JPH02214265A - Color picture reader - Google Patents

Abstract

PURPOSE:To improve the read resolution and to reduce the device scale by smoothing an output of a 2nd photoelectric conversion means in terms of MXN picture elements and generating a color difference signal from the resulting signal and a signal from a 1st photoelectric conversion means. CONSTITUTION:The reader is provided with a 1st photoelectric conversion means (CCD) 103 having the sensitivity at a prescribed wavelength region of a visual light narrow comparatively, a 2nd photoelectric conversion means (CCD) 101 having at least one of a picture element size and read pitch smaller than those of the CCD 103 and having sensitivity over nearly entire wavelength region of the visual light, a smoothing means 107 smoothing the output of the CCD 101 in terms of MXN picture elements and a color difference signal generating means generating a color difference signal from the signal from the smoothing means 107 and the signal from the CCD 103. Thus, the read resolution is improved and the reader size is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color image reading device that digitally reads a color image and outputs color separation signals.

[Prior Art] FIG. 6 shows a conventional color image reading device. This device illuminates a color original 201 placed on an original platen glass 202 with an original illumination lamp 203,
CC0205 via SELFOC lens array 204
It is designed to image at the same magnification.

Figure 7 shows the double array of CCD 205, CC02.
05, R, G, and B color separation filters 206 to 208 are applied, as shown in FIG.

FIG. 8 shows a conventional color image reading device, in which 201, 202, and 203 show the same parts as in FIG. The document illumination lamp 203 illuminates the document, and the image is formed on the CC 0305 via the reflecting mirrors 309a, 309b, 309c and the imaging lens 304.

FIG. 9 shows the CCD 305 shown in FIG. This CC
0305 is CC0 formed by process on the same substrate.
Composed of 306, 307, 308, CC9306
has an R filter, a G filter for CC0307, and a C filter for CC0307.
C0308 is provided with a B filter. Color separation signals are obtained line-sequentially.

[Problems to be Solved by the Invention] Since the conventional color image reading device is configured as described above, it has the following problems (1) and (3).

(1) Since the reading pixel densities of R, G, and 8 are basically made equal, the circuit size is required to be three times that of the case of reading a monochrome image.

(2) In order to improve the resolution, it is necessary to increase the pixel density of all R, G, and B, so especially in the color image reading device shown in Fig. 6, there was a limit due to the CCD manufacturing process. ( 3) Since the pixel area decreases in proportion to the square of the pixel density, the amount of light required from the illumination light source becomes enormous.

As a method to solve such problems, for example, Japanese Patent Application Laid-Open No. 58-22802 and Japanese Patent Application Laid-Open No. 82-21776
There is one shown in Publication No. 3. This reduces the pixel density of R and B among R, G, and B, and emphasizes the visual MTF of G, but because the high frequency components of the primary color signal are cut, unnatural color shift occurs. However, there are problems with color blurring and color bleeding.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color image reading device that solves the above-mentioned problems, improves reading resolution, and reduces the size of the device.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a first photoelectric conversion means that is sensitive to a relatively narrow predetermined wavelength region of visible light, and a pixel from the first photoelectric conversion means. a second photoelectric conversion means having at least one of small size and reading pitch and having sensitivity over almost the entire wavelength range of visible light;
Smoothing means for smoothing the output of the second photoelectric conversion means by M×N pixels, and color difference signal generation means for generating a color difference signal from the signal from the smoothing means and the signal from the first photoelectric conversion means. It is characterized by having the following.

[Function] In the present invention, the second photoelectric conversion means is smoothed with M×N pixels by the smoothing means, and a color difference signal is generated by the generation means from the signal from the smoothing means and the signal from the first photoelectric conversion means. do.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a first embodiment of the invention. This is three Cs
This is an example of color separation using a CD, and the optical system is the same as the apparatus shown in FIG.

In the figure, 101 is a CCO as a second photoelectric conversion means.
It is covered with a filter having human standard luminous efficiency characteristics, and outputs a luminance signal (hereinafter referred to as Y signal). 102 is a CCD as a first photoelectric conversion means;
It is covered with a red filter and outputs a red signal (hereinafter referred to as R signal). Reference numeral 103 denotes a CCD as a first photoelectric conversion means, which is covered with a blue filter and outputs a blue signal (hereinafter referred to as a B signal). C[:D
For 101, 102 and 103, one square shown in the figure is one pixel, and CCDs 102 and 103 are twice as large in the main scanning and sub-scanning directions (four times in area) as compared to CC0101. , are driven by a well-known CCO drive circuit (not shown).

The spectral transmission characteristics of each filter are shown in FIG. In FIG. 2, 401 is a spectral transmission characteristic of a filter having human standard luminous efficiency characteristics, 402 is a spectral transmission characteristic of a red filter, and 403 is a spectral transmission characteristic of a blue filter.

104Y is a sample and hold circuit (hereinafter referred to as S/11) that samples and holds serial data from the CGD 101. 104R is S/1 (and
It samples and holds the serial data from CC0102. 104B is S/] (and CCD 1
This is to sample and hold the serial data from 03. 105Y is an 8/DR converter (hereinafter referred to as ^/D), which performs ADD conversion on data from the S/H 104Y. 105R is 8/D, S/I+ 1048
This is to A/D convert the data from. 105B is A/D, and the data of S/1110487>) et al.
It is something that converts. 106 is a line buffer, A/
This is to temporarily store the digital data from D105Y. 107 is a smoothing circuit as a smoothing means;
The data from the line buffer 106 is smoothed 2×2 so that 2I2 pixels of Y correspond to one pixel of R and B. 108 is an IQ conversion circuit as a color difference signal generating means, which converts the average value Y of Y from the smoothing circuit 107;
and R and B from A/Ds 105R and 105B to convert into I and Q signals. 109.110
1. ll0Q is a line buffer that appropriately delays the signal and adjusts the timing. line buff 1
The digital data from ^/D 105Y is temporarily stored in line buffer 1101.109. For ll0Q, respectively! I signal and Q from q conversion circuit 108
The signal is stored once. 111 is RG
B conversion circuit, line buffer 1G9. ll0I, ll
Y signal from 0Q! It converts the signal and Q signal into R, G, and B signals.

NTSC defines Y, I, and Q signals as the three primary colors for transmission of standard television signals. Y is a luminance signal, which is the same as the Y signal described above. The I and Q signals are called color difference signals, and their frequency bands are limited due to human visual characteristics.

The color image reading device of this embodiment includes a smoothing circuit 10.
7, and the IQ conversion circuit smooths Y,
Since the R and B signals are converted to I and Q signals, the R
The GB conversion circuit 111 converts the 7% I5Q signal into R, G,
It is converted into a B signal.

That is, the I and Q signals are usually expressed by the following equation (1).

(2), and the Y signal is determined from the following equation (3) using R%G%B, so 1 = 0.6OR-0,28G-0,32B
...0JQ=0.21R-0,52G + 0.
31B...(2) Y=0.3OR+0.59
G + 0. lIB...(3) Substituting equation (3) into equations (1) and (2) and eliminating G, I, Q
The signal is represented by a Y%R5B signal as shown in equations (4) and (S).

1 = -0,47Y + 0.74R - 0,27B
...(4) Q=-0,88Y + 0.47R+
0.41B...(5) Compared to the original Y signal, these I and Q signals have only a higher pixel density in the main scanning direction and the sub-scanning direction, but this is a high-resolution signal. When combined with the Y signal and converted by the RGB conversion circuit 111, an output signal that is almost comparable to that obtained when all three colors R, G, and B are read at the same resolution is obtained. Therefore, the RlG and B signals obtained from the RGB conversion circuit 111 can be expressed as in the following equation (6).

In addition, in this embodiment, an example was explained in which the CCDs 102 and 103 output the R signal and the B signal, respectively. or may be expressed by a linear combination of these. When done in this way, the effect is not different depending on the quality of the wood. just,
In equations (4) and (5), if the transform coefficient becomes too large, the quantization error increases.

Further, in this embodiment, an example was explained in which a standard luminous efficiency filter was used to obtain the Y signal, but it is also possible to read a wide range of visible light wavelengths.

This is possible, for example, if no filter is used.

Furthermore, in this embodiment, an example using the luminance signal Y and color difference signals 1 and Q has been described, but instead of this, other color coordinate systems,
For example, CIE's L'', a'', b'', L'', ul, v
l may also be used.

Further, since the color characteristic of the charging conversion element whose pixel size should be minimized is close to white (in this embodiment, luminous efficiency), even if the pixel size is reduced, the loss of light amount can be minimized.

Furthermore, since the luminance signal and color difference signal can be directly obtained, data compression can be performed efficiently when storing and transmitting image data.

(Second Embodiment) This embodiment is different from the first embodiment in the configuration of the CCD. That is, in the first embodiment, three (7
) CGo 1G1, 102, 103 used, CCD
The CGD 101 is covered with a filter having human standard luminous efficiency characteristics, the CGD 102 is covered with a red filter, and the CCD 103 is covered with a blue filter.In this embodiment, as shown in FIG. ,503, CC[+
CC9503 was alternately covered with a red filter 504 and a blue filter 505. Although the sampling pitch of the CC9503 in the main scanning direction is half that of the CCD 502, the effects of this embodiment are essentially the same as those of the first embodiment.

(Third Example) This example differs from the second example in the configuration of the CCD. That is, in the second embodiment, the CCD
502 and 503 are provided on the substrate 501, and the CCO 502 is covered with a filter having human standard luminous efficiency characteristics.
0503 is alternately covered with a red filter 504 and a blue filter 505, but in this example, CCD 602°603
The CCD 602 is provided with a filter having human standard luminous efficiency characteristics as shown in FIG.
A filter 604, half of which is red and half of which is blue, is placed opposite to D 603, and the red and blue filters are alternately moved to the transmitting position every time one line is read. C
Light split by a half mirror 601 is incident on the CDs 602 and 603, respectively. GCD 60
The pixel arrangement of CC0603 is shown in FIG. 5(a), and the pixel arrangement of CC0603 is shown in FIG. 5(b). Since this is done, the effects of this embodiment are essentially the same as those of the second embodiment.

[Effects of the Invention] As described above, according to the present invention, with the above configuration, there is an effect that the reading resolution can be improved and the scale of the apparatus can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a color image reading device according to the first embodiment of the invention, FIG. 2 is a diagram showing an example of the spectral transmission characteristics of a filter, and FIG. 3 is a block diagram showing the color image reading device of the second embodiment of the invention. FIG. 4 is a diagram showing the optical system of the third embodiment of the invention, FIG. 5 is a diagram showing the CCO of the third embodiment of the invention, and FIG. 6 is the optical system of the conventional color image reading device. Figure 7 is a diagram showing the CCD shown in Figure 6, Figure 8 is a diagram showing the optical system of a conventional color image reading device, and Figure 9 is a diagram showing the COD shown in Figure 8. be. ...CCO. ...Smoothing circuit, ...IQ conversion circuit, ...RGB conversion circuit. Figure 3 Figure] 100 ■ Regular ■ Ward 2 (b) Go Twa [Summer] ■! [ Figure Figure Figure Figure

Claims (1)

[Scope of Claims] 1) a first photoelectric conversion means that is sensitive to a relatively narrow predetermined wavelength region of visible light; and at least one of a pixel size and a reading pitch smaller than the first photoelectric conversion means, a second photoelectric conversion means having sensitivity over almost the entire wavelength range of light; a smoothing means for smoothing the output of the second photoelectric conversion means by M×N pixels; and a signal from the smoothing means and the above. A color image reading device comprising color difference signal generation means for generating a color difference signal from a signal from the first photoelectric conversion means.