JP4940661B2 - Image processing apparatus, image processing method, and imaging apparatus - Google Patents

Description

  The present invention relates to an image processing device, an image processing method, and an imaging device, and more particularly to an image processing device, an image processing method, and an imaging device that process an image signal.

In recent years, there has been a remarkable spread of imaging devices represented by digital video cameras and digital still cameras.
In general, in devices equipped with these lens systems and imaging devices (imaging devices), for example, a phenomenon of sensitivity unevenness (non-uniformity) called shading in captured images due to a decrease in the amount of peripheral light caused by the lens system, for example. Is known to occur. This shading occurs due to the optical relationship between the microlens provided in the image sensor and the photographic lens. For example, the shading occurs in proportion to the distance of the pixel position on the image sensor from the optical axis of the photographic lens. . More specifically, when the light beam that has passed through the photographing lens is incident on the image sensor obliquely (tilted at a predetermined angle), in the peripheral area away from the optical axis of the photographing lens, Since only a part of the incident light is incident, the amount of light is reduced and shading occurs.

  As a method for preventing the occurrence of such shading, for example, a method of designing a lens system with a large number of lenses has been proposed. However, a lens system configured with a large number of lenses has a large scale and high price. There was a problem that it led to the transformation.

  Various methods have also been proposed for correcting the image pickup signal from the image pickup device described above by digital signal processing. For example, a correction coefficient corresponding to each pixel on the image sensor is held in a storage unit (memory or the like) as a two-dimensional array, the correction coefficient corresponding to each pixel position is read, and shading correction is performed by multiplying the input signal. This method has been proposed.

There is also proposed a method in which a shading correction coefficient corresponding to an imaging signal is calculated by a calculation means such as a CPU (Central Processing Unit) and the like, and shading correction is performed (for example, see Patent Document 1).
JP 2005-102134 A

However, the conventional techniques have the following problems.
First, in the method of storing the correction coefficient on the two-dimensional array in the storage means, the desired shading according to the imaging signal under various conditions such as the imaging lens position, image height, aperture amount, exit pupil position, strobe issuance amount, etc. In order to obtain the characteristics, a storage means such as a memory is separately required, which causes a problem that the scale of the device is increased and the price is increased. In particular, under the current trend of increasing the number of pixels, it is a problem that cannot be ignored because a larger storage means is required.

  In addition, the method for calculating the correction coefficient by the calculation means is based on the premise that the shading phenomenon is a concentric peripheral light amount reduction phenomenon. In the case of a shape having an angle (rotational shape), there is a problem that a desired correction coefficient cannot be obtained.

  According to the method disclosed in Patent Document 1, the imaging plane is divided into four areas, upper, lower, left, and right, and each area can be weighted, so that it faces the optical axis. Although it is possible to calculate a desired correction coefficient for an elliptical shading characteristic, there is a problem that a desired correction coefficient cannot be obtained for a shading characteristic having an angle with respect to the optical axis. there were.

  An object of the present invention is to provide an image processing device, an image processing method, and an imaging device that can easily perform correction of a shading characteristic of a rotational shape having an angle with respect to an optical axis. An object of the present invention is to provide an image processing apparatus, an image processing method, and an imaging apparatus that can eliminate the need for a large-scale storage means and can reduce the size and weight of the device and reduce the cost.

In the present invention, in order to solve the above-described problem, in an image processing apparatus that processes an image signal, a coordinate system rotation unit that rotates a coordinate system of the input image with reference to a center coordinate of the input image, and rotation of the coordinate system A distance calculation unit that calculates a distance from the center coordinate in each pixel coordinate of the input image later, and a distance calculated by the distance calculation unit for each pixel coordinate after rotation of the coordinate system A correction coefficient determining unit that determines a corresponding correction coefficient, and a correction coefficient multiplying unit that multiplies the determined correction coefficient by a corresponding pixel signal of the input image, and the coordinate system rotation unit is configured to input When cos θ (θ: rotation angle when rotating the coordinate system) can be approximated to 1 for each of the horizontal component and the vertical component at each pixel coordinate of the input image , tan θ is 2 ^−m ・ A A multiplication unit for multiplying the rotation correction coefficient A obtained by approximation, the image processing device is provided with a shift unit for multiplying the power of two portions 2 ^-m obtained by approximating the tanθ The

  According to such an image processing apparatus, the coordinate system rotation unit rotates the coordinate system of the input image with reference to the center coordinates of the input image, and the distance calculation unit rotates each pixel of the input image after the rotation of the coordinate system. The distance from the center coordinate in the coordinates is calculated, and the correction coefficient determining unit determines a correction coefficient corresponding to the distance calculated by the distance calculating unit for each pixel coordinate after the rotation of the coordinate system. The multiplication unit multiplies the determined correction coefficient by the corresponding pixel signal of the input image.

According to the present invention, in order to solve the above problems, in an image processing method for processing an image signal, the coordinate system of the input image is rotated with reference to the center coordinate of the input image, and the coordinate system after the rotation of the coordinate system is rotated. A distance from the center coordinate in each pixel coordinate of the input image is calculated, and a correction coefficient corresponding to the calculated distance is determined for each pixel coordinate after the rotation of the coordinate system. the correction coefficients are multiplied to the corresponding pixel signal of the input image, the rotation of the coordinate system of the input image for each horizontal component and a vertical component in each pixel coordinates of the input image input, cos [theta] When (θ: rotation angle when rotating the coordinate system) can be approximated to 1, the rotation correction coefficient A obtained by approximating tan θ to 2 ^−m · A is multiplied, and the tan θ is approximated. 2 An image processing method is provided that shifts the power of 2 ^−m .

  According to such an image processing method, the same processing as that of the image processing apparatus according to the present invention is realized.

  According to the present invention, it is possible to easily and accurately correct shading caused by a lens system having an elliptical shape or a shape (rotational shape) that does not face the optical axis but has an angle. Further, it is possible to reduce the size and weight of the device and reduce the cost without requiring a large-scale storage means.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram illustrating a main configuration of an imaging apparatus according to an embodiment.
An imaging apparatus 1 shown in FIG. 1 includes an optical block 2, a driver 2a, a drive unit 2b, an image sensor 3, a timing signal generation circuit (TG) 3a, an analog front end (AFE) circuit 4, a signal processing circuit 5, and a system controller 6. , An operation unit 7, a graphic I / F (interface) 8, and a display (image monitor) 8a.

  The optical block 2 includes a lens for condensing incident light from the light source and light from the subject (reflected light) on the image sensor 3, a drive mechanism for moving the lens to perform focusing and zooming, a shutter mechanism, The iris is adjusted by adjusting the diaphragm according to the illuminance of the subject and determining the amount of light (light quantity) that has passed through the lens, that is, the exposure.

Based on the control signal from the system controller 6, the driver 2a outputs a driving signal for controlling driving of each mechanism in the optical block 2, such as aperture driving.
The drive unit 2b receives the drive signal from the driver 2a and drives the drive mechanism of the optical block 2.

  The image sensor 3 is a solid-state imaging device in which photodiodes, which are photoelectric conversion elements, are arranged in a matrix, and is driven based on a timing signal output from the TG 3a to convert incident light from a subject into an electrical signal. Convert. The image sensor 3 is not particularly limited, and examples thereof include a CCD (Charged Coupled Device) and a CMOS (Complementary Metal Oxide Semiconductor).

The TG 3a outputs a timing signal for controlling the electronic shutter under the control of the system controller 6.
The AFE circuit 4 includes a holding / gain control circuit 41 and an A / D conversion circuit (A / D) 42. The AFE circuit 4 is configured as, for example, one IC (Integrated Circuit), and the holding / gain control circuit 41 performs S / N (Signal Signal) by CDS (Correlated Double Sampling) processing on the image signal output from the image sensor 3. Sample hold is performed so as to keep a good (Noise) ratio, and gain (gain) is controlled by AGC (Auto Gain Control) processing. The A / D conversion circuit 42 performs A / D conversion and outputs a digital image signal. Note that the circuit that performs the CDS process may be formed on the same substrate as the image sensor 3.

  The signal processing circuit 5 performs AF (Auto Focus), AE on the image signal from the AFE circuit 4 in accordance with the control signal from the system controller 6 with respect to the subject imaging signal converted into the digital signal by the AFE circuit 4. Various camera control processes such as (Automatic Exposure) and AWB (Auto White Balance) or a part of the processes are executed to generate a video signal (luminance signal and color difference signal) of the subject.

  The signal processing circuit 5 includes a synchronization signal generation unit 51 that generates horizontal and vertical synchronization signals and various timing signals, and a camera signal processing unit 52 that performs control processing according to a control signal from the system controller 6 and generates a subject video signal. A control arithmetic processing unit 53 that performs various arithmetic processes for performing the above-described control processing on the subject video signal, and a resolution conversion unit 54 that performs resolution conversion and distortion correction processing on the subject video signal. is doing.

FIG. 2 is a block diagram illustrating a configuration of the camera signal processing unit.
The camera signal processing unit 52 is a camera signal preprocessing unit 52a that performs various correction processes on the subject imaging signal from the AFE circuit 4, and a shading that performs a shading correction process on the signal output from the camera signal preprocessing unit 52a. It has a correction unit 52b and a camera signal post-processing unit 52c that performs post-processing of signals output from the shading correction unit 52b.

  The camera signal preprocessing unit 52a uses the various synchronization signals from the synchronization signal generation unit 51 to perform various correction processes such as correction of defective pixels caused by the image sensor and noise removal on the subject imaging signal. Further, the camera signal pre-processing unit 52a, when the input signal from the image sensor 3 is composed of so-called complementary color signals of C (light blue), M (red purple), and Y (yellow), R (red), Primary color separation processing is also performed on primary color signals (hereinafter referred to as R signal, G signal, and B signal) composed of G (green) and B (blue). The R signal, the G signal, and the B signal are input signals to the subsequent shading correction unit 52 b and the control calculation processing unit 53.

  The shading correction unit 52b is caused by the difference in brightness (shading) between the central portion and the edge portion (peripheral portion) of the captured image caused by the decrease in the peripheral light amount due to the lens system, in other words, by the decrease in the peripheral light amount. Correction processing for the generated sensitivity unevenness (non-uniformity) is performed.

The camera signal post-processing unit 52c generates a video signal including a luminance signal (Y) and color difference signals (RY, BY) from the subject imaging signal subjected to white balance adjustment.
The control arithmetic processing unit 53 performs various arithmetic processes based on the setting signal from the system controller 6 and outputs the arithmetic result to the system controller 6.

  The system controller 6 is a microcontroller including, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and is stored in a ROM or the like based on the above-described calculation results. By automatically controlling each part of the imaging device 1, such as the optical block 2, the image sensor 3, the AFE circuit 4, and the signal processing circuit 5, the automatic control processing of AF, AE, and AWB is performed. And generating a suitable video signal of the imaging subject.

  The operation unit 7 includes various operation keys such as a shutter release button, a lever, a dial, and the like, and outputs a control signal corresponding to an input operation by the user to the system controller 6.

  The graphic I / F 8 generates an image signal to be displayed on the display 8a from the image signal supplied from the signal processing circuit 5 via the system controller 6, supplies the signal to the display 8a, and displays the image. Let The display 8a is composed of, for example, an LCD (Liguid Crystal Display), and displays a camera-through image being captured or a reproduced image based on data recorded on a recording medium (not shown).

  In the image pickup apparatus 1, signals received and photoelectrically converted by the image sensor 3 are sequentially supplied to the AFE circuit 4, subjected to CDS processing and AGC processing, and then converted into digital signals. The signal processing circuit 5 converts the digital image signal supplied from the AFE circuit 4 into a luminance signal (Y) and color difference signals (RY, BY), and finally performs an image quality correction process and outputs the result.

  The signal output from the signal processing circuit 5 is supplied to the graphic I / F 8 via the system controller 6 and converted into a display image signal, whereby a camera-through image is displayed on the display 8a. Further, when image recording is instructed to the system controller 6 by a user input operation from the operation unit 7, the image data from the signal processing circuit 5 is supplied to an encoder (not shown), and a predetermined compression encoding process is performed. Is recorded on a recording medium (not shown). When recording a still image, the signal processing circuit 5 supplies image data for one frame to the encoder, and when recording a moving image, the processed image data is continuously supplied to the encoder. .

Such an imaging apparatus 1 is characterized by the processing of the shading correction unit 52b. Hereinafter, the shading correction unit 52b will be described in detail.
FIG. 3 is a block diagram illustrating an internal configuration of the shading correction unit.

  The shading correction unit 52b includes a counter generation unit 521, a distance calculation unit 522, a gain lookup table (correction coefficient determination unit) 523, and a gain multiplication unit (correction coefficient multiplication unit) 524.

  The counter generation unit 521 performs horizontal and vertical counter generation processing based on the horizontal synchronization signal and the vertical synchronization signal input from the synchronization signal generation unit 51. In this embodiment, the counter value is a coordinate on the captured image plane with the upper left (one vertex) on the captured image plane as the origin and the right direction and the downward direction (direction toward the other vertex) as positive directions, respectively. Is shown.

The distance calculation unit 522 includes an optical axis center coordinate shift unit 522a, a coordinate system rotation unit 522b, and a distance calculation unit 522c.
The optical axis center coordinate shift unit 522 a performs a difference calculation process between the horizontal direction counter value and the vertical direction counter value input from the counter generation unit 521 and the optical axis center coordinate set by the system controller 6. That is, the origin of the captured image coordinate system is shifted to coincide with the center of the optical axis. Thereby, even when the optical axis center of the lens system and the center on the captured image plane do not coincide with each other, the horizontal direction component and the vertical direction component of the distance between the position of each pixel (pixel coordinate) and the optical axis center position are reduced. It can be calculated correctly.

  The coordinate system rotation unit 522b performs a rotation process on the horizontal direction component and the vertical direction component of the distance between each pixel position calculated by the optical axis center coordinate shift unit 522a and the optical axis center position. This rotation process will be described in detail later.

The distance calculation unit 522c performs a calculation process of a distance from the optical axis center for each pixel position with respect to the horizontal direction component and the vertical direction component signal subjected to the rotation process by the coordinate system rotation unit 522b.
Here, generally, the distance d from the position of the optical axis center at the pixel position whose coordinates from the optical axis center is (x, y) is expressed by Equation 1.

  Here, the distance calculation unit 522c is configured by a hexagonal approximation circuit to reduce the circuit scale, and the distance calculation from the center of the optical axis is performed based on the hexagonal approximation formula shown in the following equation 2. Here, assuming that the coordinates from the optical axis center are (x, y) and their absolute values are X and Y, respectively, the distance d1 from the optical axis center is expressed by the following equation.

Details regarding the calculation of the hexagonal pseudorange are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2002-216136 and 2002-237998.
The gain lookup table 523 performs a correction coefficient (gain) calculation process for correcting shading according to the distance from the optical axis center calculated by the distance calculation unit 522c of each pixel position.

  The gain look-up table 523 is configured by storage means in which a shading correction coefficient table is preliminarily tabulated and stored (stored). An appropriate correction coefficient at the pixel position is selected based on the distance from the optical axis center calculated by the distance calculation unit 522c, and is supplied to the gain multiplication unit 524 at the next stage.

  The gain look-up table 523 stores an appropriate one according to the state of the captured image, such as the zoom position, focus position, image height, aperture amount, exit pupil position, and strobe emission amount of the lens. It can be rewritten by the system controller 6 according to the change in the state of the image.

  The gain multiplication unit 524 inputs an input signal (subject imaging signal) of a captured image (at a corresponding image position) at the pixel position with respect to the correction coefficient (determined correction coefficient) read from the gain lookup table 523. And a multiplication process (hereinafter referred to as a shading correction process). The imaging signal subjected to the shading correction process is input to the camera signal post-processing unit 52c, and an imaging subject video signal including a luminance signal and a color difference signal is generated.

Next, the rotation process of the coordinate system rotation unit 522b will be described in detail.
First, the principle (concept) of the rotation process of the coordinate system rotation unit 522b will be described.
In general, when a pixel whose coordinates from the optical axis center are (x, y) and rotated by an angle θ with respect to the optical axis center is (x1, y1), the coordinates (x1, y1) Is expressed as in Equation 3.

  When the rotation matrix part of Equation 3 is divided by cos θ, Equation 3 is transformed into Equation 4.

  Here, when the rotation matrix portion of the above equation is approximated, Equation 4 is expressed by Equation 5 and Equation 6.

  In Equations 5 and 6, A is a rotation correction coefficient and m is a shift selector, both of which determine the rotation amount. The values of the rotation correction coefficient A and the shift selector m are stored, for example, in the system controller 6 or the like, and are appropriately given according to the angle θ.

  FIG. 4 is a diagram schematically showing the operation of the coordinate system rotation unit, and FIG. 4A is a diagram showing shading characteristics before the coordinate axis rotation processing on a two-dimensional plane, and FIG. ) Is a diagram showing a case where a coordinate system rotation process is performed by an angle θ with respect to the optical axis center shown in FIG.

次に、前述した原理を実現するための座標系回転部５２２ｂの構成について説明する。
Here, the angle θ is expressed as in Expression 7 from Expression 6.

Next, the configuration of the coordinate system rotation unit 522b for realizing the above-described principle will be described.

FIG. 5 is a block diagram illustrating a configuration of the coordinate system rotation unit.
The coordinate system rotation unit 522b includes multiplication units 91 and 92, shift units 93 and 94, a subtraction unit 95, an addition unit 96, and absolute value conversion units 97 and 98.

The multiplication unit 91 performs a multiplication process with the rotation correction coefficient A on the horizontal component of the distance from the optical axis center position at each pixel position calculated by the optical axis center coordinate shift unit 522a.
The multiplier 92 multiplies the vertical component signal of the distance from the optical axis center position at each pixel position calculated by the optical axis center coordinate shift unit 522a with the rotation correction coefficient A.

The shift unit 93 performs a shift calculation process determined by the shift selector m on the horizontal direction component signal that has been multiplied by the multiplication unit 91.
The shift unit 94 performs a shift calculation process determined by the shift selector m on the vertical direction component signal that has been multiplied by the multiplication unit 92.

  The subtraction unit 95 performs subtraction processing on the signal subjected to the shift calculation processing by the shift unit 93 and the horizontal direction component signal obtained from the optical axis center coordinate shift unit 522a, and the horizontal direction after the rotation processing at the pixel position. Component signal calculation processing is performed.

  The addition unit 96 performs addition processing on the signal subjected to the shift calculation processing by the shift unit 94 and the vertical direction component signal obtained from the optical axis center coordinate shift unit 522a, and the vertical direction after the rotation processing at the pixel position. Component signal calculation processing is performed.

The absolute value converting unit 97 performs absolute value processing on the horizontal direction component signal after the rotation processing calculated by the subtracting unit 95.
The absolute value converting section 98 performs absolute value processing on the vertical direction component signal after the rotation processing calculated by the adding section 96.

Next, the operation of the coordinate system rotation unit 522b will be described.
The horizontal direction component signal (x) and the vertical direction component signal (y) of the distance from the optical axis center position at each pixel position calculated by the optical axis center coordinate shift unit 522a are first multiplied by a multiplication unit in the coordinate system rotation unit. 91 and the multiplier 92, respectively. The multiplication unit 91 and the multiplication unit 92 multiply the input signals by the rotation correction coefficient A, respectively. As a result, the multiplication unit 91 obtains a signal (A · y), and the multiplication unit 92 obtains a signal (A · x). Each signal subjected to the multiplication processing is subjected to shift calculation processing determined by the shift selector m by the shift section 93 and the shift section 94, respectively. As a result, the shift unit 93 obtains a signal (2- ^m · A · y), and the shift unit 94 obtains a signal (2- ^m · A · x). These signals are input to the subtraction unit 95 and the addition unit 96.

The subtraction unit 95 receives the signal (2- ^m · A · y) on which the shift calculation process has been performed and the horizontal direction component signal (x) calculated by the optical axis center coordinate shift unit 522a. By performing the subtraction process at 95, the calculation process of the horizontal direction component signal (x−2− ^m · A · y) after the rotation process at the pixel position is performed.

Further, the adder 96 receives the signal (2- ^m · A · x) subjected to the shift calculation process and the vertical direction component signal (y) calculated by the optical axis center coordinate shift unit 522a, respectively. By performing addition processing by the addition unit 96, calculation processing of the vertical direction component signal (2- ^m · A · x + y) after the rotation processing at the pixel position is performed.

The rotated horizontal component signal (x−2− ^m · A · y) calculated by the subtracting unit 95 is input to the absolute value converting unit 97, and the absolute value converting unit 97 performs the absolute value processing. Then, it is output to the distance calculation unit 522c.

Further, the post-rotation vertical direction component signal (2- ^m · A · x + y) calculated by the adding unit 96 is input to the absolute value converting unit 98, and the absolute value converting unit 98 performs the absolute value processing. Then, it is output to the distance calculation unit 522c.

  Thereafter, as described above, the processing by the distance calculation unit 522c, the calculation processing by the gain look-up table 523, and the processing by the gain multiplication unit 524 are performed in this order, so that shading characteristic correction processing is performed.

  As described above, according to the imaging apparatus 1, by providing the coordinate system rotation unit 522b, the lens of the optical block 2 is, for example, elliptical or has an angle that does not face the optical axis. Even in the case of a shape (rotation shape), shading that has occurred can be easily and accurately corrected. In addition, since the correction coefficient is determined according to the distance, it is not necessary to prepare a large-scale memory separately, and the device can be reduced in size and weight and cost can be reduced.

  Further, when the distance calculation unit 522c is configured by a hexagonal approximation circuit, and the distance calculation from the optical axis center is performed based on the hexagonal approximation formula shown in Equation 2, the distance calculation is realized by a hardware circuit. Compared to the above, it is possible to prevent an increase in the circuit scale of the imaging apparatus 1. Further, the cost can be reduced. Therefore, it is particularly suitable for a device for consumer use. In this embodiment, hexagonal approximation (polygon approximation) is used, but it goes without saying that the present invention is not limited to this.

Further, by realizing the rotation matrix portion of Equation 4 using a coordinate axis rotation method (approximate equation) as shown in Equations 5 and 6, the coordinate system rotation unit 522b is multiplied by multiplication units 91 and 92, and shift units 93 and 94. Since the subtractor 95 and the adder 96 can be configured, the circuit that requires a large-scale circuit resource such as a trigonometric function arithmetic unit is generally reduced as compared with the case where the expression 4 is realized by hardware. be able to. Therefore, an increase in the circuit scale of the imaging device 1 can be prevented. Further, the cost can be reduced.

  Further, by parameterizing the rotation correction coefficient and the shift selector, it is possible to perform shading correction with a high degree of freedom allowing fine adjustment, and it is possible to generate a suitable video signal of the imaging subject.

In the above-described embodiment, the correction coefficient is obtained using the gain look-up table 523. However, the present invention is not limited to this, and may be obtained by calculation, for example.
In the above-described embodiment, the shading correction unit 52b is provided before the camera signal post-processing unit 52c. However, the present invention is not limited to this. For example, the shading correction unit 52b may be provided after the camera signal post-processing unit 52c. . In this case, the camera signal post-processing unit 52c is configured to perform shading correction processing after the video signal is separated into a luminance signal (Y signal) and a color difference signal (Cb, Cr signal). Accordingly, the luminance signal and the color difference signal are corrected such that the luminance signal is corrected for the decrease in the amount of peripheral light (brightness shading correction), and the color difference signal is subjected to the color blur correction (color shading correction). Independent correction.

  The imaging apparatus of the present invention has been described based on the illustrated embodiment. However, the present invention is not limited to this, and the configuration of each unit is replaced with an arbitrary configuration having the same function. For example, the example in which the signal processing circuit 5 is configured by an integrated circuit (hardware) has been shown. However, all or part of the above-described configuration may be software using a PC (personal computer) or the like. In this case, the same effect as the present embodiment can be obtained. Moreover, other arbitrary structures and processes may be added to the present invention.

In addition, the present invention may be a combination of any two or more configurations (features) of the above-described embodiments.
Note that the present invention can also be applied to an image processing apparatus that processes an imaging signal or the like in a small camera such as a videophone or game software connected to a PC or the like.

It is a block diagram which shows the principal part structure of the imaging device of embodiment. It is a block diagram which shows the structure of a camera signal processing part. It is a block diagram which shows the internal structure of a shading correction | amendment part. It is the figure which showed typically operation | movement of a coordinate system rotation part. It is a block diagram which shows the structure of a coordinate system rotation part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Imaging device, 52b ... Shading correction part, 521 ... Counter production | generation part, 522 ... Distance calculation part, 522a ... Optical axis center coordinate shift part, 522b ... Coordinate system rotation part 522c: distance calculation unit, 523: gain lookup table, 524 ... gain multiplication unit, 91, 92 ... multiplication unit, 93, 94 ... shift unit

Claims (6)

In an image processing apparatus that processes an image signal,
A coordinate system rotation unit that rotates the coordinate system of the input image with reference to the center coordinates of the input image;
A distance calculation unit for calculating a distance from the center coordinate in each pixel coordinate of the input image after rotation of the coordinate system;
A correction coefficient determination unit that determines a correction coefficient according to the distance calculated by the distance calculation unit for each pixel coordinate after rotation of the coordinate system;
A correction coefficient multiplier that multiplies the determined correction coefficient by the corresponding pixel signal of the input image,
The coordinate system rotation unit is
When cos θ (θ: rotation angle when rotating the coordinate system) can be approximated to 1 for each of the horizontal component and the vertical component at each pixel coordinate of the input image to be input , tan θ is 2 ⁻ a multiplication unit for multiplying the rotation correction coefficient A obtained by approximating ^m · A ;
A shift unit for multiplying the power-of- two part 2- ^m obtained by approximating the tan θ,
An image processing apparatus.   The image processing apparatus according to claim 1, further comprising a coordinate shift unit that shifts an origin of a coordinate system of the input image so as to coincide with the center coordinate.   The image processing apparatus according to claim 1, wherein the central coordinate is a position of an optical axis of an optical system at the time of imaging.   The image processing apparatus according to claim 1, wherein the distance calculation unit calculates a distance from the center coordinate of each pixel coordinate in the input image by approximating a polygon. In an image processing method for processing an image signal,
Rotate the input image coordinate system with respect to the center coordinates of the input image,
Calculating the distance from the center coordinate in each pixel coordinate of the input image after rotation of the coordinate system,
For each pixel coordinate after the rotation of the coordinate system, determine a correction coefficient according to the calculated distance,
Multiplying the determined correction factor by the corresponding pixel signal of the input image;
The rotation of the coordinate system of the input image is
When cos θ (θ: rotation angle when rotating the coordinate system) can be approximated to 1 for each of the horizontal component and the vertical component at each pixel coordinate of the input image to be input , tan θ is 2 ^{− An} image processing method that is performed by multiplying a rotation correction coefficient A obtained by approximating ^m · A and shifting a power-of- two part 2- ^m obtained by approximating tan θ. In an imaging device that captures an image using a solid-state imaging device,
A coordinate system rotating portion for rotating the coordinate system of the captured image based on the position coordinates of the optical axis of the captured image,
A distance calculation unit that calculates the distance from the position coordinate in each pixel coordinate of the captured image after rotation of the coordinate system;
A correction coefficient determination unit that determines a correction coefficient according to the distance calculated by the distance calculation unit for each pixel coordinate after rotation of the coordinate system;
A correction coefficient multiplier that multiplies the determined correction coefficient by the corresponding pixel signal of the captured image,
The coordinate system rotation unit is
When cos θ (θ: rotation angle when rotating the coordinate system) can be approximated to 1 for each of the horizontal component and the vertical component at each pixel coordinate of the captured image , tan θ is 2 ^−m · A And a multiplication unit for multiplying the rotation correction coefficient A obtained by approximation with
A shift unit for multiplying the power-of- two part 2- ^m obtained by approximating the tan θ,
An imaging apparatus having

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