JP4349756B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning apparatus and an image forming apparatus, and more particularly to an optical scanning apparatus used in a writing system of an image forming apparatus such as a digital copying machine and a laser printer.
[0002]
[Prior art]
Conventionally, polygon mirrors and galvanometer mirrors are known as deflectors used in optical scanning devices. Among these, the galvanometer mirror is a method in which a current is passed through a movable coil supported in a magnetic field to generate an electromagnetic force, and the movable coil is reciprocally rotated in a balanced relationship between the rotational torque and the return spring. There is an advantage that the configuration is simple and the size can be reduced.
[0003]
In recent years, with the development of micromachining, as disclosed in Japanese Patent No. 2,722,314, there has been proposed a galvanometer mirror in which a movable mirror and a torsion bar that pivotally supports the movable mirror are integrally formed on a Si substrate. ing. Further, as disclosed in Japanese Patent No. 3,011,144, there is a method of swinging the movable mirror using electrostatic attraction. According to these methods, it is possible to obtain a deflector capable of high-speed operation and high productivity.
[0004]
As described above, in the method of forming the movable mirror on the Si substrate, the beam is generated at a higher speed than the polygon mirror by resonating and vibrating the period of the attractive force or repulsive force applied to the movable mirror in accordance with the natural frequency of the movable mirror. There is an advantage that it is possible to scan.
[0005]
[Problems to be solved by the invention]
By the way, the deflection angle θ is expressed by the following equation by the elastic constant G of the torsion bar that supports the movable mirror, the secondary moment I of the cross section, the spring constant K determined by the length L, and the applied torque T.
[0006]
θ = T / K where K = GI / L
[0007]
If the resonance frequency φ of the movable mirror is the moment of inertia J
[0008]
φ = √K / J
[0009]
Therefore, since the speed, that is, the resonance frequency and the deflection angle are in a contradictory relationship, it is generally difficult to increase the scanning angle to about the same as a polygon mirror (about 40 °) with a deflection angle of about 10 ° or less. For this reason, it is necessary to increase the optical path length (distance between the deflecting surface and the surface to be scanned) in order to ensure the recording width as a substitute for the polygon mirror. There was a drawback that the size would increase.
[0010]
The present invention is intended to solve these problems, and uses a movable mirror that oscillates by resonance vibration, making it possible to take advantage of its downsizing and high speed, as well as being capable of high-speed recording with low power, and is favorable. An object of the present invention is to provide an optical scanning apparatus and an image forming apparatus that can obtain image quality.
[0011]
[Means for Solving the Problems]
  In order to solve the above problems,The present inventionA movable mirror that is supported by a light source that modulates according to image data and a pair of torsion bars provided on a support base, and that can swing around the torsion bar as a rotation axis, and at both ends of the movable mirror that sandwiches the torsion bar A unit module having a movable mirror swinging means that swings the movable mirror by periodically generating an attractive force or a repulsive force between the support substrate and the movable mirror by switching the drive voltage to be applied., DoubleA plurality of light beams emitted from the light emission source are scanned in the main scanning direction by a movable mirror that oscillates, and the scanned areas are connected to perform image recording.This is an optical scanning device. In the optical scanning device of the present invention, the plurality of unit modules are aligned with the main scanning direction of each unit module, and the outside of the scanned area, which is a part of the scanning area of the movable mirror swinging unit included in each unit module, overlaps. As such, they are arranged on the circuit board. In addition, pixel frequency varying means for varying the pixel frequency for modulating the light emission source in accordance with the swinging amount of the movable mirror is provided. According to the optical scanning device of the present invention, by detecting the light beam in the scanning region where the light beams deflected by the movable mirror overlap, at least one of the scanning start end or the scanning end of the light beam is detected. A plurality of beam detecting means are provided, and the pixel frequency by the pixel frequency changing means is varied based on the scanning time between the beam detecting means.Therefore,The scanning time is measured and the deviation of the recording dot position is corrected according to the measurement result. Therefore, the recording width is kept stable even when there is an environmental change or a change with time, and the seam of the image end with the adjacent module is matched. Can get a good picture,it can.
[0012]
  Also,The beam detecting means is mounted on the circuit board on which the unit modules are arranged, and detects the light beam returned by the reflecting means provided at both ends outside the image recording area in the unit module, thereby scanning the light beam. Beam position detection of at least one of the start end and the scanning end is performed. Therefore,The seam of the image end with the adjacent module can be matched, and a good image can be obtained.
[0013]
  Furthermore,The beam detecting means is provided for each of the plurality of unit modules, is mounted between the plurality of unit modules on the circuit board, and is used in common for detecting the beam position of the unit modules arranged on both sides of the beam detecting means. Therefore,The seam of the image end with the adjacent module can be matched, and a good image can be obtained.
[0014]
Also, the pixel frequency varying means can vary the recording dot position due to the deviation of the mirror swing speed from the ideal displacement angular speed due to air resistance or the like by varying the pixel frequency for modulating the light source in multiple stages within one scan. Since the correction can be made, it is possible to ensure the constant speed on the surface to be scanned and obtain a good image with no dot position deviation.
[0015]
In addition, there is a drive current varying means for varying the drive current supplied to the light source in order to vary the amount of light emitted from the light source, and the change in the pixel frequency by varying the drive current according to the pixel frequency Since the amount of light is varied in response to the shift in the lighting time of one dot accompanying the above, the energy for exposing the surface to be scanned represented by the integration can be made uniform, and a good image with no density unevenness can be obtained.
[0016]
Further, a beam detecting means for detecting the position of the light beam deflected by the movable mirror outside the scanning area is provided at each scanning start end for each unit module, and the beam is applied with reference to the timing of the drive voltage applied to the movable mirror swinging means. By switching the detection signal used as the image writing reference signal among the detection signals output from the position detection means, the scanning direction of the beam detected by the beam detection means can be determined at the timing of the drive voltage. Even with this scanning, it is possible to reliably obtain a detection signal corresponding to each scanning without being erroneously detected.
[0018]
Further, the unit modules are arranged by shifting the scanning area by one scanning pitch in the sub-scanning direction between adjacent unit modules, and the timing phase of the drive voltage applied to the mirror swinging means is substantially matched so as to be divided. The image can be satisfactorily spliced at the position, and the beam at the end of one unit module and the beam at the start of the other unit module overlap and enter the same beam detection means. Therefore, the detection signal can be reliably obtained corresponding to each scanning.
[0019]
Further, each unit module has a pair of buffer means for reciprocally deflecting the light beam from the light emitting source with a movable mirror to optically scan the scanned area in both directions, and temporarily store the image data every other scan, By reversing the order of the image data read from each buffer means and alternately switching the buffer means to be read based on the timing of the drive voltage applied to the mirror swing means, the beam scanning direction is determined at the applied drive voltage timing. Therefore, even in bidirectional scanning, the recording image data can be reliably allocated in accordance with the synchronization detection signal (beam position detection signal at the scanning start end) of each scanning without erroneously reversing the recording image data.
[0020]
An image forming apparatus according to another invention is characterized in that image recording is performed by dividing image data for one line into the number of modules for an image forming unit that performs monochromatic image formation.
[0021]
Furthermore, an image forming apparatus according to another invention is characterized in that the image forming apparatus is provided in each image forming unit for each color forming a full color image, and image recording is individually performed with image data corresponding to each color.
[0022]
Another image forming apparatus according to another invention is characterized in that it is commonly provided for an image forming unit for each color forming a full-color image, and image recording is performed in time series using image data corresponding to each color.
[0023]
Furthermore, an image forming apparatus as another invention is provided in common for one or a plurality of colors of an image forming unit for each color forming a full color image, and performs image recording in time series with image data corresponding to each color. There is a feature.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
  Optical scanning device of the present inventionThe plurality of unit modules are arranged on the circuit board so that the main module scanning direction of each unit module is aligned and the outside of the scanned area that is a part of the scanning area of the movable mirror oscillating means of each unit module overlaps. ing. In addition, pixel frequency varying means for varying the pixel frequency for modulating the light emission source in accordance with the swinging amount of the movable mirror is provided. According to the optical scanning device of the present invention, by detecting the light beam in the scanning region where the light beams deflected by the movable mirror overlap, at least one of the scanning start end or the scanning end of the light beam is detected. A plurality of beam detecting means are provided, and the pixel frequency by the pixel frequency changing means is varied based on the scanning time between the beam detecting means.
[0025]
【Example】
FIG. 1 is an exploded perspective view showing the configuration of the optical scanning device according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the configuration of the optical scanning device of this embodiment. The optical scanning device of the first embodiment shown in both figures is a system in which the movable mirror 100 is driven by electrostatic attraction. In both figures, the mirror substrate 106 is configured by bonding a first Si substrate 102 and a second Si substrate 103. The movable mirror 100 and the torsion bar 101 that pivotally supports the movable mirror 100 are formed through the first Si substrate 102 by etching. A mirror surface is formed by evaporating a metal film or the like in the central portion, and both end portions of the mirror are formed in a planar shape having irregularities in a comb shape with the torsion bar 101 interposed therebetween, and electrodes 104 are formed on the side surfaces thereof. The second Si substrate 103 is provided with recesses having a trapezoidal cross section formed with slopes with irregularities that alternately overlap with the comb shape at intervals of several tens of μm as the oscillation space of the mirror portion, and the support substrate of the movable mirror 100 Make. Fixed electrodes 105 and 118 are formed on the concave and convex slopes and on the side surfaces of the trapezoidal cross section so as to face the electrodes 104, and electrostatically is applied between the electrodes by alternately applying a voltage to the fixed electrodes 105 and 118. The movable mirror 100 can be swung by generating an attractive force.
[0026]
Further, a driving circuit 114 for switching the voltage applied to the fixed electrodes 105 and 118 according to the input driving frequency is deposited and formed on the surface of the first Si substrate 102. The light source substrate 107 is formed of sintered metal or the like, and an LD chip 108 is bonded to an LD mounting surface formed perpendicular to the bonding surface, and a cylindrical coupling lens 110 is bonded to a positioning groove 109. The coupling lens 110 has a two-group configuration and is a lens in which the front lens is an asymmetrical aspheric lens and the rear lens is a cylinder lens having a curvature in the sub-scanning direction. The width of the groove 109 is set so that the optical axis matches the light emitting point of the LD chip 108 when the cylindrical outer peripheral surface of the coupling lens 110 abuts. Further, the divergent light beam is adjusted to a substantially parallel light beam in the main scanning direction and a focused light beam in the sub-scanning direction by the adjustment in the optical axis direction, and each is fixedly bonded. The spacer substrate 111 has a frame shape penetrating the center of the Si substrate by etching, a mirror inclined surface 112 that folds the beam from the LD chip 108 downward on one side of the inner end surface, and a back light of the LD chip 108 on the opposite end surface. PD 113 is formed by depositing a GaAs layer or the like. The terminal substrate 116 is formed of ceramic or the like, and includes a plurality of lead terminals 115 for wiring with the LD chip 108, the PD 113, and the driving circuit 114 by wire bonding or the like, and is connected to an external circuit. The mirror substrate 106, the light source substrate 107, and the spacer substrate 111 are sequentially overlapped and bonded onto the terminal substrate 116, and sealed with a window substrate 117 such as a plate glass to constitute a unit module of the optical scanning device.
[0027]
According to the unit module of the optical scanning device configured as described above, the light beam emitted from the LD chip 108 is incident on the movable mirror 100 via the coupling lens 110 and the end mirror 112. The movable mirror 100 oscillates reciprocally with the torsion bar 101 as a rotation axis, and the beam incident on the movable mirror 100 is reflected and deflected upward, emitted from the unit module, and scanned. The diameter of the emitted beam is defined by setting the outer diameter of the mirror inclined surface 112 or the movable mirror 100 to a predetermined size and extracting only the reflected portion by irradiating a beam larger than the outer diameter.
[0028]
Next, a plurality of unit modules of the optical scanning device of the first embodiment shown in FIGS. 1 and 2 are arranged, for example, three unit modules 208, 209, and 210 as shown in FIG. Constitute. The beams scanned by the unit module 208 are imaged on the scanned surface 203 by the scanning lenses 201 and 202 and image recording is performed. In the example shown in FIG. 3, the recording width for one line is divided and recorded by three unit modules 208 to 210, and the unit modules 208 to 210 are arranged on the circuit board 204 according to the main scanning direction. Is done. In each unit module, an image is recorded bidirectionally by the reciprocating vibration of the movable mirror. For example, the unit module 208 is folded in the direction of the circuit board 204 by mirrors 205 and 213 provided at both ends outside the image recording area. The beam positions on the scanning start side and the scanning end side of the reciprocal scanning are detected by the PDs 206 and 207 mounted in FIG. Since the unit modules 209 and 210 are the same, description thereof will be omitted.
[0029]
In the example shown in FIG. 3, the maximum deflection angle of the movable mirror is ± 5 °, of which ± 3 ° (θ) is within the scanning area, and the PDs 206 and 207 are arranged within the scanning angle of 3 to 5 ° outside. To do. A part of the scanning area at 3 to 5 ° overlaps with the adjacent unit module 209, and the PD 207 is also used for detecting the beam position of the unit module 209. Note that the scanning lens 202 is integrally molded and resin-molded continuously in each module, but the same is true if each is provided individually.
[0030]
In the example shown in FIG. 3, the area of the opposing electrodes is enlarged as a comb shape in order to reduce the drive voltage, but this is not restrictive.
[0031]
FIG. 4 is an exploded perspective view showing the configuration of the optical scanning device according to the second embodiment of the present invention. FIG. 5 is a cross-sectional view. The optical scanning device of the second embodiment shown in both figures is a system in which the movable mirror 302 is driven by electromagnetic force. In both figures, the mirror substrate 301 is formed by bonding a Si substrate 304 and a metal yoke substrate 306 as shown in FIG. Similar to the first embodiment, the movable mirror 302 and the torsion bar 303 that pivotally supports the movable mirror 302 are formed by penetrating the Si substrate 304 by etching. A mirror formed by metal deposition or the like is formed in the center, and a thin film coil 305 patterned in a spiral shape is formed on the periphery by wiring drawn through a torsion bar 303. The thin film coil 305 may be provided on the back side of the mirror surface. The yoke substrate 306 forms a support substrate in which a through hole is formed in the central portion to ensure a swinging space for the movable mirror. The pair of magnets 307 and 308 are arranged symmetrically with respect to the torsion bar 303 with the north and south poles facing each other, and are fixed to the side surface of the through hole of the yoke substrate 306. When a current is passed through the thin-film coil 305, Lorentz force is generated in a fixed rotational direction at both ends of the thin-film coil 305 across the torsion bar 303 by the interaction with the magnetic field by the magnets 307 and 308, and the current can be switched by switching the direction of this current. The mirror 302 can be swung. Similar to the first embodiment, a driving circuit 309 for switching the voltage applied to the thin film coil 305 according to the input driving frequency is deposited and formed on the surface of the Si substrate 304. The mirror substrate 301 is joined with the light source substrate 310 and the spacer substrate 311 configured in the same manner as in the first embodiment in order on the terminal substrate 312 and is sealed by the window substrate 313 to form a unit module. Since the configuration other than the unit module is the same as that of the first embodiment, description thereof is omitted.
[0032]
FIG. 6 is a block diagram showing a control circuit of the unit module. In the figure, a drive frequency fd common to each unit module composed of a rectangular wave of TTL level is applied to the drive circuit 401 of the movable mirror from the drive frequency varying means 402. The drive frequency varying means 402 divides the clock from the reference oscillator 403 and varies the frequency fd. Since there is a slight difference in the resonance frequency peak of the movable mirror in each unit module, the drive frequency variable means 402 sets the drive frequency fd so as to select a substantially central value of the variation width. At this time, by adjusting the drive voltage, the deflection angle can be made uniform even if the resonance frequency is deviated from the peak. The pixel frequency variable means 404 sets the pixel frequency fm in proportion to the set drive frequency fd so that the recording width (scanning magnification) does not change even if the scanning speed changes due to variations in the resonance frequency of the movable mirror. I have to. Further, as described above, in the first and second embodiments, the time difference of the detection signals at both ends detected by the PDs 406 and 407 that detect the beams at both ends outside the image area of the unit module is measured by the magnification measuring unit 405, By comparing with the initial value, the recording width is corrected for each unit module in anticipation of fluctuations with time, such as temperature expansion and refractive index fluctuation of the scanning lens, and deviation of scanning speed on the surface to be scanned due to LD wavelength change. You can also Furthermore, the pixel frequency may be changed within one scan. For example, the rotation speed of the oscillation is changed from an ideal value to a non-linear shape due to fluctuations in the air resistance facing the rotation of the movable mirror and the electrostatic attraction accompanying a change in the gap between the electrodes. Even if there is acceleration / deceleration, if the pixel frequency is switched in a plurality of stages by adding correction data 408 corresponding to the acceleration / deceleration and correction data approximating stepwise in the example shown in FIG. It is possible to correct the expansion and contraction and make the pitch uniform on the surface to be scanned. In the example shown in FIG. 6, the same drive frequency is given to all unit modules, and the pixel frequency is given to each unit module. However, even if the drive frequency is set individually, the pixel frequency is set in common. Also good.
[0033]
Also, the LD drive current varying means 409 controls the current applied to the LD 411 in inverse proportion to the frequency set by the pixel frequency varying means 404 so that the energy amount per dot becomes uniform. The buffers 412 and 413 distribute the image data every other scanning line and temporarily store the data, and from the buffer 412 at the recording start timing and a predetermined time after the beam position detection signal on the start side in each scanning direction. Is read from the first dot and from the last dot from the buffer 413, and the LD 411 is modulated to perform bi-directional image recording. In the example shown in FIG. 6, an image is recorded in both directions. However, an image can be recorded every other scanning line, and the recording direction may be unified only in any one direction.
[0034]
FIG. 7 is a time chart showing a detection signal and timing related to writing in the beam position detection PD shown in FIG. 7 corresponds to PD 206 and PD 207 in FIG. 3, respectively, and electrode 1 and electrode 2 in FIG. 7 correspond to electrode 105 and electrode 118 in FIG. 1, respectively. As shown in FIG. 7, since the beams pass in both directions in PD1 and PD2, two continuous outputs can be obtained at both the scanning start end and the scanning end. Therefore, in this example, control is performed so that only one of the beam detection signals is made effective in accordance with the on / off timing of the driving voltage applied to the movable mirror, so that the scanning direction is recognized and the detection signals are selected. I have to. That is, in the case of writing in the forward direction, the PD2 signal detected when the applied voltage to the electrode 1 is off is treated as scanning end side detection, and the PD1 signal detected when off is treated as scanning start side detection. do it. The same applies to writing in the backward direction. The effect is the same even if a separate control signal is generated based on these signals. At this time, the symmetrical buffer means for reading out the image data is switched so that only one of the buffer means is made effective in accordance with the on / off timing of the drive voltage, so that the detection signal and the image on the scanning start side in any scanning direction The data can have a one-to-one correspondence.
[0035]
In the example shown in FIG. 7, the time difference between the detection signals at both ends of the scan is measured, and the recording width is corrected in consideration of the change over time by comparison with this initial value. The time difference between the signals corresponds to T1 and T2 in the figure. The pixel frequency is varied corresponding to the fluctuations ΔT1 and ΔT2, but the times t1 and t2 from the beam detection to the start of writing are set to t1 ′ = t1−ΔT1 / 2 and t2 ′ = t2−ΔT2 / 2. The reciprocating recording position can be corrected with reference to the center of the image.
[0036]
On the other hand, in the second embodiment, the same applies if on / off of the applied voltage corresponds to the positive / negative of the voltage applied to the thin film coil.
[0037]
FIG. 8 is a time chart showing another timing. The example of FIG. 8 is another example of the PD for detecting the beam position, and the PD position or the deflection angle is set so that the beam is folded in the PD. In order to set the deflection angle, the drive voltage may be adjusted, and the beam arrival position at the maximum deflection angle of the movable mirror is matched with the PD installation position. According to this, even if the beam is scanned in both directions, the output is one, and if the rising edge is detected as the scanning end side detection and the falling edge is distinguished as the scanning start side detection, the scanning direction can be recognized. In the embodiment, since the phase of the driving frequency is set to 0 ° in the adjacent unit module, the scanning direction of each unit module at the same time is the same, and the beam position of the adjacent unit module is detected at the same timing. Never enter the PD.
[0038]
FIG. 9 is a diagram showing the state of the scanning line on the scanned surface of each unit module in consideration of the scanning surface feed. The surface to be scanned is fed by one scanning pitch P in the time from the start to the end of scanning, and an image is recorded. For this reason, as shown in FIG. 9A, when the phase of the vibration frequency between adjacent unit modules is set to 0 °, there is a shift in the recording time at the divided position, so that the sub-scanning dot position is shifted by one scanning pitch. It will be. When the scanning line density is fine, it can be ignored, but when the scanning line density is rough with respect to the feed amount, the division position is easily noticeable. In the example shown in FIG. 9A, images are stitched together by setting the scanning positions of adjacent unit modules so that the sub-scanning dot position at the recording start point is shifted by one scanning pitch P. Although there is a possibility that the beam of the adjacent unit module enters the PD for detecting the beam position at the same timing, as shown in FIG. 9B, the phase of the vibration frequency between the adjacent modules is about 180 °. By making the scanning directions opposite to each other, each scanning beam can pass through the divided positions at the same time, and similarly, it is possible to prevent the sub-scanning dot position shift caused by the feeding of the scanned surface. .
[0039]
Next, FIG. 10 shows a digital copying machine, FIG. 11 shows a laser printer, and FIG. 12 shows plain paper as an image forming apparatus using an electrophotographic process equipped with the optical scanning device according to the first and second embodiments described above. An example of a facsimile is shown. In FIG. 10, the digital copying machine main body 500 includes an optical scanning device 501, cassettes 502 and 502 ′ for storing paper, paper feed rollers 503 and 503 ′ for picking up paper one by one from the cassettes 502 and 502 ′, and conveyance A registration roller 504 for controlling timing, a transfer charger 505, a process cartridge 509 in which a photosensitive drum 506, a developing roller 507, a charging roller 508, and the like are integrated; a fixing roller 510 having a built-in halogen heater; The image forming apparatus includes a fixing device 511 including a pressure roller, a conveyance roller 512, and a paper discharge roller 513. The optical scanning device 501 in the digital copying machine having such a configuration modulates a semiconductor laser in accordance with an image signal, forms a latent image on the photosensitive drum 506 uniformly charged by the charging roller 508, and develops the developing roller. The toner is visualized by the toner supplied from 507. On the other hand, the paper taken out by the paper feed rollers 503 and 503 'is conveyed by the registration roller 504 in accordance with the timing of image writing of the optical scanning device, and the toner image is transferred. The transferred image is fixed by a fixing roller 510 and a fixing device 511, and is discharged by a transport roller 512 and a paper discharge roller 513. In FIG. 10, in the document reading apparatus main body 600, an image in the document reading unit 601 fixed on the document table is imaged on a photoelectric conversion element 603 such as a CCD via an imaging lens 602, and a mirror group 604. Are sequentially converted to electronic data. The digital copying machine shown in FIG. 10 is a monochrome copying machine, but is not limited to this. In the case of a full-color copying machine, a type in which the optical scanning device of the present invention is provided for each process cartridge for each color, a full-color image. Needless to say, the present invention can also be applied to a type provided for a single image forming unit for forming or an image forming apparatus including a plurality of image forming units.
[0040]
In FIG. 11, a laser printer 700 includes an optical scanning device 701, a cassette 702 for storing paper, a paper feed roller 703 for taking out paper one by one from the cassette 702, a registration roller 704 for controlling the conveyance timing, and transfer charging. 705, a process cartridge 709 in which a photosensitive drum 706, a developing roller 707, a charging roller 708, and the like are integrated, a fixing roller 710 including a halogen heater, a fixing device 711 including a pressure roller, A paper discharge roller 712 is included. In the optical scanning device 701 in the laser printer 700 having such a configuration, a semiconductor laser is modulated in accordance with an image signal from a host device, and a latent image is formed on a photosensitive drum 706 uniformly charged by a charging roller 708. The toner is visualized by the toner supplied from the developing roller 708. On the other hand, the paper taken out by the paper supply roller 703 is conveyed by the registration roller 704 in accordance with the timing of image writing of the optical scanning device, and the toner image is transferred. The transferred image is fixed by a fixing roller 710 and a fixing device 711 and discharged by a paper discharge roller 712.
[0041]
In FIG. 12, a plain paper facsimile 800 includes an optical scanning device 801, a cassette 802 for storing paper, a paper feed roller 803 for taking out the paper one by one from the cassette 802, a registration roller 804 for controlling the conveyance timing, and a transfer roller. A charging device 805, a process cartridge 809 in which a photosensitive drum 806, a developing roller 807, a charging roller 808, and the like are integrated, a fixing roller 810 having a built-in halogen heater, and a fixing device 811 that includes a pressure roller. The paper feeding roller 813 for taking out the original from the original table 812, a pair of conveying rollers 814 and 815 for conveying the original in the sub-scanning direction, and a reading unit 816 for optically reading the image of the original. A document image sent from the document table 812 by the paper feed roller 813 is sequentially converted into electronic data by the reading unit 816 while being conveyed by the conveyance roller pair 814 and 815. The plain paper facsimile 800 transmits the image signal from the reading unit 816 read as described above by a communication unit (not shown), and the semiconductor laser in the optical scanning device 801 responds to the image signal received through the communication unit. A latent image is formed on the photosensitive drum 806 that is modulated and uniformly charged by the charging roller 808, and is visualized by toner supplied from the developing roller 807. On the other hand, the paper taken out by the paper feed roller 803 is conveyed by the registration roller 804 in accordance with the image writing timing of the optical scanning device, and the toner image is transferred. The transferred image is fixed by a fixing roller 810 and a fixing device 811 and discharged.
[0042]
In addition, this invention is not limited to the said Example, It cannot be overemphasized that various deformation | transformation and substitution are possible if it is description in a claim.
[0043]
【The invention's effect】
  As explained above,The present inventionA movable mirror that is supported by a light source that modulates according to image data and a pair of torsion bars provided on a support base, and that can swing around the torsion bar as a rotation axis, and at both ends of the movable mirror that sandwiches the torsion bar A unit module having a movable mirror swinging means that swings the movable mirror by periodically generating an attractive force or a repulsive force between the support substrate and the movable mirror by switching the drive voltage to be applied., DoubleA plurality of light beams emitted from the light emission source are scanned in the main scanning direction by a movable mirror that oscillates, and the scanned areas are connected to perform image recording.This is an optical scanning device. In the optical scanning device of the present invention, the plurality of unit modules are aligned with the main scanning direction of each unit module, and the outside of the scanned area, which is a part of the scanning area of the movable mirror swinging unit included in each unit module, overlaps. As such, they are arranged on the circuit board. In addition, pixel frequency varying means for varying the pixel frequency for modulating the light emission source in accordance with the swinging amount of the movable mirror is provided. According to the optical scanning device of the present invention, by detecting the light beam in the scanning region where the light beams deflected by the movable mirror overlap, at least one of the scanning start end or the scanning end of the light beam is detected. A plurality of beam detecting means are provided, and the pixel frequency by the pixel frequency changing means is varied based on the scanning time between the beam detecting means.Therefore,The scanning time is measured and the deviation of the recording dot position is corrected according to the measurement result. Therefore, the recording width is kept stable even when there is an environmental change or a change with time, and the seam of the image end with the adjacent module is matched. Can get a good picture,it can.
[0044]
  Also,The beam detecting means is mounted on the circuit board on which the unit modules are arranged, and detects the light beam returned by the reflecting means provided at both ends outside the image recording area in the unit module, thereby scanning the light beam. Beam position detection of at least one of the start end and the scanning end is performed. Therefore,The seam of the image end with the adjacent module can be matched, and a good image can be obtained.
[0045]
  Furthermore,The beam detecting means is provided for each of the plurality of unit modules, is mounted between the plurality of unit modules on the circuit board, and is used in common for detecting the beam position of the unit modules arranged on both sides of the beam detecting means. Therefore,The seam of the image end with the adjacent module can be matched, and a good image can be obtained.
[0046]
Also, the pixel frequency varying means can vary the recording dot position due to the deviation of the mirror swing speed from the ideal displacement angular speed due to air resistance or the like by varying the pixel frequency for modulating the light source in multiple stages within one scan. Since the correction can be made, it is possible to ensure the constant speed on the surface to be scanned and obtain a good image with no dot position deviation.
[0047]
In addition, there is a drive current varying means for varying the drive current supplied to the light source in order to vary the amount of light emitted from the light source, and the change in the pixel frequency by varying the drive current according to the pixel frequency Since the amount of light is varied in response to the shift in the lighting time of one dot accompanying the above, the energy for exposing the surface to be scanned represented by the integration can be made uniform, and a good image with no density unevenness can be obtained.
[0048]
Further, a beam detecting means for detecting the position of the light beam deflected by the movable mirror outside the scanning area is provided at each scanning start end for each unit module, and the beam is applied with reference to the timing of the drive voltage applied to the movable mirror swinging means. By switching the detection signal used as the image writing reference signal among the detection signals output from the position detection means, the scanning direction of the beam detected by the beam detection means can be determined at the timing of the drive voltage. Even with this scanning, it is possible to reliably obtain a detection signal corresponding to each scanning without being erroneously detected.
[0050]
Further, the unit modules are arranged by shifting the scanning area by one scanning pitch in the sub-scanning direction between adjacent unit modules, and the timing phase of the drive voltage applied to the mirror swinging means is substantially matched so as to be divided. The image can be satisfactorily spliced at the position, and the beam at the end of one unit module and the beam at the start of the other unit module overlap and enter the same beam detection means. Therefore, the detection signal can be reliably obtained corresponding to each scanning.
[0051]
Further, each unit module has a pair of buffer means for reciprocally deflecting the light beam from the light emitting source with a movable mirror to optically scan the scanned area in both directions, and temporarily store the image data every other scan, By reversing the order of the image data read from each buffer means and alternately switching the buffer means to be read based on the timing of the drive voltage applied to the mirror swing means, the beam scanning direction is determined at the applied drive voltage timing. Therefore, even in bidirectional scanning, the recording image data can be reliably allocated in accordance with the synchronization detection signal (beam position detection signal at the scanning start end) of each scanning without erroneously reversing the recording image data.
[0052]
An image forming apparatus according to another invention is characterized in that image recording is performed by dividing image data for one line into the number of modules for an image forming unit that performs monochromatic image formation.
[0053]
Furthermore, an image forming apparatus according to another invention is characterized in that the image forming apparatus is provided in each image forming unit for each color forming a full color image, and image recording is individually performed with image data corresponding to each color.
[0054]
Another image forming apparatus according to another invention is characterized in that it is commonly provided for an image forming unit for each color forming a full-color image, and image recording is performed in time series using image data corresponding to each color.
[0055]
Furthermore, an image forming apparatus as another invention is provided in common for one or a plurality of colors of an image forming unit for each color forming a full color image, and performs image recording in time series with image data corresponding to each color. There is a feature.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a configuration of an optical scanning device according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a configuration of an optical scanning device according to a first embodiment.
FIG. 3 is an exploded perspective view showing a configuration in which a plurality of unit modules are arranged in the main scanning direction.
FIG. 4 is an exploded perspective view showing a configuration of an optical scanning device according to a second embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a configuration of an optical scanning device according to a second embodiment.
FIG. 6 is a block diagram showing a control circuit of a unit module.
7 is a time chart showing timings related to detection signals and writing in the beam position detection PD shown in FIG. 3; FIG.
FIG. 8 is a time chart showing another timing.
FIG. 9 is a diagram showing a state of a scanning line on a scanned surface of each unit module in consideration of feeding of the scanned surface.
FIG. 10 is a schematic cross-sectional view showing the configuration of a digital copying machine equipped with the optical scanning device of the present invention.
FIG. 11 is a schematic cross-sectional view showing the configuration of a laser printer equipped with the optical scanning device of the present invention.
FIG. 12 is a schematic cross-sectional view showing the configuration of a plain paper facsimile equipped with the optical scanning device of the present invention.
[Explanation of symbols]
100; movable mirror 101; torsion bar 102; first Si substrate;
103; second Si substrate, 104; electrode, 105, 118; fixed electrode,
106; mirror substrate, 107; light source substrate, 108; LD chip,
109; positioning groove, 110; coupling lens, 111; spacer substrate,
112; mirror slope, 113, 406, 407; PD, 114; drive circuit,
115; lead terminal, 116; terminal board, 117; window board, 401; drive circuit,
402; vibration frequency variable means; 403; reference oscillator;
404; Pixel frequency variable means; 405; Magnification measuring means; 408; Correction data;
409; LD drive current variable means; 410; write control circuit; 411; LD;
412; 413; buffer; 414, 415; switching circuit.

Claims (12)

A light-emitting source that modulates according to image data; a movable mirror that is supported by a pair of torsion bars provided on a support base and that can swing about the torsion bar; and a movable mirror that sandwiches the torsion bar. Movable mirror oscillating means that is provided at both ends and periodically generates an attractive force or a repulsive force between the support substrate and the movable mirror by switching a driving voltage to be applied, thereby oscillating the movable mirror; the unit module having, and multiple sequences, the optical scanning of performing main scanning direction is scanned by connecting each of the scanned area in the image recorded by the movable mirror to swing the light beams emitted from the light emitting source A device,
The plurality of unit modules are arranged on the circuit board so that the outside of the scanned area, which is a part of the scanning area of the movable mirror swinging unit included in each unit module, overlaps with the main scanning direction of each unit module. Arranged,
Pixel frequency varying means for varying a pixel frequency for modulating the light emitting source according to a swing amount of the movable mirror;
A plurality of beam detecting means for detecting at least one of a scanning start end or a scanning end of the light beam by detecting the light beam in the overlapping scanning region of the light beam deflected by the movable mirror; An optical scanning device characterized in that the pixel frequency is varied by the pixel frequency varying means based on a scanning time between detection means . The beam detection means is mounted on a circuit board on which the unit modules are arranged, and detects the light beam returned by reflection means provided at both ends outside the image recording area in the unit module. 2. The optical scanning device according to claim 1 , wherein at least one beam position at a scanning start end or a scanning end of the beam is detected . The beam detecting means is provided for each of the plurality of unit modules, is mounted between the plurality of unit modules on the circuit board, and is shared by the beam position detection of the unit modules arranged on both sides of the beam detecting means. 3. The optical scanning device according to claim 2, wherein the optical scanning device is used. The optical scanning device according to any one of claims 1 to 3 wherein the pixel frequency varying means for varying in a plurality of stages pixel frequency modulating said light emitting sources in one scanning. 4. The drive current varying means for varying the drive current supplied to the light emission source in order to vary the amount of light emitted from the light emission source, wherein the drive current is varied according to the pixel frequency . The optical scanning device according to any one of the above. Of the detection signal output timing of the drive voltage to be applied before Symbol movable mirror rocking means from said beam position detecting means as a reference, any one of claims 1 to 3 switches the detection signal used as a reference signal for image writing 2. An optical scanning device according to item 1 . The unit modules are arranged while being shifted by one scanning pitch in the sub-scanning direction between the unit modules adjacent to each other to be scanned, and the timing phases of the drive voltages applied to the movable mirror swinging unit substantially coincide with each other. Item 4. The optical scanning device according to any one of Items 1 to 3 . A pair of buffer means for reciprocally deflecting the light beam from the light emitting source for each unit module by the movable mirror to optically scan the scanned area in both directions and temporarily storing the image data every other scan; 4. The image processing apparatus according to claim 1 , further comprising: inverting the order of image data read from each buffer means and alternately switching the buffer means to be read based on a timing of a drive voltage applied to the movable mirror swinging means . 2. An optical scanning device according to item 1 . An image forming unit that performs monochromatic image formation uses the optical scanning device according to any one of claims 1 to 8 to perform image recording by dividing image data for one line into modules. Image forming apparatus . The image forming apparatus according to claim 9, wherein the image forming apparatus is provided in each image forming unit for each color that forms a full-color image, and performs image recording individually by image data corresponding to each color . The image forming apparatus according to claim 9 , wherein the image forming apparatus is provided in common for an image forming unit for each color forming a full-color image, and performs image recording in time series using image data corresponding to each color. The image forming apparatus according to claim 9 , wherein one or a plurality of colors of an image forming unit for each color forming a full-color image is provided in common, and image recording is performed in time series using image data corresponding to each color.

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