JP3572246B2 - Multicolor printing electrophotographic printing method and apparatus - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, a plurality of sets of electrophotographic processes for thermally fixing dot-shaped unfixed toner images formed by using a laser beam by a thermal fixing unit are arranged along a conveying direction of a printing paper, and sequentially for each color. The present invention relates to a multi-color printing electrophotographic printing method and apparatus for performing multi-color printing while performing image fixing, and in particular, matches a dot image of each color with high accuracy even when printing paper is shrunk by a heat fixing means such as a heat roll. And a multi-color electrophotographic printing method for performing multi-color printing.
[0002]
[Prior art]
Conventionally, a laser beam modulated based on image information is exposed on a photoconductor, a dot-shaped toner image developed by a developing device is transferred to a printing paper, and the transferred unfixed toner image is thermally fixed. An electrophotographic process for fixing by means is well known, and the structure and function of an exposed portion of the electrophotographic printing process will be briefly described with reference to FIGS.
First, the laser scanning device 9 which is an optical system of an electrophotographic printing machine will be described.
FIG. 5 shows a laser scanning device 9 of an exposure system in the electrophotographic process, which receives from a fiber optic cable 10 a dot pattern modulated light of an image to be printed output from a laser driver 8 shown in FIG. After being collimated through an optical system collimating lens 12, the light is scanned and imaged on a photosensitive drum 4 by a light scanning reflection mirror 1 such as a polygon mirror while scanning the light horizontally (in the main scanning direction) to form a dot pattern. Is a device for forming a matrix pixel as a latent image on a photosensitive drum.
[0003]
More specifically, image information in the form of a dot pattern of an image to be printed is input from the laser driver 8 in FIG. 5 as a digital laser signal to the laser scanning device through the optical fiber cable 10.
This laser beam input is converted into a parallel beam by a collimating lens 12, further reflected by a reflecting mirror 13 through a beam shaping lens (not shown), and reaches the polygon mirror 1 again through a beam shaping lens (not shown).
The polygon mirror 1 is rotating at a high speed in the clockwise direction in FIG. 5A, and the laser light reflected while being scanned by the polygon mirror 1 in the main scanning direction passes through the fθ lens 16 on the photosensitive drum 4. An image is formed, and a dot line pattern for one scanning line is formed on the photosensitive drum in the main scanning direction from left to right in the figure.
The end of scanning of one scanning line is detected as a horizontal synchronization signal by the detector via the reflecting mirror 14, and a signal of the next scanning line is output based on the synchronization signal.
[0004]
On the other hand, the photosensitive drum 4 is rotating in a sub-scanning direction orthogonal to the main scanning direction of the laser beam, and is formed in a two-dimensional manner on the photosensitive drum by repeatedly forming a dot line pattern for the one main scanning line. A large map-like dot pattern is formed.
[0005]
Next, a conventional device for generating a signal to be output to a laser scanning device will be described with reference to FIG.
The print memory 7 is composed of a bitmap memory, and generates page description data (for one single-color image) representing page contents for each color created by a computer or the like, and converts the description data into bits for one single-color image. A bit map is developed on the print memory 7 as map data.
This bitmap data constitutes one halftone dot from several tens of laser light spots corresponding to the gradation on the laser driver side generated according to the bitmap, and an actual monochrome color is obtained from a set of halftone dots. A dot image is configured.
[0006]
These pieces of image information are serially read out one by one scanning lines from the print memory 7 in which the two-dimensional bit map is developed, and are repeatedly scanned by the main body while rotating the photosensitive drum 4, thereby forming a single monochrome image composed of halftone dots. Can be formed on the photosensitive drum 4.
[0007]
The timing (video clock) at which the spot of the laser beam forming the halftone dot is read from the print memory 7 is controlled by the oscillation frequency of the crystal oscillator 19, that is, the clock frequency. That is, a signal of one dot corresponding to one spot of the laser light is read out serially from the print memory 7 in synchronization with one clock pulse generated from the crystal oscillator 19.
The read pixel data is input to a laser driver 8 such as a semiconductor laser oscillator, and generates laser light modulated in accordance with a dot signal. The laser light generated here is input to the laser scanning device 9 through the optical fiber 10, and a latent image is formed on the photosensitive drum 4 as described above. When the laser scanning light reaches the end of one scanning line, the laser scanning light is reflected by the reflecting mirror 14 and enters a detector 15 such as a beam detecting fiber to output a horizontal synchronization signal for cueing the next line scanning. Is done.
[0008]
Since pixel data stored in the print memory is repeatedly read out serially for each scan line, by discharging pixel data of all scan lines from the print memory, a latent image of one monochrome image is formed on the photosensitive drum. Will be imaged.
[0009]
The optical scanning device is incorporated in an electrophotographic process centered on a photosensitive drum, and a multicolor electrophotographic device is configured by arranging the electrophotographic processes for each color in series.
[0010]
FIG. 6 shows a conventional multicolor printing electrophotographic apparatus using web printing paper (roll paper) applied to the present invention.
This apparatus includes photoconductor drums 4A and 4B around which photoexposure 9 (laser scanning device), development 21, transfer 22, cleaning 23, charge removal 24, and charging 25 are arranged around photoconductor drums 4A and 4B. A plurality of sets of electrophotographic processes 4a and 4b for each color, which are composed of heat rolls 18a and 18b for thermally fixing the unfixed toner image transferred from the drums 4A and 4B to the printing paper 17, are provided along the conveying direction of the printing paper 17. A multi-color printing electrophotographic printing apparatus is provided, which performs multi-color printing while sequentially fixing images for each color.
[0011]
That is, after the latent image formed on the photosensitive drum 4 by the exposure unit 9 is developed by the developing unit 21, the developed toner image is transferred to the printing paper 17 via the transfer roll 22. After that, on the photosensitive drum side, the residual toner is removed by the cleaning unit 23, the residual charge is removed by the charge removing unit 24, and the charging unit 25 performs uniform charge resistance, and then the exposure is repeated again.
On the other hand, the printing paper 17 to which the unfixed toner image has been transferred is thermally fixed by the heat roll 18a, and then the second color toner image is transferred and fixed by the next electrophotographic process 4b. Performs multicolor printing of cyan, magenta, yellow and black by the electrophotographic process 4B.
[0012]
[Problems to be solved by the invention]
In the case of a conventional multi-color printing press, a method of performing multi-color printing while fixing an unfixed image of each color of cyan, magenta, yellow, and black for each color as in the former is described in, for example, JP-A-10-293432. As described above, there is a method in which the image fixing is not performed for each color, and the four unfixed images are superimposed, and then the image is fixed collectively by a heat roller.
In the latter case, since only one heat roll is required, miniaturization is possible, and it is used for a small-scale printing system. On the other hand, since unfixed toner images are superimposed, bleeding or the like tends to occur.
[0013]
On the other hand, the former method of fixing an image by the heat roll 18 for each of the colors shown in FIG. 6 eliminates bleeding and the like, and is suitable for a large printing machine, particularly commercial printing. In some cases, the colors may not be properly registered because they pass through the heat roll 18.
[0014]
Particularly, in the case of the web printing paper 17 formed of machine paper, the web printing paper 17 is hardly shrunk due to tension in the transport direction (vertical direction), but contracts in the horizontal direction (a direction orthogonal to the transport direction of the printing paper 17). . Further, when the tension in the vertical direction is large as in the case of the web printing paper 17, the contraction in the horizontal direction is inevitably large.
Then, the shrinkage shrinks between the images in which the heat rolls intervene, and the shrinkage causes a shift in the inter-color dot pattern in the main scanning direction (the horizontal direction of the printing paper 17), so that the inter-color registration is lost. In the case of a four-color printing press, the heat rolls are interposed between the first color and the second color, the second color and the third color, and between the third color and the fourth color. In particular, the lateral color misregistration is disturbed by the influence of the above, but the disparity has a disadvantage that the contraction between the first color image and the second color image in which heating is first performed is the largest.
[0015]
However, such a drawback does not exist in the latter small-scale printer system in which the four unfixed images are superimposed and then the images are fixed collectively by a heat roller.
For this reason, many of the conventional apparatuses consider only the pitch shift between images in the sub-scanning direction due to fluctuations in the peripheral speed of the photosensitive drum, which is a problem in small-scale printers due to the large number of developed units. As in the present invention, there is no technique for correcting a color registration error in the main scanning direction (the horizontal direction of the printing paper 17) by contraction between images interposed by a heat roll.
[0016]
For example, as a technique corresponding to a small-scale printer, there is a technique of delaying a pixel clock for a plurality of beam spots in a multi-laser printer in Japanese Patent Laid-Open No. 2000-85177, but this technique is caused by fluctuations in the rotation speed of a photosensitive drum. The multi-laser printer corrects uneven scanning line intervals generated between a plurality of beam spots in the sub-scanning direction. The main scanning direction (printing paper 17 horizontal direction) caused by shrinkage between images with a heat roll interposed therebetween. The present invention does not correct the deviation of the dot pattern between colors in the main scanning direction as in the present invention, and more specifically, the deviation in the main scanning direction between images interposed by the heat roll, more specifically, the paper conveyance lateral direction in a large-scale printer. This is a different technique because it does not correct the color misregistration. Although the prior art is described as being applicable to multiple laser spots, the present invention is also applicable to single laser spots, as will be described later.
[0017]
A technique using a test pattern, which is an elemental technique of the present invention, is also disclosed in JP-A-11-170597. However, also in this prior art, a mask signal generation timing register for setting a writing timing in the sub-scanning direction by detecting a shift in the sub-scanning direction between the first beam scanning line and the second beam scanning line in the multi-laser printer. Based on the timing signal, the interval of the beam scanning line of the multi-laser printer in the sub-scanning direction is corrected based on the interval deviation.
[0018]
Therefore, in these conventional techniques, there are techniques of delaying a pixel clock and techniques using a test pattern as elemental techniques, but all of them have a problem of a gap in the sub-scanning direction, and a heat roll is interposed. There is no disclosure or suggestion of any idea of correcting a color registration error in the main scanning direction (the horizontal direction of the printing paper 17) by contraction between images.
More specifically, none of the above-mentioned technologies correspond to multi-color printing electrophotographic printing. Even in multi-color printing, four unfixed images are superimposed and then collectively applied to a heat roller. Therefore, there is no need to consider the color registration error due to the shrinkage of the image of the heat roll as in the present invention.
[0019]
The present invention has been made in order to solve the above-mentioned problem, and an electrophotographic process of thermally fixing a dot-shaped unfixed toner image formed by using a laser beam by a heat fixing unit along a transport direction of a printing paper. In a multi-color printing electrophotographic printing apparatus that performs multi-color printing while sequentially performing image fixing for each color, a plurality of sets are provided. It is an object of the present invention to provide a multicolor electrophotographic printing method and a multicolor printing electrophotographic printing method capable of performing multicolor printing by matching dot images with high precision.
[0020]
[Means for Solving the Problems]
According to the first aspect of the present invention, a laser beam modulated based on image information for each color is exposed on a photoreceptor, and a dot-shaped toner image developed by a developing device is transferred to a printing paper. A multicolor electrophotographic printing method in which a plurality of sets of electrophotographic processes for fixing the unfixed toner image by a heat fixing unit along a conveying direction of a printing paper and performing multicolor printing while sequentially performing image fixing for each color are provided. At
Passing through the heat fixing meansTaThe test pattern of the corresponding color is compared with a reference test pattern before passing through the heat fixing unit or set in advance to correspond to the heat shrinkage.In the main scanning direction with respect to the center of the image areaDot interval deviationSeekingTherefore, in the main scanning direction of the bit map-like latent image pixels to be formed on the photosensitive drum in accordance with the deviation.Center-basedIt is characterized in that the dot pixel interval is made variable.
The variation of the dot pixel interval is preferably performed by changing a pixel clock for generating a pixel output timing from a print memory in which monochrome image data is bit-mapped, and the dot interval deviation is directly or calculated. How to ask, TeThis is performed by an optical reading device that moves in the main scanning direction on the coordinate plane on which the test pattern is placed.HighThe object of the present invention can be realized with high accuracy.
[0021]
Claim5The described invention is an invention relating to a multicolor electrophotographic printing apparatus capable of effectively achieving the above invention,A laser beam modulated based on image information for each color is exposed on a photoreceptor, a dot-like toner image developed by a developing device is transferred to a printing paper, and the transferred unfixed toner image is thermally fixed. In a multicolor electrophotographic printing apparatus, a plurality of sets of electrophotographic processes to be fixed by means are arranged along the conveying direction of the printing paper, and multicolor printing is performed while fixing images sequentially for each color.
Pass through the heat fixing meansLetA test pattern of a corresponding color, and a reference test pattern before or before passing through the heat fixing unit,
Compare the two test patternsAgainstRespondIn the main scanning direction with respect to the center of the image areaDeviation reading means for directly or by calculating the dot interval deviation,
In the main scanning direction, the bitmap-shaped latent image pixels to be imaged on the photosensitive drum corresponding to the read deviation areCenter-basedMeans for varying the dot pixel interval.
In this case, the dot pixel interval variable means is a variable frequency generator for changing a pixel clock for generating a pixel output timing from a print memory in which monochrome image data is bit-mapped, and the dot interval deviation reading means. Is preferably an optical reading device that reads the coordinates of the test pattern by moving it in the main scanning direction visually or on a coordinate plane on which the test pattern is placed.
[0022]
According to this invention, even when the printing paper is shrunk by a heat fixing unit such as a heat roll, or even when there is a device error, it is possible to perform the multicolor printing by matching the dot images of each color in the main scanning direction with high accuracy. .
[0023]
The invention described in claim 4 isA laser beam modulated based on image information for each color is exposed on a photoreceptor, a dot-like toner image developed by a developing device is transferred to a printing paper, and the transferred unfixed toner image is thermally fixed. In a multicolor printing electrophotographic printing method in which a plurality of sets of electrophotographic processes for fixing by means are arranged along the transport direction of the printing paper, and multicolor printing is performed while sequentially fixing images for each color,
Prepare a grid-like test pattern,
Passing through the heat fixing meansTaPass the corresponding color test pattern and the heat fixing meansPre-youngOr compare with a preset reference test pattern.AgainstRespondRunInspection directionA deviation of the distance between cells is obtained, and deviation data is created based on the deviation amount.Bit-mapped latent image pixels that form an image on the photoconductor drum corresponding toDot relative to the center ofCharacteristically variable intervalsTossYou.
[0024]
Claim8The described invention is an invention relating to a multicolor electrophotographic printing apparatus capable of effectively achieving the above invention,
A laser beam modulated based on image information for each color is exposed on a photoreceptor, a dot-like toner image developed by a developing device is transferred to a printing paper, and the transferred unfixed toner image is thermally fixed. In a multicolor electrophotographic printing apparatus, a plurality of sets of electrophotographic processes to be fixed by means are arranged along the conveying direction of the printing paper, and multicolor printing is performed while fixing images sequentially for each color.
Pass through the heat fixing meansLetPass the test pattern of the corresponding color and the heat fixing meansPre-youngOr a pre-set reference test patternIs a square test pattern,
Comparing the two patterns to respond to heat shrinkageCalculate the deviation of the distance between grids based on the center in the scanning directionDeviation reading means,
The deviation read by the reading meansCreating deviation data based on the quantity,Bit-mapped latent image pixels that form an image on the photoconductor drum corresponding toRunInspection directionDot centeredMeans to make the interval variableBecomeIt is characterized by the following.
[0025]
According to this invention, in the case of the web-type printing paper, the contraction in the vertical direction (sub-scanning direction) is smaller than that in the horizontal direction (main scanning direction). Even in the case of contraction, multicolor printing can be performed by matching the dot images of each color in the sub-scanning direction with high accuracy.
[0026]
The present invention is applicable not only to heat shrinkage but also to a case where a dot shift occurs in the main scanning direction due to an error in the mounting position of an exposure unit, particularly, a polygon mirror.
Claim9The described invention particularly specifies the case of such a defect, and in the multicolor electrophotographic printing method,
The test pattern for each color is compared with a preset reference test pattern to correspond to the mechanical error of each electrophotographic process.In the main scanning direction with respect to the center of the image areaA dot interval deviation is obtained directly or by calculation, and a bitmap-like latent image pixel to be formed on the photosensitive drum in the main scanning direction is formed in accordance with the deviation.Center-basedIt is characterized in that the dot pixel interval is made variable.
Claim10The described invention relates to an apparatus for achieving the above-mentioned invention effectively,
A test pattern for each color, a reference test pattern set in advance,Is a square test pattern,
Comparing the two test patterns to correspond to the mechanical error of each electrophotographic processCalculate the deviation of the distance between grids based on the center in the scanning directionDeviation reading means,
Creating deviation data based on the deviation amount read by the reading means;In the scanning direction of the bitmap-like latent image pixels to be imaged on the photosensitive drum corresponding toDot centeredMeans for making the interval variable.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail using embodiments shown in the drawings. However, the dimensions, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples, unless otherwise specified.
[0028]
In the present embodiment, as shown in FIG. 6, a laser beam modulated based on image information for each color is exposed on the photosensitive drum 4 and a dot-shaped toner image developed by the developing unit 24 is printed on the printing paper 17. , And the transferred unfixed toner image is fixed by a heat fixing heat roll 18. The present invention is applied to a multicolor printing electrophotographic printing machine in which a plurality of sets 4b are arranged along the conveying direction of the printing paper 17 and multicolor printing is performed while fixing images sequentially for each color.
More specifically, the first-color unfixed toner image transferred to the printing paper 17 is thermally fixed along the photoconductor drum 4A for forming the first-color toner image along the transport direction of the web-type printing paper 17. Multicolor printing electrophotography in which a heat roll 18a, a photosensitive drum 4B of a second color and a heat roll 18b, and a photosensitive drum of a third color and a heat roll are sequentially arranged in the transport direction of the printing paper 17 in order. This is applied to a printing device.
[0029]
Then, in order to make the description of the present embodiment easy to understand, as shown in FIG. 2, 幅 widths on the left and right sides from the center of the image forming area (color registration) of the printing paper 17 before passing through the first color heat roll. When the length is (A, A: nd), it is assumed that each side contracts by nx on both the left and right sides from the center.
(Assuming that the center does not shrink and the left and right sides shrinkYou.)
In this case, assuming that the number of beam dots to be printed in the 前 記 width length is n and the dot interval is d, basically, the dot generation timing of the first color, in other words, the video signal generation timing is set to the reference clock d by the first color. (D + x), which is increased by x. This is the first embodiment.
[0030]
FIG. 2 is an operation diagram for controlling the test pattern dot pattern based on the first embodiment, and shows the amount of misregistration between colors of the test pattern when the first color is printed with the reference clock d. As is apparent from this figure, the color registration of the dot pattern of the first color in the horizontal direction of the printing paper 17 is {A−nx = n (d−x)} due to contraction, and the basis of {A = n (d)}. Shrinks by nx intervals from the test pattern of Therefore, it can be understood that the timing setting of (d + x) in which the dot generation timing of the first color is increased by x with respect to the reference clock d may be performed.
[0031]
However, the shrinkage ratio of the printing paper 17 is not always constant depending on the temperature of the heat roll, the humidity and the type of the paper, and therefore, if a test pattern for obtaining laser dot interval setting data is taken, a more accurate and more preferable dot interval is obtained. Can be variably controlled.
Therefore, the test pattern 11 of the second embodiment shown in FIG. 3 is printed on the actual printing paper 17 with a fixed test pattern in each of the first to fourth colors on the actual printing paper 17 prior to the actual printing. By comparing the original pattern with the deviation data and inputting the deviation data to the setting device 5, the clock frequency can be set so as to correct the deviation.
[0032]
FIG. 3 is an operation diagram for controlling a dot pattern by a square test pattern based on the second embodiment. FIG. 3A shows a reference test pattern and a test pattern to be corrected for dot intervals after passing through a heat roll, and FIG. ) Are a setting signal generated by the test pattern and input to the setting device, and a variable frequency pulse changed based on the setting signal.
This deviation data may be obtained by arranging a plurality of register marks in the horizontal direction with respect to the image forming area and calculating the deviation of the distance between the individual register marks. Alternatively, as shown in FIG. The deviation of the distance between the squares in the main scanning direction with respect to the center between the test pattern 11b of the first color that has passed through the heat roll and the reference test pattern 11a that has not passed through the heat roll is determined, and the deviation amount is calculated. What is necessary is just to create deviation data based on it.
[0033]
That is, as shown in FIG. 3, when the cell spacing is A1, the color misregistration amount of the test pattern when the first color and the second color are printed with the reference clock d, respectively, is less than the first color in the printing paper 17 in the horizontal direction. The color registration of the cell at the center position of the dot pattern of the first color is {A1-mx1 = m (d-x1)} due to contraction, and the cell spacing of A1 from the test pattern based on {A1 = m (d)} In, the dot interval of each dot contracts by (d−x1). Therefore, it can be understood that the timing setting of (d + x1) in which the dot generation timing of the grid interval of A1 for the first color is increased by x1 with respect to the reference clock d.
Next, at the grid interval of A2, the color registration is {A2-mx2} = {m (d-x2)} due to contraction, and further contracts by m (d-x2). Accordingly, it can be understood that the timing setting of (d + X2) in which the dot generation timing of the grid interval of A2 is increased by X2 with respect to the reference clock d.
Similarly, the dot generation timing is (d + X3) at the cell spacing of A3.
Note that reading the test pattern is time-consuming when viewed visually, but since the shrinkage of the printing paper 17 by the heat roll 18 is almost determined by the type of printing paper, the data is stored in the setting device 5 for each type of printing paper 17. In addition, if the paper information is input at the next printing, the previous correction data can be used as it is.
Note that reading of a test pattern using such cells is effective when the thermal contraction of paper varies in the width direction due to a difference in paper density or the like.
[0034]
The deviation data may be created by visually observing the deviation of the positions of both test patterns of the respective colors after passing through the heat roll corresponding to the original test pattern 11A, and the misregistration is visually measured. Instead, using the optical reader 30 shown in FIG. 4, the measurement result corresponding to the deviation data is fetched into the horizontal position data into the setting device 5, and the frequency of the variable frequency oscillator 6 during scanning is set finely. You may do so.
Note that the positional deviation in the vertical direction may be obtained by delaying the horizontal synchronization signal output for each scanning line.
[0035]
FIG. 4 shows an optical reader that reads the deviation of the positions of both test patterns of each color after passing through the heat roll corresponding to the original test pattern A with high accuracy.
The optical reading device 30 includes a pair of X-axis stages 32 (in the sub-scanning direction) on both left and right sides of a table on which the test pattern 11 is mounted, and a Y-axis stage 34 (main In the scanning direction), a coordinate calculation unit 31 including a laser displacement meter for measuring a grid interval is mounted on a Y-axis stage 34 via a table 36. The laser light of the coordinate calculation unit 31 is also used as a laser pointer indicating a measurement position.
[0036]
At one end of the Y-axis stage 34, an X-axis driving device 35 having a driving motor for moving the stage in the X-axis direction along the X-axis stage 32 and a high-precision position detecting device such as a rotary encoder for performing position detection, On the table 36 of the Y-axis stage 34, a Y-axis driving device 33 having a driving motor for moving the table 36 in the Y-axis direction and a high-precision position detecting device such as a rotary encoder for performing position detection is provided. The unit 31 is a signal from a rotary encoder or the like included in the X-axis drive unit 35 and the Y-axis drive unit 33, and calculates a coordinate calculation unit main body that detects the current position of the measurement unit on the moving table and a measurement position coordinate. A coordinate storage unit is provided for storing the test pattern in a grid interval. The coordinate storage unit can calculate the deviation between the grid interval of the actually printed test pattern and the grid interval of the original test pattern stored in the pattern storage unit.
[0037]
According to this embodiment, the coordinate deviation between the grid interval of the actual print test pattern in grid coordinates after printing through the heat roll and the grid interval of the base test pattern stored in advance is calculated, and the main scanning direction and A dot shift amount in the sub-scanning direction can be detected.
The use of such an optical reading device 30 has an effect of facilitating the input of the frequency correction value input to the setting device 5 described later.
[0038]
According to this embodiment, as shown in FIG. 1, a frequency pulse (pixel clock) whose timing is set by a setting signal from a setting device 5 for setting a frequency is output from a variable frequency transmitter to a print memory. Thus, based on the timing set by the variable frequency transmitter, the pixel data in the print memory is input to the laser scanning device 9 via the laser driver 8 to form a latent image on the photosensitive drum with the dot deviation corrected. And printing is performed.
That is, in order to make the laser spot interval variable, the dot interval may be changed by changing the frequency of the variable frequency oscillator, that is, the pixel clock frequency.
A control circuit block diagram of the present embodiment will be described with reference to FIG. First, the oscillator for controlling the interval between laser dots to be sent to the laser scanning device 9 is changed from a crystal oscillator 19, which is a conventional fixed frequency oscillator, to a variable frequency oscillator 6 in which the frequency can be set arbitrarily.
A setting device 5 for setting a frequency is provided, and deviation data measured by the test pattern is input to the setting device. For example, in the first embodiment of FIG. 3B, when the set value of the reference clock d of the first color is set by one “ON” pulse every seven digits, such as “00000000000000010000001. When the (d + x) timing setting corresponding to the paper contraction is created, a signal for setting a clock by one “ON” pulse for every ten digits, such as “0010000000000100000000001...”, Is stored in the setting device 5. By inputting the setting signal to the variable frequency transmitter 6, the frequency of the variable frequency transmitter 6 can be set to an "ON" pulse at the timing of (d + x).
[0039]
Also, as shown in FIG. 3, even when the dot interval varies for each of the cells A3, A2, and A1, the data input to the setting device 5 is "00000100000001000000100000001000000010000000100000000001 ...".
By storing a signal for setting a clock by one "ON" pulse at an indefinite digit interval in the setting device 5 and inputting the setting signal to the variable frequency transmitter 6, the variable frequency transmitter For the frequency of No. 6, an "ON" pulse at an arbitrary timing corresponding to the dot shift can be set.
[0040]
In the sub-scanning direction, as shown in FIG. 1B, the horizontal synchronizing signal obtained by the detector 15 every time one main scanning line is completed may be delayed by the delay circuit 27 by Y time.
[0041]
As described above, in the present embodiment, the delay circuit 27 delays the horizontal synchronizing signal for each dot of the main scanning line and also for the next scanning line after the completion of one scanning line in the sub-scanning direction. Since the delay can be made in accordance with the contraction amount, it is possible to adjust the dot interval of an arbitrary dot interval portion in the main scanning direction and the sub-scanning direction in one image.
[0042]
Next, FIG. 1A is a schematic view of a main part of a laser scanning device showing the principle of matching dot images of each color with high accuracy.
In FIG. 1A, a laser beam generated by a laser driver 8 is input to a laser scanning device 9 through an optical fiber 10, and a laser spot input to the laser scanning device 9 is the same as in FIG. The light is collimated by a collimating lens 12 and is reflected by a reflecting mirror 13 to irradiate the polygon mirror 1.
When the polygon mirror that rotates at a high speed is at the angle shown in FIG. 1, the reflected laser spot is applied to the position of point 2 on the photosensitive drum 4.
Since the polygon mirror is rotating in the clockwise direction in FIG. 1, the next laser spot light is applied to a point 3 on the photosensitive drum 4 which is also separated by d from point 2. Here, the pixel spot data of the laser is output from the print memory at a timing delayed by the variable frequency oscillator at an interval increased by x by the variable frequency oscillator. Irradiation is performed at the dot position of point 3a. In this way, by making the laser spot interval variable, it is possible to adjust the left and right dimensions of the image corresponding to the contraction of the printing paper.
After the end of one scanning line, at the beginning of the next scanning line, if the horizontal synchronizing signal output at intervals L in the sub-scanning direction is delayed by α intervals, the spot light at the beginning of the next scanning line becomes Irradiation is performed on the photosensitive drum 4 not at the point 3B 'at the interval L but at the dot position at the point 3B delayed by the interval L + α.
[0043]
Therefore, in the present embodiment, the dimensions in the horizontal direction (main scanning direction) and the vertical direction (sub-scanning direction) can be adjusted at an arbitrary position in the image, so that the distortion of the image due to the shrinkage of the printing paper 17 can be finely corrected. Therefore, it is possible to easily adjust the left, right, up, and down registrations in the case of multicolor printing.
Then, the adjustment of the dimensions is performed by performing test printing based on the grid-like test pattern data 11 stored in advance, comparing the standard pattern with all the locations of the test printed image, and comparing the portions having deviations with the horizontal direction. The correction data of the vertical dimension is input to the setting device 5 and input to the variable frequency oscillator and the delay circuit, respectively.
Therefore, even in the case of the printing paper 17 contracted by the heat roll, an image without distortion can be obtained in all the portions.
[0044]
The present embodiment can cope with not only deviation deviation due to paper contraction but also deviation and inclination of the polygon mirror 1 of the exposure device 9 in the main scanning direction shown in FIG.
In this case, the scanning start point p1 of the polygon mirror 1 can be corrected based on the horizontal synchronizing signal. However, with such a configuration, the scanning direction end side p2 appears as a shift. In this case, correction can be made in the same manner as in the case of heat shrinkage of paper.
That is, the test pattern for each color is compared with a reference test pattern set in advance, and a dot interval deviation (attributable to a shift in P2) corresponding to a mechanical error or the like of each electrophotographic process is obtained directly or by calculation. The dot pixel interval in the main scanning direction of the bit image-like latent image pixels to be formed on the photosensitive drum 4 may be made variable in accordance with the deviation.
[0045]
【The invention's effect】
As described above, according to the present invention, the present invention provides an electrophotographic process in which a dot-shaped unfixed toner image formed by using a laser beam is thermally fixed by a heat fixing unit along the transport direction of the printing paper 17. In a multi-color printing electrophotographic printing apparatus that performs multi-color printing while sequentially performing image fixing for each color, a plurality of sets are provided. Multicolor printing can be performed by matching dot images with high precision.
[Brief description of the drawings]
FIG. 1A is a schematic diagram of a main part of a laser scanning device showing the principle of matching dot images of each color with high accuracy, and FIG. 1B is a block circuit diagram thereof.
FIG. 2 is an operation diagram for controlling a dot pattern by a test pattern corresponding to a width length according to the embodiment; FIG. 2A shows a reference test pattern and a test pattern to be corrected for a dot interval after passing through a heat roll; , (B) are a setting signal generated by the test pattern and input to the setting device, and a variable frequency pulse changed based on the setting signal.
FIG. 3 is an operation diagram for controlling a dot pattern by a square-shaped test pattern according to the present embodiment, showing (A) a reference test pattern and a test pattern to be corrected for a dot interval after passing through a heat roll, and (B). Is a setting signal generated by the test pattern and input to the setting device, and a variable frequency pulse changed based on the setting signal.
FIG. 4 shows an optical reading device that reads the deviation of the positions of both test patterns of each color after passing through a heat roll corresponding to a base test pattern A with high accuracy.
FIG. 5A is a schematic diagram of a main part of a conventional laser scanning device, and FIG. 5B is a block circuit diagram thereof.
FIG. 6 is a schematic diagram showing a multicolor printing electrophotographic printing apparatus applied to the present invention for performing multicolor printing while fixing an unfixed image of each color of cyan, magenta, yellow, and black for each color.
FIG. 7 is an operation diagram showing a dot shift due to a positional shift or inclination of a polygon mirror of the exposure apparatus in the main scanning direction.
[Explanation of symbols]
1 polygon mirror
3 3A laser spot
4, 4A, 4B photosensitive drum
5 Setting device
6 Variable frequency oscillator
7 Print memory
8 Laser driver
9 Laser scanning device
11 Test pattern
15 Horizontal sync signal detector
17 Printing paper
18 heat roll
32 Optical reader

Claims (10)

A laser beam modulated based on image information for each color is exposed on a photoreceptor, a dot-like toner image developed by a developing device is transferred to a printing paper, and the transferred unfixed toner image is thermally fixed. In a multicolor printing electrophotographic printing method in which a plurality of sets of electrophotographic processes for fixing by means are arranged along the transport direction of the printing paper, and multicolor printing is performed while sequentially fixing images for each color,
The main scanning based on the center of the image area corresponding to the heat shrinkage by comparing the test pattern of the corresponding color passed through the heat fixing unit with a reference test pattern before passing through the heat fixing unit or set in advance. to Me directions left and right sides respectively of the dot spacing deviations determined, the dot pixel interval relative to the main scanning direction of the center of the latent image pixels corresponding to the bit-mapped to image on the photosensitive drum to the deviation variable A multicolor printing electrophotographic printing method, characterized in that: The test pattern is a test pattern in which a plurality of register marks are arranged in a horizontal direction, and a deviation of a distance between individual register marks can be obtained, and the test pattern is moved in a main scanning direction on a coordinate plane on which the test pattern is placed. 2. The multicolor printing electrophotographic printing method according to claim 1, wherein a distance deviation between individual registration mark marks is obtained by an optical reading device . The test pattern is a grid-like test pattern, and the deviation of the distance between the grids in the main scanning direction with respect to the center is obtained by an optical reading device that moves in the main scanning direction on a coordinate plane on which the test pattern is mounted. 2. The multicolor printing electrophotographic printing method according to claim 1, wherein: A laser beam modulated based on image information for each color is exposed on a photoreceptor, a dot-like toner image developed by a developing device is transferred to a printing paper, and the transferred unfixed toner image is thermally fixed. In a multicolor printing electrophotographic printing method in which a plurality of sets of electrophotographic processes for fixing by means are arranged along the transport direction of the printing paper, and multicolor printing is performed while sequentially fixing images for each color,
Prepare a grid-like test pattern,
Determined the color of the test pattern corresponding passed through the heat fixing unit, the deviation of the squared distances before or preset reference test pattern and corresponding to that run査direction by comparing the passing said heat fixing means Deviation data is created based on the deviation amount, and the dot interval based on the center of a bitmap-shaped latent image pixel to be imaged on the photosensitive drum corresponding to the deviation data is made variable. Multicolor printing electrophotographic printing method. A laser beam modulated based on image information for each color is exposed on a photoreceptor, a dot-like toner image developed by a developing device is transferred to a printing paper, and the transferred unfixed toner image is thermally fixed. In a multicolor electrophotographic printing apparatus, a plurality of sets of electrophotographic processes to be fixed by means are arranged along the conveying direction of the printing paper, and multicolor printing is performed while fixing images sequentially for each color.
A test pattern of a corresponding color passed through the heat fixing unit, and a reference test pattern before or through the heat fixing unit,
Deviation reading means for comparing the two test patterns and directly or by calculating a dot interval deviation on each of the left and right sides in the main scanning direction based on the center of the corresponding image area ;
Means for varying the dot pixel interval with respect to the center in the main scanning direction of the bitmap-shaped latent image pixels to be imaged on the photosensitive drum in accordance with the read deviation. Multicolor electrophotographic printing equipment. It said test pattern, claim, characterized in that the register marks are laterally arrayed to test patterns of the individual register mark distance of deviation can be determined a test pattern or square shaped or lattice-like 5 The multicolor printing electrophotographic printing apparatus according to the above. The deviation reading means for obtaining the dot interval deviation directly or by calculation is an optical reading device for reading the coordinates of the test pattern by moving in the main scanning direction visually or on a coordinate plane on which the test pattern is placed. The multicolor printing electrophotographic printing apparatus according to claim 5, wherein A laser beam modulated based on image information for each color is exposed on a photoreceptor, a dot-like toner image developed by a developing device is transferred to a printing paper, and the transferred unfixed toner image is thermally fixed. In a multicolor electrophotographic printing apparatus, a plurality of sets of electrophotographic processes to be fixed by means are arranged along the conveying direction of the printing paper, and multicolor printing is performed while fixing images sequentially for each color.
A test pattern of a corresponding color passed through the heat fixing unit, and a reference test pattern before or through the heat fixing unit is a square test pattern,
Deviation reading means for comparing the two patterns to determine a deviation amount of the inter-square distance based on the center in the scanning direction corresponding to the thermal contraction;
A dot interval based on the center in the scanning direction of a bit map-like latent image pixel to be formed on the photosensitive drum in accordance with the deviation data based on the deviation amount read by the reading means. A multicolor printing electrophotographic printing apparatus comprising: A laser beam modulated based on image information for each color is exposed on a photoreceptor, a dot-like toner image developed by a developing device is transferred to a printing paper, and the transferred unfixed toner image is thermally fixed. In a multicolor printing electrophotographic printing method in which a plurality of sets of electrophotographic processes for fixing by means are arranged along the transport direction of the printing paper, and multicolor printing is performed while sequentially fixing images for each color,
The test pattern for each color is compared with a preset reference test pattern to directly or directly determine the dot interval deviation on each of the left and right sides in the main scanning direction based on the image area center corresponding to the mechanical error of each electrophotographic process. A multi-color printing electrophotograph, wherein the dot pixel interval is calculated by calculation and the dot pixel interval based on the center in the main scanning direction of a bitmap-shaped latent image pixel to be formed on the photosensitive drum in accordance with the deviation is varied. Printing method. A laser beam modulated based on image information for each color is exposed on a photoreceptor, a dot-like toner image developed by a developing device is transferred to a printing paper, and the transferred unfixed toner image is thermally fixed. In a multicolor electrophotographic printing apparatus, a plurality of sets of electrophotographic processes to be fixed by means are arranged along the conveying direction of the printing paper, and multicolor printing is performed while fixing images sequentially for each color.
The test pattern for each color and a preset reference test pattern are square test patterns,
Deviation reading means for comparing the two test patterns to determine a deviation amount of a distance between cells based on a center in a scanning direction corresponding to a mechanical error of each electrophotographic process;
A dot interval based on the center in the scanning direction of a bit map-like latent image pixel to be formed on the photosensitive drum in accordance with the deviation data based on the deviation amount read by the reading means. A multicolor printing electrophotographic printing apparatus comprising:

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