JP6950487B2 - Optical writing device and image forming device - Google Patents

Description

The present invention relates to an optical writing device and an image forming device, and more particularly to a technique for suppressing deterioration of image quality due to distortion of a microlens array in a line optical type optical writing device.

The electrophotographic image forming apparatus forms an electrostatic latent image by exposing the surface of the photoconductor using an optical writing apparatus. The optical scanning type optical writing device writes light to the photoconductor drum by deflecting and scanning the emitted light of the laser diode using a scanning optical system. Since the scanning optical system rotationally drives a rotating multifaceted mirror (polygon mirror), noise and vibration are generated. Moreover, it is difficult to miniaturize the scanning optical system due to its structure. Therefore, there is a limit to miniaturization and cost reduction of an image forming apparatus equipped with an optical scanning type optical writing apparatus.

On the other hand, the line optical type optical writing device is composed of a light source substrate in which fine light emitting elements are arranged in a line and a lens array in which lenses are arranged in a line, and emits light from the light emitting elements. The light is focused on the surface of the photoconductor with a lens array. The line optical type optical writing device does not require a mechanically driven member, does not generate vibration or noise, and is easy to miniaturize, so that it is widely used.

Japanese Unexamined Patent Publication No. 11-147326

The lens array used in the line optical optical writing device is a microlens array (MLA) in which microlenses having a diameter of several μm to several mm constituting a two-lens telecentric optical system are arranged in a two-dimensional array. ) Is generally used. By holding the light source substrate on which the light emitting element is mounted and the microlens array by the holding member, the positional relationship between the light emitting element, the microlens array, and the surface of the photoconductor is defined.

The microlens array has a long shape in the main scanning direction, and when the temperature inside the image forming apparatus rises, it expands significantly in the longitudinal direction. If the coefficient of thermal expansion differs between the microlens array and the holding member, a linear expansion difference occurs between the microlens array and the holding member due to the thermal expansion of the microlens array.

When the microlens array is distorted so as to be curved due to this linear expansion difference, the optical axis of the microlens constituting the microlens array is tilted with respect to the main ray direction of the emitted light of the light emitting element, and the position of the exposure spot is changed. There is a risk of misalignment.

Such misalignment of the exposure spot is more remarkable in the place where the change in the positional relationship between the light emitting element, the microlens array and the surface of the photoconductor is large, and the deterioration of the image quality cannot be ignored. Such problems also occur when the microlens array is distorted due to causes other than heat, such as humidity.

Such a problem may also occur when a condensing means other than the microlens array such as a rod lens array is used.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical writing device and an image forming device capable of suppressing image quality deterioration caused by distortion of a light collecting means. do.

In order to achieve the above object, in the optical writing device according to the present invention, a plurality of light emitting element matrices composed of a plurality of light emitting elements are arranged, and different light emitting element matrices are assigned to different pixels. A light-emitting device that lights a part of the light-emitting elements for each light-emitting element matrix and condenses the emitted light on the surface of the photoconductor by condensing the emitted light on the surface of the photoconductor to expose one pixel at a time. Calculation to calculate the amount of misalignment between the detected exposure position and the regular pixel position for the detection means that detects the exposure position by lighting at least a part of the light emitting elements of the matrix and the light emitting element that the detection means is lit. The regular pixel position of the plurality of light emitting elements constituting the light emitting element matrix can be exposed from the means, the light emitting element in which the detecting means is lit, and the position shift amount calculated by the calculation means. It is characterized by comprising a specific means for specifying a light emitting element and an exposure means for lighting and exposing the specified light emitting element.

In this way, since the light emitting element capable of exposing the desired pixel position is specified and exposed for each light emitting element matrix, the image quality deterioration due to the distortion of the microlens array can be suppressed.

In this case, for each light emitting element matrix, the cathode terminals of the plurality of light emitting elements are electrically connected to the common wiring, and the anode terminals are electrically connected to the individual wirings. The means may select the light emitting element to be lit by selecting the wiring electrically connected to the anode terminals of the plurality of light emitting elements.

Further, for each light emitting element matrix, the anode terminals of the plurality of light emitting elements are electrically connected to a common wiring, and the cathode terminals are electrically connected to individual wirings. , The light emitting element to be lit may be selected by selecting the wiring electrically connected to the cathode terminals of the plurality of light emitting elements.

Further, in the light emitting element matrix, the plurality of light emitting elements are arranged in a two-dimensional lattice, and the light emitting elements arranged in the same row in the two-dimensional lattice are electrically connected to a wiring in which the anode terminals are common. The cathode terminals of the light emitting elements arranged in the same row are electrically connected to a common wiring, and the detection means and the exposure means are connected to the wiring connected to the anode terminal. , The light emitting element to be lit may be selected by selecting the wiring connected to the cathode terminal.

Further, in the light emitting element matrix, the exposed areas may be the same between the light emitting elements.

Further, in the light emitting element matrix, the shape of the exposed region may be the same between the light emitting elements.

Further, in the light emitting element matrix, the plurality of light emitting elements are arranged in a two-dimensional lattice, and the row direction and the column direction of the two-dimensional lattice are obliquely intersected with each other in the arrangement direction of the light emitting element matrix. Is desirable.

Further, the image forming apparatus according to the present invention is characterized by including the optical writing apparatus according to the present invention.

It is a figure which shows the main structure of the image forming apparatus which concerns on 1st Embodiment of this invention. (A) is a cross-sectional view showing the main configuration of the optical writing device 100, and (b) is a plan view and a cross-sectional view showing the main configuration of the light emitting substrate 200. It is a block diagram which shows the main structure of the TFT circuit 214. It is a circuit diagram which shows the structure of the selection circuit 301 and the light emitting block 302. It is a block diagram which shows the structure of a driver IC 212. It is a circuit diagram which shows the main structure of a light emitting element matrix 320. It is a figure which shows the arrangement of a light emitting element matrix 320 and a light emitting element 600 on a light emitting substrate 200. (A) is a plan view showing the wiring pattern of the light emitting element matrix 320, and (b) is a cross-sectional view of the wiring pattern of the light emitting element matrix 320 on the DD line. (A) describes the white streaks appearing in the pixels when the column direction of the light emitting element matrix 320 is parallel to the sub-scanning direction, and (b) is the case where the column direction of the light emitting element matrix 320 obliquely intersects the sub-scanning direction. It is a figure which shows the pixel formed in. (A) is a cross-sectional view of the optical writing device 100, (b) is a plan view of the G1 lens 1010, and (c) is a plan view of the aperture 1020. It is a block diagram which shows the main structure of the control part 150. It is a flowchart which shows the generation process of lighting control data. It is a figure which illustrates the test image data. (A) is a diagram for explaining a position shift vector, and (b) is a diagram for explaining lighting control data. It is a circuit diagram which shows the structure of the light emitting element matrix 320 which concerns on a modification. (A) is a plan view showing the wiring pattern of the light emitting element matrix 320, and (b) is a cross-sectional view of the wiring pattern of the light emitting element matrix 320 on the EE line.

Hereinafter, embodiments of the optical writing device and the image forming device according to the present invention will be described with reference to the drawings.

The optical writing device and the image forming device according to the present embodiment are devices that form an electrostatic latent image of each pixel by using a light emitting element matrix in which a plurality of light emitting elements are arranged in a grid pattern, and form a test image. , The image is taken to detect the deviation of the pixel formation position, and the position deviation is suppressed by selecting the light emitting element to emit light in the light emitting element matrix according to the detected position deviation.
[1] Configuration of Image Forming Device First, the configuration of the image forming apparatus according to the present embodiment will be described.

As shown in FIG. 1, the image forming apparatus 1 is a so-called tandem color printer, and forms an image of forming toner images of yellow (Y), magenta (M), cyan (C), and black (K) colors. It includes forming stations 110Y, 110M, 110C and 110K. The image forming stations 110Y, 110M, 110C and 110K have photoconductor drums 101Y, 101M, 101C and 101K that rotate in the direction of arrow A.

Around the photoconductor drums 101Y, 101M, 101C and 101K, charging devices 102Y, 102M, 102C and 102K, optical writing devices 100Y, 100M, 100C and 100K, developing devices 103Y, 103M, 103C and 103K are sequentially arranged along the outer peripheral surface. Primary transfer chargers 104Y, 104M, 104C and 104K and cleaning devices 105Y, 105M, 105C and 105K are arranged.

The charging devices 102Y, 102M, 102C and 102K uniformly charge the outer peripheral surfaces of the photoconductor drums 101Y, 101M, 101C and 101K. The optical writing devices 100Y, 100M, 100C and 100K expose the outer peripheral surfaces of the photoconductor drums 101Y, 101M, 101C and 101K to form an electrostatic latent image.

The developing devices 103Y, 103M, 103C and 103K supply toner of each color of YMCK to develop an electrostatic latent image and form a toner image of each color of YMCK. The primary transfer chargers 104Y, 104M, 104C and 104K electrostatically transfer the toner image carried by the photoconductor drums 101Y, 101M, 101C and 101K to the intermediate transfer belt 106 (primary transfer).

The cleaning devices 105Y, 105M, 105C and 105K remove the electric charge remaining on the outer peripheral surfaces of the photoconductor drums 101Y, 101M, 101C and 101K after the primary transfer and remove the residual toner. In the following, when the configuration common to the image forming stations 110Y, 110M, 110C and 110K will be described, the characters of YMCK will be omitted.

The intermediate transfer belt 106 is an endless belt, which is stretched on the secondary transfer roller pair 107 and the driven rollers 108 and 109, and rotates in the direction of arrow B. By performing the primary transfer in accordance with this rotational running, the toner images of each color of YMCK are superposed on each other to form a color toner image. The intermediate transfer belt 106 rotates while carrying the color toner image to convey the color toner image to the secondary transfer nip of the secondary transfer roller pair 107.

The two rollers constituting the secondary transfer roller pair 107 are pressed against each other to form a secondary transfer nip. A secondary transfer voltage is applied between these rollers. When the recording sheet S is supplied from the paper feed tray 120 in time with the transfer of the color toner image by the intermediate transfer belt 106, the color toner image is electrostatically transferred to the recording sheet S at the secondary transfer nip (secondary). Transcription).

The recording sheet S is conveyed to the fixing device 130 while carrying the color toner image, and after the color toner image is heat-fixed, it is discharged onto the paper ejection tray 140. The in-line sensor 160 is a CCD (Charge Coupled Device) camera, which is arranged on the transport path of the recording sheet S from the fixing device 130 to the discharge port 161 and captures an image of toner fixed on the recording sheet S. Then, the image data is generated.

The image forming apparatus 1 further includes a control unit 150. When the control unit 150 receives a print job from an external device such as a PC (Personal Computer), the control unit 150 controls the operation of the image forming device 1 to execute image forming. At the time of image formation, density unevenness is suppressed by referring to the image data generated by the inline sensor 160.
[2] Configuration of Optical Writing Device 100 Next, the configuration of the optical writing device 100 will be described.

As shown in FIG. 2A, the optical writing device 100 has a configuration in which the light emitting substrate 200 and the microlens array 201 are held by the holding member 202, and the emitted light L of the light emitting substrate 200 is the microlens array 201. Condenses light on the outer peripheral surface of the photoconductor drum 101. The cables and the like for connecting the optical writing device 100 and the other devices of the image forming device 1 are not shown.

As shown in FIG. 2B, the light emitting substrate 200 includes a glass substrate 210, a sealing plate 211, a driver IC (Integrated Circuit) 212, and the like. A TFT (Thin Film Transistor) circuit 214 is formed on the glass substrate 210, and 15,000 light emitting element matrices (not shown) correspond to each other at a pitch of 21.2 μm (1200 dpi) along the main scanning direction. It is staggered for each lens.

Further, the substrate surface of the glass substrate 210 on which the light emitting element matrix is arranged is a sealing region, and the sealing plate 211 is attached with the spacer frame 213 interposed therebetween. As a result, the sealing region is sealed with dry nitrogen or the like sealed so as not to come into contact with the outside air. In addition, for moisture absorption, a hygroscopic agent may be enclosed in the sealing region together. The sealing plate 211 may be, for example, sealing glass or may be made of a material other than glass.

The driver IC 212 is mounted outside the sealing region of the glass substrate 210. The ASIC (Application Specific Integrated Circuit) 220 of the control unit 150 inputs a digital luminance signal to the driver IC 212 via the flexible wire 221. The driver IC 212 converts the digital luminance signal into an analog luminance signal (hereinafter, simply referred to as “luminance signal”) and inputs it to the drive circuit for each light emitting element matrix. The drive circuit generates a drive current of the light emitting element matrix according to the luminance signal. In the present embodiment, the luminance signal is a voltage signal.
[3] TFT circuit 214
Next, the configuration of the TFT circuit 214 will be described.

As shown in FIG. 3, in the TFT circuit 214, 15,000 light emitting element matrices 320 are grouped into 150 light emitting blocks 302, 100 each. In the present embodiment, a case where one light emitting element matrix 320 includes 100 light emitting elements and each light emitting element is an OLED (Organic Light Emitting Diode) will be described as an example, but the light emitting element is a semiconductor LED (semiconductor LED). Light Emitting Diode) may be used.

The driver IC 212 contains 150 current DACs (Digital to Analogue Converters) 300. The current DAC 300 is a digitally controllable variable current source, and has a one-to-one correspondence with the light emitting block 302, respectively. The light emitting blocks 302 are arranged in the main scanning direction. The microlens constituting the microlens array 201 and the light emitting element matrix 320 have a one-to-one correspondence, and the emitted light of the light emitting element included in one light emitting element matrix 320 is a photoconductor drum by one microlens. It is focused on the outer peripheral surface of 101.

A selection circuit 301 is arranged on each circuit from the current DAC 300 to the light emitting block 302. Further, a reset circuit 303 is connected on the circuit from the driver IC 212 to the selection circuit 301. Each current DAC 300 sequentially outputs a luminance signal to 100 light emitting element matrices 320 under its control by so-called rolling drive. One current DAC 300 is time-shared by 100 light emitting element matrices 320 included in the light emitting block 302 corresponding to one-to-one.

As shown in FIG. 4, the light emitting block 302 is composed of 100 light emitting pixel circuits, and each light emitting pixel circuit has one capacitor 321 and one driving TFT 322 and one light emitting element matrix 320. Further, the selection circuit 301 includes a shift register 311 and 100 selection TFTs 312, and the reset circuit 303 includes a reset TFT 340.

The shift register 311 is connected to the gate terminal of each of the 100 selective TFTs 312, and turns on the selected TFTs 312 sequentially every main scanning period. The source terminal of the selected TFT 312 is connected to the current DAC 300 via the write wiring 330, and the drain terminal is connected to the first terminal of the capacitor 321 and the gate terminal of the drive TFT 322.

When the shift register 311 turns on the selective TFT 312, the output current of the current DAC 300 flows to the first terminal of the capacitor 321 and charges are accumulated in the capacitor 321. The charge stored in the capacitor 321 is retained until it is reset by the reset circuit 303.

The first terminal of the capacitor 321 is also connected to the gate terminal of the drive TFT 322, and the second terminal of the capacitor 321 is connected to the source terminal of the drive TFT 322 and the power supply wiring 331. One terminal of the switch 401 is connected to the drain terminal of the drive TFT 322, the anode side terminal of the light emitting element matrix 320 is connected to the other terminal of the switch 401, and the cathode side terminal of the light emitting element matrix 320 is the ground wiring 332. It is connected to the. The ground wiring 332 is connected to the ground terminal GND, and the power supply wiring 331 is connected to the constant voltage source Vpwr.

The constant voltage source Vpwr is a supply source of the drive current supplied to the light emitting element matrix 320, and the drive TFT 322 transmits a brightness signal (voltage signal) held between the first and second terminals of the capacitor 321. By being applied as the gate-source voltage Vgs, a drive current of a current amount corresponding to the brightness signal is supplied to the light emitting element matrix 320.

For example, when a luminance signal corresponding to H is written to the capacitor 321, the drive TFT 322 is turned on and the light emitting element matrix 320 emits light. When a luminance signal corresponding to L is written to the capacitor 321, the drive TFT 322 is turned off and the light emitting element matrix 320 does not emit light. The luminance signal written to the capacitor 321 is held until the next luminance signal is written or the reset TFT 340 is turned on.

When the reset TFT 340 is turned on, the wiring from the current DAC 300 to the capacitor 321 is reset to the reset potential. The reset potential may be a Vdd potential or a ground potential, and an appropriate potential may be selected. Further, in the present embodiment, the case where the light emitting element matrix 320 does not emit light in the reset state will be described, but the light emitting element matrix 320 may emit light in the reset state.

In the present embodiment, the case where the drive TFT 322 is a p-channel is described as an example, but it goes without saying that an n-channel drive TFT 322 may be used.

Further, in the present embodiment, the reset circuit 303 is provided separately from the driver IC 212 and is placed under the control of the driver IC 212. Instead, the reset circuit 303 may be built in the driver IC 212. .. Further, the function of the reset circuit 303 may be realized by changing the polarity of the current output by the current DAC at the time of reset and at the time of writing. Further, instead of the reset TFT 340, a switching element other than the TFT may be used.
[4] Driver IC212
Next, the driver IC 212 will be described.

As shown in FIG. 5, the driver IC 212 includes a lighting control unit 510 and a lighting control table 520, and the lighting control table 520 records lighting control data for each of 15,000 light emitting element matrices 320. The lighting control unit 510 refers to the lighting control data recorded in the lighting control table 520 for each light emitting element matrix 320 to indicate the light emitting element to be emitted.
[5] Light emitting element matrix 320
Next, the light emitting element matrix 320 will be described.

As shown in FIG. 6, the light emitting element matrix 320 has 100 light emitting elements 600 arranged in 10 rows and 10 columns, and 100 switches for switching the presence or absence of energization for each light emitting element 600 under the control of the selection unit 601. It is equipped with 602.

In the light emitting element matrix 320, 10 anode wirings 603 for each row are branched from the anode terminals A, and one terminal of 10 switches 602 is connected to each anode wiring 603. Further, the end of each anode wiring 603 opposite to the anode terminal A is connected to the end of the anode wiring 603 in the adjacent row.

The other terminals of the 10 switches 602 per row are each connected to the anode terminals of the light emitting element 600. The cathode terminal of the light emitting element 600 is connected to the cathode wiring 604. Each switch 602 receives a control signal via the control wiring 605 and is on / off controlled by the selection unit 601 to control the lighting of the light emitting element 600. At the time of lighting, the light emitting element 600 emits light with a light emitting amount corresponding to the amount of driving current supplied to the anode terminal A.

Further, the light emitting element matrix 320 as a whole is controlled to be lit by the driver IC 212 controlling the switch 401 on and off according to the image data (video signal).

As shown in FIG. 7, the light emitting element matrix 320 is arranged in a staggered pattern on the TFT circuit 214. The 100 light emitting elements 600 constituting one light emitting element matrix 320 are arranged in a grid pattern of 10 rows and 10 columns so as to fit in a circular region 701 having the same size as the microlens corresponding to the light emitting element matrix 320. Has been done.

Like the anode wiring 603, the cathode wiring 604 is provided for each row and branches from the cathode terminal C. The end of each cathode wiring 604 opposite to the cathode terminal C is connected to the end of the adjacent row of cathode wiring 604.

Instead of connecting the cathode wiring 604 to the common cathode terminal C, the cathode terminal C may be provided individually for each cathode wiring 604. Further, instead of connecting the switch 602 to the anode wiring 603 and connecting the light emitting element 600 to the cathode wiring 604, the light emitting element 600 may be connected to the anode wiring 603 and the switch 602 may be connected to the cathode wiring 604. ..

As shown in FIG. 8A, in the wiring pattern of the light emitting element matrix 320, both the row direction and the column direction of the light emitting element 600 coated on the anode electrode 801 are inclined with respect to the main scanning direction in a plan view. It is a pattern that has been made. When the row direction is orthogonal to the sub-scanning direction and the column direction is orthogonal to the main scanning direction, the row-to-column spacing of the light emitting element 600 may be visually recognized as white streaks (FIG. 9A). ), White streaks can be reduced if the row direction is oblique to the sub-scanning direction and the column direction is oblique to the main scanning direction (FIG. 9B). In the example of FIG. 8A, the inclination angle is 45 degrees, but it may be other than 45 degrees.

As shown in FIG. 8 (b), looking at the cross section on the DD line of FIG. 8 (a), the TFT circuit 214 is formed on the glass substrate 210. Of the TFT circuits 214, the cathode electrode 810 is a light-shielding aluminum wiring. An insulating film 811 and a light emitting element 600 are formed on the cathode wiring 810, and an anode electrode 801 is formed on the light emitting element 600.

The anode electrode 801 is made of a translucent ITO (Indium Tin Oxide) film, and the emitted light of the light emitting element 600 passes through the anode electrode 801 and goes to the microlens array 201. The anode electrode 801 receives a drive current via the anode wiring 603.
[6] Microlens Array 201
Next, the configuration of the microlens array 201 will be described.

In the present embodiment, the microlens array 201 is made of a material having a coefficient of linear expansion larger than that of the holding member 202, and when the environmental temperature rises or falls, the linear expansion difference between the microlens array 201 and the holding member 202 Occurs. Since the microlens array 201 and the holding member 202 are long in the main scanning direction, the linear expansion difference is also particularly large in the main scanning direction.

Further, the holding member 202 is thicker than the microlens array 201, and has high rigidity and is not easily deformed. Therefore, the microlens array 201 is more easily deformed due to the occurrence of the linear expansion difference than the holding member 202.

As shown in FIG. 2A, the light source substrate 200 side of the microlens array 201 is fixed to the holding member 202, so that thermal expansion is suppressed, whereas the photoconductor drum 101 side is fixed to the holding member. Since it is not applied, thermal expansion is not suppressed. Therefore, the microlens array 201 is distorted so as to protrude toward the photoconductor drum 101 due to thermal expansion.

As shown in FIG. 10A, the microlens array 201 has a so-called telecentric optical system, and the G1 lens 1010, the diaphragm 1020, and the G2 lens 1030 are arranged in order from the side closest to the light emitting substrate 200. The G1 lens 1010 and the G2 lens 1030 are transparent members made of a resin material or a glass material.

The G1 lens 1010 has plano-convex lenses fixed to both main surfaces of the flat plate-shaped member 1012, and the G2 lens 1030 has plano-convex lenses fixed to the main surfaces of the flat plate-shaped member 1032 on the light emitting substrate 200 side. The plano-convex lens may be spherical or aspherical.

As shown in FIG. 10B, in the G1 lens 1010, 15,000 microlenses 1011 are arranged in a staggered pattern of 3 rows × 5,000 columns. Each microlens 1011 functions as a biconvex lens by combining two plano-convex lenses, and refracts the emitted light from the light emitting element matrix 320 located at overlapping positions when viewed from the optical axis direction.

Similarly to the G1 lens 1010, the G2 lens 1030 also has 15,000 microlenses 1031 arranged in a staggered pattern of 3 rows × 5,000 columns, and the microlenses 1031 overlap each other when viewed from the optical axis direction. The light emitted from the light emitting element matrix 320 at the position is refracted. However, the microlens 1031 constituting the G2 lens 1030 is a plano-convex lens.

In the G1 lens 1010, the portion where the microlens 1011 is provided in the main scanning direction is thick, and the portion where the microlens 1011 is not provided is relatively thin. Therefore, the portion where the microlens 1011 is not provided has lower rigidity and is more easily deformed than the portion where the microlens 1011 is provided.

Similar to the G1 lens 1010, the G2 lens 1030 is thicker at the portion where the microlens 1031 is provided in the main scanning direction, and the portion where the microlens 1031 is not provided is relatively thin. There is. Therefore, the portion where the microlens 1031 is not provided has lower rigidity and is more easily deformed than the portion where the microlens 1031 is provided.

As shown in FIG. 10 (c), the diaphragm 1020 is a flat plate-shaped member made of a light-shielding material such as resin or metal, and has a one-to-one correspondence with each of 150 microlenses 1011 and 1031. Thousands of through holes 1021 are provided. After passing through the microlens 1011 of the G1 lens 1010, the emitted light of the light emitting element 320 advances only to the portion incident on the through hole 1021 by the aperture 1020 to the microlens 1031 of the G2 lens 1030, and the other portions are shielded from light.

The microlens array 201 and the light emitting substrate 200 are covered with a cover (not shown) so that dust and the like do not block the emitted light of the light emitting element 320.
[7] Configuration of Control Unit 150 Next, the configuration of the control unit 150 will be described.

As shown in FIG. 11, the control unit 150 includes a CPU (Central Processing Unit) 1101, a ROM (Read Only Memory) 1102, a RAM (Random Access Memory) 1103, and the like, and the power is turned on to the image forming apparatus 1. Then, the CPU 1101 reads the boot program from the ROM 1102 and starts the boot program, and executes the OS (Operating System) and the control program read from the HDD (Hard Disk Drive) 1104 using the RAM 1103 as a working storage area.

The NIC (Network Interface Card) 1105 is used for communicating with an external device such as a PC (Personal Computer) via a communication network such as a LAN (Local Area Network). When the control unit 150 receives a print job from an external device, the control unit 150 controls each part of the image forming apparatus 1 to execute an image forming process according to the print job.

In this case, the control unit 150 controls the photoconductor drum drive motor 1111 to rotate and drive the photoconductor drum 101 while uniformly charging the outer peripheral surface of the photoconductor drum 101 by the charging device 102 to write light. It is exposed by the apparatus 100 and developed by the developing apparatus 103. The control unit 150 has a built-in ASIC 220 and controls the operation of the optical writing device 100 via the ASIC 220.

The control unit 150 can control the amount of light emitted for each light emitting element 320 by designating the luminance signal value output by the current DAC 300. The luminance signal value is also indicated to the optical writing device 100 via the ASIC 220. Therefore, the control unit 150 stores the luminance signal value to be output by the current DAC 300 in the HDD 1104 for each light emitting element 320.

Further, the control unit 150 controls the secondary transfer roller pair drive motor 1112 in accordance with the rotational drive of the photoconductor drum 101, and rotationally drives the secondary transfer roller pair 107. As a result, the intermediate transfer belt 106 rotates and travels. The control unit 150 applies a primary transfer voltage to the primary transfer charger 104 to electrostatically transfer the toner image from the outer peripheral surface of the photoconductor drum 101 to the outer peripheral surface of the intermediate transfer belt 106.

The control unit 150 heats and fixes the color toner image on the recording sheet S by controlling the fixing roller drive motor 1113 and rotating the fixing roller 131 of the fixing device 130 to raise the temperature of the fixing heater 132.

When the control unit 150 detects the head of the recording sheet S with the in-line sensor 160, the control unit 150 reads the toner image heat-fixed on the recording sheet. As a result, digital image data is generated and recorded in the HDD 1104.
[8] Lighting control of the light emitting element matrix 320 Next, lighting control of each light emitting element 600 constituting the light emitting element matrix 320 will be described.

The control unit 150 forms a predetermined test image on the recording sheet S prior to lighting control of the light emitting element matrix 320, and generates test image data by capturing the test image with the in-line sensor 160. Using this test image data, the control unit 150 generates lighting control data for controlling the lighting of the light emitting element matrix 320.

In the present embodiment, 16 light emitting elements 600 included in the light emitting region of 4 rows and 4 columns are lit out of the 100 light emitting elements 600 included in the light emitting element matrix 320. The center position of this light emitting region is recorded in the HDD 1104 as lighting control data.
(8-1) Lighting control data generation process When generating the lighting control data, the control unit 150 first reads the test image data from the HDD 1104 as shown in FIG. 12 (S1201). In the test image data, a dotted line extending in the main scanning direction is drawn for each color of YMCK. For example, as shown in FIG. 13, two dotted lines that draw one pixel every other dot are mainly drawn with the starting point of the dotted lines. The image formation position is detected for all the pixels by shifting the image by one pixel in the scanning direction and drawing with an interval of one line in the sub-scanning direction.

By doing so, since the adjacent pixels do not overlap each other, the formation position can be detected accurately for each pixel. When forming the test image, as shown in FIG. 14B, 16 light emitting elements 600 included in the light emitting region 1415 of 4 rows and 4 columns centered on the center 1412 of the light emitting element matrix 320 are used. Make it emit light.

The control unit 150 forms a test image using such test image data (S1202), captures a test image using the in-line sensor 160 (S1203), and determines the positions of individual pixels from the obtained image data. The position shift vector is calculated by comparing with the pixel formation position when the position shift is specified and there is no position shift (S1204).

Specifically, as shown in FIG. 14A, the center of gravity position 1402 of the detected pixel region 1401 is calculated, and the position toward the center of gravity 1402 calculated from the center of gravity position 1403 that should be detected when there is no misalignment. The misalignment vector 1404 is obtained.

Next, as shown in FIG. 14B, the correction vector 1411 obtained by reversing the sign of the misalignment vector 1404 is obtained, and the tip of the correction vector 1411 starting from the center 1412 of the light emitting element matrix of 10 rows and 10 columns is newly added. The region 1414 of 4 rows and 4 columns, which is the central 1413, is used as a new light emitting region. In this way, the positional deviation of the pixel forming position can be corrected.

This new center 1413 is recorded in the HDD 1104 as new lighting control data (S1205). 15,000 lighting control data are recorded for each light emitting element matrix 320.
(8-2) Lighting Control Process When executing the image forming process, the control unit 150 reads the lighting control data for each light emitting element matrix 320 from the HDD 1104 and instructs the driver IC 212 to emit light. The driver IC 212 instructs the selection unit 601 to turn on the switch 602 for the 16 light emitting elements 600 included in the light emitting region of 4 rows and 4 columns centered on the position specified in the lighting control data, and other The switch 602 is turned off for the light emitting element 600.

By doing so, it is possible to suppress the deviation of the pixel formation position due to the distortion of the microlens array 201. It should be noted that, on the toner image transport path from the optical writing device 100 to the in-line sensor 160, the deviation of the pixel formation position caused by a cause other than the distortion of the microlens array 201 can be similarly suppressed.
[9] Modified Examples Although the present invention has been described above based on the embodiments, it goes without saying that the present invention is not limited to the above-described embodiments, and the following modified examples can be implemented. ..
(9-1) In the above embodiment, the configuration in which the switch 602 is provided for each light emitting element 600 in the light emitting element matrix 320 has been described as an example, but it goes without saying that the present invention is not limited to this. You may do the following:

As shown in FIG. 15, in the light emitting element matrix 320 according to this modification, 10 row wirings 1513 for each row are branched from the anode terminal A, and each row wiring 1513 is arranged in the same row. The anode terminals of the 10 light emitting elements 600 are connected. A switch 1512 is provided in each line wiring 1513 to turn on and off the connection between the ten light emitting elements 600 and the anode terminal A. The row selection unit 1510 switches the on / off state of the switch 1512 via the control wiring 1511 in response to the control signal from the driver IC 212.

Further, 10 row wirings 1523 for each row are branched from the cathode terminal C, and the cathode terminals of 10 light emitting elements 600 arranged in the same row are connected to each row wiring 1523. There is. A switch 1522 is provided in each row wiring 1523 to turn on and off the connection between the ten light emitting elements 600 and the anode terminal A. The column selection unit 1520 switches the on / off state of the switch 1522 via the control wiring 1521 in response to the control signal from the driver IC 212.

Even in this way, since the rectangular light emitting region can be specified, the position shift of the pixel forming position is suppressed by controlling the light emitting state of the light emitting element matrix 320 according to the distortion of the microlens array 201. be able to.

As shown in FIG. 16A, in the wiring pattern of the light emitting element matrix 320, both the row direction and the column direction of the light emitting element 600 coated on the anode electrode 801 are inclined with respect to the main scanning direction in a plan view. It is a pattern that has been made. The areas of the 100 light emitting elements 600 constituting the light emitting element matrix 320 are equal to each other, and therefore the exposed areas on the outer peripheral surface of the photoconductor drum 101 are also equal to each other, and the toner image formed on the recording sheet S has the same area. The areas are also equal to each other.

In this way, even if the light emitting region is changed, the desired amount of light can be obtained without changing the amount of drive current per light emitting element matrix 320. Further, since the shapes of the light emitting elements 600 are also equal to each other, the shapes of the exposed regions on the outer peripheral surface of the photoconductor drum 101 are also equal to each other, and the shapes of the toner images formed on the recording sheet S are also equal to each other. Therefore, even if the light emitting region is changed, the beam diameter per pixel becomes the same.

As shown in FIG. 16B, looking at the cross section taken along the line EE of FIG. 16A, the TFT circuit 214 is formed on the glass substrate 210. Of the TFT circuits 214, the row wiring 1513 is an aluminum wiring. An insulating film 811 and a light emitting element 600 are formed on the row wiring 1513, and a column wiring 1523 is formed on the light emitting element 600. The row wiring 1523 is made of an ITO film, and the emitted light of the light emitting element 600 passes through the row wiring 1523 and goes to the microlens array 201.

Even in this way, the same effect as that of the above embodiment can be obtained.
(9-2) In the above embodiment, there is an example in which the light emitting element 600 included in the light emitting region 1415 of the light emitting elements 600 constituting the light emitting element matrix 320 is turned on to detect the deviation of the pixel formation position. It goes without saying that the present invention is not limited to this, but in addition to the light emitting element 600 included in the light emitting region 1415, the light emitting element 600 not included in the light emitting region 1415 is turned on to position the pixel formation position. The deviation may be detected.

Further, only the light emitting element 600 not included in the light emitting region 1415 may be turned on to detect the deviation of the pixel formation position, or a part of the light emitting elements 600 included in the light emitting region 1415 may be detected. Only 600 may be turned on to detect the deviation of the pixel formation position. Regardless of which of the light emitting elements 600 to be lit, if the deviation of the pixel forming position is detected and the light emitting element 600 to be lit is changed according to the detected position deviation, the deviation of the pixel forming position can be suppressed.
(9-3) In the above embodiment, the case where the switch 602 is connected to the anode terminal of the light emitting element 600 in the light emitting element matrix 320 has been described as an example, but it goes without saying that the present invention is not limited to this. Instead of this, the switch 602 may be connected to the cathode terminal. Even in this way, the effect of the present invention is the same.
(9-4) In the above embodiment, the case where the positional deviation at the center of the light emitting region is detected and the positional deviation is corrected has been described as an example, but it goes without saying that the present invention is not limited to this. Positional deviation may be detected and corrected with reference to a position other than the center, such as the center of gravity of the region or a specific position on the outer periphery of the light emitting region.
(9-5) In the above embodiment, the case where the pixel formation position is detected by using the in-line sensor 160 has been described as an example, but it goes without saying that the present invention is not limited to this, and it is supported on the intermediate transfer belt 106. The pixel formation position may be detected by imaging the toner image being formed or the toner image supported on the outer peripheral surface of the photoconductor drum 101.
(9-6) In the above modified example, the case where the areas of the 100 light emitting elements 600 constituting the light emitting element matrix 320 are equal to each other has been described as an example, but it goes without saying that the present invention is not limited to this. , Instead of this, the following may be done.

The state of condensing the emitted light of the light emitting element 600 by the microlens changes according to the distance from the optical axis to the light emitting element 600 when viewed in a plan view from the optical axis direction of the microlens. Therefore, among the light emitting elements 600 constituting the light emitting element matrix 320, the exposed state when the light emitting element 600 belonging to the light emitting region close to the optical axis in the plan view and the light emitting element 600 belonging to the light emitting region far from the optical axis are lit. The shape and area of the light emitting element 600 may be changed according to the distance from the optical axis to the light emitting element 600 so that the exposure state when the light is turned on is the same except for the exposure position.

Further, when the shape and area of the light emitting element 600 are made equal regardless of the distance from the optical axis to the light emitting element 600, the number of light emitting elements 600 constituting the light emitting region is increased according to the distance from the optical axis to the light emitting region. The shape of the light emitting region may be different. Even in this way, the exposure state can be kept constant except for the exposure position.
(9-7) In the above embodiment, 100 light emitting elements 600 constituting the light emitting element matrix 320 are arranged in a grid pattern of 10 rows and 10 columns, and the light emitting region is arranged in a grid pattern of 4 rows and 4 columns. Although a certain case has been described as an example, it goes without saying that the present invention is not limited to this, and the number of light emitting elements 600 constituting the light emitting element matrix 320 may be a number other than 100, and the number of rows and columns. The numbers may be different.

For example, since the microlens array 201 is long in the main scanning direction, it is deformed so that the central portion in the main scanning direction protrudes due to thermal expansion, while the amount of deformation in the sub scanning direction is small, so that the microlens array 201 is deformed. It is considered that the change in the exposure position due to the thermal expansion of 201 is exclusively limited to the main scanning direction. If the light emitting elements 600 are arranged so that the light emitting element matrix 320 becomes larger in the main scanning direction than in the sub scanning direction by measuring this characteristic, it is effective without unnecessarily increasing the number of light emitting elements 600. It is possible to suppress fluctuations in the exposure position.

The number of light emitting elements 600 constituting the light emitting region is also not limited to 16, and is not limited to a grid arrangement of 4 rows and 4 columns.
(9-8) In the above embodiment, the case where the position shift vector 1404 is obtained for each light emitting element matrix 320 and the light emitting region 1414 is determined has been described as an example, but it goes without saying that the present invention is not limited to this. , The position shift vector 1404 is obtained only for a part of the light emitting element matrix 320, the light emitting region 1414 is determined for the part of the light emitting element matrix 320 in the same manner as in the above embodiment, and for the other light emitting element matrix 320. The light emitting region 1414 may be determined according to the position shift vector 1404 obtained for the part of the light emitting element matrix 320.
(9-9) In the above embodiment, the case where the emitted light of the light emitting element 600 is focused on the outer peripheral surface of the photoconductor drum 101 by using the microlens array 201 has been described as an example. Needless to say, the emitted light of the light emitting element 600 may be condensed by using a condensing means other than the microlens array 201 such as a rod lens array including a Selfoc (registered trademark) lens array.

Further, the lens constituting the condensing means and the light emitting element matrix 320 do not have to be associated with each other on a one-to-one basis, and the emitted light of one light emitting element matrix 320 may be incident on a plurality of lenses or may emit a plurality of lights. The emitted light of the light emitting element matrix 320 may be focused by incident light of the element matrix 320 on a common lens.
(9-10) In the above embodiment, the case where the image forming apparatus 1 is a tandem color printer has been described as an example, but it goes without saying that the present invention is not limited to this, and the image forming apparatus 1 is tandem. It may be a color printer of a method other than the method, or it may be a monochrome printer. Further, the same effect can be obtained by applying the present invention to a single-function device such as a copier equipped with a scanner or a facsimile machine equipped with a facsimile communication function, or a multi-function peripheral (MFP) having these functions. Can be obtained.

The optical writing device and the image forming device according to the present invention are useful as a device for suppressing deterioration of image quality due to distortion of a microlens array in a line optical type optical writing device.

1 ... Image forming device 100 ... Optical writing device 150 ... Control unit 160 ... In-line sensor 320 ... Light emitting element matrix 600 ... Light emitting element

Claims (8)

A plurality of light emitting element matrices composed of a plurality of light emitting elements are arranged, different light emitting element matrices are assigned to different pixels, and some of the light emitting elements are lit for each light emitting element matrix. An optical writing device that exposes one pixel at a time by condensing the emitted light on the surface of the photoconductor by a condensing means.
A detection means for detecting the exposure position by lighting at least a part of the light emitting elements of the light emitting element matrix.
With respect to the light emitting element in which the detection means is lit, a calculation means for calculating the amount of misalignment between the detected exposure position and the regular pixel position, and
A light emitting element capable of exposing the regular pixel position among a plurality of light emitting elements constituting the light emitting element matrix from the light emitting element in which the detecting means is lit and the amount of misalignment calculated by the calculating means. Specific means to identify and
An optical writing device including an exposure means for lighting a specified light emitting element to perform exposure. For each light emitting element matrix, the cathode terminals of the plurality of light emitting elements are electrically connected to a common wiring, and the anode terminals are electrically connected to individual wirings.
The light according to claim 1, wherein the detection means and the exposure means select a light emitting element to be lit by selecting wiring electrically connected to the anode terminals of the plurality of light emitting elements. Writing device. For each light emitting element matrix, the anode terminals of the plurality of light emitting elements are electrically connected to a common wiring, and the cathode terminals are electrically connected to individual wirings.
The light according to claim 1, wherein the detection means and the exposure means select a light emitting element to be lit by selecting wiring electrically connected to the cathode terminals of the plurality of light emitting elements. Writing device. In the light emitting element matrix, the plurality of light emitting elements are arranged in a two-dimensional lattice.
In the two-dimensional lattice, the anode terminals of the light emitting elements arranged in the same column are electrically connected to the common wiring, and the cathode terminals of the light emitting elements arranged in the same row are connected to the common wiring. It is electrically connected and
The first aspect of the present invention is characterized in that the detection means and the exposure means select a light emitting element to be lit by selecting a wiring connected to an anode terminal and a wiring connected to a cathode terminal. The optical writing device described. The optical writing device according to any one of claims 1 to 4, wherein in the light emitting element matrix, the light emitting elements have the same exposure area. The optical writing device according to any one of claims 1 to 5, wherein in the light emitting element matrix, the shape of the exposed region is the same between the light emitting elements. In the light emitting element matrix, the plurality of light emitting elements are arranged in a two-dimensional lattice.
The optical writing device according to claim 1, wherein the row direction and the column direction of the two-dimensional lattice are obliquely intersected with each other in the arrangement direction of the light emitting element matrix. An image forming apparatus comprising the optical writing apparatus according to any one of claims 1 to 7.

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