Image writing apparatus and image forming apparatus

Abstract

Compared to controlling image writing by the illumination time of the light-emitting element, this expands the adjustable range of light intensity. [Solution] An image writing device (LHy, LHm, LHc, LHk) comprising: a writing means (3) in which a plurality of light-emitting elements (3a) for irradiating with light for writing an image are arranged in a row; and a lighting control means (C22) for controlling the lighting and extinguishing of each light-emitting element (3a), wherein the lighting time (TM1) of the light-emitting elements (3a) is set based on the image to be written, and if there is a first light-emitting element (3a-3) among the plurality of light-emitting elements (3a) whose lighting time (TM1) exceeds a predetermined range, the lighting control means (C22) changes the number of second light-emitting elements (3a-4) arranged adjacent to the first light-emitting element (3a-3) that are lit.

Description

Technical Field

[0001] The present invention relates to an image writing device and an image forming device.

Background Art

[0002] Regarding an electrophotographic image forming device that writes an image by irradiating light on an image holding means, the techniques described in Patent Documents 1 and 2 below are conventionally known.

[0003] Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2009-119798) describes a technique for correcting the light emission amount of a light emitting element array according to the density of an image in a predetermined area composed of a plurality of pixels. In Patent Document 1, in a region where the lighting rate is low (low gradation region) according to the density (gradation level) of the light emitting pixel, the output density is lower than the original density, so the current value applied to the light emitting element is corrected to be high. Patent Document 1 also describes that the correction of the image density is performed not by correcting the current value but by correcting the pulse width, that is, correcting the lighting time of the light emitting element.

[0004] Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2006-076121) describes a technique for adjusting and correcting the light amount by changing the light amount unevenness correction value according to the density value of an image when correcting the light amount unevenness (IN-OUT unevenness) in the scanning direction of LPH(14). In Patent Document 2, the adjustment and change of the light amount are performed by pulse width modulation, and the adjustment of the light amount is performed by changing the ratio of the lighting time to the extinguishing time, that is, increasing or decreasing the lighting time.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

[0006] The technical objective of this invention is to broaden the adjustable range of light intensity compared to controlling image writing by the illumination time of a light-emitting element. [Means for solving the problem]

[0007] To solve the aforementioned technical problems, the image writing device of the invention described in claim 1 is A writing means comprising multiple light-emitting elements arranged in a row to emit light for image writing, A lighting control means for controlling the lighting and extinguishing of each of the aforementioned light-emitting elements, wherein the lighting time of the light-emitting elements is set based on the image to be written, and if there is a first light-emitting element among the plurality of light-emitting elements whose lighting time exceeds a predetermined range, the lighting control means changes the number of second light-emitting elements that are arranged adjacent to the first light-emitting element to be lit. It is characterized by having the following features.

[0008] The invention described in claim 2 is an image writing device according to claim 1, If the illumination time of the first light-emitting element reaches a predetermined upper limit, the illumination control means illuminates the second light-emitting element. It is characterized by having the following features.

[0009] The invention described in claim 3 is an image writing device according to claim 1, If the illumination time of the first light-emitting element does not reach a predetermined lower limit time, the illumination control means will turn off the second light-emitting element. It is characterized by having the following features.

[0010] The invention described in claim 4 is an image writing device described in claim 1, The lighting control means corrects the lighting time of each light-emitting element according to the lighting density, which is the total number of light-emitting elements lit within a predetermined frame in the image. It is characterized by having the following features.

[0011] The invention described in claim 5 is an image writing device described in claim 4, If the illumination density is higher than a predetermined value, the number of illuminated light-emitting elements is reduced and the illumination time of the illuminated light-emitting elements is increased compared to when the illumination density is lower than a predetermined value. It is characterized by the following:

[0012] The invention described in claim 6 is an image writing device according to claim 4, If the illumination density is lower than a predetermined value, the number of illuminated light-emitting elements is increased and the illumination time of the illuminated light-emitting elements is shortened compared to when the illumination density is higher than a predetermined value. It is characterized by the following:

[0013] The invention described in claim 7 is an image writing device according to claim 1, A lighting control means that controls the lighting and extinguishing of multiple light-emitting elements as a set, It is characterized by having the following features.

[0014] The invention described in claim 8 is an image writing device according to claim 1, Optical means for irradiating light output from the light-emitting element toward the image holding means, A lighting control means that changes the number of light-emitting elements to be lit based on the characteristics of the optical means in each of the light-emitting elements, It is characterized by having the following features.

[0015] The invention described in claim 9 is an image writing device as described in claim 8, If the lighting density is higher than a predetermined value, the number of lights will be reduced compared to when the lighting density is lower than the predetermined value. It is characterized by the following:

[0016] The invention described in claim 10 is an image writing device described in claim 8, When the lighting density is lower than a predetermined value, increase the number of lit lights compared to the case where the lighting density is higher than the predetermined value. It is characterized by this.

[0017] The invention according to claim 11 is an image writing device according to claim 1, changing the number of lit lights of the second light emitting element adjacent to the first light emitting element along the main scanning direction of the image to be written. It is characterized by this.

[0018] In order to solve the above technical problem, the image forming apparatus according to claim 12 of the invention image holding means, an image writing device according to any one of claims 1 to 11 for forming a latent image on the image holding means, developing means for developing the latent image written by the image writing device, transfer means for transferring the image developed by the developing means to a medium, fixing means for fixing the image transferred to the medium, characterized by comprising.

Effect of the Invention

[0019] According to the inventions described in claims 1 and 12, the adjustable range of the light amount can be widened compared to the case where the writing of the image is controlled by the lighting time of the light emitting element. According to the invention described in claim 2, the adjustable range of the light amount can be widened compared to the case where the second light emitting element is not lit when the lighting time of the first light emitting element reaches the upper limit time. According to the invention described in claim 3, the adjustable range of the light amount can be widened compared to the case where the second light emitting element is not turned off when the lighting time of the first light emitting element reaches the lower limit time.

[0020] According to the invention described in claim 4, the reproducibility can be improved compared to the case where the lighting time is not corrected according to the lighting density. According to the invention described in claim 5, when the illumination density is high, it is possible to improve reproducibility compared to reducing the number of illuminated elements and not increasing the illumination time of the illuminated light-emitting elements. According to the invention described in claim 6, when the illumination density is low, the reproducibility can be improved compared to a case where the number of illuminated elements is increased and the illumination time of the illuminated light-emitting elements is not shortened. According to the invention described in claim 7, control can be made easier compared to not controlling the lighting and extinguishing of multiple light-emitting elements as a set.

[0021] According to the invention described in claim 8, reproducibility can be improved compared to not changing the number of lit second light-emitting elements based on the characteristics of the optical means. According to the invention described in claim 9, when the lighting density is high, reproducibility can be improved compared to when the number of lights is not reduced. According to the invention described in claim 10, when the lighting density is low, reproducibility can be improved compared to when the number of lights is not increased. According to the invention described in claim 11, it is easier to respond to an excess or deficiency of light intensity at the first light-emitting element compared to not changing the number of second light-emitting elements adjacent to the first light-emitting element along the main scanning direction. [Brief explanation of the drawing]

[0022] [Figure 1] Figure 1 is an overall diagram illustrating the image forming apparatus of Example 1. [Figure 2] Figure 2 is an explanatory diagram of the main parts of the image recording unit of Embodiment 1. [Figure 3] Figure 3 is an explanatory diagram of the exposure apparatus of Example 1, with Figure 3A being an overall explanatory diagram and Figure 3B being an explanatory diagram of the arrangement of light-emitting elements. [Figure 4] Figure 4 is a functional block diagram of the control unit of Embodiment 1. [Figure 5]Figure 5 is an explanatory diagram of an example of a low-density image in which the number of LEDs to be lit in Example 1 is changed, and is an explanatory diagram of the input image, exposure instruction, image on the photoreceptor, and image printed on paper, with Figure 5A being an explanatory diagram of the target image, Figure 5B being an explanatory diagram of the image actually formed, Figure 5C being an explanatory diagram of the conventional technology for extending the lighting time, and Figure 5D being an explanatory diagram for Example 1. [Figure 6] Figure 6 is an explanatory diagram of an example of changing the number of LEDs to be lit in Example 1, and is an explanatory diagram of the input image, exposure instruction, image on the photoreceptor, and image printed on paper. Figure 6A is an explanatory diagram of the target image, Figure 6B is an explanatory diagram of the image actually formed, Figure 6C is an explanatory diagram of the conventional technology for extending the lighting time, and Figure 6D is an explanatory diagram of the case in Example 1. [Figure 7] Figure 7 is an explanatory diagram of an example of a high-density image in which the number of LEDs to be lit in Example 1 is changed, and is an explanatory diagram of the exposure instruction and the image printed on paper, Figure 7A is an explanatory diagram of the target image, Figure 7B is an explanatory diagram of the image actually formed, Figure 7C is an explanatory diagram of the conventional technology for extending the lighting time, and Figure 7D is an explanatory diagram for Example 1. [Modes for carrying out the invention]

[0023] Next, with reference to the drawings, examples of embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. For the sake of easier understanding of the following explanation, in the drawings, the front-to-back direction is the X-axis direction, the left-to-right direction is the Y-axis direction, and the up-to-down direction is the Z-axis direction. The directions or sides indicated by the arrows X, -X, Y, -Y, Z, and -Z are defined as front, rear, right, left, up, down, or front side, rear side, right side, left side, up side, and down side, respectively. Furthermore, in the diagram, a circle with a "·" inside represents an arrow pointing from the back to the front of the paper, and a circle with an "×" inside represents an arrow pointing from the front to the back of the paper. In the following explanation using diagrams, diagrams of components other than those necessary for the explanation have been omitted as appropriate for ease of understanding. [Examples]

[0024] Figure 1 is an overall diagram illustrating the image forming apparatus of Example 1. In Figure 1, the copier U, as an example of an image forming apparatus in Embodiment 1 of the present invention, has a printer unit U1, which is an example of an image recording means and an example of an image recording device. A scanner unit U2, which is an example of a reading means and an example of an image reading device, is supported above the printer unit U1. An auto feeder U3, which is an example of a document transport device, is supported above the scanner unit U2.

[0025] At the top of the auto feeder U3 is a document tray TG1, which is an example of a means for storing media. Multiple documents Gi to be copied can be stacked and stored in the document tray TG1. Below the document tray TG1 is a document output tray TG2, which is an example of a document discharge section. Between the document tray TG1 and the document output tray TG2, a document transport roller U3b is positioned along the document transport path U3a.

[0026] A platen glass PG, an example of a transparent document tray, is positioned on the upper surface of the scanner unit U2. Below the platen glass PG in the scanner unit U2 of Embodiment 1, a reading unit U2a, an example of a reading unit, is positioned. The reading unit U2a of Embodiment 1 is supported so as to be movable in the left-right direction, an example of a sub-scanning direction, along the lower surface of the platen glass PG. The reading unit U2a is electrically connected to the image processing unit GS.

[0027] Figure 2 is an explanatory diagram of the main parts of the image recording unit of Embodiment 1. The image processing unit GS is electrically connected to the writing circuit DL of the printer unit U1. The writing circuit DL is electrically connected to the exposure devices LHy, LHm, LHc, and LHk, which are examples of image writing devices. The exposure apparatus LHy~LHk of Example 1 is configured, as an example, with an LED head in which multiple LEDs (Light Emitting Diodes), as an example of a light-emitting element, are arranged in a row on a substrate along the main scanning direction. The exposure apparatus LHy~LHk is configured to output writing light corresponding to yellow (Y), magenta (M), cyan (C), and black (K) in response to signals input from the writing circuit DL. The writing circuit DL and the power supply circuit E are controlled according to control signals from the control unit C, which is an example of a control means, to control the writing timing and power supply timing. In Figure 1, above the exposure apparatus LHy~LHk, photoreceptors PRy, PRm, PRc, and PRk are arranged as an example of an image holding means. In Figures 1 and 2, the writing areas Q1y, Q1m, Q1c, and Q1k are formed by the regions on each photoreceptor PRy~PRk that are irradiated with writing light.

[0028] With respect to the rotation direction of each photoreceptor PRy to PRk, charging rollers Cry, CRm, CRc, and CRK, as an example of a charging means, are arranged on the upstream side of the writing area Q1y to Q1k. In Example 1, the charging rollers Cry to CRK are supported in contact with the photoreceptors PRy to PRk so as to be able to rotate by them. With respect to the rotational direction of the photoreceptors PRy to PRk, developing devices Gy, Gm, Gc, and Gk, as an example of a developing means, are arranged downstream of the writing areas Q1y to Q1k. The developing areas Q2y, Q2m, Q2c, and Q2k are formed by the regions where each photoreceptor PRy to PRk and each developing device Gy to Gk face each other.

[0029] With respect to the rotation direction of the photoreceptors PRy to PRk, primary transfer rollers T1y, T1m, T1c, and T1k, as an example of a primary transfer means, are positioned downstream of the developing apparatus Gy to Gk. The regions where each photoreceptor PRy to PRk and each primary transfer roller T1y to T1k face each other constitute primary transfer regions Q3y, Q3m, Q3c, and Q3k. Downstream of the primary transfer rollers T1y to T1k, relative to the rotation direction of the photoreceptors PRy to PRk, photoreceptor cleaners CLy, CLm, CLc, and CLk are positioned as an example of cleaning means. Downstream of the photoreceptor cleaners CLy to CLk, in relation to the rotational direction of the photoreceptors PRy to PRk, static eliminators Jy, Jm, Jc, and Jk, which are examples of static elimination means and examples of static elimination devices, are arranged.

[0030] The image-forming unit Uy of the Y color is configured as an example of a means for forming a visible image of the Y color in Example 1, which forms a Y color toner image using the Y color photoreceptor PRy, charging roller CRy, exposure device LHy, developing device Gy, primary transfer roller T1y, photoreceptor cleaner CLy, and static eliminator Jy. Similarly, the image-forming units Um, Uc, Uk of the M, C, K colors are configured using the respective photoreceptors PRm, PRc, PRk, charging rollers CRm, CRc, Crk, exposure devices LHm, LHc, LHk, developing devices Gm, Gc, Gk, primary transfer rollers T1m, T1c, T1k, photoreceptor cleaners CLm, CLc, CLk, and static eliminators Jm, Jc, Jk.

[0031] Above the photoreceptors PRy~PRk, a belt module BM is positioned as an example of an intermediate transfer device. The belt module BM is an example of an image holding means and has an intermediate transfer belt B as an example of an intermediate transfer means. The intermediate transfer belt B is composed of an endless strip-shaped member. In Example 1, the intermediate transfer belt B is rotatably supported by a tension roller Rt as an example of a tensioning means, a walking roller Rw as an example of a bias correction means, an idler roller Rf as an example of a driven means, a backup roller T2a as an example of a counter means for the secondary transfer region, primary transfer rollers T1y to T1k, and a drive roller Rd as an example of a drive member. In Example 1, the intermediate transfer belt B rotates when drive is transmitted to the drive roller Rd. Furthermore, between the primary transfer rollers T1y~T1k and the backup roller T2a An image detection sensor SN1, which is an example of a detection means for detecting an image on the intermediate transfer belt B, is positioned opposite the surface of the intermediate transfer belt B.

[0032] A secondary transfer roller T2b, as an example of a secondary transfer means, is positioned opposite the backup roller T2a across the intermediate transfer belt B. The backup roller T2a and the secondary transfer roller T2b, etc., constitute the secondary transfer unit T2 of Embodiment 1, which is an example of a transfer device. Furthermore, the area where the secondary transfer roller T2b and the intermediate transfer belt B come into contact constitutes the secondary transfer area Q4. The secondary transfer roller T2b in Example 1 is configured to be movable between a contact position in contact with the intermediate transfer belt B and a separation position away from the intermediate transfer belt B. A belt cleaner CLb is positioned downstream of the secondary transfer region Q4 with respect to the rotation direction of the intermediate transfer belt B, as an example of a cleaning device for the intermediate transfer body. The primary transfer rollers T1y to T1k, the intermediate transfer belt B, and the secondary transfer unit T2, etc. constitute a transfer apparatus T1+T2+B as an example of the transfer means of Example 1. Furthermore, the image-making unit Uy to Uk and the transfer apparatus T1+T2+B constitute an image recording unit Uy to Uk+T1+T2+B of Example 1.

[0033] In Figure 1, below the image-making section Uy~Uk, four pairs of left and right guide rails GR are provided as an example of a guide mechanism. Each guide rail GR supports paper feed trays TR1, TR2, TR3, and TR4, which are an example of a medium storage mechanism, so that they can move in and out in the front-to-back direction. Recording paper S, an example of a medium, is stored in the paper feed trays TR1~TR4. A pickup roller Rp, as an example of an ejection mechanism, is positioned in the upper left of the paper feed trays TR1 to TR4. Downstream of the pickup roller Rp, with respect to the transport direction of the recording paper S, a paper handling roller Rs, as an example of a paper handling mechanism, is positioned. Downstream of the paper handling roller Rs, with respect to the transport direction of the recording paper S, a paper feed path SH1 extending upward is formed, as an example of a medium transport path. Multiple transport rollers Ra, as an example of a transport mechanism, are positioned in the paper feed path SH1.

[0034] A manual feed tray TR0, an example of a media storage method, is located in the lower left of the copier U. A pickup roller Rp0 is located in the upper right of the manual feed tray TR0, and the manual feed path SH0 extends from it. The manual feed path SH0 merges with the feed path SH1. In the paper feed path SH1, a register roller Rr is positioned upstream of the secondary transfer area Q4 as an example of a means for adjusting the transport timing. The transport path SH2 extends from the register roller Rr towards the secondary transfer area Q4.

[0035] A fixing device F, as an example of a fixing means, is positioned downstream of the secondary transfer region Q4 with respect to the transport direction of the recording paper S. The fixing device F includes a heating roller Fh as an example of a fixing member for heating, and a pressure roller Fp as an example of a fixing member for pressurizing. The fixing region Q5 is formed by the contact area between the heating roller Fh and the pressure roller Fp. A lower paper output tray TRh, which is an example of a media output section, is formed on the upper surface of the printer unit U1. In Embodiment 1, a finisher U4, which is an example of a post-processing device, is installed on the lower paper output tray TRh. Above the fuser unit F, a paper output path SH3, which is an example of a transport path, extends toward the lower paper output tray TRh. A paper output roller Rh, which is an example of a media transport means, is positioned at the downstream end of the paper output path SH3.

[0036] Above the lower output tray TRh, the upper output tray TRh2 is positioned as an example of a media discharge section. Above the fuser unit F, an upper transport path SH4 is formed, branching off from the output path SH3 and extending toward the upper output tray TRh2. The upper transport path SH4 is equipped with a reversible roller Rb that can rotate in both forward and reverse directions as an example of a medium transport means. Above the branching point between the paper discharge path SH3 and the upper transport path SH4, the medium As an example of a transport path, the reversal path SH6 branches off to the lower left from the upper transport path SH4.

[0037] A gate GT1, as an example of a switching mechanism, is positioned across the branching point between the paper output path SH3 and the upper transport path SH4, and the branching point between the upper transport path SH4 and the reversal path SH6. The gate GT1 guides the recording paper S from the fuser unit F toward the lower paper output tray TRh and is supported so as to be switchable between a first guiding position (second position) that guides the recording paper S from the upper transport path SH4 to the reversal path SH6, and a second guiding position (first position) that guides the recording paper S from the fuser unit F toward the upper transport path SH4. The reversing path SH6 is equipped with multiple transport rollers Ra, which serve as an example of a means for transporting the media. The downstream end of the reversing path SH6 merges with the paper feed path SH1 upstream of the register roller Rr.

[0038] (Explanation of image formation process) In the copier U of Embodiment 1, which has the above configuration, when an operator manually places the original document Gi on the platen glass PG to perform copying, the reading unit U2a moves from its initial position to the left and right, and the original document Gi on the platen glass PG is scanned while being exposed. Also, when the original document Gi is automatically transported and copied using the auto feeder U3, multiple original documents Gi placed in the original tray TG1 are sequentially transported and passed through the reading positions of the originals on the platen glass PG and discharged into the original output tray TG2. Each original document Gi passing sequentially through the reading positions on the platen glass PG is exposed and scanned by the reading unit U2a. The reflected light from the original document Gi is received by the reading unit U2a. The reading unit U2a converts the received reflected light from the original document Gi into an electrical signal. When double-sided reading of the original document Gi is performed, the original document Gi is also read by the reading sensor.

[0039] The image processing unit GS receives the electrical signal output from the reading unit U2a. The image processing unit GS converts the R, G, and B color electrical signals read by the reading unit U2a into image information for latent image formation using yellow (Y), magenta (M), cyan (C), and black (K). The image processing unit GS outputs the converted image information to the writing circuit DL of the printer unit U1. If the image is a monochrome image, the image processing unit GS outputs only black (K) image information to the writing circuit DL. The writing circuit DL outputs control signals corresponding to the input image information to the exposure devices LHy~LHk. The exposure devices LHy~LHk output writing light corresponding to the control signals.

[0040] Each photoreceptor PRy~PRk is driven to rotate when image formation begins. A charging voltage is applied to the charging rollers CRy~CRk from the power supply circuit E. Therefore, the surface of the photoreceptors PRy~PRk is charged by the charging rollers CRy~CRk. In the writing area Q1y~Q1k, an electrostatic latent image is formed on the surface of the charged photoreceptors PRy~PRk by the exposure unit LHy~LHk. The electrostatic latent image of the photoreceptors PRy~PRk is developed into a toner image, an example of a visible image, by the developing unit Gy~Gk in the developing area Q2y~Q2k.

[0041] The developed toner image is transported to the primary transfer region Q3y~Q3k, which is in contact with the intermediate transfer belt B, an example of an intermediate transfer medium. In the primary transfer region Q3y~Q3k, a primary transfer voltage with the opposite polarity to the toner's charge polarity is applied from the power supply circuit E to the primary transfer rollers T1y~T1k. Therefore, the toner image on each photoreceptor PRy~PRk is transferred to the intermediate transfer belt B by the primary transfer rollers T1y~T1k. In the case of a multi-color toner image, the downstream toner image is transferred on top of the toner image transferred to the intermediate transfer belt B in the upstream primary transfer region. After primary transfer, any residue or deposits on the photoreceptor PRy~PRk are cleaned with the photoreceptor cleaner CLy~CLk. After cleaning, the surface of the photoreceptor PRy~PRk is destaticized with the static eliminator Jy~Jk. After destaticization, the surface of the photoreceptor PRy~PRk is recharged with the charging roller CRy~CRk. It will be done. The monochromatic or multicolor toner images transferred onto the intermediate transfer belt B by the primary transfer rollers T1y to T1k in the primary transfer region Q3y to Q3k are then transported to the secondary transfer region Q4.

[0042] The recording paper S on which images are recorded is picked up by the pickup roller Rp of the paper feed tray TR1 to TR4 used. If multiple sheets of recording paper S are picked up together by the pickup roller Rp, they are separated one by one by the separator roller Rs. The recording paper S separated by the separator roller Rs is transported along the paper feed path SH1 by the transport roller Ra. The recording paper S transported along the paper feed path SH1 is sent to the register roller Rr. Recording paper S loaded in the manual feed tray TR0 is also sent to the paper feed path SH1 via the manual feed path SH0 by the pickup roller Rp0. The register roller Rr transports the recording paper S to the secondary transfer area Q4 at the same time that the toner image formed on the intermediate transfer belt B is transported to the secondary transfer area Q4. The secondary transfer roller T2b is supplied with a secondary transfer voltage opposite to the charge polarity of the toner by the power supply circuit E. Therefore, the toner image on the intermediate transfer belt B is transferred from the intermediate transfer belt B to the recording paper S.

[0043] After secondary transfer, the intermediate transfer belt B is cleaned of any deposits or other materials adhering to its surface using the belt cleaner CLb. The recording paper S on which the toner image has been secondarily transferred is heated and fixed as it passes through the fixing area Q5. If post-processing is required, the image-fixed recording paper S is transported to the finisher U4 located on the lower output tray TRh. If no post-processing is required for the recording paper S, it is transported to the upper output tray TRh2. When the recording paper S is transported to the lower output tray TRh, the gate GT1 moves to the first guide position. Therefore, the recording paper S sent out from the fuser F is transported along the output path SH3. The recording paper S transported along the output path SH3 is then transported by the output roller Rh towards the finisher U4 and the lower output tray TRh. The finisher U4 performs a binding process on the recording paper S as an example of post-processing, and then ejects the recording paper S into the lower output tray TRh.

[0044] When the recording paper S is to be ejected to the upper output tray TRh2, the gate GT1 moves to the second guide position and is ejected to the upper output tray TRh2. When the recording paper S is to be printed on both sides, gate GT1 moves to the second guide position. Then, when the trailing edge of the recording paper S passes through gate GT1, gate GT1 moves to the first guide position and the reversing roller Rb rotates in the reverse direction. As a result, the recording paper S is guided by gate GT1 and sent to the reversing path SH6. The recording paper S that has been transported along the reversing path SH6 is sent to the register roller Rr with its front and back sides reversed.

[0045] (Explanation of the exposure equipment) Figure 3 is an explanatory diagram of the exposure apparatus of Example 1, with Figure 3A being an overall explanatory diagram and Figure 3B being an explanatory diagram of the arrangement of light-emitting elements. In Figure 3, the exposure apparatus LHy~LHk of Embodiment 1 has a frame 1 as an example of a frame. Frame 1 extends along the main scanning direction. A substrate 2 extending along the main scanning direction is supported on frame 1. An LED array 3 as an example of a writing means is arranged on the substrate 2. Multiple LEDs 3a as an example of light-emitting elements are arranged on the LED array 3 along the main scanning direction of the substrate 2. In Figure 3B, multiple LEDs 3a are arranged in a row along the main scanning direction Y1, and also in a row along the sub-scanning direction Y2. In the exposure apparatus LHy~LHk of Example 1, multiple LEDs 3a are treated as a set of light-emitting groups 3b, and the on / off state of the LEDs 3a is controlled on a unit basis (set unit) of the light-emitting group 3b. Therefore, it is easier to control the LEDs 3a in units of light-emitting groups 3b than to control each LED 3a individually. In other words, control is made easier by controlling the on / off pattern of the LEDs 3a included in a light-emitting group 3b with the same on / off pattern for other light-emitting groups 3b. In Figure 3A, a refractive index distribution type lens array 4, as an example of an optical element, is supported on the frame 1 on the photoreceptor PRy~PRk side of the LED array 3.

[0046] (Description of the control unit in Example 1) Figure 4 is a functional block diagram of the control unit of Embodiment 1. In Figure 4, the control unit (controller) C of the copier U has an input / output interface (I / O) for inputting and outputting signals to and from the outside. The control unit C also has a ROM (read-only memory) where programs and information for necessary processing are stored. Furthermore, the control unit C has a RAM (random-access memory) for temporarily storing necessary data. Finally, the control unit C has a CPU (central processing unit) that performs processing according to the programs stored in the ROM, etc. Therefore, the control unit C in Embodiment 1 is composed of a small information processing device, a so-called microcomputer. Thus, the control unit C can realize various functions by executing programs stored in the ROM, etc. In Embodiment 1, the control unit C receives a signal from the signal output element and outputs a signal to the controlled element to control it.

[0047] (Description of signal output elements) Control unit C receives signals from the user interface UI and other signal output elements such as sensors (not shown). The user interface (UI) inputs the information entered by the user or worker into the control unit (C).

[0048] (Description of controlled elements) The control unit C outputs signals to the power supply circuit E, the programming circuit DL, a motor (not shown), and other controlled elements (not shown). The power supply circuit E controls the charging bias of the charging rollers Cry~CRk, the developing bias of the developing unit Gy~Gk, the primary transfer bias of the primary transfer rollers T1y~T1k, the secondary transfer bias of the secondary transfer roller T2b, and the power supply to the heater of the fixing unit F. The programming circuit DL controls the on / off state of each LED in the LED array 3 of the exposure devices LHy~LHk.

[0049] (Functions of Control Unit C) The control unit C of Example 1 has the following functional means (functional module, program module). The job control means C1 controls the job, which is an image forming operation. When a job is started, it controls the photoreceptors PRy~PRk and the power supply circuit E, etc., to form an image on the recording paper S. The write control means C2 includes a density detection means C21 and a lighting control means C22. The write control means C2 controls the exposure apparatus LHy~LHk via the write circuit DL to control the writing of the image. In Embodiment 1, the write control means C2 selects the LEDs to be lit based on the image read by the scanner unit U2, and controls the timing and duration of lighting each LED based on the position and density of the image.

[0050] The density detection means C21 detects the density of the image read by the scanner unit U2. In Example 1, the density detection means C21 determines the density of each pixel in the read image. The lighting control means C22 includes a lighting time setting means C22a, a range exceedance determination means C22b, a lighting density determination means C22c, a lighting time correction means C22d, and a lighting number changing means C22e. The lighting control means C22 controls the lighting and extinguishing of each LED (light-emitting element). The lighting time setting means C22a sets the lighting time for each LED according to the concentration detected by the concentration detection means C21. In Example 1, the lighting time setting means C22a sets a longer lighting time as the concentration increases.

[0051] The range exceeding determination means C22b determines whether there are any LED3a whose lighting time TM1, set by the lighting time setting means C22a, reaches a predetermined upper limit lighting time TMa. In addition, the range exceeding determination means C22b of Embodiment 1 determines whether there are any LED3a whose lighting time TM1 does not reach a predetermined lower limit lighting time TMb. In the following explanation, LED3a that reaches the upper limit illumination time TMa will be referred to as "upper limit exceeding LED," and LED3a that does not reach the lower limit illumination time TMb will be referred to as "lower limit exceeding LED." Both upper limit exceeding LED and lower limit exceeding LED are light-emitting elements that exceed a predetermined range (from lower limit illumination time TMb to upper limit illumination time TMa), and correspond to the "first light-emitting element" in the claims.

[0052] Generally, there are individual differences in LED3a, and before product shipment, a reference illumination time (reference illumination time TM0) is set for each LED3a to ensure that the amount of light output from each LED3a is approximately the same. Therefore, the reference illumination time TM0 differs from one LED3a to another, with some having a long reference illumination time TM0 and others a short one. Consequently, even when illuminating with a light intensity corresponding to a high-density image, some LED3a units with a long reference illumination time TM0 from the start may have insufficient light intensity even when the illumination time TM1 is set to the maximum (upper limit illumination time TMa), resulting in an image with insufficient density. Similarly, even when attempting to form a low-density image and setting the illumination time TM1 to the minimum (lower limit illumination time TMb), some units may still have too much light intensity, resulting in an image with excessive density.

[0053] The illumination density determination means C22c determines the illumination density, which is the total number of illuminated light-emitting elements within a predetermined frame in the image. In Example 1, the illumination density determination means C22c, as an example, derives the illumination density M1 by counting the number of illuminated LEDs 3a within a determination range corresponding to 10 LEDs (main scanning direction) × 10 LEDs (sub-scanning direction) within a predetermined frame in the image. Then, it determines whether the illumination density M1 is higher than a predetermined high-density threshold Ma or lower than a predetermined low-density threshold Mb.

[0054] The lighting time correction means C22d corrects the lighting time TM1 of the LED 3a according to the lighting density M1 determined by the lighting density determination means C22c. In the lighting time correction means C22d of Example 1, if the lighting density M1 is higher than the high-density threshold Ma, the lighting time of the LED 3a to be lit is increased. Also, in the lighting time correction means C22d of Example 1, if the lighting density M1 is lower than the low-density threshold Mb, the lighting time of the LED 3a to be lit is shortened compared to when the lighting density M1 is higher than the low-density threshold Mb. When the lighting density is high, even if the same correction is applied as for medium to low lighting densities, the change in density becomes relatively large because the number of LEDs 3a to be lit is large. Therefore, when the lighting density M1 is higher than the high-density threshold Ma, the lighting time of the LED 3a is shortened as the lighting density M1 increases. On the other hand, when the illumination density is low, even if the same correction is applied as for medium to high illumination densities, the change in density becomes relatively small because the number of illuminated LEDs 3a is small. Therefore, when the illumination density M1 is lower than the low-density threshold Mb, the illumination time of LEDs 3a is corrected to be longer as the illumination density M1 decreases. The amount of correction for illumination time is confirmed in advance through experiments, etc., and set to be close to the density of the target image. In other words, individual differences and optical characteristics of LEDs 3a are confirmed in advance through experiments, etc., and the correction amount is set accordingly.

[0055] The number of lit LEDs changing means C22e changes the number of lit LEDs (an example of a second light-emitting element) adjacent to the LED 3a (an LED exceeding the upper limit or an LED exceeding the lower limit) if the range exceedance determination means C22b determines that there is an LED 3a whose lighting time TM1 exceeds the range of upper limit lighting time TMa to lower limit lighting time TMb. The LED number changing means C22e in Example 1 lights up an LED adjacent to an LED that exceeds the upper limit if there is an LED that exceeds the upper limit. In other words, it increases (changes) the number of LEDs 3a that are lit. Furthermore, the lighting count changing means C22e of Example 1, if there are LEDs exceeding the lower limit, will turn off the LEDs 3a that are positioned adjacent to the LEDs exceeding the lower limit. In other words, it reduces (changes) the number of LEDs 3a that are lit.

[0056] Figure 5 is an explanatory diagram of an example of a low-density image in which the number of LEDs to be lit in Example 1 is changed, and is an explanatory diagram of the input image, exposure instruction, image on the photoreceptor, and image printed on paper, with Figure 5A being an explanatory diagram of the target image, Figure 5B being an explanatory diagram of the image actually formed, Figure 5C being an explanatory diagram of the conventional technology for extending the lighting time, and Figure 5D being an explanatory diagram for Example 1. In Figure 5, as shown in Figure 5A, when writing to the third pixel 11-3 among the six pixels 11 from the input image, the corresponding three LEDs 3a-3 are controlled to light up. When LEDs 3a-3 light up, an image (dot) is formed at the corresponding position on the photoreceptor PRy~PRk. Then, the image (dot) on the photoreceptor PRy~PRk is transferred and fixed to the paper. However, due to individual differences in LEDs 3a-3 and the optical characteristics of the lens array 4, the amount of light may be insufficient even when lit for the same duration as a standard LED 3a. In this case, as shown in Figure 5B, the density and size of the image on the photoreceptor PRy~PRk are not reproduced as in the input image. Therefore, the image transferred to the paper also has poor reproducibility compared to the input.

[0057] In contrast, the prior art described in Patent Documents 1 and 2 attempts to improve the reproducibility of image density by extending the illumination time of the LEDs 3a-3, which have poor reproducibility. However, in high-speed machines that print many sheets per unit time, the photoreceptors PRy~PRk also rotate at high speed, and the exposure units LHy~LHk can only irradiate light for a limited time. Therefore, there is a limit to how long the illumination time can be extended. Consequently, as shown in Figure 5C, even when the illumination time is extended to its limit, the reproducibility of image density and position on paper may not be sufficient. In Example 1, if an LED 3a-3 exceeds its upper limit, LED 3a-4, which is positioned adjacent to the LED 3a-3 exceeding its upper limit, is illuminated. Therefore, as shown in Figure 5D, the amount of light that was insufficient even when one LED 3a-3 was illuminated to its upper limit can be secured by the two LEDs 3a-3 and 3a-4. Thus, compared to the conventional technology shown in Figure 5C, the reproducibility of the input image in terms of image density and position on paper is improved.

[0058] In the example shown in Figure 5D, the case where LED 3a-4, which is to the right of the LED 3a-3 exceeding the upper limit, is illuminated is illustrated. This is because LED 3a-3 exceeds the upper limit, and addressing this with the adjacent LED 3a-4 makes it easier to resolve the insufficient light output of LED 3a-3. However, it is not limited to the LED 3a-4 to the right. For example, it is also possible to illuminate LED 3a-2 to the left in the main scanning direction. In addition, it is also possible to illuminate adjacent LEDs in the sub-scanning direction. Furthermore, the number of LEDs to be illuminated is not limited to one; if it is necessary to illuminate two or more LEDs to ensure reproducibility depending on the experiment, it is possible to illuminate two or more LEDs. Therefore, in Example 1, the number of LEDs 3a to be illuminated when LED 3a-3 exceeds the upper limit is determined not only by individual differences in LED 3a, image density and position, but also by the optical characteristics of the lens array 4.

[0059] Figure 6 is an explanatory diagram of an example of changing the number of LEDs to be lit in Example 1, and is an explanatory diagram of the input image, exposure instruction, image on the photoreceptor, and image printed on paper. Figure 6A is an explanatory diagram of the target image, Figure 6B is an explanatory diagram of the image actually formed, Figure 6C is an explanatory diagram of the conventional technology for extending the lighting time, and Figure 6D is an explanatory diagram of the case in Example 1. In Figure 6, if the illumination time is too short, the illumination time ends before the current and voltage stabilize in the circuit, and the amount of light emitted by LED 3a is not stable. Therefore, the illumination time is ensured to be at least the lower limit illumination time TMb at which the amount of light emitted stabilizes. However, due to individual differences in LED 3a and the optical characteristics of lens array 4, even if only the lower limit illumination time TMb is illuminated, dots with excessively high image density may occur. Therefore, compared to the ideal state shown in Figure 6A, in reality, due to individual differences and optical characteristics, the reproducibility may deteriorate as shown in Figure 6B. In contrast, simply shortening the illumination time of LED 3a' as in the conventional technology of Patent Documents 1 and 2 resulted in poor reproducibility compared to the target image in Figure 6A, as shown in Figure 6C. In contrast, in Example 1, LED 3a-11, which is adjacent to the LED 3a-10 that exceeds the lower limit and was scheduled to be illuminated, is turned off. Therefore, as shown in Figure 6D, an image closer to the target image in Figure 6A is formed compared to the conventional technology in Figure 6C, and the reproducibility is improved.

[0060] In the example shown in Figure 6D, the case where LED 3a-11 to the right of the lower limit-exceeding LED 3a-10 is turned off is illustrated, but the method is not limited to this. As explained in Figure 5D, it is also possible to turn off the LED to the left, or LEDs adjacent in the sub-scanning direction, or to turn off two or more LEDs. Therefore, in Example 1, the change in the number of LEDs 3a that are lit when the lower limit-exceeding LED 3a-10 is present is made based not only on individual differences in LEDs 3a, image density and position, but also on the optical characteristics of the lens array 4.

[0061] Furthermore, the number of lit LEDs changing means C22e of Example 1 corrects the number of lit LEDs 3a according to the lighting density determined by the lighting density determination means C22c. When the lighting density M1 is higher than the high-density threshold Ma, the number of lit LEDs 3a within the determination range is reduced by the number of lit LEDs 3a in Example 1 compared to when the lighting density M1 is lower than the high-density threshold Ma. When the lighting density is high, even if the same correction is made as for medium to low lighting densities, the change in density becomes relatively large because the number of lit LEDs 3a themselves is large. Therefore, when the lighting density M1 is higher than the high-density threshold Ma, the number of lit LEDs 3a is reduced as the lighting density M1 increases, and the lighting time of the lit LEDs 3a is increased to approach the desired light intensity and density. The numerical value for reducing the number of lit LEDs and the lighting time are confirmed in advance through experiments, etc., and set to approach the density of the desired image. Therefore, depending on the individual differences of the LEDs 3a and the optical characteristics of the lens array 4, it may be the case that only the number of lit LEDs is reduced and the lighting time is not corrected.

[0062] Figure 7 is an explanatory diagram of an example of a high-density image in which the number of LEDs to be lit in Example 1 is changed, and is an explanatory diagram of the exposure instruction and the image printed on paper, Figure 7A is an explanatory diagram of the target image, Figure 7B is an explanatory diagram of the image actually formed, Figure 7C is an explanatory diagram of the conventional technology for extending the lighting time, and Figure 7D is an explanatory diagram for Example 1. In Figure 7, when forming an image with a high illumination density, the image shown in Figure 7B may be formed due to individual differences in LED 3a and the optical characteristics of the lens array 4, compared to the target image shown in Figure 7A. In the techniques described in Patent Documents 1 and 2, as shown in Figure 7C, the illumination time of some LEDs is shortened to approach the target image (Figure 7A). In contrast, in Example 1, the LED 3a-22, which is scheduled to be illuminated and is adjacent to the off LED 3a-21, is turned off, that is, the number of illuminated LEDs is reduced. Therefore, as shown in Figure 7D, an image closer to the target image in Figure 7A is obtained than in the case of Figure 7C. Thus, the reproducibility is improved compared to the conventional technique.

[0063] Furthermore, the LED count changing means C22e of Example 1 increases the number of LEDs 3a lit within the discrimination range when the illumination density M1 is lower than the low-density threshold Mb, compared to when the illumination density M1 is higher than the low-density threshold Mb. When the illumination density is low, even if the same correction is applied as for medium-density to high-density illumination, the number of LEDs 3a lit is small, so the change in density becomes relatively small. Therefore, when the illumination density M1 is lower than the low-density threshold Mb, the number of LEDs 3a lit is increased as the illumination density M1 decreases, and the illumination time of the lit LEDs 3a is shortened to approach the desired light intensity and density. The value of the number of lit LEDs to increase and the illumination time are confirmed in advance through experiments, etc., and set to approach the density of the desired image. Therefore, depending on the individual differences of the LEDs 3a and the optical characteristics of the lens array 4, it may be possible to increase the number of lit LEDs without correcting the illumination time.

[0064] In Example 1, discrimination was performed based on the illumination density M1, but this is not limited to this. For example, since the illumination density M1 is also related to the density of the image, it is also possible to increase or decrease the number of lights based on the density of the image.

[0065] (Effect of Example 1) In the copier U of Embodiment 1, which has the above configuration, the number of lit LEDs is changed if there are LEDs exceeding the upper limit or the lower limit. Therefore, even if the light intensity cannot be adjusted and corrected by adjusting the lighting time, it is possible to adjust the light intensity to the desired level by increasing or decreasing the number of lit LEDs. Thus, it is possible to widen the adjustable range of light intensity compared to the cases described in Patent Documents 1 and 2, which control image writing only by the lighting time of the LEDs. Furthermore, the number of LEDs 3a lit and their illumination time are corrected according to the illumination density, improving reproducibility even at high or low illumination densities. In addition, in Example 1, the optical characteristics of the lens array 4 are also taken into consideration when correcting the number of LEDs lit and their illumination time. Therefore, reproducibility is improved compared to the case where optical characteristics are not considered.

[0066] (Example of change) Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the gist of the present invention as described in the claims. Examples of modifications to the present invention (H01) to (H04) are shown below. (H01) In the above embodiment, a copier U was given as an example of an image forming apparatus, but the apparatus is not limited to this, and can also be configured with, for example, a printer, a fax machine, or a multifunction device having multiple or all of these functions.

[0067] (H02) In the above embodiment, a configuration in which four-color developer is used as the copier U was illustrated, but the invention is not limited to this, and can also be applied to, for example, a single-color image forming apparatus or a multi-color image forming apparatus with three or fewer colors or five or more colors. (H03) In the above embodiment, an endless band-shaped intermediate transfer belt B was exemplified as an example of an image holding means, but the invention is not limited thereto. For example, it can also be applied to a cylindrical intermediate transfer drum, a photoreceptor drum, or a photoreceptor belt. Furthermore, it can also be applied to a configuration in which there is no intermediate transfer body and the image is recorded directly from the photoreceptor onto the recording paper S.

[0068] (H04) In the above embodiment, the arrangement of LEDs 3a is not limited to the example configuration, but can be any configuration. For example, it is possible to have LEDs 3a arranged in only one row in the main scanning direction, or to have multiple rows arranged in the sub-scanning direction. Also, for example, it is possible to have two or more LED arrays 3 with a length corresponding to A4 size in the main scanning direction arranged in the main scanning direction on an A3-compatible copier U.

[0069] (Note) (((1))) A writing means comprising multiple light-emitting elements arranged in a row to emit light for image writing, A lighting control means for controlling the lighting and extinguishing of each of the aforementioned light-emitting elements, wherein the lighting time of the light-emitting elements is set based on the image to be written, and if there is a first light-emitting element among the plurality of light-emitting elements whose lighting time exceeds a predetermined range, the lighting control means changes the number of second light-emitting elements that are arranged adjacent to the first light-emitting element to be lit. An image writing device characterized by having the following features. (((2))) If the illumination time of the first light-emitting element reaches a predetermined upper limit, the illumination control means illuminates the second light-emitting element. The image writing device according to (((1))), characterized by comprising the above. (((3))) If the illumination time of the first light-emitting element does not reach a predetermined lower limit time, the illumination control means will turn off the second light-emitting element. The image writing device according to (((1))) or (((2))), characterized by comprising the above. (((4))) The lighting control means corrects the lighting time of each light-emitting element according to the lighting density, which is the total number of light-emitting elements lit within a predetermined frame in the image. An image writing device according to any one of (((1))) to (((3))), characterized by comprising: (((5))) If the illumination density is higher than a predetermined value, the number of illuminated light-emitting elements is reduced and the illumination time of the illuminated light-emitting elements is increased compared to when the illumination density is lower than a predetermined value. The image writing device according to (((4))), characterized in that (((6))) If the illumination density is lower than a predetermined value, the number of illuminated light-emitting elements is increased and the illumination time of the illuminated light-emitting elements is shortened compared to when the illumination density is higher than a predetermined value. The image writing device according to (((4))) or (((5))), characterized in that (((7))) A lighting control means that controls the lighting and extinguishing of multiple light-emitting elements as a set, An image writing device according to any one of (((1))) to (((6))) characterized by comprising: (((8))) Optical means for irradiating light output from the light-emitting element toward the image holding means, A lighting control means that changes the number of light-emitting elements to be lit based on the characteristics of the optical means in each of the light-emitting elements, An image writing device according to any one of (((1))) to (((7))) characterized by comprising: (((9))) If the lighting density is higher than a predetermined value, the number of lights will be reduced compared to when the lighting density is lower than the predetermined value. The image writing device according to (((8))), characterized in that (((10))) If the lighting density is lower than a predetermined value, the number of lights will be increased compared to when the lighting density is higher than the predetermined value. The image writing device according to (((8))) or (((9))), characterized in that (((11))) The number of lights illuminated by the second light-emitting element adjacent to the first light-emitting element is changed along the main scanning direction of the image being written. An image writing device according to any one of (((1))) to (((10))), characterized by the above. (((12))) Image holding means, An image writing device according to any one of (((1))) to (((11))) that forms a latent image in the image holding means, A developing means for developing the latent image written by the aforementioned image writing device, A transfer means for transferring the image developed by the developing means onto a medium, Fixing means for fixing the image transferred to the aforementioned medium, An image forming apparatus characterized by comprising the following:

[0070] According to the image writing device described in (((1))), the adjustable range of light intensity can be widened compared to the case where image writing is controlled by the lighting time of the light-emitting element. According to the image writing device of (((2))), the adjustable range of light intensity can be widened compared to the case where the second light-emitting element is not lit when the lighting time of the first light-emitting element reaches the upper limit time. The image writing device according to (((3))) allows for a wider range of adjustable light intensity compared to a case where the second light-emitting element is not turned off when the illumination time of the first light-emitting element reaches the lower limit. According to the image writing device described in (((4))), reproducibility can be improved compared to when the lighting time is not corrected according to the lighting density. According to the image writing device described in (((5))), when the illumination density is high, it is possible to improve reproducibility compared to reducing the number of illuminated elements and not increasing the illumination time of the illuminated light-emitting elements. According to the image writing device described in (((6))), when the illumination density is low, the reproducibility can be improved compared to a device in which the number of illuminations is increased and the illumination time of the illumination light-emitting elements is not shortened. According to the image writing device described in (((7))), control can be made easier compared to a case where multiple light-emitting elements are treated as a set and the lighting and extinguishing of the light-emitting elements are not controlled as a set. According to the image writing device described in (((8))), reproducibility can be improved compared to not changing the number of lights on the second light-emitting element based on the characteristics of the optical means. According to the image writing device described in (((9))), when the illumination density is high, the reproducibility can be improved compared to when the number of illuminations is not reduced. According to the image writing device (((10))), when the illumination density is low, the reproducibility can be improved compared to when the number of illuminated lights is not increased. The image writing device according to (((11))) makes it easier to respond to excesses or deficiencies in the light intensity of the first light-emitting element compared to not changing the number of lights on the second light-emitting element adjacent to the first light-emitting element along the main scanning direction. According to the image forming apparatus described in (((12))), the adjustable range of light intensity can be widened compared to the case where image writing is controlled by the lighting time of the light-emitting element. [Explanation of Symbols]

[0071] 3…Method of writing, 3a... Light-emitting element, 3a-3, 3a-10... First light-emitting element 3a-4, 3a-11... Second light-emitting element, 4...optical means, C22... Lighting control means, F... means of fixing, Gy, Gm, Gc, Gk...developing means, LHy, LHm, LHc, LHk... Image writing device, M1...Lighting density, PRy, PRm, PRc, PRk...image holding means, S...medium, T1 + T2 + B... Transfer method, TM1...Lighting time, TMa…Maximum time, TMb…lower limit time, U...Image forming apparatus.

Claims

1. A writing means comprising multiple light-emitting elements arranged in a row to emit light for image writing, A lighting control means for controlling the lighting and extinguishing of each of the aforementioned light-emitting elements, wherein the lighting time of the light-emitting elements is set based on the image to be written, and if there is a first light-emitting element among the plurality of light-emitting elements whose lighting time exceeds a predetermined range, the lighting control means changes the number of second light-emitting elements that are arranged adjacent to the first light-emitting element to be lit. An image writing device characterized by having the following features.

2. If the illumination time of the first light-emitting element reaches a predetermined upper limit, the illumination control means illuminates the second light-emitting element. The image writing device according to claim 1, characterized by comprising the following features.

3. If the illumination time of the first light-emitting element does not reach a predetermined lower limit time, the illumination control means will turn off the second light-emitting element. The image writing device according to claim 1, characterized by comprising the following features.

4. The lighting control means corrects the lighting time of each light-emitting element according to the lighting density, which is the total number of light-emitting elements lit within a predetermined frame in the image. The image writing device according to claim 1, characterized by comprising the following features.

5. If the illumination density is higher than a predetermined value, the number of illuminated light-emitting elements is reduced and the illumination time of the illuminated light-emitting elements is increased compared to when the illumination density is lower than a predetermined value. The image writing device according to feature 4.

6. If the illumination density is lower than a predetermined value, the number of illuminated light-emitting elements is increased and the illumination time of the illuminated light-emitting elements is shortened compared to when the illumination density is higher than a predetermined value. The image writing device according to feature 4.

7. A lighting control means that controls the lighting and extinguishing of multiple light-emitting elements as a set, The image writing device according to claim 1, characterized by comprising the following features.

8. Optical means for irradiating light output from the light-emitting element toward the image holding means, A lighting control means that changes the number of light-emitting elements to be lit based on the characteristics of the optical means in each of the light-emitting elements, The image writing device according to claim 1, characterized by comprising the following features.

9. If the lighting density is higher than a predetermined value, the number of lights will be reduced compared to when the lighting density is lower than the predetermined value. The image writing device according to feature 8.

10. If the lighting density is lower than a predetermined value, the number of lights will be increased compared to when the lighting density is higher than the predetermined value. The image writing device according to feature 8.

11. The number of lights illuminated by the second light-emitting element adjacent to the first light-emitting element is changed along the main scanning direction of the image being written. The image writing device according to feature 1.

12. Image holding means, An image writing device according to any one of claims 1 to 11, which forms a latent image in the image holding means, A developing means for developing the latent image written by the aforementioned image writing device, A transfer means for transferring the image developed by the developing means onto a medium, Fixing means for fixing the image transferred to the aforementioned medium, An image forming apparatus characterized by comprising the following:

Images