JP2009300499A - Exposure device, image forming device, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure device, image forming device, and program for reducing stripe density unevenness in an image formed by using a plurality of light beams for a plurality of main scannings. <P>SOLUTION: A plurality of surface emission lasers sna and expose a predetermined region including a boundary part of an image formed by each of the plurality of scannings. One of the surface emission laser (first light source) for scanning the part nearest to the boundary part and one of the surface emission laser (second light source) adjacent to the surface emission laser are turned on, and the light quantity of the surface emission lasers adjacent to the turned-on surface emission lasers is made lower than the light quantity of the turned-on surface emission lasers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exposure apparatus, an image forming apparatus, and a program.

In Patent Document 1, m light beams are arranged in a line so that a part of adjacent light beams overlap on the photosensitive surface, and main scanning and light beam scanning are performed in a direction crossing the arrangement direction of the light beams. In performing the two-dimensional scanning exposure by performing the sub-scan that scans in the array direction, N is an integer equal to or greater than 1, and the m-th light beam in the light beam for performing the N-th main scan and the (N + 1) -th main light. Disclosed is a scanning exposure method characterized in that scanning exposure is performed by setting the power of at least one light beam of the first light beam in the scanning light beam to a power different from the power of the other light beams. ing.
JP-A-4-149522

  An object of the present invention is to provide an exposure apparatus, an image forming apparatus, and a program that can reduce streaky density unevenness in an image formed by performing main scanning with a plurality of light beams a plurality of times.

  In order to achieve the above object, an exposure apparatus according to claim 1, wherein a light source array in which a plurality of light sources each emitting light are arranged along a first direction, and the light source array in the first direction. Scanning a predetermined area including a boundary portion of the image formed by each of the scans, and a formation control means for controlling to form an image on the surface to be scanned by scanning exposure a plurality of times in a second direction intersecting A first light source that scans a portion closest to the boundary portion among a plurality of light sources to be exposed or at least one second light source adjacent to the first light source and the first light source is turned on and the light is turned on. Lighting control means for controlling the light source of the light source adjacent to the light source that has been lit on both sides of the light source so that the light amount is reduced to be lower than the light amount of the lit light source.

  The invention according to claim 2 is the invention according to claim 1, wherein the number of the second light sources is three or less.

  Further, in the invention according to claim 3, in the invention according to claim 1 or 2, n represents the number of lights that reduce the amount of light compared to the light of the light source that is lit in one scanning exposure, When T represents the light amount of the lit light source, the light amount reduction rate R (%) is calculated by the following equation (1), and based on the light amount reduction rate R and the light amount T of the lit light source, And a lighting means for lighting the one first light source, or the first light source and at least one second light source, and Control is performed so that the light amount of the light source adjacent to the lit light source on both sides of the lit light source is reduced by a predetermined value Y obtained by the calculation means and lower than the light amount of the lit light source. To do.

R ≦ 16 / n (1)
Y = (R / 100) × T (2)
On the other hand, in order to achieve the above object, the image forming apparatus according to claim 4 is emitted from the exposure apparatus according to any one of claims 1 to 3 and each light source of the exposure apparatus. A photosensitive member on which an electrostatic latent image is formed by receiving a light beam, a developing means for developing the electrostatic latent image formed on the photosensitive member, and an image obtained by developing with the developing means are recorded. Transfer means for transferring to a medium.

  Furthermore, in order to achieve the above object, the program according to claim 5 is directed to a computer, wherein a light source array in which a plurality of light sources each emitting light is arranged along a first direction is defined as the first direction. A formation control step for controlling to form an image on the surface to be scanned by scanning exposure a plurality of times in the intersecting second direction, and scanning exposure for a predetermined area including a boundary portion of the image formed by each of the scans A first light source that scans a portion closest to the boundary portion among a plurality of light sources, or at least one second light source adjacent to the first light source and the first light source, and the light source And a lighting control step for performing control so that the light amount of the light source adjacent to the light source that is lit on both sides of the light source is reduced to be lower than the light amount of the light source that is lit.

  According to the first, fourth, and fifth aspects of the invention, streaky density unevenness in an image formed by main scanning a plurality of light beams a plurality of times can be reduced. An effect is obtained.

  According to the second aspect of the present invention, there is an effect that it is possible to reduce streak-like density unevenness in a screen image formed by performing main scanning a plurality of light beams a plurality of times.

  Furthermore, according to the third aspect of the invention, it is possible to reduce the amount of light that is appropriate for reducing streak-like density unevenness in an image formed by performing main scanning a plurality of light beams a plurality of times. The effect of is obtained.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a side view showing a configuration of an image forming apparatus 10 according to the present embodiment.

  As shown in FIG. 1, the image forming apparatus 10 includes a photosensitive drum 12 that is rotated by a motor (not shown) at a predetermined rotational speed in the direction of the arc arrow A that is the sub-scanning direction (first direction). A charger 14 for charging the outer peripheral surface (scanned surface) of the photosensitive drum 12 is provided above the photosensitive drum 12.

  A laser beam scanning device 16 is disposed above the charger 14. The laser beam scanning device 16 modulates a plurality of laser beams emitted from a light source in accordance with an image to be formed and deflects the laser beam in the main scanning direction (second direction). The top is scanned parallel to the axis of the photosensitive drum 12. As a result, an electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 12.

  A developing device 18 is disposed on the side of the photosensitive drum 12. The developing device 18 includes a roller-shaped container that is rotatably arranged. Inside this container, four accommodating parts corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) are formed. 18Y, 18M, 18C, and 18K are provided. Each of the developing devices 18Y, 18M, 18C, and 18K includes a developing roller 20, and stores toners of Y, M, C, and K colors therein. Further, on the opposite side of the developing device 18 with the photoconductor drum 12 interposed therebetween, a charge eliminating / cleaning function having a function of discharging the outer peripheral surface of the photoconductive drum 12 and a function of removing unnecessary toner remaining on the outer peripheral surface. A vessel 22 is arranged.

  The full-color image is formed by the image forming apparatus 10 according to this embodiment while the photosensitive drum 12 is rotated four times. That is, while the photosensitive drum 12 is rotated four times, the charger 14 continues to charge the outer peripheral surface of the photosensitive drum 12, the static elimination / cleaning device 22 continues to eliminate the outer peripheral surface, and the laser beam scanning device 16 should be formed. Every time the photosensitive drum 12 rotates, the laser beam modulated according to any of the Y, M, C, and K image information indicating a color image is scanned on the outer peripheral surface of the photosensitive drum 12. The image information used for modulation of the laser beam is repeated while switching. Further, the developing device 18 operates the developing unit corresponding to the outer peripheral surface in a state where any of the developing rollers 20 of the developing units 18Y, 18M, 18C, and 18K corresponds to the outer peripheral surface of the photosensitive drum 12. The photosensitive drum 12 has the function of developing the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 12 to a specific color and forming a toner image of the specific color on the outer peripheral surface of the photosensitive drum 12. Each time it rotates, the process is repeated while rotating the container so that the developing unit used for developing the electrostatic latent image is switched.

  Thus, every time the photosensitive drum 12 makes one rotation, Y, M, C, and K toner images are sequentially formed on the outer peripheral surface of the photosensitive drum 12 so as to overlap each other. When the drum 12 rotates four times, a full-color toner image is formed on the outer peripheral surface of the photosensitive drum 12.

  An endless intermediate transfer belt 24 is disposed substantially below the photosensitive drum 12. The intermediate transfer belt 24 is wound around rollers 26, 28, and 30, and is disposed so that the outer peripheral surface is in contact with the outer peripheral surface of the photosensitive drum 12. The rollers 26 to 30 are rotated by the driving force of a motor (not shown) being transmitted, and rotate the intermediate transfer belt 24 in the direction of arrow B.

  A transfer device 32 is disposed on the opposite side of the photosensitive drum 12 with the intermediate transfer belt 24 interposed therebetween, and the toner image formed on the outer peripheral surface of the photosensitive drum 12 is transferred to the image on the intermediate transfer belt 24 by the transfer device 32. Transferred to the forming surface. When the toner image formed on the outer peripheral surface of the photoconductive drum 12 is transferred to the intermediate transfer belt 24, the area of the outer peripheral surface of the photoconductive drum 12 that holds the transferred toner image is eliminated. -It is cleaned by the cleaner 22.

  A tray 34 is disposed below the intermediate transfer belt 24, and a large number of sheets P as recording media are accommodated in the tray 34 in a stacked state. In the drawing, a take-out roller 36 is disposed obliquely above and to the left of the tray 34, and a roller pair 38 and a roller 40 are sequentially arranged on the downstream side in the take-out direction of the paper P by the take-out roller 36. The uppermost sheet P in the stacked state is taken out from the tray 34 when the take-out roller 36 is rotated, and is conveyed by the roller pair 38 and the roller 40.

  A transfer device 42 is disposed on the opposite side of the roller 30 with the intermediate transfer belt 24 in between. The sheet P conveyed by the roller pair 38 and the roller 40 is sent between the intermediate transfer belt 24 and the transfer device 42, and the toner image formed on the image forming surface of the intermediate transfer belt 24 is transferred by the transfer device 42. . A fixing device 44 having a pair of fixing rollers is arranged downstream of the transfer device 42 in the conveyance direction of the paper P. The paper P on which the toner image is transferred is transferred to the paper P by the fixing device 44. After being fused and fixed, the image forming apparatus 10 is discharged out of the machine body.

  Next, the laser beam scanning device 16 will be described with reference to FIG. The laser beam scanning device 16 includes a surface emitting laser array 50. The surface emitting laser array 50 includes m surface emitting lasers 50a (m is “11” in the present embodiment) arranged in a line along the sub-scanning direction that intersects the main scanning direction. A laser beam is emitted from each surface emitting laser 50a. Each surface emitting laser 50a has an interval in the sub-scanning direction smaller than the diameter of the laser beam so that a part of the laser beam emitted from the adjacent surface emitting laser 50a overlaps when the laser beam is emitted. Are arranged as follows.

  2 shows only three laser beams for simplification, the surface emitting laser array 50 formed by arraying the surface emitting lasers 50a is configured to emit several tens of laser beams. Further, the arrangement of the surface emitting lasers 50a (arrangement of laser beams emitted from the surface emitting laser array 50) is also arranged two-dimensionally (for example, in a matrix) in addition to the arrangement in one column. It is also possible.

  A collimating lens 52 and a half mirror 54 are sequentially arranged on the laser beam emission side of the surface emitting laser array 50. The laser beam emitted from the surface emitting laser array 50 is made into a substantially parallel light beam by the collimator lens 52 and then incident on the half mirror 54, and a part of the laser beam is separated and reflected by the half mirror 54. A lens 56 and a light amount sensor 58 are arranged in this order on the laser beam reflecting side of the half mirror 54, and a part of the laser beam separated and reflected from the main laser beam (laser beam used for exposure) by the half mirror 54 is The light passes through the lens 56 and enters the light quantity sensor 58, and the light quantity is detected by the light quantity sensor 58.

  An aperture 60, a cylinder lens 62 having power only in the sub-scanning direction, and a folding mirror 64 are arranged in this order on the main laser beam emission side of the half mirror 54, and the main laser beam emitted from the half mirror 54 is emitted from the aperture 60. Then, the light is refracted by the cylinder lens 62 so as to form a long linear image in the main scanning direction in the vicinity of the reflection surface of the rotary polygon mirror 66, and reflected by the folding mirror 64 to the rotary polygon mirror 66 side. Note that the aperture 60 is desirably disposed in the vicinity of the focal position of the collimating lens 52 in order to uniformly shape a plurality of laser beams.

  The rotary polygon mirror 66 is rotated in the direction of the arc C by transmission of the driving force of a motor (not shown), and deflects / reflects the incident laser beam reflected by the folding mirror 64 along the main scanning direction. Fθ lenses 68 and 70 having power only in the main scanning direction are arranged on the laser beam emission side of the rotary polygon mirror 66, and the laser beam deflected and reflected by the rotary polygon mirror 66 is the outer periphery of the photosensitive drum 12. It is refracted by the Fθ lenses 68 and 70 so as to move on the surface at a substantially constant speed and so that the image forming position in the main scanning direction coincides with the outer peripheral surface of the photosensitive drum 12.

  Cylinder mirrors 72 and 74 having power only in the sub-scanning direction are sequentially arranged on the laser beam emission side of the Fθ lenses 68 and 70, and the laser beams transmitted through the Fθ lenses 68 and 70 are connected in the sub-scanning direction. The image position is reflected by the cylinder mirrors 72 and 74 so as to coincide with the outer peripheral surface of the photosensitive drum 12, and is irradiated on the outer peripheral surface of the photosensitive drum 12. The cylinder mirrors 72 and 74 also have a surface tilt correction function that conjugates the outer peripheral surfaces of the rotary polygon mirror 66 and the photosensitive drum 12 in the sub-scanning direction.

  A pickup mirror 76 is disposed on the laser beam emission side of the cylinder mirror 72 at a position corresponding to an end portion (scanning start position) on the scanning start side in the scanning range of the laser beam. A beam position detection sensor 78 is disposed on the beam emission side. Of the laser beams emitted from the surface emitting laser array 50, the reflecting surface of the rotary polygon mirror 66 reflects the laser beam in a direction corresponding to the scanning start position. Is reflected by the pickup mirror 76 and enters the beam position detection sensor 78 (see also the two-dot chain line in FIG. 2).

  The signal output from the beam position detection sensor 78 modulates the laser beam scanned on the outer peripheral surface of the photosensitive drum 12 as the rotary polygon mirror 66 rotates to form an electrostatic latent image each time. Used to synchronize the modulation start timing in main scanning.

  Further, in the laser beam scanning device 16 according to the present embodiment, the collimating lens 52, the cylinder lens 62, and the two cylinder mirrors 72, 74 are arranged so as to be afocal in the sub-scanning direction. As described in Japanese Patent Application Laid-Open No. 2001-215423 already filed by the present applicant, the difference in the scanning line curvature (BOW) of the plurality of laser beams and the variation in the scanning line interval due to the plurality of laser beams. It is for suppressing.

  FIG. 3 is a block diagram showing a main configuration of the electrical system of the image forming apparatus 10 according to the present embodiment.

  As shown in the figure, the image forming apparatus 10 includes a CPU (Central Processing Unit) 80, a ROM (Read Only Memory) 82, a RAM (Random Access Memory) 84, an NVM (Non Volatile Memory) 86, a UI (user / user memory). An interface panel 88 and a communication interface 90 are included.

  The CPU 80 controls the operation of the entire image forming apparatus 10. The ROM 82 functions as a storage unit that stores in advance a control program for controlling the operation of the image forming apparatus 10, an image formation processing program to be described later, various parameters, and the like. The RAM 84 is used as a work area or the like when executing various programs. The NVM 86 stores various types of information that must be retained even when the power switch of the apparatus is turned off.

  The UI panel 88 is composed of a touch panel display or the like in which a transmissive touch panel is superimposed on a display. Various information is displayed on the display surface of the display, and desired information and instructions are input when the user touches the touch panel. Is done.

  The communication interface 90 is connected to a terminal device 92 such as a personal computer and transmits / receives various information such as image information indicating an image formed on the paper P to / from the terminal device 92.

  The CPU 80, ROM 82, RAM 84, NVM 86, UI panel 88, and communication interface 90 are connected to each other via a system bus BUS. Therefore, the CPU 80 accesses the ROM 82, RAM 84, and NVM 86, displays various information on the UI panel 88, grasps the user's operation instruction content on the UI panel 88, and communicates with the terminal device 92 via the communication interface 90. Various types of information can be transmitted and received.

  Further, the image forming apparatus 10 includes an image formation control unit 94. The image forming control unit 94 includes a motor for applying a rotational driving force to the photosensitive drum 12, a charger 14, a laser beam scanning device 16, a developing device 18, a static elimination / cleaning device 22, and rotational driving forces for the rollers 26 to 30. Are connected to each unit used when image formation is performed on the paper P by a xerographic method such as a motor that applies rotational driving force to the rotary polygon mirror 66, and the image formation control unit 94 Control the operation of each part. The image formation control unit 94 is also connected to the system bus BUS described above. Therefore, the CPU 80 can control the operation of the image formation control unit 94.

  Next, the lighting control of the surface emitting laser array 50 that is executed at the time of image formation in the image forming apparatus 10 according to the present embodiment will be described.

  When a plurality of (here, 11) laser beams are simultaneously scanned and exposed on the outer peripheral surface of the photosensitive drum 12 to form an image (specifically, an electrostatic latent image), a plurality of laser beams in each main scan are formed. In the vicinity of the boundary of the scanning area, the laser beam is exposed by overlapping one line, and unless some measure is taken, near the boundary of the scanning area by the multiple laser beams in each main scan (the laser beam is exposed twice) High density streaky density unevenness occurs in the part).

  Therefore, in order to reduce high-density streaky density unevenness, an image for one main scan (hereinafter referred to as “unit image”) is formed as schematically shown in FIG. 4A as an example. The surface emitting laser array 50 allows the amount of laser beams emitted from the surface emitting lasers 50a at both the upper and lower ends of the surface emitting lasers 50a that emit laser beams to be smaller than those of the other surface emitting lasers 50a. A technique for adjusting the amount of emitted laser beam (hereinafter referred to as “first technique”), or a surface on which a laser beam for forming the unit image is emitted, as shown in FIG. 4B as an example. The surface-emitting laser array 5 is designed so that the amount of laser beams emitted from the two surface-emitting lasers 50a at both the upper and lower ends of the light-emitting laser 50a is smaller than that of the other surface-emitting lasers 50a. Techniques for adjusting the light amount of the laser beam emitted (hereinafter, referred to as "second technique".) It has been proposed by.

  Table 1 shows one laser beam when the normal light amount of the laser beam (the light amount of the white circle laser beam in FIGS. 4A and 4B) is 100% in each of the first technique and the second technique. A light amount adjustment amount converted into, a light amount reduction rate per laser beam for light amount adjustment, a light amount per one laser beam in a one-dot chain rectangular frame in FIGS. 4A and 4B (one-dot chain rectangle) An example of an average value of the amount of laser beam in the frame) and an amount of light per one laser beam in the broken-line rectangular frame in the figure (an average value of the amount of laser beam in the broken-line rectangular frame) is shown. Table 1 also shows the number of laser beams for adjusting the amount of light in one main scan of each of the first technique and the second technique.

By the way, the inventors of the present invention performed a simulation for estimating the exposure energy when main scanning by each surface emitting laser 50a is simultaneously performed in the case where each of the surface emitting lasers 50a is 1 to 31.

  FIG. 5 shows the result of the simulation. As shown in the figure, it was found that the exposure energy was not stable from the first scanning line to the seventh scanning line, and the exposure energy was stable from the eighth to the 31st scanning line. .

  As shown in Table 2, when forming an image with 150 screen lines at 2400 dpi (dot per inch), 16 laser beams are used per main scan, and 200 screen lines with 2400 dpi. When forming an image, twelve laser beams are used per main scan, and when forming an image with 2400 dpi and 300 screen lines, eight laser beams are used per main scan. In these cases, as described above, the light quantity of the laser beam emitted from each one or two surface emitting lasers 50a at both the upper and lower ends of the surface emitting laser 50a emitting the laser beam forming the unit image is as follows. Even if the light quantity of the laser beam emitted by the surface emitting laser array 50 is adjusted so as to be smaller than that of the other surface emitting laser 50a, Simulation As can be seen from the results, the impact is not that appears as a density unevenness. However, when an image with 2400 dpi and 600 screen lines is formed, four laser beams are used. In this case, if the above-described light amount adjustment is performed, the above-described simulation results can be understood. In addition, the effect appears as uneven density.

FIG. 6 shows a state in which a line image having a thickness of four laser beams is formed on the paper P at a predetermined pitch (interval of four laser beams) in the sub-scanning direction in the image forming apparatus 10 according to the present embodiment. An example is shown.

  As shown in the figure, the light quantity of the laser beam emitted from the surface emitting lasers 50a at the upper and lower ends of the surface emitting lasers 50a emitting the laser beam forming the unit image is compared with that of the other surface emitting lasers 50a. When the light quantity of the laser beam emitted by the surface emitting laser array 50 is adjusted so as to decrease, the surface emitting lasers 50a emitting the laser beam forming the unit image are emitted from the surface emitting lasers 50a at both the upper and lower ends. The density unevenness occurs in the line image formed by the laser beam.

  By the way, the inventors of the present invention use the image forming apparatus 10 according to the present embodiment to form a halftone image by performing a plurality of main scans under the following five conditions, An experiment was performed in which the maximum amplitude of the spatial frequency of the halftone image corresponding to the density unevenness of the tone image was calculated with an FFT (Fast Fourier Transformation) analyzer. Note that the dot interval of the halftone image is 0.3 mm.

  First condition: The amount of laser beam light is not adjusted.

  Second condition: the amount of laser beams emitted from the surface emitting laser 50a located at one end of the surface emitting laser array 50 in the sub-scanning direction and the surface emitting laser 50a located at the other end is different from that of the other surface emitting laser 50a. The light quantity of the laser beam emitted by the surface emitting laser array 50 is adjusted so as to be smaller than that in FIG.

  Third condition: From the surface emitting laser 50a located at one end of the surface emitting laser array 50 in the sub-scanning direction toward the other end, from the first surface emitting laser 50a and the surface emitting laser 50a located at the other end Laser beams emitted by the surface-emitting laser array 50 so that the amount of laser beams emitted from each of the first surface-emitting lasers 50a toward one end is smaller than that of the other surface-emitting lasers 50a. Adjust the amount of light.

  Fourth condition: From the surface emitting laser 50a located at one end of the surface emitting laser array 50 in the sub-scanning direction toward the other end, from the second surface emitting laser 50a and the surface emitting laser 50a located at the other end. Laser beams emitted by the surface emitting laser array 50 so that the amount of laser beams emitted from each of the second surface emitting lasers 50a toward one end is smaller than that of the other surface emitting lasers 50a. Adjust the amount of light.

  Fifth condition: From the surface emitting laser 50a located at one end of the surface emitting laser array 50 in the sub-scanning direction toward the other end, from the third surface emitting laser 50a and the surface emitting laser 50a located at the other end Laser beams emitted by the surface emitting laser array 50 so that the amount of laser beams emitted from each of the third surface emitting lasers 50a toward one end is smaller than that of the other surface emitting lasers 50a. Adjust the amount of light.

FIG. 7 shows the experimental results. In addition, the vertical axis | shaft of the same figure has shown the value which multiplied the magnitude | size of the maximum amplitude of the spatial frequency calculated by the FFT analyzer, and the horizontal axis has shown the 1st-5th conditions. Also,
It can be seen from the figure that the density unevenness when the halftone image is formed under the first condition is larger than the density unevenness when the halftone image is formed under the second to fifth conditions. In addition, among the second to fifth conditions, the density unevenness of the halftone image formed under the fifth condition may be extremely larger than the density unevenness of the halftone image formed according to the second to fourth conditions. I understand.

  In addition, when a sensory test for visually evaluating the density unevenness of the halftone image formed under the first to fifth conditions was performed, the density unevenness was visually recognized in the halftone image formed according to the first and fifth conditions. However, density unevenness was not visually recognized in the halftone image formed under the second to fourth conditions.

  Therefore, in the image forming apparatus 10 according to the present embodiment, an image forming process for forming an image under the third condition is executed.

  Next, the operation of the image forming apparatus 10 when image information indicating an image to be formed on the paper P is input will be described with reference to FIG. FIG. 8 is a flowchart showing the flow of processing of an image forming processing program executed by the CPU 80 of the image forming apparatus 10 at this time, and the program is stored in a predetermined area of the ROM 82 in advance.

  In step 100 of FIG. 9, the image forming control unit 94 performs drive control of the motor so as to start rotation of the photosensitive drum 12 and the rotary polygon mirror 66 in order to start sub-scanning and main scanning. In step 102, the process waits until the photosensitive drum 12 and the rotary polygon mirror 66 reach a rotation speed determined to be able to form a good image.

  In the next step 104, as shown in FIG. 9 as an example, the image forming control unit 94 receives an image of the second line of each unit image from the boundary between adjacent unit images in the sub-scanning direction. The surface emitting laser 50a that forms the first surface emitting laser 50a toward the other end from the surface emitting laser 50a located at one end of the surface emitting laser array 50 in the sub-scanning direction and the surface emitting located at the other end The light amount of the laser beam emitted from the first surface emitting laser 50a toward the one end from the laser 50a is a predetermined value Y (here, (normal light amount) × 0) compared to the normal light amount of the other surface emitting laser 50a. .08) The amount of laser beams emitted from the surface emitting laser array 50 is controlled so as to decrease, and the laser beams are modulated and emitted according to image information. Performs control to perform a more main scanning.

  Therefore, in the image forming apparatus 10 according to the present embodiment, as shown in the figure, by repeating the process of step 104, a predetermined area including a boundary portion between unit images formed by each main scan. One surface emitting laser 50a (first light source) that scans a portion closest to the boundary portion among the four surface emitting lasers 50a that scan and expose (here, a region corresponding to four lines across the boundary portion) and the The surface emitting laser 50a (second light source) adjacent to the surface emitting laser 50a across the boundary portion is turned on, and the surface emitting light adjacent to the lighted surface emitting laser 50a on both sides of the lighted surface emitting laser 50a. The light amount of the laser 50a is turned on with being lower than the light amount of the surface emitting laser 50a that has been turned on.

  By the way, in the image forming apparatus 10 according to the present embodiment, the predetermined value Y is stored in advance in the NVM 86. In the image forming apparatus 10 according to the present embodiment, prior to executing the image forming process, the number n of laser beams for reducing the amount of light in one main scan is input via the UI panel 88, and the following (3) is performed by the CPU 80. The light quantity reduction rate R (%) is calculated by the equation. Then, the CPU 80 calculates a predetermined value Y by the following equation (4) based on the light amount decrease rate R (%) and the normal light amount T of another laser beam, and stores the predetermined value Y in the NVM 86.

R ≦ 16 / n (3)
Y = (R / 100) × T (4)
In the image forming apparatus 10 according to the present embodiment, the expression (3) is expressed by the inventors of the present invention from the surface emitting laser 50a positioned at one end in the sub-scanning direction of the surface emitting laser array 50 toward the other end. Forming a halftone image while changing the light quantity of the laser beam emitted from the first surface emitting laser 50a and the surface emitting laser 50a located at the other end toward the one end, A sensory test for visually evaluating the density unevenness of the halftone image for each light quantity, and the first surface emission from the surface emitting laser 50a located at one end in the sub-scanning direction of the surface emitting laser array 50 toward the other end. While changing the light quantity of the laser beam emitted from the first surface emitting laser 50a toward the one end from the laser 50a and the surface emitting laser 50a located at the other end, the amount of four laser beams is changed. A line image having a thickness is formed on the paper P at a predetermined pitch (interval of four laser beams) in the sub-scanning direction, and is derived by performing a sensory test that visually evaluates the density unevenness of the line image for each light quantity. It is a formula.

  Table 3 shows the light amount adjustment amount converted to one laser beam when the normal light amount (white light amount) of the laser beam in FIG. 9 is 100%, and the light amount reduction per laser beam for adjusting the light amount. Rate, the amount of light per laser beam in the dashed-dotted rectangular frame in the figure (the average value of the amount of laser beam in the dashed-dotted rectangular frame), and per laser beam in the dashed-line rectangular frame in the figure An example of the light quantity (average value of the light quantity of the laser beam in the broken-line rectangular frame) is shown. Table 3 also shows the number of laser beams for adjusting the light amount in one main scan of the image forming apparatus 10 according to the present embodiment. Here, the light amount reduction rate per laser beam for adjusting the light amount is set to 8%. However, the present invention is not limited to this, and the light amount reduction rate only needs to satisfy the expression (3).

In the next step 106, it is determined whether or not all the main scans have been completed. If the determination is affirmative, the process proceeds to step 108. If the determination is negative, the process returns to step 104.

  In step 108, the image forming control unit 94 is controlled to develop the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 12 by the developing device 18, and in the next step 110, the image forming control unit 94 is controlled. 94, the toner image formed on the outer peripheral surface of the photosensitive drum 12 by the transfer device 32 is transferred to the image forming surface of the intermediate transfer belt 24, and formed on the image forming surface of the intermediate transfer belt 24 by the transfer device 42. Control is performed so that the toner image thus transferred is transferred to the paper P, and in the next step 112, drive control of the motor is performed so that the image formation controller 94 stops the rotation of the photosensitive drum 12 and the rotary polygon mirror 66. After that, the image forming processing program is terminated.

  In the present embodiment, steps 100 to 102 correspond to the formation control step of the present invention, and step 104 corresponds to the lighting control step of the present invention.

  As mentioned above, although this invention was demonstrated using the said embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various changes or improvements can be added to the above-described embodiment without departing from the gist of the invention, and forms to which the changes or improvements are added are also included in the technical scope of the present invention.

  Moreover, the said embodiment does not limit the invention described in the claim, and all the combinations of the characteristics demonstrated in the said embodiment are essential for the solution means of invention. Is not limited. The above-described embodiments include various stages of the invention, and various inventions can be extracted by combinations according to the situation in a plurality of disclosed constituent requirements. Even if some constituent requirements are deleted from all the constituent requirements shown in the above-described embodiment, as long as an effect is obtained, a configuration in which these some constituent requirements are deleted can be extracted as an invention.

  For example, in the above embodiment, one surface that scans a portion closest to the boundary portion among the four surface emitting lasers 50a that scan and expose a predetermined region including the boundary portion between unit images formed by each of the main scans. The surface emitting laser 50a and the surface emitting laser 50a adjacent to the surface emitting laser 50a across the boundary portion are turned on, and the surface emitting light adjacent to the lighted surface emitting laser 50a on both sides of the lighted surface emitting laser 50a. The embodiment in the case where the light amount of the laser 50a is turned on with the light amount lower than that of the surface emitting laser 50a that has been turned on has been described. However, the present invention is not limited to this, and FIG. As shown in Fig. 5, the image is scanned in a predetermined area including a boundary portion between unit images formed by each main scanning (here, an area corresponding to six lines across the boundary portion). Among the six surface emitting lasers 50a to be exposed, one surface emitting laser 50a (first light source) that scans a portion closest to the boundary portion and three surface emitting lasers 50a (second light sources) adjacent to the surface emitting laser 50a. ) Is turned on, and the light quantity of the surface-emitting laser 50a adjacent to the light-emitting surface-emitting laser 50a on both sides of the light-emitting surface-emitting laser 50a is lower than the light quantity of the light-emitting surface-emitting laser 50a. You may be made to do.

  As an example, as shown in FIG. 11, there are three scanning exposures for a predetermined region including a boundary portion between unit images formed by each of the main scans (here, a region corresponding to three lines across the boundary portion). One surface emitting laser 50a (first light source) that scans a portion of the surface emitting laser 50a that is closest to the boundary portion is turned on, and the lighted surface emitting laser 50a is turned on both sides of the lighted surface emitting laser 50a. The surface light emitting laser 50a adjacent to the surface emitting laser 50a may be turned on with a light amount lower than that of the lighted surface emitting laser 50a.

  Further, among the five surface emitting lasers 50a that scan and expose a predetermined region including a boundary portion between unit images formed by main scanning (for example, a region corresponding to five lines across the boundary portion) One surface emitting laser 50a (first light source) that scans the nearest portion and two surface emitting lasers 50a (second light source) adjacent to the surface emitting laser 50a are turned on, and the surface emitting laser 50a that is turned on The light amount of the surface emitting laser 50a adjacent to the surface emitting laser 50a that is lit on both sides may be turned on with the light amount of the surface emitting laser 50a being lit lower than that of the surface emitting laser 50a that is lit.

  Table 4 shows the light amount adjustment amount and light amount converted into one laser beam when the normal light amount of the laser beam in FIG. 10 and FIG. 11 (the light amount of the white circle laser beam in FIG. 10 and FIG. 11) is 100%. The light amount reduction rate per one laser beam to be adjusted, the light amount per laser beam in the one-dot chain line rectangular frame in the figure (average value of the light amount of the laser beam in the one-dot chain rectangular frame), and the same An example of the amount of light per laser beam in the broken-line rectangular frame (average value of the amount of laser beam in the broken-line rectangular frame) is shown. Table 4 also shows the number of laser beams for adjusting the light amount in one main scan shown in FIGS.

Moreover, although the said embodiment gave and demonstrated the example at the time of using the surface emitting laser 50a as a light source of this invention, this invention is not limited to this, LED (Light Emitting Diode) etc. Other light sources may be used.

  In the above-described embodiment, a case has been described in which high-density streak-like density unevenness occurs in the vicinity of the boundary of the scanning area due to a plurality of laser beams in each main scanning. For example, the rotational speed of the photosensitive drum 12 is slow. In this case, a gap is generated in the vicinity of the boundary of the scanning area by a plurality of laser beams in each main scanning, and this may cause low density streak density unevenness. In this case, a low-density streak is produced by emitting a laser beam to the surface emitting laser array 50 in which the light amount is reduced compared to the normal light amount in the above embodiment so that the light amount is increased compared to the normal light amount. The density unevenness in the shape is eliminated.

  In addition, the configuration of the image forming apparatus 10 described in the above embodiment (see FIGS. 1 to 3) is merely an example, and unnecessary portions are deleted or new portions are deleted without departing from the gist of the present invention. Needless to say, it can be added.

  The processing flow of the image forming processing program described in the above embodiment (see FIG. 8) is also an example, and unnecessary steps are deleted or new steps are added without departing from the gist of the present invention. Needless to say, the processing order can be changed.

1 is a side view illustrating a configuration of an image forming apparatus according to an embodiment. It is a perspective view which shows the structure of the laser beam scanning apparatus which concerns on embodiment. 1 is a block diagram illustrating a main configuration of an electrical system of an image forming apparatus according to an embodiment. It is a conceptual diagram which shows an example of the scanning pattern of the laser beam in the conventional image forming apparatus. It is a graph which shows the exposure energy of the laser beam which concerns on embodiment. 4 is a schematic diagram illustrating a state in which line images are formed on a sheet at a predetermined pitch in the sub-scanning direction in the image forming apparatus according to the embodiment. FIG. 6 is a graph illustrating the density unevenness of a halftone image formed under the first to fifth conditions in the image forming apparatus according to the embodiment. 6 is a flowchart showing a flow of processing of an image forming processing program according to the embodiment. 4 is a conceptual diagram illustrating an example of a scanning pattern of a laser beam in the image forming apparatus according to the embodiment. FIG. It is a conceptual diagram which shows the other example of the scanning pattern of the laser beam in the image forming apparatus which concerns on embodiment. It is a conceptual diagram which shows the other example of the scanning pattern of the laser beam in the image forming apparatus which concerns on embodiment.

Explanation of symbols

10 Image forming apparatus 12 Photosensitive drum (photosensitive member)
16 Laser beam scanning device 18 Developing device (developing means)
32, 42 Transfer device (transfer means)
50 Surface emitting laser array (light source array)
50a Surface emitting laser (light source)
80 CPU (formation control means, lighting control means, calculation means)

Claims (5)

A light source array in which a plurality of light sources each emitting light are arranged along a first direction;
Formation control means for controlling the light source array to form an image on the surface to be scanned by scanning and exposing a plurality of times in a second direction intersecting the first direction;
One first light source that scans a portion closest to the boundary portion among a plurality of light sources that scan and expose a predetermined region including a boundary portion of an image formed by each of the scans, or the first light source and the first At least one second light source adjacent to the light source is turned on, and the light amount of the light source adjacent to the light source that is lit on both sides of the light source is turned on to be lower than the light amount of the lit light source. Lighting control means to control;
An exposure apparatus comprising:   The exposure apparatus according to claim 1, wherein the number of the second light sources is three or less. When n represents the number of lights that reduce the amount of light compared to the light of the lit light source in one scanning exposure, and T represents the amount of light of the lit light source, the light quantity reduction rate according to the following equation (1) R (%) is calculated, and further comprises a calculation means for calculating a predetermined value Y by the following equation (2) based on the light quantity reduction rate R and the light quantity T of the lighted light source.
The lighting control unit turns on the one first light source, or the first light source and at least one second light source, and the light amount of the light source adjacent to the light source that is lit on both sides of the lit light source. The exposure apparatus according to claim 1 or 2, wherein the exposure apparatus is controlled so as to be turned on by reducing a predetermined value Y obtained by the calculation means from the light amount of the lighted light source.
R ≦ 16 / n (1)
Y = (R / 100) × T (2) An exposure apparatus according to any one of claims 1 to 3,
A photoreceptor on which an electrostatic latent image is formed by receiving a light beam emitted from each light source of the exposure apparatus;
Developing means for developing the electrostatic latent image formed on the photoreceptor;
Transfer means for transferring an image obtained by development by the developing means to a recording medium;
An image forming apparatus. On the computer,
A light source array in which a plurality of light sources each emitting light is arranged along a first direction is scanned and exposed a plurality of times in a second direction intersecting the first direction, thereby forming an image on the surface to be scanned. Forming control step to control,
One first light source that scans a portion closest to the boundary portion among a plurality of light sources that scan and expose a predetermined region including a boundary portion of an image formed by each of the scans, or the first light source and the first At least one second light source adjacent to the light source is turned on, and the light amount of the light source adjacent to the light source that is lit on both sides of the light source is turned on to be lower than the light amount of the lit light source. A lighting control step to control,
A program for running