JPH02113764A - Chrominance signal separating circuit for image sensor - Google Patents

Abstract

PURPOSE:To improve a resolution by enlarging each dynamic range of two chrominance signals among three primary colors of red, blue and green. CONSTITUTION:A multiplying means 23 to multiply a while signal digitized by an A/D converter 16 doubles the data of the while signal by adding one bit to the resolution eight bits of the A/D converter 16, and making the most significant digit into '0'. Consequently, when an input to the A/D converter 16 of the white signal is 1, respective signal inputs of the red and blue are made into 1/3X2=2/3. Namely, respective signals of the red and blue can obtain the double dynamic ranges. Thus, in the case of using the A/D converter 16 having the resolution of 256 in eight bits, respective resolutions of red and blue signals can be increased up to 256/3X2=170, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color signal separation circuit for an image sensor applied to a color image scanner or the like.

<Prior art and problems> In a color image scanner, as shown in FIG. It has been proposed that the color light-receiving section 11 is constructed of white (W) light-receiving elements i\11W without filters arranged side by side with a half-pitch shift in the two color rows.

Using such a light receiving section 11, red (R) and blue (B)
When obtaining signals of the three primary colors of green (G) and green (G), an amplifier circuit 12 .
13, and a switch 14 at each output terminal of the amplifier 1213.
．． Each color signal output from the amplifiers 12 and 13 is digitized at 16 to the A/D converter 8 connected via 15,
The red, blue, and white color registers l 7 , 1.8 , and 1.9 connected to the /D converter 16 separate the signal into each color signal, and the blue register is extracted from the value of the white register 19 by the subtractor 20 . By subtracting the value of 18 and the value of the red register 17 by the subtractor 21, green image data can be obtained by the green register 22.

However, in the above configuration, the value of the white signal when a white original is read is approximately three times the value of each red and blue signal, and based on this, the red and blue signals input to the A/D converter 16 are The signal ends up being a 1-white signal. That is, if an 8-bit A/D converter 16 having a resolution of 256 is used, the red and blue signals can only be obtained at a resolution of about 85 for that station.

<Object of the invention> This invention was made to solve the above-mentioned problems.
The present invention aims to provide a color signal separation circuit for an image sensor that can widen the dynamic range of two color signals.

<Structure and Effects of the Invention> The color signal separation circuit of the image sensor according to the present invention includes a row of light receiving element groups arranged in a cross direction W in the scanning direction with filters for two of the three primary colors red, blue and green. Also, a light-receiving section consisting of a row of white light-receiving elements without filters arranged in parallel with a half-pitch shift from this row, an A/D converter that digitizes each color signal from this light-receiving section, and this A/D. A subtracter that subtracts the color signals of the above two colors among the digital signals from the converter from the white signal to obtain the remaining color signals of the three primary colors; and a multiplication means for performing multiplication prior to the above-mentioned subtraction.

According to this invention, the white signal from the A/D converter is multiplied and then the signals of two of the three primary colors are subtracted. Since the input of the two color signals is multiplied by the multiplier, the dynamic range of these two color signals can be expanded.

<Explanation of Examples> Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a color signal separation circuit for an image sensor according to the present invention, and the same parts as those in FIGS. 3 and 4 are given the same reference numerals and their explanation will be omitted.

In the figure, 23 is a multiplication means for multiplying the white signal digitized by the A/D converter 16; By adding this and setting the highest digit to ``0'', the data for the ``-'' symbol is doubled.

With this configuration, if the input of the white signal to the A/D converter 16 is 1, then each red and blue signal input will be station x 2-%. That is, compared to the one in FIG. 4, each of the red and blue signals can have twice the dynamic range, for example, 8 bits has a dynamic range of 25
When using an A/D converter with a resolution of 6,
The resolution of each of the red and blue signals is 25El/3.
Each can be increased up to X 2 =170.

FIG. 2 shows another example of the present invention, in which a multiplier 25 for multiplying the contents of the white signal register 19 by the value of the register 24 and the register 24 constitute a multiplier 26.

Now, by giving, for example, "3" to the K register 24, the white signal will be tripled. Therefore, each red and blue No. 48 input the same l/bell as the white signal to the A above.
/D converter 16, and A/D converter 16 can be applied.
The full resolution of the D converter 16 can be used for each color signal.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of a color signal separation circuit of an image sensor according to the present invention, Fig. 2 is a block diagram showing another embodiment of the invention, and Fig. 3 is a block diagram showing an example of a color signal separation circuit of an image sensor according to the present invention. FIG. 4 is a block diagram showing the configuration of a color signal separation circuit of a general image sensor using the light receiving section of FIG. 3. 11... Light receiving section, 11R, IIB, IIW... Light receiving element f-116... A/D converter, 20.21...
- Subtractor, 23.26...multiplying means.

Claims (1)

[Claims] (1) Rows of light-receiving element groups alternately arranged in the scanning direction with filters for two of the three primary colors red, blue, and green, and filters arranged in parallel with the two color rows shifted by half a pitch. A light-receiving section consisting of a row of white light-receiving elements having no color, and an A/R that digitizes each color signal from this light-receiving section.
a D converter, a subtracter that subtracts the color signals of the two colors of the digital signal from the A/D converter from the white signal to obtain the remaining color signals of the three primary colors, and the A/D converter.
1. A color signal separation circuit for an image sensor, comprising: multiplication means for multiplying a white signal digitized by a D converter prior to the subtraction.