JPH0414377A - Color copying machine - Google Patents

Abstract

PURPOSE:To obtain a sharp copy picture without color slurring with respect to a character or a line drawing with a small line width by discriminating a noted area to be a colored area when plural color data corresponding to a block area are all white level data. CONSTITUTION:A color discrimination section identifies a color and a density in the unit of picture elements based on color data R, G, B with respect to one picture element to generate a color data and a density data. An area discrimination section discriminates the noted area into a color area and a monochroic area based on a color data C and a density data with respect to the erase unit area in an area discrimination matrix comprising a noted area X and plural peripheral areas Y surrounding the area X. Then the area discrimination section discriminates the noted area to be the color area when plural color data are all white level data corresponding to the block area of a prescribed size comprising at least the area X and the area Y.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color copying machine having a plurality of developing means for developing different colors.

[Conventional technology]

Generally, in color copying using an electrophotographic process, three primary color toners, yellow (Y), magenta (M), and cyan (C), are used, and by overlapping toner images of these colors, full-color copies including black are produced. An image is formed.

By the way, in a color copy image, if there is a slight misalignment in the overlapping of the toner images of each color, such misalignment may be visually noticeable, especially in parts of the copy image where the line width is small, such as characters or line drawings. This is noticeable as so-called roughness, which may reduce the image quality.

In order to prevent such deterioration in image quality, conventional color copying machines use yellow (Y),
The three subtractive primary colors of magenta (M) and cyan (C), -C
A blank (B) corresponding to the black color used for letters and line drawings.
A developing device corresponding to each of the four toner colors (K), an image sensor that reads the original image by dividing it into pixels, and a latent image on the photoconductor divided into erase unit areas of a predetermined size. Based on the document information read by the image sensor, the color of each pixel of the document is discriminated between black and other colors, and the color of each pixel of the document is discriminated between black and other colors. In the image forming process of each toner image, the latent image corresponding to the pixel determined to be black is erased (preventing toner adhesion by eliminating static electricity); conversely, in the image forming process of a blank toner image, the latent image corresponding to the pixel determined to be black is It is configured to erase a latent image corresponding to a pixel.

In other words, when reproducing a document image in full color, the black portion of the document image is formed using only black toner, and the other portions are formed using an appropriate combination of three primary color toners. There is.

Normally, an eraser is composed of a large number of light emitting elements that are selectively controlled to turn on and off, and in order to uniformize the amount of light irradiated onto the photoreceptor, the eraser is placed on the photoreceptor so that the irradiation areas of adjacent light emitting elements partially overlap. placed against.

[Intelligence to be Solved by the Invention No. 8] According to the conventional color copying machine described above, a general case where a color image portion and a monochrome image portion coexist, such as a document image consisting of a color photograph and its explanatory text, can be processed. A clear copy image without color shift can be obtained for characters or line drawings with small line widths expressed in black in a color original image.

In this specification, the term "monochrome image area" and "color image area" refers to the classification of manuscript images based on the observer's recognition of their significance as information such as characters and designs, rather than microscopically. The area represented by the base color of the paper (usually white, although it includes transparency) and a specific color other than the base color (usually black) is called the monochrome image area. An area other than the monochrome image area, that is, an area represented by a plurality of colors including at least the base color and one color (usually colored) other than the specific color, is referred to as a color image area.

However, conventionally, all the different color parts of the original image are created using only black toner, regardless of whether it is a monochrome image part or a color image part. Part of the original image may disappear (so-called color fading) due to the overlap of the irradiation areas of each light emitting element of the eraser in areas where the colored part is adjacent to the colored part of the paper other than the base color. It was alive. In other words, Y in the area where the irradiation areas overlap.

During image formation using M and C toners, and during image formation using BK toner, the image is erased redundantly, and no toner of any color adheres.

In addition, due to errors in image sensor resolution and color discrimination, non-black areas may be reproduced as black, resulting in color unevenness, or the subtle color tones of black images in color image areas may appear uniform. It can be reproduced as black, or even
In images where the color tone changes gradually, a phenomenon occurs in which the boundary between a black part and the surrounding part is unnaturally emphasized.

For this reason, there is a problem in that the reproducibility of the color image portion of the original image is poor, and the copied image as a whole becomes unnatural and visually unnatural.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a color copying machine that can suppress the occurrence of color fading in images and obtain color copy images with as high color reproducibility as possible.

Means for Solving Problem C718] In order to solve the above-mentioned problem, a color copying machine according to the invention of claim 1 has a plurality of developing means with different developing colors, and uses the developing means to develop an image of a document. In a color copying machine that copies images in color, a manual scanner reads an image of the original, and a unit area for each unit area into which the image of the original is divided based on the original information read by the original reading means. color data output means for outputting color data indicating a hue of the unit area, and a plurality of the colors corresponding to a block area of a constant size consisting of a unit area of interest in the unit area and a plurality of peripheral unit areas around the unit area; an area discriminating means for discriminating the unit area of interest into a monochromatic area and a colored area based on the data; and for the monochromatic area, image formation is performed by only a specific one of the developing means; and an image formation control means for controlling the colored area to be imaged by a plurality of developing means, and the area determination means is configured to detect that at least a plurality of the color data corresponding to the block area are formed. When the data is all white indicating white, the area of interest is determined to be a colored area.

The color copying machine according to the invention of claim 2 is a color copying machine that has a plurality of developing means with different developing colors, and that uses the developing means to copy an image of a document in color, and that reads the image of the document. A reading unit and an image that outputs color data indicating the hue and density data indicating the density of the unit area for each unit area obtained by dividing the image of the original based on the original information read by the original reading unit. an information output means, and a plurality of pieces of color data and density data corresponding to a block area of a certain size consisting of a unit area of interest in the unit area and a plurality of peripheral unit areas around the unit area; an area discriminating means for discriminating a unit area into a monochromatic area and a colored area; image formation is performed for the monochromatic area by only a specific one of the developing means; and an image formation control means for controlling image formation by a plurality of developing means, and the area determination means is configured such that at least the plurality of color data corresponding to the block area are all black data indicating black. If the block area is present and the density of the block area is light, the area of interest is determined to be a colored area.

[Work] The document reading means reads an image of the document.

The color data output means outputs color data indicating the hue of each unit area into which the image of the original is divided, based on the original information read by the original reading means.

The image information output means outputs, for each unit area obtained by dividing the image of the original, color data indicating the hue and density data indicating the density of the unit area, based on the original information read by the original reading means.

The area determination means is configured to classify the unit of interest into a single color based on a plurality of pieces of color data or color data and density data corresponding to a bronc area of a certain size consisting of the unit of interest and a plurality of peripheral unit areas around the unit of interest. At this time, when at least the color data is all white data indicating white, or at least when the color data is all black data indicating black and the density of the block area is light, attention is paid to the block area. Determine the area as a colored area.

The image formation control means controls the electrophotographic process so that images are formed using only one specific developing means for monochromatic areas, and images are formed using a plurality of developing means for colored areas. .

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a front sectional view showing the general structure of the copy Ill, and FIG. 3 is a plan view of the editing eraser 5. As shown in FIG.

A photoreceptor drum 3 having a photoreceptor PC on its surface is rotatably arranged approximately in the center of the copy Ill, and around the photoreceptor drum 3 are a charger 4, an editing eraser 5, a developing device 6, a transfer device 11, A cleaning device 22 and a main eraser 23 are provided.

As shown in FIG. 3, the editing eraser 5 is an LED in which a large number of LEDs 65, 65... are arranged in a row in a holder.
Consists of an array. Each LED 65 has an erase bit dl (dl=0.254m+
), and the timing of lighting and extinguishing the lights is individually controlled. Further, the erase pitch in the sub-scanning direction is determined by the rotation speed of the photosensitive drum 3 and the processing time of blinking control of the LED 65, but in this embodiment, it is 0. 25
It is set in 4 cabinets. Therefore, the size of the erase unit area on the surface of the photosensitive drum 3 is 0.25
It is 4■X0.254 kaku. Note that on the surface of the photosensitive drum 3, the unit irradiation area hi irradiated by each LED 65 is slightly larger than the erase unit area (Cd2>di).

That is, in the adjacent LEDs 65, the corresponding unit irradiation areas hi partially overlap with each other. This compensates for the unevenness of the irradiation caused by the directivity of the light emitted from the LED 65, and makes the amount of irradiation substantially equal between the center and the periphery of the erase unit area, making uniform erasing possible.

Returning to FIG. 2, the developing device 6 includes four developing units 78, 9, .
10, and these are integrated in the vertical direction (arrow M
2. M3 direction), and toner can be supplied to the surface of the photoreceptor drum 3 from any developing device. Developer device 7
10 contain yellow toner (Ty), magenta toner (Tm), cyan toner (Tc), and black toner (Tbk), respectively. Note that the developing device 6 is not limited to a type that can move up and down, but may be of a type that can selectively supply toner of different colors to the photoreceptor drum 3.

The transfer device 11 temporarily transfers and holds the toner attached to the surface of the photosensitive drum 3 onto the surface of a transfer belt (intermediate transfer medium) 15. This transfer heald 15 is made of a conductive material containing carbon resin or the like. A conductive substrate made of polyester is provided with a derivative such as polyethylene on the surface thereof, and is supported by being wound around rollers 12, 13, and 14 arranged parallel to the photosensitive drum 3.

A pressure roller I6 is arranged between the roller 12 and the roller 13 inside the transfer belt 15, and these move integrally with respect to the photosensitive drum 3, and the transfer heald 15 is moved by the vertical movement of the pressure roller 16. It contacts or separates from the photoreceptor drum 3. Also, roller 13. A guide plate 18 is provided along the transfer belt 15 between the transfer belts 14, and a cleaning device I9, a charger 20, and a charger 21 are arranged outside the guide plate 18 so as to face the guide plate. Further, a secondary transfer charger 24 is provided below the roller 14 to face the transfer belt 15 , and a separation charger 25 is provided on the side of the secondary transfer charger 24 .

An optical system 27 that exposes the surface of the photosensitive drum 3 is arranged at the top of the copying machine 1 . The optical system 27 is installed below the document platen glass 26 so that the document image can be scanned in the direction of arrow M5 (sub-scanning direction), and includes a first slider 28 having an exposure lamp 29 and a mirror 31, and mirrors 33, 34.
It consists of a second slider 32, a filter section 38, a main lens 35, fixed mirrors 36 and 37, and the like.

The first slider 28 is driven to move at a speed of v/n (n is the copying magnification) with respect to the circumferential speed V of the photosensitive drum 3, and the second slider 32 is driven to move at a speed of v/2n. #Be controlled. The filter section 38 has B (blue), BK (black), and BK (black), depending on the color of the toner used for developing the latent image, Y (yellow), M (magenta), C (cyan), and BK (black).
G (green), R (red) spectral filters,
It is configured such that four types of filters, including a ND filter and an ND filter having uniform light transmission characteristics in the visible range, can be inserted into the exposure optical path by switching between them.

Near the main lens 35, there is a color image sensor 51 for detecting the color of each pixel obtained by subdividing the original image.
A lens 51a for forming a document image on the color image sensor 51 is arranged.

The color image sensor 51 has three element rows in the sub-scanning direction, each consisting of a large number of light-receiving elements arranged in the main-scanning direction.
A filter, a G filter, and a B filter are provided.

One light receiving element corresponds to one pixel of the original image, and each light receiving element outputs a photoelectric conversion signal corresponding to the intensity of reflected light for one color of the pixel. In the following explanation, the signal or data corresponding to the light receiving element provided with the R filter will be referred to as R data, and similarly the signal or data corresponding to the light receiving element provided with G and B filters will be referred to as G data, respectively. It is sometimes called B data.

The pixel pitch of the color image sensor 51 in the main scanning direction is 0.127 mm. The pixel pitch in the sub-scanning direction is determined by the scanning speed of the optical system 27, etc., but in this embodiment, it is set to 0.
It is set to be 127°. Therefore, the size of pixel g is 0°127×0.127°, which is one quarter of the erase unit area h (see FIG. 10).

On the other hand, a paper feed section 40 is provided at the lower left side of the copying machine 1 for feeding paper P on which a copy image is formed, and a paper feed section 40 is provided at the lower right side to accommodate paper P on which a copy image is formed. A paper tray 30 is provided. The paper feed section 40 is composed of a manual paper feed section 41 each equipped with paper feed rollers 45, 44, and 47, an upper paper feed cassette 42, and a lower paper feed cassette 43. Paper P is supplied. The paper P supplied from the paper feed section 40 passes through a conveyance path including a timing roller 46, a conveyance belt 48, and a fixing device 49, and is discharged onto the paper discharge tray 30.

The basic color copying operation of the copying machine 1 configured as above will be explained.

First, when the operator instructs the start of copying operation with the document tray placed on the document table glass 26,
Arrow M of the photosensitive drum 3 based on the drive of the main motor 2
As the photoreceptor drum 3 rotates in one direction, the outer circumferential surface (photoreceptor PC) of the photoreceptor drum 3 is uniformly charged to a predetermined potential due to the discharge of the electrification charger 4 .

In the optical system 27, the first slider 28 and the second slider 3
2 move in the direction of arrow M5, and the reflected light of the light irradiated onto the document sheet from the exposure lamp 29 is reflected by the mirrors 31 and 33.
．． 34, filter section 38, lens 35 and mirror 36.
The photoreceptor drum 3 is exposed through 37. This results in
A latent image is formed on the surface of the photoreceptor drum 3 by projecting an image of the document (original image).

Next, the editing eraser 5 erases the surface charges within a predetermined range around the latent image on the photosensitive drum 3. This prevents excess toner from adhering to the photoreceptor drum 3, and a copy image with a margin provided around the paper P is formed. At the same time, charges in a predetermined area other than the boundary area EV (described later) are also erased based on area data DX, which will be described later.

Subsequently, development is performed using toner supplied from a predetermined developing device at a portion where the photoreceptor drum 3 and the developing device 6 face each other, and a toner image is formed on the photoreceptor drum 3.

On the other hand, in the transfer device 11, the pressure roller 16 is moved upward as shown in FIG. 2 by the drive of the main motor 2.
The transfer belt 15 lightly contacts the outer circumferential portion of the photoreceptor drum 3 between the pressure roller 16 and the roller 13, and is rotated in the direction of arrow M4 in this state, while being uniformly charged by the charger 21. Ru. Note that the moving speed of the transfer belt 15 is set to be the same as the circumferential speed of the photosensitive drum 3.

When the toner image formed on the surface of the photoreceptor drum 3 faces the contact portion with the transfer belt 15, the toner image is primarily transferred to the transfer belt 15 electrostatically.

After the primary transfer, residual toner is removed from the surface of the photosensitive drum 3 by a cleaning device 22, and the main motor 2
3 erases residual charges and prepares for the next exposure.

The toner image transferred to the transfer belt 15 is transferred to the transfer belt 1
5 is conveyed in the direction of arrow M4.

The above operation is repeated for each color in the order of yellow, magenta, cyan, and black, and a multicolor toner image is formed by overlappingly transferring the toner images formed in each color onto the transfer heald 15. Note that marks are attached to the transfer heald 15, which are detected by a sensor (not shown), and the toner images of each color transferred to the transfer heald 15 are aligned.

On the other hand, the paper P supplied from the paper feed section 40 is transferred to the timing roller 4 in synchronization with the movement of the transfer belt 15.
6, and the toner image on the transfer belt 15 is secondarily transferred onto the paper P by the discharge of the secondary transfer charger 24 at a portion facing the secondary transfer charger 24.

The paper P on which the toner image has been transferred is separated from the transfer belt 15 by the separation charger 25 and sent to the fixing device 49 by the conveyance belt 48. In the fixing device 49 , the toner image is subjected to thermal spacing fixing, and the paper P on which the toner image is fixed as a copy image is discharged to the paper discharge tray 30 .

The cleaning device 19 removes residual toner from the surface of the transfer belt 15 that has passed through the portion facing the second transfer charger 24, and the residual charge is erased by the neutralization charger 20, thereby preparing the surface for the next transfer.

Figure 4 shows the operation panel 7 attached to the top of the copying machine 1.
FIG.

The operation panel 70 includes a print key 300 for starting the copying operation and a 7-segment L for displaying the number of copies.
ED301, numeric keypad 3 for setting the number of copies, etc.
02, clear/stop key 303, interrupt key 30
4. Copy magnification setting keys 305, 306, LED 307 to display the copy magnification, up and down keys 310, 308 to change and set the density of the copied image step by step, auto/manual switch key 309 for density setting, Density display LED 311, development color selection sections 325 to 330 consisting of keys and display LEDs, copy mode selection sections 331, 3
32 are provided.

FIGS. 1A to 1C are diagrams schematically showing the state of color copying according to the present invention.

In FIG. 1(A), the manuscript is a printed matter using white paper, and the manuscript image G is composed of a color image portion Gc such as a color photograph, and a monochrome image portion Gm such as a black character string. shall be carried out.

When such a document is placed on the document table glass 26 with the document image G on the bottom side and the print key 300 is pressed, the document image G is read by the color image sensor 51 before starting image formation. A preliminary scan is performed for this purpose.

The output signal SO of the color image sensor 51 is sent to the image processing section 100. The image processing unit 100 discriminates the original image G into a colored region EC and a monochromatic region EM based on the signal SO, as described later, and uses the result of the discrimination as region data DX.
be memorized as .

In the example of FIG. 1(A), for the sake of simplicity, the entire head of the color image area GcO is determined to be the colored area EC, and the entire area of the monochrome image area Gm is determined to be the monochromatic area EM. shall be.

After the above preliminary scanning process is completed, a first image is formed on the document. At this time, the Y developing device 7 and the B filter of the filter section 3 are selected and set at predetermined positions.

Through exposure scanning, the charge on the photoconductor PC uniformly charged by the charger 4 is removed by light transmitted through the B filter, and a color image area Gc (i.e., colored area EC) and a monochrome image area are formed on the photoconductor drum 3. Latent images ZCb and ZMb corresponding to each of Gm (that is, monochrome area EM)
is formed (state al in the figure).

In parallel with this, the editing eraser 5 erases the latent images Z in the latent images ZCb and ZMbO based on the discrimination results during preliminary scanning.
Mb is erased (state of bl), and the remaining latent image ZCb is developed with Y toner to form a toner image T.
Cy is formed (cl state). The toner image TC7 is transferred to the transfer belt 15 (state of di).

Next, in the second image formation using the G filter, the latent image Z
Cg and ZMg are formed (state of C2), and these latent images Z
Latent image ZMg corresponding to monochrome area EM of Cg and ZMg
is erased (state b2).

The latent image ZCg is developed with M toner (state of C2), and the formed toner image TCm is transferred onto the transfer belt 15 in a superimposed manner on the Y toner image TCy previously transferred (state of d2). 1ri.

In addition, in the third image formation using the R filter, the latent image Z
Cr and ZMr are formed (state of C3), and these latent images Z
Latent image ZMr corresponding to monochromatic area EM in Cr and ZMr
is erased (state b3).

The latent image ZCr is developed with the C toner (state C3), and the toner image TCC formed by the development is transferred onto the transfer belt 15 so as to be superimposed on the toner images TCy and TCm previously transferred (state d3). condition).

Subsequently, in the fourth image formation using BK (blank) as the developing color, a latent image ZC corresponding to each of the colored area EC and monochromatic area EM is created by exposure scanning using an ND filter.
n, ZMn is formed (C4 state 1!i).

In this image formation, contrary to the case of the first to third image formation, the latent image ZCn corresponding to the colored area EC among the latent images ZCn and ZMn is erased (the shape 1 of b4 is .

The latent image ZMn remaining after erasing is developed with BK) toner, and a toner image TMk is formed on the photoreceptor drum 3 (as shown in C4, the toner image TMk is formed on the transfer heald 1).
5 (state of d4).

Thereafter, the toner image Tymc, which is a superimposed three-color toner image, and the black toner image TMk on the transfer belt 15 are secondarily transferred and fixed onto the paper P, whereby the color corresponding to the original image G is printed on the paper P. A copy image FC is obtained (state e).

As described above, in copying Ill, only the color image portion Gc of the original image G is visualized, and the monochrome image portion Gm is visualized in the first to third image formation in which the three primary colors are combined. Not visualized. That is, for the color image area Gc determined to be the colored area EC, each color is reproduced by a combination of three primary color toners, but for the monochromatic area E
For the monochrome image portion Gm determined to be M, copying is performed using only a single toner (BK toner).

In other words, for example, if there is a black part (black spot) about 1 mm square in the color image area GcO, a conventional copying machine that creates an image by distinguishing between black and colors other than black will
When forming an image with primary color toner, the latent image corresponding to the black spot is erased, and the black spot is developed with BK toner, but in the copying machine 1 of this embodiment, the black spot is developed with toner of the three primary colors. . Therefore, in the area around the black spot, there is no color fading caused by the overlapping of the unit irradiation areas hi corresponding to adjacent erase unit areas, and the copied image becomes natural.

Next, the state of color copying by the copying machine will be explained in more detail with reference to FIG. 1(B).

In the copying machine 1, during the preliminary scanning described above, the original image G
The part of the boundary between the monochrome image part Gm and the color image part Gc in is determined to be the boundary area EV, and the other part is determined to be the monochrome area EM.

Regarding the boundary region EV, the latent image is not erased by the editing eraser 5 during any of the first to fourth image formations. It is assumed that the entire area of the color image portion Gc is determined to be the colored area EC.

The image forming process will be described below, focusing on one row of erase unit areas in the main scanning direction corresponding to the monochromatic area EM, the boundary area EV, and the colored area EC.

As described above, in the first to third image formations, the monochromatic area EM is erased (shape fl B in the figure). At this time, since the unit irradiation area hi is larger than the erase unit area as explained in FIG. The image is erased.

The areas that have not been erased, that is, most of the colored area EC and the colored area EC side within the boundary area EV are Y, M
, C, and are sequentially developed each time image formation is performed ([2-like M).

Next, in the fourth image formation, as shown in the state f3 in the figure, the colored area EC and a part of the colored area EC side (the shaded area in the figure) in the boundary area EV are erased. The unreceived areas are developed with BK toner (state of f4).

The BK toner image is transferred onto the transfer belt 15, onto which the Y, M, and C toner images have been sequentially transferred (as shown in f5).

By going through the above image forming process, in the boundary area E■,
Each of the Y, M, and C toner images and the BK toner image are superimposed on each other at the central width d3.

As a result, even if the black portion of the monochrome image portion Gm and the color image portion Gc are adjacent to each other, the unit irradiation area hi of the editing eraser 5 overlaps at the boundary between the monochrome image portion Gm and the color image portion Gc. It is possible to obtain a natural copy image FG in which color fading due to color loss does not occur and the continuity of the monochrome image portion Gm and the color image portion Gc is maintained.

In addition, in the copying machine 1 of this embodiment, as described later, 1.27
Using a mm square area discrimination matrix J, coloring area EC
and a monochromatic area EM.

Therefore, in the original image G, an achromatic (black or white) part that is visually determined to be part of the color image area Gc by image recognition based on experience, for example, the hair part (black) in a portrait photograph. Even if the area of clouds or snow (white) in a landscape painting is larger than the area discrimination matrix J, that area is determined to be a monochromatic area EM and is targeted for development with BK toner. .

However, even in such a case, as shown in Part 1 (C), the monochrome area EM surrounded by the colored area EC
The periphery of the image FG is developed as a boundary area EV with four colors of toner, and the continuity of the image is maintained, so that the copied image FG has a natural appearance without any visual discomfort.

FIG. 5 is a block diagram schematically showing the configuration of the image processing section 100, FIG. 10 is a diagram showing the relationship between the pixel g and the erase unit area, and FIG. 11 is a diagram showing the area discrimination matrix J.

The output signal SO of the color image sensor 51 is an A/D
It is input to the converting section 101.

The A/D converter 101 amplifies the signal SO to a predetermined level, then quantizes it, and converts it into 6-bint (64-gradation) image data.

The shading correction unit 102 performs shading correction corresponding to the light distribution (unevenness in light amount) of the exposure lamp 29 and the sensitivity difference between each pixel of the color image sensor 51.

The image data that has undergone shading correction is sent to a sub-scanning direction position correction unit 103 (hereinafter referred to as “position correction unit”). The position correction unit 103 performs timing adjustment to match the output timings of R data, G data, and B data for the same portion of the document.

The color determination unit 104 determines RlG for one pixel g,
Color and density are identified for each pixel based on the value of each data of B, and color data dc and density data dn are generated.

The pitch conversion unit 105 converts the reading unit of the color image sensor 51, that is, the size of the pixel g and the editing eraser 5.
By performing data conversion to compensate for the difference in the size of the erase unit head coverage (see Figure 10), and by averaging the density data dn for 4 pixels, the color data DC corresponding to the erase unit area is calculated. and concentration data DN
generate.

As shown in FIG. 11, the area determination unit 106 selects an erase unit area h of interest (hereinafter referred to as "attention area X").
Color data DC and density data DN for 25 (5×5) erase unit areas in an area discrimination matrix J consisting of Based on this, the region of interest X is distinguished into a colored region EC and a monochromatic region EM.

The boundary conversion unit 107 converts the attention area χ into a boundary area E corresponding to the boundary between the colored area EC and the monochromatic area EM, based on the area discrimination data DJ output from the area discrimination unit 106.
It is determined whether it is V or not.

Note that the area determination unit 106 and the boundary conversion unit 107 perform the above-mentioned determination by processing each erase unit area as a region of interest X in the order in which it is arranged.

In the memory 108, each erase unit area is a colored area E.
Area data DX from the boundary conversion unit 107 indicating whether it is the C1 monochromatic area EM or the boundary area EV is stored.

The erase control unit 109 controls the editing eraser 5 based on the area data DX in the first to fourth image creation described above.
The respective LEDs 65 are selectively turned on. That is, when the area data DX indicates a monochromatic area EM, the latent images ZMb, ZMg, and ZMr of the corresponding erase unit area are erased, and when the area data DX indicates a colored area EC, the corresponding erase unit is erased. Erase the latent image ZCn in the area. However, when the area data DX indicates a boundary area EV, erasing is not performed on the corresponding erase unit area. Therefore, the boundary area EV is to be developed with each of the Y, M, and CBK toners as described above.

FIGS. 6(a) to 6(c) are circuit diagrams of the image processing section 1oo.

The A/D converter 101 includes amplifiers 111 to 113 that amplify the output signals SO of the color image sensor 51 corresponding to each color of R, G, and B, and each amplifier 111 to 1.
A/D converter 114 ~ which A/D converts the output of 13
It consists of 116.

The shading correction unit 102 includes the A/D converter 11
A selector 121 selectively selects each of the R, G, and B data input from 4 to 116, and R and G for one line read from the reference image (white).

RAM 12 for shading correction that stores B data
2. It consists of an address creation unit 123 for specifying addresses in the RAM 122, a buffer 124, and a shading correction ROM 125 in which a conversion table for correction is stored. During preliminary scanning, the data read from the document is stored in RAM.
It is input to the ROMI 25 as a conversion input together with the data read out from the ROMI 122 and corrected.

The position correction unit 103 includes a latch circuit 130 and G that launch data inputted in the order of RG and B every time one line is scanned.
It is comprised of a line memory 131 for delaying the data output timing by one line's worth of scanning time, and line memories 132 and 133 for delaying the R data output timing by two lines' worth of scanning time.

The color judgment unit 104 is a color judgment RO provided with a conversion table.
color data dC and density data dn for each pixel corresponding to the mutual relationship and absolute value of R, G, and B data;
Output.

For example, the color data dc indicates black when the values of R, G, and 'B are approximately equal and the absolute values are small, and indicates white when the values of R, G, and B are approximately equal and the absolute values are large.
When the values of R, G, and B are different, it indicates a color other than black and white, that is, a color such as red or yellow.

The pitch conversion unit 105 converts the four pixels g corresponding to one erase unit area spanning the buffer 141, line memory 142, and address generation unit 143.2 lines into black, black, and black based on the color data dc. A selector 144, a decoder 145 and a data counter 146 for counting by dividing into white and colored, and a pitch conversion RO which outputs color data DC according to each count value of the three classifications using a conversion table.
MI47, latch circuit 149 for generating density data DN indicating the average density of four pixels g based on density data dn, adder 150, multiplier 151, and output timing of color data DC and density data DN. It is composed of launch circuits 148 and 152 for matching.

The area determination unit 106 includes a data counter 165 that divides and counts the color data DC according to its value, an adder 166 that adds the counted values from the data counter 165 that are input at the same timing for each of the above-mentioned divisions, Adder 167, ], 6B for adding density data DN, area discrimination ROM 169 for outputting area discrimination data DJ according to the output of adder 166, 168 using a conversion table, line memory 161 for delaying data in the sub-scanning direction. 164, launch circuits 170 to 177 for delaying data in the main scanning direction, and a latch circuit 178 for timing data transmission.
, 179.

The boundary conversion unit 107 includes latch circuits 181 and 182 that each delay data by one data, and area data D according to a combination of three area discrimination data DJ in the main scanning direction.
It consists of a boundary conversion ROM 183 that outputs X. During preliminary scanning, area data DX for one document sheet is stored in the memory 108 via the buffer 184.

Further, the erase control unit 109 includes a CPU 201 and an erase controller 202 that drives each LED 65 of the editing eraser 5.

FIG. 7 is a flowchart showing pinch conversion processing by the pitch conversion unit 105.

First, color data dc and density data dn are extracted for four pixels g corresponding to the region of interest X (step #
21).

Next, in step #22, the color data dc and the density data d
Sort out n.

Regarding the fi degree data dn, the average density of the region of interest X is calculated in step #23. In other words, the attention area
Generate density data DN for.

On the other hand, regarding the color data dc, in step #24, 4
All of the color data dc are white data dc indicating white.
Check whether it is w.

If YES in step #24, the color data DC is set to white data DCw in step #25.

If NO in step #24, it is checked in step #26 whether all of the color data dc except for the white data dcw in the four color data dcO are black data dck indicating black.

If YES in step #26, the color data DC is set to black data DCk in step #27.

Also, if no in step #26, step #28
Here, the color data DC is colored data DCf indicating a color other than white and black.

The eighth time is a flowchart showing area discrimination processing by the area discrimination unit 106.

First, in step #31, the area discrimination matrix J
, the 25 color data DC are classified and the density data DN values are added.

Next, cases are divided according to the classification results of the color data DC.

In the area discrimination matrix J, when all the color data DC is colored data DCf (case a in the figure), when black data DCk or white data DCw and colored data DCf are mixed (case a in the figure), and All white data D
If Cw (C in the figure), step #33
Proceed to , and set the region of interest X to be the colored region EC.

That is, in cases a, b, and c in the figure, the attention area X is determined as the colored area EC.

By determining it as a colored area EC when all data is white data DCw, even if the color determining unit 104 erroneously determines that a light color is white, the colored area EC is determined as white, as explained in FIG. Since erasing by the editing eraser 5 is not performed during image formation using Y, M, and C toners, light colors will be reproduced in the copied image.

If the color data DC is all black data DCk (case d in the figure), in step #32, the density data D
By comparing the value of N with a predetermined value, it is determined whether the overall density of the area discrimination matrix J is smaller than the predetermined value, that is, whether the area discrimination matrix J is light.

If YES in step #32, the region of interest X is set as the colored region EC in step #33.

If no in step #32, the region of interest X is made into a monochromatic region EM in step #34.

In this way, area discrimination (step #32 to step #34)
), region discrimination can be optimized by referring to the density data DN.

In other words, among the colors determined to be black by the color determination unit 104,
Colors close to gray are often used together with other colors in so-called colored patterns, so it is better to reproduce images with colors close to gray with Y, M, and C toners than with BK) toners. Also, the copied image FG becomes natural. On the other hand, images of true black and colors close to it are
Since most of the images are monochrome images such as text and line drawings,
Reproduction with BK toner is preferred.

In addition, in the area discrimination matrix J, black data DC
When k and white data DCw coexist (case e in the figure), the area discrimination matrix J is based on the background (white) of the manuscript paper.
It is determined that the region corresponds to a monochrome image portion Gm consisting of black characters and line drawings, and the region of interest X is set as a monochrome region EM.

FIG. 9 is a flowchart showing boundary determination processing by the boundary conversion unit 106.

First, the attention area X and both sides of the attention area X in the main scanning direction (
Attention is paid to the erase unit area h (hereinafter referred to as "adjacent area WJ") of the erase unit area (see FIG. 11) (step #41).

In step #42, it is checked whether the region of interest X is a monochromatic region EM, that is, whether the region discriminating section 106 has determined that it is a monochromatic region EM.

If the result in step #42 is No, that is, if the region of interest X is the colored region EC, the region of interest X is directly set as the colored region EC.

If YES in step #42, the process proceeds to step #43, where it is checked whether at least one of the two adjacent areas W is a colored area EC.

If the answer is NO in step #43, the region of interest X is directly set as a monochromatic region EM.

If YES in step #43, the process advances to step #44, and the region of interest It is considered an EV.

According to the above-described embodiment, the area discrimination unit 106 performs area discrimination when all 25 color data DC corresponding to the area discrimination matrix J are white data DCw, and when all color data DC are black data DCk, and the area discrimination unit 106 performs area discrimination. Matrix J
If the density of The original coloring is reproduced using Y, M, and C toners, and will not be replaced by BK toner colors in the copied image FC.

According to the above-mentioned embodiment, even if there is a black part (black spot) about 1 mm square in the color image part Gc constituting the original image G, the black spot is different from other colored spots. Because the area is developed with three primary color toners at the same time,
In the area around the black spot, there is no color fading caused by the overlapping of the unit irradiation areas hi corresponding to adjacent erase unit areas, and the copied image becomes natural.

According to the above embodiment, the boundary between the monochrome image area Cm and the color image area Gc is determined as the boundary area EV, and the boundary area EV is targeted for development with four color toners, so that the monochrome image area Gm The black part and color image part G
Even if the monochrome image area Gm and the color image area Gc are adjacent to each other, color fading due to the overlap of the unit irradiation areas hi of the editing eraser 5 does not occur at the boundary between the monochrome image area Gm and the color image area Gc, and the monochrome image area Gm and color image area Gc are adjacent to each other. A natural copy image FG that maintains continuity with the color image portion Gc can be obtained.

According to the above-described embodiment, the area determination unit 106 determines the monochrome area E.
With respect to the region of interest Therefore, the BK toner does not adhere to areas that should originally be colored, and image reproducibility can be improved.

In the above embodiment, the erase unit areas on both sides of the attention area X in the main scanning direction are defined as adjacent areas W, and the boundary area E
Although an example of determining V is shown, the erase unit areas h on both sides (upper and lower) in the sub-scanning direction of the area of interest The boundary area EV may be determined as follows.

In the embodiments described above, the size and shape of the area discrimination matrix J can be appropriately selected.

[Effects of the Invention] According to the present invention, it is possible to suppress the occurrence of color fading in an image, and it is possible to obtain a color copy image with as high color reproducibility as possible.

[Brief explanation of drawings]

Fig. 1 is a schematic representation of color copying according to the present invention. Fig. 2 is a front sectional view showing the general structure of the copying machine, Fig. 3 is a plan view of the editing eraser, and Fig. 4 is a diagram of the copying machine. A plan view of the operation panel attached to the top, Part 5 is a block diagram schematically showing the configuration of the image processing unit, Figure 6 is a circuit diagram of the image processing unit, and Figure 7 is pitch conversion processing by the pinch conversion unit. FIG. 8 is a flowchart showing area discrimination processing by the area discrimination unit; FIG. 9 is a flowchart showing boundary discrimination processing by the boundary conversion unit; FIG. 10 is a diagram showing the relationship between pixels and erase unit areas; FIG. 11 is a diagram showing an area discrimination matrix. 1... Copy machine (color copy machine), 7, 8, 9.10.
...Developer (developing means), 51...Color image sensor (original reading means), 106...Area discriminating section (
(area discrimination means), 201...CPU (monochrome image formation control means), D...original document, EC...colored area, EM...
・Single color area, G... Original image (image), J... Area discrimination matrix (block area), x... Area of interest (
unit area of interest), Y...peripheral area (peripheral unit area). Figure 5 Applicant Minolta Camera Co., Ltd. Figure (B) Figure (C) Figure (C) Figure 5 Applicant Minolta Camera Co., Ltd.

Claims (2)

[Claims] (1) In a color copying machine that has a plurality of developing means with different developing colors and uses the developing means to copy an image of a document in color, a document reading means reads the image of the document, and the document reading means color data output means for outputting color data indicating the hue of the unit area for each unit area into which the image of the original is divided based on the read original information; area determining means for determining the unit of interest into a monochromatic area and a colored area based on the plurality of pieces of color data corresponding to a block area of a constant size made up of a plurality of peripheral unit areas; an image forming control means for forming an image on the area by using only one specific developing means among the developing means, and forming an image on the colored area by using a plurality of developing means; The area determining means is configured to determine that the area of interest is a colored area at least when all of the plurality of color data corresponding to the block area are white data indicating white. Color copying machine. (2) In a color copying machine that has a plurality of developing means with different developing colors and uses the developing means to copy an image of an original in color, the original reading means reads the image of the original; and the original reading means image information output means for outputting color data indicating the hue and density data indicating the density of the unit area for each unit area into which the image of the original is divided based on the read original information; Based on the plurality of color data and density data corresponding to a block area of a certain size consisting of a unit area of interest and a plurality of peripheral unit areas around it, the unit area of interest is divided into a monochromatic area and a colored area. an area discriminating means for discriminating the monochromatic area, and forming an image by using only one specific developing means of the developing means for the monochromatic area, and forming an image for the colored area by using a plurality of developing means. and an image forming control means for controlling the image formation to be performed, and the area discrimination means is configured to control at least one of the plurality of color data corresponding to the block area to be black data indicating black, and the density of the block area is light. A color copying machine characterized in that, in some cases, the area of interest is determined as a colored area.