Image forming apparatus and image position adjustment method

Abstract

To provide an image forming apparatus that can perform color matching control with higher accuracy.SOLUTION: An image forming apparatus of an embodiment has an image forming unit, a sensor, and a control unit. The image forming unit forms a pattern composed of a plurality of straight lines on an image carrier. The sensor detects the plurality of straight lines composing the pattern formed on the image carrier. The control unit compares an added value of a first value between a first straight line and a second straight line in the plurality of straight lines detected by the sensor and a second value between the second straight line and a third straight line in the plurality of straight lines, with a threshold, and determines, according to a result of comparison, whether to use a measured value obtained from the pattern for correction of color matching control.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] An embodiment of the present invention relates to an image forming apparatus and an image position adjusting method. [Background technology]

[0002] In the image forming apparatus, color matching is controlled by reading, with a sensor, a detection pattern formed on a transfer belt and consisting of straight lines at different angles. However, in this method, if there is a large deviation in the correction values ​​used in the color matching control, the accuracy of the color matching control may decrease. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-107842 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide an image forming apparatus capable of controlling color matching with higher accuracy. [Means for solving the problem]

[0005] The image forming apparatus of the embodiment has an image forming unit, a sensor, and a control unit. The image forming unit forms a pattern composed of a plurality of straight lines on an image carrier. The sensor detects the plurality of straight lines constituting the pattern formed on the image carrier. The control unit compares a sum of a first value between a first straight line and a second straight line among the plurality of straight lines detected by the sensor and a second value between the second straight line and a third straight line among the plurality of straight lines with a threshold value, and determines whether or not to use a measurement value obtained from the pattern for correction of color matching control according to a comparison result. The control unit determines whether or not to use the sum. A plurality of sum values ​​are obtained by performing the calculation ofand performing a comparison between the threshold and the measured value a plurality of times to obtain a plurality of measured values, The correction value is calculated by finding the statistical value of the remaining measurement values, excluding the measurement values ​​obtained from the patterns whose added values ​​are outside the range. [Brief description of the drawings]

[0006] [Figure 1] 1 is an external view showing an example of the overall configuration of an image forming apparatus according to an embodiment; [Diagram 2] FIG. 4 is a view showing an example of a correction pattern in the embodiment. [Diagram 3] 11A and 11B are diagrams illustrating an example of correction patterns for each color formed on a transfer belt in an embodiment in which no color misregistration occurs. [Figure 4] 11A and 11B are diagrams illustrating an example of correction patterns for each color formed on a transfer belt in an embodiment when color misregistration occurs. [Diagram 5] 6A and 6B are diagrams for explaining correction patterns in which positional deviation occurs in the embodiment. [Figure 6] 6A and 6B are diagrams for explaining correction patterns in which positional deviation occurs in the embodiment. [Figure 7] FIG. 2 is a block diagram showing a hardware configuration of the image forming apparatus according to the embodiment. [Figure 8] 4 is a flowchart showing the flow of processing performed by the image forming apparatus according to the embodiment. [Figure 9] FIG. 11 is a diagram showing an example of another correction pattern. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, an image forming apparatus and an image position adjusting method according to an embodiment will be described with reference to the drawings. FIG. 1 is an external view showing an example of the overall configuration of an image forming apparatus 1 according to an embodiment. The image forming apparatus 1 according to the embodiment is a multi-function peripheral (MFP). The image forming apparatus 1 executes printing by image formation processing and image fixing processing. The image formation processing is processing for forming an image on a sheet. The image fixing processing is processing for fixing the image formed on the sheet. The sheet is, for example, paper on which characters, images, etc. are formed. The sheet may be any object as long as the image forming apparatus 1 is capable of forming an image thereon.

[0008] The image forming apparatus 1 includes an image reading section 10, a control panel 20, an image forming section 30, a sheet storage section 40, a fixing unit 50, conveying rollers 611 and 612, paper discharge rollers 621 and 622, and a control device . The image reading unit 10 reads the image of the document to be read as light and dark. For example, the image reading unit 10 reads the image printed on the document to be read that is set on a document reading table. The image reading unit 10 records the read image information. The recorded image information may be transmitted to another information processing device via a network. The recorded image information may be formed into an image on a sheet by the image forming unit 30.

[0009] The control panel 20 includes a display unit and an operation unit. The display unit is a display device such as a liquid crystal display or an organic EL (Electro Luminescence) display. The display unit displays various information related to the image forming apparatus 1 according to the control of the control device 70. The operation unit includes a plurality of buttons and the like. The operation unit receives operations by the user. For example, the operation unit receives an instruction to execute image position adjustment. The operation unit outputs a signal according to the operation performed by the user to the control device 70. The display unit and the operation unit may be configured as an integrated touch panel.

[0010] The image forming unit 30 executes an image forming process. Specifically, the image forming unit 30 forms an image on a sheet based on image information generated by the image reading unit 10 or image information received via a communication path. For example, the image forming unit 30 forms a toner image on a sheet using toner. The image forming unit 30 in this embodiment forms a correction pattern for each color on the transfer belt 31 (image carrier) in order to perform color matching control for multiple colors. Here, the color matching control is a control in which a correction pattern for each color is formed on the transfer belt 31 to correct positional deviation and magnification for each color. The image forming unit 30 may form the correction pattern on a sheet (image carrier) or on a photosensitive drum (image carrier). The correction pattern is composed of multiple straight lines (for example, three straight lines). More specifically, in the correction pattern, the first straight line and the third straight line have the same angle, and the angle of the second straight line is different from the angles of the first straight line and the third straight line. Furthermore, the correction pattern is a pattern that is arranged so that the center point of the second straight line is point-symmetric with respect to the pattern.

[0011] Image forming unit 30 includes a transfer belt 31, an exposure unit 32, a plurality of developing units 33 (developing units 331, 332, 333, and 334), a plurality of photosensitive drums 34 (photosensitive drums 341, 342, 343, and 344), a transfer unit 35, a plurality of primary transfer rollers 36 (36-1 to 36-4), and a plurality of sensors 37. The transfer belt 31 is an endless intermediate transfer body. The transfer belt 31 rotates in the direction indicated by the arrow (counterclockwise) by the rotation of the rollers.

[0012] The exposure unit 32 is provided at a position facing the photoconductor drum 34 between the developer 33 and the charger (not shown). The exposure unit 32 irradiates the surfaces (photoconductor layers) of the photoconductor drums 341, 342, 343, and 344 with laser light based on image information. The direction in which the laser light scans the photoconductor drums is the main scanning direction, and the direction perpendicular to the main scanning direction is the sub-scanning direction. For example, in this embodiment, the main scanning direction coincides with the axial direction of the photoconductor drum, and the sub-scanning direction coincides with the rotation direction of the transfer belt.

[0013] By the irradiation of the laser light, the electric charge on the surface (photoconductor layer) of each of the photoconductor drums 341, 342, 343, and 344 disappears. As a result, a static electricity pattern is formed on the surface of the photoconductor drums 341, 342, 343, and 344 at the position where the laser light was irradiated. That is, by the irradiation of the laser light by the exposure unit 32, an electrostatic latent image is formed on the surface of the photoconductor drums 341, 342, 343, and 344. The exposure unit 32 may use LED (Light Emitting Diode) light instead of the laser light. The exposure unit 32 is controlled to emit light based on image information under the control of the control device 70.

[0014] Developing units 331, 332, 333, and 334 supply toner to photoconductor drums 341, 342, 343, and 344. For example, developing unit 331 develops the electrostatic latent image on the surface of photoconductor drum 341 with yellow (Y). Developing unit 332 develops the electrostatic latent image on the surface of photoconductor drum 342 with magenta (M). Developing unit 333 develops the electrostatic latent image on the surface of photoconductor drum 343 with cyan (C). Developing unit 334 develops the electrostatic latent image on the surface of photoconductor drum 344 with black (K) toner.

[0015] The developing devices 331, 332, 333, and 334 form toner images as visible images on the photosensitive drums 341, 342, 343, and 344. The toner images formed on the photosensitive drums 341, 342, 343, and 344 are transferred (primary transfer) onto the transfer belt 31 by the primary transfer rollers 36-1 to 36-4. The primary transfer roller 36-1 is provided at a position facing the photosensitive drum 341 across the transfer belt 31. The primary transfer roller 36-2 is provided at a position facing the photosensitive drum 342 across the transfer belt 31. The primary transfer roller 36-3 is provided at a position facing the photosensitive drum 343 across the transfer belt 31. The primary transfer roller 36-4 is provided at a position facing the photosensitive drum 344 across the transfer belt 31.

[0016] The transfer unit 35 has a support roller 35a and a secondary transfer roller 35b. The transfer unit 35 transfers the toner image on the transfer belt 31 to the sheet 41 at a secondary transfer position U. The secondary transfer position U is a position where the support roller 35a and the secondary transfer roller 35b face each other with the transfer belt 31 in between. The transfer unit 35 applies a transfer bias to the transfer belt 31 that is controlled by a transfer current. The transfer unit 35 transfers the toner image on the transfer belt 31 to the sheet 41 by the transfer bias. The transfer current is controlled by a control device 70.

[0017] The sensor 37 detects the correction pattern formed on the transfer belt 31 for each color (Y, M, C, K). The sensor 37 is provided at two locations (front position and rear position) or three locations (front position, rear position, and center between the front and rear positions) in the main scanning direction. The sensor 37 transmits the detection result of the correction pattern to the control device 70.

[0018] The sheet storage unit 40 includes one or more paper feed cassettes. The paper feed cassette stores sheets 41 of a predetermined size and a predetermined type. The paper feed cassette includes a pickup roller. The pickup roller picks up sheets 41 one by one from the paper feed cassette. The pickup roller supplies the picked-up sheets 41 to the conveying unit 80.

[0019] The fixing device 50 performs an image fixing process. Specifically, the fixing device 50 fixes an image (for example, a toner image) formed on the sheet 41 to the sheet 41 by applying heat and pressure to the sheet 41. The fixing device 50 includes a heat source 51, a heat roller 52, and a pressure roller 53. The heat source 51 is a heater lamp having a halogen lamp or an induction heating (IH) type heater, or the like. The heat source 51 is turned on or off depending on whether or not electricity is applied from the control device 70. The heat roller 52 is warmed by heat generated by the heat source 51 being applied with electricity. The heat roller 52 applies heat to the sheet 41. The pressure roller 53 is disposed opposite the heat roller 52. The pressure roller 53 presses the sheet 41 against the heat roller 52.

[0020] The transport rollers 611 and 612 supply the sheet 41 fed from the paper feed cassette to the image forming unit 30. The transport rollers 611 and 612 are disposed at positions facing each other. The paper discharge rollers 621 and 622 discharge the sheet 41, on which the image has been formed by the fixing unit 50, to a discharge section. The paper discharge rollers 621 and 622 are disposed at positions facing each other.

[0021] The control device 70 controls each functional unit of the image forming apparatus 1 . The conveying unit 80 conveys the sheet 41. The conveying unit 80 includes a conveying path and a plurality of rollers (not shown). The conveying path is a path along which the sheet 41 is conveyed. The rollers convey the sheet 41 by rotating under the control of the control device 70.

[0022] FIG. 2 is a diagram showing an example of a correction pattern 100 in the embodiment. As shown in FIG. 2, the correction pattern 100 is composed of a first straight line 101, a second straight line 102, and a third straight line 103. In the correction pattern 100 shown in FIG. 2, the first straight line 101 and the third straight line 103 are parallel to the main scanning direction. The second straight line 102 constituting the correction pattern 100 is a straight line at an angle different from the first straight line 101 and the third straight line 103. Furthermore, the center point 104 of the second straight line 102 is arranged so that the arrangement of the three straight lines is point symmetric. The distance L1 from the first straight line 101 to the second straight line 102 is the same as the distance L2 from the second straight line 102 to the third straight line.

[0023] Here, distance L1 is the distance from the position of center line 111 of first straight line 101 to the position of center line 112 of second straight line 102 on detection line 110. Distance L2 is the distance from the position of center line 112 of second straight line 102 to the position of center line 113 of third straight line 103 on detection line 110. In this case, the distance from the position of center line 111 of first straight line 101 to the position of center line 113 of third straight line 103 on detection line 110 is the sum of distance L1 and distance L2. Hereinafter, the sum of distance L1 and distance L2 is referred to as added value W. The length of first straight line 101 in the main scanning direction is approximately 5 mm to 20 mm.

[0024] Detection lines 110 indicate the range in which the sensor 37 detects the correction pattern formed on the transfer belt 31. When the correction pattern 100 shown in Fig. 2 is formed, the sensor 37 detects straight lines at three points. Although the correction pattern for only one color is shown in Fig. 2, the correction pattern 100 corresponding to each color is formed on the transfer belt 31 or the sheet.

[0025] Fig. 3 is a diagram showing an example of the correction pattern 100 for each color formed on the transfer belt 31 in an embodiment in which no color misregistration occurs, and Fig. 4 is a diagram showing an example of the correction pattern 100 for each color formed on the transfer belt 31 in an embodiment in which color misregistration occurs. In FIGS. 3 and 4, sensor 37-1 is a sensor that detects correction pattern 100 at the front position. Sensor 37-2 is a sensor that detects correction pattern 100 at the center position. Sensor 37-3 is a sensor that detects correction pattern 100 at the rear position. As shown in FIGS. 3 and 4, image forming unit 30 sets one set of correction patterns 100 for each color, and forms N sets of correction patterns 100 on transfer belt 31. Here, N is an integer of 2 or more. The reason why image forming apparatus 1 forms N sets of correction patterns 100 is that the measured values of correction pattern 100 may vary due to mechanical fluctuations or the like. Then, in image forming apparatus 1, the average value of the measured values is calculated for each color, and the calculated average value is calculated as the correction amount for color matching control. In FIG. 4, there are displacements in colors K, C, and M compared to FIG. 3.

[0026] FIGS. 5 and 6 are diagrams for explaining correction pattern 100 in which positional displacement has occurred in the embodiment. In FIG. 5, the center point of correction pattern 100 (for example, center point 104 of the second straight line 102) is located at a position displaced from detection line 110 (for example, on line 120). In sensor 37, since a straight line is detected on detection line 110, the relationship between distance L1 and distance L2 is L1 < L2. On the other hand, the added value of distance L1 and distance L2 in the state of FIG. 5 is the same as the added value W of the distances obtained with correction pattern 100 shown in FIG. 2.

[0027] In contrast, FIG. 6 shows a state in which a behavior variation of the transfer belt 31 has occurred at the position indicated by reference numeral 120. In this case, since the sensor 37 detects a straight line on the detection line 110, the relationship between the distance L1 and the distance L2 is L1 < L2. And the added value of the distance L1 and the distance L2 in the state of FIG. 6 is smaller than the added value W obtained from the correction pattern 100 shown in FIG. 2. This is because, due to the occurrence of the behavior variation of the transfer belt 31 at the position indicated by reference numeral 120, the correction pattern 100 is different from the correction pattern 100 shown in FIG. 2. Such a phenomenon is not limited to the behavior variation of the transfer belt 31, but may occur due to the rotation speed of the transfer belt 31, the unevenness of the surface of the transfer belt 31, etc. And when a correction pattern 100 different from the correction pattern 100 shown in FIG. 2 is formed, the obtained measurement value also becomes incorrect. When the image forming apparatus 1 uses this incorrect measurement value, the accuracy of the color adjustment control will decrease.

[0028] Therefore, in the image forming apparatus 1, when the added value W is outside the range defined as the threshold value, the measurement value obtained from the correction pattern 100 in which the added value W is outside the range is excluded. That is, the image forming apparatus 1 does not use the measurement value obtained from the correction pattern 100 in which the added value W is outside the range for calculating the correction value of the color adjustment control. Here, the threshold value is in the range of ±α of the added value W. α is, for example, 100 microns.

[0029] FIG. 7 is a block diagram showing the hardware configuration of the image forming apparatus 1 according to the embodiment. Note that FIG. 7 shows only the characteristic hardware configuration of the image forming apparatus 1 in the present embodiment. The image forming apparatus 1 includes an image reading unit 10, a control panel 20, an image forming unit 30, a sensor 37, a sheet storage unit 40, a fixing unit 50, a control device 70, an auxiliary storage device 120, and a network interface 130. Each functional unit is connected so as to be able to communicate data via the system bus 2.

[0030] The image reading unit 10, the control panel 20, the image forming unit 30, the sensor 37, the sheet storage unit 40, and the fixing unit 50 have been described above, so their description will be omitted. The control device 70, the auxiliary storage device 120, and the network interface 130 will be described below.

[0031] The control device 70 includes a control unit 71, a read only memory (ROM) 72, and a random access memory (RAM) 73. The control unit 71 is, for example, a processor such as a central processing unit (CPU) or a graphics processing unit (GPU). The control unit 71 controls the operation of each functional unit of the image forming apparatus 1. The control unit 71 executes various processes by expanding a program stored in the ROM 72 into the RAM 73 and executing the program. An application specific integrated circuit (ASIC) may be responsible for an appropriate function realized by the control unit 71. The ASIC is a dedicated circuit for realizing a specific function.

[0032] Next, a specific operation of the control unit 71 will be described. The control unit 71 calculates an added value of the distance L1 between the first line 101 and the second line 102 detected by the sensor 37 and the distance L2 between the second line 102 and the third line 103. The control unit 71 compares the calculated added value with a threshold value, and determines whether or not to use the measurement value obtained from the correction pattern 100 for correcting the color matching control according to the comparison result. If the added value is outside the range defined as the threshold value, the control unit 71 determines not to use the measurement value obtained from the correction pattern 100 whose added value is outside the range for correcting the color matching control.

[0033] The ROM 72 stores a program for operating the control unit 71. The RAM 73 temporarily stores data used by each functional unit of the image forming apparatus 1. For example, the RAM 73 stores the correction pattern 100 and the shift amount in the main scanning direction. The RAM 73 may store digital data generated by the image reading unit 10. The RAM 73 may temporarily store jobs and job logs.

[0034] The auxiliary storage device 120 is, for example, a hard disk or a solid state drive (SSD), and stores various data, such as digital data, jobs, job logs, the correction pattern 100, and the amount of shift in the main scanning direction.

[0035] The network interface 130 transmits and receives data to and from other devices. Here, the other devices are, for example, information processing devices such as personal computers. The network interface 130 operates as an input interface and receives data or instructions transmitted from other devices. An example of an instruction transmitted from another device is an instruction to execute printing. The network interface 130 also operates as an output interface and transmits data to other devices.

[0036] 8 is a flowchart showing the flow of processing performed by the image forming apparatus 1 in the embodiment. The processing in FIG. 8 is executed when an instruction for color matching control is given. The image forming unit 30 forms the correction pattern 100 for each color on the transfer belt 31 (ACT101). The sensor 37 reads the correction pattern 100 formed on the transfer belt 31 and outputs the detection result of the correction pattern 100 to the control device 70 (ACT102). The sensor 37 outputs the detection result for each color to the control device 70. For example, the sensor 37 outputs the detection result to the control device 70 as 1 while the sensor 37 detects a straight line and as 0 while the sensor 37 does not detect a straight line. When the sensor 37 reads the correction pattern 100, one correction pattern 100 is detected three times (first straight line, second straight line, and third straight line). Therefore, the detection result includes a result indicating that the straight line has been detected three times.

[0037] The control unit 71 acquires the detection result for each color output from the sensor 37. The control unit 71 refers to the acquired detection result for each color and calculates the distances L1 and L2 in one correction pattern 100 (ACT103). As an example, a case where a detection result for one color is obtained from the sensor 37 will be described. First, the control unit 71 calculates the distance L1 from the position of the center line 111 of the first straight line 101 to the position of the center line 112 of the second straight line 102 using the detection result obtained from the sensor 37. The position of the center line 111 of the first straight line 101 is the center position of the first rising portion included in the detection result. The position of the center line 112 of the second straight line 102 is the center position of the second rising portion included in the detection result. The control unit 71 calculates the distance L1 based on the elapsed time from the position of the center line 111 of the first straight line 101 to the position of the center line 112 of the second straight line 102.

[0038] Next, the control unit 71 calculates a distance L2 from the position of the center line 112 of the second straight line 102 to the position of the center line 113 of the third straight line 103 using the detection result obtained from the sensor 37. The position of the center line 113 of the third straight line 103 is the center position of the third rising portion included in the detection result. The control unit 71 calculates the distance L2 based on the elapsed time from the position of the center line 112 of the second straight line 102 to the position of the center line 113 of the third straight line 103. The control unit 71 calculates an additional value W of the calculated distance L1 and distance L2 (ACT 104).

[0039] The control unit 71 compares the sum W with a threshold value to determine whether the sum W is within a predetermined range (ACT105). If the sum W is within the predetermined range (ACT105: YES), the control unit 71 determines that the correction pattern 100 used to calculate the sum W is a normal pattern (ACT106). If the added value W is outside the predetermined range (ACT105: NO), the control unit 71 determines that the correction pattern 100 used to calculate the added value W is an abnormal pattern (ACT107).

[0040] The control unit 71 performs the process from ACT103 to pattern determination for the correction pattern 100 of each color. Then, the control unit 71 calculates the amount of deviation for each correction pattern 100 of each color. The method of calculating the amount of deviation is the same as the calculation method for conventional color matching control, so the explanation is omitted. The control unit 71 records the calculated amount of deviation information and the pattern determination result in the RAM 73 for each color in association with each other. After that, the control unit 71 determines whether or not the process from ACT102 to pattern determination has been performed for N sets (ACT108).

[0041] If the process from ACT102 to pattern determination has not been executed for N sets (ACT108: NO), the control unit 71 executes the process from ACT102 onwards. When the process from ACT102 to pattern determination has been executed for N sets (ACT108: YES), the control unit 71 calculates the correction amount (ACT109). Specifically, the control unit 71 calculates the correction amount using only the deviation amount of the normal pattern among the deviation amounts recorded in the RAM 73. For example, the control unit 71 calculates the correction amount for each color by calculating the average deviation amount of the normal pattern for each color.

[0042] According to the image forming apparatus 1 configured as above, it becomes possible to perform color matching control with higher accuracy. Specifically, the image forming apparatus 1 includes an image forming section 30, a sensor 37, and a control section 70. The image forming section 30 forms a correction pattern 100 consisting of a plurality of straight lines on the transfer belt 31. The sensor 37 detects the plurality of straight lines constituting the correction pattern 100 formed on the transfer belt 31. The control section 70 compares the sum of the distance L1 and the distance L2 with a threshold value, and determines whether or not to use the measurement value obtained from the correction pattern 100 for correction of the color matching control according to the comparison result. As a result, the image forming apparatus 1 does not calculate the correction value of the color matching control for each color using all the measurement values ​​detected by the sensor 37 as in the conventional case. For example, even if a pattern different from the original correction pattern is formed due to a behavioral change of the transfer belt 31, the measurement value obtained from the correction pattern 100 was also used in the conventional case. In this case, the correction value may also be shifted, and the accuracy of the color matching control may be reduced. In contrast, the image forming apparatus 1 in this embodiment determines whether or not to use the obtained measurement value for each correction pattern 100 in correcting the color matching control. This prevents the correction value from being calculated using all the measurement values ​​as in the past. For example, it becomes possible to select not to use the measurement value of an abnormal correction pattern 100 in calculating the correction value. This makes it possible to perform color matching control with higher accuracy.

[0043] When the sum is outside the range defined as the threshold, the image forming apparatus 1 determines not to use the measurement value obtained from the correction pattern 100 whose sum is outside the range for correcting the color matching control. This prevents the measurement value of the abnormal correction pattern 100 from being used to calculate the correction value. This makes it possible to perform color matching control with higher accuracy.

[0044] The image forming apparatus 1 forms a correction pattern 100 on the transfer belt 37, in which the distance L1 and the distance L2 are the same value. This allows the image forming apparatus 1 to determine that the correction pattern 100 is not formed correctly when there is a deviation between the values ​​of the distance L1 and the distance L2. Then, the image forming apparatus 1 determines whether or not to use the measurement value for correcting the color matching control depending on the degree of deviation of the formed correction pattern 100. This makes it possible to avoid using the measurement value obtained from the correction pattern 100 that is significantly deviated from the original correction pattern 100 for correcting the color matching control. As a result, it becomes possible to perform color matching control with higher accuracy.

[0045] The image forming apparatus 1 forms a correction pattern 100 arranged so that the center point of the second straight line as shown in FIG. 2 is point-symmetric with respect to the pattern. In this way, since the correction pattern 100 is a point-symmetric pattern, it is easy to detect positional deviation. Therefore, it is easy to determine whether the correction pattern 100 is to be used for calculating the correction value. As a result, it is possible to perform color matching control with higher accuracy.

[0046] Below, modified examples of the image forming apparatus 1 will be described. In the above embodiment, the control unit 71 is configured to compare the sum W of the distance L1 and the distance L2 with the threshold value. The control unit 71 may be configured to compare the sum W1 of the elapsed time t1 and the elapsed time t2 with the threshold value. In this case, the elapsed time t1 is the elapsed time from the position of the center line 111 of the first straight line 101 to the position of the center line 112 of the second straight line 102 on the detection line 110. The elapsed time t2 is the elapsed time from the position of the center line 112 of the second straight line 102 to the position of the center line 113 of the third straight line 103 on the detection line 110. The elapsed time from the position of the center line 111 of the first straight line 101 to the position of the center line 113 of the third straight line 103 on the detection line 110 is the sum of the elapsed time t1 and the elapsed time t2. The threshold value in this case is within the range of ±β of the sum W1. β is, for example, 0.5 milliseconds.

[0047] In the above embodiment, as an example of the correction pattern 100, the correction pattern 100 shown in FIG. 2 was shown. The correction pattern 100 does not need to be limited to the above pattern. For example, the pattern shown in FIG. 9 may be used as the correction pattern 100. FIG. 9 is a diagram showing an example of another correction pattern 200. As shown in FIG. 9, the correction pattern 200 is composed of a first straight line 201, a second straight line 202, and a third straight line 203, similar to the correction pattern 100. The difference between the correction pattern 200 and the correction pattern 100 is that the first straight line 201 and the third straight line 203 are not parallel to the main scanning direction. For example, the first straight line 201 and the third straight line 203 have an angle of +45 degrees with respect to the main scanning direction, and the second straight line 202 has an angle of -45 degrees (+135 degrees) with respect to the main scanning direction. That is, the first straight line 201 and the third straight line 203 have an angle of +45 degrees with respect to the detection line 110, and the second straight line 202 has an angle of -45 degrees with respect to the detection line 110. Further, the center point 204 of the second straight line 202 is arranged so that the arrangement of the three straight lines is point-symmetrical. The distance from the center point of the first straight line 201 to the center point 204 of the second straight line 202 and the distance from the center point 204 of the second straight line 202 to the center point of the third straight line 203 are the same value.

[0048] Here, the distance Z1 is the distance from the position of the center line of the first straight line 201 on the detection line 110 to the position of the center line of the second straight line 202. The distance Z2 is the distance from the position of the center line of the second straight line 202 on the detection line 110 to the position of the center line of the third straight line 203. In this case, the distance from the position of the center line of the first straight line 201 to the position of the center line of the third straight line 203 on the detection line 110 is the sum of the distance Z1 and the distance Z2. Let the sum of the distance Z1 and the distance Z2 be the addition value W1. Also in the correction pattern 200 in FIG. 9, when a displacement occurs, the distance Z1 and the distance Z2 do not become the same value, similar to the correction pattern 100. That is, the relationship between the distance Z1 and the distance Z2 becomes Z1 < Z2 or Z1 > Z2. Since the specific process using the correction pattern 200 is the same as that in the case of the correction pattern 100, the description is omitted.

[0049] The functions of the image forming apparatus 1 in the above-described embodiment may be realized by a computer. In that case, a program for realizing the functions may be recorded in a computer-readable recording medium, and the program recorded in the recording medium may be read into a computer system and executed to realize the functions. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. The term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into a computer system. The term "computer-readable recording medium" may also include a medium that dynamically holds a program for a short period of time, such as a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line, and a medium that holds a program for a certain period of time, such as a volatile memory inside a computer system that is a server or client in such a case. The above-described program may be a program for realizing a part of the above-described functions, or may be a program that can realize the above-described functions in combination with a program already recorded in the computer system.

[0050] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0051] 1... image forming apparatus, 30... image forming section, 37... sensor, 71... control section

Claims

1. an image forming unit that forms a pattern composed of a plurality of straight lines on an image carrier; a sensor for detecting the plurality of straight lines constituting the pattern formed on the image carrier; a control unit that compares a first value between a first straight line and a second straight line among the plurality of straight lines detected by the sensor and a second value between the second straight line and a third straight line among the plurality of straight lines with a threshold value, and determines whether or not to use a measurement value obtained from the pattern for correction of color matching control according to a comparison result; Equipped with The control unit obtains multiple sum values ​​by calculating the sum value multiple times, obtains multiple measurement values ​​by comparing the obtained multiple sum values ​​with the threshold value multiple times, and calculates a correction value by determining a statistical value of the remaining measurement values ​​from the obtained multiple measurement values, excluding measurement values ​​obtained from patterns where the sum value is outside the range.

2. 2. The image forming apparatus according to claim 1, wherein the control unit determines that when the sum is outside a range defined as the threshold, the measurement value obtained from the pattern for which the sum is outside the range will not be used to correct the color matching control.

3. the first value and the second value are distance or time; 3 . The image forming apparatus according to claim 1 , wherein the image forming section forms the pattern in which the first value and the second value detected in a sub-scanning direction read by the sensor are the same value.

4. 4. The image forming apparatus according to claim 1, wherein the image forming unit forms the pattern such that the first straight line and the third straight line are at the same angle, the angle of the second straight line is different from the angles of the first straight line and the third straight line, and the center point of the second straight line is point-symmetric with respect to the pattern.

5. A pattern consisting of a plurality of straight lines is formed on an image carrier; detecting the plurality of straight lines constituting the pattern formed on the image carrier; comparing a first value between a first straight line and a second straight line among the plurality of straight lines detected by a sensor and a second value between the second straight line and a third straight line among the plurality of straight lines with a threshold value, and determining whether or not to use the measurement value obtained from the pattern for correction of color matching control according to a comparison result; Calculating the sum value a plurality of times to obtain a plurality of sum values; acquiring a plurality of measurement values ​​by performing a comparison between the acquired plurality of added values ​​and the threshold value a plurality of times; An image position adjustment method in which a correction value is calculated by finding a statistical value of the remaining measurement values, excluding measurement values ​​obtained from patterns whose added values ​​are outside the range, from the plurality of acquired measurement values.

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