JP5376106B2 - Color misregistration detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably and precisely correct displacement at a low cost by preventing scratches and foreign matter on a transfer belt and recesses and projections on its surface from being erroneously recognized as displacement correction patterns. <P>SOLUTION: A plurality of sets of black patterns are formed in an area of the surface of the transfer belt including spaces between lines of color patterns. The straight line segments of both ends of each of the black patterns are parallel to the leading end or trailing end of the color pattern lines and perpendicular to or at an angle to the direction of conveyance. A plurality of sets of lines of color patterns are formed in the direction of conveyance so that the spaces are left parallelly. The color patterns include a straight line pattern perpendicular to the direction of conveyance and a pattern inclined at 45&deg; in the direction of conveyance. By detecting the black patterns and color patterns with reflected light, displacement is detected and corrected. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

The present invention relates to a color misregistration detection apparatus, and in particular, in an electrophotographic printer or the like that obtains a visualized image by superimposing a plurality of colors, detects misregistration of image positions of a plurality of colors by reflected light of a misregistration detection pattern. The present invention relates to a color misregistration detection apparatus.

  FIG. 9 shows a configuration of an image forming apparatus represented by a conventional tandem laser beam printer. Different image forming means are used for all four colors. In the image forming apparatus in FIG. 9A, the toner images are directly superimposed on the paper. In the image forming apparatus in FIG. 9B, the toner images are formed on the intermediate transfer belt. By superimposing, a color image is formed.

  As shown in FIG. 9A, the image forming apparatus is a tandem type having a configuration in which image forming units of respective colors are arranged along a conveyor belt which is an endless moving unit. A plurality of papers are sequentially fed from the upstream side in the transport direction of the transport belt 5 along the transport belt 5 that transports the paper (recording paper) 4 separated and fed by the paper feed roller 2 and the separation roller 3 from the paper feed tray 1. Image forming units (electrophotographic process units) 6BK, 6M, 6C, 6Y are arranged. The plurality of image forming units 6BK, 6M, 6C, and 6Y have the same internal configuration except that the colors of the toner images to be formed are different. The image forming unit 6BK forms a black image, the image forming unit 6M forms a magenta image, the image forming unit 6C forms a cyan image, and the image forming unit 6Y forms a yellow image. The image forming unit 6BK will be described in detail. The other image forming units 6M, 6C, and 6Y are the same as the image forming unit 6BK. Therefore, the components of the image forming units 6M, 6C, and 6Y are as follows. Instead of BK attached to each component of the image forming apparatus 6BK, only the symbols distinguished by M, C, and Y are displayed in the drawing, and the description thereof is omitted.

  The conveyor belt 5 is an endless belt wound around a driving roller 7 and a driven roller 8 that are rotationally driven. The drive roller 7 is driven to rotate by a drive motor (not shown). The drive motor, the drive roller 7, and the driven roller 8 function as drive means for moving the conveyor belt 5 that is endless movement means. At the time of image formation, the sheets 4 stored in the paper feed tray 1 are sent out in order from the top, and are attracted to the conveyor belt 5 by electrostatic attraction, and the first image is formed by the conveyor belt 5 that is rotationally driven. The black toner image is transferred to the unit 6BK.

The image forming unit 6BK includes a photosensitive drum 9BK as a photosensitive member, a charger 10BK disposed around the photosensitive drum 9BK, an exposure unit 11, a developing unit 12BK, a photosensitive member cleaner (not shown), and a static eliminator 13BK. Etc. The exposure device 11 is configured to irradiate laser beams 14BK, 14M, 14C, and 14Y that are exposure beams corresponding to image colors formed by the image forming units 6BK, 6M, 6C, and 6Y.
FIG. 9C shows an internal view of the exposure unit 11. Laser beams 14BK, 14M, 14C, and 14Y that are exposure beams for the respective image colors are emitted from laser diodes 21BK, 21M, 21C, and 21Y that are light sources, respectively. The irradiated laser light passes through the optical systems 22BK, 22M, 22C, and 22Y by the reflecting mirror 20, and the optical path is adjusted, and then scanned onto the surfaces of the photosensitive drums 9BK, 9M, 9C, and 9Y.

  The reflecting mirror 20 is a hexahedral polygon mirror. By rotating, the reflecting mirror 20 can scan the exposure beam for one line in the main scanning direction per one surface of the polygon mirror. The four laser diodes of the light source are scanned by one polygon mirror. By dividing the exposure beam for each of 14BK, 14M, 14C, and 14Y into two colors and performing scanning using the opposing reflection surface of the polygon mirror, it is possible to simultaneously expose to four different photosensitive drums. . The optical system 22 includes an f-θ lens that aligns reflected light at equal intervals and a deflection mirror that deflects laser light.

  At the time of image formation, the outer peripheral surface of the photosensitive drum 9BK is uniformly charged by the charger 10BK in the dark, and then exposed by the laser beam 14BK corresponding to the black image from the exposure device 11, thereby forming an electrostatic latent image. It is formed. The developing device 12BK visualizes the electrostatic latent image with black toner. As a result, a black toner image is formed on the photosensitive drum 9BK. This toner image is transferred onto the sheet 4 by the action of the transfer unit 15BK at a position (transfer position) where the photosensitive drum 9BK and the sheet 4 on the conveying belt 5 are in contact with each other. By this transfer, an image of black toner is formed on the paper 4. After the toner image transfer has been completed, unnecessary toner remaining on the outer peripheral surface of the photosensitive drum 9BK is wiped off by the photosensitive cleaner, and then is neutralized by the static eliminator 13BK and stands by for the next image formation.

  As described above, the sheet 4 on which the black toner image is transferred by the image forming unit 6BK is conveyed to the next image forming unit 6M by the conveying belt 5. In the image forming unit 6M, a magenta toner image is formed on the photosensitive drum 9M by a process similar to the image forming process in the image forming unit 6BK, and the toner image is converted into a black image formed on the paper 4. Superimposed and transferred. The sheet 4 is further transported to the next image forming units 6C and 6Y, and a cyan toner image formed on the photosensitive drum 9C and a yellow toner image formed on the photosensitive drum 9Y by the same operation. Are superimposed on the paper 4 and transferred. Thus, a full-color image is formed on the paper 4. The paper 4 on which the full-color superimposed image is formed is peeled off from the conveying belt 5 and fixed on the image by the fixing device 16 and then discharged to the outside of the image forming apparatus.

  In FIG. 9B, the endless moving means 5 is not the conveyance belt but the intermediate transfer belt 5. The intermediate transfer belt 5 is an endless belt wound around a driving roller 7 and a driven roller 8 that are rotationally driven. The toner images of the respective colors are transferred onto the intermediate transfer belt 5 by the action of the transfer units 15BK, 15M, 15C, and 15Y at the positions (primary transfer positions) where the photosensitive drums 9BK, 9M, 9C, and 9Y are in contact with the intermediate transfer belt 5. Is transcribed. By this transfer, a full color image is formed on the intermediate transfer belt 5 by superimposing the images of the respective color toners. At the time of image formation, the paper 4 stored in the paper feed tray 1 is sent out in order from the uppermost one, conveyed onto the intermediate transfer belt 5, and a position where the intermediate transfer belt 5 and the paper 4 are in contact (secondary transfer position). Then, a full-color toner image is transferred.

  In the color image forming apparatus configured as described above, errors in the interaxial distances of the photosensitive drums 9BK, 9M, 9C, and 9Y, parallelism errors in the photosensitive drums 9BK, 9M, 9C, and 9Y, and deflection in the exposure unit 11 The toner images of each color do not overlap at positions that should originally overlap due to errors in the installation of mirrors, errors in the writing timing of electrostatic latent images on the photosensitive drums 9BK, 9M, 9C, and 9Y. There may be a problem that a shift occurs. As components of such color misregistration, there are mainly known skew, sub-registration misregistration, magnification error in the main scanning direction, and misregistration in the main scanning direction.

In the tandem image forming apparatus, the position where the images of the respective colors are overlapped may be slightly shifted, so that a stable color image cannot be obtained. Therefore, the misalignment detecting pattern for each color is formed, and detects the image position of each color, the positional deviation detection superimposing all four colors at the same position, is generally performed. As shown in FIG. 9 (d), the image detection means irradiates light onto the transfer belt or the conveyance belt, and the reflected light is detected by the light receiving means. The light reflectance is high on the transfer belt and the conveyance belt, and the reflectance is low because the light is irregularly reflected on the toner image. The light receiving means recognizes the belt when detecting strong reflected light, and recognizes it as a toner image when detecting weak reflected light, so that the image detecting means detects a misregistration detection pattern.

A conventional method for detecting the positional deviation of each color toner image will be described. Misregistration detection is performed by aligning the image positions of three colors M, C, and Y with the image position of BK. FIG. 10 shows a misregistration detection pattern 25 that forms a misregistration detection pattern row 26 that is conventionally employed. As shown in FIG. 10A, sensors 17, 18, and 19 that face the conveyor belt 5 are provided on the downstream side of the image forming unit 6Y. The sensors 17, 18, and 19 are supported on the same substrate so as to follow a main scanning direction orthogonal to the conveyance direction of the paper 4. FIG. 10 (b) shows an enlarged view of the image detection means, and FIG. 10 (a) shows the image detection means (sensors 17, 18, 19) and their peripheral portions. The image detection means includes a light emitting unit 23 and a light receiving unit 24. From the light emitting unit 23, the light containing the diffused light component is applied to the misregistration detection pattern 25 formed on the transport belt 5. The light receiving unit 24 receives the reflected light including the regular reflection component and the diffuse reflection component, and the image detection unit detects the misregistration detection pattern 25. The image detection means are arranged at both ends and the center in the main scanning direction, and a positional deviation detection pattern row 26 is formed for each. FIG. 10A shows a minimum set of pattern rows necessary for obtaining various color misregistration amounts for each color.

A conventional misregistration detection pattern has a total of eight pattern rows including a linear pattern composed of four colors of BK, M, C, and Y and a hatched pattern, and forms a set of pattern rows. This pattern row is created for each image detection means, and a plurality of sets are created in the sub-scanning direction. FIG. 10C shows an output signal when the image detection means detects a conventional misregistration detection pattern . The output signal of the image detection means is a signal when the reflected light of the light receiving unit 24 is received, 27 indicates the output signal of the light receiving unit 24, and 28 indicates the detection timing. In the detection of the conventional misregistration detection pattern shown in FIG. 11, the light receiving unit 24 detects only the regular reflection light component on the misregistration detection pattern .

  The change in the waveform when detecting the color pattern in FIG. 11 is caused by a slight incidence of the diffuse reflected light component from the color pattern on the light receiving unit 24. The image detecting means determines that the edges 30BK_1, 30BK_2, 30M_1, 30M_2, 30C_1, 30C_2, 30Y_1, and 30Y_2 of the pattern are detected at the position where the threshold line 29 and the detected waveform intersect. The image detection means determines the image position by taking the average of the detection points of the edges 30BK_1 and 30BK_2 of the BK linear pattern. Similarly, the straight line patterns of M, C, and Y are determined as image positions by taking the average of the detection points of 30 * _1 and 30 * _2. As for the detection of the oblique line pattern, the average of the detection points of the edges at both ends is determined as in the case of the straight line pattern, and the image position is determined. Below are some examples of prior art related to this.

  The “overlapping image misregistration amount detection device” disclosed in Patent Document 1 detects an image misregistration between images of respective colors in a color image forming apparatus. A color image is obtained on a recording medium by sequentially superimposing and transferring an image formed by a plurality of electrophotographic process units arranged along the conveying belt onto a single recording medium conveyed by the conveying belt. . A conveyance belt capable of transmitting light is used. The conveyor belt is irradiated with a light emitting element. A slit is provided at a spatial position facing the light emitting element with the conveyance belt interposed therebetween. A light receiving element is provided at a position facing the light emitting element with the conveying belt and the slit interposed therebetween. When the light receiving surface of the light receiving element is rectangular, the light receiving element is separated from the entrance surface where the light emitted from the light emitting element enters the slit by a distance corresponding to the long side of the light receiving surface. When the light receiving surface of the light receiving element is circular, the light receiving surface is separated by a distance corresponding to the circular diameter.

The “image forming apparatus” disclosed in Patent Document 2 can ensure image overlay accuracy at low cost. Images are formed on the conveyor belt at a plurality of image forming stations. At an image station that forms a first image, a first registration mark composed of lines arranged at a predetermined interval is formed on a conveyor belt. At the image forming station for forming the second image, a second resist mark having substantially the same shape as the first resist mark is formed so as to overlap the first resist mark. Based on the detection result of the degree of registration of both registration marks, the positional deviation of the first or second image is detected .
Japanese Patent No. 3734116 (Japanese Patent Laid-Open No. 10-268609) JP 2002-221842 A

However, the conventional color misregistration detection method has the following problems. If the transfer belt or transport belt is scratched, foreign matter is attached, or there are subtle irregularities on the belt surface, the light emitted from the light source of the image detection means Causes irregular reflection, and the reflected light cannot be detected accurately. In the conventional misregistration detection pattern, there is a possibility that the image detection means may erroneously recognize that the misregistration detection pattern has been detected when it detects a scratch, a foreign object, or a belt unevenness.

An object of the present invention is to solve the above-described conventional problems so that scratches, foreign matter, and surface irregularities on a transfer belt and a conveyance belt are not erroneously recognized as a misregistration detection pattern in a color misregistration detection apparatus. In other words, it is possible to stably and accurately detect misalignment at a low cost.
In other words, if there is a scratch on the conveyor belt, if there is a foreign object attached, or if there are subtle irregularities on the belt surface when using a low-cost conveyor belt, the scratch or foreign object In other words, a toner pattern is painted on the unevenness so that a scratch, a foreign object, or an unevenness is not erroneously recognized as a misregistration detection pattern .

In order to solve the above problems, the present invention, the color misalignment detecting apparatus, and the reference color image means for creating a solid of the reference color pattern black on the carrier, on the reference color pattern, the than the reference color pattern to create a plurality of color non-reference color pattern other than black having a large length in the main scanning direction, and a plurality of non-reference color image forming means, said reference color pattern, the positive from the light emitting element Image detection means for detecting a reflected light component by receiving it with a light receiving element, and detecting the non-reference color pattern by receiving a diffuse reflected light component from the light emitting element with the light receiving element, and the reference color The pattern is a color misregistration detection device characterized in that the width in the main scanning direction is substantially equal to the region where the regular reflection light of the light receiving means of the image detecting means is received.

By doing so, scratches, foreign matter, and surface irregularities on the transfer belt and the conveyance belt are not erroneously recognized as misregistration detection patterns, and stable and accurate misregistration detection can be performed at low cost.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to FIGS.

In Example 1 of the present invention, a plurality of black patterns having ends that are perpendicular to the transport direction or inclined at the transport direction are formed on the transport belt, and then spaced in parallel in the transport direction of the transport body. A color misregistration detection device that detects a misregistration by detecting a black pattern and a color pattern by forming a plurality of sets of color pattern arrays each composed of a linear pattern perpendicular to the transport direction and an oblique line pattern having an inclination angle in the transport direction. .

The basic configuration of the image forming apparatus having the color misregistration detection apparatus in Embodiment 1 of the present invention is the same as that described with reference to FIG. FIG. 1 is a diagram illustrating a misregistration detection pattern used in the color misregistration detection apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram illustrating the detection principle of the misregistration detection pattern . FIG. 3 is a functional block diagram showing a configuration for processing detected data. FIG. 4 is a flowchart illustrating a procedure for executing the positional deviation detection method in the color positional deviation detection apparatus.
1 to 3, a belt 5 is a conveyance belt that conveys a sheet. An intermediate transfer belt may be used. Sensors 17, 18, and 19 are optical sensors that detect patterns. The light emitting unit 23 is a light source that irradiates a misregistration detection pattern . The light receiving unit 24 is sensors 17 , 18 , and 19 that detect reflected light. The misregistration detection pattern 25 is a mark for detecting the position. The threshold line 29 is a threshold value. Edge 30 is the position of the detection signal corresponding to the end of the pattern.

  The amplifier 31 is means for amplifying the output signal of the sensor. The filter 32 is means for removing noise from the output signal of the sensor. The A / D converter 33 is means for converting the output signal of the sensor into a digital signal. The sampling control unit 34 is means for controlling sampling of the output signal of the sensor. The FIFO memory 35 is a buffer memory for sensor output signals. The I / O port 36 is an input / output interface for taking in data and controlling a light source. The data bus 37 is a common bus for data processing. The CPU 38 is a central processing unit that performs data processing. The RAM 39 is a temporary memory for data processing. The ROM 40 is a fixed memory that stores programs and the like. The light emission amount control unit 41 is means for controlling the light amount of the light emitting unit.

The principle and processing procedure of color misregistration detection in Embodiment 1 of the present invention will be described. First, the principle of color misregistration detection will be described.
In order to prevent detection of scratches, foreign matter, and belt irregularities on the belt, a toner image is superimposed on the scratches, foreign matter, and irregularities. If the misregistration detection pattern is accidentally formed on a scratch, a foreign object, or an uneven surface, only the misregistration detection pattern can be normally detected. For this reason, the misregistration detection pattern is usually formed in a linear shape, but it is formed as thick and solid as possible to reduce the area where the belt surface is exposed. The possibility of erroneous recognition as a detection pattern can be reduced. Furthermore, since it is necessary to lower the threshold line in order to detect the position shift detection pattern on the black solid pattern, it is difficult to detect scratches, foreign matter, and irregularities. In addition, since the width of scratches, foreign matter, and irregularities is usually 1 mm or less, even if scratches, foreign matters, or irregularities just appear on the exposed part of the belt surface, the line width is small compared to the solid pattern. Makes it easy to distinguish.
In this way, a system can be constructed that greatly reduces the possibility that the image detection means will erroneously recognize scratches, foreign matter, and irregularities on the belt.

Next, an outline of color misregistration detection will be described. Multiple sets of black (reference color) patterns are formed in a predetermined area on the transport body including the space between color pattern rows, and then multiple sets of color pattern rows are formed in parallel with the transport direction of the transport body. Then, a black pattern and a color pattern are detected and a signal is output. Alternatively, a plurality of color pattern rows are formed at intervals in parallel in the carrying direction of the carrier, and then a plurality of black patterns are formed in a predetermined area on the carrier including the interval portion of the color pattern rows, and black A pattern and a color pattern are detected and a signal is output. Alternatively, the black pattern is formed so as to continuously fill the space area and the area immediately below the color pattern row, and the color pattern is formed on the portion where the black pattern is filled.

The reference color pattern is preferably formed with the color of the image forming means located farthest from the image detecting means. The reference color pattern may not be a black pattern. A predetermined area ahead in the transport direction from the front end and end of the color pattern row is filled with a black pattern. A black pattern is formed only in a range in which a pattern in the vertical direction in the transport direction can be detected. The color pattern has a linear pattern having a first straight portion perpendicular to the transport direction of the transport body and a diagonal pattern having a second straight portion having an inclination angle in the transport direction of the transport body. The inclination angle is ± 45 °. The black pattern has straight portions parallel to the front end and the end of the pattern row at both ends, and the straight portions are a straight portion perpendicular to the transport direction of the transport body and a straight portion forming an inclination angle in the transport direction of the transport body. . The width of the color pattern and the region where the surface of the carrier is exposed are the same in the direction of the carrier.

Irradiate light onto the carrier, receive the reflected light from the carrier on the carrier, output a signal, and irradiate the color pattern with the output signal when the black pattern is illuminated Compare the output signals of the hour and detect the color pattern. An output signal when the black pattern and the color pattern are irradiated with light and an output signal when the carrier is irradiated with light are compared to detect the black pattern and the color pattern. Alternatively, the black pattern and the color pattern are detected from the output signal when detecting the front edge of the black pattern and the color pattern and the output signal when detecting the rear edge of the black pattern and the color pattern. Alternatively, the black pattern and the color pattern are detected from the average of the output signal when detecting the front edge of the black pattern and the color pattern and the output signal when detecting the rear edge.
When it is determined that the line width in the transport direction of the detected pattern is smaller than a predetermined value, the pattern detection result is discarded. The predetermined value is determined from the minimum value of the distance at which the reference color pattern and the non-reference color pattern are continuously formed in the transport direction.

Next, the misregistration detection pattern will be described with reference to FIG. A BK pattern 25BK_B, which serves as a reference for detecting misalignment, is formed as a rectangular solid pattern, and linear patterns 25M_Y, 25C_Y, and 25Y_Y are superimposed on the pattern. Next, a solid pattern 25BK_P having a parallelogram shape of BK is formed, and hatched patterns 25M_S, 25C_S, and 25Y_S are superimposed on the pattern.
This set of pattern rows is created for each image detection means, and a plurality of sets are created in the sub-scanning direction. 25BK_B and 25BK_P are created to extend as much as possible even in areas where M, C, and Y straight and oblique lines are not created. This reduces the area of the conveyor belt where the surface of the conveyor belt is exposed, and damages the image detection means. And the possibility of false detection of foreign objects and irregularities.
However, as the area for creating the BK pattern increases, the amount of toner consumption increases, so the area in the main scanning direction where the BK pattern is formed is narrowed down to an area that can be detected by the image detection means, saving toner consumption. To do.

Next, detection of a misregistration detection pattern will be described with reference to FIG. The detection of the misregistration detection pattern shown in FIG. 1 is different from the conventional misregistration detection pattern detection method shown in FIG.
The light receiving unit 24 detects the specular reflection light component and the diffuse reflection light component at the same time, thereby detecting the BK pattern on the surface of the conveyor belt with the specular reflection light component, and the M, C, and Y patterns on the BK pattern, It can be detected by the diffuse reflected light component. As shown in FIGS. 2A and 2B, the image detection means has edges 30BK_1, 30BK_2, 30BK_3, 30BK_4, 30M_1, 30M_2, 30M_3, 30M_4, 30C_1, at positions where the threshold line 29 and the detection waveform intersect. It is determined that 30C_2, 30C_3, 30C_4, 30Y_1, 30Y_2, 30Y_3, and 30Y_4 have been detected.
The image detection means determines the image position of 25BK_B by taking the average of the detection points of the edges 30BK_1 and 30BK_2 of the rectangular solid pattern 25BK_B of BK. Similarly, for 25M_Y, 25C_Y, and 25Y_Y, the average of the detection points of 30 * _1 and 30 * _2 is taken to determine the image position. Similarly, for the detection of the BK parallelogram solid pattern 25BK_P, the edges 30BK_3 and 30BK_4 are averaged to determine the image position, and the detection of 25M_S, 25C_S, and 25Y_S is similarly performed for 30 * _3 and 30 * _4. The average of the detection points is taken to determine the image position.

With respect to pattern detection, when a scratch, foreign matter, or unevenness has just come to the exposed portion of the belt surface, it is necessary to distinguish the misalignment detection pattern 25 from the scratch, foreign matter, or unevenness on the belt. Since the width of scratches, foreign matter, and unevenness on the belt is usually 1 mm or less, the line width is smaller than that of the solid pattern. Therefore, the image detection means crosses the position where the threshold line 29 and the detection waveform intersect next. When the position interval is smaller than a predetermined value, the detection result is determined as an error, and the detection result is discarded.

Based on the detection result of the misregistration detection pattern 25, the image position of 25BK_B and the image positions of 25M_Y, 25C_Y, and 25Y_Y are obtained, and the CPU performs a predetermined calculation process, whereby the deviation amount and skew of the sub-scanning resist Can be requested. Further, in addition to the 25BK_B image position and the 25M_Y, 25C_Y, and 25Y_Y image positions, the 25BK_P image position and the 25M_S, 25C_S, and 25Y_S image positions are obtained, and when the CPU performs predetermined calculation processing, the magnification in the main scanning direction is obtained. The error and the amount of registration deviation in the main scanning direction are respectively obtained. Correction is performed based on this result.

  Regarding the skew, for example, the deflection mirror in the exposure unit 11 or the exposure unit 11 itself is corrected by adding an inclination by an actuator. The registration deviation in the sub-scanning direction is corrected by, for example, line writing timing and surface phase control of the polygon mirror. For example, the magnification error in the main scanning direction is corrected by changing the writing image frequency. The registration deviation in the main scanning direction can be corrected by changing the writing timing of the main scanning line.

Next, processing for processing detected data will be described with reference to FIG. The signal obtained from the light receiving unit 24 is amplified by the AMP 31, passes only the line detection signal component by the filter 32, and is converted from analog data to digital data by the A / D converter 33. Sampling of data is controlled by the sampling controller 34, and the sampled data is stored in the FIFO memory 35. After the detection of the pair of misalignment detection patterns 25 is completed, the stored data is loaded to the CPU 38 and the RAM 39 by the data bus 37 via the I / O port 36, and the CPU 38 performs predetermined arithmetic processing. To obtain the above-described various shift amounts.

The ROM 40 stores various programs for controlling the misregistration detection device and the image forming apparatus, in addition to the programs for calculating the various misalignment amounts described above. In addition, the CPU 38 monitors the detection signal from the light receiving unit 24 at an appropriate timing, and the light emission amount control unit 41 emits light so that it can be reliably detected even if the conveyance belt and the light emitting unit 23 are deteriorated. The amount is controlled so that the level of the received light signal from the light receiving unit 24 is always constant.
In this way, the CPU 38 and the ROM 40 function as control means for controlling the operation of the entire image forming apparatus.

Next, with reference to FIG. 4, a processing procedure of the positional deviation correction calculation control method will be described. In step 1, exposure of a plurality (N sets) of misregistration detection patterns is started. The misregistration detection pattern is the pattern shown in FIG. In step 2, reading of positional information of the N-th set of misregistration detection patterns is started. When the position information of the N-th set of misregistration detection patterns is detected by the sensors 17, 18, 19 in step 3, when the prescribed number of patterns in one set is detected, the process proceeds to step 4. In step 4, it is determined whether or not all detected pattern widths are equal to or greater than a specified value.

If there is a pattern having line width information equal to or less than the specified value, the pattern is determined as noise in step 5, the data is discarded, and the process proceeds to step 6. If all the pattern widths are equal to or larger than the specified value, the process proceeds to step 6 as it is. In step 6, the position information of the pattern in the Nth set is stored in the RAM. In step 7, it is determined whether or not the storage of the position information of all sets of patterns in the RAM has been completed. If not completed, the process returns to step 3. In step 9, based on the position information stored in the RAM, the CPU calculates various deviation amounts. In step 10, the CPU calculates a correction amount corresponding to the deviation amount, and stores the detected amount in the RAM.
As described above, the positional deviation detection and correction control is completed.

As described above, in the first embodiment of the present invention, color misregistration detection is performed after forming a plurality of black patterns having end portions that are perpendicular to the conveyance direction or inclined at the conveyance direction on the conveyance belt. Forms multiple sets of color pattern rows, each consisting of a linear pattern perpendicular to the transport direction and a diagonal pattern that forms an inclination angle in the transport direction, spaced in parallel with the transport direction of the body, and detects the black pattern and the color pattern. Since the displacement is detected , scratches on the transfer belt and the conveying belt, foreign matter, and surface irregularities are not erroneously recognized as a displacement detection pattern, and stable and accurate displacement detection can be performed at low cost.

In Example 2 of the present invention, a plurality of black patterns having ends that are perpendicular to the transport direction or inclined at the transport direction are formed on the transport belt, and then spaced in parallel in the transport direction of the transport body. A color misregistration detection device that detects a misregistration by detecting a black pattern and a color pattern by forming a plurality of sets of color pattern arrays each composed of a linear pattern perpendicular to the transport direction and an oblique line pattern having an inclination angle in the transport direction. .

The basic configuration of the image forming apparatus that executes the color misregistration detection reference method according to the second embodiment of the present invention is the same as that described with reference to FIG. FIG. 5 is a diagram illustrating a misregistration detection pattern used in the color misregistration detection apparatus according to the second embodiment of the present invention. FIG. 6 is a diagram illustrating a detection principle of a misregistration detection pattern used in the color misregistration detection apparatus.

The misregistration detection pattern will be described with reference to FIG. First, a BK pattern 25BK_T1 serving as a reference for detecting misregistration is formed as a solid pattern having a trapezoidal shape (the edge in the main scanning direction is on the image detection means side), and linear patterns 25M_Y, 25C_Y, and 25Y_Y are superimposed on the pattern. Form. Next, a BK trapezoidal solid pattern 25BK_T2 (an edge inclined in the sub-scanning direction is on the image detection means side) is formed, and oblique line patterns 25M_S, 25C_S, and 25Y_S are formed on the pattern. This set of pattern rows is created for each image detection means, and a plurality of sets are created in the sub-scanning direction. 25BK_T1 and 25BK_T2 are created by expanding as much as possible even in areas where M, C, Y straight / slanted patterns are not created. This reduces the area of the conveyor belt where the surface of the conveyor belt is exposed. Reduces the possibility of false detection of irregularities. However, as the area for creating the BK pattern increases, the amount of toner consumption increases. For this reason, the area in the main scanning direction for forming the BK pattern is narrowed down to an area that can be detected by the image detection means, thereby saving toner consumption. .

Next, with reference to FIG. 6, a method for detecting a misregistration detection pattern will be described. The light receiving unit 24 detects the specular reflection light component and the diffuse reflection light component at the same time, thereby detecting the BK pattern on the surface of the conveyor belt with the specular reflection light component and diffusing the M, C, and Y patterns on the BK pattern. It can be detected by the reflected light component. As shown in FIGS. 6A and 6B, the image detecting means has edges 30BK_1, 30BK_2, 30BK_3, 30BK_4, 30M_1, 30M_2, 30M_3, 30M_4, 30C_1, at positions where the threshold line 29 and the detected waveform intersect. It is determined that 30C_2, 30C_3, 30C_4, 30Y_1, 30Y_2, 30Y_3, and 30Y_4 have been detected.

  The image detection means takes the average of the detection points of 30 * _1 and 30 * _2 for 25M_Y, 25C_Y, and 25Y_Y to determine the image position, and the rear edge 30BK_1 of the BK trapezoidal solid pattern 25BK_T2 and the trapezoid of the BK The average of the detection points of the trailing edge 30BK_2 of the solid pattern 25BK_T1 is taken to determine the image position of BK corresponding to 25M_Y, 25C_Y, and 25Y_Y. For the detection of 25M_S, 25C_S, and 25Y_S, the image detection means determines the image position by averaging the detection points of 30 * _3 and 30 * _4, and determines the rear edge 30BK_3 and BK of the BK trapezoidal solid pattern 25BK_T1. The average of the detection points of the leading edge 30BK_4 of the trapezoidal solid pattern 25BK_T2 is taken and determined as the BK image position corresponding to 25M_S, 25C_S, and 25Y_S.

Based on the detection result of the misalignment detection pattern 25, the BK image position corresponding to 25M_Y, 25C_Y, and 25Y_Y and the image position of 25M_Y, 25C_Y, and 25Y_Y are obtained, and the CPU performs a predetermined calculation process. The shift amount and skew of the sub-scanning resist can be obtained. Further, in addition to the BK image positions corresponding to 25M_Y, 25C_Y, and 25Y_Y and the 25M_Y, 25C_Y, and 25Y_Y image positions, the BK image positions corresponding to 25M_S, 25C_S, and 25Y_S and the image positions of 25M_S, 25C_S, and 25Y_S are obtained. When the CPU performs a predetermined calculation process, a magnification error in the main scanning direction and a registration deviation amount in the main scanning direction are obtained. Correction is performed based on this result. The procedure of misregistration detection and correction in the second embodiment is as shown in FIG.

As described above, in Example 2 of the present invention, a plurality of sets of black patterns having ends that are perpendicular to the transport direction or inclined at the transport direction are formed on the transport belt, and then parallel to the transport direction of the transport body. Since a plurality of color pattern rows consisting of a linear pattern perpendicular to the transport direction and a diagonal pattern having an inclination angle in the transport direction are formed at intervals, a black pattern and a color pattern are detected to detect misregistration. Scratches, foreign matter, and surface irregularities on the transfer belt and the conveyance belt are not erroneously recognized as misregistration detection patterns, and stable and accurate misregistration detection can be performed at low cost.

In Example 3 of the present invention, a plurality of black patterns having ends that are perpendicular to the transport direction or inclined at the transport direction are formed on the transport belt, and then spaced in parallel in the transport direction of the transport body. Color misregistration for detecting misregistration by forming multiple sets of triangular color pattern arrays with straight line portions perpendicular to the transport direction and straight line portions having an inclination angle in the transport direction, and detecting black patterns and color patterns It is a detection device.

The basic configuration of an image forming apparatus that performs color misregistration detection according to Embodiment 3 of the present invention is the same as that described with reference to FIG. FIG. 7 is a diagram illustrating a misregistration detection pattern used in the color misregistration detection apparatus according to the third embodiment of the present invention. FIG. 8 is a diagram illustrating a detection principle of a misregistration detection pattern used in the color misregistration detection apparatus.

FIG. 7 is a configuration diagram of a misregistration detection pattern used in the third embodiment. First, a BK pattern 25BK_T serving as a reference for detecting misregistration is formed as a trapezoidal solid pattern, and triangular patterns 25M_TR, 25C_TR, and 25Y_TR are formed on the pattern. This set of pattern rows is created for each image detection means, and a plurality of sets are created in the sub-scanning direction. 25BK_T is created by expanding as much as possible to the area where the triangular pattern of M, C, Y is not created, thereby reducing the area where the conveyor belt surface is exposed on the conveyor belt, and the image detection means can remove scratches, foreign objects, and irregularities. Reduce the possibility of false detection. However, as the area for creating the BK pattern increases, the amount of toner consumption increases. Therefore, the region in the main scanning direction in which the BK pattern is formed is narrowed down to a region that can be detected by the image detection means, thereby saving the amount of toner consumption.

Next, detection of a misregistration detection pattern will be described with reference to FIG. The light receiving unit 24 detects the specular reflected light component and the diffuse reflected light component at the same time, thereby detecting the BK pattern on the surface of the conveyor belt with the specular reflected light component, and diffusely reflects the M, C, and Y patterns on the BK pattern. It can be detected by the light component. As shown in FIGS. 8A and 8B, the image detection means detects edges 30BK_1, 30BK_2, 30M_1, 30M_2, 30C_1, 30C_2, 30Y_1, and 30Y_2 at positions where the threshold line 29 and the detection waveform intersect. Judge. The image detection means determines that the image position of the edge in the main scanning direction of 25BK_T from the detection point of the leading edge 30BK_1 of the BK trapezoidal solid pattern 25BK_T, and for 25M_TR, 25C_TR, 25Y_TR, 25M_TR, 25C_TR from the detection point of 30 * _1 , 25Y_TR is determined as the image position of the edge in the main scanning direction. The image detection means determines the image position of the inclined edge inclined in the sub-scanning direction of 25BK_T from the detection point of the trailing edge 30BK_2 of the BK trapezoidal solid pattern 25BK_T, and detects 25 * _2 for 25M_TR, 25C_TR, and 25Y_TR. It is determined that the image position is 25M_TR, 25C_TR, 25Y_TR from the point.

Based on the detection result of the misregistration detection pattern 25, the image position of the 25BK_T main scanning direction edge and the image position of the 25M_TR, 25C_TR, 25Y_TR main scanning direction edge are obtained, and the CPU performs a predetermined calculation process. Thus, the shift amount and skew of the sub-scanning resist can be obtained. Further, in addition to the image position of the 25BK_T main scanning direction edge and the image position of the 25M_TR, 25C_TR, 25Y_TR main scanning direction edge, the image position of the 25BK_T inclined edge and the image position of the 25M_TR, 25C_TR, 25Y_TR inclined edge are obtained. When the CPU performs predetermined arithmetic processing, the magnification error in the main scanning direction and the registration deviation amount in the main scanning direction are obtained. Correction is performed based on this result. The procedure for detecting and correcting misalignment is as described with reference to FIG.

As described above, in the third embodiment of the present invention, color misregistration detection is performed after a plurality of black patterns having ends that are perpendicular to the conveyance direction or inclined at the conveyance direction are formed on the conveyance belt, and then conveyed. A plurality of triangular color pattern rows having a linear portion perpendicular to the conveying direction and a linear portion forming an inclination angle in the conveying direction are formed in parallel with the conveying direction of the body, and the black pattern and the color pattern are formed. Because it detects and detects misalignment, scratches, foreign matter, and surface irregularities on the transfer belt and conveyor belt are not mistakenly recognized as misalignment detection patterns, and stable and accurate misalignment detection can be achieved. .

The color misregistration detection apparatus of the present invention is optimal as an apparatus for detecting misregistration stably at low cost in an electrophotographic printer or the like that obtains a visualized image by superimposing a plurality of colors.

It is a figure which shows the pattern for position shift detection used with the color position shift detection apparatus of Example 1 of this invention. It is a figure which shows the detection principle of the pattern for a position shift detection used with the color position shift detection apparatus of Example 1 of this invention. It is a functional block diagram which shows the hardware constitutions of the color misregistration detection apparatus of Example 1 of this invention. It is a flowchart which shows the procedure which performs the position shift detection and correction method in the color position shift detection apparatus of Example 1 of this invention. It is a figure which shows the pattern for a position shift detection used with the color position shift detection apparatus of Example 2 of this invention. It is a figure which shows the detection principle of the pattern for position shift detection used with the color position shift detection apparatus of Example 2 of this invention. It is a figure which shows the pattern for a position shift detection used with the color position shift detection apparatus of Example 3 of this invention. It is a figure which shows the detection principle of the pattern for a position shift detection used with the color position shift detection apparatus of Example 3 of this invention. It is a conceptual diagram which shows the structure of the conventional image forming apparatus. It is a figure which shows the detection principle of the pattern for a conventional position shift detection. It is a figure which shows the conventional pattern for position shift detection.

DESCRIPTION OF SYMBOLS 1 ... Paper feed tray, 2 ... Paper feed roller, 3 ... Separation roller, 4 ... Paper, 5 ... Belt, 6 ... Image formation part, 7 ... Drive roller, 8 ... driven roller, 9 ... photoconductor drum, 10 ... charger, 11 ... exposure device, 12 ... developing device, 13 ... static eliminator, 14 ... laser beam, 15 ... transfer device, 16 ... fixer, 17 ... sensor, 18 ... sensor, 19 ... sensor, 20 ... reflecting mirror, 21 ... laser diode, 22 ... optical system, 23 ... light-emitting section, 24 ... receiving unit, 25 ... positional deviation detecting pattern (detection mark), 26 ... misalignment detecting pattern array, 27 ... output signal, 28 ... Detection timing, 29 ... Threshold line, 30 ... Edge, 32 ... Filter, 33 ... A / D converter, 34 ... Sampling control unit, 35 ... FIFO memory 36 ・ ・ ・ I / O port, 37 ... data bus, 38 ... CPU, 39 ... RAM, 40 ... ROM, 41 ... light emission amount control unit.

Claims (11)

Reference color image forming means for creating a black solid reference color pattern on the carrier,
On the reference color pattern, to create a plurality of non-reference color pattern of the color other than black with a large length in the main scanning direction than the reference color pattern, and a plurality of non-reference color image forming means,
The reference color pattern is detected by receiving a regular reflection light component from a light emitting element by a light receiving element, and the non-reference color pattern is detected by receiving a diffuse reflection light component from the light emitting element by the light receiving element. Image detecting means for detecting,
The color misregistration detection apparatus according to claim 1, wherein the reference color pattern has substantially the same width in the main scanning direction as an area where the regular reflection light of the light receiving means of the image detecting means is received.   The image detection unit is configured to detect the reference color pattern by a change in a detection level of specular reflection light from a carrier with respect to irradiated light by the light receiving unit, and to detect a change in a detection level of diffuse reflection light. The color misregistration detection apparatus according to claim 1, wherein a reference color pattern is detected. The image detecting means includes: a light emitting means for irradiating light on the transport body; and the light receiving means for receiving a reflected light from the transport body and outputting a signal.
The color misregistration detection apparatus according to claim 2 , wherein an edge of the reference color pattern and the non-reference color pattern is determined at a position where the detection level and a predetermined threshold line intersect.   The image detecting means is configured to output the reference color pattern from an output signal when detecting a front edge of the reference color pattern and the non-reference color pattern in a sub-scanning direction and an output signal when detecting a rear edge. The color misregistration detection apparatus according to claim 1, wherein an image position of the non-reference color pattern is determined.   The image detecting unit is configured to calculate an output signal when detecting a front edge in a sub-scanning direction of the reference color pattern and the non-reference color pattern and an average of detection timings of an output signal when detecting a rear edge. 3. The color misregistration detection apparatus according to claim 1, wherein image positions of a reference color pattern and the non-reference color pattern are determined.   The color according to claim 1, wherein the image detection unit discards the detection result of the pattern when a line width of the detected pattern in the transport direction is smaller than a predetermined value. Misalignment detection device.   The non-reference color pattern has a linear pattern having a first straight portion perpendicular to the transport direction of the transport body and a diagonal pattern having a second straight portion having an inclination angle in the transport direction of the transport body. The color misregistration detection apparatus according to claim 1 or 2.   The non-reference color pattern has a pattern having a first linear portion perpendicular to the transport direction of the transport body and a pattern having a triangular shape having a second straight portion forming an inclination angle in the transport direction of the transport body. The color misregistration detection apparatus according to claim 1 or 2,   Each of the reference color patterns has a linear portion parallel to the front end and the end of the pattern row at both ends, and has a linear portion perpendicular to the transport direction of the transport body and an inclination angle in the transport direction of the transport body. The color misregistration detection device according to claim 1, wherein the color misregistration detection device is a pattern having a straight line portion.   3. The color misregistration according to claim 1, wherein the reference color pattern is a pattern having a linear portion perpendicular to the conveying direction at one end and a linear portion forming an inclination angle in the conveying direction at the other end. Detection device. In the region on the carrier on which the reference color pattern and the non-reference color pattern are formed, the width of the region in which the carrier surface is exposed is equal between the non-reference color pattern and the non-reference color pattern. The color misregistration detection apparatus according to claim 10.

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