JPS62284577A - Color image processor - Google Patents

Abstract

PURPOSE:To improve resolution by allowing an image processing means to decide the characteristics of an image read by a color image read means and generated a color image signal to be outputted according to the decision result. CONSTITUTION:Image processing means 8 and 9 correct the irregularity in the illuminance on an original surface and the sensitivity irregularity of a color image sensor 1 by a shading correcting circuit 4a. A monochromatic image signal read by a monochromatic image sensor 2 with high resolution is passed through an A/D converter 3b and corrected by a shading correcting circuit 4b, and then inputted to a filtering circuit 6b. The filtering circuit 6b has by-pass characteristics and extracts abrupt variation of an input image signal. The output of the filtering circuit 6b is supplied to a trailing binary deciding circuit 7 as the edge detection signal of a binary image to decide a multivalued or binary image area with the output of the filtering circuit 6b, thereby generating a multivalued/binary recording switching signal. Consequently, the high-resolution processing of the binary image is performed.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a device that performs a series of processes of reading, processing, and outputting color images, and in particular, The present invention relates to a color image processing device that classifies and processes images into multivalued images and binary images.

(Prior Art) Generally, when processing a color image, the degree of color and contrast is almost completely determined by a combination of the three primary colors (red, green, blue) or their complementary colors (cyan, magenta, yellow). It is well known that it can be reproduced. Even in a digital color copying machine using a thermal transfer recording method, a color image is recorded using the above three primary colors or complementary colors.

The basic configuration of a digital color copying machine using a thermal transfer recording method is shown in FIG. This apparatus is roughly composed of three blocks: a color image reading section A, an image processing section B, and a color image 28 section C, which is a color image output means.

The image reading section A is a block for converting an image on a color document into an electrical signal, and includes a color C0D21, a block for converting nine bright and dark colors, etc. on the document into an analog image signal.
It is comprised of a fluorescent lamp 22 for illuminating the original, an A/D converter 23 for converting an analog image signal into a digital signal, and the like.

The image processing unit B converts the three-color image signals output from the color image reading unit into yellow, cyan, and magenta necessary for the next-stage color double-edge recording unit C.

It mainly performs processing to convert information into four colors of black. The shading correction circuit 24 is a color CCD sensor 2
The matrix circuit 25 separates the three color image signals into a luminance signal and a color difference signal for processing by the filtering circuit 26 at the next stage. This is a circuit that does this.

The filtering circuit 26 is composed of a low-pass filter and a bypass filter.The color difference signal is processed by the low-pass filter in order to improve the S/N, and the luminance signal is processed by the bypass filter in order to determine the binary image contrast. After being detected, the determination circuit 27 performs a binary determination. The color conversion/binarization circuit 28 is a circuit that converts luminance and color difference signals into ink amount information for each color of yellow, magenta, cyan, and black, and is used when a recording section that can only handle binary images is used. , dithering, and other processing for converting into a pseudo medium 1tII tone is also performed.

Recording section C is for recording (output) generated by image & processing section B
The color image signal is sent to the thermal head 30 for thermal transfer recording.
This block performs printing by supplying each color separately, and includes a heat storage control circuit 29 and a control circuit (not shown) for transporting the ink ribbon and recording paper.

In order to improve the recording resolution in a digital copying machine having such a configuration, the present inventors have proposed a multivalued fixed pattern method (Japanese Patent Application No. 16768/1982). In dithering and regular fixed pattern methods, the number of gradations required to obtain a comparable image takes human visual characteristics into consideration.
It is difficult to satisfy both resolution requirements. In addition, due to the effect of heat storage in the thermal head, discontinuities in gradation occur, such as crushing areas that should be treated as white, especially in medium and high density areas, and instability in low and medium density areas. There are problems such as noticeable roughness of the iii image due to ink adhesion. According to the multivalued fixed pattern method described above by the present inventors, by making use of the heat storage effect of the thermal head, which has been considered an obstacle to good recording in the past,
It is possible to record high-quality images with stable gradation and less graininess.

This multi-value fixed pattern method, for example, as shown in Figure 5,
One pixel is constituted by a matrix of a plurality of dots such as 3 x 3, and the density level range of the multivalued image signal is divided into a plurality of partial densities fI4Fa, for example, a low m degree region, a medium! The pattern is divided into three areas: a single-degree area and a high-density area, and three fixed patterns A to C are used in correspondence with each of these partial density areas. The fixed patterns A to C change the recording energy given to the dots constituting them into 111 of the multivalued image signal.
13 [It is a multi-value pattern that can be modulated according to the level (see Fig. 6).

Specifically, for example, the fixed pattern A for MS degrees is an isolated dot pattern formed by isolating one dot in one pixel, and is an isolated dot pattern formed by isolating one dot in one pixel. The @ key is expressed by changing the size of the dots by modulating the recording energy (the energy injected into the thermal head). Fixed pattern B for medium density is a striped pattern extending in the direction of relative movement between the thermal head and the recording paper (sub-scanning direction), and the gradation in the medium density area is determined by the thickness of the stripe depending on the energy injected by the thermal head. It is expressed by changing. Furthermore, the high-density fixed pattern C is a single character-shaped pattern with a white part of 2 x 2 dots, and the high-density gradation can be achieved by changing the area of the white part by the injection energy of the thermal head. is expressed by If halftone recording is performed using such a multivalued fixed pattern method, the problems that occur with the dither method or the normal fixed pattern method can be solved.

By using the multilevel fixed pattern method in this way, it is possible to more than double the recording resolution when obtaining the same number of gradations as the dither method. In addition, the resolution of the input image needs to match the output resolution in the dither method, but in recording using the multivalued fixed pattern method, an N x M image matrix is regarded as one pixel of the recorded image, so the resolution is 1/1 of the dither method. (
An input image of NX~1) pixels is sufficient.

Therefore, when recording using the multiple fixed pattern method,
It is now possible to lower the resolution of the image sensor in the color image reading section. ! It is possible to reduce the processing speed of the reading section and the image signal processing section. However, while it has the effect of reducing the number of processing pixels as described above for multi-1iii@ reading/output, on the other hand, for binary images, the resolution is 1/(NXM) compared to the dither method. It will drop.

(Problems to be Solved by the Invention) As described above, the multi-value fixed pattern method is effective for multi-value images when processing color images, but by using a low-resolution color image sensor, !
There was a problem that the image resolution was insufficient.

Therefore, it is an object of the present invention to provide a color image processing device that can obtain high resolution even for 211 images when reading and processing color images using a low resolution color image sensor.

[Structure of the Invention] (Means for Solving the Problem) In the present invention, the color image reading means is provided with a color image sensor and a monochrome image sensor having a higher resolution than the color image sensor. When performing image@processing, the characteristics of the image read by the color image reading means (for example, whether the image is a multivalued g!ii elephant or a 2@image) are determined, and an output color image signal is generated according to the determination result. is generated and supplied to a color image output means.

(Function) A high resolution color output image can be obtained even for binary images by compensating for the reduction in reading resolution caused by the low resolution color image sensor by the two-way signal from the high resolution monochrome image sensor.

(Embodiment) As shown in FIG. 1, a low [1 degree] color line image sensor 1 and a high resolution monochrome (black and white) image sensor 2 are provided as color 1iiiea capturing means. The resolution of the color image sensor 1 is determined by the matrix size of the image processing means and color image output means (recording means). This color image sensor 1
The color image signal read by A/D conversion B
3a, the signal is converted into a multivalued digital signal (for example, P!J is converted into an 8-pitched signal) and then input to an image processing means.

In the image processing means, first, the shading correction circuit 4a corrects the illumination unevenness on the document surface and the sensitivity unevenness of the color image sensor 1. The matrix circuit 5 is a circuit for correcting the hue of 9m degrees, etc., but it is also possible to perform this correction processing with a color conversion circuit 8, which will be described later, and is provided as necessary. The filtering circuit 6a is a circuit with O-pass characteristics, and is a color ii! ii 1i unnecessary for image recording
This is to remove the 2iI#I component and create a smooth halftone image.

On the other hand, the high-resolution monochrome image sensor 2 is arranged as shown in FIG. 2 in order to read the same line as the color image sensor 1.

The resolution ratio between the monochrome image sensor 2 and the low resolution color image sensor 1 is 1:3. In other words, if the number of dots on the monochrome image sensor 2 is the same as the total number of dots on the color image sensor 1, the color image sensor 1 needs to read three colors with the same number of dots, so the resolution is the same as the total number of dots on the monochrome image sensor 2. 3 times (
The larger the number, the lower the resolution.)

Similar to the color image signal from the color image sensor 1, the monochrome image signal read by the high-resolution monochrome image sensor 2 is corrected by the shading correction circuit 4b via the A/D converter 3b, and then is corrected by the filtering circuit. 6b. Filtering circuit 6b
Unlike the filtering circuit 6a described above, it has a bypass characteristic and extracts steep fluctuations in the input image signal. The output of the filtering circuit 6b is used as an edge detection signal of the binary image in the next stage binary judgment circuit 7. The 21i1 determination circuit is a circuit that determines multi-value/2Ii 1-picture division 1fII11 based on the output of the filtering circuit 6b, and generates a multi-value Ml/2@ recording switching signal.

The color conversion circuit 8 is a circuit that converts image signals of three colors (for example, R, G, and 8) read by the color image sensor 1 into information of four colors, yellow, magenta, cyan, and black, necessary for thermal transfer recording. It consists of a circuit for determining the color of an area determined to be a binary image and a circuit for determining the binary image density.

The multi-cylinder fixed pattern recording circuit 9 converts the multi-value image signal data into an NXM multi-value fixed pattern, converts the recording of each dot in the NXM matrix into information on the printing pulse width, that is, the recording energy, and Based on this, the thermal head 10 in the color image recording means is driven to perform thermal transfer recording.

Moreover, this multi-value fixed pattern recording circuit 9 has a multi-value/2W1
It has the ability to record mixed images. That is, as shown in FIG. 5, one pixel is composed of an N×M71 to Rix matrix, and the density level range of the multivalued image signal is divided into a plurality of partial densities, for example, a low density region,
It is divided into three regions, a medium density wi region and a high density region, and three fixed patterns A to C are used in correspondence with each of these partial density i regions, and the recording energy given to the dots forming the fixed patterns A to C is calculated. Modulation is performed according to the density level of the multivalued image signal. When recording a 211 image, the recording energy given to each dot is individually modulated according to the binary image signal.

In the above embodiment, the color image processing system and the monochrome 1iill processing system are separated, but as shown in FIG. 3, it is also possible to use a configuration that is almost the same as that of color copying machines currently in practical use. . In FIG. 3, a switching circuit 14 is provided which switches between the output of the color image sensor 1 and the output of the monochrome image sensor 2, and connects the A/D converter 3 to the shading correction circuit 4. The matrix circuit 5 and filtering circuit 6 are commonly used in the color image processing system and the monochrome IIA processing system.

Furthermore, in the above embodiment, the image sensors 1 and 2 are 1
Although a dimensional image sensor is shown, a two-dimensional image sensor may also be used.

Furthermore, in the above embodiment, it is determined whether the image is a multivalued image or a binary image, and an output color image signal is generated based on the determination. However, for example, image edges may be detected based on an image signal from a monochrome image sensor. , an output color image signal that has been subjected to edge enhancement processing may be generated.

Furthermore, although the above-mentioned actual b@'M has been described using an example of a digital color copying machine, the present invention can also be applied to, for example, a color facsimile machine. Facsimile transmission of color images cannot be implemented using the same binary image compression technology found in current facsimile transmissions, and an extremely large amount of data must be transferred, so practical implementation has been delayed. In this regard, according to the present invention, for color images, it is sufficient to send low-resolution data, that is, a relatively small amount of data, and it is possible to significantly shorten the transmission time. By compressing the image signal data obtained by the monochrome image sensor and transmitting the 2rfi image, it is possible to reproduce the 2rfi image without deterioration.

[Effects of the Invention] According to the present invention, the device cost can be reduced by using a color image sensor with low fallout, and by adding an inexpensive monochrome image sensor, high resolution of images can be achieved. processing becomes possible.

[Brief explanation of the drawing]

FIG. 1 shows color image processing I according to an embodiment of the present invention]! FIG. 2 is a block diagram showing the configuration of the apparatus; FIG. 2 is a diagram showing the arrangement of image sensors constituting the color image capturing means in the same embodiment; FIG. 3 is a color image processing according to another embodiment of the present invention. FIG. 4 is a block diagram of a color copying machine, which is a conventional color image processing device, and FIGS. It is a figure for explaining. 1... Color image sensor, 2... Monochrome image sensor, 3a, 3b-A10 converter, 4, 4a, 4
b, 5.5a, 5b, 6.6a, 6b, 7.8.9...
- Uniformity processing means, 10... Color image recording means (color image output means). Applicant's agent Patent attorney Takehiko Suzue Figure 5 Figure 6

Claims (6)

[Claims] (1) A color image reading means, an image processing means for processing the color image signal obtained by this means to generate an output color image signal, and a color image reading means based on the output color image signal obtained by this means. A color image processing device comprising: a color image output means for outputting a color image;
The color image reading means has a color image sensor and a monochrome image sensor having a higher resolution than the color image sensor, and the image processing means determines the characteristics of the image read by the color image reading means and processes the determination. A color image processing device that generates an output color image signal according to a result. (2) The image processing means includes means for determining whether the image read by the color image reading means is a multivalued image or a binary image, and if the result of this determination is a multivalued image, an image signal from the color image sensor is provided. , and in the case of a binary image, generating a color image signal for output based on the image signal from a monochrome image sensor. 2. The color image processing device according to item 1. (3) The image processing means determines the characteristics of the image read by the color image reading means based on the image signal from the monochrome image sensor. Or the color image processing device according to item 2. (4) Color image processing according to claim 1, wherein the image processing means determines the color of the image read by the monochrome image sensor based on a color image signal from the color image sensor. Device. (5) When the image read by the color image reading means is a multivalued image, the image processing means configures one pixel as a matrix of a plurality of dots, and selects a fixed pattern formed within the matrix. to generate an output color image signal, and in the case of a binary image, the output energy of the color image output means corresponding to each of the dots is individually modulated according to the binary image signal. A color image processing apparatus according to claim 2. (6) The color image processing apparatus according to claim 1, wherein the color image output means records a color image.