JPH0450964A - Digital image forming device - Google Patents

Abstract

PURPOSE:To prevent the disturbance of an image by detecting that the picture data of the first color is adjacent to the picture data of the second color, converting an adjacent picture element into a blank, and carrying out writing. CONSTITUTION:When first picture data is adjacent to second picture data, the data of an adjacent part is detected, and converted, into the blank, and a region where the writing is not carried out is provided between first and second pictures. Therefore, the circumference of a first toner image has a high surface potential part, and the barrier of potential can be formed between the toner and a part where the potential is reduced by second writing, even if potential difference is the same. Simultaneously, a distance with respect to the part where the potential is reduced is great, so that an influence to the toner caused by the low potential of a written part is lessened. Thus, force acting on the toner is weakened, and the movement of the toner and the disturbance of the image can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention sequentially writes recording signals of two colors on a photoreceptor,
The present invention relates to a digital image forming apparatus that is applied to an electrophotographic digital copying machine, an electrophotographic printer, a facsimile machine, etc., which has a color identification function that produces two-color hard copies (duplicates) in one transfer.

[Conventional technology]

Conventionally, electrophotographic digital technology scans a light beam from a light source onto a scanning medium such as a photoreceptor to form an electrostatic latent image, and this electrostatic latent image is developed with toner or the like to make it visible. This digital image forming apparatus is widely used not only as a copying machine but also as a facsimile machine, a computer output device, etc. In particular, with the spread of color displays, color recording 2. Description of the Related Art In accordance with the demand for color copying machines and the spread of color copying machines, two-color or multi-color recording has come to be performed.

As such a digital image forming apparatus, for example, a non-impact printer as described in Japanese Patent Application Laid-Open No. 51-28963 is known. After this, reversal development is repeated multiple times to form toner images of multiple colors on the recording medium, which are simultaneously transferred onto a transfer medium.

[Problem to be solved by the invention]

By the way, claim 2 of the above-mentioned publication states that the toner images of multiple colors formed on the recording medium are toner images of multiple colors formed at mutually different positions on the recording medium. There is. Moreover, looking at the examples, it is explained that due to the nature of the two-time writing electrophotographic process, two toner images do not overlap, but are formed in different colors and at different positions.

Therefore, in this method, if image data of different colors exist adjacently, images will be formed adjacently.

Such image forming devices repeat the image forming process of charging, negative exposure, and development multiple times to form multiple color images on a photoreceptor, and simultaneously transfer multiple color toner images onto transfer paper. Since this is a method in which image formation is performed by using a second image, when an image is written for the second time, an electrostatic latent image has already been formed by the first writing, and a toner image that is developed from the electrostatic latent image is formed on the photoreceptor. . Therefore, if the image data for which the first writing is to be performed and the image data for which the second writing is to be performed are adjacent to each other, it is possible to perform the second optical writing adjacent to the toner image formed in the first image forming process. become. In this case, a low potential portion of the photoreceptor is created close to the toner image.

Toner is charged with a polarity that causes it to receive a force that moves toward the lower potential, so the potential gradient between adjacent pixels causes some toner to move toward the area of the pixel that was written later, causing image disturbance. occurs.

However, the above-mentioned publication does not disclose any specific means for eliminating this image disturbance.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a digital image forming apparatus equipped with a means for solving the problem of image disturbance as described above.

[Means to solve the problem]

In order to achieve the above object, the invention according to claim 1 of the present application includes a reading means for receiving a light image from an object to be copied and separating image data of a predetermined color to obtain first and second recording signals; a first writing means for writing on a photoreceptor to form an electrostatic latent image on the photoreceptor based on the first recording signal; and developing the electrostatic latent image formed by the first writing means. a first developing means; a second writing means for writing on the photoreceptor developed by the first developing means based on the second recording signal to form an electrostatic latent image on the photoreceptor; A second developing means for developing the electrostatic latent image formed by the second writing means, and a means for simultaneously transferring the toner images formed by the first and second developing means onto a transfer paper. The digital image forming apparatus may further include means for converting at least one of the recorded data into blank when the write data of the first recording signal and the write data of the second recording signal are adjacent to each other. Features.

Further, in the invention according to claim 2, in the digital image forming apparatus, when write data of the first recording signal and write data of the second recording signal exist adjacently, at least one of the recording data It is characterized by comprising means for reducing the amount of light used for writing.

That is, in the digital image forming apparatus according to the present invention, it is detected that the first color image data and the second color image data are adjacent to each other, and the adjacent pixels are converted to blanks or the adjacent pixels are written. The feature is that writing is performed by reducing the amount of light.

[For production]

The operation of the present invention will be explained below, but in order to make the explanation easier to understand, the problem to be solved by the above-mentioned invention will first be explained with reference to FIG.

The upper part of FIG. 1 shows the potential profile of the surface of the photoreceptor and the position where toner adheres, and the lower part shows the charging state of the photoreceptor in terms of charge and the position where toner adheres. Also, in the upper and lower rows of Figure 1 (
A) to (d) correspond to each other, and in the lower diagram, they are shown broken down into (e) to (g) as corresponding to (e) in the upper diagram.

In FIG. 1, when the photoreceptor is charged by a charger prior to image formation, charges are attached to the photoreceptor as shown in (a), and the surface potential becomes VD.

Next, when optical writing is performed according to the first image data,
As shown in (b), the charges in the portion irradiated with light are discharged, and the potential of that portion becomes V. Then, when the formed electrostatic latent image is subjected to reversal development by applying a bias voltage ■1, (
As shown in C), toner adheres to areas with low potential, and the potential after development becomes V,,' due to the charge held by the toner.

Next, a second charging is performed to return Vt,' to the original potential, VD, as shown in (d). Note that even if the potential before the second writing is returned to VD or the potential after development is left as is without returning to a value close to VD, the bias voltage for the second development can be set to the predetermined value. By setting this, it is possible to form a good monochrome image. Alternatively, by increasing the charge amount of the toner used in the first development or by decreasing the capacitance of the photoreceptor, VL' can be increased and brought closer to v+, so the second charge is not always necessary. It doesn't belong to.

Next, while the first developed image remains formed on the photoreceptor, optical writing is further performed using second image data. (e)
and (e) to (g) are cases where the image data of the second writing is adjacent to the image data of the first writing, and as can be seen from the potential profile, the image data of the first toner image is As a result of the second writing performed next to it, the potential of that portion decreases, and a large potential difference occurs between the toner image and the toner image.

Due to this potential difference, the toner of the first toner image acts to develop the area where the second writing has been performed, and moves to the area where the second writing has been performed. In other words, a portion of the toner forming the first toner image is scattered in the area of the second image, causing bleeding. Since the above-mentioned moving toner has an electric charge, the surface potential of the photoreceptor lowered by the second writing is reduced by an amount corresponding to the amount of electric charge, and the second The amount of toner adhesion due to development is reduced. Therefore, even if the same writing is performed, the color tone and density will differ depending on the presence or absence of adjacent images.

On the other hand, in the invention according to claim 1 of the present application, when the first image data and the second image data are adjacent to each other, the data in the adjacent part is detected and converted to blank, and the first image data and the second image data are Since there is an area where no writing will be done between the two images,
There is a part with high surface potential around the first toner image,
Even though the potential difference is the same, a potential barrier is formed between the toner and the portion where the potential decreases in the second writing. At the same time, since the distance to the portion where the potential decreases increases, the influence of the low potential of the written portion on the toner becomes smaller. As a result, the force acting on the toner is weakened, and it is possible to prevent the toner from moving as described in the explanation of the problem above.

Further, in the invention according to claim 2 of the present application, when the first image data and the second image data come into contact with each other instantaneously, the data in the adjacent portion is detected and written while reducing the amount of light to be written.
The decrease in potential due to the second exposure in (e) in the upper row of Figure 1 is (e
′).

Therefore, the difference in surface potential between the pixels formed by the second writing written adjacent to the first toner image becomes smaller, and the force acting on the toner becomes weaker, causing the toner image to become smaller as described in the explanation of the problem above. can prevent the movement of

Note that if the data is converted to blank as in the invention described in claim 1, the data of that pixel will be completely lost, so there is a risk that the image will be missing in that part.
If writing is performed by lowering the writing light as in the invention described in claim 2, the pixel is formed as a light-colored pixel, and the existence of the pixel can be shown on the transferred image. The problem of omission can also be prevented.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

First, as an image forming apparatus of the present invention, an outline of a copying apparatus for forming an identification monochrome image will be explained with reference to the block diagram of FIG.

In Figure 2, the reading system scans the original in a direction perpendicular to the slit while illuminating the original with a light source in the form of a slit, and uses a lens, reflector, etc. to produce a reflected light image in a direction parallel to the slit for illumination. An image is formed on two line-shaped imaging sections in which a large number of photoelectric conversion elements are arranged. At this time, an optical image that does not include image data of a predetermined color is formed in one imaging section through a transmission type filter of the color to be identified, and an illumination light source and a lens are formed in the other imaging section. , an optical image of the entire spectrum of light determined by a mirror or the like is formed.

Next, a color separation circuit performs color separation from the output signals of these two imaging means, converting all colors including the color to be separated into brightness signals, and a monochrome image signal and a filter color image. Separate into signals.

Then, A/D conversion is further performed, and if there are adjacent pixels, the adjacent pixels are removed or the removed pixels are written into the memory, and after this, a predetermined image is converted to the image data as necessary. Each image data is processed and written as an electrical signal to a buffer memory for timing adjustment with a writing system, which will be described later.

A writing system that writes image data onto a photoreceptor using light is
Image data sent by a command signal from the controller 1 is converted into an optical signal at a predetermined timing and written on the photoreceptor.

The controller 2 that controls the image forming section is the controller 1
By exchanging data with the controller 1, the writing system sends a timing signal for starting writing to the controller 1, and also controls an image forming section that forms an image using an electrophotographic method in accordance with the timing. A monochrome hard copy corresponding to the identified color data (
make a copy).

These reading system, writing system, and image forming section are controlled with timing adjusted by a controller 1 and a controller 2, which are connected through a mutual communication path.
Each function is executed while sending and receiving data necessary for each operation under the control of the controller 1.2.

Hereinafter, each function will be explained based on the block diagram of FIG. 2.

Here, FIG. 3 shows an imaging lens placed between the original illumination and photoelectric conversion in FIG. The devices CCD1 and CCD2 are shown.

As shown in FIG. 3, the reflected light from the original is collected by a lens and is incident on two prisms each having a half mirror on the boundary surface. The light split into transmitted light and reflected light by the half mirror is totally reflected by each prism and then sent to CCD1 and CCD.
Image is formed on CD2.

On the CCD 2 side, a filter of the color to be identified from the original is inserted. For example, when identifying red from a document, a red absorption filter is inserted. The advantage of using two prisms here is that CCD 1 and CCD 2 can be placed on the same plane. That is, if the CCD 1 and the CCD 2 are placed on the same plane, assembly, adjustment, etc. will be easier.

The reflective surfaces of the lens, prism 1, and half mirror have characteristics that do not absorb light in a specific spectrum in the visibility band from the light reflected from the original, and an image of the original in white light is formed on the CCD 1. Image. In other words, information about the image of the original is received as information about the brightness of the reflected light. When a red filter is inserted in the CCD2, light other than red is absorbed, so images of colors other than red and black on the original are black, light reflected from the red image is transmitted, and light reflected from white is colored red. Only the components pass through. Therefore, as image data received by the CCD 2, the level of reflection from the white part of the original and the reflection from the red part of the original are the same, resulting in data in which white and red cannot be distinguished.

When receiving reflections from areas of other colors, the amount of light decreases due to absorption by the filter, and is interpreted as dark data. In other words, the image data is obtained by removing the red image data from the image data of the CCD 1.

Furthermore, by inserting a filter of another color, you can similarly obtain image data excluding the image data of that color.

The purpose of inserting a filter as shown in Figure 3 is to identify the changed color when changing the color of the toner stored in the second color developing device, which will be described later. This is because when you want to match the colors, you can easily do this by replacing the filter. In addition, if it is not necessary to replace the filter alone, you can use methods such as giving the prism 2 a filter function, giving the half mirror a filter effect on the transmitted light, or gluing the filter to the CCD 2. I can do it.

Next, FIG. 4 shows another example of color separation in place of FIG.
A light receiving section 1 and a light receiving section 2 are arranged adjacent to each other at an interval corresponding to one pixel of a two-line CCD, and the arrangement of functional blocks for manipulating signals obtained by receiving light is shown. These are housed in an IC package with a window on the top for receiving light.

Here, the light receiving section 2 has a filter formed on the surface of the IC chip and has the function of the CCD 2 shown in FIG. 3, and the light receiving section 1 has the same function of <CCDI.

Further, the lines of the light receiving sections 1 and 2 are arranged so as to line up with the image formation plane formed by the imaging lens in a direction perpendicular to the scanning direction of the reading system while illuminating the document with slit exposure. Since the image formed on the two-line CCD moves according to scanning for reading the original, the light receiving section 1 is arranged so as to be on the upstream side in the direction of movement on the image forming plane.

The image formed on the light receiving sections arranged in the direction in which the document is scanned moves in accordance with the speed at which the document is scanned. The distance between lines is equivalent to 1 pixel, and the scanning speed is determined so that the time to scan 1 pixel corresponds to a moving distance of 1 pixel, so the image detected by the light receiving unit 1 located on the upstream side is , is detected by the light receiving unit 2 with a delay corresponding to one pixel in the sub-scanning direction.

To identify the color of a document, image data at the same position on the document is compared, so an analog memory is provided on the upstream side of the light receiving section 1 in order to compensate for a delay of one pixel.

Each light-receiving section converts light into an electrical signal, and more specifically, it changes the flowing current depending on the intensity of the light, integrates the change in current, and converts it into an amount of charge.

The photo storage gate controls the start and stop of integration, and the charge accumulated by integration for a predetermined period of time is transferred to the shift register by the shift gate. The charge transferred to the shift register is sequentially moved in the direction of the arrow in the figure by a shift lock (not shown in the figure) that transfers in the line direction of the shift register, and the amount of charge is converted into voltage at the output section. Outputs image data as analog voltage data.

Note that the data of the light receiving section 1 is the same as that of the light receiving section 2 except that it is delayed by one line in the analog memory. Further, output 1 and output 2 are respectively output from CCD1. Corresponds to the output of C0D2.

The feature of this color identification method is that compared to color identification using a 3-line CCD equipped with R, G, and B filters, only a specific color can be identified, but because it uses 2 lines, various gates other than the light receiving section and shift Since peripheral circuit elements such as resistors can be placed on both sides of the light receiving section, the two light receiving sections can be brought into instantaneous contact. Since the two light receiving sections are adjacent to each other, only one buffer line is required to adjust the time difference between the lines. Furthermore, since IC manufacturing technology can be applied as is, it is easy to increase the degree of parallelism and alignment between the two lines, making it easy to adjust the reading system. However, since it has a built-in filter, it is no longer possible to change the color it identifies by simply replacing the filter.

Next, FIG. 5 is a more detailed block diagram of the reading system shown in FIG. 2 after the photoelectric conversion section. (B) is a block diagram when writing is performed by converting the pixels adjacent to the WJ to blanks. FIG. 3 is a block diagram when writing is performed by reducing the amount of writing light of a pixel.

Here, CCD1 and CCD2 in Fig. 5 (A) and (E3)
correspond to CCD1 and CCD2 in FIGS. 3 and 4, and output an image signal not passed through a filter and an image signal excluding an image signal of the color of the filter, respectively.

As an example, the signal of CCD1 is W (white), and the signal of CCD2 is
The signal is represented by W (white) - R (red).

In FIGS. 5A and 5B, W is input to an amplifier A1 whose amplification degree can be set by an external signal AGCI. This A
The GCI is set to A1 from the memory in synchronization with the image data by a start command from the controller 1 in Fig. 2, and is set to A1 from the memory in synchronization with the image data. Variations in sensitivity are corrected. That is, so-called shading correction is performed.

Here, A1 is an inverting amplifier, and its output is assumed to be B. In addition, W and W-R are input to input terminals with different polarities in A2, and W-R is reduced from W, and at the same time, image data R is corrected by AGC2 in the same way as A1, and has the same color as the filter color. is output.

Output B (black) from A1 is converted to 6-bit digital data by an A/D converter, and simultaneously binarized at a predetermined density level to obtain data for detecting adjacent pixels of B and R. . The threshold level for binarization is
This is the density level at which it is necessary to remove pixels when they are adjacent to each other. Normally, it is desirable to set the density to a low level in order to prevent toner from scattering to adjacent pixels, but if the level is close to the background data of the document, the background will be judged as data and adjacent pixels will be unnecessarily removed. Since there is a possibility that it will be removed, the level should be set to at least allow for the density of the skin. In the embodiment, the level can be changed using binary level command data from the controller 1. Further, the user can select and set the binarization level from the operation section as necessary, and the controller 2 transmits the selection and setting to the controller 1.

Image data R is subjected to 1-bit A/D conversion, that is, binarized. This binarization level is configured to be variable by a signal from the controller, similar to the binarization levels of Al and A2. For example, if the paper of the original to be copied is pale pink, there are cases in which the background of the original is desired to be copied in red and in cases in which it is desired to be copied in white. In such a case, each case can be handled by changing the level of binarization using a selection signal from the operation section.

6 obtained by A/D converting B using this binary signal of R.
The gate before inputting the bit data to the γ converter is R
The gate is closed when a binary signal exists, and the gate is opened when there is no signal.

This gate is pulled down on the output side so that the output data is blank data when it is closed. Therefore, when there is a signal obtained by binarizing R, blanks are inserted as B data, and when there is no signal, B data is passed through as is.

In other words, since the B data is switched using the binarized R data, even if there is a problem with the alignment or parallelism of the CCDI and CCD2, the image at a certain position will not be red and black at the same time. The configuration is such that it essentially does not occur.

The 6-bit B-R data input to the γ conversion section is 8
It is converted into 8-bit data using a table configured to select any 64 states that can be expressed in 6 bits from 256 states that can be expressed in bits, and written to the buffer memory.

This conversion unit corrects the input/output characteristics of the reading system, corrects the relationship between the writing light amount of the image forming unit using electrophotography and the image density of the copy, and performs binarization by rewriting the data in the table to be converted by the controller 1. ,negative·
You can perform positive inversion, etc.

Next, FIGS. 5(A) and 6 show an example of converting a red pixel into a blank when there is an adjacent black pixel.
This will be explained with reference to Figure (A).

The portion constituted by the shift register SRI, SR2° adjacent pixel determination section, and gate in FIG. 5(A) fulfills this function. A detailed block diagram of this part is shown in FIG. 6(A). The operation will be explained below with reference to FIG. 6(A).

The shift register SRI is constituted by two line memories, and a selector 1 sequentially switches the two lines for each line of COD reading, and alternately inputs red binary data. A selector 3 for selecting and outputting data is also provided on the output side.

The shift register SR2 is composed of four line memories, and the selector 2 switches the four lines in the order of 1, 2, 3, 4, 1, 2, etc. for each line read by the CCD. The binarized data is input. The number of registers required to detect and remove adjacent pixels is 1 for red and 13 for black, but a buffer is required to continuously process the entire surface of the image to be copied in synchronization with the CCD reading clock. One more tube is provided for each.

Selector 2, which controls the input of SR2, not only switches the input line for the input binarized image data, but also switches the three lines used for determining adjacent pixels to operate as a ring buffer. . Three bits at the rear ends of these four line memories are connected to selectors 4, respectively.

Since the selector 4 determines adjacent pixels from the connected 12-bit data, it selects 8 bits of data corresponding to the surroundings of the red pixel to be determined. 0 The selected 8-bit data is processed by the decoder as follows: It is determined whether it is O or not. If it is other than 0, it is determined that there is a black pixel adjacent to the red pixel of interest.

In this embodiment, when there is a black pixel adjacent to a red pixel, that red pixel is blanked, so when determining whether there is a black pixel adjacent to it, the red pixel of interest is It is not necessary to determine whether or not a pixel exists; in other words, when it is determined that a black pixel exists, the purpose is achieved by converting the red pixel of interest into a blank.

Now, when the decoder determines that a black pixel exists, the determination result is held in a register within the decoder.
The gate is controlled by the data in the determination result register in synchronization with the timing when the red pixel of interest passes through the gate, and a red pixel that has an adjacent black pixel is converted into a blank.

In FIG. 6A, the data shown with diagonal lines in SRI indicates the red pixel of interest at a certain timing, and the data shown with diagonal lines in SR2 shows the surrounding black pixels. At this time, the selector 4 selects eight pieces of data indicated by diagonal lines from the twelve connected pieces of data. Then, the decoder determines whether the value of the selected data is 0 or not, stores the determination result in a determination result register, and controls opening and closing of the gate at the timing when the red pixel of interest passes through the gate. In addition, the six line memories shift data using the same clock as the pixel clock of the CCD, and by determining the existence of adjacent pixels each time the data is shifted, the data for the length of the line is sequentially stored in this connection. Make a judgment. Next, selectors 1 to 4 are switched to determine the existence of adjacent pixels based on the three data items 2.3.4 of SR2, and processing of the red pixel in line 1 of SRI is performed.

The processed red data is then written to the buffer memory that holds the red data shown in FIG. 5(A).

In the embodiment shown here, the data for two lines corresponding to the leading edge of the red image and the two pixels at the beginning of each line cannot be determined because the data for determination is not available. By adding a processing unit to determine this part, it is possible to determine the existence of adjacent pixels in the main scanning direction and the existence of adjacent pixels in the sub-scanning direction, etc. It is possible to make possible judgments based on the data alone, or write the data as is without processing it, or convert all data that cannot be judged to blanks. Since this is a problem only with lines, it has little effect on the finished copy, so either method may be used.

Next, FIGS. 5(B) and 6 show an example of writing a red pixel with a low light intensity when there is an adjacent black pixel.
This will be explained with reference to Figure (B).

The portion constituted by the shift registers SRI and SR2, the adjacent pixel determination section, and the gate shown in FIG. 5(B) fulfills this function. A detailed block diagram of this part is shown in FIG. 6(B). The operation will be explained below with reference to FIG. 6 CB).

The shift register SRI is constituted by two line memories, and a selector 1 sequentially switches the two lines for each line of COD reading, and alternately inputs red binary data. The 6-shift register SR2, which is also provided with a selector 3 that selects and outputs data on the 8-output side, is composed of 4 line memories. is 1.2.3.4.1.2,...
, and black binary data is input. The number of registers required to detect adjacent pixels is one for red and three for black, but each register is used as a buffer to continuously process the entire surface of the image to be copied in synchronization with the CCD reading clock. One more tube is provided.

Selector 2, which controls the input of SR2, not only switches the input line for the input binarized image data, but also switches the three lines used for determining adjacent pixels to operate as a ring buffer. . Three bits at the rear ends of these four line memories are connected to selectors 4, respectively.

In order to determine adjacent pixels from the connected 12-bit data, the selector 4 selects 8 bits of data corresponding to the surroundings of the red pixel to be determined and 1 bit of red data of interest.

The surrounding 8-bit data of the selected one is processed by the decoder.
It is determined whether it is 0 or not. If it is other than 0 and there is a red pixel of interest, it is determined that there is a black pixel adjacent to the red pixel of interest.

In this embodiment, when there is a black pixel adjacent to a red pixel, that red pixel is written with a low light intensity.
When it is determined that there is an adjacent black pixel, it is written into the buffer memory 3 as write light amount control data.

In FIG. 6(B), the data shown with diagonal lines in SRI indicates the red pixel of interest at a certain timing, and the data shown with diagonal lines in SR2 shows the surrounding black pixels. At this time, the selector 4 selects data of eight adjacent pixels indicated by diagonal lines and data of one pixel of interest from the 14 connected data. Then, the decoder determines whether the data value of the selected adjacent pixel is 0 or not, and if there is data for the pixel of interest at that time, the decoder uses the result as data for light intensity control separate from the red image data buffer. Write to holding buffer 3.

In addition, the six line memories shift data using the same clock as the pixel clock of the COD, and by determining the existence of adjacent pixels each time the data is shifted, the data for the length of the line is sequentially stored in this connection. Make a judgment. Next, selectors 1 to 4 are switched to determine the existence of adjacent pixels based on the three data items 2.3.4 of SR2, and processing of the red pixel in line 1 of SRI is performed.

The processed red data is then written to the buffer memory that holds the red data shown in FIG. 5(B).

Next, as an embodiment of a digital image forming apparatus to which the present invention is applied, an outline of the structure of a digital copying machine for forming an identification monochrome image will be described.

FIG. 7 is a sectional view showing the outline of the structure of a digital copying machine.

This apparatus is divided into an upper document scanning/reading section 100 and a printer section 200 that forms images using an electrophotographic method. The document scanning/reading section 100 includes a contact glass 101 on which a document to be copied is placed, a document pressure plate 102 that presses the placed document, a light source 103 that illuminates the document, and a reflector 109 that focuses the light from the light source onto a part of the document that is to be read. , mirrors 104, 105, and 106 that guide reflected light from the original to the imaging device 108 to form an image, a lens 107, and a drive mechanism including a motor (not shown) for scanning the original.

The imaging device 108 includes a CCD 1 shown in FIGS. 2 to 5.
．． It has a function corresponding to CCD2.

FIG. 7 shows an example using the two-line CCD shown in FIG. 4, but of course the embodiment using the prism shown in FIG. 3 can also be applied.

In the apparatus configured as shown in FIG. 7, when a document is set on the contact glass 101 and copying is started by pressing the print button on the operation panel, the lamp 103 that illuminates the document lights up and the motor that scans the document is driven. . The reflected light from the original forms an image on the imaging device 108, and image data of the original is sequentially output line by line in response to changes in the scanning position of the original.

The output data is subjected to the processing described above and written to a buffer memory for timing matching with the writing section described later.

The printer section is the writing section 2 surrounded by a chain line in the figure.
50, concrete developing unit 210, red developing unit 220,
Transfer/transport unit 230, cleaning unit 240
, a photoconductor 201, a static elimination charger 202 that eliminates static electricity before cleaning the photoconductor, a main charger 205 that charges the photoconductor, a fixing unit 260, a belt cleaning unit 270 that cleans the transfer/conveyance unit 230, and a feeder that supplies transfer paper. It is composed of a paper unit 290, a registration unit 280 that aligns the transfer paper and the image on the photoreceptor, and the like.

The writing section 250 is equipped with a motor that integrates an eight-sided polygon mirror 251, and inputs a laser beam modulated by a black image signal into the polygon mirror 251 rotated by the motor, and converts the reflected beam from the polygon mirror 251 into one. There is a light beam 252 formed through optical components such as an Fθ lens, a reflector, and a dustproof glass for scanning the photoreceptor 201 at a constant speed, and black data that is modulated by a red image signal or adjacent to it. Then, the laser light modulated by the red image signal while the light intensity is controlled by the determined data enters the polygon mirror 251 rotated by the motor, and the reflected beam from the polygon mirror 251 scans the photoreceptor 201 at a constant speed. Two-color image data is written onto the photoreceptor 2o1 by a light beam 253 formed through similar optical components.

Note that when writing a red pixel with a low light intensity when there is an adjacent black pixel, a buffer memory 3 is required instead of the gate for blanking, but here, the buffer memory 3 for storing the red image is required. The relationship and function between the memory and the buffer memory 3 that holds red data in which an adjacent black image exists will be explained.

As already explained with reference to FIG. 5 (B) and FIG. 6 (B), the red image memory is used to hold the red data write time delay and to adjust the timing. . The buffer memory 3 extracts and holds only red image data in which adjacent black pixels exist. The capacity of this memory is the same as the red memory, and when modulating the laser diode and writing, both memories are read at the same time, and one is used as image data to modulate the laser diode, and the presence of adjacent pixels Data regarding the laser diode is input to a terminal that controls the emission level of the laser diode, and is configured to reduce the intensity of the laser emission when the data is present. Furthermore, the 10th
The figure shows this relationship.

Now, since both of the aforementioned beams 252 and 253 scan using both sides of one polygon mirror, the scanning directions of the beams on the photoreceptor are reversed. Figure 8 shows the polygon mirror 25
1 viewed from above and with the reflecting mirror omitted, the beam 252.
253 is a planar view of the scanned surface of 253. The arrow of the polygon mirror 251 indicates the rotation direction, and the arrow indicates the scanning direction of each beam on the photoreceptor 201 at that time.

Here, by setting the positional relationship of the semiconductor laser LDI that outputs the beam 252 corresponding to black and the semiconductor laser LD2 that outputs the beam 253 corresponding to red to a predetermined position with respect to the polygon mirror 251, the positional relationship between the beams is determined. is determined, the sensor D for detecting the position of the laser beam and obtaining the timing to start modulation based on the data for each line is installed only on the equipped beam 252, and The timing for starting modulation of is generated from the signal from the same sensor.

Also, since the equipped beam 252 writes at position A on the photoreceptor drum, and the pedometer beam 253 writes at position B, the red beam is delayed by the number of lines corresponding to the distance between AB. By performing writing, an image without any deviation between black and red image data can be obtained. For this reason, the red data to be written downstream is read and subjected to predetermined processing, and then written to the buffer memory of the number of lines corresponding to this shift to compensate for the time shift.

Next, a series of image forming processes using the electrophotographic method in the copying machine shown in FIG. 7 will be described.

First, the main charger 205 uniformly charges the photoreceptor 201 rotating in the direction of the arrow in the figure, and a light beam 252 modulated with black image data applies A to the charged photoreceptor 201.
Write with points. The electrostatic latent image formed by this writing is developed by a black developing unit to form a black developed image on the photoreceptor.

Furthermore, writing is performed at point B on the photoreceptor on which a black image has been formed using a light beam 253 modulated with red image data.

Next, while not disturbing the black developed image, the red developing unit 220 develops only the latent image portion formed by the red image data, thereby forming a two-color developed image on the photoreceptor. . In parallel with this, transfer paper is sent out from the paper feed section 290,
The sheet is sent to the transfer/conveyance unit 230 so that the position of the leading edge of the formed two-color developed image and the leading edge of the transfer paper are aligned by the registration unit 280. The transfer paper sent out in this manner is carried by the belt of the conveyance unit 230, comes into contact with the two-color developing image on the photoreceptor 201, and is corona charged by a transfer charger installed on the back side of the belt. The upper two-color developed image is transferred to transfer paper. After the transfer, the transfer paper is further conveyed, fixed by the fixing unit 260, and discharged outside the machine. In addition, the photoconductor 2 after transfer
01 is neutralized by the static eliminating charger 202, and then cleaned by the cleaning unit 240, and is ready for image formation in the next cycle. Further, the belt of the transfer/conveyance unit 230 that conveyed the transfer paper to the fixing unit is cleaned by the belt cleaning unit 270, thereby preventing the back side of the next transfer paper from becoming dirty.

Now, in the copying machine shown in FIG. 7, in the series of operations described above, if there is a red part in the document placed on the contact glass 101 of the copying machine, that part is automatically separated. Two-color copies are made at exactly the same copying speed as for black-only originals.

Of course, if the original is only black, it will make a black copy just like a normal copying machine, so the person scanning the copying machine doesn't have to worry about whether there are any red parts on the original. It is not troublesome as it is processed automatically.

Of course, the color recognition function allows the machine to not only make copies in color, but also to have functions similar to those of conventional monochrome copying machines or copying machines that have a partial color change function.

Next, FIG. 9 is a block diagram mainly showing the control system of the printer section of the controller 2, which controls everything other than image reading, image data processing, and writing sections.

This control system includes the printer motor, solenoid, clutch, various detection switches, input/output, sorter, AD
a microcomputer 1 that controls peripheral devices such as F;
The microcomputer 2 includes a microcomputer 2 that controls a display section and an operation section, and a microcomputer 3 that controls the drive for scanning a document, the document illumination lamp, and the temperature of a fixing heater. Each of them is connected by a communication path with the microcomputer 1 as the master. As shown in the figure, a path for exchanging signals that cannot be completed in time by this path alone is also provided between the microcomputers 1 and 3 and the controller 1 that controls image reading and writing. . Note that the control system is the same as that of a conventional copying machine except that it has an interface with the controller 1 that handles image data, so a description thereof will be omitted.

Now, in the above description of the embodiment, the color of the first developing device is black, the color of the second developing device is red, and the function for identifying the color of the original is made to match the respective colors. However, you can also aim for special effects by changing the color to be identified and the color to be developed. Also, in this case, regardless of the color to be identified,
The set color to be identified will be changed to match the color of the toner stored in the second developing unit, which can be set in the printer section in different colors, so the color to be identified as the toner color will be displayed on the operation panel. It is also possible to provide these separately to support such uses.

Furthermore, among the adjacent pixels, processing to convert to blank or processing to reduce the amount of writing light is performed on red data in the embodiment, but it is almost the same as in the embodiment that other data can be processed in the same way. You can do it the same way, or you can process both adjacent colors to further increase the distance between pixels. In addition, it is possible to convert not only adjacent pixels but also pixels of different colors within a two-pixel range to blanking or to reduce the amount of writing light.

〔Effect of the invention〕

As explained above, in the invention according to claim 1 of the present application,
Since it is detected that the image data of the first color and the image data of the second color are adjacent and the adjacent pixels are converted to blanks and written, a blank area is formed between the adjacent images. This eliminates problems such as toner movement, and prevents image distortion.

Further, in the invention according to claim 2, since it is detected that the first color image data and the second color image data are adjacent to each other, and writing is performed by reducing the amount of writing light of the adjacent pixels,
The same effect as the invention described in claim 1 can be obtained, and furthermore, the problem of missing images, which is a problem when blanking as described above, can be prevented.

Next, the effects of the inventions recited in claims 3, 4, and 5.6 will be described.

Effects of the invention according to claim 3.

Since the processing targets data that is written with a time delay, even if a processing method that uses a large number of line memories is used, the time lag in the second write is compensated for by the number of lines used for processing. Since the number of lines can be reduced, there is no need to increase the number of lines as a whole, and the system can therefore be configured with a minimum buffer memory capacity.

Effects of the invention according to claim 4.

Converting data to blank or recording with reduced light intensity reduces the amount of data or changes the data, and in some cases, information that should be conveyed due to these processes may be missing. There is also gender. In general, manuscripts to be copied are often documents containing mainly text information, especially text information is often in black.
In such documents, colored parts such as red are stamps,
It is often used to attract attention for a specific purpose, such as a date stamp, marking, or postscript. In other words, the primary aim is to attract attention through color, so even if adjacent pixels that are developed with brighter toner are converted to blanks or the light intensity is reduced and recorded, the image should be conveyed. There is less possibility of a situation where information is missing and the copy cannot function as a copy.

In addition, although the example described the case of two colors, black and red,
For example, when using two colors, red and yellow, the transfer paper for copying is usually white, so the less bright red will stand out in terms of contrast with the background of the copy than the brighter yellow. . Therefore, in this case, it is desirable to convert the yellow side to a blank or record it with a lower light intensity for the same reason as for processing adjacent gait measurements in the relationship between black and red.

Effects of the invention according to claim 5.

In general, multivalued data often carries important information, so it is better to convert binary information to blank or record it with a lower light intensity, for the same reason as the inventions of claims 2 and 3. few.

In other words, if you compare one pixel of multivalued data with one pixel of binary data, the multivalued data naturally has more information, so you can convert one pixel to a blank or reduce the amount of light. When recording, less data is lost if binary data is used.

Effects of the invention according to claim 6.

The alignment accuracy of the two writing means is not sufficient,
If there is a shift in the writing position and processing for one pixel cannot compensate for the creation of a blank or a writing area with low light intensity between the written pixels, increase the width of the blank between the two colors or increase the number of pixels to be processed. You will need to do more. In such a case, a copy that is more faithful to the original can be obtained by processing each color one pixel at a time, rather than processing one color data in a width of 2 pixels.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the potential profile of the photoreceptor surface during image formation, the toner adhesion position, and the relationship between D and D. FIG. 2 is a block diagram showing the outline of the configuration of the image forming apparatus according to the present invention.
FIG. 3 is a schematic configuration diagram showing one embodiment of an imaging device equipped with a color separation function, FIG. 4 is a schematic configuration diagram showing another embodiment of an imaging device equipped with a color separation function, and FIG. 2 is a block diagram showing a more detailed configuration after the photoelectric conversion section of the reading system of the device shown in FIG. 2, in which (A) is a block diagram showing the configuration when writing is performed by converting adjacent pixels to blanks;
(B) is a block diagram showing the configuration when writing by reducing the light intensity of adjacent pixels, and FIGS. 6(A) and (B) are shift registers SRI and SR2 of FIGS. 5(A) and (B), respectively.
, an adjacent pixel determination unit, and a detailed block diagram of the portion constituted by the gate; FIG. 7 is a sectional view showing the outline of the structure of a digital copying machine to which the present invention is applied; FIG. 8 is a beam optical scanning optical system. Figure 9 shows the surface to be scanned expanded into a plane.
The figure is a block diagram centered on the control system of the printer section of the controller 2, and FIG. 10 is a block diagram showing an example of the light amount control section when writing by reducing the light amount of adjacent pixels. 100... Original scanning/reading unit, 101... Contact glass, 102... Original pressure plate, 103...
... light source, 104, 105, 106 ... mirror 1
07... Lens, 108... Imaging device, 109
... Reflector, 200 ... Printer section, 201
... Photoreceptor, 202 ... Static elimination charger, 20
5...Charging main charger, 210...Representative developing unit, 220...Red developing unit, 230
...Transfer/transport unit, 240...Cleaning unit, 250...Writing section, 251...
... Polygon mirror, 252, 253 ... Light beam, 260 ... Fixing unit, 270 ... Belt cleaning unit, 280 ... Registration unit, 290 ... Paper feeding unit.

Claims (1)

[Scope of Claims] 1. Reading means for receiving a light image from an object to be copied and separating image data of a predetermined color to obtain first and second recording signals; a first writing means for writing on the photoreceptor and forming an electrostatic latent image on the photoreceptor; a first developing means for developing the electrostatic latent image formed by the first writing means; a second writing means for writing on the photoreceptor developed by the first developing means based on the second recording signal to form an electrostatic latent image on the photoreceptor; A digital image forming apparatus comprising: a second developing means for developing an electrostatic latent image; and a means for simultaneously transferring toner images formed by the first and second developing means onto a transfer paper; 1. A digital image forming apparatus comprising means for converting at least one of the recorded data into blank when write data of the first recording signal and write data of the second recording signal exist adjacently. 2. A reading means for receiving a light image from an object to be copied and separating image data of a predetermined color to obtain first and second recording signals; and writing on a photoreceptor based on the first recording signal. a first writing means for forming an electrostatic latent image on the photoreceptor; a first developing means for developing the electrostatic latent image formed by the first writing means; and a developing device by the first developing means. a second writing means for writing on the photoreceptor based on the second recording signal and forming an electrostatic latent image on the photoreceptor; Writing the first recording signal in a digital image forming apparatus comprising a second developing means for developing and a means for simultaneously transferring toner images formed by the first and second developing means onto a transfer paper. A digital image forming apparatus characterized in that, when data and write data of the second recording signal exist adjacent to each other, means for reducing the amount of light for writing at least one of the recording data. 3. The digital image forming apparatus according to claim 1 or 2, wherein the data to be converted to blank or the data to reduce the amount of light is a second recording signal. 4. The digital image forming apparatus according to claim 1 or 2, wherein the data to be converted into blank or the data to reduce the amount of light is a recorded signal developed with toner having high brightness. Forming device. 5. In the digital image forming apparatus according to claim 1 or 2, when one recording signal is multi-value density data for each pixel and the other recording signal is binary data for each pixel, the recording signal is blank. A digital image forming apparatus characterized in that the data to be converted or the data to reduce the amount of light is a binary recording signal. 6. In the digital image forming apparatus according to claim 1 or 2, when the first recording signal and the second recording signal are adjacent to each other, both recording signals are converted to blanks or both recording signals are blanked. A digital image forming device characterized by reducing the amount of light.