JPH01302964A - Color picture reading device - Google Patents

Abstract

PURPOSE:To reduce the noise of the color boundary part of a read picture by providing a color signal converting means consisting of a luminance signal extracting means, a detecting means, an interpolating means and a selecting means. CONSTITUTION:The luminance signal extracting means 61 considers a signal from a prescribed light receiving element as a luminance signal, and extracts the luminance signals corresponding to an (n-1)-th, an n-th and an (n+1)-th picture elements, where (n) is a positive integer, as the luminance signals existing at the same time. The detecting means 62 detects the differences between the (n+1)-th and the n-th luminance signals and between the n-th and the (n-1)-th luminance signals among said extracted luminance signals. The interpolating means 63 obtains the color signal between the n-th color signal and the (n-1)-th or the (n+1)-th color signal from the n-th and the (n-1)-th or the (n+1)-th color signals of the same kind by interpolation. Then, one signal among the n-th color signal, the (n-1)-th color signal or the (n+1)-th color signal and an interplated signal obtained from the means 63 is outputted as the n-th color signal according to a detected difference signal detected by the means 62 by the selecting means 64.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color image reading device that converts a color image into an electrical signal, and particularly to a color image reading device that can improve the quality of the read image.

[Conventional technology]

FIG. 3 is a block diagram showing a general color image reading device. In FIG. 3, an original (1) is placed on an original table (2) at 10°C. The document (1) is placed below this document table (2).
A fluorescent lamp (3) is arranged as an illumination means for illuminating the area. Further, a rod lens array (5) as an imaging means for forming a color image of the original (1) on the image sensor (4) is also arranged near the fluorescent lamp (3).

- The color image reading device installed on a boat is constructed as described above, and the document (1) placed on the document table (2) is illuminated by a fluorescent lamp (3), and the color of the document (1) is illuminated by a fluorescent lamp (3). The image is captured by an image sensor (
4) A fluorescent lamp (3), an image sensor (4), and a Rotunda Nzua V are imaged as an erect, same-size real image.
A (5) moves together in the direction of arrow A relative to the original (1) and the original platen (2), so the original (
The image information in 1) is sequentially converted into electrical signals for each scanning line.

Figures 4 and 5 are, for example, Japanese Patent Application No. 61-18440.
FIG. 2 is a plan view of the image sensor (4) shown in No. 2, and a plan view showing the arrangement of color filters in the light receiving portion on the image sensor (4). In FIG. 4, the image sensor (4) includes an insulating substrate (41) and an insulating substrate (41).
1) Multiple CCDs (Char
ge-Coupled Device) image sensor chip (42). In FIG. 5, one pixel (43) corresponds to one CCD image sensor chip (43).
2) Light receiving elements (431) to (434) with 6e function on top
Consists of. The light receiving element (431) has no color filter (5), and the light receiving elements (432), (433), and (434) have yellow (Y), green (G), and cyan (C) color filters, respectively. is a light receiving element formed on the surface. The light incident on the light-receiving elements (431) to (434''l) is converted into an electrical signal and taken out to the outside by CCD channels (not shown) arranged on both sides of the light-receiving element array.

Next, a method of converting the output value extracted as described above into an m value, which is a general color signal, will be described. The light receiving element (43) constituting the n-th pixel (43)
The output values obtained from 1) to (434) are
, Any , Ang , Anc, the RGB values are obtained by the following equation (1).

The 3-by-4 matrix used in equation (1) is the transformation matrix) 1
It is called 727M and has the following elements, for example.

Next, the operation of the conventional color filter array will be explained. For example, the size of one pixel (43) is "2".
”, the output value Anw of each light receiving element (431) to (434) in the pixel (43) is
Any, Ang, Anc is Anw=2, Any
=2, Ang=1, Anc=1. Using these values and formulas (1) and (2), RlG,
When B is determined, R=1, G=1, B=0, and it can be seen that the color of the light incident on the pixel (43) is yellow.

However, the image of document (1) is not of one type of color, and there are always boundaries between colors. What happens to the values of R2G and H in this case will be explained in the case where the color boundary is located approximately at the center of the pixel (line L in FIG. 5). For example, white light having a size of "3" enters the light receiving elements (431) and (433), and the light receiving element (432).

If black light with a magnitude of 0° is incident on (434), the output value An of each light receiving element (431) to 434) is
lol.

A n '/ + A n g + A n C is A
nw= 3, Any= 0 +Ang= 1 +
Anc = 0 tonal. Formula (1), (2) K twist R
, a, B ([EwoiX'\, Rn = 3, Gn = 1, Bn = 3. This indicates a magenta color, and magenta is mixed on the boundary between white and black. It can be seen that the noise is caused by

[Problem to be solved by the invention]

As described above, when reading a color image, the conventional color image reading device scans the image g when the color boundary part on the document (1) is in the center of one pixel (43). There was a problem in that the photo-sleep conversion output of (43') was completely different from the color of original (1), and noise was introduced into the outline of the read image.

The present invention has been made to solve these problems, and an object of the present invention is to provide a color image reading device that can reduce noise at color boundary portions of a read image with a simple configuration.

[Means to solve the problem]

The color image reading device according to the present invention uses a signal from a light receiving element without a color filter as a luminance signal, and luminance signals corresponding to the (n-1)th and nth (n+1)th pixels, where n is a positive integer. A luminance signal extracting means extracts the luminance signals existing at the same time, the (n+1)th and nth, and the nth and (n-1)th of the extracted luminance signals.
)-th luminance signal detection means for detecting the difference between the n-th and (
an interpolation unit that interpolates and obtains a color signal between the n-1)th or (n+i)th color signals of the same type; an nth color signal according to the detection difference signal detected by the detection unit;
Color signal conversion means having a selection means for outputting one signal from among the (n-1)th or (n+1)th color signal and the interpolated signal obtained from the interpolation means as the nth color signal. It has been established.

[For production]

In this invention, the luminance signal extracting means and the detecting means detect a change in the image in the vicinity of the n-th pixel.

Then, if the change in the image is local, the selection means selects the color signal of the n-th pixel by a combination of light receiving elements that do not include the change area, and if the change in the image is smooth, the selection means selects the color signal of the nth pixel by using a combination of light receiving elements that do not include the change area, and if the change in the image is smooth, the selection means Selecting a color signal containing the output of the means. This makes it possible to achieve color signal conversion that is optimal for the original image, and to significantly reduce noise in the contours of the image.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram showing a color signal conversion circuit as a color signal conversion means which is a signal processing section of a color image reading device according to the present invention. This color signal conversion circuit (6) includes latches (611) to (61) as luminance signal extraction means (61).
3), a subtracter (621) as a detection means (62), (
622), insulation value calculation circuit (623L (624), comparators (625), (626), sign determiner (627),
Latches (631) to (636) as interpolation means (63)
), interpolation circuits (637'), (638), and selection means (
64) as a selector (641).

(642), and latches (651) and (652) that temporarily hold and delay the green (G) signal.

In addition, input terminals (661), (662), (663),
(664) contains the signal W input by AD converting the signal from the light-receiving element (431) without a color filter in FIG. A light receiving element (G) with a color filter formed on its surface (
432').

Signals Y, C1 and G obtained by AD converting the signals from (434') and (433) are input.

These signals W, Y, C, and G are respectively input in order from the output of the first light receiving element (431) in synchronization with a reference clock (not shown). Also, the output terminal (671), (
672) and (673L (674) output the processed color signals W', Y', C', and G'.

The embodiment of the present invention is constructed as described above, and its operation will be explained below using the color signal conversion circuit (6) shown in FIG.
The operation of the selectors (641) and (642) will be explained in detail with reference to an explanatory diagram.

In this embodiment, the signal W from the light receiving element (431) on which no color filter is formed is regarded as a luminance signal.

The (n-1)th, nth, and (n+1)th signals W input to the input terminal (661) are latched (611).
The signal W(n-1
') +Wn +W(n+1). These signals W
(n-1), wn, W(n+1) are subtractors (621
).

(622). Subtractor (621), (62
2) subtracts the input signal, the subtracter (621) outputs a subtraction signal Wn-W(n-1), and the subtracter (622) outputs a subtraction signal W(n+1)-Wn. Sign determiner (627
) operates as an exclusive OR circuit, extracts only the most significant bit of the input subtraction signal Wn - W (n-1) + W (n+1) - Wn, and calculates (W (n+1) - Wn
) , or whether it is an extreme value. In Fig. 2, the sign of S is indicated by + and -. On the other hand, the outputs from the subtractors (621) and (622) The subtracted signals (WCn-+) -Wn) and (
Wn-W(n+1)) is the absolute value calculation P path (623L(
624) through the absolute value signal l W(n+1) −W
n l and l Wn -W (n +1) l, which are compared with a constant value a in comparators (625) and (626), and are sent to selectors (641) and (6
42).

On the other hand, the light receiving element (4) inputted to the input terminal (662)
The (n-1)th and nth signals Y from 32) are
Signal Y at the same time through latches (631) to (633)
(n-1) Jn, Y(n+1). Then, by the interpolation circuit (637), (Yn+Y(n-1))/2
An interpolated signal Yn, (n-1) corresponding to is obtained and sent to the selector (641). The selector (641) selects the input signal Y(n'
) t(Yn+Y (n-1))/2, select the signal shown in Figure 2 from Yn, and connect it to the output terminal (β7
2) as an output signal Y'.

Furthermore, the signal C input to the input terminal (663) is also processed in exactly the same way as the signal Y described above, and the selector (642) selects the input C according to the signals S, Ml, and M2.
(n-+), (Cn+C(n-1)')/lcn, select the signal shown in Figure 2, and connect the output terminal (6
73) as an output signal C'.

Furthermore, regarding the signal W input to the input terminal (661) and the signal G input to the input terminal (664), the n-th signal is left unchanged at the output terminals (671'l, (674)
) are output as output signals wl and cl.

Next, a detailed explanation will be given below of how the color signal conversion circuit (6) can reduce noise in the contour portion of a read image.

First, a case will be explained in which the outline of the read image is very sharp. As shown in Fig. 5, the outline of the read image is (
n-1') If it is located at a position corresponding to between the I-th light-receiving element and the n-th light-receiving element (431) without a color filter, that position is the (n-1)-th yellow color filter Y. It is thought that it is located on a light receiving element having (n-1) formed on its surface.

In this case, the read image does not change significantly between Wn and W(n+1), and therefore, noise in the contour does not occur even if the color signal for the n-th pixel is set to Wn+Yn, Gn, and cn. At this time, a comparator (625).

The input of (626) is l Wn −W(n-1) l > aIW(n+1)
-Wn l < a, so M
l is dog, M2 is small, and from FIG. 2, Yn and Cn are output as output signals Y' and C'.

Assuming that the contour of the read image is located at a position corresponding to between the n-th and (n+1')-th color filters and the light receiving elements, that position corresponds to the position where the n-th yellow color filter Yn is formed on the surface. It is thought that the light-receiving element is located above the At this time, since the read image has not changed significantly between W(1-t) and Wn, the color signals for the n-th pixel are Wn, Y(n-1), and Gn.

If C(n-+), no noise will occur on the contour.

In this case, the inputs of comparators (625) and (626) are l
Wn −W(n-1) l < al W(n+
1) Since the relationship -Wn l n a is satisfied, Ml is small and M2 is a dog, and from Fig. 2 Y(
n-+), C(n-s>) are output as output signals Y' and C'.

Next, a case where the contour of the read image is smooth will be explained. In this case, the (n-1)th, nth and (n+1)th
)-th pixel, there is no significant change in the color signal, and the following relationships hold: l Wn - W(n-1) l < a l W(n+x) - Wn l < a. Therefore, both Ml and M2 become small, and the color signal for the nth pixel becomes Wn.

Even with Yn, Gn, and Cn, noise does not occur on the contour. The outline of the read image is l Wn - W(n-]) l > al
When the relationship W(n+1) -Wn l > a is satisfied, W(n-1), Y(n-1), Wn+
It is considered that the image changes relatively significantly in the region of Yn and W(n+1). Therefore, the color signal for the n-th pixel is Wn +
Y (n-1) + G n + C (n 1)
However, the color will be different from the original. Therefore, S in Figure 2 is +
, Ml is dog and M2 is large, the color signal of the nth pixel is Wn, (Yn+Y(n-+))/2,G
n, (Cn+C(n-1))/2, Yn,
If the output signals Y' and C' at the position Cn are predicted by interpolation and used as the value of the n-th pixel, it is possible to reduce noise in the contour part.

In addition, although the signal S is normally "+", there is almost no change in the image, and due to noise (W (n + 1) - W
If n') and (Wn-W(n-1)) have different signs, or if the image is extremely fine, it may become "-". In the former case, the signal S can be treated in exactly the same way as when the signal S is "+", and in the latter case, the reading limit of this type of image reading device is exceeded, so Wn+Yn, Gn
, Cn are the output signals of the n-th pixel. in this case,
Since the change is one pixel, the read image quality itself hardly changes.

In the above embodiment, one pixel is composed of a light-receiving element having four types of color filters formed on its surface, but the combination of color filters is not limited to this. or green.

Even if a color filter such as blue is used, the same effect as in the above embodiment can be obtained.

Further, in the above embodiment, the output signal from the light receiving element without a color filter was used as the luminance signal, but (Wn+G
n ), (Yn+Cn), Gn, etc. may be used, and the same effects as in the above embodiments can be achieved.

〔Effect of the invention〕

As detailed above, the present invention uses a signal from a light receiving element without a color filter as a luminance signal, and corresponds to the (n-1)th, nth, and (n+1)th pixels, where n is a positive integer. A luminance signal extracting means for extracting a luminance signal as a luminance signal existing at the same time;
Detection means for detecting the difference between the n-1)th luminance signals; an interpolation means for interpolating the color signal between the n-th and (n-1)th or (n+1)-th similar color signals; and said detection means. color signal conversion means comprising a selection means for outputting one signal from among the nth color signal and the interpolation signal obtained from the interpolation means as the nth color signal according to the detected difference signal detected by the means; By providing this, the brightness signal extraction means and the detection means can detect changes in the image of the original, and based on the characteristics of the original image, the selection means can convert the color signal most suitable for the original image. This has the effect of significantly reducing noise in the area.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a color signal conversion circuit according to an embodiment of the present invention, FIG. 2 is a diagram showing a function table explaining the operation of the selector of this color signal conversion circuit, and FIG. 3 is a block diagram showing a color signal conversion circuit according to an embodiment of the present invention. 4 is a plan view showing the image sensor used in the color image reading device shown in FIG. 3; FIG. 5 is an enlarged plan view of the light-receiving element portion of the image sensor shown in FIG. 4. It is a diagram. In the figure, (1) is the original, (3) is the fluorescent lamp, (4) is the image sensor, (5) is the rod lens array, and (6) is the image sensor.
is a color signal conversion circuit, (61) is a luminance signal extraction means, (6
2) is a detection means, (63) is an interpolation means, and (64) is a selection means. 1 Hara Akira 3 Fluorescent 1-4, Zumage 5 Mouth/Sodoshi Yuzu'7L Procedures Amendment December 22, 1988

Claims (1)

[Claims] an illumination device that illuminates the original; a plurality of light receiving elements that converts a color image obtained by illuminating the original into an electrical signal; and an imaging device that forms the color image on these light receiving elements; A plurality of color filters disposed on the light-receiving element and color-separating the formed color image and a signal from a light-receiving element without a color filter are defined as luminance signals, and n is a positive integer (n- 1) Luminance signal extracting means for extracting the luminance signals corresponding to the pixel, nth, and (n+1)th pixel as luminance signals existing at the same time;
detection means for detecting the difference between the n-th and (n-1)th luminance signals;
+1)th color signal of the same type by interpolating the color signal between them, and according to the detection difference signal detected by the detection means, the nth color signal, the
n+1)th color signal, and a color signal conversion means having a selection means for outputting one signal from among the interpolated signals obtained from the interpolation means as the nth color signal. Image reading device.