JPS6159456A - Formation of polychromatic image - Google Patents

Abstract

PURPOSE:To reproduce the image of an original in a short time by omitting a developing and a transferring process which use toner of specific color unless the output signal of an image pickup element contains a signal corresponding to the toner of the specific color. CONSTITUTION:An exposure optical system 14 makes a prescan on the original O before a color electronic copying process and the image of the original O is read by the image pickup element 403 of a readout optical system 40 while color-separated into red, green, and blue. If the output signal of the image pickup element 403 which is obtained by the prescanning does not contain a signal corresponding to the toner of the specific color, an exposing process using the film of the color complementary to said specific color is omitted and a developing and a transfer process which use the toner of the specific color are omitted; only a developing and a transferring process which use toner of other color and an exposing process before them are carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a multicolor image forming method, and in particular, to a multicolor image forming method that allows the development and transfer steps with specific toners to be omitted depending on the color original. The present invention relates to a color image forming method.

(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 cyan, magenta, and yellow visible images are sequentially transferred onto the recording sheet 2 and overlap each other, thereby reproducing the color image of the color original. 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, regardless of the types of colors used in a color original, development and transfer using cyan toner is based on color separation exposure using a red filter, and magenta development and transfer is based on color separation exposure using a green filter. Each process of development and transfer using toner and development and transfer using yellow toner based on color separation exposure using a blue filter is always performed. Therefore, even if you are trying to reproduce an image of a color original that requires development and transfer using cyan and yellow toner, for example, development and transfer using magenta toner will also be performed, resulting in unnecessary operations. It takes a long time to do this.

(Purpose) An object of the present invention is to detect unnecessary toner of a specific color in advance by pre-scanning, and to omit the development and transfer process with the toner of that color. It is an object of the present invention to provide a multicolor image forming method which enables reproduction of an image of a document having a small number of colors in a short time.

(Structure) The multicolor image forming method of the present invention prescans a document, separates and reads the document using an image sensor, and detects toner of a specific color in the output signal of the image sensor obtained by the prescan. If the corresponding signal is not included,
It is characterized in that the development and transfer steps using the toner of that color are omitted, and only the development and transfer using the L-toner of the other color is performed.

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
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 placing glass, on which an original O to be copied is placed flatly.

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 image of the illumination portion of the document = 5-0 is formed on the photoreceptor 10 by the lens 144, and the lens 402
As a result, the image of the illumination section of the document 0 is formed on the light receiving section 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 "interference 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 general color electronic copying process using the apparatus shown in FIG. 1 will be briefly described.

Now, when the document O is placed on the document placement glass 16 and the apparatus is operated, the photoconductor 10 rotates in the direction of the arrow and the charger 12 uniformly charges the photoconductor 10 -6=. The photoconductive layer of the photoreceptor 10 is formed of a photoconductive material having panchromatic spectral sensitivity, such as As2Se3.

Subsequently, the original ◯ 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, and therefore the original O is filtered through the red filter F1.
A cyan latent image is formed on the photoreceptor 10 through color separation exposure. At the same time as the photoreceptor 10 is exposed, the original O is read by the reading optical system 40.

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

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

The output of the image sensor 403 of the reading optical system 40 identifies the color image area and the neutral area of the original O.

original! When the neutral portion of f&0 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 the 0, and the nib and tral portions of this magenta latent image are 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 portion of the yellow latent image formed on the photoreceptor 10 is erased by the eraser 18, the remaining yellow latent image is developed by the developing device 24 using yellow toner, and the resulting yellow visible image is is transferred onto the transfer paper S.

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 document 0, and one light-receiving element is designed to signal information of 125/3 μm square at a time. 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 μm thick.
Small LEDs having corner light emitting areas are closely arranged in a direction perpendicular to the drawing of FIG. 1, and these LEDs can be used in any combination to emit light. now,
When one of the LEIIs emits light, its same-magnification image is formed on the photoreceptor 10 by the imaging action of the convergent light transmitter 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 pre-scanned by the exposure optical system 14, and the image sensor 403 in the reading optical system 40
The original ○ is separated into red, green, and blue colors and read. If the output signal of the image sensor obtained by this pre-scan does not contain a signal corresponding to a specific color of toner, the exposure step using a filter of a color complementary to that toner color is omitted. At the same time, the development and transfer process using toner of the specific color is omitted, and only the development and transfer process using toner of other colors and the exposure process that is a prerequisite for the development and transfer process are performed. For example, if the color image part of document O is only green, even if document O is prescanned, the light receiving element 4
03, a signal is output only from the light-receiving element portion covered with the green filter, and no signal is output from the light-receiving element portion covered with the red filter and the blue filter. Therefore, when executing the copying process next time, the exposure process using the green filter F2 of the filter device F and the development and transfer process using the magenta toner are omitted, and the exposure process using the red filter F1 of the filter device F and the development using the cyan toner based on the exposure process are omitted. Only the transfer process, the exposure process using the blue filter F3, and the development and transfer process using yellow toner based on the exposure process are performed. By doing so, it is possible to omit the development and transfer process using toner of a specific color and the exposure process that is a prerequisite thereof, and therefore, the time required for the copying process can be shortened. Similarly, when the color image portion of document 0 is only red, only the exposure process using a green filter and a blue filter and the development and transfer process using magenta toner and yellow toner based on the output of the color image sensor 403 are performed.

Furthermore, if there is a neutral part in the document O, the neutral part is identified by pre-scanning, so after exposure is performed by placing the ND filter F4 of the filter device F in the exposure optical path, the developing device 26 uses black toner. Development is performed and then transfer is performed. The portion of the photoreceptor 10 corresponding to the neutral portion of the original O has been erased by the eraser 18 as described above, and this erased portion is exposed through the ND filter F4, developed with black toner, and transferred. .

If there is a neutral part in document 0, that part is the output signal of the part covered with the red filter, the part covered with the green filter, and the part covered with the blue filter in the light receiving element 403 of the reading optical system 40. are equal, it is possible to easily identify that the document O has a neutral portion by prescanning. If it is found through pre-scanning that there is no neutral portion, exposure using an ND filter and development and transfer using black toner based on the exposure are omitted.

Next, a specific means for determining whether or not document 0 contains a signal corresponding to a specific color toner will be described.

Now, assuming that it is possible to copy up to A3 size originals and that there is a resolution of 8 lines per 11,
420 (mm) x 8 (pieces) = 3360 in the direction
(pieces), 297 (mm) x 8 (pieces) in the Y direction
-2376 (memories) memories are provided. Therefore, a portion to be developed with a specific color toner, for example, magenta toner, is identified from the output signal of the light receiving element 403 obtained by pre-scanning, and the identification signal is stored at each address in the memory. If the stored signals in this memory do not include any signal indicating that development should be performed with magenta toner, development and transfer are performed using only cyan toner, yellow toner, and black toner, and development and transfer using magenta toner are performed.
Omit transcription.

However, it is not necessarily necessary to use the memory described above, and it is possible to continuously read the output of the light receiving element 403 during pre-scanning and check whether a signal indicating that development should be performed with toner of a specific color appears. If a signal indicating that the toner of a specific color should be used for development does not appear anywhere, development and transfer using the toner of that color may be omitted.

Further, even if a signal indicating that development is to be performed with a toner of a specific color appears, if the signal is limited to a small area, development and transfer using that toner may be omitted.

Whether development and transfer with toner of a specific color should be omitted may be determined based on masking, that is, the density after color correction. That is, if the cyan toner, magenta toner, and yellow toner are pure cyan, magenta, and yellow, respectively, there is no need for color correction, but each color toner contains components of other colors as impure components. Therefore, for example, when superimposing a magenta visible image on an actual cyan visible image, magenta toner components as impurities already contained in the cyan visible image are added to the magenta visible image in advance. By subtracting , it is possible to improve the color reproducibility of a blue copy image as a mixture of cyan and magenta. The operation for improving the color reproducibility of a color copy image in this way is called color correction. To explain this based on the example in Figure 1, when trying to superimpose a magenta visible image on a cyan visible image, the impurity components contained in the cyan visible image The magenta toner component is calculated and subtracted from the magenta visible image in advance. According to this calculated value, the eraser 18 performs area modulation erasing, and then develops and visualizes it with magenta toner. Superimpose it on the visible image. In this way, the density to be visualized using toner of a specific color is calculated after color correction. Therefore, if the concentration value obtained by this calculation is below a certain value at any location,
Development and transfer using toner of that color is omitted.

Next, an example of an electrical system for implementing the present invention will be explained with reference to FIG.

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
, Gd, and Rd are color-separated read signals of blue, green, and red, respectively, and are output as multi-value signals of, for example, 16 levels.

Next, the photoreceptor 10 in FIG. 1 is exposed to light to form a cyan latent image. The switch SW in Fig. 3 is first connected to the terminal C1.
is 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 11
4, alignment with the cyan latent image is performed, and the light emission of the eraser 181 is controlled via the eraser drive circuit 116, thereby erasing the neutral latent image from the C1Fuan latent image.

Next, when a magenta latent image is formed, switch SU selects terminal B1. At this time, the arithmetic processing circuit 100 outputs a multivalued signal Md. 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 is "1" for the neutral part,
It takes "1" for erase, and "0" for other cases.

This signal M erases the neutral latent image from the magenta latent image, and performs color correction erase for the magenta latent image.

Similarly, when a yellow latent image is formed, switch SW
selects terminal A1. The arithmetic processing circuit 100 outputs a multivalued signal Yd including information on the amount of masking, and inputs it to the comparator 102 . Comparator 102 is memory circuit 104
The signal Yd is compared with the content of the signal Yd, and a signal Y is output which is "1" for the neutral portion 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 separated into colors, the switch or terminal port is selected.

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.

The above is a case where development is performed using cyan, magenta, yellow, and black toners. However, if it is found through pre-scanning that one of the above color toners is unnecessary, use that toner. Omit development. For example, the signal Md obtained during pre-scanning is sent to the comparator 1.
06, compared with the storage signal from the storage circuit 108,
When the signals M obtained by this are all "1", it means that development with magenta toner is unnecessary, so development and transfer with magenta toner are omitted.

Similarly, as a result of prescanning, if development with one or both of cyan, yellow, or black toners is unnecessary, development with that toner is omitted and only development with other toners is performed. .

(Effects) According to the present invention, a document is pre-scanned, the document is color-separated and read by an image sensor, and a signal corresponding to a specific color of toner is included in the output signal of the image sensor obtained by the pre-scan. If it is not included, the development and transfer process using the toner of that color is omitted and only the development and transfer using the toner of the other color is performed, so for example,
When copying documents that use only a small number of colors, such as office documents, part of the series of multicolor image formation processes is omitted, and in the conventional process, for example, the photoreceptor rotates four or three times. According to the present invention, what was previously required is three or two rotations, or one rotation depending on the original, and rapid multicolor image formation is possible.

[Brief explanation of the drawing]

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, FIG. 2 is a front view showing an enlarged example of a light receiving element used in the same device, and FIG. The figure is a block diagram showing an example of an electrical system for implementing the present invention. 〇-Original, 403-Image sensor, Bd, Gd, R
d - Output signal of the image sensor. Procedural amendment November 22, 1980 1 Display of the case Patent Application No. 182022 of 1982 2 Name of the invention Multicolor image forming method 3 Person making the amendment Relationship to the case Patent applicant name Title (674) Ricoh Co., Ltd. 4th 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 with an image sensor, and when the output signal of the image sensor obtained by the pre-scan does not contain a signal corresponding to a specific color toner, A multi-color image forming method characterized in that the steps of developing and transferring with toner of that color are omitted and only developing and transferring with toner of another color is performed.