JPH0227371A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To decrease an omission of image information caused by a fact that the tone of a color is scarcely varied and an erasion has a larger pitch than that of ready by converting color data of a read unit to color data of an erasion unit and reconverting it in accordance with a real image. CONSTITUTION:Color data of a read unit by a color CCD 51 of an original reading means is converted to color data of an erasion unit by an LED editing eraser 5 whose size is different and stored in a memory 70. Also, an original image is divided into block units containing prescribed number of erasion units, the corresponding data is read out successively from the memory 70 at every block unit and a distributing state of the color is detected, and in accordance with the state, the data is reconverted successively and re-stored in the memory, and based on this reconverted data, the LED eraser 5 is controlled. In such a way, the omission of image information of adjacent erasion units, especially, the variation of a shape is decreased, and also, the variation of the tone of a color can be minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus that reproduces multicolor images using an electrophotographic process.

(Prior art) Conventionally, an original image is read as image data for each color by an original reading means such as a CCD array, and a laser is driven and controlled based on the read color data to create electrostatic latent images for each color on a photoreceptor. Multicolor image forming apparatuses that reproduce multicolor images by repeating the steps of forming an image, developing it using toner of a corresponding color, and transferring the toner image to an intermediate transfer medium are well known.

On the other hand, an electrostatic latent image is formed on a photoreceptor by scanning the original, and depending on the color to be reproduced, the electrostatic latent image other than the part to be converted into a toner image is used with an LED array or the like for each toner developer used. There is also known a multicolor image forming apparatus that reproduces a read document in color by repeating the operations of erasing the toner with an eraser, converting it into a toner image, and transferring it to an intermediate transfer medium for each toner ( (See Japanese Patent Application Laid-open No. 194469/1983).

Compared to the former method using a laser, this latter method does not require the use of a mechanical drive mechanism, so it has the advantage of being significantly simpler mechanically. The arrangement pitch (erase unit) of the elements is determined by the CC of the CCD array as the document reading means.
If the arrangement pitch (reading unit) of D elements is about the same, L
Costs similar to write heads using ED arrays;
Since the cost is higher than the original purpose, there is a problem in that the erased area cannot actually be reproduced with the accuracy read by the document reading means.

More specifically, the erase pitch is usually manufactured to be an integral multiple of the read pitch (generally 3.4 times), and the area of the erase unit on the photoreceptor is 9 times or more than the area of the COD read unit. It becomes 16 times. Therefore, during one erase unit,
Although there are 9 or 16 pieces of color information, these pieces of color information are not necessarily all the same and often differ. In the latter case, when erasing, colors that should be erased and colors that should not be erased exist in one erase unit, and whether or not that erase unit is erased There was a problem that one of the image information was missing.

In order to solve the above problem, Japanese Patent Application Laid-Open No. 60-23517
In Publication No. 0, the surface potential of the electrostatic latent image formed on the photoconductor differs depending on the brightness of the color. By erasing only the electrostatic latent image with a lower surface potential, it is possible to distinguish between colors that should be erased and colors that should not be erased, and to prevent changes in shape during image formation. Proposed. However, with this method, if there is a large difference in brightness, such as black and red, the red electrostatic latent image is certainly erased, but
When the black electrostatic latent image is visualized, the black toner image inevitably overlaps the red (or magenta and yellow) toner image, resulting in a change in color tone. Furthermore, when colors with small differences in brightness are included in the same erase unit, the difference in surface potential generated on the photoreceptor is small, and it is difficult to erase only the electrostatic latent image of one color.
This results in a change in the shape of the original image.

Even if erasing is successful, when visualizing a color with low brightness, avoid overlapping the toner image of a low brightness color on the toner image used for a high brightness color. However, the color still changes. In particular, this change in hue occurs throughout the reproduced image, giving a distinct visual sense of discomfort.

The applicant has filed a separate application dated the same date as the present application, in which color C.
The color data of the reading unit by OD is converted into LE of different sizes.
We have proposed a multicolor image forming apparatus that converts the data into erase unit color data using a D editing eraser and stores it in memory, and controls the editing eraser based on the converted data, thereby reducing the storage capacity and improving the original document described above. Efforts are being made to prevent image information from being lost.

By the way, the light emitted from an LED element generally has the property that the amount of light is greatest at the center and decreases toward the edges. If you do not overlap the lights to some extent and arrange them so that they mutually compensate for the lack of light at the edges,
The range within the erase unit cannot be completely erased.

(Problems to be Solved by the Invention) To address this problem, in a conventional multicolor image forming apparatus that uses an LED array to erase an electrostatic latent image, the light irradiated onto the photoconductor from adjacent LEDs is mutually Designed to overlap. However, this means that one LED
In addition to erasing the electrostatic latent image in one erase unit that is the target of erasing, it also erases the periphery of the electrostatic latent image in the adjacent erase unit, resulting in unnecessary erasing. ,Therefore, there was a risk that more image information would be lost.

The present invention has been made in order to solve the above-mentioned problems, and is a multicolor image forming apparatus that erases an electrostatic latent image using a light emitting element array such as an LED array. The purpose of this invention is to reduce the loss of image information, especially changes in shape, caused by the size and light emitting characteristics of LED elements, and to minimize changes in color tone.

(Means for Solving the Problems) In order to solve the above problems, a multicolor image forming apparatus according to the present invention irradiates a document with light and applies the reflected light to a uniformly charged surface of a photoreceptor. The electrostatic latent image is exposed to light to form an electrostatic latent image corresponding to the original image, while the original image is separated and read by the original reading means for each color, and based on the obtained image data for each color, the electrostatic latent image is erased by the erasing means. The photoconductor on which the electrostatic latent image has been formed is selectively irradiated with light to leave the area to be developed with toner and erase the rest, and then the remaining electrostatic latent image is developed using toner of the corresponding color. The process of transferring the developed toner image to an intermediate transfer medium is repeated at least once to form a multicolor toner image on the intermediate transfer medium, and then transferred to paper and fixed to form a multicolor toner image. In a multicolor image forming apparatus that forms a color image, a means for converting color data read by an original reading means into an erase unit of an erase means having a size different from a reading unit of the original reading means by a predetermined method; a storage means for storing color data converted into units; a document image divided into blocks each including a predetermined number of erase units; color data corresponding to each block unit sequentially read from the storage means; means for detecting a color distribution state, sequentially re-converting the data according to the detected color distribution state, and storing the result again in the storage means; and a drive for driving the erase means based on the color data stored in the storage means. It is characterized by comprising a control means.

(Function) In a multicolor image forming apparatus, color data in units of reading by a color CD is converted into color data in units of erasing by LED editing erasers of different sizes and stored in memory, and furthermore, the original image is converted into color data in units of erasing by LED editing erasers of different sizes. The color data is divided into blocks including the same number of erase units, and the color data corresponding to each block is sequentially read out from the memory, the color distribution state is detected, and the color data is sequentially reconverted according to this distribution state and stored in the memory. The LED collection eraser is controlled based on this reconversion data.

(Examples) Examples of the present invention will be described below with reference to the accompanying drawings.

Structure of Copying Machine FIG. 1 is a schematic sectional view of a copying machine to which a multicolor image forming apparatus according to the present invention can be applied.

A photoreceptor drum 3, which is an electrostatic latent image carrier, is installed approximately in the center of the copying machine main body l so that it can be rotated in the direction of arrow a. An eraser 5, a developing device 6, a transfer device 11, a cleaning device 22, and a main eraser 23 are installed.

The editing eraser 5 is a solid LED array in which LED elements are arranged in a holder disposed along the axial direction of the photosensitive drum 3, and this editing eraser 5 is schematically shown in FIG. Each LED 65 faces the photosensitive drum 3, and is arranged in a line in a direction perpendicular to the plane of the paper of FIG. Furthermore, the pitch P of each LED 65 is 1.2nw in this embodiment.
It is set to n°C. As described later, each LED 65
The timing of turning on and turning off the lights is controlled individually.

The developing device 6 consists of four developing units 7, 8, 9, and 10.
As a whole, these directions are in the vertical direction (arrows).

b' direction) and remove the photoreceptor drum 3 from any developing device.
The toner can be supplied to the surface of the developing device 7.
to 10 contain toners including yellow toner ("ry), magenta toner (Tm), cyan toner (Tc), and black toner (Tbk), respectively. As described above, the developing device 6 has an upper and a lower The toner is not limited to a form in which the toner can be moved in different directions, but may be in any form as long as it can selectively supply toner of different colors to the photoreceptor drum 3.

The transfer device 11 temporarily transfers the toner supplied onto the photosensitive drum 3 onto the transfer belt 15 and holds it.
This transfer belt 15 has a dielectric material such as polyethylene on the surface of a conductive base made of conductive polyester containing carbon resin, etc., and is wound around rollers 12, 13, and 14 arranged parallel to the photoreceptor drum 3. It is supported by

A pressure roller 16 is disposed inside the transfer belt 15 between the rollers 12 and 13, and these rollers approach and separate from the photoreceptor drum 3 integrally, and the vertical movement of the pressure roller 16 causes the transfer belt 15 to be is in contact with the photoreceptor drum 3 and separated from it. Further, a guide plate 18 is provided along the transfer belt 15 between the rollers 13 and 14, and a cleaning device 19 is provided on the outside facing the guide plate.
, a static eliminating charger 20, and a charging charger 21 are arranged. Further, a transfer belt 15 is provided below the roller 14.
A secondary transfer charger 24 facing the secondary transfer charger 24 and a separation charger 25 located on the side thereof are provided.

An optical system 27 is arranged at the top of the copying machine main body 1.

In this optical system 27, an exposure lamp 29 and a first mirror 31 are installed on the first slider 28, and the first slider 28 is moved along the arrow d along the document table glass 26 provided at the top of the copying machine main body l. It is possible to scan in the direction.

A second slider 32 is arranged at the rear of the first slider 28, and a second mirror 33 and a third mirror 34 are provided therein, and the second slider 32 is moved in the direction of arrow d in synchronization with the first slider 28. In this case, the scanning is performed at half the speed of the first slider 28. Further, a main lens 35 and a fourth mirror 36 are fixed in front of the second slider 32 (on the scan side), and a fifth mirror 37 is arranged above the photosensitive drum 3. Furthermore, a filter 38 is provided between the main lens 35 and the fourth mirror. In the vicinity of the main lens 35, a color CD51 and a color CCD5 are provided.
CCD lens 51a for focusing the original image on 1
is fixedly placed.

As the filter 38, two types of filters, an infrared cut filter and a cyan filter, are configured to be switchable in front of the main lens 35.

A copy paper feeding/conveying system is provided at the bottom of the copying machine main body l, and the paper feeding section 40 is composed of a first paper feeding section 41, a second paper feeding section 42, and a manual paper feeding section 43. has been done.

The copy paper 100 in the first paper feed section 41 is fed to the paper feed roller 4
4. The copy paper 100 manually fed from the manual paper feeder 43 is transferred to the transport roller pair 45.
Accordingly, the copy paper 100 in the second paper feed section 42 is further fed by the paper feed roller 47. Then, the fed copy paper 100 is moved to a timing roller 46, respectively.
The copy paper 100 is conveyed to the opposing part between the transfer belt 15 and the secondary transfer charger 24, and passes there.
The sheet is sent to a fixing device 49 by a conveyor belt 48 and then discharged to a paper discharge section 30 .

Operation of the Copying Machine The basic copying operation of the copying machine having the above configuration will be explained with reference to FIG.

When the print switch is turned on with an original placed on the original table glass 26, the photosensitive drum 3 rotates in the direction of arrow a based on the drive of the main motor 2, and
Its outer peripheral surface is charged to a predetermined potential by the discharge of the charger 4.

In the optical system 27, the sliders 28, 32 each correspond to the arrow d.
The reflected light of the light irradiated onto the document from the exposure lamp 29 is reflected by the mirrors 31, 33, 34 and the filter 3.
8. The photoreceptor drum 3 is exposed to light through the lens 35 and mirrors 36 and 37 to form an electrostatic latent image.

Next, the surface of the photoreceptor drum 3 is irradiated with light from the editing eraser 5 to the portions corresponding to the front end, rear end, and both ends of the image area on which the electrostatic latent image is formed, so that electric charges are generated. removed. As will be described later, based on the detection result of color 〇〇D51, the charge of the image corresponding to the predetermined color is also erased.

Subsequently, toner is supplied to the electrostatic latent image from a predetermined developing device at a portion facing the developing device 6, and a toner image is obtained.

On the other hand, in the transfer device 11, the main motor 2 drives the pressure roller 16 to move upward to the state shown in FIG. is lightly touched, and in this state arrow C
While being rotated in the direction, a charge is uniformly applied by the electrification charger 21. Note that the moving speed of the transfer belt 15 is set to be the same as the circumferential speed of the photoreceptor drum 3, so that there is no relative variation between the two.

With the transfer device 11 set as described above,
When the toner image formed on the surface of the photosensitive drum 3 is sent to the contact portion with the transfer belt 15, the toner image is electrostatically transferred to the transfer belt 15 based on the charge applied by the charger 21. Primary transfer is performed.

After the photosensitive drum 3 has passed through the portion facing the transfer belt 15, residual toner is removed by a cleaning device 22, and then the residual charge is erased by a main motor 23 in preparation for the next image formation.

The toner image transferred to the transfer belt 15 is transferred to the transfer belt 1
5 is conveyed in the direction of arrow C.

The above copying operation is repeated for each color of yellow, magenta, cyan, and black, and toner images formed in each color are transferred onto the transfer belt 15 in an overlapping manner to form a multicolor image.

On the other hand, the copy paper lOO supplied from the paper feed section 40 is fed out from the timing roller 46 in synchronization with the toner image, and is caused by the discharge of the secondary transfer charger 24 at the portion facing the secondary transfer charger 24. The toner image is secondarily transferred onto copy paper 100.

The copy paper 100 on which the toner image has been transferred is separated from the transfer belt 15 by the separation charger 25 and conveyed to the fixing device 49 by the conveyor belt 48, where the toner image is melted and fixed, and then transferred to the paper discharge section 30. is discharged.

Note that, after passing through a portion facing the second transfer charger 24,
The belt 15 that has lost toner is removed by a cleaning device 19
The residual toner is removed at the part facing the charger 2.
At 0, residual charges are erased to prepare for the next transfer operation.

Operation Panel FIG. 3 is a plan view of an operation panel provided in the copying machine main body 1 and for instructing the copying machine main body 1 to perform various operations.

A key 300 is a print switch for starting a copying operation, and a key group 302 is a numeric keypad for setting the number of copies and inputting other information. Also, 30
1 is L'ED for displaying the number of copies set using the numeric keypad 302.

Keys 305 and 306 are keys for setting the copy magnification, and 307 is an LED that displays the copy magnification. Keys 308 and 310 are manual exposure setting keys, key 308 is used to increase the exposure, and key 310 is used to decrease the exposure. This exposure level is displayed by LED group 311. Further, the key 309 is a key for setting automatic exposure, and the LED 322 is for indicating that automatic exposure is set. Key 303 is a clear/stop key, and key 304 is an interrupt key. 323 is a display area showing the status of the copying machine. 323a is a display indicating that the capacity of waste toner is exceeded, and 323b is an interrupt key 304.
323c is a paper jam display, and 323d is a toner empty display. 325
330 are switches and selection display LEDs corresponding to the developing devices of each color, respectively. Also, 331 and 332 are l
These are a switch for switching between the development copy mode and the multiple development copy mode, and a selection display LED.

Color Copying Operation FIGS. 4 and 5 are diagrams for explaining the operation during color copying.

FIGS. 4(a) and 4(b) show the flow of document reading and image formation, respectively.

In document reading, first, the R, G, and B data output from the color CD 51 is converted into color data for each COD reading unit (step #1), and then the C
A process of converting the color data of the reading unit of the OD into color data of the erase unit by the editing eraser 5 is performed (step #2), and the data is stored in the memory (step #3
). This process is performed, for example, for A3 size documents.

Further, although the process is divided into steps #1 to #3, in reality, these processes are repeatedly performed.

In the image forming operation, first, the document is irradiated with a lamp, and an electrostatic latent image is formed on the photoreceptor drum through a lens and a mirror (formation of an electrostatic latent image using an analog process) (step #4). ), the unnecessary latent image is erased by the editing eraser 5 in correspondence with the developing color to be currently operated based on the data stored in the memory by scanning the original (step #5), and the currently selected developing color is erased using the editing eraser 5. The device performs visualization using toner (step #6).
, transfer the toner image onto the transfer belt (step #7).

Additionally, the processes of steps #4 to #7 are repeated for each color toner, and when the process is completed for gold (
YES in step #8), the image is transferred to paper (step #9), fusing and fixing is performed (step #lO), and the paper is ejected (step #11).

In this embodiment, normally the first developing device 7 (yellow), the second developing device 8 (magenta), and the third developing device 9 (cyan)
After each of the and fourth developing devices 10 (black) performs the processing in steps #4 to #7, the process moves to step #9 and realizes a color copying operation.

FIG. 5 explains the color copying operation using an example.

FIG. 5(a) is an example of a color original 50. As shown in FIG.

It consists of a black rectangle, a yellow square, a red circle, and a green triangle on a white background. These are separated and separated from each other.

This original 50 is placed on the original table glass 26, and scanning for reading the original is executed. The light reflected from the original is C
The light enters the color CD 51 through the CD lens 51a. Image processing, which will be described later, is performed on the output from the color 〇〇D51, and black, yellow, red, green, and white of each color-coded portion of the original image is determined. Color 〇CD
For 51, a conventional red (R) filter, green (G) filter, and blue (B) 7 (filter) are used, which are alternately provided in each light receiving part of the COD.As one unit of color reading, the red ,green,
3 CCDs each with 3 blue color filters in 1
The reflected light from the original passes through these filters and is output for each of R, G, and B. These output R
, G, and B signals to determine the color of the original image.

A first scan is performed on the document (a), and the photosensitive drum 3 is exposed. Prior to this exposure, the photoreceptor drum 3 is uniformly charged to a predetermined polarity by a charging charger 4, and by exposure, an electrostatic latent image of the entire document is formed on the photoreceptor drum 3. This is shown in (bl) of FIG. In this example, yellow (y), magenta (m), cyan (C), black (b)
Since the developing devices are selected in the order of toner color k) and are developed, in the first time, only an electrostatic latent image containing a yellow component is left, so a black rectangular part that does not require development with yellow toner is left behind. The latent image of Edit Eraser 5
will be erased by This situation is shown in FIG. 5 (cl). Note that since red is created by a mixture of yellow and magenta toners, and green is created by a mixture of yellow and cyan toners, the electrostatic latent images in the red circular portion and the green triangular portion are not erased.

Then, this yellow latent image passes through the first developing device f17, and the yellow toner is deposited on the photosensitive drum 3, as shown in FIG.
It is visualized as in di). This photosensitive drum 3
The upper yellow toner image is transferred to the transfer belt I5. This is shown in FIG. 5 (el).

The same operation as the first time is repeated for the second time. An electrostatic latent image is formed on the photoreceptor drum 3 from the document (a) ((b2) in FIG. 5), and includes a black rectangular area, a yellow square area, and a green triangular area that do not require development with magenta toner. The electrostatic latent image is erased by the editing eraser 5, leaving only the red circular latent image ((c in Fig. 5).
2)). Then, this is visualized by the magenta toner of the second developing device 8 ((a2) in FIG. 5), and the magenta toner is transferred onto the transfer belt 15 on which the yellow toner image was transferred in the first time. ((e2) in Figure 5). As shown in (e2) of FIG. 5, the circular area where yellow and magenta toners are mixed becomes red.

The same operation as above is repeated for the third time as well.

An electrostatic latent image is formed on the photosensitive drum 3 from the document (a) ((b3) in FIG. 5), and includes a black rectangular area, a yellow square area, and a red circular area that do not require development with cyan toner. The electrostatic latent image is erased by the editing eraser 5, leaving only the green triangular latent image ((see Fig. 5).
c3)). This is visualized by the cyan toner of the third developing device 9 ((d3) in FIG. 5), and the first yellow toner image and the second magenta toner image are transferred to the transfer belt H5. Transfer cyan toner on top (
(e3) in Figure 5). As shown in (e3) in Figure 5,
The triangular area where the yellow and cyan toners are mixed becomes green.

The same operation as above is repeated for the fourth time as well.

An electrostatic latent image is formed on the photoreceptor drum 3 from the document (a) ((b4) in FIG. 5), and a yellow square part, a red circular part, and a green triangular part that do not require development with black toner are formed on the photoreceptor drum 3 ((b4) in FIG. 5). The electrostatic latent image is erased by the editing eraser 5, leaving only a black rectangular latent image ((c4) in FIG. 5). Then, this is visualized by the black toner of the fourth developing device IO (Fig. 5 (d4)), and the first yellow toner image, the second magenta toner image, and the third cyan toner image. The black toner is transferred onto the transfer belt 15 onto which has been transferred ((e4 in FIG. 5).
)).

In this way, the first to fourth operations are performed, and a toner image corresponding to the color of the original image is formed on the transfer belt 15. This is transferred onto the fed paper (FIG. 5(f)), and the actual color of the original is reproduced on the paper.

Note that marks are attached to the transfer belt 15, which are detected by a sensor (not shown) so that the toners of each color are transferred onto the transfer belt 15 without misalignment.

FIGS. 6(a) and 6(b) are schematic block diagrams of the image processing section and the editing eraser 5 control section. This will be explained below.

The image information detected by the color CCD 51 is R,
G and B are output as serial analog signals, and timing is taken to separate each of R, G, and B into parallel signals in the color separation unit 52, and the amplifiers 202a to 2
Signal amplification with 02c, A/DI inverter 203a to 203
A/D conversion is performed at c to convert it into a digital signal. This digital signal is sent to the shading correction section 53.

In the shading correction unit 53, the digital signals are selected for each of R, G, and B by the selector 204, read out via the buffer 205, and stored in the shading correction RAM 207 according to the address signal from the address generation unit 206 and the shading. According to the contents of the shading correction ROM 208 in which a table for correction is stored, variations in output inherent to the pixels of color CI) 51 and variations in output caused by the optical system 27 are corrected.

Note that the shading correction RAM 207 stores data obtained by reading one line of a reference white pattern (not shown) provided on the back side of a document scale provided at the end of the document placement portion of the document placement table.

The shading-corrected data is sent to the color determining section 54. The sent data is latched 209 for each R, G, and B.
latched by a to 209c, and refer to the table in the color determination ROM 210 to determine which of the seven colors yellow, magenta, cyan, black, red, green, and white it is based on the values of each component of R, G, and H. and converted to color data. The content of this conversion is the color data of the document reading unit described above.

The data converter 55 converts the color data in units of reading by the color ○○D 51 to the color data in units of erase by the editing eraser 5.

In this embodiment, processing is performed every three lines.

The data of the 1st line and 2nd line is R for line memory.
AM213 and AM214 respectively, and when the third line data comes in, it is synchronized by a synchronization signal (not shown), and the selector 216 selects three pieces of color data for each line via latches 215a to 215c. Total 9
The gate 218a corresponding to each color is selected by the decoder 217 depending on which color is yellow, magenta, cyan, red, green, black, or white from the top. Output to ~218g.

Each gate 218a to 218g is opened by a signal output from the decoder 217 and a data counting pulse input in synchronization with the signal output, and therefore, the data counting section 2
19a to 219g each count the colors included in nine pieces of data. Although not shown, once the nine colors have been counted, the data counting units 219a to 219a
219g are each reset to prepare for the next count.

The selector 220 first selects the data count section 219a.
The values of ~219d (yellow, magenta, cyan, red) are sent to the next pitch conversion ROM 221, the converted values are held in the latch 222 while referring to the table therein, and then the data count units 219e to 219g The values of (green, black, white) are sent to the pitch conversion ROM 221, and by referring to the values held in the latch 222 and the table in the ROM 221, one color is selected, converted, and held in the latch 223. The data latched by the latch 223 is color data for each erase unit, and is sent to the color limitation detection section 57 in parallel with the memory section 56, as shown in FIG. 6(b).

The memory unit 56 stores the color data in erase units from the data conversion unit 55 in the RAM 227 in accordance with the address signal created by the address creation unit 225. The data from the data converter 55 and the address signal from the address generator 225 are sent to the buffer 224 and the buffer 2, respectively.
26 to the RAM 227.

The color limitation detecting section 57 is provided to check and store the contents of the output data from the data converting section 55 in the memory section 56 in parallel with storing the output data in the memory section 56. For example, if the original color is only black, as explained in Figure 5, even though developing devices for yellow, magenta, and cyan toners are not used, the first to third toner In other words, the editing eraser 5
As a result, each electrostatic latent image is erased, resulting in a huge waste of time and cost.
By referring to the contents of this color limitation detection section 57,
By omitting the development of yellow, magenta, and cyan colors,
Only black development is performed to prevent loss.

The one-screen information of the color data of the document stored in the memory unit 56 is read out from the RAM 227 of the memory unit 56 via the buffers 228 and 229 by the microcomputer CPU 232 in the ECP 58 during the development operation, and is sent to the editing eraser 5. Edit eraser controller 59 that controls
is output to.

The color information of the original is read by COD and stored in the memory 227.
The storage process and the color limitation detection process are performed using hardware, thereby reducing the processing time.

Control configuration of the copying machine FIG. 7 is a schematic block diagram of the control of the copying machine in this embodiment.

Usually, a copying machine is not controlled by one microcomputer, but by multiple microcomputers. In this embodiment, it is controlled by three microcomputers.

The main control unit 150 is a part that controls the processes of the copying machine, that is, sequence control of paper feeding, conveyance, fixing, exposure, etc., and control of input and display of the operation panel and communication between microcomputers.

The ECP 58 mainly controls the data processing section 70, as described above.

The scanner control unit 160 controls a scan motor (not shown) that drives the first slider 28 and the second slider 32 of the optical system 27.

The three blocks mentioned above are connected by communication lines for exchanging data and are synchronized.

Data Conversion Method The data conversion method performed by the data conversion section 55 described above will be described below. Therefore, first of all, color CCD51
The following describes the reading unit.

Color COD reading unit> The effective light-receiving pixels of the color CCD 51 used in this example are 2.
The number shall be 250. Assuming that the scanning width of the original is 3001 m, the three data of R, G, and B are considered as one set.
Image reading pitch is 300-(2250-3)=0.4
(mm), and the color of the document can be identified for each pitch. This pitch relates to the main scanning direction, and the reading pitch in the sub-scanning direction changes depending on the scanning speed of the optical system and the charge accumulation time of the COD, but in this embodiment, it is set to 0°4nyo. Therefore, the reading unit data for color 〇〇D51 in this embodiment is data for an area of 0.4 mm x 0, 4 mm on the original.

FIG. 8 shows an example of the output of the color CCD 51.

As shown in the figure, it can be seen that the outputs obtained when light passes through the R, G, and B filters are sequentially generated as serial analog values. The shaded area represents the signal level that is document information. (R,,G□B,) of the signal in the figure.

(R1+1.G, 4.B, .), etc. are each set as one set, and one set is the original 0.4nvn x 0.4
This is color information for an area of mm. The aforementioned color determination section extracts only the signal components of these signals, separates them into R, G, and B, performs A/D conversion, and performs shading correction. From this data, for example, yellow, magenta, cyan, Converts colors into seven colors: red, green, black, and white.

FIG. 9 shows an example of output data from the color determining section described above. The color data is coded for each color as shown in the figure, and 3
Outputs as a bit digital signal. "000"
, “OOl”, “010”, “011”, “100”,”
101" and "llO# represent yellow, magenta, cyan, green, red, black, and white, respectively.

<Conversion from reading unit to erase unit> Edit eraser 5
As mentioned above, the LED array of 1.
Each LED 65 is arranged at a pitch of 2 mm. Therefore, the erase unit in the main scanning direction on the photosensitive drum 3 is also a pitch of 1.2 m. Furthermore, the pitch of each erase unit in the sub-scanning direction on the photoconductor drum 3 depends on the rotation speed of the photoconductor drum 30 and the time it takes for the data processing section 70 to rewrite and output data to the LED eraser 5; In the example, it is set to 1.2 rrn. Therefore, the erase unit on the photosensitive drum 3 is 1.2++n+X1.
．． The area will be 2 mm. On the other hand, as mentioned above, the reading unit of the original by color 〇〇D51 is 0.4+nnX9.
4mm, and the erase unit is larger, so if you erase it as is, there will be inconveniences such as necessary image information being lost. It is necessary to convert the color data to the same size as the erase unit. The data conversion section 55 is for performing this processing.

FIG. 10 schematically shows this data conversion. Reading unit by color CCD51 is 0.4mmX
The length of the sail is 4 m, and the erase unit by the LED array of the editing eraser 5 is 1.2 m + w x 1.2 mm, so the color data for 3 x 3 COD units in Figure 1O is calculated for one piece using the predetermined calculation method. Convert to color data in units of LED erase.

FIG. 11 shows a simplified flow of an example of the calculation method for the above data conversion, and will be described below.

First, the color data of nine color COD reading units is checked and divided into the following four cases.

(1) When one color data other than white is the most common.

(2) When the color with the most white data can be selected from among the other colors.

(3) In case of own data only.

(4) When there are many colors other than white melon, but the color with the highest number cannot be selected, or when the own data has the highest number, but among other colors, the color with the highest number cannot be selected.

In case (1), the most common color is stored in the memory section as color data for each LED erase unit.

In the case of (2), the second most common color after white is stored in the memory as color data for each LED erase unit.

In the case of (3), white is the color data for each LED erase unit.

In the case of (4), if the colors are completely different, in such a case there is no problem in determining that it is black to the human eye, so the color data of each LED erase unit is treated as black data, and similar colors are used. If many colors (for example, red and magenta) are mixed, a priority is given in advance and the one with the higher priority is selected.

In the cases (1) to (4) above, the reason why white is given lower priority than other colors is that white can be erased by the photosensitive drum due to the reflected light from the light irradiation on the original, even if it is not forcibly erased. This is because no electrostatic latent image is formed by exposure to light. Conversely, if you give priority to white, especially (1), (
In the cases 2) and (4), the color of the LED erase unit is set to white, which is inconvenient because information on the document is lost.

Specific conversion examples in cases (1) to (4) are shown in FIGS. 12 and 13.

(1) in FIG. 12 is an example in which red is the color data for the LED erase unit because red is the most common color data among the color data for nine units read by the CCD.

(2) in Figure 12 shows that among the color data for nine reading units by COD, red is the second most common color after white.
This is an example of color data in erase units.

(3) in FIG. 12 is an example in which white is used as the color data for the LED erase unit since the color data for nine COD reading units are all white.

(4) in Figure 12 is an example in which black is used as the color data for the LED erase unit, since the color data for 9 COD reading units are completely different and do not include similar colors. .

Figure 13 shows that when similar colors such as red and magenta are mixed in the color data read by the CCD in units of 91', and red is given a higher priority, red is used as color data in the LED erase unit. This is an example.

Furthermore, although majority voting is used to select the color that is most commonly used, all colors may be prioritized (weighted) and determined.

An example of how to determine priorities will be explained. As mentioned above, it is necessary to lower the priority of white, and considering the actual color development of plotters, printers, felt-tip pens, markers, etc., the colors are usually black, red, cyan, green, and yellow.
After all, it is preferable that the priority order is 1...black 2...red 3...cyan 4...green 5...yellow 6...magenta 7...white.

FIG. 14(a) is an example of the structure of color data for each LED erase unit in the data conversion section, and is represented by 4-bit data. Bit B3. B2. Bl.

BO is a first developing device 7, a second developing device 8, and a third developing device, respectively.
They are assigned correspondingly to the developing device 9 and the fourth developing device IO. Here, if the bit is "1n", the LED lights up,'
0" means that the LED is off. Specifically, the 14th
This will be explained using the example shown in (b) of the figure. In this example, the LED
The color data for each erase unit is red. The upper two bits are “O” and the lower two bits are “1”. In other words, the first
When operating the developing device 7 (yellow toner), since the pitches 1-83 corresponding to the first developing device 7 are 0'', the electrostatic latent image on the photosensitive drum 3 remains without being erased, and the yellow toner remains. The toner is applied, visualized, and transferred to the transfer belt 1.
5. Next, when the second developing device 8 (magenta toner) is operated, the bit B2 corresponding to the second developing device 8 is ``0'', so the electrostatic latent image on the photosensitive drum 3 is not erased. Then, the magenta toner is visualized and multiple-transferred onto the yellow toner previously placed on the transfer belt 15, creating a red color.

When the third developing device 9 and the fourth developing device 10 are operated, the bits Bl and BO corresponding to these are "B", respectively, so the electrostatic latent image on the photoreceptor drum 3 is erased, and the cyan toner and No black toner.

With this data structure, in the ECP58 program that controls the editing eraser 5,
Edit eraser 5's LE can be erased by simply checking the status of each bit.
It becomes possible to control the D array, improving control speed.

Principle of data reconversion> Incidentally, the light emitted from each LED element 65 of the actual editing eraser 5 has the property that the amount of light is greatest at the center and decreases toward the edges. . Therefore, unless the LED elements 65 overlap each other's light to some extent on the surface of the photoreceptor and mutually compensate for the lack of light intensity at the edges, it will not be possible to completely erase the range within the erase unit. , the light amount ripple becomes large and erase defects occur.

FIGS. 16(a), (b), and (c) are diagrams for explaining the above-mentioned overlapping of lights (for simplicity, only the main scanning direction will be explained), and they show the overlap of the LEDs on the photoreceptor surface. Indicates the state of light irradiation. Here, L
An example is shown in which the erase bit due to ED is 1.2m. The shaded area in FIG. 16(a) is the area where the lights of adjacent LED elements overlap when the editing eraser 5 is fully lit. Further, FIG. 16(b) is a graph showing the intensity of the amount of light on the photoreceptor surface, with the horizontal axis representing the length of the editing eraser 5 in the main scanning direction when the editing eraser 5 is fully lit. From this graph, it can be seen that in the overlapping part of the light, the light amount is LE
It can be seen that the recovery has been made to the same extent as the center of the D element.

On the other hand, as described above, although it is good to turn on all the LEDs, in actual use, it is not always the case that only each LED is turned on. Figure 16(c) shows that every other LED
It shows the irradiated and non-irradiated portions of the photoreceptor surface when the light is turned on. It can be seen that the area of the irradiated portion is larger than the area of the non-irradiated portion, and is also larger than the ideal erase bit. Therefore, the end portion of the portion that should not be erased may also be erased. This results in omission or alteration of image information, resulting in a multicolor image forming apparatus with poor reproducibility. This example will be explained with reference to FIG.

FIG. 17(a) shows a part of the document to be read, and FIG. 17(b) shows it in nine erase units. For the sake of simplicity, it is assumed that the color, shape, and arrangement of the manuscript exactly match those expressed in erase units.

One central square is black, and the surrounding eight squares are magenta.

Image creation is performed using this FIG. 17(b) as image data. First, in magenta development, since the black portion is erased, the LED of the editing eraser irradiates the black portion on the photoreceptor surface with light. However, Fig. 16 (
As explained in a), (b), and (c), L
The ED light does not fit exactly within the erase unit, but also shines on the slightly adjacent erase unit, so instead of erasing only the erase unit that should be erased, The magenta part around the black part is also slightly erased. After the black portion has been erased, the image visualized with magenta toner is shown in FIG. 17(c). In Fig. 47(c), the black part is shown as "no image", but due to the characteristics of the editing eraser's LED, it is darker than the actual black part.
The rotation is getting bigger.

Next, in black development, the magenta portion is erased, but as mentioned above, when the magenta is erased, the adjacent black portion is exposed to light, and the black portion is also slightly erased. A visualization of this is shown in FIG. 17(d). It can be seen that the area of the "no image" part is larger, and the area of the black part is smaller than that of the actual original.

Fig. 17(c) and Fig. 17(d) are superimposed and transferred to the transfer belt, and the visualized image is shown in Fig. 17(d).
Shown in e). As explained above, the shaded area is a part that is not converted into a toner image because the LED of the editing eraser is erased more than the erase unit.

As explained above, conventionally, the editing eraser L
Due to the characteristics of ED, it is inevitable that the original image information of the document, especially the shape, will change. The present invention has been made to solve this drawback.

FIG. 17(f) shows an example to which the present invention is applied. In order to prevent unnecessary erasure, black data in the center is converted to magenta data. Therefore, during image formation, all of this area is developed with magenta, but on the photoconductor, the potential of the electrostatic latent image corresponding to black is higher than the potential of the electrostatic latent image corresponding to magenta, and the black area More magenta toner adheres to this area, resulting in a darker magenta area than the rest of the area, and although the color changes from the original black to magenta, information regarding the shape of the document is not lost.

Further, although it is inevitable that a change in hue occurs, the area of the portion where the hue changes is minute when viewed from the entire document image, so it does not feel strange.

Figure 18 (a), (b), (c), (d)
Next, an example of a change in image information caused by the erase bit of the LED being larger than the reading pitch of the COD will be explained. Here, for simplicity, we will use the LE of the above editing eraser.
- The characteristics of D are assumed to be ideal.

FIG. 18(a) shows a part of the document to be read. There is a black triangular part in the center of the flap.

Other parts are magenta. FIG. 18(b) shows it divided into erase units. This figure 18 (
When the original in a) is read and converted into erase units, the color data becomes as shown in FIG. 18(c), and a visualized image of this is shown in FIG. 18(d). As you can see, the original black triangle has been transformed into a square. That is, it means that the information regarding the shape of the document is changing. This is not desirable in a copying machine. FIG. 18(e) shows an example in which the color data in FIG. 48(c) is converted by applying the present invention and visualized using this data.

The principle of this visualization is that an electrostatic latent image corresponding to FIG. 18(a) is actually formed on the photoreceptor.
The fact that the electrostatic potential corresponding to the black triangular portion is higher than the electrostatic potential corresponding to the other magenta portions is utilized.

That is, the entire image including the black triangular portion is converted and stored as magenta (12), and this data is used to erase the electrostatic latent image on the photoreceptor. In this case, color components other than magenta, that is, cyan, yellow, and black, will be erased, and conversely, magenta will not be erased. Then, the triangular part, which is originally black, becomes magenta, and when magenta toner is visualized, because the electrostatic potential of the black part is high, a lot of toner adheres to that part, resulting in a dark color. This results in the formation of a toner image of . Therefore, the triangular part is visualized in magenta, and although the color changes, no image information about the shape is lost. Also, the triangular part is not black,
If the electrostatic potential is lower than magenta, for example yellow, the amount of toner adhering to the triangular area will be reduced and the image will be visualized as a lighter magenta, but information about the shape will not be lost. .

In this way, when visualizing an image using the converted color data, it is inevitable that the hue will change, but when looking at the entire original image, the area of the part where the hue changes is
Since it is a minute portion, information regarding the shape of the document is not lost, and there is almost no sense of discomfort.

<Data reconversion> FIG. 19 shows the data converted from the color data of the read unit to the color data of the erase unit according to the present invention.
Furthermore, an example of a schematic flow for converting color data into image-based erase unit color data to prevent changes in shape will be shown.

In this embodiment, in order to save memory capacity, the erase unit data is divided into 3.times.3 blocks, and data reconversion is performed for each block.

First, the color data for each erase unit of the block to be converted (9 pieces in total) is examined and divided into the following five types.

(1) When one color data other than white is the most common.

(2) In case of own data only.

(3) When white data is the most abundant and the color data that is the most abundant can be selected from among the other colors.

(4) There are two or more types of colors that are the most common except for white data,
And if they are not of similar colors.

(5) There are two or more types of colors that are the most common except for white data,
And if they are only of similar colors.

In the case of (1), the color is converted to the most common color.

In case (2), no conversion is performed and the LED corresponding to this erase unit is turned off during all toner development steps. This is because there is no need to erase the electrostatic latent image for white, and unnecessary erasing causes a lack of information regarding the shape of the document image during image formation due to the light emitting characteristics of the LED element, and also wastes power. This is because the heat is consumed and furthermore, the heat exerts an adverse effect on the photoreceptor.

In the case of (3), the color data is converted to the second most common color data after white.

In case (4), convert to black data.

In the case of (5), the color is converted to the color with the higher priority.

The above data reconversion is performed by the CPU 232 of the ECP 58 in FIG. Ru. Here, the RAM 227 is also used to store the reconverted data to save storage capacity, but a separate storage means may be provided and the data may be stored there.

Figure 20 (a), (b), (c), (d)
, (e) shows an example of conversion according to the above flow.

FIG. 20(a) is an example of case (1) of the flow of FIG. 19. Since red is the most common color, it is converted to red.

FIG. 20(b) is an example of case (3) of the flow of FIG. 19. Red is the most common color next to white, so it is converted to red.

FIG. 20(c) is an example of case (4) of the flow of FIG. 49. The most common colors other than white are red, green, and black, two of each, and since these are not all similar colors, they are converted to black.

FIG. 20(d) is an example of case (5) of the flow of FIG. 19. Red and magenta both have 4 pieces,
Moreover, since these are similar colors, they are converted to red, which has a higher priority.

FIG. 20(e) is an example of case (2) of the flow of FIG. 19. Since the data is for white only, all LEDs are erased.

Color Limitation Detection Section FIG. 15 shows a schematic block diagram of the color limitation detection section 57.

As described above, the color limitation detection unit 57 is configured to detect color reproduction in advance in order to shorten the image forming operation time without operating the developing device for toner that is not used in color copying of an original that has only a certain limited number of colors. , is provided to check the colors on the original. The configuration and operation of this color limitation detection section 57 will be explained below by giving an example.

In the figure (7) B3. B2. B1. BO is each bit of color data in units of LED erase explained in FIG.

Furthermore, the data count pulse is a pulse that is output in synchronization with the data conversion of each LED erase unit, and is a pulse that is output in synchronization with the data conversion of each LED erase unit.
) is input along with 83~BO, and the contents of 83~BO (
"O" or "IN" determines whether or not to output a count pulse to the next stage data counting section.Gates (gl) to (B4) are used when the contents of B3 to BO are "0". Only outputs a data count pulse to the data count section.To explain when the color data is yellow as an example,
The data is "Q II, 11" in order from the upper bit.
．． 1", "1", and "l", only the gate (gl) is open. Therefore, "c1 data count section (h
A count pulse is output to 1). The same applies to other cases, and for each color data of the LED erase unit, the data count section (hl),
Count operations (h2), (h3), and (h4) are executed.

If the above operation is performed once [integration is performed, the data count section (
In hl), (h2), (h3), and (h4), data necessary and unnecessary for the operation of the developing devices 7 to 10 is accumulated for one document, respectively.

1 [After the reading of the integral is completed, the ECP 58 sends a signal to the data selector i, and the data count section (hl), (h
2) The contents of (h3) and (h4) can be selectively read out, and if some have a count value of zero,
Color-limited detection becomes possible by not using the developing device of the corresponding color. Note that in this color limitation, if the count value is not zero, but is a value that can be ignored compared to the maximum value, it may be ignored.

This color-limited detection eliminates the need to operate a developing device that does not need to operate, thereby improving the image forming speed.

Although various embodiments have been listed above, the present invention is not limited to these embodiments, and various changes and modifications can be made within the scope of the claims.

(Effect of the invention) In a multicolor image forming apparatus that erases an electrostatic latent image using a light emitting element array such as an LED array, color data in units of reading is converted to color data in units of erase, and this converted color data is converted into color data in units of erase. By reconverting the color data according to the actual image, it reduces the lack of image information regarding the shape due to the light emitting characteristics of light emitting elements such as LEDs and the erase bit of the light emitting elements being larger than the reading pitch of COD etc. be able to.

Regarding the change in the hue of the reproduced image according to the present invention, since the area of the portion where the hue changes is minute when viewed from the entire document, it is possible to create a reproduced image with a hue that is almost faithful to the original.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a copying machine to which the present invention can be applied. FIG. 2 is a schematic diagram of the COD array eraser. FIG. 3 is a plan view of an example of the operation panel of the copying machine. FIGS. 4(a) and 4(b) are flowcharts of document reading and image formation, respectively. FIG. 5 is a diagram showing the progress of a color copying operation. FIGS. 6(a) and 6(b) are schematic block diagrams of the data processing section. FIG. 7 is a schematic control block diagram of the copying machine. FIG. 8 is a diagram showing an example of color COD output. FIG. 9 is a diagram showing an example of encoding of output data. FIG. 10 is a schematic diagram of conversion from read unit data to erase unit data in the data converter. FIG. 11 is a simplified flowchart of data conversion. 12 and 13 are specific examples of data conversion according to FIG. 11. FIG. 14(a) is a diagram showing the structure of color data for each LED erase unit in the data converter. FIG. 14(b) is a diagram showing the structure of color data for red. FIG. 15 is a schematic block diagram of the color detection and limitation section. FIGS. 16(a), (b), and (c) are diagrams each illustrating the light emission characteristics of the LED array. Figure 17 (a), (b), (c), (d)
, (e) are diagrams each illustrating the loss of image information due to the LED erasing a range larger than the erase unit. FIG. 17 (D is the result of applying the present invention to FIG. 17(a),
It is a figure which shows the effect of the omission prevention of image information demonstrated in (b), (c), (d), and (e). Figure 18 (a), (b), (c), (d)
are diagrams each illustrating the loss of image information due to the erase bit being larger than the reading pitch. Figure 18(e) is similar to Figure 18(a), (b),
It is a figure which shows the effect of the omission prevention of image information explained in (c) and (d). FIG. 19 is a schematic flowchart of data reconversion according to the present invention. Figure 20 (a), (b), (c), (d)
, (e) are examples of data reconversion using the schematic 70-chart in FIG. 19, respectively. l... Copying machine, 3... Photosensitive drum, 5... Editing eraser, 7... First developing device, 8... Second developing device, 9... Third developing device, 10 ...Fourth developing device,
15...Transfer belt, 29...Lamp, 4...
Fixing device, 50... Original, 51... Color CCD,
55... Data conversion section, 56... Memory section, 57.
...Color limited detection unit, 58...ECP, 70...Data processing device, 100...Peichi/Riichi patent applicant Minolta Camera Co., Ltd. agent
Patent attorney Aohaku Ao Haka 1 person 4a4 Figure 7 Figure 10. . o (7) tsmiyY 1J Mu iq:
0.4X0.4 mrn/dotLED 7 L=
Erase Hayabusa tL: 1.2X+, 2mm/
dat Figure 8 Figure 9 Figure 11 Section (a) Figure 13 Figure 14 (b) Figure 15 Figure 16 (C) (e) Figure 17 (d) 18th Zuma Vinter (''θ 20th figure

Claims (1)

[Claims] (1) The original is irradiated with light, and the reflected light is exposed to the uniformly charged surface of the photoreceptor to form an electrostatic latent image corresponding to the original image, while the original image is colored by the original reading means. Based on the obtained image data for each color, the photoreceptor on which the electrostatic latent image has been formed is selectively irradiated with light by an erase means, leaving the area to be developed with toner. After erasing the other parts, the remaining electrostatic latent image is developed using toner of the corresponding color, and the process of transferring the developed toner image to the intermediate transfer medium is repeated at least once, and then the intermediate transfer medium is In a multicolor image forming apparatus that forms a multicolor toner image on paper and then transfers it to paper and fixes it to form a multicolor image, the color data read by the original reading means is used as the reading unit of the original reading means. means for converting into erase units of erase units of different sizes in a predetermined manner, storage means for storing color data converted into erase units, and dividing the original image into blocks each including a predetermined number of erase units. Then, the color data corresponding to each block is sequentially read out from the storage means, the color distribution state is detected, and the color data is sequentially re-converted according to the detected color distribution state and stored again in the storage means. What is claimed is: 1. A multicolor image forming apparatus, comprising: means for erasing; and drive control means for driving the erase means based on color data stored in the storage means.