JP2005271351A - Image forming apparatus and method of adjusting recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To fix a lighting point for forming a marker image when a correction of an output of each lighting point in a recording head is carried out by using the marker image. <P>SOLUTION: A side register adjustment value for adjusting a register in a main scanning direction is set in an LPH 14. A test pattern is output in order to form correction data for adjusting a quantity of light of an LED 64 forming the LPH 14 by using the LPH 14. The marker image formed by energizing a predetermined LED 64 in the main scanning direction and a density image formed by energizing all the LEDs are included in the test pattern. The side register adjustment value set in the LPH 14 is reset before outputting the test pattern. As a result, the marker image is always written by the same LED 64. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that forms an image using a recording head configured by arranging a plurality of recording elements, and more particularly to output correction and adjustment of each recording element.

  In image forming apparatuses such as printers, copiers, and facsimiles that employ an electrophotographic method, an electrostatic latent image is obtained by irradiating image information onto a uniformly charged photoreceptor by optical recording means. The electrostatic latent image is visualized by adding toner, and the image is formed by transferring and fixing on the recording paper. In addition to the optical scanning method in which a laser is used as the optical recording means and exposure is performed by scanning the laser beam in the main scanning direction, in recent years, an LED (Light Emitting Diode) has been received in response to a request for downsizing of the apparatus. A writing device using an LED print head (LPH) arranged in a large number in the main scanning direction is employed.

  LPH is generally an LED array in which a large number of LEDs are arranged in the main scanning direction, and a cell in which a large number of rod lenses are arranged to form an image of the light output from the LEDs on the surface of the photosensitive member (photosensitive drum). And a fock lens. In the image forming apparatus, each LED of the LPH is driven based on input image data, light is output toward the photosensitive member, and light is imaged on the surface of the photosensitive member by the SELFOC lens. An electrostatic latent image is formed in the sub-scanning direction by relatively moving the photoconductor and LPH.

  In this LPH, since a plurality of light emitting elements and lenses are arranged side by side in the main scanning direction, variation in each light emitting point has a great influence on image quality. In particular, when there is a variation in the amount of light emitted from the light emitting points or when the lens characteristics vary, streaks and density unevenness in the sub-scanning direction occur, and image quality defects are likely to occur. Therefore, as a conventional technique, there is a technique in which a test pattern formed and output on a sheet using LPH is read by a scanner, and an output correction value of each LED in LPH is set based on the obtained reading result (patent) Reference 1).

  Further, instead of the above-mentioned LPH, an exposure device is formed using an optical shutter array composed of a line-type light source and a plurality of optical shutters arranged in the main scanning direction, and the surface of the photoreceptor is exposed using this exposure device. There is also an image forming apparatus. Also in this type of image forming apparatus, variations in light emission points due to the respective light shutters have a great influence on image quality. Therefore, as a conventional technique, there is a technique in which a test pattern formed and output on a sheet using this exposure device is read by a scanner, and an output correction value of each optical shutter in the exposure device is set based on the obtained reading result. (See Patent Document 2).

  By the way, when such a recording head is used, in order to improve the above-described output correction, it is necessary to accurately associate each light emitting point with the position of the test pattern image formed by each light emitting point. There is. Therefore, in Patent Document 2 described above, a marker image is formed by using a specific optical shutter (for example, an even or odd number) together with a test pattern, so that the position of each optical shutter and each light from the reading result read by the scanner. Correspondence with the test pattern image formed by the shutter is possible.

In recent image forming apparatuses, colorization is progressing rapidly. For example, four image forming units of yellow (Y), magenta (M), cyan (C), and black (K) are arranged in parallel. A so-called tandem type image forming apparatus for forming a full-color image has been put into practical use. In this tandem type image forming apparatus, if the LPH mounting position in each image forming unit is shifted, registration shift occurs, and a desired full-color image cannot be obtained.
Therefore, for example, there is a technique for correcting a shift in the main scanning direction of LPH (side registration shift) by adjusting the position of the LED that emits light in the LPH (see Patent Document 3).

Japanese Patent Laid-Open No. 11-240202 (page 3-7, FIG. 3) JP-A-10-337906 (page 4-5, FIG. 3) Japanese Patent No. 3298497 (page 4, FIG. 7)

  However, in the image forming apparatus described in Patent Document 3, when a marker image is formed using the method described in Patent Document 2, there is a problem that the LED to which the marker image is written is shifted by the side registration deviation adjustment. did. That is, since the marker image is written with an LED different from the original purpose, the correspondence between the test pattern and the LED is mistaken. As a result, there is a problem that correction data for different LEDs is written as correction data for a certain LED, and the correction does not converge.

In addition to the above-mentioned side registration adjustment, for example, when the LPH is mounted obliquely or in a bow shape, the electrostatic latent image formed by the LEDs constituting the LPH is linearly formed along the main scanning direction. It is necessary to correct electrically so that Further, when the LEDs constituting the LPH are mounted in a state of extending or contracting in the main scanning direction, it is necessary to electrically correct so as to adjust the length in the main scanning direction.
However, when this type of correction is performed, streaks in the sub-scanning direction may occur in the output image, resulting in a decrease in image quality.

  Such a problem is not limited to an image forming apparatus using a recording head using light such as an LPH or an optical shutter. For example, a plurality of nozzles are arranged in parallel, and ink is supplied from the plurality of nozzles. This can also occur in an image forming apparatus using an ink jet head that forms an image by discharging.

The present invention has been made in order to solve such a technical problem, and an object of the present invention is to use a marker image when correcting the output of each light emitting point in the recording head. The purpose is to fix the light emitting point to be formed.
Another object is to suppress the generation of streaks in the image when adjusting the recording head.

For this purpose, an image forming apparatus to which the present invention is applied has a recording head in which a plurality of recording elements are arranged, and an output start position of the recording head with respect to the recording elements is shifted in the main scanning direction. Side registration adjustment means for adjusting the side registration, input means for inputting test image data for adjusting the recording head to the recording head, and test image data input from the input means are recorded without performing side registration adjustment by the side registration adjustment means. Output means for outputting using a head.
Here, the input means inputs, as test image data, marker image data to be recorded by a specific recording element in the recording head and image data including density image data having the same density in the main scanning direction to the recording head. It can be. In addition, the image forming apparatus further includes storage means for storing marker image data for recording by a specific recording element in the recording head, and the output means uses the recording head to output the marker image data input from the storage means together with the test image data. It can be characterized by outputting.

  The present invention also relates to a method for adjusting a recording head in which a plurality of recording elements are arranged, the light amount correcting step for correcting the light amount of the plurality of recording elements, and the recording of the recording head after the light amount correcting step is completed. A side registration adjustment step of adjusting the side registration in the main scanning direction by shifting the output start position with respect to the element.

  Furthermore, the present invention is a method for adjusting a recording head in which a plurality of recording elements are arranged, and includes a magnification correction step for electrically correcting a magnification in the main scanning direction of the recording elements in the recording head, and a magnification correction step. And a light amount correction step for correcting the light amounts of the plurality of recording elements after completion.

  Furthermore, the present invention is a method for adjusting a recording head in which a plurality of recording elements are arranged, a positional deviation correction step for electrically correcting a positional deviation of the recording elements in the recording head in the sub-scanning direction, And a light amount correction step for correcting the light amounts of the plurality of recording elements after the deviation correction step is completed.

According to the present invention, when the output correction of each light emitting point in the recording head is performed using the marker image, the light emitting point forming the marker image can be fixed.
Further, according to the present invention, it is possible to suppress the generation of streaks in the image when adjusting the recording head.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below in detail with reference to the accompanying drawings.
—Embodiment 1—
FIG. 1 is a diagram showing an overall configuration of an image forming apparatus using an LED print head to which this embodiment is applied, and shows a so-called tandem type digital color printer. An image forming apparatus shown in FIG. 1 includes an image processing system 10 that forms an image corresponding to gradation data of each color, an image output control unit 30 that controls the image processing system 10, such as a personal computer (PC). 2 and an image reading device (IIT) 3 and an image processing system (IPS) 40 that performs predetermined image processing on image data received from these.

  An image processing system 10 as an output unit includes an image forming unit 11 including a plurality of engines arranged in parallel at regular intervals in the horizontal direction. The image forming unit 11 is composed of four image forming units 11Y, 11M, 11C, and 11K of yellow (Y), magenta (M), cyan (C), and black (K). A photosensitive drum 12 that is an image carrier (photosensitive member) that forms an image and carries a toner image, a charger 13 that uniformly charges the surface of the photosensitive drum 12, and a photosensitive drum that is charged by the charger 13. 12 is an LED print head (LPH) 14 that is a recording head that exposes 12 and a developing unit 15 that develops a latent image obtained by the LPH 14. Further, the image process system 10 conveys the recording paper in order to multiplex-transfer the toner images of the respective colors formed on the photosensitive drums 12 of the image forming units 11Y, 11M, 11C, and 11K onto the recording paper. The sheet conveying belt 21, the driving roll 22 which is a roll for driving the sheet conveying belt 21, the transfer roll 23 for transferring the toner image on the photosensitive drum 12 to the recording sheet, and the toner image on the recording sheet after the transfer are fixed. A fixing device 24 and a patch detection sensor 25 for detecting a patch toner image formed on each of the image forming units 11Y, 11M, 11C, and 11K and transferred onto the paper conveying belt 21 are provided.

  Each of the image forming units 11Y, 11M, 11C, and 11K has substantially the same configuration except for the toner accommodated in the developing device 15. Image signals input from the PC 2 or IIT 3 are subjected to image processing by the image processing unit 40 and supplied to the image forming units 11Y, 11M, 11C, and 11K through the interface. The image process system 10 operates based on a control signal such as a synchronization signal supplied from the image output control unit 30.

  First, in the yellow image forming unit 11Y, an electrostatic latent image is formed on the surface of the photosensitive drum 12 charged by the charger 13 by the LPH 14 based on the image signal obtained from the image processing unit 40. A yellow toner image is formed on the electrostatic latent image by the developing unit 15, and the formed yellow toner image is transferred to the recording paper on the paper transport belt 21 that rotates in the direction of the arrow in the figure. It is transcribed using. Similarly, magenta, cyan, and black toner images are formed on the respective photosensitive drums 12, and sequentially transferred onto the recording paper on the paper transport belt 21 using the respective transfer rolls 23. The multiple transferred toner images on the recording paper are conveyed to the fixing device 24 and fixed on the recording paper by heat and pressure.

  FIG. 2 is a diagram showing the configuration of the LED print head (LPH) 14 described above. The LPH 14 includes an LED array 51 formed by arranging a large number of LED chips 63 (described later), a printed circuit board 52 on which a circuit for supporting the LED array 51 and controlling the drive of the LED array 51 is formed, and each LED. A SELFOC lens array (SLA: registered trademark) 53 for forming an image of the light beam emitted from the photosensitive drum 12 on the surface of the photosensitive drum 12 is provided, and the printed circuit board 52 and the SLA 53 are held in a housing 54.

  The LED array 51 is formed by arranging a plurality of LED chips in the main scanning direction (the axial direction of the photosensitive drum 12) and attaching the LED chip to a printed circuit board 52. These LED chips are arranged in a line. In the LED array 51, LEDs corresponding to the number of pixels corresponding to the resolution are arranged in the main scanning direction. For example, when the A3 size short (297 mm) is used as the main scanning direction, 14040 LEDs are arranged every about 21.2 μm at a resolution of 1200 dpi.

  In the SLA 53, a gradient index lens as an imaging lens is formed corresponding to the number of pixels corresponding to the resolution (for example, 1070 in the present embodiment). The SLA 53 condenses the light beams emitted from the LED arrays 51 of the image forming units 11Y, 11M, 11C, and 11K and forms an image on the corresponding photosensitive drum 12 to thereby form a main image on the photosensitive drum 12. An electrostatic latent image for one line is formed in the scanning direction. Further, the printed circuit board 52 is mounted on the housing 54 so that the mounting surface of the LED array 51 faces the surface of the photosensitive drum 12.

  FIG. 3 is a circuit diagram showing the relationship between the image output control unit 30 as a correction unit and the LPH 14. As shown in FIG. 1, the LPH 14 is connected to the image output control unit 30, and the operation of each circuit built in the LPH 14 is controlled by the image output control unit 30. The image output control unit 30 is provided with a memory 31 for storing side registration adjustment values described later. The printed circuit board 52 shown in FIG. 2 has a shift register 61 for storing image data for one line, a latch circuit 62 for latching image data, and a lighting time corresponding to the image data latched by the latch circuit 62. A driver 65 is provided as output means for driving each LED 64 of the LED chip 63 by being supplied to the LED chip 63. The driver 65 is connected to an EEPROM (Electrically Erasable and Programmable ROM) 66 as a storage unit for storing correction data (output correction data) described later.

  When image data is input from the image processing unit 40, the image output control unit 30 outputs image data for one line to the shift register 61 in synchronization with the transfer clock. Further, the image output control unit 30 outputs the SET signal to the latch circuit 62 after outputting the image data for one line to the shift register 61. As a result, the image data for one line stored in the shift register 61 is latched in the latch circuit 62. When the image output control unit 30 outputs the STROB signal to the driver 65, each driver 65 supplies the lighting time corresponding to the corresponding pixel data to the LED 64 as the corresponding recording element. Accordingly, each LED 64 emits light according to the lighting time supplied from the driver 65.

  Each driver 65 is provided with a register (not shown) for correcting a current value output (supplied) from the driver 65 to the LED 64. This register holds correction data for correcting the light emission amount of the LED 64. The driver 65 corrects the current value based on the image data latched by the latch circuit 62 with the correction data held in the register, and then supplies the current value to the LED 64. The correction data is calculated in advance and stored in the EEPROM 66, and is written from the EEPROM 66 to the register of each driver 65 and held at a predetermined timing such as when the image forming apparatus is turned on.

  Next, side registration adjustment in the LPH 14 will be described. In this tandem type image forming apparatus, the image forming units 11Y, 11M, 11C, and 11K are provided for each color, and therefore the LPH 14 is also provided for each color. Since there is a limit to the accuracy of the frame of the image forming apparatus to which each LPH 14 is mounted and the accuracy of the LPH 14 itself, it is difficult to mount the LPH 14 so that the positions of the LPHs 14 in the main scanning direction coincide with each other. . If each LPH 14 is used in a state shifted in the main scanning direction (a state where the side registration does not match), an image shift in the main scanning direction (side registration shift) occurs, and the image quality deteriorates.

Therefore, in the image forming apparatus according to the present embodiment, a patch image is formed on the sheet conveying belt 21 by using the image forming units 11Y, 11M, 11C, and 11K by the image output control unit 30 as a side registration adjusting unit. The formed patch image is read by the patch detection sensor 25, and the position shift of the LPH 14 for each color in the main scanning direction is detected based on the read result, and the side registration adjustment for each LPH 14 is performed.
FIG. 4 illustrates the LPHs 14 (specifically, 14Y, 14M, 14C, and 14K) of the respective colors that are attached to the frame (not shown) of the image forming apparatus in a state in which the positional deviation in the main scanning direction has occurred. ing. In this example, for example, the first LED 64 in yellow LPH 14Y is shifted in the main scanning direction by 8 pixels in magenta LPH 14M, 4 pixels in cyan LPH 14C, and 6 pixels in black LPH 14K.

  In the present embodiment, for example, the first LED 64 of each LPH 14Y, 14M, 14C, 14K (leftmost in the figure) is turned on to form a patch image, and the patch image formed by the above-described patch detection sensor 25 is read. As a result, the lighting start positions (positions of the LEDs 64 to be lit) of the LPHs 14Y, 14M, 14C, and 14K are shifted, and the side registration is adjusted. In this example, for example, to match yellow LPH 14Y, the ninth LED 64 is the first pixel in magenta LPH 14M, the fifth LED 64 is the first pixel in cyan LPH 14C, and the seventh LED 64 is in the black LPH 14K. A side registration adjustment value to be set for the first pixel is obtained. Then, the obtained side registration adjustment values of the LPHs 14Y, 14M, 14C, and 14K are stored in the memory 31 provided in the image output control unit 30. When actually forming an image, the side registration adjustment value stored in the memory 31 is read, and after 9 pixels of blank data are sent from the first LED 64 for yellow LPH 14Y and 8 pixels for magenta LPH 14M. Write 4 pixels of blank data for cyan LPH 14C from the 5th LED 64 and send 6 pixels of blank data for black LPH 14K, then write 7 pixels from the 7th LED 64. A control signal is output to the shift register 61 so as to start.

  Next, a description will be given of the correction data generation device 70 that functions as a correction device and is used as a jig for generating the correction data written in the EEPROM 66 described above. FIG. 5 is a block diagram illustrating a functional configuration of the correction data generation device 70. The correction data generation device 70 includes a reading unit 71 that reads an image formed on a recording sheet as image data, and an image data calculation that performs a predetermined calculation based on the image data read by the reading unit 71. 72, density unevenness calculation unit 73 for obtaining density unevenness data in the image data calculated by image data calculation unit 72, and density unevenness suppression based on the density unevenness data calculated by density unevenness calculation unit 73. A correction data calculation unit 74 that calculates correction data for correction, and a correction data generation unit (correction data generation unit) 75 that generates correction data to be stored in the image forming apparatus based on the calculation result in the correction data calculation unit 74. The correction data generated by the correction data generation unit 75 is written to the EEPROM 66 provided in the image forming apparatus. And a driver 76. The driver 76 is connected to the EEPROM 66 provided in the image forming apparatus via, for example, a predetermined cable and an interface (both not shown). Then, the correction data formed by the correction data generation device 70 based on the density information of the test pattern formed on the recording paper is written into the EEPROM 66 via the cable and interface described above. The image data calculation unit 72, the density unevenness calculation unit 73, the correction data calculation unit 74, and the correction data generation unit 75 constitute a scanner correction unit.

The reading unit 71 reads a predetermined output image (hereinafter referred to as a test pattern) as test image data output from the image forming apparatus as image data, and outputs the image data to the image data calculation unit 72. As the reading unit 71, for example, IIT3 provided in the image forming apparatus can be used.
The image data calculation unit 72 detects the inclination of the image data obtained by reading the test pattern formed on the recording paper by the reading unit 71 and corrects the inclination. Then, the image data whose inclination is corrected is output to the density unevenness calculation unit 73.
The density unevenness calculation unit 73 obtains density unevenness data from the image data input from the image data calculation unit 72 by averaging the density data for each LED 64 in the main scanning direction and the sub-scanning direction. In addition, the magnification correction is performed by performing a scaling process (enlargement or reduction) in a one-dimensional manner in the main scanning direction (main scanning direction at the time of test pattern formation), and the LED 64 in which the number of pixels of density unevenness data and the test pattern are formed. Are matched with the position of each LED 64. Thus, the density distribution in the main scanning direction generated on the image formed by the image forming apparatus is obtained, and the result is output to the correction data calculation unit 74 as density unevenness data.

The correction data calculation unit 74 calculates correction data (referred to as correction data B) for making the density distribution in the main scanning direction substantially flat based on the density unevenness data input from the density unevenness calculation unit 73. That is, the correction data B is a correction value for correcting the light emission intensity of each LED 64 so that the density of each pixel of the image formed by each LED 64 of the image forming apparatus is uniform.
The correction data generation unit 75 can access an EEPROM 66 as a storage means or a storage unit via a driver 76, and the correction data (referred to as correction data A) stored in advance in the EEPROM 66 from the correction data calculation unit 74. By combining with the input correction data B, new correction data (referred to as correction data C) is generated, and this correction data C is written to the EEPROM 66 via the driver 76. Thereby, the correction data C as the output correction data generated by the correction data generation device 70 is stored in the EEPROM 66 of the image forming apparatus. Thereafter, in each of the image forming units 11Y, 11M, 11C, and 11K of the image forming apparatus, An image forming process based on the correction data C is performed.

Next, creation and reading of a test pattern used for generating the correction data described above will be described in detail. This test pattern is formed on a recording sheet by the image forming apparatus and is read by the reading unit 71 of the correction data generating apparatus 70.
FIG. 6 schematically shows the relationship between the LED array 51 and the test pattern formed on the recording paper P. The LED array 51 has 14040 LEDs 64 as a plurality of recording elements arranged in parallel in the main scanning direction, specifically, L1, L2, L3,. Then, when forming the test pattern, A4 size recording paper P is set so that the longitudinal direction thereof is the main scanning direction, and these LEDs 64 are used to make the same in different colors as the test pattern in the sub-scanning direction. An electrostatic latent image such as a black 50% density test image K (Cin50), a 30% density test image K (Cin30), and a 20% density test image K (Cin20). Forming.
In the present embodiment, electrostatic latent images for forming the marker images MK1 and MK2 are also formed on the upstream side and the downstream side of the recording paper P for the purpose of obtaining more accurate correction data. Here, the marker images MK1 and MK2 are formed by turning on the first LED 64 in each LED chip 63 shown in FIG. 3 for a predetermined time. Therefore, the number of the marker images MK1 and MK2 is arranged. The number is the same as the number of LED chips 63.

  On the other hand, FIG. 7 is a diagram schematically showing the relationship between the line sensor 77 provided in the reading unit 71 of the correction data generation device 70 and the test pattern formed on the recording paper P. The line sensor 77 has 7020 sensors S1, S2, S3,... Arranged in the main scanning direction and has a resolution of 600 dpi. When the test pattern is read, the A4 size recording is performed so that the short direction is the main scanning direction, that is, the main scanning direction and the sub-scanning direction are switched from the time when the test pattern is created. Black paper 50% density test image K (Cin50), 30% density test image K (Cin30), 20% density test image K (Cin20) created on recording paper P with paper P loaded thereon, and The marker images MK1 and MK2 are read by the line sensor 77. By using this method, it becomes possible to read a test image of the same color (for example, test image K (Cin50) of 50% density of black) with the same sensor (for example, sensors S1, S2, and S3), and different sensors are read. It is possible to reduce the influence of errors caused by this. Further, there is an advantage that image data substantially corresponding to each of the LEDs L1, L2, L3,... Can be obtained every time one line is read by the line sensor 77.

  Next, a procedure for setting correction data performed before shipment of the image forming apparatus according to the present embodiment will be described with reference to FIG. FIG. 8 is a flowchart showing a correction data setting procedure. First, prior to generating the correction data, the main body 1 for forming an image such as a test pattern on the recording paper P is assembled by mounting the LPH 14 or the like on the image forming apparatus, and attaching each part. Correction is performed. The EEPROM 66 incorporated in the image forming apparatus holds an initial value (correction data A) of correction data. When the power of the image forming apparatus is turned on, the correction data A is read out and each of the LPHs 14 is read. It is stored in a register of each driver 65 for driving the LED 64.

  Then, an instruction to form a test pattern is given together with the contents of the test pattern from the PC 2 as input means. When an instruction relating to this test pattern formation is given, the image output control unit 30 resets the side registration adjustment values of the LPHs 14Y, 14M, 14C, and 14K stored in the memory 31 (step 101). This reason will be described later. Then, when an instruction relating to test pattern formation is given, each LED 64 of the LPH 14 emits light whose light amount is corrected based on the correction data A, and an electrostatic latent image is formed on the photosensitive drum 12 by this light emission. On the recording paper P, as shown in FIG. 6, a black 50% density test image K (Cin50) and a 30% density test image K (Cin30) having a predetermined length in the sub-scanning direction, respectively. , A test pattern consisting of a 20% density test image K (Cin20) and marker images MK1 and MK2 is output (step 102). Next, based on the image formed on the recording paper P, the correction data generating device 70 generates correction data for suppressing density unevenness. For this purpose, the main body 1 of the image forming apparatus and the correction data generating apparatus 70 are connected.

  As shown in FIG. 7, the image formed on the recording paper P in step 102 is read by the reading unit 71 of the correction data generating device 70 with the main scanning direction and the sub-scanning direction at the time of image formation being switched. (Step 103), the test pattern included in this image is acquired as image data. Then, the image data calculation unit 72 performs skew correction of the image data based on the read image data (step 104). Here, as shown in FIG. 7, the skew correction is performed, for example, in the test image K (Cin20) of black 20% density on the outer edge a on the rear end side of the recording paper P and the test image K (Cin50 of 50% density). ) Is detected, the inclination of the entire image data is calculated from the position information of the outer edge a and the outer edge b, and the inclination is corrected. Realized. In addition, since the outer end part a and the outer end part b are formed by the same LED 64 in Step 101, it is possible to improve the accuracy of the detected position. Thereby, an inclination error component between the test pattern actually formed on the recording paper P and the image data read by the reading unit 71 is removed.

  The density unevenness calculation unit 73 averages the density of the image data subjected to the skew correction in step 104 in the main scanning direction and the sub-scanning direction, and noise is removed (step 105). Further, the density unevenness calculation unit 73 performs magnification correction in the main scanning direction (main scanning direction during test pattern formation), thereby correcting the number of pixels in the main scanning direction so as to match the number of LEDs 64 (14040). (Step 106). In step 106, when the number of pixels in the main scanning direction is corrected, the LED 64 and the position of the test pattern image to be formed are associated with each other using the read data of the marker images MK1 and MK2.

  For the image data that has undergone pixel number correction in step 106, the average density for each color is calculated in the correction data calculation unit 74 (step 107), and the average density for each color obtained in step 107 and the input density Cin for each color are calculated. The deviation from the output density of each LED 64 is calculated (step 108). Then, correction data (correction data B) is calculated by dividing the deviation obtained for each input density and for each LED 64 by the correction resolution (step 109). Further, the correction data B calculated by the correction data calculation unit 74 and the correction data A acquired from the EEPROM 66 of the image forming apparatus via the driver 76 are combined in the correction data generation unit 75, thereby density unevenness. Correction data (correction data C) for forming an image having no image is generated.

  The correction data C generated as described above is written into the EEPROM 66 of the image forming apparatus via the driver 76 (step 110) and stored in the EEPROM 66. When the correction data C is stored in the EEPROM 66, the correction data setting is completed. The main body 1 of the image forming apparatus is shipped after the correction data generating apparatus 70 attached to the main body 1 is removed.

  Therefore, the image forming apparatus is shipped in a state where correction data (correction data C) changed so as not to cause density unevenness is stored in the EEPROM 66. Therefore, the LPH 14 performs this correction when used by the user after shipment. An image can be formed while performing light amount correction using data. Thereby, it is possible to form a good image in which uneven density is suppressed.

Next, the reason why the side registration adjustment value of each LPH 14 is reset in step 101 prior to the generation of the correction data of LPH 14 described above will be described.
First, let us consider a case where correction data is generated without resetting the side registration adjustment value, that is, with the side registration adjustment made. For example, in the black LPH 14K shown in FIG. 4, the latent image is written by shifting the LED 64 by 6 pixels by side registration adjustment. Therefore, even if an instruction to turn on the first LED 64 of each LED chip 63 is issued, the seventh LED 64 in each LED chip 63 is actually turned on. As a result, the marker images MK1 and MK2 are recorded on the recording paper P in a state in which the position is shifted by 6 pixels in the main scanning direction.

On the other hand, the density unevenness calculation unit 73 of the correction data generation device 70 performs calculation assuming that the marker images MK1 and MK2 are formed by the first LED 64 in each LED chip 63. For this reason, the correction data generation device 70 creates correction data for the seventh LED 64 in each LED chip 63 as the correction data for the first LED 64 in each LED chip 63 and writes the correction data in the EEPROM 66. As a result, in the black LPH 14K, the light amount correction is performed with correction data created for the different LEDs 64 for each LED 64, and accurate correction cannot be performed.
Such a problem does not occur in the standard yellow LPH 14Y, but similarly occurs in the magenta LPH 14M and the cyan LPH 14C, although the number of pixels is different.

On the other hand, in the present embodiment, since the correction data of the LPH 14 is generated after the side registration adjustment value is reset, the marker images MK1 and MK2 are always the same LED 64, specifically, each LED chip 63. Is written by the first LED 64. Therefore, the correction data generation device 70 can generate correction data corresponding to each LED 64, and as a result, output correction defects can be prevented.
Note that the side registration adjustment value reset in step 101 can be obtained again by performing the above-described side registration adjustment again. Further, in step 101 described above, the side registration adjustment may not be performed without resetting the side registration adjustment value stored in the memory 31.
Also, at the time of factory shipment, for the reasons described above, it is preferable that correction data is generated, that is, light amount unevenness correction (density unevenness correction) is performed before the side registration adjustment is performed in each LPH 14Y, 14M, 14C, and 14K.

-Embodiment 2-
The present embodiment is substantially the same as the first embodiment. However, by providing the image data of the marker images MK1 and MK2 in each LPH 14, the side register adjustment values of the LPHs LPH14Y, 14M, 14C, and 14K are set. A desired test pattern can be obtained without resetting. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 9 is a block diagram showing the driver 65 of the LPH 14 in the present embodiment. The driver 65 includes a marker image storage unit 81 as storage means for storing marker image data corresponding to the marker images MK1 and MK2, and video data (Video Data) input from the image processing unit 40 or the marker image storage unit 81. Based on the correction data stored in the EEPROM 66, the selector 82 for switching the marker image data stored in the image data, the image data switching signal generator 83 for generating the switching signal of the image data output from the selector 82, and the EEPROM 66 A lighting clock number calculation unit 84 that calculates the lighting time of each LED 64 with respect to image data, and a serial / parallel conversion unit 85 that converts the calculated lighting time into parallel data and supplies the parallel data to each LED 64 are provided. Yes. Note that a page sync (Page_sync) is input from the image processing unit 40 to the marker image storage unit 81. The marker image storage unit 81 stores image data for forming a latent image by the first LED 64 in each LED chip 63.

  FIG. 10 shows a timing chart in the test pattern output processing according to the present embodiment. As shown in the figure, an image data valid period during which image data can be output while page sync is activated. At the first point of the image data valid period, the selector 82 is switched so that the image data switching signal is output from the image data switching signal generator 83 and the marker image data stored in the marker image storage unit 81 is output. Thereby, latent image formation and image formation based on marker image data are performed. Next, after a predetermined time has passed, the selector 82 is switched so that an image switching signal is output from the image data switching signal generator 83 and this time video data input from the image processor 40 is output. Thereby, latent image formation and image formation based on video data are performed. Then, before the predetermined period of time elapses and the image data valid period ends, the image data switching signal generation unit 83 outputs an image switching signal, and the marker image data stored in the marker image storage unit 81 is output again. The selector 82 is switched. Thereby, latent image formation and image formation based on marker image data are performed. In the following description, a period during which marker image data is output is referred to as a marker image output period, and a period during which video data is output is referred to as a video data output period.

  FIG. 11 schematically shows a test pattern formed by the above-described process. In the video data output period, as shown in FIG. 11A, for example, a black test image K (Cin50) of 50% density, a test image K (Cin30) of 30% density, and a test image K (20% density). Cin20) is output. On the other hand, in the marker image output period, for example, marker images MK1 and MK2 are output as shown in FIG. Therefore, the test pattern that is finally output is in a state where both are combined as shown in FIG.

  In this embodiment, since the marker image data is built in the driver 65 of each LPH 14, even if the side registration adjustment of each LPH 14 is performed, the marker images MK1 and MK2 are always the same LED 64, Specifically, writing is performed by the first LED 64 in each LED chip 63. Therefore, the correction data generation device 70 can generate correction data corresponding to each LED 64, and as a result, output correction defects can be prevented.

-Third embodiment-
The present embodiment is substantially the same as the first embodiment, but in addition to the side registration adjustment of each LPH 14 described above, the skew generated when the LPH 14 is mounted obliquely, and the LPH 14 is mounted in a bow shape. It defines the order of correction execution when various corrections such as the bow and the main scanning magnification adjustment performed to adjust the length of each LPH 14 in the main scanning direction are performed together with the creation of light quantity correction data. is there. In addition, in this Embodiment, about the thing similar to Embodiment 1, the code | symbol similar to Embodiment 1 is attached | subjected and the detailed description is abbreviate | omitted.

  FIG. 12 is a flowchart showing the flow of each adjustment process in the LPH 14. In this process, first, it is determined whether or not correction data (light amount correction data of each LED 64 in the LPH 14 described in the first embodiment) is to be created (step 201). Return to step 201. On the other hand, when creating correction data, it is next determined whether or not registration adjustments other than side registration, specifically bow adjustment, skew adjustment, and magnification adjustment in the main scanning direction are performed (step). 202). If adjustment is performed, bow adjustment, skew adjustment, and magnification adjustment in the main scanning direction are executed (step 203). On the other hand, when the adjustment is not performed, the process proceeds to the next step 204 as it is. Next, the side registration adjustment value set in each LPH 14 is reset (step 204), and a test pattern is output in a state where the side registration adjustment value is reset (step 205), and correction is performed using the output test pattern. Data is calculated (step 206). Steps 204 to 206 are as described in the first embodiment. Then, after the correction data is calculated, the side registration adjustment for each LPH 14 is executed (step 207), and the series of processing ends.

Next, the reason why bow adjustment, skew adjustment, and magnification adjustment in the main scanning direction are performed before the correction data is calculated in the above-described processing will be described.
First, skew adjustment will be described. The skew is a problem that occurs when the LPH 14 is mounted obliquely with respect to the photosensitive drum 12 or when the photosensitive drum 12 is mounted diagonally. Here, the skew will be specifically described. For example, as shown by a broken line in FIG. 13A, the skew is actually formed when it is desired to write a horizontal straight line in the main scanning direction using the LPH 14 (not shown). As shown by the solid line in the figure, the line is inclined. As shown in FIG. 13B, the skew correction is performed by adjusting the light emission timing of the LED 64 in the LPH 14 for each predetermined interval c (the interval c is set for each LED chip 63, for example). This electrically reduces the deviation in the oblique direction.

However, when such skew correction is performed, as shown in FIG. 13B, the line continuity is lost at the boundary point of the interval c, for example, the portion corresponding to the joint of the LED chip 63, and the sub-scanning is performed. A step in the direction is likely to occur. And when such a level | step difference is continuously formed in the subscanning direction, this site | part will emerge as a streak in an image.
Therefore, in the present embodiment, correction data used for light amount correction of each LED 64 is created after electrical skew correction is performed. Thereby, it becomes possible to obscure the level difference formed between the LED chips 63, and the generation of streaks in the image can be prevented.

  Bow is a problem that occurs when the LPH 14 is mounted on the photosensitive drum 12 in a curved state. In other words, the bow is such that when the LPH 14 is used to write a horizontal straight line in the main scanning direction, the actually formed line becomes a bow. The bow correction is performed by adjusting the light emission timing of the LED 64 in the LPH 14 at predetermined intervals, as in the skew correction described above. May cause streaks. Therefore, in the present embodiment, correction data used for light amount correction of each LED 64 is created after performing electrical bow correction. As a result, as in the case of skew correction, it is possible to obscure the level difference formed between the LED chips 63, and it is possible to prevent the generation of streaks in the image.

  Next, the magnification adjustment in the main scanning direction will be described. In each LPH 14, the actual position of each LED 64 varies depending on the mounting accuracy of the LED chip 63 and the mounting accuracy of each LED 64 in each LED chip 63. Then, when the same number of LEDs 64 are lit by different LPHs 14 and it is desired to write lines at equal intervals, the intervals differ depending on the colors. As shown in FIG. 14A, for example, when an image is formed using the n-6th LED 64 and the n + 1006th LED 64 with the LPH 14 of black and magenta, the position of the image to be formed is The situation that it shifts by color arises. The magnification correction in the main scanning direction is performed so that the intervals are electrically the same by thinning out the lighting signals in the LPH 14 where the intervals become longer. Specifically, when a signal as shown in FIG. 14B (turning on the n-6th and n + 1006th LEDs 64) is output to the magenta LPH 14, for example, n The signal for the + 1001st LED 64 is thinned out by one dot, and a signal as shown in FIG. 14C (the n-6th and n + 1005th LEDs 64 are turned on) is output. Adjustment is performed so that the same interval as the LPH 14 is obtained. The adjustment is also possible by increasing the signal for the black LPH 14 by one dot instead of subtracting the signal for the magenta LPH 14 by one dot.

However, in the case where oblique lines tilted in the main scanning direction are formed after performing such magnification correction in the main scanning direction, as shown in FIG. Steps in the sub-scanning direction are likely to occur before and after (n + 1001). If such a level difference is continuously formed in the sub-scanning direction, this portion appears as a streak in the image as in the above-described bow correction and skew correction.
Therefore, in the present embodiment, correction data used for correcting the amount of light of each LED 64 is created after correcting the magnification in the electrical main scanning direction. Thereby, it becomes possible to obscure the level difference before and after the thinned lighting signal, and it is possible to prevent the generation of streaks in the image.

  In the present embodiment, the LPH 14 in which the LED chips 63 are arranged in a straight line has been described. However, the LED chips 63 may be arranged in a staggered pattern to constitute the LPH 14. In this case, since the LED chip 63 is arranged in a state shifted in the sub-scanning direction, the lighting timing is adjusted by the LED chip 63 on the upstream side in the sub-scanning direction and the LED chip 63 on the downstream side in the sub-scanning direction. It is necessary to perform so-called staggered adjustment. Also in this case, as described above, the stagger adjustment is performed first, and then the correction data used for the light amount correction of each LED 64 is generated, so that the steps generated by arranging the LED chips 63 in a staggered manner (staggered steps). ) Can be obfuscated, and streaks in the image can be prevented.

1 is a diagram illustrating an overall configuration of an image forming apparatus. It is the figure which showed the structure of the LED print head (LPH). It is a circuit diagram which shows the relationship between an image output control part and LPH. It is a figure for demonstrating LPH of each color attached in the state which the position shift of the main scanning direction produced. It is a block diagram which shows the function structure of a correction data generation apparatus. It is a figure which shows typically the relationship between a LED array and the test pattern formed on a recording paper. It is a figure which shows typically the relationship between the line sensor provided in the reading part, and the test pattern formed on a recording paper. It is a flowchart which shows the setting procedure of correction data. FIG. 10 is a block diagram illustrating an LPH driver according to a second embodiment. It is a timing chart in the output process of a test pattern. (a)-(c) is the figure which showed typically the test pattern formed. It is a flowchart which shows the flow of each adjustment process in LPH. (a) is a diagram showing an image formed when skew occurs in LPH, and (b) is a diagram showing an image formed after skew correction. (a) is a diagram for explaining a magnification shift in the main scanning direction, (b) and (c) are diagrams showing an example of image data before and after magnification correction in the main scanning direction, and (d) is generated after magnification correction in the main scanning direction. It is a figure explaining a malfunction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Main body, 2 ... Personal computer (PC), 3 ... Image reader (IIT), 10 ... Image process system, 11Y, 11M, 11C, 11K ... Image forming unit, 12 ... Photosensitive drum, 13 ... Charger, DESCRIPTION OF SYMBOLS 14 ... LED print head (LPH), 15 ... Developing device, 21 ... Paper conveyance belt, 30 ... Image output control part, 40 ... Image processing part (IPS), 51 ... LED array, 52 ... Printed circuit board, 53 ... Selfock Lens array (SLA) 54 ... Housing 63 ... LED chip 64 ... LED 65 ... Driver 66 ... EEPROM 70 ... Correction data generator 71 ... Reading unit 72 ... Image data calculation unit 73 ... Uneven density Calculation unit 74 ... Correction data calculation unit 75 ... Correction data generation unit 76 ... Driver 77 ... Line sensor 81 ... Marker image storage unit 82 ... 83: Image data switching signal generator 84: Lighting clock number calculator 85: Serial / parallel converter

Claims (6)

A recording head in which a plurality of recording elements are arranged;
Side registration adjusting means for adjusting the side registration in the main scanning direction by shifting the output start position of the recording head to the recording element in the main scanning direction;
Input means for inputting test image data for adjusting the recording head to the recording head;
And an output unit that outputs the test image data input from the input unit using the recording head without performing side registration adjustment by the side registration adjustment unit.   The input means inputs, as the test image data, marker image data to be recorded by a specific recording element in the recording head and image data including density image data having the same density in the main scanning direction to the recording head. The image forming apparatus according to claim 1, wherein: Storage means for storing marker image data to be recorded by a specific recording element in the recording head;
2. The image forming apparatus according to claim 1, wherein the output unit outputs the marker image data input from the storage unit together with the test image data using the recording head. A method for adjusting a recording head in which a plurality of recording elements are arranged,
A light amount correction step for correcting the light amount of the plurality of recording elements;
A recording head adjustment method comprising: a side registration adjustment step of adjusting a side registration in a main scanning direction by shifting an output start position of the recording head with respect to the recording element after the light amount correction step is completed. A method for adjusting a recording head in which a plurality of recording elements are arranged,
A magnification correction step for electrically correcting a magnification in the main scanning direction of the recording element in the recording head;
And a light amount correction step of correcting a light amount of the plurality of recording elements after the magnification correction step is completed. A method for adjusting a recording head in which a plurality of recording elements are arranged,
A displacement correction step for electrically correcting a displacement in the sub-scanning direction of the recording element in the recording head;
And a light amount correction step of correcting light amounts of the plurality of recording elements after the positional deviation correction step is completed.

Images