JP2019093587A - Optical writing device and image formation apparatus - Google Patents

Abstract

To provide an optical writing device and an image formation apparatus which can accurately and efficiently detect the positional deviation between a micro-lens and a light-emitting element due to the temperature unevenness.SOLUTION: An optical writing device which includes a light source substrate provided with a plurality of light-emitting elements generating heat with turn-on, and a long optical member made of a plurality of imaging lenses forming an image of the emission light of the light-emitting elements on the photoreceptor surface, in which the light source substrate and the optical member are fixed to a support member at one end in the longitudinal direction, and linear expansion coefficients are different from each other, (a) estimates the temperature rise amount from the turn-on state of the light-emitting element corresponding to the imaging lens for each imaging lens, (b) obtains the linear expansion amount using the estimated temperature rise amount, thereby (c) predicts the positional deviation amount in the longitudinal direction between the imaging lens and the light-emitting element, and corrects the imaging state in accordance with the predicted positional deviation amount.SELECTED DRAWING: Figure 10

Description

  The present invention relates to an optical writing device and an image forming apparatus, and more particularly, to a technique for accurately suppressing light amount fluctuation due to fluctuation of environmental conditions in a line optical type optical writing device.

  In recent years, as an optical writing device used in an electrophotographic image forming apparatus, a line optical type optical writing device has lower noise and is easier to miniaturize than a light scanning type optical writing device with a mechanical operation. Because of that, it is widely spread.

  The line optical type optical writing device is a micro lens array (MLA in which micro lenses of a few μm to a few mm in lens diameter are arranged in a two-dimensional array) of emission light of light emitting elements arranged in a line on a light source substrate. An electrostatic latent image is formed on the photoreceptor surface by imaging using a Micro Lens Array.

  When the temperature inside the image forming apparatus rises, the light source substrate and the microlens array also rise in temperature and thermally expand. In this case, when the linear expansion coefficient differs between the light source substrate and the microlens array, a linear expansion difference occurs between them. Since both the light source substrate and the microlens array are long in the main scanning direction, the difference in linear expansion becomes remarkable particularly in the main scanning direction, and the positional relationship between the individual light emitting elements and the microlenses changes.

  When the positional relationship between the light emitting element and the micro lens changes, the imaging light amount of the light emitted from the light emitting element by the micro lens changes, or the image forming position shifts, and the image quality is degraded.

  To solve this problem, for example, a table is provided which represents the relationship between the positional deviation between the microlens and the light emitting element and the in-machine temperature of the image forming apparatus and the relationship between the positional deviation and the light quantity correction value for the light emitting element. A light emitting device has been proposed which corrects the light amount of the light emitting element according to the detected temperature (see, for example, Patent Document 1). In this way, it is possible to suppress the fluctuation of the imaging state caused by the positional deviation between the micro lens and the light emitting element caused by the change of the temperature in the apparatus.

JP 2008-155458 A

  However, the microlens array and the light source substrate also thermally expand due to factors other than the in-machine temperature of the image forming apparatus. For example, although the light emitting element generates heat at the time of lighting, which light emitting element is turned on differs depending on the image data, and all the light emitting elements are not always turned on simultaneously. For this reason, while the temperature of the microlens array rises due to heat generation of the light emitting element in the vicinity where the light emitting element is turned on, the temperature of the microlens array does not rise much in the vicinity where the light emitting element is turned off.

  As described above, if the degree of thermal expansion of the micro lens array is different for each position in the main scanning direction, the positional deviation amount may be different for each light emitting element. It can not be suppressed precisely.

  On the other hand, when it is attempted to detect the amount of positional deviation using a sensor for all the microlenses, for example, every sheet interval during image formation, the detection time takes the same number as the number of microlenses. There is also a problem that the printing speed is reduced due to the lack of

  The present invention has been made in view of the above problems, and an optical writing device and an image capable of accurately and efficiently detecting positional deviation between a microlens and a light emitting element caused by temperature unevenness. The purpose is to provide a forming device.

  In order to achieve the above object, in the optical writing device according to the present invention, a plurality of light emitting elements are disposed on the upper surface, and a long length is provided with a circuit for modulating the emitted light of the plurality of light emitting elements according to a print job. A light source substrate, a long optical member having a plurality of imaging lenses for focusing the light emitted from the plurality of light emitting elements on the surface of the photosensitive member, and the light source at one end in the long direction An optical writing device having a substrate and a support member fixed to the optical member, wherein the light source substrate and the optical member have different linear expansion coefficients, and the image formation is performed for each of the imaging lenses. The light source substrate and the light source substrate are calculated using heat generation amount estimation means for estimating the total amount of heat generation amount of one or more light emitting elements for forming emitted light by a lens and the total amount of heat generation amount estimated by the heat generation amount estimation means. The above caused by the difference in the amount of linear expansion with the optical member And a correction unit configured to predict an amount of displacement of the light element in the longitudinal direction, and a unit for correcting an imaging state in accordance with the amount of displacement predicted by the amount of displacement prediction unit. It is characterized by

  In this way, the total amount of heat generation of the corresponding light emitting element is estimated, and the amount of positional deviation between the imaging lens and the light emitting element is predicted using the total amount of heat generation thus obtained. The positional deviation between the microlens and the light emitting element due to the unevenness can be detected accurately and efficiently.

  In this case, the heat generation amount estimation unit may estimate the total amount of the heat generation amount using a total of lighting times from the start of the print job of the one or more light emitting elements, or one or more of the one or more The total amount of heat generation may be estimated using the total of the power consumption of the light emitting element from the start of the print job.

  Further, an optical path change detection means for detecting, for each of the imaging lenses, a change in an optical path from the light emitting element which has emitted the emitted light to the surface of the photosensitive member, of the emitted light formed by the imaging lens; Position shift detecting means for detecting a position shift amount between the light emitting element relating to the light path change and the imaging lens for imaging the emitted light of the light emitting element using the light path change detected by the light path change detecting means; The misregistration amount prediction means uses the misregistration amount detected by the misregistration amount detection means for the two imaging lenses at mutually different positions in the longitudinal direction, and uses the two imaging lenses other than the two imaging lenses. The amount of positional deviation of the imaging lens may be predicted.

  Further, the two imaging lenses at different positions in the longitudinal direction are imaging lenses in which the total amount differs by a predetermined threshold value or more from the average value of the total amount for each imaging lens estimated by the heat generation amount estimation means It may be

  The two imaging lenses at different positions in the longitudinal direction are two imaging lenses adjacent to each other in the longitudinal direction, and the heat generation amount estimation is performed between the two adjacent imaging lenses. The difference of the total amount for each imaging lens estimated by the means may be equal to or greater than a predetermined threshold.

  The two imaging lenses at different positions in the longitudinal direction are two imaging lenses adjacent to each other in the longitudinal direction, and the heat generation amount estimation is performed between the two adjacent imaging lenses. The sum of the total amount for each imaging lens estimated by the means may be equal to or greater than a predetermined threshold.

  Further, the misregistration amount predicting means performs linear interpolation using the misregistration amount detected by the misregistration amount detection means with respect to the two imaging lenses at different positions in the longitudinal direction. The amount of displacement of the imaging lens other than the image lens may be predicted.

  In addition to the positional deviation amount detected by the positional displacement amount detecting means, the positional displacement amount predicting means may add to the two imaging lenses other than the two imaging lens which are detected at different positions in the longitudinal direction. The positional deviation amount of the imaging lens may be predicted using the total amount of the calorific value estimated by the calorific value estimation unit with respect to the imaging lens.

  An image forming apparatus according to the present invention is characterized by including the optical writing device according to the present invention.

FIG. 1 is a diagram showing a main configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 3A is a plan view and a cross-sectional view showing the main configuration of a light source substrate 200. FIG. (A) is a block diagram showing the main configuration of the TFT circuit 214, and (b) is a circuit diagram showing the configuration of the selection circuit 301 and the light emission block 302. It is a block diagram which shows the main structures of driver IC212. (A) is a cross-sectional view of the optical writing device 100 in a cross section perpendicular to the sub-scanning direction, (b) is a plan view of the G1 lens 510, and (c) is a plan view of the diaphragm 520. FIG. 6 is a plan view showing the arrangement of light emitting elements 320 in the light source substrate 200 and the light emitting element group 600. It is a flowchart showing position shift detection processing by driver IC212. (A) is a table illustrating a temperature rise amount table, and (b) is a table illustrating a light emission amount correction table. FIG. 6 is a diagram illustrating a positional relationship between an original exposure position and an actual exposure position in the main scanning direction. (A) is a bar graph illustrating the amount of temperature rise for each microlens, (b) is a bar graph illustrating the amount of linear expansion for each microlens, and (c) illustrates the amount of misalignment for each microlens It is a bar graph. (A) is a cross-sectional view of the microlens array 201 in a cross section orthogonal to the sub-scanning direction, (b) is a plan view of the diaphragm 520. It is a flowchart showing the detection process of the positional offset amount which concerns on the 3rd Embodiment of this invention. It is a graph which illustrates the amount of temperature rise for every micro lens. It is a table which illustrates a position shift amount table. It is a graph which illustrates the amount of position gap for every micro lens. It is a flowchart showing the detection process of positional offset amount which concerns on the 4th Embodiment of this invention. It is a graph which illustrates the amount of temperature rise for every micro lens. It is a graph which illustrates the amount of temperature rise for every micro lens. It is a flowchart showing the detection process of positional offset amount which concerns on the 5th Embodiment of this invention. (A) is a bar graph illustrating the amount of temperature rise for each microlens, (b) is a bar graph illustrating the measured value of the amount of misalignment of the microlens, and (c) is a measurement of the amount of misalignment of the microlens It is a bar graph which illustrates the predicted value calculated from value.

Hereinafter, embodiments of an optical writing device and an image forming apparatus according to the present invention will be described with reference to the drawings.
[1] First Embodiment The optical writing device and the image forming device according to the present embodiment count the number of times of lighting for each light emitting element during execution of a print job, and calculate the number of times of lighting as each in the main scanning direction. As temperature information at the position of the light emitting element, the amount of positional deviation for each microlens is estimated.
(1-1) Configuration of Image Forming Apparatus 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 type color printer, and an image for forming toner images of yellow (Y), magenta (M), cyan (C) and black (K) colors. The forming stations 110Y, 110M, 110C and 110K are provided. The image forming stations 110Y, 110M, 110C and 110K have photosensitive drums 101Y, 101M, 101C and 101K which rotate in the direction of arrow A.

  Around the photosensitive drums 101Y, 101M, 101C and 101K, charging devices 102Y, 102M, 102C and 102K, optical writing devices 100Y, 100M, 100C and 100K, and developing devices 103Y, 103M, 103C and 103K along the outer peripheral surface. The primary transfer chargers 104Y, 104M, 104C and 104K and the cleaning devices 105Y, 105M, 105C and 105K are disposed.

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

  The developing devices 103Y, 103M, 103C, and 103K supply toners of Y, M, C, and K colors, develop electrostatic latent images, and form toner images of Y, M, C, and K colors. The primary transfer chargers 104Y, 104M, 104C and 104K electrostatically transfer the toner images carried by the photosensitive drums 101Y, 101M, 101C and 101K onto the intermediate transfer belt 106 (primary transfer).

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

  The intermediate transfer belt 106 is an endless belt and is stretched around the secondary transfer roller pair 107, the driven roller 108, and the tension roller 109, and rotationally travels in the arrow B direction. By performing the primary transfer in synchronization with the rotational travel, the toner images of the Y, M, C, and K colors are superimposed on each other to form a color toner image. The intermediate transfer belt 106 conveys the color toner image to the secondary transfer nip of the secondary transfer roller pair 107 by rotating and traveling with the color toner image carried.

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

  The recording sheet S is conveyed to the fixing device 130 in a state of carrying a color toner image, thermally fixed on the color toner image, and then discharged onto the sheet discharge tray 140.

  The image forming apparatus 1 further includes a control unit 150. When the control unit 150 receives a print job from an external apparatus such as a PC (Personal Computer), the control unit 150 controls the image forming apparatus 1 to execute image formation.

  The control unit 150 forms a toner image on the transfer belt 112 at each of the black, cyan, magenta, and yellow image forming stations at a timing when the image formation is not performed, and the resist sensor 160 generates the density and the relative positional deviation between the colors. The amount is measured and fed back to each condition of the electrophotographic system to correct the deterioration of the image caused by the environment or the like.

The control unit 150 also includes a temperature sensor (not shown), detects the in-apparatus temperature of the image forming apparatus 1, and notifies the optical writing apparatus 100 of the detected temperature.
(1-2) Configuration of Optical Writing Device 100 Next, the configuration of the optical writing device 100 will be described.

The optical writing device 100 is configured to support the light source substrate and the microlens array by the support member, and condenses the light L emitted from the light source substrate on the outer peripheral surface of the photosensitive drum 101 by the microlens array. The support member is fixed to one of the light source substrate and the microlens array at one end in the main scanning direction.
A cable or the like for connecting the optical writing device 100 and another device of the image forming device 1 is not shown.

  As shown in FIG. 2, the light source 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 a glass substrate 210, and 15,000 light emitting elements (not shown) are staggered along the main scanning direction at a pitch of 21.2 μm (1200 dpi). There is.

  Further, the substrate surface of the glass substrate 210 on which the light emitting element is disposed 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 in a state of sealing dry nitrogen or the like so as not to be exposed to the outside air. In order to absorb moisture, a hygroscopic agent may be additionally sealed in the sealing region. The sealing plate 211 may be, for example, sealing glass, or may be made of a material other than glass.

Outside the sealing area of the glass substrate 210, a driver IC 212 is mounted. The control unit 150 is connected to the driver IC 212 and includes an application specific integrated circuit (ASIC) 220 to control the light source substrate 200. The ASIC 220 transmits the digital luminance signal of the image data to the driver IC 212 via the flexible wire 221. Enter 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 a drive circuit for each light emitting element. The drive circuit generates a drive current for the light emitting element according to the luminance signal. In the present embodiment, the luminance signal is a voltage signal.
(1-3) TFT circuit 214
Next, the configuration of the TFT circuit 214 will be described.

  As shown in FIG. 3A, in the TFT circuit 214, 100 15,000 light emitting elements are grouped into 150 light emitting blocks 302 each.

  The driver IC 212 incorporates 150 current to digital converters (analog to digital converters) 300. The current DAC 300 is a digitally controllable variable current source, and corresponds to the light emitting block 302 one to one, respectively. The light emitting blocks 302 are arranged in the main scanning direction. The microlenses constituting the microlens array and the light emitting block 302 correspond to each other on a one-to-one basis, and the light emitted from the 100 light emitting elements 320 included in one light emitting block 302 is a photosensitive drum 101 by one microlens. The light is collected on the outer peripheral surface of the

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

  As shown in FIG. 3B, the light emitting block 302 is composed of 100 light emitting pixel circuits, and each light emitting pixel circuit has one capacitor 321, one driving TFT 322 and one light emitting element 320. Although the case where the light emitting element 320 is an OLED (Organic Light Emitting Diode) will be described as an example in this embodiment, the light emitting element 320 may be a semiconductor LED (Light Emitting Diode).

  The selection circuit 301 includes a shift register 311 and 100 selection TFTs 312. The shift register 311 is connected to the gate terminal of each of the 100 selection TFTs 312, and sequentially turns on the selection TFTs 312. The source terminal of the selection 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 selection TFT 312, the output current of the current DAC 300 flows to the first terminal of the capacitor 321, and charge is accumulated in the capacitor 321. The charge stored in the capacitor 321 is held until reset by the reset circuit 303. The reset circuit 303 includes a reset TFT 340.

  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. The drain terminal of the driving TFT 322 is connected to the anode terminal of the light emitting element 320, and the cathode terminal of the light emitting element 320 is connected to the ground wiring 332. 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 320. The drive TFT 322 emits a drive current of an amount corresponding to the luminance signal by applying the luminance signal (voltage signal) held between the first and second terminals of the capacitor 321 as the gate-source voltage Vgs. The element 320 is supplied.

  For example, when a luminance signal corresponding to H is written to the capacitor 321, the driving TFT 322 is turned on, and the light emitting element 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 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 driver IC 212 turns on the reset TFT 340, the line from the current DAC 300 to the capacitor 321 is reset to the reset potential. The reset potential may be the Vdd potential or the ground potential, and an appropriate potential may be selected. Further, although a case where the light emitting element 320 does not emit light in the reset state is described in this embodiment, the light emitting element 320 may emit light in the reset state.

  Although the case where the drive TFT 322 is a p-channel is described as an example in this embodiment, 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 under the control of the driver IC 212. Alternatively, the reset circuit 303 may be incorporated in the driver IC 212. . The function of the reset circuit 303 may be realized by changing the polarity of the current output from the current DAC at the time of reset and at the time of writing. Also, instead of the reset TFT 340, a switching element other than a TFT may be used.
(1-4) Driver IC 212
Next, the driver IC 212 will be described.

  As shown in FIG. 4, the driver IC 212 includes a drive current correction unit 410, a dot count unit 420, a temperature increase amount table 430, and a light emission amount correction table 440. The dot count unit 420 has 15,000 light emitting element counters 421 as dot counters corresponding to the respective light emitting elements 320, and 150 light emitting block counters 422 as the dot counters corresponding to the respective light emitting blocks 302. .

  A predetermined count value is added to the light emitting element counter 421 each time the corresponding light emitting element 320 emits light. The drive current correction unit 410 corrects the amount of drive current each time the counter value of the light emitting element counter 421 reaches the dot count threshold for each light emitting element 320. At the time of correction of the drive current amount, the drive current amount correction unit 410 refers to the drive current amount, light emission efficiency, light emission amount and deterioration degree for each light emitting element 320. Alternatively, the in-machine temperature of the image forming apparatus 1 may be measured using a temperature sensor (not shown), and the amount of driving current may be corrected using a temperature correction coefficient stored in advance for each in-machine temperature.

  A predetermined count value is added to the light emission block counter 422 each time the light emitting element 320 under the corresponding light emission block 302 emits light for each print job, and is reset when the print job is completed. The counter value of the light emission block counter 422 is considered to be correlated with the temperature of the microlens corresponding to the light emission block 302. Therefore, the drive current correction unit 401 predicts the temperature increase amount for each microlens from the counter value of the light emission block counter 422.

  The temperature increase amount table 430 is a table showing the relationship between the counter value of the light emission block counter 422 and the temperature increase amount of the microlens corresponding to the light emission block (FIG. 8A).

The light emission amount correction table 440 is provided for each of the 15,000 light emitting elements 320, and the light emission belonging to the light emission block 302 according to the positional deviation amount between the micro lens and the light emission block 302 corresponding to the micro lens. A correction coefficient for correcting the light emission amount of the element 320 is recorded (FIG. 8 (b)).
(1-5) Microlens Array Next, the configuration of the microlens array will be described.

  In the present embodiment, the microlens array is made of a material having a linear expansion coefficient larger than that of the light source substrate 200, and when the environmental temperature rises or falls, a linear expansion difference occurs between the microlens array and the light source substrate 200. Do. Since both the microlens array and the light source substrate 200 are long in the main scanning direction, the linear expansion difference is also particularly large in the main scanning direction.

  As shown in FIG. 5A, the microlens array 201 is a so-called telecentric optical system, and a G1 lens 510, an aperture 520 and a G2 lens 530 are disposed in this order from the side closer to the light source substrate 200. The G1 lens 510 and the G2 lens 530 are transparent members made of a resin material or a glass material. The G1 lens 510 and the G2 lens 530 disposed at the same position in the main scanning direction constitute one microlens.

  The G1 lens 510 has a plano-convex lens fixed to both main surfaces of the flat member 512, and the G2 lens 530 has a plano-convex lens fixed to the main surface of the flat member 532 on the light source substrate 200 side. The plano-convex lens may be spherical or aspheric. The optical axes of the G1 lens and the G2 lens coincide with each other.

  The microlens array 201 and the glass substrate 210 are fixed to the support member 500 at one end in the main scanning direction. Therefore, when the temperature rises, the microlens array 201 expands to the side opposite to the support member 500 in the main scanning direction due to thermal expansion. By this expansion, the individual microlenses constituting the microlens array 201 are also moved in the main scanning direction, and a positional deviation occurs with the light emitting element 320.

  As shown in FIG. 5B, in the G1 lens 510, 150 microlenses 511 are arranged in a staggered manner in 3 rows and 50 columns. Each of the micro lenses 511 functions as a biconvex lens by combining two plano-convex lenses, and refracts the emitted light from the 100 light emitting elements 320 located at an overlapping position as viewed from the optical axis direction.

  Also in the G2 lens 530, as in the G1 lens 510, 150 micro lenses 531 are arranged in a staggered pattern of 3 rows and 50 columns, and 100 micro lenses 531 are at overlapping positions when viewed from the optical axis direction The light emitted from the light emitting element 320 is refracted. However, the micro lens 531 constituting the G2 lens 530 is a plano-convex lens.

  In the G1 lens 510, the portion where the micro lens 511 is provided in the main scanning direction is thick, and the portion where the micro lens 511 is not provided is relatively thin. For this reason, the rigidity is low and it is easy to deform | transform the part which is not provided rather than the part in which the micro lens 511 is provided.

  As for the G2 lens 530, as in the G1 lens 510, the portion where the micro lens 531 is provided in the main scanning direction is thick, and the portion where the micro lens 531 is not provided is relatively thin. There is. For this reason, the rigidity is low and it is easy to deform | transform the part which is not provided rather than the part in which the micro lens 531 is provided.

  As shown in FIG. 5C, the diaphragm 520 is a flat member made of a material having a light shielding property such as resin or metal, and 150 corresponding to each of the 150 microlenses 511 and 531. Each through hole 521 is provided. The light emitted from the light emitting element 320 passes through the micro lens 511 of the G1 lens 510, and then only the part incident on the through hole 521 by the diaphragm 520 proceeds to the micro lens 531 of the G2 lens 530, and the other part is blocked.

The microlens array 201 and the light source substrate 200 are covered with a cover (not shown) in order to prevent dust and the like from blocking the light emitted from the light emitting element 320.
(1-6) Light source substrate 200
Next, the configuration of the light source substrate 200 will be described.

  As shown in FIG. 6, in the TFT circuit 214 of the light source substrate 200, light emission consisting of 100 light emitting elements 320 in a circular region 601 corresponding to each microlens of the microlens array 201 when viewed from the optical axis direction. An element group 600 is provided. The light emitting element group 600 corresponds to the light emitting block 302 in a one-to-one manner, and 100 light emitting elements 320 are arranged in a 10-row × 10-column zigzag form.

In addition, since the 100 light emitting elements 320 are arranged at intervals of 21.2 μm in the main scanning direction, the diameter of the circular area 601 needs to be 300 μm or more, and the micro lenses are also the same. The light emitting element groups 600 adjacent to each other in the main scanning direction are positioned most downstream in the main scanning direction of the light emitting element 320 located at the uppermost stream of the one light emitting element group 600 in the main scanning direction and the other light emitting element group 600. The distance from the light emitting element 320 is also 21.2 μm.
(1-7) Detection Processing of Misalignment Amount The light emitting element 320 generates heat during light emission, and the temperature rises in proportion to the accumulated light emission time from the start of the print job. The amount of local expansion of the microlens array 201 correlates to the temperature rise in the light emission block facing the location. Further, since the light source substrate 200 and the microlens array 201 are fixed to the support member 500 at one end in the main scanning direction, the positional deviation amount of each position in the main scanning direction of the microlens array 201 is It is equal to the sum of local expansion amounts at various points on the support member 500 side.

  Based on such knowledge, as shown in FIG. 7, when executing a print job (S701: YES), the driver IC 212 initializes the counter values of all the light emission block counters 422 to 0 (S702). After initializing the variable value of the variable n to 0, which indicates the number line in the image (S703), the processing from step S703 to S709 is executed for each line designated by the print job.

  First, exposure of the nth line is performed (S704). If the variable value of the variable n has reached the total number N of lines to be imaged in the print job (S 705: NO), the process is ended. Next, if n is less than N (S 705: YES), the process proceeds to step S 706.

  Then, referring to the image data of the n-th line subjected to the exposure and counting the number of black pixels for every 100 pixels corresponding to 100 which is the number of light emitting elements 320 for each light emitting block 302, The number of light emitting elements 320 to be turned on is confirmed for each light emitting block 302, and the counter value of the light emitting block counter 422 is increased by the number (S706). The counter value of the light emission block counter 422 is temperature information of the microlens facing the light emission block.

  Next, the amount of temperature rise for each microlens is predicted (S 707). For this reason, the driver IC 212 predicts the temperature rise amount for each microlens from the counter value of the light emission block counter 422 for each light emission block 302 with reference to the temperature rise amount table (FIG. 8A). The amount of temperature increase obtained by the prediction is added to the in-apparatus temperature of the image forming apparatus 1 notified from the control unit 150, and the obtained temperature of the microlens is multiplied by the linear expansion coefficient with the microlens array 201. Further, by multiplying the length of the microlens in the main scanning direction, the amount of linear expansion of the microlens can be obtained.

  Further, when the linear expansion coefficient of the light source substrate 200 is multiplied by the in-apparatus temperature of the image forming device 1 and further the length of the microlens in the main scanning direction is multiplied, the linear expansion amount of the light source substrate 200 is calculated. When the linear expansion amount of the light source substrate 200 is subtracted from the linear expansion amount of the microlens thus calculated, a partial line for each microlens in the linear expansion difference between the light source substrate 200 and the microlens array 201 An expansion difference can be obtained.

  By calculating the total of the partial linear expansion differences, the amount of positional deviation for each microlens is calculated (S 708). The positional shift amount Ln between the nth micro lens and the light emitting block 302 counted from the end on the support member 500 side in the main scanning direction can be calculated using the following equation (1).

Ln = .SIGMA. (Dc.times.Ti) (1)
Here, sigma is the sum of i = 1 to n, and Ti is the amount of temperature rise of the ith micro lens.

  Next, the image data of the line to be exposed next is corrected according to the positional shift amount Ln (S709). When the n-th positional deviation amount Ln is a positive value, as shown in FIG. 9, the n-th pixel is located closer to the n + 1-th pixel planned formation position 903 in the main scanning direction than the n-th pixel planned formation position 901. The detection position 902 is located, and the distance from the n-th planned formation position 901 to the n-th detection position 902 is the positional deviation amount Ln.

  Further, the distance Lp from the planned formation position 901 of the n-th pixel to the planned formation position 903 of the (n + 1) -th pixel is equal to 21.2 μm, which is the pixel pitch. In such a case, assuming that the pixel value of the n-th pixel before correction is Pn and the pixel value of the n + 1-th pixel before correction is Pn + 1, the pixel value P after correction of the n-th pixel is the following equation (2) It can be calculated using

P = {Pn × (Lp−Ln) + (Pn + 1) × Ln} ÷ Lp (2)
The unit of Ln is the same as the pitch of the pixel [μm].

  When the nth positional deviation amount Ln is a negative value, the pixel value Pn−1 of the n−1th pixel before correction is used for the nth pixel, using the same equation (3) as above. The pixel value P after correction can be calculated. Needless to say, when the positional displacement amount Ln is 0, there is no need to correct the pixel value.

P = {Pn × (Lp−Ln) + (Pn−1) × Ln} ÷ Lp (3)
Thereafter, the light emission amount of the nth light emitting element 320 is corrected using the nth positional deviation amount Ln (S710). In the present embodiment, when the light emission amount of the nth pixel is corrected, the correction coefficient CClan_i corresponding to the positional shift amount Ln is referred to with reference to the nth light emission amount correction table 440 (FIG. 8B). read out. Then, the light emission amount after correction is calculated by multiplying the light emission amount before correction by the read correction coefficient CClan_i. If there is no field in which the positional displacement amounts Ln match, the correction coefficients may be calculated by linear interpolation using the correction coefficients corresponding to the two most recent positional displacement amounts.

  Thereafter, the variable value of the variable n is increased by 1 (S711), the process proceeds to step S704, and the above process is repeated.

As described above, the sum of the number of times of lighting of the light emitting element 320 subordinate to the light emitting block 302 is calculated, and the temperature increase amount for each microlens corresponding to the light emitting block 302 is predicted (FIG. 10A). The linear expansion amount for each micro lens is predicted from the predicted value of the temperature rise amount of (Fig. 10 (b)), and the micro lens and the light emission block 302 corresponding to the micro lens are estimated from the predicted value for the linear expansion amount for each micro lens By predicting the positional displacement amount of the microlens array 201 (FIG. 10C), it is possible to compensate for the image quality deterioration due to the thermal expansion of the microlens array 201.
[2] Second Embodiment Next, a second embodiment of the present invention will be described. The image forming apparatus according to the present embodiment has a configuration substantially common to that of the image forming apparatus according to the first embodiment, but differs in the prediction of the temperature rise amount of the microlens. The following description will focus on differences. In the present specification, the same reference numerals are given to members and the like common to the embodiments.

  In the first embodiment, although the temperature rise amount of the microlens is predicted by counting the number of times of lighting of the light emitting element 320 subordinate to each light emitting block 302, the calorific value of the light emitting element 320 is the light emitting time Is the same, the more the amount of light emission, the more. Therefore, even if the light emission time of the light emitting element 320 is the same, the temperature increase amount of the microlens increases as the light emission amount of the light emitting element 320 increases.

  Taking this characteristic into consideration, in the present embodiment, the 150 light emission block counters 422 provided in the dot count section 420 of the driver IC 212 are subordinate to the light emission block 302 as a value indicating the amount of heat generation of each light emission block 302. The accumulated light emission amount of the light emitting element 320 is recorded.

  Then, when the light emission block counter 422 is updated in step S706 in FIG. 7, not the number of light emitting elements 320 to be lit but the sum S of the light emission amounts La of the light emitting elements 320 is determined.

S = La La_i (4)
Needless to say, the light emission amount La of the light emitting element 320 which is not turned on is zero. Then, a value obtained by adding the total sum S of the light emission amounts La to the original counter value of the light emission block counter 422 is set as a new counter value of the light emission block counter 422.

  Next, when predicting the temperature rise amount for each microlens in step S 707, the temperature rise amount table 430 is referred to as in the first embodiment. In the present embodiment, the temperature increase amount table 430 records the relationship between the counter value indicating the accumulated light emission amount of the light emitting element 320 under the light emitting block 302 and the temperature increase amount of the microlens. By referring to the temperature rise table 430, the temperature rise of the microlens can be predicted.

  The processes after step S 708 are the same as in the first embodiment.

In this way, since the difference in linear expansion difference caused by the difference in the light emission amount of the light emitting element 320 is predicted, it is possible to more accurately suppress the image degradation due to the linear expansion difference.
[3] Third Embodiment Next, a third embodiment of the present invention will be described. The image forming apparatus according to the present embodiment has a configuration that is generally common to the image forming apparatuses according to the first and second embodiments, while some of the micro lenses in the micro lens array 201 are configured. The difference is that the amount of displacement of the lens is measured, and the amount of displacement of another microlens is predicted from the measured amount of displacement. The following description will be made focusing on the differences.
(3-1) Misalignment Detection Sensor As shown in FIG. 5A, the microlens 210 according to the present embodiment is a misalignment detection sensor 522 all around the through hole 521 provided in the diaphragm 520. Is provided. The misalignment detection sensor 522 is a so-called light receiving element (PD: Photo Detector), and is provided over the entire circumference of the through hole 521 as shown in FIG. . The amount of light received may be detected using a CCD (Charge Coupled Device) instead of the PD.

  The micro lens array 210 is a telecentric optical system, and a light emitting element 320 c disposed on the optical axis of the G1 lens 510 and the G2 lens 530 and a light emitting element 320 s disposed at a position away from the optical axis The light emitted from any of the above is collimated by the G1 lens 510, passes through the through hole 521 of the stop 520, and is imaged on the surface of the photosensitive member 101 by the G2 lens 530.

  Therefore, when positional deviation occurs between the micro lens and the light emitting element 320, light emitted from the light emitting element 320 deviates from the through hole 521 of the diaphragm 520, and the amount of light incident on the positional deviation detection sensor 522 increases. That is, the light reception amount detected by the positional deviation detection sensor 522 is correlated with the positional deviation amount between the microlens and the light emitting block 302 corresponding to the microlens.

Therefore, by referring to the light reception amount detected by the positional deviation detection sensor 522, it is possible to detect the positional deviation amount between the micro lens and the light emitting block 302 corresponding to the micro lens.
(3-2) Detection Process of Misalignment Amount As described above, although the misregistration amount detection sensor 522 is provided in one-to-one correspondence with each micro lens, detection of the misregistration amount of each micro lens In the processing, among the positional displacement amount detecting sensors 522, the positional displacement amounts of all the microlenses are predicted from only the positional displacement amounts detected by the positional displacement amount detecting sensor 522.

  Specifically, in step S 708 of FIG. 7, unlike in the first embodiment, first, as shown in FIG. 12, an average value M of the temperature rise amount for each microlens is obtained (S 1201). Next, an absolute value A of the difference between the average value M and the temperature increase amount for each microlens is obtained (S1202), and a microlens whose absolute value A of the difference is equal to or more than a predetermined threshold is specified (S1203) .

  FIG. 13 is a graph illustrating the amount of temperature increase for each microlens, where the vertical axis represents the amount of temperature increase, and the horizontal axis represents the number of the microlens when counted from the side of the support member 500 in the main scanning direction. ing. In the example of FIG. 13, the absolute value A of the difference between the temperature rise amount and the average value is equal to or greater than the threshold value in the micro lenses # 3, # 6, # 10, # 17 to # 20, # 22, and # 27 to # 29. It has become.

  The displacement amount of the micro lens having a large absolute value A also largely deviates from the average value. Therefore, from the linear expansion amount of the entire micro lens array 201, the displacement amount is calculated using only the position of the micro lens in the macro lens array 201. If it predicts, a prediction error will become large. Therefore, for a microlens having a large absolute value A, the prediction accuracy can be improved by predicting the positional displacement amount from the light reception amount by the positional displacement amount detection sensor 522.

  Therefore, for each of the microlenses whose absolute value A is equal to or greater than a predetermined threshold value, the light reception amount is acquired with reference to the output of the positional deviation detection sensor 522, and the light reception is further referred with reference to the positional deviation amount table shown in FIG. The positional deviation amount corresponding to the amount is acquired (S1204). Note that if there is no light reception amount that matches the light reception amount detected by the misregistration detection sensor 522 in the misregistration amount table, the misregistration detection sensor 522 detects the light reception amount recorded in the misregistration amount table. The positional deviation amount may be calculated by linear interpolation using the two light receiving amounts closest to the light receiving amount.

  For microlenses whose absolute value A is not equal to or greater than a predetermined threshold value, among microlenses whose absolute value A is equal to or greater than a predetermined threshold value, linear interpolation is performed using displacement amounts of the two closest microlenses in the main scanning direction. The amount of positional deviation is calculated (S1205).

  FIG. 15 is a graph illustrating the positional deviation amount for each microlens. For the micro lenses # 3 and # 6, since the absolute value A is larger than the threshold value, the positional shift amount is determined from the light reception amount detected by the positional shift amount detection sensor 522. Further, for the # 4 and # 5 microlenses, the misalignment amount is predicted from the misalignment amounts of the # 3 and # 6 microlenses by linear interpolation. The # 1 and # 2 microlenses are predicted only from the displacement amount of the # 3 microlens.

As described above, the positional displacement amount is detected using the positional displacement amount detection sensor 522 for a part of the micro lenses, and the positional displacement amount can be predicted from the positional displacement amounts of the part of the micro lenses for the other micro lenses. For example, since the prediction accuracy can be improved, it is possible to suppress the image deterioration due to the positional deviation between the microlens and the light emitting block 302.
[4] Fourth Embodiment Next, a fourth embodiment of the present invention will be described. The image forming apparatus according to the present embodiment has a configuration substantially similar to that of the image forming apparatus according to the third embodiment, and a method of selecting micro lenses for detecting the light reception amount using the positional deviation detection sensor 522 Is different. The following description will be made focusing on the differences.

  When the temperature rise amount is significantly different between two microlenses adjacent to each other, the prediction error of the misregistration amount due to the linear interpolation may be large. On the other hand, in the present embodiment, the absolute value A of the difference between the temperature rise amounts is determined between two adjacent microlenses, and the positional deviation amount is obtained for the microlens whose absolute value A is greater than or equal to the threshold value. The amount of received light is measured using the detection sensor 522, and the amount of positional deviation is predicted from the amount of received light.

  Specifically, as shown in FIG. 16 in step S 708 in FIG. 7, first, the temperature increase amount of the second microlens from the temperature increase amount of the first microlens counted from the support member 500 side in the main scanning direction Find the absolute value A of the difference value from which the amount is subtracted. Similarly, an absolute value A of a difference value obtained by subtracting the temperature increase amount of the (i + 1) th microlens from the temperature increase amount of the ith microlens is sequentially calculated (S1601), and the absolute value A is equal to or more than a predetermined threshold A micro lens is specified (S1602).

  FIG. 17 is a graph illustrating the amount of temperature increase for each microlens, where the vertical axis represents the difference in the amount of temperature increase between adjacent microlenses, and the horizontal axis is counted up from the side of the support member 500 in the main scanning direction It represents the number of the microlens in the case. The micro-lens number i + 1-th bar graph represents a difference value obtained by subtracting the temperature increase amount of the (i + 1) th microlens from the temperature increase amount of the i-th microlens.

  In the example of FIG. 17, since the absolute value A of the difference value indicated by the bar graphs in which the microlens numbers are # 10, # 11, # 18, # 23 and # 28 is equal to or greater than the threshold, The difference in the amount of temperature rise is large in the combination of each of the combinations of # 9 and # 10, # 10 and # 11, # 17 and # 18, # 22 and # 23, and # 27 and # 28 become.

  Next, for each of the microlenses constituting the combination of microlenses whose absolute value A is equal to or greater than a predetermined threshold value, the light reception amount is acquired with reference to the output of the misalignment detection sensor 522, and the misalignment shown in FIG. The positional deviation amount corresponding to the light receiving amount is acquired with reference to the amount table (S1603). Note that if there is no light reception amount that matches the light reception amount detected by the misregistration detection sensor 522 in the misregistration amount table, the misregistration detection sensor 522 detects the light reception amount recorded in the misregistration amount table. The positional deviation amount may be calculated by linear interpolation using the two light receiving amounts closest to the light receiving amount.

  For microlenses that do not constitute a combination of microlenses whose absolute value A is not equal to or greater than a predetermined threshold value, among microlenses whose absolute value A is equal to or greater than a predetermined threshold, displacement amounts of two closest microlenses in the main scanning direction The misregistration amount is calculated by linear interpolation using S.sub.1604 (S1604).

Even in this case, the prediction accuracy can be improved, so that image deterioration due to the positional deviation between the microlens and the light emitting block 302 can be suppressed. Further, if the amount of displacement is measured for at least one microlens using the displacement amount sensor 522 to predict the amount of displacement in the main scanning direction of all the lenses, the prediction accuracy can be improved.
[5] Fifth Embodiment Next, a fifth embodiment of the present invention will be described. The image forming apparatus according to the present embodiment has a configuration substantially in common with the image forming apparatuses according to the third and fourth embodiments, and a micro lens that detects the amount of received light using the misalignment detection sensor 522 The selection method of is different. The following description will be made focusing on the differences.

  The heat generation of the light emitting block 302 contributes to the temperature rise of the adjacent light emitting block 302 on the TFT circuit 324 in addition to the microlens facing the light emitting block 302. When the temperature of the light emission block 302 rises due to the heat generation of the adjacent light emission block 302 in addition to the heat generation due to the light emission of the lower light emitting element 320, the temperature increase amount of the microlens facing the light emission block 302 also increases. Therefore, when predicting the positional deviation amount of the microlens, the prediction can be made by considering not only the light emission time of the light emission block 302 facing the microlens but also the light emission time of the light emission block 302 next to the light emission block 302. Accuracy can be improved.

  FIG. 18 is a graph illustrating the amount of temperature increase for each microlens, where the vertical axis represents the difference in the amount of temperature increase between adjacent microlenses, and the horizontal axis is counted from the side of the support member 500 in the main scanning direction It represents the number of the microlens in the case. The micro-lens number i-th bar graph is the sum of the temperature rise of the i-th micro-lens and the temperature rise of the i-th micro-lens plus the temperature rise of the i + 1-th micro-lens It represents.

  As shown in FIG. 19, such a total value S is calculated for all the micro lenses (S1901), an average value M of these total values S is obtained (S1902), and the average value M is calculated from each total value S. The absolute value A of the difference value subtracted is determined (S1903), and if the absolute value A is equal to or greater than the threshold (S1904), the amount of light received is detected for the microlens using the displacement amount detection sensor 522, and the light reception is performed. The amount of positional deviation is predicted from the amount (S1905). For microlenses whose absolute value A is less than the threshold, the amount of misalignment is predicted by linear interpolation using the amount of misalignment of the microlens whose absolute value A is greater than or equal to the threshold (S1906).

As described above, when the positional deviation amount is predicted in consideration of the influence given by the adjacent light emitting blocks 302, the prediction accuracy of the positional deviation amount can be improved.
[6] Sixth Embodiment Next, the sixth embodiment of the present invention will be described. The image forming apparatus according to the present embodiment has a configuration substantially common to the image forming apparatuses according to the third to fifth embodiments, and a micro lens that does not detect the light reception amount using the positional deviation detection sensor 522 There are differences in the method of predicting the amount of misalignment with respect to. The following description will be made focusing on the differences.

  In the above embodiment, the amount of positional deviation is estimated from the amount of received light detected using the positional deviation detection sensor 522 for only some of the microlenses, and the amount of positional deviation of the some of the microlenses for the other microlenses From the above, the case of predicting the positional deviation amount by linear interpolation has been described.

  However, in the other microlenses, the temperature rise amount is not always constant, and the temperature rise amount often differs for each microlens. Therefore, if the amount of displacement of another microlens is predicted based on only the positional relationship (number of the microlens) in the main scanning direction from the amount of displacement of some of the microlenses, an error corresponding to the variation in the amount of temperature rise May occur.

  Therefore, in the present embodiment, the amount of positional deviation of the microlens is predicted based on the amount of temperature rise instead of the positional relationship (number of the microlens) in the main scanning direction.

  For example, as illustrated in FIG. 20A, the absolute value A of the difference value obtained by subtracting the average value M of the temperature rise amount from the temperature rise amount of the microlenses # 5 and # 9 is larger than the threshold, and the microlens # 5 The position of the microlenses # 6 to # 8 when the absolute value A of the difference value obtained by subtracting the average value M of the temperature rise amount from the temperature rise amount of the microlenses # 6 to # 8 between # and # 9 is smaller than the threshold The amount of displacement is estimated from the amount of displacement of the microlenses # 5 and # 9.

  Therefore, first, the amount of displacement of the microlenses # 5 and # 9 is measured using the displacement amount detection sensor 522. As shown in FIG. 17B, the displacement amount of the microlens # 9 corresponds to the displacement amount of the microlens # 5, which corresponds to the temperature increase amount T6 to T9 of the microlenses # 6 to # 9. The result is a sum of

  The position of the microlenses # 6 to # 8 can be estimated from the position shift amount (measured value) of the microlenses # 5 and # 9 by linear interpolation according to the number of the microlenses. The deviation amounts become equal values 1616, 1617, and 1618 when the distance between the displacement amount of the micro lens # 9 and the displacement amount of the micro lens # 5 is equally divided into four. Such a prediction correctly reflects the actual positional deviation amount when the temperature increase amounts of the microlenses # 6 to # 8 are uniform.

  However, when the amount of temperature increase of the microlenses # 6 to # 9 is not uniform, for example, the amount of temperature increase of the microlens # 9 is particularly large in FIG. When the displacement amounts of the microlenses # 6 to # 8 are predicted by the linear interpolation, the predicted displacement amounts are larger than the actual displacement amounts by the errors E6, E7 and E8.

  On the other hand, if linear interpolation is performed according to the temperature rise amount for each micro lens, it is possible to improve the prediction accuracy of the positional shift amounts of the micro lenses # 6 to # 8. Specifically, assuming that the numbers of microlenses whose positional deviations are measured are s and s + n, the positional deviation of the ith micro lens is Zi, and the temperature rise of the ith micro lens is Ti, the kth The positional displacement amount Zk of the micro lens of can be predicted as in the following equation (5).

Zk = {Zs x (Tk + 1 + ... + Ts + n) + Zs + n x (Ts + 1 + ... + Tk)} ÷ (Ts + 1 + ... + Ts + n) (5)
However, it is assumed that s <k <s + n.

If the positional displacement amount of the microlens is predicted using the above equation (5), it is possible to improve the prediction accuracy of the positional displacement amount as shown by predicted values 1626, 1627, and 1628 in FIG.
[7] Modifications Although the present invention has been described above based on the embodiment, it goes without saying that the present invention is not limited to the above embodiment, and the following modifications can be implemented. .
(7-1) In the embodiment described above, the number of lightings from the start of the print job of the light emitting element under the control of each light emitting block 302 is counted as the temperature increase amount. Needless to say, the present invention is not limited to this, and instead of the number of times of lighting, the total power consumption from the start of the print job of the light emitting element under the control may be used. The present invention can produce effects regardless of the method of evaluating the temperature rise.
(7-2) In the above embodiment, although the case where the light emitting blocks 302 are arranged in a staggered manner in 3 rows and 50 columns in the TFT circuit 214 has been described as an example, it goes without saying that the present invention is not limited thereto. In addition, the number of rows and the number of columns may be different, and arrays other than zigzag may be used. Non-staggered arrays include single-row or grid-like arrays. Similarly, in the microlens array 201, the arrangement of the microlenses is not limited to the zigzag shape of 3 rows and 50 columns, but it is desirable to match the arrangement of the light emitting blocks 302.
(7-3) In the above embodiment, although the case where the arrangement of the light emitting elements for each light emitting block 302 is in a staggered form of 10 rows and 10 columns has been described as an example, it goes without saying that the present invention is not limited thereto. The number of rows and the number of columns may be different, and the arrangement may be other than zigzag. Non-staggered arrays include single-row or grid-like arrays.
(7-4) In the above embodiment, although the case where the positional displacement amount is detected using the positional displacement amount detection sensor 522 has been described as an example, it goes without saying that the present invention is not limited to this. The displacement amount may be detected using another means. For example, the positional shift amount may be detected using the resist sensor 160, or the positional shift amount of the pixel formation position after fixing may be detected using an in-line sensor such as a CCD, etc. The effects of the present invention can be obtained regardless of the situation.
(7-5) In the above embodiment, although the case where the light emitted from the light emitting element 320 is imaged on the outer peripheral surface of the photosensitive drum 101 using the microlens array 201 has been described as an example, the present invention is not limited thereto. Needless to say, the present invention is not limited to this, and instead of the microlens array 201, other optical members such as a rod lens array may be used to image the emitted light of the light emitting element 320.
(7-6) In the above embodiment, the case of predicting the positional displacement amount for each microlens has been described as an example, but it goes without saying that the present invention is not limited to this, and instead of this, the following is performed May be For example, three microlenses of each row of microlenses arranged in a staggered pattern of 3 rows and 50 columns may be set as one set, and the amount of positional deviation may be predicted for each set, and furthermore, a wide range in the main scanning direction The displacement amount may be predicted as one unit. In this way, the processing load for positional deviation correction can be reduced.

Also, conversely, the amount of positional deviation may be predicted with a range narrower than one microlens in the main scanning direction as one unit. In this way, it is possible to improve the prediction accuracy of the variation in the amount of linear expansion in the main scanning direction.
(7-7) In the above embodiment, the case where the image forming apparatus 1 is a tandem type color printer has been described as an example, but it goes without saying that the present invention is not limited to this. It may be a color printer or a monochrome printer. In addition, the same effects can be obtained even when the present invention is applied to a single function machine such as a copying machine equipped with a scanner or a facsimile machine equipped with a facsimile communication function, or a multifunction machine (MFP: Multi-Function Peripheral) having these functions. You can get

  The optical writing apparatus and the image forming apparatus according to the present invention are useful as an apparatus capable of accurately suppressing the light amount unevenness caused by the fluctuation of the environmental conditions in the line optical type optical writing apparatus.

1 ... ... image forming apparatus 100 ... light writing apparatus 200 ... light source substrate 210 ... microlens array 212 ... driver IC
302: Light emitting block 320: Light emitting element 522: Misalignment detection sensor

Claims (10)

A plurality of light emitting elements are disposed on the upper surface, and a long light source substrate is provided with a circuit for modulating the light emitted from the plurality of light emitting elements according to the print job; It has a long optical member in which a plurality of imaging lenses for forming an image on the surface are disposed, and a support member fixed to the light source substrate and the optical member at one end in the long direction. The light writing device, wherein the light source substrate and the optical member have different linear expansion coefficients,
Heat generation amount estimation means for estimating, for each of the image forming lenses, a total amount of heat generation amounts of one or more light emitting elements for forming emitted light by the image forming lens.
Using the total amount of heat generation amount estimated by the heat generation amount estimation means, the positional deviation amount in the longitudinal direction of the light emitting element due to the difference between the linear expansion amount of the light source substrate and the optical member is predicted. Misregistration amount prediction means;
And a correction unit configured to correct an imaging state according to the displacement amount predicted by the displacement amount prediction unit. The optical writing according to claim 1, wherein the heat generation amount estimation unit estimates a total amount of the heat generation amount using a total of lighting times of the one or more light emitting elements from the start of the print job. apparatus. The optical writing according to claim 1, wherein the heat generation amount estimation unit estimates a total amount of the heat generation amount using a total of power consumption of the one or more light emitting elements from the start of the print job. apparatus. An optical path change detection unit that detects, for each of the imaging lenses, a change in an optical path from the light emitting element that has emitted the emitted light to the surface of the photosensitive member, of the emitted light formed by the imaging lens;
Position shift amount detecting means for detecting a position shift amount between a light emitting element relating to the light path change and an imaging lens for imaging the emitted light of the light emitting element using the light path change detected by the light path change detecting means; Equipped with
The misregistration amount prediction means
With regard to the two imaging lenses at different positions in the longitudinal direction, the amount of misalignment related to an imaging lens other than the two imaging lenses is calculated using the amount of misalignment detected by the misalignment detection means. The optical writing device according to claim 1 or 2, wherein prediction is performed. The two imaging lenses at different positions in the longitudinal direction are imaging lenses in which the total amount differs by a predetermined threshold or more from the average value of the total amount for each imaging lens estimated by the heat generation amount estimation unit. The optical writing device according to claim 4, The two imaging lenses at mutually different positions in the longitudinal direction are two imaging lenses adjacent to each other in the longitudinal direction, and the heat generation amount estimation unit is the two imaging lenses adjacent to each other. 5. The optical writing device according to claim 4, wherein the difference between the estimated total amounts for each imaging lens is equal to or greater than a predetermined threshold. The two imaging lenses at mutually different positions in the longitudinal direction are two imaging lenses adjacent to each other in the longitudinal direction, and the heat generation amount estimation unit is the two imaging lenses adjacent to each other. 5. The optical writing device according to claim 4, wherein the sum of the estimated total amounts for each imaging lens is equal to or greater than a predetermined threshold. The misregistration amount prediction means
The positions of the imaging lenses other than the two imaging lenses by linear interpolation using the positional displacement amount detected by the positional displacement amount detection unit for the two imaging lenses at different positions in the longitudinal direction. The optical writing device according to any one of claims 4 to 7, wherein the amount of deviation is predicted. The misregistration amount prediction means
With regard to the two imaging lenses at different positions in the longitudinal direction, the heat generation amount estimation means for the imaging lenses other than the two imaging lenses in addition to the positional deviation amount detected by the positional deviation amount detecting means The optical writing device according to any one of claims 4 to 7, wherein the positional deviation amount related to the imaging lens is predicted by using the total amount of heat generation amount estimated by. An image forming apparatus comprising the optical writing device according to any one of claims 1 to 9.

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