JPS62263770A - Color recorder - Google Patents

Abstract

PURPOSE:To eliminate a gradation error, to reproduce a correct color and to enhance the gradation of a recording picture by selecting an using threshold table to correct a signal. CONSTITUTION:A picture processing unit 100 converts three color picture signals R, G, B read by CCDs 7r, 7g, 7b into the respective recording signals of BK, Y, M, C required for a recording, a semiconductor laser is energized through a laser driver 112 to outgo the laser beam modulated by a recording chrominance signal. A gradation processing circuit 106 is provided with the threshold table in which respectively different thresholds are assigned to the respective dot positions of a dot area, one threshold at the position corresponding to a recording position at that time in the threshold table is selected and the binary signals of the area gradation processed Y, M, C are obtained in an output terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a color recording device such as a digital color copying machine, and in particular to a color recording device such as a digital color copying machine, and in particular to a color recording device such as a digital color copying machine.
, using multiple colorants such as cyan (C).

It is effective to use a color recording device that expresses any color by sequentially overlapping images recorded with each color material.

[Prior Art 1] For example, in a digital color copying machine, the light reflected from a document is divided into three primary colors by an optical filter.

That is, the original color is separated into red (R), green (G), and blue (B), and document information is read for each basic color separated into one color.

On the other hand, in a recording system, a predetermined color is reproduced on recording paper by recording a combination of three primary colors of ink, ie, cyan (C), magenta (M), and yellow (Y). Therefore, in a digital color copying machine, the R, G, and B information obtained from the reading system is converted into C, M, and Y signals, and the recording system for each color is energized by the C, M, and Y signals. .

By the way, in principle, the correlation between R, G, and B and Y, M, and C can be expressed by a relatively simple formula. However, in reality, these relationships change depending on various factors, so it is difficult to perform accurate conversion.

One of the causes of the change is a change in parameters depending on the degree of overlapping of each recording color.

That is, in general, in digital recording, it is not possible to change the recording density in multiple steps, so 1! a Binary recording of "recording" or "non-recording" is performed in units of small dots, and for each predetermined area (e.g. 8 x 8 dots), the ratio between the number of recorded dots and the number of non-recorded dots is adjusted to create an arbitrary number of dots. It expresses the recording density. That is, the recording density is determined according to the area ratio between the predetermined area and the area where dots are actually recorded. In the case of color recording, generally the surfaces of each recording color are sequentially recorded in the order of Y, M, and C. Therefore, in an area where a color expressed by combining multiple colors of Y, M, and C is recorded, Y,
Color materials of multiple colors M and C overlap. However, when expressing colors in which the recording area ratios of Y, M, and C are different from each other, there are portions where the plurality of recording materials overlap and portions where they do not overlap. For example, 70%, 50% for Y, M and C, respectively.
When recording is performed on 50% of the area, 50% of the area becomes black due to the overlap of Y, M, and C, 20% of the area becomes yellow due to Y, and the remaining 30% area becomes the background color ( The principle of additive color mixing holds true for the overlapping parts (white), but it does not hold true for the non-overlapping parts. Therefore, if the degree of overlap of Y, M, and C changes,
R, G accordingly.

The correlation between B, Y, M, and C changes.

In other words, the relationship between the level of each color signal of Y, M, and C (corresponding to the number of recorded dots) and the actual recording area ratio is nonlinear.

Therefore, in the technique of JP-A-60-109967, a non-linear conversion circuit is provided after the masking (R, G, B/Y, M, C conversion) processing circuit to perform color correction according to the influence of the overlap. Processing is in progress.

However, since there is a difference between the recording signal level and the actual recorded content due to various factors in addition to the above-mentioned overlap, the above-mentioned color correction alone is often insufficient.

For example, in color recording in which toner images of each color of Y, M, and C are generated and the images of each color are transferred and recorded on one recording sheet in surface order, the image transfer from the second side (second color) onward is During the process, the toner image transferred in the previous image transfer process may be reverse-transferred (that is, separated from the recording sheet), or the toner image recorded during the process may be subjected to mechanical force, causing its area to become wider than when it was recorded. Phenomena occur, and these produce errors in color.

By the way, methods for expressing an arbitrary recording density by adjusting the ratio between the number of recorded dots and the number of non-recorded dots in a potential gradation processing area (for example, 8x8 dots) include the dither method, density gradation method, and submatrix method. However, when performing any of these gradation processes, a threshold table in which different threshold values are assigned to each dot position within a unit gradation processing area is generally used, and the corresponding The threshold value at the corresponding dot position in the table is compared with the input level or its average value, and a binary signal is generated depending on their magnitude.

In this kind of threshold table.

Although various threshold array patterns have been proposed, each has advantages and disadvantages, and it is preferable to use one according to the type of image to be recorded.

Therefore, it is desirable to prepare in advance a plurality of types of threshold tables having mutually different threshold array patterns, and to enable the operator to switch the threshold table to be actually used by operating a key or the like.

However, the correlation between the number of recorded dots and the actual recording area ratio changes depending on the type of threshold table. Therefore,
When the threshold table used is switched, the reproduced colors change.

[Object of the Invention] An object of the present invention is to reproduce accurate colors in a color recording device and to increase the resolution of a recorded image by making it possible to use a plurality of types of threshold tables.

[Structure of the invention] To achieve the above object, we have devised one invention.

By providing multiple types of threshold tables with different threshold array patterns, it is possible to select the type of threshold table to actually use, and the threshold array pattern of the selected threshold table can be changed. Accordingly, signal correction processing is performed.

That is, for each threshold array pattern in the threshold table, the characteristics of the correlation between the number of recorded dots and the actual recording area ratio are determined in advance, and multiple types of signal correction are performed to compensate for each nonlinear characteristic. The processing contents are prepared in advance, and the contents of the signal correction processing are selected according to the selection of the threshold table, and the optimum signal correction is performed for each threshold table.

According to this, no matter which threshold (direct table is used), the number of recorded dots is corrected so that the actual recording area ratio becomes equal to the gradation of the input image, eliminating gradation errors. In color recording, colors that are faithful to the input image can be reproduced.

By the way, when toner is used as the recording material and the fixing process is performed using a heat roller fixing method or the like.

When looking at an area the size of several dots, the extent to which the toner image expands in area due to the fixing process compared to that during transfer is not constant, but changes depending on the amount of toner adhered to that area. Therefore, color errors caused by this influence cannot be sufficiently corrected by correction processing with fixed processing contents.

Therefore, in a preferred embodiment of the present invention, a determining means is provided for determining the magnitude relationship between the levels of a plurality of input image signals, and the contents of the signal correction process are switched in accordance with the determination result of the determining means. According to this, optimal color correction (signal correction) processing can be performed according to the amount of toner adhesion.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the structural components of a mechanical section of a digital color copying machine of one type that embodies the present invention, and FIG. 2 shows an outline of the configuration of the electrical equipment section.

First, referring to FIG. 1, an original l is placed on a platen (contact glass) 2, and a fluorescent lamp 31+3 for illuminating the original is placed on a platen (contact glass) 2.
2, the reflected light is illuminated by a movable first mirror 41. The light is reflected by the second mirror 42 and the third mirror 43, passes through the imaging lens 5, and enters the dichroic prism 6, where the light of three wavelengths, red (R) and green (
G) and blue (B). The separated light enters solid-state imaging devices C OD 7 r, 7 g, and 7 b, respectively. In other words, red light is CO
D 7 r, green light enters C007g, and blue light enters C0D7b.

The fluorescent lamp 31132 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 by moving the second carriage 9 at half the speed of the first carriage 8, the original 1
The optical path length from the CCD to the CCD is kept constant, and the first and second carriages are scanned from right to left during original image and reading. The first carriage 8 is connected to a carriage drive wire 12 that is wound around a carriage drive pulley 11 fixed to the shaft of a carriage drive motor 10, and the wire 12 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 1/2 the speed of the first carriage 8.

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

Referring now to FIG. 2, C0D7r, 7K.

The output of 7b is analog/digital converted and subjected to necessary processing in the image processing unit 100 to produce recorded color information of black (BK), yellow (Y), and magenta (
M) and cyan (C) are converted into binary signals for recording activation. Each of the binary signals is sent to a laser driver 112bk.

112y, 112m and 112c, and each laser driver outputs a semiconductor laser 113bk, 113y,
By energizing 113m and 113c, laser light modulated with a recording color signal (binarized signal) is emitted.

Referring again to FIG. The emitted laser beams are transmitted through rotating polygon mirrors L 3bk, 13y+ 13+n, respectively.
and 13c, f-θ lens 14bk,
14y.

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

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

Anti on 16y, 16m and 16c! 1-t, h, polygonal mirror surface tilt correction cylindrical lens 17bk, 17
y.

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

L 8Y? 18m and 18ck: Imaging irradiation 6
Rotating polygon mirrors 13bk, 13y, 13m and 1
3c is a polygon mirror drive motor 4 lbk, 41y, 4
1m and 41c, each motor rotates at a constant speed and rotates the multifaceted VT 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.

Cyan color record a′! The laser scanning system of Am is shown in detail in FIG. 43c is a semiconductor laser. Photosensitive drum 18
A sensor 44c, which is a charging conversion element, is arranged to receive the laser beam at one end of the laser scanning direction (double-dot chain line) along the axis of c, and this sensor 44c detects the laser beam, and 1 at the time it changes to non-detection
Detecting the starting point of line scanning. That is, sensor 44
The laser light detection signal (pulse) at c is processed as a line synchronization pulse for laser scanning. Magenta recording device.

The configuration of the yellow recording neck and black recording device is also the fourth.
The configuration is exactly the same as that of the Cyan Note 8 device shown in the figure.

Further, referring to FIG. 1, the surface of the photosensitive drum is uniformly charged by charge scorotrons I 9bk, L 9y+ L 9n+, and 19c connected to a negative high voltage generator (not shown). Note th At
When the laser beam modulated by the signal is uniformly irradiated onto the photoreceptor surface which is charged with a Tr, the electric charge on the photoreceptor surface flows to the device ground of the drum body and disappears due to a photoconductive phenomenon. Here, the laser is not turned on in areas where the original density is high, and the laser is turned on in areas where the original density is low. From this point, the parts of the surfaces of the photoreceptor drums 18bk, 18y, 18m, and 18c that correspond to the high-density parts of the original have a potential of -800V, and the parts that correspond to the light parts of the original atL have a potential of about -100V. An electrostatic latent image is formed corresponding to the density of the image. Each of these electrostatic latent images is
Developed by a black developing unit 20bk, a yellow developing unit 20y, a magenta developing unit 20m, and a cyan developing unit 71"20C, and the photoreceptor drum 18b
Black, yellow, magenta and cyan toner images are formed on the surfaces of K, 18y, 48m and 18c, respectively.

Incidentally, 1 to 2 in the developing unit are positively charged by stirring, and the unit R51 is biased by a regrettable bias generator (not shown); about -200y from then, and the surface potential of the photoreceptor becomes higher than the developing bias. At this point, 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, 18t+ and 18c sequentially, and each photoreceptor drum 18bk, 18y, 1
8m and 18c, black, yellow, magenta, and cyan toner images are sequentially transferred onto the recording paper by the action of a transfer corotron at the lower part of the transfer belt.

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, 21l111 and 21
removed at c.

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 unit 21bk is collected by the developing unit 20bk. Note that the cleaner unit 21y is caused by reverse transfer of black toner from the recording paper during transfer to the photoreceptor drum 18y.

The yellow, magenta, and cyan toners actually collected in 21a+ and 21c are not collected for reuse because they are mixed with toner from the different color developing device in the previous stage of those units.

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 21bk by the spiral pump action of the auger 43.
Sent to bk.

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 . A plunger 35 of a black mode setting solenoid (not shown) is pivotally attached to the right end of the lever 31. A compression coil spring 34 is disposed between the plunger 35 and the shaft 32, and this spring 3
4 applies clockwise rotational force to the lever 31.

When the black mode setting solenoid is de-energized (color mode), as shown in FIG. 1, the transfer belt 25 on which the recording paper is placed is the photosensitive drum 44bk, 44y.

It is in contact with 44m and 44c. In this state, when recording paper is placed on the transfer belt 25 and toner images are formed on all drums, each toner image is transferred onto the recording paper as the recording paper moves (color mode), and the black mode setting solenoid is energized. (black mode), the lever 31 rotates counterclockwise against the repulsive force of the compression coil spring 34, and the rF
The A moving roller is lowered by 5aus, and the transfer belt 25 is moved down to the photosensitive drum 44y.

44m and 44c, and remains in contact with the photosensitive drum 44bk. In this state, the transfer belt 25
Since the upper recording paper only contacts the photosensitive drum 44bk, only the black toner image is transferred to the recording paper (black mode). Since the recording paper does not come into contact with the photoreceptor drums 44y, 44m, and 44c, the toner (residual toner) attached to the photoreceptor drums 44y, 44+++, and 44c does not stick to the recording paper, and stains such as yellow, magenta, and cyan are completely avoided. It won't happen. In other words, when copying in black mode, copies similar to those produced by a normal monochromatic black copying machine can be obtained.

The console board 300 includes a copy start switch and a color mode/black mode designation switch.

It is also equipped with other input key switches, character displays, indicator lights, etc.

Next, the operation timing of the main parts of the copying mechanism will be explained with reference to the time chart shown in FIG. FIG. 6 shows the case when two identical full-color copies are made. 1st
Almost at the same timing as the start of the exposure scan of the carriage 8, modulation energization of the laser 43bk based on the recording signal is started, and the lasers 43y+43m and 43c are activated, respectively.
Photosensitive drum 44bk to 44y+44m and 44c
Modulation energization is started after a delay of travel times Ty, Tm, and Tc of the transfer belt 25 corresponding to the distance. Transfer roller 1
- Ron 29bk, 29y, 29m and 29c are respectively laser 43bk, 43y, 43I11 and 4
3c for a predetermined period of time from the start of modulation energization (on the r'6 optical drum).

It is energized after a delay (time required for the laser irradiated site to reach the transfer corotron).

See Figure 2. The image processing unit 100.

The three color image signals read by CCD 7r, 7a and 7b are converted into black (BK) and yellow (Y) necessary for recording.
, magenta (M), and cyan (C) recording signals. The BK recording signal is sent directly to the laser driver 112.
The Y, M and Cia recording signals are respectively sent to the buffer memory 108y.

After the signal is held at 108m and 108c, the signal is read out after the delay times T yr T m and Tc shown in FIG. 6, and converted into a recorded negative signal, after which it is applied to the laser drivers 112y, 11211, and 112c. Note that in the copying machine mode, one image processing unit 100 is given three color signals from C0D7rt 7g and 7b as described above, but in the graphics mode, three color signals are given from outside the copying machine through the external interface 117.

Shading correction circuit 10 of image processing unit 100
1 is color gradation data obtained by A/D converting the output signals of CCDs 7r, 7g, and 7b into 8 bits.

The read color gradation data is created by correcting optical illuminance unevenness, sensitivity variations of the internal unit elements of the CCDs 7r, 7g, and 7b, and the like.

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.

An input γ correction circuit 103 that receives the output (color gradation data) of the multiplexer 102 corrects the signal it outputs in accordance with the characteristics of the image input device.

It is also used to obtain arbitrary input characteristics according to preference.

The graph in Figure 8a shows the correlation between the actual reflectance of the document surface for each of R, G, and B in four types of general image input devices and the data input by the image input device. e f ro ) fgo and fbo respectively indicate the R, G and B characteristics of the first image input device, and f
rl, fgl, fb+ respectively indicate the R, G and B characteristics of the second image input bag, and fr2. fg
2 and fb2 indicate the R, G, and B characteristics of the third image input device, respectively, and frJ.

fga and fbJ indicate the characteristics of RlG and B at the fourth image input \2 position.

Referring to FIG. 8a, it can be seen that the characteristics of the image input device are different from 1. In other words, when we look at the first image input device and the second image input device, the input data is almost proportional to the reflectance, but some of them include off-seno1-, and some of them contain the same input data. Even in the neck, R, G, and B each have slightly different characteristics. Also, the third
Regarding the image input device and the fourth image input bag U, the five input data are proportional or inversely proportional to the image density (-iog (reflectance)).

The graph in FIG. 8b shows the correlation between the reflectance of the actual document surface and the data output by the input γ correction circuit 103 that processes the signal obtained by reading the document surface. In this example, the four types of characteristics go+gl+g2 and g3 shown in FIG. 8b can be arbitrarily selected using switches on the console board 300.

Characteristic g. By selecting , the actual reflectance of the document surface and the data output by the manual gamma correction circuit 103 will be in an accurate proportional relationship. Note that the characteristics gt and g3 are selected when it is desired to improve the gradation of bright parts of the image, and the characteristics g
2 is selected when it is desired to improve the gradation of dark parts of the image.

A specific configuration of the input T correction circuit 103 is shown in FIG. 7a. Referring to FIG. 7a, this manual gamma correction circuit 103 includes three read-only memories (hereinafter referred to as ROM) 13
1, 132 and 133 and three latches 134, 135 and 136. Each ROM131-13
3 each have a 12-bit address terminal and a 7-bit data terminal.

8-bit Rin of address terminal of ROM13L.

8-bit Gin and RO of address terminals of ROM132
The red signal R, green signal G, and blue signal B output from the multiplexer 102 are applied to the 8-bit Bin of the address terminal of M132, respectively. Each ROM
Two bits of addresses 131 to 133 are connected in common, and the console board 30 is connected to this signal line.
The switching signal 5ELin (see FIG. 7e) is applied to the input device that outputs 0. In addition, each ROM 131-133
The remaining two bits of the address are connected in common,
Input γ switching (SELγ), which the console board 300 outputs, is applied to this signal line.

Each data terminal of ROM 131, 132 and 133 is. They are connected to input terminals of latches 134, 135 and 136, respectively. Output terminal Rout of latch 134
,,l 35 output terminal G out and output terminal 13G output terminal B out are respectively connected to the masking processing circuit 104.
It is connected to the R, G, and 13 input terminals of the. The control terminals of the latches 134 to 136 are connected in common,
A synchronization signal output from the synchronization control circuit 114 is applied to these terminals.

The relationship between each input signal of this human input γ correction circuit 103 and correction processing will be shown in the following first device.

Note that in the first device, i is each input terminal R,in.

Indicates the input level of the signal applied to Gin or Bin, f rk (i), f gk (i) and f
bk(i) are each k.

Correction functions (
k is 0, 1.2 or 3: S [corresponding to ELγ].

gj(x) is a correction function corresponding to each characteristic shown in FIG. 8b, and parameter j is 0, 1.2 or 3 (SELi
n), x is f rk(i) y f gk(i)
or f bk(i).

What is the relationship between the input (i) and the output signal of the first device?

It is stored in each ROM 131, 132 and 133 in advance. That is, the ROM 13L stores each parameter i.

The value of g j < f rk(i)) under that condition is stored in the address corresponding to each position in j, and R
The OM132 assigns g j(f gk(i
)), and the ROM 132 stores the value of g j (f bk(i)) under that condition at the address corresponding to each position of each parameter t+J+k.

Therefore, when inputting the parameters, i.e. each signal, each RO
A signal corrected by the correction function is immediately output from M. In other words, the characteristics shown in FIG. 8b are obtained. R,
What are the differences in characteristics between G and 8?

f rk(i) , f gk(i) and fbk(i)
is corrected by the correction function of g
Since the correction function of j(x) is commonly applied to R, G, and B, the go rg shown in Fig. 8b is obtained by No. 44 SELγ.
Regardless of which characteristic of l rg2 or g J is selected, gray balance can be maintained. In other words, f rk(i) ” f gk(i) = f b
If k(i), then gk(f rk(i
)) = gk(f gk(i)) = gk(f bk(
i) become).

The masking processing circuit 104 connected to the output terminal of the input γ correction circuit [03 has R (red), G (green),
The B (blue) color signal is processed and the Y (yellow) 1M (
Magenta) and C (cyan) color signals are generated.

Here, the reading system colors R, G, B and the recording system colors Y, M.

The correlation with C will be explained. In general, the following relationship holds: y=yo +y l'R+Y2'G+)
'3' BM = m O+ m I -R+ y
2 ・G + y3 ・BC=eg +c 1
・R+y2 'G+'/s -s ・-a) When R, G and B are superimposed on the same part or when there is no overlap at all, each coefficient yoo 1 in the above equation (1)
1+ y2+ 7J, mQ, m], C2°C3, CQ
, e l , C2 and C3 are constants, and Y.

The relationship between M, C and R, G, and B is a relatively simple function.

However, in digital color recording, it is generally possible to perform only binary recording by combining recorded dots and non-recorded dots, so the number of recorded dots and the number of non-recorded dots within a unit gradation processing area must be adjusted. , the gradation is expressed by changing the recording area ratio.

If the recording area ratios of Y, M, and C are the same, then Y, M
, C can be overlapped only at the same position, but under other conditions, as shown in FIG. 9, there will be overlapping parts and non-overlapping parts. Therefore, considering the composite color of Y, M, and C after actual recording, from R, G, and B to Y,
When converting to M and C, each coefficient in the above equation (1) is no longer a constant.

When expressing the gradation of each color by adjusting the recording area ratio of each Y, M, and C toner (recording material), Y, M.

When each color of C is superimposed so that their overlapping area is maximized, the resulting color (reflection rate r, g, b for each of R light, G light, and B point) is Each area ratio (i.e., gradation) of toner Y, M.

It can be expressed by six types of linear equations depending on the magnitude relationship of C.

If C≧M≧Y: ・・・・・・(2a) If C≧Y≧M: ・・・・・・(2b) If Y≧C≧M: ・・・・・・(2c) Y≧ If M≧C: ・・・・・・(2d) If M≧Y≧C; ・・・・・・(2e) If M≧C≧Y; ・・・・・・(2f) However, l” IVl rCr rrn+ r Yl
r r+ r g+rb and rk are the recording material (recording sheet) itself, C, M, Y, M+Y, Yl, respectively.
Reflectance of C, C+M and C+M+Y for R light, gw
, gc.

gm+ g'i+ gr+ gg, gb, and gk are the recording material itself, C, M, Y2M+Y, and YlC, respectively.

Reflectance of C+M and C+M+Y for G light, bw, b
e, bm, by+ br, bg, bb, and bk are the recording material itself, C, M, and Y, respectively.

These are the reflectances of M+Y, YlC, C+M, and C+ M + 'Y with respect to the B destination.

That is, depending on the size relationship of the area ratios of C, M, and Y, each coefficient of the above formula (1) MO+ 71+ 72+ 7J+m
O, ml, m2, m3, CQ, Cl, C2
and C3 will each take the value of the 6th type.

FIG. 7b shows a specific configuration of the masking processing circuit 104. Referring to FIG. 7b, the σ) circuit 104 includes an area determination unit 1 =10 , a cyan component generation unit 150C, a magenta component generation unit 150m, and a yellow component generation unit 150y.

The area determination unit 140 is composed of one ROM, and each 4 bits of its 13-bit address terminal is
Of the 7 bits of R, G, and B, the upper 4 bits of ff1 are applied. A 3/4 color mode switching signal 5EL34 (see FIG. 7e) output from the console board 300 is applied to the remaining 1 bit of the address terminal. The data terminal of the ROM (140) is 3 bits.

In addition, in the 3-color mode selected by the 374-color mode switch No. 61 SP L34, recording is performed using three-color toners of Y, M, and C, but in the 4-color mode, toners of Y, M, and C are used.
The partial image where C overlaps in three stages is recorded with Y + M + C replaced by Plankchromatic toner.

Cyan component generation unit 150c, magenta component generation unit 150m and yellow component generation unit h l
50 y is outside 111. h have the same circuit configuration. Each of these units 150e, 150n,
150y is ROM151,152. ! 5], 156
．． Consisting of adders 154, 155 and Laso 157,
The desk area determination unit 140 determines the magnitude relationship of the predicted Y, M, and C levels (i.e., area ratio) based on the input R, G, and B signals, and converts the result into 3-bit data. of(
Output as number i. Note that since the levels of Y, M, and C change between the 3-color mode and the 4-color mode, the determination result also changes depending on the mode. The contents of the 3-bit signal output by the area determination unit 140 are shown in Table 2 below.

Table 2 H indicates high level, L indicates low level, and bit 0.
Levels 1 and 2 are M, C9Y and C and Y, respectively.
It corresponds to the size relationship between and M.

This information indicating the magnitude relationship is obtained by applying six types of coefficients to the equation (1) above for all values of the 4-bit R, G, and B signals in each of the 3-color mode and 4-color mode. It is determined by checking whether the magnitude relationship of Y, M, and C of each of the six results calculated by applying the coefficients matches the magnitude relationship of Y, M, and C determined in advance for each of the applied coefficients. Ru. Each 3-bit information determined in this way is stored in advance in all corresponding addresses of the ROM (140). Therefore, R, G, B
When the equal sign is input, a 3-bit signal indicating the magnitude relationship of Y, M, and C is immediately output.

The reason why only the upper 4 bits of each of R, G, B are subject to determination is to reduce the storage capacity of the ROM. If all 7 bits of data for each of R, G, and 'B are to be processed, a huge amount of storage capacity (approximately 12 megabits) is required. However, the area determination unit 140
, M, and C, and 7-bit precision is not required, so only the upper 4 bits of each of R, G, and B are processed. As a result, the storage capacity of the area determination unit 140 is only about 24 kilobits.

The cyan component generation unit 150c will be explained. Each ROM
151, 152 and 153 are respectively No. (
1) Process cl-R2C2・G and C3・B in formula.However, if the result becomes a negative number, subsequent calculations will become complicated, so to avoid this, add a predetermined constant K to the result. , that is, C7-G+ to c1・B+
Output K and C3・B+K. Therefore, each ROM 1
The data output by 51 to 153 always takes a positive value.

Each of the ROMs 151, 152, and 153 stores all of the processing results in advance at addresses associated with the respective states of the input signals. Coefficient C1 to select during calculation
C2 and C3 are a 3-bit signal output from the area determination unit 140 and a 3-layer 4-color mode selection signal 5EL3.
4. The reason why the coefficients are switched according to the three-layer, four-color mode is that the reflectance characteristics of the surface are different between the three-layered Y, M, and C toner and the BK toner.

The adder 154 outputs the output data of the ROM 152 and the ROM
Add the result of 153 and the data. Therefore.

Outputs C2・G + K +e a・B+K. The adder 155 outputs the output data of the adder 154 and the ROM 151.
and the output data of . Therefore, adder 154 is c
Outputs the values of H・B+c2・G+c, 1−B+3・K.

The ROM 156 subtracts 3·K and adds the coefficient Co of the equation (1) to the data output by the adder 8155, and obtains the result of the equation (1).

The calculation result of co +c 1 ・B+e2 ・G+c3 ・s is output as 7-bit data. The results of this calculation are stored in advance at each address associated with the input data in the ROM 156. The latch 157 is.

To adjust the timing of output data.

Temporarily holds the data output by ROM 156.

The magenta component generation unit 150m, like the cyan component generation unit described above, satisfies M=m in the equation (1) above.
□ + m I-R+ m 2 ・G + m 3 ・
The yellow component generation unit 150y outputs the calculation result of B, that is, M, and the yellow component generation unit 150y similarly calculates C=co+c1・B+C2・G+C3 in equation (1).
-Output the calculation result of B, that is, C.

Y and M output by the masking processing circuit 104.

Each 7-bit signal of C is applied to the output γ correction circuit 105. Roughly speaking, the output γ correction circuit 105 is caused by the recording system. Processing is performed to correct the nonlinear characteristic between the number of recorded dots and the actual recording area ratio (effective area ratio).

In other words, ideally, the correlation between the number of recording dots controlled by an electric circuit and the recording area ratio of the surface actually recorded by the dots is one to one, but in reality, there are various causes such as the following. It changes depending on.

(A) In the copying machine of the embodiment, since the recording* (transfer) process of each BK, Y, M, and C toner is processed in a field-sequential manner, in the recording process from the second day onwards, The transferred toner image is reversely transferred (i.e. separated from the recording sheet)
do.

(B) Since the transfer process is performed multiple times, the toner transferred in one process is subjected to mechanical force in the subsequent process, and the area becomes larger than that at the time of transfer.

(C) In the example, a heat roller fixing method is adopted, and this fixing process makes the toner recording area larger than before fixing, but the The degree of spread changes.

(D) The gradation processing circuit 106, which will be described later, uses a threshold table to determine the number of "1"s and "O"s in the output recording signal according to the level (value) of the input multi-value data. However, the number of recorded dots and the recording area ratio of the surface to be actually recorded change depending on the arrangement pattern of the threshold values in the threshold value table.

Examples of phenomena that actually occur due to the various causes mentioned above are shown in FIGS. 80, 8d, 8e, 8f, 8g, 8h, 81, 8j, and 8. Each episode will be explained.

Figures 8c, 8d, and 8e are for the case where the threshold table of the array pattern shown in Figure 10c is used, and Figures 8f, 8g, and 8h are for the array pattern shown in Figure LOe. This is the case when using the threshold table. In addition, each characteristic F LY, F IYc shown in FIG. 8C
, F IYm and FIYmc are respectively Y alone,
Combination of Y and C with area ratio 100%, Y and area ratio 1
00% of M and a combination of Y and M+C with an area ratio of 100%. Each characteristic FLM, FIMc, F1yM, and FlyMc shown in Fig. 8d is 1M alone, 2M, and an area ratio of 100%.
A combination of 2M with C and Y with an area ratio of 100%.

and the case of a combination of M and Y+C with an area ratio of 100%. In addition, each characteristic F 1c shown in FIG. 8e,
, F 1mc, F 1yC, and FlymC are C alone, a combination of C and M with an area ratio of 100%, and a combination of C and Y with an area ratio of 100%.

and the case of a combination of C and Y 10M with an area ratio of 100%.

Similarly, each characteristic F 2Y, F 2Yc shown in Fig. 8f
.

F2Y+m and l”2Ymc are Y alone, Y
A combination of and C with an area ratio of 100%, Y and an area ratio of 10
Combination with M of 0% and M+ with Y and area ratio of 100%
This is for the case of combination with C.

Each characteristic F 2M, F 2Mc, F shown in Fig. 8g
2yM and F2yMc are for the combination of M alone 1M and C with an area ratio of 100%, 2M and Y with an area ratio of 1OO%, and the combination of M and Y+C with an area ratio of 100%, respectively. . In addition, each characteristic F 2C, F 2mC, F 2yC and F2y shown in Fig. 8h
mC is for C alone, a combination of C and M with an area ratio of 100%, a combination of C and Y with an area ratio of 100%, and a combination of C and Y+M with an area of 100%. It is.

Furthermore, FIY and F2Y shown in FIG. 81 are Y gradation data (the number of recorded dots in an 8×8 dot area) when using the threshold table of the array pattern shown in FIGS. 10c and 10e, respectively. This is a characteristic that shows the relationship between the effective area ratio (corresponding to the actual recording surface) and the effective area ratio (area ratio on the actual recording surface).

In addition, F IBk, F 1'/, F shown in Fig. 8j
LM and FIC are characteristics that indicate the relationship between each gradation data and effective area ratio when recording BK, Y, M, and C toners in a single color, respectively (the threshold table is from Figure LOc). .

In addition, FIBK and F2BK shown in Figure 8 are calculated using the threshold tables shown in Figures 10c and 10e, respectively, to calculate the gradation data and effective area ratio when BK toner is recorded in a single color. It is a characteristic that indicates a relationship.

Referring to FIGS. 8c to 8, it can be seen that the correlation between the gradation data value and the effective area ratio shows various changes.

In order to correct this change, an output γ correction circuit 105 is used.

FIG. 7c shows a specific circuit configuration of the output T correction circuit 105. Referring to FIG. 7c, this circuit 105 includes comparators 171, 172 and 173° ROM 174,1
75 and 176, and latches 177, 178 and 179.

Comparators 171, 172, and 173 receive 7 bits of Y and M output from masking processing circuit 104, respectively.

The magnitude relationship between the levels of the C signals is determined.

The ROMs 174, 175, and 176 each perform correction processing on the input Y, M, and C signals, and output the correction results. Latch 177°178 and 17
．． 9 is for adjusting the output timing of the correction results.
Temporarily retains the correction result data.

The comparator 171 compares the Y signal applied to the input terminal Yin and the M signal applied to the input terminal Min, and the comparator 172 compares the Y signal applied to the input terminal Yin and the M signal applied to the input terminal Cin. Comparator 1
73 compares the signal of M applied to the input terminal Min with the signal <ff of C applied to the input terminal Cin. The 6-bit signals output from the comparators 171, 172 and 173 are applied to each 6-bit 1- of the address terminals of the ROMs 174, 175 and 176, respectively.

Each of the ROMs 174, 175, and 176 has a 15-bit address terminal, and a Y signal, 9 lock signals, and a C signal are applied to each of the 7 bits. The 3/4 color mode selection signal 5EL34 and the threshold table selection signal SELmx (see FIG. 7e) are stored in the ROMs 174 and 175.
and 176 address terminals in common.

ROM174, 175 and 176 respectively.

Address terminal device\All correction results corresponding to the states of various input signals are stored in advance at these addresses. Therefore, when each signal is applied to the address terminals of ROMs 17.1, 175 and 176, the correction results are immediately output as 6-bit data from the data terminals of each I(OM). Since the characteristics are different for each color, ROM174, 175 and 176
Each of the ROMs performs different corrections.), that is, each ROM stores different data.

In this example, the correction contents are changed depending on the size relationship of Y, M, and C, the type of threshold table used (SELmx), and the selection of 3/4 color mode, so under what conditions? Also, the one-to-one gradation; -ta (input data of the circuit 105) and the effective area ratio are corrected so that there is a one-to-one correspondence, and variations in characteristics between each color are also corrected.

Regarding Y (yellow), C4M, Y explains the specific details of correction processing according to the size relationship of C, M, and Y.
If the magnitude relationship of (area ratio) is Y>C,M, the output γ characteristic (gradation data vs. effective area ratio characteristic) of Y toner can be considered to be equal to the characteristic when Y toner is output as a single color (the (See FIG. 9) Therefore, correction is performed according to the characteristic FIY shown in FIG. 8c or the characteristic F2Y shown in FIG. 8f to make the correspondence between the input signal of one circuit 105 and the effective area ratio one to one.

Further, if C>Y>M, the output cuff' characteristic of Y toner can be considered to be equal to the characteristic of the combination of Y and C with an area ratio of 100%, so the characteristic FIVc shown in FIG. 8c or the characteristic FIVc shown in FIG. 8f Correction is performed according to the characteristic F2Yc shown in FIG.

If M > Y > C, then Y and M with area ratio 100%
Since it can be considered to be equal to the characteristic of the combination of
The characteristic FIVm shown in the figure or the characteristic F:l' shown in Fig. 8f
Correction is performed according to n.

Also, if C, M>Y, then Y and C+ with area ratio 100%
Since it can be considered to be equal to the characteristic of the combination with M, the characteristic FIYmc shown in Fig. 8c or the characteristic F shown in Fig. 8f
Perform correction according to 2Ymc.

In addition, in this example, ¥=M, Y=C or M=
When condition C is satisfied, priority is given to the characteristic with more overlap.

For example, under the condition of Y=C=M, as in the case of C, M>Y, the characteristics FIYmc shown in FIG.
Alternatively, correction is performed according to the characteristic F2'/mc shown in FIG. 8f.

The above is a case of three-color mode. For 4-color mode, Y
If the area ratio of is the smallest (Y≦C, M), in the portion corresponding to the area ratio of Y, the Y, M, and C toners are not transferred, but the BK)-toner is transferred instead. Therefore, Y≦C,
In the case of M, the output γ characteristic of Y is considered to be equal to the characteristic FIBK or F2BK shown in the eighth figure, and correction is performed according to the characteristic.

In the following third device, under various conditions, the output γ correction circuit 10
5 indicates the assignment of characteristic curves to be corrected (characteristic symbols correspond to those described in FIGS. 8c to 8k). Note that the equal sign (=), inequality sign (<), and (>) shown in the third device are obtained by decoding the 2-bit signals output from the comparators 171, 172, and 173 as follows.

<: A>B rises, A=B becomes L =: A>B rises, A=B becomes H >: A>B becomes H, A=B becomes L As described above, in this embodiment, the output γ correction circuit 105
However, the type of toner and the amount of other toner transferred.

Different corrections are performed depending on the recording mode (3 colors/4 colors) and the type of threshold table used, and the Y, M, and C applied to the output γ correction circuit 105 are adjusted under any conditions. The output signal of the circuit 105 is corrected so that there is a one-to-one correspondence between the gradation level of the signal and the effective area ratio.

Each of the 6-bit Y, M, and C signals output from the output γ correction circuit 105 is converted into a binary signal by a 1-gradation processing circuit 106. That is, in this example, the recording dots are 8x8.
For each area, the number of "1"s indicating recorded dots and the number of "0"s indicating non-recorded dots are adjusted, and gradation is expressed based on the area ratio of the recorded dots. Therefore, Figure toe and Figure 1
As shown in Figure 0e, a threshold table is provided in which different threshold values are assigned to respective dot positions in the 8×8 dot area.

That is, for example, if the data shown in FIG. 10b is obtained as input data to the gradation processing circuit when a document corresponding to an 8×8 dot area as shown in FIG. 10a is read, then each dot position is The multi-valued data is compared in size with the threshold value at the corresponding position in the threshold table in FIG. 10c, and is set to "1" or "0" depending on the comparison result.
'', and the result shown in Fig. 10d is obtained. In Fig. 10d, hatched dots indicate black pixels (recorded pixels: rN), and other pixels indicate white pixels (rN).
Non-recorded pixel: rOJ).

A specific configuration of the gradation processing circuit 106 is shown in FIG. 7d.

Referring to FIG. 7d, this circuit 106 includes a ROM 19
1. Comparators 192, 193 and 194, inverter 19
5,196 and 197. Comparator 192,1
6-bit data of Y, M and C is applied to each input terminal A of 93 and 194, respectively.

Each input terminal B of the comparators 192, 193 and 194 is R
It is commonly connected to the data output terminal of OM 191. Each of the comparators 192, 193 and 194 outputs a binary equal sign depending on the magnitude of the values of the input terminals A and B, respectively.

The input terminal (address terminal) of the ROM 191 receives a 3-bit main scanning direction position signal AX, a 3-bit sub-scanning direction position signal AY, and a threshold table selection signal SELmx.
is applied.

Inside the ROM 191, all data of two types of threshold tables shown in FIG. 10e and FIG. 10e are stored in advance. To switch the threshold table, use the signal SE.
This is done by Lmx. Signals AX and AV correspond to the recording scanning position at that time. Therefore, ROM 1
91 selects one threshold value at a position corresponding to the current recording position in the threshold table and outputs it to the data output terminal.

Therefore, the output terminal of the gradation processing circuit 106 is subjected to one area adjustable processing. Two short signals of Y, M, and C are obtained.

The 2-short signal output from the gradation processing circuit 106 is applied to a black separation/undercolor removal circuit 107. In this circuit 107,
When 3-color mode is selected, Y, M,
Each of the two short signals of C is output as is, and BK is set to "0" (non-recording level).

However, when the four-color mode is selected, the circuit 107 outputs BK if the AND of the input Y, M, and C is "1".
is set to "1" and Y, M, and C are set to roj. Y, M,
If the logical product of C is "0", BK is set to "0" and each of the two input short signals Y, M, and C is output as is.

Each color output from the black separation/undercolor removal circuit 107.

Binary data for each color (M, C, BK) is given to laser drivers 43y, 43m, 43c and 43bk for each color. It should be noted that Y, M, and C are temporarily stored in the buffer memory by the time delay described in 11 with respect to BK, and then output.

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. A second processor system 200 controls the copying in various modes set on the console (including the image reading and recording systems shown in FIG. 2, as well as the photoreceptor power system and the exposure system).

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

FIG. 11 shows an interface between the multi-column motor, etc. and the microprocessor system (200: FIG. 2). The input/output coupler 1-207 shown in FIG. 11 is connected to the bus 206 of the system 200.

In addition, in FIG. 11, 45 is the photosensitive drum 18bk.
, 18y, 18m, and 18c, and is energized by a motor driver 46.

In addition, the input/output board 20 is equipped with a driver that energizes each part of the copying machine, a processing circuit connected to the sensor, etc.
7 or other input/output ports 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, the power switch (not shown) is turned on and 7. Then, the device starts a warm-up operation, ・Raising the temperature of the fixing unit 36, ・Starting the polygon mirror to rotate at a constant speed, ・Home positioning of the carriage 8.

・Generation of line synchronous m clock (1,26K)! z),
・Clock generation for video synchronization (8, 42 MIIZ),
・Perform operations such as initializing various counters. The line synchronization clock is supplied to a polygonal mirror motor driver and a CCD driver, and the former uses this signal as a reference signal for a phase-locked loop (p+-+-) servo, and provides feedback signals to beam sensors 44bk, 44y, 44m and The beam detection signal 44c is controlled to have the same frequency as the line synchronization clock and to have a predetermined phase relationship. The latter is used as a main scanning start signal for cco;x protrusion. Note that the signal for synchronizing the start of laser beam main scanning is transmitted to beam sensors 44bk, 44y, 44m and 44.
Since the detection signal (pulse) of c is output for each color (each sensor), this is utilized. 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 CCD driver and laser driver.

The various counters are (1) read line counter, (2) BK, Y, M, C8 write line counter,
(3) read dot counter, and (4) 8, Y
, M, C@@ included dot counter, but the above (1
) and (2) are program counters substituted by the operation of the CPU 202 of the microprocessor system 200, and (3) and (4) are individually provided on the hardware, although not shown.

Next, the timing of the print cycle is shown in FIG. 12 and will be explained. After completing the warm-up operation,
When the state becomes ready for printing and the copy start key switch 301 is turned on, the CPU of the system 200
Due to the operation of 202, the first carriage 8 drive septa (Fig. 11) starts to rotate and the carriages 8 and 9 (1/1/8 of
2 speed) starts scanning to the left (n-light scanning). When the carriage 8 is at the home position, the output of the home position sensor 39 is H, and the exposure scan (sub-scan) is soon started. At the time of this transition from H to L, the read line counter is cleared and at the same time the count is enabled. Note that the time point at which this change from H to L occurs 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 l 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 first line is read in 1 pixel, 12 pixels, 2... after the home position sensor 39 becomes L, in synchronization with the video synchronization clock immediately after the input of the first line synchronization clock. . . . Pixel 4667 is read sequentially. Sho 1
Pixel counting is done by a read dot counter. Also, the content of the read/line counter at this time is 1.

For the second and subsequent lines, the reading line counter is similarly incremented using the primary line synchronization clock, the reading dot counter is cleared, synchronized with the next incoming 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 at least two clocks of the line synchronization clock signal.

Next, in writing, first clear the write line counter and enable the count. When the -H read line counter is 2, the BK9 write counter is; When the read line counter is 1577, the Y write counter is;
When the read line counter is 3152, the J3 write counter is; and the read line counter is 4727.
At this time, 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, 44'y, 44m and 44c. Further, the write dot counters (BK, Y, M, C) are cleared at the rising edge of the detection signal of each beam sensor, and counting up is performed by the 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 count reaches a predetermined value, the laser driver is driven to perform writing. Dot count is 1-4
00 is dummy data, 401 to 5077 (4
677) are writable. Here, the dummy data includes beam sensors 44bk, 44y, 44- and 44c and photosensitive drums 18bk, 18y, 18.
This is for adjusting the physical distance between m and 18c. Also, write data (1 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 FIG. 12, after starting exposure scanning, C
Since recording data is obtained at I3 from the time of scanning the third line of OD, the BK recording apparatus starts recording energization 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 bags are shifted in the paper feeding direction, the recording start delay times Ty, Tm, and Tc (Fig. 6) corresponding to the amount of shift from the BK recording device are It is necessary to store recording signals, and for this purpose buffer memories LO8y, 108m and 108C are provided.

In the above embodiment, a case where a plurality of toners are overlapped and recorded is explained, but the present invention is also applicable to a case where a different screen angle is given to each color to reduce overlapping.
Further, in the embodiment, gradation processing is performed after color correction, but WI tone processing and color correction processing may be performed simultaneously. Further, in the embodiment, the density of each dot is binary, but the present invention can also be applied to cases where densities of three or more values can be set.

[Effects] As described above, according to the present invention, signal correction processing is performed according to the type of threshold table used, so even when changing the type of threshold table depending on the type of document, , errors in the recording area ratio caused by the non-linear correlation between the number of recorded dots and the effective area ratio are completely corrected.

[Brief explanation of drawings]

FIG. 1 is a sectional view mainly showing the configuration of the main mechanical parts of a digital color copying machine of one type that implements the present invention, FIG. 2 is a block diagram showing the configuration of the electrical image processing section, and FIG. 1st
FIG. 4 is an exploded perspective view of the BK recording device section shown in FIG. 1, and FIG. FIG. 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. Figures 7a, 7b, 7c and 7d are respectively 2r:! Input γ correction circuit 103 shown in i. Masking processing circuit 104. 2 is a block diagram showing the configuration of an output T correction circuit 105 and a gradation processing circuit 106. FIG. FIG. 7e is an electrical circuit diagram showing a portion of the console board 300. FIG. 8a is a graph showing the correlation between the reflectance on the surface of each R, G, and B document and the data input by various input devices.
Figure b is a graph showing the correlation between the reflectance of the document surface and the data output by the input γ correction circuit 103. Figures 8c, 8d and 8e are respectively 10c.
Y, M and C when using the threshold table in the figure
3 is a graph showing the correlation between each gradation data and effective area ratio. Figures 8f, 8g and 8h are respectively 10e.
Y, M and C when using the threshold table in the figure
3 is a graph showing the correlation between each gradation data and effective area ratio. Figure 8i is a graph showing the correlation between Y gradation data and effective area ratio; Figure 8j is a graph showing the correlation between each gradation data of BK, ¥, M, and C and effective area ratio; The figure is BK
It is a graph showing the correlation between the gradation data and the effective surface &2 ratio. FIG. 9 is a vertical cross-sectional view of the recording surface showing an example of the overlapping state of Y, M, and C toners.5 FIG. 10a is a partial area of the original image corresponding to the unit area of gradation processing FIG. 10b, a plan view showing an example, is a plan view showing multivalued data obtained by reading the image shown in FIG. 10a in a two-dimensional manner. FIGS. 10c and 10e are plan views showing two-dimensionally expanded contents of two types of threshold tables used in gradation processing, respectively. FIG. 10d is a plan view showing a two-dimensional expansion of the result of converting the multivalued data shown in FIG. 10b into binary data using the threshold value chip pool shown in FIG. 10c. FIG. 11 is a block diagram illustrating a portion of the copier bt components connected to microprocessor system 200. FIG. 12 is a time chart showing the relationship between exposure scanning and recording energization of the copying machine shown in FIG. Original 2 Nibraten 3, +"2: Fluorescent lamp 4) - 4 Mirror 5: Variable magnification lens unit 6: Dichroic prism 7r, 7g, 7b: CCD 8: First carriage 9: Second carriage 10: Carriage drive motor 11: Pulley 12: Wire L3bk, 1
3y, 13n+, 13c: polygon mirror 14bk, 14y,
14I11, 14c: f O lens 15bk, 1
5y, 157n, 15c, 16bk, L6y, 161R
, 16c: Mirror 17bkJ7y, 17m, 17c
Nijilintorical lens 18bk, 18y, 18m, 1
8c: Photosensitive drum IQbk, L9y, 19
m, 19c: Charge Scorotron 20bk,
20y, 20m, 20c: Current great 21bk
, 21y, 21m, 21c: Cleaner 22: Paper feed cassette 23: Paper feed roller 24 Ni registration roller 2
5: Transfer bell 1 to 26.28.30: Idle roller 27: Drive roller 29bk, 29y, 29m, 29c: Transfer corotron 31 nil lever 32: i mountain 3
3: Pin 34: Compression coil spring 35:
Black copy mode setting solenoid plunger 36: Fixing device 37: Tray 39: Home position sensor 40: Carriage guide bar 41bk, 41y, 4111, 41c: Polygon mirror drive motor 42: Toner recovery pipe 43bk, 43y, 43m, 43c: Laser 44bk, 44y, 44m, 44c
: Beam sensor 45: Photosensitive drum drive motor 46: Motor driver 100: Image processing unit 10
3: Input T correction circuit 104: Masking processing circuit 10
5: Output T correction circuit (color correction circuit) 106: Gradation processing circuit 107: Black separation/undercolor removal circuit 140; Area determination unit 150c: Nisian component generation unit 150m: Magenta component generation unit 150y:
Yellow component generation unit 171.172.173:
Ratio 'v, vessel (judgment means) 174.175.176:
ROM (signal correction means) 191: ROM1 threshold table) 300: Console board (table selection means) name 4
Ennan 5 Sengatsu 67 □Bakuichi Figure 7a Figure 81 Figure 81 ■ Senior 8 Ni What P 100 υ Town 7-'/Tomoe k M 1 oalK No. +Ob 'Q East 10c Figure East 10d Figure East IQe Zuko Pl 9 Wa

Claims (5)

[Claims] (1) A threshold table including a plurality of mutually different threshold values associated with each dot position of a unit gradation processing area corresponding to a plurality of recording dot positions, and using the threshold table In a color recording apparatus that includes a gradation processing means for converting an input color signal into a recording color signal and performs recording processing on each dot position according to the recording color signal; threshold table; table selection means for selecting some of the threshold tables to be actually used from among the plurality of types of threshold tables; and according to the type of threshold table selected by the table selection means; A color recording device comprising: signal correction means for performing signal correction processing; (2) The color recording apparatus according to claim 1, wherein the signal output terminal of the signal correction means is connected to the signal input terminal of the gradation processing means. (3) The input image signal processed by the gradation processing means is a parallel digital signal consisting of multiple bits, and the recorded color signal outputted by the processing means is a 1-bit binary signal. The color recording device according to item (1). (4) The signal correction means includes a determination means for determining the magnitude relationship between the levels of a plurality of input color signals applied to the input terminal thereof, and performs a correction process according to the determination result. The color recording device according to the range (1). (5) Claim (1) above, wherein the signal correction means includes storage means that stores each correction result in an address associated with each level of the input color signal to be corrected by the signal correction means. , the color recording device according to item (2), item (3), or item (4).