JP2009098390A - Light deflector and optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely adjust a resonance frequency while preventing soiling and distortion of a deflection face. <P>SOLUTION: An optical deflector 21 is provided with a plate member 1 comprising: a deflecting unit 2 having a deflection face 50 for deflecting a laser beam; a driving unit 3 for driving the deflecting unit 2; and torsion springs 6, 7 continuously and integrally connecting the deflecting unit 2 and the driving unit 3. The optical deflector is characterized in that the driving unit 3 has a rod like member 5 and that the rod like member 5 projects from the external size of the driving unit 3 in a plane parallel with the deflection face 50 of the deflection unit 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical deflection apparatus that deflects a laser beam and an optical scanning apparatus that performs optical writing using the optical deflection apparatus.

  Conventionally, various optical scanning devices using an optical deflecting device that performs sinusoidal vibration have been proposed as an optical deflecting device that deflects and scans a photosensitive member with a laser beam modulated based on image information. The optical deflector using Si single crystal is theoretically free from metal fatigue and can be expected to have high durability. Also, it has low vibration due to the small deflection member compared to the conventional deflector using a rotating polygon mirror, and There are merits such as high image quality, small size and low cost.

  Further, the following proposals have been made as methods for adjusting the resonance frequency of the deflecting member.

JP2003-084226 JP2004-219889

  However, Patent Document 1 and Patent Document 2 have the following problems. In Japanese Patent Laid-Open No. 2003-084226, the resonance frequency is adjusted by cleaving the tab portion provided on the deflection surface with a laser. In that case, the substance scattered by the laser irradiation adheres to the deflecting surface, causing contamination of the deflecting surface. Further, since the high-power laser is irradiated in the vicinity of the deflection surface, the deflection surface is distorted due to a partial temperature rise of the deflector. In addition, when the same-shaped movable element is swung at various resonance frequencies, the tab part needs to be enlarged because the tab part has the same specific gravity as the movable element. As a result, in the low frequency band, the area of the mover increases and the air resistance increases, which may cause jitter deterioration and deflection of the deflection surface. On the other hand, the material loss increases because the tab portion to be broken is large in a high frequency band.

  In Japanese Patent Laid-Open No. 2004-219889, the resonance frequency is adjusted by applying an ultraviolet curable resin to the back surface of the deflector. In this case, thermal shrinkage occurs when the ultraviolet curable resin is cured, and there is a possibility that peeling of the resin or distortion of the deflection surface may occur.

  An object of the present invention is to reliably adjust the resonance frequency while preventing contamination and distortion of the deflecting surface.

A typical configuration according to the present invention for achieving the above object is as follows:
A deflector having a deflecting surface for deflecting the laser beam, a driver for driving the deflector, and a torsion spring for connecting the deflector and the driver continuously and integrally are formed. In an optical deflecting device having a plate member,
The driver has a rod-shaped member,
The rod-shaped member protrudes from the outer shape of the driver in a plane parallel to the deflection surface of the deflector.

  Since the present invention has the above-described configuration, the resonance frequency can be reliably adjusted while preventing contamination and distortion of the deflection surface.

[First Embodiment]
A first embodiment of the present invention will be described with reference to the drawings. First, after describing the image forming apparatus, the optical scanning apparatus and the optical deflection apparatus will be described.

(Image forming apparatus 60)
An outline of the configuration and operation of the image forming apparatus will be described. FIG. 1 is a cross-sectional view illustrating the configuration of an image forming apparatus 60 that includes an optical scanning device 40.

  As shown in FIG. 1, in an image forming operation, first, a laser beam 31 modulated based on image information is emitted from an optical scanning device 40 and scanned on a photosensitive drum 26 as a scanning target. As a result, a latent image is formed on the photosensitive drum 26. This latent image is formed on the surface of the photosensitive drum 26 that is uniformly charged by the primary charger 61.

  The latent image is visualized by the developer (toner) of the developing device 62. Thereafter, the toner images formed on the surface of the photosensitive drum 26 are sequentially transferred onto the transfer material 64 conveyed to the transfer nip portion by the transfer roller 63, and a toner image is formed on the transfer material 64. The transfer material 64 on which the toner image is formed is heat-fixed by a fixing device 65 and then output to the outside of the apparatus by a discharge roller 66 or the like.

(Optical scanning device 40)
The optical scanning device 40 will be described with reference to FIGS.

  FIG. 2 is a perspective view of the optical scanning device 40. The collimated light extracted from the light source device 24 passes through the cylindrical lens 23, is then deflected and scanned by the light deflecting device 21, and sequentially passes through the fθ lens 22 and the reflection mirror 25, and finally reaches the photosensitive drum 26. Reach the surface.

  Each stroke will be described in detail based on the order in which the laser beam passes. The collimated light is shaped by the fθ lens 22 so as to be scanned as an optimally narrowed beam within the width of the photosensitive drum 26.

  A part of the scanning beam is deflected by the BD mirror 27, detected by the BD sensor 28, and the writing signal for each scanning time is synchronized with the output signal from the BD sensor 28 as a reference. Thereby, the beam writing position shift is prevented. Here, BD is an abbreviation for beam detect.

  In order to prevent a beam position shift in the sub-scanning direction on the photosensitive drum 26 due to a tilting error of the deflecting surface of the optical deflecting device 21, the cylindrical lens 23 is used to cause the beam extracted from the light source device 24 on the deflecting surface. A line image is formed by compression in the sub-scanning direction. At the same time, the deflection surface and the surface of the photosensitive drum 26 have a conjugate relationship in the sub-scanning direction. The sub-scanning direction is a direction perpendicular to the optical axis and the beam scanning direction, and is a transfer material feeding direction.

  The optical element group such as the optical deflecting device 21, the fθ lens 22, and the reflecting mirror 25 described above is contained in an optical box (housing) 20 made of resin. The upper opening of the optical box 20 is closed by a lid member or the like (not shown).

(Light deflection device 21)
The light deflection apparatus 21 will be described with reference to FIGS.

  3A and 3B are perspective views showing the optical deflecting device 21 provided in the optical scanning device 40, where FIG. 3A is an arrow view in the B direction in FIG. 2, and FIG. 3B is an arrow view in the C direction in FIG. FIG. The plate member 1 is integrally fixed to the holder 8. On the fixed surface side of the plate member 1, an actuator unit 9 for driving the deflector 2 and the driver 3 and a circuit board 10 for supplying electric power to the actuator unit 9 are arranged.

  FIG. 4 is an exploded perspective view of the light deflector 21. The actuator portion 9 is composed of an iron core (core) 14 and a bobbin 13 that are integrally formed, and a winding 12 that circulates around the core. The actuator portion 9 is inserted into the hole portion 15 of the holder 8 in the direction of arrow D, and is positioned and fixed.

  A circuit board 10 for supplying power to the actuator unit 9 is fixed to the holder 8 with screws 11. Thus, the control circuit (not shown) provided in the image forming apparatus is electrically connected. The plate member 1 is fixed integrally to the holder 8 after the actuator portion 9 is fixed to the holder 8.

(Plate member 1)
The plate member 1 will be described with reference to FIG.

  5A and 5B are perspective views of the plate member 1 according to the first embodiment, wherein FIG. 5A is an arrow view in the B direction in FIG. 2, and FIG. 5B is an arrow view in the C direction in FIG. The plate member 1 is made by etching a Si single crystal wafer. The plate member 1 includes a deflector 2 and a driver 3.

  The deflector 2 and the driver 3 are supported so as to be connected continuously and integrally by torsion springs 6 and 7. A rod-like permanent magnet 4 (magnet) is fixed to the back surface 51 of the driver element 3 by means such as adhesion. The driver 3 is driven by forming a magnetic circuit in the gap between the winding 12 of the actuator unit 9 and the permanent magnet 4 and applying a predetermined current to the winding 12. Further, a rod-like member 5 made of, for example, copper is fixed to the surface side of the driver element 3 by means such as adhesion. Here, the surface of the driver 3 is a surface that lies in a plane parallel to the deflection surface 50 of the deflector 2 in the initial stationary state (state before being driven) of the driver 3. Since the rod-shaped member 5 is longer than the length of the driver element 3 in the Y direction in the figure, it is in a state of protruding from the outer shape of the driver element 3. Further, the specific gravity of the driver 3 is larger than the specific gravity of the plate member 1. Since the permanent magnet 4 (magnet) and the rod-shaped member 5 are fixed to the back surface 51 side of the driver element 3 and the opposite surface surface, respectively, there is no balance in the X direction in the figure, and the deflector 2 Warping and falling can be reduced. Aluminum or the like is vapor-deposited on the surface of the deflector 2 to form a deflecting surface 50 suitable for deflecting the laser beam. The laser beam is deflected as indicated by an arrow A on the deflection surface 50 of the deflector 2.

(Driving of the optical deflection device 21)
The optical deflecting device 21 is driven by overlapping a plurality of resonance frequencies of the plate member 1. This will be described with reference to FIG. FIG. 6 is a graph showing the time change of the amplitude of the optical deflecting device 21 of the plate member 1.

The amplitude angle θ of the deflector 2 used for the deflection of the laser beam is A ₁ : amplitude at the fundamental frequency (fundamental wave), A ₂ : amplitude at twice the fundamental frequency (harmonic wave), A ₃ : static angle Error (angle error of the posture when the deflector is not vibrating). where ω is the fundamental frequency, φ is the phase difference between the fundamental wave and the harmonic wave, and t is the time.
θ (t) = A ₁ sin (ωt) + A ₂ sin (2ωt + φ) + A ₃
It is represented by

  Here, by appropriately setting each parameter, it is possible to approximate θ (t) ≈kt + α, (k, α: constant) in a specific range within one cycle.

  In this range, the deflector 2 vibrates at a substantially equal angular velocity, and the laser beam incident on the deflector 2 is deflected at a substantially equal angular velocity.

(Adjustment method of driver 3)
FIG. 7 is a diagram showing how the center of gravity position of the driver 3 is adjusted and the resonance frequency is adjusted.

  In the present embodiment, adjustment is performed by cleaving the rod-like member 5 of the driver element 3. A laser light source 30 is used to cleave the rod-shaped member 5. The laser light source 30 irradiates, for example, a picosecond laser having a wavelength of 532 μm. When the rod-shaped member 5 is cleaved, as shown in FIG. 7, the laser light source 30 irradiates the rod-shaped member 5 with the laser beam 31 from the deflecting surface 50 side of the deflector 2 and rapidly raises the temperature. Cleave.

  First, the center-of-gravity position shift is adjusted. When the permanent magnet 4 (magnet) or the rod-shaped member 5 is fixed to the drive element 3, even when the center of gravity of the drive element 3 is displaced, the driver element 3 can be changed by changing the left and right breaking amounts of the rod-shaped member 5. The position of the center of gravity and the position of the swing axis can be made to be substantially coaxial.

For example, one end of the driver 3 is enlarged with a microscope or the like, and the protrusion amount Δd ₁ of the rod-like member 5 is confirmed by image recognition or the like. Thereafter, the other end is similarly enlarged to check the protrusion amount Δd ₂ . The difference is divided by a picosecond laser or the like so that Δd ₁ = Δd ₂ . Thereby, the center-of-gravity position shift resulting from the rod-shaped member 5 can be adjusted.

  If the entire plate member 1 is scanned and image recognition is performed, the center of gravity including the symmetry of the plate member 1 with respect to the swing axis can be estimated. At this time, the center-of-gravity position deviation can be adjusted by converting the center-of-gravity position deviation as the protruding amount of the rod-like member 5 and cleaving the predetermined amount. In this way, the displacement of the center of gravity of the swing shaft of the driver 3 is suppressed.

Next, the resonance frequency is adjusted. The change Δf of the resonance frequency associated with the cleaving is expressed as _follows : f _a : resonance frequency before adjustment, f _b : resonance frequency after adjustment,
Δf = f _b −f _a ,
Is given by

Here, the resonance frequency f is generally f = 1 / 2π (k / I) ^0.5 where f: resonance frequency, k: spring constant determined by a torsion spring, and I: moment of inertia.
Is given by

  From the above formula, the moment of inertia decreases by the ratio of the cleaved rod-like member 5.

For example, the moment of inertia I a ^{2.53 × 10 -10 g · cm 2} , when the spring constant k and 0.04 Nm / rad, the resonance frequency _{f a} before adjustment is about 2 kHz. Here assuming that fractured the rod-like member 5 so as to reduce the moment of inertia of 10%, the resonance frequency f _b after adjustment is about 2.1 kHz. That is, the resonance frequency has changed by about 100 Hz. In this way, the resonance frequency is adjusted quantitatively. Further, when the specific gravity of the rod-shaped member 5 is much larger than that of Si, the resonance frequency and the center of gravity can be finely adjusted only by slightly cutting the plate member 1.

(Special effects of this embodiment)
Effects unique to the present embodiment are as follows.

  Since the rod-like member 5 fixed to the driver element 3 is cut and the resonance frequency is adjusted, the size of the driver element 3 can be minimized. For this reason, the air resistance received by the driver 3 can be reduced, and it can be expected that the deterioration of jitter (fluctuation in delay time) is suppressed and the image quality is improved.

  Even when compared with Patent Document 1, since the specific gravity of the rod-shaped member 5 is larger than Si and the portion protruding from the driver element 3 is cleaved, the same effect can be obtained even if the cleaving amount is very small. Since the cleaving amount of the rod-shaped member 5 is very small, the material loss of the rod-shaped member 5 is small, and the balance in the X direction in FIG.

  Since the rod-shaped member 5 is fixed to the drive element 3, the scattered material does not adhere to the deflector 2 when the rod-shaped member 5 is cleaved by laser irradiation, and the temperature of the deflector does not increase. Therefore, contamination and distortion of the deflection surface can be prevented. For this reason, on the photosensitive drum 26, it is possible to improve the printed image by reducing the light amount decrease, the spot collapse, and the like.

  Further, similarly to the resonance frequency adjustment, it is possible to adjust the displacement of the center of gravity without distorting or contaminating the deflector 2. By adjusting the displacement of the center of gravity, it is possible to reduce dynamic tilting of the swing shaft, suppress spot rotation on the photosensitive drum 26, collapse, and the like, and improve print image quality.

  In addition, by changing the length, specific gravity, and cleaving amount of the rod-like member 5 fixed to the driver 3, fine adjustment and coarse adjustment to various resonance frequencies can be performed. For this reason, even if the plate member 1 and the driver element 3 have the same shape, a wide resonance frequency band adjustment region can be provided. Specifically, even if the shape of the plate member 1 or the driver element 3 is not changed, a desired resonance frequency can be obtained by changing the cleaving amount of the rod-like member 5 or changing the length of the rod-like member 5. An optical deflecting device can be provided.

  As described above, in the present embodiment, the resonance frequency of the driver element 3 is adjusted by cleaving the rod-shaped member 5. For this reason, dirt and distortion do not occur on the deflecting surface which is the surface of the deflector 2, and the size of the driver 3 can be reduced to the minimum necessary. As a result, the air resistance received by the driver 3 is reduced, the operations of the driver 3 and the deflector 2 can be controlled reliably, and high image quality and suppression of jitter deterioration can be expected.

  Further, the specific gravity of the bar-shaped member 5 to be cleaved is larger than the specific gravity of the driver element 3. For this reason, it is possible to perform so-called fine adjustment in which the resonance frequency is adjusted to a desired resonance frequency with a small amount of cleaving, and at the same time, so-called rough adjustment in which the resonance frequency is greatly shifted with a small amount of cleaving.

  Thereby, the versatility corresponding to various resonance frequencies and the effect of suppressing material loss can also be expected. In addition, the center-of-gravity position shift of the driver element 3 can be suppressed by changing the left and right breaking amounts of the rod-shaped member.

  In the present embodiment, the permanent magnet (magnet) 4 is fixed to the back surface 51 side of the driver element 3 and the rod-shaped member 5 is fixed to the front surface side opposite to the back surface 51. However, the permanent magnet 4 and the rod-shaped member 5 are fixed to the driver element 3. Even if it is fixed to both sides, the same effect as described above can be obtained. The permanent magnet 4 is not limited to a bar shape, and may be a flat type or a button type.

  Even if the plate member 1, the deflector 2, and the driver 3 are separate, the same effect as described above can be obtained. There may be one or more drivers and deflectors provided in the plate member 1.

  In addition, even if the laser beam for cleaving the rod-like member 5 is irradiated from the side where the permanent magnet 4 (magnet) of the driver 3 is fixed, the same effect as described above can be obtained. Even if the rod-like member 5 is fixed to the surface opposite to the deflection surface of the deflector 2, the same effect as described above can be obtained.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a perspective view of the plate member 1 according to the second embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 8, a permanent magnet as a rod-shaped member having a specific surface longer than the length of the driver 3 in the Y direction in the figure and having a larger specific gravity than the plate member 1 is provided on the back surface 51 of the driver 3 and the surface opposite thereto. 4 (magnet) is fixed. Here, a magnetic circuit is formed in the gap between the permanent magnet 4 (magnet) and the winding of the actuator portion, and the driver 3 is driven by applying a predetermined current to the winding. As described above, the permanent magnet 4 can be cleaved by the laser light source 30, and the resonance frequency of the driver 3 can be adjusted by this cleaving.

  Effects unique to the present embodiment are as follows.

  Since only the permanent magnet 4 (magnet) needs to be mounted on the driver 3, the process tact can be shortened, and the cost can be reduced. Further, if the two permanent magnets 4 (magnets) are cleaved at the same time, the balance of the driver 3 is less likely to be unbalanced. Even when the center of gravity position deviation occurs when the permanent magnet 4 (magnet) is fixed to the driver 3, the center of gravity position deviation can be adjusted by splitting the permanent magnet 4 (magnet) one by one. . As a result, it is possible to reduce the dynamic collapse at the time of swinging, suppress the spot rotation or collapse on the photosensitive drum 26, and improve the print image quality.

  In the present embodiment, the permanent magnet 4 (magnet) longer than the length in the Y direction in the figure is fixed to the back surface 51 of the driver element 3 and the opposite surface, but the same effect as described above can be obtained even on one side. It is done.

FIG. 3 is a cross-sectional view illustrating a configuration of an image forming apparatus 60 including an optical scanning device 40. The perspective view of the optical scanning device 40. FIG. FIG. 3 is a perspective view showing an optical deflecting device 21 provided in an optical scanning device 40. FIG. 3 is an exploded perspective view of the light deflection apparatus 21. The perspective view of the plate member 1 which concerns on 1st Embodiment. The graph which shows the time change of the amplitude of the optical deflection | deviation apparatus 21 of the plate member 1. FIG. The figure which showed the mode of the gravity center position shift adjustment of the driver element 3, and the adjustment of the resonant frequency. The perspective view of the plate member 1 which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Plate member, 2 ... Deflector, 3 ... Driver, 5 ... Bar-shaped member, 6 ... Torsion spring, 7 ... Torsion spring, 21 ... Optical deflection device, 31 ... Laser beam, 40 ... Optical scanning device

Claims (4)

A deflector having a deflecting surface for deflecting the laser beam, a driver for driving the deflector, and a torsion spring for connecting the deflector and the driver continuously and integrally are formed. In an optical deflecting device having a plate member,
The driver has a rod-shaped member,
The optical deflecting device according to claim 1, wherein the rod-shaped member protrudes from an outer shape of the driver in a plane parallel to a deflection surface of the deflector.   The optical deflection apparatus according to claim 1, wherein a specific gravity of the rod-shaped member is larger than a specific gravity of the driver element.   The light deflection apparatus according to claim 1, wherein the rod-shaped member is configured by a permanent magnet.   An optical scanning device that deflects a laser beam using the optical deflection device according to claim 1.

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