JPH03146982A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To obtain an image having high picture quality by making the information quantity of an achromatic color component which is written on an image forming body by synchronizing with read scanning larger than the information quantity of a chromatic color component which is accumulated in a storage part and which is written and reducing memory quantity. CONSTITUTION:The driving of a scanner means A, an exposure means B, a color processing part D and an image forming part C are controlled by a control circuit 63. According to the movement of the means A, the color information of an original is read by a CCD sensor C1 and a video signal is inputted to a complementary color conversion circuit 52 through an A/D conversion circuit 51. After B, G and R chrominance signals are converted to the complementary colors of Y, M and C by the circuit 52 and the gradation thereof is corrected, a black component is extracted by a black component extraction circuit 53. Then, it is separated to the chromatic component and the achromatic component and the color thereof is corrected by a masking circuit 54. Besides, it is respectively converted to a binarized or a multi-valued dot pattern by a pattern generator 55. An achromatic color pattern is directly sent to a laser driving circuit 41 and a chromatic pattern is sent to the circuit 41 through frame memories 56M - 58M and write is executed.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a multicolor image forming apparatus, and in particular, the steps of exposing an image forming member to form a latent image and developing the latent image to form a toner image are repeated to form a toner image of each color. The present invention relates to an improvement in a multicolor image forming apparatus that forms images by overlapping them on a forming body.

[Conventional technology]

Conventionally, for example, to form a multicolor image using electrophotography, the copying steps of charging, exposure, development, and transfer are repeated for each component color, and toner images of each color are transferred onto copy paper in an overlapping manner. There is. For example, an electrostatic charge image (hereinafter referred to as a latent image) is formed in each step using separated light of green, red, etc. obtained through a color separation filter, and yellow, magenta, cyan, and if necessary black toners are formed. A toner image is formed by developing the toner image, and the toner image for each color is layered and transferred onto recording paper to form a multicolor image. However, in such a multicolor image forming method, it is necessary to transfer the image to the transfer body each time the development of each color is completed;
In addition to the increased size of the machine, there are other drawbacks such as the long time it takes to form an image, and the need to ensure positional accuracy due to repeated operations. Therefore, multiple toner images are superimposed on the same image forming body and the images are overlapped during development (the toners may or may not overlap). Images are written on the image forming body to form a latent image. Since this is a multicolor image forming apparatus that repeatedly performs the process of developing the latent image to form a toner image and superimposing each color toner image on the image forming body, the transfer process can be performed only once. There is a multicolor image forming method that solves the above drawbacks, but even in this method, the toner image obtained by the previous development may be disturbed during the subsequent development.
The toner in the developer in the previous stage is mixed into the developer in the latter stage, causing problems such as disturbance of the color balance of the multicolor image. In order to avoid such adverse effects, the image forming body and the developer layer that develops the latent image formed on the image forming body are made non-contact, and a direct current bias applied to the developing device or an alternating current component is further superimposed. 2. Description of the Related Art A method of forming a multicolor image by employing a method of developing by causing toner in a developer to fly has been proposed. In this method, the developer layer does not rub the toner image formed up to the previous stage, so that image disturbance does not occur. FIG. 14 shows the process of exposing an image forming body to form a latent image, developing the latent image to form a toner image, and repeating the process to form a toner image of each color overlappingly on the image forming body. 2 is a flowchart showing the principle of a multicolor image forming method. The principle of this image forming method will be explained below with reference to the flowchart shown in FIG. FIG. 14 shows changes in the surface potential of the image forming body, taking as an example the case where the charging polarity is positive. PH is the exposed area of the image forming body, DA is the unexposed area of the image forming body,
DIP indicates the increase in potential caused by the positively charged toner T adhering to the exposed area PH during the first development, and CUP indicates the increase in potential of the exposed area PH caused by the second charging. The image forming body is uniformly charged by a scorotron charger, etc.
A constant positive surface potential E is given. This surface potential E decreases to a point close to zero potential at the exposed portion RH due to the first image exposure by an exposure source such as a laser, cathode tube, liquid crystal shutter, or LED. Here, by applying a positive bias whose DC component is approximately equal to the surface potential E of the unexposed area to the developing device to perform development, the positively charged toner T in the developing device is transferred to the exposed area PH where the potential is relatively low. , and a first visible image is formed. In the area where the visible image is formed, the potential increases by DIP due to the adhesion of the positively charged toner T, but then the second charging is performed by the charger, and the potential further increases by CUP. As a result, the initial surface potential E is obtained as in the non-exposed area DA. Next, a second image exposure is performed on the surface of the image forming body on which a −-like surface potential E is obtained to form an electrostatic latent image, and after a similar development operation, a second visible image is formed. is obtained. By repeating the above process, a multicolor toner image is obtained on the image forming body, and this is transferred to recording paper and further fixed by heating or pressurizing to obtain a multicolor image. Here, the toner remaining on the image forming body and the charge on the image forming body are cleaned and prepared for the next multicolor image formation. A static elimination step using an exposure lamp or corona static elimination may be performed before each charging. Furthermore, the exposure sources used for each image exposure may be the same or different. In the multicolor image forming method, toner images of four colors, for example, yellow, magenta, cyan, and black, are often formed on an image forming member by superimposing them, and this is for the following reasons. A black image should be obtained by overlapping the three primary colors of yellow, magenta, and cyan, but the toners for the three primary colors in practical use do not have the ideal absorption wavelength range, and the toners for the three primary colors do not have the ideal absorption wavelength range. Because it is difficult to accurately align images, it is difficult to reproduce the clear black required for characters, line drawings, etc. using only the three primary colors. Therefore, as described above, toner images of four colors including black in addition to the 3W colors are superimposed to obtain a multicolor image closer to the original. Further, in the multicolor image forming method, a reversal development method is used as a method for developing an electrostatic latent image. In the reversal development method, it is only necessary to expose the toner image forming area of the image forming body, and there is no need to expose the background area without any gaps as in the case of regular development, so it is not necessary to expose the background area without gaps. A latent image can also be formed relatively easily on a forming body. Further, there are advantages such as less fatigue of the image forming body and a longer life. Furthermore, since the second and subsequent charging is performed with the same polarity as the toner, there is no problem with electrostatic transfer. Two typical configuration examples for applying the above-described multicolor image forming method will be described below. FIG. 15 is a block diagram showing a schematic configuration of a first multicolor image forming apparatus to which the above multicolor image forming method is applied. The first multicolor image forming apparatus rotates the image forming body 11 each time yellow, magenta, cyan, and black toner images are formed on the image forming body. That is, a color toner image is formed on the image forming body 11 by rotating the image forming body 11 many times and then transferred. This multicolor image forming apparatus includes a single image exposure means B that performs image exposure based on dot pattern data of yellow, magenta, cyan, and black, and developing devices 13, 14, 15, and 16 loaded with developing devices for each color. , a scorotron charger 18, a transfer device 19, a separator 20, a cleaning device 24, a scorotron charger 12, and the like. FIG. 16 is a block diagram showing the general configuration of a second multicolor image forming apparatus to which the above-described multicolor image forming method is applied. The multicolor image forming apparatus stacks toner images of four colors, yellow, magenta, cyan, and black, in one rotation of the image forming body 51. In FIG. 16, the image forming body 51 is a drum-shaped photoreceptor, and is rotated in the direction of the arrow. A scorotron charger 52 for forming a yellow toner image, an exposure section 53, and a developing device 54 are arranged on the surface of the image forming body 51, followed by a scorotron charger 56 for forming a magenta toner image, an exposure section 57, A developing unit 58 is arranged, followed by a scorotron charger 60 for forming a cyan toner image, an exposure unit 61 . A developing device 62 is provided, followed by a scorotron charger 64 for forming a black toner image, an exposing device 65, and a developing device 66. Therefore, one cycle of the image forming body 51 forms a layered toner image of each color. A large capacity image memory is required to store image data to ensure registration between exposed areas. Note that 55, 59, 63, and 67 are developing rollers, 68 is a paper feeding device, 70 is a transfer pole, 7I is a separation pole, 72 is a fixing device, and 74 is a cleaning device.

[Problems to be solved by the invention]

However, in the image forming apparatus shown in FIG. 15 above, the image forming body has a circumferential length that corresponds to the maximum image size, that is, a circumferential length that corresponds to the scanning return of the optical system and the image size. The total length of the image forming member is determined to be the total length (which may have the shape of a drum or a belt), which has the disadvantage that the waste portion of the image forming body becomes large. For this reason, a device was proposed to change the rotation speed of the image forming body according to the image size (Japanese Patent Laid-Open No. 6
l-223857). However, although this proposal allows for miniaturization of the image forming body, it has the drawback of reducing the printing speed for large image sizes. Furthermore, reading the image data input from the reading device every time it is written makes it difficult to guarantee the positional accuracy of the reading scan. Furthermore, the multicolor image forming apparatus shown in FIG. 16 has a high printing speed, but this apparatus requires four units consisting of charging, exposure, and development processes, which increases the size of the apparatus and increases the distance between the exposure parts. Since a large capacity image memory is required to ensure registration, the cost increases. In order to avoid the above-mentioned problems, it is conceivable to provide a memory for storing image data in these multicolor image forming apparatuses. That is, by scanning the optical system through reading scanning, it is possible to guarantee the registration between images of each color and to omit the time corresponding to the scanning return of the optical system. However, in the multicolor image formation described above, high resolution and gradation expression are necessary to obtain a high-quality image, but image expression using such a method has the drawback of requiring a large amount of image data. was. On the other hand, in a method in which each pixel is binarized and recorded and pseudo gradation is expressed based on its distribution, the amount of image data can be small, but a reduction in resolution becomes a problem.

[Purpose of the invention]

The present invention eliminates the drawbacks of the conventional devices as described above, and provides a multicolor image forming apparatus that rotates an image forming body multiple times, that is, a maximum image size can be achieved by effectively utilizing the image forming body with a small amount of image memory. To provide a multicolor image forming apparatus in which the circumferential length of an image forming body which had a blank part of considerable length is shortened, and also in a multicolor image forming apparatus that forms an image in one rotation of the image forming body. An object of the present invention is to provide a multicolor image forming apparatus that can obtain high quality images with a small memory capacity.

[Means to solve the problem]

In the present invention, a toner image of each color is formed by repeatedly performing a step of exposing an image forming body to form a latent image and developing the latent image to form a toner image, thereby superimposing each color toner image on the image forming body. In a multi-color image forming apparatus, the amount of information of image data corresponding to an achromatic color component is synchronously written on the image forming body through reading scanning, is stored in a storage section through reading scanning, and then written onto the image forming body. It is characterized in that the amount of information is larger than the amount of information of image data corresponding to each chromatic color component. The usefulness of this invention will be explained. It is important that high-quality images generally depend on the reproducibility of achromatic color components. In other words, the image data corresponding to the achromatic color component (using black toner) maintains high resolution and high gradation, and the image data corresponding to the chromatic color component (using black toner) maintains high resolution and high gradation.
, Y, M, C1-color), emphasis is placed on color reproduction, that is, high gradation is maintained and output. The chromatic color components used in the resulting high-quality image have a small amount of information and can be stored in the storage unit. On the other hand, the achromatic color component is handled as a large amount of information and is written onto the image forming body in synchronization with the reading scan without being stored in the storage section. 1-2 In this way, by using a high amount of information to reproduce the achromatic color component, it is possible to obtain a high-quality image and to solve the above-mentioned problems associated with reading scanning.

【Example】

The multicolor image forming apparatus used in this embodiment will be described below, but the embodiments of the present invention are not limited thereto. FIG. 1 is a block diagram showing a schematic configuration of an embodiment of the multicolor image forming apparatus of the present invention, FIGS. 2 and 3 are conceptual diagrams illustrating black component extraction processing in the color processing section, and FIG. FIG. 5 is a schematic diagram showing a laser device as an embodiment of the exposure device, and FIG. 5 is a schematic diagram showing a developing device employed in the multicolor image forming apparatus of this embodiment. In FIG. 1, the image forming body 11 moves at a linear velocity of 140 in the direction of the arrow.
A selenium photoreceptor with a diameter of 140 mm rotates at a rate of mm/see, and a charge of, for example, 10 aoov is applied to the image forming body 11 by a scorotron charger I2. This --like charge is subjected to image exposure by image exposure means B, which will be described later, to form an electrostatic latent image. The multicolor image forming apparatus 100 of this embodiment includes a scanner means A.
1 exposure means B1 image forming section C and system control circuit 60
The system control circuit 6o includes a scanner means A1.
By comprehensively controlling the exposure means B, image forming section C, etc., the image data corresponding to the achromatic color component (using black toner) maintains high resolution and high gradation, and the image data corresponding to the chromatic color component (Y,
Image data corresponding to M and C toners (using M and C toners) places emphasis on color reproduction, that is, maintains high gradation and superimposes toner images on an image forming body to form a multicolor image. The scanner means A is connected to the exposure means B through a color processing section, and the image forming section C is connected to a process control circuit 25.
Controlled by Note that the multicolor image forming apparatus of this embodiment can also store output signals from image pickup devices such as televisions, video cameras, and still cameras, transmission signals from other devices such as facsimiles, or signals thereof in a storage device. The data may be used as image data. The scanner means A is a device that optically scans an original on a platen glass 3 4 times and forms a light image from the original onto a color image sensor C1, and converts the B, G, and H color separated lights into electrical signals. It is something to do. The exposure means B uses, for example, the semiconductor laser device 4 of FIG.
The image forming body 11 is image-exposed by laser light from 0
Electrostatic latent images corresponding to each color are formed thereon. The details of the semiconductor laser device 40 are as follows: A semiconductor laser 42 driven by an oscillation source is modulated by the multivalued or binary image data, oscillates, and emits laser light. This modulated laser light is transmitted through the collimator lens 4
3. The light passes through a condensing lens 44, is polarized by a mirror scanner 45 made of a rotating hexahedron, and is sent to an imaging f-θ lens 46.
Image exposure is performed by scanning the surface of the image forming body 11 at a constant speed through the cylindrical lens 47. Note that 49 is an inspection device that determines the writing position of the laser beam. The electrostatic latent image corresponding to each color is image data Yll+
M O+ Co. They are sequentially formed by irradiation with laser light modulated by B K o. The image forming section C includes a scorotron charger 12 and a developing device 13.
~16, static elimination lamp 17, transfer pole 19. Separation pole 20, conveyor belt 21. Consisting of a fixing device 22, a paper feed tray 23, and a cleaning device 24, the image forming body 11 is sequentially exposed to light under the control of a process control circuit 25 to form an electrostatic latent image, and the latent image is developed to form a toner. The process of forming an image is repeated to form a layered toner image of four colors on the image forming body, which is then transferred and fixed onto a recording paper that is fed in synchronization with the image forming body 11 to form a multicolor image. Form. The scorotron charger 12 uniformly charges the surface potential of the image forming body 11 by controlling corona discharge. The first developing device 13 is loaded with a developer consisting of yellow toner and magnetic carrier, and the second developing device 14 is loaded with a developer consisting of yellow toner and magnetic carrier.
is loaded with a developer consisting of magenta toner and magnetic carrier, the third developing device 15 is loaded with a developer 5 6 consisting of cyan toner and magnetic carrier, and the fourth developing device 16 is loaded with a developer 5 6 consisting of magenta toner and magnetic carrier. is loaded with a developer consisting of black toner and magnetic carrier, and is sequentially stacked on the image forming body 11 based on a drive signal from the process control circuit 25 to form a four-color toner image. The developing devices 13 to 16 of this embodiment will be explained based on FIG. 5. The developing devices 13 to 16 are provided with developer transport carriers 13A to 16A, stirring members 13D to 16D, etc. in the developer tank, and the developer transport carriers 13A to 16A are connected to the image forming body 1.
1, and is composed of sleeves 13B-16B made of a non-magnetic material such as aluminum, and magnet rolls 13c-16G having a plurality of magnetic poles in the circumferential direction. The magnetic pole of magnet roll 13C-16c is usually 500~
It is magnetized to a magnetic flux density of 1500 Gauss. and,
In order to prevent fogging, a developing bias circuit is provided to apply a bias voltage to the sleeves 13B-16B via a protective resistor R. The developing bias circuit includes an AC power supply that supplies an AC bias for causing the toner to fly between the sleeve and the image forming body in the development area A, and a high voltage DC power supply that supplies a DC bias. In this way, the developer bias circuit generates an oscillating electric field between the sleeve and the imager, causing the toner particles to vibrate between the sleeve and the imager, causing contact between the developer and the imager. A toner image of toner particles is formed on the image forming body even if the toner particles are not used. The charger 18 re-charges the four-color toner image formed on the image forming body 11 as described above, and the transfer pole 19
The recharged toner image is transferred onto the recording paper P supplied from the paper feeding device 23. The recharging here preferably has a charging property comparable to that of the charging by the scorotron charger 12. By doing so, the conditions of the previously recharged toner can be made the same, and the transferability is improved. Charger 1
8 is preferably a scorotron charger. 23 is a paper feed roller, and 27 is a guide plate. Separation electrode 2
0 separates the recording paper P carrying the transfer toner image from the image forming body 11 by discharging. Recording paper P is guide 28
and the fixing roller 22, which is transported by the transport belt 21.
The sheet is carried into the paper tray 29, heated and fixed, and then discharged onto the paper discharge tray 29. 7 8 The cleaning device 24 cleans the image forming body 11 after the transfer has been completed.
After the static electricity is removed by the static eliminator 24a, which was not used during toner image formation, the toner remaining on the surface of the image forming body 11 is removed by the blade 24b1, which was released during toner image formation, or a fur brush or magnetic brush that replaces it. Remove it so that it does not interfere with the next multicolor image formation. The color processing section is a scanner means A to B.
, G, R video signals A/D conversion color complementary color conversion Y,
Obtain M and C image data, further extract a black component (BK image data) from the image data, and process the BK image data by pulse width modulation, a multilevel dither method using pulse width modulation, or pulse width modulation. One pixel is converted into a large and small dot pattern consisting of 8 bits of multivalued information using an error diffusion method using width modulation, and on the other hand, one pixel is converted into one bit using a dither method or an error diffusion method for the Y, M, and C image data. It changes into a dot pattern and outputs it. The color processing section includes an A/D conversion circuit 51, a complementary color conversion circuit 52, a black component extraction circuit 53, a masking circuit 54, a pattern generator 55, frame memories 56M, 57M,
It consists of 58M. The A/D conversion circuit 51 converts the electrical signal from the solid-state image sensor CI into a digital signal with, for example, 256 gradations, and outputs B, G, and H image signals. The complementary color conversion circuit 52 obtains image data Y, M, and C from the B, G, and R image (digital) signals. The black component extraction circuit 53 extracts the image data Y and M by, for example, removing the under color (referred to as UCR). Black data BK is extracted from C. The masking circuit 54 performs color correction on the image data Y, M, and C after UCR. The pattern generator 55 generates each image data Y, M, C,
Threshold values and matrix patterns for BK are stored in ROM, and each pixel is converted into 1 bit by calculating the image data of chromatic color components (Y, M, C) using a 4 x 4 matrix pattern using the dither method. Convert it to a dot pattern (binary value consisting of 0 or 1) and output it,
The image data of the achromatic color component (BK) is 4
By performing calculations using the matrix pattern 9 0 , one pixel is converted into an 8-bit (256 gradation) dot pattern and output. Frame memory 56M. 57M and 58M are memories for storing one screen worth of Y, M, and C image data each subjected to dither calculations. The outline of the system is configured as shown above. As a result, the portion of the circumference corresponding to the time required for the recovery of the scanning system can be shortened. When a toner image is formed in the order of yellow, magenta, cyan, and black, among this image data, the image data of the chromatic color components of yellow, magenta, and cyan are temporarily stored in memory by reading scanning, and then the image data of the achromatic color components are stored in the memory. Reads and writes occur synchronously. Image formation is output to the exposure means B in response to a command from the system control circuit 60, and the image forming body l
An electrostatic latent image is formed on l. This electrostatic latent image is reversely developed, preferably in a non-contact manner, by four types of developing devices 13 to 16 containing yellow, magenta, cyan, and black toners, each driven by a command from the process control circuit 25. . Thus, a four-color toner image is formed on the image forming body 11, and is transferred and fixed onto a recording paper fed in synchronization with the image forming body 11, thereby forming a multicolor image. Furthermore, when a toner image is formed in the order of black, yellow, magenta, and cyan, reading and writing of achromatic color components in this image data are performed synchronously.
The image data of the cyan chromatic color component is once docked in the memory and then output to the exposure means B in response to a command from the system control circuit 60, and an electrostatic latent image is formed on the image forming body 11. This electrostatic latent image is reversely developed, preferably in a non-contact manner, by four types of developing devices 13 to 16 containing yellow, magenta, cyan, and black toners, each driven by a command from the process control circuit 25. . Thus, a four-color toner image is formed on the image forming member 11, and is transferred and fixed onto the recording paper fed in synchronization with the image forming member 11, thereby forming a multicolor image. 1 2- Next, an outline of the operation of the multicolor image forming apparatus of the present invention will be explained. A control signal from the system control circuit 60 controls and drives the scanner means A1, the exposure means B1, the color processing section, and the image forming section C. For example, the exposure means A (lamp 2
．． As the mirrors 6a, 6b, 6c) move, the CCD image sensor C1 reads the horizontal B (blue), G (green), and R (red) color information of the A-3 size document and outputs a video signal. do. After A/D conversion, this signal is subjected to shading correction to remove distortion caused by the CCD and optical system, etc., and is temporarily inputted to a buffer memory (not shown) for each B, G and G signal.
, R correspond to the same image position. Next, the B, G, and R signals from the buffer memory are converted into complementary colors of Y (yellow), M (magenta), and C (cyan), and after gradation correction is performed, each of the Y, M, and C data is converted into The black component is extracted (0CR) and separated into a chromatic color component and an achromatic color component. Here, the black component extraction circuit 53 and the masking circuit 54
The processing in will be explained in more detail based on FIGS. 2 and 3. Image pig Yi in the three primary colors of yellow, magenta, and cyan,
An image consisting of Mi and Ci is input to the black component extraction circuit 53, and image data of four desired colors Y o, M o, Co are obtained by, for example, the following arithmetic expression [I]. BK is calculated. Arithmetic formula (I) Y o −a r Y l−β+min (Yi, Mi
, Ci: ]M , -a 2M i-β2m1n (Yi
+Mi, C1) C6= az Cr-β, min (
Yi, Mi, C1) BK, = β4m1n (Yi, Mi
,Ci) where Y, ,M,,C, is the data after the operation, Y
i+M r +Ci is input image data, a□,
C2, C1, β1°β2. β3. β is a color correction coefficient based on external factors such as input system and development conditions, min (Yi,
Mi, Ci) indicates the color tone having the minimum density value among the three primary colors of yellow, magenta, and cyan. Next, in order to understand the calculation formula [■], C1C3゜β1~β
, are all l as an example. 2:( 4 Now, if the color tone of the minimum density value is cyan (Ci) as shown in Figure 2, then if we subtract the density corresponding to cyan from each of the three primary colors and put them together, we get the achromatic color component. A black component is obtained. This black component is used as black image data as shown in Figure 3. Also, the remainder after subtracting the cyan density equivalent from each of the three primary colors is converted to Y, which is a chromatic color component, as shown in Figure 13. , M, and C. This improves the color balance during development, saves toner consumption, and improves the efficiency of the development operation. Here, the chromatic color components Y, , M, , C are the colors. The color is corrected by the correction coefficients σ, ~σ1, β, ~β4, and is input together with the black component (BK) to the pattern generator 55. Here, the Y, M, and C data are processed using the dither method or error diffusion method as described above. The black component is converted into a binary digital dot pattern signal by processing based on the law, etc., while the black component is converted into a multi-value signal (it does not need to be passed through a pattern generator, or it can be combined with the multi-value process using a pattern generator to perform the above processing). The Y dot pattern signal that is written first is stored in the page memory, and is output to the exposure means A via the line memory required as a buffer, almost synchronously with the reading. The M and C dot patterns stored in the frame memory at the same time as the Y dot pattern are stored in the A-3 size frame memory, and during the return movement of the optical system, the M and C dot patterns are stored in the frame memory. Writing and image formation are performed in synchronization with the movement.Next, BK
The dot pattern is written using 8-bit pulse width modulation in accordance with the movement timing of the image forming body. If a 7-frame memory is used, it is possible to print without synchronizing with image reading, but since frame memory is expensive, it would be too expensive to prepare multi-value data for multiple sheets, so it is possible to print without synchronizing with image reading. While synchronizing image formation to form image data of a colored component (black), image read data corresponding to the next color is stored in a frame memory and used for previous or subsequent image formation. 5 6 That is, even though multivalued image data is output, it is only necessary to prepare a frame memory for three screens of three colors of the maximum image size, for example, A-3. Furthermore, when one sheet of A-4 original is prepared, the image reading and image formation of this original are performed synchronously only when the achromatic color component is present, while the signal from reading the chromatic color image is transferred to the frame. Store it in memory once, then recall it to display the first and second images.
Writing is performed on the first sheet and image formation is performed. Thereby, two identical toner images can also be formed on the image forming body. After this process is performed for each of the colors Y, M, and C to form two multicolor toner images, it is also possible to transfer the toner images to a sheet of paper conveyed in synchronization with each image and discharge the toner images. When reading and writing achromatic color components for the first time, writing is performed in synchronization with the first reading scan, and Y, , M,
, C0 are once docked in the frame memory, and then the image data of Y, M are sequentially retrieved from the frame memory. A color toner image is formed from C. When reading and writing the achromatic color component last, the Y, M, and C image data are stored in the frame memory by one reading scan at the beginning, and at the same time, the first chromatic color image is formed, and the black At the end of forming a toner image, the second reading scan and writing are performed synchronously. Hereinafter, the operation of each part in the multicolor image forming apparatus of this embodiment will be described in detail in Examples 1 and 2 for the case where an A-3 size original is used and the case where an A-4 size original is used. [Embodiment 1] FIG. 6 is a time chart showing the operation of each device when an A-4 size document is read and scanned by the scanner means A to copy a multicolor image. In the figure, RA l+ RA 2 indicates the forward movement time for image reading among the timings at which the optical system in the image scanner performs reciprocating scanning. The image forming body 11 indicates, for example, the number of revolutions from the exposure point of the laser device 40 to the image forming body 11, and the frame memory 56M. 57M and 58M indicate that image data has been written to the frame memory 56M when they are at a high level, and the charger 12 and developing devices 13 to 16 are in an operating state when they are at a high level. It shows. In the scanner means A, the frame memory 5
Dot pattern data Y, M, on 6M, 57M, 58M
While writing C, the yellow dot pattern data modulates the laser beam. EY,,EM,. EC,, EB2 indicate the exposure timing of the exposure means B, and the exposure means B has E Y 2 , E M x ,
The E Cx reads 1-bit yellow, magenta, and cyan dot pattern data Yo, Mo, and Co from the frame memories 56M, 57M, and 58M, and staticizes the image forming body 11 with laser light that is binary-modulated using the 1-bit dot pattern data. Write the electric latent image and read the second scan RA2
The image data read in is written in EB2. EB2
is the timing at which 8-bit black dot pattern data BK is written using a multilevel pulse width modulated laser beam.
This information is DY2. DM. Yellow, magenta, cyan, and black are developed by the developing devices 13, 14, and 15.1 at the timings of D C, , and D B .
6. FIG. 8 also shows an A-3 size document being scanned by scanner means A.
2 is a time chart showing the operation of each device when reading and scanning a multicolor image. In the figure, RA, RA2 indicate the reciprocal scanning timing of the optical system in the image scanner, during which image reading is performed, as described above. The image forming body 11 shows, for example, the number of rotations from the laser device 40 to the image forming body 11 from the exposure point, and the 7-frame memories 56M, 5
7M, 58! J indicates that image data was written to the frame memory when it was at the No\I level,
The charger 12 and the developing devices 13 to 16 are in operation when they are at the noise level. E Y 2. 'E Mz, E C! + E B 2
indicates the exposure timing of the exposure means B, and the exposure means B has an exposure timing of EM2°EM2. EC2 with 7 RAM memory 56M
, 57M, 58M to yellow, magenta, cyan 1
While writing 1-bit dot pattern data Y, M, and C, the yellow dot pattern data is modulated with laser light. The image data read in the second reading scan RA is written at EB2. EB2 is 8-bit dot pattern data BK, which is the timing to write with multi-level pulse width modulated laser light. This information is at timing D
Y,,DM2. According to DC2, D B , yellow, magenta, cyan, and black development is performed in developing devices 13.14 and 15.16. In the image formation shown in FIGS. 6 and 8, yellow, magenta, and cyan dot pattern data Y, M, and C are used.
are written in the frame memories 56M, 57M, and 58M, so when copying from the second copy onward, the black information is created using the accumulated yellow, magenta, and cyan dot pattern data Y, M, and C. It is also possible to do just one scan to read the . Note that the frame memory 56 for yellow dot pattern data can be omitted. Here, yellow and magenta are chromatic color components. The cyan image data Yi, Mi, and Ci are color-corrected by the masking circuit 54 and are converted into image data Y along with the black component (BK). , M o, and Co are input to the pattern generator 55. The pattern generator 55 generates yellow, magenta, and cyan image data Y, M0°co.
is digital dot pattern data Y that has been binarized by processing based on the dither method as described above. On the other hand, the black component is converted into multi-value data (it does not need to be passed through the pattern generator D, or the above processing is performed by the multi-value dither combined with dither and pulse width modulation in the pattern generator 55) as data BK. Output. The yellow dot pattern signal Y, which is written first, is written into the frame memory 56M, and is also output to the exposure means B via a line memory required as a buffer, and is written and imaged almost in synchronization with the reading. While forming a yellow dot pattern, magenta and cyan dot pattern data M,
C is an A-3 size frame memory 57M. 58M, and during the return movement of the optical system, the image forming member 1
Writing and image formation are performed in synchronization with the movement of 1 2 . Next, approximately in synchronization with the reading, the black dot pattern data is set to 8 in synchronization with the movement timing of the image forming body 11.
Writing is performed using bit multilevel modulation. FIG. 7 is a time chart showing the operation of each device when an A-4 size document is read and scanned by scanner means A to copy a multicolor image, and the image formation order is black, Y, M,
The difference from FIG. 6 is that the order is C, but everything else is the same, and in this case, a multicolor image can be copied by one reading scan. 8b with black dot pattern data BK from the laser device 40 in synchronization with the reading scan of the optical system in the scanner means A.
A latent image is formed by exposing the image forming body 11 to a laser beam modulated in pulse width of the image forming member 11. On the other hand, the binary dot pattern data Y, M, and C of yellow, magenta, and cyan are temporarily stored in the frame memory 56M. Written to 57M and 58M. Yellow, magenta, and cyan dot pattern data Y written in frame memories 56M, 57M, and 58M
, M, and C are EY, by the laser exposure device 40. The image forming body 11 is exposed to light at timings EM, , EC2 to form a latent image, and DB2. Black, yellow, magenta, and cyan development is performed by the developing devices 16, 13, 14, and 15 at the timings Dy, DME, and Dc. FIG. 9 also shows an A-3 size document being scanned by scanner means A.
This is a time chart showing the operation of each device when copying a multicolor image by reading and scanning with
, M, and C in this order, but everything else is the same. In this case, a multicolor image can be copied by one reading scan as in the case shown in FIG. 7. . In the figure, as in FIG. 7, EB2 is the timing at which the black image data read by RA is converted into 8-bit dot pattern data BK, and the image is exposed in synchronization with the rotation of the image forming body 11, and EY,... E.M. EC2 is read by RA, frame memory 56M,
This is the 33 4 timing when the 1-bit yellow, magenta, and cyan dot pattern data Y, M, and C written in 57M and 58M are written on the image forming body 11 by exposure using the laser exposure device 40, and D B 2 , D Y 2 ,
D M 2 , D Ct are the latent images formed on the image forming body 11 based on the above-mentioned respective dot pattern data Y, M, C, by the developing device 16° 13.14. This is the timing for sequential development by l'5. In the image formation shown in FIGS. 7 and 9, yellow, magenta, and cyan dot pattern data Y, M,
C reads frame memories 56M, 57M,
Since the images are stored in 58M, there is no color shift in the image. In the case of the second and subsequent copies, by replacing and using the stored image data each time in the same way as for the first copy, it is possible to obtain a good copy image without image color shift. Of course, the image data may be used without being replaced. Therefore, as shown in the time charts shown in FIGS. 6 to 10, in the case of an A-4 size original, the frame memories 56M, 5
7M and 58M, image reading scanning is performed at the first or fourth rotation of the image forming body 11, depending on the order of toner image formation.
Even if the optical system is not ready in time for the next rotation after image reading scanning and image exposure, the optical system can be moved back during the next rotation.
Meanwhile, dot pattern data Y from frame memories 56M, 57M, and 58M. The image forming body 11 is exposed to laser light modulated based on M and C. That is, the circumferential length of the image forming body 11 can be shortened without changing the overlapping process on the image forming body 11 according to the image size, and the entire apparatus can be made compact. [Example 2] Figure 1O shows that before performing image exposure, image reading scanning is performed in advance to store dot pattern data Y, M, and C in the frame memory 5.
Write to 6M, 57M, 58M, then Y. 7 is a flowchart showing an image forming process when toner images are formed in the order of M, C, and BK. Here, yellow, magenta, and cyan image data Yi
, Mi, and C4 are color-corrected by a black component extraction circuit 53 and a masking circuit 54, and become image data Y. , Mo. CGr B K o is input to the pattern generator 55 . The pattern generator 55 generates yellow, maze, and cyan image data Y. , M, , Co are digital dot pattern data Y that has been binarized by processing based on the dither method or error diffusion method as described above. On the other hand, the black component is converted into multi-value data (it does not need to be passed through the pattern generator D, and the pattern generator 55 performs the above processing by multi-value processing combining the dither method, error diffusion method, and pulse width modulation). ) Data BK
is output as The yellow dot pattern signal Y, which is written first, is output from the frame memory 56M to the exposure means B via a line memory required as a buffer, which is synchronously transferred, and image formation is performed. The magenta and cyan dot pattern data M and C written to the frame memory at the same time as the yellow dot pattern are A-3 size frame memories 57M and 58.
M, and writing and image formation are performed in synchronization with the movement of the image forming body 11. Next, approximately in synchronization with the reading, black dot pattern data is written using 8-bit modulation in synchronization with the movement timing of the image forming body 11. In this image formation, Y, M, and C dot pattern data Y, M, and C are stored in the frame memory 56M. 57M and 58M, for the second and subsequent copies, the yellow, magenta, and cyan dot pattern data Y, written in the frame memory.
Using M and C, it is also possible to complete with one scan to read black image data. In this image formation, yellow and magenta are used. Cyan dot pattern data Y, M, and C are stored in frame memories 56M, 57M, and 58M in one scan.
It is characterized by the fact that there is no color shift in the image. In this case, the frame memory is output without storing the entire screen (for four colors). In the case of copying the second and subsequent copies, the dot pattern data written in the frame memory each time is used as is, as in the case of the first copy. By rewriting and using the dot pattern data, it is also possible to obtain a good copy image without image color shift. In this case, two reading scans are required for every copy. 7;;8 [Example-3] The present invention provides a method for producing yellow magenta, yellow magenta, and
The present invention can also be applied to the multicolor image forming apparatus shown in FIG. 16, in which cyan and black toner images are superimposed, if the image processing section shown in FIG. 1 is provided.
This will be explained below. FIG. 11 is a flowchart when image formation is performed by writing dot pattern data Y, M, and C into a frame memory in advance by image reading scanning before performing image exposure. As described above, the yellow, magenta, and cyan image data Yi, Mi, and Ci are color-corrected by the black component extraction circuit 53 and the masking circuit 54, and the image data Y0゜ylo,
Co and BKo are input to the pattern generator 55. The pattern generator has yellow magenta and cyan image data Y. , M o , and Co are converted into binary digital dot pattern data Y, M, and C by processing based on the dither method and error diffusion method as described above, while the black component is converted into multivalued data (using a pattern generator). It is not necessary to pass the data through D, or the above processing is performed by a pattern generator using a multi-value processing combining a dither method, an error diffusion method, and a pulse width modulation). The yellow dot pattern signal Y written in the first frame memory is output to the exposure means via a line memory required as a buffer, and image formation is performed synchronously. magenta and cyan dot pattern data M written in the frame memory during one direction;
C is outputted to the exposure means in synchronization with the movement of the image forming body during the backward movement of the optical system, and image formation is performed in synchronization with the movement of the image forming body. Next, approximately in synchronization with the reading, black dot pattern data is written using 8-bit modulation in synchronization with the movement timing of the image forming body. In this image formation, since the Y, M, and C dot pattern data Y, M, and C are written in the frame memory in advance, in the case of copying from the second sheet onward, the yellow dot pattern data written in the frame memory, It is also possible to use the magenta and cyan dot pattern data Y, M, and C to read the black image data in just one scan of 94θ. [Example 4] Figure 12 shows a method for forming a multicolor image with one reading scan.
0-Chart. The image forming apparatus shown in FIG. 17 is different from the image forming apparatus shown in FIG. 16 in that the charger 64. Exposure section 65. The developing device 66 is arranged at the most upstream position with respect to the image forming body. In other words, the image formation order is black, Y
, M, and C. 8-bit black dot pattern data BK is output from the exposure section 65 in synchronization with the reading scan of the optical system in the scanner means A.
A latent image is formed by exposing the image forming body to a pulse width modulated laser beam. On the other hand, yellow, magenta, and cyan dot pattern data Y. M and C are once written into the frame memory. 1-bit dot pattern data Y of yellow, magenta, and cyan written in the 7-frame memory. M, C are E Y z by exposure parts 57, 61.53
,E.M. The image forming body is exposed to light at the timing of EC to form a latent image, and sequentially D B 2. DY! , DME, DCs
At this timing, black, yellow, magenta, and cyan development is performed by the developing devices 66, 54, 58, and 62. In this image formation, since the Y, M, and C dot pattern data Y, M, and C are written in the frame memory in advance, in the case of copying the second and subsequent copies, they are immediately written in the frame memory. Yellow, magenta, and cyan dot pattern data Y, M, and C are used, and the data is replaced each time each copy is made. [Example 5] FIG. 13 is a flowchart for forming a multicolor image by one reading scan. FIG. 13 is a flowchart when image formation is performed by writing dot pattern data Y, M, and C into a frame memory in advance by image reading scanning before performing image exposure. This example uses the same image forming apparatus (FIG. 17) as in Example 4. That is, the image forming apparatus shown in FIG. 17 is different from the image forming apparatus shown in FIG. 16 in that the charger 64. The configuration is such that the exposure section 65° and the developing device 66 are placed at the most upstream side of the image forming body. That is, the order of image formation is black, Y, and M. It is C. In synchronization with the reading scan of the optical system in the scanner means A, a laser beam pulse width modulated with 8-bit black dot pattern data BK is exposed from the exposure section 65 onto the image forming body to form a latent image. On the other hand, yellow, magenta, and cyan dot pattern data Y, M, and C are written into the -H frame memory. As described above, the yellow, magenta, and cyan image data Yi, Mi, and Ci are color-corrected by the black component extraction circuit 53 and the masking circuit 54, and are converted into image data Yo. MO, CD, and BKO are input to the pattern generator 55. In the pattern generator, yellow magenta,
The cyan image data Yo, Mo, and C- are converted into digital dot pattern data Y, M, and C, which are binarized by processing based on the dither method and error diffusion method as described above.On the other hand, the black component is Multivalued data (it may not be passed through the pattern generator D, or the pattern generator performs the above processing by multivalued processing in combination with the dither method, error diffusion method, and pulse width modulation) is output as data BK. Next, approximately in synchronization with the reading, the black dot pattern is written for the first time using 8-bit modulation in synchronization with the movement timing of the image forming body. The yellow dot pattern signal Y written in the second frame memory is output to the exposure means via a line memory required as a buffer, and image formation is performed synchronously. On the other hand, magenta and cyan dot pattern data M written in the frame memory,
C is outputted to the exposure means in synchronization with the movement of the image forming body, and image formation is performed in synchronization with the movement of the image forming body. In this image formation, since the Y, M, and C dot pattern data Y, M, and C are written in the frame memory in advance, in the case of copying from the second sheet onward, the yellow dot pattern data written in the frame memory, It is also possible to use the magenta and cyan dot pattern data Y, M, and C, and only need one scan to read the black image data. In the above embodiment used in the present invention, the data per pixel stored in the 743 4 frame memory is Y o
, M o, Co, l b it s B
Although K n is set to 8 bits, the number is not limited to this. For example, Y. , Mo, and Go can be set to 2 bits or 3 bits, and %BK can be set to 4 to 8 bits or more. To obtain high quality color images, Y o, M o, C
. It is also desirable to take 2 to 3 bits. In this case, similarly to BK, one pixel can be used for pulse width modulation or a combination of pulse width modulation and dither method or error diffusion method. In addition to pulse width modulation, intensity modulation or density pattern method can also be used as the multi-level modulation means. Although this embodiment did not show an example of monochrome printing, when trying to copy a monochrome black image, Y
By combining the frame memories used in O+M a and Co into a bit-plane configuration, they can also be used as a multi-level memory. For example, if Y, ,M, ,C, has 7 frame memories of 2 bits each, when used as a single color frame memory, it is used as a 2 x 3 = 6 bit frame memory when copying a single color. be able to. This allows high-quality monochrome images to be copied at high speed. In addition, in this example, in addition to Y o and M O + Co, -b
It is also possible to prepare a frame memory of 1 BK. By doing this, in the normal color copy mode, a high-speed copy image can be obtained by storing the image in the frame memory by performing image reading scans of Yo, M, , Co, and BK times. In the high-quality color copying mode, the usage method of this embodiment is adopted. In this way, copies can be made according to the usage situation.

【Effect of the invention】

As explained above, the steps of exposing the image forming body to form a latent image and developing the latent image to form a toner image are repeated, and the toner images of each color are superimposed on the image forming body. In a multi-color image forming apparatus that forms an image using a multi-color image forming apparatus, the amount of information of image data corresponding to an achromatic color component written on the image forming body 5 6 in synchronization with the reading scan is accumulated in the storage unit by the reading scan. By increasing the information amount of image data corresponding to each chromatic color component to be written on the image data, the disadvantages of the conventional ones mentioned above can be eliminated, and the image forming body can be used effectively with a small amount of image memory and maximized. To obtain a high-quality image by forming an image in one revolution of a multicolor image forming device and by shortening the circumference of an image forming body that has a blank portion of a considerable length relative to the image size. We were able to provide a multicolor image forming apparatus that can perform

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the schematic configuration of the multicolor image forming apparatus of the present invention, FIGS. 2 and 3 are conceptual diagrams explaining the processing in the black component extraction/extraction circuit, and FIG. A schematic diagram showing a laser device as an example; FIG. 5 is a schematic diagram showing a developing device employed in the multicolor image forming apparatus of this example;
Figures 6 and 7 show the case when using A-4 size and
9 is a time chart when A-3 size is used, and FIG. 10 is dot pattern data Y before image exposure. Write M and C into the frame memory in advance, then write Y and M.
, C, and BK in the order of toner images. FIG. 11 shows dot pattern data Y before image exposure. A time chart when forming an image by writing M and C to the frame memory. Fig. 12 is a time chart when forming a multicolor image by one reading scan. Fig. 13 is a time chart when performing a pre-read scan before performing image exposure. FIG. 14 is a time chart when image formation is performed by writing dot pattern data of chromatic color components into a frame memory. FIG. FIG. 15 is a flowchart showing the principle of a multicolor image forming method in which the step of forming an image is repeated to form each color toner image on the image forming body by superimposing them. FIG. 16 is a block diagram showing a schematic configuration of a first multicolor image forming apparatus to which the application is applied, FIG. 16 is a block diagram showing a schematic structure of a second multicolor image forming apparatus, and FIG. 17 is a block diagram showing a schematic structure of a third multicolor image forming apparatus. FIG. 7 is a diagram showing a schematic configuration of the processor. DESCRIPTION OF SYMBOLS 11... Image forming body 12... Scorotron charger 13-16... Developing device 25... Process control circuit 41... Laser drive circuit 42... Transmission source 43...
・Collimator lens 44...Mirror scanner 45...
・f-θ lens i 46...Reflection lens 51...
・A/D conversion circuit 52... Complementary color conversion circuit 53...
Black component extraction circuit 54...Masking circuit 55...
Pattern generators 56M, 57M, 58M...Frame memory 60...
・System control circuit

Claims (1)

[Claims] A multicolor image formed by repeatedly performing the steps of exposing an image forming body to form a latent image, developing the latent image to form a toner image, and superimposing each color toner image on the image forming body. In the forming apparatus, the amount of information of image data corresponding to the achromatic color components written on the image forming body in synchronization with the reading scan is accumulated in the storage unit by the reading scan, and then each chromatic color component is written on the image forming body. A multicolor image forming apparatus characterized in that the amount of information is larger than that of image data corresponding to the above.