JPH0863048A - Color image forming device - Google Patents

Abstract

PURPOSE: To match the number of single/full color image forming times actually performed with the counted value of a monochrome counter/full color counter by discriminating whether an image to be formed is chromatic color or achromatic color. CONSTITUTION: A chromatic color decision unit 790 decides whether the inputted image is chromatic or achromatic for every picture element or every fine area block. In the case of an achromatic that is, monochrome mode, transfer paper on which a toner image has been transferred once is separated from a transfer drum and ejected to a paper ejection tray after the toner image is fixed by a fixing device, then the monochrome counter 234m counts up by one. Meanwhile, in the case of a chromatic, that is, full color mode, one color image is formed on the transfer paper by repeating processes for forming and transferring the toner image four times. At the time of all finishing transferring the toner image, the transfer paper is separated from the transfer drum and ejected to the paper ejection tray after the toner image is fixed by the fixing device, then the full color counter 234 counts up by one.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus, and more particularly to a chromatic or achromatic image to be formed on the basis of a given image signal or a color signal obtained by converting the image signal into a recording signal of each color component. If it is achromatic, a specific color (for example, Bk, C, M, Y, R, G, B 1
Image formation is performed to complete one image formation, and when the color is chromatic, four colors Bk, C, M, Y or three colors C, M,
The present invention relates to a color image forming apparatus that forms a Y image and completes the formation of one image.

[0002]

2. Description of the Related Art Conventionally, in a digital color copying machine, a color facsimile or the like, a chromatic color area and an achromatic color area of an input image are discriminated by an input image signal, and based on the result, the entire input image is an achromatic color original or a chromatic color. It is determined that the document is an original and various processing contents are switched according to the determination result.

For example, a color copying machine of a certain type is provided with a scanner for inputting an image by performing optical scanning as an input means, with only one set of image reproducing unit, and by repeating a copying process a plurality of times, a full color image is obtained. Get the image. That is, the copy process for each of the four basic colors of cyan (C), magenta (M), yellow (Y), and black (Bk) (or only three of C, M, and Y) is sequentially executed,
These color images are transferred onto one recording sheet in an overlapping manner. When the single color mode is executed, only one image is transferred onto the recording sheet by one copy process (in the case of any one of Bk, C, M and Y colors). If it also has R, G, and B monochromatic modes, when these are selected, two images of C, M, and Y, that is, two copy processes form one image. Therefore, in this type of copying machine, the time required for the copying operation is significantly different between the full color mode and the single color mode, and the operator must be careful when switching the color mode. It is necessary to perform a switching operation as appropriate.

In order to eliminate the troublesomeness of this kind of mode switching, in the technique disclosed in Japanese Patent Laid-Open No. 63-107274, it is determined whether the original image is a specific color (specific single color), and the specific color is determined. Only the sequence operation of full color and the sequence operation of full color are switched. A color copier equipped with an automatic chromatic / achromatic color switching function with a specific color black has already been released. By the way, as an operation, the one that determines whether the original is chromatic color or achromatic color (black single color) by prescan, and then decides and controls whether to operate in full color mode or monochrome mode (prescan method) , The first image forming color is black, and whether the chromatic color or the achromatic color is determined at the time of black image formation and whether the operation for the subsequent image forming color (C, M, Y) is continued or whether the transfer discharge is performed as it is There are two methods, one that decides (pre-scanless method) and the other.

As a mode of the copying machine, the automatic chromatic color determination (ACS) described above is used.
In addition to ct), it is equipped with a full color mode and a single color mode for forming an image in a single color such as Bk, C, M and Y. By adding R, G, B and the like to the single color mode, There is also a mode in which two colors of C, M, and Y are used for each image formation (expressing a single color by two copy processes), and each single color is selected.

It goes without saying that a desired single-color image can be obtained even if the original is colored by these selections, but the maintenance and maintenance fee of the copying machine differs between the full-color mode and the single-color mode (full-color mode). Therefore, the counter is set separately according to the selected mode (full color or single color). That is, a full color counter and a single color counter are provided, and when one image is recorded in a single color mode, the single color counter is incremented by 1 and when one image is recorded in a full color mode, a full color is recorded. The counter is incremented by 1.

[0007]

If the full-color mode is selected even if the original is a black-and-white original, the full-color counter operates even if black monochromatic recording is automatically selected by the automatic chromatic color determination (ACS). Counting up, consumption of toner etc. becomes at least a full color fee. For this reason, the operator must switch to the single color mode designation in order to make the count by the monochromatic counter in the case of a black and white document.

Further, there is a control of the Bk amount in various image processing for forming an output image with respect to an input image. This is a technique called undercolor removal (UCR), which uses C, M,
From the data amount of Y, for example, the common part, that is, C, M, Y
Is set to Bk, and this value is subtracted from C, M and Y to obtain new C, M and Y values. In this technology, 100% UCR processing in which the minimum value of C, M, and Y is Bk is generally used for line drawings, etc. However, if 100% UCR is used in the design area, black is left on the entire floor, There are various problems such as lack of control, and a skeleton black method has been proposed in which the amount of black is switched between 50% and 90% of the minimum values of C, M, and Y, and this ratio is switched according to the amount of data. ing. In addition, it is determined whether the fine area of the image is black and whether it is the character area or the picture area, or when the character mode is selected, the color component is output for the black character. There are some that are trying to improve the reproducibility of black characters by suppressing it. When the full color mode is selected from these two points, the color component amount of the output image may not be determined only by the color component amount of the input image, and black single color recording is selected by automatic chromatic color determination (ACS). If there is, full color
Recording may be selected, and operator single /
In some cases, the full color designation does not match the image formation result.

An object of the present invention is to match the number of single / full color image formations actually performed by the color image forming apparatus with the count value of the single color counter / full color counter.

[0010]

In the color image forming apparatus of the present invention, the input means for inputting an image signal and the input image signal are black (Bk), cyan (C), magenta (M).
And means for converting a color signal for one or more of yellow (Y) image formation, means for determining whether an image to be formed is a chromatic color or an achromatic color, A means for forming an image represented by a color signal and, when the judging means judges that the color is chromatic, the image forming means carries out overprinting of at least three of the four colors, and when one recording is completed, a full color is completed. The counter is incremented by one, and when the discriminating means determines that the color is achromatic, the image forming means records two or less colors out of the four colors, and when the recording of one sheet is completed, the single color counter is incremented by one. Image forming control means.

[0011]

When the discriminating means determines that the color is chromatic, the image forming control means performs the superposed recording of at least three colors of the four colors Bk, C, M and Y by the image forming means and completes the recording of one sheet. When the full color counter is incremented by 1 and the determination means determines that the color is achromatic, the image forming control means causes the image forming means to record two or less of the four colors and completes the recording of one sheet. Is incremented by 1, the number of single / full color image formations actually performed by the color image forming apparatus and the count value of the single color counter / full color counter match.
Even if the operator does not switch to single color mode designation, the correct number of single / full color image formations is counted.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0013]

【Example】

First Embodiment FIG. 2 shows a one-drum type digital color copying machine as one of image forming apparatuses for carrying out the present invention. In FIG. 2, 100 is a laser printer, 200 is an automatic document feeder, 300 is a repeating board, and 400 is an image scanner.

The ADF 200 is an image scanner 400.
It is located above. It is possible to hold a large number of originals placed on the original table 210. When performing the paper feeding operation, the calling roller 212 abuts on the upper surface of the uppermost document, and rotates to feed the abutted document. Reference numeral 312 is a separation roller for avoiding double feeding. The document fed to the predetermined position is pulled out by the pull-out roller 217 and the conveyance belt 216.
Image scanner contact glass 4 driven by
01 is further conveyed to a predetermined reading position, that is, stopped when the leading edge of the document reaches the left end position of the contact glass. When the reading is completed, the conveyance belt 216 is driven again, so that the original on the contact glass is discharged and the next original is sent to the reading position. An optical sensor 211 for detecting whether or not there is a document table is provided in front of the calling roller 212. An optical sensor 214 for detecting the leading edge and size of the document is provided between the separation roller 213 and the pullout roller 217. The optical sensor 214 is composed of a plurality of sensors arranged at different positions in the main scanning direction (perpendicular to the paper surface), and the size of the original in the main scanning direction, that is, the original, depending on the combination of the detection states of these sensors. The width can be detected. Further, a drive motor (not shown) is provided with a pulse generator that outputs a pulse corresponding to the rotation amount, and the ADF control device causes the document to pass through the optical sensor 214 so that the document size in the sub-scanning direction, that is, the document size. Detect the length. The calling roller 212 and the separation roller 213 are driven by a paper feeding motor, and the pullout roller 217 and the transportation belt 216 are driven by a transportation motor. The optical sensor 215 arranged downstream of the pull-out roller 217 is a registration sensor.

The image scanner 400 mechanically drives the image reading unit arranged below the contact glass 401 in the left-right direction in the drawing, and sub-scans it. The light emitted from the illumination lamp 402 is reflected on the surface of the original placed on the contact glass 401 according to the density of the original image. The reflected light, that is, the detected light image passes through many mirrors and lenses and is incident on the dichroic prism 410.

The dichroic prism 410 splits the incident light into three colors of R, G and B according to the wavelength. The three separated lights are incident on different one-dimensional CCD image sensors. Therefore, the image scanner 400
The R, G, and B color components of one line in the main scanning direction on the original image are simultaneously detected by the three one-dimensional image sensors provided in the image information processing device 700.
(Fig. 1). Next, the laser printer 100 will be described. Reproduction of an image is performed on the photosensitive drum 1. Around the photosensitive drum 1, a charger 5, a writing unit 3, a developing unit 4, a transfer drum 2, a cleaning unit 6 and the like are provided.

First, the surface of the photosensitive drum 1 is uniformly charged to a high potential by the corona current generated by the charging charger 5. When this surface is irradiated with laser light emitted from the laser diode of the writing unit 3, the charging potential changes according to the intensity of the light. That is, a potential distribution according to the presence or absence of laser light irradiation is formed on the photosensitive drum 1.

The laser light emitted from the laser diode of the writing unit 3 is polygonal mirror 3b, lens 3c and mirror 3.
It is irradiated onto the surface of the photosensitive drum 1 through d and the lens 3e. The polygonal mirror 3b is rotationally driven at a high speed and a constant speed by the electric motor 3a. The control device applies a binary signal (recording / non-recording) for each pixel to be recorded to the laser diode so that each pixel position is synchronized with the rotation position of the polygon mirror 3b. That is, at each scanning position of the image, the laser light is turned off / off according to the density (recording / non-recording) of the pixel. Therefore, the potential distribution formed on the photosensitive drum 1 corresponds to the light and shade of the original image and forms an electrostatic latent image.

This electrostatic latent image is visualized by the toner of the developing device arranged downstream of the writing unit 3. In this embodiment, the developing unit 4 is provided with four sets of developing devices 4M, 4C, 4Y, and 4BK,
Toners of different colors of M (magenta), C (cyan), Y (yellow) and BK (black) are held in the respective developing devices.

In the case of this printer, any one of the four developing devices is selectively energized, and the electrostatic latent image formed once is visualized with toner of M, C, Y or BK color.

On the other hand, the transfer paper held in the cassette 11 is fed out by the paper feed roller 12 and the registration roller 1
It is sent to the surface of the transfer drum 2 via 3 and moves with the rotation of the transfer drum 2 in a state of being superposed on the surface. Then, in the state of being close to the surface of the photosensitive drum 1,
The toner image formed on the photosensitive drum 1 is transferred to the surface of the transfer paper by the bias of the transfer charger 7.

In the single color mode, the transfer paper after one transfer of the toner image (one color) is separated from the transfer drum 2, fixed by the fixing device 9 and discharged to the discharge tray 10. The single color counter 234m counts up by 1. In the case of the full color mode, it is necessary to superimpose the four colors of BK, M, C and Y on one sheet of transfer paper. In that case, first, a BK color toner image is formed on the photosensitive drum 1 and transferred to a transfer paper, and then the transfer paper is not separated from the transfer drum 2 and then the M color toner image is transferred onto the photosensitive drum 1. A toner image is formed, and the toner image is transferred to the transfer paper again. Further, for the C color and the Y color, the toner image is formed on the photosensitive drum 1 and the toner image is transferred to the transfer paper. That is, one color image is formed on the transfer paper by repeating the process of forming and transferring the toner image four times. When the transfer of all the toner images is completed, the transfer paper is separated from the transfer drum 2, the toner image is fixed by the fixing device, and then discharged to the paper discharge tray 10, and the full color counter 234f counts up by one.

FIG. 1 shows an outline of the structure of the electric component part of the apparatus shown in FIG. The control of the entire apparatus is controlled by the system controller 50 mainly including a microcomputer. The synchronization control circuit 60 generates various clock pulses as a reference of control timing, and in order to synchronize the signals between the control units, various signals are given to the synchronization control circuit 60, and the synchronization control circuit 60 receives the signals. Various signals are given to each control unit. In this example, the main scanning synchronization signal that is the basis of the scanning timing appears in synchronization with the scanning position of the polygonal mirror of the laser printer 100.

The image scanner 400 A / D-converts the read image signals of R, G, and B colors and outputs each as 8-bit color image information. The image color information is output to the laser printer 100 after undergoing various processes in the image information processing apparatus 700. Image information processing device 700
Each unit includes a γ correction unit 730, a color conversion (complementary color generation) unit 750, a UCR (under color separation) unit 760, a selector 770, a gradation processing unit 780, and a chromatic color determination unit 790. In the complementary color generation by the color conversion unit 750, each information of R, G, B (color reading information) is converted into information of each color of C, M, Y (recording color information) using a masking equation or the like. UC
In the R unit 760, the lower color Bk (Bk density determined by the minimum value) is calculated from the minimum value of C, M, Y, and the black component (Y, corresponding to the lower color Bk, from the input Y, M, C signals) is calculated. M, C
Level) is removed. This is the undercolor removal (Under C
color Remove). UCR unit 76
At 0, different lower color levels are extracted in the character mode (text mode) and the photograph mode (halftone mode). The UCR unit 760 will be described in more detail later.

The output of the γ correction unit 730 is sent to the color conversion unit 750 and the chromaticity judgment unit 790. The chromatic determination unit 790 determines whether the input image is chromatic or achromatic for each pixel or each minute area block. The chromatic determination unit 790 also performs image separation. In this case, it is determined whether it is a line drawing or a pattern portion for each pixel or each minute area block. The determination signal is sent to the color conversion unit 750, the UCR unit 760 and the gradation processing unit 780, and the UCR unit 7
In 60, it is used to select the black amount (the lower color Bk level to be extracted), and in the gradation processing unit 780, it is used to select the dither pattern.

The selector 770 receives the color signals Y, M, C, B according to the instruction from the system controller 600.
Any one of K is selectively output and given to the gradation processing circuit unit 780. The gradation processing unit 780 is adapted to perform dither processing on the inputted 8-bit density information. The image information that has been subjected to dithering is laser printer 1
Given to 00.

The UCR unit 760, when in the character mode or the separation mode, if the image separation signal is a character,
C, M, Y are calculated from R, G, B by a non-linear matrix operation, and the minimum value of C, M, Y is set as Bk. Further, Bk is subtracted from C, M, Y, and new C ', M',
Y'is output as a C, M, Y signal. This relationship is shown in FIG. Here, if the chromatic / achromatic color determination for each pixel or each minute area block is an achromatic color, the C, M, and Y signals may be set to 0. In the photo mode or the image separation mode, if the image separation signal is a pattern, C, M,
The minimum value of Y itself is not set to Bk, but 70% to 90% of the minimum value is set to Bk. This ratio does not have to be constant with respect to all the minimum values, and when the data is small, it is almost 0%, and the ratio may be increased as the data becomes larger (skeleton black method). In any case, the reason why the black amount is not set to 100% in this way is that if it is set to 100%, the black component is mixed over the entire printed image, so that it is difficult to match C, M, and Y with the gradation. This is because there is a problem that the depth of the full-color image disappears. However, even with 100%, it is a fact that image deterioration can be suppressed as much as possible by controlling the parameters of the gradation processing after this, as compared with the case of about 80%. The Bk calculated in this way is subtracted from C, M and Y to obtain new C, M and Y, as in the case of characters. Here, in order to simplify the UCR circuit, Bk is calculated at the same time when C, M, and Y are calculated from R, G, and B, and in the UCR, the Bk is simply
It is also possible to subtract from M and Y.

In the case of a single color mode such as Bk, C, M, Y, R, G, B, a signal including all color components is calculated in advance from the R, G, B signals by color correction. (For example, R: G: B is set to 3: 6: 1), the UCR unit 760 outputs this signal itself. When the single color selection is Bk, C, M or Y, the system controller 600 selects and controls one of the image forming units. If a color such as R, G, B that requires image formation more than twice is selected, this operation is repeated. The colors that can be selected as a single color are Bk,
If the values of C, M, and Y cannot be realized with the same value, it goes without saying that the values that match the values are calculated by color correction. In the single color mode, the signal is calculated regardless of the mode or the image separation result.

FIG. 4 shows the configuration of the chromatic color determination unit 790. R for each pixel output from the scanner 400
Each 8-bit GB data is stored in the γ of the image information processing device 700.
The gradation balance for each color is adjusted by the correction unit 730, and the result is supplied to the chromatic color determination unit 790. The chromatic color determination unit 790 determines the maximum value (d) of the RGB difference.
[I, j] = ΔRGB) is calculated (791 in FIG. 4).
Next, the number of pixels in which d [i, j] is smaller than a threshold Th1 defined in units of 4 lines × 4 pixels is counted (792).
~ 795). When this number is larger than the threshold value Th2 of 16 pixels, this block is determined to be a chromatic color block (795 to 798). The determination signal for each block has two counters 797, 799 for counting the chromatic color block frequency and continuity, and both count up. Continuity counter 799
When the block determination result becomes achromatic, it is reset. When one of the two counters 797 and 799 reaches a preset value, it is determined that this document is chromatic. The chromatic color determination is operated only during Bk image formation, or the determination result is valid only during Bk image formation.

When it is not determined that the color is chromatic at the time of Bk image formation, the system controller 600 controls so that the transfer sheet is discharged as it is, and when the transfer sheet is set, the monochromatic counter 234m is incremented by one. The image obtained here is exactly the same as in the single color monochrome mode.

Color correction of the color conversion unit 750 using the chromatic / achromatic judgment signal (output of 798 in FIG. 4), and U
Switching of the removal rate of the lower color Bk of the CR unit 760 will be described with reference to FIG. When creating Bk, first
For the color, set Bk single mode color correction (753 in FIG. 5).
The "achromatic color coefficient" is selected by the selector 752 and given to the masking circuit 751), and undercolor removal is set in the UCR unit 760. Here, a scanning operation for Bk image formation is performed, and at the same time, chromatic color determination is started. If the chromatic color determination unit 790 determines that the color is chromatic, the scan line No. at that time is determined. Is written in the register 803 of FIG. 4, a signal representing a chromatic color is sent to the color conversion unit 750 and the UCR unit 760, and these are switched for full color. That is, the low-color lower color Bk removal is set (the “color coefficient 80% of 753 in FIG. 5 is selected by the selector 752 and given to the masking circuit 751), and the lower color removal is set in the UCR unit 760. To do.
When the scan for Bk image formation is finished, C image formation is started next. At the start, the immediately preceding Bk image formation is the "achromatic color coefficient".
Since it is a high-density process using, "corresponding to this, a 100% chromatic color coefficient" that is suitable for high-density undercolor Bk removal
Is set (selected by the selector 752 in FIG. 5). Then, the scan scans the line No. stored in the register 803.
Then, the comparator 802 generates a switching signal, and in response thereto, the color conversion unit 750 sets "a chromatic color coefficient of 80%" adapted to the removal of the low density lower color Bk (FIG. 5).
Selected by the selector 752). This is the “chromatic color coefficient 80 set after the determination of chromatic color during Bk image formation.
% ”. When the C image formation is completed, the M image formation and the Y image formation are executed by the same coefficient switching as in the C image formation described above. As described above, a full-color image in which the Bk image, the C image, the M image, and the Y image are superimposed and transferred is formed on the recording paper of the transfer drum 2, and when the transfer of the Y image is completed, the recording paper is separated from the transfer drum 2. Then, it is sent to the fixing device 9. The system controller 600 increments the full color counter 234f by 1 when transfer discharge (delivery to the fixing device 9) is set. When the copy number setting value is 2 or more, the image formation of the second sheet is started, but in the continuous copy after the second sheet, the "chromatic color" is displayed during the image formation of the first sheet. Since it has been obtained, the low density undercolor Bk removal is set from the beginning of the Bk image formation (FIG. 5).
753 “Coefficient for chromatic color 80%” is selected by the selector 752 and given to the masking circuit 751). Other colors (C,
The same applies to the image formation of M, Y). Even in the image formation of the second and subsequent sheets, if the Bk image, C image, M image and Y image are superposedly transferred onto the recording paper of the transfer drum 2 and the transfer discharge (sending to the fixing device 9) is set, a full color image is formed. The counter 234f is incremented by 1.

In order to maintain the gradation of the entire image, the gradation processing parameter may be switched in association with the above-mentioned coefficient switching. For switching between C, M, and Y, a switching signal may be output from the chromatic color determination unit 790, or an address (line N) determined to be chromatic during Bk image formation.
o. ) May be sent to the system controller 600 and a switching signal may be output from here.

By the way, the above-mentioned chromatic color judging unit 79
At 0, since the chromatic / achromatic color determination is performed with the 4 × 4 pixel area as the minimum unit, there is a delay of at least 3 lines and 3 pixels. Therefore, the γ correction unit 730 and the color conversion unit 750 or the color conversion unit 750 and the UC
A memory for delaying data is arranged between the R units 760 so that 3 lines and 3 pixels or more are delayed. The delay amount may be determined for each line in order to facilitate synchronization.

Second Embodiment In the first embodiment, in full-color image formation, Bk, C, M, and Y images are repeatedly formed on the photosensitive drum 1 and transferred onto the recording paper of the transfer drum 1 in an overlapping manner. However, in the second embodiment, as shown in FIG. 6, four sets of image forming units are arranged on the transfer belt 221, and in full color image formation,
This is a four-drum type full-color image forming apparatus that sequentially forms Bk, C, M, and Y images from the upstream side in synchronism with the conveyance of recording paper by the transfer belt 221, and transfers the images to the recording paper. 201 to 211 are scanners 40 for image input
Reference numerals 0, 212 to 234 denote a printer 100 that outputs image data obtained from the scanner 400 and converted into recording colors by the image information processing apparatus 700 onto paper. The contact glass 202 supports a document placed between the document reading plate and the document pressure plate 201.

The fluorescent lamp 204 is a light source for irradiating an original in the scanner 400 and is mounted on the carriage. The CCD 205 is a photoelectric conversion device that changes the reflected light reflected from the original document into a read charge amount in pixel units and is arranged in the direction perpendicular to the paper surface (main scanning direction) and reads the original document in line units.

The scanner controller 201 controls the carriage, the system controller 600, and the printer 100.
It also controls control signals with external devices. Also,
In the above-mentioned reading device, the read image data is A / D
It is to convert. The image information processing device 700 is a device that performs image processing such as color conversion and density conversion on read image data. The storage device 207 and an interface board 208 with an external device are devices for sending and receiving data to and from the scanner 400 and the system controller 600.

The storage device 207 is a device for writing image data to and reading image data from a storage medium such as a floppy disk. The connector 211 is a connection device for transmitting and receiving image data and control data with an external device.

The printer controller 230 is the printer 100.
Is a device for controlling the above and outputting an image on a sheet. The laser beam emitted from the laser output device 212 is reflected by the polygon mirror 226 focused by the collimator lens 213 and diffused in the main scanning direction. The diffused light beam passes through the cylindrical lens 215 and irradiates the photoconductor 216 in the main scanning direction. At this time, the photoconductor is charged to a constant potential by the charging device 217, and the potential is raised by being irradiated with a laser beam. On the other hand, the toner carrier of the developing device 218 has a potential between them, and the negatively charged toner adheres to the laser irradiation portion on the photoconductor having a high potential. Further, since the photoconductor rotates clockwise, it is possible to attach the toner to an arbitrary place on the photoconductor by turning on / off the laser output device.

On the other hand, the sheet is selected from the sheet trays 224 and 225, fed by the sheet feed rollers 222 and 223, and conveyed to the registration roller 220. Accurately control the paper transport timing with registration rollers. After passing through the registration rollers, the sheet is conveyed to the photoconductor by the conveying belt 221, and the toner image on the photoconductor is transferred onto the sheet there. After the transfer, the surface of the photoconductor is initialized by the cleaning device 219 and charged again by the charging device.

In this embodiment, four image forming units are provided, and each unit has the same structure as 212 to 219, and an image corresponding to each color of Bk, C, M and Y is formed. To do. A full-color image is created by stacking them on the sheet conveyed by the transfer belt 221. After the transfer of each color, the transfer belt 221 is separated by the separation charger 231.
The sheet separated from is sent to the fixing device 232. The sheet after fixing is discharged to the sheet discharge tray 233.

FIG. 7 shows the structure of the electrical equipment of the color copying machine shown in FIG. In this example, four image forming units are arranged along the transfer belt 221, and the image forming unit on the downstream side with respect to the image forming unit on the upstream side with respect to the conveying direction of the recording paper fed by the transfer belt 221 forms an image on the image forming unit on the downstream side. Since it is necessary to delay the delay, it is necessary to hold the output color signals (Bk, C, M, Y) of the UCR unit 760 for the delay (however, regarding Bk in which image formation is performed in the most upstream image forming unit). Is not necessarily a delay). Therefore, in this example, the color signals (recording color component data) Bk, C, M, and Y output from the UCR unit 760 are stored in the image memory (buffer memory for aligning each color image) 800.
To the signal Bk, and the signals C, M, and Y are read after being delayed by the required delay of the image forming unit that forms those images, and each of them is set to a total of four floors for Bk, C, M, and Y. The gradation processing circuit 780 outputs the gradation data to the four image forming units of the printer 100. The chromatic color judging unit 790 of the second embodiment is the one shown in FIG. 4 with the line counter 801, the comparator 802 and the register 803 removed, and the system controller 600 uses a full color controller by an operator. −
If the document is specified, it is determined by the prescan method whether the document is chromatic.

That is, the system controller prescans the original document and monitors the output signal of the chromatic color determination unit 790. When the chromatic color signal is generated, the selector outputs the output of "coefficient for chromatic color 80%". 752 is set, scanning of the original is started again, and full color recording is started.
That is, in synchronization with the progress of the scanning of the original, first, the image formation by the most upstream Bk image forming unit is started, and then sequentially with a predetermined time delay (movement of a predetermined amount of the recording paper), the three sets of the downstream side. Start image formation by the image forming unit. When the recording paper passes directly below the most downstream image forming unit, the full color counter 234f is incremented by one. When the set number of continuous copies is 2 or more, the prescan is not performed in the image formation of the second and subsequent images, and the above-described full color recording is performed. When the chromatic color determination unit 790 does not determine that the color is chromatic in the prescan, the output of the “achromatic color coefficient” is set in the selector 752, the scanning of the original is restarted, and only the most upstream image forming unit is used. When the Bk recording is started and the Bk recording is ended, the single color counter 234m is incremented by 1. When the set number of continuous copies is two or more, the pre-scan is not performed in the image formation of the second and subsequent images, and the above Bk recording is performed.

In both the first and second embodiments described above, the case where the original image is read by the scanner 400 and directly output to the printer 100 has been described. However, since the scanner 400 is not provided, an external device is provided before the color conversion unit 750. The present invention can be similarly applied to a printer having an interface and receiving image data from the outside through an external interface.

Further, in the first embodiment, when full color mode is designated, Bk is set in the prescanless system.
During image formation, chromatic colors / based on the input image signals R, G, B
The achromatic color determination is performed, but the present invention can be realized by using this as a prescan method.

In any of the first and second embodiments, the chromatic / achromatic color determination may be performed based on the output color signals Bk, C, M and Y. Further, when the operator can selectively specify three modes of single mode / ACS mode / full color mode, when the ACS mode is specified, it is based on the input image signals R, G, B. Chromatic / achromatic color determination is performed, and when full color mode is specified, output color signal Bk,
The chromatic / achromatic color determination may be performed based on C, M, and Y. This eliminates the problem that the reproducibility deteriorates because the color is overlaid on black characters due to an error in black character determination, especially when the entire image is composed of only black characters. An image without color moire can be obtained.

[0046]

According to the present invention, the number of single / full color image formations actually performed by the color image forming apparatus and the count value of the single color counter / full color counter match. Correct single / full color without the operator having to switch to single color mode
The number of times of image formation is counted.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a vertical sectional view showing a mechanical element according to the first embodiment of the present invention.

FIG. 3 is a graph showing the contents of undercolor Bk removal in full color recording.

4 is a block diagram showing a schematic configuration of a color conversion unit 750 shown in FIG.

5 is a block diagram showing a schematic configuration of a chromatic color determination unit 790 shown in FIG.

FIG. 6 is a vertical sectional view showing a mechanical element according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

[Explanation of symbols]

1: Photoconductor drum 2: Transfer drum 3: Writing unit 4: Developing unit 5: Charging charger 6: Cleaning unit 7: Transfer charger 8: Separation charger 9: Fixing device 10: Paper ejection tray 11: cassette 12: paper feed roller 13: registrar 100: laser printer 200: ADF 300: operation button
Code 400: Image Scanner 600: System Controller 700: Image Information Processing Device

Claims (1)

[Claims] 1. Input means for inputting an image signal and one or more of the input image signals for forming images of black (Bk), cyan (C), magenta (M) and yellow (Y). Means for converting into a color signal, means for determining whether an image to be formed is chromatic or achromatic, means for forming an image represented by the color signal, and the determining means. When it is determined that the color is chromatic, the image forming means performs overprinting of at least three of the four colors, and when the recording of one sheet is completed, the full color counter is incremented by 1, and when the determinating means determines that the color is achromatic. A color image forming apparatus, comprising: an image forming control unit that increments a single color counter by 1 when one or more of the four colors are recorded by the image forming unit and one sheet of recording is completed.