JP5375104B2 - Misregistration amount calculation device, misregistration amount calculation method, misregistration amount calculation program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a deviation amount computing device, method, and program which are able to compute an amount of deviation quickly even when an image formation process is being performed. <P>SOLUTION: A deviation amount computing device is for use in an electrophotographic color image forming apparatus that has a printing medium transport belt or intermediate transfer belt, scans a light beam corresponding to an image signal, thereby forming an image on an image carrier, and computes an amount of deviation of the image. The computing device includes: a first computing means configured to read a detection pattern formed on the belt; a second computing means configured to measure a scanning time between a start and an end of one scan of a light beam, thereby computing a deviation amount containing both an amount of deviation in the main scanning direction and an amount of deviation in the running direction of the belt member in a mixed manner; and a third computing means configured to calculate an amount of deviation in the main scanning direction and an amount of deviation in the running direction of the belt member. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an apparatus for calculating a positional deviation amount relating to each image of a plurality of colors when obtaining an image visualized by superimposing a plurality of colors.

  A so-called tandem image forming apparatus uses different image forming means for all four colors, and forms a color image by superimposing a toner image directly on paper or on an intermediate transfer belt.

  In such a tandem type image forming apparatus, the position where the images of the respective colors are superimposed is slightly shifted, so that a stable color image cannot be obtained. For this reason, a positional deviation correction is generally performed in which a positional deviation correction pattern for each color formed on the carrier is detected and all four colors are superimposed on the same position. In general, the detection result of the color pattern (cyan, magenta, yellow) and the detection result of the reference color pattern (black) are compared, and the amount of positional deviation of the color pattern with respect to the reference color pattern is calculated (Patent Document 1). .

  However, even if the positional deviation amount is calculated and the positional deviation correction is performed, the positional deviation again occurs due to various factors as time passes. In particular, a change in the reflection characteristics of the reflection mirror accompanying a rise in temperature in the exposure apparatus of the image forming apparatus tends to cause misalignment.

  Therefore, in order to correct the positional deviation caused by the temperature rise in the exposure apparatus, it has been conventionally necessary to frequently perform the positional deviation correction processing using the positional deviation correction pattern.

JP 2005-156992 A

  However, in the misregistration correction using the misregistration correction pattern, it is necessary to form a color pattern on the carrier. Accordingly, there has been a problem that image formation cannot be executed while the positional deviation correction processing is being performed.

  In addition, the misregistration correction process using the misregistration correction pattern requires a series of processes such as image formation of the color pattern on the carrier, reading of the color pattern by the sensor, and calculation on the read result. There was also a problem that it took.

  Accordingly, in view of the above problems, in the present invention, a positional deviation amount calculation device, a positional deviation amount calculation method, and a positional deviation that can be calculated even when an image forming process is being performed in the image forming apparatus. An object is to provide a quantity calculation program.

According to an embodiment of the disclosed misregistration amount calculation apparatus, the image forming apparatus includes a belt member that is a print medium conveyance belt or an intermediate transfer belt in an electrophotographic color image forming apparatus, and scans a light beam corresponding to an image signal to generate an image. A misregistration amount calculation device for forming an image on a carrier and calculating a misregistration amount of an image position on the image carrier,
In order to detect the positional deviation amount, a first positional deviation detection pattern formed on the belt member is read, and a positional deviation amount in the main scanning direction and the sub-scanning direction is calculated based on the reading result. A calculation means;
Measurement of the scanning time during which the light beam is scanned from the scanning start side to the scanning end side is performed at least twice at predetermined intervals , and a positional deviation amount based on the scanning time is calculated based on the change amount of the scanning time . Two calculating means;
Using the calculation result by the first calculation means, the positional deviation amount based on the scanning time calculated by the second calculation means and the positional deviation amount in the main scanning direction and the running direction of the belt member. A third calculating means for calculating and storing a correction coefficient for calculating the amount of positional deviation, and
Further, the third calculation means calculates the amount of displacement of the image position using a stored correction coefficient .

  According to the present invention, it is possible to provide a misregistration amount calculation device, a misregistration amount calculation method, and a misregistration amount calculation program capable of calculating a misregistration amount even when an image forming process in the image forming apparatus is being executed. it can.

1 is a diagram illustrating a configuration of a color image forming apparatus according to an exemplary embodiment. It is a figure which shows the inside of the exposure device which concerns on this Embodiment. It is a figure which shows the operation | movement principle of the positional offset amount calculation apparatus which concerns on this Embodiment. It is a figure which shows an example of the pattern for a position shift detection which concerns on this Embodiment. It is the figure which expanded the sensor which the pattern reading means concerning this Embodiment has. It is a figure which shows the sensor which the pattern reading means which concerns on this Embodiment has, and its periphery. It is a figure explaining the principle in which the sensor which the pattern reading means concerning this Embodiment has detects a pattern for position shift detection. It is a figure explaining the principle which calculates the amount of position shifts using the pattern for position shift detection concerning this embodiment. It is a figure which shows the structure of the 1st calculation means of the position shift amount calculation apparatus which concerns on this Embodiment. It is a flowchart which shows the procedure which concerns on the calculation process of the positional offset amount in the positional offset amount calculation apparatus which concerns on this Embodiment.

DESCRIPTION OF EMBODIMENTS Embodiments for carrying out the present invention will be described with reference to the drawings.
(Image forming means of misregistration amount calculation apparatus according to this embodiment)
The image forming means of the positional deviation amount calculation apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram showing a configuration of a color image forming apparatus including a misregistration amount calculation apparatus 100 to which the present invention is applied. The color image forming apparatus is a so-called electrophotographic image forming apparatus.

  The misregistration amount calculation device 100 is a device for correcting misregistration of the image positions of the respective colors formed in the tandem color image forming apparatus. Accordingly, the image forming unit of the positional deviation amount calculating apparatus 100 and the image forming unit of the tandem color image forming apparatus perform the same processing operation using the same mechanism. The configuration of the image forming means and the processing operation of the image forming means will be described.

  A color image forming apparatus according to this embodiment includes a paper feed tray 1, a paper feed roller 2, a separation roller 3, a recording paper 4, a belt member (hereinafter referred to as a conveyance belt) 5, and image forming units 6BK, 6M, and 6C. , 6Y, driving roller 7, driven roller 8, photosensitive drums 9BK, 9M, 9C, 9Y, chargers 10BK, 10M, 10C, 10Y, exposure unit 11, developing units 12BK, 12M, 12C, 12Y, static eliminator 13BK, 13M, 13C, and 13Y, transfer units 15BK, 15M, 15C, and 15Y, a fixing unit 16, and sensors 17, 18, and 19. Reference numerals 14BK, 14M, 14C, and 14Y denote laser beams that are exposure beams of the respective image colors.

  As shown in FIG. 1, the color image forming apparatus according to the present embodiment includes black as a reference color and magenta, cyan, and yellow as other colors along a conveyor belt 5 that is an endless moving device. The image forming units 6BK, 6M, 6C, and 6Y that form the images of the respective colors are arranged. That is, 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, the transport belt 5 is sequentially transported from the upstream side in the transport direction. A plurality of image forming units 6BK, 6M, 6C, and 6Y are arranged.

  The plurality of image forming units 6BK, 6M, 6C, and 6Y have the same internal configuration except that the color of the toner forming the image is different. Therefore, in the following description, each component of the image forming unit 6BK will be specifically described, and the other image forming units 6M, 6C, and 6Y have the same processing operation as the image forming unit 6BK. , 6C, 6Y will not be described.

  The conveyor belt 5 is an endless belt wound around a driving roller 7 and a driven roller 8 that are rotationally driven. The driving roller 7 is driven to rotate by a driving motor, and the driving motor, the driving roller 7 and the driven roller 8 function as a driving device that moves the conveying belt 5 that is an endless moving device.

  At the time of image formation, the sheets 4 stored in the sheet feeding tray 1 are sent out in order from the uppermost one, and the first image forming unit 6BK is transported by the transport belt 5 that is attracted to and rotated by the transport belt 5 by electrostatic attraction. The black toner image is transferred here.

  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 cleaner, a static eliminator 13BK, and the like. Yes. 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.

  Here, the exposure unit 11 will be described with reference to FIG. FIG. 2 is a view showing the inside of the exposure unit 11. Laser beams 14BK, 14M, 14C, and 14Y that are exposure beams for the respective image colors are emitted from respective laser diodes 21BK, 21M, 21C, and 21Y that are light sources. The irradiated laser beams 14BK, 14M, 14C, and 14Y pass through the optical systems 22BK, 22M, 22C, and 22Y by the reflecting mirror 20, and the optical paths are adjusted, and then to the surfaces of the photosensitive drums 9BK, 9M, 9C, and 9Y. Is scanned. The reflecting mirror 20 is a hexahedral polygon mirror, and can rotate the exposure beam for one line in the main scanning direction per one polygon mirror surface by rotating. Further, the scanning is performed with one polygon mirror for the four laser diodes of the light source.

  The exposure to four different photosensitive drums is simultaneously performed by scanning the laser beam 14BK and 14M and the laser beam 14C and 14Y into two exposure beams for each of the colors and using the opposed reflecting surface of the polygon mirror. It is possible. 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, so that an electrostatic latent image is formed. It is formed. The developing device 12BK visualizes the electrostatic latent image with black toner, thereby forming a black toner image 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 transport belt 5 are in contact with each other. By this transfer, an image of black toner is formed on the paper 4.

  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 superimposed on the black image formed on the paper 4. And is transcribed.

  Further, the sheet 4 is conveyed to the next image forming units 6C and 6Y, and a cyan toner image formed on the photoconductive drum 9C and a yellow toner formed on the photoconductive drum 9Y by the same operation. An image is superimposed and transferred on the paper 4. Thus, a full-color image is formed on the paper 4. The sheet 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.

  Here, in the color image forming apparatus including the misregistration amount calculation apparatus 100 according to the present embodiment, the toner images of the respective colors do not overlap at positions where they should overlap, and misregistration may occur between the colors. . As described above, when a misregistration occurs between the colors, it is necessary to correct the misregistration of the toner images of the respective colors. In this embodiment, the misregistration correction is performed with respect to the black image position. , Cyan, and yellow are performed in the form of matching the image positions. It should be noted that the correction may be made with the image position of the other color as a reference.

(Operational principle of misregistration amount calculation apparatus according to this embodiment)
The operation principle of the positional deviation amount calculation apparatus according to the present embodiment will be described with reference to FIG. The positional deviation amount calculation apparatus 100 includes a first light beam reading unit 110, a second light beam reading unit 120, a measurement unit 130, a second calculation unit 140, an image forming unit 150, a pattern reading unit 160, and a first reading unit. A calculation unit 170, a third calculation unit 180, and a storage unit 190 are included.

  The first light beam reading unit 110 reads the light beam on the scanning start side in the main scanning direction. The first light beam reading unit 110 reads the light beam using a synchronization detection sensor that is arranged outside the image area on the scanning start side and is arranged perpendicular to the main scanning direction.

  The second light beam reading unit 120 reads the light beam on the scanning end side in the main scanning direction. The second light beam reading means 120 is disposed outside the image area on the scanning end side, and uses a synchronous detection sensor disposed so as to form an inclination angle of π / 4 with respect to the main scanning direction. Read.

  Here, the scanning start side synchronization detection sensor may be arranged to form a predetermined inclination angle with respect to the main scanning direction, and the scanning end side synchronization detection sensor may be arranged perpendicular to the main scanning direction.

  The measuring unit 130 measures a scanning time from when the first light beam reading unit 110 reads the light beam until the second light beam reading unit 130 reads the light beam.

  When the measuring unit 130 measures the scanning time over a plurality of times, the second calculating unit 140 calculates the amount of change in the scanning time, and multiplies the amount of change by the scanning speed by the light beam, thereby shifting the position shift. Calculate the amount. However, the positional deviation amount calculated by the second calculation unit 140 includes a positional deviation amount in the main scanning direction (hereinafter referred to as a main deviation amount) and a positional deviation amount in the sub scanning direction (hereinafter referred to as a sub deviation amount). Are mixed.

  In this embodiment, the main scanning direction refers to the direction in which scanning with a light beam is performed, and the sub-scanning direction refers to the conveyance direction of the conveyance body or intermediate transfer belt.

  Here, the principle by which the second calculation unit 140 calculates the positional deviation amount will be described in more detail with reference to FIG. In FIG. 2, the synchronization detection sensors are indicated by 23_T and 23_S, and the synchronization detection folding mirrors are indicated by 22C_D1, 22C_D2, 22C_D3, 22C_D4, 22C_D5, 22C_D6, 22M_D1, and 22M_D2.

  The synchronization detection sensor 23_T is disposed outside the image area on the scanning start side in the main scanning direction, and the synchronization detection sensor 23_S is disposed outside the image area on the scanning end side in the main scanning direction. In addition, the light receiving unit 61_T of the synchronization detection sensor 23_T is perpendicular to the main scanning direction, and the light receiving unit 61_S of the synchronization detection sensor 23_S has an inclination of π / 4 with respect to the main scanning direction.

  The synchronization detection sensor 23_T detects the laser beams 14BK, 14M, and 14C for each scanning of one line, and adjusts the exposure start timing at the time of image formation.

  The laser beam 14C is incident on the synchronization detection sensor 23_T via the mirrors 22C_D1, 22C_D2, and 22C_D3. Here, since the synchronization detection sensors 23_T and 23_S only detect the laser beams 14M and 14C, magenta and cyan can be detected in calculating the positional deviation amount based on the change amount of the scanning time, but yellow. Cannot be detected. Accordingly, since the writing start timing of the laser beam 14Y cannot be adjusted by the synchronization detection sensor, the yellow exposure start timing is made to coincide with the cyan exposure start timing so that the image positions of the respective colors are aligned.

  Here, the reason why the synchronization detection sensor 23_T detects the laser beam 14BK is to support black monochrome printing.

  On the other hand, the synchronization detection sensor 23_S detects the laser beams 14M and 14C for each scanning of one line. After the laser light 14C enters the synchronization detection sensor 23_T, the path changes with the rotation of the polygon mirror 20, and enters the synchronization detection sensor 23_S via the synchronization detection folding mirrors 22C_D4, 22C_D5, and 22C_D6.

  The measuring unit 130 measures the scanning time from when the synchronization detection sensor 23_T detects the laser beams 14M and 14C until the detection by the synchronization detection sensor 23_S.

  The scanning time measured by the measuring unit 130 has a characteristic that it changes depending on the exposure position of the laser beams 14M and 14C in the sub-scanning direction and the magnification of the f-θ lens in the main scanning direction. That is, when the internal temperature of the exposure device 11 rises and the shape and position of the optical system 22 change, the scanning time of the laser beams 14M and 14C between the synchronization detection sensor 23_T and the synchronization detection sensor 23_S changes.

  Therefore, the second calculating unit 140 measures the amount of change in the scanning time measured by the measuring unit 130, thereby determining the amount of positional deviation in the sub-scanning direction caused by the change in the exposure position of the laser light 14, and f-θ. It is possible to detect the amount of positional deviation in the main scanning direction due to the change in the main scanning magnification of the lens.

  The image forming unit 150 generates a misregistration detection pattern for detecting a misregistration amount between an image position of a specific color and an image position other than the specific color in a tandem color image forming apparatus. Create an image on top.

  The pattern reading unit 160 is a sensor that reads the displacement detection pattern formed by the image forming unit 150.

  The first calculation unit 170 calculates the main shift amount and the sub shift amount using the position information of the position shift detection pattern read by the pattern reading unit 160, respectively. Details of the operating principle of the first calculation means 170 will be described later.

  In the misregistration amount calculation device 100, the misregistration correction is performed by the first calculation unit 170, and the positions of the black, magenta, cyan, and yellow images are aligned. Then, the scanning time between the synchronization detection sensors 23_T and 23_S measured by the measurement unit 130 when the first calculation unit 170 executes the positional deviation correction is used as a reference value when the second calculation unit 140 performs processing. .

  The third calculation unit 180 corrects the value calculated by the second calculation unit 140 using the positional shift amount calculated by the first calculation unit 170, and calculates the main shift amount and the sub shift amount, respectively. .

  First, the third calculation means 180 is a ratio of the sub-shift amount calculated by the first calculation means 170 in the sum of the main shift amount and the sub-shift amount calculated by the first calculation means 170 (hereinafter, The first correction coefficient α is calculated. Here, the first correction count α represents the ratio between the sub-shift amount and the main shift amount in the shift amount detected by the second detection means 140 by the synchronization detection.

  Next, the third calculation means 180 is a ratio of the sum of the main deviation amount and the sub deviation amount calculated by the first calculation means 170 and the positional deviation amount calculated by the second calculation means 140 (hereinafter referred to as the first deviation amount). 2) is calculated. Here, the second correction count β is a ratio of the sum of the sub shift amount and the main shift amount detected using the positional shift detection pattern and the sum of the sub shift amount and the main shift amount detected using the synchronization detection signal. Represents.

  Next, the third calculation means 180 calculates the second correction coefficient β a plurality of times, and calculates the rate of change of the second correction coefficient β (hereinafter referred to as the third correction coefficient γ). calculate. Here, the third correction count γ represents a ratio of β in the latest process calculated by the third calculation unit 180 and β in the previous process calculated by the third calculation unit 180.

  Here, misregistration amount calculation apparatus 100 according to the present embodiment detects misregistration amounts using misregistration detection patterns at predetermined time intervals. Then, the misregistration amount calculation device 100 uses correction coefficients α, β, and γ calculated based on the most recent result of the detection process between the misregistration amount detection processes using the misregistration detection pattern. The misregistration amount calculated by the second calculation means 140 is corrected. As described above, although the main deviation and the sub deviation are mixed in the misregistration amount detected by the synchronization detection signal, the misregistration amount calculation device 100 uses the correction coefficients α, β, and γ to obtain the main misalignment and the misregistration. Sub slip can be separated. The separated main shift and sub-shift can be expected to have the same detection accuracy as when the position shift amount is detected using the position shift detection pattern.

  The third calculation unit 180 repeatedly calculates the positional deviation amount in the main scanning direction and the positional deviation amount in the sub-scanning direction within the predetermined time, and the first half of the predetermined time is calculated as the first half. The second half of the phase is called the second phase. Here, the first phase and the second phase are equal to each other (for example, in the case where the positional deviation amount calculation by the positional deviation detection pattern 26 is performed every 30 minutes, the first half is the first phase, The second half 15 minutes may be the second phase), and a predetermined time may be allocated at an appropriate ratio (for example, when the positional deviation amount calculation by the positional deviation detection pattern 26 is performed every 30 minutes, The first 20 minutes may be the first phase, and the latter 10 minutes may be the second phase).

In the first phase, the third calculation unit 180 corrects the positional deviation amount in the sub-scanning direction by multiplying the positional deviation amount calculated by the first calculation unit by the first correction coefficients α and β. To do. Further, the third calculation unit 180 multiplies the positional deviation amount calculated by the first calculation unit by a value obtained by subtracting the first correction coefficient α from 1 and the correction coefficient β to thereby adjust the position in the main scanning direction. Correct the deviation. That means
<First phase>
The amount of positional deviation in the sub-scanning direction = the amount of positional deviation calculated by the second calculating unit 140 × α × β
The amount of misregistration in the main scanning direction = the amount of misregistration calculated by the second calculating means 140 × (1−α) × β
It becomes.

On the other hand, in the second phase, the third calculation unit 180 multiplies the misregistration amount calculated by the first calculation unit by correction coefficients α, β, and γ, thereby obtaining the misregistration amount in the sub-scanning direction. Correct it. Further, the third calculation means 180 multiplies the positional deviation amount calculated by the first calculation means by a value obtained by subtracting the first correction coefficient α from 1, a correction coefficient β, and a correction coefficient γ. Correct the misregistration amount in the direction. That means
<Second phase>
The amount of positional deviation in the sub-scanning direction = the amount of positional deviation calculated by the second calculating means 140 × α × β × γ
A displacement amount in the main scanning direction = a displacement amount calculated by the second calculation means 140 × (1−α) × β × γ
It becomes.

  Here, the misregistration amount calculation device 100 calculates the first correction coefficient α, the second correction coefficient β, and the third correction coefficient γ for each color, and uses each calculated coefficient for the position shift for each color. The amount is calculated.

  The storage unit 190 stores the positional deviation amount in the main scanning direction and the positional deviation amount in the sub-scanning direction calculated by the third calculation unit 180 in the storage device.

(Detection of misalignment amount using misalignment detection pattern)
(1) Configuration of Misalignment Detection Pattern The misalignment detection pattern will be described with reference to FIG. The misregistration detection pattern 26 is composed of four colors of black, magenta, cyan, and yellow. The misregistration detection pattern 26 is a first misregistration detection pattern (26BK_Y1, 26M_Y1, 26C_Y1, 26Y_Y1) that is a linear pattern parallel to the main scanning direction. A set of a total of eight patterns of second misregistration detection patterns (26BK_S1, 26M_S1, 26C_S1, 26Y_S1), which are diagonal lines having an inclination angle of π / 4 with respect to the scanning direction, and the first misregistration detection A total of 8 patterns (26BK_Y2, 26M_Y2, 26C_Y2, 26Y_Y2) and a third misregistration detection pattern (26BK_S2, 26M_S2, 26C_S2, 26Y_S2) which is a diagonal line pattern having an inclination angle of 3π / 4 with respect to the main scanning direction A set of misregistration detection patterns is configured by combining a set of book patterns.

  The set period of the misregistration detection pattern in the carrying direction is 1/3 of the circumference of the photosensitive drums 9BK, 9M, 9C, 9Y and 1/2 of the drive roller 7. Yes. By doing so, three sets of the positional deviation detection patterns 26 are formed over one period of the photosensitive drum 9, and the positional deviation amount is averaged to average the positional deviation amount due to rotation unevenness of the photosensitive drum 9. Can be offset. The same applies to the drive roller 7.

  Further, the positional deviation amount calculation device 100 combines eight patterns of the first positional deviation detection pattern, the second positional deviation detection pattern, or the third positional deviation detection pattern as the positional deviation detection pattern 26. 24 sets are formed in the conveying direction. The length of one set of the positional deviation detection patterns 26 is equal to the circumferential length of the transport belt 5, and the detection error due to uneven thickness of the transport belt 5 can be canceled.

  In addition, of the 24 sets constituting the misregistration detection pattern 26 shown in FIG. 4, the first 12 sets are only a set including the second misregistration detection pattern, and the latter 12 sets are the third misregistration detection. It is only a set including a pattern for use. The first 12 sets and the last 12 sets have the same period in the conveying direction, and the first 12 sets and the latter 12 sets have the same period in the conveying direction as four periods of the photosensitive drum 9 and six periods of the driving roller 7. By continuously forming a set including the second misalignment detection pattern or the third misalignment detection pattern in one cycle or more of the photosensitive drum 9 and the driving roller 7, the second misalignment is generated. Rotation unevenness can be offset by each set including the detection pattern or the third misregistration detection pattern.

  Here, in the misregistration amount calculation apparatus 100 according to the present embodiment, the misregistration detection pattern, which is a black, magenta, cyan, and yellow toner image, is the same as when a color image is formed on the paper 4. It is formed on the conveyor belt 5 by a process. In addition, each of the image forming units 6BK, 6M, 6C, and 6Y is the image forming unit 150 in the present embodiment.

  In the present embodiment, the conveying belt 5 may be an intermediate transfer belt. In this case, the image forming unit 150 forms an image of a displacement detection pattern on the intermediate transfer belt. Become.

(2) Outline of Pattern Reading Unit The configuration and operation of the sensor that is the pattern reading unit of the positional deviation amount calculating apparatus 100 according to the present embodiment will be described with reference to FIGS. FIG. 5 shows an enlarged view of the sensor 17 (18, 19), and FIG. 6 shows the sensor 17, 18, 19 and its peripheral portion.

  The sensor 17 (18, 19) includes a light emitting unit 24 and a light receiving unit 25. Irradiated light is emitted from the light emitting unit 24 onto the conveyor belt 5, and the reflected light is received by the light receiving unit 25, and the sensor 17 (18, 19) detects the positional deviation detection pattern 26.

  As shown in FIG. 6, the sensors 17, 18, and 19 are provided on the downstream side of the image forming unit 6 </ b> Y so as to face the conveyance belt 5, and are the same substrate along the main scanning direction of the paper 4. Supported on top.

(3) Detection of Misregistration Detection Pattern The detection principle of the misregistration detection pattern according to this embodiment will be described with reference to FIG. In FIG. 7, the detection result of the reflected light received by the light receiving unit 25 is 31, the detection intensity of the diffuse reflected light received by the light receiving unit 25 is 33, and the detection intensity of the regular reflected light received by the light receiving unit 25 is 33, respectively. Show. Here, the detection result 31 of the reflected light received by the light receiving unit 25 is obtained by adding the detection intensity 32 of the diffuse reflection light received by the light receiving unit 25 and the detection intensity 33 of the regular reflection light received by the light receiving unit 25. It will be a thing.

  In addition, the vertical axis 34 of the graph in FIG. 7 indicates the received light intensity of the light receiving unit 25, and the horizontal axis 35 indicates time.

  Here, the specularly reflected light is the reflected light reflected to the opposite side of the incident direction at the same angle as the incident angle of the irradiated light (that is, the reflected light having a reflection angle of π-θ where the incident angle is θ). In other words, diffuse reflected light refers to reflected light other than regular reflected light.

  Then, the sensors 17 (18, 19) have positions 37BK_1, 37BK_2, 37M_1 (37C_1, 37Y_1), 37M_2 (37C_2, 37Y_2) where the predetermined threshold value 36 and the detection result 31 of the reflected light received by the light receiving unit 25 intersect. ), It is determined that the edge of the misregistration detection pattern 26 has been detected. In the present embodiment, the midpoint of two edges detected from each misregistration detection pattern 26 (for example, the midpoint between 37BK_1 and 37BK_2) is determined as the image position. The edge 37BK_1, 37BK_2, 37M_1 (37C_1, 37Y_1), 37M_2 (37C_2, 37Y_2) detected from the pattern 26 may be determined as the image position.

  Further, in order to improve the S / N ratio (ratio between the intensity of the signal to be detected and the intensity of the noise) at the time of detecting the color misregistration detection pattern, the line width 29 in the transport direction of the misregistration detection pattern is The light receiving area 25 of the light receiving unit 25 is substantially the same as the light receiving area 27 (spot diameter of the photodiode). Furthermore, if the irradiation light is simultaneously applied to the two misregistration detection patterns, the diffused light is simultaneously reflected from the two patterns, so that one pattern cannot be detected normally. The interval 30 between the misalignment detection patterns is made larger than the spot diameter 28 of the irradiation light.

(4) Calculation of misregistration amount The misregistration amount calculation using the misregistration detection pattern will be described with reference to FIG. In FIG. 8, as an example, the misregistration amount is calculated from the black and magenta misregistration detection pattern 26, but the magenta misregistration detection pattern is replaced with cyan and yellow misregistration detection patterns. The misregistration amounts for cyan and yellow images based on the image can also be calculated in the same manner as for magenta.

  In FIG. 8, the sensor 17 (18, 19), the first misregistration detection patterns 26BK_Y1, 26BK_Y2 related to black, the first misregistration detection patterns 26M_Y1, 26M_Y2 related to magenta, and the second positions related to black. A displacement detection pattern 26BK_S1, a second displacement detection pattern 26M_S1 related to magenta, a third displacement detection pattern 26BK_S2 related to black, and a third displacement detection pattern 26M_S2 related to magenta are illustrated.

  In FIG. 8, 42BK_1 represents the interval between the first misregistration detection pattern 26BK_Y1 related to black and the second misregistration detection pattern 26BK_S1 related to black, and 42BK_2 represents the first misregistration detection related to black. 42M_1 represents the interval between the first pattern 26M_Y1 for magenta and the second position detection pattern 26M_S1 for magenta. The interval between the pattern 26BK_Y2 for black and the third position detection pattern 26BK_S2 for black is 42M_1. 42M_2 indicates the interval between the first misregistration detection pattern 26M_Y2 related to magenta and the third misregistration detection pattern 26M_S2 related to magenta.

  Here, the positions of the respective misregistration detection patterns necessary for calculating the interval between the misregistration detection patterns are the first half edge and the second half edge of each detection pattern detected by the sensor 17. Let it be a point.

Then, the positional deviation amounts 43D_1 and 43D_2 in the main scanning direction calculated from the respective sets of positional deviation detection patterns are the second positional deviation detection patterns 26M_S1 related to magenta and the third positional deviation detection related to magenta. Considering that the angle of the pattern 26M_S2 with respect to the main scanning direction is π / 4 and 3π / 4, respectively.
43D_1 = 42BK_1-42M_1,
43D_2 = 42M_2-42BK_2
It can be expressed as.

A displacement 43D in the main scanning direction of the magenta image with respect to the black image is represented by an average value of 43D_1 and 43D_2.
43D = (43D_1 + 43D_2) / 2
Further, the positional deviation amount 44D in the sub-scanning direction of the magenta image with respect to the black image is a detected value 44D_1 of the distance between the first positional deviation detection pattern 26BK_Y1 related to black and the first positional deviation detection pattern 26M_Y1 related to magenta. (44D_2) and the distance between the desired first displacement detection pattern 26BK_Y1 related to black (which should be imaged by the displacement calculation device 100) and the first displacement detection pattern 26M_Y1 related to magenta Is calculated by calculating the difference between

(5) Configuration and Operation of First Calculation Unit of Misregistration Amount Calculation Device Next, the configuration and operation of the first calculation unit of the misregistration amount calculation device according to the present embodiment will be described using FIG. To do. The first calculation means 170 according to the present embodiment includes an amplifier 50, a filter 51, an A / D conversion unit (Analog / Digital conversion unit) 52, a sampling control unit 53, a FIFO memory (First In First Out memory) 54, An I / O port (Input / Output port) 55, a data bus 56, a CPU (Central Processing Unit) 57, a RAM (Random Access Memory) 58, a ROM (Read-Only Memory) 59, and a light emission amount control unit 60 are configured. .

  The reflected light signal received by the light receiving unit 25 is amplified by the amplifier 50. Then, only the signal component for detecting the misregistration detection pattern 26 is extracted from the amplified signal using the filter 51. Next, the reflected light signal is converted from analog data to digital data by the A / D converter 52. Sampling of data accompanying this A / D conversion is controlled by the sampling control unit 53, and the sampled signal is stored in the FIFO memory 54.

  After the detection of all the misregistration detection patterns 26 consisting of four colors of black, magenta, cyan, and yellow is completed, the data stored in the FIFO memory 54 is transferred via the I / O port 55 and the data bus 56. It is loaded into the RAM 58. Then, the CPU 57 performs arithmetic processing for calculating the above-described positional deviation amount on the data loaded in the RAM 58.

  The ROM 59 stores various programs for controlling the positional deviation amount calculation apparatus according to the present embodiment, including the above-described program for calculating the positional deviation amount. Further, the CPU 57 monitors the detection signal from the light receiving unit 25 at an appropriate timing, and the light emission amount control unit 60 emits light so that it can be reliably detected even if the conveyance belt 5 and the light emitting unit 24 are deteriorated. The amount is controlled so that the level of the received light signal from the light receiving unit 25 is always constant. Further, the CPU 57 and the ROM 59 also function as a control unit that controls the operation of the entire misregistration amount calculation apparatus 100 according to the present embodiment.

(Processing procedure of misregistration amount calculation apparatus according to this embodiment)
The misregistration amount calculation process in the misregistration amount calculation apparatus according to the present embodiment will be described with reference to FIG. In S1, the processing of the misregistration amount calculation apparatus 100 according to the present embodiment is started.

  When the correction coefficients α, β, and γ are stored in the storage device in S2 (Yes in S2), the specified time that is the execution period of the positional deviation amount detection processing using the synchronization detection sensors 23_T and 23_S in S10 Wait (for example, 1 minute).

  When the correction coefficients α, β, and γ are not stored in the storage device in S2 (No in S2), the amount of misalignment is calculated using the misalignment detection pattern 26 in S3.

  First, the image forming unit 150 forms an image of the misregistration detection pattern 26 shown in FIG. 4 on the carrier. Next, the pattern reading unit 170 (sensors 17, 18, 19) reads the position deviation detection pattern 26, and the position information of the position deviation detection pattern 26 is recorded in the RAM 58.

  Next, the first calculation means 170 uses the positional information of the first positional deviation detection pattern and the second positional deviation detection pattern (the first 12 sets in FIG. 4) stored in the RAM 58 to obtain magenta. , Cyan, and yellow are calculated for the amount of displacement 43D_1. In the case of magenta, 43D_1 in FIG. 8 is calculated for each set for the black and magenta misregistration detection patterns included in the first 12 sets in FIG. 4, and the average value of these is calculated. Similar processing is performed for cyan and yellow.

  Further, the first calculation means 170 uses the position information of the first position deviation detection pattern and the third position deviation detection pattern (the latter half 12 sets in FIG. 4) stored in the RAM 58 to obtain magenta, A positional deviation amount 43D_2 is calculated for each color of cyan and yellow. In the case of magenta, 43D_2 in FIG. 8 is calculated for each set with respect to the black and magenta misregistration detection patterns included in the latter 12 sets in FIG. 4, and the average value thereof is calculated. Similar processing is performed for cyan and yellow.

  Then, an average value 43D of 43D_1 and 43D_2 is calculated for each color of magenta, cyan, and yellow. This 43D is the amount of positional deviation in the main scanning direction calculated by the first calculation means 170.

  In parallel, the first calculation unit 170 calculates a positional deviation amount 44D in the transport direction of each of the magenta, cyan, and yellow images with respect to the black image. In calculating the misregistration amount 44D, 44D_1 and 44D_2 in FIG. 8 are calculated for the detection results of all misregistration detection patterns for each color of magenta, cyan, and yellow, and the average value is calculated. . This 44D is the amount of positional deviation in the sub-scanning direction calculated by the first calculation means 170.

  Furthermore, using the misregistration amount detected in S3, the misregistration of each color image position in the main scanning direction and the sub scanning direction is corrected.

  Here, in detecting the amount of displacement using the following correction coefficients α, β, and γ, each process is executed for each color.

  In S4, the synchronization detection sensor 23_T as the first light beam reading means 110 and the synchronization detection sensor 23_S as the second light beam reading means 120 detect the laser light 14, and then the measurement means 130 detects the synchronization. The scanning time of the laser beam 14 detected by the sensor 23_T and the synchronization detection sensor 23_S is measured. Then, the second calculation means 140 sets the scanning time measured by the measurement means 130 in S4 as a processing reference value.

  In S5, a predetermined time (for example, 5 minutes) is waited until the position shift amount is detected using the next position shift detection pattern 26.

  In S6, the same amount of misalignment is detected using the misalignment detection pattern 26 as in the process executed in S3.

  In S7, similarly to the process executed in S4, the scanning time of the laser beam 14 is measured using the synchronization detection sensor 23_T and the synchronization detection sensor 23_S. Then, the second calculation unit 140 calculates the amount of change between the scanning time set as the reference value in S4 and the scanning time measured in S7.

  Further, at this time, the measuring unit 130 measures the scanning time of the laser light 14 detected by the synchronization detection sensor 23_T and the synchronization detection sensor 23_S, and the second calculation unit 140 sets the time as a new reference value. The previous reference value is deleted.

  In S8, the first calculation unit 190 first calculates the amount of displacement by multiplying the amount of change in scanning time calculated in S7 by the scanning speed of the laser light 14. The positional deviation amount is calculated in a state where the positional deviation amount in the main scanning direction and the positional deviation amount in the sub-scanning direction are mixed.

Next, the second calculation means 190 calculates correction coefficients α, β, and γ. At this time, the first correction coefficient α is calculated by using the most recent calculation result of the first calculation means 170 in the sum of the positional deviation amount 44D in the main scanning direction and the positional deviation amount 43D in the sub scanning direction. The ratio (= 43D / (43D + 44D)) occupied by the displacement amount 43D in the scanning direction is obtained and calculated.

In addition, the second correction coefficient β is calculated by using the most recent calculation result of the second calculation unit 140 and the first calculation unit 170 and the positional deviation amount 44D in the main scanning direction calculated by the first calculation unit 170. A ratio between the sum of the positional deviation amount 43D in the sub-scanning direction and the positional deviation amount calculated by the second calculation unit 140 is obtained and calculated.

  And the 3rd calculation means 180 calculates | requires the change rate of (beta) calculated over multiple times, and calculates the 3rd correction coefficient (gamma). However, if the second correction coefficient β is calculated for the first time, the third correction coefficient γ cannot be calculated. In this case, the third calculation means 180 uses the initial value as the third correction coefficient γ. Set 1 ".

  The correction coefficients α, β, γ calculated by the third calculation unit 180 in S9 are stored in the RAM 58.

  When the standby state for the specified time ends in S10, the laser beam 14 is read by the synchronization detection sensor 23_T and the synchronization detection sensor 23_S in S11, and the measuring unit 130 measures the scanning time.

  Then, the second calculation means 140 calculates the amount of change between the scanning time set as the reference value in S7 and the scanning time measured in S11.

  In S <b> 12, the second calculation unit 140 multiplies the scanning time variation calculated in S <b> 11 by the scanning speed of the light beam 14 to calculate the positional deviation amount. Further, the third calculation unit 180 corrects the misregistration amount calculated by the second calculation unit 140 using the correction coefficients α, β, and γ stored in the RAM 58, and the misregistration amount and the sub scan amount in the main scanning direction are corrected. A positional deviation amount in the scanning direction is calculated.

  Here, the misregistration amount calculation apparatus 100 according to the present embodiment detects the misregistration amount using the misregistration detection pattern 26 every predetermined time (for example, every 30 minutes), and the misregistration. Between the detection of the misregistration amount using the detection pattern 26, the misregistration amount calculated by the second calculating means 140 using the coefficients α, β, γ is used as the misregistration amount in the main scanning direction. And the amount of positional deviation in the sub-scanning direction is corrected.

  Each time the positional deviation amount calculation / correction using the positional deviation detection pattern 26 is performed, the measuring unit 130 scans the laser light 14 detected by the synchronization detection sensor 23_T and the synchronization detection sensor 23_S at this time. The second calculation means 140 sets the scanning time to a new reference value.

  Here, the third calculation unit 180 repeatedly calculates the positional deviation amount in the main scanning direction and the positional deviation amount in the sub-scanning direction within the predetermined time, and the first half of the predetermined time is calculated in the first half. The latter half of the phase is called the second phase.

In the first phase, the third calculation unit 180 multiplies the positional deviation amount calculated by the second calculation unit 140 by the first coefficient α and multiplies it by the second coefficient β. A displacement amount in the scanning direction is calculated. Further, the third calculation unit 180 multiplies the positional deviation amount calculated by the first calculation unit by a value obtained by subtracting the first coefficient α from 1 and multiplies it by the second coefficient β. The amount of displacement in the direction is calculated. That means
The amount of positional deviation in the sub-scanning direction = the amount of positional deviation calculated by the second calculating unit 140 × α × β
The amount of misregistration in the main scanning direction = the amount of misregistration calculated by the second calculating means 140 × (1−α) × β
The amount of displacement in each direction is calculated according to the equation

On the other hand, in the second phase, the third calculation unit 180 multiplies the positional deviation amount in the sub-scanning direction by the first coefficient α and the positional deviation amount calculated by the first calculation unit. It is calculated by multiplying the coefficient β of 2 and further multiplying it by the third coefficient γ. The third calculation unit 180 multiplies the positional deviation amount in the main scanning direction by the value obtained by subtracting the first coefficient α from 1 to the positional deviation amount calculated by the first calculation unit. It is calculated by multiplying by the coefficient β and further multiplying it by the third coefficient γ. That means
The amount of positional deviation in the sub-scanning direction = the amount of positional deviation calculated by the second calculating means 140 × α × β × γ
A displacement amount in the main scanning direction = a displacement amount calculated by the second calculation means 140 × (1−α) × β × γ
The amount of displacement in each direction is calculated according to the equation

  Then, the storage unit 190 stores the positional deviation amount in the main scanning direction and the positional deviation amount in the sub-scanning direction calculated by the third calculation unit 180.

  If a predetermined time (for example, 30 minutes) has elapsed since the detection processing of the positional deviation amount by the previous positional deviation detection pattern 26 in S13 (Yes in S13), the positional deviation detection pattern 26 is used in S6. The detected misalignment amount detection process is executed, and the correction coefficients α, β, and γ are rewritten with newly calculated values.

  In S13, when the specified time has not elapsed since the previous position error detection process by the position error detection pattern 26 (No in S13), after waiting for the specified time in S10, the synchronization detection sensors 23_T and 23_S are used. Detection processing for the amount of misregistration is executed.

  When the process of the positional deviation amount calculation apparatus 100 ends in S14 (Yes in S14), the process of the positional deviation amount calculation apparatus 100 according to the present embodiment ends in S15. If the processing of the positional deviation amount calculation device 100 is not completed in S14 (No in S14), after waiting for a specified time in S10, a positional deviation amount detection process using the synchronization detection sensors 23_T and 23_S is executed.

  As described above, in the present invention, the interval for performing the misregistration amount detection process using the misregistration detection pattern 26 is lengthened, and the position without affecting the function provided by the image forming apparatus is between these intervals. A shift amount calculation process can be executed. Therefore, it is possible to calculate the positional deviation amount without interrupting the image forming process of the image forming apparatus.

  Further, since the correction by the synchronization detection signal is executed using the result of the positional deviation detection pattern, it is necessary to adopt a special configuration (such as the configuration disclosed in Japanese Patent Application Laid-Open No. 2005-156992) for the positional deviation detection. Therefore, it is possible to detect misalignment at a low cost.

  Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications are possible within the scope of the gist of the present invention described in the claims.・ Change is possible.

100 misregistration amount calculation device 110 first light beam reading means 120 second light beam reading means 130 measuring means 140 second calculation means 150 image forming means 160 pattern reading means 170 first calculation means 180 third calculation Means 190 Storage means 14BK, 14M, 14C, 14Y Light beam 20 Polygon mirrors 21BK, 21M, 21C, 21Y Laser diode 23_T Synchronization detection sensor 23_S Synchronization detection sensor

Claims (12)

An electrophotographic color image forming apparatus has a belt member that is a print medium conveyance belt or an intermediate transfer belt, and forms an image on an image carrier by scanning a light beam corresponding to an image signal, and the image carrier A misregistration amount calculation device for calculating a misregistration amount of an image position on a body,
In order to detect the positional deviation amount, a first positional deviation detection pattern formed on the belt member is read, and a positional deviation amount in the main scanning direction and the sub-scanning direction is calculated based on the reading result. A calculation means;
Measurement of the scanning time during which the light beam is scanned from the scanning start side to the scanning end side is performed at least twice at predetermined intervals , and a positional deviation amount based on the scanning time is calculated based on the change amount of the scanning time . Two calculating means;
Using the calculation result by the first calculation means, the positional deviation amount based on the scanning time calculated by the second calculation means and the positional deviation amount in the main scanning direction and the running direction of the belt member. A third calculating means for calculating and storing a correction coefficient for calculating the amount of positional deviation, and
Furthermore, the third calculation means calculates a positional shift amount of the image position by using a stored correction coefficient .   The second calculation means reads the light beam using a sensor arranged perpendicular to the main scanning direction on the scanning start side, and then forms a predetermined inclination angle with respect to the main scanning direction on the scanning end side. The positional deviation amount calculation apparatus according to claim 1, wherein a time until the light beam is read is measured using a sensor disposed.   The misregistration amount calculation device according to claim 1, wherein the second calculation unit calculates the mixed misregistration amount based on a change amount of the measurement result when the measurement is performed a plurality of times. . The first calculation means calculates a positional deviation amount in the main scanning direction and a positional deviation amount in the running direction of the belt member based on the result of reading the positional deviation detection pattern;
The third calculation means includes a ratio between a sum of the two positional deviation amounts calculated by the first calculation means and a positional deviation amount related to the running direction of the belt member calculated by the first calculation means. The second calculation means calculates the ratio between the sum of the two misregistration amounts calculated by the first calculation means and the mixed misregistration amount calculated by the second calculation means. 4. The positional deviation amount in the main scanning direction and the positional deviation amount in the running direction of the belt member are calculated from the mixed positional deviation amount. 5. Position deviation amount calculation device.   The positional deviation amount calculation apparatus according to claim 2, wherein the predetermined inclination angle is π / 4. An image forming apparatus including the misregistration amount calculation device according to claim 1,
The positional deviation of the image position is corrected using the positional deviation amount in the main scanning direction and the positional deviation amount in the running direction of the belt member calculated by the third calculation unit. Image forming apparatus. An electrophotographic color image forming apparatus has a belt member that is a print medium conveyance belt or an intermediate transfer belt, and forms an image on an image carrier by scanning a light beam corresponding to an image signal, and the image carrier A positional deviation amount calculation method of a positional deviation amount calculation device for calculating a positional deviation amount of an image position on a body,
The first calculating means reads the position deviation detection pattern formed on the belt member in order to detect the position deviation amount, and based on the read result, the position deviation in the main scanning direction and the sub scanning direction. Calculating a quantity;
The second calculating means measures the scanning time during which the light beam is scanned from the scanning start side to the scanning end side at least twice at predetermined intervals , and based on the amount of change in the scanning time, based on the scanning time Calculating a displacement amount;
The third calculation means uses the calculation result by the first calculation means to calculate the positional deviation amount in the main scanning direction from the positional deviation amount based on the scanning time calculated by the second calculation means, and Calculating and storing a correction coefficient for calculating a positional deviation amount related to the running direction of the belt member ; and
Further, the third calculation means includes a step of calculating a positional shift amount of the image position using a stored correction coefficient .   In the second calculation means, the light beam is read using a sensor arranged perpendicular to the main scanning direction on the scanning start side, and then a predetermined inclination angle is set with respect to the main scanning direction on the scanning end side. 8. The positional deviation amount calculation method according to claim 7, wherein a time until the light beam is read using a sensor arranged and measured is measured.   The misregistration amount calculation according to claim 7 or 8, wherein the second calculation means calculates the mixed misregistration amount based on a change amount of the measurement result when the measurement is performed a plurality of times. Method. In the first calculation means, based on the result of reading the misregistration detection pattern, the misregistration amount in the main scanning direction and the misregistration amount in the running direction of the belt member are calculated.
In the third calculation means, a ratio between the sum of the two positional deviation amounts calculated by the first calculation means and the positional deviation amount in the running direction of the belt member calculated by the first calculation means. And the ratio of the sum of the two misregistration amounts calculated by the first calculation means and the mixed misregistration amount calculated by the second calculation means, and calculated by the second calculation means. 10. The positional deviation amount in the main scanning direction and the positional deviation amount in the running direction of the belt member are calculated from the mixed positional deviation amounts. Misregistration amount calculation method.   11. The positional deviation amount calculation method according to claim 8, wherein the predetermined inclination angle is π / 4.   A misregistration amount calculation program for causing a computer to execute the misregistration amount calculation method according to any one of claims 7 to 11.

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