of the present invention provided in an electronic camera according to an embodiment of the present invention. In FIG.
Reference numeral 10 denotes a lens system as an optical system, and reference numeral 12 denotes a CCD (Charge Coupled Device) for optical images transmitted through the lens system 10.
The stop is used to adjust the amount of light reaching the imaging surface of the imaging device 14 such as e).

The lens system 10 is configured such that its optical magnification is variable by a control system (not shown) or manually by a user, and the aperture 12 is configured such that the amount of transmitted light is variable by the control system or the user's manual. The image sensor 14 has about 1 million pixels arranged on the imaging surface in an X-axis direction (H direction) as a first direction and a Y-axis direction (V direction) as a second direction. Each pixel photoelectrically converts the formed optical image and outputs the image as an imaging signal. In the present embodiment, it is assumed that an A / D converter is provided in the image sensor 14 for convenience of description, and a digital image signal is output from the image sensor 14.

Reference numeral 16 denotes a frame memory for temporarily storing an image signal output from the image sensor 14. 18
Reference numeral denotes a CCD data input unit for reading out an image signal stored in the frame memory 16 at a predetermined timing in accordance with a synchronization signal such as a vertical synchronization signal and a horizontal synchronization signal. In addition, CC
From the D data input unit 18 to the offset calculation unit 24 described later
The timing signal is output to the gain calculator 30.

Reference numeral 20 denotes a CCD data accumulating section as an accumulating means, which accumulates an image pickup signal output from the CCD data input section 18 for each frame (screen) for a predetermined time. The above-mentioned timing signal output from the CCD data input unit 18 is based on the fact that the image pickup signal output from the CCD data input unit 18 to the CCD data integrator 20 is output from a pixel located at any position on the image pickup surface of the image pickup device 14. This is a signal indicating whether the signal is a captured image signal.

Reference numeral 22 denotes an offset table serving as a second correction function storage unit, which stores a second correction function for correcting color unevenness of an image pickup signal generated according to electric characteristics of the image pickup device 14. As the second correction function, the electrical characteristics of the image sensor 14 (dark current generated according to the temperature distribution of the image sensor 14) are determined in advance, and the second correction function is determined as a function for correcting the color unevenness caused by the electrical characteristics. The second correction function is a linear function, a quadratic function, or another function in the form of an offset table 22.
Is stored.

Reference numeral 24 denotes an offset calculation unit which forms a part of the second correction means, and calculates an offset for correcting color unevenness based on the second correction function stored in the offset table 22. Reference numeral 26 denotes an offset addition unit which forms a part of the second correction unit, and adds the offset calculated by the offset calculation unit 24 to the imaging signal integrated by the CCD data integration unit 20 to obtain an electrical characteristic of the imaging device 14. The color unevenness of the imaging signal generated accordingly is corrected.

Reference numeral 28 denotes a gain table as first correction function storage means, which stores a first correction function for correcting color unevenness of an image pickup signal generated according to the optical characteristics of the optical system 10. Similarly to the second correction function, the first correction function determines the optical characteristics of the lens system 10 (aberration of the lens system 10) in advance, and determines the first correction function as a function for correcting color unevenness caused by the optical characteristics. The first correction function is stored in the gain table 28 in the form of a linear function, a quadratic function, or another function.

Reference numeral 30 denotes a gain calculator which forms part of the first correction means, and calculates a gain for correcting color unevenness based on the first correction function stored in the gain table 28. Reference numeral 32 denotes a gain multiplication unit that forms part of the first correction unit, and multiplies the gain calculated by the gain calculation unit 30 with the imaging signal output from the offset addition unit 26 according to the optical characteristics of the optical system 10. This corrects the color unevenness of the imaging signal that occurs. Reference numeral 34 denotes a CCD data output unit that outputs an imaging signal output from the gain multiplying unit 32 and in which color unevenness has been corrected. The imaging signal output from the CCD data output unit 34 is stored in a memory as a storage unit included in the electronic camera according to the present embodiment.

Next, a detailed description will be given of the operation of the color non-uniformity correcting apparatus according to the embodiment of the present invention having the above-described configuration when correcting color non-uniformity. Now, XY set in the imaging plane
It is assumed that white light having a constant light intensity in a plane forms an image on the imaging surface of the imaging element 14 via the lens system 10 and the aperture 12. FIG. 2 is a diagram for explaining color unevenness caused by aberrations of the lens system 10. In FIG. 2A, P indicates an imaging surface of the imaging element 14. When aberration occurs in the lens system 10, the light intensity of the optical image formed on the central portion CP1 of the imaging surface P increases, and the light intensity of the optical image formed on the peripheral portion CP2 of the imaging surface P decreases. . FIG.
FIG. 2B is a diagram showing a light intensity distribution of the optical image along a line L1 in FIG.

FIG. 2C shows an image pickup signal having an intensity distribution on the image pickup surface of the image pickup device 14 output from the frame memory 16 and the CCD data input section 18 and integrated by the CCD data integration section 20. As described above, the difference between the signal strength of the imaging signal obtained in the central part CP1 and the signal strength of the imaging signal obtained in the peripheral part CP2 is large.

Therefore, in the present embodiment, first, the offset calculating section 24 reads the second correction function from the offset table 22 and outputs the second correction function from the CCD data accumulating section 20 based on the timing signal output from the CCD data input section 18. From which pixel in the imaging plane P the imaging signal to be output is obtained by specifying the position in the X-axis direction and the Y-axis direction, and a correction value corresponding to the position is calculated by calculation. . Then, the offset adding unit 26 outputs the correction value output from the offset calculating unit 24 to the CCD.
Addition to the image signal output from the data accumulating unit 20 corrects color unevenness caused by the electric characteristics of the image sensor 14.

Next, the gain calculating section 30 reads out the first correction function from the gain table 28 and, based on the timing signal output from the CCD data input section 18, converts the imaging signal output from the offset adding section 26 into an imaging surface. From which pixel in P the image signal is output is determined by specifying the position in the X-axis direction and the Y-axis direction, and a correction value corresponding to the position is calculated by calculation. Then, the gain multiplying unit 32 multiplies the correction value output from the gain calculating unit 30 by the imaging signal output from the offset adding unit 26 to correct color unevenness caused by the optical characteristics of the lens system 10. An imaging signal in which color unevenness has been corrected through the above processing is output from the CCD data output unit 34.

In the embodiment described above, the image pickup device 14
The first correction function is stored in the gain table 28 and the second correction function is stored in the offset table 22 in the form of a function in order to correct color unevenness caused by the electrical characteristics of the optical system 10 and the optical characteristics of the optical system 10. Was. And the gain calculator 3
0 and the offset calculator 24 are the CCD data input unit 18
The position in the X-axis direction and the Y-axis direction in the imaging plane is specified based on the timing signal output from the CPU, and the correction value is calculated by calculation. Next, an embodiment will be described in which a gain as a correction value is stored in each of the gain table 28 and the offset table 22, instead of storing the first correction function and the second function as functions in the gain table 28 and the offset table 22, respectively. I do.

A correction value for correcting color unevenness caused by the electrical characteristics of the image sensor 14 and a correction value for correcting color unevenness caused by the optical characteristics of the lens system 10 for all the pixels included in the image sensor 14 Requires an enormous storage capacity, which leads to an increase in the price of the device. Therefore, in the embodiment described below, a correction value for correcting color unevenness caused by the optical characteristics of the lens system 10 is a discrete value in which the degree of discreteness varies according to the position in the X-axis direction and the Y-axis direction. The values are stored in the gain table 28. Further, a correction value for correcting color unevenness caused by the electric characteristics of the image sensor 14 is stored as a discrete value whose degree of discreteness varies according to the position in the X-axis direction and the Y-axis direction.

In the following description, the correction values stored in the gain table 28 will be described, but the same applies to the correction values stored in the offset table 22. In order to store a gain as a correction value in the gain table 28, first, the imaging surface is divided into a plurality of blocks. FIG.
FIG. 4 is a diagram showing a state in which the imaging surface of the imaging element 14 is divided into a plurality of blocks. Then, the representative value of each block is stored in the gain table 28.

Here, as shown in FIG. 3, the present embodiment is characterized in that the size of each block is made different depending on the position in the X-axis direction and the Y-axis direction. This is because, for example, the approximation value of the first correction function or the second correction function is more accurately obtained by reducing the degree of discreteness for a portion having a large variation in color unevenness and increasing the degree of discreteness for a portion having a small variation. That's why.

For example, the region denoted by reference numeral B11 and the region denoted by reference numeral B21 correspond to the central portion of the imaging plane P1,
The size of the block is large because the variation amount of the color unevenness is not so large (for example, a size including 64 pixels in the X-axis direction).
The set area B13 and the area B23 correspond to the peripheral portion of the imaging plane P1 and have a large block size due to a large variation in color unevenness (for example, in the X-axis direction). (A size including 16 pixels).

At the time of imaging, to correct the imaging signal output from the pixel in which the gain is stored, the gain stored in the gain table 28 may be directly multiplied by the gain multiplying unit 32. To correct an image signal output from a pixel for which no gain is stored, first, the gain calculation unit 30 stores a correction value in the gain table 28 for a pixel adjacent to the pixel for which gain is to be obtained. By performing an interpolation process such as linear interpolation using the gain of at least two pixels, an approximate value of the gain defined by the first correction function is calculated.

FIG. 4 is a diagram showing how to calculate the approximate value of the gain. In FIG. 4, it is assumed that the gain is stored in the gain table 28 in advance for the pixel located at the position X1 and the pixel located at the position X4, and the gain is stored for the pixel located at the position X2 and the pixel located at the position X3. Suppose not. First, based on the timing signal output from the CCD data input unit 18, the gain calculation unit 30 converts the imaging signal output from the offset addition unit 26 into
For example, it is determined that the pixel is output from the pixel located at the position X2.

Next, since the gain for the pixel located at X2 is not stored in the gain table 28, the gain (value A1) stored for the adjacent pixel, for example, the pixel located at the position X1 is stored. And the gain (value A2) stored for the pixel located at position X4. Then, the read gain and the position X2 and the position X
Interpolation processing is performed based on the relative relationship between X1 and X4, and the gain of the pixel located at position X2 is calculated. The gain calculated here is an approximate value of the gain defined by the first correction function. Similarly, the gain is determined for the pixel located at the position X3. Then, the color unevenness can be corrected by multiplying the imaging signal output from the offset addition unit 26 by the gain calculated by the gain calculation unit 30.

The processing for interpolating the one-dimensional (X-axis) gain has been described above for easy understanding. Next, the processing for interpolating the gain in consideration of the X-axis direction and the Y-axis direction will be described. . FIG. 5 is a diagram illustrating a process of interpolating a gain in consideration of the X-axis direction and the Y-axis direction. FIG.
, Four points (X11, Y
11), (X12, Y11), (X12, Y12),
To obtain the gain of a point located between (X11, Y12) by interpolation means that the gain at that point is on a plane indicated by hatching in the figure.

Now, the general formula of the plane is represented by the following formula (1). pX + qY + rG = s (1) where p, q, r, and s are constants. By substituting the values of the above four points into this equation (1), the values of the constants p, q, r, and s are obtained, and thus the hatched plane in FIG. 5 is specified. Therefore, the gain of an arbitrary point can be obtained by substituting an arbitrary value of X and an arbitrary value of Y into an expression indicating the specified plane. In the above description, for simplicity,
The case where the gain of each point is simply obtained without distinguishing R, G, and B has been described.
The gain may be obtained for each of R, G, and B.

In the above description, the processing for obtaining the gain by performing the interpolation processing from the correction values discretely stored in the gain table 28 has been described as an example. The correction processing to be stored in the offset table 22 is similarly performed. To determine the offset. As described above, by storing the gain and the offset discretely, the storage capacity can be reduced, and the cost of the apparatus can be suppressed. Further, by obtaining the gain and the offset by performing the interpolation processing, the color unevenness can be satisfactorily removed.

The processing for correcting the color unevenness of the two-dimensional image signal picked up by the image sensor 14 has been described above.
The present invention includes an imaging element that captures a three-dimensional imaging signal,
Color unevenness caused by the optical characteristics of the lens system 10 and the electrical characteristics of the image sensor 14 can also be corrected. In order to obtain a three-dimensional image pickup device, in addition to providing the three-dimensional image pickup signal with the image pickup device, a plurality of two-dimensional images are obtained at a plurality of positions where the focal position of the lens system 10 is changed, and these are combined. Can also be obtained by

Hereinafter, a process for correcting color unevenness caused by a three-dimensional image pickup signal will be described. In order to correct the color unevenness caused by the three-dimensional imaging signal, a gain for which the degree of discreteness is defined according to the amount of change in the color unevenness in the Z-axis direction is stored in the gain table 28. When correcting color unevenness caused by a three-dimensional imaging signal, it is preferable to perform a process of correcting color unevenness for each of R, G, and B to obtain gains for each of R, G, and B. In the description, for the sake of simplicity, the R, G, and B gains will be represented by a common gain G. In the following description, a process for obtaining a gain will be described, but a similar process is performed for a process for obtaining an offset.

FIG. 6 is a diagram for explaining a process for correcting color unevenness occurring in a three-dimensional image pickup signal. Now, it is assumed that a two-dimensional image signal is obtained at the position of Z = 0 and the position of Z = Z1 by changing the focal position of the lens system 10. At the position of Z = 0, four points (X11, Y
11), (X12, Y11), (X12, Y12),
It is assumed that the gain of (X11, Y12) is stored in the gain table 28, and the respective gains are G1 to G4. At this time, the gain is set to G1 by the method using FIG.
A plane passing through the four points of G4 is obtained.

When Z = Z1, the four points (X11, Y11), (X12, Y11), (X12,
The gains of Y12) and (X11, Y12) are stored in the gain table 28, and the respective gains are G11 to G1.
Assume that it is 4. Also at this time, a plane passing through four points having gains of G11 to G14 is obtained by the method using FIG. Now, the position Z = Z2 where the imaging signal is not obtained.
When calculating the gain at (0 <Z2 <Z1), linear interpolation is performed between the plane obtained when Z = 0 and the plane obtained when Z = Z1.

FIG. 7 is a diagram for explaining interpolation processing between planes when correcting color unevenness of a three-dimensional image. FIG.
In, the gain of the point (X11, Y11, 0) is stored in the gain table 28, and the point (X11, Y11, 0)
The gain of Z1) is also stored in the gain table 28. Now, when calculating the gain of the point (X11, Y11, Z2), the point (X11, Y11, 0) and the point (X1
1, Y11, Z1), a change in gain per unit length in the Z-axis direction is obtained, and a gain corresponding to the position of Z2 is obtained.

By performing the above-described processing, even in the case of a three-dimensional image, color unevenness caused by the optical characteristics of the optical system 10 or the electric characteristics of the image sensor 14 can be almost completely removed. Moreover, in this case, it is possible to remove the color unevenness without causing the device to be complicated and expensive. When correcting color unevenness of a three-dimensional image, gains at arbitrary points can be obtained as long as there are at least six gains. In this embodiment, it is preferable that the correction amount of the color unevenness is suppressed to about 10% of the signal intensity.

The color non-uniformity correcting apparatus and the electronic camera according to the embodiment of the present invention have been described above. However, the present invention is not limited to the above-described embodiment, and can be freely changed within the scope of the present invention. For example, in the above-described embodiment, a CCD is used as the image sensor 14, but a CMOS image sensor or an artificial retinal sensor may be used.

[0043]

As described above, according to the present invention, the first correction function for correcting the color unevenness of the image pickup signal generated according to the optical characteristics of the optical system is stored in advance in the first correction function storage means. In addition, since the first correction unit reads out the first correction function from the first correction function storage unit at the time of imaging and corrects the color unevenness of the imaging signal, the color unevenness caused by the aberration of the optical system is removed. There is an effect that can be. Also,
Since the function for correcting the color unevenness is stored, the effect that the apparatus is not expensive is obtained. Further, according to the present invention, the second correction function for correcting the color unevenness of the imaging signal generated according to the electrical characteristics of the imaging device is stored in advance in the second correction function storage means, and the second correction function is used when the imaging is performed. Since the second correction function is read from the second correction function storage means to correct the color unevenness of the imaging signal, it is possible to remove the color unevenness caused by the electric characteristics of the image sensor. Here, since the color unevenness caused by the temperature distribution of the image sensor can be removed in addition to the color unevenness caused by the aberration of the optical system described above, the color unevenness of the image signal is almost completely removed. There is an effect that can be. Further, since the function for correcting the color unevenness is stored, there is also obtained an effect that the apparatus is not expensive. Further, according to the present invention, the first correction function is stored in advance as a discrete value whose discrete value changes, and the discrete value stored at the time of imaging is interpolated to approximate the gain defined by the first correction function. Is corrected for, so that it is possible to almost completely eliminate the color unevenness caused by the aberration of the optical system and the temperature distribution of the image sensor without inviting the apparatus to be complicated and expensive. This has the effect. Further, according to the present invention, the approximate value of the offset defined by the second correction function is stored by previously storing the second correction function as a discrete value whose discrete value changes, and interpolating the discrete value stored at the time of imaging. Is corrected for, so that it is possible to almost completely eliminate the color unevenness caused by the aberration of the optical system and the temperature distribution of the image sensor without inviting the apparatus to be complicated and expensive. This has the effect. Further, according to the present invention, the above-described discrete value is set according to the variation amount of the color unevenness of the imaging signal. For example, the discreteness is reduced for a portion where the variation amount of the color unevenness is large, and the variation amount is small. By increasing the degree of discreteness of the portion, an approximate value of the first correction function or the second correction function can be obtained more accurately. Therefore, the color unevenness can be almost completely reduced without increasing the complexity and cost of the apparatus. This has the effect of being suitable for removal. Further, according to the present invention, even when the light intensity of the optical image formed on the image sensor via the optical system is low, the integrating means integrates the image signal output from the image sensor for a predetermined time. The intensity of the imaging signal is increased. When the imaging signals are integrated, color unevenness caused by the aberration of the optical system and the temperature distribution of the image sensor is also integrated, so that the color unevenness is remarkable. However, the present invention is caused by the aberration of the optical system. Is corrected using the first correction function, and the color unevenness caused by the temperature distribution of the image sensor is corrected using the second correction function. There is an effect that color unevenness can be corrected. Further, according to the present invention, the first direction, the second direction,
And even in the case of capturing a three-dimensional optical image in the third direction, it is possible to correct the color unevenness caused by the aberration of the optical system and the temperature distribution of the image sensor in each direction. There is. Further, according to the present invention, when capturing a three-dimensional optical image, it is necessary to handle more pixels, the processing amount for correcting color unevenness also increases,
The first correction function or the second correction function is stored in advance as a discrete value whose discrete value changes, and by interpolating the discrete value stored at the time of imaging, the approximate value of the gain specified by the first correction function or the second value is calculated. Since the color unevenness is corrected by obtaining an approximate value of the offset defined by the correction function, the color generated due to the aberration of the optical system and the temperature distribution of the image sensor without complicating the apparatus and increasing the price. The effect is that unevenness can be almost completely removed. According to the present invention,
Since a color non-uniformity correction device capable of almost completely removing color non-uniformity caused by aberrations of the optical system and temperature distribution of the image pickup device is provided without causing the apparatus to be complicated and expensive, the optical There is an effect that a high-definition electronic camera capable of correcting color unevenness caused by system aberration and temperature distribution of the image sensor can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating a configuration of a color shading correction apparatus according to an embodiment of the present invention provided in an electronic camera according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining color unevenness caused by aberrations of the lens system 10;

FIG. 3 is a diagram illustrating a state in which an imaging surface of an imaging element is divided into a plurality of blocks.

FIG. 4 is a diagram showing a manner of calculating an approximate value of a gain.

FIG. 5 is a diagram illustrating a process of interpolating a gain in consideration of an X-axis direction and a Y-axis direction.

FIG. 6 is a diagram for explaining a process for correcting color unevenness occurring in a three-dimensional image pickup signal.

FIG. 7 is a diagram for describing interpolation processing between planes when performing color unevenness correction of a three-dimensional image.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Lens system (optical system) 14 Image sensor 20 CCD data integration part (integration means) 22 Offset table (second correction function storage means) 24 Offset calculation part (offset calculation means, second
Correction means) 26 offset addition section (second correction section) 28 gain table (first correction function storage section) 30 gain calculation section (gain calculation section, first correction section) 32 gain multiplication section (first correction section)

Claims (13)

[Claims] 1. An image sensor for photoelectrically converting an optical image via an optical system to output an image signal, and a first correction function for correcting color unevenness of the image signal generated according to optical characteristics of the optical system. A first correction function storing means for storing; and a first correction means for correcting color unevenness of the imaging signal based on the first correction function stored in the first correction function storage means. Color unevenness correction device. 2. A second correction function storage means for storing a second correction function for correcting color unevenness of the image signal generated according to an electrical characteristic of the image sensor, and a second correction function storage means for storing the second correction function. 2. The color unevenness correction apparatus according to claim 1, further comprising: a second correction unit configured to correct the color unevenness of the imaging signal based on a second correction function. 3. The first correction function defines a gain corresponding to a position in a first direction set in an imaging plane of the imaging device and a position in a second direction orthogonal to the first direction. The color unevenness correction apparatus according to claim 1, wherein the first correction unit multiplies the imaging signal by a gain defined by the first correction function. 4. The second correction function is a function that defines an offset corresponding to the position in the first direction and the position in the second direction. 4. The color non-uniformity correction apparatus according to claim 3, wherein the offset defined by the following is added to the image signal. 5. The first correction function storage means, wherein:
A correction function is stored as a discrete value whose degree of discreteness varies according to the position in the first direction and the position in the second direction, and the discrete value is interpolated to obtain a gain defined by the first correction function. The color non-uniformity correction apparatus according to claim 3, further comprising a gain calculation unit configured to calculate an approximate value. 6. The second correction function storage means, wherein:
The correction function is stored as a discrete value whose degree of discreteness varies according to the position in the first direction and the position in the second direction, and the discrete value is interpolated to obtain an offset defined by the second correction function. 6. The color non-uniformity correcting apparatus according to claim 5, further comprising an offset calculating means for calculating an approximate value. 7. The discrete degree of the discrete value is set according to a change amount of color unevenness of the image pickup signal in the first direction and the second direction. 6. The color non-uniformity correction device according to 6. 8. The color non-uniformity correcting apparatus according to claim 1, further comprising an integrating unit that integrates an image signal output from the image sensor for a predetermined time. 9. The imaging signal is an imaging signal obtained by imaging at a plurality of different positions in a third direction orthogonal to an imaging surface of the imaging device, and the first correction function is The color non-uniformity correction device according to claim 3 or 4, wherein the function is a function that defines a gain according to positions in the first direction, the second direction, and the third direction. 10. The apparatus according to claim 9, wherein the second correction function is a function that defines an offset according to positions in the first direction, the second direction, and the third direction. Color unevenness correction device. 11. The first correction function storage means stores the first correction function with a variable degree of discreteness according to the position in the first direction, the position in the second direction, and the position in the third direction. Calculate an approximate value of the gain defined by the first correction function by performing interpolation using the discrete values of six or more adjacent points stored in the first correction function storage means. 11. The gain calculating means according to claim 9, wherein:
The uneven color correction device described in the above. 12. The second correction function storage means, wherein the degree of discreteness of the second correction function is variable according to the position in the first direction, the position in the second direction, and the position in the third direction. Calculate the approximate value of the offset defined by the second correction function by performing interpolation using the discrete values of six or more adjacent points stored in the second correction function storage means. The color non-uniformity correction apparatus according to claim 11, further comprising an offset calculation unit that performs the offset calculation. 13. A color non-uniformity correction apparatus according to claim 1, further comprising: a storage unit configured to store an image signal corrected by the color non-uniformity correction apparatus. Electronic camera.