JP2000134475A - Method and device for image formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform correction control over a gradation skip which becomes remarkable especially when a gradational multi-valued full-color image is outputted. SOLUTION: A random-number maximum value calculation part 220 calculates the random-number maximum value of random-number data 218 generated by a random-number generation part 210 and outputs it as a maximum random-number signal 226 to a random-number addition quantity calculation part 230. Then the maximum random-number signal 226 is adjusted to the gradations of an image and a random-number addition quantity is calculated. Further, a random-number addition quantity selection part 240 selects and outputs random-number data in the section corresponding to a gradation of image data among random-number data found by sections by a random-number addition quantity calculation part 230 according to the gradations of input image data. Then a random-number addition part 250 adds the random-number data to the input image data. A random-number addition control part 280 controls a selector 260 according to an image process (image data) and selects and outputs either the image data after the random-number adding process or the input image data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming method for performing gradation editing and an apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, there is an image forming apparatus for forming a toner image corresponding to input image data on a sheet. For example, a digital copying machine or the like that performs image copying by electrically reading a document and outputting the obtained image data on paper is cited, but such image forming apparatuses have been remarkably developed. With the rapid growth of technology in the image forming apparatus industry, it has become possible to provide a user with a beautiful color image with higher image quality and higher accuracy.

One of the problems in improving the image quality of an image formed by an image forming apparatus is a problem of image gradation skipping. This is a phenomenon in which an image is actually formed with a density change different from the set gradation change (data density change), and is considered to be caused by the influence of the characteristics of the toner. For example, even if the density is set to change in proportion, the toner adhesion amount does not change in proportion, so that the difference in toner density is different for each gradation from the preceding and following gradations. As a result, a portion having a large density difference appears as a streak in the image. At the quantization level, for example, as shown in FIG. 15, the toner density changes.

[0004]

In particular, when the input image data is output by adding a continuously and smoothly changing gradation image by using the editing function of the image processing, the above phenomenon becomes remarkable. Come. Therefore, in order to further improve the image quality of the image forming apparatus, it is necessary to establish a new technique for solving the problem of the gradation skip.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to add a gradation image to an input image without causing a gradation jump and providing a high quality image. It is an object of the present invention to provide an image processing apparatus and an image processing method capable of outputting an image to which the gradation is added.

[0006]

In order to achieve the above object, in an image forming method according to the present invention, a gradation processing step of performing data processing to add a gradation image to input image data; A random number adding step of adding random number data to the image data subjected to the data processing by the gradation processing step.

It is preferable that the method further includes a document reading step of reading a document image and converting the image data into image data.

It is preferable that the method further includes a recording step of recording the image data to which the random number data is added in the random number adding step.

In the recording step, an electrostatic latent image corresponding to the image data to which the random number data has been added is formed on an image carrier, the electrostatic latent image is visualized with a transfer agent, and the visible image is formed. It is also preferable that the step is a step of transferring to a recording medium.

It is preferable that the method further includes a selecting step of selecting whether to output the image data to which the random numbers have been added in the random number adding step.

In the selecting step, it is preferable to select whether or not to output the image data to which the random numbers have been added based on a user's instruction.

[0012] The image processing apparatus further includes a gradation processing detecting step of detecting that the gradation processing step has been performed, and the selecting step includes automatically adding a random number when the gradation processing is detected by the gradation processing detecting step. It is also preferable to output data.

In the random number adding step, it is preferable that the maximum value of the added random numbers is controlled according to the density value of the input image data.

There is provided gradation processing means for performing data processing to add a gradation image to the input image data, and random number addition means for adding random number data to the image data processed by the gradation processing means. It is characterized by the following.

It is preferable that the apparatus further comprises a document reading means for reading a document image and inputting it as image data.

[0016] It is also preferable that the apparatus further comprises a recording means for recording the image data to which the random number data has been added by the random number adding means.

The recording means forms an electrostatic latent image on the image carrier corresponding to the image data to which the random number data has been added, visualizes the electrostatic latent image with a transfer agent, and It is also preferable to use an electrophotographic recording unit for transferring the image to a recording medium.

It is preferable that the image processing apparatus further comprises a selection unit for selecting whether to output the image data to which the random number has been added by the random number addition unit.

It is also preferable that the selection means selects whether or not to output image data to which random numbers have been added based on a user's instruction.

The image processing apparatus further includes a gradation processing detecting means for detecting that the gradation processing has been performed, and the selecting means automatically selects a random number added image when the gradation processing is detected by the gradation processing detecting means. It is also preferable to output data.

The selecting means has an instruction inputting means for inputting, from an external device connected to the image forming apparatus, an instruction as to whether or not to output the image data to which the random numbers have been added. It is also preferable to make the selection according to the instruction given above.

It is also preferable that the random number adding means controls the maximum value of the added random numbers according to the density value of the input image data.

According to the present invention, there is provided a computer readable memory storing a control program for controlling an image forming apparatus, the program code being a gradation processing step for performing data processing for adding a gradation image to input image data; And a program code for a random number addition step of adding random number data to the image data subjected to the data processing in the gradation processing step.

Thus, when a gradation image is given to the image data obtained by scanning the original image and taken in by using the gradation editing function, an appropriate noise data is output to the output image data. By adding and outputting, it is possible to effectively suppress the gradation jump which is a problem when outputting a gradation image.

[0025]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the relative arrangement of components described in this embodiment, formulas, numerical values, etc., unless otherwise specified,
It is not intended to limit the scope of the present invention only to them.

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described.
An image processing apparatus according to an embodiment will be described in detail with reference to the drawings. In the present embodiment, when adding gradation to an input image by gradation editing processing, random numbers are added in order to reduce gradation jumps. Hereinafter, “gradation” refers to an image data density value, and “density” refers to a toner density at which an image is actually formed.

FIG. 1 is a schematic sectional view of a color image forming apparatus according to an embodiment of the present invention.

In this embodiment, a digital color image reader unit 100 is provided at the upper part, and a digital color image printer unit 200 is provided at the lower part.
Having.

In the reader section 100, the original 30 is placed on an original platen glass 31, and a known original scanning unit including an exposure lamp 32 is driven by an optical reading drive motor 35 to a predetermined fixed magnification determined according to a preset copying magnification. Exposure scanning at the speed of The reflected light image from the original 30 is condensed by a lens 33 on a full-color sensor (CCD) 34,
A color separation image signal is obtained. As this full-color sensor, R (red), G
A three-line CCD provided with (green) and B (blue) filters is used. The color-separated image signal is subjected to image processing in an image processing unit 36 and a controller unit 37, and is sent to a printer unit.

An operation section is provided around the platen glass 31, and switches for setting various modes related to a copy sequence, a display for display, and a display are arranged.

In the printer section 200, the photosensitive drum 1 serving as an image carrier is rotatably supported in the direction of the arrow, and a pre-exposure lamp 11, a corona charger 2,
A laser exposure optical system 3, a potential sensor 12, four developing units 4y, 4c, 4m, and 4Bk of different colors, an on-drum light amount detecting unit 13, a transfer device 5, and a cleaning unit 6 are arranged.

In the laser exposure optical system 3, the reader unit 1
The image signal from 00 is converted into an optical signal by a laser output unit (not shown), and the converted laser light is reflected by the polygon mirror 3a, passes through the lens 3b and the mirror 3c,
The image is projected on the surface of the photosensitive drum 1.

When an image is formed by the printer unit 200, the photosensitive drum 1 is rotated in the direction of the arrow, and the photosensitive drum 1 after the charge is removed by the pre-exposure lamp 11 is uniformly charged by the charger 2, so that each of the separated colors is separated. The light image E is irradiated to form a latent image.

Next, a predetermined developing device is operated to develop the latent image on the photosensitive drum 1 to form a toner image on the photosensitive drum 1 using a resin as a base. The developing units 4y, 4
c, 4m, and 4Bk are eccentric cams 24y and 24, respectively.
According to the operations of m, 24c, and 24Bk, the photosensitive drum 1 is arranged so as to be selectively approached in accordance with each of the separated colors.

Further, the toner image on the photosensitive drum 1 is
The image is transferred from one of the preselected recording material cassettes 7 a, b, and c to the recording material supplied to a position facing the photosensitive drum 1 via the transfer system and the transfer device 5. The selection of the recording material cassette is performed by driving any one of the pickup rollers 27a, 27b, and 27c according to a control signal from the controller unit 37 in advance according to the size of the recording image.

In the present embodiment, the transfer device 5 includes a transfer drum 5a,
A transfer charger 5b, a suction roller 5g opposed to a suction charger 5c for electrostatically sucking the recording material, an inner charger 5d,
A recording material carrying sheet 5f made of a dielectric material is integrally stretched in a cylindrical shape in a peripheral opening area of a transfer drum 5a having an outer charger 5e and rotatably supported by a shaft. .
The recording material supporting sheet 5f uses a dielectric sheet such as a polycarbonate film.

As the drum-shaped transfer device, that is, the transfer drum 5a is rotated, the toner image on the photosensitive drum is transferred by the transfer charger 5b onto the recording material carried on the recording material carrying sheet 5f.

As described above, a desired number of color images are transferred to the recording material sucked and conveyed to the recording material carrying sheet 5f to form a full-color image.

In the case of forming a full-color image, when the transfer of the toner images of the four colors is completed in this way, the recording material is separated from the transfer drum 5a by the action of the separation claw 8a, the separation push-up roller 8b and the separation charger 5h. The sheet is discharged to the tray 10 via the roller fixing device 9.

On the other hand, after the transfer, the photosensitive drum 1 is subjected to the image forming process again after the residual toner on the surface is cleaned by the cleaning device 6.

When forming images on both sides of a recording material,
Immediately after the fixing unit 9 is ejected, the transport path switching guide 19 is driven, and once guided to the reversing path 21a via the transport vertical path 20, the rear end of the sheet fed by the reverse rotation of the reversing roller 21b is moved to the top. And is retracted in the direction opposite to the direction in which the sheet is fed, and stored in the intermediate tray 22. Thereafter, an image is formed on the other surface again by the above-described image forming step.

Further, in order to prevent scattering of powder on the recording material carrying sheet 5f of the transfer drum 5a and adhesion of oil on the recording material, the fur brush 14 and the recording material carrying sheet 5f interpose the brush. 14, a backup brush 15, an oil removing roller 16, and a recording material carrying sheet 5.
Cleaning is performed by the action of the backup brush 17 facing the roller 16 via f.

Such cleaning is performed before or after image formation, and at any time when a jam (paper jam) occurs.

In the present embodiment, the gap between the recording material carrying sheet 5a and the photosensitive drum 1 is reduced by operating the eccentric cam 25 at a desired timing and operating the cam follower 5i integrated with the transfer drum 5f. The configuration can be set arbitrarily. For example, during standby or when the power is off, the interval between the transfer drum and the photosensitive drum is increased.

[Image Processing Block] FIGS. 2A and 2B show the detailed configuration of the image processing unit 36, the controller unit 37, and the peripheral controlled units shown in FIG. Hereinafter, the detailed configurations of the image processing unit 36, the controller unit 37, and the peripheral controlled units in the present embodiment will be described with reference to FIGS. 2A and 2B.

The full-color sensor (CCD) 34 has 10
It is composed of CCDs of 1, 102, 103 red, green, and blue, and separates one line of light information from a document into colors to output R, G, B electrical signals at a resolution of 400 dpi. In this embodiment, since reading is performed at a maximum of 297 mm (A4 length) as one line, 4677 pixel images are output from the CCD for each of R, G, and B lines.

Reference numeral 104 denotes a synchronizing signal generation circuit, which comprises a main scanning address counter, a sub scanning address counter, and the like. The main scanning address counter is cleared line by line by a BD signal which is a synchronization signal for laser recording on the photosensitive drum 1 line by line, and the pixel clock generator 105
And outputs a count output H-ADR corresponding to each pixel of one line of image information read from the CCD 34.

The H-ADR ranges from "0" to "500".
It counts up to "0", and the image signal for one line from the CCD 34 can be sufficiently read. The synchronization signal generating circuit 104 outputs various timing signals such as a line synchronization signal LSYNC, a main scanning effective section signal VE and a sub-scanning effective section signal PE of an image signal.

Reference numeral 106 denotes a CCD drive signal generation unit.
-ADR is decoded and a CCD-DRIVE which is a set pulse or a transfer clock from a shift pulse of the CCD 34 is used.
Generate a signal. As a result, the R, G, and B color separation image signals for the same pixel are sequentially output from the CCD 34 in synchronization with VCLK. An A / D converter 107 converts red, green, and blue image signals into 8-bit digital signals.

Reference numeral 150 denotes a shading correction circuit.
This is a circuit for correcting variations in signal output for each pixel in the CCD. In the shading correction circuit,
Each line of R, G, and B signals has a memory for one line, and an image of a white plate having a predetermined density is read by an optical system and used as a reference signal.

Reference numeral 151 denotes a sub-scanning connection circuit, which is a CCD
34 is a circuit for absorbing the displacement of the image signal read by the scanning line in the sub-scanning direction by eight lines.

Reference numeral 152 denotes an input masking circuit for removing dust from the colors of the input signals R, G, and B.

Reference numerals 153 and 163 denote buffers, and ZO-
When the ED signal is at the L level, the image signal is passed and the ZO-ED
When the signal is at the H level, the image signal is not passed. Normal,
It is at the L level when the editing function is used.

155 of the editing circuit 154 is a filter for smoothing an image signal, and performs a 5 × 5 matrix operation. Reference numeral 156 denotes a color conversion circuit, which has a function of converting an RGB image signal into HSL color space coordinates, converting a previously designated color into another designated color, and returning the color to the RGB color space again. . It is also possible to convert a multi-value signal into a binary signal at a fixed threshold value.

Reference numeral 159 denotes an external device, which comprises a memory device for storing image signals up to A3 size, a computer for controlling the memory device, and the like. The image signal of the external device 159 is a red, green, blue (RGB) signal or a cyan, magenta, yellow, black (C
MYK) signal and a binary signal.
The external device 159 is, for example, a gradation C
A G image or the like can be output.

Reference numeral 158 denotes an interface (I / F) circuit for adjusting the timing and speed of an image signal from an external device and an internal image signal. 160
Is an area generation circuit that generates and stores an area specified by an editor or the like.

A MARKER signal obtained by extracting an image of a marker pen or the like drawn on a document is also stored in the memory as an area area. An SC-BI signal obtained by binarizing the image signal read by the CCD 34 is represented by Z
-Used for BI output signal. This area generation circuit 16
The memory write unit and the memory read unit for the area out of 0 will be described later in detail.

Reference numeral 157 denotes an RGB synthesizing circuit.
4 and the external device 159
This is a circuit for synthesizing the RGB image signals from. It is also possible to combine an RGB image signal from the CCD 34 with a binary image from an external device.

The area to be synthesized is specified by the AREA signal from the area generation circuit 160 or by the IPU-BI signal from an external device. In addition, for the synthesis, replacement synthesis in which the image signal from the CCD 34 and the external image signal are independently synthesized for each area, and watermark synthesis in which two images are simultaneously overlapped and watermarked and synthesized are also possible. In this watermark synthesis, it is also possible to specify a watermark rate of which of two images is to be watermarked and synthesized.

Reference numeral 161 denotes a contour generating circuit,
, An SC-BI signal obtained by binarizing the image signal read by the above, an IPU-BI signal which is binary data from the external device 159, or a binary data Z-B from the area generating circuit 160.
A contour is extracted from the I signal to generate a shadow.

Reference numeral 162 denotes a black character judging circuit which judges the characteristics of the input image signal, and outputs eight kinds of character thickness signals (thickness degree) FTMJ, edge signal EDGE, and color signal I.
Outputs RO.

A color space compression circuit 108 performs the following matrix operation.

| R '| | R | | a11 a12 a13 a14 a15 a16 a17 a18 | | RX | | G' | = | G | + | a21 a22 a23 a24 a25 a26 a27 a28 | × | GX | | B '| | B | | a31 a32 a33 a34 a35 a36 a37 a38 | | BX | | (RX) (GX) | | (GX) (BX) | | (BX) (RX) | | RGB | | (255-R) ( 255-G) (255-B) | where X represents the minimum value of R, G, and B.

By setting in advance whether or not to perform color space compression in the color space compression circuit 108, ON / OFF of color space compression is performed by the area signal AREA.
Can be switched.

Reference numeral 109 denotes a light quantity-density converter (LOG)
The conversion unit converts the red, green, and blue 8-bit light amount signals into 8-bit density signals of cyan (C), magenta (M), and yellow (Y) by logarithmic conversion.

Reference numeral 173 denotes a buffer that passes an image signal when the ZO-PRV signal is at an L level and blocks an image signal when the ZO-PRV signal is at an H level. Normally, the level is H level, and when the preview function is used, the level is L level.

Reference numeral 174 denotes a thinning control circuit which is used when a preview function is used. At the time of preview, the same signal is output every four lines by writing the input image signal to the FIFO memory one line at a time for every four lines.

Reference numeral 110 denotes an output masking processing unit which extracts a black density signal from the C, M, and Y density signals by a known UCR process (under color removal process).
A known masking operation for removing color turbidity of the developer corresponding to each density signal is performed. The selector 111 selects a color signal corresponding to the developer currently being used from the density signals M ′, C ′, Y ′, and K ′ thus generated.

The ZO-TONER signal is a 2-bit signal generated from the toner color generation circuit 178 for this color selection. When the ZO-TONER is 0, the M 'signal is output, and when the ZO-TONER is 1, In this case, the signal C '
When −TONER is 2, the Y ′ signal is ZO-TON
When ER is 3, the K 'signal is output as a READ-DT signal. Note that the toner color generation circuit 178 directly outputs the SLTNR signal output from the CPU 130 according to the development color during normal copying as a ZO-TONER signal.

Reference numeral 164 denotes a CMYK synthesizing circuit for synthesizing the image signal read by the CCD and the CMYK format image signal input from the external device 159. When performing CMYK synthesis, a color signal corresponding to the developer currently used is input from an external device for each page in accordance with an image signal from the CCD. The area to be combined is switched by the AREA signal or the IPU-BI signal, similarly to the RGB combining circuit 157. Similarly, watermark synthesis is also possible.

Reference numeral 165 denotes a coloring circuit which performs processing such as adding a preset color to a monochrome image, for example. Coloring can also be performed on a binary image signal IPU-BI from an external device. Further, it is possible to create a gradation pattern in which the gradation gradually changes.

Reference numeral 166 denotes an F value correction circuit which performs gamma processing according to the development characteristics of the printer and can set the density for each mode. 114 is a variable power circuit,
It has a memory for one line of an image signal, and performs enlargement and reduction of the image signal in the main scanning direction and italics for outputting an image obliquely. At the time of sampling, the sampling data is stored in a memory and used for creating a histogram.

A texture circuit 168 combines a color image signal read by the CCD with a binarized pattern of an image signal read by the CCD in advance or a binarized pattern input from an external device, and outputs it. .

Reference numeral 169 denotes a smoothing circuit composed of 5 × 5 filters, and 170 denotes an edge emphasis circuit composed of 5 × 5 filters.

Reference numeral 171 denotes an add-on circuit which outputs an image signal in a specific coded pattern. Reference numeral 180 denotes a random number addition block, which will be described in detail later. Reference numeral 115 denotes a laser and a laser controller, which is an 8-bit density signal VI.
The light emission amount of the laser is controlled according to the DEO signal. This laser light is scanned in the axial direction of the photosensitive drum 1 by the polygon mirror 3a to form a one-line electrostatic latent image on the photosensitive drum.

Reference numeral 116 denotes a photodetector provided in the vicinity of the photosensitive drum 1, which detects the passage of laser light immediately before scanning the photosensitive drum 1 and detects a one-line synchronization signal BD.
Occurs.

Reference numeral 141 denotes an area LUT (look-up table) circuit, which outputs an ARE signal from the area generation circuit 160.
Each mode is set according to the A signal. Area LUT1
The LOGCD signal, which is the output of 41, is
Is used to switch the LOG table to a through setting or the like. UCRCD output of area LUT 141
The signal is used by the output masking 110 for trimming and masking. The FCD signal output from the area LUT 141 is used to change the magnitude of the F value of the F value correction 166.

The ACD6 signal is supplied to the coloring circuit 165.
The NCD signal is connected to the MCYK synthesizing circuit 164, and the KCD signal is connected to the black character LUT circuit 172, for setting various modes.

A black character LUT 172 performs various processes according to the output of the black character determination circuit 162. For example, U
The CR-SL signal is output from the UCR of the output masking circuit 110.
For an area determined to be a darker character by changing the amount, processing such as developing with a larger amount of black and a smaller amount of C, M, and Y is performed.

In the EDGE-SL signal, the smoothing circuit 169 and the edge emphasizing circuit 170 are set so as to switch to a filter such that the edge of a black character area is emphasized in a black character area. Further, the SNS-SL signal is a black character L
The output of the UT 172 switches the number of 400/200 lines under PWM control in the laser controller 115. In other words, development is performed with 400 lines to increase the resolution in an area determined to be a black character, and development is performed with 200 lines in other image areas to increase the gradation.

Reference numeral 118 denotes a photo sensor which detects that the transfer drum 5a has reached a predetermined position and detects a page synchronization signal I.
A TOP is generated, a sub-scanning address counter of the synchronization signal generation circuit 104 is initialized, and is input to the CPU 130. Reference numeral 130 denotes a CPU which controls image reading and image recording operations.

Reference numeral 131 denotes a controller for controlling the forward / reverse and speed of the reading motor 35. Reference numeral 132 denotes an I / O port for controlling other sensors and actuators required for controlling the copying operation. The I / O port also includes a PF signal for feeding paper from a paper cassette. As other signals, the size of the paper is detected by a paper size sensor (not shown) attached to the paper cassette, and is input to the CPU from an I / O port.

An operation unit 51 is used to instruct the number of copies and various operation modes. 133 is a ROM, CP
An operation control program of U130 and a predetermined set value are stored. Reference numeral 134 denotes a RAM that temporarily stores data and stores newly set values and the like.

[Gradation Editing] In the present embodiment, gradation editing is performed by the coloring circuit 165 in the image processing section 36.

The gradation pattern has various shapes such as a pattern in which a continuous gradation image changes in proportion to each unit step gradation, a pattern in which gradation gradually increases or decreases with a certain period, and the like. A pattern is assumed. Gradient editing includes anything that outputs only a gradation pattern, one that outputs as a background of an image pattern, one that specifies and outputs an area using a digitizer, or one that outputs a gradation of characters or image patterns. Arbitrary gradation editing is possible.

[Addition of Random Number Data] The detailed configuration of the random number addition block in the image forming apparatus of the present embodiment shown in FIGS. 2A and 2B will be described below with reference to FIG. FIG.
FIG. 3 is a block diagram illustrating a detailed configuration of a random number addition block 200 in the image forming apparatus according to the present embodiment.

In FIG. 3, reference numeral 210 denotes a random number generation unit for generating a random number source signal which is a source of a random number signal to be added to image data. 220 denotes a gain of the random number source signal in accordance with a step of gradation jump in an image. Is a random number maximum value calculation unit that controls the maximum value in order to adjust. For example, the random number source signal is converted into a random number signal having an amplitude twice as large as the step of the gradation jump. Here, the maximum value may be set to a value at which the gradation skip is most inconspicuous. 230 is a random number addition amount calculation unit,
This block calculates a random number addition amount according to the data density value of the pixel of interest in order to adjust the maximum value of the random numbers to be added according to the gradation of the image. Specifically, all the gradations are divided into several sections, and the random number addition amount is derived assuming that the input pixel belongs to each section.

Reference numeral 240 denotes a random number addition amount selection unit which selects and outputs a random number signal corresponding to the gradation of the pixel of interest from the random number signals obtained by the random number addition amount calculation unit 23. Reference numeral 250 denotes a random number adding unit that adds a random number signal to the input image data.

Reference numeral 260 denotes a selector for selecting and outputting one of the image data subjected to the random number addition processing and the input image data. Reference numeral 270 denotes a register unit, which is configured by a register group, and the set value of each block is set as a register value via the CPU. A random number addition control unit 280 controls the selector 260 to determine whether or not the random number addition is necessary.

The detailed configuration of the above-described random number generation section 210 will be described below with reference to FIG. FIG. 4 is a detailed block configuration diagram of the random number generation unit 210 according to the present embodiment.

As shown in FIG. 4, a random number generator 210 mainly includes a shift register 211 composed of a large number of shift registers and an exclusive OR circuit (ExOR gate) 212.
It is constituted by. The shift register 211 is reset when the power is turned on. A selector 213 switches a load signal of the shift register 211.

The selector 213 switches the input signal of either A or B according to the value of the select signal 216 set in the register 270 and outputs it as the load signal 215 of the shift register 211.

When the A input is selected by the select signal 216, the load signal 215 is output at the timing when the first line image leading signal arrives, and the register is output at the timing when the first line image leading signal arrives. The load value set in 270 is output as the load signal 215 of the shift register 211.

The select signal 216 is output from the selector 21
When the B input of 3 is selected, the set value to the register 270 is output as the load signal 215 of the shift register 211. This loading is performed for each color.

When the load signal 215 of the shift register 211, which is the output signal of the selector 213, becomes active, the shift register 211 reads the load input signal 217 input to the load input terminal. Load input signal 2
17 can be controlled by the value set in the register 270. The shift register 211 outputs the loaded load input signal 217 as a random number source signal 218 in synchronization with the image clock signal 219. Further, the shift operation is repeated.

A part of the output of the shift register 211 is subjected to an exclusive OR (ExO) by the subsequent ExOR gate 212.
R) and is connected to the D input terminal of the D type flip-flop 214. Then, the image clock signal 2
After being delayed by one clock of 19, the shift register 21
It is output as 1 shift input data.

The detailed configuration of the above-described maximum random number calculating section 220 will be described below with reference to FIG. FIG. 5 is a block diagram showing a detailed configuration of the maximum random number calculating unit 220 according to the present embodiment. Random number maximum calculation unit 2 of the present embodiment shown in FIG.
Reference numeral 20 mainly includes a multiplier.

Random number source signal 218 from random number generation section 210
Is input, the random number maximum value calculation unit 220 outputs the random number maximum value signal 225 from the random number original signal 218 and the resist 270.
Is adjusted so that the value indicated by the random number maximum value signal 225 becomes the maximum value of the generated random number.
Output as

The value of the maximum random number signal 225 is
130 can be set to an arbitrary value depending on the value set in the register 270.

The detailed configuration of the above-described random number addition amount calculating section 230 will be described below with reference to FIGS. FIG. 6 is a block diagram illustrating a detailed configuration of the random number addition amount calculation unit 230 according to the present embodiment, and FIG. 7 is a diagram illustrating a maximum value of random number data to be added to image data according to the present embodiment.

In the present embodiment, as shown in FIG. 7, the value of the random number data to be added to the image data is changed and added for each gradation. That is, the maximum random number signal to be added to the image signal in the section A which is a low gradation part, the section B which is an intermediate gradation part, and the section C which is a high gradation part are equal to or less than a certain value as shown in FIG. To control. This is such that the amount of addition of random numbers can be controlled in accordance with the process characteristics.

For this reason, the random number addition amount calculating section 230 of the present embodiment uses the grayscale threshold signal 1 and the grayscale threshold signal 2 to determine whether the image data of the pixel of interest belongs to each section. Output a random number signal. Note that the number of divided sections is not limited to three, and may be divided into four or more sections. In such a case, the slope of the change in the maximum value of the random number signal in each section may be changed. Further, in FIG. 7, the control is performed such that the maximum value of the random number signal in the section B is constant. However, the present invention is not limited to this, and may have a slope.

[0103] Random number addition amount calculating section 230 of the present embodiment
Takes a configuration as shown in FIG. 6 to adjust the maximum value of the random numbers as shown in FIG. That is, mainly the multiplier 231
(Section A) and a multiplier 232 (section C).

The random number addition amount calculation unit 230 receives the random number signal 226 from the random number maximum value calculation unit 220, and generates a gradation threshold signal 1 (section AB) indicating a gradation change point at which the maximum value of the random number switches. , The tone threshold signal 2 (section BC) in the register 2
70, and an input image signal.

The multiplier 231 outputs the random number signal 22
A random number signal (section A) 235 is output according to 6 × input image signal / tone threshold signal 1, and the multiplier 232 outputs
Random number signal 226 × (input image signal−gradation threshold signal 2) /
A random number signal (section C) 237 is output according to (maximum gradation-gradation threshold signal 2).

The maximum gradation means, for example, 255 if the number of gradations is 8 bits, and is density value data for outputting black.

The random number signal (section B) 236 uses the random number signal 226 output from the maximum random number calculation section 220 as it is.

The threshold data of each of the tone threshold signals 1 and 2 is a set value in the register 270.
, An arbitrary value can be set.

The detailed configuration of the above-described random number addition amount selecting section 240 will be described below with reference to FIG. FIG. 8 is a block diagram illustrating a detailed configuration of the random number addition amount selection unit 240 according to the present embodiment. The random number addition amount selection unit 240 of the present embodiment illustrated in FIG. 8 mainly includes a comparator 241 and a selector 242.

The random number addition amount selection unit 240 compares the input image signal with the gradation threshold signals 1 and 2 using the comparator 241.
As a result of the comparison, the selector 24 outputs the section selection signal 245 that indicates which section of the input image signal corresponds to the gradation.
Feed to 2.

The selector 242 outputs the random number signals 235 to 237 for each gradation section to the random number addition amount calculating section 23 shown in FIG.
The selector 242 switches the selector 242 in accordance with the section selection signal 245, selects a random number signal of the corresponding section, and outputs the selected signal as the added random number signal 246.

A detailed configuration of the above-described random number adding section 250 will be described below with reference to FIG. FIG. 9 is a block diagram illustrating a detailed configuration of the random number adding unit 250 according to the present embodiment. The random number adder 250 according to the present embodiment mainly includes a flip-flop group 251, a selector 252, an adder 253, and an addition timing generator 254.

In this embodiment, in order to shift the position of the random number to be added to the image, the position of the random number to be added for each line is alternately changed by one pixel in the main scanning direction as shown in FIG. .

Then, in order to cancel the added amount of the random numbers, control is performed such that data having a polarity different from that of the random number data two pixels before is added to a position corresponding to a position two pixels after the added random number position in the main scanning direction. It shall be. For example, at a position two pixels after the addition of the random number data, control is performed so that the random number data is subtracted from the input image data.

The input A of the selector 252 in the random number adding unit 250 has the random number signal 24
6 and the polarity signal 255 are input. The input B receives the random number data delayed by one flip-flop 251 two pixels before and the signal obtained by inverting the polarity signal 255 by an inverter circuit. This polarity signal 255 is
30 to the register 270.

The addition timing generator 254 is a block that controls a select A signal 256 and a select B signal 257, which are timing signals for adding random numbers to image data, and receives an image clock signal 219 and a main scanning synchronization signal. . FIG. 11 shows the generation timing of the select A signal 256 and the select B signal 257 in the addition timing generator 254 in the present embodiment.

The select A signal 256 and the select B signal 257 become active at a period of four pixels, respectively, and the phase relationship between the select A signal 256 and the select B signal 257 is generated so as to have a phase difference of two pixels. Further, the generation phases of the select A signal 256 and the select B signal 257 are controlled so as to be alternately shifted by one pixel in the main scanning direction for each line.

Select A signal 256 and select B signal 257 generated by addition timing generation section 254
Is input as a switching signal for the selector 252, the selector 252 outputs the random number data and the polarity signal 255 input to the A terminal when the select A signal is active, and is input to the B terminal when the select B signal is active. The inverted random number data and the polarity signal two pixels before the main scanning direction are output.

The random number data and the polarity signal 255 selected by the selector 252 are input to the subsequent adder 253 together with the input image signal. The adder 253 performs addition / subtraction processing of random number data with respect to the input image. The addition / subtraction is controlled by the input polarity signal. When the polarity signal is “L”, the addition is performed, and when the polarity signal is “H”, the subtraction is controlled. The image data subjected to the addition / subtraction processing is subjected to overflow and underflow control. If the calculation result at the time of addition exceeds the maximum value of the image data ("255" at the time of 8 bits), it is set to the maximum value, and the calculation result at the time of subtraction is negative. In the case of, each is controlled to be zero.

The output of the random number addition unit 253 is supplied to the subsequent selector 260 as image data obtained by adding random numbers.

The detailed configuration of the above-described selector 260 is shown in FIG.
2 will be described below. FIG. 12 is a block diagram illustrating a detailed configuration of the selector 260 according to the present embodiment. The selector 260 of the present embodiment is a block that selects and outputs one of the random number added image data 259 subjected to the random number addition process and the input image data.

FIG. 12 is a block diagram showing a detailed configuration of selector 260. The selector 260 is a block for selecting and outputting one of the random number added image data 259 subjected to the random number addition processing and the input image data.

The gradation selection signal 289 supplied from the operation unit 280 is input to the switching terminal of the selector 260. When the gradation selection signal 289 is "L", the input image signal is output as it is as the through image data of the random number addition processing block. On the other hand, when the gradation selection signal 289 is “H”, the image data subjected to the random number addition processing in the random number addition processing block is output as output image data. With the above configuration,
The image forming apparatus according to the present embodiment is configured to apply appropriate noise data to image data captured by scanning a document image, particularly when a gradation image is given using an editing function in the image processing unit and output. By adding and outputting, it is possible to effectively suppress the gradation jump (see FIG. 13).
reference). Furthermore, since whether or not to perform the random number addition process can be operated by the operation unit, the user can arbitrarily instruct the suppression of the gradation skip.

(Second Embodiment) Next, an image forming apparatus according to a second embodiment of the present invention will be described with reference to FIG.

The control configuration in the image forming apparatus and the configuration of the image processing section, the controller section and the peripheral controlled sections are the same as those of the first embodiment.
Since this embodiment is the same as the first embodiment, the description thereof is omitted.

FIG. 14 is a diagram for explaining a block for adding random number data to image data according to the present embodiment. 2 are given the same numbers.

In the first embodiment, the operation unit 280
Although the necessity of the random number addition processing is controlled by the input from, the present embodiment automatically determines that the gradation editing processing is performed and performs the random number addition processing.

When the gradation editing is performed by the coloring circuit 165 in the image processing section 36, the detecting means (not shown) in the coloring circuit 165 detects the gradation editing processing and sends a control signal for the random number addition processing to the random number addition processing section 180. Is supplied.

To the switching terminal of the selector 260, the gradation selection signal supplied from the coloring circuit 165 in the image processing section 36 is input. The image data is output as through image data. When the gradation selection signal is “H”, image data subjected to random number addition processing is output.

With the above configuration, the image forming apparatus of the present invention outputs the addition processing control signal by the gradation reduction processing detecting means when the gradation editing processing is performed, and adds the random number data to the image signal. Thus, it is possible to perform the control of correcting the gradation jump that occurs when a gradation image is output.

(Third Embodiment) Next, a third embodiment of the present invention will be described.

In the random number addition block 180 according to the first embodiment, the random number addition control signal 289 is output from the random number addition control unit 280 shown in FIG. On the other hand, in the present embodiment, a gradation selection signal 289 such as a gradation command flag is output under the control of an external device such as a host computer.

The basic configuration of this embodiment is the same as that of the above-described first embodiment, and the configuration of the random number addition block 180 is only partially different. That is, the control configuration shown in FIGS. 1, 2A and 2B in the image forming apparatus,
Since the configurations of the image processing unit, the controller unit, and the peripheral controlled unit are the same as those of the first embodiment, a detailed description thereof will be omitted. explain.

FIG. 15 is a block diagram showing a detailed configuration of a random number addition block in the image forming apparatus according to the present embodiment. The same components as those in FIG. 3 described above are denoted by the same reference numerals, and detailed description is omitted.

In this embodiment, the random number addition control is performed by the external device 159 constituted by a host computer or the like and the controller 282. The configuration of the selector 260 is shown in FIG.
2 is the same as the configuration shown in FIG. 2, except that a gradation selection signal 289 supplied from the external device 159 via the controller 282 is input to the switching terminal of the selector 260. The image signal is output as it is as the through image data of the random number addition processing unit, and when the gradation selection signal is “H”, the image data subjected to the random number addition processing is output.

With the above configuration, appropriate random number data can be added to the image data sent from the external device 159 via the controller 282 and output. In addition, by using a host computer and a controller to control the addition of the random number data, when a gradation jump occurs when necessary, particularly when performing gradation editing processing, the gradation jump is effectively suppressed. can do.

That is, according to the present embodiment, the addition control of the random number data can be controlled by another external device 159 that can be connected to the device. For example, appropriate random number addition control according to the type of image supplied by the host computer can be performed, and appropriate gradation skip suppression control can be performed as necessary.

The gradation selection signal 289
May be controlled not by the host computer itself supplying the gradation image, but by another host computer. For example, the image data for gradation editing is received from a CD-ROM driver or a LAN, and the gradation selection signal is It may be controlled so as to be input from another control computer, for example.

(Other Embodiments) A recording medium storing software program codes for realizing the functions of the above-described embodiments is supplied to a system or an apparatus, and a computer (or CPU or MPU) of the system or apparatus is supplied. Needless to say, the object of the present invention can also be achieved by reading and executing the program code stored in the recording medium.

In this case, the program code itself read from the recording medium realizes the novel function of the present invention, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM,
DR, magnetic tape, nonvolatile memory card, RO
M, EEPROM and the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) And the like perform part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the program code is read based on the instruction of the program code. The CPU provided in the function expansion board or function expansion unit performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

The present invention may be applied to a system constituted by a plurality of devices or to an apparatus constituted by a single device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus. In this case, by reading a storage medium storing a program represented by software for achieving the present invention into the system or the device, the system or the device can enjoy the effects of the present invention.

Further, by reading and reading a program represented by software for achieving the present invention from a database on a network by a communication program, the system or apparatus can be
It is possible to enjoy the effects of the present invention.

In the present invention, a full-color copying machine has been described as an example, but it is needless to say that the present invention is not limited to a full-color copying machine.

[0147]

As described above, random numbers are added when gradation processing is performed on an input image, so that gradation skipping can be suppressed. In particular, there is an effect that it is possible to perform the gradation jump correction control that is conspicuous when a gradation-like multi-value full-color image is output.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2A is a block configuration diagram of an image processing unit, a controller unit, and a peripheral controlled unit shown in FIG. 1;

FIG. 2B is a block configuration diagram of an image processing unit, a controller unit, and a peripheral controlled unit shown in FIG. 1;

FIG. 3 is a block diagram illustrating a detailed configuration of a random number addition block in the image forming apparatus according to the first embodiment of the present invention.

FIG. 4 is a block diagram illustrating a detailed configuration of a random number generation unit in the random number addition block of FIG. 3;

FIG. 5 is a block diagram illustrating a detailed configuration of a random number maximum value calculation unit in the random number addition block of FIG. 3;

FIG. 6 is a block diagram showing a detailed configuration of a random number addition amount calculation unit in the random number addition block of FIG. 3;

FIG. 7 is a diagram for explaining control of changing random number data to be added to the gradation of image data in the random number addition amount calculation unit in FIG. 6;

FIG. 8 is a block diagram illustrating a detailed configuration of a random number addition amount selection unit in the random number addition block of FIG. 3;

FIG. 9 is a block diagram illustrating a detailed configuration of a random number adding unit in the random number adding block of FIG. 3;

FIG. 10 is a diagram for explaining a random number adding position in the random number adding unit in FIG. 9;

11 is a timing chart showing random number addition timings in the addition timing generation unit shown in FIG. 9;

FIG. 12 is a block diagram illustrating a detailed configuration of a selector in the random number addition block of FIG. 1;

FIG. 13 is a diagram illustrating a phenomenon caused by adding a random number to a skipped tone portion.

FIG. 14 is a block diagram illustrating a detailed configuration of a random number addition block in the image forming apparatus according to the second embodiment of the present invention.

FIG. 15 is a block diagram illustrating a detailed configuration of a random number addition block in the image forming apparatus according to the third embodiment of the present invention.

FIG. 16 is a diagram illustrating gradation skipping.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 2 corona charger 3 laser exposure optical system 3a polygon mirror 3a 3b, 33 lens 3c mirror 4y, 4c, 4Bk developing device 5 transfer device 5a transfer drum 5b transfer charger 5c adsorption charger 5d inner charger 5e outer charger Device 5f Recording material carrying sheet 5g Suction roller 5h Separation charger 5i Cam follower 6 Cleaning device 7a, 7b, 7c Recording material cassette 8a Separation claw 8b Roller 9 Heat roller fixing device 10 Tray 11 Pre-exposure lamp 12 Potential sensor 13 Light amount detection on drum Means 14 Fur brush 15 Backup brush 16 Oil removal roller 17 Backup brush 19 Transport path switching guide 20 Transport vertical path 21a Reverse path 21b Reverse roller 22 Intermediate tray 24y, 24m, 24c, 24Bk Eccentric cam 25 Eccentric cam 7a, 27b, 27c pickup roller 30 document 31 document glass 32 exposure lamp 33 lens 34 full-color sensor (CCD) 35 optical reading driving motor 36 image processing unit 37 the controller unit 51 operation unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C262 AA24 AA26 AB07 AC04 AC11 DA13 GA21 GA23 2H027 EA02 EB01 5B057 BA26 CA01 CB01 CE11 CH18 5C077 LL04 LL19 MP08 PP05 PQ08 TT06

Claims (18)

[Claims] 1. A gradation processing step of performing data processing to add a gradation image to input image data; and a random number addition step of adding random number data to image data processed by the gradation processing step. An image forming method, comprising: 2. The image forming method according to claim 1, further comprising a document reading step of reading a document image and converting the image into image data. 3. The image forming method according to claim 1, further comprising a recording step of recording the image data to which the random number data is added in the random number adding step. 4. The recording step, wherein an electrostatic latent image corresponding to the image data to which the random number data is added is formed on an image carrier, and the electrostatic latent image is visualized with a transfer agent. 4. The image forming method according to claim 3, further comprising a step of transferring the image to a recording medium. 5. The image forming method according to claim 1, further comprising a selecting step of selecting whether to output the image data to which the random numbers are added in the random number adding step. . 6. The image forming method according to claim 5, wherein said selecting step selects whether or not to output image data to which random numbers have been added based on a user's instruction. 7. A gradation processing detecting step for detecting that the gradation processing step has been performed, wherein the selecting step automatically adds a random number when the gradation processing is detected by the gradation processing detecting step. And outputting the image data.
Or the image forming method according to 6. 8. The image according to claim 1, wherein in the random number adding step, a maximum value of the added random numbers is controlled according to a density value of the input image data. Forming method. 9. A gradation processing means for performing data processing to add a gradation image to input image data; a random number addition means for adding random number data to the image data processed by the gradation processing means; An image forming apparatus comprising: 10. An image forming apparatus according to claim 9, further comprising a document reading means for reading a document image and inputting it as image data. 11. The image forming apparatus according to claim 9, further comprising recording means for recording image data to which random number data has been added by said random number adding means. 12. The recording means forms an electrostatic latent image on an image carrier corresponding to the image data to which the random number data has been added, and visualizes the electrostatic latent image with a transfer agent. The image forming apparatus according to claim 11, wherein the image forming apparatus is an electrophotographic recording unit that transfers an image to a recording medium. 13. The image forming apparatus according to claim 9, further comprising a selection unit that selects whether to output the image data to which the random number has been added by the random number addition unit. . 14. An image forming apparatus according to claim 13, wherein said selection means selects whether or not to output image data to which random numbers have been added based on a user's instruction. 15. A gradation processing detecting means for detecting that the gradation processing has been performed, wherein the selecting means automatically adds a random number when the gradation processing is detected by the gradation processing detecting means. The image forming apparatus according to claim 12, wherein the image forming apparatus outputs the output image data. 16. An instruction input unit for inputting, from an external device connected to the image forming apparatus, an instruction as to whether or not to output image data to which random numbers have been added, wherein the selection unit includes the instruction input unit. 14. The image forming apparatus according to claim 13, wherein the selection is performed according to an instruction input by the user. 17. An image according to claim 9, wherein said random number adding means controls a maximum value of the added random numbers according to a density value of input image data. Forming equipment. 18. A computer readable memory in which a control program for controlling an image forming apparatus is stored, wherein a program code of a gradation processing step for performing data processing to add a gradation image to input image data; And a program code for a random number adding step of adding random number data to the image data subjected to the data processing in the processing step.