Image forming device and control method of the same

Abstract

To provide an image forming device and a control method of the same which can prevent jaggy from deteriorating to sufficiently exert performance in specified resolution, in prescribed image modes of character / CAD or the like.SOLUTION: An electrophotographic image forming device, which scans multi-beams emitted from a plurality of light emitting elements on a surface of an image carrier on the basis of image data, comprises: a light quantity correcting part that corrects a light quantity to eliminate density level differences of an image and sets differentials in corrected values of light quantities of the plurality of light-emitting elements; and a control part that controls the light-quantity correcting part so that differences are not set on set light quantities of the plurality of light-emitting elements, in prescribed image modes of character / CAD or the like.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an image forming apparatus and the like. [Background technology]

[0002] 2. Description of the Related Art Electrophotographic image forming apparatuses are known in which a light beam emitted from a light source such as a laser diode is focused on a photosensitive drum (image carrier) by a scanning optical system to form an electrostatic latent image on the surface of the photosensitive drum.

[0003] In this type of image forming apparatus, the photoconductor drum experiences a reciprocity failure, where the latent image formation state differs when the relationship between the light amount and the exposure time differs even if the total amount of light applied is the same. In other words, when the photoconductor is exposed for a very short time, the amount of change in potential of the photoconductor is smaller than when the photoconductor is exposed for a relatively long time, even though the total amount of exposure is the same, resulting in a reciprocity failure. In the case of a multi-beam scanning optical system, this appears as uneven image density.

[0004] Conventionally, in order to deal with the uneven density of an image caused by this reciprocity law failure, Patent Document 1 discloses a method of using a VCSEL (Vertical Cavity Surface Emitting Laser) with many light emitting points arranged in the main scanning direction and the sub-scanning direction as a light source, performing multiple exposure so as to reach a certain scanning frequency or higher, and making density steps invisible. However, the technology in Patent Document 1 requires a huge number of beams, such as 32 beams, and the driving system is complicated. In addition, there are problems such as a significant increase in costs.

[0005] Another method has been proposed in which the sign of the exposure correction value is inverted so that it gradually decreases toward the light source located at the center of the multiple light sources, thereby preventing density differences from occurring in the halftone image (see Patent Document 2). This is a simple configuration to implement, but in a specified image mode where the image has edges such as characters / CAD, jaggies worsen and the performance of the specified resolution cannot be fully demonstrated. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2010-176094 A [Patent Document 2] Patent No. 5262602 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above circumstances, the present disclosure provides an image forming apparatus and the like that can prevent deterioration of jaggies in a predetermined image mode such as text / CAD and can fully demonstrate the performance of a specified resolution. [Means for solving the problem]

[0008] The present disclosure relates to an electrophotographic image forming apparatus that scans a multi-beam emitted from a plurality of light-emitting elements based on image data onto a surface of an image carrier, the image forming apparatus being characterized in that it is equipped with a light intensity correction unit that corrects the amount of light to eliminate density differences in an image and sets a difference in the light intensity correction values ​​of the plurality of light-emitting elements, and a control unit that controls the light intensity correction unit so as not to set a difference in the set light intensities of the plurality of light-emitting elements when the image data is in a specified image mode such as character / CAD.

[0009] The present disclosure relates to an electrophotographic image forming apparatus that scans a multi-beam emitted from a plurality of light-emitting elements based on image data onto a surface of an image carrier, the image forming apparatus being characterized in that it is equipped with a light intensity correction unit that corrects the amount of light so as to eliminate density differences in an image and sets a difference in the light intensity correction values ​​of the plurality of light-emitting elements, and a control unit that controls the light intensity correction values ​​of the plurality of light-emitting elements so as to invert the sign of the correction value of each light-emitting element while decreasing the value from one end side of the light-emitting element to the other end side.

[0010] The present disclosure relates to a control method for an electrophotographic image forming device that scans a multi-beam emitted from a plurality of light-emitting elements based on image data onto a surface of an image carrier, the control method comprising: a light intensity correction process for correcting the amount of light so as to eliminate density differences in an image and setting a difference in the light intensity correction values ​​of the plurality of light-emitting elements; and a control process for controlling the light intensity correction so as not to set a difference in the set light intensities of the plurality of light-emitting elements when the image data is in a specified image mode such as character / CAD. Effect of the Invention

[0011] According to the image forming apparatus and the like of the present disclosure, in an image in a predetermined image mode such as character / CAD, deterioration of jaggies can be prevented and performance of the specified resolution can be fully demonstrated. Also, in a halftone image in a mode other than the predetermined image mode such as character / CAD, differences are provided in the light quantity correction values ​​of the multiple light sources, so that even if electronic bow correction is performed, there is an excellent effect that the halftone image is not affected by reciprocity law failure and does not have density steps. [Brief description of the drawings]

[0012] [Figure 1] 1 is an external view of an image forming apparatus equipped with an optical scanning device according to an embodiment. [Diagram 2] FIG. 2 is a control block diagram of the image forming apparatus and the optical scanning device. [Diagram 3] 2 is a circuit diagram of a signal transmission path of a laser emitting unit and a laser driver of the optical scanning device. [Figure 4] FIG. 2 is a diagram for explaining the flow of signal processing in the optical scanning device. [Diagram 5] FIG. 1 is an explanatory diagram of electronic bow correction. [Figure 6] FIG. 13 is an explanatory diagram of a side effect of bow correction. [Figure 7] FIG. 1 is an image diagram of a reciprocity law failure illustrating a cause of a density step. [Figure 8] FIG. 11 is a shading image diagram for explaining the cause of density differences. [Figure 9]FIG. 11 is an explanatory diagram showing a case where there is a difference in the set light amount when the image is in a predetermined image mode such as text / CAD. [Figure 10] 5A and 5B are explanatory diagrams for setting a light quantity correction value, in which FIG. 5A illustrates a method for setting a light quantity correction value in a comparative example, and FIG. 5B illustrates a method for setting a light quantity correction value in this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. It should be noted that the following embodiment is an example for explaining the present disclosure, and the technical scope of the invention described in the claims is not limited to the following description.

[0014] [1. Embodiment] First, a configuration of an image forming apparatus 10 according to an embodiment will be described. Fig. 1 is an external view of the image forming apparatus 10 equipped with an optical scanning device 200 according to an embodiment, and Fig. 2 is a control block diagram of the image forming apparatus 10 and the optical scanning device 200.

[0015] [1.1 Overall structure] 1, the image forming apparatus 10 is an information processing apparatus that includes an original reading unit 112 on the upper portion of the image forming apparatus 10, reads an image of an original, and outputs the image by an electrophotographic method. An example of the image forming apparatus 10 is a multifunction printer.

[0016] As shown in the control system diagram of Figure 2, image forming device 10 mainly includes a control unit 100, an image input unit 110, a document reading unit 112, an image processing unit 120, an image forming unit 130, an operation unit 140, a display unit 150, a memory unit 160, and a communication unit 170, and also has the functions of an optical scanning device 200.

[0017] [1.2 Image forming device 10] As shown in FIG. 2, the control unit 100 is a functional unit for controlling the entire image forming apparatus 10.

[0018] The control unit 100 realizes various functions by reading and executing various programs, and is configured, for example, by one or more arithmetic devices (for example, CPUs (Central Processing Units)).

[0019] The image input unit 110 is a functional unit for reading image data to be input to the image forming apparatus 10. The image input unit 110 is connected to an original reading unit 112, which is a functional unit for reading an image of an original, and inputs image data output from the original reading unit 112.

[0020] The image input unit 110 may input image data from a storage medium such as a USB memory or an SD card. Image data may also be input from another terminal device via a communication unit 170 that connects to the other terminal device.

[0021] The document reading unit 112 has a function of optically reading a document placed on a contact glass (not shown) and transferring the scan data to the image processing unit 120 .

[0022] The image forming unit 130 is a functional unit for forming output data based on image data on a recording medium (e.g., recording paper). For example, as shown in Fig. 1, recording paper is fed from a paper feed tray 122, and after an image is formed on the surface of the recording paper in the image forming unit 130, the recording paper is discharged from a paper discharge tray 124. The image forming unit 130 is configured by a laser printer that utilizes an electrophotographic process using an electrophotographic method.

[0023] The electrophotographic process of the image forming unit 130 involves using an optical scanning device 200 (described later) to scan a laser beam (corresponding to laser light) corresponding to image data onto the surface of a photosensitive drum (image carrier) (not shown) using an optical scanning unit 220 having a polygon mirror or the like to form an electrostatic latent image, developing the electrostatic latent image with toner, and transferring and fixing the developed toner image onto a recording medium to form an image.

[0024] The image processing unit 120 has a function of converting the image data read by the document reading unit 112 into a set file format (TIFF, GIF, JPEG, etc.) and then forms an output image based on the image data that has been subjected to image processing.

[0025] The operation unit 140 is a functional unit for receiving operation instructions from a user, and is composed of various key switches, devices for detecting input by contact, etc. The user inputs functions to be used and output conditions via the operation unit 140.

[0026] The display unit 150 is a functional unit for displaying various information to the user, and is configured, for example, by an LCD (Liquid Crystal Display) or the like.

[0027] That is, the operation unit 140 provides a user interface for operating the image forming apparatus 10, and the display unit 150 displays various setting menu screens and messages of the image forming apparatus.

[0028] 1, the image forming apparatus 10 may include a touch panel in which the operation panel 141 and the display unit 150 are integrally formed as a configuration of the operation unit 140. In this case, the method for detecting input to the touch panel may be any common detection method, such as a resistive film method, an infrared method, an electromagnetic induction method, or a capacitive method.

[0029] The storage unit 160 is a functional unit that stores various programs including a control program necessary for the operation of the image forming apparatus 10, various data including read data, and user information. The storage unit 160 is configured, for example, with a non-volatile ROM (Read Only Memory), a RAM (Random Access Memory), an HDD (Hard Disk Drive), etc. Also, it may include an SSD (Solid State Drive) which is a semiconductor memory.

[0030] The communication unit 170 establishes a communication connection with an external device. A communication interface (communication I / F) used for transmitting and receiving data is provided as the communication unit 170. The communication I / F allows data stored in a storage unit of the image forming apparatus 10 to be transmitted and received to another computer device connected via a network by a user's operation on the image forming apparatus 10.

[0031] [1.3 Optical scanning device 200] As shown in FIG. 2, the image forming apparatus 10 is equipped with an optical scanning device 200 .

[0032] FIG. 3 is an explanatory diagram of a signal transmission path from a laser scanning unit 220a that electronically processes laser light to a laser driver 210 in the optical scanning device 200. As shown in FIG.

[0033] As shown in FIGS. 2 and 3, the optical scanning device 200 includes a laser emitting section 200a having a plurality of laser light emitting elements (semiconductor laser elements (LD: Laser Device)) and emitting a plurality of beams of laser light (corresponding to "multi-beams"); a laser driver 210 for controlling the laser emitting section 200a; a laser scanning unit 220a for scanning a photosensitive drum (not shown) with the multi-beams emitted from the laser emitting section 200a based on image data; a bow correction section 230 for electronically correcting the bow of the image data; a light amount correction section (density correction section) 250 for correcting the light amount so as to eliminate density steps in the image and for providing differences in the light amount correction values ​​of the plurality of laser light emitting elements; The light intensity correction unit 250 includes a control unit 100 that controls a light intensity correction unit 250 that does not set a difference in light intensity correction values ​​of multiple light-emitting elements in a predetermined image mode with edges such as a computer-aided design (CAD) and sets a light intensity correction value difference in a half-tone image mode other than the predetermined image mode, a shading correction unit 300 that performs shading correction processing on the image, and a laser driver control unit 270 that transmits a control signal to a laser driver 210 based on bow-corrected data and a control signal for light intensity correction to control emission of multiple laser light-emitting elements provided in a laser emission unit (LD) 200a.

[0034] 3, multiple beams emitted by a plurality of laser light-emitting elements of the laser emission unit 200a are received by a plurality of photodiodes (PD) 280a, respectively. Output signals of the photodiodes 280a are input to a light amount detection unit (PD detection unit) 280 provided in the laser driver 210, and the light amount detection unit 280 detects the amount of light emitted by each laser light-emitting element based on the output signal.

[0035] The laser driver 210 includes an APC section 260 that performs APC (Automatic Power Control) to control the output of the laser light emitting element to a constant value based on the light emission amount of each laser light emitting element (laser emission section 200a) detected by a light amount detection section 280.

[0036] The laser driver 210 receives a Vshade signal (via a filter circuit 290), a Vref signal, an XSH signal, and an image signal output from a laser scanning unit (LSU) 220a, and controls the amount of light emitted from a laser light emitting element (laser emitting section 200a).

[0037] The reference clock signal generating unit 200m generates a reference clock signal for control, and the BD (Beam Detect) sensor 200k is provided at the start side of the scanning area of ​​the light beam and controls the timing of writing an electrostatic latent image onto the photosensitive drum. In addition, in Fig. 3, Vcc is the power supply voltage.

[0038] 3, the bow correction section 230, the light amount correction section (density correction section) 250, the shading correction section 300, and the laser driver control section 270 are realized by controlling a laser scanning unit 220a having an electronic control configuration mounted on the optical scanning device 200 based on a command signal from the control section 100. The details of each section will be described later. Specifically, the laser scanning unit 220a is configured as an application specific integrated circuit (ASIC).

[0039] [1.4 Contents of control] In this embodiment, the amount of laser light outputted according to the reference voltage (Vref) in the sub-scanning direction is set so as to differ for each beam. A Vshade signal, a Vref signal, an XSH signal, and an image signal are input to the laser driver 210. The Vshade signal is an analog voltage for shading the laser scanning unit 220a. In the shading correction unit 300 of the laser scanning unit 220a (LSU ASIC), the correction value setting unit 300a sets a shading correction value obtained in advance by an experiment or the like, and the PDM wave outputted through the PDM generation unit 300b is converted into an analog voltage Vshade signal by an external filter circuit 290. The signal is inputted from the filter circuit 290 to the laser driver 210. The shading correction value is obtained in advance by an experiment or the like, and may be stored in the ROM of the storage unit 160 of the image forming apparatus in addition to the storage unit 220b.

[0040] The Vref signal is a sub-scanning reference voltage. It is the reference voltage for APC, and the amount of light is proportional to the Vref voltage. By adjusting the gain of the light amount detection unit (PD detection unit) 280 in the laser driver 210, even if the current flowing through the photodiode 280a or the lens transmittance varies, a constant amount of light according to Vref is output to the image surface.

[0041] In this embodiment, the gain of the light amount detection section (PD detection section) 280 is adjusted so that the light amount outputted to the image plane according to Vref differs for each beam in the multi-beam light emitting section 200a.

[0042] The XSH signal is a control signal for the APC signal, and when this XSH signal is valid (low), the APC unit 260 executes APC.

[0043] FIG. 4 is a diagram for explaining the outline of signal processing and signal flow of the optical scanning device 200 shown in FIG. As shown in FIG. 4, image data before bow correction is subjected to bow correction processing by a bow correction section 230, and the image after bow correction is subjected to required processing by a laser scanning unit 220a and input to a laser driver (LDD) 210.

[0044] Fig. 5 is a diagram for explaining the electronic bow correction performed by the bow correction unit 230. As shown in Fig. 5, the electronic bow correction is a process for suppressing color misregistration by shifting image data in the sub-scanning direction in segments so as to cancel out the curvature components that differ for each color.

[0045] In detail, even if the input image data does not have a curve in the sub-scanning direction as shown in Fig. 5(a), the output image may have a bow-shaped curve in the sub-scanning direction as shown in Fig. 5(b) due to the influence of the actual state of the optical system, etc. Therefore, as shown in Fig. 5(c), bow correction is performed on the image data to bend it in the opposite direction, and as shown in Fig. 5(d), bow correction is performed on the image so that the output image becomes linear. Fig. 5(e) shows examples of output images before and after bow correction.

[0046] FIG. 6 illustrates the side effects of bow correction. As shown in Fig. 6, density steps occur because the process simply involves sliding the image segment by segment in the sub-scanning direction. As shown in Fig. 6(a), density steps occur simply by shifting part of the image down one line in the sub-scanning direction (the shift is indicated by the symbol L). Note that density steps can also occur due to registration adjustment in the sub-scanning direction (examples of Ref, 1st line, 2nd line, etc. are shown) as shown in Fig. 6(b).

[0047] FIG. 7 is an explanatory diagram of the cause of the density difference. Reciprocity failure, a phenomenon in which areas that cross scanning (surface crossings) become darker in a multi-beam light-emitting unit that has multiple laser light-emitting elements, changes the distribution of dark areas in the dither pattern, resulting in density differences.

[0048] For example, Fig. 7 shows a schematic diagram of image density unevenness that occurs in a multi-beam scanning system that uses four semiconductor laser channels (LD1 to LD4). In the example of Fig. 7, the area that spans from one surface to the second surface of the polygon in the scanning direction is the surface straddling area.

[0049] During scanning, the boundary area between LD1 and LD2 is exposed almost simultaneously, so a strong amount of light hits it for a short period of time. On the other hand, the boundary area between LD4 and LD1 is exposed first by LD4, and then by LD1, which has a different polygon surface, so a time lag occurs, and as a result, a weak amount of light hits it for a long period of time. As a result of this reciprocity law failure, the image density in the boundary area between LD4 and LD1 is higher than in other areas, resulting in uneven density (see academic paper "Research on Electrostatic Latent Image Measurement in Electrophotography" by Hiroyuki Suhara; published in July 2015).

[0050] 8 shows a micro-level shading image of a dither pattern in a multi-beam laser, affected by reciprocity failure. The light-emitting element has an 8-beam configuration (LD1 to LD8).

[0051] It can be seen from FIG. 8 that the image density is higher in the portion straddling the boundary region between LD8 and LD1 than in other portions, resulting in density unevenness.

[0052] 3, the processes of the bow correction section 230, the light quantity correction section 250, and the shading correction section 300 in FIG. 2 are mainly realized by the laser scanning unit 220a, and corresponding specific configurations will be described.

[0053] As shown in FIG. 3, in the optical scanning device 200, a laser scanning unit (LSU) 220a is controlled by a control unit 100.

[0054] A reference clock (200m) and a BD signal (BD sensor 200k) are input to the laser scanning unit 220a.

[0055] In the laser scanning unit 220a, the bow correction unit 230 performs electronic bow correction processing on the image data according to a control signal from the control unit 100. The light quantity correction unit 250 performs density correction on the image electronically bow-corrected by the bow correction unit 230, and in the case of a predetermined image mode such as character / CAD, no difference is provided in the light quantity correction values ​​of the multiple light-emitting elements, but a difference is provided for a halftone image other than the predetermined image mode. The shading correction unit 300 performs shading correction processing on the image. For this purpose, the shading correction unit 300 creates a shading correction signal Vshade, and the laser driver control unit 270 controls the output of control signals (such as bow correction, density correction using light quantity correction values, and shading correction signals) to the laser driver 210. Based on the control signal output by the laser driver control unit 270, the laser driver 210 controls the multi-beam emission operation of the laser emission unit 200a.

[0056] The laser scanning unit 220a receives a control signal from the control unit 100, image data, a horizontal synchronization signal HSYNC, a reference clock signal 200m, a detection signal from a BD (Beam Detect) sensor 200k, and the like.

[0057] The light amount correction unit 250 calculates a correction value, and inputs the calculated light amount correction value to the laser driver 210 as a light amount correction signal, so that the laser driver 210 controls and corrects the multi-beam emission.

[0058] [Light intensity correction processing] Here, the light amount correction unit 250 in Fig. 2 corrects the light amount of the bow-corrected image so as to eliminate density steps, and the control unit 100 causes the laser scanning unit 220a shown in Fig. 3 to function so as to provide a difference in the light amount correction of the multiple laser light-emitting elements. The laser scanning unit 220a controls the laser driver 210 by the light amount correction with this difference, and adjusts the gain of the light amount detection unit (PD detection unit) 280 so that the light amount output to the image plane according to Vref differs for each beam in the multi-beam light emission unit 200a.

[0059] The control unit 10 controls the light intensity correction values ​​of the multiple light-emitting elements not to have a difference (no gain adjustment) in a specified image mode in which the image has edges such as text / CAD (Computer Aided Design), but to have a difference (gain adjustment) for halftone images other than the specified image mode.

[0060] Here, we will explain the problems that arise when the image is in a specified image mode such as text / CAD, etc. In the case of a specified image mode such as text / CAD, if there is no difference in the set light amount, the jaggies of the diagonal lines will be uniform, as shown in Fig. 9(a), but conversely, if there is a difference in the set light amount, as shown in Fig. 9(b), a problem occurs in which the jaggies of the diagonal lines become uneven (the area around the uneven part where the difference is provided is indicated by the symbol j in a two-dot chain line).

[0061] Therefore, in this embodiment, when the image is not a halftone image but a predetermined image mode such as character / CAD, control is performed so that no difference is provided in the light amount setting value. Images in a specified image mode such as text / CAD basically do not contain halftones, so there is no effect of density differences. Conversely, if a difference is introduced, the problem of uneven jaggies shown in Figure 9(b) will arise, so it is preferable not to introduce a difference.

[0062] On the other hand, in image modes other than the specified image modes such as character / CAD, differences are set in the set light amounts of the multiple light sources, so that even if electronic bow correction is performed, no density steps occur in the halftone image due to the influence of reciprocity law failure.

[0063] In order to confirm the effect of the embodiment, in regard to the setting of the light intensity correction value, (a) of FIG. 10 shows a comparison between the light intensity correction value of the conventional technology (Patent No. 5262602) and (b) of the embodiment.

[0064] In the image forming apparatus of the embodiment, a difference is set in the set light intensities of the multiple light sources so that even if the light intensity correction unit 250 performs light intensity correction, there is no effect of reciprocity law failure and density steps do not occur in the halftone image. In this configuration, the control unit 100 controls the light intensity correction values ​​of the multiple light-emitting elements to invert the sign while decreasing the value from one end side (LD8) of each light-emitting element to the other end side (LD1) (-12, 10.29, ... -1.7, 10.00), as shown in the example of setting the light intensity correction values ​​in Figure 10 (b).

[0065] On the other hand, the conventional light intensity correction value shown in Fig. 10(a) is a method to prevent density steps from occurring in the halftone image by inverting the sign so that the absolute value of the exposure correction value gradually becomes smaller toward the light source located at the center of the multiple light sources (-6, 4, -2, 0 from LD1 to LD4). However, in a specified image mode such as character / CAD, as shown in Fig. 9(b), jaggies worsened and the performance of the specified resolution could not be fully demonstrated.

[0066] That is, it is believed that the reason is that in the conventional technology, the total change in the amount of light for the two lines is large (-2, 2, -2, 0), making the density difference easy to see, as shown in Fig. 10(a). In contrast, in this embodiment, the total change in the amount of light for the two lines is small (1.72, -1.72), as shown in Fig. 10(b), making it possible to make the density difference difficult to see.

[0067] [Selection of laser light emitting element for BD detection] In the embodiment, control is performed to perform BD detection using the beam of a light-emitting element whose correction value is equal to or greater than 0. In particular, it is preferable to perform BD detection using the BD sensor 200k using the beam of a light-emitting element whose correction value is the maximum value. The amount of light on the image plane in the 2400 dpi 8-beam configuration is about half that of the 1200 dpi 4-beam configuration, so the amount of light detected by the BD sensor 200k is also small. When the amount of BD detected light is small in this way, the number of types of BD sensors that can be detected decreases and the BD jitter increases.

[0068] Therefore, in the embodiment, BD detection is performed using a beam that has a large amount of light on the image plane, such as the seventh laser light-emitting element LD7 shown hatched in Figure 10(b), thereby ensuring the type of BD sensor that can be detected and making it possible to reduce BD jitter.

[0069] As described above, the image forming apparatus according to the embodiment has the following advantageous effects. [1] In certain image modes with edges, such as binary images of text / CAD, the jaggies of diagonal lines are made uniform, allowing the performance of the specified resolution to be achieved. [2] In image modes other than character / CAD, such as halftones, the light intensity of the multiple light sources is set to a different level, so even if electronic bow correction is performed, there is no effect of reciprocity failure and no density steps occur in the halftone image. [3] In a configuration in which differences are set in the light intensity of multiple light sources, as shown in FIG. 10, the change in the total light intensity of two lines is small, making density differences less noticeable. [4] By performing BD detection with a beam that has a large amount of light on the image plane, it is possible to ensure the type of BD sensor that can be used for detection and reduce BD jitter.

[0070] Although the embodiments have been described above, the specific configuration is not limited to the embodiments, and designs that do not deviate from the gist of the present invention are also included in the scope of the claims.

[0071] In the embodiment, in a multi-beam type laser emission unit 200a in which multiple laser light-emitting elements emit light, a phenomenon is corrected in which an area across scanning (surface crossing) becomes darker due to reciprocity law failure as a side effect of bow correction, but this embodiment can also be applied to cases where reciprocity law failure has an adverse effect not only in bow correction but also in, for example, surface magnification correction and paper-to-paper registration adjustment.

[0072] In the embodiments, the programs that run on each device are programs that control the CPU and the like (programs that make a computer function) to realize the functions of the above-described embodiments. Information handled by these devices is temporarily stored in a temporary storage device (e.g., RAM) during processing, and is then stored in various ROMs and HDDs, and is read, modified, and written by the CPU as necessary.

[0073] Here, the recording medium for storing the program may be any of semiconductor media (e.g., ROM, non-volatile memory cards, etc.), optical recording media, magneto-optical recording media (e.g., DVD (Digital Versatile Disc), MO (Magneto Optical Disc), MD (Mini Disc), CD (Compact Disc), BD (Blu-ray (registered trademark) Disc, etc.)), magnetic recording media (e.g., magnetic tape, flexible disk, etc.), etc.

[0074] In addition, not only are the functions of the above-described embodiments realized by executing the loaded program, but the functions of the present disclosure may also be realized by processing in cooperation with an operating system or other application programs, etc., based on the instructions of the program.

[0075] Furthermore, when distributing the program on the market, the program can be distributed by storing it in a portable storage device, or by transferring it to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is of course included in the present invention.

[0076] In addition, a part or all of each device in the above-mentioned embodiments may be realized as an LSI (Large Scale Integration), which is typically an integrated circuit. Each functional block of each device may be individually chipped, or may be integrated into a chip in part or in whole. The integrated circuit method is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. Furthermore, if an integrated circuit technology that replaces LSI appears due to the advancement of semiconductor technology, it is of course possible to use an integrated circuit based on that technology. [Explanation of symbols]

[0077] 10 Image forming device 200 Optical Scanning Device 200a Laser emitting unit 200k BD sensor 210 Laser Driver (LDD) 220a Laser scanning unit 250 Light quantity correction unit 260 APC Department 270 Laser driver control unit 280 Light quantity detection unit (PD detection unit)

Claims

1. In an electrophotographic image forming apparatus, a multi-beam emitted from a plurality of light-emitting elements is scanned onto a surface of an image carrier based on image data, a light amount correction unit that corrects the amount of light so as to eliminate density differences in an image and provides differences in light amount correction values ​​of the plurality of light emitting elements; and a control unit for controlling a light amount correction unit so that there is no difference in the set light amounts of a plurality of light emitting elements when the image data is in a predetermined image mode such as character / CAD.

2. In an electrophotographic image forming apparatus, a multi-beam emitted from a plurality of light-emitting elements is scanned onto a surface of an image carrier based on image data, a light amount correction unit that corrects the amount of light so as to eliminate density differences in an image and provides differences in light amount correction values ​​of the plurality of light emitting elements; and a control unit that controls the light intensity correction values ​​of the plurality of light-emitting elements so that the correction value of each light-emitting element is reduced in value from one end side to the other end side of the light-emitting element while inverting its sign.

3. The image forming apparatus according to claim 2 , wherein the control unit detects the BD using a beam from a light emitting element that produces a correction value of 0 or more.

4. A bow correction unit that performs electronic bow correction on image data, 3. The image forming apparatus according to claim 1, wherein the light amount correction unit corrects the light amount of the bow-corrected image so as to eliminate density differences in the cross-exposure segments.

5. 1. A method for controlling an electrophotographic image forming apparatus that scans a surface of an image carrier with multiple beams emitted from a plurality of light-emitting elements based on image data, comprising: a light amount correction step of correcting the light amount so as to eliminate density differences in an image and providing a difference between the light amount correction values ​​of the plurality of light emitting elements; and controlling a light amount correction so as not to cause a difference in the set light amounts of a plurality of light-emitting elements when the image data is in a predetermined image mode such as character / CAD.

6. a bow correction step of electronically bow correcting the image data; 6. The method for controlling an image forming apparatus according to claim 5, wherein the light amount correcting step corrects the light amount of the bow-corrected image so as to eliminate density differences in the cross-exposure segments.

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