JP2002077930A - Method for preventing pseudocolor by single ccd solid- state image pickup element and recording medium with pseudocolor preventing program for single ccd solid- state image pickup element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a pseudocolor by small quantity of calculation that is apt to be generated in an edge especially. SOLUTION: A specified area necessary to be color-interpolated is set adjacent to a target pixel to be color-interpolated (step s1), color interpolation is conducted in the area, and the obtained color information is used to convert the color and obtain tint components Cb and Cr (definer appropriately as linear combinations of cyan(Cy), yellow(Ye), magenta(Ma) and green(Gr), respectively) (step s2). Then, the tint component Cb is set by selecting respective color information so as to interpolate in a manner that the tint component Cb to be obtained by the color conversion may become almost zero (step s3). Specifically, the maximum and minimum values of the tint component Cb are found out, and the respective color information to be interpolated is selected so that the tint component value may become zero or almost zero in a range of the minimum value to the maximum value. The tint component Cr is obtained by using a value that 3 pixels × 3 pixels is uniformly averaged for color interpolation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suppressing false colors in a single-chip solid-state image sensor and a method for suppressing false colors in a single-chip solid-state image sensor in which false colors generated in an image captured by a single-chip CCD are suppressed. The present invention relates to a recording medium on which a program is recorded.

[0002]

2. Description of the Related Art Single-chip solid-state imaging device (referred to as CCD)
False color often appears in an image obtained by imaging in the above. This false color is a phenomenon in which an unintended color component appears alternately in a band shape, and is particularly noticeable in an edge portion where a change in luminance is large. For example, in a single-chip CCD having a color arrangement as shown in FIG. 1, even when blue or yellow does not exist in the original image, these blue and yellow components tend to appear as false colors.

[0003]

Conventionally, various methods for making such false colors inconspicuous have been proposed, but they have problems such as complicated processing and a large amount of calculation.

Accordingly, the present invention provides a false color suppression method for a single-chip solid-state imaging device which requires a small amount of calculation and can suppress false colors, and a recording medium on which a false-color suppression program for a single-chip solid-state imaging device is recorded. It is an object.

[0005]

In order to achieve the above object, a false color suppressing method for a single-chip solid-state imaging device according to the present invention uses a pixel information corresponding to a pixel output from the single-chip solid-state imaging device. A false-color suppression method for a single-chip solid-state imaging device that prevents false colors that occur when image decoding is performed by performing color interpolation on pixels. False color is suppressed by performing color interpolation that lowers the saturation.

In this false color suppression method for a single-chip solid-state image pickup device, the color interpolation for lowering the saturation of a certain pixel of interest is performed by a predetermined color setting for performing color interpolation around the certain pixel of interest. In the region, the color interpolation is such that the saturation becomes the lowest among the possible saturations.

[0007] The color interpolation to provide the lowest saturation in the possible range of the saturation is performed by using a color component obtained by a color conversion process in a predetermined area set around the certain pixel of interest. A maximum value and a minimum value which can be taken by at least one of the color components Cb and the color component Cr are obtained, and the color component value is 0 or a value closest to 0 within the range between the maximum value and the minimum value. Then, each color information to be interpolated is selected.

Further, the recording medium in which the false color suppression processing program for a single-chip solid-state image sensor according to the present invention is recorded performs color interpolation on the pixel using pixel information corresponding to the pixel output from the single-chip solid-state image sensor. A recording medium that records a false color suppression processing program for a single-chip solid-state imaging device that prevents false colors that occur when image decoding is performed, wherein the false color suppression processing program is a target for color interpolation. A procedure for setting a predetermined area for performing color interpolation around a pixel, and performing a color interpolation process in the predetermined area and performing a color conversion process using each color information of the pixel of interest obtained by the color interpolation processing And in the color interpolation process and the color conversion process, at least one of the color components Cb and Cr obtained by the color conversion process is obtained. The maximum value and the minimum value are calculated, and each color information to be interpolated is selected so that the color component value becomes 0 or a value closest to 0 within the range of the maximum value and the minimum value. I have.

As described above, according to the present invention, false color is suppressed by performing color interpolation so as to lower the saturation of a target pixel to be subjected to color interpolation. by this,
An undesired color, that is, a color that should not originally appear, is less likely to be expressed, and false colors can be reduced.

[0010] The color interpolation processing for lowering the saturation of the target pixel is performed in a predetermined area set for performing color interpolation around the certain target pixel in the range of possible saturations. Color interpolation that results in low saturation,
Specifically, in a predetermined area set around a certain pixel of interest, a maximum value and a minimum value which can be taken by at least one of the tint components Cb and Cr obtained by the color conversion process are obtained. Color interpolation is performed such that each color information to be interpolated is selected so that the color component value becomes 0 or a value closest to 0 within the range between the maximum value and the minimum value.

That is, a low saturation is equivalent to a small value of the color components Cb and Cr. Therefore, the color information of each color component to be interpolated is selected so that at least one of the color components Cb and Cr is 0 or as close to 0 as possible. This calculation processing is mainly addition and subtraction and multiplication, and does not include division with a large amount of calculation, so that the amount of calculation can be reduced and the false color suppression processing itself can be sped up. Moreover,
A certain effect can be obtained in suppressing false colors.

[0012]

Embodiments of the present invention will be described below. The contents described in this embodiment are as follows.
The present invention also includes the specific processing content of the false color suppression processing program in the recording medium in which the color interpolation method of the single-chip solid-state imaging device and the false-color suppression processing program of the single-chip solid-state imaging device of the present invention are recorded.

The present invention is intended to suppress false colors, and considers that false colors express strong colors that are not intended, so that the saturation of a portion where false colors easily occur may be reduced. It is made from the idea. However, when color interpolation is performed on a pixel of interest instead of simply lowering the saturation, color interpolation is performed so that the saturation becomes the lowest in the range of saturation of the pixel of interest. Hereinafter, specific embodiments will be described. Note that a false color tends to occur particularly in a portion where luminance changes greatly, such as an edge portion. Therefore, the following embodiment will be described mainly on the assumption of an edge portion.

Here, a single-color CCD of complementary colors is considered, and it is assumed that cyan Cy, yellow Ye, magenta Mg, and green Gr have a color arrangement as shown in FIG.
In FIG. 1, Cy00, Ye01, Mg10, Gr1
Numerical values such as "00" and "01" are given as 1, 1,..., Which are numerical values indicating the positions of the respective color components. For the sake of simplicity, the luminance Y and the color components Cb and Cr are as follows: Y = a1 · Cy + a2 · Ye + a3 · Mg + a4 · Gr (1) Cb = b1 · Mg + b2 · Ye−b3 · Gr + b4 · Cy (2) Cr = c1・ Mg + c2 ・ Cy-c3 ・ Gr + c4 ・ Ye (3) These (1), (2),
In the formula (3), a1 to a4, b1 to b4, c1 to c
4 are coefficients, Cy is a cyan component at a certain pixel position, Ye is a yellow component at that pixel position,
Mg is the value of the magenta component at that pixel position, and Gr is the value of the green component at that pixel position.

As can be seen from the equations (1), (2) and (3), the luminance Y and the color components Cb and Cr are Cy, Y
It is obtained by performing a linear addition of e, Mg, and Gr. Further, in the present algorithm, each coefficient needs to be a value including white balance processing.
This is because, when the present algorithm is applied using a coefficient that does not take white balance, a specific color may be generated in an image edge portion after white balance. Generally, it is considered that blue tends to occur when photographing is performed in an environment having a low color temperature, and red tends to occur when photographing is performed in an environment having a high color temperature.

By the way, in the above equation, Cb and Cr represent color, and it can be said that the saturation is high if the values of Cb and Cr are large. The processing that the present invention attempts to perform is as follows:
By performing color interpolation such that the saturation becomes the lowest among the saturations in the range of the pixel of interest, false colors are suppressed as much as possible. Therefore, if Cy, Ye, Mg, and Gr are selected such that the values of Cb and Cr become as small as possible at a certain pixel position, the saturation of the pixel of interest can be made as small as possible, which is particularly likely to cause false colors. It is considered that the generation of the false color in the edge portion can be suppressed by performing the process on the pixels in the edge portion.

Here, in FIG. 1, when Cy22 is set as a target pixel, it is considered that color interpolation is performed at that position. The position of Cy22 is such that the cyan color component is Cy.
22 exists, the cyan color component is Cy2
2 may be used as it is, but other color components need to be obtained by interpolation. As a color interpolation method, there is a method of obtaining a value of a color component to be interpolated by a uniform average of 3 pixels × 3 pixels. Note that 3 × 3 pixels set for the target pixel Cy22 is a range surrounded by a broken line in FIG.
2. If the value of the magenta component is Mg22 and the value of the green component is Gr22, and they are determined by a uniform average of 3 × 3 pixels, Ye22, Mg22, Gr22 to be interpolated
Ye22 = (Ye21 + Ye23) / 2 Mg22 = (Mg12 + Mg32) / 2 Gr22 = (Gr11 + Gr13 + Gr31 + Gr33) / 4 (4)

Here, for example, when Ye is considered, it is assumed that Ye22 to be obtained is a yellow value existing between Ye21 and Ye23 in FIG.
That is, when Ye21 ≦ Ye23, Ye22 satisfies Ye21 ≦ Ye22, and Ye22 ≦ Ye23 (5) When Ye21> Ye23, Ye22 satisfies either Ye21> Ye22 and any of Ye22> Ye23 (6) And Change the way of writing,
If the function for selecting the minimum value of the argument is described as min (x1, x2,...) And the function for selecting the maximum value is described as max (x1, x2,. Equation (6) can be rewritten as min (Ye21, Ye23) ≦ Ye22 ≦ max (Ye21, Ye23) (7) Similarly, for other colors (Mg, Gr), min (Mg12, Mg32) ≦ Mg22 ≦ max (Mg12, Mg32) (8) min (Gr11, Gr13, Gr31, Gr33) ≦ Gr22 ≦ max (Gr11, Gr13) , Gr31, Gr33) (9). Hereinafter, the discussion will proceed assuming that the above conditions are satisfied.

Next, assuming that lowering the saturation as much as possible means that the values of the color components Cb and Cr are as close to 0 as possible.
Or select the value closest to 0.

First, consider the color component Cb (represented by Cb22) in the target pixel Cy22. From the above equations (5) to (9), the minimum value Cb22min and the maximum value Cb22max that the color component Cb22 can take are respectively Cb22min = b1 · min (Mg12, Mg32) + b2 · min (Ye21, Ye23) −b3 -Max (Gr11, Gr13, Gr31, Gr33)-b4-Cy22 (10) Cb22max = b1-max (Mg12, Mg32) + b2-max (Ye21, Ye23) -b3-min (Gr11, Gr13, Gr31, Gr33)- b4 · Cy22 (11). According to the gist of the algorithm of the present invention, 0 or a value closest to 0 may be selected in the range of Cb22min to Cb22max. Specifically, Cb22min ≦ 0
And Cb22max ≧ 0, that is, Cb22min and Cb22max
Is, for example, in the range as shown in FIG.
b22 selects 0.

Cb22max <0, that is, Cb22min
For example, if Cb22max is in the range as shown in FIG. 2B, Cb22 selects Cb22max at that time. Also,
Cb22min> 0, that is, Cb22min and Cb22max are, for example,
If it is in the range as shown in FIG. 2C, Cb22 selects Cb22min at that time. That is, if (Cb22min ≦ 0 and Cb22max ≧ 0) → Cb22 = 0 else if (Cb22max <0) → Cb22 = Cb22max else if (Cb22min <0) → Cb22 = Cb22min (12)

As described above, by using the expressions (10) to (12), the color component Cb of the pixel of interest Cy22 is converted into a physical space of 3 pixels × 3 pixels centered on the pixel of interest Cy22. When color interpolation is performed, color components Ye22, Mg to be color-interpolated so that the saturation becomes lowest.
22 and Gr22 can be selected (Cy22 uses Cy22 which originally exists).

On the other hand, the same operation should be performed for the color component Cr to perform processing to select the value closest to 0 within the range of Cr22min to Cr22max. Analysis has revealed that in the case of an image sensor having a color arrangement as shown in FIG. 1, the influence of the tint component Cr on the generation of false colors is small. Therefore, the color component C
Regarding r, the calculation like the color component Cb is not performed,
A value obtained by simply performing color interpolation using a uniform average of 3 pixels × 3 pixels is used. That is, the color component Cr in Cy22 is
Ye22, Mg22, Gr22 determined by equation (4)
And Cy22 originally existing at that position,
From equation (3), it is calculated as Cr22 = c1 · Mg22 + c2 · Cy22−c3 · Gr22 + c4 · Ye22 (13).

FIG. 3 is a flowchart showing the outline of the processing described above. First, a predetermined area (color pixel Cy22 in the above example) necessary for color interpolation is set around a pixel of interest to be color-interpolated. (Surrounding 3 pixels × 3 pixels) is set (step s1), color interpolation processing is performed in the area, and color conversion processing is performed using the respective color information obtained by the color interpolation processing, and the color component Cb is set. , Cr (step s2). In this embodiment, as described above, the color component Cr is obtained from Expression (4) using a value obtained by color interpolation using a uniform average of 3 pixels × 3 pixels.

On the other hand, regarding the color component Cb, the color interpolation process and the color conversion process described above (1)
Using the equations (0) to (12), each piece of color information to be interpolated is selected so that the tint component Cb obtained by the color conversion processing becomes 0 or a value closest to 0 (step s3). Specifically, the maximum value and the minimum value that the color component Cb can take are obtained, and the color component value is set to 0 within the range between the maximum value and the minimum value.
Alternatively, each color information to be interpolated is selected so as to be a value closest to 0.

By performing the above-described processing, color interpolation processing is performed so that the saturation becomes lowest at a certain target pixel, and a false color at the target pixel is suppressed.

In the above description, the pixel of interest is Cy2
2, Cb22, Cr at the position of Cy22
Although the method of obtaining 22 has been described, the same processing is performed at other positions. Thereby, at each pixel position of the edge portion, the saturation of each pixel can be made as small as possible, thereby suppressing generation of a false color.

In the embodiment described above, the edge portion is considered because false colors are particularly likely to occur at the edge portion. However, the present invention can of course be applied to other than the edge portion. . Further, in the above-described embodiment, as described above, the color component Cr is simply calculated without performing the calculation like the color component Cb.
Although a value obtained by color interpolation using a uniform average of pixels × 3 pixels is used, it is a matter of course that the same algorithm ((1)
(0) to (12) and FIG. 2) may be used to determine the color component Cr.

In the above-described embodiment, 3 pixels × 3 pixels
Although the pixel area is considered, this area is not limited to 3 pixels × 3 pixels. In addition, the present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention.

Further, according to the present invention, a processing program describing a processing procedure for realizing the present invention described above can be recorded on a recording medium such as a floppy disk, an optical disk, or a hard disk. It also includes a recording medium on which the processing program is recorded. Further, the processing program may be obtained from a network.

[0031]

As described above, according to the present invention, false color is suppressed by performing color interpolation so as to lower the saturation of a target pixel to be color-interpolated. Therefore, it is difficult to express an unintended color, that is, a color that should not originally appear, and it is possible to reduce false colors. The color interpolation processing for lowering the saturation of the target pixel is performed in the predetermined region set for performing color interpolation around the certain target pixel, and is the lowest saturation in the range of possible saturations. Color interpolation, and specifically, in a predetermined region set around a certain pixel of interest,
The maximum value and the minimum value that can be taken by at least one of the color components Cb and Cr obtained by the color conversion processing are obtained, and the color component value is set to 0 within the range between the maximum value and the minimum value.
Alternatively, color interpolation is performed such that each piece of color information to be interpolated is selected so as to have a value closest to 0.

That is, it can be said that that the saturation is low is equivalent to the fact that the color components Cb and Cr are small.
Therefore, at least one of the color components Cb and Cr is 0.
Alternatively, color information of each color component to be interpolated is selected so as to be as close to 0 as possible. This calculation processing is mainly addition and subtraction and multiplication, and does not include division with a large amount of calculation, so that the amount of calculation can be reduced and the false color suppression processing itself can be sped up. In addition, a certain effect can be obtained in suppressing false colors.

[Brief description of the drawings]

FIG. 1 is a diagram showing a part of a color arrangement of a CCD used in an embodiment of the present invention.

FIG. 2 is a diagram illustrating a process of selecting a value such that Cb is 0 or the value closest to 0 within a range between a minimum value and a maximum value of a color component Cb.

FIG. 3 is a flowchart schematically illustrating a processing procedure according to the embodiment of the present invention, in which color information to be interpolated such that a tint component Cb at a certain pixel of interest becomes 0 or a value closest to 0; 9 is a flowchart illustrating a process for selecting a.

[Explanation of symbols]

 Cy Cyan (its pixel value) Ye Yellow (its pixel value) Mg Magenta (its pixel value) Gr Green (its pixel value) Cb, Cr Tint component (its value)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5B057 BA19 BA24 CA01 CA16 CB01 CB16 CE17 DA08 DB06 5C065 BB13 CC01 DD02 EE07 GG13 GG15 GG50 5C079 HB02 HB06 JA23 LA10 LA28 LA31 LB01 MA01 MA11 NA03 NA11

Claims (4)

[Claims] 1. A single-panel solid-state image sensor which prevents false colors that occur when image decoding is performed by performing color interpolation on the pixel using pixel information corresponding to the pixel output from the single-panel solid-state image sensor. A single-plate solid, which is a color suppression method, wherein false color is suppressed by performing color interpolation on a certain target pixel to be subjected to color interpolation so that the saturation of the target pixel becomes lower. False color suppression method for image sensor. 2. The color interpolation in which the saturation of a certain pixel of interest is lower than the saturation of a possible range in a predetermined area set for performing color interpolation around the certain pixel of interest. 2. The false color suppression method for a single-chip solid-state imaging device according to claim 1, wherein the color interpolation is such that the lowest saturation is obtained. 3. The color interpolation for obtaining the lowest saturation in the possible range of the saturation is performed by using a color component obtained by a color conversion process in a predetermined region set around the certain pixel of interest. A maximum value and a minimum value which can be taken by at least one of the color components Cb and the color component Cr are obtained, and the color component value is 0 or a value closest to 0 within the range between the maximum value and the minimum value. 3. The false color suppression method for a single-chip solid-state imaging device according to claim 2, wherein each color information to be interpolated is selected. 4. A single-chip solid-state image sensor for preventing false colors that occur when image decoding is performed by performing color interpolation on a pixel using pixel information corresponding to the pixel output from the single-chip solid-state image sensor. A recording medium on which a color suppression processing program is recorded, the false color suppression processing program comprising: a procedure for setting a predetermined area for performing color interpolation around a certain target pixel to be color-interpolated; Performing a color interpolation process and performing a color conversion process using the color information of each of the target pixels obtained by the color interpolation process, wherein in the color interpolation process and the color conversion process, The maximum value and the minimum value which can be taken by at least one of the color components Cb and Cr obtained by the conversion processing are obtained, and the color component value is set to 0 within the range between the maximum value and the minimum value.
2. The recording medium according to claim 1, wherein each color information to be interpolated is selected so as to have a value closest to zero.