JPH08337007A - Device and method for image processing - Google Patents

Abstract

PURPOSE: To reduce the thinning of a developed image by a toner, which is formed on a photosensitive drum. CONSTITUTION: An RGB image signal which is input, is converted into a YMCK image signal at a color conversion means 205. At the same time, whether the RGB image signal is a white signal or a color signal is judged, and if it is a white signal, a laser control means 206 controls a laser light source 201 in such a manner that the laser light source may emit a small amount of light, and if it is a color signal, the laser control means 206 controls the light emission of the laser light source 201 in response to the YMCK image signal. A photosensitive body 201 is irradiated with the laser light, and an electronic latent image is formed, and a development means 203 makes a toner stick to the photosensitive body 201, and forms a toner image. The toner image is transferred to a transfer paper by a transfer means 204. By the small amount of light emission, the down buckling of an electrical field by the edge of the electronic latent image on the photosensitive body is weakened, and the thinning of the developed image is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and method for color correction.

[0002]

2. Description of the Related Art A conventional color image forming apparatus forms a color image by repeating a process of transferring a recording image formed by charging, exposing and developing on a photosensitive drum onto a transfer paper for a plurality of colors. I am trying to do it.

FIG. 18 shows the structure of a conventional color image forming apparatus. In the figure, around the photosensitive drum 101, a roller charger 102, a cleaning device 103, and a developing device 10 are provided.
4 and the transfer drum 105 are arranged.

The developing device 104 is formed in a rotatable cylindrical shape and has four developing devices 106a, 106b, 10 inside.
6c and 106d are provided, and each developing device 106a to 106d.
Yellow, magenta, cyan, and black toners are stored in d.

FIG. 19 shows a developing device 106 (106a-106).
The configuration of d) is shown. The coating roller 107, the developing roller 108, the toner regulating member 109, and the toner containing portion 110.
Etc. are provided. As shown in FIG. 18, the developing roller 108 has openings 111a of the developing devices 106a to 106d.
It is exposed to the outside from ~ 111d. Then, the application roller 107 is rotated to apply the toner accommodated in the toner accommodating portion 110 to the developing roller 108, and the toner regulating member 109 imparts necessary tribo to the toner.

The transfer drum 105 is a metal cylinder 1
12 is provided with an elastic layer 113, and PVDF 114 is provided thereon. Around the transfer drum 105, a paper feed roller 115, a gripper 116, a suction roller 1
17, a separation claw 118, a fixing device 119, a cleaning device 120, a charge eliminating roller 121 and the like are arranged.

An optical unit 122 and a folding mirror 123 are arranged above the photosensitive drum 101. The optical unit 122 includes a laser diode, a laser driver, a rotary polygon mirror rotated by a high speed motor, a lens, and the like.

Further, below the photosensitive drum 101, there is provided a paper feed cassette 123 for accommodating transfer paper (not shown).

The photosensitive drum 101 is driven in the direction of arrow a at a peripheral speed of 100 min / sec by a driving means (not shown). The photosensitive drum 101 has a diameter of 40 mm.
The outer peripheral surface of the aluminum cylinder is coated with a photoconductor composed of an organic photoconductor (OPC). OPC above
As such, A-Si, CdS, Se or the like is used. Further, as the material of the toner regulating member 109, nylon or the like is used when the toner has a negative polarity, and silicone rubber or the like is used when the toner is positively charged, and the material is charged opposite to the polarity of the toner. Is used. Further, the coating roller 107 has a peripheral speed of 1.0 to 1.0
The peripheral speed is selected in the range of 2.0 times. Further, the transfer drum 105 is configured by winding an elastic layer 113 made of urethane foam having a thickness of 2 mm around a metal cylinder 112 having a diameter of 156 mm, and winding a PVDF 114 having a thickness of 100 μm around the elastic layer 113.

A conventional color image forming apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 50-50935. Further, regarding the driving means of the developing device 104,
For example, it is disclosed in Japanese Patent Laid-Open No. 50-93437.

Next, the operation of the above configuration will be described. First, the laser diode in the optical unit 122
For example, when driven through a laser driver by a yellow image signal, the laser light emits the laser light.
The photosensitive drum 101 is irradiated via the.

At this time, the charging roller 102 has -700
An AC voltage of Vpp (peak to peak) of 1500 V is superimposed on the DC voltage of V at a frequency of 1000 Hz, and the surface of the photosensitive drum 101 is uniformly charged to about -700 V. Then, in the photosensitive drum 101, the light-irradiated portion becomes approximately −100 V, and an electrostatic latent image is formed. When the photosensitive drum 101 moves in the direction of arrow a, the developing device 106a containing the yellow toner makes the toner visible on the electrostatic latent image.

On the other hand, the transfer paper (not shown) fed from the paper feed cassette 123 by the paper feed roller 115 is held by the gripper 116, and then electrostatically attracted to the transfer drum 105 by the attracting roller 117 to which a voltage is applied. . Then, the toner image on the photosensitive drum 101 is transferred onto the transfer paper attracted to the transfer drum 105 by a voltage applied to the transfer drum 105 from a power source (not shown).

By repeating the above steps for each color of magenta, cyan and black, toner images of a plurality of colors are superposed on the transfer paper. This transfer paper is peeled off from the transfer drum 105 by the separating claw 118, and then fused and fixed by a fixing device 119 by heating and pressurization, so that a full-color image is obtained.

The transfer residual toner on the photosensitive drum 101 is cleaned by a cleaning device 103 including a fur brush, blade means and the like. Further, the photosensitive drum 101
Is neutralized by the static eliminator and initialized. In the case of this example, the charging roller 102 is used for charging the photosensitive drum 101. When the photosensitive drum 101 is to be neutralized, the AC voltage to be applied is kept as it is, and the DC voltage is approximately OV to perform the neutralization. be able to.

The toner on the transfer drum 105 is also cleaned by a cleaning device 120 including a fur brush, a web, etc., if necessary. Furthermore, the transfer drum 105 is neutralized by the static elimination roller 121 and initialized.

Here, the developing system is preferably a one-component developing system which does not require a complicated structure such as an ATR or a screw and can adopt a process cartridge system which improves user maintenance. Further, among the one-component developing methods, the non-contact developing method has an advantage that the configuration can be simplified. The color image forming apparatus described above is of the contact developing type, and in this type, one of the developing roller 108 and the photosensitive drum 101 is in contact with each other, so that one of them has to be an elastic body. However, in the non-contact developing method, these members can be used as they are, for example, as an aluminum substrate, so that the cost merit is large.

Further, as the color toner, in order to improve the color developability of the output image, it is desirable to use a sharp-melt type toner that melts and mixes colors instantaneously at a fixing temperature during fixing. However, this type of toner often has a low glass transition point, and in the contact developing method, there is a possibility that the toner may be fused to one or both members due to the sliding friction between the photosensitive drum 101 and the developing roller 108. is there. It is desirable to use a non-contact developing method also to prevent this fusion.

FIG. 20 shows a non-contact developing system. Four developing devices 202a, 20a are provided around the photosensitive drum 101.
2b, 202c and 202d are fixedly arranged, and the photosensitive drum 201 and the developing devices 202a to 202d are arranged.
It is possible to form a color image without contact and separation with.

[0020]

When a color image is formed by using the above-mentioned non-contact developing method, the present inventor found that the color and the color of the image formed adjacently in different colors as shown in FIG. In between, I found a phenomenon that white stripes occur due to a white gap that should not have existed. This is an electrostatic latent image originally formed on the photosensitive drum when a latent image in which the drum surface potential suddenly changes is formed on the photosensitive drum, for example, when an image edge portion is formed by a developing device. It occurs when the visible image is formed thinner than that. In the case of monochromatic image formation, since there is no adjacent color, there is no problem even if the image becomes slightly thin.

However, when a color image is formed in such a state, as shown in FIG. 21, for example, in the case of an image in which a cyan band and a black band are adjacent to each other, originally the cyan band is originally formed. The black image and the black band should be adjacent to each other, but both the cyan image and the black image are thinly formed, so the final image on the transfer paper has a gap between the cyan and black colors. Will be possible.

As shown in FIG. 22, such an image thinning occurs because an electric field is involved in the edge portion (shown as a latent image portion in the figure) of the electrostatic latent image formed on the photosensitive drum. This is a phenomenon that occurs when the edge portion becomes thin as shown in the visible portion, and the influence thereof becomes remarkable in the non-contact developing method.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a color image forming apparatus capable of eliminating thinning of an image.

[0024]

According to a first aspect of the present invention, there is provided input means for inputting image data composed of a plurality of color components, color correction means for performing color correction on the image data, and Output means for outputting the color-corrected image data to an image forming means for forming an image using an electrophotographic method, wherein the color correcting means emits light in the image forming means when the color component is below a predetermined value. Color correction is performed so that the device emits a small amount of light.

According to a sixth aspect of the invention, in an image processing apparatus for color-correcting image data and outputting it to the image forming means, an input means for inputting the image data and a judgment for judging whether or not the image data has a predetermined color. Means, color correction means for performing color correction so that the light emitting element emits a small amount of light in the image forming means even if the image data is less than or equal to a predetermined value, and the color corrected image data based on the result of the determination. Alternatively, there is provided output means for outputting image data showing substantially white to the image forming means.

According to the invention of claim 8, an image forming means for performing color correction on the image data composed of a plurality of color components and forming an image by the electrophotographic method on the color corrected image data. The color-corrected image data is generated such that the light-emitting element in the image forming means emits a minute amount of light when the color component is equal to or less than a predetermined value in the color correction.

[0027]

According to the first and eighth aspects of the invention, when color correction is performed on the input image data, the light emitting element in the electrophotographic image forming apparatus is used even if the color components forming the image data are below a predetermined value. By generating the color-corrected image data that can emit a small amount of light, it is possible to reduce the thinning of the formed image.

According to the invention of claim 6, when the color of the input image data is corrected, the color-corrected image data capable of emitting a small amount of light is generated in the same manner as described above, and the color of the input image data is judged. By giving the image forming means color-corrected image data or substantially white image data to the image forming means, it is possible to eliminate the above-mentioned white stripes and to clearly define the edge of the boundary between the white image area and the color image area. Can be kept.

[0029]

1 is a block diagram conceptually showing an image processing apparatus. In FIG. 1, 201 is a laser light source that generates a laser beam, 202 is a photoconductor on which an electronic latent image is formed by irradiating the laser light from the laser light source, and 203 is toner attached to the photoconductor. Then, developing means for developing the latent image to form a toner image, and 204 is a transfer means for transferring the toner image onto a transfer paper.

Reference numeral 205 denotes a color conversion means for converting RGB image data into YMCK (yellow, magenta, cyan, black) image signals, and 206 outputs a laser control signal for controlling light emission of the laser light source 201 according to the YMCK image signals. It is a laser control means for outputting a laser control signal.

Next, the operation will be described. R entered
The GB image signal is converted into a YMCK image signal by the color conversion unit 205. The laser control means 206 controls the light emission of the laser light source 201 according to the YMCK image signal.

The photoconductor 201 is irradiated with laser light to form an electronic latent image, and the developing means 203 forms a toner image by attaching toner to the photoconductor 201. This toner image is transferred onto the transfer paper by the transfer means 204. By performing the above operation for each color of YMCK, a color image is formed on the transfer paper.

Here, the YMCK image signal that alleviates the phenomenon of electric field entrainment that causes the phenomenon that the edge portion becomes thin is converted into color conversion means 2 based on the input RGB image signal.
Generate with 05. The concept of a method for alleviating the phenomenon of electric field entrainment is shown below.

FIG. 2 shows the surface potential on the photoconductor 202.
FIG. 10A shows the surface potential during conventional image formation, in which the potential of the printing area is set to about −100V and the potential of the non-printing area is set to −700V. FIG. 6B shows the surface potential during image formation according to the present invention. The potential of the printing area is set to −100V and the potential of the non-printing area is set to −700V. In the state of (a), the electric potential is sharply changed at the boundary (A portion) between the printed area and the non-printed area as described above, so that the electric field is strongly entrained.
However, as shown in (b), the minute laser emission is performed even in the non-printing area, so that the potential change at the boundary (B portion) between the printing area and the non-printing area becomes gradual, and the electric field is also involved. Can be weakened. Therefore, it is possible to prevent thinning of the visible image on the photosensitive drum in the non-contact developing method, and thus it is possible to prevent white lines due to a gap that has been conventionally generated between different colors.

When the laser light source 201 emits a small amount of light, the surface potential of the photoconductor 202 due to the small amount of light emission does not affect the image quality of a color image.

FIG. 3 is a block diagram showing a first embodiment of the present invention based on the above principle. In the figure, image information in a predetermined language obtained from a host computer 1 as an external device is a printer 2 as a color image forming device.
Will be received at. The printer 2 is composed of a printer controller 3 and a printer engine 4.

The image information is received by the printer controller 3, the image is developed here, and the image data 5 is sent to the printer engine 4. The printer engine 4 prints based on the image data 5 to form a full-color image on the transfer paper.

In the following description, it is assumed that the image data 5 is multi-valued image data showing 8-bit R (red), G (green) and B (blue) luminance. The main signal sent from the printer controller 3 to the printer engine 4 is the image data 5 (RD
ATA0 to RDATA7, GDATA0 to GDATA
7, BDATA0 to BDATA7), an image transfer clock (VCLK), a line synchronization signal (LSYNC), and a page synchronization signal (PSYNC). Further, the printer engine 4 prints at a resolution of 600 dpi (dots / inch).

FIG. 4 shows a configuration example of the printer controller 3. The image information sent from the host computer 1 is expanded into multi-valued brightness data of R, G, and B in the image expansion unit 6, and the data for one page is temporarily stored in the image memory 7, and then the image data 5 And is sent to the printer engine 4.

FIG. 5 shows a configuration example of the signal processing unit of the printer engine 4. The R, G, and B image data 5 sent from the printer controller 3 is RF (Reproduce).
The color conversion circuit 8 converts the color into magenta (M), cyan (C), yellow (Y), and black (K), and outputs it as frame sequential image data 9 in the order of M, C, Y, and K. The image data 9 is written in the line memory 10 by the image transfer clock VCLK, then read by the clock PCLK and sent to the gamma correction unit 11. The clock PCLK is generated by the control clock generator 12.

The gamma correction unit 11 is a gamma correction table as a look-up table (LUT) composed of RAM or ROM. The read image data 9 is at addresses A0 to A7 and the color designation signal 13 is A8. , A9. The address map of this gamma correction table is shown in FIG. As shown in FIG. 6, the gamma correction is different depending on the toner color.

Here, the gamma correction table is set based on the processing performed in the RF circuit 8 described later.

The gamma-corrected image data 14 shown in FIG. 7 is converted into an analog image signal 16 by the D / A converter 15.
After being converted to, the signal is input to the comparator 17 as a positive input. The negative input of the comparator 17 has a triangular wave generator 1
At 8, the triangular wave signal 19 shown in FIG. 7 generated in synchronization with the clock PCLK is input.

The comparator 17 has the triangular wave signal 19
By comparing the image signal 16 with the image signal 16, the laser control signal 20 PWM-modulated as shown in FIG. 7 is output. The laser control signal 20 controls the light emission of the laser diode via the laser driver, so that the potential of the surface of the photosensitive drum is controlled by the laser control signal 2 as shown in FIG.
It changes according to the pulse width of 0.

Printing is performed at the portion where the surface potential of the photosensitive drum exceeds a predetermined printing threshold value. In the example of FIG. 7, when the image data 14 is 00 _H and 01 _H , since the pulse width of the laser control signal 20 is narrow, the irradiation time of the laser beam to the photosensitive drum is short, and the surface potential is below the printing threshold value. No printing is done because it does not exceed. That is, the toner image is not formed on the transfer paper. The image data 14 is 8
In the case of 0 _H and FF _H , since the pulse width is wide and the irradiation time of the laser beam is long, the surface potential exceeds the printing threshold value, printing is performed, and a toner image is formed on the transfer paper. Become.

FIG. 8 shows a configuration example of the RF circuit 8. In the figure, reference numeral 21 is a white data discriminating circuit which discriminates whether or not the input RGB image data 5 is white data and outputs a white data discriminating signal 22, and 24, 25 and 26 have LUTs for logarithmic conversion. ROM, 27, 28, 29 and 34 are switches controlled by the mode switching signal (MODE) 23,
30 is UCR (Under color removal: Under Color R
emulation circuit, 31 is a masking circuit including a product-sum operation circuit, 32 is an LU for masking coefficients, UCR coefficients, etc.
This is a ROM having T and an address map is shown in FIG. 33
Is a selector and 35 is a control signal.

FIG. 11 shows a configuration example of the white data discrimination circuit 21. In this circuit, the multi-input AND gate 40,
8 bits of B, G, and R are respectively input to 41 and 42, B = FF _H , G = FF _H , and R = FF _H are detected, and each AND output is further fed to an AND gate 43.
By inputting to, H (high level) when white data
The white data discrimination signal 22 is output.

FIG. 12 shows a configuration example of the selector 33. This circuit is AND gates 44 to 47, 49, OR gate 4
When the white data discriminating circuit 21 discriminates the white data, the YMCK data is output at 00 _H regardless of the YMCK image signal input to the selector 23. On the other hand, when the white data discrimination circuit 21 discriminates the color data, it outputs one of the YMCK image signals input to the selector 33 corresponding to the color designation signal.

Next, the operation when the white data discriminating circuit 21 discriminates data other than white data will be specifically described. At this time, the switches 27, 28, 29 and 34 are MOD
It is assumed that the color signal is closed to the side a by the E signal 23. The image data 5 of 8 bits for each color of R, G, B output from the printer controller is stored in the ROM 24,
Logarithmic conversion is performed by the LUTs stored in 25 and 26, and density of blue (B) is changed to yellow (Y), green (G) is changed to magenta (M), and red (R) is changed to cyan (C). Converted switches 27, 28, 2
It is input to the UCR circuit 30 via 9.

Next, when the control signal 35 of "100" is input, it is sent to A8 to A10 of the ROM 32 shown in FIG. 9 to select the UCR table of magenta (M),
The UCR circuit 30 detects the minimum value of the input 8-bit data of Y, M, and C colors. Then, the detected minimum value is sent to A0 to A7 of the ROM 32 for addressing, and magenta (M) UCR data corresponding to the input data is output from DATA.

Next, the control signal 35 of "000" is sent.
Is input, it is sent to A8 to A10 of the ROM 32 to set a bank, and address data is sent from the register of the masking circuit 31 to A0 to A7 of the ROM 32.
The ROM 32 sets the masking coefficient data of the addressed magenta (M) in the masking circuit 31. Then, the magenta (M) image data output from the UCR circuit 30 is subjected to sum-of-products operation with the masking coefficient set in the masking circuit 31 and output to the selector 33. Next, the selector 33 is switched by the color designation signal 13, and the magenta (M) image data 9 is output to the subsequent stage via the switch 34.

When the above operation is performed for one screen, the control signal 35 of "101" is next sent to A8 of the ROM 32.
.. to A10, the cyan (C) UCR table is selected, the UCR circuit 30 detects the minimum values of Y, M, and C, and the minimum values are transmitted to A0 to A7 of the ROM 32 for addressing. , Cyan (C) corresponding to the input data
The UCR data of is output from DATA. Next, "00
The control signal 35 of "0" is A8 to A1 of the ROM 32.
0, the bank is set, and the masking circuit 31
Address data from the register
7 and the ROM 32 sets the addressed masking coefficient data of cyan (C) in the masking circuit 31. Then, the cyan (C) image data output from the UCR circuit 30 is subjected to sum-of-products operation with the masking coefficient set in the masking circuit 31, and output to the selector 33. Next, the selector 33 is switched by the color designation signal 13, the cyan (C) image data is output to the subsequent stage, and this operation is performed for one screen.

Next, the control signal 35 of "110" is sent to A8 to A10 of the ROM 32, and yellow (Y)
Select the UCR table of the
The minimum value of C is detected, and the minimum value is read from A0 of ROM 32.
The data is sent to A7 for addressing, and the UCR data of yellow (Y) corresponding to the input data is output from DATA. Next, the control signal 35 of "000" is RO
The bank is set by being sent to A8 to A10 of M32.
R is the address data from the register of the masking circuit 31.
The data is sent to A0 to A7 of the OM 32, and the ROM 32 sets the addressed yellow (Y) masking coefficient data in the masking circuit 31. Then, the yellow (Y) image data output from the UCR circuit 30 is subjected to a product-sum operation with the masking coefficient set in the masking circuit 31 and output to the selector 33. Then, the selector 33 is switched by the color designation signal 13 to output the yellow (Y) image data to the subsequent stage, and this operation is performed for one screen.

Next, the control signal 35 of "111" is sent to A8 to A10 of the ROM 32, and black (K)
Select the UCR table of the
The minimum value of C is detected, and the minimum value is read from A0 of ROM 32.
The data is sent to A7 for addressing, and black (K) UCR data corresponding to the input data is output from DATA. The black (K) image data output from the UCR circuit 30 is output to the selector 33. Next, the selector 33 is switched by the color designation signal 13, the black (K) image data is output to the subsequent stage, and this operation is performed for one screen.

By the operation of the above-described four steps, 1
Performs screen color conversion processing. The UCR and masking coefficient corresponding to each color of Y, M, C, and K used in the color mode has a predetermined value for each Y, M, C, and K image signal after color correction regardless of the input RGB image signal. In this embodiment, it is preset to be 10 _H or higher.

When the image data is in the monochrome mode, the MODE signal 23 is used to switch the switches 27, 28, 29, and 3.
4 is connected to the b side, and R, G, B image data 5 is UCR
It is input to the circuit 30, and is input to the masking circuit 31 as it is. Next, the control signal 35 of "000" is R
The bank is set by being sent to A8 to A10 of the OM 32, the address data is sent from the register of the masking circuit 31 to A0 to A7 of the ROM 32, and the ROM 32 sets the coefficient data of the addressed luminance conversion to the masking circuit 31. . Then, the image data is subjected to luminance conversion by the same operation as that for the color image, and is output from the selector 33. Next, "010" control signal 35 is RO
The data sent to A8 to A10 of M32, the bank is set to monochrome mode, and the data output from the selector 33 is stored in the ROM.
The data is sent to 32 A0 to A7 for addressing, and the logarithmic conversion data corresponding to the input data is output from DATA. By this operation, a monochrome mode image is output.

Unlike the data output from the ROMs 24, 25, and 26 in the color mode, the logarithmic conversion data used in the monochrome mode is converted into image data according to the level of the brightness data input to the ROM 32. is there.

Next, a specific example of the processing result in the RF circuit will be described with reference to FIG. 10 (a) (b)
(C) and (d) show G data = FF _H and B data = FF _H.
In the case of, the color conversion result to YMCK data when the R data takes a value of 00 _{H to} FF _H is shown.

In (a), when R = FF _H , it is determined to be white data, and at this time, all YMCK data is set to 00 _H. Further, when R = FE _H , it is determined that it is not white data, and at this time, all YMCK data is set to 10 _H. Therefore, the photosensitive drum is irradiated with the pulse width of the laser control signal 20 corresponding to 10 _H , but as described with reference to FIG. 7, the pulse width at 10 _H is narrow, so the surface potential of the photosensitive drum is It does not change so much that toner adheres.
Therefore, the color tone of the printed image is not affected and only the surface potential of the photosensitive drum is slightly changed, so that the above-mentioned electric field involvement is reduced and the thinning of the visible image on the photosensitive drum is prevented. be able to. FIG. 10 (b)-
Similarly, in (d), when CYK is FF _H , it is determined as white data,
FE _H determines that the data is not white data, and outputs the laser control signal 20 of 10 _H, so that the visible image can be prevented from becoming thin.

FIG. 13 shows RGB image data, and FIG.
Is the YMCK image data obtained by converting the RGB image data of FIG.
Data. As shown in FIG. 14, all RGB are FF._H
In the case of, it is recognized as white data and MCYK is all 00_HTosu
It In addition, all RGB are FF _HIf not, YMCK
YMCK emits laser light for all of
10 for each concentration_HRGB → Y so that the density becomes higher
Perform MCK conversion.

As described above, according to the present embodiment, it is possible to prevent white stripes due to the gaps between different colors as shown in FIG. Can be provided. Further, by providing the white data discriminating circuit 21 and changing the processing for white data and color data, it is possible to perform processing suitable for each data.
That is, in the case of white data, even if the edge portion is thin, the area of the white image is only slightly increased, which is not so noticeable. Rather, the image becomes higher in quality when the edge that is the boundary between the white image region and the color image region is emphasized.
That is, processing suitable for each case can be performed. Further, it is possible to prevent white lines due to image thinning without causing fog and obtaining a sufficient image density.

(Modification) In the above-mentioned embodiment, the white data or the color data is judged and the processing is changed based on the judgment result. The present invention is not limited to this, and for example, the above processing may be uniformly performed on all image data without determining white data. Also, as shown in FIG.
The circuit may be configured.

FIG. 15 shows a case where the RF circuit 8 in the above-mentioned embodiment is incorporated in the printer controller 50. In the figure, the printer controller 50 converts the RGB luminance signal into a YMCK density signal and sends the YMCK image data 9 to the printer engine 51.

FIG. 16 shows a configuration example of the printer controller 50. In the figure, in the RF circuit 8, RDATA [7: 0] and GD of the image data 5 sent from the image memory 7
It receives ATA [7: 0] and BDATA [7: 0] and outputs YMCK image data 9.

In the printer engine 51 in the subsequent stage, the YM
The CK image data 9 is received and a color image is formed based on the signal. FIG. 17 shows a configuration example of the printer engine 51, which has a configuration in which the RF circuit 8 in FIG. 5 is omitted. The structure and processing method of the RF circuit 8 in FIG. 16 are the same as those in the first embodiment.

The advantage of this embodiment is that the number of image signal lines of the interface between the printer controller 50 and the printer engine 51 can be reduced to 8 as compared with 24 in the first embodiment. is there.

[0067]

As described above, according to the inventions of claims 1 and 8, it is possible to prevent thinning of an image and to output a high-quality image.

According to the sixth aspect of the present invention, by performing an appropriate color correction according to the input image data, white stripes are prevented and the edge at the boundary between the white image area and the color image area is maintained. Therefore, it is possible to output a high-quality image.

[Brief description of drawings]

FIG. 1 is a block diagram conceptually showing the present invention.

FIG. 2 is a waveform diagram showing a potential on a photoconductor for explaining the principle of the present invention.

FIG. 3 is a block diagram showing a first embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration example of the printer controller of FIG.

5 is a block diagram showing a configuration example of the printer engine of FIG.

6 is a configuration diagram showing a correction table of a gamma correction unit in FIG.

7 is a timing chart showing the operation of the circuit of FIG.

8 is a block diagram showing a configuration example of the RF circuit of FIG.

9 is a configuration diagram showing an address map of the ROM of FIG.

FIG. 10 is a graph for explaining color conversion.

11 is a circuit diagram showing a configuration example of a white data discrimination circuit of FIG.

12 is a circuit diagram showing a configuration example of a selector shown in FIG.

FIG. 13 is a configuration diagram of RGB image data.

FIG. 14 is a configuration diagram of YMCK image data.

FIG. 15 is a block diagram showing a second embodiment of the present invention.

16 is a block diagram showing a configuration example of the printer controller of FIG.

17 is a block diagram showing a configuration example of the printer engine of FIG.

FIG. 18 is a configuration diagram showing a conventional color image forming apparatus using a contact development system.

19 is a configuration diagram showing the developing device of FIG. 18. FIG.

FIG. 20 is a configuration diagram showing a color image forming apparatus according to a conventional non-contact developing method.

FIG. 21 is a configuration diagram showing an example of a color image formed by a conventional color image forming apparatus using a non-contact developing method.

FIG. 22 is a configuration diagram showing a state of an electric field in a part of a conventional non-contact development type color image forming apparatus.

[Description of Reference Signs] 201 laser light source 202 photoconductor 203 developing means 204 transfer means 205 color conversion means 206 laser control means 2 printer 3 printer controller 4 printer engine 5 RGB image data 8 RF circuit 9 YMCK image data 15 D / A converter 16 image signal 17 comparator 18 triangular wave generator 19 triangular wave signal 20 laser control signal 21 white data discrimination circuit

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Claims (9)

[Claims] 1. An input unit for inputting image data composed of a plurality of color components, a color correction unit for performing color correction on the image data, and an electrophotographic system for the color-corrected image data. Output means for outputting the image to an image forming means for forming an image, and the color correcting means performs color correction so that the light emitting element in the image forming means emits a small amount of light when the color component is below a predetermined value. A characteristic image processing device. 2. The color correction means comprises masking processing and U
The image processing apparatus according to claim 1, wherein CR processing is performed. 3. The image processing apparatus according to claim 1, wherein the minute light emission is performed in pixel units. 4. The image processing apparatus according to claim 1, wherein an image is not formed on a recording medium by the minute light emission. 5. The color correction means performs color correction on the image data and outputs the color-corrected image data composed of color component signals corresponding to a recording medium used in the image forming means. The image processing apparatus according to claim 1, wherein 6. An image processing apparatus for color-correcting image data and outputting it to an image forming means, input means for inputting image data, judging means for judging whether or not the image data has a predetermined color, and the image data. Is less than or equal to a predetermined value, color correction means for performing color correction so that the light emitting element emits a small amount of light in the image forming means; An image processing apparatus having output means for outputting data to the image forming means. 7. The image processing apparatus according to claim 5, wherein the color correction unit outputs the color-corrected image data such that an image is not formed on the recording medium by the minute light emission. 8. A color correction is performed on image data composed of a plurality of color components, and the color-corrected image data is output to an image forming unit that forms an image using an electrophotographic method. In the color correction, the image processing method is characterized in that color-corrected image data is generated so that the light emitting element in the image forming means emits a minute amount of light when the color component is equal to or less than a predetermined value. 9. The color correction is performed during the color correction so as to obtain the color-corrected image data composed of color components corresponding to a recording medium used in the image forming unit. The described image processing method.