WO1999025123A1

WO1999025123A1 - Color signal processing circuit

Info

Publication number: WO1999025123A1
Application number: PCT/JP1998/005018
Authority: WO
Inventors: Shinji Ukita
Original assignee: Sanyo Electric Co., Ltd.
Priority date: 1997-11-11
Filing date: 1998-11-06
Publication date: 1999-05-20

Abstract

A digital camera includes a CCD imager having complementary color filters. Ye data, Cy data, Mg data and Gr data are outputted from the CCD imager. Since one pixel has only one color component, the interpolation of three color components which the pixel concerned does not have is performed by a RAM, and thus four color components of the pixel are produced. In an operation circuit, the Gr component is multiplied by a predetermined coefficient α and then the product is subtracted from the Mg component, in other words, the remainder Mg' is Mg-αGr. The Ye data, the Cy data, the Gr data and the Mg' data are subjected to a matrix operation by a matrix circuit and, r data and b data whose green band components are attenuated are generated.

Description

Akira Itoda Color signal processing circuit Technical field

The present invention relates to a color signal processing circuit, and more particularly to a color signal processing circuit which is applied to, for example, a digital camera and generates a plurality of second color signals based on a plurality of first color signals.

Conventional technology

As a conventional digital camera, a complementary color filter having Ye (yellow), Cy (cyan), Mg (magenta) and Gr (green) filter elements of complementary colors is mounted on a CCD imager, Based on the four pixel data output from the imager, ie, Ye data, Cy data, Mg data and Gr data, primary color r (red) data and g (green) by the color signal processing circuit. Some of them generate data overnight and b (bullet) data. The complementary color filter had the spectral sensitivity characteristics as shown in Fig. 11, and the color signal processing circuit generated the primary color data with the spectral sensitivity characteristics as shown in Fig. 12.

However, as can be seen from FIG. 12, there was a problem that the r-de-night component and the b-data component contained in the green band were large, and the color reproducibility was poor. On the other hand, in other digital cameras in which a primary color filter is attached to a CCD imager and r data, g data and b data are obtained directly from the CCD imager, the primary color filter has a spectral sensitivity characteristic as shown in Figure 13 In the green band, the r data component and the b data overnight component are much smaller than those in Fig. 12.

In other words, in both Fig. 12 and Fig. 13, white balance correction is applied to r data, g data and b data so that each peak output is almost normalized to "1". However, for example, the response of r data at a wavelength of 545 nm is 44% in FIG. 12, which is much larger than 2% in FIG. Summary of the Invention Therefore, a main object of the present invention is to provide a novel color signal processing circuit.

Another object of the present invention is to provide a color signal processing circuit capable of improving color reproducibility.

A color signal processing circuit according to the present invention comprises: a first pixel signal input means for inputting a first pixel signal in which each pixel has a plurality of first color components; and a first pixel signal based on: Output means for outputting a second pixel signal in which a pixel has a plurality of second color components and at least one predetermined band level of the plurality of second color components is increased or decreased.

The first pixel signal input means inputs a first pixel signal in which each pixel has a plurality of first color components. Then, the output means outputs, based on the first pixel signal, a second pixel signal in which each pixel has a plurality of second color components and at least one predetermined band level of the plurality of second color components has been increased or decreased. .

In one aspect of the present invention, the adjusting means adjusts one of the plurality of first color components. In the output unit, the generation unit performs a matrix operation on the first color component and the remaining first color component output from the adjustment unit, and generates a plurality of second color components.

In one embodiment of the present invention, the adjusting means multiplies any one of the first color components by a predetermined coefficient, and subtracts the multiplication result from the other one of the first color components.

In another embodiment of the present invention, the third pixel signal input means inputs a third pixel signal in which each pixel has one of a plurality of first color components. Further, the interpolation means performs an interpolation process on the third pixel signal to generate a first pixel signal. The above-described level adjustment is performed by interpolation means.

In another aspect of the present invention, in the output unit, the generation unit performs a matrix operation on the plurality of first color components to generate a plurality of second color components with the predetermined band level increased or decreased.

In another aspect of the present invention, the plurality of first color components include a Ye component, a Cy component, a Mg component, and a Gr component, and the plurality of second color components include an r component, a g component, and a b component. The predetermined band includes a green band.

In still another aspect of the present invention, the plurality of first color components are Ye component, Cy component, The second color component includes an Mg component and a Gr component, and the plurality of second color components include an r component, a g component, and a b component.

In another aspect of the present invention, the plurality of first color components include a Y component, a Cy component, a Mg component, and a G r component, and the plurality of second color components include an r component, a g component, and a b component. The amplification means included in the output means amplifies the green band level of the g component.

According to the present invention, when outputting a second pixel signal based on a first pixel signal, at least one predetermined band component of a plurality of second color components is increased or decreased, so that color reproducibility is improved. Can be.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram showing one embodiment of the present invention;

FIG. 2 is an illustrative view showing a complementary color filter;

FIG. 3 is a flowchart showing a part of the operation of the embodiment of FIG. 1;

Figure 4 is a block diagram showing part of the embodiment of Figure 1;

FIG. 5 is a block diagram showing a part of another embodiment;

FIG. 6 is a block diagram showing a part of another embodiment;

FIG. 7 is a block diagram showing another embodiment of the present invention;

Figure 8 is a flowchart showing a part of the operation of the embodiment of Figure 7;

Figure 9 is a flowchart showing another part of the operation of the embodiment of Figure 7;

FIG. 10 is a graph showing the spectral sensitivity characteristics of r data, g data, and b data generated by the embodiment of FIGS. 1 to 9;

FIG. 11 is a graph showing the spectral sensitivity characteristics of the complementary color filter used in the embodiment of FIGS. 1 to 9;

Fig. 12 is a graph showing the spectral sensitivity characteristics of r data, g data, and b data obtained in the prior art; FIG. 13 is a graph showing the spectral sensitivity characteristics of the primary color filters. BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, a digital camera 10 of this embodiment includes a lens 12, and a light image incident from the lens 12 is irradiated on a CCD imager 16 via a complementary color filter 14. . As shown in FIG. 2, the complementary color filter 14 has a filter element of Ye, Cy, Gr or Mg corresponding to each pixel. Specifically, filter elements of Ye and Cy are alternately arranged for each pixel on odd lines, and filter elements of Gr and Mg are alternately arranged for each pixel on even lines. Note that a Gr filter element is placed above and below the Y filter element, and a Mg filter element is placed above and below the Cy filter element.

The CCD imager 16 performs so-called all-pixel reading in response to a timing signal from the timing generator 20. That is, the pixel signals are output in order line by line. The A / D converter 18 converts the pixel signal output from the CCD imager 16 into digital data, that is, pixel data, and inputs the digital data to the RAM 26 included in the color signal processing circuit 22. The input pixel data is written to the memory area 26a by the memory control circuit 28 that operates according to the timing signal from the timing generator 20.

Since each pixel has only one color component of Ye, Cy, Gr, and Mg, the memory control circuit 28 processes the flow chart shown in Fig. 3 when reading from the memory area 26a. Then, the three color components for which each pixel is missing are interpolated. That is, first, in step S1, the memory control circuit 28 calculates the count value X of the counter 28a indicating the address in the row direction (horizontal direction) and the count value y of the counter 28b indicating the address in the column direction (vertical direction). Is set to "1", then (X, y), (x + 1, y), (x, y + 1) and (x + 1, y + 1) in steps S3 to S9, respectively. Are sequentially read out. Then, in step S11, it is determined whether or not the count value X is a predetermined value, that is, the number of horizontal pixels is 11. If "N〇" here, the count value X is incremented in step S13 to process the next four pixels in the row direction, and then the process returns to step S3. on the other hand, If "YE S" is determined in step S11, it is determined in step S15 whether the count value y is a predetermined value, that is, the number of vertical pixels is one. If "NO", in step S17, the count value X is returned to 1 and the count value y is incremented in order to process the four pixels located at the left end of the next line, and the process returns to step S3. If "YES" in the step S15, the process ends.

The interpolation process is performed in this manner, and four color components at positions indicated by black circles in FIG. 2 are obtained.

Since the RAM 26 outputs the Y component, the Cy component, the Mg component, and the Gr component in a serial format, the serial Z-parallel conversion circuit 30 converts the input serial data into serial Z-parallel data for every four components. Is applied. Therefore, the Ye component, the Cy component, the Mg component, and the Gr component of the same pixel are simultaneously output from the serial / parallel conversion circuit 30.

The arithmetic circuit 32 is configured as shown in FIG. The Ye component, the Cy component, and the Gr component output from the serial / parallel conversion circuit 30 are directly input to the matrix circuit 32c. Further, the Gr component is multiplied by a coefficient H (for example, 0.75) by the multiplier 32a, and the output of the multiplier 32a is input to the subtractor 32b. The Mg component from the serial Z-parallel conversion circuit 30 is subtracted by the subtracter 32 b from the output of the multiplier 32 a, that is, aG r, and the Mg ′ component (= Mg—aG r) is output from the subtracter 32 b . The matrix circuit 32c also receives the M g 'component, and performs a matrix operation on the four color components according to Equation 1.

[Equation 1]

As a result, the luminance component Y and the color difference components Cr and Cb are output from the matrix circuit 32c and input to the matrix circuit 32d. The matrix operation is performed again according to Equation 2, and the r, g, and b components of the primary color system are obtained based on the luminance component Y and the chrominance components Cr and Cb. [Equation 2]

As shown in FIG. 5, a matrix circuit 32e is provided in which the matrix circuits 32c and 32d are integrated into one, and the matrix operation shown in Equation 3 is performed by the matrix circuit 32e. Is also good.

[Equation 3]

The r component, g component, and b component generated in this way are subjected to white balance correction in the signal processing circuit 34, and their peak levels are normalized to approximately one. Specifically, the r component, the g component, and the b component are multiplied by “1.74”, “1.12”, and “1.73”, respectively. As a result of such normalization, each color component has characteristics as shown in FIG. In other words, as can be seen from comparison with Fig. 12, the green band (495 nm to 570 nm) level of the r component and the b component is attenuated. For example, the normalized output of the r component at a wavelength of 545 nm is 11%, which is an improvement over the conventional 44%. Note that the negative output of each color component is underflow clipped by the same signal processing circuit 34 and can be ignored. The output from the signal processing circuit 34 is then recorded on the recording medium 36.

As described above, by adjusting the Mg component level, the green band levels of the finally obtained r component and b component are attenuated, so that the color reproducibility can be improved.

In a digital camera 10 of another embodiment, an arithmetic circuit 32 is configured as shown in FIG. 6, and a matrix circuit 32 f is composed of a Ye component, a Cy component, a Mg component, and a Gr component according to Equation 4. Figure 1 except that the r, g, and b components are generated from It is the same as the example, and a redundant description is omitted _c

[Equation 4]

In Equation 4, the matrix coefficient multiplied by Gr is “−1−2”, “3 + α”, or “−1_2”. In other words, the embodiment of FIG. 1 generates M g ′ == M g—G r before the matrix operation. In this embodiment, the multiplier 32 a and the subtractor 32 b are omitted and the matrix is omitted. Some of the coefficients have been changed. Specifically, a value obtained by multiplying the matrix coefficient of Mg by −α is added to the matrix coefficient of Gr. As a result, the r, g, and b components output from the matrix circuit 32 f have the same values as the r, g, and b components output from the matrix circuit 32 d or 32 e. Having. That is, in this embodiment, the green band levels of the r component and the b component are attenuated by changing the matrix coefficient, and the color reproducibility is improved.

Referring to FIG. 7, digital camera 10 of another embodiment has a memory area 26 b in RAM 26, and memory control circuit 28 performs interpolation processing according to the flow charts shown in FIGS. 8 and 9. Since the arithmetic circuit 32 includes the matrix circuit 32g shown in FIG. 6 and the matrix circuit 32g performs the arithmetic operation according to Equation 5, the operation circuit 32 is the same as the embodiment in FIG. The explanation given above is omitted.

[Equation 5]

Referring to FIGS. 8 and 9, the memory control circuit 28 first sets the count value m of the counter 28 a 'and the count value n of the counter 28 b' to "1" in step S21. In step S23, the address (x, Set y) to (m, n). Next, in step S25, it is determined whether both x and y are even numbers. If "NO", the pixel data D (x, y) of (X, y) is determined in step S27. Is held in the work area 26 b and the process proceeds to step S 31. If “YE S”, the calculation of the formula 6 is performed in step S 29, and the pixel data D ′ obtained thereby is obtained. (x, y) is stored in work area 26 b. Then, the flow shifts to step S31.

[Equation 6]

D '(x, y) = D (x, y)-Ό (x-1, y)

D (x, y): Pixel data at (x, y)

D (x—1, y): pixel data at (x-1, y)

D '(X, y): Pixel data after correction at (x, y) Steps 3 31 to 3 37, Steps S 39 to S 45, and Steps S 47 to S 53 3 The memory control circuit 28 performs almost the same interpolation processing as in steps S23 to S29. The difference is that in step S31 the address (x, y) is changed to (m + l, n), in step S39 the address (x, y) is changed to (m, n + 1), and The only difference is that the address (x, y) is changed to (m + 1, n + 1) in step S47.

As can be seen from Fig. 2, the Mg component is always written at even-numbered positions in both the column address and the row address. The memory control circuit 28 adjusts the level of the Mg component according to Equation 6 to generate Mg ′ (= Mg−Gr).

In step S55, the memory control circuit 28 outputs the four color components held in the work area 26b, that is, the Ye component, the Cy component, the Gr component, and the Mg 'component in a serial manner. Then, in step S57, it is determined whether or not the count value m is equal to the number of horizontal pixels—1. If "NO" here, the count value m is incremented in step S59 to specify the next address in the horizontal direction, and the process returns to step S23. On the other hand, if “YE S” in step S57, it is determined in step S61 whether or not the count value n is a predetermined value, that is, the number of vertical pixels is one. If "NO", specify the leftmost address of the next line In step S63, the count value m is returned to "1" and the count value n is incremented, and the process returns to step S23. On the other hand, if “YES” in the step S61, the process is ended.

Also in this embodiment, since the level of the Mg component is adjusted similarly to the above-described embodiment, the generated r component, g component, and b component have characteristics as shown in FIG. Can be improved.

The digital cameras of this embodiment include a so-called digital still camera that records only a still image and a video movie that records a moving image ₍ a digital camera that records both a still image and a moving image is also considered). In this embodiment, the green band levels of the r component and the b component are attenuated, but for example, the matrix coefficient of the matrix circuit 32 f is changed to amplify the green band level of the g component. You may do so.

While this invention has been described and illustrated in detail, it is obvious that it is used by way of illustration and example only and should not be construed as limiting, the spirit and scope of the invention being set forth in the appended claims. Limited only by the language of the claim made.

Claims

Scope of word blue

1. A color signal processing circuit comprising:

A first pixel signal input means in which each pixel inputs a first pixel signal having a plurality of first color components; and

Output means for outputting a second pixel signal in which each pixel has a plurality of second color components and at least one predetermined band level of the plurality of second color components is increased or decreased based on the first pixel signal.

2. A color signal processing circuit dependent on claim 1,

Adjusting means for adjusting the level of any one of the plurality of first color components;

The output unit includes a generation unit that performs a matrix operation on the first color component and the remaining first color component output from the adjustment unit to generate the plurality of second color components.

3. A color signal processing circuit dependent on claim 2,

The adjusting means includes a multiplying means for multiplying any one of the first color components by a predetermined coefficient, and a subtracting means for subtracting an output of the multiplying means from another one of the first color components.

4. A color signal processing circuit dependent on claim 2,

Third pixel signal input means for inputting a third pixel signal in which each pixel has one of the plurality of first color components; and

Interpolating means for performing an interpolation process on the third pixel signal to generate the first pixel signal,

The interpolation means includes the adjustment means.

5. A color signal processing circuit dependent on claim 1,

The output unit includes a generation unit that performs a matrix operation on the plurality of first color components to generate the plurality of second color components with the predetermined band level increased or decreased.

6. A color signal processing circuit dependent on claims 1-5,

The plurality of first color components include a Ye component, a Cy component, a Mg component, and a Gr component; the plurality of second color components include an r component, a g component, and a b component;

The predetermined band includes a green band.

7. A color signal processing circuit dependent on claim 1,

The plurality of first color components include a Y e component, a Cy component, an Mg component, and a G r component; the plurality of second color components include an r component, a g component, and a b component;

The output means includes attenuating means for attenuating the green band levels of the r component and the b component.

8. A color signal processing circuit dependent on claim 1,

The plurality of first color components include a Ye component, a Cy component, an Mg component, and a G r component; the plurality of second color components include an r component, a g component, and a b component;

The output means includes amplifying means for amplifying the green band level of the g component.

9. A digital camera equipped with the color signal processing circuit according to any one of claims 1 to 8.