JP2006020251A - Photographing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain satisfactory image quality having less noise sense without deteriorating the resolution of an image. <P>SOLUTION: A multiplexer 24 separates image data into R, G and B data, and a block forming circuit 32 separates the G data in m×n unit blocks. A DCT circuit 34 applies DCT operation to each block, and a high-pass component accumulating circuit 36 accumulates high-pass components. Each block is ranked in eight stages in accordance with the size of accumulated value, is provided with any of indices 0-7 according to its rank, and is stored in a coring table 38. A process circuit 26 converts the R, G and B data into a luminance signal Y and color difference signals Cr, Cb, a two-dimensional contour emphasis processing circuit 28 divides the subtracted luminance signal Y into a low-pass component and a high-pass component, and contour emphasis processing is applied to the high-pass component. This luminance signal Y and the color difference signals Cr, Cb are transmitted to a coring processing circuit 30, and the coring table 38 is referred to perform coring table processing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photographing apparatus, and more particularly to a photographing apparatus such as a digital camera or a camera-equipped mobile phone.

  An invention is known that reduces noise generated in a still image of a digital camera to make it inconspicuous (for example, Patent Document 1). In the present invention, the luminance signal Y and the color difference signals Cr and Cb obtained by performing predetermined processing on the image signal output from the solid-state imaging device (CCD or the like) are frequency-resolved by a discrete cosine transform circuit, and the components are quantized. Divide by the table value, encode the obtained quotient, compress the data, and record it on the recording medium. When quantizing, the normal quantization table and the frequency band with a lot of visual noise Thus, the visual compensation table for making the noise less noticeable by switching the corresponding divisor to a large value is switched as necessary.

JP-A-6-006748

  As described in the above-mentioned Patent Document 1, the above-described visual correction table includes a defect that the resolution of an image is lowered. To avoid this, it is limited to long-time exposure that is easily affected by noise. It is said that it is better to use it, and there is a problem in practicality.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a photographing apparatus capable of obtaining a good image quality with little noise feeling without reducing the resolution of an image.

  The image capturing apparatus of the present invention converts an image signal output from a solid-state image sensor into digital image data, and performs image coring processing on the image data. Divide and perform discrete cosine transform on the luminance data of each block to measure the high frequency component contained in each block, and for the block with relatively few high frequency components, the coring amount used for coring processing And a coring amount is reduced for a block having a relatively high frequency component.

  Further, in an imaging device that converts an image signal output from a solid-state image sensor into digital image data and performs coring processing on the image data, image data for one screen is divided into a plurality of blocks, and each block The high-frequency component included in each block is measured by passing the luminance data of each block through a high-pass filter, and the amount of coring used for coring processing is increased for blocks with relatively low high-frequency components. The feature is that the coring amount is reduced for a block having a relatively large number of components.

  Further, in an imaging device that converts an image signal output from a solid-state image sensor into digital image data and performs coring processing on the image data, image data for one screen is divided into a plurality of blocks, and each block The luminance data is passed through a high-pass filter, contour enhancement processing is performed on the luminance data, and a difference between the result passed through the high-pass filter and the result of contour enhancement processing is calculated. For a small block, the coring amount used for the coring process is increased, and for a block having a relatively large difference value, the coring amount is decreased.

  According to the photographing apparatus of the present invention, the image data for one screen is divided into a plurality of blocks, and the luminance data of each block is subjected to discrete cosine transform to measure the high frequency component, and the block having relatively few high frequency components Since the coring amount is increased and the coring amount is decreased for blocks having a relatively high frequency component, it is possible to obtain a good image quality with less noise without reducing the resolution of the image. Further, instead of performing discrete cosine transform on the luminance data of each block, a high-pass filter may be used. Further, the difference between the result obtained by passing the high-pass filter and the result obtained by performing the edge enhancement process may be calculated, and the coring amount may be determined based on the magnitude of this value.

  In FIG. 1 showing the electrical configuration of a digital camera 10 as a first embodiment as a photographing apparatus to which the present invention is applied, a CCD 14 is disposed behind a photographing lens 12. As is well known, the CCD 14 includes a photocathode by arranging a large number of light receiving elements in a matrix, and photoelectrically converts subject light that has passed through the photographing lens 12 and imaged on the photocathode. In front of the photocathode, a microlens array for condensing light on each pixel, and a color in which filters of each color are regularly arranged so that each pixel corresponds to one of R, G, and B, respectively. A filter array is arranged.

  The CCD 14 outputs the charges accumulated for each pixel as a serial imaging signal line by line in synchronization with the vertical transfer clock and the horizontal transfer clock supplied from the CCD drive circuit 16. The charge accumulation time (exposure time) of each pixel is determined by an electronic shutter drive signal given from the CCD drive circuit 16.

  An analog imaging signal captured from the CCD 14 is input to a CDS & AMP 18 including a correlated double sampling circuit (CDS) and an amplifier circuit (AMP). The CDS removes noise from the analog signal, and the AMP amplifies the analog signal. The analog signal output from the CDS & AMP 18 is input to the ADC 20. The ADC 20 digitally converts an analog signal to generate image data. This image data is CCD-RAW data, and this CCD-RAW data is input to a DSP (Digital Signal Processor) 22.

  The DSP 22 includes a multiplexer 24, a process circuit 26, a two-dimensional contour enhancement processing circuit 28, a coring processing circuit 30, a blocking circuit 32, a DCT circuit 34, a high frequency component integrating circuit 36, and a coring table 38. The multiplexer 24 converts the CCD-RAW data into R, G, B data.

  The process circuit 26 performs YC processing for converting R, G, B data into a luminance signal Y and color difference signals Cr, Cb. The two-dimensional contour enhancement processing circuit 28 divides the luminance signal Y into a low-frequency component and a high-frequency component, performs a contour enhancement process by increasing the gain of the high-frequency component, The color difference signals Cr and Cb are sent to the coring processing circuit 30.

  On the other hand, as shown in FIG. 2, the blocking circuit 32 divides the G data for one screen outputted from the multiplexer 24 into m × n unit blocks (8 × 8 pixels). The DCT circuit 34 performs two-dimensional discrete cosine transform (DCT (Discrete Cosine Transform)) for each unit block, and frequency-decomposes a two-dimensional picture of 8 × 8 pixels.

  The high-frequency component integrating circuit 36 integrates the high-frequency components (high-frequency components) for each unit block subjected to DCT, and ranks it in eight stages according to the magnitude (logarithm) of this DCT integrated value. , 1,..., 7 (see FIG. 3) and stored in the coring table 38. The higher the rank, the higher the index. Moreover, natural noise reduction can be realized by performing the ranking logarithmically.

  The coring processing circuit 30 cuts the noise component of the high frequency component of the luminance signal Y input from the two-dimensional contour enhancement processing circuit 28 based on the index information from the coring table 38. Thus, it is stored in the image memory 42 via the memory control circuit 40 from which the noise component has been removed.

  The memory control circuit 40 is connected to the system bus 44. In addition to the memory control circuit 40, the system bus 44 includes a memory card 60, a video encoder 62, and an external communication circuit 64 via a CPU 46, ROM 48, RAM 50, DMAC 52, PIO 54, JPEG compression circuit 56, and external storage control unit 58. It is connected. A power supply unit 66 that supplies power to each part of the digital camera 10 is provided.

  The CPU 46 controls the entire digital camera 10 according to a program stored in the ROM 48. The RAM 50 is used as a work area for the CPU 46. The DMAC 52 is a well-known DMA controller that performs data transfer without using the CPU 46. The PIO 54 is a program I / O used for emergency when the DMAC 52 does not operate normally.

  The JPEG compression circuit 56 performs compression processing on the image data in the JPEG format to generate an image file. This image file is stored in the memory card 60 via the external storage control unit 58. The video encoder 62 displays an image on a liquid crystal panel (not shown) based on the image data. The external communication circuit 64 is an interface circuit for communicating with an external USB device or the like.

  The operation of the digital camera 10 configured as described above will be described with reference to the flowchart shown in FIG. When a photographing operation is performed, an analog image signal output from the CCD 14 is converted into digital image data by the ADC 20 via the CDS & AMP 18 (st1). When the image data which is the CCD-RAW data for one screen is input to the DSP 22, it is separated into R, G, B data by the multiplexer 24, and the G data therein is input to the blocking circuit 32. Divided into x unit blocks (st2).

  Each unit block is subjected to DCT calculation by the DCT circuit 34 (st3), and then each high frequency component is integrated by the high frequency component integrating circuit 36 (st4). Each unit block is ranked in eight stages according to the magnitude of this integrated value (st5), and indexes 0, 1,..., 7 are assigned to each rank and stored in the coring table 38 ( st6).

  On the other hand, the R, G, B data separated by the multiplexer 24 is converted into the luminance signal Y and the color difference signals Cr, Cb by the process circuit 26 (st7), and the luminance signal Y is extracted (st8). The luminance signal Y is divided into a low-frequency component and a high-frequency component by the two-dimensional contour enhancement processing circuit 28 (st9), and the high-frequency component is gained up (st10), and contour enhancement processing is performed. Note that the degree of this contour enhancement processing is constant.

  The luminance signal Y and the color difference signals Cr and Cb subjected to the contour enhancement process are sent to the coring processing circuit 30, and the coring table process is performed with reference to the coring table 38 (st11). Image data composed of the luminance signal Y from which the noise component has been cut by the coring table processing and the color difference signals Cr and Cb are stored in the image memory 42 via the memory control circuit 40 (st12). The image processed in this way has a good image quality because the noise feeling of the entire image is improved and the detail details are enhanced.

  Next, in FIG. 5 showing the electrical configuration of the digital camera 70 according to the second embodiment and FIG. 6 showing the main sequence, the same reference numerals are given to the same components as those in the first embodiment, and description thereof will be omitted. To do. The configuration of the DSP 71 of the digital camera 70 is different from that of the first embodiment. The CCD-RAW data for one screen is separated into R, G, B data by the multiplexer 24, and the G data therein is input to the blocking circuit 32 and divided into m × n unit blocks (st2). Thereafter, it is sent to the HPF 72 and passed through a high pass filter for each block (st13). Thereby, only a signal having a frequency equal to or higher than the cutoff frequency is passed and a signal having a frequency equal to or lower than the cutoff frequency is attenuated, so that a noise component included in the G data is cut. Since the following is the same as in the first embodiment, a description thereof will be omitted.

  In addition, about the step number attached | subjected to the flowchart of FIG. 6, since the same number is attached | subjected to the step which is common in the said 1st Embodiment, a new number is attached | subjected only to a different step, Therefore The order of the numbers does not represent the order of the steps.

  Next, in FIG. 7 showing the electrical configuration of the digital camera 80 according to the third embodiment and FIG. 8 showing the main sequence, components common to the first and second embodiments will be described with the same reference numerals. Is omitted. The configuration of the DSP 81 of the digital camera 70 is different from the first and second embodiments. The process circuit 26 converts the R, G, B data into the luminance signal Y and the color difference signals Cr, Cb (st7) and sends them to the two-dimensional contour enhancement processing circuit 28. The luminance signal Y output from the process circuit 26 is It is taken out (st8) and inputted to the blocking circuit 32.

  The luminance signal Y is divided for each unit block by the block forming circuit 32 (st14), sent to the HPF 72, passed through a high-pass filter for each unit block (st13), and then sent to the subtracting circuit 84. The reason why the luminance signal Y is divided for each block is that the image data for one screen is divided for each unit block, so that the divided blocks are addressed in a one-to-one relationship.

  In addition, about the step number attached | subjected to the flowchart of FIG. 8, since the same number is attached | subjected to the step which is common in the said 1st, 2 embodiment, a new number is attached | subjected only to a different step. The order of the numbers does not necessarily represent the order of the steps.

  On the other hand, the luminance signal Y subjected to the contour enhancement processing by the two-dimensional contour enhancement processing circuit 28 is also sent to the subtraction circuit 84, and the luminance signal Y passed through the high-pass filter and the contour enhancement processing are performed by the subtraction circuit 84. The difference from the brightness signal Y is calculated (st15). The calculation results are sent to the integration circuit 86 and integrated, and ranks of 8 levels are performed according to the magnitude of the integrated value (st5), and indexes 0, 1,. And stored in the coring table 38 (st6). Hereinafter, since it is the same as that of 1st, 2 embodiment, description is abbreviate | omitted.

  In the embodiments described above, an example of a digital camera has been given as an example of a photographing apparatus. However, the present invention is not limited to this, and a mobile phone with a camera, a PDA with a camera, or the like may be used.

It is a block diagram which shows the electrical structure of the digital camera of 1st Embodiment. It is explanatory drawing which represents typically the state which divided | segmented G data into the mxn block. It is explanatory drawing which represents typically the state which gave the rank to each block. It is a flowchart which shows the main sequences of a digital camera. It is a block diagram which shows the electrical structure of the digital camera of 2nd Embodiment. It is a flowchart which shows the main sequences of 2nd Embodiment. It is a block diagram which shows the electrical structure of the digital camera of 3rd Embodiment. It is a flowchart which shows the main sequences of 3rd Embodiment.

Explanation of symbols

10, 70, 80 Digital camera 22, 71, 81 DSP
24 multiplexer 26 process circuit 28 two-dimensional contour enhancement processing circuit 30 coring processing circuit 32 blocking circuit 34 DCT circuit 36 high frequency component integrating circuit 38 coring table 42 image memory 72 HPF
84 Subtraction circuit 86 Integration circuit

Claims (3)

In an imaging device that converts an image signal output from a solid-state image sensor into digital image data and applies a coring process to the image data.
The image data for one screen is divided into a plurality of blocks, the luminance data of each block is subjected to discrete cosine transform to measure the high frequency component contained in each block, and this high frequency component is reduced to a relatively small block On the other hand, a photographing apparatus characterized in that the coring amount used for the coring process is increased and the coring amount is decreased for a block having a relatively high frequency component. In an imaging device that converts an image signal output from a solid-state image sensor into digital image data and applies a coring process to the image data.
The image data for one screen is divided into a plurality of blocks, the luminance data of each block is passed through a high-pass filter, and the high-frequency component contained in each block is measured. On the other hand, a photographing apparatus characterized in that the coring amount used for the coring process is increased and the coring amount is decreased for a block having a relatively high frequency component. In an imaging device that converts an image signal output from a solid-state image sensor into digital image data and applies a coring process to the image data.
The image data for one screen is divided into a plurality of blocks, the luminance data of each block is passed through a high-pass filter, and the edge enhancement process is performed on the brightness data, and the result of passing through the high-pass filter and the edge enhancement process The difference is calculated, and the coring amount used for coring processing is increased for blocks having a relatively small difference value, and for blocks having a relatively large difference value. An imaging apparatus characterized by reducing the coring amount.

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