JPH0227375A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To eliminate unnaturalness caused by the naked eye and to decrease the omission of image information by converting color data to black at the time when colors whose number is the largest except white exist by two kinds or more at the time of converting plural color data of a read unit to single color data of an erasion unit. CONSTITUTION:Color data read by a color CCD 51 of an original reading means is converted to color data of an erasion unit of an erasing means 5 whose size is different from that of a read unit and stored in a memory 70, and based on its color data, the erasing means 5 is controlled. In this case, a single color is converted to colors whose number if the largest except white when two colors or more are mixed in its color and converted to black when it exists more than two kinds. In such a way, unnaturalness caused by the naked eye is eliminated, image information is not erased at the time of erasion, and also, the memory capacity can be reduced and the cost is reduced, and the control speed and the operation speed can be improved.

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 print static images for each color on a photoreceptor. A multicolor image forming apparatus that reproduces a multicolor image by repeating the steps of forming an electrostatic latent image, developing it using toner of a corresponding color, and transferring the toner image to an intermediate transfer medium is well known. There is.

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. 1984-194469).

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 simplified mechanically. The arrangement pitch (erase unit) of the elements is determined by the CCD array used as a document reading means.
If the arrangement pitch (reading unit) of CCD elements is the same, the cost will be the same as that of a writing head using an LED array, and the cost will be higher than the original purpose. There was a problem in that the erased area could not be reproduced with the accuracy read by the .

More specifically, the erase pitch is usually made to be an integral multiple of the reading pitch (-3.4 times for boat fishing), and the area of the erase unit on the photoreceptor is 9 times the area of the CCD read unit. Or 16 times. Therefore, in 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 is either There was a problem that one of the image information was missing.

(Problem to be solved by the invention) 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 photoreceptor differs depending on the brightness of the color. , it has been proposed to distinguish between colors that should be erased and colors that should not be erased by erasing only the electrostatic latent image with a lower surface potential. However, with this method, when there is a large difference in brightness, such as black and red, the red electrostatic latent image is certainly erased, but the black electrostatic latent image is visualized. When this happens, the black toner image inevitably overlaps the red (or magenta and yellow) toner image, resulting in a change in color tone. Furthermore, if colors with small differences in brightness are 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, making it difficult to erase the image information. This results in a lack of information. 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 addition, since color data is stored in memory for each COD reading unit, a large capacity memory is required, resulting in poor memory efficiency (and the process of accessing its contents takes time; furthermore, manufacturing There are also costs involved.

In another application dated the same date as the present application, the applicant has disclosed that the color data of the reading unit by the color CD is
A multicolor image forming apparatus is proposed in which color data is converted into erase unit color data by a D editing eraser and stored in a memory, and the editing eraser is controlled based on the converted data.The problem is that image deletion occurs. However, in order to convert color data in units of reading to color data in units of erase, it is necessary to
Various methods are possible.

An object of the present invention is to convert color data in units of reading into color data in units of erase, drive and control an editing eraser based on the converted color data, thereby reducing memory capacity and manufacturing costs. To provide a color data conversion method that can prevent image information from being lost as much as possible, regardless of the magnitude of the difference in brightness of color information in a document, in a multicolor image forming device designed to improve processing speed. That's true.

(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 image is exposed to light to form an electrostatic latent image corresponding to the original image, while the original image is separated into colors by the original reading means, and based on the image data for each color obtained, the electrostatic latent image is formed 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 step 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 image. In the multicolor image forming apparatus, the color data read by the original reading means is converted into an erase unit of the erase means having a size different from the reading unit of the original reading means in a predetermined manner, and a means for converting the color data into the erase unit. and drive control means for driving the erase means based on the color data stored in the storage means. When converting data into color data of a single erase unit, if the color data of a predetermined number of original scanning units included in the erase unit are all the same color, convert to that color, and two or more colors are mixed. However, if there is one color that is the most common color other than white, it is converted to that color, and if there are two or more colors that are the most common color other than white, it is converted to black.

(Function) In a multicolor image forming apparatus, when color data in units of reading by a color CCD is converted to color data in units of erase by an erase unit and stored in memory, in the case of a single color, converting to that color, If two or more colors are mixed, convert to the color with the largest number other than white, and if there are two or more colors with the largest number other than white, convert to black, and erase based on the converted data. Control the means.

(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 body 1 so as to be rotatable 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 an LED array in which LED elements are arranged in a holder arranged 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. Further, the pitch P of each LED 65 is set to 1.2 mm in this embodiment. As will be described later, the timing of turning on and turning off each LED 65 is individually controlled.

The developing device 6 consists of four developing units 7, 8, 9, and 10.
These move in the vertical direction (in the direction of arrow bb') as a whole, and are configured so that toner can be supplied to the surface of the photosensitive drum 3 from any developing device. , magenta toner (Tm)
, cyan toner (Tc), black toner (Tbk)
) contains toner. Note that the developing device 6 is not limited to a type that can move up and down as described above, but may be of a type that can selectively supply toner of different colors to the photosensitive drum 3. The device 11 temporarily transfers and holds the toner supplied onto the photoreceptor drum 3 onto a transfer belt 15, and this transfer belt 15 is made of a conductive base made of conductive polyester containing carbon resin or the like. Rollers 12 and 13 are provided with a dielectric material such as polyethylene on their surfaces and are arranged parallel to the photosensitive drum 3.
．． 14 and is supported.

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 between the rollers 13 and 14 along the transfer belt 15, 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 sliter 32 (on the scanning 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 CCD 51 and a color CCD 5 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 i, 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 4I 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 second configuration will be explained with reference to FIG.

When the button switch is turned on with an original placed on the original platen 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 6. The photoreceptor drums 1 and 3 are exposed to light through mirrors 31, 33, 34, filter 38, lens 35 and mirror 36, 37 to form electrostatic latent images.

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 the color CCD 51, the charge of the image corresponding to a 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 no relative fluctuation occurs 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 of the colors yellow, magenta, cyan, and plaque, and the 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 100 fed from the paper feed section 40 is fed out from the timing roller 46 in synchronization with the toner image, and at the portion facing the secondary transfer charger 24, the copy paper 100 is fed by the discharge of 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.

Cow-300 is a print switch for starting a copying operation, and key group 302 is a numeric keypad for setting the number of copies and inputting other information. Also, 30
1 is an LED 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 3 ] and O are keys for manual exposure setting, 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 amount of waste toner is over, 323b is a display indicating that the interrupt key 304 has been pressed, 323C is a paper jam display, and 323d is a toner empty display.

325 to 330 are switches and selection display LEDs corresponding to the developing devices of each color, respectively. Also, 331.33
Reference numeral 2 denotes a switch for switching between the single 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 CCD 51 is converted into color data for each CCD reading unit (step #l), and then the CCD data is converted into color data for each CCD reading unit.
A process of converting the color data of the CD read unit 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).
). In this process, for example, an A3 size document is analyzed.

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 original is irradiated with a lamp, and an electrostatic latent image is formed on the photoreceptor drum through a lens and mirror (formation of an electrostatic latent image using an analog process). #4) Based on the data stored in the memory by scanning the original, the editing eraser 5 erases the unnecessary latent image in correspondence with the developing color to be operated currently (step #5), and the currently selected latent image is erased using the editing eraser 5. Visualization is performed using toner in the developing device (step #6).
), transfer the toner image to 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 CCD 51 through the CD lens 51a. The output from the color CCD 51 is subjected to image processing, which will be described later, to determine black, yellow, red, green, and white of each color-coded portion of the original image. Color CCD
51, a conventional one in which a red (R) filter, a green (G) filter, and a blue (B) filter are alternately provided in each light receiving section of the CCD is used. One unit of color reading is 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 is erased by the editing eraser 5. 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 7, and the yellow toner is deposited on the photosensitive drum 3, as shown in FIG.
It is visualized as in i). The yellow toner image on the photosensitive drum 3 is transferred onto the transfer belt 15. This is shown in (e[) of FIG. 5.

The same operation as the first time is repeated for the second time. A static 74 latent image is formed on the photoreceptor drum 3 from the original (a) (
(b2) in Fig. 5), the electrostatic latent images in the black rectangular area, yellow square area, and green triangular area that do not require development with magenta toner are erased by the editing eraser 5, and only the red circular area is erased. A latent image is left (see Figure 5).
c2)). Then, this is visualized by the magenta toner of the second developing device 8 ((d2) in FIG. 5), and the first
Magenta toner is transferred onto the transfer belt 15 onto which the yellow toner image was transferred in the second transfer ((e2) in FIG. 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 is transferred to the transfer belt 15 to which the first yellow toner image and the second magenta toner image are transferred. Cyan toner is transferred thereon ((e3) in FIG. 5). As shown in (e3) of FIG. 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). This is visualized by the black toner of the fourth developing device 10 (FIG. 5 (d4)), resulting in a first yellow toner image, a second magenta toner image, and a 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 ((r) in FIG. 5), 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,
The signals are output as serial analog signals of G and B, and timing is taken to separate them into parallel signals for each of R, G, and B in the color separation section 52, and the signals are sent to the amplifier 202a.
~ Signal amplification at 202C, A/D:) inverter 203a ~
A/D conversion is performed at 203c to convert it into a digital signal. This digital signal is sent to an aging 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 are processed according to the address signal from the address generation unit 206 and the contents stored in the shading correction RAM 207 and/or According to the contents of the shading correction ROM 208 in which a table for kneading correction is stored, variations in output inherent to pixels of the color CCD 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 data subjected to the aging correction is sent to the color determining section 54. The sent data is latched 209 for each R, G, and B.
It is latched by a to 209C, and the value of each component of R, G, and B determines which of the seven colors yellow, magenta, /un, black, red, green, and white is stored in the color judgment ROM 21.0. Converted to color data by referring to a table. The content of this conversion is the color data of the document reading unit described above.

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

In this embodiment, processing is performed every three lines.

1st line and 2nd line data are for line memory R
They are stored in the 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 the latches 215a to 215C. Total 9
The decoder 217 selects each color data and selects a game corresponding to each color (in the figure, depending on which color is yellow, magenta, cyan, red, green, black, or white from the top) 218a to 218g.

Each of the gates 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, each of the data counting units 219a to 219g counts the colors included in the nine pieces of data. count. Although not shown, when the counting of nine colors is completed, the data counting section 219a
~219g are each reset to prepare for the next count.

The selector 220 first selects the data counting units 219a to 219a.
The values of 219d (yellow, magenta, cyan, red) are sent to the next pitch conversion ROM 221, and while referring to the table therein, the converted values are held in the latch 222, and then the data count units 219e to 219g ( The values (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 each color of yellow, magenta, and red,
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. is output to five edit eraser controllers that control the.

The color information of the original is read by COD and memo IJ 2
The processing for storing data in the 27 and the color limitation detection processing are performed by 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 section 150 is a section that controls the processes of the copying machine, that is, sequence control of paper feeding, conveyance, fixing, exposure, etc., as well as human power of the operation panel, display, and communication control 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.

Color COD Reading Unit The reading unit of the color CCD 51 will now be described.

The effective light receiving pixels of the color CD51 used in this example are 2.
The number shall be 250. Assuming that the scanning width of the original is 300 mm, the three data of R, G, and B are considered as one set, so the image scanning pitch is 300 ÷ (2250 ÷ 3) - 〇,
4 (ms), and the color of the document can be identified for each pitch. This pitch is related 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 CCD, but in this example, it is 0.4 mps.
shall be. Therefore, the reading unit data of the color CCD 51 in this embodiment is data for an area of 0.4 an x 0.4 m 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 by passing the light through the R filter, G filter, and B filter, respectively, are sequentially generated as unreal analog values. The shaded area represents the signal level that is document information. (R,, Gn, Bn) of the signal in the figure.

(R11,,,Gn,,,Bn,,),... are each set as one set, and one set is 0.4w x 0.
This is the color information of the area bone of 4■. The aforementioned color determination unit extracts only the signal components of these signals, separates them into R, G, and B, performs A/D conversion, and performs aging correction. From this data, for example, yellow, magenta, Color conversion to seven colors: cyan, 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
It is output as a pit digital signal. "000"
, “00F,” “oto” “011”, “100”, “l
ot" and "110" represent yellow, magenta, cyan, green, red, black, and white, respectively.

As described above, in the LED array of the data conversion unit editing eraser 5, the LEDs 65 are arranged at a pitch of 1.2 m in the main scanning direction. Therefore, the erase unit on the photosensitive drum 3 in the main scanning direction is also 1.2 pitches. Also,
The pitch of each erase unit in the sub-scanning direction on the photoconductor drum 3 depends on the rotational speed of the photoconductor drum 3 and the time it takes for the data processing section 70 to rewrite and output data to the LED eraser 5, but in this implementation In the example, it is 1.2 mm. Therefore, the erase unit on the photosensitive drum 3 is 1.2WX
1.2ff1! The area will be l. On the other hand, color CCD
As mentioned above, the reading unit of the manuscript according to 51 is 0.4a.
I11 x 0.4-, and the erase unit is larger, so if you erase it as is, there will be problems such as missing necessary image information, so color CCD
It is necessary to convert the color data in the reading unit of the document by the editing eraser 51 into color data having the same size as the erase unit by the editing eraser 5. The data conversion section 55 is for performing this processing.

FIG. 1O schematically shows this data conversion. Color 〇 Reading unit by CD51 is 0.4 kan x 0
14■, and the erase unit by the LED array of the editing eraser 5 is 1.2m x 1.2IIn.
The color data for 3×3 CCD units shown in FIG. 10 is converted into color data for one LED erase unit using a predetermined calculation method.

FIG. 11 shows a simplified flow of the calculation method for the above data conversion.

For data conversion, in the example shown in Figure 10, it is necessary to select one out of nine pieces of color data, but the color to be selected must be determined so that as little image information as possible is lost during erasing. . Therefore, it is usually appropriate to select the most common color from nine color data, but if the most common color is white, if you decide on white as is, the white part of the document will not be visible when reading the document. The reflected light erases the charge on the photoreceptor drum and no electrostatic latent image is formed, so there is no need to erase it again using the LED eraser.

Therefore, in the present invention, first, the color data of nine color CCD reading units belonging to one erase unit 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 data that has the most own data can be selected from among the other colors.

(3) In case of white data only.

(4) When there are many color data other than 1, but the most common color data cannot be selected, or when white data is the most common, but the most common color data cannot be selected for other colors.

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), there is often no problem in determining that the color is black to the human eye, so it is convenient to use black data as the color data for each LED erase unit because only one development operation is required.

In the above cases (1) to (4), white is given lower priority than other colors. This is because, as described above, in white, an electrostatic latent image is not formed by exposing the photosensitive drum 3 to light reflected from the light irradiated on the original, even if it is not forcibly erased.

Conversely, if you give priority to white, especially (1), (2),
In the case of (4), the color of the LED erase unit is set to white, which is inconvenient because the information of the document is lost.

Although not specifically mentioned, the paper used is usually white, and if paper of another color is used, it is preferable to lower the priority of that color to prevent unnecessary erasing. result.

FIG. 12 shows specific conversion examples in cases (1) to (4).

(1) in FIG. 12 is an example in which red is used as the color data for the LED erase unit because red is the most common color data among the color data for nine COD reading units.

In (2) of Figure 12, red is the second most common color among the nine CCD reading units, so red is used as an LED.
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 units read by the CCD are all white.

(4) in Figure 12 shows that the color data for 9 reading units by COD includes 2 each of red, cyan, white, black, and 1 green, and it is not possible to determine the most common color other than white. , is an example in which black is used as color data for each LED erase unit.

FIG. 13(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 10. Here, if the bit is “1”, the LED lights up, “
0'' means the LED is off. Specifically, the 13th
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. upper 2 biy')
is "O" and the lower two bits are "l". In other words,
When operating the first developing device 7 (yellow toner), since the bit B3 corresponding to the first developing device 7 is "0", the electrostatic latent image on the photosensitive drum 3 remains without being erased. The yellow toner is applied, becomes a visible image, and is transferred to the transfer belt 15. Next, when the second developing device 8 (magenta toner) is operated, since the pins 1-82 corresponding to the second developing device 8 are "0", the electrostatic latent image on the photoreceptor drum 3 is erased. Instead, the magenta toner is visualized and multiple-transferred onto the yellow toner previously placed on the transfer belt 15, creating a red color.

When operating the third developing device 9 and the fourth developing device 10, the corresponding bits B1 and BO are set to "1", respectively.
Therefore, the electrostatic latent image on the photoreceptor drum 3 is erased, and the cyan toner and blur are removed.

Kutner does not ride.

With this data structure, in the ECP58 program that controls the editing eraser 5,
Just by checking the status of each bit, the L of editing eraser 5
It becomes possible to control the ED array, improving control speed.

Color Limited Detection Section FIG. 14 shows a schematic diagram of the configuration of the color limited 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.

B3 in the diagram. B2. Bl and BO are each bit of the color data of the LED erase unit explained in FIG. In addition, the data count pulse is a pulse that is output in synchronization with data conversion for each LED erase unit, and is a pulse that is output at the gate (g
l), (g2), (g3), (g4) 83~B
It is input together with O, and depending on the contents of 83 to BO (0" or 1"), the data count section (hl) of the next stage, (t
It is determined whether or not to output count pulses to (r2), (h3), and (h4). Gate (gl) ~ (g4)
outputs a data count pulse to the data count section only when the contents of 83 to BO are 'O'. Taking the case where the color data is yellow as an example, the data is sequentially "0", " 1”.

Since 'l'' and 'vi, only the gate (gl) is ovend. Therefore, a count pulse is output to the data counter (hi). The same applies to other cases, and LE
For each D-erase unit color data, the data count section (hl), (h2)
, (h3), and (h4) are executed.

If you perform the above operation for one document, the data count section (
hr), (bz), (h3), and (h4) respectively store data necessary and unnecessary for the operations of the developing devices 7 to IO in the document bone.

After the reading of one document is completed, a signal is sent from the ECP58 to the data selector i, and the data count section (hl), (
The contents of h2), (h3), and (h4) can be selectively read out, and if there is a count value of zero, it is possible to avoid using the developing device of the corresponding color. Color-limited detection becomes possible. 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.

(Effects of the Invention) Utilizing the fact that the erase unit by the LED erase device is larger than the reading unit by the CCD document reader, data in the original reading unit is converted into data in the erase unit in advance and stored in the memory. This allows the memory capacity to be reduced.

Specifically, the color CCD reading unit is 0.4wXO4-
When 1 LED erase unit is 1.2m x 1.2mm, 300mm in the main scanning direction and 43mm in the sub-scanning direction
4. Consider reading and storing the original data of 4-. If the color CCD reading unit is stored in memory as it is, (30010,4) X (434,410,4) =
814,500 color data are stored.

On the other hand, if you store it in memory in LED erase units, (300/1.2) x (434,4/1.2) =
90,500 (pieces) of color data are stored.

As can be seen from this example, the read and erase unit size of this embodiment requires only 1/9th the memory capacity.
Since a memory with a small capacity can be used, manufacturing costs are reduced.

In particular, when converting multiple color data in a reading unit to single color data in an erase unit, the color with the largest number is basically selected from a predetermined number of reading units included in the erase unit. If white is the most abundant color, choose the next most numerous color, or if you cannot choose the most abundant color other than white, do not force yourself to choose any color. In addition, by using black as the conversion color data, it eliminates unnaturalness that appears to the naked eye, eliminates important image information during erasing, reduces the loss of image information when forming multicolor images, and improves sharpness and color tone. You can get color cubes with little change.

Furthermore, the LED eraser can be controlled simply by referring to the converted data, improving control speed.

Furthermore, as in this embodiment, the color data storage process is performed only by hardware during the document reading operation, so the operating speed is improved.

[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 (1)) 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. FIG. 12 is a specific example of data conversion according to FIG. 11. FIG. 13(a) is a diagram showing the structure of color data for each LED erase unit in the data converter. FIG. 13(b) is a diagram showing the structure of color data for red. FIG. 14 is a schematic block diagram of the color detection and limitation section. ■... 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, 49...Fixing device, 50...Original, 5I...Color CCD, 55...
Data conversion section, 56... Memory section, 57... Color limitation detection section, 58... ECP, 70 - Data processing device, 10
0...Beichinomer Figure 4 (a) (b) Patent applicant Minolta Camera Co., Ltd. Agent
Patent attorney Blue and White 葆 Haka 1 person Figure 13 Figure 7 (b) Figure 8 Figure 10 CCDn mymi T2 Rimu fL: 0.4X0.4
mrn/dotLED 7 Ray Erase
1.2X1.2 mm/dat Fig. 11

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 erase units of different sizes into erase units by a predetermined method, storage means for storing color data converted into erase units, and driving the erase means based on the color data stored in the storage means. and drive control means for converting the color data of a predetermined number of document reading units into the color data of a single erase unit. If the color data of a scanning unit is all the same color, convert it to that color, and if two or more colors are mixed and the largest number of colors other than white is one, convert it to that color, and convert it to that color if it is a color other than white. The most common color is 2
A multicolor image forming apparatus characterized in that when there are more than one type, the image is converted to black.