Image forming apparatus and light emitting element head

Abstract

The present application provides an image forming apparatus and a light emitting element head. The image forming apparatus has: a toner image forming unit which forms a toner image using a first light emitting element column, a second light emitting element column, and an optical element for imaging light output of the light emitting element and exposing a photosensitive body to form a latent electrostatic image; a transfer unit which transfers the toner image to a recording medium; a fixing unit which fixes the toner image transferred to the recording medium to form an image; a switching unit which switches light emission of the first light emitting element column and the second light emitting element column at a switching position, the switching position being provided at any position in an overlapping position where the first light emitting element column and the second light emitting element column overlap; an acquisition unit which acquires information about a density difference at the switching position of the image formed on the recording medium; and a correction unit which corrects the density difference based on the information about the density difference.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an image forming apparatus and a light emitting element head. BACKGROUND

[0002] In an image forming apparatus such as a printer, a copier, a facsimile, and the like using an electrophotographic system, after a latent electrostatic image is obtained by irradiating an image information using a light recording unit on a charged photoreceptor, toner is applied to the latent electrostatic image to form a visible image, and after being transferred to a recording medium, the visible image is fixed, whereby image formation is performed. As the light recording unit, in addition to a light scanning system in which a laser is used to scan a laser in a main scanning direction and exposure is performed, in recent years, a light recording unit using a light emitting element head in which a plurality of light emitting elements such as LEDs (Light Emitting Diodes) are arranged in the main scanning direction has been adopted.

[0003] An image forming apparatus is disclosed in Japanese Patent Application Publication No. 2017-37217. In the image forming apparatus, a test pattern in which an image forming section is formed on a recording medium is read by a scanning section. A control section determines a density of a region corresponding to a chip of an LPH (LED Print Head) of an exposure device for each chip in an image of the test pattern read by the scanning section. The control section determines a correction amount of an amount of light of light emitted from the chip of the LPH according to the density of the image of the test pattern. The control section corrects the amount of light of the light emitted from the chip according to the specific correction amount. The image of the test pattern is formed again by the LPH whose amount of light is corrected, and the formed image is read by the scanning section. The control section determines the correction amount of the amount of light of the light emitted from the chip of the LPH according to the density of the image of the test pattern, and changes a coefficient for adjusting the correction amount using the specific correction amount and the correction amount of the last time. SUMMARY

[0004] However, it is difficult to manufacture a light emitting element head in which all light emitting elements are arranged in the main scanning direction on one substrate. Therefore, sometimes a method is adopted in which a plurality of substrates are arranged in the main scanning direction so as to be partially overlapped in a sub-scanning direction and in a staggered manner, and the light emitting elements are switched to emit light at the overlapped portions. However, in this case, an image formed on a recording medium sometimes has a density difference at a switching portion where switching is performed.

[0005] An object of the present disclosure is to provide an image forming apparatus and the like in which an image formed on a recording medium is less likely to have a density difference at a switching portion of a light emitting element, as compared to a case where a correction unit that corrects a density difference is not provided.

[0006] According to a first aspect of the present disclosure, there is provided an image forming apparatus including: a toner image forming unit that forms a toner image using a first light emitting element column, a second light emitting element column, and an optical element, the first light emitting element column being composed of light emitting elements arranged in a column shape in a main scanning direction, the second light emitting element column being composed of light emitting elements arranged in a column shape in the main scanning direction, at least a portion of the second light emitting element column being arranged in overlap with the first light emitting element column in a sub scanning direction, the optical element being used to image light output from the light emitting elements and expose a photoreceptor to light to form an electrostatic latent image; a transfer unit that transfers the toner image to a recording medium; a fixing unit that fixes the toner image transferred to the recording medium to form an image; a switching unit that causes the first light emitting element column and the second light emitting element column to emit light at a switching position, the switching position being provided at any position in an overlapping position where the first light emitting element column and the second light emitting element column overlap; an acquisition unit that acquires information about a density difference at the switching position of the image formed on the recording medium; and a correction unit that corrects the density difference based on the information about the density difference.

[0007] According to a second aspect of the present disclosure, the correction unit is a change mechanism that changes a distance between the first light emitting element column and the second light emitting element column and the photoreceptor.

[0008] According to a third aspect of the present disclosure, the change mechanism is a lifting mechanism that lifts at least one of the first light emitting element column and the second light emitting element column.

[0009] According to a fourth aspect of the present disclosure, the lifting mechanism lifts the first light emitting element column and the second light emitting element column at the same time.

[0010] According to a fifth aspect of the present disclosure, the correction unit is a light amount correction mechanism that corrects a light amount of the light emitting elements adjacent to the switching position.

[0011] According to a sixth aspect of the present disclosure, the acquisition unit acquires information about a density difference at the switching position of the image formed on the recording medium when a distance between at least one of the first light emitting element column and the second light emitting element column and the photoreceptor is changed.

[0012] According to a seventh aspect of the present disclosure, the correction unit moves at least one of the first light emitting element column and the second light emitting element column to a position where a density difference at the switching position is smallest in a result of visual inspection by a user as information about the density difference at the switching position.

[0013] According to a ninth aspect of the present disclosure, the correction unit corrects the light amount of the light emitting element to a light amount that eliminates the density difference, based on a reading result of an image when the distance between the first light emitting element column and the second light emitting element column and the photosensitive body is not changed.

[0014] According to a ninth aspect of the present disclosure, the correction unit corrects the light amount of the light emitting element to a light amount that eliminates the density difference, based on a reading result of an image when the distance between the first light emitting element column and the second light emitting element column and the photosensitive body is not changed.

[0015] According to a tenth aspect of the present disclosure, the correction unit corrects the light amount of the light emitting element in addition to the light amount of the light emitting element located at the overlapping position.

[0016] According to an eleventh aspect of the present disclosure, the first light emitting element column and the second light emitting element column are each configured by arranging a light emitting element array chip in which the light emitting elements are arranged in the main scanning direction.

[0017] According to a twelfth aspect of the present disclosure, there is provided a light emitting element head including: a first light emitting element column configured by light emitting elements arranged in a column shape in a main scanning direction; a second light emitting element column configured by light emitting elements arranged in a column shape in the main scanning direction, at least a portion of the second light emitting element column being arranged to overlap the first light emitting element column in a sub-scanning direction; an optical element for imaging light output from the light emitting elements and exposing a photosensitive body to form an electrostatic latent image; a switching unit that causes the first light emitting element column and the second light emitting element column to emit light at a switching position, the switching position being provided at any position in an overlapping position where the first light emitting element column and the second light emitting element column overlap; and a correction unit that corrects a density difference generated in an image formed on a recording medium at the switching position.

[0018] (EFFECTS)

[0019] According to the first aspect, it is possible to provide an image forming apparatus that is less likely to cause a density difference in an image formed on a recording medium at a switching position of a light emitting element, as compared to a case where a correction unit that corrects a density difference is not provided.

[0020] According to the second aspect, it is possible to correct a focus deviation generated in a light emitting element at a switching position of the light emitting element.

[0021] According to the third aspect, it is possible to more easily correct a focus deviation.

[0022] According to the 4th aspect, it is possible to correct the focus deviation by a simpler structure.

[0023] According to the 5th aspect, it is possible to correct the density difference at the switching position of the light emitting element by adjustment of the light amount.

[0024] According to the 6th aspect, it is possible to obtain information on the density difference generated at the switching position of the light emitting element.

[0025] According to the 7th aspect, it is possible to correct the density difference generated at the switching position of the light emitting element using the visual result of the user.

[0026] According to the 8th aspect, it is possible to correct the density difference generated at the switching position of the light emitting element based on the reading result of the image such as a test pattern.

[0027] According to the 9th aspect, it is possible to correct the density difference generated at the switching position of the light emitting element by adjustment of the drive signal.

[0028] According to the 10th aspect, it is possible to correct the density difference generated at a position other than the overlapping position.

[0029] According to the 11th aspect, it is possible to more easily form the 1st light emitting element row and the 2nd light emitting element row.

[0030] According to the 12th aspect, it is possible to provide a light emitting element head which is less likely to cause a density difference in an image formed on a recording medium at the switching position of the light emitting element, as compared with a case where a correction unit which corrects the density difference is not provided. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a diagram showing an outline of an image forming apparatus of the present embodiment.

[0032] Figure 2 is a diagram showing a structure of a light emitting element head to which the present embodiment is applied.

[0033] Figure 3 (a) of is a perspective view of a circuit board and a light emitting portion in a light emitting element head. Figure 3 (b) of is a view of the light emitting portion as viewed from Figure 3 (a) of is a view of the light emitting portion as viewed from the IIIb direction of

[0034] Figure 4 (a) to (b) of are diagrams for explaining a structure of a light emitting chip to which the present embodiment is applied.

[0035] Figure 5 is a diagram showing a structure of a signal generating circuit and a wiring structure of a circuit board in a case where a self-scanning type light emitting element array chip is employed as the light emitting chip.

[0036] Figure 6 is a diagram for explaining a circuit structure of a light emitting chip.

[0037] Figure 7 (a) to (b) of FIG. 8 are diagrams showing a relationship between a focus deviation and a concentration.

[0038] Figure 8 (a) to (d) of FIG. 9 are diagrams showing a focus deviation generated between LPH bars and an image formed when the focus deviation is generated.

[0039] Figure 9 is a block diagram showing a functional configuration example of a signal generating circuit in the present embodiment.

[0040] Figure 10 is a flowchart for explaining an operation of an image forming apparatus in a case where the acquisition unit is an image reading device and the correction unit is a focus adjustment pin.

[0041] Figure 11 (a) to (c) of FIG. 10 are diagrams showing an image of a test pattern printed out in step 101.

[0042] Figure 12 is a flowchart for explaining an operation of an image forming apparatus in a case where the acquisition unit is a UI and the correction unit is a focus adjustment pin.

[0043] Figure 13 is a flowchart for explaining an operation of an image forming apparatus in a case where the acquisition unit is an image reading device and the correction unit is a light amount correction mechanism.

[0044] Figure 14 (a) to (b) of FIG. 11 are diagrams showing a connection portion and light amount correction of LEDs adjacent to the connection portion. DETAILED DESCRIPTION

[0045] <Explanation of overall structure of image forming apparatus>

[0046] Hereinafter, an embodiment of the present disclosure will be explained in detail with reference to the drawings.

[0047] Figure 1 is a diagram showing an outline of the image forming apparatus 1 of the present embodiment.

[0048] The image forming apparatus 1 is an image forming apparatus generally called a tandem type. The image forming apparatus 1 has an image forming section 10 that forms an image corresponding to image data of each color. Also, the image forming apparatus 1 has an intermediate transfer belt 20 that sequentially transfers (primary transfer) and holds toner images of each color component formed in each image forming unit 11. Further, the image forming apparatus 1 has a secondary transfer apparatus 30 that collectively transfers (secondary transfer) the toner images transferred to the intermediate transfer belt 20 to a sheet P as an example of a recording medium. Further, the image forming apparatus 1 has a fixing apparatus 50 as an example of a fixing unit that fixes the toner images secondary transferred to the sheet P to form an image. Further, the image forming apparatus 1 has an image output control section 200 that controls each mechanism section of the image forming apparatus 1 and performs predetermined image processing on the image data.

[0049] Further, the image forming apparatus 1 has an image reading apparatus 300 that reads the image formed on the sheet P by the image forming section 10 in order to perform adjustment of the image. Further, the image forming apparatus 1 is composed of a touch panel or the like, and has a user interface (UI) 400 that outputs an instruction received from a user (operator) to the image output control section 200 and that prompts information from the image output control section 200 to the user.

[0050] The image forming section 10 has, for example, a plurality of (four in the present embodiment) image forming units 11 (specifically, 11Y (yellow), 11M (magenta), 11C (cyan), and 11K (black)) that form toner images of each color component in an electrophotographic manner. The image forming unit 11 is an example of a toner image forming unit that forms a toner image.

[0051] The image forming units 11 (11Y, 11M, 11C, 11K) have the same structure except for the color of the toner used. Therefore, the yellow image forming unit 11Y will be described as an example. The yellow image forming unit 11Y has a photosensitive layer not shown, and has a photosensitive drum 12 disposed so as to be rotatable in the direction of arrow A. A charging roller 13, a light emitting element head 14, a developer 15, a primary transfer roller 16, and a drum cleaner 17 are disposed around the photosensitive drum 12. Among these, the charging roller 13 is disposed so as to be rotatable and in contact with the photosensitive drum 12, and causes the photosensitive drum 12 to be charged to a predetermined potential. The light emitting element head 14 irradiates light to the photosensitive drum 12 charged to the predetermined potential by the charging roller 13, and writes an electrostatic latent image. The developer 15 contains a corresponding color component toner (in the yellow image forming unit 11Y, a yellow toner), and develops the electrostatic latent image on the photosensitive drum 12 with the toner. The primary transfer roller 16 primary transfers the toner image formed on the photosensitive drum 12 to the intermediate transfer belt 20. The drum cleaner 17 removes the residue (toner, etc.) on the photosensitive drum 12 after the primary transfer.

[0052] The photosensitive drum 12 functions as an image holding body that holds an image. Also, the charging roller 13 functions as a charging unit that charges the surface of the photosensitive drum 12, and the light emitting element head 14 functions as an electrostatic latent image forming unit (light emitting device) that forms an electrostatic latent image by exposing the photosensitive drum 12. Also, the developer 15 functions as a developing unit that develops the electrostatic latent image to form a toner image.

[0053] The intermediate transfer belt 20, which is an image transfer body, is tensioned and supported so as to be rotatable by a plurality of (five in this embodiment) support rollers. The drive roller 21 of these support rollers tensions the intermediate transfer belt 20, and drives the intermediate transfer belt 20 to rotate. Also, the tension rollers 22 and 25 tension the intermediate transfer belt 20, and rotate along with the intermediate transfer belt 20 driven by the drive roller 21. The correction roller 23 tensions the intermediate transfer belt 20, and functions as a deflection roller (disposed so as to be able to deflect with the axial end portion as a fulcrum) that restricts the meandering in the direction substantially perpendicular to the conveyance direction of the intermediate transfer belt 20. Also, the standby roller 24 tensions the intermediate transfer belt 20, and functions as a component of the secondary transfer device 30 described later.

[0054] Also, a belt cleaner 26 that removes the residue (toner, etc.) on the intermediate transfer belt 20 after the secondary transfer is disposed at the position opposite the drive roller 21 across the intermediate transfer belt 20.

[0055] As will be described later in detail, in the present embodiment, the image forming unit 11 forms a density correction image based on a predetermined density (reference patch, density correction toner image) for correcting the density of an image. This density correction image is an example of an image for adjusting the state of the apparatus.

[0056] The secondary transfer device 30 has a secondary transfer roller 31 arranged in pressure contact with the toner image bearing surface side of the intermediate transfer belt 20, and a backup roller 24 arranged on the back surface side of the intermediate transfer belt 20 to form a counter electrode of the secondary transfer roller 31. The backup roller 24 is in contact with a power roller 32 that applies a secondary transfer bias voltage of the same polarity as the polarity of the toner charge. On the other hand, the secondary transfer roller 31 is grounded.

[0057] In the image forming apparatus 1 of the present embodiment, a transfer unit that transfers a toner image to a sheet P is composed of the intermediate transfer belt 20, the primary transfer roller 16, and the secondary transfer roller 31.

[0058] Further, the sheet conveying system has a sheet tray 40, a conveying roller 41, a registration roller 42, a conveying belt 43, and a discharge roller 44. In the sheet conveying system, after the sheet P loaded on the sheet tray 40 is conveyed by the conveying roller 41, it is temporarily stopped at the registration roller 42, and then fed to the secondary transfer position of the secondary transfer device 30 at a predetermined timing. Further, the sheet P after secondary transfer is conveyed to the fixing device 50 by the conveying belt 43, and the sheet P discharged from the fixing device 50 is discharged outside the apparatus by the discharge roller 44.

[0059] The image reading device 300, also referred to as an on-line sensor, is arranged on the downstream side in the conveying direction of the sheet P with respect to the fixing device 50. Further, the image reading device 300 reads the image after the toner image is fixed to the sheet P by the fixing device 50.

[0060] The image reading device 300 has a light source, an optical system, and a CCD (Charge Coupled Device) sensor (not shown). Further, light emitted from the light source is irradiated to the image, and light reflected from the image is imaged on the CCD sensor via the optical system. In the CCD sensor, CCDs are arranged in a line as pixels that receive light reflected from the fixed image. In the present embodiment, the CCDs corresponding to each of R (Red), G (Green), and B (Blue) are arranged in three columns, and the toner image is measured in each of the colors of RGB. Note that, here, the image reading device 300 reads the image after being fixed to the sheet P, but can also read the (fixed) image formed on the intermediate transfer belt 20.

[0061] Next, the basic image forming process of the image forming apparatus 1 will be described. Now, if the start operation of the start switch not shown is performed, a predetermined image forming process is executed. Specifically, in the case where the image forming apparatus 1 is configured as a printer, for example, first, the image data externally input from a PC (personal computer) or the like is received by the image output control section 200. The received image data is subjected to image processing by the image output control section 200, and is supplied to the image forming units 11. Then, the image forming units 11 form toner images of respective colors. That is, the respective image forming units 11 (specifically, 11Y, 11M, 11C, 11K) are driven in accordance with digital image signals of respective colors. Next, in the respective image forming units 11, the photoreceptor drums 12 charged by the charging rollers 13 are irradiated with light corresponding to the digital image signals by the light emitting element heads (LPH) 14, whereby electrostatic latent images are formed. Then, the electrostatic latent images formed on the photoreceptor drums 12 are developed by the developers 15, whereby toner images of respective colors are formed. Also in the case where the image forming apparatus 1 is configured as a copying machine, as long as a document set on a document table not shown is read by a scanner, and the obtained read signal is converted into a digital image signal by a processing circuit, the formation of toner images of respective colors is performed in the same manner as described above.

[0062] After that, the toner images formed on the respective photoreceptor drums 12 are sequentially primary-transferred to the surface of the intermediate transfer belt 20 at a primary transfer position where the photoreceptor drums 12 and the intermediate transfer belt 20 contact each other, by the primary transfer rollers 16. On the other hand, the toner remaining on the photoreceptor drums 12 after the primary transfer is cleaned by the drum cleaners 17.

[0063] In this way, the toner images primary-transferred to the intermediate transfer belt 20 are superimposed on the intermediate transfer belt 20, and are carried to a secondary transfer position by the rotation of the intermediate transfer belt 20. On the other hand, the paper sheet P is carried to the secondary transfer position at a predetermined timing, and the paper sheet P is pinched by the secondary transfer roller 31 and the backup roller 24.

[0064] Then, the toner images held on the intermediate transfer belt 20 are secondary-transferred to the paper sheet P at the secondary transfer position by the action of a transfer electric field formed between the secondary transfer roller 31 and the backup roller 24. The paper sheet P on which the toner images are transferred is carried to the fixing device 50 by the carrying belt 43. In the fixing device 50, the toner images on the paper sheet P are fixed by being heated and pressed, and are then discharged to a paper discharge tray (not shown) provided outside the apparatus. On the other hand, the toner remaining on the intermediate transfer belt 20 after the secondary transfer is cleaned by the belt cleaner 26.

[0065] <Light emitting element head 14>

[0066] Figure 2is a view showing a structure of the light emitting element head 14 to which the present embodiment is applied.

[0067] The light emitting element head 14 has a housing 61, a light emitting section 63 having a plurality of LEDs as light emitting elements, a circuit board 62 on which the light emitting section 63 and a signal generating circuit 100 (to be described later Figure 5 ) and the like are mounted, and a rod lens (radial refractive index distribution type lens) array 64 as an example of an optical element for imaging light output from the LEDs and exposing the photosensitive drum 12 to form an electrostatic latent image.

[0068] The housing 61 is formed of, for example, metal, supports the circuit board 62 and the rod lens array 64, and is set so that the light emitting points of the light emitting section 63 coincide with the focal plane of the rod lens array 64. Also, the rod lens array 64 is arranged in the axial direction (main scanning direction) of the photosensitive drum 12.

[0069] <Explanation of the light emitting section 63>

[0070] Figure 3 (a) of FIG. 8 is a perspective view of the circuit board 62 and the light emitting section 63 in the light emitting element head 14.

[0071] As shown in (a) of FIG. 8, the light emitting section 63 has LPH bars 631a to 631c, focus adjustment pins 632a to 632b, and a signal generating circuit 100 as an example of a control unit that controls the light emission of the LEDs. Figure 3

[0072] The LPH bars 631a to 631c are arranged in a staggered manner in the main scanning direction on the circuit board 62. Also, two of the LPH bars 631a to 631c that are adjacent in the main scanning direction are arranged so that a part thereof overlaps in the sub-scanning direction, forming connection sections 633a to 633b. In this case, the connection section 633a is formed by the LPH bar 631a and the LPH bar 631b being arranged so as to overlap in the sub-scanning direction, and the connection section 633b is formed by the LPH bar 631b and the LPH bar 631c being arranged so as to overlap in the sub-scanning direction.

[0073] Also, in the following, the LPH bars 631a to 631c are sometimes simply referred to as LPH bars 631 without distinguishing them. Also, in the following, the focus adjustment pins 632a to 632b are sometimes simply referred to as focus adjustment pins 632 without distinguishing them. Also, in the following, the connection sections 633a to 633b are sometimes simply referred to as connection sections 633 without distinguishing them.

[0074] Figure 3 (b) of FIG. 8 is a view of the light emitting section 63 from the side of the circuit board 62. Figure 3 ​The image (a) showing the light-emitting part 63 viewed from direction IIIb is a magnified view of a portion of the light-emitting part 63. Figure 3 The diagram in (b) shows the connection 633a between LPH rod 631a and LPH rod 631b.

[0075] like Figure 3 As shown in (b), light-emitting chips C, as an example of light-emitting element array chips, are disposed on LPH bars 631a and 631b. The light-emitting chips C are arranged in two rows facing each other in a staggered pattern along the main scanning direction. For example, 60 light-emitting chips C are disposed on each of LPH bars 631a and 631b. These 60 light-emitting chips C are sometimes referred to as light-emitting chips C1 to C60 below. Furthermore, as shown, LEDs 71 are disposed on the light-emitting chips C. That is, in this case, the LEDs 71 are mounted on the light-emitting chips C in a predetermined number and arranged along the main scanning direction. The LEDs 71 are lit sequentially, with each light-emitting chip C facing the main scanning direction or in the opposite direction to the main scanning direction.

[0076] Furthermore, not shown here, LPH rod 631c has the same structure as LPH rods 631a and 631b. Also, connecting portion 633b has the same structure as connecting portion 633a.

[0077] Based on the structure described above, the plurality of LEDs 71 disposed on LPH bar 631a and LPH bar 631c can be configured as a first light-emitting element column consisting of LEDs 71 arranged in a column in the main scanning direction. Furthermore, the plurality of LEDs 71 disposed on LPH bar 631b can be configured as a second light-emitting element column, at least a portion of which overlaps with the first light-emitting element column in the sub-scanning direction and consists of LEDs 71 arranged in a column in the main scanning direction.

[0078] Furthermore, the connecting portions 633a to 633b can be configured as an overlapping portion where the first light-emitting element row and the second light-emitting element row overlap.

[0079] Furthermore, it can be said that the first light-emitting element column and the second light-emitting element column are respectively formed by arranging light-emitting chips C, wherein LEDs 71 are arranged in the main scanning direction.

[0080] Furthermore, in the connecting portions 633a to 633b, the first and second light-emitting element rows are switched at a switching point Kp located at any position within this portion. That is, the LPH rod 631 to be illuminated is switched at this switching point Kp. In this case, the order in which the LPH rods 631 that illuminate the LED 71 is LPH rod 631a → LPH rod 631b → LPH rod 631c.

[0081] exist Figure 3 In (b), LED71, indicated by a white circle, is lit, while LED71, indicated by a black circle, is not lit. That is, in Figure 3 (b) shows the switching at the switching point Kp, where the illumination of LED 71 on LPH lever 631a is switched to the illumination of LED 71 on LPH lever 631b. Moreover, on the left side of the diagram of the switching point Kp, LED 71 on LPH lever 631a is illuminated, while on the right side of the diagram of the switching point Kp, LED 71 on LPH lever 631b is illuminated.

[0082] The switching point Kp can be freely set in the connecting parts 633a to 633b, and the switching is controlled by the signal generating circuit 100. Thus, the signal generating circuit 100 functions as a switching unit that causes the first light-emitting element row and the second light-emitting element row to switch light emission at the switching point Kp.

[0083] The circuit board 62 can be moved along the focus adjustment pins 632a-632b. Figure 3 The circuit board 62 can move in the up-down direction as indicated by the double-headed arrows in (a). That is, the circuit board 62 can be raised and lowered. Furthermore, by raising and lowering the circuit board 62, the distance between the light-emitting part 63 and the photosensitive drum 12 can be changed. As a result, the distance between the LPH rods 631a-631c and the photosensitive drum 12 is changed, allowing adjustment of the focus of the light output emitted from the LED 71 and imaged on the photosensitive drum 12. Additionally, the circuit board 62 can be moved upwards on both the focus adjustment pin 632a and focus adjustment pin 632b sides using the focus adjustment pins 632a-632b. It can also be moved downwards on both the focus adjustment pin 632a and focus adjustment pin 632b sides. Moreover, it can be moved upwards on either the focus adjustment pin 632a or focus adjustment pin 632b side, and downwards on the other side. The focus adjustment pins 632a to 632b can operate under the control of the signal generation circuit 100 or manually.

[0084] The focus adjustment pins 632a to 632b can be understood as an example of a lifting mechanism that raises or lowers at least one of the first light-emitting element row and the second light-emitting element row.

[0085] <Description of the LED array chip>

[0086] Figure 4 Figures (a) to (b) illustrate the structure of the light-emitting chip C to which this embodiment is applied.

[0087] Figure 4 (a) is a diagram showing the light-emitting chip C as viewed from the direction of light emitted by the LED. Furthermore,Figure 4 (b) is Figure 4 (a) Sectional view of IVb-IVb.

[0088] As an example of a light-emitting element array, a plurality of LEDs 71 are arranged at equal intervals on the light-emitting chip C, and the plurality of LEDs 71 are arranged in a row in the main scanning direction. Furthermore, pads 72 are arranged at both ends of the substrate 70, with the light-emitting element array separated by a gap; these pads 72 are examples of electrode portions used for inputting and outputting signals driving the light-emitting element array. Moreover, each LED 71 has a microlens 73 formed on the side where light is emitted. Through these microlenses 73, the light emitted from the LED 71 can be concentrated, and the light can be efficiently incident onto the photoreceptor drum 12 (see reference 12). Figure 2 ).

[0089] Preferably, the microlens 73 is made of a transparent resin such as a photocurable resin, and the surface of the microlens 73 is aspherical in order to concentrate light more efficiently. Furthermore, the size, thickness, focal length, etc. of the microlens 73 are determined according to the wavelength of the LED 71 used and the refractive index of the photocurable resin used.

[0090] <Description of Self-Scanning Light Emitting Array Chip>

[0091] Furthermore, in this embodiment, as an example of a light-emitting chip C, a self-scanning light-emitting device (SLED) chip is preferably used. The self-scanning light-emitting device chip is configured to enable the self-scanning of the light-emitting elements using light-emitting thyristors with a pnpn structure, which are components of the light-emitting device array chip.

[0092] Figure 5 This is a diagram showing the structure of the signal generation circuit 100 and the wiring structure of the circuit board 62 when a self-scanning light-emitting element array chip is used as the light-emitting chip C.

[0093] In the signal generation circuit 100, the image output control unit 200 (see reference) Figure 1 The input includes various control signals such as the horizontal synchronization signal Lsync, image data Vdata, clock signal clk, and reset signal RST. Furthermore, the signal generation circuit 100 outputs light-emitting signals to each of the light-emitting chips C (C1 to C60) based on various externally input control signals, such as reordering the image data Vdata and correcting the output value. In addition, in this embodiment, the light emission signal They are supplied one by one to each of the light-emitting chips C (C1 to C60).

[0094] And, the signal generating circuit 100 outputs the start transmission signal to each light emitting chip C1-C60 according to various control signals inputted from the outside The first transmission signal And the second transmission signal

[0095] The circuit board 62 is provided with a power supply line 101 of Vcc=-5.0V connected to the Vcc terminal of each light emitting chip C1-C60 for power supply and a power supply line 102 connected to the GND terminal for grounding. And, the circuit board 62 is further provided with a start transmission signal line 103, a first transmission signal line 104, and a second transmission signal line 105 which transmit the start transmission signal of the signal generating circuit 100 The first transmission signal The second transmission signal And, the circuit board 62 is further provided with 60 light emitting signal lines 106 (106_1-106_60) which output the light emitting signal of the signal generating circuit 100 to each light emitting chip C (C1-C60) In addition, the circuit board 62 is provided with 60 light emitting current limiting resistors RID for preventing the flow of excess current in the 60 light emitting signal lines 106 (106_1-106_60). And, as will be described later, the light emitting signal Can take two states of high level (H) and low level (L) respectively. And, the low level is a potential of -5.0V and the high level is a potential of ±0.0V.

[0096] Figure 6 Is a diagram for explaining the circuit structure of the light emitting chip C (C1-C60).

[0097] The light emitting chip C has 60 transmission thyristors S1-S60 and 60 light emitting thyristors L1-L60. In addition, the light emitting thyristors L1-L60 have the same pnpn connection as the transmission thyristors S1-S60, and by utilizing the pn connection therein, also function as light emitting diodes (LEDs). And, the light emitting chip C has 59 diodes D1-D59 and 60 resistors R1-R60. Furthermore, the light emitting chip C has 60 light emitting current limiting resistors RID for preventing the flow of excess current supplied with the first transmission signal The second transmission signal And the start transmission signal excess current flowing in the signal line. In addition, the light emitting thyristors LI to L60 constituting the light emitting element array 81 are arranged in the order of LI, L2,..., L59, L60 from the left side of the figure, forming a light emitting element column. Further, the transfer thyristors SI to S60 are also arranged in the order of SI, S2,..., S59, S60 from the left side of the figure, forming a switching element column, i.e., a switching element array 82. Moreover, the diodes DI to D59 are also arranged in the order of DI, D2,..., D58, D59 from the left side of the figure. Further, the resistors Rl to R60 are also arranged in the order of Rl, R2,..., R59, R60 from the left side of the figure.

[0098] Next, the electrical connection of each element in the light emitting chip C will be described.

[0099] The anode terminals of each of the transfer thyristors SI to S60 are connected to a GND terminal. A power supply line 102 (see FIG. 2) is connected to this GND terminal, and is grounded. Figure 5

[0100] Further, the cathode terminals of the odd-numbered transfer thyristors SI, S3,..., S59 are connected to a first transfer signal line 104 (see FIG. 2) via transfer current limiting resistors RIA, respectively. A first transfer signal is supplied to this first transfer signal line 104. Figure 5

[0101] On the other hand, the cathode terminals of the even-numbered transfer thyristors S2, S4,..., S60 are connected to a second transfer signal line 105 (see FIG. 2) via transfer current limiting resistors R2A, respectively. A second transfer signal is supplied to this second transfer signal line 105. Figure 5

[0102] Further, the gate terminals Gl to G60 of each of the transfer thyristors SI to S60 are connected to a Vcc terminal via the resistors Rl to R60, respectively, which are provided corresponding to each of the transfer thyristors SI to S60. A power supply line 101 (see FIG. 2) is connected to this Vcc terminal, and is supplied with a power supply voltage Vcc (-5.0 V). Figure 5

[0103] Further, the gate terminals Gl to G60 of each of the transfer thyristors SI to S60 are connected one-to-one to the gate terminals of the same-numbered light emitting thyristors LI to L60, respectively.

[0104] ​​​​​​​​Further, the anode terminal of the diode Dl, that is, the gate terminal Gl of the transfer thyristor Sl is connected to the GND terminal via a transfer current limiting resistor R3A. A start transfer signal

[0105] Further, the anode terminal of the diode Dl, that is, the gate terminal Gl of the transfer thyristor Sl is connected to the GND terminal via a transfer current limiting resistor R3A. A start transfer signal terminal. The start transfer signal is supplied to the terminal via a start transfer signal line 103 (refer to Figure 5 ).

[0106] Next, the anode terminal of each of the light emitting thyristors Ll to L60 is connected to the GND terminal as with the anode terminal of each of the transfer thyristors Sl to S60.

[0107] Further, the cathode terminal of each of the light emitting thyristors Ll to L60 is connected to the terminal. The terminal is connected to a light emission signal line 106 (light emission signal line 106_1 in the case of the light emitting chip Cl: refer to Figure 5 ), and is supplied with a light emission signal (light emission signal in the case of the light emitting chip Cl). In addition, the other light emitting chips C2 to C60 are respectively supplied with the corresponding light emission signal

[0108]

[0109] In the present embodiment, as described above, the LPH bars 631 that light up the LED 71 are switched in the order of the LPH bar 631a → the LPH bar 631b → the LPH bar 631c. However, at this time, sometimes a focal point deviation occurs between each of the LPH bars 631. Further, if the focal point deviation occurs, the density of the image formed on the paper P is different.

[0110] Figure 7 (a) to (b) of FIG. 10 are graphs showing the relationship between the focal point deviation and the density.

[0111] The image formed in the image forming apparatus 1 described above is composed of dots. Further, the dots are composed of a plurality of points Dt. Moreover, Figure 7 (a) of FIG. 11 is a graph showing the shape of the point Dt formed when the focal point is aligned and the density distribution of the point Dt. Further, Figure 7 ​​(b) is a diagram showing the shape of point Dt formed when the focus is not aligned and the concentration distribution of point Dt.

[0112] like Figure 7 As shown in (a), when the focus is aligned, the light distribution around the halftone dot becomes clearer, and the density distribution of the dot point Dt becomes clearer. As a result, the shape of the dot Dt is more easily reduced. In contrast, as... Figure 7 As shown in (b), when the focus is not aligned, the density distribution of the dots becomes wider, and the density of the dots Dt becomes wider. As a result, the shape of the dots Dt is more likely to become larger. That is, if a focus deviation occurs, the density distribution and size of the resulting dots will differ, resulting in differences in the density of the resulting image.

[0113] Figure 8 Figures (a) to (d) are diagrams showing the focus deviation generated between LPH rods 631 and the images formed when the focus deviation occurs.

[0114] in, Figure 8 Figure (a) shows an example where the focal length differs at the respective connection 633 of adjacent LPH bars 631, resulting in focus deviation. In this figure, the length of the arrow represents the focal length, indicating the variation of the focal length relative to the main scanning direction. In this case, it indicates that the focal length differs at the connection 633a-633b of LPH bars 631a-631c, resulting in focus deviation.

[0115] In this case, a concentration difference is generated at the switching point Kp between the connecting parts 633a and 633b. As a result, as... Figure 8 As shown in (b), the resulting image exhibits uneven density at the connection points 633a to 633b.

[0116] and, Figure 8 Figure (c) shows an example where the focal length is inherently different for each LPH bar 631, resulting in focus deviation. Similarly, in this figure, the length of the arrow indicates the focal length, representing the change in focal length relative to the main scanning direction. This also indicates that the focal length differs at the connection points 633a to 633b between LPH bars 631a and LPH bars 631c, resulting in focus deviation.

[0117] In this case, a concentration difference is generated at the switching point Kp between the connecting parts 633a and 633b. As a result, as... Figure 8 As shown in (d), the resulting image exhibits uneven density at the connection portions 633a to 633b.

[0118] <Explanation of the method for correcting the concentration difference generated by Kp at the switching site>

[0119] Therefore, in this embodiment, the problem is suppressed by setting the following two units: an acquisition unit that acquires information about the concentration difference at the switching part Kp of the image formed on the paper P; and a correction unit that corrects the concentration difference based on the information about the concentration difference.

[0120] In this case, the acquisition unit is, for example, an image reading device 300. That is, it can acquire information related to the concentration difference at the switching point Kp by reading an image on the paper P. Furthermore, the acquisition unit is, for example, a UI 400. That is, by having a user who observes an image formed on the paper P input information about the presence and degree of the concentration difference into the UI 400, information related to the concentration difference at the switching point Kp can be acquired.

[0121] Furthermore, the correction unit is, for example, a mechanism for changing the distance between the first and second light-emitting element rows and the photoreceptor. Specifically, the mechanism is, for example, a... Figure 3 The focus adjustment pins 632a to 632b described in (a) allow the distance between the light-emitting part 63 and the photoreceptor to be changed by moving the circuit board 62 up and down. However, the changing mechanism is not limited to the focus adjustment pins 632a to 632b. For example, a mechanism that changes the distance between the light-emitting part 63 and the photoreceptor by moving the photoreceptor drum 12 could also be used.

[0122] In addition, such as Figure 3 As explained in (a), the focus adjustment pins 632a to 632b are mechanisms for raising and lowering the circuit board 62, and the LPH rods 631a to 631c rise and fall together with the circuit board 62. It can also be said that the focus adjustment pins 632a to 632b raise and lower the first and second light-emitting element rows together.

[0123] Alternatively, the lifting mechanism can be configured to independently raise and lower each of the LPH rods 631a to 631c. This lifting mechanism can be implemented, for example, by providing focus adjustment pins 632 at both ends of the length direction of each of the LPH rods 631a to 631c. In this case, the distance between the light-emitting part 63 and the photoreceptor can be independently changed for each of the LPH rods 631a to 631c. Therefore, compared with [the previous method]... Figure 3 Compared to the lifting mechanism of the focus adjustment pins 632a to 632b described in (a), it is possible to adjust the distance between the light-emitting part 63 and the photosensitive element more finely.

[0124] Furthermore, the correction unit can also be configured as a light quantity correction mechanism to correct the light quantity of the LED 71 adjacent to the switching section Kp. That is, it corrects the light quantity of the LED 71 adjacent to the switching section Kp, similar to correcting the concentration difference mentioned above. This light quantity correction mechanism can be understood as one of the functions of the signal generation circuit 100.

[0125] <Explanation of functional configuration of signal generating circuit 100>

[0126] Next, the functional configuration of the signal generating circuit 100 at the time of processing the concentration difference generated at the switching position Kp will be explained.

[0127] Figure 9 is a block diagram showing an example of the functional configuration of the signal generating circuit 100 in the present embodiment. Also, Figure 9 In the present embodiment, the functions of the signal generating circuit 100 that are relevant to the present embodiment are selected from among various functions that the signal generating circuit 100 has and are illustrated.

[0128] As illustrated, the signal generating circuit 100 has an information acquiring section 111 that acquires image data and the like, a correction amount acquiring section 112 that calculates a correction amount for correcting the concentration difference, a switching control section 113 that controls switching of the LEDs 71 between the LPH bars 631, and a drive signal generating section 114 that generates a drive signal.

[0129] The information acquiring section 111 receives image data from the image output control section 200. As described above, this image data can be used to perform image processing and the like on image data inputted from the outside, such as a PC, at the image output control section 200 and form an image at the image forming unit 11. Specifically, the image processing is, for example, a rasterizing process, a color conversion process, a build-up height process, a screen process, and the like.

[0130] Also, the information acquiring section 111 acquires information related to the concentration difference at the switching position Kp from the image reading device 300 or the UI 400 that functions as a correction unit.

[0131] The correction amount acquiring section 112 calculates a correction amount for correcting the concentration difference based on the information related to the concentration difference at the switching position Kp acquired by the information acquiring section 111. In the case where the correction unit is the changing mechanism that changes the distance between the first and second light emitting element columns and the photosensitive body, this correction amount is the amount of change in the distance. Also, in the case where the correction unit is the focus adjustment pin 632a to 632b, this correction amount is the amount of lifting of the circuit board 62. Also, in the case where the correction unit is the light amount correction mechanism, this correction amount is the correction amount of the light amount of the LEDs 71 adjacent to the switching position Kp.

[0132] The switching control section 113 performs control of switching the LPH bars 631 to be lit at the switching position Kp.

[0133] The drive signal generating section 114 generates a drive waveform for lighting the LEDs 71 and outputs it as a drive signal. Specifically, for example, the above-mentioned light emitting signal Start transmission signal the first transmission signal and the second transmission signal the driving waveform, and outputs it as a driving signal. In addition, in the case where the correction unit is a light amount correction mechanism, a driving signal corresponding to the correction amount of the light amount of the LED 71 is output. Specifically, the light amount of the LED 71 can be corrected by adjusting at least one of the voltage, the current, and the output time of the driving signal.

[0134] <Explanation of the operation of the image forming apparatus 1>

[0135] Next, the operation of the image forming apparatus 1 when correcting the density difference generated at the switching position Kp will be explained.

[0136] Figure 10 is a flowchart explaining the operation of the image forming apparatus 1 in the case where the acquisition unit is the image reading apparatus 300 and the correction unit is the focus adjustment pin 632a to 632b.

[0137] First, the focus adjustment pin 632a to 632b is moved, and the circuit board 62 is set to a plurality of lift amounts that are predetermined to print a test pattern (step 101).

[0138] Figure 11 (a) to (c) of FIG. 10 are graphs showing the image Tp of the test pattern printed in step 101. The test pattern is composed of gray images whose densities are changed to 20%, 30%, 40%, 50%, and 60%.

[0139] wherein Figure 11 (b) of FIG. 10 shows the image Tp of the test pattern when printing is performed without moving the focus adjustment pin 632a to 632b. Also, Figure 11 (a) of FIG. 10 shows the image Tp of the image of the test pattern when printing is performed with the focus adjustment pin 632a to 632b moved and the circuit board 62 moved in the upward direction by βμm (+βμm). Also, Figure 11 (c) of FIG. 10 shows the image Tp of the image of the test pattern when printing is performed with the focus adjustment pin 632a to 632b moved and the circuit board 62 moved in the downward direction by βμm (-βμm).

[0140] Also, the image Tp of the image of the test pattern is shown in the case where a density difference is generated at the switching position Kp.

[0141] Returning to Figure 10 Next, the image reading apparatus 300 reads the image Tp of the image of the test pattern (step 102).

[0142] Further, the information acquisition section 111 of the signal generating circuit 100 acquires image information of the test pattern from the image reading device 300 (step 103).

[0143] Then, the correction amount acquisition section 112 finds the positions of the LPH bars 631a to 631c in which the density difference is eliminated based on the reading result of the test pattern (step 104).

[0144] Further, the LPH bars 631a to 631c are moved to the positions by the focus adjustment pins 632a to 632b (step 105). That is, the LPH bars 631 are moved to the positions.

[0145] Figure 12 is a flowchart for explaining the operation of the image forming apparatus 1 in the case where the acquisition unit is the UI 400 and the correction unit is the focus adjustment pins 632a to 632b.

[0146] First, the focus adjustment pins 632a to 632b are moved, and the circuit board 62 is set to print the test pattern as shown in Figure 11 (step 201) at a plurality of lift amounts which are predetermined.

[0147] Next, the user observes the images Tp of the test patterns, selects the image Tp of the test pattern in which the density difference at the switching position Kp is the smallest, and inputs to the UI 400 (step 202). In this case, it can be said that the UI 400 as the acquisition unit acquires the information of the positions of the LPH bars 631a to 631c in which the density difference at the switching position Kp is the smallest in the result of the user's visual observation, as the information related to the density difference at the switching position Kp.

[0148] Then, the correction amount acquisition section 112 acquires the positions of the circuit board 62 in which the density difference at the switching position Kp is the smallest (step 203).

[0149] Further, the LPH bars 631a to 631c are moved to the positions by the focus adjustment pins 632a to 632b (step 204).

[0150] In addition, it can also be said that in the manner explained in Figure 11 , 12 , the image reading device 300 or the UI 400 as the acquisition unit acquires the information related to the density difference at the switching position Kp of the image formed on the paper P when the distance between at least one of the first light emitting element column and the second light emitting element column and the photosensitive body is changed.

[0151] Figure 13 is a flowchart for explaining the operation of the image forming apparatus 1 in the case where the acquisition unit is the image reading device 300 and the correction unit is the light amount correction mechanism.

[0152] First, the test pattern is printed without moving the focus adjustment pins 632a to 632b (step 301). In this case, the test pattern is as shown in (b) of FIG. 10. Figure 11

[0153] Next, the image reading apparatus 300 acquires the image Tp of the test pattern (step 302). It can also be said that the image reading apparatus 300 as the acquisition unit acquires information about the density difference at the switching position Kp of the image formed on the paper P without changing the distance between the first and second light emitting element columns and the photosensitive body.

[0154] Further, the information acquisition unit 111 of the signal generating circuit 100 acquires the image information of the test pattern from the image reading apparatus 300 (step 303).

[0155] Then, the correction amount acquisition unit 112 calculates the light amount of the LED 71 that eliminates the density difference based on the reading result of the test pattern (step 304).

[0156] Further, the drive signal generation unit 114 corrects the light amount of the LED 71 to the light amount calculated by the correction amount acquisition unit 112 (step 305).

[0157] Also at this time, the light amount of the LED 71 adjacent to the connection portion 633 is corrected at the same time in addition to the LED 71 at the connection portion 633.

[0158] Figure 14 (a) to (b) of FIG. 11 are diagrams showing the light amount correction of the connection portion 633 and the LED 71 adjacent to the connection portion 633. Here, the density of the image with respect to the main scanning direction is shown.

[0159] Figure 14 (a) of FIG. 12 shows the density of the image before the light amount correction. Further, it is shown that the density difference is generated at the connection portion 633a of the LPH rod 631a and the LPH rod 631b. That is, at the connection portion 633a, the density difference is generated between the LED of the light emitting chip C60 of the LPH rod 631a and the LED of the light emitting chip C1 of the LPH rod 631b.

[0160] On the other hand, Figure 14 ​(b) shows the density of the image after the light amount correction. In this case, the light amount of the LED of the light emitting chip C1 of the LPH bar 631b is corrected and made uniform with the light amount of the LED of the light emitting chip C60 of the LPH bar 631a. Here, if only the light amount of the LED of the light emitting chip C1 of the LPH bar 631b is corrected, a density difference occurs between the LED of the adjacent light emitting chip C2. Thus, the light amount of the LED of the light emitting chip C adjacent to the connection portion 633 is also corrected at the same time, except for the LED of the light emitting chip C at the connection portion 633. In this case, the light amount of the LED of the light emitting chip C2 is also corrected at the same time, except for the LED of the light emitting chip C1 of the LPH bar 631b.

[0161] According to the above-described manner, the image forming apparatus 1 and the light emitting element head 14 in which the image formed on the paper P is less likely to have a density difference at the switching position Kp of the LED 71 can be provided.

[0162] Further, in the above-described example, the correction of the density difference at the connection portion 633 between the LPH bars 631 is described, but the correction of the density difference occurring between the light emitting chips C can also be applied.

[0163] The above-described embodiment has been described, but the technical scope of the present disclosure is not limited to the scope described in the above-described embodiment. It is clear from the description of the claims that various modifications and changes to the above-described embodiment are included in the technical scope of the present disclosure.

Claims

1. An image forming apparatus comprising: A toner image forming unit uses a first light-emitting element column, a second light-emitting element column, and an optical element to form a toner image. The first light-emitting element column consists of light-emitting elements arranged in a column in the main scanning direction, and the second light-emitting element column consists of light-emitting elements arranged in a column in the main scanning direction. At least a portion of the second light-emitting element column overlaps with the first light-emitting element column in the sub-scanning direction. The optical element is used to image the light output of the light-emitting elements and expose a photoreceptor to form an electrostatic latent image. A transfer unit that transfers the toner image onto a recording medium; A fixing unit that fixes the toner image transferred to the recording medium to form an image; A switching unit that causes the first light-emitting element column and the second light-emitting element column to switch light emission at a switching location, wherein the switching location is located at any location in the overlapping area of ​​the first light-emitting element column and the second light-emitting element column; The acquisition unit prints the test pattern formed at the switching location onto a recording medium and acquires information about the concentration difference at the switching location related to the test pattern formed on the recording medium. as well as The correction unit corrects the concentration difference based on information related to the concentration difference.

2. The image forming apparatus according to claim 1, wherein, The correction unit is a mechanism for changing the distance between the first and second light-emitting element columns and the photoreceptor.

3. The image forming apparatus according to claim 2, wherein, The changing mechanism is a lifting mechanism that raises or lowers at least one of the first light-emitting element column and the second light-emitting element column.

4. The image forming apparatus according to claim 3, wherein, The lifting mechanism causes the first light-emitting element column and the second light-emitting element column to rise and fall simultaneously.

5. The image forming apparatus according to claim 1, wherein, The correction unit is a light quantity correction mechanism that corrects the light quantity of the light-emitting element adjacent to the switching part.

6. The image forming apparatus according to claim 1, wherein, When the distance between at least one of the first and second light-emitting element columns and the photoreceptor is changed, the acquisition unit acquires information about the concentration difference at the switching location of the test pattern formed on the recording medium.

7. The image forming apparatus according to claim 6, wherein, The correction unit moves at least one of the first and second light-emitting element columns to a position where the concentration difference at the switching location is minimized, as information related to the concentration difference at the switching location, in the result of visual observation by the user.

8. The image forming apparatus according to claim 6, wherein, When the correction unit changes the distance between the first and second light-emitting element columns and the photoreceptor, it moves at least one of the first and second light-emitting element columns to a position where the concentration difference is eliminated, as determined by the reading results of the test pattern.

9. The image forming apparatus according to claim 6, wherein, The correction unit corrects the light intensity of the light-emitting elements to the light intensity that eliminates the concentration difference based on the reading results of the test pattern when the distance between the first light-emitting element column and the second light-emitting element column and the photoreceptor is not changed.

10. The image forming apparatus according to claim 9, wherein, In addition to correcting the light intensity of the light-emitting element located at the overlapping portion, the correction unit also corrects the light intensity of the light-emitting element adjacent to the overlapping portion.

11. The image forming apparatus according to claim 1, wherein, The first and second light-emitting element columns are respectively formed by arranging light-emitting element array chips, wherein the light-emitting elements are arranged in the main scanning direction.

Images