JP2007140399A - Optical scanner and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a fine beam spot on a face to be scanned by adjusting the focused position of a light beam in an optical scanner in which the light beam is scanned on the face to be scanned in a main scanning direction with a deflecting mirror face. <P>SOLUTION: A so called diagonal incident structure, in which the light beam from a light source 62 is made incident diagonally on a subscanning cross section with respect to the deflecting mirror face 651 of a deflector, is adopted. Further, in the deflector, a movable member (the deflecting mirror face 651) is dislocated in a normal line direction Z by adjusting an electric voltage applied on a first and a second piezo laminated actuator parts. Thus, the focused position of the light beam also moves by an amount of distance corresponding to the dislocation of the deflecting mirror face 651 by the adjustment of the electric voltage. In this way, the fine beam spot is scanned on the surface of a photoreceptor (the face to be scanned) 21 by adjusting the focused position of the light beam. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical scanning device that deflects a light beam by a vibrating deflection mirror surface and scans the light beam in a main scanning direction on a surface to be scanned, and an image forming apparatus equipped with the device.

  Examples of apparatuses using this type of optical scanning apparatus include image forming apparatuses such as laser printers, copiers, and facsimile machines. In this image forming apparatus, an image signal such as a gradation reproduction process is added to image data related to a toner image to be formed on the surface of a latent image carrier such as a photoconductive drum to form an image signal. In this image forming apparatus, an exposure unit is provided as an optical scanning device, and the exposure unit forms a latent image corresponding to the image data on the latent image carrier. For example, in an exposure unit equipped in an image forming apparatus described in Patent Document 1, a laser diode is used as a light source, and a light beam from the light source is modulated based on the image signal, and the modulated light beam is converted into a light deflection element. The light beam is scanned in the main scanning direction by being deflected by the deflection mirror surface. The scanning light beam is applied to the surface of the latent image carrier in a spot shape to form a spot latent image. The spot latent image formed in this way is developed by the developing unit, dots are formed at the spot latent image position, and a toner image corresponding to the image data is formed.

JP-A-9-230277 (FIGS. 1, 5 and 7)

  As described above, in the image forming apparatus, the latent image is formed by irradiating the surface of the latent image carrier (scanned surface) with the scanning light beam in a spot shape by the exposure unit (optical scanning device). The beam diameter of the light beam on the surface of the carrier greatly affects the image quality. That is, the focal position may move in the optical axis direction of the exposure unit due to environmental factors such as temperature and humidity, and the relative inclination of the latent image carrier with respect to the exposure unit. For this reason, there is a problem that a latent image cannot be formed with a predetermined beam diameter and a good image cannot be obtained.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems. In an optical scanning apparatus that scans a light beam on a surface to be scanned in a main scanning direction by a deflecting mirror surface, a high-definition beam spot is obtained by adjusting the focal position of the light beam. Is formed on the surface to be scanned.

  A second object of the present invention is to provide an image forming apparatus capable of forming a high-definition latent image on a latent image carrier to obtain a high-quality image.

  The present invention is an optical scanning device that scans a light beam on a surface to be scanned in the main scanning direction. In order to achieve the first object, a light source that emits a light beam and a light beam from the light source are reflected. A deflecting means for deflecting the light beam in the main scanning direction by vibrating a movable member having a deflecting mirror surface about a drive axis substantially orthogonal to the main scanning direction, and an optical system for imaging the light beam on the surface to be scanned The light beam from the light source is obliquely incident on the deflection mirror surface in a sub-scan section substantially perpendicular to the main scanning direction, and the deflection means is a normal line of the deflection mirror surface with the movable member stationary. In the direction, the movable member is displaced to adjust the focal position of the light beam in the optical axis direction.

  In the invention configured as above, the light beam from the light source is incident obliquely on the deflection mirror surface in the sub-scan section, so-called oblique incidence. For this reason, when the deflection mirror surface is displaced in the normal direction, the focal position of the light beam is also moved in the optical axis direction in accordance with the amount of displacement. Therefore, in the present invention, the movable member is displaced in the normal direction of the deflection mirror surface with the movable member stationary, and the focal position of the light beam is adjusted in the optical axis direction. As a result, a high-definition beam spot can be formed on the surface to be scanned.

  In addition, a high-definition latent image can be formed by forming a latent image on the latent image carrier using the optical scanning device configured as described above, and a high-quality image can be obtained by developing the latent image. An image can be obtained.

  FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. This image forming apparatus is a so-called four-cycle color printer. In this image forming apparatus, when an image forming command is given to the main controller 11 from an external device such as a host computer in response to an image forming request from a user, the main controller 11 responds to image data included in the image forming command. Image processing such as gradation reproduction processing is added to provide an image signal to the engine unit EG, and a control signal corresponding to an image formation command is supplied to the engine controller 10. The engine controller 10 controls each unit of the engine unit EG to form an image corresponding to the image formation command on a sheet such as copy paper, transfer paper, paper, and an OHP transparent sheet.

  In the engine unit EG, the photosensitive member 2 is provided so as to be rotatable in the arrow direction (sub-scanning direction) in FIG. Further, a charging unit 3, a rotary developing unit 4, and a cleaning unit (not shown) are arranged around the photoconductor 2 along the rotation direction. A charging controller 103 is electrically connected to the charging unit 3 and applies a predetermined charging bias. By applying this bias, the outer peripheral surface of the photoreceptor 2 is uniformly charged to a predetermined surface potential. Further, the photosensitive member 2, the charging unit 3, and the cleaning unit integrally constitute a photosensitive member cartridge, and the photosensitive member cartridge is integrally detachable from the apparatus main body 5.

  Then, the light beam L is irradiated from the exposure unit 6 toward the outer peripheral surface of the photosensitive member 2 charged by the charging unit 3. The exposure unit 6 scans the photosensitive member 2 with a light beam L based on an electric signal from the exposure control unit 102 to form an electrostatic latent image corresponding to the image signal. As described above, the exposure unit 6 is an optical scanning device according to the present invention, and the configuration and operation thereof will be described in detail later.

  The electrostatic latent image thus formed is developed with toner by the developing unit 4. That is, in this embodiment, the developing unit 4 is configured as a support frame 40 that is rotatably provided around the axis, and a cartridge that is detachable with respect to the support frame 40, and for yellow that contains toner of each color. A developing unit 4Y, a magenta developing unit 4M, a cyan developing unit 4C, and a black developing unit 4K are provided. Then, based on a control command from the developing device controller 104 of the engine controller 10, the developing unit 4 is driven to rotate, and the developing devices 4Y, 4C, 4M, and 4K are selectively brought into contact with the photoreceptor 2. Alternatively, when positioned at a predetermined developing position facing each other with a predetermined gap, toner is applied to the surface of the photoreceptor 2 from a developing roller 44 provided in the developing unit and carrying toner of a selected color. As a result, the electrostatic latent image on the photoreceptor 2 is visualized with the selected toner color.

  The toner image developed by the developing unit 4 as described above is primarily transferred onto the intermediate transfer belt 71 of the transfer unit 7 in the primary transfer region TR1. The transfer unit 7 includes an intermediate transfer belt 71 that is stretched over a plurality of rollers 72, 73, and the like, and a drive unit (not shown) that rotates the intermediate transfer belt 71 in a predetermined rotation direction by rotationally driving the roller 73. It has.

  In the vicinity of the roller 72, a transfer belt cleaner (not shown), a density sensor 76 (FIG. 2), and a vertical synchronization sensor 77 (FIG. 2) are arranged. Among these, the density sensor 76 is provided facing the surface of the intermediate transfer belt 71 and measures the optical density of the patch image formed on the outer peripheral surface of the intermediate transfer belt 71. The vertical synchronization sensor 77 is a sensor for detecting the reference position of the intermediate transfer belt 71, and is a synchronization signal output in association with the rotational drive of the intermediate transfer belt 71 in the sub-scanning direction, that is, a vertical synchronization signal. It functions as a vertical sync sensor for obtaining Vsync. In this apparatus, the operation of each part of the apparatus is controlled based on the vertical synchronization signal Vsync in order to align the operation timing of each part and to superimpose toner images of each color accurately.

  When transferring a color image to a sheet, each color toner image formed on the photoreceptor 2 is superimposed on the intermediate transfer belt 71 to form a color image and taken out from the cassette 8 one by one. The color image is secondarily transferred onto the sheet conveyed along the conveyance path F to the secondary transfer region TR2.

  At this time, in order to correctly transfer the image on the intermediate transfer belt 71 to a predetermined position on the sheet, the timing of feeding the sheet to the secondary transfer region TR2 is managed. Specifically, a gate roller 81 is provided on the transport path F on the front side of the secondary transfer region TR2, and the gate roller 81 rotates in accordance with the timing of the circumferential movement of the intermediate transfer belt 71. Are sent to the secondary transfer region TR2 at a predetermined timing.

  Further, the sheet on which the color image is formed in this way is conveyed to the discharge tray portion 51 provided on the upper surface portion of the apparatus main body 5 via the fixing unit 9 and the discharge roller 82. When images are formed on both sides of the sheet, the sheet on which the image is formed on one side as described above is switched back by the discharge roller 82. As a result, the sheet is conveyed along the reverse conveyance path FR. Then, it is put again on the transport path F before the gate roller 81. At this time, the image is transferred to the surface of the sheet that is in contact with the intermediate transfer belt 71 and transfers the image in the secondary transfer region TR2. The surface is the opposite of the surface. In this way, images can be formed on both sides of the sheet.

  In FIG. 2, reference numeral 113 denotes an image memory provided in the main controller 11 for storing image data given from an external device such as a host computer via the interface 112, and reference numeral 106 is executed by the CPU 101. A ROM for storing calculation data, control data for controlling the engine unit EG, and the like, and a reference numeral 107 are RAMs for temporarily storing calculation results in the CPU 101 and other data.

  FIG. 3 is a main scanning sectional view showing the structure of the exposure unit provided in the image forming apparatus of FIG. FIG. 4 is a sub-scan sectional view of the exposure unit. 5 and 6 are diagrams showing a deflector as one component of the exposure unit. 7 and 8 are cross-sectional views showing the operation of the deflector. Hereinafter, the configuration and operation of the exposure unit 6 will be described in detail with reference to these drawings.

  The exposure unit 6 has an exposure housing 61. A single laser light source 62 is fixed to the exposure housing 61 so that a light beam can be emitted from the laser light source 62. The laser light source 62 is turned on / off based on an image signal from the main controller 11, and a light beam modulated in accordance with image data is emitted from the laser light source 62. Thus, in this embodiment, the laser light source 62 corresponds to the “light source” of the present invention.

  Further, in the exposure housing 61, a collimator lens 631, a cylindrical lens 632, a mirror 64, a deflector are provided in order to scan and expose the light beam from the laser light source 62 onto the surface (scanned surface) of the photosensitive member 2. 65, a scanning lens 66 and a folding mirror 67 are provided. That is, as shown in FIG. 4, the light beam from the laser light source 62 is shaped into collimated light of an appropriate size by the collimator lens 631 and then incident on the cylindrical lens 632 having power only in the sub-scanning direction Y. Is done. The collimated light is focused only in the sub-scanning direction Y, and is linearly imaged in the vicinity of the deflecting mirror surface 651 of the deflector 65. Thus, in this embodiment, the collimator lens 631 and the cylindrical lens 632 function as the beam shaping system 63 that focuses the light beam from the laser light source 62 in the sub-scanning direction Y. Further, the beam shaping system 63 makes the focused light beam Li obliquely incident on the deflecting mirror surface 651 as shown in FIG. That is, the focused light beam Li has an acute angle γ with respect to the reference plane SS orthogonal to the swing axis (corresponding to the “driving axis” of the present invention) AX of the deflecting mirror surface 651 of the deflector 65 so as to form an acute angle γ. Is incident on.

  The deflector 65 is formed by using a micromachining technique in which a micromachine is integrally formed on a semiconductor substrate by applying a semiconductor manufacturing technique. The deflector 65 reflects the light beam reflected by the deflection mirror surface 651 in the main scanning direction X. Deflection is possible. More specifically, the deflector 65 is configured as follows. The deflector 65 has a base portion 652 having first and second support portions 652a and 652b that are spaced apart by a predetermined distance. The first and second vibrators 653a and 653b are attached to the first and second support portions 652a and 652b, respectively. That is, with respect to the first (left) vibrator 653a, the two left first arm portions 654a and 654a whose left outer end is fixed to the first (left) support portion 652a and whose inner end is a free end. It has become. The second (right) vibrator 653b has two left arm portions 654b and 654b whose left outer end is fixed to the second (right) support portion 652b and whose inner end is a free end. It has become. Further, a rectangular flat plate shape is formed so that the swing axis AX passing through the center of gravity position 655 is substantially parallel to each arm portion 654a, 654b at an intermediate position between the first arm portions 654a, 654a and the second arm portions 654b, 654b. The movable member 656 is disposed. In the movable member 656, one side (left side) portion of the gravity center position 655 is connected to the first arm portions 654a and 654a by the first torsion spring portions 657a and 657a, and the other side (right side) of the gravity center position 655. The site | part is connected with 2nd arm part 654b, 654b by 2nd torsion spring part 657b, 657b. That is, in the deflector 65, the first (left) vibrator 653a and the second (right) vibrator 653b face each other to form an outer frame portion, and the first and second vibrators 653a and 653b The first and second torsion spring portions 657a, 657a, 657b, and 657b are integrally connected to the movable member 656. Note that an aluminum film or the like is formed as a deflection mirror surface 651 on the surface of the movable member 656.

  In addition, a vibration drive unit 658 is provided in the deflector 65 in order to vibrate the movable member 656 around the swing axis AX. The vibration drive unit 658 includes first piezo-stack actuator portions 659a and 659a disposed on one side (left side) with respect to the swing axis AX, and a second piezo-stack layer disposed on the other side (right side) with respect to the swing axis AX. Actuators 659b and 659b are provided. That is, the first piezo laminated actuator portions 659a and 659a are disposed between the upper left and lower lower end portions 652c and 652c of the base portion 652 and the free ends of the two arm portions 654a and 654a of the first vibrator 653a. The upper and lower end surfaces are fixed to the base portion 652 and the first arm portions 654a and 654a, respectively. The second piezo-stack actuator portions 659b and 659b are disposed between the upper right and lower lower end portions 652d and 652d of the base portion 652 and the free ends of the two arm portions 654b and 654b of the second vibrator 653b. The upper and lower end surfaces thereof are fixed to the base portion 652 and the second arm portions 654b and 654b, respectively. Then, voltages having opposite phases to each other are periodically applied from the exposure control unit 102 to the first and second piezoelectric laminated actuator units 659a and 659b.

  Since each piezo laminated actuator section 659a, 659b varies in volume in the laminating direction (normal direction Z) depending on the applied voltage, a reverse phase voltage is applied to the first and second piezo laminated actuator sections 659a, 659b. Then, the movable member 656 swings about the swing axis AX passing through the center of gravity position 655. When a voltage is applied only to the first piezo-stack actuator portion 659a, for example, as shown in FIG. 7, the arm portion 654a of the first vibrator 653a moves in the normal direction (upward direction in the figure) Z. Then, the movement of the arm portion 653a is transmitted to the movable member 656 via the first torsion spring portion 657a, and this becomes rotational torque, and the movable member 656 is clockwise about the swing axis AX passing through the center of gravity position 655. Rocks. Further, when a voltage is applied only to the second piezo-stack actuator portion 659b, the arm portion 654b of the second vibrator 653b moves in the normal direction (upward direction in the figure) Z, and the above is applied to the movable member 656. A reverse rotational torque is applied, and as a result, the movable member 656 swings counterclockwise about the swing axis AX. Here, the “normal direction” means the normal direction of the deflection mirror surface 651 in a state where the movable member 656 is stationary.

  As described above, the deflector 65 swings the movable member 656, deflects the light beam from the light source 62, and scans in the main scanning direction X. This scanning light beam forms an image on the photosensitive member 2 via the scanning lens 66 and the folding mirror 67, and a light beam spot is formed on the photosensitive member surface 21. Thus, in this embodiment, the scanning lens 66 corresponds to the “optical system” of the present invention.

  Here, the apparatus employing the deflector 65 having the above configuration has the following characteristics. That is, in this deflector 65, the movable member 656 can be displaced in the normal direction Z by adjusting the voltage applied to the first and second piezoelectric laminated actuator portions 659a and 659b. For example, when the same voltage is applied to both piezoelectric actuator units 659a and 659b, the volume variation in the normal direction Z becomes the same as shown in FIG. 8, for example, and the movable member 656 is displaced in the normal direction Z. In addition, since the amount of displacement is determined according to the voltage, when voltages having phases opposite to each other are applied to the first and second piezoelectric laminated actuator portions 659a and 659b in a state where the voltage is superimposed, the movable member 656 according to the voltage. The deflection mirror surface 651 can be swung while displacing the rocking axis AX in the normal direction Z.

  When the swing axis AX of the movable member 656 is displaced in the normal direction Z in this way, the optical distance from the light source 62 to the photosensitive member surface 21 changes, and as a result, the photosensitive member 2 passes through the scanning lens 66 and the folding mirror 67. The position at which the image is formed, that is, the focal position FP of the scanning light beam is displaced in the optical axis direction. For example, when the oscillating axis AX of the deflecting mirror surface 651 is set to the mirror position MP1, the focal position of the scanning light beam is a position FP1 away from the surface 21 of the photosensitive member 2 in the optical axis direction as indicated by a broken line in FIG. Even if it is, the focal position can be adjusted by voltage adjustment. That is, when the vibrating movable member 656 is displaced in the normal direction Z so that the swing axis AX of the deflecting mirror surface 651 coincides with the mirror position MP2, as shown by the solid line in FIG. Is a position FP2 on the surface 21 of the photoreceptor 2. As a result, the beam spot on the photosensitive member surface 21 has high definition.

  In this embodiment, as shown in FIG. 3, the start and end of the scanning light beam from the deflector 65 are guided to the light detection sensor 60 by the folding mirror 69a. That is, in this embodiment, the light detection sensor 60 functions as a horizontal synchronization reading sensor for obtaining a synchronization signal in the main scanning direction X, that is, a horizontal synchronization signal.

  Further, as shown in the figure, a spot diameter measuring unit (measuring means) 68 for measuring the diameter of the beam spot formed on the photosensitive member surface 21 is disposed at a position symmetrical to the optical detection sensor 60 with respect to the optical axis OA. Has been. FIG. 9 is a plan view showing the configuration of the spot diameter measuring unit. FIG. 10 is an explanatory diagram of the operation of the spot diameter measuring unit. This spot diameter measuring unit 68 is formed by masking a mask member 682 provided with a slit 681 having a width W substantially equal to the desired beam diameter in the main scanning direction X on the sensing surface of the photosensor 683. The spot diameter measuring unit 68 is arranged so that the sensing surface of the photosensor 683 is optically conjugate with the surface 21 of the photoreceptor 2. For this reason, the spot diameter measurement unit 68 can measure the spot diameter on the photoreceptor surface 21. The reason is that the output from the photosensor 683 changes according to the displacement of the focal position with respect to the photoreceptor surface 21, and the sensor output becomes the largest at the so-called best focus where the focal point is located on the photoreceptor surface 21. It is. This is because a high-definition beam spot is formed on the photoconductor surface 21 at the best focus, and the intensity distribution of the scanning light beam is sharp even on a sensing surface optically conjugate with the photoconductor surface 21. As a result, when the light beam scans the spot diameter measuring unit 68, when the scanning light beam coincides with the slit 681, most of the scanning light beam is received by the sensing surface of the photosensor 683 through the slit 681. The output from the photosensor 683 is increased. On the other hand, the light beam at the slit 681 becomes out of focus as the focal position moves away from the photoreceptor surface 21 due to the swing axis AX being displaced in the normal direction Z, and the amount of light blocked by the mask member 682 increases. As a result, the output from the photosensor 683 is reduced. Therefore, in this embodiment, the maximum value of the sensor output output from the photosensor 683 is peak-held for each scan, and the position of the swing axis where the maximum value is the highest is detected as the best focus. Thus, in this embodiment, the photosensor 683 functions as a beam diameter sensor that detects the beam diameter of the scanning light beam on the photoreceptor surface 21, and the beam in the main scanning direction X is based on the output of the photosensor 683. The diameter is measured indirectly. Of course, the beam spot shape may be imaged using an imaging element such as a two-dimensional CCD, and the beam diameter may be directly measured based on the imaging data.

  FIG. 11 is a flowchart showing the operation of the image forming apparatus. In the apparatus configured as described above, when an image formation command is given in a state where the deflector 65 is stopped in vibration, the engine controller 10 executes a start-up process before the image forming operation is started. That is, the operation of the deflector 65 is started in step S1. At this time, the amplitude of the deflector 65 gradually increases from zero as shown in FIG. Then, the detection signal Hsync is output from the light detection sensor 60 at a timing when the amplitude reaches a sensor position corresponding to the arrangement position of the light detection sensor 60, that is, when the scanning light beam passes through the light detection sensor 60. Therefore, in this embodiment, it is detected by the output of the detection signal Hsync that the deflector 65 is oscillating at a predetermined angle (amplitude angle corresponding to the sensor position) or more (step S2). Confirmation of light beam emission. However, at this point in time, it is unclear whether the focal position of the scanning light beam coincides with the photosensitive member surface 21, so the following steps S <b> 3 to S <b> 7 are executed so that the focal position of the scanning light beam becomes the photosensitive member surface 21. The deflector 65 is adjusted so as to substantially match.

  In step S3, the voltage applied from the exposure control unit 102 to the first and second piezo stacked actuator units 659a and 659b is changed to a preset default value. Thereby, the movable member 656 moves in the normal direction Z corresponding to the default voltage. Further, every time the scanning light beam passes through the arrangement position (beam diameter sensor position) of the spot diameter measuring unit 68, a signal corresponding to the beam diameter is output from the beam diameter sensor (photo sensor) 683. Therefore, in step S4, the beam diameter of the scanning light beam on the photosensitive member surface 21 is calculated based on the output signal from the beam diameter sensor (photosensor) 683.

  In the next step S5, the difference between the current beam diameter and a preset predetermined beam diameter is obtained, and the voltage applied to the first and second piezo-stack actuator portions 659a and 659b is increased or decreased by a value corresponding to the difference. As a result, the position of the movable member 656 in the normal direction Z is adjusted. Further, immediately after the position adjustment, the beam diameter of the scanning light beam on the photosensitive member surface 21 is calculated based on the output signal from the beam diameter sensor (photo sensor) 683 (step S6). Then, it is determined whether or not the adjusted beam diameter matches the predetermined beam diameter (step S7). If not, the process returns to step S5 and repeats steps S5 and S6. As a result, the focal position of the scanning light beam can be made substantially coincident with the photosensitive member surface 21, and the beam spot on the photosensitive member surface 21 becomes high definition. If “YES” is determined in step S7, the focus adjustment process is completed, and the process proceeds to a normal image forming operation (step S8).

  As described above, in this embodiment, in the exposure unit 6 corresponding to the optical scanning device of the present invention, the light beam from the light source 62 is applied to the deflection mirror surface 651 of the deflector 65 in the sub-scan section (FIG. 4). A so-called oblique incidence configuration in which the incidence is oblique is employed. Further, in the deflector 65, the vibration driving unit 658 displaces the movable member 656 in the normal direction Z during vibration by adjusting the voltage applied to the first and second piezoelectric laminated actuator units 659a and 659b. For this reason, the focal position of the light beam moves in the optical axis direction by a distance corresponding to the amount of displacement of the deflection mirror surface 651 by the vibration drive unit 658. As described above, according to this embodiment, it is possible to adjust the focal position of the light beam and to scan the photosensitive member surface (scanned surface) 21 with a high-definition beam spot. In addition, a high-definition latent image can be formed by using such a high-definition beam spot, and a high-quality image can be obtained by developing the latent image.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the driving force applied to the vibrators 653a and 653b by the actuator units 659a and 659b is adjusted by adjusting the voltage applied to the piezoelectric laminated actuator units 659a and 659b, so that the vibrating movable member 656 is normal. Although it is displaced in the direction Z, the movable member 656 that is vibrating in another method may be displaced in the normal direction Z. For example, FIG. 13 illustrates a configuration in which the moving movable member 656 is displaced in the normal direction Z by electrostatic force. In this apparatus, the electrode 650 a is fixedly disposed on the base portion 652 at a position directly below the movable member 656. A power source 650b is connected to the electrode 650a and the vibrator 653b. Therefore, by controlling the output of the power source 650b, the electrostatic force acting between the electrode 650a and the movable member 656 can be changed, and the position of the movable member 656 relative to the electrode 650a can be changed. Therefore, the vibrating movable member 656 can be displaced in the normal direction Z by the output control of the power source 650b. Thus, in this embodiment, the electrode 650a and the power source 650b function as the “displacement drive unit” of the present invention.

  FIG. 14 shows a configuration in which the movable member 656 that is vibrating is displaced in the normal direction Z by electromagnetic force. In this apparatus, a permanent magnet 650 c is fixedly disposed on the base portion 652 at a position directly below the movable member 656. In addition, a coil pattern 650d is provided in a part of the movable member 656, and a Lorentz force acts between the permanent magnet 650c by power supply from the power source 650e to change the position of the movable member 656 with respect to the permanent magnet 650c. Can do. Therefore, the vibrating movable member 656 can be displaced in the normal direction Z by the output control of the power source 650e. Thus, in this embodiment, the permanent magnet 650c, the coil pattern 650d, and the power source 650e function as the “displacement drive unit” of the present invention.

  Further, FIG. 15 shows a configuration in which the movable member 656 is displaced by separately providing piezo laminated actuator portions 650f and 650g for moving in the normal direction and displacing the base portion 652 in the normal direction Z. That is, in the deflector 65 in this embodiment, the entire deflector shown in FIG. 5 corresponds to the “deflection element” of the present invention, and the deflector body 650 h so as to surround the bottom side of the base portion 652 of the deflection element. Is provided. Piezo-stack actuator portions 650f and 650g are interposed between the deflector body 650h and the base portion 652. For this reason, each piezo lamination actuator part 650f, 650g can change the volume in the lamination direction (normal direction Z) according to the applied voltage, and can change the position of the movable member 656 in the normal direction Z. Therefore, the vibrating movable member 656 can be displaced in the normal direction Z by controlling the voltage applied to each of the piezoelectric laminated actuator portions 650f and 650g. Thus, in the present embodiment, the piezoelectric laminated actuator portions 650f and 650g function as the “displacement driving portion” of the present invention. Of course, it goes without saying that another actuator may be used as the “displacement driving unit” instead of the piezoelectric laminated actuator units 650f and 650g.

  In the embodiment shown in FIGS. 13 to 15, the piezoelectric laminated actuator is used similarly to the embodiment shown in FIG. 5 in order to vibrate the movable member 656, but the movable member 656 is vibrated by another driving method. You may comprise as follows.

  In the above embodiment, the beam diameter in the main scanning direction X is measured by the spot diameter measuring unit 68, but the beam diameter in the sub-scanning direction Y is measured to adjust the focal position of the scanning light beam. Also good. Here, in order to measure the beam diameter in the sub-scanning direction Y, for example, a spot diameter measuring unit shown in FIG. 16 can be used. The spot diameter measuring unit 68 is greatly different from the spot diameter measuring unit in FIG. 9 in that an oblique slit 684 is employed. That is, in this embodiment, the slit 684 is provided obliquely with respect to the scanning locus of the light beam. Other configurations and operations are basically the same. Further, the arrangement position of the spot diameter measuring unit 68 is not limited to the above embodiment, and is arbitrary as long as the beam diameter of the scanning light beam on the photosensitive member surface 21 can be measured. Further, the configuration for measuring the beam diameter is not limited to the above embodiment, and is arbitrary.

  In the above-described embodiment, the light detection sensor 60 that detects the signal Hsync and the spot diameter measuring unit 68 are provided separately and independently, but both may be shared.

  In the above embodiment, the optical scanning device according to the present invention is applied to the exposure unit of a four-cycle color image forming apparatus. However, the application target of the present invention is not limited to this, and so-called tandem. The present invention can be applied to an exposure unit of a type color image forming apparatus or a monochrome image forming apparatus for forming a monochromatic image. The application target of the optical scanning device is not limited to the exposure unit provided in the image forming apparatus, and can be applied to all optical scanning devices that scan a scanning surface with a light beam.

1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus in FIG. 1. 2 is a main scanning sectional view of an exposure unit provided in the image forming apparatus of FIG. FIG. 2 is a sub-scan sectional view of an exposure unit provided in the image forming apparatus of FIG. 1. The figure which shows the deflector which is one component of an exposure unit. The figure which shows the deflector which is one component of an exposure unit. Sectional drawing which shows operation | movement of a deflector. Sectional drawing which shows operation | movement of a deflector. The figure which shows an example of a spot diameter measurement part. The figure which shows operation | movement of a spot diameter measurement part. 6 is a flowchart showing the operation of the image forming apparatus. FIG. 6 is a diagram illustrating an operation of the image forming apparatus. FIG. 6 is a diagram showing another embodiment of the image forming apparatus according to the present invention. FIG. 5 is a diagram showing another embodiment of the image forming apparatus according to the present invention. FIG. 6 is a view showing still another embodiment of the image forming apparatus according to the present invention. The figure which shows the other example of a spot diameter measurement part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Photoconductor (latent image carrier), 6 ... Exposure unit (optical scanning device), 21 ... Photoconductor surface (scanned surface), 62 ... Laser light source, 65 ... Deflector, 66 ... Scanning lens (optical system) 68 ... Spot diameter measuring unit (measuring means), 650a ... Electrode (displacement driving unit), 650b, 650e ... Power source (displacement driving unit), 650c ... Permanent magnet (displacement driving unit), 650d ... Coil pattern (displacement driving unit) ), 650f, 650g: Piezo-stacked actuator unit (displacement driving unit), 650h: External base unit (deflector body), 651 ... Deflection mirror surface, 652 ... Base unit, 652a ... First support unit, 652b ... Second support 653a ... first vibrator, 653b ... first vibrator, 654a ... first arm part, 654b ... second arm part, 655 ... center of gravity, 656 ... movable part 657a ... first torsion spring part, 657b ... second torsion spring part, 658 ... amplitude drive part, 659a, 659b ... piezo lamination actuator part (drive part), AX ... oscillation shaft (drive shaft), FP1, FP2 ... focal position, L ... light beam, OA ... optical axis, X ... main scanning direction, Y ... sub-scanning direction, Z ... normal direction

Claims (8)

In an optical scanning device that scans a light beam in a main scanning direction on a surface to be scanned,
A light source that emits a light beam;
Deflection means for oscillating a movable member having a deflecting mirror surface for reflecting a light beam from the light source around a drive axis substantially orthogonal to the main scanning direction to deflect the light beam in the main scanning direction;
An optical system for imaging a light beam on the surface to be scanned,
A light beam from the light source is incident obliquely with respect to the deflection mirror surface in a sub-scan section substantially perpendicular to the main scanning direction;
The deflection means adjusts the focal position of the light beam in the optical axis direction by displacing the movable member in the normal direction of the deflection mirror surface with the movable member stationary. apparatus. The deflection means includes
A base portion having first and second support portions spaced apart by a predetermined interval;
A first vibrator having two first arm portions whose outer end portions are fixed to the first support portion and whose inner end portions are free ends;
A second vibrator having two second arm portions whose outer end portions are fixed to the second support portion and whose inner end portions are free ends;
The movable member arranged so that the drive shaft is positioned between the first arm portion and the second arm portion, and the first arm portion on the first vibrator side with respect to the drive shaft. A first torsion spring portion to be coupled;
A second torsion spring portion connecting the movable member to the second arm portion on the second vibrator side with respect to the drive shaft;
A vibration drive unit that vibrates the movable member by applying a driving force to the first and second vibrators independently and reciprocally moving each arm unit in the normal direction;
The optical scanning device according to claim 1, wherein the vibration driving unit controls the driving force applied to the first and second vibrators to displace the vibrating movable member in the normal direction. The deflection means includes
A base portion having first and second support portions spaced apart by a predetermined interval;
A first vibrator having two first arm portions whose outer end portions are fixed to the first support portion and whose inner end portions are free ends;
A second vibrator having two second arm portions whose outer end portions are fixed to the second support portion and whose inner end portions are free ends;
The movable member arranged so that the drive shaft is positioned between the first arm portion and the second arm portion, and the first arm portion on the first vibrator side with respect to the drive shaft. A first torsion spring portion to be coupled;
A second torsion spring portion connecting the movable member to the second arm portion on the second vibrator side with respect to the drive shaft;
A vibration drive unit that vibrates the movable member by applying a driving force to the first and second vibrators independently and reciprocally moving each arm unit in the normal direction;
The optical scanning according to claim 1, further comprising: a displacement driving unit that applies an external force to the movable member in a non-contact state from the opposite side of the deflection mirror surface to displace the vibrating movable member in the normal direction. apparatus.   The optical scanning device according to claim 3, wherein the displacement driving unit displaces the movable member in vibration in the normal direction by electrostatic force.   The optical scanning device according to claim 3, wherein the displacement driving unit displaces the movable member in vibration in the normal direction by electromagnetic force.   The deflecting means includes a deflector body, a deflecting element in which the movable member is provided so as to vibrate around the drive shaft with respect to a base portion, and an external force is applied to the deflecting element to place the deflecting element in the deflector body. The optical scanning device according to claim 1, further comprising: a displacement driving unit configured to displace in the normal line direction. Measuring means for detecting a scanning light beam at a position optically conjugate with the scanned surface and measuring a beam diameter of the light beam on the scanned surface;
The optical scanning device according to claim 1, wherein the movable member is displaced in the normal direction based on a measurement result obtained by the measurement unit.   An image forming apparatus comprising: forming a latent image on a latent image carrier using the optical scanning device according to claim 1; and developing the latent image to form an image.

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