JP4353399B2 - Vibrating mirror - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning device having a micro optical system to which micromachining technology is applied, for example, an optical scanning device used in a writing system such as a digital copying machine and a laser printer, or a reading device such as a barcode reader. This is a suitable technique.
[0002]
[Prior art]
In a conventional oscillating mirror, a mirror substrate supported by two beams provided on the same straight line is twisted by electrostatic attraction between an electrode provided at a position facing the mirror substrate. A reciprocating vibration is used as a rotating shaft (see Non-Patent Document 1, for example). This oscillating mirror formed by micromachining technology has a simple structure and can be formed in a batch in the semiconductor process compared to a conventional optical scanning device using a polygon mirror rotating using a motor. In addition, the manufacturing cost is low, and since there is a single anti-slope, there is no variation in accuracy due to multiple surfaces, and further, since it is a reciprocating scan, it is possible to expect effects such as high speed.
[0003]
As such an electrostatically driven vibrating mirror, the beam is made into an S-shape to reduce the rigidity so that a large deflection angle can be obtained with a small driving force (for example, see Patent Document 1). A mirror substrate, a substrate thinner than the frame substrate (for example, refer to Patent Document 2), a fixed electrode disposed at a position that does not overlap the vibration direction of the mirror part (for example, refer to Patent Document 3, Non-Patent Document 2), or In some cases, the drive voltage is lowered without changing the deflection angle of the mirror by installing the counter electrode so as to be inclined from the center position of the deflection of the mirror (for example, see Non-Patent Document 3). The above is an example using electrostatic attraction as a driving method, but other driving force using electromagnetic force or using a piezoelectric element has been proposed.
[0004]
In general, these oscillating mirrors are driven at a resonance frequency of a structure determined by the material, shape, and dimensions of the mirror substrate and the torsion beam so that a large deflection angle can be obtained with low energy.
[0005]
[Non-Patent Document 1]
IBM J.M. Res. Develop Vol. 24 (1980)
[Non-Patent Document 2]
The 13th Annual International Workshop on MEMS2000 (2000) p. 473-478
[Non-Patent Document 3]
The 13th Annual International Workshop on MEMS2000 (2000) p. 645-650
[Patent Document 1]
Japanese Patent No. 2924200
[Patent Document 2]
Japanese Patent Laid-Open No. 7-92409
[Patent Document 3]
Japanese Patent No. 30111144
[0006]
[Problems to be solved by the invention]
The resonance frequency f of the oscillating mirror can be expressed by the following equation where k is the torsional elastic coefficient of the beam and I is the moment of inertia of the mirror substrate.
[0007]
f = 1 / 2π√ (k / I)
The torsional elastic coefficient k can be expressed by the following equation where the beam width is c, the beam height is t, and the beam length is L.
Where β is the cross-sectional shape factor, E is the Young's modulus, and ν is the Poisson's ratio.
[0008]
k = βtc³E / L (1 + ν)
The moment of inertia I of the mirror substrate can be expressed by the following equation when the mirror weight is M, the density is ρ, and the width, length, and thickness of the mirror substrate are b, a, and t, respectively.
[0009]
I = M (a²+ B²) / 12
= Ρtab (a²+ B²) / 12
The vibration mirrors supported by torsion beams generally set the resonance frequency of the structure determined by the material, shape and dimensions of the mirror substrate and torsion beam as the drive frequency so that a large deflection angle can be obtained with low energy. . As can be seen from these relational expressions, the dimensions of the torsion beam (c, t, L) and the mirror substrate (a, b, t) greatly affect the resonance frequency of the vibrating mirror.
[0010]
However, since the dimensions of the torsion beam and the mirror substrate are determined by the mask accuracy, processing method, and processing accuracy in the manufacturing process, a dimensional error always occurs in the completed vibrating mirror. Therefore, strictly speaking, the resonance frequency is different for each device. There is no problem when the operating frequency is individually set for using the device, but the drive is usually set as a unified frequency specification. Therefore, the drive frequency and the resonance frequency do not exactly match, and the deviation from the resonance point appears as a decrease in the deflection angle. In addition, when multiple vibrating mirrors are used at the same time in the same device, the deviation of the resonance frequency of each vibrating mirror with respect to a common drive frequency is a variation in the swing angle of each vibrating mirror. It becomes impossible to unify.
[0011]
An object of the present invention is to provide a vibrating mirror capable of solving such a problem of variation in resonance frequency and individually adjusting the resonance frequency with high accuracy.
[0012]
[Means for Solving the Problems]
  According to another aspect of the present invention, the vibrating mirror includes: a mirror substrate that reflects the light beam; two beams that are provided on the same straight line that supports the mirror substrate; and a mirror driving unit that generates a rotational force on the mirror substrate. A mirror substrate, wherein the mirror substrate reciprocally vibrates at a predetermined scanning frequency using the beam as a torsional rotation axis.Has a concave portion formed on the surface opposite to the surface that reflects the light beam, and attaches a mass piece at a position that is symmetric with respect to the corner of the concave portion and with respect to the rotation axis and with respect to the center of gravity of the mirror substrate,The resonance frequency is variable.
[0013]
According to another aspect of the present invention, the resonance frequency of the mirror substrate is set to be higher than the scanning frequency in advance, and the resonance frequency of the mirror substrate is matched to the scanning frequency.
[0014]
According to a third aspect of the present invention, the mass piece for adjusting the resonance frequency of vibration is added to at least two portions of the mirror substrate that are symmetric with respect to the rotation axis.
[0015]
According to another aspect of the present invention, a mass piece for adjusting the resonance frequency is added to the end of the mirror substrate farthest from the rotation axis.
[0016]
According to another aspect of the present invention, the mass piece is attached to a straight line that passes through the center of gravity of the mirror substrate and is orthogonal to the rotation axis.
[0017]
According to a sixth aspect of the present invention, the vibration mirror according to the first aspect is provided with a recess, and a mass piece is attached to at least a part of the recess.
[0018]
According to a seventh aspect of the present invention, in the vibration mirror according to the sixth aspect, the concave portion is provided on a surface opposite to the mirror surface of the mirror substrate.
[0019]
According to an eighth aspect of the present invention, in the vibration mirror according to the sixth aspect, the concave portion has a surface parallel to the rotation axis and perpendicular to the mirror substrate surface and a surface parallel to the mirror substrate surface. Mass pieces are attached to the intersecting sides.
[0020]
According to a ninth aspect of the present invention, in the vibration mirror according to the first to fifth aspects, the mass piece is attached to the mirror substrate in a solid state.
[0021]
According to a tenth aspect of the present invention, in the vibration mirror according to the first to fifth aspects, the mass piece is attached to the mirror substrate in a film shape.
[0022]
An oscillating mirror according to an eleventh aspect includes a sealing means having a light beam transmitting portion deflected by the mirror substrate in the oscillating mirror according to the first aspect and a terminal connected to the mirror driving means. The mirror substrate is sealed in a reduced pressure state.
[0023]
In a vibrating mirror manufacturing method according to a twelfth aspect, the mass piece is attached to the mirror substrate by discharging droplets from a nozzle.
[0024]
The optical scanning device according to claim 13 is provided with a plurality of vibrating mirrors that have a mirror substrate that reflects a light beam and a beam that supports the mirror substrate, and that reciprocally vibrates the mirror substrate using the beam as a torsional rotation axis. In this optical scanning device, a mass piece is attached to at least one location of the mirror substrate for at least one oscillating mirror among the plurality of oscillating mirrors to make the resonance frequency uniform, and reciprocally vibrate at a common scanning frequency.
[0025]
According to a fourteenth aspect of the present invention, in the optical scanning device according to the thirteenth aspect, among the plurality of oscillating mirrors, the resonance frequencies of the other oscillating mirrors are aligned so as to match the oscillating mirror having the minimum resonance frequency. Yes.
[0026]
In the optical writing device according to claim 15, the vibrating mirror according to any one of claims 1 to 9, a light source driving unit that modulates the light source in accordance with an amplitude of the vibrating mirror, and the mirror surface And means for forming an image on the surface to be scanned.
[0027]
17. The image forming apparatus according to claim 16, wherein the vibrating mirror according to any one of claims 1 to 9 and means for causing a light beam modulated by a recording signal to enter a mirror surface of a mirror substrate of the vibrating mirror. And means for forming an image of the light beam reflected by the mirror surface, an image carrier on which an electrostatic latent image is formed according to the recording signal, and developing the electrostatic image with toner Developing means and transfer means for transferring the visualized toner image onto the recording paper.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be specifically described below with reference to the drawings.
[0029]
Example 1
FIG. 1 shows a configuration of a vibrating mirror according to a first embodiment of the present invention. FIG. 1A is a plan view of a vibration mirror, and FIG. 1B is a cross-sectional view of the center of the vibration mirror perpendicular to the torsion beam.
[0030]
The mirror substrate 101, the two torsion beams 102 and 103, and the upper frame 104 that fixes the torsion beam from the outside are capable of high-precision fine processing and have an appropriate rigidity when used as an elastic body, and The single-crystal silicon substrate having a low resistance is integrally formed so that it can be used as an electrode as it is.
[0031]
The mirror substrate 101 is supported at the center of one side by two torsion beams 102 and 103 provided on the same axis, and a metal thin film having a sufficient reflectivity with respect to the light used on the mirror substrate 101. 130 is formed. The dimensions of each part of the mirror substrate 101 and the two torsion beams 102 and 103 are designed so as to obtain a required resonance frequency.
[0032]
The upper frame 104 is bonded via an insulating film 105 to the lower frame 106 from which the region where the mirror substrate vibrates is removed. The thickness of the lower frame 106 is set in consideration of the fact that the vibration range of the mirror substrate does not go out of the frame and does not hinder the handling of the vibrating mirror.
[0033]
The upper frame 104, the torsion beams 102 and 103, and the mirror substrate 101 are integrally formed by through-etching the same substrate by high-density plasma etching using SF6 etching gas with an oxide film as an etching mask. At this time, movable electrodes 107 and 108 for driving by electrostatic attraction were processed and formed in a comb-teeth shape on the side surface of the mirror substrate where the torsion beam is not coupled. The lower frame 106 is formed by removing the mirror substrate vibration region by anisotropic etching using a KOH solution with the SiN film as an etching mask. The upper frame 104, the torsion beams 102 and 103, the upper substrate for forming the mirror substrate 101, and the lower substrate for forming the lower frame 106 are planarized and cleaned, and then directly bonded via the thermal oxide film 105. After that, the upper substrate is ground and polished to match the thickness of the mirror substrate (the thickness of the torsion beam).
[0034]
The comb-shaped side surfaces 107 and 108 that are not supported by the torsion beam of the mirror substrate are formed on the upper frame 104 of the same portion through a minute gap, and the comb-shaped driving fixed electrodes 109 and 110 are also provided. It is facing in the form of meshing with. A part of the upper frame 104 in which the fixed electrodes 109 and 110 are formed is insulated and separated from the upper frame region to which the torsion beam is coupled by the slits 111, 112, 113 and 114.
[0035]
An oxide film is formed on the surface of the upper frame 104, and the oxide film is removed by mask etching in a part of the upper frame where the fixed electrodes 109 and 110 are formed and insulated and the low resistance silicon substrate is exposed. In this portion, electrode pads 115 and 116 made of an Al thin film formed with a mask by sputtering are formed. Similarly, the oxide film is also removed by mask etching from a part of the upper frame to which the torsion beam is connected, and the low resistance silicon substrate is exposed. This part is also formed by the Al thin film formed by masking by sputtering. An electrode pad 117 is formed. Here, although an Al thin film is formed by sputtering as an electrode pad, other materials such as Au can be selected as long as sufficient adhesion and conduction with a silicon substrate can be obtained. Also, the film may be formed by other methods such as a vacuum deposition method and an ion plating method.
[0036]
In addition, although the structure at the time of using electrostatic attraction was demonstrated here as a drive method of a vibration mirror, it can also be set as the structure at the time of using an electromagnetic force or a piezoelectric element.
[0037]
On the surface opposite to the surface on which the metal thin film 130 is formed as the reflecting surface of the oscillating mirror, ultraviolet curable resins 131 and 132 as two mass pieces are symmetrical with respect to the rotation axis, and a line connecting the two Is attached at a position that passes through the center of gravity of the mirror. By arranging it symmetrically with respect to the rotation axis, the reproducibility of the operation during reciprocating vibration is ensured, and by arranging it symmetrically at the center of gravity of the mirror, the uniformity of the operation in the beam direction is ensured and unnecessary Vibration generation is suppressed.
[0038]
Next, the operation of the vibrating mirror according to the first embodiment of the present invention will be described. In order to ground both ends of the mirror substrate 101 supported by the two torsion beams 102 and 103 as movable electrodes, the electrode pads 117 formed on the upper frame are grounded. At this time, since the upper frame, the torsion beam, and the mirror substrate are integrally formed of a low-resistance silicon substrate, they have the same potential. When voltage is simultaneously applied to the fixed electrodes 109 and 110 from the electrode pads 115 and 116 formed on the upper frame, an electrostatic attractive force is generated between the fixed electrodes 109 and 110 and the movable electrodes 107 and 108 facing each other through a minute gap. When there is a slight initial position shift between the two electrodes, a moment of rotation acts on the movable electrode, that is, the mirror substrate so that the two become the shortest distance. After starting in this way, the deflection angle can be increased by resonance vibration. Although the case where electrostatic attraction is used as the driving force for resonantly vibrating the mirror substrate is described here, an electromagnetic force or a piezoelectric element may be used for driving.
[0039]
As described above, the resonance frequency at this time is determined by the moment of inertia of the mirror substrate and the rigidity of the torsion beam, that is, the respective material, structure, and dimensions. The dimensions at the time of processing are adjusted by adjusting the dimensions of the photomask in consideration of exposure in the photolithography process, excess of development time, or overetching at the time of etching.
[0040]
However, the target resonance frequency may not be obtained depending on the processing accuracy. At this time, the resonance frequency of the vibrating mirror is set in advance higher than the scanning frequency in actual use. For example, the torsion beam is set to be slightly thicker than the design value, and the mirror substrate is set to be slightly lighter than the design value. The frequency difference at this time is set so as to be suppressed within the range of adjustment by a mass piece to be attached later.
[0041]
As the mass pieces 131 and 132, ultraviolet curable resin was used. Here, the liquid droplets were ejected from the nozzles to be adhered onto the vibrating mirror, and the liquid droplets were ejected by vibrating the wall of the liquid chamber with a piezoelectric element. The resin before curing has a sufficiently low viscosity resistance and can be easily discharged, and the displacement amount of the liquid chamber wall and the droplet discharge amount, the attached droplet amount and the resonance frequency change amount are correlated. Note that, according to one displacement, the discharge amount is several picoliters. The droplets were attached to the surface of the vibrating mirror according to the required amount of change in the resonance frequency, and at the same time, irradiated with ultraviolet rays, cured as a resin, and formed into mass pieces.
[0042]
In addition, a sealing means (a decompression container) having a light beam transmission portion deflected by the mirror substrate and a terminal connected to the mirror driving means is provided, and at least the mirror substrate is sealed in a decompressed state.
[0043]
(Example 2)
FIG. 2 shows a configuration of a vibrating mirror according to the second embodiment of the present invention. (A) is a top view of a vibration mirror, (b) is sectional drawing of the direction orthogonal to the torsion beam of a vibration mirror.
[0044]
The configurations of the two torsion beams excluding the mirror substrate 200 and the upper frame that fixes the torsion beam from the outside are the same as those in the first embodiment, and thus the description thereof is omitted. Here, the features of the present invention are described. Only a mirror substrate having a configuration for adjusting the resonance frequency will be described. Here, a configuration in which electrostatic attraction is used as the driving method of the vibrating mirror is shown, but an electromagnetic force or a piezoelectric element can also be used as the driving means.
[0045]
On the surface opposite to the surface on which the metal thin film 201 is formed as the reflection surface of the vibration mirror, the metal thin films 202 and 203 are attached to the surface symmetrical to the rotation axis as two mass pieces. By arranging them symmetrically with respect to the rotation axis, the reproducibility of the operation during reciprocating vibration is ensured. Here, Cr was used as the metal thin film, and a mask provided with a desired opening in a stainless steel sheet was placed on the mirror substrate, and the film was formed by sputtering through the opening. As the metal thin film, other metal such as Cr, Ni, Al, Ti, etc., which has sufficient adhesion and is easy to form and stable, may be used. It is necessary to save.
[0046]
When the metal thin film is formed as described above for attaching the mass piece, the increase in the mass of the mirror substrate can be controlled with high accuracy, and therefore the resonance frequency can be finely adjusted. On the other hand, since the mass is increased in the thin film, it is not suitable for a significant resonance frequency adjustment. Sputtering was used here as the method for forming the thin film, but such a stencil mask can be used if the method of supplying atoms or ions from a solid source has directionality, such as vacuum deposition or ion plating. Easy film formation is possible. Further, the mass increase rate during film formation can be changed by setting the opening area of the stencil mask.
[0047]
(Example 3)
FIG. 3 shows a configuration of a vibrating mirror according to the third embodiment of the present invention. (A) is a top view of a vibration mirror, (b) is sectional drawing of the center of an orthogonal direction with the torsion beam of a vibration mirror.
[0048]
Since the configuration of the two torsion beams excluding the mirror substrate 400 and the upper frame that fixes the torsion beam from the outside is the same as that of the first embodiment, a description thereof will be omitted. Only the mirror substrate 400 having a configuration for adjusting the resonance frequency will be described. Here, a configuration in which electrostatic attraction is used as the driving method of the vibrating mirror is shown, but an electromagnetic force or a piezoelectric element can also be used as the driving means.
[0049]
On the surface opposite to the surface on which the metal thin film 401 is formed as the reflection surface of the vibration mirror, a plurality of recesses 402 and 403 are formed in the vicinity of the comb-tooth electrodes at both ends of the mirror substrate in the direction parallel to the torsion beam. . This recess can be formed simultaneously by reducing the thickness of the etching mask when the comb electrode is formed by through etching. Hereinafter, the formation method will be described with reference to FIG.
[0050]
In the silicon substrate 500 on which the oxide films 501 and 502 are formed on both sides, the gap region of the oxide film 501 on the surface side is patterned by dry etching with a resist mask (a). Next, patterning is performed by dry etching with the same resist mask while leaving a part of the oxide film 501 in the region where the recess is to be formed (b). Next, silicon in the gap region is dug by dry etching. At this time, the thickness of the oxide film is set in advance so that the oxide film in the region where the recess is formed does not disappear (c). Next, the oxide film in the recess is removed by dry etching (d). Next, the silicon in the gap region and the recess is simultaneously dug by dry etching, and the recess is simultaneously formed by stopping the etching when the silicon substrate in the gap region where the etching depth precedes penetrates (e).
[0051]
Part of the plurality of recesses formed on the mirror substrate is filled with ultraviolet curable resins 404 and 405. The filling is symmetric with respect to the rotation axis and is also symmetric with respect to the center of gravity of the mirror.
[0052]
By arranging it symmetrically with respect to the rotation axis, the reproducibility of the operation during reciprocating vibration is ensured, and by arranging it symmetrically at the center of gravity of the mirror, the uniformity of the operation in the beam direction is ensured and unnecessary Vibration generation is suppressed. As described above, since the region to which the UV curable resin is attached is concave, the region to which mass is applied is defined, so that the mass in the mirror substrate surface can be easily balanced and stable resonance vibration can be obtained. be able to.
[0053]
(Example 4)
FIG. 5 shows a configuration of a vibrating mirror according to Embodiment 4 of the present invention. (A) is a top view of a vibration mirror, (b) is a cross-sectional view of the vibration mirror and a torsion beam and a perpendicular direction.
[0054]
Since the configuration of the two torsion beams excluding the mirror substrate 600 and the upper frame that fixes the torsion beam from the outside is the same as that of the first embodiment, a description thereof will be omitted. Here, the feature of the present invention is described. Only the mirror substrate 600 having a configuration for adjusting the resonance frequency will be described. Here, a configuration in which electrostatic attraction is used as the driving method of the vibrating mirror is shown, but an electromagnetic force or a piezoelectric element can also be used as the driving means.
[0055]
On the surface opposite to the surface on which the metal thin film 601 as the reflection surface of the vibration mirror is formed, a plurality of recesses 602 and 603 are formed in the vicinity of the comb electrodes on both ends of the mirror substrate in the direction parallel to the torsion beam. . This recess can be formed simultaneously by reducing the thickness of the etching mask when the comb electrode is formed by through etching. The formation method has been described with reference to FIG. 4 in Example 3 of the present invention.
[0056]
Some of the plurality of recesses formed on the mirror substrate are filled with UV curable resins 404 and 405 at the corners 600. The filling is symmetric with respect to the rotation axis and is also symmetric with respect to the center of gravity of the mirror.
[0057]
By arranging it symmetrically with respect to the rotation axis, the reproducibility of the operation during reciprocating vibration is ensured, and by arranging it symmetrically at the center of gravity of the mirror, the uniformity of the operation in the beam direction is ensured and unnecessary Vibration generation is suppressed. In this way, by adhering the ultraviolet curable resin to the corners of the concave region, it is possible to increase the bonding area, and high-strength bonding without peeling or the like is possible.
[0058]
(Example 5)
FIG. 6 shows a configuration of a vibrating mirror according to the fifth embodiment of the present invention. (A) is a top view of a vibration mirror, (b) is a sectional view of the torsion beam of the vibration mirror and the center in the orthogonal direction.
[0059]
The configurations of the two torsion beams excluding the mirror substrate 700 and the upper frame that fixes the torsion beam from the outside are the same as those in the first embodiment, and thus the description thereof is omitted. Here, the features of the present invention are described. Only a mirror substrate having a configuration for adjusting the resonance frequency will be described. Here, a configuration in which electrostatic attraction is used as the driving method of the vibrating mirror is shown, but an electromagnetic force or a piezoelectric element can also be used as the driving means.
[0060]
On the surface opposite to the surface on which the metal thin film 701 is formed as the reflecting surface of the vibrating mirror, the metal thin films 702 and 703 are attached as two mass pieces at a position where the line connecting the two passes through the center of gravity of the mirror. Yes. By arranging symmetrically about the center of gravity of the mirror, the uniformity of the motion in the beam direction is ensured and unnecessary vibrations are suppressed. Here, Cr was used as the metal thin film, and a mask provided with a desired opening in a stainless steel sheet was placed on the mirror substrate, and the film was formed by sputtering through the opening. As the metal thin film, sufficient adhesion such as Cr, Ni, Al, Ti, etc. can be obtained, and other metal that is easy to form and stable can be used. It is necessary to keep correlation. When the metal thin film is formed as described above for attaching the mass piece, the increase in the mass of the mirror substrate can be controlled with high accuracy, and therefore the resonance frequency can be finely adjusted. On the other hand, since the mass is increased in the thin film, it is not suitable for a significant resonance frequency adjustment. Sputtering was used here as the method for forming the thin film, but such a stencil mask can be used if the method of supplying atoms or ions from a solid source has directionality, such as vacuum deposition or ion plating. Easy film formation is possible. Further, the mass increase rate during film formation can be changed by setting the opening area of the stencil mask.
[0061]
The vibrating mirror of the present invention described above is most suitable as an optical scanning device for an image forming apparatus such as a photographic printing type printer or a copying machine. Next, an example of such an image forming apparatus will be described with reference to FIG.
[0062]
In FIG. 7, reference numeral 301 denotes an optical writing device, and 302 denotes a photosensitive drum that provides a scanned surface of the optical writing device 301. The optical writing device 301 scans the surface (scanned surface) of the photosensitive drum 302 in the axial direction of the drum with one or a plurality of laser beams modulated by a recording signal. The photosensitive drum 302 is rotationally driven in the direction of the arrow 303, and an optical latent image is formed by optical scanning of the surface charged by the charging unit 304 by the optical writing device 301. The electrostatic latent image is visualized as a toner image by the developing unit 305, and the toner image is transferred to the recording paper 307 by the transfer unit 306. The transferred toner image is fixed on the recording paper 307 by the fixing unit 307. Residual toner is removed by a cleaning unit 309 from the surface portion of the photosensitive drum 302 that has passed through the transfer unit 306. It is obvious that a configuration using a belt-like photoconductor in place of the photoconductor drum 302 is also possible. It is also possible to adopt a configuration in which the toner image is once transferred to a transfer medium, and the toner image is transferred from the transfer medium to a recording sheet and fixed.
[0063]
The optical writing device 301 includes a light source unit 320 that emits one or a plurality of laser beams modulated by a recording signal, the vibration mirror 321 of the present invention, and a light source unit 320 on the mirror surface of the mirror substrate of the vibration mirror 321. And an image forming optical system 322 for forming an image of the laser beam from the laser beam, and a scan for forming an image on the surface (scanned surface) of the photosensitive drum 302 by one or a plurality of laser beams reflected by the mirror surface. An optical system 323 is included. The vibration mirror 321 is incorporated in the optical writing device 301 in a form mounted on the circuit board 325 together with the integrated circuit 324 for driving the vibration mirror 321.
[0064]
The optical writing device 301 having such a configuration has the following advantages. The oscillating mirror 321 according to the present invention is advantageous in terms of the accuracy and stability of the resonance frequency as described above, and consumes less power for driving than the rotary polygon mirror, so that it can save power in the image forming apparatus. It is advantageous. Since the wind noise during vibration of the mirror substrate of the vibrating mirror 321 is smaller than that of the rotating polygon mirror, it is advantageous for improving the quietness of the image forming apparatus. The optical scanning device 321 requires much less installation space than the rotary polygon mirror, and the heat generation amount of the oscillating mirror 321 is small, so that the optical writing device 301 can be easily downsized, and therefore image formation is possible. It is advantageous for downsizing of the apparatus.
[0065]
The transport mechanism for the recording paper 307, the driving mechanism for the photosensitive drum 302, the control means such as the developing unit 305 and the transfer unit 306, the driving system for the light source unit 320, and the like may be the same as those in the conventional image forming apparatus. It is omitted.
[0066]
【The invention's effect】
  As explained above,According to the present invention, the following effects can be obtained.
(1)Even if the resonance frequency of the completed oscillating mirror varies due to variations in the manufacturing process, it can be adjusted and unified, so that the yield of products can be improved.
(2)Since the vibration conditions in both directions of the reciprocating vibration are equivalent, a stable resonance vibration without fluctuation can be obtained.
(3)By arranging symmetrically about the center of gravity of the mirror, it is possible to ensure the uniformity of the operation in the beam direction and suppress the occurrence of unnecessary vibrations, so that a stable resonance operation is possible.
(4)Since the area to which the mass piece is attached is concave, the area to which the mass is added is irregularly shaped and does not expand, so the area is regulated, so the mass on the mirror substrate surface is easily balanced and stable resonant vibration Can be obtained.
(5)Since the mirror surface can use the entire surface of one side of the mirror substrate, it is possible to cope with a large beam diameter and to be applied to various applications.
(6)By adhering to the corners of the concave region, it is possible to increase the adhesion area, and the adhesion with high strength without peeling or the like is possible and the reliability of the device is improved.
(7)Since the mass piece greatly contributes to the moment of inertia of the mirror substrate, the adjustment range of the resonance frequency can be widened, devices with large variations can be corrected, and the yield is improved.
[0067]
According to the second aspect of the present invention, since the adjustment direction is limited to the direction in which the resonance frequency is lowered, the mass piece is attached to the mirror substrate as an adjustment method, and easy and highly flexible adjustment is possible. Become.
[0068]
According to the third aspect of the invention, since the vibration conditions in both directions of the reciprocating vibration are equal, stable resonance vibration without fluctuation can be obtained.
[0069]
According to the invention described in claim 4, since the moment of the mass piece contributes greatly, the adjustment range of the resonance frequency can be widened, and a device with a large variation can be corrected, thereby improving the yield.
[0070]
According to the fifth aspect of the invention, by arranging symmetrically about the center of gravity of the mirror, it is possible to ensure the uniformity of the operation in the beam direction and suppress the generation of unnecessary vibrations, so that a stable resonance operation is possible. .
[0071]
According to the invention described in claim 6, since the area to which the mass piece is attached is concave, the area to which the mass is added is irregularly shaped and does not expand, so the mass within the mirror substrate plane is determined. It is easy to balance the above and stable resonance vibration can be obtained.
[0072]
According to the seventh aspect of the present invention, since the mirror surface can use the entire surface of one side of the mirror substrate, it is possible to cope with a large beam diameter and to be applied to various applications.
[0073]
According to the eighth aspect of the present invention, by adhering to the corners of the concave region, it is possible to increase the adhesion area, and adhesion with high strength without peeling or the like is possible, and the reliability of the device is improved.
[0074]
According to the ninth aspect of the invention, since the mass piece contributes greatly to the moment of inertia of the mirror substrate, the adjustment range of the resonance frequency can be widened, devices with large variations can be corrected, and the yield is improved.
[0075]
According to the tenth aspect of the present invention, when the metal thin film is deposited as the mass piece, the increase in the mass of the mirror substrate can be controlled with high accuracy, so that the resonance frequency can be finely adjusted. .
[0076]
According to the invention described in claim 11, since the mirror substrate can be operated in a clean environment, the reliability is improved and the viscous resistance of air can be ignored, so that the deflection angle can be expanded.
[0077]
According to the invention of claim 12, since the droplet amount can be controlled with high accuracy, the resonance frequency can be controlled with high accuracy, and the product yield can be improved.
[0078]
According to the thirteenth aspect of the present invention, since the resonance frequencies of the plurality of vibrating mirrors can be aligned by an easy method, the yield is improved.
[0079]
According to the invention described in claim 14, since the adjustment direction is limited to the direction in which the resonance frequency is lowered, the mass piece is attached to the mirror substrate as an adjustment method, and the adjustment can be easily performed with a high degree of freedom. Become.
[0080]
According to the fifteenth aspect of the invention, since the resonance frequency of the oscillating mirror is adjusted with high accuracy, the performance as the optical writing device can be secured stably.
[0081]
According to the invention described in claim 16, since the resonance frequency of the oscillating mirror is adjusted with high accuracy, the performance as the image forming apparatus can be secured stably, and the power consumption for driving compared with the rotary polygon mirror Is small, which is advantageous for power saving of the image forming apparatus. Further, since the wind noise during vibration of the mirror substrate of the vibrating mirror 321 is smaller than that of the rotary polygon mirror, it is advantageous for improving the quietness of the image forming apparatus. Furthermore, since the optical scanning device 321 requires much less installation space than the rotary polygon mirror, and the heat generation amount of the vibration mirror 321 is also small, the optical writing device 301 can be easily reduced in size, and thus the image is reduced. This is advantageous for downsizing the forming apparatus.
[Brief description of the drawings]
FIG. 1 shows a configuration of a vibrating mirror according to Embodiment 1 of the present invention.
FIG. 2 shows a configuration of a vibrating mirror according to Embodiment 2 of the present invention.
FIG. 3 shows a configuration of a vibrating mirror according to Embodiment 3 of the present invention.
4 is a diagram for explaining a method of forming a vibrating mirror according to Embodiment 3. FIG.
FIG. 5 shows a configuration of a vibrating mirror according to Embodiment 4 of the present invention.
FIG. 6 shows a configuration of a vibrating mirror according to a fifth embodiment of the present invention.
FIG. 7 shows a configuration example of an image forming apparatus to which the present invention is applied.
[Explanation of symbols]
101 mirror substrate
102, 103 torsion beam
104 Upper frame
105 Insulating film
106 Lower frame
107, 108 Movable electrode
109, 110 Fixed electrode
111-114 slit
115, 116 electrode pad
131, 132 mass pieces

Claims (1)

A mirror substrate for reflecting the light beam; two beams provided on the same straight line that support the mirror substrate; and mirror driving means for generating a rotational force on the mirror substrate; Is a oscillating mirror that reciprocally vibrates at a predetermined scanning frequency, and the mirror substrate has a recess formed on the surface opposite to the surface that reflects the light beam, and is at the corner of the recess and on the rotation axis. A vibrating mirror characterized in that a mass piece is attached at a position that is symmetrical and symmetric with respect to the center of gravity of a mirror substrate, and the resonance frequency is variable.

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