JP2010004472A - Image conversion device, and electronic apparatus including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image conversion device capable of reducing deterioration in a resolution feeling of an edge portion of an output image even when the number of pixels in RAW data is converted. <P>SOLUTION: The image conversion device for converting the number of pixels in RAW data outputted by converting optical information passed through a color filter into an electric signal includes: a luminance component filter circuit for applying low pass filter processing to the RAW data and generating a luminance component signal; a circuit for converting number of pixels for the luminance component for applying processing of converting the number of pixels for the luminance component signal and generating a signal converted in the number of pixels for the luminance component; a color component filter circuit for performing band pass filter processing for finding a difference between a digital image signal and the luminance component signal and generating first and second color component signals; a circuit for converting numbers of pixels for first and second color components for applying processing of converting the number of pixels for the first and second color component signals; and a synthesizing circuit for synthesizing the signal converted in the number of pixels for the luminance component and signals converted in the numbers of pixels for the first and second color components. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image conversion apparatus and an electronic apparatus including the same, and more particularly to an image conversion apparatus using RAW data and an electronic apparatus including the same.

  2. Description of the Related Art Conventionally, in an image conversion apparatus included in a camera or the like, various pixel number conversion processes such as aspect conversion and thumbnail generation are performed on digital data. Specifically, the pixel number conversion process is to convert frame data of a video signal configured with a predetermined number of pixels into data configured with a number of pixels different from the original frame data by a filtering process or the like. . The pixel number conversion process is generally performed using digital image data (Y, Cr, Cb) that has been subjected to luminance / color difference separation processing. In order to obtain the digital image data (Y, Cr, Cb), it is necessary to perform a plurality of processes such as a color difference matrix process, a white balance process, and a gamma correction process before performing the luminance / color difference separation process.

  However, in recent years, due to the demand for space saving accompanying the downsizing of electronic devices, circuit space cannot be secured, and electronic devices having a function of outputting RAW data (hereinafter referred to as RAW data) have been developed. Therefore, it is required to handle RAW data as processed data without performing the above-described plurality of processes.

  In this case, for example, as shown in FIG. 6, in an image conversion apparatus 200 including an image sensor 215 such as a CCD, analog RAW data for each pixel output from the image sensor 215 and converted into an analog signal by the analog signal processing circuit 217. Are converted into digital RAW data by the A / D conversion circuit 218, and the RAW data after the digital conversion is directly processed. The image conversion apparatus 200 includes a drive timing control circuit that controls operations and timings of the image sensor 216 and the analog signal processing circuit 217.

  Here, the image sensor 215 includes a color filter. For this reason, the output signal includes a color component. And when performing pixel number conversion with respect to RAW data containing this color component, the filtering process part 23 performs a filtering process with respect to data, and a thinning-out process is performed after that. As shown in FIG. 6, in the filtering process when RAW data is handled, the RAW data is delayed by one clock by the DFFs 219 to 222, and the filtering process is performed on the data using a predetermined filtering coefficient.

In addition, the RAW data in the image conversion apparatus 200 including the image sensor 215 to which the color filter is attached is composed of a plurality of pixels having different color arrangements. Therefore, in order to prevent the colors synthesized by the filtering process from being mixed, it is necessary to perform the filtering process for each color. The RAW data output from the A / D conversion circuit 218 is the same color data every other clock due to the periodicity of the color in the color filter. Therefore, in such a configuration, the filtering process is performed on RAW data every other clock.
JP 2003-346143 A (published on December 5, 2003) JP 2004-260813 A (published on September 16, 2004)

  However, due to the color arrangement of the RAW data as described above, in the filtering process performed on the data every other clock, the relevance with the temporally adjacent data is lost. Accordingly, the continuity of the luminance component is lost and the frequency characteristics are deteriorated, so that the resolution (look) of the edge portion in the output image is deteriorated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image conversion apparatus that can reduce deterioration in the resolution of an edge portion in an output image even if the number of pixels is converted to RAW data.

  An image conversion apparatus according to a first aspect of the present invention is an image conversion apparatus that performs pixel number conversion on a RAW-format digital signal that is output after optical information that has passed through a color filter is converted into an electrical signal, and includes a luminance component A filter circuit, a luminance component pixel number conversion circuit, a color component filter circuit, a first color component pixel number conversion circuit, a second color component pixel number conversion circuit, and a synthesis circuit are provided. The luminance component filter circuit generates and outputs a luminance component signal by performing low-pass filtering on the RAW format digital signal. The luminance component pixel number conversion circuit performs a pixel number conversion process on the luminance component signal and outputs a luminance component pixel number conversion signal. The color component filter circuit generates and outputs a first color component signal and a second color component signal by performing band-pass filter processing that takes a difference between the digital video signal and the luminance component signal. The first color component pixel number conversion circuit performs a pixel number conversion process on the first color component signal and outputs a first color component pixel number conversion signal. The second color component pixel number conversion circuit performs a pixel number conversion process on the second color component signal and outputs a second color component pixel number conversion signal. The combining circuit combines the luminance component pixel number conversion signal, the first color component pixel number conversion signal, and the second color component pixel number conversion signal.

  Here, in an image conversion apparatus that performs pixel number conversion such as enlargement or reduction on a RAW-format digital signal (RAW data) having color information, in an output image, while reducing deterioration in frequency characteristics of luminance components. In order to enable conversion of the number of pixels without impairing the resolution of the edge portion, the following configuration is adopted.

  The image conversion apparatus according to the present invention is not directed to RAW data that is skipped by one as in the conventional case, but also to RAW data that is temporally adjacent to the RAW data converted into a digital format, that is, all The RAW data is subjected to low-pass filter processing to extract a luminance component signal. Further, the color component signal is extracted by taking the difference between the luminance component signal and the RAW data (by performing band-pass filter processing). Here, the data that has undergone the bandpass filter processing is separated into two types of color component signals due to the periodicity of the color arrangement. That is, a first color component signal and a second color component signal are generated. In the component pixel number conversion circuit, pixel number conversion processing is performed on the luminance component signal and the two types of color component signals. Further, the respective signals subjected to the pixel number conversion are synthesized by the synthesis circuit and become RAW data again.

  Here, the pixel number conversion is an enlargement process or reduction process of the number of pixels in various signals. The low-pass filter process is a process that allows only a signal having a frequency equal to or lower than a predetermined frequency to pass. The band-pass filter process is a process that allows only a signal having a frequency within a predetermined range to pass. The RAW format digital signal (RAW data) is data in a state where processing for image conversion is not performed.

  With such a configuration, in the RAW data, it is possible to perform the conversion processing of the number of pixels on the data corresponding to all the pixels for each clock. Therefore, the continuity of the luminance component is maintained, and it is possible to prevent the resolution of the edge portion in the output image from being impaired.

  As a result, it is possible to perform conversion of the number of pixels while suppressing deterioration in image quality even with a simpler circuit configuration than in the past.

  An image conversion apparatus according to a second invention is the image conversion apparatus according to the first invention, and further comprises a first color component band limiting circuit and a second color component band limiting circuit. The first color component band limiting circuit limits the frequency band of the first color component signal provided between the color component filter circuit and the first color component pixel number conversion circuit. The second color component band limiting circuit limits the frequency band of the second color component signal provided between the color component filter circuit and the second color component pixel number conversion circuit.

Here, the component band of the first color component signal is limited by the first color component band limiting circuit, and the component band of the second color component signal is limited by the second color component band limiting circuit.
Here, the limitation of the component band means that a predetermined frequency component is limited by filtering processing among the frequency components of the signal.

As a result, the color component signal is limited by the color component band limiting circuit depending on the frequency band before the conversion of the number of pixels. This is because when the first and second color component pixel number conversion circuits reduce (decimate) color component data, false colors are generated in the output image. That is, by performing frequency band restriction (for example, low-pass filter processing) before performing pixel number conversion (for example, reduction) on the color components, it is possible to prevent the occurrence of false colors.
As a result, it is possible to reduce the deterioration of the texture of the output image due to the pixel number conversion.

  An image conversion device according to a third invention is the image conversion device according to the second invention, and further includes a control unit. The control unit sets the filtering coefficient in the luminance component filter circuit based on the magnification of enlargement or reduction applied in the luminance component pixel number conversion circuit.

Here, the filtering coefficient in the luminance component filter circuit is set by the control unit based on the conversion rate of the number of pixels in the luminance component pixel number conversion circuit.
Thereby, for example, when the output image is reduced to ½ in the luminance component pixel number conversion circuit, a filtering coefficient corresponding to the reduction rate can be used.

  As a result, it is possible to limit an extra frequency in the luminance component signal, and it is possible to prevent the sense of resolution in the output image from being impaired while reducing the processing load.

  An image conversion apparatus according to a fourth aspect of the present invention is the image conversion apparatus according to the third aspect of the present invention, in which the control unit calculates the first and second filtering coefficients in the first and second color component band limiting circuits. This is set based on the magnification of enlargement or reduction applied in the color component pixel number conversion circuit.

Here, the respective filtering coefficients in the first and second color component band limiting circuits are changed based on the conversion rate of the number of pixels in the color component pixel number conversion circuit.
As a result, before the conversion of the number of pixels is performed in the first and second color component pixel number conversion circuits, it is possible to limit to data having an appropriate frequency band.

  As a result, for example, even when reduction conversion is performed, the high frequency component is limited by the frequency band limiting circuit, so that it is possible to reduce the occurrence of false colors in the output image.

  An image conversion apparatus according to a fifth aspect of the present invention is the image conversion apparatus according to any one of the first to fourth aspects of the present invention, comprising an imaging device, an analog signal processing circuit, a drive timing control circuit, an A / And a D conversion circuit. The imaging device has a color filter, converts optical information into an electrical signal, and outputs the electrical signal. The analog signal processing circuit converts the electrical signal into an analog video signal and outputs it. The drive timing control circuit performs drive control of the image sensor and timing control of the analog signal processing circuit. The A / D conversion circuit converts the analog video signal into a digital video signal and outputs the digital video signal.

Here, the image conversion apparatus further includes a circuit for converting a signal having color information output by an imaging device having a color filter into a digital video signal.
Here, for example, the image sensor may convert optical information such as a CCD into an electrical signal. The output digital video signal is RAW format digital data.

Thereby, the optical information acquired through the color filter can be converted into digital data in RAW format to which a synchronization signal is added.
As a result, it is possible to form RAW format digital data suitable for image processing. Therefore, various data processing and image conversion can be performed in the subsequent data processing.

An electronic apparatus according to a sixth aspect of the invention includes the image conversion apparatus according to any one of the first to fifth aspects of the invention.
Here, the electronic device may be, for example, a camera that captures a moving image or a still image.

  Accordingly, it is possible to provide an image conversion apparatus capable of performing pixel number conversion without deteriorating the luminance component and impairing the resolution of the edge portion even by processing with raw data.

  According to the present invention, it is possible to generate an output image in which the frequency characteristics of the edge portion are good even when the number of pixels of the RAW format data is converted.

  A camera (electronic device) 110 including an image conversion apparatus 100, a lens 1, a storage unit 30, and an input unit 32 according to an embodiment of the present invention will be described below with reference to FIGS. .

[Configuration of the entire camera 110]
As shown in FIG. 1, the camera 110 of the present embodiment includes a lens 1, a color filter 2 a, an image sensor 2, an analog signal processing circuit 3, a drive timing control circuit 4, and an A / D conversion circuit 5. The luminance component filter circuit 6, the color component filter circuit 7, the luminance component pixel number conversion circuit 8, the first and second color component band limiting circuits 9, 10, and the first and second color component pixel number conversion circuits. , A storage unit 30, a control unit 31, and an input unit 32.

  The lens 1 is a transparent convex lens, and incorporates reflected light from a subject as a light image into a camera casing. The acquired light image is condensed in the direction of the color filter 2 a and formed on the light receiving surface of the image sensor 2.

  The color filter 2 a allows light of a specific wavelength in the optical image taken in by the lens 1, and is provided in the image sensor 2. As shown in FIG. 2, the color filter 2a according to the present embodiment has a field color difference sequential arrangement, and four types of color filters of Ye (yellow), Cy (cyan), and Mg (magenta) G (green). It is constituted by. Specifically, the color filter 2a is arranged such that lines in which Ye and Cy are alternately arranged in the horizontal direction and lines in which Mg and G are alternately arranged in the horizontal direction are alternately arranged in the vertical direction. ing.

  The image pickup device 2 converts optical information contained in the light that has passed through the color filter 2a into an electrical signal. In the present embodiment, a CCD (Charge Coupled Device) is employed. The CCD has a plurality of light receiving elements on the light receiving surface of the light acquired through the lens 1. The plurality of light receiving elements perform so-called photoelectric conversion in which the acquired light energy is converted into electrical energy.

  The analog signal processing circuit 3 is electrically connected to the image sensor 2, performs a sample and hold process on the electric signal converted by the image sensor 2, and outputs an analog video signal. The analog signal processing circuit 3 adds a synchronization signal (clock frequency) to the generated analog video signal.

  The drive timing control circuit 4 is electrically connected to the image sensor 2 and the analog signal processing circuit 3, and performs drive control of the image sensor 2 and timing control of the analog signal processing circuit 3.

  The A / D conversion circuit 5 is electrically connected to the analog signal processing circuit 3, and converts the analog video signal generated and output by the analog signal processing circuit 3 into a digital video signal and outputs the digital video signal. Here, the digital video signal output from the A / D conversion circuit 5 is RAW-format digital data (RAW data).

  The luminance component filter circuit 6 is electrically connected to the A / D conversion circuit 5 and includes a low-pass filter 28 including a plurality of DFFs (Delay Flip Flops) 24-27 formed from a plurality of electronic elements ( (See FIG. 3). The luminance component filter circuit 6 generates a luminance component signal from the digital video signal output from the A / D conversion circuit 5 using the low-pass filter 28.

  The low-pass filter 28 removes a signal having a frequency exceeding a predetermined frequency. The filtering coefficient of the low-pass filter 28 is set by the control unit 31 based on the conversion rate of the number of pixels desired by the user. Specifically, as illustrated in FIG. 5, a filtering coefficient corresponding to the pixel number conversion rate input by the user is stored in the control unit 31 in advance. For example, when the reduction ratio is 3/4, the filtering coefficient is, for example, [1 · 4 · 6 · 4 · 1]. When the reduction ratio is 1/2, the filtering coefficient is, for example, [1 · 6 · 10 · 6 · 1]. When the enlargement ratio is 1 or more, the filtering coefficient is [0 · 1 · 2 · 1 · 0]. That is, basically, a coefficient is set such that the cutoff frequency of the low-pass filter decreases as the reduction ratio increases.

  The luminance component pixel number conversion circuit 8 is electrically connected to the luminance component filter circuit 6 and receives the luminance component signal output from the luminance component filter circuit 6. The luminance component pixel number conversion circuit 8 first performs a filtering process on the luminance component signal based on the conversion rate of the number of pixels desired by the user. In this embodiment, the filtering coefficient here includes five coefficients, and is set by the control unit 31 based on the reduction rate (or enlargement rate) of the pixel number conversion. Specifically, a filtering coefficient corresponding to the pixel number conversion rate determined by the user is stored in the control unit 31 in advance. These filtering coefficients are, for example, [0.1.2.2.0] when the pixel number conversion desired by the user is enlargement processing. On the other hand, when the pixel number conversion is a reduction process, the filtering coefficient further restricts the high-frequency component as the reduction ratio increases (for example, from a reduction ratio of 3/4 to a reduction ratio of 1/5). It is set to a value that makes the signal smoother.

  Next, the luminance component pixel number conversion circuit 8 converts the number of pixels. For example, in the case of reduction to 1/2, the luminance component pixel number conversion circuit 8 thins out one data every two. The luminance component pixel number conversion circuit 8 outputs a luminance component pixel number conversion signal by performing these processes.

  The color component filter 7 is electrically connected to the A / D conversion circuit 5 and the luminance component filter circuit 6 and has a band pass filter. Specifically, bandpass filter processing is performed by taking the difference between the digital video signal output from the A / D conversion circuit 5 and the luminance component signal output from the luminance component filter circuit 6. The luminance component filter circuit 6 outputs a luminance component signal, while the color component filter 7 generates and outputs a first color component signal and a second color component signal. Here, as shown in FIG. 2, the first color component is composed of Ye + Mg in the N1 line, and the second color component is composed of Cy + G. On the other hand, in the N2 line, the first color component is Ye + G, and the second color component is Cy + Mg.

  The first color component band limiting circuit 9 performs a filtering process for limiting the frequency band of the first color component signal. This filtering process is performed in order to suppress the occurrence of false colors in the output image, particularly in the reduction conversion when the color component signal includes a high frequency component. The filtering coefficient here is set by the control unit 31 based on the conversion rate of the pixel number conversion, that is, the reduction rate (enlargement rate) desired by the user (see FIG. 5). Then, a first color component band limited signal in which frequency components (mainly high frequency components) are limited by this filtering process is generated and output.

  The second color component band limiting circuit 10 performs a filtering process for limiting the frequency band of the second color component signal. The filtering process here is the same as the filtering process performed by the first color component band limiting circuit 9. Then, by this filtering process, a second color component band limited signal is generated and output.

  The first color component pixel number conversion circuit 11 is electrically connected to the first color component band limiting circuit 9 and receives the first color component band limiting signal. Then, the first color component pixel number conversion circuit 11 performs filtering processing and pixel number conversion processing (for example, reduction conversion) on the band-limited first color component signal based on the enlargement ratio or reduction ratio desired by the user. If so, the data is thinned out. By this processing, a first color component pixel number conversion signal is generated. The first color component pixel number conversion signal is transmitted to the synthesis circuit.

  The second color component pixel number conversion circuit 12 is electrically connected to the second color component band limiting circuit 10 and receives the second color component band limiting signal. Then, the second color component pixel number conversion circuit 12 performs filtering processing and pixel number conversion processing (for example, reduction conversion) on the band-limited second color component signal based on the enlargement ratio or reduction ratio desired by the user. If so, the data is thinned out. By this filtering process, a second color component pixel number conversion signal is generated. The second color component pixel number conversion signal is transmitted to the synthesis circuit.

  The composition circuit 13 is electrically connected to the luminance component pixel number conversion circuit 8, the first color component pixel number conversion circuit 11, and the second color component pixel number conversion circuit 12, and outputs a luminance component pixel number conversion signal. The first color component pixel number conversion signal and the second color component pixel number conversion signal are received. The synthesis circuit 13 synthesizes and outputs the received signals. The signal synthesized by the synthesizing circuit 13 becomes the same RAW data (RAW data) as the data formation after A / D conversion.

The storage unit 30 stores the RAW data output from the synthesis circuit 13.
The input unit 32 is for a user to input a desired operation to the camera 110. Specifically, the input unit 32 includes a touch panel, a plurality of buttons, a switch, and the like. The user can operate the camera 110 by operating input means such as these buttons.

  The control unit 31 is functionally formed in the image conversion apparatus 100 by a CPU, a RAM, a ROM, and the like, and controls the operation of the camera 110. The control unit 31 mainly controls the operation of the image conversion apparatus 100 based on the input information transmitted from the input unit 32. For example, when the conversion rate of pixel number conversion such as enlargement or reduction in the image conversion apparatus 100 is input, or when an operation in which a predetermined conversion rate such as thumbnail creation is set in advance is input, the control unit 31. As described above, the filtering coefficient of the filtering circuit provided in the image conversion apparatus 100 is set. In addition, as shown in FIG. 5, a correspondence table between the conversion rate of the number of pixels and the filtering coefficient is stored in the ROM of the control unit 31 in advance. Therefore, when the conversion rate of the number of pixels desired by the user is transmitted from the input unit 32, the control unit 31 reads this correspondence table and sets each filtering coefficient in each corresponding circuit.

<Pixel Number Conversion Process in Camera 110>
Hereinafter, the pixel number conversion processing in the camera 110 of the present embodiment will be described. Here, it is assumed that the RAW data output from the image sensor 2 forms a pixel array in the color filter 2a of the camera. Here, the color filter 2a is a complementary single plate type filter as shown in FIG.

  First, reflected light or the like reflected by the subject is captured from the lens 1 as an optical image (optical information). The light image taken from the lens 1 is formed on the light receiving surface of the image sensor 2 via the color filter 2a.

  The formed optical image is read into the image sensor 2 by performing interlace reading for each field. Further, as shown in FIG. 2, the pixel area read out by the field is changed one pixel at a time in the vertical direction. Further, the color component of the pixel read out varies from line to line. For this reason, the color component added vertically changes. Specifically, for example, in the first field, scanning is performed with an N1 line from which Ye + Mg and Cy + G are read dot-sequentially and an N2 line from which Ye + G and Cy + Mg are read point-sequentially. Thereafter, data read by this scanning is transferred as time-series data for each line.

  The light image formed on the light receiving surface of the image sensor 2 is photoelectrically converted and converted into an electrical signal. The electric signal is converted into an analog video signal by the analog signal processing circuit 3. Here, an electrical signal is sampled and held, and an analog video signal to which a synchronization signal is added is generated.

  The analog video signal is converted into digital video signals D1 to D6 by the A / D conversion circuit 5. Specifically, an analog video signal is processed in two steps: spatial discretization that converts image coordinates into discrete values, and signal intensity discretization that converts image shading into discrete values. Then, the digital video signals D1 to D6 are converted. The digital video signals D1 to D6 are signals generated every one clock, and one digital video signal D1 is generated for a predetermined clock T1, and thereafter, the digital video signal D2 and the digital video signal are in chronological order. D3,... Are generated. Here, the digital video signals D1 to D6 generated in each of the clocks T1 to T6 will be described.

  The digital video signals D1 to D6 are transferred to the luminance component filter circuit 6 and the color component filter circuit 7. In the luminance component filter circuit 6, the digital video signals D1 to D6 pass through the low-pass filter. Thereby, the luminance component signals Y1 to Y6 are generated from the digital video signals D1 to D6.

  The low-pass filter processing is performed using a filtering circuit (low-pass filter 28) as shown in FIG. This filtering circuit is a FIR (Finite Impulse Response) filter and includes, for example, four DFFs 24 to 27. Then, the respective data (digital video signals D1 to D6) generated by the DFFs 24 to 27 so that the timing is delayed by one clock are set by the control unit 31, for example, the filtering coefficients [0, 1, 2,. The luminance component signals Y1 to Y6 are generated by processing (multiplication, addition, division) using 1 · 0].

  Specifically, as shown in FIG. 4, the luminance component includes pixel data in a predetermined RAW format (referred to as Dn) and pixel data D (n−1) and D (n + 1) adjacent to the pixel data Dn. ) And generated. Therefore, the low-pass filter processing when the multiplication coefficient is [0 · 1 · 2 · 1 · 0] is represented by (D (n−1) + 2Dn + D (n + 1)) / 4 = Yn.

  The generated luminance component signals Y1 to Y6 are transferred to the luminance component pixel number conversion circuit 8 and the color component filter circuit 7, respectively. The luminance component signals Y1 to Y6 pass through an FIR filter that converts (reduces in this case) the number of pixels of the luminance component in the luminance component pixel number conversion circuit 8. Thereby, a luminance component pixel number conversion signal is generated. Next, when the pixel number conversion is a reduction process, a thinning process according to the reduction rate is performed. On the other hand, when the pixel number conversion is an enlargement process, a process such as data interpolation (pixel interpolation) is performed. Then, the signal subjected to these processes is transferred to the synthesis circuit 13.

  On the other hand, the digital video signals D1 to D6 transferred to the color component filter circuit 7 are subjected to a process excluding the luminance component signals Y1 to Y6 generated by the luminance component filter circuit 6, that is, a bandpass filter process. The color component signals Ca1 to Ca3 and the second color component signals Cb1 to Cb3 are converted.

  Specifically, as shown in FIG. 4, the color component signal is generated by taking the difference between the RAW format data and the luminance component generated from the RAW format data. For this reason, the band-pass filter processing is represented by Dn − ((D (n−1) + 2Dn + D (n + 1)) / 4) = Can (Cbn when n is an even number).

  As shown in FIG. 2, RAW format data is generated by reading each pixel of the N1 line and the N2 line in a dot-sequential manner. For this reason, different color components are generated by the clock T1 and the clock T2. That is, the first color component signal Ca1 (Ye + Mg) is generated at the clock T1 in the N1 line, and the second color component signal Cb1 (Cy + G) is generated at the clock T2. Specifically, the first color component signal Ca1 is Ca1 = D1-Y1 = (Ye-Cy) / 2, and the second color component signal Cb1 is Cb1 = D2-Y2 = (Cy-Ye) / 2. Become. Thus, since different color components are generated for each clock, two types of color component signals for each clock are generated for the filtered data.

  The first color component signals Ca <b> 1 to Ca <b> 3 are transferred to the first color component band limiting circuit 9 and subjected to a process for reducing the frequency band of the color component to half. The second color component signals Cb <b> 1 to Cb <b> 3 are transferred to the second color component band limiting circuit 10, and subjected to processing in which the frequency band of the color component is reduced to, for example, half. That is, the first and second color component band limiting circuits 9 and 10 limit the frequency band of the color component, and the first and second color component band limited signals are generated.

  The first color component band limited signal whose frequency band is limited is transferred to the first color component pixel number conversion circuit 11. Here, a pixel number conversion process is performed on the first color component band limited signal to generate a first color component pixel number conversion signal. The filtering process here is an FIR filtering process. Next, pixel number conversion processing is performed by thinning out data or interpolation. Note that the conversion rate of the pixel number conversion process here is the same as the conversion rate of the pixel number conversion process performed in the luminance component pixel number conversion circuit 8 described above.

  Further, the second color component band limit signal is transferred to the second color component pixel number conversion circuit 12. Here, a pixel number conversion process is performed on the second color component band limited signal to generate a second color component pixel number conversion signal. The filtering process here is an FIR filtering process. Next, pixel number conversion processing is performed by thinning out data or interpolation. Note that the conversion rate of the pixel number conversion process here is the same as the conversion rate of the pixel number conversion process performed in the luminance component pixel number conversion circuit 8 described above.

  The signals subjected to the conversion processing of the number of pixels in this way are combined by the combining circuit 13 and returned to RAW data (RAW data). The RAW data is stored in the storage unit 30.

[Features of camera 110]
(1)
In the image conversion apparatus 100 according to the present embodiment, as shown in FIG. 1, the number of pixels is converted to a RAW digital signal that is output after optical information that has passed through a color filter is converted into an electrical signal. The luminance component filter circuit 6, the luminance component pixel number conversion circuit 8, the color component filter circuit 7, the first color component pixel number conversion circuit 11, the second color component pixel number conversion circuit 12, and the synthesis circuit 13 And.

  Thereby, in the RAW data, it is possible to perform the conversion processing of the number of pixels on the data corresponding to all the pixels for each clock. Therefore, the continuity of the luminance component is maintained, and it is possible to prevent the resolution of the edge portion in the output image from being impaired. As a result, it is possible to perform conversion of the number of pixels while suppressing deterioration in image quality even with a simpler circuit configuration than in the past.

(2)
As shown in FIG. 1, the image conversion apparatus 100 according to the present embodiment includes a first color component band limiting circuit 9 and a second color component band limiting circuit 10.

  As a result, the first color component signals Ca1 to Ca3 and the second color component signals Cb1 to Cb3 are transmitted by the first and second color component band limiting circuits 9 and 10 so that the signals passing through the frequency band are converted before the pixel number conversion. Limited depending on. Therefore, generation of false colors can be prevented by performing frequency band restriction (for example, low-pass filter processing) before performing pixel number conversion (for example, reduction) on the color components. As a result, it is possible to reduce the deterioration of the texture of the output image due to the pixel number conversion.

(3)
In the image conversion apparatus 100 according to the present embodiment, as shown in FIG. 6, the filtering coefficient in the luminance component filter circuit 6 is based on the enlargement or reduction magnification applied in the luminance component pixel number conversion circuit 8. Set by

  Thereby, the filtering coefficient according to the reduction rate (magnification rate) which a user desires can be used. As a result, it is possible to limit an extra frequency in the luminance component signals Y1 to Y6, and it is possible to prevent the resolution in the output image from being impaired while reducing the processing load.

(4)
In the image conversion apparatus 100 according to this embodiment, as shown in FIG. 5, the filtering coefficients in the first and second color component band limiting circuits 9 and 10 are the first and second color component pixel number conversion circuits 11 and 10, respectively. 12 is set by the control unit 31 based on the magnification of enlargement or reduction applied at 12.

As a result, before the conversion of the number of pixels is performed in the first and second color component pixel number conversion circuits 11 and 12, it is possible to limit the data to an appropriate frequency band.
As a result, for example, it is possible to reduce the occurrence of false colors in the output image even for conversion rates of various numbers of pixels.

(5)
As shown in FIG. 1, the image conversion apparatus 100 according to the present embodiment further includes a lens 1, an image sensor 2, an analog signal processing circuit 4, a drive timing control circuit 3, and an A / D conversion circuit 5. I have.
As a result, it is possible to form RAW digital data suitable for image processing from the optical information taken from the lens 1.

[Other Embodiments]
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of invention.

(A)
In the above embodiment, the image conversion apparatus 100 has been described using an example in which the first color component band limiting circuit 9 and the second color component band limiting circuit 10 are provided. However, the present invention is not limited to this.

For example, the image conversion apparatus 100 may be configured not to include the first and second component band limiting circuits 9 and 10.
Also with such a configuration, the pixel number conversion apparatus 100 can process all adjacent data associated with each clock in the RAW data. Therefore, even with a simple configuration, the pixel number conversion apparatus 100 can perform pixel number conversion with reduced deterioration of luminance components.

(B)
In the above embodiment, an example in which the filtering coefficient is variable in the luminance component filter circuit 6, the first and second color component band limiting circuits 9, 10, and the first and second color component pixel number conversion circuits 11, 12 is given. Explained. However, the present invention is not limited to this.

  For example, the filtering coefficient may be fixed. This also makes it possible to convert the number of pixels by handling all the data in the RAW format data. Therefore, it is possible to reduce the deterioration of the luminance component as compared with the conventional case.

(C)
In the above embodiment, an example in which the image conversion apparatus 100 is provided in the camera 110 has been described. However, the present invention is not limited to this.

  For example, it may be mounted on other electronic devices that handle images and videos. Also by this, the same effect as the above-mentioned embodiment can be produced.

  The image conversion apparatus according to the present invention has an effect that the frequency characteristic of the luminance component does not deteriorate even if the conversion processing of the number of pixels is performed on the RAW format data of the acquired image (video). Widely applicable to electronic devices to be performed.

1 is a block diagram illustrating a configuration of a camera according to an embodiment of the present invention. The figure which shows the color component of the color filter of the camera shown in FIG. 1, and the color component of the data read from there. The block diagram which shows the structure of the filter of the camera shown in FIG. 2 is a time-series diagram for each clock of signal processing in the filtering of the camera shown in FIG. The figure which shows the correspondence table of the filtering coefficient and the pixel number conversion rate which the control part in the camera shown in FIG. 1 has memorize | stored. The block diagram which shows the structure of the conventional image converter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens 2 Image pick-up element 2a Color filter 3 Drive timing control circuit 4 Analog signal processing circuit 5 A / D conversion circuit 6 Luminance component filter circuit 7 Color component filter circuit 8 Luminance component pixel number conversion circuit 9 1st color component band limitation circuit 10 Second color component band limiting circuit 11 First color component pixel number conversion circuit 12 Second color component pixel number conversion circuit 13 Synthesis circuits 24-27 DFF
28 Low-pass filter 30 Storage unit 31 Control unit 32 Input unit 100 Image conversion device 110 Camera (electronic device)

Claims (6)

An image conversion device that performs pixel number conversion on a RAW-format digital signal that is output after optical information that has passed through a color filter is converted into an electrical signal,
A luminance component filter circuit that performs low-pass filtering on the data signal in the RAW format to generate and output a luminance component signal;
A luminance component pixel number conversion circuit that performs a conversion process of the number of pixels on the luminance component signal and outputs a luminance component pixel number conversion signal;
A color component filter circuit that performs band-pass filter processing for taking a difference between the digital video signal and the luminance component signal, and generates and outputs a first color component signal and a second color component signal;
A first color component pixel number conversion circuit that performs a pixel number conversion process on the first color component signal and outputs a first color component pixel number conversion signal;
A second color component pixel number conversion circuit that performs a pixel number conversion process on the second color component signal and outputs a second color component pixel number conversion signal;
A combining circuit that combines the luminance component pixel number conversion signal, the first color component pixel number conversion signal, and the second color component pixel number conversion signal;
An image conversion apparatus comprising:
A first color component band limiting circuit that limits a frequency band of the first color component signal provided between the color component filter circuit and the first color component pixel number conversion circuit;
A second color component band limiting circuit that limits a frequency band of the second color component signal provided between the color component filter circuit and the second color component pixel number conversion circuit;
Further equipped with,
The image conversion apparatus according to claim 1.
A control unit that sets a filtering coefficient in the luminance component filter circuit based on an enlargement or reduction ratio applied in the luminance component pixel number conversion circuit;
The image conversion apparatus according to claim 2.
The control unit sets respective filtering coefficients in the first and second color component band limiting circuits based on magnification of enlargement or reduction performed in the first and second color component pixel number conversion circuits;
The image conversion apparatus according to claim 3.
An image sensor having a color filter and converting optical information into an electrical signal and outputting the electrical signal;
An analog signal processing circuit that converts the electrical signal into an analog video signal and outputs the analog video signal;
A drive timing control circuit that performs drive control of the image sensor and timing control of the analog signal processing circuit;
An A / D conversion circuit for converting the analog video signal into a digital video signal and outputting the digital video signal;
Further comprising
The image conversion apparatus of any one of Claim 1 to 4.
  An electronic device comprising the image conversion apparatus according to claim 1.

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