JP4687454B2 - Image processing apparatus and imaging apparatus - Google Patents

Description

  The present invention relates to an image processing apparatus that performs color correction processing on an input image signal, and an imaging apparatus having such a function, and more particularly to an image processing apparatus and an imaging apparatus having a linear matrix calculation function.

  In an imaging apparatus using a solid-state imaging device such as a digital still camera or a digital video camera, various functions for improving image quality are incorporated. For example, a so-called white balance processing function is common as a function for faithfully reproducing colors, but recently, a function for improving color reproducibility using a linear matrix operation has attracted attention. This function performs the matrix operation of the following formula (1) on the input RGB (Red, Green, Blue) signals (R, G, B), thereby converting the spectral characteristics of each RGB component into human visibility characteristics. The color reproducibility is improved by approaching to.

FIG. 10 is a block diagram showing a main configuration of a conventional imaging apparatus including a linear matrix calculation function.
In FIG. 10, light incident through the optical block 101 is photoelectrically converted by the image sensor 102. An analog image signal from the image sensor 102 is digitally converted by an A / D (analog / digital) conversion circuit 103, and then a digital clamp process for adjusting a black level in a pre-correction circuit 104, and a signal of a defective pixel of the image sensor 102. Correction processing (pre-correction processing) related to the image sensor 102 and the optical system, such as defect correction processing for correcting the image quality, and shading correction processing for correcting a light amount drop around the lens. Further, the output signal of the pre-correction circuit 104 is subjected to a so-called demosaicing process in which the image interpolation processing circuit 105 generates three RGB plane signals (RGB signals at the same spatial position) from RGB signals whose spatial phases are shifted. Is done.

  The RGB signal output from the image interpolation processing circuit 105 is subjected to the linear matrix calculation described above by the linear matrix (LM) calculation circuit 106. The matrix coefficient used for the calculation in the linear matrix calculation circuit 106 is set by the calculation processing unit 107 including a microcomputer. The arithmetic processing unit 107 sets a matrix coefficient for the RGB signal such that the spectral characteristics of each component of the image sensor 102 approach a color matching function that is substantially equal to the human visibility characteristic.

  For the RGB signals output from the linear matrix arithmetic circuit 106, the gain of each RGB component is further adjusted by the white balance (WB) adjustment circuit 108. The input image signal to the white balance adjustment circuit 108 is also input to the integration circuit 109 to be detected, and the arithmetic processing unit 107 applies the white object on the input image to the white object on the basis of the RGB integration value by the integration circuit 109. Thus, the gain of the white balance adjustment circuit 108 is controlled so that the values of the RGB components are equal.

  The RGB signal after white balance adjustment is further subjected to γ correction by a γ (gamma) correction circuit 110, and the corrected signal is sent to a Y signal (luminance signal) processing circuit 111 and a C signal (color difference signal) processing circuit 112. The signals are inputted and separated into Y signal, Cr (R−Y) signal and Cb (B−Y) signal by calculation in each circuit. The separated signal is output to a graphic processing circuit that generates a display image on a monitor or a compression encoding circuit that generates a recording signal to a recording medium.

In addition, as a conventional imaging device having such a linear matrix calculation function, a coefficient conversion means for deriving six variables necessary for matrix conversion from two control parameters is provided, the number of parameters is reduced, and the circuit scale is reduced. There was one that prevented the enlargement of the image (for example, see Patent Document 1).
JP 2000-50299 A (paragraph numbers [0013] to [0021], FIG. 1)

  By the way, the linear matrix calculation processing for the purpose of improving the color reproducibility as described above has a side effect of increasing noise. The linear matrix calculation process is an effective means under ideal conditions without noise, but for the purpose of improving color reproducibility, the off-diagonal components (b, c, d, f, g, h) may be a negative value, and when RGB signals are subtracted by such coefficients, the signal level (S component) decreases, but the noise amount (N component) ) Does not decrease, the signal / noise ratio S / N decreases. As described above, when the linear matrix calculation process is performed, the improvement in color reproducibility and the S / N deterioration are often in a trade-off relationship, and a sufficient image quality improvement effect can be obtained by balancing the two. It became a problem.

SUMMARY An advantage of some aspects of the invention is that it provides an image processing apparatus that can output a high-quality image with high color reproducibility and good S / N.
Another object of the present invention is to provide an imaging apparatus that can capture high-quality images with high color reproducibility and good S / N.

  In the present invention, in order to solve the above problem, in an image processing apparatus that performs color correction processing on an input image signal, band separation means for separating the input image signal into a high frequency component and a low frequency component, and the band separation Linear matrix computing means for matrix-converting the color components of the low frequency components separated by the means, the low frequency components matrix transformed by the linear matrix computing means, and the high frequency components separated by the band separating means There is provided an image processing apparatus characterized by comprising signal adding means for adding.

  In such an image processing apparatus, the input image signal is separated into a high frequency component and a low frequency component by the band separation unit, and the matrix conversion of the color component is performed only on the low frequency component by the linear matrix calculation unit. The Then, the low frequency component after matrix conversion and the separated high frequency component are added by the signal adding means.

  According to the image processing apparatus of the present invention, for low frequency components, color reproducibility is improved by matrix conversion, but matrix conversion is not performed for high frequency components containing a lot of noise components. Deterioration of is suppressed. Therefore, it is possible to output a high-quality image with high color reproducibility and inconspicuous noise.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a main configuration of the imaging apparatus according to the first embodiment of the present invention.

  The imaging apparatus shown in FIG. 1 includes an optical block 1, an imaging device 2, an AFE (Analog Front End) circuit 3, a camera signal processing circuit 4, a system controller 5, and an input unit 6. Further, the imaging apparatus is provided with a driver 11 for driving various mechanisms in the optical block 1, a timing generator (TG) 12 for driving the imaging device 2, and the like.

  The optical block 1 includes a lens for condensing light from a subject on the image sensor 2, a drive mechanism for moving the lens to perform focusing and zooming, a mechanical shutter, a diaphragm, and the like. The driver 11 controls driving of the mechanism in the optical block 1 in accordance with a control signal from the system controller 5.

  The image pickup device 2 is a solid-state image pickup device such as a CCD (Charge Coupled Device) type or a CMOS (Complementary Metal Oxide Semiconductor) type, and is driven based on a timing signal output from the TG 12 to receive incident light from a subject. Convert to electrical signal. The TG 12 outputs a timing signal under the control of the system controller 5.

  The AFE circuit 3 samples and holds the analog image signal output from the image sensor 2 by CDS (Correlated Double Sampling) processing so as to keep the S / N good, and further, under the control of the system controller 5. The gain is controlled by AGC (Auto Gain Control) processing, A / D conversion is performed, and a digital image signal is output.

  The camera signal processing circuit 4 executes various types of camera signal processing such as AF (Auto Focus), AE (Auto Exposure), and white balance adjustment on the image signal from the AFE circuit 3, or a part of the processing. In the present embodiment, the camera signal processing circuit 4 is provided with a linear matrix operation circuit 41 that performs a matrix operation on each color component of the input image signal, and a white balance adjustment circuit 42 that adjusts the gain for each color component. ing.

  The system controller 5 is a microcomputer including, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and this imaging is performed by executing a program stored in the ROM or the like. Each part of the apparatus is comprehensively controlled, and various operations for the control are executed. The input unit 6 includes operation keys, dials, levers, and the like that receive user operation inputs, and outputs a control signal corresponding to the operation inputs to the system controller 5.

  In this image pickup apparatus, the signals received and photoelectrically converted by the image pickup device 2 are sequentially supplied to the AFE circuit 3, subjected to CDS processing and AGC processing, and then converted into digital signals. The camera signal processing circuit 4 performs image quality correction processing on the digital image signal supplied from the AFE circuit 3, and finally converts the digital image signal into a Y signal and a C signal for output.

  The image data output from the camera signal processing circuit 4 is supplied to a graphic interface circuit (not shown) and converted into a display image signal, whereby a camera-through image is displayed on a monitor (not shown) such as an LCD (Liquid Crystal Display). Is done. When the system controller 5 is instructed to record an image by a user input operation from the input unit 6, the image data from the camera signal processing circuit 4 is supplied to a CODEC (enCOder, DEcoder) (not shown), A predetermined compression encoding process is performed and recorded on a recording medium (not shown). When recording a still image, one frame of image data is supplied to the CODEC from the camera signal processing circuit 4, and when recording a moving image, the processed image data is continuously supplied to the CODEC. The

FIG. 2 is a block diagram illustrating a configuration of a main part of the camera signal processing circuit.
As shown in FIG. 2, the camera signal processing circuit 4 includes a linear matrix calculation circuit 41, white balance adjustment circuits 42a and 42b, a pre-correction circuit 43, an image interpolation circuit 44, a low-pass filter (LPF) circuit 45, a subtraction circuit 46, Integration circuits 47a and 47b, a MIX (synthesis) circuit 48, a γ correction circuit 49, a Y signal processing circuit 50, and a C signal processing circuit 51 are provided.

  The pre-correction circuit 43 corrects the black level of the digital image signal from the AFE circuit 3, the defect correction process for correcting the output signal of the defective pixel of the image sensor 2, and the light loss at the periphery of the lens. Correction processing related to the image sensor 2 and the optical system, such as shading correction processing to be performed.

  The image interpolation circuit 44 is a block that performs so-called demosaic processing, and generates three RGB plane signals (RGB signals at the same spatial position) from RGB signals that are out of spatial phase with respect to the image signal after the pre-correction processing. To do.

The low-pass filter circuit 45 limits the output band of the output image signal from the image interpolation circuit 44 and passes only a low-frequency component suitable for color signal processing.
The linear matrix calculation circuit 41 performs matrix calculation of the following expression (2) on the RGB signals (R _LPF , G _LPF , B _LPF ) from the low-pass filter circuit 45.

  The linear matrix calculation circuit 41 performs signal correction on the input image signal so that color reproducibility is improved. For this reason, a matrix coefficient is set for the linear matrix operation circuit 41 so that the spectral characteristics of the RGB components of the image sensor 2 approach a color matching function that is substantially equal to the human visual sensitivity characteristic. At this time, at least one of the off-diagonal components (b, c, d, f, g, h) of the matrix coefficient may be a negative number.

  The white balance adjustment circuit 42 a receives the output image signal from the linear matrix calculation circuit 41 and adjusts the gain of each RGB component based on the gain control value from the system controller 5.

  The subtraction circuit 46 subtracts the output image signal from the low-pass filter circuit 45 from the output image signal from the image interpolation circuit 44 for each RGB component. That is, the subtracting circuit 46 outputs an image signal including only a high-frequency component obtained by removing the low-frequency component signal that has passed through the low-pass filter circuit 45 from the output image signal from the image interpolation circuit 44.

The white balance adjustment circuit 42 b receives the output image signal from the subtraction circuit 46 and adjusts the gain of each RGB component based on the gain control value from the system controller 5.
The integration circuits 47 a and 47 b generate and integrate a luminance signal from the output signals from the linear matrix calculation circuit 41 and the subtraction circuit 46, respectively, and output the integration value to the system controller 5. Here, the system controller 5 uses the white balance adjustment circuits 42a and 42b so that the values of the RGB components are equal to the white subject on the input image based on the integration values from the integration circuits 47a and 47b. Control each gain. In the calculation of the gain control value, for example, on the basis of empirical prediction that the high luminance portion in the screen is likely to be white, the gain control value is set so that the RGB components of the high luminance portion are equal. Calculate. By such calculation, different gain control values are set in the white balance adjustment circuits 42a and 42b.

  The low-pass filter circuit 45, the linear matrix calculation circuit 41, and the white balance adjustment circuit 42a constitute a low-frequency processing unit 401 that performs a correction process on the low-frequency component of the output image signal from the image interpolation circuit 44. On the other hand, the subtraction circuit 46 and the white balance adjustment circuit 42 b constitute a high frequency processing unit 402 that performs correction processing on the high frequency component of the output image signal from the image interpolation circuit 44.

The MIX circuit 48 adds the image signals output from the low-frequency processing unit 401 and the high-frequency processing unit 402 for each RGB component.
The γ correction circuit 49 performs γ correction on the image signal output from the MIX circuit 48. The Y signal processing circuit 50 and the C signal processing circuit 51 perform Y signal processing and C signal processing on the image signal after γ correction, respectively, and Y signal, Cr (R−Y) signal, and Cb (BY). Generate a signal. For example, when outputting an SD (Standard Definition) video signal, assuming that the image signal after γ processing is (Rγ, Gγ, Bγ), the Y signal processing circuit 50 outputs the Y signal according to the following equation (3). The C signal processing circuit 51 generates a Cr (R−Y) signal and a Cb (B−Y) signal in accordance with the following equations (4) and (5).
Y = 0.3Rγ + 0.6Gγ + 0.1Bγ (3)
Cr (R−Y) = 0.7Rγ−0.6Gγ−0.1Bγ (4)
Cb (B−Y) = − 0.3Rγ−0.6Gγ + 0.9Bγ (5)
In the camera signal processing circuit 4 described above, the low-frequency processing unit 401 performs linear matrix calculation for improving color reproducibility on an image signal having only a low-frequency component suitable for color signal correction, and performs processing. The later low frequency component and the high frequency component not subjected to the linear matrix calculation are added by the MIX circuit 48 and output.

  For example, as in the conventional configuration shown in FIG. 10, processing for improving color reproducibility by linear matrix calculation including a negative coefficient is uniformly applied to the entire band of the RGB signal output from the image interpolation circuit 44. In this case, a subtraction process that degrades the S / N is performed on a signal that includes a high-frequency component that is unnecessary in the band of the final color signal. For this reason, the influence of noise included in the high-frequency signal affects the low-frequency color signal, and the S / N of the color signal is more significantly degraded.

  On the other hand, by adopting the configuration as shown in FIG. 2, the linear matrix operation is performed only on the low frequency component, thereby producing the effect of improving the color reproducibility, but the S / N degradation due to the subtraction process. Can be suppressed.

FIG. 3 is a diagram illustrating a signal band in each part of the camera signal processing circuit according to the first embodiment.
FIG. 3 schematically shows signal bands of components G, B, and R at points A1, B1, C1, and D1 in the block diagram of FIG. In this figure, fs indicates a sampling frequency.

  First, in the output stage (point A1) of the image interpolation circuit 44, k and l in the figure are real numbers that satisfy l ≧ k> 0, and the pixel arrangement (filter coding) of the image sensor 2 and the image interpolation circuit 44 are the same. It is determined based on the signal processing method in In FIG. 3, as an example, a case will be described in which a frequency characteristic such that l = k is obtained by devising demosaic processing such as interpolation with pixel signals in an oblique direction.

  With respect to the image signal at the point A1, the image signal at the output stage (point B1) of the low-pass filter circuit 45 has a characteristic in which the band is limited to (1 / m) fs or less by the low-pass filter circuit 45. Further, the image signal at the output stage (point C1) of the subtracting circuit 46 has a band characteristic obtained by removing the component of the image signal at point B1 from the image signal at point A1.

  The image signal at the output stage (point D1) of the MIX circuit 48 has the same band characteristics as the point B1, and the low-frequency component subjected to signal correction in the linear matrix arithmetic circuit 41 and the white balance adjustment circuit 42a, This is a signal having the same band characteristic as that of the point C1 and a high frequency component subjected to signal correction in the white balance adjustment circuit 42b.

  Here, m is a real number that satisfies m> k> 0. In the low-pass filter circuit 45, basically, m is set so as to remove a high-frequency component that has an extremely small influence on the generation of a color signal (that is, a human can hardly visually recognize as a fine color change). Actually, the final output image format by the Y signal processing circuit 50 and the C signal processing circuit 51, the color signal processing after the low-pass filter circuit 45 (including the processing of the white balance adjustment circuit 42b), and the like are taken into consideration. The optimum value of m is set by a trade-off between image quality degradation such as noise and color blur and improvement in color resolution.

  With the above processing, the image quality correction processing by the linear matrix arithmetic circuit 41 is performed only on the low frequency components necessary for color recognition in terms of human visual characteristics, so that the color reproducibility of the output signal is ensured. improves. On the other hand, even when a calculation using a negative linear matrix coefficient is performed in the linear matrix calculation circuit 41, this linear matrix is not required for color signal processing and for a high frequency component containing a lot of noise components. Since no calculation is performed, the noise component is not increased as a result, and the deterioration of S / N is prevented. Therefore, it is possible to capture a high-quality image with high color reproducibility and inconspicuous noise.

Next, FIG. 4 is a block diagram showing a main configuration of an imaging apparatus according to the second embodiment of the present invention.
The camera signal processing circuit 4a shown in FIG. 4 is a functional block corresponding to the camera signal processing circuit 4 in the first embodiment, and the configuration of the high frequency processing unit 403 is different from that in the first embodiment. Different. The high frequency processing unit 403 includes a subtracting circuit 46 a that subtracts the G component of the output image signal from the low-pass filter circuit 45 from the G component of the output image signal from the image interpolation circuit 44. The output signal of the subtraction circuit 46a is input to the MIX circuit 48 as RGB signal components and added to the RGB components of the output image signal from the white balance adjustment circuit 42a.

FIG. 5 is a diagram showing signal bands in each part of the camera signal processing circuit according to the second embodiment.
In the output stage (point A2) of the image interpolation circuit 44, k and l in the figure are the pixel arrangement (filter coding) of the image sensor 2 and the signal processing in the image interpolation circuit 44, as in the first embodiment. It depends on the method. However, in FIG. 5, as in FIG. 3, as an example, a description will be given assuming that a frequency characteristic such that l = k is obtained.

  In contrast to the image signal at the point A2, the image signal at the output stage (point B2) of the low-pass filter circuit 45 has a characteristic whose band is limited to (1 / m) fs or less by the low-pass filter circuit 45. The image signal at the output stage (point C2) of the subtracting circuit 46a has a band characteristic obtained by removing the G component of the image signal at the point B2 from the G component of the image signal at the point A2.

  The image signal at the output stage (point D2) of the MIX circuit 48 has the same band characteristic as that of the point B2, and the low-frequency component subjected to signal correction in the linear matrix arithmetic circuit 41 and the white balance adjustment circuit 42a. Thus, the G component that combines only the high frequency components at the point C2 is a synthesized signal.

  In the camera signal processing circuit 4a according to the second embodiment, the spatial frequency characteristic of the G component is extremely high with respect to the R component and the B component, and the influence of the R component and the B component is small on the generation of the color signal. Suitable for the system. In such a system, by applying the above-described camera signal processing circuit 4a, it is possible to achieve both improvement in color reproducibility and prevention of S / N deterioration, and a circuit configuration as compared with the first embodiment. Is simplified and the processing load is reduced, so that effects such as circuit miniaturization, manufacturing cost reduction, and power consumption reduction can be obtained.

FIG. 6 is a diagram illustrating an example of filter coding suitable for the second embodiment. FIG. 7 is a diagram showing the spatial frequency characteristics when the filter coding of FIG. 6 is used.
The color filter array shown in FIG. 6 has a so-called oblique pixel array configuration in which a square lattice-like array such as a Bayer array is inclined by 45 °. In this pixel arrangement, the first line is a GR line in which G and R are alternately arranged, the second line is a G line in which only G is arranged, the third line is a GB line in which B and G are alternately arranged, and 4 lines The eye is a G line in which only G is arranged, and thereafter, the color filter is arranged by repeating these four rows as a unit.

  Here, as shown in FIG. 6, when the sampling rate of the G component in the horizontal / vertical direction is d, the G component is (1/2) fs (where fs = 1) in the horizontal / vertical direction from the sampling theorem. / D) can be captured. On the other hand, with respect to the R component and the B component, the sampling rate in the horizontal and vertical directions is 4d, and from the sampling theorem, signals with a frequency of (1/8) fs can be captured. The graph of FIG. 7 represents the above spatial frequency characteristics.

  On the other hand, the case of the Bayer array will be described for comparison with reference to FIGS. 8 and 9 below. FIG. 8 is a diagram illustrating filter coding of the Bayer array, and FIG. 9 is a diagram illustrating spatial frequency characteristics when the Bayer array is used.

  As shown in FIG. 8, in the case of the Bayer array, if the sampling rate corresponding to the pixel pitch in the horizontal / vertical direction is d, the G component is a signal having a frequency of (1/2) fs in the horizontal / vertical direction. As for the R component and the B component, a signal having a frequency of (1/4) fs can be captured. The graph of FIG. 9 represents the above spatial frequency characteristics.

  Here, it can be seen that when the filter coding of FIG. 6 is used, the difference in frequency characteristics between the G component, the R component, and the B component is larger than in the case of the Bayer array of FIG. The filter coding feature of FIG. 6 is that the G component is more sensitive than the R component and the B component in terms of human visual characteristics. It is the point which raises.

  When the G component band is sufficiently wide in the high frequency direction as compared with the R component and B component bands as in the filter coding of FIG. 6, the high frequency components of the R component and B component are finally Substantially does not contribute to the generation of a reliable image signal. For example, the high frequency component may contain almost no R component and B component signals.

  Therefore, in such a case, as in the configuration shown in FIG. 4, even if the G component is added as each color component in the MIX circuit 48, the image quality of the generated image is hardly affected. do not do. Therefore, by using the camera signal processing circuit 4a as shown in FIG. 4, it is possible to achieve both improved color reproducibility and S / N degradation while suppressing the circuit scale and processing load.

  However, even when Bayer array image sensors are used, or when individual image sensors are used for each color component, the sensitivity of the G component is relatively high and the R component and B component are high due to human visual characteristics. Since it can be said that the influence of the band component on the final image quality is small, even if the configuration of FIG. 4 is applied, it is possible to obtain the effect of achieving both improved color reproducibility and S / N degradation. .

  In each of the above embodiments, the case where functions such as a low-frequency processing unit, a high-frequency processing unit, a MIX circuit, and an integration circuit are incorporated as hardware on a camera signal processing circuit has been described. These functions or a part thereof can also be realized by software processing in the system controller 5. In this case, a program for realizing the function is stored in a ROM or a nonvolatile memory in the system controller 5.

  The present invention also provides various imaging devices using solid-state imaging devices such as digital video cameras and digital still cameras, and devices such as mobile phones and PDAs (Personal Digital Assistants) having such imaging functions. Can be applied. Furthermore, the present invention can also be applied to a processing device and a recording device for an image signal by a small camera such as a videophone or game software connected to a PC (personal computer) or the like. The present invention can also be applied to an image processing apparatus that receives image signal input and corrects image quality.

  Further, the above processing functions can be realized by a computer. In that case, a program describing the processing contents of the functions that the apparatus should have (image quality correction function in the camera signal processing circuit, composition ratio setting function by the microcontroller, etc.) is provided. And the said processing function is implement | achieved on a computer by running the program with a computer. The program describing the processing contents can be recorded on a computer-readable recording medium. Examples of the computer-readable recording medium include a magnetic recording device, an optical disk, a magneto-optical disk, and a semiconductor memory.

  In order to distribute the program, for example, portable recording media such as an optical disk and a semiconductor memory on which the program is recorded are sold. It is also possible to store the program in a storage device of a server computer and transfer the program from the server computer to another computer via a network.

  The computer that executes the program stores, for example, the program recorded on the portable recording medium or the program transferred from the server computer in its own storage device. Then, the computer reads the program from its own storage device and executes processing according to the program. The computer can also read the program directly from the portable recording medium and execute processing according to the program. Further, each time the program is transferred from the server computer, the computer can sequentially execute processing according to the received program.

1 is a block diagram illustrating a main configuration of an imaging apparatus according to a first embodiment of the present invention. It is a block diagram which shows the principal part structure of a camera signal processing circuit. It is a figure which shows the signal band in each part of the camera signal processing circuit which concerns on 1st Embodiment. It is a block diagram which shows the principal part structure of the imaging device which concerns on the 2nd Embodiment of this invention. It is a figure which shows the signal band in each part of the camera signal processing circuit which concerns on 2nd Embodiment. It is a figure which shows an example of the filter coding suitable for 2nd Embodiment. It is a figure which shows the spatial frequency characteristic at the time of using the filter coding of FIG. It is a figure which shows the filter coding of a Bayer array. It is a figure which shows the spatial frequency characteristic at the time of using a Bayer arrangement | sequence. It is a block diagram which shows the principal part structure of the conventional imaging device containing a linear matrix calculation function.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical block, 2 ... Image sensor, 3 ... AFE (analog front end) circuit, 4 ... Camera signal processing circuit, 5 ... System controller, 6 ... Input part, 11 ... Driver, 12 ... ... TG (timing generator), 41... Linear matrix arithmetic circuit, 42, 42 a, 42 b... White balance adjustment circuit, 43 ... pre-correction circuit, 44 ... image interpolation circuit, 45 ... low-pass filter circuit, 46. ... subtraction circuit, 47a, 47b ... integration circuit, 48 ... MIX circuit, 49 ... γ correction circuit, 50 ... Y signal processing circuit, 51 ... C signal processing circuit, 401 ... low-frequency processing unit, 402 ...... High frequency processing section

Claims (8)

In an image processing apparatus that performs color correction processing on an input image signal,
Band separation means for separating the input image signal into a high frequency component and a low frequency component;
Linear matrix computing means for matrix-converting the color components of the low frequency components separated by the band separating means;
Signal adding means for adding the low frequency component subjected to matrix conversion by the linear matrix calculating means and the high frequency component separated by the band separating means;
I have a,
The band separation means outputs a signal obtained by band-limiting each color component of the input image signal as the low-frequency component, and outputs a signal obtained by band-limiting only the G component of the input image signal as the high-frequency component,
The signal adding means adds the same high frequency component including only the G component output from the band separating means to each color component of the low frequency component subjected to matrix conversion by the linear matrix calculating means,
An image processing apparatus.   In an image processing apparatus that performs color correction processing on an input image signal,
  Band separation means for separating the input image signal into a high frequency component and a low frequency component;
  Linear matrix computing means for matrix-converting the color components of the low frequency components separated by the band separating means;
  Signal adding means for adding the low frequency component subjected to matrix conversion by the linear matrix calculating means and the high frequency component separated by the band separating means;
  Have
  An image processing apparatus according to claim 1, wherein a frequency to be separated is set in the band separation unit so that the high frequency component does not affect generation of a color signal in a subsequent stage of the signal addition unit.   In an imaging device that captures an image using a solid-state imaging device,
  Band separation means for separating an image signal obtained by imaging into a high-frequency component and a low-frequency component;
  Linear matrix computing means for matrix-converting the color components of the low frequency components separated by the band separating means;
  Signal adding means for adding the low frequency component subjected to matrix conversion by the linear matrix calculating means and the high frequency component separated by the band separating means;
  Have
  The band separation unit outputs a signal obtained by band-limiting each color component of the image signal as the low-frequency component, and outputs a signal obtained by band-limiting only the G component of the image signal as the high-frequency component,
  The signal adding means adds the same high frequency component including only the G component output from the band separating means to each color component of the low frequency component subjected to matrix conversion by the linear matrix calculating means,
  An imaging apparatus characterized by that.   In an imaging device that captures an image using a solid-state imaging device,
  Band separation means for separating an image signal obtained by imaging into a high-frequency component and a low-frequency component;
  Linear matrix computing means for matrix-converting the color components of the low frequency components separated by the band separating means;
  Signal adding means for adding the low frequency component subjected to matrix conversion by the linear matrix calculating means and the high frequency component separated by the band separating means;
  Have
  The imaging apparatus according to claim 1, wherein a frequency to be separated is set in the band separation unit so that the high-frequency component does not affect generation of a color signal in a subsequent stage of the signal addition unit.   In an image processing method for performing color correction processing on an input image signal,
  Band separation means separates the input image signal into a high frequency component and a low frequency component,
  A linear matrix computing means matrix-converts the color component of the low frequency component separated by the band separating means;
  A signal adding means adds the low frequency component subjected to matrix conversion by the linear matrix calculating means and the high frequency component separated by the band separating means;
  Execute the process,
  The band separation means outputs a signal obtained by band-limiting each color component of the input image signal as the low-frequency component, and outputs a signal obtained by band-limiting only the G component of the input image signal as the high-frequency component,
  The signal adding means adds the same high frequency component including only the G component output from the band separating means to each color component of the low frequency component subjected to matrix conversion by the linear matrix calculating means,
  An image processing method.   In an image processing method for performing color correction processing on an input image signal,
  Band separation means separates the input image signal into a high frequency component and a low frequency component,
  A linear matrix computing means matrix-converts the color component of the low frequency component separated by the band separating means;
  A signal adding means adds the low frequency component subjected to matrix conversion by the linear matrix calculating means and the high frequency component separated by the band separating means;
  Execute the process,
  An image processing method according to claim 1, wherein a frequency to be separated is set in the band separation unit so that the high frequency component does not affect generation of a color signal in a subsequent stage of the signal addition unit.   In an image processing program for causing a computer to execute color correction processing on an input image signal,
  The computer,
  Band separation means for separating the input image signal into a high frequency component and a low frequency component;
  Linear matrix computing means for matrix-converting the color components of the low frequency components separated by the band separating means;
  A signal adding means for adding the low frequency component subjected to matrix conversion by the linear matrix calculating means and the high frequency component separated by the band separating means;
  Function as
  The band separation means outputs a signal obtained by band-limiting each color component of the input image signal as the low-frequency component, and outputs a signal obtained by band-limiting only the G component of the input image signal as the high-frequency component,
  The signal adding means adds the same high frequency component including only the G component output from the band separating means to each color component of the low frequency component subjected to matrix conversion by the linear matrix calculating means,
  An image processing program characterized by that.   In an image processing program for causing a computer to execute color correction processing on an input image signal,
  The computer,
  Band separation means for separating the input image signal into a high frequency component and a low frequency component;
  Linear matrix computing means for matrix-converting the color components of the low frequency components separated by the band separating means;
  A signal adding means for adding the low frequency component subjected to matrix conversion by the linear matrix calculating means and the high frequency component separated by the band separating means;
  Function as
  An image processing program characterized in that a frequency to be separated is set in the band separation unit so that the high-frequency component does not affect generation of a color signal in a subsequent stage of the signal addition unit.

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