JPS6159458A - Formation of polychromatic image - Google Patents

Abstract

PURPOSE:To maintain the toner concn. in a developer accurately by calculating the quantity of toner of each color necessary for one sheet of transfer paper and supplementing toner of each color by an amount which is calculated by the arithmetic at every time. CONSTITUTION:An original O is prescanned before a color electronic copying process to read the original O by an image pickup element 403 by performing color separation previously. Respective read signals are stored in a memory; the ratio of area where a color separation signal of each color is outputted is calculated on the basis of the stored signals and the supplementary amount of toner of each color corresponding to the rate is calculated. Respective toner particles of the respective colors are supplied to developing devices 20, 22, 24, and 26 previously according to the calculated supplementary amounts and a developing process is carried out by using the supplied toner particles.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a multicolor image forming method, and in particular, calculates the amount of toner required for each color by pre-scanning a document, and calculates the amount of toner for each color in advance. The present invention relates to a multicolor image forming method that replenishes.

(Prior Art) A method using the Carlson process is well known as a multicolor image forming method for obtaining a multicolor image of two or more colors from a single multicolor original.

A typical process is as follows.

A light image of a color document is irradiated onto a uniformly charged photoconductive photoreceptor through a red filter. Exposing the photoreceptor to light through a filter in this manner is called color separation exposure of a color original. The electrostatic latent image formed as a result of color separation exposure is called a color separation latent image. The color separation latent image formed by color separation exposure is a color that is complementary to the color of the filter used for color separation exposure, that is, toner colored cyan (hereinafter referred to as "cyan toner") with respect to the red filter. The resulting cyan visible image is transferred onto a white recording sheet such as paper.

Next, color separation exposure is performed using a green filter, and the formed color separation latent image is visualized with magenta toner.
A magenta visible image is also transferred onto the recording sheet.

Next, color separation exposure using a blue filter and development using yellow toner are performed, and a yellow visible image is also transferred onto the recording sheet.

In this way, the visible images of cyan, magenta, and yellow are sequentially transferred onto the recording sheet and overlap each other.

Color images of color originals can be reproduced. Note that in this specification, "blue" refers to a color that should be accurately called blue-purple.

Now, in the multicolor image forming method as described above, a detector for detecting the toner concentration in the developer is provided, and the amount of toner replenishment is controlled so that the output of this detector is stabilized within a certain range. is kept within a certain range. However, in the case of a color image, unlike a black and white image, there are many so-called solid image parts where the image is formed without leaving any background parts, and therefore there is a large variation in the required amount of toner of each color. Therefore, even if you install a toner density detector as in the past and try to control the amount of toner replenishment based on its detection output, it may not be possible to control the toner density within the appropriate range, making it difficult to obtain good color images. There were times when it was not possible.

(Purpose) The purpose of the present invention is to calculate the required amount of toner for each color by pre-scanning the original and replenish the 1-toner of each color in advance, thereby determining the 1-toner density more accurately. It is an object of the present invention to provide a multi-color image forming method that can maintain the color of the image and thereby always obtain a good color image.

(Structure) The multicolor image forming method of the present invention prescans an original, separates the original into colors and reads the original using an image sensor, and determines the colors required for one sheet of transfer paper based on the read color separation signals. It is characterized by calculating the amount of toner for each color and replenishing the calculated amount of toner for each color in advance.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 schematically shows only the main parts of an example of a color electronic copying machine to which the present invention is applied. Since this is an explanatory diagram, the relative size relationship of each part is not necessarily accurate.

In the figure, reference numeral 10 indicates a photoconductive photoreceptor. Photoreceptor 10
It is drum-shaped and can be rotated in the direction of the arrow. Around the photoreceptor 10, there are a charger 12, an eraser 18, a developing device 20, 22, 24, 26, a holder 28, and a static eliminator 32.
, and a cleaner 34 are arranged. Reference numeral 16 denotes a document placement glass, and the document 0 to be copied is placed flatly on the cumulative placement glass 16.

The exposure optical system indicated by the reference numeral 14 includes a lamp 140, a plane mirror 141, a roof mirror 142, 143, and a lens 144.
, a filter device F. Further, the reading optical system indicated by the reference numeral 40 is a half mirror 401.
, a lens 402, and a color solid-state image sensor 403, and a half mirror 401 is provided in the exposure optical path so as to guide a part of the light beam to the image sensor 403.

In order to scan the original 0 with illumination, the lamp 140 is turned on and the lamp 140 and the plane mirror 141 are integrally moved to the left from the illustrated position, and at the same time the roof mirror 142 is moved towards the plane mirror 1.
Move it to the left at 1/2 the movement speed of 41. Then, the lens 144 forms an image of the illuminated portion of the original O on the photoreceptor 10 , and the lens 402 forms an image of the illuminated portion of the original 0 on the light receiving portion of the image sensor 403 .

The filter device F includes a red filter F1 and a green filter F.
2. It has a blue filter F3 and a neutral density filter (hereinafter referred to as "rND filter") F4, and each filter can be selectively placed in the optical path of the exposure optical system.

The eraser 18 is composed of an LED array 181 and a convergent light transmitter array 182.

The holder 28 is for holding plain paper (hereinafter referred to as "transfer paper") S as a recording sheet, and is formed into a drum shape and rotates in the direction of the arrow as the photoreceptor 10 rotates. It looks like this.

Next, before entering into a detailed description of the present invention, a color electronic copying process using the apparatus shown in FIG. 1 will be briefly described.

Now, when the document 0 is placed on the document placement glass 16 and the apparatus is operated, the photoreceptor 10 rotates in the direction of the arrow and the charger 12 charges the photoreceptor 10 uniformly. Photoreceptor 1
The photoconductive layer of 0 is formed of a photoconductive material having panchromatic spectral sensitivity, such as As2Se3.

Subsequently, the original O is scanned by the exposure optical system 14.

At this time, the red filter F1 of the filter device F is placed in the exposure optical path.
1, color separation exposure is performed, and a cyan latent image is formed on the photoreceptor 10. At the same time as the photoreceptor 10 is exposed, the original O is read by the reading optical system 40.

Document 0 has an achromatic image and a color image on a white background.

The white area and achromatic area on document 0 are referred to as neutral areas.

The color image area and the neutral area of the original document 0 are identified by the output of the image sensor 403 of the reading optical system 40.

When the neutral portion of the document O is identified, the latent image portion corresponding to this neutral portion is erased by the eraser 18. As a result, a cyan latent image corresponding to only a color image is left on the photoreceptor 10. This cyan latent image is visualized by the developing device 20 using cyan toner.

Thus, a cyan visible image is formed on the photoreceptor 10 and moves as the photoreceptor 10 rotates.

The leading end of the transfer paper S is clamped to the holder 28 according to the process sequence, and as the holder 28 rotates, it is held so as to wrap around the periphery of the holder, and is superimposed on the cyan visible image on the photoreceptor 10. . At this time, the transfer device 30 discharges a polar charge that electrically attracts the visible image to the holder 2.
8 is charged and a visible image is transferred onto the transfer paper S by electric force. After the visible image has been transferred, the photoreceptor 10 is neutralized by a static eliminator 32, and residual toner is removed by a cleaner 34.

The green filter F2 of the filter device F is then placed in the exposure beam path and the same process is repeated. Photoreceptor 1
A magenta latent image is formed on 0, but the neutral portion of this magenta latent image is erased by the eraser 18.

The magenta latent image is developed with magenta toner by the developing device 22. The magenta visible image thus obtained on the photoreceptor 10 is transferred onto the transfer paper S in a superimposed manner with the cyan visible image. The blue filter F3 of the filter device F is then placed in the exposure optical path and the above process is repeated. After the neutral part of the yellow latent image formed on the photoconductor 10 is erased by the eraser 18, the remaining yellow latent image is developed by the developing device 24 using yellow toner, and the obtained yellow visible image is Transfer paper S”
It is transferred to the second page.

Next, the ND filter F4 of the filter device F is placed in the exposure optical path and the above process is repeated. As a result, the portion of the electrostatic latent image formed on the photoreceptor 10 corresponding to the color image is erased by the eraser 18, leaving only the latent image corresponding to the neutral portion (hereinafter referred to as "neutral latent image"). The neutral latent image is developed by developing device 2.
6, the image is developed using black toner. When the black visible image thus obtained is transferred onto the transfer paper S, the transfer paper S
is separated from the holder 28 and sent to a fixing device 36, where the toner image is fixed and then discharged from the device as a color copy.

The above is an outline of the color electronic copying process using the example of the apparatus shown in FIG.

The multicolor image forming method of the present invention that can be added to such a color electronic copying process will be specifically described below.

The color solid-state image sensor 403 in the reading device 40 has a large number of minute light-receiving elements arranged closely in a row in a direction perpendicular to the paper plane of FIG. Each light-receiving element corresponds to an image element of 125/3 μm square on the original O, so that one light-receiving element converts information of 125/3 μm square at a time into a signal. Each light receiving element is covered with a minute filter. The filters have three colors: red, green, and blue, and are arranged cyclically in the order of red, green, and blue, as shown in FIG. Looking at the three adjacent photodetectors, one photodetector is covered with a red filter, another photodetector is covered with a green filter, and the remaining photodetector is covered with a blue filter. .

These three light receiving elements correspond to one pixel on the document. Therefore, the image information of one pixel is separated into red, green, and blue and converted into a signal.

On the other hand, the LED array 181 of the eraser 18 is 125. t
Miniature LEDs having a +m square light-emitting surface are closely arranged in a direction perpendicular to the drawing in Fig. 1, and these LEDs
D can be emitted in any combination.

Now, when one of the LEDs emits light, its same-size image is formed on the photoreceptor 10 by the imaging action of the convergent light transmitting array 182. When one LED emits light, a latent image portion corresponding to one pixel can be erased.

In the present invention, before performing the color electronic copying process as described above, the original O is illuminated and scanned by the exposure optical system 14 in the same manner as illumination scanning in a normal copying apparatus. This is called a pre-scan. While performing this pre-scanning, the image sensor 403 in the reading optical system 40 separates the original O into red, green, and blue colors and reads them. Based on the read color separation signals, the amount of toner for each color required for one sheet of transfer paper is calculated, and toner of each color is replenished in advance in the amount determined by the calculation.

Now, if you want to copy a 3-size manuscript, 336
0 (pixels) x2376 (pixels) = 8 XIO
'(pixels) and replenishes toner of that color in advance according to this ratio. Average toner adhesion amount is 0.7m
If g is 7cm2, then 29.7x42. OxO, 7xlO' = 0.87 (
g), the above ratio is subtracted to 0.87 (g) to determine the required amount of toner of that color, which is replenished in advance, and then the color copying process described above is executed.

FIG. 3 shows an example of an electrical system for implementing the invention.

In FIG. 3, symbols 403b, 403g, 403
r indicates a portion covered with a blue filter, a portion covered with a green filter, and a portion covered with a red filter of the color solid-state image sensor 403 in FIGS. 1 and 2, respectively. Each of these element portions separates the color original O in FIG. 1 by pre-scanning, and outputs a signal corresponding to each separated color. Each color separation signal is amplified by an amplifier 41.42.43 and then an analog-to-digital converter 51.
52 and 53 into digital signals Bd, Gd, and Rd, which are input to the arithmetic processing circuit 100. Signal Bd
XGdXl? d are color-separated read signals of blue, green, and red, respectively, and are output as, for example, a 16-step multi-value signal.

Next, the photoreceptor 10 in FIG. 1 is exposed to light to form a cyan latent image. In the switch needle of FIG. 3, terminal CI is first selected. The arithmetic processing circuit 100 outputs a signal Bk. The signal Bk is a binary signal depending on whether a certain pixel is a neutral part or a color image part, and takes "1" when it is a neutral part and "0" when it is a color image part. The signal Bk is stored in the memory 112, and the control circuit 114 performs alignment with the cyan latent image, and the light emission of the eraser 181 is controlled via the eraser drive circuit 116, so that the neutral latent image is erased from the cyan latent image. Ru.

Next, when a magenta latent image is formed, switch SW selects terminal B1. At this time, the arithmetic processing circuit 100 outputs a multivalued signal. This multilevel signal includes information regarding the amount of masking. This signal is input to the comparator 106, and by comparison with the contents of the storage circuit 108, a binary signal M is output which determines whether or not to erase the pixel. Signal M takes "1" for the neutral section, "1" for erase, and "0" for other parts. This signal M erases the neutral latent image from the magenta latent image, and erases the magenta latent image for color correction.

Similarly, when a yellow latent image is formed, switch SW
selects the terminal elbow. The arithmetic processing circuit 100 outputs a multivalued signal Yd including information on the amount of masking, and inputs it to the comparator 102 . The comparator 102 compares the contents of the memory circuit 104 with the signal Yd, and outputs a signal Y which is "1" for the neutral section and color correction erase and "0" for the others. As a result, the neutral latent image is erased from the yellow latent image, and erasing for color correction is also performed.

When an electrostatic latent image is formed for a color image that is not color separated, the switch SW selects the terminal DI.

Binary signal Bk output from arithmetic processing circuit 100 is inverted by inverter 110 and input to memory 112. Therefore, in this case, the latent image portion corresponding to the color image is erased from the electrostatic latent image.

In the present invention, before executing such a color electronic copying process, by pre-scanning the document, the image sensor 4
03, the original is color-separated in advance and read. Each read signal Bd, Gd, I? d is stored, for example, in a memory included in the arithmetic processing circuit 100 at an address corresponding to each part of the document. Based on this stored signal, as described above, the ratio of the area to which the color separation signal is output for each color is calculated, and the amount of each toner to be replenished is calculated in accordance with this ratio. Each toner is replenished in advance according to the replenishment amount calculated in this manner, and the above-described developing process is executed using the replenished toner.

In order to reduce the memory capacity mentioned above, the following may be used. Collect 100 addresses from X=n address) (=n+9 address and Y=m address to Y=m+9 address, and if 50 or more of these 100 addresses are "1", the entire 100 addresses are "1". 1". In this way, the memory size will be approximately 8X], 04 pieces to accommodate the introduction size.

Hereinafter, h identifies whether there is a portion to be developed with toner of each color, that is, whether it is "1" or "0" and calculates the toner replenishment amount based on the ratio of the area, but each color separation signal The value of the,
That is, a signal corresponding to the image density of each color of a color original may be stored, and the toner supply amount may be determined by integrating this density signal. For example, when the concentration is divided into 16 levels from 1 to 16, the maximum adhesion amount is 0.7.
5 (mg/cm2), and if the average concentration in 1 cmz is 14, then let be the replenishment amount per l cm''.

Alternatively, the recording paper may be divided into an appropriate number of parts, and the amount of toner may be calculated and replenished for each divided range. For example, if the recording paper is 3 size, 1 to 1.12 in the X direction.
0 (pixel), 1121 to 2240 (pixel), 2
It is divided into three ranges from 241 to 3360 (pixels), and the amount of I/ner is calculated and replenished for each range. The calculation of the amount of toner may be performed based on a signal of "1" or "0" indicating the presence or absence of toner for each color, as described above, or based on a signal representing the density of the image for each color. You can go.

In the example shown in Figure 1, the neutral area is erased with an eraser before being developed with chromatic toner, and the erased neutral area is separately exposed and then developed with black toner. In the present invention, providing an eraser and exposing and developing the neutral area separately from the chromatic area are not inseparable, and it is also possible to develop only with basic chromatic toner. .

According to the present invention, an original is pre-scanned, the original is color-separated and read by an image sensor, and the amount of toner for each color required for one sheet of transfer paper is determined based on the read color separation signals. Since the toner of each color is replenished in advance by calculating the amount determined by the calculation, even if the required amount of toner of each color changes greatly depending on the color image, the toner concentration in the developer can be maintained accurately. and you can always get good color images.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing only the essential parts of an example of a color electronic copying device to which the present invention is applied, and FIG. 2 is a front view showing an enlarged example of a light-receiving element used in the same device. FIG. 3 is a block diagram showing an example of an electrical system for implementing the present invention. 〇-Original, S-Transfer paper, 403-Image sensor, Bd,
Gd, I? d - Color separation signal. =18- Procedural Amendment Band November 1982 220 Patent Application No. 1.8202/I No. 1 2 Name of Invention Multicolor Image Forming Method 3 Relationship with Person Making Amendment Case Name of Patent Applicant Name (674) Stocks Company Ricoh 4 Representative Director Address 4-5-4 Kyodo, Setagaya-ku, Tokyo
Contents of amendments to the "Detailed Description of the Invention" column and Drawing 6 (1) The 9th line of page 5 of the specification is amended as follows.

Claims (1)

[Claims] Pre-scanning the original, color-separating and reading the original using an image sensor, calculating the amount of toner for each color required for one sheet of transfer paper based on the read color separation signals,
A multicolor image forming method characterized in that toner of each color is replenished in advance in an amount determined by calculation.