JPS6177060A - Color correction method of color electrophotographic copying system - Google Patents

Abstract

PURPOSE:To rationalize color correction by reading a color picture after color separation and determining an outline part on a basis of picture information to determine a masking quantity and erasing partially color separation latent images at an erase rate corresponding to this masking quantity. CONSTITUTION:The color picture is scanned on an original O by an optical system 14 and is inputted to many R, G, and B solid-state image pickup elements by a mirror 401 and is compared with a density inputted preliminarily from a reference density plate 42 and is inputted to a mu computer omitted in the figure. Next, the mirror 401 is laid down, and the light from the optical system 14 is projected to a photosensitive body 10 through a lens 144 and a filter F. Color separation latent images are formed in accordance with colors F1-F4 of the filter F. The mu computer determines the outline by the sudden change of the density, and an eraser 18 erases these latent images in accordance with the erase rate of each color by the input of the mu computer, and latent images are developed with cyan, magenta, yellow, and black toners successively by developing devices 20-26 and are transferred to a recording paper S successively by a means 30 and are fixed finally. Thus, accurate color correction is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a color correction method in a color electronic copying system.

(Prior Art) Color electronic copying systems using the Carlson process are well known. A typical process of such a color electronic copying method is as follows.

A uniformly charged photoconductive photoreceptor is illuminated with a light image of a color original through a red filter at 0°C. In this way, exposing the photoreceptor to light through a color filter,
This is called color separation exposure, and this color is called color separation a [elephant], which is an electrostatic latent image that is excellent as a result of separation exposure. Now, the color separation latent image formed by the color separation exposure described above is a toner colored red, that is, a color complementary to the color of the filter used in the color separation exposure, that is, cyan (hereinafter referred to as 7 antoner). The thus obtained Noan color visible image is transferred onto a white recording medium such as paper.

Next, color separation exposure using a green filter is performed, and the formed color separation image is visualized with magenta toner colored magenta, which is the complementary color of green, and a magenta visible image is also recorded. transferred onto the paper.

At the same time, a color separation using a blue filter and an IAj image using a yellow toner are performed, and a visible image of yellow color is also transferred onto the recording medium.

Thus, on the recording/-t, the elephants in each color of /an, magenta, and yellow are transferred sequentially to each other.
＋It will appear.

It should be noted that in this specification, when we refer to the back, this color refers to the color that should be called blue-purple.

In addition, in the following explanation, when differentiating the color separation m images obtained by color separation exposure, the color separation images are distinguished by the color of the toner. For example, for color separation exposure using a red filter! %, the color separation good image is represented by a block of 7 antoners vcj, so we will call this the /un latent image.When the color separation colors are green and blue, each color separation latent image is , magenta A1, and yellow A images.

In the color electronic copying system as described above, the color of the color copy image is determined by the combination of toner colors on the recording/printing sheet. Therefore, if the relative quantitative distribution of the color toners constituting the color copy [image] differs, the color copy 1'
The color tone of the elephant will be different.

For this reason, in the color electronic copying system as described above, an operation called color balance is performed to stabilize the color tone. However, even if this color balance is performed implicitly, the color copy image residue will not accurately reproduce the colors on the color original. The reason for this is the color of Tonark.

Considering the five types of toners mentioned above, a neutral toner is theoretically a toner that completely absorbs red light (1-1 green light) and completely reflects blue light.

An ideal magenta toner would completely absorb green light and completely reflect red light and blue light. The ideal yellow toner would be six-packed, completely absorbing blue light, 1-1 red color, and completely reflecting green light.

However, in reality, such a logical toner does not exist (... Therefore, for example, the actual toner does not absorb red light completely, but partially reflects it, and green light,
It also absorbs some of the blue light.

This real/Antona? If we consider the example further, we can think of the following.

That is, the role of magenta toner is originally to absorb green light, and the role of yellow toner is to absorb blue light. However, assuming that the real antoner absorbs green light and blue light, the 7 antoners in Boji contain magenta toner and yellow toner as non-component components. If we develop the /an latent image with actual 7 ant toners, we can consider that the convex image appearing on f4 also contains magenta toner and yellow toner as impurities.

If you think about this
When applying a magenta visible image to one visible image of seven colors, the magenta toner component, which is considered to be already included as an impurity in the cyan visible image, is removed from the actual magenta visible image. By subtracting from the color, it is possible to improve the color reproducibility of the blue copy image line as a mixture of /an and magenta.

An operation for improving the color reproducibility of a color copy image based on this concept is called color correction.

Color correction is originally a concept in the technical field of color printing.
The masking method is known as a method for actually doing this. Therefore, by applying this masking i:l: to the color electronic copying system VC, it is expected that the color reproducibility of color copied images will be improved.

Conventionally, as an example of applying a masking method to a color electronic copying system, a method disclosed in Japanese Patent Laid-Open No. 53-3232 is known. However, this method requires a pair of photoconductive photoreceptors, which increases the size of the copying machine.

(Objective) The object of the present invention is to provide a completely new color correction method that digitally corrects color by using the above-mentioned Maskifugu 1 in a color electronic fJJ copying system.

(composition) Is this invention the following? explain.

The sensu square, yun of the present invention has the following four steps.

In other words, there is a reading process, a process of contouring, a masking process, and a partial erasing process using an eraser. This is a process of reading with a single-zoom element.In this process, each pixel is separated into colors and converted into signals.

Reading by the solid-state image sensor may be performed using a filter for color 5+ resolution and six solid-state image sensors, or may be performed using a star plate type color solid-state image sensor described later. is the first color separation exposure, i.e. the above glue U-
・In other words, cyan, +C simultaneously with exposure to form a replacement image.
This may be done, or it may be done prior to exposing the photoreceptor.

Next, in the ring>+S portion detection step, a contour portion in the original stroke iron is detected. This detection is performed based on the image obtained in the reading process. Specifically, for each pixel of a color document, a determination is made as to whether or not the pixel is a contour portion.

The determination of the masking amount will be described above.

In the partial and dark erasing step, the color separation image A is partially erased at an erase rate according to the masking amount determined in the masking determination step. This partial erasure is performed using an eraser in an area-modulated manner.

Ru.

The eraser uses a dot emitter array along with an imaging system. The dot light emitter array is LE, which will be described later.
Examples include the D array and the well-known dot fluorescent tube array. Further, as a focusing system used with the dot light emitter play, a well-known converging light transmitter array or Dano mirror lens array is used.

Here, we will briefly explain the amount of masking and its determination. Let us now assume that the filter colors used for color separation are red, green, and back, and the toner colors are cyan, magenta, and yellow.

First, if we perform color separation exposure using a red filter to form an ant image, and then further peak this using real 7 ant toners, the resulting visible image will contain magenta toner and yellow toner as impurities. It is thought that there are.

Therefore, when we visualize the magenta latent image using actual magenta toner, we take into account the magenta component that has adhered to the cyan latent image as an impurity due to the development using the seven ant toners. The amount of magenta toner applied to one elephant is reduced.How much to reduce is determined by multiplying the latent image by the value of the latent image, A, which is smaller than 1.

Next, the yellow a image is developed with yellow toner, but since it is thought that the yellow toner is also present as an impurity during the development of ant toner and magenta toner (Kl'), the magenta '1fJf fang is As a basic rule, the yellow toner adhesion is reduced by the value obtained by subtracting the coefficient B (<1).

The above coefficients A and B are referred to as 5 masking rates. The masking rate may be theoretically calculated by VC, or may be determined experimentally. In the case of color printing, A is generally 0.38 and B is often 0.45.

The masking rate A is multiplied by the above NAR elephant, and
Magenta toner multiplied by 7 skin iB can be used as the masking amount.

The amount of masking referred to in this specification is the amount that should serve as a guideline for how much of the latent 1 phenomenon is to be erased, and is not necessarily
It does not necessarily mean that they have a unique sense of ownership.

For example, when trying to improve color reproducibility on average for each color in a color painting, and when trying to improve color reproducibility on average for each color in a color painting,
The amount of masking also differs depending on the case where the performance is improved. However, in any case, from what perspective should you perform color correction (for a specific color or a combination of colors, or for each color on average?)
Once determined, the amount of masking can be determined theoretically or experimentally.

FIG. 2.1 is an explanatory diagram schematically showing only the main parts of an example of a color copying machine to which the present invention is applied. Since this is an explanatory drawing, the relative size relationship of the dimensions of each part is not necessarily a constant V.

First, this copying apparatus will be briefly explained, then the color copying process will be explained, and then the real gun 1/'c of the present invention will be explained.

In Figure 3'1, reference numeral 10 indicates a light-conducting photoreceptor. This photoreceptor 10 is drum-shaped, and is directed in the direction of the arrow '
\times? tb is possible. As the material of the photoconductive layer, a photoconductive substance having a resiliency, a resemblance to As2Se3, and a panchromatic distribution is used.

The surroundings of this photoreceptor 10 (here, charger 12, eraser 18, dust mound device 20, 22, 24, 26,
A holder 28, a static eliminator 32, and a cleaner 34 are provided.

Reference numeral 16 indicates the document placement glass, on which the document O to be copied is placed.
is placed flatly on this document placement glass 16.

The exposure optical system designated by reference numeral 14 is composed of a lamp 140, a plane mirror 141, a roof mirror 142, a plane mirror 143, a lens 144, and a filter device F.

Further, the reading optical system indicated by the reference numeral 40 is a mirror 40.
1. Lens 402, single-plate color solid-state image sensor 406
The mirror 401 is configured to selectively take the position shown by the solid line and the position shown by the broken line by swinging.

A reference plate 42 is provided at the right end of the document placement glass 16.

Further, in Figure 1, reference numeral 50 indicates a transfer device, and reference numeral 36 indicates a fixing device. Further, the symbol S indicates transfer paper (plain paper) used as a recording notebook.

℃, returning to the exposure optical system 14, in order to scan the original 0 with illumination, the lamp 140 is made to emit light, the lamp 140 and the plane mirror 141 are integrally moved to the left, and at the same time, the roof mirror 142 is moved to the plane @ Move to the left at 1/2 of the moving speed of 141. Then, when the mirror 401 is in the position shown by the broken line, the lens 144 forms an image of the illuminated portion of the document Q on the photoreceptor 10.

If the mirror 401 of the reading optical system 40 is placed in the position shown by the solid line, the image of the illuminated portion of the original O is formed on the color solid-state image pickup element 406.

The filter device hF includes a red filter F1. Green filter F2. - the color filter F6. Neutral Den/
ND filter F4 (hereinafter referred to as ND filter F4)
), and selectively select each filter ((
It can be placed in the optical path of the exposure element system.

The eraser 18 includes an LED array 181 and a convergent light transmission array 1182.

The holder 28 is drum-shaped and is used to hold the transfer paper S for the transfer of the visible [image], and is used to hold the transfer paper S for the transfer of visible images.
It is configured to rotate in the direction of the arrow in accordance with the 0 rotation ≧b.

Now, in the color solid body quadrant 403, minute light-receiving elements are closely arranged in a single row in a direction perpendicular to the drawing of Figure 1. 7. corresponding to each received image element; The i light receiving elements simultaneously detect the
The above image element? signal.

Each individual light-receiving element is covered with a tiny filter. The colors of these filters are red,
There are five types: green, back, red, and green.

They are arranged cyclically in the order of their backs. Therefore, when looking at three adjacent light receiving elements, one of them is covered with a red filter, the other with a green filter, and the other with a blue filter.

These three light receiving elements correspond to one pixel on the document, that is, an area of 125 μm×125 μm on the original. Therefore, if the original O is scanned along with the illumination pattern, each pixel of the original O will be red and green.

The color will be separated into blue and read.

In Figure 1.1, the length of the document O in the left and right direction is e+
+ If the length in the direction perpendicular to the drawing VC is g2, then
This means that it is matrixed into rows and N columns, separated into colors, and read. In this pixel matrix, the pixel located at the m-row, n-column position will be denoted as pixel (m, n).On the other hand, the LIED array 181 of the eraser 18 has 12
Small light emitting elements (LEDs) with a light emitting area of 58 m x 125 μm &F' are closely arranged in the direction orthogonal to the drawing in Figure 1, and these light emitting elements (hereinafter referred to as LEDs) 8 can emit light in any combination. It has become.

When one LED (LEDO) is emitted, due to the condensation effect of the focusing light transmitter array 182, the emitted LED is
An image is formed on the photoreceptor 10. Therefore, the static latent image on the photoreceptor 10 can be erased pixel by pixel by the eraser 18. Of course, each pixel read by the reading optical system 40 and the pixel of the eraser 18 correspond to each other.

The outline of the color copying process in the color electronic copying machine shown in FIG. 1 will be explained below. The present invention has not yet been applied to this process.

The original O to be copied is placed on the original placing glass 16. , when the document is placed as shown in the figure and the device is operated, the mirror 401 of the reading optical system 40 that reads the original is placed in the position shown by the solid line.
Next, illumination scanning of the original O is performed, and the color original O is
A color solid-state sensor 403 separates each pixel into five primary colors, red, green, and primary colors, and converts it into a signal.

By the way, prior to reading the original O, the image of the reference m scale plate 42 is projected onto the color solid-state image sensor 403, and the contents of the reference # scale plate 42 are read.

The standard A scale board 42 has 16 levels of gray scale,
The contents are as shown in Table 1.

The density numbers 1-16 are convenient indicators given to the corresponding density.

One word read from the standard vacancy board 42 is sent to a microcomputer (not shown).

Next, manuscript Q is read, but manuscript 0 is
It has a chromatic image and an achromatic image on a white background. this house,
Chromatic painting [The elephant part is called the color painting 1 elephant part, and the parts other than the 5-power color image part are neutral! ! It is called image section II.

Now, the original 017:) The reading signal is composed of six types of signals for each pixel, that is, it is a signal that is read after being separated into π colors of red, green, and spine. Therefore, the pixel (m,
In n), the signals separated into red, green, and evening are respectively R(m, n).

0(m, n) and B(m, n).

Now, the reading signal R (m, n) etc. of the original O is sent to the aforementioned microcomputer, and is compared with the contents of the previously input standard information board 42. ~16
will be converted to either That is, the signal R(m,n) is the density number Ln(m,n), and the signal G(m,n) is Lo(m,n
), B(m,n) is transformed into Lday(m,n)K.

Next, it is determined for each pixel whether the current image belongs to the color image area or the neutral area.

Achromatic painting [The elephant is the same no matter what color it is separated into, so if we look at the pixels (m, n), if 'Lu(
m, n) = Lo(m, n) and L5(m,
'n) = Le (m + n), then
Pixel (m, n) belongs to the neutral part, otherwise it belongs to the color pixel part.

Subsequently, the mirror 401 is placed in the position shown by the broken line, the photoreceptor 10 is rotated, and uniform charging is performed by the charger.

Subsequently, the original O is illuminated and the photoreceptor 10 is exposed. At this time, the red filter of filter device F is placed in the exposure optical path. Therefore, the electrostatic latent image formed on the photoreceptor 10 is a color-separated latent image, that is, a latent image corresponding to the red color-separated image.

When this color-separated latent image passes through the erase section of the eraser 18, the microcomputer
81, LED corresponding to the pixel belonging to the neutral part
*Make it emit light. As a result, the above color separation layer (the elephant is
The sub-1 elephant part corresponding to the neutral part? will be erased.

This electrostatic latent image is then transferred to the imager 20 using a magnetic toner colored toner of 717 colors (in the red and complementary colors of the color separation).
It is clearly visualized using the elephant method. or <Lt, 7 is on the photoreceptor 10
A seven-color visible image is formed and moves as the photoreceptor rotates.

Transfer paper S&M according to process 7-Knins.

The distal end portion is clamped to the holder 28, and as the holder 28 rotates, it is held so that it wraps around the circumferential surface of the holder 28, and is superimposed on the visible image of Noah's seven colors on the photoreceptor 10. At this time, the transfer device 60 binds the holder 28 from the back side with a polar charge that electrically attracts the visible image, and transfers the visible image onto the transfer paper S using electric force. The photoreceptor 10 after the visible (image transfer) is charged is neutralized by a static eliminator 62, and residual toner is removed by a cleaner 64.

Then, the green filter F2 of the filter device F is placed in the exposure optical path and the same process is repeated. The color separation layer 1 image thus formed is a magenta latent image, which corresponds to the document image color-separated into green. It is developed with magenta toner by the imaging device 22. The resulting magenta visible image I is transferred onto the transfer paper S so as to be superimposed on the Noan color visible image.

The same process is repeated using the blue filter F4 of the filter device F and the phenomenon device 24.

The current device 24 uses yellow toner.

Finally, the ND filter F4 of the filter device F is placed in the exposure source, and on the photoreceptor 10 there is an electrostatic a[elephant] (non-color separation layer [elephant]) that is not color-separated and corresponds to the original 0. ) is formed. In this electrostatic latent image, one latent portion corresponding to one color image portion is erased by the eraser 18.

This electrostatic layer is formed by using black toner (using the developing device 26
It is developed with

When the thus obtained black visible image is transferred onto the transfer paper S, the transfer paper S is separated from the holder 28 and transferred to the charge increasing device 6.
6, the toner image is fixed thereon, and the copy is discharged from the apparatus as a color copy.

The above is an outline of the color copying process in the case where the present invention is not used as a live gun in the example of the apparatus shown in FIG.

Hereinafter, the present invention will be explained in detail by taking this color copying process as an example. This explanation will be given in order of process.

First, there is a reading process, which is the same as the reading already explained, so it will be omitted.

Next, the detection of an outline is performed by determining whether a certain pixel corresponds to an outline.

is the lifetime 1 of one pixel (m, n) in the pixel matrix
This is the imaginary number when the colors are separated.

In addition, in the device shown in Figure 1, which is currently taken up as %l, the part corresponding to the neutral image □□□ is developed with black toner, so it is necessary to perform color correction for the neutral image f area. There isn't.

Now, in general, in the contour part, LR(m+n) +L
(+ (m, n), Ls (I+1+ n)
A sudden change occurs in either of these cases. Therefore, the following judgment is made for one quadrant of a color image. Now, the pixel at row M and column 1 is the pixel at row m and column n of IJ Nox,
In other words, the pixel (m, n) and the adjacent pixel (m,
n+1), Lu(m, n+1) −L R(m,
n) ≧ 8L o (m + n + 1
) −Lo (m, n)≧8LB(m, n+1
-La (m, n) ≧ 8, and if one or more of these five relationships holds, the pixel (m, H+1) is defined as an outline. Also, LR(m,n+1)-LR(m+n)(knee 3LO(
m, n + 1) -LR(m+n)≦-8L
a(m, n + 1) −La (
If any one or more of m+n)≦-8 is satisfied, the pixel (m+n) is defined as the contour portion.

Furthermore, if the pixel (m, n+1) belongs to the first part of the neutral image, and the pixel (m, n) does not belong to the first part, then the pixel (m, n) belongs to the contour part. If pixel (m, n) is a neutral image (belongs to the beam part, and pixel (m, n+1) is not), pixel (
m, n+1) is the contour part.

The contour portion is detected at this voltage of 5VcL. This detection is performed by calculations by a microcomputer.

Figure 9 shows a flowchart at this time, and the pixels of the detected contour are stored in the i-memory section.

Next, the determination of the amount of masking will be explained. even here,
When using masking rates A and B? For example, A=0
．． 38, B = 0.45.

In Figure 2, C, the diagram at the bottom is Tax 1;i! , shows the output value of the color solid-state image sensor 406 after the temperature plate 42 is color-separated and read in degrees Celsius. In the figure, the code 406F is
The arrangement of microscopic filters in a color solid-state photographic one-zoom filter 403 is shown.

In addition, for manuscript ○, as shown in Figure 3, yellow, red, magenta, spine, cyan, and green on a white background.

Assume that there are a color image of , and achromatic images of gray and black. The white background area and the achromatic color image l are neutral images (area a).

Figure 5 (I) shows the output values for each color image when the original O is color-separated and read, and Figure 3 (III) shows the state in which these output values are calculated by a clarity number.

Now, if each of the 16 levels of density is multiplied by 0.38 and 0.45, the result will be as shown in Figure 4.

Now, the numbers in the red column in Figure 6 (1) are the output of the color solid-state image sensor when the original O is color-separated and read using a red filter, and should correspond to the 7-an latent image. .

If this output is converted to the standard concentration using the correspondence in Figure 6, and then 0.38 times that value is obtained from Figure 4, the result will be as shown in Table 3.2.

Finally, based on Figures 6 and 2, when we express the results of color separation decoding using the green filter in terms of standard density, we find that 5.
This is the number in the standard width column in Figure (1). Spear 5 (
The numbers under this standard assignment column in 1) correspond to the above 2.
The numbers in the bottom column of the table are the masking amount for the magenta latent image.

How much erasing should be done depending on the amount of masking? Take a look at the masking site (Yoko 2) in figure 5 (1).
The value of (1) in the standard concentration was calculated using the number 5: 6 (parameter 11) in Figure (1). For example, Haragi 4o's I20-ga fa Vc
In the corresponding area, it is sufficient to erase 24%. However, in reality, it is difficult to erase in 1% increments, so here we will explain the parameters and
Let us consider a case where erasing is performed in five stages by corresponding the erase rate as shown in Figure 5 (I). The value thus obtained is the erase rate shown in Figure 5 (1).

In Figure 5 (I), the standard density of 1@ indicates the standard d degree value of the original that has been color-separated and decoded using a blue filter.

This corresponds to ieo-a@.

Column 2 of the figure corresponds to column 1 of figure 5 (1), that is, the rule th! corresponding to the magenta latent image! This is the value obtained by multiplying the density by 0.45, and this is the amount of masking for the yellow a iron. Parameters of the spear 5 diagram (group).

The erase rate was calculated in the same manner as in the case of Figure 5 (1).

Figure 6 shows a method of erasing according to the erase rate determined as described above. Four square pixel arrays are used as one unit for erasing. and,
25% When erasing, 1m f8 for 1 pixel
, and each time the erase rate increases by 25, 1
The area to be erased is expanded by pixels. In Figure 316, the part where Hatsuchi is killed shows the unerased part of the thunder elephant.

Now, let's look back at what we've covered so far and summarize it.

First, read the reference density plate using the 16-step standard i?
# The correspondence relationship between 11m and the output of the color solid-state image sensor is determined.

Then, the original is read. If we consider an arbitrary pixel on a document, this pixel can be read by being separated into red, green, and back by six adjacent light receiving elements on a color solid-state camera. and from its output the criterion degree for each color separation will be found. Standard '54 (a degree is
In this case, the masking amount for the magenta latent image is 0.38X, and the masking amount for the yellow latent I is 0.45Y. Y
Z compatible (spear 6 diagram (If))
Determined by K. In this way, the erase rate for one pixel of interest is determined, so the erase rate for four pixels including this one pixel? One unit is used, and erasing is performed by emitting light from the corresponding LED of the eraser. Partial erasure by the eraser is of course controlled by a microcomputer.

Here, the meaning of reading the standard A scale board 42 will be explained.

The output of a color solid-state camera with a single quadrant varies depending on the brightness of the light source, dirt on the optical system, etc. Therefore, the manuscript? When reading, just because the output is the same does not mean that the same concentration is always being read.

Therefore, by reading the standard a grade board, always "i"
, correctly connect the output of the il quadrant and the standard #degree,
This allows us to properly know the degree of temperature and color separation of the original. However, changes over time such as the brightness of the light source and the dirt on the optical system occur relatively slowly, so reading the standard waste rate plate may be carried out after each copy, but it may be necessary to read it periodically. It may be done only occasionally or as needed.

The process of calculating the erase rate by performing calculations on the output of the color solid-state sensor 1a is performed by a microcomputer.
You can do row 5. In the above example, the standard for calculating the amount of masking - darkness value? However, since the solid-state imaging sensor G output corresponds to the reference density value, the masking amount may be calculated using the above output.

Incidentally, since the amount of masking is determined by the relationship between the read outputs separated into one color, these values may be stored in advance.

In Figure 117, the column R indicates the number of densities when color separation is performed with a red filter, and i'lJ in G indicates the number of times when color separation is performed with a green filter. ) corresponds to the number in column 6.

For example, if we look at the blue image on the original, the number of densities is 416 whether it is separated by a red filter or by a green filter, so the masking amount is immediately 58%. From Figure 25 (n),
You can immediately know the erase amount of 50%.

Based on the relationship shown in Figure 7, and similarly, the value of the masking amount due to the relationship π between the density number when color separation is performed with a green filter and the I# frequency when color separation is performed with a blue filter,
The microcomputer memorizes the reading result V
The masking information may be read out from the memory contents depending on the situation.

In the above description, the displayed masking award is converted into five levels of erase rate according to the relationship shown in Figure 5 (11), but the erase rate can also be set to six levels or more.

For example, let's consider the case of changing to 16 levels as shown in the following table.

In this case, one area modulation method of erasing can be performed using a well-known dither matrix or submatrix method.

For example, (1) in Figure 48 shows a dither matrix. This dither matrix is made to correspond to pixels arranged in 4 rows and 4 columns. Now, if the amount of masking for the pixels in these 4 rows and 4 columns is 25%, the erasure rate will be 2 ↓.
It becomes 4. This is shown in Figure 8 (II) Ic.

Then, the LED is turned on when the erase value is greater than or equal to the value of the dither matrix. In corner diagram 8 (IV), white circles indicate pixels that emit light from the LED.

Figure 8 (V) shows a mother matrix in which the 2 rows and 2 columns of sub-matrices are combined in 2 rows and 2 columns.If this mother matrix is used instead of the 0 dither matrix shown,
The pixels that emit light from the LED look like the white circles in Figure 9 (IY).

In the previous example, the masking ratios A and B are 0.38 and 0.45 to obtain the masking amount? Using.

However, as described above, the amount of masking is a measure of determining the erase rate, and there are various ways of determining this amount. An example of a method for determining the amount of masking without using masking will be described below.

Table 4 - In this Table 4, 1 item, that is, the top column, is the standard! ! , 21).cj is the relative value of the output voltage of the color solid imager corresponding to this standard density, expressed as a percentage? show. This relative pressure value, the level of chivalry when AD is changed, is 1 (-16) like j-3 Kusunoki.

5. The 5th table is the color image part of the manuscript O, red (R), green (G).
), blue CB) when separated and read with a filter,
Is it the AD transformation level of the output of Yuko Zui? It shows.

In Fang 6 table O 6 Tatsu, 3-1 @ number 6.16.9.14.
10.14.15 are the numbers in column G in the 5th table, and should correspond to 11 magenta elephants. here,
For example, if we focus on the color 7 Ann, even when it is separated using a green filter, it shows a single color of 9. Therefore, when developed with magenta toner, the mixed color Kj becomes cyan. Therefore, RJ of O.4 table
If we consider subtracting a constant from i+J so that (once of /an) is equal to the falsity of 77 in column 5, which corresponds to the magenta latent f-elephant, the above constant becomes , it turns out that it is better to choose 4.

Table 6/I'-2 column is 3.5 Table 1.1 橢 (Ri (I)
) minus 4? and this is the masking tk
give.

The number 26 on the 6th table is obtained by subtracting the number in the 2nd column from the number on the 1st column on the 6th table, and this number is a parameter that gives the erase rate.

spear 7 table What is the correspondence between this parameter and the erase rate?

The bottom column of Table 7, given in Tables 3 and 7, gives the erase rate.

Table 8 shows similar content for the case of color separation using a blue filter.

E 8 Table In this case, magenta has a high degree of a, so when developed with yellow toner, the color of the visible magenta image will be slightly different. Therefore, the value obtained by subtracting 2 from the green filter's color separation a (Gji station) (Yo 8 table Sai 2 column) is set as the masking amount, and this is parameterized (Gji 8 table Gji 6j). In correspondence with the table, the values that determine the erase rate are the values in the bottom column of Table E8.

Color correction using the 6th and 8th tables improves the reproducibility of 5-inch, maze/red, and yellow colors, but the reproducibility of red, for example, becomes insufficient. In this case, to improve the reproducibility of red, for example, magenta (yellow; 50
%, magenta; 0%, /an; 75 cm, back; 5u section, green; 75 cm, red; 0%, violet; 25
Erasing is performed at a ratio of %, and yellow: 0ch for yellow toner.

It is recommended to perform iso-22 with magenta: 75%, / that, 100% for blue, green: 25%, red: 50%, and violet: 100%.

In this way, the electrostatic latent image is partially erased at an erase rate determined according to the amount of masking, but at this time, this partial erasure is not performed with the ring IS.

That is, in the partial portrait process, pixels (m,'
When a command to erase pixel (m, n) is issued, pixel (m, n)
is referred to as the outline part information already stored in the storage unit, and it is determined whether the pixel (m, n) is in the outline part.

When n) is an outline portion, the above-mentioned partial erasure is not performed.

Therefore, is partial erasure by the eraser just one contour? It will be done in person.

Although color reproducibility is improved when the masking is expanded by area-modulated partial erasure, if this partial erasure is also performed on the outline, the outline of the image becomes blurred on the color copy image. Therefore, by not partially erasing the outline, the outline in the color copy image can be made clear.

Note that instead of completely not erasing the contour, it may be possible to erase the contour at a lower erase rate than other areas. Also,
Depending on the color of the toner, for example a yellow latent image,
Erasing may be performed up to the outline.

(Effects) As described above, the present invention can provide a novel color correction method for color electronic copiers. Appropriate color correction is possible without increasing the size of the copy.Furthermore, since the color correction is not performed on the outline, the outline of the color copy image does not become blurred.

[Brief explanation of drawings]

11th is one of the glass electronic copying devices to which the invention is applied.
FIGS. 2 to 1'8 are diagrams for explaining the present invention in detail. FIGS. Figure 9 is a flowchart for detecting a contour. O...Manuscript, 18...Eraser, 406...Color solid-state photography 1 Elephant Island e. Crow 6 figure

Claims (1)

[Scope of Claims] A reading process of color-separating a color original and reading it with a solid-state image sensor, a process of detecting the outline of the original image based on image information read in this reading process, and color separation latent to be masked. a step of determining a masking amount for the image based on the image information, and partially erasing the color separation latent image to be masked in an area modulation manner using an eraser using a dot light emitter array at an erase rate corresponding to the masking amount. A color correction method in a color electronic copying system, comprising the steps of: not performing partial erasure with an eraser in the contour part.