JPS62169A - Digital color image processor - Google Patents

Abstract

PURPOSE:To record cleary a black color by separating black information with the aid of each binary-coded color data. CONSTITUTION:After multivalued data is binary-coded, that is, dither-processed, a black component is separated from the binary data to remove a base color. Accordingly, the data which is completely dither-processed can correspond to each recorded dot one vs one. As a result, when data on all color components Y, M and C stand at '1' (recording), data on the black component BK are set to '1' and data on Y, M and C are set to '0' (non-recording). Then the black color is hardly superimposed with other colors for each unit of a dot (picture element). Namely the output of a gradation processing circuit 106 is connected to a black component separation and base color removal circuit 107.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a digital color image processing device, and more particularly to black image separation and undercolor removal in a device that expresses halftones by area coverage modulation.

[Conventional technology] When recording images using the Dramato Trif Ku method.

In ordinary recording devices, the density level of each dot can only be divided into four levels at most. However, in digital color copying machines, for example, generally yellow (Y)
, magenta (M), cyan (C), black (BK)
64 levels of gradation expression are required for each basic color in recordings such as .

Conventionally, when performing such multi-gradation expression.

A relatively large dot area consisting of multiple dots (for example, 8 x 8) is used as a unit of gradation processing area, and the number of recorded dots and the number of non-recorded dots are 1111 for each dot area to form each gradation processing area. expresses the concentration level of This type of halftone expression method is called a one-area gradation method.

By the way, in general, in a color image, the black image component greatly influences the sharpness of the entire image, so it is very important to faithfully reproduce the black image.

Generally, in a digital color recording device, Y.

An arbitrary color such as black is expressed by overlapping the basic color developers M and C. In principle, the same amount of Y
By overlapping the 3JJK colors of , M, and C, black can be expressed. However, the developer of each color actually used also contains a small amount of color components other than those of each color. Therefore, when black is expressed by superimposing Y, M, and c, a colored black is actually recorded.

Therefore, conventionally, an original image material exclusively for black recording (black: B
K), if the input data includes a black component, the black component is separated from the image data in advance, and the black component is processed in an independent system. In this case, density correction (referred to as undercolor removal) equivalent to black component extraction is performed on the remaining Y, M, and C color data. This type of technology is disclosed in, for example, Japanese Patent Laid-Open No. 161981/1981.

Each color component Y obtained by black separation and undercolor removal.

The data for M, C, and BK are then calculated as 1 in each independent system.
Each image is binarized (dithered) and recorded for gradation expression. Here, if the entire input data in a unit area (e.g. 8x8 matrix) for one-gradation processing is only a pure black component, there is no rIfJM, but if there is a black component and other color components,
For example, if magenta is included, black and magenta will be recorded independently in the same area, so
There are cases where the black original image agent and the magenta original image agent are recorded in an overlapping manner on a dot basis. In that case, if a magenta color component is recorded under black, it is the same as if magenta is not recorded. Conversely, when a magenta color component is recorded on black, the black becomes colored. That is,
In any case, if black and original image materials of other colors overlap, a color error will occur between the input data and the recorded result.

[Objective of the Invention] The present invention is directed to faithfully reproducing colors by preventing overlap between a black original image agent and an original image agent of other colors when performing gradation expression using the area gradation method. The first objective is to reproduce a clear image even if there is a relative shift in the recording position of each color.

[Structure of the invention] In order to achieve the above object, in the present invention.

After the multivalued data is binarized, ie, dithered, the black component is separated from the binary data and the undercolor is removed.

According to this, the data that has been dithered has a one-to-one correspondence with each recorded dot, so for example, Y
, M and C all color component data is “1” (recorded)
In this case, if you set the black component BK data to "l" and set all the Y, M, and C data to "O" (not written*), the overlap between black and other colors will be reduced in dot (pixel) units. will not occur.

By the way, in this type of color recording device.

Each recording color is an independent system, and for example, in a digital color copying machine, the positions of the recording systems for each color are physically far apart. Therefore, each recording system is W! Even if the dots are closely aligned, there is a high possibility that the positions of the recording dots of each color will be relatively shifted by about ±1 dot. As mentioned above, when all recording of other colors is prohibited (removal of undercolor) at the dot position where black recording is performed, if a relative positional shift of one dot occurs in the recording position of each color, the area that should be recorded is Dots are created where nothing is recorded, and the quality of the recorded image is degraded.

Therefore, in a preferred embodiment of the present invention, undercolor removal is performed when the pixel of interest is a black recorded pixel, and the pixels on the upper, lower, left, and right sides adjacent to the pixel of interest are also black recorded pixels. limited to. Thereby, it is possible to prevent the recording quality from deteriorating due to the relative recording position shift of each colored thread as described above.

[Example] Hereinafter, the present invention will be explained in detail with reference to the @ page.Part 1 @1 shows the structural components of a digital color copying machine of one type in which the present invention is implemented, and FIG. An overview of the configuration of the electrical equipment section is shown.

First, referring to FIG. 1, an original 1 is placed on a platen (contact glass) 2, and fluorescent lamps 31+3 for illuminating the original are placed on a platen (contact glass) 2.
2, the reflected light is illuminated by a movable first mirror 41. It is reflected by the second mirror 42 and the third mirror 43 and passes through the imaging lens 5.

Enters the dichroic prism 6, where the three wavelengths of light, red (R), green (G) and blue (B)
It is spectrally separated into The separated light is captured by CC, which is a solid-state image sensor.
The light is incident on D7r, 7g and 7b, respectively. That is, red light enters the COD 7r, green light enters the COD 7g, and blue light enters the CCD 7b.

The fluorescent lamps 31+32 and the first mirror 41 are connected to the first carriage 8.
The second mirror 42 and the third mirror 43 are mounted on the second carriage 9, and the second carriage 9 moves at a speed of 172 of the first carriage 8.
The optical path length from to COD is kept constant, and the first and second carriages are scanned from right to left when reading the original image. The first carriage 8 is coupled to a carriage drive wire 12 that is wound around a carriage drive pulley 11 fixed to the shaft of a carriage drive motor IO, and a wire I2 is wound around a movable pulley (not shown) on a second carriage 9. As a result, by rotating the motor 10 in the forward and reverse directions,
The first carriage 8 and the second carriage move forward (original image reading and scanning) and backward (return), and the second carriage 9 moves at the speed of the first carriage 8 at 172.

When the first carriage 8 is at the home position shown in FIG. 1, the first carriage 8 is detected by a home position sensor 39 which is a reflective photosensor. This detection mode is shown in FIG. 3. When the first carriage 8 is driven to the right during exposure scanning and moves away from the home position, the sensor 39 does not receive light (carriage is not detected), and the first carriage 8 returns to the home position. When the sensor 39 returns to the position, the sensor 39 starts receiving light (carriage detection), and the carriage 8 is stopped when the sensor 39 changes from not receiving light to receiving light.

Referring now to FIG. 2, CCD 7 r t 7
g.

The output of 7b is analog/digital converted and subjected to necessary processing in the image processing unit 100.

Recorded color information: black (BK), yellow (Y),
The signals are converted into binary signals for magenta (M) and cyan (C) recording activation. Each of the binary signals is sent to a laser driver 112bk.

input to LL2y, 112I11 and 112c,
Each laser driver is a semiconductor laser 113bk, 113
By energizing y, 113Ia and 113c, a laser beam modulated with a recording color signal (binarized signal) is emitted.

Referring again to FIG. The emitted laser beam is reflected by the one-rotation polygon IA 13bk, 13y, 13m and 13c, respectively, and the f-theta lens L 4bk,
L 4y.

After passing through 14ta and 14c, the fourth mirror 15bk.

15y, 15m and 15c and 5th mirror 16bk.

Reflected by 16y, 16m and 16c, polygonal mirror surface tilt correction cylindrical lens l7bk, I7y.

After passing through 17m and 17c, photosensitive drum 18bk.

18y, 18m and L8c are imaged and irradiated.

Rotating polygon mirror 13bk, 13y* 13m and 13
c is polygon mirror drive motor 4 lbk, 41y, 41
m and 41c, and each motor rotates at a constant speed to rotate the polygon mirror at a constant speed.

As the polygon mirror rotates, the laser beam is scanned in a direction perpendicular to the rotation direction (clockwise) of the photoreceptor drum, that is, in a direction along the drum axis.

FIG. 4 shows the laser scanning system of the cyan color recording device in detail. 43c is a semiconductor laser. A sensor 44c made of a photoelectric conversion element is arranged to receive the laser beam at one end of the laser scan (double-dot chain line) in the direction along the axis of the photoreceptor drum 18c, and this sensor 44c detects the laser beam. The starting point of one line scan is detected at the time when the detection changes from detection to non-detection. That is, the laser light detection signal (pulse) from the sensor 44c is processed as a line synchronization pulse for laser scanning. Magenta recording device.

The configuration of the yellow recording device and the black recording device is also the fourth one.
The configuration is exactly the same as that of the cyan recording apparatus shown in the figure.

Further, referring to FIG. 1, the surface of the photoreceptor drum is connected to charge scorotrons 19bk, 19y, 19m and 19 connected to a negative voltage high voltage generator (not shown).
It is uniformly charged by c. When a laser beam modulated by a recording signal is irradiated onto the uniformly charged surface of the photoreceptor, the electric charge on the surface of the photoreceptor flows to the equipment ground of the drum body and disappears due to a photoconductive phenomenon. Here, the laser is not turned on in areas where the document density is high, and the laser is turned on in areas where the density of the J7X manuscript is light. As a result, the portions of the surfaces of the photoreceptor drums 18bk, 18y, 18m and 18c, which correspond to the areas with high document density, receive a voltage of -800V.
The potential of the part corresponding to the light density part of the original is -to
ov, and an electrostatic latent image is formed corresponding to the density of the document. These electrostatic latent images are transferred to a black developing unit 20bk, a yellow developing unit 20y, a magenta developing unit 20+m, and a cyan developing unit 20c.
Developed by photoreceptor drum 18 bk + 18
Form black, yellow, magenta and cyan toner images on the surfaces of y*18m and 18c, respectively.

Note that the toner in the developing unit is positively charged by stirring, the IFA image unit is biased to about -200V by a developing bias generator (not shown), and the Fs light body is attached to a location where the surface potential is higher than the developing bias. A toner image corresponding to the original is formed.

On the other hand, the recording paper 267 stored in the transfer paper cassette 22 is fed out by the paper feeding operation of the feed roller 23, and transferred to the transfer belt 267 by the registration roller 24 at a predetermined timing.
Sent to 5. The recording paper placed on the transfer belt 25 is
Due to the movement of the transfer belt 25, the photosensitive drums 18bk,
18y, 18m+ and 18c sequentially, and each photoreceptor drum 18bk, L 8y+
While passing through 18m and 18c, black, yellow,
Magenta and cyan toner images are sequentially transferred onto recording paper.

The transferred recording paper is then sent to a thermal fixing unit 36, where the toner is fixed to the recording paper, and the recording paper is discharged to a tray 37.

On the other hand, residual toner on the photoreceptor surface after transfer is removed by cleaner units 2 lbk, 21y, 2 IvA and 21c.
will be removed.

A cleaner unit 21bk and a black developing unit 20bk that collect black toner are connected to a toner collection pipe 42.
The black toner collected by the cleaner units 2+ and bk is collected by the developing unit 20bk. Incidentally, the cleaner unit l-21y is damaged due to reverse transfer of black toner from the recording paper during transfer to the photoreceptor drum 18y.

The yellow, magenta and cyan toners collected in units 2111 and 21c are mixed with toner from the different color developing device in the preceding stage of those units 1-.

It will not be collected for reuse.

FIG. 5 shows the inside of the toner recovery pipe 42.

Inside the toner recovery pipe 42, a toner recovery auger 4 is installed.
Contains 3. The auger 43 is formed of a coil spring and is freely rotatable inside the toner collection pipe 42 bent into a channel shape.

The auger 43 is rotationally driven in one direction by a driving means (not shown), and the toner collected in the unit 21bk is transferred to the developing unit 20b by the spiral pump action of the auger 43.
sent to k.

The transfer belt 25 that conveys the recording paper in the direction from the photoreceptor drums 18bk to 18c includes an idle roller 26° and a drive roller 2.
7. It is stretched between an idle roller 28 and an idle roller 30, and is rotated counterclockwise by a drive roller 27. The drive roller 27 is pivotally connected to the left end of a lever 31 that is pivotally connected to a shaft 32 .

Normally, as shown in FIG. 1, the transfer belt 25 on which the recording paper is placed is in contact with the photosensitive drums 44bk, 44y, 44+s, and 44c. In this state, transfer belt 25
When recording paper is placed on the drum and toner images are formed on all drums, each toner image is transferred onto the recording paper as the recording paper moves (
color mode).

The console board 300 includes a copy start switch 301. Color mode designation switch 302 (Immediately after the power is turned on, the switch key is off, Y, M.

4-color mode setting for C and BK; the switch key lights up when the switch is closed for the first time, and 3-color mode setting for Y, M, and C occurs;
When the switch is closed the second time, the switch key goes out and the 4-color mode is set again) and other input key switches,
Equipped with character display and indicator lights.

Next, refer to the time chart shown in FIG.

The operation timing of the main parts of the copying mechanism will be explained. FIG. 6 shows the case when two identical full-color copies are made. The modulation energization of the laser 43bk based on the recording signal is started at almost the same timing as the start of the exposure scan of the first carriage 8, and the lasers 43yy43m and 43c are energized by distances 44y, 44m and 44c from the photoreceptor drum 44bk, respectively. The moving time TV+ of the transfer belt 25
Modulation energization is started with a delay of T11 and Tc.

Transfer corotrons 29bk, 29y, 29m and 29c are lasers 43bk* 43y, 4, respectively.
3rm and 43c are energized after a delay of a predetermined time (time for the laser irradiation position on the photosensitive drum to reach the transfer corotron) from the start of modulation energization.

See Figure 2. The three color image signals read by COD 7 r * 7 g and 7 b are each A/D converted and image processed as digital multi-value data with 2 nits of 100
is applied to The image processing unit lOO performs various color correction processing on the data, converts it into binary data by area WI adjustment processing, and converts it into black (BK) data necessary for recording.
), yellow (Y), magenta (M) and cyan (C
) into each recording signal. The BK recording signal is supplied as is to the laser driver 112bk, but the Y, M and C recording signals are supplied by delay times Ty and T shown in FIG. * and after a time delay of reading and converting into a recording signal after Tc, the laser driver 112
y, 112m+ and 112c;
Three color signals are given from D7r, 7g and 7b,
In the graphics mode, three color signals are applied from outside the copying machine through the external interface 117.

Shading correction circuit 10 of image processing unit 100
1 is the color WII data obtained by A/D converting the output signals of CCDs 7r, 7g and 7b into 8 bits, and is corrected for optical illuminance unevenness, sensitivity variations of internal unit elements of CCDs 7r, 7g and 7b, etc. Create reading color gradation data.

The multiplexer 102 is a multiplexer that selectively outputs either the output gradation data of the correction circuit 101 or the output gradation data of the interface circuit 117.

The γ correction circuit 103 that receives the output (color gradation data) of the multiplexer 102 not only changes the gradation (input gradation data) according to the characteristics of the photoreceptor, but also changes the gradation arbitrarily using the operation button of the console 300. and further change the input 8-bit data to output 6-bit data. Since the output is 6 bits, data representing one of 64 gradations will be output. Red (R) output from the γ correction circuit 103
), green (G), and blue (B), respectively, are supplied to a complementary color generation circuit 104.

Complementary color generation is the conversion of the name of each color read signal to the recording color signal, red (R) # tone data becomes cyan (CC) tone data, and green (G) tone data becomes magenta (M) tone data. Tone data and blue tone data (B)
is converted (read) as yellow gradation data (Y).

Each of Y, M, and C data output from the complementary color generation circuit 104 is provided to a masking processing circuit 105.

The calculation formula for masking processing is generally Yi, Mi, Ci: data before masking.

Y(1, MO, CO: data after masking.

It can be expressed as Therefore, the coefficients (811, etc.) of the above calculation formula are calculated in advance and substituted into the above calculation formula, and the masking processing port @
Calculated values (Yo, etc.) associated with the scheduled inputs Yi, Mi, and Ci (6 bits each) of 105 are stored in advance in the ROM. Therefore, in this embodiment, the masking processing circuit 105 is composed of a set of ROMs, and data at addresses specified by the inputs Y, M, and C to the masking processing circuit 105 is sent to the gradation processing circuit 106. Given.

Generally speaking, the masking processing circuit I05 performs Y, Y, etc. according to the characteristics of the spectral reflection wavelength of the toner for forming a recorded image.
This corrects the M and C signals.

Next, the gradation processing circuit 106 of the image processing unit 100 will be explained. This circuit 109 converts each multivalued input data of Y, M, and C into binary data, and performs one-area gradation processing to reflect the gradation of the input data in the output data. .

The 6-bit gradation data can represent density information of 64 gradations. Ideally, if the dot diameter of one dot could be varied in 64 steps, there would be no need to reduce the resolution, but in laser beam electrophotography, the dot diameter modulation stabilizes the gradation by only about 4 steps at most, so it is generally A combination of gradation method, area gradation method and beam modulation is used. Here, area gradation processing is performed for each 8×8 pixel matrix to express 64# halftones.

Specifically, the R'ff tone processing circuit 106 generates binary data according to the result of comparing input multi-value data with a predetermined threshold. This threshold value is assigned a different value to each pixel in the 8×8 matrix, as shown in FIG. 8a. Therefore, "l" of the binary data generated within the 8x8 matrix area, that is, the number of recording pixels, increases in proportion to the average gradation of the input data. Therefore, the gradation of input data is reflected in the number of recording pixels for each matrix.

In this embodiment, specifically, the gradation processing port 1IIt.

6 is comprised of three read-only memories (ROM: not shown) that process data for each color of Y, M, and C. Each of these memories has a memory address corresponding to the gradation value of the input data and the position in the 8×8 matrix at that time.
The result of comparing the gradation value with the threshold value of the pixel position is stored in advance.

In this embodiment, the threshold values are arranged in a spiral systematic pattern as shown in FIG. 8a, and are common to each color.

For example, as a result of reading an image in which the 8x8 matrix area is divided into two types of color areas with a diagonal edge as a boundary as shown in Figure 8b, the multi-valued digital data shown in Figure 8c for each color has a gradation level. If the voltage is applied to the processing circuit 106, each output of Y, M, and C of the 1st gradation processing circuit IQ6 contains the binary data shown in FIG. 8d (hatched pixels are recording pixels "l", etc. However, a non-recorded pixel "0") is obtained.

The 8x8 matrix area of binary data is Y, M.

Since all C correspond to the same position on the recording sheet, if the data of Y, M, and C shown in Fig. 8d are output to the recording system as they are, all of the pixels of Y, M, and C are recorded (transferred). occurs. This pixel can be considered a black pixel. However, even if Y, M, and C are recorded overlappingly at the same pixel position, pure black cannot be obtained.

Therefore, in order to eliminate the above-mentioned inconvenience, the gradation processing circuit 10
A black separation/undercolor removal circuit 107 is connected to the output of 6.

FIG. 7a shows the configuration of the black separation/undercolor removal circuit 107,
An example of the schematic operation timing of the circuit is shown in FIG. 7b. Referring to FIG. 7a, this circuit includes latches 211,
215. A Nant gate 212 is equipped with a gate unit 213 and an inverter 214. Gate unit 2
13 is made up of three AND gates. The Nant gate 212 generates black data.

The signal line SL connected to one input terminal of the NAND game-1-212 is set to a low level L in the three-color color mode, and to a high level H in the four-color color mode. In 3-color color mode, input Y
, M, and C data.

It will be output as is. The output data of black BK at that time is always "0" (corresponding to low level L: 11-p level).

In 4-color mode, at least one of Y, M, and C
If it is "0", it is the same as the case of three-color color mode. However, when the input data of Y, M, and C all become "1" (corresponding to high level H; recording level), the output of Nant gate 212 becomes low level L, and the output of inverter 214 becomes high level H. , BK output data becomes "1". Also, at this time, the 3
The two AND gates each have one input terminal at a low level.
Therefore, the output terminal becomes low level L regardless of the input data. That is, Y of input data.

When M and C become 'IJt rlJ and "1", output data Y, M, C and BK become rOJ, rob, roJ and "1".

Therefore, in the four-color mode, if the data shown in FIG. 8c, for example, is input, the data shown in FIG. 8e is output. When recording is performed based on this output data, colors as shown in FIG. 8f are recorded at each pixel position in the corresponding 8×8 matrix area. Referring to Figure 8f.

It can be seen that yellow Y and cyan C are sometimes recorded overlappingly at the same pixel position, but black BK and other colors are not recorded overlappingly at the same pixel position.

Note that the signal lines S2 and S3 that control data retention in the latches 211 and 215 are provided at timings for each pixel that are synchronized with image reading.

A predetermined pulse signal is applied from the synchronization control circuit 114.

The buffer memory 108 of the image processing unit 100 simply generates a time delay corresponding to the distance between the photosensitive drums. The writing timing of each memory for Y, M, and C is simultaneous, but the reading timing is matched to the modulation energization timing of the laser, which is different for each color, as shown in FIG. When A3 is the maximum size, the capacity of each memory should be at least 24% of the maximum required capacity of an A3 original for yellow Y, 48% for magenta M, and 72% for cyan C.

The binary data for each color (Y, M, C, BK) whose timing has been adjusted by the buffer memory 108 is transmitted to the laser drivers 43y, 43I11, 43c and 43bk for each color.
given to.

The synchronization control circuit 114 determines the activation timing of each of the above elements and matches the timing between each element. 200 is a microprocessor system that controls all the elements shown in FIG. 2 described above, that is, controls the copying machine. This processor system 200 controls copying in various modes set on the console, and controls not only the image reading and recording system shown in FIG. 2, but also the photoreceptor power system and exposure system.

Sequences such as charger system, developing system, fixing system, etc. are performed.

FIG. 9 shows an interface between the polygon mirror drive motor etc. and the microprocessor system (200: FIG. 2). The input/output boat 207 shown in FIG.
00 bus 206.

In addition, in FIG. 9, 45 is a photosensitive drum 18bk,
This is a motor that rotationally drives 18y, 18m, and 18c, and is energized by a motor driver 46.

In addition, it is equipped with a driver that energizes each part of the copying machine, a processing circuit connected to the sensor, etc., and an input/output port 20.
7 or other input/output capo-1 to system 2
00, but illustration is omitted.

Next, the operation timing of each part based on the control operations of the microprocessor system 200 and the synchronous control circuit 114 will be explained.

First, when a power switch (not shown) is turned on, the device starts a warm-up operation.

- Increase the temperature of the fixing unit 36.

・Starting the polygon mirror at a constant speed, ・Home positioning of the carriage 8, ・Generation of line synchronization clock (1, 26KHz), ・Generation of video synchronization clock (8, 42M) IZ), ・Management of various counters Performs operations such as initialization. The line synchronization clock is supplied to the polygon mirror motor driver and the COD driver, and the former uses this signal as a reference signal for the phase-locked loop (PLL) servo, and the feedback signal to the beam sensor 4.
So that the beam detection signals of 4bk, 44y, 44m and 44c have the same frequency as the line synchronization clock.
Further, it is controlled to have a predetermined phase relationship. The latter is
It is used as a main scanning start signal for CCD reading. Note that the detection signals (pulses) of the beam sensors 44bk, 44y, 44+a, and 44c are output for each color (each sensor) and are used as the signal for synchronizing the start of laser beam main scanning. Note that the frequency of the line synchronization signal and the detection signal of each beam sensor are locked by PLL and are the same, but there may be a slight phase difference, so the scanning reference is not the line synchronization signal but the frequency of each beam sensor. The detection signal is used.

The video synchronization clock has a frequency of one dot (one pixel) and is supplied to the COD driver and laser driver.

Various counters are (1) Reading line counter, (2) BK, V, M, C line counters.

(3) read dot counter, and (4) BK,
It is a dot counter that includes Y, M, and C parts, but the above (
1) and (2) are microprocessor system 200
This is a program counter substituted for the operation of the CPU 202, and (3) and (4) are provided individually on the hardware, although not shown.

Next, the timing of the print cycle is shown in Figure 1O,
Let me explain this. When the warm-up operation is completed, the state becomes ready for printing, and when the copy start key switch 301 is turned on, the CPU 2 of the system 200
By the operation of 02, the first carriage 8yjA movement motor (
Carriages 8 and 9 (Fig. 9) begin to rotate.
2 speed) starts scanning (exposure scanning) to the left. When the carriage 8 is at the home position, the output of the home position sensor 39 is H, and the exposure scan (IJ constant scan starts shortly afterward.At the time when the carriage 8 changes from H to L, the read line counter is cleared and at the same time , the count is enabled.The time point when this change from H to L is the position where the leading edge of the document is exposed.

With the line synchronization clock that comes in after the sensor 39 goes low, the read line counter is counted up every pulse. Also, when the line synchronization clock comes in, the reading dot counter is cleared at the rising edge of the clock to enable counting.

Therefore, the reading of the first line is performed after the home position sensor 39 turns on, in synchronization with the video synchronization clock immediately after the input of the first line synchronization clock, and both $
1. Pixel 2. . . . Pixel 4667 is read sequentially. still,
Pixel counting is done by a read dot counter. Further, the content of the read line counter at this time is 1.

Similarly, for the second and subsequent lines, the reading line counter is incremented by the next line synchronization clock, the reading dot counter is cleared, and synchronized with the next video synchronization clock, the reading counter is incremented, and pixels are read. Do the following.

In this way, the lines are sequentially read, and when the reading line counter counts up to 6615 lines, the last reading is performed on that line, and the carriage drive motor is reversely energized to return the carriages 8 and 9 to their home positions.

The pixel data read in the above manner is sequentially sent to the image processing unit 100 and subjected to various image processing. The time required to perform this image processing is only two clocks of the line synchronization clock signal.

At least it takes.

Next, in writing, first clear the write line counter and enable the count: When the read line counter is 2, the BKf write counter is; when the read line counter is 1577, the Y$ write counter is = the read line counter is When the read line counter is 4727, the 1M write counter is cleared and the C write counter is cleared and enabled, respectively.

These count ups are calculated by each beam sensor 4.
This is done at the rising edge of the detection signals 4bk, 44y, 44m and 44c. Further, the write driver 1 counters (BK, Y, M, C) are cleared at the rising edge of the detection signal of each beam sensor.

Count-up is performed by a video synchronization signal.

Writing for each color begins when the content of the reading counter reaches a predetermined value, the writing line counter for each color becomes counting enable, and counting starts with the first beam sensor detection signal (content 1). When the dot counter reaches a predetermined value, the laser driver is driven to perform a writing force. Dot count is 1~
The data between 400 and 401 to 5077 (401 to 5077) are dummy data.
677) are writable values. Here, the dummy data includes beam sensors 44bk, 44y, 44m and 44c and photosensitive drums 18bk, 18y, 18.
This is for adjusting the physical distance between m and 18c. Also, write data (l or 0) is captured at the falling point of the video synchronization signal. The writing range in the line direction is when each writing line counter is 1 to 6615 lines.

Now, as shown in Figure 10, after starting exposure scanning, C
Since BK recording data is obtained from the time of scanning the third line of OD, the recording activation of the BK recording apparatus is started in synchronization with the acquisition of BK data. Therefore, the frame buffer memory is omitted in the BK signal processing line. On the other hand, since the Y, M, and C recording devices are shifted in the paper feeding direction, the recording start delay times Ty, T+++, and T c correspond to the amount of shift from the BK recording device.
It is necessary to store the recording signal between (FIG. 6), and this is accomplished by the buffer memory 108.

Next, one modified embodiment will be described. Y, M, C and BK
When the recording position of each basic recording color is accurately positioned dot by dot, it is most preferable to use the method described in the above embodiment. However, since the recording systems for each color are physically far apart, it is difficult to , the recording position of each color may be relatively shifted. In particular, positional deviations of about ±1 dot (minimum unit of recording) are likely to occur.

In the above embodiment, when black recording data is generated, all data of other colors ('Y, M, C) are set to the non-recording level "0".
Therefore, if a relative shift occurs in the recording positions of Y, M, C, and BK, blank (unrecorded) portions will occur at dot positions where black or other colors should originally be recorded. This type of blank space reduces the recording quality of one image. In the embodiment shown in FIG. 11, this blank space is prevented from occurring.

FIG. 11 shows a modification of the black separation/undercolor removal circuit. In this embodiment, Y, M
and C data is set to “0”, otherwise, Y
, M, and C are made the same as the input data. That is, when pixel A shown in FIG. 12 is the pixel of interest, A, B
, C, D, and E are all black, undercolor removal is performed.

Referring to FIG. 11, this black separation/undercolor removal circuit is as follows:
Latches 221, 232. AND gate 222, shift registers 223, 224, 225.22G, 231. Gate unit 227. It consists of latches 228, 230 and Nant gate 229. Shift register 223, 22
4 and 225 have the number of bits to hold all pixel data for one line of main scanning, and shift registers 226 and 23
1 has the number of bits to hold data for l line-1 pixel.

Four-color color mode, that is, signal line St is at high level ■(
Let's explain the case. Input data of Y, M and C, r1
4. l'l' and '1', the AND gate 222
The output terminal becomes high level H1, that is, the black recording level. Y
, M, and C are outputted through one line of shift registers 223, 224, and 225, respectively, so black data appears at the output terminal of latch 228 at the same timing as these output data.

In other words, the data at the output terminal of the latch 228 can be regarded as the black data (A in FIG. 12) of the pixel of interest. Also, an output terminal of the AND gate 222.

The data appearing at each position of the output terminal of the shift 1 register 226, the output terminal of the latch 230, and the output terminal of the shift register 231 are shown in FIG.
Corresponds to E and B black data.

The data of these five pixels A, B, C, , D and E are
applied to each input terminal of the Nandt gate 229. Therefore, the output terminal of the gate 229 becomes a low level L only when the pixel of interest and pixels located above, below, left, and right of the pixel are all at a high level H, and under other conditions, the output terminal becomes a high level H. become. The output terminal of Nant Gate 229 is low level L
Then, the output terminals of the AND gates constituting the gate unit 227 become low level L, and the undercolor removal is performed.

In this embodiment, for example, Y and M shown in FIG. 8C.

When data C is input, data as shown in FIG. 13 is output. In this case, the black BK data is the 8th
It is the same as that in figure e. As can be seen from these results, if each color of Y, M, and C and the color of BK were to have a one-dot recording position shift in the upper, lower, left, or right direction relative to each other during recording. Even so, no extra blank pixels are generated in which none of Y, M, C, and BK are recorded. Therefore, even if a positional shift occurs, there is little deterioration in recording quality.

Note that in this embodiment, when the pixel of interest and the pixels above, below, left, and right of the pixel are inappropriate, undercolor removal is performed.
This combination of pixels may be changed.

For example, if there is no possibility of positional deviation in the main scanning direction, it is sufficient to refer to only the pixel of interest and the pixels above and below it.

[Effects] As described above, according to the present invention, since black information is separated using the binarized data of each color, it is possible to prevent overlap between black and other colors from occurring in dot units, and this records black clearly and clearly.

In addition, by removing undercolor using a combination of multiple black pixels, it is possible to prevent recording quality deterioration due to recording position misalignment6.

[Brief explanation of drawings]

FIG. 1 is a sectional view mainly showing the structure of the main mechanical parts of a digital color copying machine of one type that embodies the present invention. Figure 2 is a block diagram showing the configuration of the electrical image processing section;
3 is an enlarged perspective view of a part of the first carriage 8 shown in FIG. 1, FIG. 4 is an exploded perspective view of the BK recording device section shown in FIG. 1, and FIG. 5 is an exploded perspective view of the BK recording device section shown in FIG. FIG. 3 is an enlarged perspective view showing a toner recovery pipe in a broken state. FIG. 6 is a time chart showing the relationship between original reading scanning timing, recording biasing timing, and transfer biasing timing in the above embodiment. FIG. 7a is a block diagram showing the configuration of the black separation/undercolor removal circuit 107 shown in FIG. 2, and FIG. 7b is a time chart showing the operation of the circuit shown in FIG. 7a. FIG. 8a is a plan view showing a two-dimensional expansion of the data of the threshold table. Figure 8b is a plan view showing an example of an image to be read, Figure 8c is a plan view showing two-dimensional expansion of the data obtained by reading the image in Figure 8b, and Figure 8d is a plan view of the data in Figure 8c that is dithered. Fig. 8e is a plan view showing the result of processing the data in Fig. 8d in the circuit 107, and Fig. 8f is a plan view showing the result of processing the data in Fig. 8e by the data in Fig. 8e. FIG. 3 is a plan view showing colors recorded at each pixel position. FIG. 9 is a block diagram illustrating some of the copying mechanism elements connected to microprocessor system 200. FIG. 10 is a time chart showing the relationship between exposure scanning and recording energization of the copying machine shown in FIG. FIG. 11 is a block diagram showing one modification of the black separation/undercolor removal circuit. FIG. 12 is a plan view showing the positional relationship of a plurality of pixels that determine the conditions for undercolor removal in the circuit of FIG. 11. FIG. 13 is a plan view showing a two-dimensional expansion of the Y, M, and C output data obtained by inputting the data shown in FIG. 8c to the circuit shown in FIG. 11. 1: Original 2 Nibraten 31 t32
: Fluorescent lamp 41 to 43: Mirror 5: Variable magnification lens unit 6: Dichroic ink prisms 7r, 7g, 7b: CCD (image reading means)
8: First carriage 9: Second carriage IO: Carriage drive motor 11: Pulley 12: Wire 13bk,
13y, 13m, L3c: polygon mirror 14bk, 14
y, 14m, 14c: f-θ lens 15bk, 15
y, 15m, 15c, 16bk, 16y, 16m, 16
c: Mirror 17bk, 17y, 17m, 17c Nijilintorical lens 18bk, 18y, 18m, 18e
: Photosensitive drum 19bk, 19) 1, 19m, 19c
:Charge Scorotron 20bk, 20y,
20w+, 20c: developing device 21bk, 21y, 2
1mg, 21c: Cleaner 22: Paper cassette
23: Paper feed roller 24 registration roller 25: Transfer belt 26, 28, 30: Idle roller 27: Drive roller 29bk, 29y, 29+s, 29c:
Transfer corotron 31 lever 32: Shaft 33: Pin 34: Compression coil spring 3
5: Black copy mode setting solenoid plunger 36:
Fixing device 37: Tray 39: Home position sensor 40: Carriage guide bar 41bk, 41y, 41m, 41c: Polygon mirror drive motor 42: Toner collection pipe 43bk, 43y, 43m, 43c: Laser (recording means) 44bk, 44y, 44m , 44c: Beam sensor 45: Photosensitive drum drive motor 4G: Motor driver 100: Image processing unit

Claims (4)

[Claims] (1) Image reading means that separates and reads the original image; Analog/digital conversion means that converts analog image signals for each color obtained from the image reading means into digital signals each consisting of a plurality of bits; multiple types; area gradation processing means that includes a threshold value and converts the digital image signal for each color obtained from the analog/digital conversion means to a binary signal by comparing it with one of the threshold values; a black separation means for processing the binary image signal obtained from the tone processing means and generating binary information of a black component; and recording visible information for each color according to the binary image signal that has passed through the black separation means; A digital color image processing device comprising: a recording means for recording. (2) The black separation means refers to each of yellow, magenta, and cyan binary data for each minimum unit of recording, and when all of them are at the recording level, sets the black component data to the recording level; A digital color image processing apparatus according to claim (1). (3) When the black separation means sets the black component data to the recording level, the black separation means applies a yellow color to the recording means;
The digital color image processing apparatus according to claim 1, wherein all binary data of magenta and cyan are set to a non-recording level. (4) When the pixel whose black component data is set to the recording level is located not only at the pixel of interest but also at the upper, lower, left, and right positions of the pixel of interest, the black separation means ,
The digital color image processing apparatus according to claim 1, wherein all binary data of yellow, magenta, and cyan are set to a non-recording level.