JP5146204B2 - Optical device, optical scanner, and image forming apparatus - Google Patents

Description

  The present invention relates to an optical device capable of scanning light, an optical scanner, and an image forming apparatus.

Conventionally, as a mirror that tilts due to torsion of a beam that supports the reflecting surface, a rib that reinforces the flat mirror portion has been provided on the back side of the flat mirror portion whose surface is the reflecting surface, and distortion (moving deflection) of the reflecting surface of the flat mirror portion has been provided. ) Is known to be small (see, for example, Patent Document 1).
JP 2004-325588 A

  However, in the prior art, by providing the rib, the center of gravity of the plane mirror part to be tilted is shifted to the side where the rib is provided with respect to the tilt axis, so vibrations other than torsion, for example, lateral vibrations within the reflecting surface In addition, there is a problem that vertical vibrations are superimposed.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an optical device, an optical scanner, and an image forming apparatus capable of reducing the deformation of the reflecting surface and suppressing vibrations other than torsion. One.

  An optical device according to the present invention supports a plate-like movable portion, a reflective film that is formed on the movable portion and reflects light, and supports the movable portion so that it can swing around a X axis with respect to a support member. A vibration system comprising: a first shaft member; a rib disposed on the movable portion; and drive means for swinging the movable portion with respect to the support member. With respect to one shaft member, they are arranged on each of the one and other surfaces so that the moment of inertia of one surface of the movable part and the moment of inertia of the other surface are equal.

  According to such a configuration, the ribs are arranged on each of the one and other surfaces so that the moment of inertia of one surface of the movable portion and the moment of inertia of the other surface are equal to the first shaft member. Therefore, the center of gravity of the movable part substantially coincides with the center of the rotation axis of the vibration system. Accordingly, the rib can reduce deformation of the movable portion having the reflective surface (reflective film) and can suppress vibrations other than torsion.

  Preferably, a rib disposed on at least one of the one and other surfaces is provided in the vicinity of the first shaft member.

  According to this configuration, the rib on at least one of the one and the other surfaces is provided in the vicinity of the first shaft member, and therefore the first deformation that causes a very large deformation by swinging while being torsionally deformed. The vicinity of the shaft member is reinforced by ribs. Thereby, the dynamic bending (deformation) which arises in a movable part can be reduced.

  Preferably, the movable part includes a reflective film support part in which the reflective film is formed, and a connection part connected to the first shaft member outside the reflective film support part. The rib of the surface arrange | positioned at at least 1 surface among surfaces is provided in the said connection part.

  According to this configuration, the movable portion has the connection portion connected to the first shaft member outside the reflective film support portion, and the rib disposed on at least one of the one and other surfaces is connected. Therefore, the vicinity of the first shaft member that causes a very large deformation by swinging while being twisted is reinforced by the rib, and the rib is not provided in the reflective film. Thereby, the effective area of a reflecting film can be ensured and the optical device can reflect light reliably.

Preferably, the planar shape of the movable part is a circle or an ellipse.
According to such a configuration, since the planar shape of the movable part is a shape that matches the spot shape of the incident light, for example, a circle or an ellipse, the moment of inertia of the movable part is not increased unnecessarily.

Preferably, the rib disposed on the other surface is provided on the back side of the rib disposed on the one surface.
According to such a configuration, since the rib on the other surface is provided on the back side of the rib on the one surface, the moment of inertia on one surface and the moment of inertia on the other surface can be easily equalized.

  Preferably, the driving means includes a permanent magnet disposed as the rib on at least one surface, a coil disposed at a position facing the permanent magnet, and an alternating current that applies an alternating current signal having a predetermined frequency to the coil. It comprises an electric current signal generator, and the movable part is swung by an electromagnetic force generated between the magnetic field generated by the coil by the alternating current signal and the permanent magnet.

  According to such a configuration, since the rib is formed of a permanent magnet, it is not necessary to separately provide an actuator for swinging the movable portion on the movable portion.

  Preferably, the permanent magnet is magnetized at an angle with respect to the first shaft member.

  According to this configuration, the permanent magnet is magnetized at an angle with respect to the first shaft member, and is not magnetized parallel to the first shaft member. The electromagnetic force generated during the period acts to twist the first shaft member.

  Preferably, the torsional resonance frequency of the vibration system substantially matches the predetermined frequency.

  According to such a configuration, the torsional resonance frequency of the vibration system substantially coincides with the predetermined frequency, so that resonance can be used and the deflection angle in the swinging motion of the movable part can be increased with less power consumption.

  Preferably, the movable part, the first shaft member, and the support member are the first of the substrates in which a first silicon layer and a second silicon layer are formed via an oxide film layer. A rib formed from a silicon layer and disposed on at least one of the one and other surfaces is formed from the second silicon layer and the oxide film layer.

  According to this configuration, the movable portion, the shaft member, the support member, the rib disposed on at least one of the other surfaces, the first silicon layer and the second silicon layer are the oxide film layers. The substrate can be integrally formed by etching a substrate generally called an SOI substrate.

  Preferably, the movable portion has a recess on at least one of the one and other surfaces, and the rib is fitted into the recess.

  According to such a configuration, the movable portion has a recess on at least one of the one and other surfaces, and the rib is fitted into the recess, so that the distance between the rotation axis center of the vibration system and the rib is shortened. be able to. Thereby, the inertia moment of a movable part can be reduced.

  Preferably, the support member is a frame-shaped flat plate, and further includes a second shaft member that supports the vibration system so as to be swingable with respect to the support member in a Y-axis direction orthogonal to the X-axis.

  According to such a configuration, the support member is a frame-shaped flat plate, and further includes the second shaft member that supports the vibration system so as to be swingable in the Y-axis direction orthogonal to the X-axis with respect to the support member. The movable part can be swung in two orthogonal directions. Thereby, the optical device can scan the light reflected by the reflecting film two-dimensionally.

An optical scanner according to the present invention includes the above-described optical device according to the present invention.
According to this configuration, since the optical device according to the present invention described above is provided, the center of gravity of the movable portion substantially coincides with the center of the rotation axis of the vibration system, and vibrations other than torsion can be suppressed. Thereby, it is possible to prevent the reflected light from being shaken or shifted, and an optical scanner having excellent drawing characteristics can be realized.

An image forming apparatus according to the present invention includes the above-described optical scanner according to the present invention.
According to this configuration, since the optical scanner according to the present invention described above is provided, the center of gravity of the movable portion substantially coincides with the center of the rotation axis of the vibration system, and vibrations other than torsion can be suppressed. Accordingly, it is possible to prevent the reflected light from being shaken or shifted, and an image forming apparatus having excellent drawing characteristics can be realized.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Here, the case where the rib arranged on one surface of the movable part is a permanent magnet and the movable part is swung by electromagnetic force generated between the coils arranged at opposing positions will be described. However, the driving principle for swinging the movable part of the present invention is not limited to electromagnetic driving.
(Optical device)
First, an optical device according to the present invention will be described with reference to FIGS. FIG. 1 is a top view illustrating the configuration of an optical device according to the present invention. 2 is a cross-sectional view taken along line AA shown in FIG. 3 is a cross-sectional view in the direction of arrows BB shown in FIG. In the following description, the front side in FIG. 1 is referred to as “up”, the back side in FIG. 1 is referred to as “down”, the right side is referred to as “right”, the left side is referred to as “left”, and the upper side in FIG. The lower side is called “lower”, the right side is called “right”, the left side is called “left”, the upper side in FIG. 3 is “upper”, the lower side is “lower”, the right side is “right”, and the left side is “left” That's it.

The optical device 1 is for scanning light, and is used in, for example, an optical scanner, and scans light irradiated from a light source onto an object. As shown in FIG. 1, the optical device 1 includes a base 2.
The base 2 includes a movable portion 211, ribs 211d and 211e disposed on the upper surface of the movable portion, ribs 211f and 211g disposed on the lower surface of the movable portion, and the movable portion 211 with respect to the frame-shaped support member 22 in the X axis. The vibration system 21 includes a pair of shaft members 212 and 213 that are supported so as to be swingable around.
The movable part 211 has a reflection film support part 214 on which the reflection film 211a is formed, and connection parts 211b and 211c outside the reflection film support part 214, and is connected by the shaft members 212 and 213 and the connection parts 211b and 211c. doing.
As shown in FIGS. 2 and 3, the optical device 1 includes driving means 6 that swings the movable portion 211 relative to the support member 22.
The driving means 6 includes permanent magnets 211f and 211g disposed as ribs on one surface of the movable portion 211, a coil 62 disposed at a position facing the permanent magnets 211f and 211g, and an alternating current having a predetermined frequency in the coil 62. In the alternating current signal generator 63 for applying a signal, the movable portion 211 swings by an electromagnetic force generated between the magnetic field generated by the coil 62 by the alternating current signal and the permanent magnets 211f and 211g.
The permanent magnets only need to be disposed on one surface of the movable portion 211, and instead of 211f and 211g, 211d and 211e may be disposed, or all may be permanent magnets.
Further, the permanent magnet may not be perpendicular to the shaft members 212 and 213, and may be magnetized at an angle.

  Each shaft member 212, 213 has a rod shape and is elastically deformable.

  On the upper surface of the reflective film support 214, a substantially circular reflective film 211a having light reflectivity is provided. In addition, the movable portion 211 includes connection portions 211b and 211c that are connected to the shaft member 212 or the shaft member 213, respectively, outside the reflective film support portion 214. The planar shape of the movable portion 211 is not particularly limited as long as it can be disposed inside the support member 22. However, as shown in FIG. 1, the shape of the movable portion 211 is preferably a shape matched to the spot diameter of incident light, for example, a circle or an ellipse. Thereby, the increase in the unnecessary moment of inertia of the movable part 211 can be suppressed.

  As shown in FIG. 2, permanent magnets 211 f and 211 g arranged as ribs are provided on the lower surface of the movable portion 211, and ribs 211 d and 211 e are provided on the upper surface of the movable portion 211. The ribs 211d and 211e and the ribs 211f and 211g are configured so that the inertia moment on the upper surface side and the inertia moment on the lower surface side of the movable portion 211 are equal to each other with respect to the shaft members 212 and 213.

  The ribs 211d and 211e and the ribs 211f and 211g only have to be configured such that the inertia moment on the upper surface side and the inertia moment on the lower surface side of the movable portion 211 are equal to the shaft members 212 and 213. There are no particular restrictions on the number, size, arrangement, etc. However, as shown in FIG. 2, it is preferable that the ribs 211f and 211g provided on the lower surface are arranged on the back side with respect to the ribs 211d and 211e provided on the upper surface. Thereby, the inertia moment on the upper surface side and the inertia moment on the lower surface side can be easily equalized.

  FIG. 4 is an essential part enlarged view for explaining a modification of the movable part shown in FIG. As shown in FIG. 4, for example, only the rib 211h may be provided on the lower side of the reflective film support 214 instead of the ribs 211f and 211g, and the position of the rib is not particularly limited. In such a case, the rib 211h is made of the same material as the permanent magnet described later. However, it is preferable that at least one of the ribs 211d and 211e is provided in the vicinity of the shaft members 212 and 213. As a result, the vicinity of the shaft members 212 and 213 that cause a very large deformation by swinging while being twisted is reinforced by the ribs 211d and 211e.

  Further, it is more preferable that the ribs 211d and 211e on the upper surface are provided in the connection part 211b or the connection part 211c, respectively. As a result, the vicinity of the shaft members 212 and 213 that cause a very large deformation by swinging while being twisted is reinforced by the ribs, and the ribs 211d and 211e are not provided on the reflective film 211a.

  Of the base body 2 configured in this way, the movable portion, the shaft member, the support member, and the rib formed on one surface of the movable portion are, for example, a first silicon layer and a second silicon layer. It may be integrally formed from a substrate having a laminated structure constituted through an oxide film layer.

  As shown in FIGS. 2 and 3, the driving means 6 includes permanent magnets 211 f and 211 g arranged as ribs, a coil 62, and an alternating current signal generator 63. The permanent magnet is magnetized at an angle with respect to the shaft members 212 and 213. In FIG. 3, for convenience of explanation, a case will be described in which the left side of the permanent magnets 211f and 211g is an N pole and the right side is an S pole, and the shaft members 212 and 213 are magnetized at 90 °.

  As the material of the permanent magnet, a material obtained by magnetizing a hard magnetic material such as a neodymium magnet, a ferrite magnet, a samarium cobalt magnet, an alnico magnet, or a bonded magnet can be suitably used. In addition, after providing a hard magnetic body in the movable part 211, it is good also as a permanent magnet by magnetizing a hard magnetic body.

  The coil 62 is for applying a magnetic field to the permanent magnets 211f and 211g, and is provided to face the permanent magnets 211f and 211g.

  The coil 62 is electrically connected to the alternating current signal generator 63. When a current is applied to the coil 62 by the alternating current signal generator 63, a magnetic field is generated from the coil 62. The coil 62 may be wound around a magnetic core. Thereby, the magnetic field generated from the coil 62 can be efficiently applied to the permanent magnets 211f and 211g.

  The frequency of the current generated by the AC current signal generator 63 is set so as to substantially match the torsional resonance frequency of the vibration system 21. By utilizing resonance in this way, the swing angle in the swinging motion around the X axis of the movable portion 211 can be increased with less power consumption.

  The optical device 1 configured as described above operates as follows. That is, when a current is applied from the alternating current signal generator 63 to the coil 62 in the direction I1, torque is generated so as to rotate the movable portion 211 clockwise with respect to the X axis. Next, when a current is applied to the coil 62 in the I2 direction, torque is generated so as to rotate the movable portion 211 counterclockwise with respect to the X axis. That is, in the case of an alternating current signal, the direction of the current is alternately switched between I1 and I2, so that the movable portion 211 swings with respect to the X axis.

  Here, the ribs 211d, 211e, 211f, and 211g are provided to the shaft members 212 and 213 so that the inertia moment on the upper surface side and the inertia moment on the lower surface side of the movable portion 211 are equal. The center of gravity of 211 substantially coincides with the rotational axis center of the vibration system 21.

  In the optical device 1, permanent magnets 211f and 211g are provided on the movable portion 211, and a coil 62 is provided so as to face the permanent magnets 211f and 211g. That is, the coil 62 that is a heating element is not provided on the vibration system 21. Therefore, the thermal expansion of the base 2 due to the heat generated from the coil 62 by energization can be suppressed. Thereby, even if the optical device 1 is continuous use for a long time, it can exhibit a desired vibration characteristic.

  In the present embodiment, electromagnetic force is used as the driving means 6 to cause the movable portion 211 to swing around the X axis. However, the present invention is not limited to this. For example, the movable portion 211 is moved by electrostatic attraction or the like. You may make it rock | fluctuate around the X-axis.

  Next, a method for manufacturing an optical device according to the present invention will be described with reference to FIGS. 5 to 7 are cross-sectional views illustrating an example of a method for manufacturing the optical device shown in FIG. In order to explain the manufacturing method in an easy-to-understand manner, FIGS. 5 (a) to 5 (f) and FIGS. 6 (g) to 6 (i) describe the BB cross section of FIG. Shows both the BB cross section and the AA cross section, and FIG. 7 (k) and FIG. 7 (l) show the AA cross section. In the following description, the upper side in FIGS. 5 to 7 is referred to as “upper” and the lower side is referred to as “lower”.

First, as shown in FIG. 5A, a substrate 100 in which a first silicon layer 100a, an oxide film layer 100b, and a second silicon layer 100c are stacked is prepared. This substrate is generally called an SOI substrate.
Thereafter, the movable portion 211, the shaft members 212 and 213, and the support member 22 are formed on the first silicon layer 100a, and ribs 211d and 211e made of the oxide film 100b and the second silicon layer 100c are integrally formed on the SOI substrate. The case will be described.

  Next, as shown in FIG. 5B, an oxide film 100d is formed on the upper surface side of the second silicon layer 100c using a method such as thermal oxidation.

  Next, as shown in FIG. 5C, a resist is applied to the surface of the oxide film 100d.

  Next, as shown in FIG. 5D, an etching mask 200b for the oxide film 100d is formed by a photolithography process.

  Next, as shown in FIG. 5E, the oxide film 100d is etched to form an oxide film mask 100d '. As an etching method, chemical wet etching using buffered hydrofluoric acid (BHF) or the like, or physical etching, for example, plasma etching, reactive ion etching, beam etching, photo-assisted etching, or the like may be used. In addition, one or more of the above etching methods can be used in combination. It should be noted that the same method can also be used for etching in each step below.

  Next, the resist 200b is removed, and a new resist 200c is applied to the lower surface side of the first silicon layer 100a in order to pattern the first silicon layer 100a as shown in FIG.

  Next, as shown in FIG. 6G, an etching mask (resist mask) 200c 'for the first silicon layer 100a is formed by a photolithography process. For alignment in the photolithography process, alignment with the already formed oxide film mask 100d '(so-called double-sided alignment) is performed.

Next, as shown in FIG. 6H, the first silicon layer 100a is etched. At this time, the oxide film layer 100b functions as an etching stop layer. In this step, a DRIE (Deep Reactive Ion Etching) apparatus is used as a dry etching apparatus in order to form a structure having a high aspect ratio. Later, the resist mask 200c ′ is removed.
Here, the vibration system 21 and the support member 22 including the movable portion 211 and the shaft members 212 and 213 are formed. However, since the oxide film 100b is not removed, the vibration system 21 remains fixed and cannot be moved.
The formation of the support member 22 is not limited to the first silicon layer, and an oxide film 100b and a second silicon layer formed in a process described later (see FIG. 6J) immediately below the first silicon layer, It may be formed integrally.

  Next, as shown in FIG. 6I, the first silicon layer 100a is protected by the protective material 300a, and the second silicon layer 100c is processed by DRIE. At this time, the oxide film layer 100b functions as an etching stop layer. After the DRIE, the protective material 300a is peeled off.

Next, as shown in FIGS. 6 (j) and 6 (j) ′ (FIG. 6 (j) ′ is an AA cross section in FIG. 1), the oxide film 100b is wet etched with hydrofluoric acid. At this time, the oxide film mask 100d ′ is also removed together. Here, ribs 211d and 211e made of the oxide film 100b and the second silicon layer 100c are formed. Since some of the ribs 211d and 211e include the oxide film 100b, this step is slightly etched, but the rib has a sufficient area, so that the rib does not peel from the movable portion 211.
Further, the vibration system 21 including the movable portion 211 and the shaft members 212 and 213 is released by wet etching using hydrofluoric acid, and can be moved around the X axis.

  Next, as shown in FIG. 7 (k), a metal film is formed on the upper surface of the movable portion 211, and a reflective film 221a is formed. Examples of a method for forming such a metal film include dry plating methods such as vacuum deposition, sputtering, and ion plating, wet plating methods such as electrolytic plating and electroless plating, thermal spraying methods, and metal foil bonding. Here, an aluminum film was formed by sputtering.

  Next, as shown in FIG. 7L, permanent magnets 211 f and 211 g are obtained as ribs on the lower surface of the movable portion 211. The permanent magnet may be bonded to a hard magnetic material (that is, a permanent magnet) that has already been magnetized, or may be magnetized using a magnetizer or the like after bonding and fixing.

(Optical scanner)
Since the optical device 1 as described above includes the reflective film 211a, for example, it is suitable for an optical scanner provided in an image forming apparatus such as a laser printer, a barcode reader, a scanning confocal laser microscope, or an imaging display. Can be applied. Since the optical scanner of the present invention has the same configuration as that of the optical device 1 described above, the description thereof is omitted.

  Thus, according to the optical scanner according to the present invention, since the optical device 1 according to the present invention described above is provided, the center of gravity of the movable portion 211 substantially coincides with the center of the rotation axis of the vibration system 21, and therefore vibration other than torsion is generated. Can be suppressed. Thereby, it is possible to prevent the reflected light from being shaken or shifted, and an optical scanner having excellent drawing characteristics can be realized.

(Image forming device)
Next, an image forming apparatus according to the present invention will be described with reference to FIG. FIG. 8 is a schematic cross-sectional view showing an example of an image forming apparatus including the optical scanner according to the present invention.

  An image forming apparatus (imaging display) 119 illustrated in FIG. 8 includes an optical device 1 that is an optical scanner, light sources 191, 192, and 193 of three colors of R (red), G (green), and B (blue), and a cross A dichroic prism (X prism) 194, a galvano mirror 195, a fixed mirror 196, and a screen 197 are provided.

  In such an image forming apparatus 119, light of each color is irradiated from the light sources 191, 192, 193 to the optical device 1 (reflecting unit 211 a) via the cross dichroic prism 194. At this time, the red light from the light source 191, the green light from the light source 192, and the blue light from the light source 193 are combined by the cross dichroic prism 194. Then, the light reflected by the reflective film 211a (the combined light of the three colors) is reflected by the galvanometer mirror 195, then by the fixed mirror 196, and irradiated on the screen 197.

  At that time, the light reflected by the reflecting portion 211a is scanned in the horizontal direction of the screen 197 (main scanning) by the operation of the optical device 1 (the swing of the movable portion 211 around the X axis). On the other hand, the light reflected by the reflecting portion 211 a due to the rotation of the galvano mirror 195 around the axis Y is scanned (sub-scanned) in the vertical direction of the screen 197. In addition, the intensity of light output from the light sources 191, 192, and 193 of each color changes according to image information received from a host computer (not shown).

  As described above, according to the image forming apparatus 119 according to the present invention, since the optical scanner according to the present invention is provided, the center of gravity of the movable portion 211 substantially coincides with the rotation center axis of the vibration system 21. Vibration can be suppressed. As a result, the reflected light can be prevented from being shaken or shifted, and an image forming apparatus 119 having excellent drawing characteristics can be realized.

  In addition, the structure of this invention is not limited only to the above-mentioned embodiment, You may add a various change within the range which does not deviate from the summary of this invention.

It is a top view explaining the structure of the optical device which concerns on this invention. It is AA arrow direction sectional drawing shown in FIG. It is a BB arrow directional cross-sectional view shown in FIG. It is a principal part enlarged view explaining the modification of the movable part shown in FIG. It is sectional drawing explaining an example of the manufacturing method of the optical device shown in FIG. It is sectional drawing explaining an example of the manufacturing method of the optical device shown in FIG. It is sectional drawing explaining an example of the manufacturing method of the optical device shown in FIG. 1 is a schematic cross-sectional view illustrating an example of an image forming apparatus including an optical scanner according to the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical device, 6 ... Driving means, 21 ... Vibration system, 211 ... Movable part, 211a ... Reflecting part, 211b, 211c ... Connection part, 211d, 211e, 211f, 211g, 211h ... Rib, 212, 213 ... Shaft member 119: Image forming apparatus.

Claims (9)

A plate-shaped movable part;
A reflective film that is formed on the movable part and reflects light;
A first shaft member that supports the movable portion so as to be swingable about the X axis with respect to the support member;
A permanent magnet as a first rib provided on one surface of the movable part, a coil, and an alternating current signal generator for applying an alternating current signal to the coil, and the movable part with respect to the support member Drive means for rocking movement,
A second rib provided on the other surface of the movable part;
With
It said first rib and said second rib is provided so that the moment of inertia of the one surface of the movable portion relative to said first shaft member, and the moment of inertia of the other surface of the movable portion is equal And
The movable portion, the first shaft member, and the support member are formed from the first silicon layer of the substrate in which a first silicon layer and a second silicon layer are formed through an oxide film layer. Formed,
The optical device is characterized in that the second rib is formed of the second silicon layer and the oxide film layer . The optical device according to claim 1, wherein the first rib and the second rib are provided only in the vicinity of the first shaft member. The movable part is
A reflection film support portion formed with the reflection film; and a connection portion connected to the first shaft member outside the reflection film support portion;
The optical device according to claim 2, wherein the first rib and the second rib are provided in the connection portion. The optical device according to any one of claims 1 to 3, wherein the planar shape of the movable portion is a circle or an ellipse. The optical device according to any one of claims 1 to 4, wherein the second rib is provided on a back side of the first rib. The permanent magnet, the optical device according to any one of claims 1 to 5, characterized in that it is magnetized at an angle to said first shaft member. The support member is a frame-shaped flat plate;
According to any one of claims 1 to 6, further comprising a second shaft member for pivotally supporting the vibration system in the Y-axis direction orthogonal to the X-axis relative to the support member Optical device. A plate-shaped movable part;
A reflective film that is formed on the movable part and reflects light;
A first shaft member that supports the movable portion so as to be swingable about the X axis with respect to the support member;
A permanent magnet as a first rib provided on one surface of the movable part, a coil, and an alternating current signal generator for applying an alternating current signal to the coil, and the movable part with respect to the support member Drive means for rocking movement,
A second rib provided on the other surface of the movable part;
With
It said first rib and said second rib is provided so that the moment of inertia of the one surface of the movable portion relative to said first shaft member, and the moment of inertia of the other surface of the movable portion is equal And
The movable portion, the first shaft member, and the support member are formed from the first silicon layer of the substrate in which a first silicon layer and a second silicon layer are formed through an oxide film layer. Formed,
2. The optical scanner according to claim 1, wherein the second rib is formed of the second silicon layer and the oxide film layer . A plate-shaped movable part;
A reflective film that is formed on the movable part and reflects light;
A first shaft member that supports the movable portion so as to be swingable about the X axis with respect to the support member;
A permanent magnet as a first rib provided on one surface of the movable part, a coil, and an alternating current signal generator for applying an alternating current signal to the coil, and the movable part with respect to the support member Drive means for rocking movement,
A second rib provided on the other surface of the movable part;
With
It said first rib and said second rib is provided so that the moment of inertia of the one surface of the movable portion relative to said first shaft member, and the moment of inertia of the other surface of the movable portion is equal And
The movable portion, the first shaft member, and the support member are formed from the first silicon layer of the substrate in which a first silicon layer and a second silicon layer are formed through an oxide film layer. Formed,
The image forming apparatus , wherein the second rib is formed of the second silicon layer and the oxide film layer .

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