JPH0511563A - Image forming device and method - Google Patents

Abstract

PURPOSE:To eliminate color deviation caused by the fluctuation of a writing position, to form a high-quality multicolor image and to reduce toner consumption in case of forming the multicolor image. CONSTITUTION:This is an image forming device where an electrostatic latent image is formed for every color on a photosensitive body based on original picture information outputted from an original picture information part 101 and developed by a color developing means corresponding to each color, so that the multicolor image based on the original picture information is formed. Then, this device is provided with an image processing part 102 which executes color separating processing 102a for color-separating the original picture information outputted from the original picture information part 101 and UCA processing 102b for adding black corresponding to the gray part of three colors, and a write control means 103 which executes writing in the order of black, yellow, magenta, and cyan under the multilevel control of one dot by the modulation of pulse width based on output from the image processing part 102.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and method for forming a multicolor image using a copying process,
In particular, an image forming apparatus that eliminates color misregistration at the time of image formation by utilizing the advantages of UCR processing and UCA processing as color reproduction processing, reduces toner consumption, and realizes low running cost And its method.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus such as a color printer using a general electrophotographic process reproduces color by subtractive color mixing using complementary color toners (Y: yellow, M: magenta, C: cyan). Was going on. in this case,
Various color correction processes are required to achieve ideal color reproduction by using color toner having the spectral characteristics shown in FIG.

As a method of the above color correction processing, as shown in FIG. 3, (a) UCR processing (Under Color)
Removal) and (b) UCA processing (Under
It is common to use Color Addition).

The UCR process shown in FIG. 3A is a process in which the gray portion is removed from the three color toners and replaced with one black toner color. According to this UCR processing, it is possible to reduce the consumption of color toner, and further improve the image quality such as the color reproducibility of the shadow portion and the reproducibility of black characters. In addition, it is possible to form a higher quality color image with a wide color reproduction range by performing this UCR processing on the image information in one dot and writing it by one-dot multi-value control such as pulse width modulation. There are features.

The UCA process shown in FIG. 3B is a technique often used in the printing field and the like. The UCA process is a process of adding black toner corresponding to the gray portion of the three-color toner. Similar to the UCR process, this UCA process improves the color reproducibility of the shadow portion, the reproducibility of black characters, and the like. Further, by combining with the one-dot multi-value control, it is possible to form a high quality color image having a wide color reproduction range. In the UCA processing in this case, since black is added to a normal multicolor image with three-color toner, the allowable range for the writing position shift is wider than that of the UCR processing.

FIG. 3 is an explanatory view showing an example in which one dot is formed by the UCR processing of (a) and the UCA processing of (b) in the image forming apparatus of the color superimposing one-time transfer system. In this case, in consideration of the spectral characteristics of the color toner (laser beam oscillation wavelength = 780 nm) shown in FIG.
(Yellow) → M (Magenta) → C (Cyan) → B
_{Set to K} (black). Further, FIG. 3 shows an example of forming a dark orange color, and an example of forming a dark orange color by the color reduction of the UCR processing of (a) is shown in (a) → (b), and UCA of (b).
Example of forming a dark orange color by processing addition (e) →
It is shown in (to).

[0007]

However, in the color correction processing method of the color image as described above, when the position variation at the time of writing the image occurs, the process shown in FIG.
As shown in (c), in the UCR processing of (a), a dark orange color close to red is formed and accurate color reproduction cannot be obtained. Further, in the UCA process of (b), as shown in (g), there is a problem that the toner consumption amount becomes larger than that of the UCR process.

The present invention has been made in view of the above, and a latent image of each color written by multi-value control of one dot on a photoconductor for forming an image is formed by four-color toner (Y, M, C,
B _K ), superimposing development is performed, and a color image is formed on a recording paper by a single transfer process. It is an object of the present invention to realize reduction of toner consumption when forming a multicolor image.

[0009]

In order to achieve the above object, the present invention forms an electrostatic latent image on a photoconductor for each color of the original image information output from the original image information output means, and for each color. In the image forming apparatus for forming the multicolor image based on the original image information by visualizing the electrostatic latent image by the color developing means corresponding to, the original image information output from the original image information output means is color-separated. Image processing means for performing color separation processing and UCA processing for adding black corresponding to a gray portion of three colors, and black by 1-dot multi-value control by pulse width modulation based on the output of the image processing means,
The present invention provides an image forming apparatus including a writing control unit that performs writing in order of yellow, magenta, and cyan.

Further, it is desirable that the write control means executes pulse width modulation control by centering pulses.

Further, UCA processing is performed in which the original image information is color-separated into each color of yellow, magenta, and cyan, and black is added to each color obtained by color separation, and black, yellow, magenta, and cyan are obtained by one dot multivalue. The present invention provides an image forming method in which writing is performed in the order of 1 to obtain a multicolor image.

[0012]

The image processing means of the image forming apparatus according to the present invention comprises:
Color separation of the original image information output from the original image information output means,
UCA that adds black corresponding to the gray portion of the three colors
Perform processing. The writing control means executes writing in the order of black, yellow, magenta, and cyan by one-dot multi-valued control by pulse width modulation control by centering the pulses based on the output of the image processing means.

In the image forming method according to the present invention, the original image information is color-separated into each color of yellow, magenta, and cyan, and UCA processing is performed to add black to each color obtained by color separation, and black is obtained by one-dot multivalue. , Yellow, magenta, and cyan are written in this order to obtain a multicolor image by the copying process.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory diagram showing an example of forming one dot in an image forming apparatus according to the present invention. Reference numeral 101 is an original image information section for outputting original image information, 102 is an image processing section for performing color separation processing 102a and UCA processing 102b on the original image information output from the original image information section 101, and 103 is based on output data of the image processing section 102. A write controller that controls the write operation.

In the above configuration, as shown in the figure, the original image information (dark orange in this embodiment) from the original image information unit 101 is subjected to the color separation processing 102a by the image processing unit 102.
And UCA processing 102b, and the writing control unit 103 prints B _K on the photoconductor (not shown) as shown in FIG.
(Black) → Y (Yellow) → M (Magenta) → C
A writing electrostatic latent image is formed in the order of (cyan).

Next, as shown in FIG. 1B, a developing device (not shown) is used to make B _K (black) → Y (yellow) → M.
Toner is attached in the order of (magenta) to C (cyan) to visualize the image. The above process yields the final formed dots (dark orange) shown in FIG.

In the writing by the writing control unit 102, the original image information is color-separated by the image processing unit 102 and UC is performed.
After processing A, pulse width control (here, pulse width control by centering the pulse) is used to perform the above B _K (black).
Writing is performed in the order of → Y (yellow) → M (magenta) → C (cyan).

Even if optical writing is performed on the black toner image formed on the photoconductor as described above, all the light is absorbed and an electrostatic latent image is not formed on the photoconductor. Toner is not overlaid and developed. Therefore,
Even if the write signal is subjected to UCA processing, the actually obtained image is an image formed with the same toner consumption amount as that of UCR processing.

In the above, even if the writing position varies during writing, the writing process is performed based on the UCA-processed signal as shown in FIG. 1B, so that the normal UCA process is performed. As a result, the allowable range of positional deviation becomes wider than in the UCR processing.

As described above, according to the present embodiment, by utilizing the merits of the UCR processing and the UCA processing, the color misalignment accuracy is the same as that when the UCA processing is performed with respect to the writing position variation, and the toner consumption is further increased. The amount can be reduced to the same level as when UCR processing is performed, and a high-quality multicolor image with a wide color reproduction range can be obtained at low running cost.

[0021]

As described above, according to the image forming apparatus of the present invention, the original image information output from the original image information output means forms an electrostatic latent image on the photoconductor for each color and corresponds to each color. In the image forming apparatus for forming the multicolor image based on the original image information by visualizing the electrostatic latent image by the color developing means, color separation for color-separating the original image information output from the original image information output means. Means, image processing means comprising UCA processing means for adding black corresponding to a gray portion of three colors, and black, yellow, magenta, by one-dot multi-value control by pulse width modulation based on the output of the image processing means. to and a writing control means for writing in the order of cyan, each color latent image written by one dot multi-level control on the photosensitive member to form an image four-color toner (Y, M, C, B K In the image forming apparatus of the color superposition transfer method, in which the color development is performed on the recording paper by performing the superimposing development with a single transfer process, the color misregistration due to the writing position variation is eliminated to form a high-quality multicolor image. In addition, it is possible to reduce the toner consumption when forming a multicolor image.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of forming one dot in an image forming apparatus according to the present invention.

FIG. 2 is a graph showing spectral characteristics of color toner.

FIG. 3 is an explanatory diagram showing an example of conventional color correction processing.

[Explanation of symbols]

101 Original Image Information Section 102 Image Processing Section 102a Color Separation Processing 102b
UCA processing 103 Write controller

Claims (3)

[Claims] 1. The original image information output from the original image information output unit forms an electrostatic latent image on a photoconductor for each color, and the electrostatic latent image is visualized by a color developing unit corresponding to each color. In the image forming apparatus for forming a multicolor image based on the original image information, color separation processing for color-separating the original image information output from the original image information output unit and black corresponding to a gray portion of three colors are added. Image processing means for executing UCA processing, and write control means for writing in the order of black, yellow, magenta, and cyan by one-dot multi-valued control by pulse width modulation based on the output of the image processing means. An image forming apparatus characterized by. 2. The image forming apparatus according to claim 1, wherein the writing control unit executes pulse width modulation control by centering pulses. 3. UCA processing for color-separating original image information into each color of yellow, magenta, and cyan, and adding black to each color obtained by color separation is performed, and black, yellow, magenta, and cyan are obtained by one-dot multivalue. An image forming method, characterized in that writing is performed in order to obtain a multicolor image.