JPH01116657A - Method and device for forming two-color image - Google Patents

Abstract

PURPOSE:To prevent relative deviation from occurring in case of forming a latent image even if some characteristics of two optical systems are different by obtaining the relative deviation in the position of the image formed through two optical systems respectively and correcting the position of forming the latent image by a portion equal to the relative deviation. CONSTITUTION:The title device is provided with 1st and 2nd latent image forming means 4 and 6 for forming the corresponding latent images by guiding an optical image to a sensitive material 3 with respect to an original 1 which is an object. And development with toner in different colors is respectively executed to the respective latent images formed by the latent image forming means 4 and 6 and toner images in the respective colors are transferred and recorded so as to form two-color images. In such a case, the relative deviation of the position of forming the image based on the respective latent images obtained by the 1st and 2nd latent image forming means 4 and 6 with respect to the same optical image is previously obtained and the position of the latent image formed by the 1st latent image forming means 4 is corrected by the portion equal to the obtained deviation. Even if some characteristics of two optical systems are different, the relative deviation in case of forming the latent image can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to two systems of FMI image forming means in which optical images obtained through different optical systems are paired, and specifically, to A first step that extracts a light image of a specific color from a light image obtained from the first optical system about the original, converts it into image information, and forms a latent image on the sensitive material by light irradiation based on the image information. and a second latent image forming means that guides a light image of a color other than the specific color obtained from the same document through a second optical system onto the sensitive material to form a corresponding latent image. Each latent image formed is developed with toner of a different color, and the toner image of each color is transferred and recorded in a two-color image forming apparatus and the apparatus.

[Prior Art 1] Various image forming apparatuses have been proposed in the past for producing multicolor images of two or more colors on a multicolor original. A common method for image formation is to separate the image on the original using three color separation filters: red (R), blue (B), and green (G), and then to separate the separated optical images. An image forming process is executed and images of each color are superimposed on two sheets of paper to obtain a so-called full-color image.

These so-called full-color image forming devices require synchronization (registration) in order to superimpose images of each color on a single sheet of paper, making the configuration and control of the device extremely complex and making the device large. and become expensive.

On the other hand, if the target manuscripts are limited to document manuscripts, except in very special cases, black characters and figures occupy the majority, and other colors such as underlines and marks are rarely added. be. Therefore, when such @documents are targeted, it is uneconomical to use a full-color image forming apparatus as described above. Furthermore, in this type of full-color image forming device, black is reproduced by mixing three colors (for example, yellow, magenta, and cyan), but it is not pure black, and the image is reproduced with black toner. Compared to a monochrome image forming apparatus that performs black and white image forming apparatuses, the reproducibility of one-to-sixteen colors is inferior to black.

From this point of view, when dealing with originals that are mostly black images, such as document originals, a so-called two-color image forming device that reproduces images in black and one other color is sufficient. Considering the reproducibility of black images, which account for most of the image, this two-color image forming apparatus is even more suitable.

Conventionally, in forming this two-color image, a method using the same optical path has been proposed. For example, in a normal electrophotographic copying machine, a half mirror is installed in the optical system that guides the light reflected from the exposure light source on the document surface onto the sensitive material, and the half mirror separates the light. They are processed separately. Specifically, one type of light is guided onto the photosensitive material with the specific color "red" component cut off, and black toner is developed on the latent image formed on the photosensitive material. Regarding the light, a light image such as an underline of the characteristic color "red" is extracted and converted into image information, and a laser beam modulated based on the image information is superimposed on the black toner developed area. Form a latent image. Then, red toner development is performed on this latent image, and then each color toner image is transferred and recorded onto a single sheet of paper to create a "black" and "red" image.
A two-color image is formed.

When forming a two-color image using the same optical path method that has only one main optical system as described above, half mirror
, there is a large loss in the amount of light guided onto the photosensitive material, and in order to maintain the optimal exposure amount, it is necessary to increase the output of the exposure light source or increase the exposure time, that is, increase the image forming speed. I have to slow down.

The separate optical path system solves this drawback of the same optical path system. This has two independent optical systems and two systems of latent image forming means for optical images obtained through the respective optical systems. In other words, the light reflected from the exposure light source on the document surface is guided onto the photosensitive material with the specific color "red" cut off, and the latent image formed on the photosensitive material is thereby developed with black toner. On the other hand, the light image of the specific color "red" is extracted from the light image obtained from the light reflected by the document surface from another exposure light source via another optical system and converted into image information, and the same as above is performed. Based on this image information, a latent image is formed using radar light, red toner is developed, and the toner images of black and red are transferred and recorded onto a sheet of paper.

If separate optical systems are used to obtain optical images corresponding to each color in this way, there is no particular loss of light quantity, and the drawbacks of the same optical path system can be overcome.

Note that when this function is added to a flash exposure copying machine, two-color image formation using the separate optical path method makes it difficult to perform two-dimensional light detection when extracting a light image of a specific color. For some reason, it is inevitably adopted.

[Problems to be Solved by the Invention] By the way, in the conventional two-color image formation using the separate optical path method as described above, there is a possibility that relative positional displacement of images of each color may occur. For example, if a red underline is drawn on a text document with narrow line spacing, there is a risk that the red underline will overlap the text in the two-color image that is formed.

This is because two independent optical systems are used, so the aberrations, color shift characteristics, etc. of each optical system do not completely match, and even if a latent image is formed using the same optical image, this This is because the latent image forming position is relatively shifted due to differences in aberrations, color shift characteristics, etc. of each optical system.

Therefore, it is an object of the present invention to eliminate the relative deviation when forming a latent image even if the characteristics of the two optical systems are different.

[Means for Solving the Problems] As shown in FIG. 1, the present invention extracts a light image of a specific color from a light image obtained through a first optical system 2 for a target document 1. a first latent image forming means 4 that converts the image information into image information and forms a latent image on the sensitive material 31 by irradiating light based on the image information; and a second latent image forming means 6 for guiding a light image of a color other than the t2 specific color onto the photosensitive material 3 to form a corresponding latent image, the first and second latent image forming means 4.6 It is assumed that a two-color image forming device is used, in which each latent image formed in the image forming apparatus is developed with a different color toner, and each color toner image is transferred and recorded. The technical means for solving the above problem is to determine the image forming position based on each latent image obtained by the first and second latent image forming means 4 and 6 for the same optical image. The relative shift of the first latent image forming means 4 is determined in advance.
This is to correct the position of the latent image formed by the above-determined deviation.

In the above-mentioned two-color image forming apparatus, the apparatus using this is an image based on each latent image obtained by the above-mentioned first and second latent image forming means 4.6 for the same light image. A deviation information holding means 7 inputs and holds information on the relative deviation of the formation positions, and the position of the latent image formed by the first latent image forming means 4 is input and held by the deviation information holding means 7. It is equipped with an image position correction means 8 that corrects the relative deviation determined by the information regarding the image position.

The displacement information holding means for the above-mentioned device includes an information input means for inputting information regarding displacement measured in advance by a person;
Even in a configuration having a storage means for storing information regarding the deviation inputted from this information input means, it is also possible to form latent images by the first and second latent image forming means 4.6 aiming at the same optical image. It can also be realized by a configuration including a displacement amount measuring means for measuring the positional displacement amount of each latent image, and a storage means for storing the displacement measured by the displacement amount measuring means. The latter case is a preferred embodiment in that it is possible to retain the shift information without any special human intervention. In the case of this latter aspect, the deviation measuring means may measure the positional deviation of latent image formation in each latent image forming means 4.6 on a test original with a predetermined image pattern, or it may measure the deviation of the latent image forming position in each latent image forming means 4. and test light source (
It is also possible to measure the iI image forming position in each latent image forming means 4.6 for the light image from LED*).

Further, the deviation information holding means holds the relative deviation bl of each image to be formed at a predetermined test position within the entire image forming range, and the image position correction means , the basic information for latent image formation position correction and the deviation calculating means for calculating the deviation opening corresponding to an arbitrary position of /2 based on the relative deviation of the image at the test position are arranged in the right-hand manner. This will be further specified. In such an embodiment, since the relative displacement amount at each position of the entire image forming range is not retained, it is a preferable embodiment in that the capacity of the memory that specifically implements the displacement information retention means does not need to be increased more than necessary. be.

[Operation] An image based on each latent image obtained by the first and second latent image forming means 4.6 for the same optical image obtained via the first and second optical systems 2 and 5, respectively. Find the relative deviation of the formation position. When a latent image is formed on a predetermined document by two systems of latent image forming means, the first and second latent image means 4 and 6, a latent image is formed by the first latent image forming means. The position of the latent image is corrected by the amount of deviation determined above. Then, each latent image is developed with toner of a different color, and the toner image of each color is transferred and recorded to form a two-color image.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is an illustration of an example of a two-color image forming apparatus according to the present invention, and this example is an embodiment of the two-color image forming apparatus in a flash exposure type copying machine.

In the figure, a flash lamp 12 and an imaging lens 13 are arranged below the platen 11, and the original on the platen 11 is exposed on the other side by light from the flash lamp 13, and the reflected light is transmitted through the imaging lens 13. The image is formed on the photosensitive belt 20. Further, a red filter 14 is disposed in front of the imaging lens 13, so that the optical image formed on the photosensitive belt 20 has no red component.
-become what was done. Around the photosensitive belt 20, a charger 21, a first developing device 22 for developing black toner, a pre-transfer corotron 23, a transfer device 24, and a peeling corotron 25 are arranged to carry out the image forming process. A cleaning device 26 is disposed therein.

On the other hand, in the lower part of the platen 11, in addition to an optical system related to flash exposure (hereinafter referred to as an imaging optical system) consisting of the above-mentioned flash lamp 12, imaging lens 13, red filter 14, etc., other exposure equipment is installed. Another optical system (hereinafter referred to as a writing optical system) is arranged in which the light emitted from the lamp 31 is reflected by the document on the platen 11 and reaches the one-dimensional image sensor 33 via the cell 7 lens 32. . This old optical system is of MIi construction and can be moved below the platen 11 to scan the original. Further, in correspondence with the writing optical system, the first developing device 22 and the pre-transfer roller 1-ron 23 are provided around the photosensitive belt 20.
A charger 34, a light output device 35 that performs exposure processing based on image information corresponding to information detected by the image sensors 3, and a second developer 1 that performs red 1 to toner phenomena.
36 are arranged respectively. The light output device 635 is composed of a light emitting diode array (LED RO8) etc. which is modulated on and off based on the image information.

Then, the latent image formed on the photosensitive belt 20 by the exposure process through the imaging optical system is developed with black toner by the first developing device 22, and the latent image is extracted from the image by the optical system (n). A latent image formed on the photosensitive belt 20 by the light output from the light output device 35 based on the image information corresponding to the specific color "red" component is developed with red toner by the second developer 136, and the black toner image and the red toner image are developed by the second developer 136. The red toner image is transferred onto the paper supplied to the transfer position (transfer unit 24, peeling corotron 25 arrangement position).The transferred paper is further fixed with an image in the fixing unit 27, and then ejected from the machine. be done.

A processing system for the optical image obtained by the writing optical system is shown in FIG. 3, for example.

In this example, an image sensor 33 configured with COD
The structure is such that two adjacent light receiving elements constitute one cell corresponding to a pixel, and a red filter is provided in front of one of the light receiving elements. In FIG. 3, a red light image is extracted and converted into image information using two processing systems for the light receiving element 33a provided with the red filter 37 and the light receiving element 33b in the same state. .

The reflected light from the original 10 via the writing optical system is received by each light receiving element 33a, 33b, and each light receiving element 33a,
A detection signal at a level corresponding to the received light m outputted from 33b is converted to pixel-corresponding desert data as a digital signal via an amplifier 41 and an A/D conversion circuit 42, and is further outputted by a known shading correction circuit 43. The irregularities have been corrected. A gain compensation coefficient circuit 45 is used to compensate for the level difference between the two systems due to the minimum optical attenuation in the red filter 37.
A multiplier 44 multiplies the a degree data via the shading correction circuit 43 by the coefficient values corresponding to each system set in . The wide density data (a) output from one multiplier 44 and the density data (b) output from the other multiplier 44 corresponding to the optical image obtained through the red filter 37 are sent to a comparator 46. Meanwhile, the red 11 degree data is further compared with a reference density value from a gray level coefficient circuit 48 in a comparator 48. Comparator 46
The wide concentration data (a) is lower than the concentration data (b) (
While outputting high aii>i'' bits, the comparator 47 outputs a red image with a certain angle of 81 degrees or higher as a black image. When the brightness is low (low brightness), an O" bit is output, and in other states, a "1" bit is output.

Since "red" becomes indistinguishable from "white" when it passes through the red filter 37, the reason why the comparison 346 output is "1" bit is because the wide density data (a) truly corresponds to red. Therefore, the output of the AND circuit 49, which inputs the bit data corresponding to the pixels from the comparators 46 and 47, is the red ii! which excludes the particularly high-density red part. ii@information. In this red image information, bit 111 II corresponds to a pixel corresponding to red.

On the other hand, 50 is a memory that stores information regarding the relative deviation caused by the difference between the imaging optical system and the writing optical system, and 51 is a red image output from the AND circuit 49 based on the information regarding the deviation stored in the memory 50. This is a positional deviation correction circuit that corrects information, and the red 11! Image memory 52 in which i-image information is configured as a bitmap
It is designed to be stored in . And image memory 5
The output light from the light output device 35 is modulated based on the red image information stored in the photoreceptor belt 20, and a corresponding latent image is formed on the photoreceptor belt 20.
formed on top.

The information regarding the deviation stored in the memory 50 is collected, for example, during the final manufacturing process of the copying machine or at the user's location. Specifically, as shown in FIG. 4, position A (0,0) and position B (Xi, y
A two-color image with the same light image obtained by the imaging optical system and the writing optical system is formed on the paper using the reference document on which the test pattern is drawn in (1), and the position of the formed test pattern of each color is determined. Measure the deviation aO1 in the X direction at A, the deviation bO1 in the y direction, the deviation Δx1 in the X direction, and the deviation Δy1 in the
, bo) and B=(xi+Δx1, yl+ΔVl) are written into the memory 50 in association with the position information A (0, O) and B (xi, yl). This information writing is performed by input operations using a numeric keypad and special operation keys provided on the copying machine. The correction algorithm in the positional deviation correction circuit 51 based on the information regarding this deviation is as follows. That is, assuming that the shift occurs linearly within the image forming range, any position C'(x', y') in FIG.
The position specified by is x=x −−x =・α ... (1) α−(Δx1
-ao)/(Xl-1-Δx1-ao)y-y--y
−・β ...(2) β=(Δyl −bo)/(yl ”−Δyl −b
o) is corrected to the position C(x, y) specified.

A specific configuration of the positional deviation correction circuit 51 that realizes such correction is shown in FIG. 5, for example.

In this positional deviation correction circuit 51, an AND circuit 49
The position of the red image information is corrected via the light output device 35.
When sending a signal to the line memory 67, the red image information is first addressed and stored in the line memory 67 by the write 0 block 63 via the multiplexer 65. At this time, ΔX
Write modulation is performed based on the ΔX correction data stored in the correction data storage circuit 61 and according to the above equation (1). Specifically, when reducing the position (distance) (Δx<0)
The red image signal is thinned out using the ΔX correction data (for Δx<O), and is left as it is when the position (distance) is expanded (Δx>0).

Next, the red image information in the line memory 67 is read out by the read clock 64 via the multiplexer 65 and stored in the image memory 52 via the multiplexer 68. At this time, readout is modulated based on the ΔX correction data in the same manner as above. Specifically, when expanding the position (Δx>0), the interval is expanded using ΔX correction data (Δx>Q) and stored in the image memory 52, and the position (
(distance) is output as is.

That is, if the position is to be shortened, the position is corrected when it is stored in the line memory 67, and if the position is to be expanded, the position is corrected when it is read from the line memory 67.

When one page of red image information is sequentially written into the image memory 52 in the X direction corresponding to the corrected position, the position data corrected according to the above equation (2) becomes Δ
The data is read out from the y correction data storage circuit 62, and based on this correction flow position data, the y address designation circuit 69 controls the read timing of the bit data in the X direction from the image memory 52.

As described above, in the positional deviation correction circuit 51, the positional deviation correction in the X direction is performed when filling the image memory 52, and the positional deviation correction in the X direction is performed when reading from the image memory 52. There is.

Note that the above correction can also be performed for each block by dividing an area of one page into a plurality of blocks. There may be some expansion and contraction in some areas.

When using a copying machine as described above to target a red and black two-color image @ original, when the two-color image copying mode is selected and the start operation is performed, the writing optical system first scans the original,
The light image corresponding to red is extracted and converted into red image information, and further, the position is corrected in the X direction as described above according to the information regarding the deviation in the memory 50, and the red image information is bit mapped in the image memory 52. will be questioned on the matter. Next, flash exposure is performed using the imaging optical system, and the photosensitive material 20
A latent image corresponding to a non-red light image formed on the photosensitive drum is developed with black toner by a first developing device 22. Then, based on the red image information read from the image memory 52 so as to correct the positional deviation in the y direction, the light output device 35 writes a latent image over the black toner image area on the photosensitive material 20. After that, the latent image formed by writing with the optical output device 35 is developed with red toner in the second developing device 36, and the black toner image and the red toner image are transferred onto the sheet of paper that is conveyed to the transfer position.
Furthermore, a fixing process is performed in a fixing device 27, and a two-color image corresponding to the original is reproduced.

Note that the processing system for the optical image obtained through the optical system shown in FIG. Processing may be performed in two systems by time sharing in one system.

As described above, according to this embodiment, a first image is formed based on a light image obtained through the writing optical system for the test pattern of the test document, and a first image is formed based on the light image obtained through the imaging exposure system. The relative deviation from the formed image is measured, and the deviation is corrected at any position based on the information regarding the deviation, so it is possible to create a two-color image based on the optical image obtained through each optical system. is now formed without any displacement.

In the above embodiment, the deviation of the image forming position is actually measured by a person, but it is also possible to configure it so that it is measured automatically. For example, an image sensor for detecting the toner image forming position in the X direction and the Y direction on the photosensitive belt 20 is provided downstream of the first developing device 22, and the above-mentioned test pattern is exposed through an imaging optical system. At this time, the position of the black toner image formed on the photosensitive belt 2° is detected by this image sensor, and the relative positional relationship between the detection result and the test pattern position on the original document is determined.

On the other hand, for the same test pattern, the relative positional relationship between the positional data of the optical image obtained by the writing optical system and the position of the test pattern on the original document is determined. By using the deviations between the relative positional relationships in each optical system obtained in this way as the above-mentioned deviation information, the same effect as in the above embodiment can be obtained.

Note that it is preferable to collect information regarding the deviation from test patterns at more positions in order to perform accurate correction. That is, the above-mentioned correction calculation is performed in a more detailed range. Ideally,
The purpose of this method is to collect shift information for each pixel in the image forming range (one page) and store it in the image memory in a corresponding manner.

In addition, to collect misregistration information, in addition to performing the actual copying process on the manuscript with the test pattern described above, we also use a test light source (such as an LED) installed at a predetermined position.
It is also possible to use the optical image from the . In this case, the test light source is fixedly provided, so
More accurate information can be collected.

Further, in the above embodiment, a light emitting diode array is used as the light output device 35, but the present invention is not limited to this, and for example, a liquid crystal shutter array, a laser scanner, etc. may be used.

[Effect of the Invention J As explained above, according to the present invention, the relative shift of the image positions formed through the two optical systems is determined, and the latent image is formed by the amount of this relative shift. Since the position is corrected (the first latent image forming means is opposite), there is no relative shift when forming the latent image even if the characteristics of the two optical systems are different. Therefore, when forming a two-color image, it is possible to correct the relative positional deviation of each color image, and for example, it is possible to prevent a red underline from overlapping a character portion.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, and FIG. 2 is a two-color ii! according to the present invention! FIG. 3 is a block diagram showing an optical image processing system obtained through a writing optical system; FIG. 4 is a diagram showing an example of a positional deviation correction algorithm; FIG. 5 FIG. 2 is a block diagram showing a detailed configuration example of a positional deviation correction circuit. [Explanation of symbols] 1.10... Original 2... First optical system 3... Sensitive material 4... First latent image forming means 5... Second optical system 6... - Second latent image forming means 7... Displacement information holding means 8... Image position correcting means 11... Platen 12... Flash lamp 13... Imaging lens 14... Red filter 20. ...Photosensitive belt 22...First developing machine 31...Exposure lamp 32...Selfoc lens 33...Image sensor 35...Light output device 36...Second developing machine 41... Amplifier 43... Shading correction circuit 44... Multiplier 45... Gain correction coefficient circuit/16.47... Comparator 50... Memory 51... Position deviation correction circuit 52... Image memory Patent applicant: Fuji Xerox Co., Ltd. Agent
Patent Attorney Tomohiro Nakamura (2 others) Figure 1 Figure 2 Figure 4 B' (X1+AX4.y1+, ay4) Figure 5

Claims (1)

[Claims] 1) First optical system (2) for target original (1)
A first latent image formation process in which a light image of a specific color is extracted from the light image obtained through the process and converted into image information, and a latent image is formed on the sensitive material (3) by light irradiation based on the image information. Means (4)
and a second latent image for forming a corresponding latent image by guiding a light image of a color other than the above-mentioned specific color obtained from the same original (1) through a second optical system (5) onto the sensitive material (3). A two-color image is formed by developing different color toners for each latent image formed by the two systems of latent image forming means (6) and transferring and recording the toner images of each color. In doing so, the first and second latent image forming means (4) are applied to the same optical image.
) The relative shift of the image forming position based on each latent image obtained in step (6) is determined in advance, and the position of the latent image formed by the first latent image forming means (4) is determined as above. A two-color image forming method characterized by correcting only the amount of deviation. 2) First optical system (2) for the target document (1)
A first latent image formation process in which a light image of a specific color is extracted from the light image obtained through the process and converted into image information, and a latent image is formed on the sensitive material (3) by light irradiation based on the image information. Means (4)
and a second latent image for forming a corresponding latent image by guiding a light image of a color other than the above-mentioned specific color obtained from the same original (1) through a second optical system (5) onto the sensitive material (3). forming means (6), each of the latent images formed by the first and second latent image forming means (4) and (6) is developed with a different color toner, and the toner of each color is developed. In a two-color image forming apparatus that transfers and records images, the first and second latent image forming means (4
) (6) A deviation information holding means (7) for inputting and holding information regarding the relative deviation of the image forming position based on each latent image obtained in step (6); and the first latent image forming means (4). and an image position correction means (8) for correcting the position of the formed latent image by the relative deviation determined by the information regarding the deviation in the deviation information holding means (7). Image forming device. 3) The deviation information holding means (7) has an information input means for inputting information regarding the deviation, and a storage means for storing information regarding the deviation inputted from the information input means. The two-color image forming apparatus according to scope 2. 4) The deviation information holding means (7) holds the relative deviation amount of each image to be formed at a predetermined test position within the image forming range, and the image position correction means (7)
8) is characterized by having a deviation amount calculation means for calculating the deviation amount corresponding to an arbitrary position, which is basic information for latent image formation position correction, based on the relative deviation amount of the image at the test position. A two-color image forming apparatus according to claim 2. 5) The displacement information holding means (7) measures the amount of positional displacement of each latent image formed by the first and second latent image forming means (4) and (6) targeting the same optical image. 2. The two-color image forming apparatus according to claim 1, further comprising a deviation measuring means and a storage means for storing the deviation measured by the deviation measuring means. 6) The two-color image according to claim 5, wherein the deviation amount measuring means measures the deviation of the latent image forming position in each latent image forming means for a test document. Forming device. 7) According to claim 5, the deviation amount measuring means measures the deviation of the latent image forming position in each latent image forming means with respect to the light image from the test light source. Two-color image forming device.