JP2008179051A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of shortening a waiting time by the start of image formation. <P>SOLUTION: A controller 70 of the image forming apparatus reads out positional deviation information predetermined from a storing part 74 for storing the amount of positional deviation. From the amount of the positional deviation indicated by the positional deviation information, the amount of correction of light emitting timing to all the LED 52 is calculated to correct a positional deviation to the sub-scanning direction of the image indicated by an electrostatic latent image formed on the surface of a photo-conductor drum 30. Designating information for designating the quality of the image formed by an operating panel 76 is received, and the controller 70 determines the positional deviation information to be an object to be read out so that as the quality of the image indicated by the received designated information is low, the number of data of the positional deviation information to be read out is decreased. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus including a recording head in which a plurality of light emitting elements are arranged along a main scanning direction.

  Conventionally, an image forming apparatus that forms an image using an electrophotographic system such as a laser printer or a digital copying machine is known. Some image forming apparatuses of this type form a color image by superimposing four color toner images of yellow (Y), magenta (M), cyan (C), and black (K). As an example, there is a printer equipped with a long print head for each color in which light emitting elements such as LEDs (light emitting diodes) are arranged along the main scanning direction.

  When manufacturing such a long print head, it is ideal to manufacture the LEDs so that they are linearly arranged along the main scanning direction, but there are slight errors in manufacturing accuracy and manufacturing variations. If there is, the position of the dot recorded by the LED in the sub-scanning direction may deviate from the set value. Since the degree of this positional deviation differs for each print head, when recording a color image by overlaying a plurality of color images using the print head for each color as described above, each color image has a predetermined position. This causes a phenomenon (so-called “color misregistration”) that does not overlap with each other, resulting in a decrease in image quality.

As a technique for suppressing the deterioration in image quality due to this color misregistration, Patent Document 1 discloses, for each print head, data relating to the recording position in the sub-scanning direction of each dot recorded by each light emitting element of each print head. Store in advance in the storage unit, read out data relating to the recording position from the storage unit for each print head, and based on the read-out data, dot recording of the print heads of other colors relative to the dot recording position of the reference color print head A correction amount for each print head of the other color for calculating the positional deviation amount with respect to the sub-scanning direction within the predetermined amount is calculated, and each dot recording position of the print head of the other color is calculated. A technique for controlling the light emission timing of the light emitting element of each print head so as to move in the sub-scanning direction by a correction amount is disclosed.
JP 2006-88394 A

  By the way, when the technique of Patent Document 1 is applied, the image forming apparatus, when starting image formation, reads out data relating to the recording position from the storage unit for each print head and completes the calculation of the correction amount in the sub-scanning direction. Need to be.

  However, in an image forming apparatus provided with a long print head, the number of light emitting elements provided in the print head is large, so that the reading time for reading data relating to the recording position for each light emitting element from the storage unit becomes long. There is a problem that the waiting time until the start of image formation becomes long.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of shortening a waiting time until the start of image formation.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a recording head in which a plurality of light emitting elements are arranged along a main scanning direction, and a sub scanning direction in which a surface is charged and intersects the main scanning direction. An image holding body on which an electrostatic latent image showing an image is formed by light emission of each light emitting element of the recording head based on image information on the surface, and each light emission of the recording head A storage unit that stores in advance positional deviation information indicating the amount of positional deviation of the element in the sub-scanning direction, and a predetermined positional deviation information are read from the storage unit, and based on the positional deviation amount indicated by the positional deviation information, With respect to all the light emitting elements for correcting the positional deviation of the image indicated by the electrostatic latent image formed on the surface of the image carrier by the light emitting elements of the recording head with respect to the sub-scanning direction. Calculation means for calculating the correction amount of the light emission timing, reception means for receiving designation information for designating the image quality of the image to be formed, and reading by the calculation means as the image quality indicated by the designation information received from the reception means is lower Determining means for determining positional deviation information to be read by the calculating means so as to reduce the number of pieces of positional deviation information.

  According to the first aspect of the present invention, a plurality of light emitting elements are arranged along the main scanning direction on the surface of the image carrier that is charged in the surface and moves in the sub-scanning direction that intersects the main scanning direction. Each of the light emitting elements of the recording head thus formed emits light based on the image information, whereby an electrostatic latent image indicating an image is formed, and the light emitting element of the recording head in the sub-scanning direction is formed by the storage means. Misalignment information indicating the misalignment amount is stored in advance. The storage means includes a semiconductor storage element such as a RAM (Random Access Memory) and a flash memory, an xD picture card (xD-Picture Card (registered trademark)), a compact flash (CompactFlash (registered trademark)). ), A portable storage medium such as a microdrive (registered trademark), a fixed storage medium such as a hard disk, or an external storage device provided in a server computer connected to a network.

  Then, the present invention reads out the predetermined positional deviation information from the storage means by the calculating means, and forms it on the surface of the image carrier by each light emitting element of the recording head based on the positional deviation amount indicated by the positional deviation information. The correction amount of the light emission timing for all the light emitting elements for correcting the positional deviation of the image indicated by the electrostatic latent image in the sub-scanning direction is calculated. Specification information for specifying the image quality is received, and the determination unit reads the position deviation information read by the calculation unit so that the lower the image quality indicated by the specification information received from the reception unit, the less the number of pieces of positional deviation information read by the calculation unit. The target misalignment information is determined.

  As described above, according to the first aspect of the present invention, the predetermined positional deviation information is read, and the electrostatic latent image formed on the surface of the image holding body is based on the positional deviation amount indicated by the positional deviation information. The correction amount of the light emission timing for all the light emitting elements for correcting the positional deviation of the displayed image in the sub-scanning direction is calculated, and the specification information specifying the image quality of the image to be formed is received. Since the misregistration information to be read is determined so as to reduce the number of misregistration information data to be read as the displayed image quality is lower, the waiting time until the image formation starts becomes lower as the image quality of the image to be formed becomes lower. It can be shortened.

  According to a first aspect of the present invention, the determining means determines the positional deviation information to be read out including the positional deviation information of the light emitting elements at both ends of the recording head in the main scanning direction. Is preferred.

  Further, the determining means according to claim 1 or 2, wherein, as described in claim 3, when determining three or more pieces of misregistration information to be read, the main means of the light emitting element from which misregistration information is read out. It is preferable to determine misalignment information to be read so that the intervals in the scanning direction are uniform.

  According to a first aspect of the present invention, as in the fourth aspect, the calculating means reads the positional deviation information whose positional deviation amount is a predetermined amount or more from the storage means and calculates the correction amount. The determining unit may determine the predetermined amount to be a larger value as the image quality indicated by the designation information is lower.

  Further, according to a fourth aspect of the present invention, as in the fifth aspect, the storage means stores the positional deviation information of each light emitting element in the order of the positional deviation amount in the main scanning direction. May be stored in advance in the order of addresses in the storage area together with the position information indicating the position information, and the calculation means may read out the positional deviation information from the storage means in the order of addresses in the storage area.

  Further, according to the present invention, as described in claim 6, the recording head includes a plurality of unit recording heads in which a plurality of light emitting elements are arranged along the main scanning direction. The light emitting timing correction amount for the light emitting element may be calculated for each unit recording head.

  As described above, according to the present invention, predetermined positional deviation information is read out, and is indicated by an electrostatic latent image formed on the surface of the image carrier based on the positional deviation amount indicated by the positional deviation information. The light emission timing correction amount for all the light emitting elements for correcting the positional deviation of the generated image in the sub-scanning direction is calculated, and designation information designating the image quality of the image to be formed is received and indicated by the received designation information. Since the misalignment information to be read is determined so as to reduce the number of misalignment information to be read as the image quality is lower, the waiting time until the start of image formation is shortened as the image quality of the image to be formed becomes lower It has an excellent effect of being able to.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a color laser printer 10 (hereinafter referred to as a printer) which is an example of an image forming apparatus according to an embodiment of the present invention.

  As shown in the figure, the printer 10 includes image forming units 12Y, 12M, 12C, and 12K that respectively form yellow (Y), magenta (M), cyan (C), and black (K) toner images. The image forming units 12Y, 12M, 12C, and 12K are arranged in parallel to face the intermediate transfer belt 14, and the toner images of four colors are superimposed while the intermediate transfer belt 14 makes one turn. This is a so-called tandem full-color laser printer.

  The printer 10 includes a paper feed tray 16 at the bottom. A paper feed roll 18 is in contact with the leading end of the paper P set in the paper feed tray 16 in the transport direction, and the paper P is fed one sheet at a time by the paper feed roll 18 and a paper handling means (not shown). Paper is fed from the tray 16 to the downstream side in the transport direction. A pair of transport rolls 20 is arranged on the downstream side of the paper feed roll 18 in the transport direction, and the paper P is transported to the upper transfer unit 22 by the transport force from the transport roll 20.

  The transfer unit 22 is provided with a belt transport roll 24A around which the intermediate transfer belt 14 is wound, and a transfer roll 26 pressed against the belt transport roll 24A. The intermediate transfer belt 14 is sandwiched between the nip portion of the belt conveyance roll 24A and the transfer roll 26, and the toner image is transferred from the intermediate transfer belt 14 when the paper P passes through the nip portion.

  A fixing unit 28 is disposed downstream of the transfer unit 22 in the conveyance direction. The fixing unit 28 is provided with a heat roll 28A that becomes high temperature and a backup roll 28B that is pressed against the heat roll 28A, and the paper P passes through the nip portion between the heat roll 28A and the backup roll 28B. At this time, the toner is melted and solidified, fixed on the paper P, and discharged out of the apparatus.

  Here, the printing unit 11 in which the image forming units 12Y, 12M, 12C, and 12K superimpose the toner images on the intermediate transfer belt 14 will be described. Note that when distinguishing each color of yellow, magenta, cyan, and black, Y, M, C, and K are added after the code. However, if there is no need to distinguish each color, Y, M, C, and K are omitted.

  The intermediate transfer belt 14 includes the belt conveyance roll 24A described above, a belt conveyance roll 24B disposed on the left side of the belt conveyance roll 24A, and a belt conveyance roll 24C disposed obliquely below the belt conveyance roll 24A. , Is wrapped around. Image forming units 12Y, 12M, 12C, and 12K are sequentially arranged on the surface of the intermediate transfer belt 14 between the belt conveyance roll 24A and the belt conveyance roll 24B so as to face each other along the circumferential direction of the intermediate transfer belt 14. Thus, the toner images of the respective colors formed by the respective image forming units 12 are transferred so as to be superimposed on the intermediate transfer body belt 14.

  FIG. 2 shows a detailed configuration of the image forming unit 12 according to the present embodiment.

  As shown in the figure, the image forming unit 12 includes a cylindrical photosensitive drum 30 as an image holding member, and the photosensitive drum 30 is rotated in the arrow direction by a driving force of a motor (not shown). The intermediate transfer belt 14, the charge eliminating / cleaning device 34, the charging roller 36, and the developing device 38 are in contact with the photosensitive surface 31 of the photosensitive drum 30 in order along the rotation direction. Further, the light beam L is irradiated from the print head 40 to the photosensitive surface 31 between the charging roll 36 and the developing device 38.

  The charging roller 36 is applied with a predetermined bias voltage from a power source (not shown), and uniformly charges the abutting photosensitive surface 31.

  The print head 40 has a long shape in which a plurality of light emitting elements are arranged along a main scanning direction parallel to the axis of the photosensitive drum 30. The light emitting elements are arranged on the basis of image information. Make it emit light. Thereby, the potential of the region irradiated with the light beam on the photosensitive surface 31 is lowered, and an electrostatic latent image is formed.

  The developing device 38 includes a developing roll 38 </ b> A that can rotate about a rotation axis parallel to the photosensitive drum 30. The developing roll 38A is applied with a predetermined developing bias voltage from a power source (not shown) to charge the toner to a negative polarity, and rotates in the same direction as the rotation direction of the photosensitive drum 30 to transfer the charged toner to the photosensitive surface 31. Supply. That is, the developing device 38 rotates the developing roll 38A in the reverse direction with respect to the photosensitive drum 30 at the nip portion that contacts the photosensitive surface 31, and the developing efficiency of the toner from the developing roll 38A to the photosensitive drum 30 by the toner is improved. It is increasing. The electrostatic latent image formed on the photosensitive surface 31 is developed into a toner image (image) by the charged toner supplied from the developing device 38.

  A contact point (transfer position) with the intermediate transfer belt 14 is located downstream of the developing device 38 in the rotation direction, and the transfer roll 42 is sandwiched between the photosensitive drum 30 and the intermediate transfer belt 14. Is arranged. A positive transfer voltage having a polarity opposite to that of the toner is applied to the transfer roll 42 from a power source (not shown). The developed toner image on the photosensitive surface 31 is transferred to the intermediate transfer belt 14 when passing through the transfer position.

  Discharge / cleaning provided with a function of discharging the peripheral surface of the photosensitive drum 30 and a function of removing unnecessary toner remaining on the peripheral surface downstream of the transfer position on the peripheral surface of the photosensitive drum 30 in the rotation direction. A vessel 34 is provided. The peripheral surface of the photoconductive drum 30 after the toner image is transferred is cleaned by a static elimination / cleaning device 34.

  FIG. 3 is a cross-sectional view showing a detailed configuration of the print head 40 according to the present embodiment.

  As shown in the figure, the print head 40 includes an LED array 50 in which a plurality of LEDs 52 are arranged as light emitting elements in the main scanning direction. A selfoc lens array 60 is provided on the light emission side of the LED array 50. The light emitted from the LED array 50 is imaged on the photosensitive drum 30 via the SELFOC lens array 60. In the present embodiment, an LED is applied as the light-emitting element of the present invention. However, the present invention is not limited to this, and other light-emitting elements such as an EL (Electro-Luminescence) element may be applied.

  FIG. 4 shows a detailed configuration of the LED array 50 according to the present embodiment.

  As shown in the figure, the LED array 50 includes a plurality of LED chips 56 alternately arranged in a staggered manner in the sub-scanning direction on a printed circuit board 54. Each LED chip 56 includes: A plurality of LEDs 52 are linearly formed at predetermined intervals in the main scanning direction.

  In the LED array 50 according to the present embodiment, 57 LED chips 56 are arranged in a staggered pattern on a printed circuit board 54, and each LED chip 56 has 256 LEDs 52 formed linearly. However, in FIG. 4 and FIGS. 7, 8, 10, and 11 described later, the number of LED chips 56 and the number of LEDs 52 are reduced and shown in a simplified manner.

  FIG. 5 shows the configuration of the control system of the printer 10 for driving each print head 40.

  As shown in the figure, each print head 40 includes a print head driving unit 72 for driving the LED array 50 described above, and dots formed by the respective LEDs 52 of the LED array 50 measured when the print head 40 is manufactured. A misregistration amount storage unit 74 that prestores misregistration information indicating the misregistration amount with respect to the sub-scanning direction (for example, data indicating the misregistration amount of the LED 52 in the sub-scanning direction with respect to the design position).

  The printer 10 is provided with a controller 70. The controller 70 includes a microcomputer including a CPU, a ROM, a RAM, and the like, and controls the entire printer 10.

  The controller 70 is connected to a print head driving unit 72 provided in each print head 40. The light emission of each LED 52 constituting the LED array 50 is controlled by the print head driving unit 72. The print head drive unit 72 controls the light emission of each LED 52 of the LED array 50 based on the image information input from the controller 70. A latent image is formed on the photosensitive surface 31 of the photosensitive drum 30 by the light emission of each LED 52.

The controller 70 is connected to each misregistration amount storage unit 74 through a serial bus such as an I ² C bus (Inter Integrated Circuit Bus). The controller 70 uses the electrostatic latent image formed on the photosensitive surface 31 of the photosensitive drum 30 by each LED 52 of the print head 40 based on the positional shift amount indicated by the positional shift information stored in the positional shift amount storage unit 74. The correction amount of the light emission timing for all the LEDs 52 for correcting the positional deviation of the displayed image in the sub-scanning direction is calculated, and the light emission timing of each LED 52 is corrected based on the correction amount.

  In addition, the printer 10 according to the present embodiment is provided with an operation panel 76 that receives various designation inputs related to printing from the user, and can designate the image quality of an image to be formed.

  The controller 70 is connected to the operation panel 76, and designation information indicating the designated image quality is input from the operation panel 76.

  The controller 70 determines misregistration information to be read so that the lower the image quality indicated by the designation information received by the operation panel 76, the smaller the number of misregistration information data read from the misregistration amount storage unit 74. .

  FIG. 6 shows an example of the data structure of the misregistration information stored in the misregistration amount storage unit 74 of the print head 40 for each color.

  When the LED array 50 is configured by arranging a plurality of LED chips 56 on the printed circuit board 54 as in this embodiment, as shown in FIG. 7 due to manufacturing variations such as mounting errors of the LED chips 56. In addition, an error may occur in each LED 52 at a position in the sub-scanning direction.

  In the present embodiment, each LED 52 of the print head 40 is numbered sequentially from one side in the main scanning direction to identify each LED 52, and the position of each LED 52 in the main scanning direction is indicated. In FIG. 7, numbers in “” indicate numbers. Then, in the manufacture of the print head 40, as shown in FIG. 8, the amount of displacement of the LED chip 56 with respect to the design position of each LED 52 is obtained, and as shown in FIG. 6, the amount of displacement is stored in association with the number. Stored in the unit 74.

  Next, the operation of the printer 10 according to the present embodiment will be described.

  FIG. 9 is a flowchart showing the flow of the correction amount calculation processing program executed by the controller 70 when printing an image on the paper P is started. The program is stored in advance in a predetermined area of a ROM included in the controller 70.

  In step 100 in the figure, the misregistration information to be read from the misregistration amount storage unit 74 is determined according to the image quality indicated by the designation information received from the operation panel 76.

  Specifically, for example, when “low image quality”, “standard image quality”, and “high image quality” can be designated as the image quality on the operation panel 76, in this step 100, as shown in FIG. When the image quality indicated by the designation information is low, the positional deviation information of the two LEDs 52 (numbers “1” and “256” in FIG. 10) at both ends in the main scanning direction of each LED chip 56 is read. When the image quality indicated by the designation information is the standard image quality, the three LEDs 52 (numbers “1”, “128”, “256” in FIG. When the positional deviation information of the LED 52) is to be read and the image quality indicated by the designation information is high quality, each LED chip 56 has both ends in the main scanning direction, the center, and the middle between the ends and the center. Five LED 52 of (in FIG. 10 number, "1", "64", "128", "192", LED 52 of the "256") to determine the reading target positional displacement information.

  In the misregistration amount storage unit 74 according to the present embodiment, when the misregistration amounts read according to the image quality indicated by the designation information are duplicated, the addresses of the storage areas are sequentially read from the one read out with the lower image quality. They are stored in advance.

Specifically, as shown in FIG. 6, the LEDs 52 (the LEDs 52 with numbers “1” and “256” in FIG. 10) serving as both ends of each LED chip 56 to be read when the designated image quality is low. The amount of displacement, and then the amount of displacement of the central LED 52 (the LED 52 with the number “128” in FIG. 10) to be read when the designated image quality is the standard image quality, then the designated image quality is high. The information is stored in order from the amount of positional deviation of the above-mentioned intermediate LED 52 (numbers “64” and “128” in FIG. 10) read out in the case of image quality, and from the one read out with lower image quality. As a result, the controller 70 can read out all the necessary misregistration amounts by reading out the misregistration amounts in the order of addresses from the misregistration amount storage unit 74 according to the image quality indicated by the designation information. In the I ² C bus or the like, the data reading speed is improved by continuously reading data in the order of addresses in this way.

  In the next step 102, the misregistration information determined to be read in step 100 is read from the misregistration amount storage unit 74 of the print head 40 for each color.

  In the next step 104, based on the positional shift amount indicated by the read positional shift information, the positional shift amount of the LEDs 52 other than the read target is derived.

  In the present embodiment, for each LED chip 56, a straight line connecting the positional deviation amounts for the respective positions of the LEDs 52 to be read is obtained, and the positional deviation amounts of the LEDs 52 other than the reading target are calculated based on the straight lines. To derive.

  In FIG. 11, for example, when the image quality indicated by the designation information is low image quality, the positional deviation information of the LEDs 52 at both ends in the main scanning direction is read from the positional deviation amount storage unit 74 for each LED chip 56. An example of a straight line connecting the amount of positional deviation for each position of each LED 52 to be read is shown.

  In the next step 106, the correction amount of the light emission timing for each LED 52 for correcting the positional deviation in the sub-scanning direction for each LED 52 calculated in step 104 is calculated, and this correction amount calculation processing program is terminated.

  In the printer 10 according to the present embodiment, when an image is formed based on input image information, the light emission timing of each LED 52 is corrected by the correction amount obtained by the correction amount calculation processing program.

  By correcting the light emission timing in this manner, the amount of positional deviation in the sub-scanning direction caused by manufacturing variations of the print head is reduced, and thus the positional deviation is reduced (corrected).

  As described above, according to the present embodiment, the controller 70 reads out the predetermined positional deviation information from the positional deviation amount storage unit 74, and based on the positional deviation amount indicated by the positional deviation information, the photosensitive drum. The correction amount of the light emission timing for all the LEDs 52 for correcting the positional deviation in the sub-scanning direction of the image indicated by the electrostatic latent image formed on the surface of 30 is calculated. The controller 70 receives the designation information for designating the image quality, and determines the misregistration information to be read so that the controller 70 decreases the number of data of the misregistration information to be read as the image quality indicated by the accepted designation information is lower. Therefore, the lower the image quality of the image to be formed, the shorter the waiting time until the start of image formation.

  In the printer 10 according to the present embodiment, when the image quality indicated by the designation information is low image quality, the positional deviation information of the two LEDs 52 is to be read, and when the image quality is standard quality, the positional deviation information of the three LEDs 52 is read. In the above description, the positional deviation information of the five LEDs 52 is determined as a reading target when the image quality is high. However, the present invention is not limited to this, and is indicated by, for example, designation information. When the positional deviation information of the four LEDs 52 is to be read so that the intervals in the main scanning direction of the light emitting elements from which the positional deviation information is read out when the image quality is the standard image quality, and the image quality indicated by the designation information is high image quality The positional deviation information of the eight LEDs 52 is read so that the intervals in the main scanning direction of the light emitting elements from which the positional deviation information is read out are equal. Ri may be used as the target.

  Further, in the printer 10 according to the present embodiment, a straight line connecting the positional deviation amounts for the respective positions of the LEDs 52 to be read is obtained, and the positional deviation amounts of the LEDs 52 other than the reading target are derived based on the straight lines. Although the case where the correction amount of the light emission timing for each LED 52 is calculated has been described, the present invention is not limited to this. For example, for each LED chip 56, the amount of positional deviation of each LED 52 to be read is determined. The average value may be obtained, and the correction amount of the light emission timing of all the LEDs 52 of the LED chip 56 from which the average value was obtained may be calculated based on the average value.

  Further, the correction amount of the light emission timing of each LED 52 is included in each range divided into substantially equal ranges including one LED 52 whose LED chip 56 is to be read in the main scanning direction. It may be calculated on the basis of the amount of positional deviation of the LED 52 to be read.

  Further, in the misregistration amount storage unit 74 according to the present embodiment, when the misregistration amounts read according to the image quality overlap, the case of storing in order from the one read out with the lower image quality has been described. For example, as shown in FIG. 12, the positional deviation information of each LED 52 is stored together with positional information indicating the position of the LED 52 in the main scanning direction in descending order of the positional deviation amount. The controller 70 may store the information in advance in the address order, and the controller 70 may read out the positional deviation information whose positional deviation amount is a predetermined amount or more from the positional deviation amount storage unit 74 in the address order of the storage area and calculate the correction amount. In this case, the controller 70 may determine the predetermined amount as a larger value as the designated image quality is lower. Thereby, the lower the designated image quality is, the more data can be read out. In this case, for example, for each LED chip 56, the average value of the positional deviation amounts of the respective LEDs 52 to be read is obtained, and the light emission timings of all the LEDs 52 of the LED chip 56 from which the average value is obtained based on the average value. The amount of correction may be calculated. Further, when the LED chip 56 is divided into a plurality of substantially equal ranges with respect to the main scanning direction and the positional deviation amount of the LED 52 included in the range is read for each range, the LED chip 56 is based on the positional deviation amount. Thus, the correction amount of the light emission timing of each LED 52 in the range may be calculated.

  Furthermore, in the printer 10 according to the present embodiment, the case where the misregistration amount storage unit 74 is provided in each print head 40 has been described. However, the present invention is not limited to this, and for example, each print head 40 is provided with each print head 40. A storage unit that stores the unique serial number and the positional deviation information of each print head 40 in association with each other is provided in the printer 10 or an external device capable of mutually transmitting and receiving data, and the serial number of the print head 40 is controlled by the controller. 70 may be read out, and the corresponding misregistration information may be read out from the storage means.

  In addition, the configuration of the printer 10 described in the present embodiment (see FIGS. 1 to 3), the configuration of the LED array 50 (see FIGS. 4, 7, 8, 10, and 11) and the printer 10. The configuration of the control system (see FIG. 5) is an example, and it is needless to say that the control system can be changed as appropriate without departing from the gist of the present invention.

  Further, the data structure of the positional deviation information (see FIGS. 6 and 12) described in this embodiment is also an example, and it is needless to say that it can be appropriately changed without departing from the gist of the present invention.

  Furthermore, the processing flow of the correction amount calculation processing program (see FIG. 9) described in the present embodiment is also an example, and it goes without saying that it can be changed as appropriate without departing from the gist of the present invention.

1 is a configuration diagram illustrating a configuration of a printer according to an embodiment. 2 is a configuration diagram illustrating a detailed configuration of an image forming unit according to an embodiment. FIG. It is a block diagram which shows the detailed structure of the print head which concerns on embodiment. It is a block diagram which shows the detailed structure of the LED array which concerns on embodiment. FIG. 3 is a block diagram illustrating a configuration of a control system of the printer according to the embodiment. It is a schematic diagram which shows the data structure of the positional offset information which concerns on embodiment. It is a figure which shows an example of the print head in which the dispersion | variation in manufacture generate | occur | produced. It is a figure which shows an example of the positional offset amount with respect to the design position of LED of the LED chip which the dispersion | variation in manufacture generate | occur | produced. It is a flowchart which shows the flow of a process of the correction amount calculation processing program which concerns on embodiment. It is a figure which shows an example of LED used as the reading object according to the image quality which concerns on embodiment. It is a figure which shows an example of the straight line which connects the positional offset amount of each LED made into the reading object which concerns on embodiment. It is a schematic diagram which shows another example of the data structure of the positional offset information which concerns on embodiment.

Explanation of symbols

10 Printer 40 Print head (recording head)
30 Photosensitive drum (image carrier)
74 Position shift amount storage unit (storage means)
70 controller (calculation means, determination means)
76 Operation panel (reception means)

Claims (6)

A recording head in which a plurality of light emitting elements are arranged along the main scanning direction;
The surface is charged and moved in the sub-scanning direction intersecting the main scanning direction, and each light emitting element of the recording head emits light on the surface based on image information, thereby indicating an electrostatic latent image indicating an image. An image carrier on which an image is formed;
Storage means for storing in advance misregistration information indicating the misregistration amount of each light emitting element of the recording head with respect to the sub-scanning direction;
Predetermined misregistration information is read from the storage means, and based on the misregistration amount indicated by the misregistration information, an electrostatic latent image formed on the surface of the image carrier by each light emitting element of the recording head Calculating means for calculating a correction amount of the light emission timing for all the light emitting elements for correcting the positional deviation of the displayed image in the sub-scanning direction;
Accepting means for accepting designation information for designating the image quality of the image to be formed;
Determining means for determining misregistration information to be read by the calculating means so that the number of data of misregistration information read by the calculating means decreases as the image quality indicated by the designation information accepted by the accepting means decreases. When,
An image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the determination unit determines the positional deviation information to be read out including positional deviation information of light emitting elements at both ends in the main scanning direction of the recording head. When the determination unit determines three or more pieces of positional deviation information to be read, the positional deviation information to be read is set so that the intervals in the main scanning direction of the light emitting elements from which the positional deviation information is read are equalized. The image forming apparatus according to claim 1, wherein the image forming apparatus is determined. The calculation means reads the positional deviation information whose positional deviation amount is a predetermined amount or more from the storage means, calculates the correction amount,
The image forming apparatus according to claim 1, wherein the determination unit determines the predetermined amount to be a larger value as the image quality indicated by the designation information is lower. The storage means stores in advance the positional deviation information of each light emitting element in descending order of positional deviation amount together with positional information indicating the position of the light emitting element in the main scanning direction in the order of addresses in the storage area,
The image forming apparatus according to claim 4, wherein the calculation unit reads the misregistration information from the storage unit in the order of addresses of storage areas. The recording head comprises a plurality of unit recording heads arranged along the main scanning direction in which a plurality of light emitting elements are arranged along the main scanning direction,
The image forming apparatus according to claim 1, wherein the calculation unit calculates a correction amount of light emission timing for the light emitting element for each unit recording head.

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