JPS58215665A - Image adjusting method of color copying machine - Google Patents

Abstract

PURPOSE:To permit even a user who does not have technical knowledge to take a copy with desired color reproduction, by classifying originals into several groups by the contents of originals and the purposes of copying, and using both a color reproduction selecting and a brightness adjusting means. CONSTITUTION:Originals are classified into several groups by the purposes of satisfied color reproduction adjustment and process conditions are set respectively. For color tone selection, a program device is provided, and the amounts of electrification and exposure of a photoreceptor for the image formation of respective color components of yellow, magenta, and cyan and the bias voltage of a developing device are set previously for each group of originals. For example, some original group is selected by the selecting means such as a selection button, etc., to set its process condiction automatically. An brightness and a ground adjustment are made by adjusting the overall quantity of light through the diaphragm mechanism of an optical system 4. Thus, even an unskilled user takes a copy with desired color reproduction easily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image color reproduction adjustment method for a color electrophotographic copying machine of a color overlay type.

The essential features of a color electrophotographic copying system using a three-color superposition method will be explained with reference to FIG. 1. In this system, the photosensitive drum 1 rotates three times to produce one copy. The light reflected from the original 6 placed on the contact dove plus 2-1- is switched to the optical path of the exposure optical system 4, which forms an image on the photoreceptor drum 1. The latent images are separated by the six color filters 5 and six types of latent images are formed on the photoreceptor drum 1.

Around the photosensitive drum 1, development devices 6, 7.8 each having toner-containing developers of six colors of yellow, magenta, and cyan are arranged in this order following the exposure position.
The latent image formed by the light beam passing through the blue filter is developed by a yellow developing device, and the toner image □ is transferred to the transfer drum 9 provided in contact with the photoreceptor drum 1 at a position after the six developing devices. Transfer drum to wrapped transfer KS? The image is transferred by a transfer charger 10 inside. Next, the latent image formed by the light beam passed through the green filter is developed by a magenta developing device 7, and the toner image is transferred to the same transfer paper S of the transfer drum 9, which has rotated once, together with the yellow toner image. They are combined and transferred. Next, the latent image formed by the red filter is developed by a cyan color developing device (48), and the toner image is also transferred onto the same transfer paper in a double layered manner.The three color toner images are combined and transferred. The transfer tram 9 is transferred by the separation charger 11 and the separation claw 12.
The paper is separated from the paper, fixed by the fixing device 13, and discharged to the tray 14 outside the machine to be copied or completed.

In the above color copying method, the spectral transmittance of ideal blue, green, and red color separation filters is shown in FIG. 2(a).

(b) +' The spectral reflectances of ideal yellow, magenta, and cyan toners are shown as solid lines in (c), and the spectral reflectances of ideal yellow, magenta, and cyan toners are shown as solid lines in Figure 6 (a), (b), and (e). If each separation filter and toner have such ideal characteristics, color reproducibility faithful to the original image should be obtained.

As color separation filters for color copying machines, for example, the blue filter is the bandpass filter BPB45 manufactured by Fuji Photo Film Co., Ltd., the green filter is the bandpass filter BPB53 manufactured by the same company, and the red filter is the bandpass filter manufactured by the same company Sharp. Cut filter 5C60 is widely used. The spectral transmittance characteristics of these filters are shown by broken lines in FIGS. 2(a) and 2(b)+(c), respectively. In addition, the spectral reflectances of yellow, magenta, and cyan toners commonly used in color duplex machines are shown in Figure 6 (a), (o), and (c), respectively.
) as shown by the broken line. In FIGS. 2 and 6, the horizontal axis shows wavelength in nm, and the vertical axis shows spectral transmittance or spectral reflectance in %.

As is clear from these figures, the spectral transmittance of each color separation filter actually used and the spectral reflectance characteristics of each color toner are the same as the spectral transmittance of the ideal color separation filter and the spectral reflectance characteristics of each color toner. It is difficult to completely match the color of the copy image with the color of the original image because there is a considerable difference between the two colors. For example, black is hard to be completely black, and red and orange are difficult to distinguish. This phenomenon occurs where violet and green colors turn black.

Therefore, the process conditions (electrification!'it knee,
(exposure meter, developing bias, etc.) must be set separately.

A method of stratifying the original to be copied into several groups and selecting the process line 1'1 to perform copying to obtain the desired color reproduction includes a color separation exposure time adjustment means, a projection exposure @ adjustment means, and a charging adjustment. at least one or more of the adjustment means,
There is a known method for adjusting the color balance by providing a predetermined number of color separations and providing means for operating these predetermined number of adjusting means in a correlated manner. The above-mentioned interlock adjustment is performed using, for example, a rotary switch.

However, this method mainly suffers from changes in characteristics due to fatigue of the photoreceptor.
This is a temporary color correction method when a slight change occurs in the set color reproduction due to a change in the light intensity of the light source, a change in the characteristics of toner replenishment, etc., and it is a temporary color correction method that corresponds to the color content of the original and the purpose of copying, which is the object of the present invention. This is different from the copy color tone selection.Also,
It is considered that this method does not reduce the number of copy failures.

Further, there has been proposed a reproduction machine that can selectively operate means for producing a functional copy that reproduces a line drawing with high contrast and a pictorial copy. This device is designed to adjust the reproducibility of line drawings and solid images by selectively inserting strips and leans into each exposure path.It is easy to operate and can be used for functional copying and pictorial copying. It is possible to copy well by switching the
This method adjusts the contrast, and the color adjustment that matches the content of the original document and the purpose of copying, which is the object of the present invention, cannot be achieved by this method.

In view of the above-mentioned current state of the image adjustment method for color electrophotographic copying machines using a three-color superimposition method, the present invention provides a color system that allows even users without specialized knowledge to easily obtain copies with desired color reproduction. The purpose is to provide a reproduction adjustment method.

As mentioned above, it is difficult to perform color reproduction adjustment that satisfies all types of originals under the same process conditions. Therefore, in order to achieve this objective, the present invention stratifies the original into several groups according to the content of the original and the purpose of copying, and provides a selection means so that process conditions corresponding to color reproduction can be easily selected. , the brightness and shading of the copy) are now adjusted using a separate adjustment means. In this way, it is a feature of the present invention that the color reproduction selection means and the brightness adjustment means are provided together.
ii) This is a feature of the image color adjustment means.

Hereinafter, the present invention will be explained in detail along with examples.

Manuscripts are stratified into the following three groups based on their content, purpose, and purpose.

■ Primary color/skin color group This is a group that requires color reproduction such as yellow, magenta, cyan, red, purple, green, and skin color, and the content of the manuscript includes photographs, catalogs, designed fist posters, etc. .

■ Black and white group This is a group that focuses on the reproducibility of white, gray, and black, and even if the color tone is a little bad, it is good as long as it can be distinguished by color.Manuscripts include drawings, ground usage maps, reports, etc. Graphs, control charts, etc.

■Light color group This is a group that improves halftone color reproduction.
Manuscripts include maps, posters, drawings, control charts, reports, etc., which are mainly in light colors.

The reason why the color reproduction is poor for the above six groups of originals under the same process conditions will be explained below.

As for the reason why groups ■ and ■ do not have the same conditions, for example, regarding the relationship between the blue filter and yellow toner, the blue filter is ideally as shown in Figure 2 (a).
As shown in Fig. 2 (only light of 400 to 500 nm is passed through and light of other colors is absorbed), it is possible to extract the yellow component of the original.

Therefore, if the latent image formed on the photoreceptor by this light beam is developed with yellow toner, an amount of yellow toner corresponding to the yellow component of the image will be deposited.

In the same way, magenta toner and cyan toner are deposited in amounts corresponding to the respective components of the image.

However, the commonly used spectral reflectance of each color component is shown in Figure 3 (a), (b), and (c), and there are deviations from the ideal curve, and the one with the largest deviation is is the reflectance of the magenta component from 400 to 500 nrn. When the magenta component is used as an original, the reflectance of this area is low, so when exposing the blue filter, only the magenta toner (=J) will be deposited in the area where it should not be (=J).As a result, the yellow toner (=J) will be deposited. The yellow image area uses only yellow toner, the magenta image area uses yellow+magenta toner, and the cyan image area uses only cyan toner.

In order to improve the color reproduction of the monochrome group, it is sufficient to make the adhesion amounts of yellow, magenta, and cyan, especially in the low-density areas, the same, and a monochrome image and a copy with a certain degree of color reproduction can be obtained.

However, under these conditions, if a copy is made of an original in the primary color group (■), the color will be yellowed throughout the copy because there is a lot of yellow toner. Especially at low concentrations, the yellow color is strong, and the difference between red and orange, and the difference between purple and black becomes smaller.

In order to reproduce primary colors and skin tones, balance can be achieved by reducing the amount of yellow toner. However, solid black areas only have a slight bluish tinge, but fine black lines lack the yellow component and end up becoming blue lines.

After all, since the reflectance of the magenta component in the 400 to 500 nm range is small, the optimum conditions for color reproduction of primary colors and color reproduction of white, gray, and black do not match.

Next, regarding the light color group, as a basis of Shigeko photography, an ideal γ curve cannot be obtained, and if an attempt is made to guarantee a constant density in high density areas, the gradation reproduction in low density areas will deteriorate. If you try to improve the gradation in low-density areas, the density in high-density areas will not increase, and the colors will lose their brilliance.

For the above reasons, it is necessary to classify documents into a plurality of groups according to the purpose and set process conditions for each group. Conditions for selecting a color tone are set for charging the photosensitive member, for exposing the photoreceptor, and for the developing device. -1- The charging company of the photoreceptor mentioned above adjusts the power supply voltage control, the exposure amount by controlling the illumination lamp, and the development amount by developing bias control? It's convenient.

The overall brightness adjustment and background 1 adjustment are performed by adjusting the overall light h1 using the aperture mechanism of the optical system.

A brochure device is installed for color tone selection, and the photoreceptor is charged to form images for each color component of yellow, magenta, and cyan.
The exposure rate and developer bias voltage can be set in advance for each layered group of documents, and the above process conditions can be automatically set by selecting the document group using a selection means such as a selection button. Make it.

Can I adjust the overall brightness using another knob or other adjustment method? ” Now.

By using the color selection means and the brightness adjustment means together, as shown in -1 above, even users without specialized knowledge can easily obtain color copies with optimal color reproducibility depending on the purpose of copying, with fewer mistakes. I can do it.

An example of processing conditions for each group stratified according to the content of the original and the purpose of copying, and a γ curve of image density (ID) versus original density (OD) obtained under these process conditions are shown below.

0 example The above exposure values are set values on a 5-stage dial.

Based on the conditions for the monochrome group, in the primary skin color group, the exposure for the yellow image is increased to reduce the yellow toner's ζJ multiplication.

In addition, in the light color group, by reducing the exposure amount and increasing the development bias for each color, the overall toner
Reduces doubling and improves gradation in low density areas.

Copy image density (ID) for original density (OD) for each color in each group obtained under
) are shown in FIG. 4 for the primary color/skin color group, FIG. 5 for the monochrome group, and FIG. 6 for the light color group. In the diagram, Y is yellow, M
indicates magenta, and C indicates cyan.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the schematic structure of a color electrophotographic composite using a six-color combination method; Figures 2 (a) and (b) CO
) are curve diagrams showing a comparison between the ideal spectral transmittance characteristics of the green and red color separation filters and the spectral transmittance characteristics of the filters actually used. )
(c) is a curve diagram showing a comparison between the ideal spectral reflectance characteristics of yellow, magenta, and cyan components and the spectral reflectance characteristics of the face/dye actually used, Figures 4 and 5. , and FIG. 6 are γ characteristic curves of each color original density versus copy image density for each original group obtained by the adjustment method according to the embodiment of the present invention. 1... Photosensitive drum 6... Color original 5...
Color separation filter 6... Yellow developer 7... Magenta developer 8... Cyan developer 9... Transfer drum S... Transfer assembly Figure 4 Sushi Figure 6 Figure 5

Claims (2)

[Claims] (1) Separate the colors of a color original, expose it to light, and attach it to the photoreceptor.
11J The created color separation images are developed with toners of different colors, and then transferred onto the same transfer paper to form a color image.
In the image adjustment method of a color copying machine that obtains a By stratifying the document into multiple groups according to the purpose, and selecting the color image and current mode that correspond to the group of multiple originals, you can create a color image that is set for each color image formation mode. An image adjustment method characterized in that the photoreceptor potential, exposure, and development amount are automatically selected, and the brightness adjustment is performed by a brightness adjustment means using an aperture of an optical system according to the brightness of the original. (2) Adjustment of the photoreceptor potential for image formation of each color by selecting color 11 in -1- is done by controlling the power supply voltage, adjustment of the exposure amount is done by controlling the illumination lamp electric EE, and adjustment of the amount of development is done by the development. The image adjustment method according to claim 1, characterized in that the image adjustment method is carried out by bias potential control.