JPH0683355B2 - Color image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a color image forming apparatus, and more particularly to a color image forming apparatus having a multiple color reproduction mode and a single color reproduction mode.

<Prior Art> Conventionally, in a copying system of a color copying machine, an original is separated into three primary colors of B, G, and R and input, and a copied image is formed by Y, M, and C color materials whose complementary colors are converted. Toner and ing were used as color materials. The copying process includes electrophotography, thermal transfer, ink jet, etc. However, in any copying process, each color material is sequentially superposed for each separated color to form a color image, so that color misregistration occurs especially in the copying of fine lines such as black characters, and black becomes a color unevenness. Hard to see. In addition, in digital copying machines that have been developed in recent years, it is attempting to improve the quality of black characters by techniques such as black extraction, UCR, and edge tension, but it is not perfect, and as a harmful effect, In copying a document containing a mixture of photographs, noise is generated in the photograph portion due to edge enhancement, which deteriorates the quality of the image. In order to avoid this, it is considered to perform the optimum processing for the edge portion and the halftone portion by separating the image area, but it is not yet complete.

<Object> In view of such a point, the present invention has a high resolution, for example, in a black character portion, and further reproduces a color photograph, a color image, etc. in high gradations, respectively, and even in an image in which a color photograph, a color image and characters are mixed. An object of the present invention is to provide an image forming apparatus capable of forming each of them in a good state.

The image forming apparatus of the present invention for achieving such an object has an input means for inputting a color image signal for forming an image of one screen (details thereof are shown in FIGS. 3A and 3B in the embodiment). 2 corresponds to the CCD 6 shown in FIG. 2 and the circuits shown in FIGS. 4 (A) and 5 (especially the circuit including the selector 139 shown in FIG. 5). 7th according to the setting by the digitizer of Fig. 2
The data set to Vreg1 and Vreg2 in S25 and S26 in FIG. 1A) and the areas where images are formed in a plurality of colors (data set to Vreg1 and Vreg2 in steps S7 and S8) are respectively identified. Generating means for generating a signal (also in FIG. 7 (A) -1)
iNT1 and iNT2 interrupt control), image forming means capable of switching the linear density for image formation (also the main portion capable of switching 133 lines and 400 lines by the selector 612 in FIG. 15A). In the digital color printer 2) shown in FIG. 2, the linear density of the image forming means is switched to the first linear density in the area where the image is formed in the plurality of colors based on the signal generated by the generating means, and the area where the image is formed in the single color is formed. Then, the control means for switching and controlling the linear density of the image forming means to the second linear density higher than the first linear density (also S10 of FIG. 7 (A) -1,
The CPU 69 of FIG. 2 for executing S24).

〔Example〕

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

FIG. 1 shows an example of a schematic internal configuration of a digital color image processing system according to the present invention. As shown in the figure, this system has a digital color image reading device (hereinafter, referred to as a color reader) 1 in the upper part and a digital color image printing device (hereinafter, referred to as a color printer) 2 in the lower part. The color reader 1 is provided with a color separation means described later.
The color image information of the original is read for each color by a photoelectric conversion element such as a CCD and converted into an electrical digital image signal. The color printer 2 is an electrophotographic laser beam color printer that reproduces a color image for each color according to the digital image signal, transfers the color image to a recording paper a plurality of times in a digital dot form, and records the image.

First, the outline of the color reader 1 will be described. 3 is the manuscript,
Reference numeral 4 is an original scanning unit for scanning the original 3. The original scanning unit 4 includes a rod array lens 5, a unity color separation line sensor (color image sensor) 6 and an exposure lamp 7. Reference numeral 8 is a wiring code of the document scanning unit 4, 9 is a cooling fan, and 10 is an image processing unit connected to the document scanning unit 4 through the wiring code 8.

When the original scanning unit 4 moves and scans in the direction of arrow A in the figure by the scanner drive motor 49 to read the image of the original 3 on the original table, the exposure lamp 7 in the original scanning unit 4 is turned on at the same time and the original 3 is read. The reflected light is guided by the rod array lens 5 and focused on the same-size disassembly licensor 6 which is a color information reading sensor.

Reference numeral 21 is an actuator provided below the document scanning unit 4, and 22-1 and 22-2 are position sensors for detecting the scanning position of the document scanning unit 4 via the actuator 21, and are composed of a photo interrupter or the like.

Next, the outline of the color printer 2 will be described. Reference numeral 11 denotes a scanner, which is a laser output unit (see FIG. 5) for converting an image signal from the color reader 1 into an optical signal, a polygon mirror 12 having a polyhedron (for example, octahedron), and a motor (not shown) for rotating the mirror 12. ) And an f / θ lens (imaging lens) 13 and the like. Reference numeral 14 is a reflecting mirror that changes the optical path of the laser light, and 15 is a photosensitive drum. The laser light emitted from the laser output section is reflected by the polygon mirror 12,
The surface of the photosensitive drum 15 is linearly scanned (raster scan) through the lens 13 and the mirror 14 to form a latent image corresponding to the original image.

Further, 17 is a primary charger, 18 is an entire surface exposure lamp, 23 is a cleaner section for collecting the untransferred residual toner, 24 is a pre-transfer charger, and these members are arranged around the photosensitive drum 15. ing.

26 is a developing unit for developing the electrostatic latent image formed on the surface of the photosensitive drum 15 by laser exposure, 31Y,
31M, 31C and 31BK are developing sleeves that are in direct contact with the photosensitive drum 15 for direct development, 30Y, 30M, 30C and 30BK are toner hoppers that hold preliminary toner, and 32 is a screen for transferring developer. The sleeves 31Y to 31BK, the toner hoppers 30Y to 30BK and the screen 32 constitute a developing device unit 26, and these members are arranged around the rotation axis P of the developing device unit. For example, when a yellow toner image is formed, yellow toner development is performed at the position shown in the figure, and when a magenta toner image is formed, the developing unit 26 is rotated about the axis P in the figure to expose the toner. Body 15
The developing sleeve 31M in the magenta developing unit is arranged at a position in contact with. Development of cyan and black works similarly. The rotational movement of the developing device is performed by a motor 530.

Further, 16 is a transfer drum for transferring the toner image formed on the photosensitive drum 15 onto a sheet, 19 is an actuator plate for detecting the moving position of the transfer drum 16, and 20 is a proximity to this actuator plate 19. A position sensor for detecting that the transfer drum 16 has been moved to the home position position by 25, a transfer drum cleaner 25, a paper pressing roller 27, a neutralizer 28, and a transfer charger 29. 20, 25, 27 and 29 are arranged around the transfer roller 16.

On the other hand, 35 and 36 are paper feed cassettes for storing paper (paper sheets), 37 and 38 are paper feed rollers for feeding paper from the cassettes 35 and 36, and 39, 40 and 41 are timings for paper feed and conveyance. These are timing rollers, and the paper fed and conveyed through these rollers is guided to a paper guide 49 and is wound around the transfer drum 16 while being supported by a gripper (see 51 in FIG. 6) described later to form an image. Shift to the process.

Further, 550 is a drum rotation motor that rotates the photosensitive drum 15 and the transfer drum 16 in synchronization. 50 is after the image formation process
A peeling claw that removes the paper from the transfer drum 16, 42 is a conveyor belt that conveys the removed paper, and 43 is a conveyor belt 42.
The image fixing unit 43 is an image fixing unit that fixes the sheet conveyed by the above, and the image fixing unit 43 has a pair of thermal pressure rollers 44 and 45.

First, with reference to the block diagram of FIG. 2, a portion related to the present invention in the overall configuration of the electric circuit of the embodiment will be described.

The reader 1 and the printer 2 are controlled by a controller 74 including a CPU 69, a ROM 71, a RAM 72, an I / O port 73, and a CPU bus 70 connecting them. The CPU 69 communicates with the operation unit 67 and the digitizer 68 via the serial communication line 240 and receives a command from the operator. From the digitizer 68, coordinate information relating to editing of a document to be copied, such as area designation information and area movement position information, is input. From the operation unit 67, in addition to the normal number of copies and the scaling factor, designated areas and reproduction mode information outside the designated areas, such as multicolor, single color, gradation conversion characteristics, resolution, color conversion mode, etc. are input. Further, the controller 74 gives a scaling mode signal and a movement control signal to the driver 61 of the scanner driving motor 49 (stepping motor) which controls the movement of the document scanning unit 4 of the reader 1 via lines 237 and 238, respectively, and The movement direction, speed, and position of the scanning unit 4 are controlled. A stepping motor pulse is input from the stepping motor driver 61 to the interrupt terminal INT of the CPU 69 via the line 236, and is counted as position information of the document scanning unit 4. Further, the detection signal of the home position sensor (SR1) 22 when the copy of the document scanning unit 4 is at rest is input through the line 242. The controller 74 also gives an ON / OFF command to the motor driver 62 of the drum drive motor 50 of the printer 2 via the line 239.

The drum drive motor 550 consists of a combination of a DC motor and a rotary encoder (E).
The speed is controlled by the internal PLL control circuit. Another transfer drum 1
The detection signal of the home position sensor (SP1) 20 of 6 is input to the controller 74 via the line 243. The controller 74 also controls the control circuit 6 of the exposure lamp 7 via the line 241.
Give ON / OFF command to 3. The lamp control circuit 63 also controls the constant voltage of the exposure lamp 7.

Also, the laser beam output from the laser scanner 11 generates a BD signal detected by the BD detection circuit 52 for each scanning of the photosensitive drum 15. The BD signal is input to the synchronization signal generation circuit 82 via the line 226, and the line from the controller 74 is input.
Generates HSYNC, V.ENABLE, RVENABLE, and PVENABLE which are video synchronization signals together with a copy interval signal input via 235, a counter set signal input via line 234, a mode select signal, and a clock VCLK of a video signal. To do. In addition, the synchronization signal generation circuit 82 simultaneously receives the laser OFF (▲ from the controller 74 via the line 233).
▼) signal to laser control signal line 23
Output via 2.

Here, referring to FIGS. 10 (A) and 11, synchronization signal generating circuit 82
The operation of will be described. The copy section signal 450 generates a sync signal at "H" during the copy operation, and further controls the whole of turning off the laser. When the copy interval signal 450 becomes “H”, J
/ K-FF402 is cleared and BD rises to DF / F401
Is synchronized with VCLK and input to J / K-FF402,403,405. J / K-FF402AND417 starts HSY from VCLK1 cycle immediately after BD is generated.
Generate NC and simultaneously raise V.ENABLE in synchronization with the fall of HSYNC (J / K-FF402Q is "H"). As a result, the load () on the counter 407 is released. Here, SET1 to SET5 are counter set signals input from the controller 74 and serve as count data of the counters 407 to 411. Counter 40
When the load () of 7 is released, the counter 407 counts the value by SET1, outputs RC at count-up, resets J / K-FF402, and ends V.ENABLE.

Next, J / K-FF403 counters at the same time when V.ENABLE rises.
The load of 408 is released and the counter 408 counts the value by SET2. RC output by counting up J / K-FF403
At the same time as resetting, set J / K-FF412. At the same time, J / K-FF404 is set and the load of counter 409 is released.Counter 409 counts the value by SET3 and outputs RC by counting up to reset J / K-FF404 and reset J / K-FF412. To do. As described above, J / K-FF412
Is set after the left margin of SET2 is taken from the rising edge of V.ENABLE, and reset after the end of the valid section by SET3. Q output of J / K-FF412 together with D.ENABLE selector 414
Is input to RVENA by selecting the mode select signal 463.
It becomes a BLE signal. Similarly, J / K-FF413 is set with the left margin set by SET4 from the rising edge of V.ENABLE, and SE is set.
Reset after the end of the valid area by T5. Q of J / K-FF413
The output is input to the selector 415 together with V.ENABLE and becomes the PVENABLE signal by the selection of the mode select signal 464. Again J
The output of / K-FF413 is input to the selector 416 together with V.ENABLE and becomes a laser control signal by the mode select signal 465. The laser control signal is gated as ▲ ▼ by AND 417 and the laser off control of the controller 74 is received.

RVENABLE and PVENABLE are input to the synchronous memory circuit via the line 231 and determine the video effective section in the main scanning direction of the reader and printer, respectively. The laser control signal is input to the PWM circuit via line 232 to determine the masking range in the main scanning and sub scanning directions of the printer.

Further, 60 is a clock, a timing pulse generating circuit, various timing pulses synchronized with the crystal unit 64, clock (φ)
To occur. φ is a symbol that represents various pulses, and is a video clock VCLK and a clock with a half cycle of the video clock 2
Includes VCLK.

Next, the CCD6 analog color processing & A / D circuit 75 will be described with reference to FIGS. 3 (A) and (B) and FIGS. 4 (A) and (B).

As shown in FIG. 3 (A), a unit color separation line sensor (CCD) 6 has a chip of 62.5 μm (1/16 mm) square with one pixel having 1024 pixels, and the chips are arranged in a zigzag pattern. Each pixel has about 20.8 pixels as shown in FIG.
It is divided into three parts with a size of μm × 62.5 μm, and B (blue), G (green), and R (red) color separation filters are attached to each of the three parts, and FIG. ) The document is run in the direction of the arrow and the color separated image of the document 3 (see FIG. 1) is read.

FIG. 4 (A) shows 8-bit data of each color separation image read by the above-mentioned staggered arrangement of 5-chip equal-size color separation line sensors (hereinafter referred to as color reading sensors) 101 to 105. Analog color processing to quantize digital data and output to the color processing circuit (see FIG. 5) described later.
An analog-to-digital conversion (A / D) circuit 75 is shown.

FIG. 4 (A) will be described with reference to the timing chart of FIG. 4 (B).

First, the analog pixel signals color-separated into the R, G, and B color components of the original 3 by the above-described color reading sensors 101 to 105 are amplified by the amplifiers 106 to 110 at the first stage, and the logarithm (lo
g) Converted into pixel density values by the conversion circuits 111 to 115. At this time, each pixel signal is converted into a pixel signal transfer clock (CLK) 201 as shown by As202 in the timing chart of FIG. In synchronism with, the color reading sensor outputs serially in the order of R1 → G1 → B1.

Next, the sample and hold circuits (S / H) 116 to 120 sample and hold the input image data at the timing of the sampling signal S / HP203 shown in FIG. 4 (B), and then perform analog / digital (A / D) conversion. A / D conversion is performed by the devices 121 to 125, and quantized into image data of 8 bits (bits) and 256 gradations.

In this way, the color-separated and quantized image data is serially transferred in a time-division manner with respect to the same pixel, as shown by DETA204 in the timing chart of FIG. In order to perform the color correction processing on the data DETA204 by the color correction circuit (see FIG. 5) described later, each DR _{1 of} the DETA204, DG ₁ , DB ₁ , (where R, G, B are red, green, Corresponds to blue. The same shall apply hereinafter).

Therefore, LP, which is a latch pulse with a temporal phase difference
R ₁ 205, LPG ₁ 206, LPB ₁ 207 to DETA 204 DR ₁ , DG ₁ , DB ₁ …
Latch output of the latch circuits 126 to 130 sequentially LP _R , LP _G , LP _B
The latch pulse 131 (LCH)
I am in a rush. This finally causes the latch circuit 13
In 1, the color separation data of the same pixel is latched in the same phase.

Further, since the color reading sensors 101 to 105 are arranged in a staggered pattern as shown in FIG. 3 (A), a plurality of lines are stored in the buffer memories 132 to 134 in order to connect the sensor output to one output line. The minute data is buffered and output to the next stage as image data DR, DG, DB for one line continuous for each color of R, G, B.

For the same pixel obtained as described above, the 8-bit color separation image data DR, DG, and DB having the same phase are subjected to a predetermined process by the color processing circuit 76 shown in FIG. That is,
The color correction circuit 135 shown in the figure performs the processing disclosed in the following section, which is generally called masking, and the black (black) plate generation and undercolor removal circuit 136 performs the processing disclosed in the following section.

Masking process: In the color correction circuit 135, the input pixel data DR, DG, and DB301 to 303 are subjected to a matrix operation represented by the following equation (1) to absorb the unnecessary color component of the print toner.

Here, the coefficients ai, bi, ci (i = 1 to 3) are masking coefficients that should be determined as appropriate values. Y ₁ , M ₁ , and C ₁ are output signals 304 to 306 corresponding to the colors of yellow, magenta, and cyan.
Is.

Screen generation and undercolor removal processing ... In the screen generation and undercolor removal circuit 136, the minimum value MIN of the above signals Y, M, C
When (Y, M, C) = k, Y ₂ = Y ₁ −αk, M ₂ = M ₁ −βk, C
₂ ′ = C ₁ −γk Amount of toner to be printed Y ₂ , M ₂ , C
₂ (307 to 309), and then the BK (black) signal BK =
δk (310) is used for black printing as a printing plate. Here, the coefficients α, β, γ, and δ are set to appropriate values in advance.

Also, at the same time, the signals of Y ₁ , M ₁ , and C ₁ are respectively transmitted to lines 311, 312,
The data is input to the address of the coefficient ROM via 313, and each type is multiplied by the coefficient (a4, b4, c4) by table conversion of the ROM, and output as data from lines 314, 315, 316 as Y ₃ , M ₃ , C ₃ . Y ₃ , M ₃ and C ₃ are added by adder 138 and ND
The signal is output to line 317.

Here, there is a relation of Y ₃ = a 4 · Y ₁ , M ₃ = b ₄ · M ₁ , C ₃ = c ₄ · C ₁ , a ₄ + b ₄ + c ₄ ≈1.

Therefore, the ND signal is an average of the image signals color-separated by the R, G, and B filters, and is considered to approximate the density of the image signal in the entire visible region.

Next, each image data Y ₂ , M ₂ , C ₂ , BK obtained by the above circuit 136
307 to 310 are the basic data of the toner image finally printed by the printer 2, but as will be described later,
The color printer in this system uses a Y (yellow) toner image, an M (magenta) toner image, and a C toner image.
The (cyan) toner image and the BK (black) toner image cannot be printed out on the transfer paper at the same time. By transferring each toner image to the transfer paper one after another and sequentially superimposing the four colors, the final image can be obtained. Since it is a printing system for obtaining a color print image, it is necessary to select each color data Y ', M', C ', BK and ND obtained by the above circuit 136 in accordance with the operation of the color printer 2. .

The selector 139 in the next stage is for this selection, and by the combination of the color select signals S ₀ , S ₁ , S ₂ from the controller 74 , the above-mentioned five types of image data Y ₂ , M ₂ , Select one image data from C ₂ , BK, ND and output it to the printer. Therefore,
This system requires a document exposure operation for a number of toner colors used for reading and printing out one color image document and a toner image forming process.

The color signals Y, M, C, BK, and ND selected here can be reproduced in arbitrary colors, that is, color conversion can be performed. This is the development color selection signal S ′ ₁ , for the color selection signals S ₁ , S ₂ .
It can be achieved by varying the S _'2. S _'1, S' ₂
Is yellow development at (0,0); magenta development at (0,1),
The developing device drive motor driver 85 of FIG. 2 is driven so as to select cyan development at (1,0) and black development at (1,1). Therefore, the ND signal can be reproduced not only in black but also in any of cyan, magenta, and yellow.

The image signal selected as described above is output to the synchronous memory 77 via the line 319.

The synchronous memory 77 is a scaling operation in the main scanning row direction of the video signal,
A buffer memory for performing position movement trimming, which is controlled by address signals ADR-W, ADR-R and R, V.ENABLE, PVENABLE signals input from the scaling control circuit 81. 12th
A description will be given with reference to FIGS. CNT1 from the R / V.ENABLE section in Fig. 12, that is, the end of the main scanning read image of the reader
When moving the image from (P point) to Q point after b ₁ from the end of the printer main scanning writing to CNT2 (P point) and Q ′ point after 2b ₁ by scaling (note that CNT1, CNT2, b ₁ , 2b ₁ respectively represent the VCLK count number), and the copy interval signal of the synchronizing signal generating circuit 82 is set as follows.

SET2 ＝ CNT1, SET3 ＝ b ₁ , SET4 ＝ CNT2, SET5-2b ₁ By this, the left margin counters 454,456 and effective area counters 455,457 of the reader and printer are set,
After HSYNC, we do a cout, RVENABLE, PVENAB in Fig. 12
Generate LE.

When the writing and reading operations to and from the synchronous memory 77 described above are performed by the main scanning effective section signal RVENABLE of image reading and the main scanning effective section signal PVENABLE of the print position, the above-mentioned position movement in the main scanning direction is achieved. That is, in FIG. 12, the image data for one line written in the synchronous memory 77 between the point P and the point Q of the main scanning effective section signal RVENABLE is from the point P'to the point Q of the main scanning effective section signal PVENABLE. The data is read in the section of point ', and the position movement in the main scanning direction of P.fwdarw.P' and Q.fwdarw.Q 'is performed.

FIG. 13 shows a configuration example of a scaling control circuit that performs scaling in the main scanning direction. Here, 480 and 483 are address counters which give an address to the synchronous memory 77. The write address in 480 and the read address in 483 are pixel transfer clocks V.
CLK or this clock is thinned out and the clock Cka is counted. 482 is a B / R / M that produces this thinned clock Cka
(Binary rate multiplier)
As shown in FIG. 14 (A), the input clock VCLK is thinned out at a ratio set by the set signal SET8. For example, if the set signal SET8 is 8 bits (2 ⁸ = 256), the output frequency fout is expressed by the following equation with respect to the input frequency fin.

fout = M / 256fin (where M is the set value by SET8) That is, in the example of FIG. 14 (A), since it is set to M = 192, it is thinned out to fout = 3 / 4fin.

The scaling is performed by inputting the thinning clock Cka and the input clock VCLK (Ckb) to the clock generation selector 407 of each of the address counters 405 and 406. 14th
By selecting each of the clocks Cka and Ckb in the combination shown in FIG. (B), the desired scaling can be achieved. Also, the set signal SE
It goes without saying that if the value M of T8 is changed steplessly, stepless scaling is performed.

The video signal subjected to the scaling and position movement processing in the synchronous memory circuit is input to the PWM circuit 78 via the line 223. PWM
The circuit 78 D / A converts the digital video signal and compares it with a triangular wave of a predetermined screen to perform pulse width modulation. Further, the screen line number switching signal SCRSEL input from the controller 74 switches the screen according to the image signal, and the tone switching signals K ₀ , K ₁ , K ₂ switch the tone of the image signal. Next, the details of the PWM circuit 78 will be described.

FIG. 15 (A) shows a block diagram of the PWM circuit, and FIG. 15 (B) shows a timing diagram.

The input VIDEO DATA 700 is VCLK701 in the latch circuit 600.
It is latched at the rising edge of and is synchronized with the clock. (See (B) Fig. 700, 701) V output from the latch
Gradation correction of IDEO DATA 715 with LUT (lookup table) 601, D / A (digital / analog) converter 602
D / A conversion is carried out with to generate one analog video signal, and the generated analog signal is the comparator 610,
It is input to 610 and compared with a later-described triangular wave. The signals 708 and 709 input to the other side of the comparator are each synchronized with VCLK and are individually generated triangular waves ((B) in FIG. 70).
8,709). That is, a synchronous clock 2VCLK703 having a frequency twice that of VCLK701, one of which is divided into two by, for example, a JK flip-flop 606, according to a reference signal 706 for generating a triangular wave,
Triangle wave WV1 generated by the triangle wave generation circuit 608, the other is 2
Signal 707 which is generated by dividing VCLK by 6 by dividing circuit 605
The triangular wave WV2 is generated by the triangular wave generation circuit 609 according to ((B) FIG. 707). Each triangular wave and VIDEO DATA are all generated in synchronization with VCLK as shown in FIG. In addition, each signal is generated in synchronization with VCLK.
Inverted HSYNC connects circuits 605 and 606 in order to synchronize with
Initialize at the HSYNC timing. With the above operation, CMP
1 610, CMP2 611 output 710, 711 is input VIDEO DA
Depending on the value of TA700, a signal having a pulse width as shown in FIG. That is, in this system, the laser is turned on when the output of the AND gate 613 of FIG. (A) is "1", dots are printed on the print paper, and when the output is "0", the laser is turned off and nothing is printed on the print paper. Not printed. Therefore, the control signal LO
You can control the turning off with N (705). FIG. 6C shows a state where the level of the image signal D changes from left to right from “black” to “white”. The input to the PWM circuit is "FF" for "white",
Since "black" is input as "00", the output of the D / A converter 602 changes like Di in FIG. On the other hand, the triangular wave is similar to WV1 in (a) and WV2 in (b), so the output of CMP1 and CMP2 becomes narrower as they move from “black” to “white” like PW1 and PW2, respectively. I'm becoming. Also, as is clear from the figure, when PW1 is selected, the dots on the print paper are formed at the intervals of P ₁ → P ₂ → P ₃ → P ₄ , and the pulse width change amount has the dynamic range of W1. On the other hand, if you select PW2 dots are formed at intervals of P ₅ → P _6, the dynamic range of the pulse width is W2 becomes PW1
Compared with each other, it is three times. Incidentally, for example, the print density (resolution) is set to about 400 lines / inch for PW1, and about 133 lines for PW2. Also, as is clear from this, when PW1 is selected, the resolution is about 3 times better than when PW2 is selected, while when PW2 is selected, the pulse width dynamic range is about 3 times wider than when PW1 is selected. Therefore, the gradation is remarkably improved. As described above, in the present embodiment, by appropriately selecting one of PW1 and PW2, a region that requires high resolution, that is, a region in which an image is formed with a single black color such as a black character has a high resolution. In a region where tonality is required, that is, in a region where images are formed with a plurality of colors, the dynamic range of the pulse width can be widened and images can be formed with high gradation. Therefore, for example, when high resolution is required, PW1 is selected, and when high gradation is required, PW2 is selected by the external circuit to provide SCRSEL704. That is, 612 in FIG.
A input selection when CRSEL704 is “0”, that is, P when PW1 is “1”
W2 is output from the output terminal, the laser is turned on for the finally obtained pulse width, and the dots are printed. LUT601 is a table conversion ROM for gradation correction,
The table switching signals of K ₀ , K ₁ , K ₂ , K 714 of 2,713 and the video signal of 715 are input, and corrected VIDEO DATA is obtained from the output. For example, if SCRSEL704 is set to "0" to select PW1, the output of ternary counter 603 will be all "0" and PW in 601
The correction table of 1 is selected. Further, S ₀ and S ₁ are switched according to the output color signal, and for example, K ₀ , K ₁ and K ₂ = “0,
Yellow output when 0,0 ", magenta output when" 0,1,0 "
When "1,0,0", cyan output, and when "1,1,0", black output. This is due to the difference in gradation characteristics due to the difference in image reproduction characteristics depending on the color of the laser beam printer. Also K ₂
It is possible to carry out a wider range of gradation correction by combining K ₀ and K ₁ . For example, the gradation conversion characteristics of each color can be switched according to the type of input image. Then PW2
When SCRSEL is set to "1" to select "3", the ternary counter counts the line synchronization signal and selects "1" → "2" → "3".
→ "1" → "2" → "3" → ... is output to the address 714 of the LUT. Thereby, the gradation correction table is switched for each line, thereby further improving the gradation.

This will be described in detail according to FIG. A curve A in FIG. 10A is a characteristic curve of input data versus print density when PW1 is selected and the input data is changed from "FF" or "white" to "0" or "black". . As standard, the characteristic is K
It is desirable that A is in the gradation correction table.
B, which is the inverse characteristic of B, is set. The same figure (B) shows PW2
Are the gradation correction characteristics A, B, C for each line when is selected, and the pulse width in the main scanning direction (laser scan direction) is varied with the triangular wave described above, and at the same time the figure is displayed in the sub-scanning direction (image feed direction). As described above, the gradation characteristics are further improved by giving gradation of three stages. That is, the characteristic A becomes dominant in the portion where the density change is sharp, the sharp reproducibility is reproduced, the smooth gradation is reproduced by the characteristic C, and the gradation B is effective for the middle portion. Therefore, even when PW1 is selected as described above, a high resolution is guaranteed to some extent, and when PW2 is selected, extremely excellent gradation is guaranteed. Further, regarding the above-mentioned pulse width, for example, in the case of PW, the pulse width W is ideally 0 ≦ W ≦ W2, but due to the electrophotographic characteristics of the laser beam printer and the response characteristics of the laser drive circuit, a certain width There is a region in which dots are not printed (no response) with a shorter pulse width (Fig. 17) 0 ≤ W ≤ wp, and a region in which the density is saturated, Fig. 17 wq ≤ W ≤ W2. Therefore, the pulse width and density are set so that the pulse width changes within the linear effective region wp ≦ W ≦ Wq. That is, as shown in FIG. 17 (B), when the input data changes from 0 (black) to FF _H (white), the pulse width changes from wp to wq, further guaranteeing the linearity between the input data and the density. .

The video signal converted to pulse width as described above is a line
It is applied to the laser driver 11L via 224 to modulate the laser light LB.

The laser beam LB modulated corresponding to the image data is reflected by the polygon mirror 12 rotating at high speed by the arrow AB in FIG.
High-speed horizontal scanning with f / θ lens 13 and mirror
An image is formed on the surface of the photosensitive drum 15 through 14, and the dot exposure corresponding to the image data is performed. One horizontal scan of the laser light corresponds to one horizontal scan of the original image, and in this embodiment, corresponds to a width of 1/16 mm in the feeding direction (sub-scanning direction).

On the other hand, since the photosensitive drum 15 is rotating at a constant speed in the direction of arrow L in the figure, the above-mentioned laser beam scanning is performed in the main scanning direction of the drum, and the photosensitive drum 15 in the sub scanning direction of the drum. Since the rotation is performed at a constant speed, the planar images are successively exposed to form latent images. From the uniform charging by the charger 17 prior to this exposure → the above-mentioned exposure → and the toner development by the developing sleeve 31, a toner development is formed. For example, by developing with the yellow toner of the developing sleeve 31Y corresponding to the first original exposure scanning in the color reader, a toner image corresponding to the yellow component of the original 3 is formed on the photosensitive drum 15.

Then, the tip of the transfer drum 16 is supported by the gripper 51.
A yellow toner image is transferred and formed on the paper sheet 54 wound around the paper by a transfer charger 29 provided at the contact point between the photosensitive drum 15 and the transfer drum 16. The same processing steps are repeated for M (magenta), C (cyan), and BK (black) images, and each toner image is superimposed on the paper sheet 54 to form a full-color image with four-color toner. It

After that, the transfer paper 91 is separated from the transfer drum 16 by the movable separation claw 50 shown in FIG. 1, guided to the image fixing section 43 by the conveyor belt 42, and transferred by the thermal pressure rollers 44 and 45 of the fixing section 43. The toner image on 91 is fused and fixed.

Next, a moving method in the sub-scanning direction will be described with reference to FIG.

FIG. 8A schematically shows a cross section in the sub-scanning direction (feeding direction). A is a home position at the time of standby, B and C are home positions at the time of reading by moving the reading area in the sub-scanning direction, respectively, and are positions that stop at the time of reciprocating each scan.

8 (B) -1, 2, and 3 show the relationship of the positions recorded on the recording paper of the printer, which can be considered in association with FIG. 8 (A). In FIG. 8 (B) -1, the diagonal line diagram on the circumference of the transfer drum 16 is an actuator plate 19 that generates a signal indicating the leading edge of the paper, and from the point that the sensor S detects the leading edge of the recording paper, When rotated by the distance (l + h), the toner image on the photosensitive drum is transferred to the recording paper. That is, during normal copying, when the reading unit of the reader is started from the home position A from the rising edge of the signal S, the signal when the leading edge of the document at the position of the distance T is read is just PH of the photosensitive drum. Modulates the laser light that hits a point. Therefore, at this time, the leading edge of the recording paper 91 is (B) -2.
As shown in the figure, since it is a distance h before the transfer point Tr,
The image of the leading edge T of the document is formed on the leading edge of the recording paper 91. By the way, next, (x ₁ , y ₁ ) (x ₂ , y ₂ ) on the platen in Fig. (C)
The procedure in the sub-scanning direction when reading only the portion a and moving it to the position (x ₃ , y ₃ ) (x ₄ , y ₄ ) on the recording paper will be described.

Also, set the reading home position of the reader unit to the B position,
That is, the reading operation is performed by moving the reading start position x _{1 in the} sub-scanning direction to the front by ₁ and reading the point B as a reference. That is, the distance between the reading start position and the home position at that time is always maintained at l. On the other hand, assuming that the writing start position on the recording paper, that is, the position of the trace of movement, is a point at a distance x ₃ from the leading edge of the paper, it is sufficient to delay from S from the printer by a distance n2 and start from the reading home position B described above. Recognize. That is, as a result, the image read from x ₁ on the platen is recorded on the recording paper at a position x ₃ from the front edge of the paper (distance n 2 in FIG. 3B-3) and moves in the sub-scanning direction. It has been done. In this embodiment, a stepping motor is used to drive the scanning of the reading unit, and the number of pulses used to drive the stepping motor and the moving distance correspond to 1: 1. That is, since the distance can be defined by the number of pulses given to the drive regardless of the scanning speed, in other words, the scaling factor, all the distances described above are values converted into the pulses used for driving the stepping motor.
Therefore, even if the scaling ratio changes and the scanning speed changes, the value to be set is not influenced by it, and the control becomes simple.

Fig. 7 (A) -1 shows a CP when outputting a high-gradation full-color image in the designated area designated by the digitizer and a high-resolution image (text, line drawing, etc.) in the other colors in a single color (eg, black).
Figure 6 shows a control flow chart for U69.

FIG. 7A-2 shows an area (coordinates (x ₁ , y ₁ ) (x ₂ , y ₂ )) designated by the digitizer. The specified area is output in full color, and the outside of the area is output in single color.

First, when it is detected that the copy button is turned on in step S1, the areas in the main scanning direction are set in steps S2 to S6. In S2, SET1 is set to Y ₀ to specify the entire effective image section in the main scanning direction, and the value of SET1 is set in the counter 407 in FIG. S3, the S4 SET2 trimming leader in the scanning direction in order to define the area or masking (white) area (extraction of the image) in a y _2, the SET3 and y _1, to excisional respectively counter 408. This is to form the signal RVENABLE for reading only the designated area. Next S5, S6 in the main scanning direction of the printer trimming, the SET4 to define the masking region and y _2, the SET5 and y _1, to excisional respectively counter 410 and 411.

In the case of this example, the reading position and the recording position match, so SE
The values of T2 and SET4 and SET3 and SET5 match. Then, at the time of reading and forming an actual image, as shown in FIG.
The RVENABLE signal b, the PVENABLE signal d, and the laser control signal e or e'are output. At the time of color recording in the designated area, the mode signals M ₀ , M ₁ and M _{2 in} FIG. 11 are set to ₁ , ₁ , ₀ , the signal d is selected as RVENABLE, the signal d is selected as PVENABLE, and the laser control signal e ′ is selected. The specified area is trimmed. On the other hand, during black recording outside the specified area, (M ₀ , M ₁ , M ₂ ) = (0,0,1) is set, and R.
The entire section on V.ENABLEC is selected as V.ENABLE and PVENABLE, the laser control signal e is selected, and masking of the designated area is performed.

Return to the flow chart shown in FIG.
At 7, S8, set the numerical value for controlling the image area in the sub-scanning direction.

Here, Vreg1 and Vreg2 are internal register counters of the CPU 69, and since the stepping motor drive pulse (Fig. 236 in Fig. 2) is input to this counter input, the pulses corresponding to the values set in S7 and S8 are generated. When input, an interrupt occurs internally and INT1 (S28 to S2 for Vreg1 = 0)
9), for Vreg2 = 0, the process of INT2 (S30, S31) is performed. Therefore, a point in the sub-scanning direction x ₂ (from home position to l
+ Distance x _1), the FIG. 10 _{(B) (l + n 1} ) points x ₂ from, namely the process (x ₁ + l + x ₂₎ of Vreg1 = 0 because between the image output section to the point, that is, INT1S28 LOFF = 1, the laser output is enabled. After that, the yellow output signals S ₀ , S ₁ , S ₂ = 000, which is the first output color, are output (S9),
The selection signal SCRSEL = 1 of the above-described high gradation image quality sent to the PWM circuit (S10), the main scanning direction of the image effective interval control signals described above (RVENABLE, PVENABLE, laser control signal) in order to set the M ₀ M ₁ M ₂ = Set 110 and start the printer (S11). In S13, a lamp lighting signal 241 for original exposure scanning is sent, the lamp 7 is lit, and the paper leading edge signal S from the printer (FIG. 10 (B)) is provided. S14 ′ V
Since reg3 is an internal counter that counts HSYNC and has been set to 0 by S8 ', it exits to S15 at the same time as S and advances the skimmer motor for driving the leader. INT1 and INT2 are sequentially applied at the points of x ₁ and x _{2 in} the forward movement, and the laser lighting in the sub-scanning direction is controlled here. The motor moves backward in S17, and stops in the home position in S18 and S19. Here, since the same number of pulses as the stepping motor driving pulse number required for the forward movement is given to move backward, the home position sensor is unnecessary. S20
After that, by repeating the same step and changing the color, the second
The area inside the broken line in FIG. 2A is Y, M, C, BK (yellow,
A halftone image of magenta, cyan, and black) is formed (corresponding to the timing of the copy section in the designated area in FIG. 10 (B)). That is, a pulse width of 133 lines / inch is set in the area to be imaged in a plurality of colors as shown in S10 of FIG. 7 (A) -1.

Next, in S23, the black reproduction of the ND signal is selected by setting S ₀ S ₁ S ₂ = 100, S ′ ₁ and S ′ ₂ = 11, and the mode select signal M ₀ M ₁ M ₂ = 0.11
Then, the laser control signal of FIG.
e, RVENABLEP.V.ENABLE is selected so that V.ENABLE (C) is output, and in S24, the image quality selection signal SCRSEL = 0 is set to select a high resolution image (that is, a region to be formed in a single color. Is
A pulse width of 400 lines / inch is set. ), L to Vreg1
Set Vreg2 to (l + n3) to enable laser lighting over the entire area in the sub-scanning direction (S25, S26), S14 to S
If step 19 is repeated, the area outside the broken line area in FIG. 7 (A) -2 is printed out, and the area inside the area is not printed out. As a result, a multicolor high-gradation image can be obtained in the designated region and a multicolor high-resolution image can be obtained outside the designated region. This is very effective for copying a document in which a halftone image and a character line drawing are mixed. Although the designated area is designated as a multicolor high gradation, the designated area can be set as a single color high resolution and the outside of the area can be set as a multicolor high gradation.
Further, it is of course possible to provide a plurality of designated areas and arbitrarily designate a multicolor high gradation and a single color high resolution for each designated area.

Next, another embodiment will be described. In this embodiment, as shown in FIG. 8C, a second-order document is placed on the document table, and the area a of the color first document placed between the points T and S is set to the point S.
Area b of the second manuscript of characters and line drawings placed between point U and point U
The multi-color high gradation reproduction is performed by moving to, and the single color high resolution reproduction is performed outside the area b of the second document. When moving from the area a to the area b, zooming is required. The control flow chart of this embodiment is shown in FIG. 7 (B), and the timing chart is shown in FIG.

A description will be given along the timing chart. First, when copy ON is detected in S40, the designated area is output in multi-colored and high gradation. Therefore, in the designated area for yellow, magenta, cyan and black, as in the sequence described above with reference to FIG. Output a multicolor high gradation image. So from S42 to S48
SET4 = y _4, SET5 = except that excisional movement values and y ₃ are the same as the view the 7 (A). In S49 and S49 ', scaling ==
Set x ₂ −x ₁ / x ₄ −x ₃ | = α. Since the scaling ratio in the sub-scanning direction is realized by changing the speed of the stepping motor, in other words, the frequency of the drive pulse, the scaling ratio α is set by the scaling mode signal to the stepping motor driver 61. Then, the speed of the driven motor changes. As described above, SET8 = α in S49 'is the scaling factor in the main scanning direction, which causes scaling in the main scanning direction. In the case of this example, the magnification is set to be the same as that in the sub-scanning direction, but different values may be set. Next, the home position is moved to point B (see FIG. 9). The output image is output from the position x ₃ from the leading edge of the recording paper, so the scanning start of the reader is 1 + x ₃ from SP1 of the printer.
It is realized by delaying only, this is Verg3 = 0 in S58
Is indicated at the start of the reader scanning.
Select yellow, the first color in S52, and SCRSEL = in S53
Since the steps from setting to 1 to stopping at S63 and subsequent steps at S64, S65 and S66 are the same as those described with reference to FIG. After S67, a sequence for outputting a high resolution image of a single color except the designated area b of the second original of the character line image placed between ΔS and ΔU in FIG. 8C is shown. There is. In S66 ', the home position is moved to the front position ΔC by the run-up distance l with respect to the document reading position ΔS, and in S66 ″, the scaling ratio is set to equal magnification, that is, α = 1,
To set the scanning run-up distance 1 to Vreg3 (S67) and S68 so that the laser light can be turned on in the entire main scanning direction (M ₀ , M ₁ ,
M ₂ ) = (0,0,0) is set, and in S69, the achromatic color density signal ND synthesized from the color separated three color signals is selected.
Outputs S ₀ , S ₁ , S ₂ = 100. Vreg1 = l Vreg2 = l + n3 is laser lighting control in the sub-scanning direction as described above (S70, S71)
Immediately after the printer image signal SP1 is detected by (S72)
Since Vreg3 = 0, the scan motor starts forward scanning. At the same time, with LOFF = 1, the laser can be turned on (S76) M ₀ M ₁ M ₂ = 001 at the position in the sub scanning direction x _1.
In order to blank the designated area, the laser control signal is selected as shown by e in FIG. 7 (A) -3 (S78). In this way, white is drawn to the position of x ₂ (S7
9), in S80, the entire area is output again, and in S81, the forward skiing ends. Thereafter, the same operation as S61 to S63 is performed, and this sequence is ended. By the above operation, it is understood that the designated area on the first page can be scaled and moved to another designated area with multicolor high gradation, and the outside of the designated area can be combined and output with a single color high resolution.
In the above example, only one of the scaling and movement was performed, but both can be moved and scaled independently, and the order of colors and colors can be freely selected. Variable magnification is possible. Also for gradation correction, by selecting K ₀ , K ₁ , and K ₂ , it is possible to output the designated area to be moved and other areas with different gradation correction characteristics.

Furthermore, S ₁ ′, S
By selecting ₂ ', it is possible to reproduce the designated area to be moved and other areas in different color conversion modes.

In this example, two different originals have been described, but the same thing can be done when an area to be moved and an area to be moved are set for one original.

Further, in this embodiment, the color image forming apparatus using electrophotography has been described, but not limited to electrophotography, various recording methods such as ink jet recording, thermal recording, and thermal transfer recording can be applied. is there. Further, although an example in which the reading unit and the image forming unit are arranged close to each other as the copying apparatus has been described, the present invention can be applied to a form in which the image information is transmitted by a communication line while being separated from each other.

<Effects of the Invention> According to the present invention, even if a character portion, a color photograph, a color image, and the like are mixed in one screen, the linear density for forming an image in a region reproduced in a single color is increased, and Since the linear density for image formation in the area to be reproduced in multiple colors has been lowered, areas such as black characters can be reproduced with high resolution, and color photographs and color images can be reproduced with rich gradation. Each of them can be optimally imaged.

[Brief description of drawings]

1 is an internal configuration diagram showing an example of a digital color copying apparatus to which the present invention is applied, FIG. 2 is a block diagram of an electric circuit of the digital color copying apparatus of FIG. 1, and FIG. 3 (A) is FIG. FIG. 3B is an arrangement diagram showing an example of a unity-size color separation line sensor in the original scanning unit, FIG. 3B is an explanatory view showing an enlarged main part thereof, and FIG. 4A is a color reading circuit. 4B is a timing chart showing the signal waveform of the circuit, and FIG. 5 is a circuit for performing color processing of the color image signal, generation of the ND image signal, and selection of the color image signal. 6 is a block diagram showing an example of the configuration of FIG. 6, FIG. 6 is a perspective view showing in detail the main part of the printer portion of FIG. 1, and FIG. 7 (A) -1 is a high-gradation full-color image in the designated area in the same document. , Others are output as high resolution images in single color FIG. 7 (A) -2 is an explanatory view of the coordinates of the designated area of the mode of FIG. 7 (A) -1, and FIG. 7 (A) -3 is FIG. 7 ( FIG. 7B is a timing chart of the image control signal in A) -1 mode, and FIG. 7B is a CPU in a mode in which two originals are used to perform trimming and combining at a desired position by mixing a single color and a full color.
A control flow chart, FIG. 8 (A) is an explanatory view of the document table in the reader section of FIG. 1, the scaner home position, and the scan distance of scanner, FIG. 8 (B) -1, FIG. B) -2 and FIG. 8 (B) -3 are diagrams showing the relative relationship with the scanner position in FIG. 8 (A) of the transfer drum in the printer section of FIG. 1, and FIG. 8 (C) is FIG. 7 (B) is an explanatory view of designated coordinates in the mode, FIG. 9 is a sequence timing chart of scan drive and drum drive in the mode of FIG. 7 (B), and FIG. 10 (A) is from a video detection signal. Timing chart of image sync signal generation, Fig. 10 (B) is sequence timing chart of scan drive and drum drive in mode of Fig. 7 (A) -1, Fig. 11 is reader (original), printer (copy) Image) image signal in the main scanning direction Circuit diagram of the synchronizing signal generating circuit for generating the control signal, FIG. 12 is a timing chart of signals for position movement and scaling in the main scanning direction, FIG. 13 is a block diagram of the scaling control circuit in the main scanning direction, FIG. 14 (A) is a signal waveform diagram showing an example of the signal waveform of FIG. 13, FIG. 14 (B) is an explanatory diagram showing the contents of the selector signal of FIG. 13, and FIG. 15 (A) is an image signal. Circuit diagram of pulse width modulation of (laser), FIG. 15 (B) is a timing chart of the circuit operation of FIG. 15 (A), and FIG. 15 (C) is pulse width modulation of an image signal (laser) and floor. Fig. 16 (A) and (B) show the tone correction characteristics of different tone screens, and Fig. 17 (A) and (B) show the effective pulse width and floor of the laser. It is a figure which shows the relationship of a key.

Claims (1)

[Claims] 1. An input unit for inputting a color image signal for forming an image on one screen, and a signal for identifying an area for forming an image in a single color and an area for forming an image in a plurality of colors in the one screen. Generating means for generating, image forming means capable of switching the linear density for image formation, and a linear density of the image forming means in the area where the image is formed in the plurality of colors based on the signal generated by the generating means. And a control means for switching to a linear density and controlling the linear density of the image forming means to a second linear density higher than the first linear density in the area where the image is formed in the single color. Image forming apparatus.