JP2011191422A - Optical deflector, optical scanner, image forming device, and image projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact optical deflector that allows a resonance frequency of a deflecting mirror to be changed. <P>SOLUTION: The optical deflector includes: a mirror substrate 2 which has a deflecting mirror 4 to deflect a light beam from a light source by reciprocally vibrating first torsion beam members 3a and 3b; an outer frame member 5 which holds the mirror substrate 2; and second torsion beam members 6a and 6b whose outsides are fixed to and held with a frame member 7 and insides are joined with both sides of the outer frame member 5. The shapes and dimensions of the deflecting mirror 4, and the first and second torsion beam members 3a, 3b, 6a and 6b are set so that when the deflecting mirror 4 is reciprocally vibrated by receiving vibration from an external force generating means 8, the first resonance frequency, which is generally determined by inertia of the outer frame member 5 and torsional rigidity of the second torsion beam members 6a and 6b, is equal to a half of the second resonance frequency which is generally determined by inertia of the deflecting mirror 4 and torsional rigidity of the first torsion beam members 3a and 3b. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical deflector having a mirror that deflects a light beam emitted from a light source by reciprocatingly vibrating a pair of beam members provided on both sides as a torsional rotation axis, an optical scanning device including the optical deflector, The present invention relates to an image forming apparatus and an image projection apparatus.

  2. Description of the Related Art Conventionally, there has been known an optical scanning device that writes an image on a surface to be scanned by deflecting a light beam emitted from a laser light source by an optical deflector and scanning the deflected light beam on the surface to be scanned such as a photosensitive member. ing. In such an optical scanning device, a polygon mirror is generally used as an optical deflector that scans a light beam. The polygon mirror rotates at high speed to scan the light beam. However, in image formation using the polygon mirror, the polygon mirror is rotated at higher speed to achieve higher resolution and high-speed image formation. There is a need to.

  However, in order to further rotate the polygon mirror at a higher speed, it is necessary to solve problems such as durability of the bearing, heat generation, and noise, so that there is a limit to increasing the polygon mirror at a higher speed.

  In order to solve such a problem, an optical deflector having a mirror that deflects a light beam emitted from a light source by reciprocally vibrating a pair of beam members provided on both sides as a torsional rotation axis has been proposed in recent years. (For example, refer to Patent Document 1 and Patent Document 2).

  The optical deflector (twisted hinge type mirror device) of Patent Document 1 is configured as shown in FIGS.

  As shown in FIG. 23A, this optical deflector (twisted hinge type mirror device) includes a reflecting portion 101, a supporting portion 102, and a hinge layer 103 that provide a pair of rotations around a pivot axis 104. Torsion hinges 103a and 103b are defined. Further, as shown in the figure, there is a permanent magnet 106 around the turning shaft 105. For this reason, the reflection part 101, the support part 102, and the hinge layer 103 are arrange | positioned symmetrically. Further, since the permanent magnet 106 is centered on the pivot axis 104, the center of mass of the mirror structure 107 in which these are combined is centered on the pivot axis 105.

  As shown in FIG. 23B, in order to generate a rotational torque in the mirror structure 107, a magnetic drive mechanism 108 that interacts with the permanent magnet 106 is provided. Furthermore, the mirror structure 107 is arranged so that its vertical axis 109 is located in the middle between the magnetic core arms 110a and 110b. Thus, when the core arms 110a and 110b are continuously switched alternately between providing N and N poles, the magnetic interaction with the permanent magnet 106 causes the mirror structure 107 around the pivot 105 to move. Provides a magnetic force to vibrate.

  In the optical deflector of Patent Document 2, a plurality of torsion springs and a plurality of vibrators are alternately connected, and the torsion axes of the plurality of torsion springs are on the same straight line, and at least one of the plurality of vibrators. There are two vibration modes, including vibration means for applying torsional vibration to one and frequency switching means for switching the vibration frequency of the vibration means in at least two stages. This resonance type optical deflector has resonance frequencies corresponding to two display modes of SVGA (800 × 600 pixels, 20 kHz) and XGA (1024 × 768 pixels, 25.6 kHz) for a raster scanning display.

  Incidentally, in the optical deflector (twisted hinge type mirror device) of Patent Document 1, the frequency characteristics of the mirror twist angle (swing angle) when the mirror structure 107 is vibrated around the turning shaft 105 by the magnetic force are shown in FIG. As shown, it has one resonance point peak (resonance frequency).

  Therefore, when this optical deflector (twisted hinge type mirror device) is used in an optical scanning device (optical writing device) of an image forming apparatus such as a printer or a copying machine, the image forming speed (process speed) is one predetermined value. There is no problem with a normal image forming apparatus that is fixed at a speed, but an image forming apparatus that can switch the image forming speed (process speed) depending on the type of recording medium such as paper cannot cope with it.

  In the optical deflector of Patent Document 2, the resonance frequency of the mirror is about 20 kHz to 25 kHz, but the resonance frequency of the mirror used in the optical scanning device (optical writing device) of an image forming apparatus such as a printer or a copying machine is It is as low as 3kHz-6kHz.

  For this reason, when the optical deflector of Patent Document 2 is used in an optical scanning device (optical writing device) of an image forming apparatus, the length of a torsion spring coupled to both sides of the mirror is reduced in order to lower the resonance frequency of the mirror. Since it is necessary to lengthen the length, there arises a problem that the entire optical deflector becomes large.

  SUMMARY An advantage of some aspects of the invention is that it provides an optical deflector, an optical scanning device, an image forming apparatus, and an image projection apparatus that can switch the resonance frequency of a mirror and can be downsized.

  In order to achieve the above object, the optical deflector according to claim 1 deflects the light beam from the light source by reciprocally oscillating a pair of first torsion beam members joined to both sides about a torsional rotation axis. A mirror substrate having a deflecting mirror, an outer frame member for holding the mirror substrate, and the first torsion beam member are provided on the same straight line, both outer sides are fixedly held, and both inner sides are the outer frame members. A pair of second torsion beam members joined to both sides, and an external force generation means for vibrating the outer frame member or the pair of second torsion beam members, and the outer frame from the external force generation means By applying an oscillating force to the member or the pair of second torsion beam members, the deflection mirror is reciprocally oscillated using the pair of second torsion beam members and the first torsion beam member as a torsion rotation axis. An optical deflector, When the deflection mirror reciprocally vibrates, the first resonance frequency determined approximately by the inertia of the outer frame member and the torsional rigidity of the pair of second torsion beam members is the inertia of the deflection mirror and the first torsion beam member. The shape dimensions of the deflection mirror and the first and second torsion beam members are set so as to be approximately ½ of the second resonance frequency that is generally determined by the torsional rigidity.

  The optical deflector according to claim 2, wherein the mirror substrate is made of a Si substrate, the outer frame member and the second torsion beam member are made of a metal material, and the mirror substrate is made of the outer substrate. It is characterized by being joined to a frame member.

  The optical deflector according to claim 3 is characterized in that the outer frame member and the pair of second torsion beam members are formed by laminating metal plate materials.

  The optical deflector according to claim 4 is characterized in that the outer frame member and the pair of second torsion beam members are formed by laminating and joining metal plate materials by diffusion bonding.

  The optical deflector according to a fifth aspect is characterized in that the pair of first torsion beam members are formed in a folding spring shape having a plurality of linear portions and bent portions.

  The optical deflector according to claim 6, wherein a pair of arm members extending in a direction orthogonal to the second torsion beam member are provided in the vicinity of both outer sides where the pair of second torsion beam members are fixedly held. The external force generating means is provided on the pair of arm members.

  The optical deflector according to claim 7, wherein the external force generating means is a piezoelectric element that expands and contracts in a thickness direction corresponding to an applied voltage, and the piezoelectric element is provided at both ends of the pair of arm members, respectively. It is characterized by providing.

  The optical deflector according to claim 8 has a phase of 180 for each piezoelectric element provided at both ends of the one arm member and each piezoelectric element provided at both ends of the other arm member. It is characterized in that drive signals that are shifted in degree are applied.

  The optical deflector according to claim 9, wherein the external force generating means is disposed on both sides of the outer frame member in a direction orthogonal to the coil disposed on the outer frame member and the pair of first torsion beam members. The outer frame member is formed by a Lorentz force generated by an interaction with a magnetic field formed between the pair of permanent magnets when a sinusoidal current is applied to the coil. It is characterized by being vibrated.

  The optical deflector according to a tenth aspect is characterized in that the coil is integrally formed on a flexible substrate fixed to the back surface of the outer frame member.

  An optical scanner according to an eleventh aspect includes the optical deflector according to any one of the first to tenth aspects.

  An image forming apparatus according to a twelfth aspect includes the optical scanning device according to the eleventh aspect.

  An image projection apparatus according to a thirteenth aspect includes the optical scanning apparatus according to the eleventh aspect.

  According to the optical deflector of the present invention, the second resonance frequency, which is generally determined by the inertia of the outer frame member and the torsional rigidity of the pair of second torsion beam members, is the inertia of the deflection mirror and the first torsion beam member. By setting the shape dimensions of the deflecting mirror and the first and second torsion beam members so as to be approximately ½ of the first resonance frequency that is generally determined by the torsional rigidity, for example, such shape dimensions When the optical deflector set to 1 is used in an optical scanning device (optical writing device) of an image forming apparatus such as a printer or a copying machine, the image forming speed (process speed) is set to a normal one depending on the type of recording medium such as paper. / Even if the image forming apparatus can be switched to the 2nd speed, at a normal image forming speed (process speed), the deflection mirror is set to reciprocate at the second resonance frequency, and a thick paper sheet is fed. Normal 1/2 speed image shape For speed (process speed), thereby enabling the corresponding fact by setting to reciprocating movement of the deflection mirror in the first resonant frequency.

Schematic which shows the structure of the optical deflector which concerns on Embodiment 1 of this invention. The figure which modeled and approximated the optical deflector shown in FIG. 1 as a 2 degree-of-freedom system. (A) is the figure which showed the measurement result of the frequency characteristic of the displacement angle (deflection angle) of a movable mirror, (b) shows the measurement result of the deflection angle phase characteristic of the displacement angle (deflection angle) of the movable mirror 4. Figure. Schematic which shows the structure of the optical deflector which concerns on Embodiment 2 of this invention. The perspective view which shows the mirror substrate of the optical deflector which concerns on Embodiment 2 of this invention. Schematic which shows the structure of the optical deflector which concerns on the modification of Embodiment 2 of this invention. The disassembled perspective view which shows the structure of a mirror frame member and a frame member. The perspective view which shows the intermediate member at the time of producing a mirror frame member and a frame member. The figure which shows the apparatus for producing a mirror frame member and a frame member. The figure which shows the piezoelectric element as an external force generation means in Embodiment 2 of this invention. Schematic which shows the structure of the optical deflector which concerns on Embodiment 3 of this invention. (A), (b) is a figure which shows the 1st torsion beam member of the optical deflector which concerns on Embodiment 3 of this invention. Schematic which shows the structure of the optical deflector which concerns on Embodiment 4 of this invention. The perspective view which shows the back side of the mirror frame member in Embodiment 4 of this invention. The figure which shows the Lorentz force which generate | occur | produces with the magnetic field and coil current as external force generation means in Embodiment 4 of this invention. The figure which shows the structure of the drive circuit which applies a drive current to the coil in Embodiment 4 of this invention. Schematic which shows the structure of the coil in the modification of Embodiment 4 of this invention. Schematic which shows the structure of the optical scanning device which concerns on Embodiment 5 of this invention. Schematic which shows the structure of the image forming apparatus which concerns on Embodiment 6 of this invention. 18 is a flowchart showing a process speed switching selection operation according to the sixth embodiment of the present invention. (A) is a figure which shows the change state of the vibration amplitude of a movable mirror at the time of performing the process speed switching selection operation in Embodiment 6 of this invention, (b) is the process speed in Embodiment 6 of this invention. The figure which shows the change state of the fixing temperature at the time of performing switching selection operation | movement. Schematic which shows the structure of the image projector which concerns on Embodiment 7 of this invention. (A), (b) is the schematic which shows the structure of the conventional optical deflector. The figure which shows the frequency characteristic of the conventional optical deflector.

Hereinafter, the present invention will be described based on the illustrated embodiments.
<Embodiment 1>
FIG. 1 is a schematic diagram showing a configuration of an optical deflector according to Embodiment 1 of the present invention.

  In the optical deflector 1 according to the present embodiment shown in FIG. 1, reference numeral 2 denotes a mirror substrate, and a deflection mirror 4 that deflects light by reciprocally oscillating about a pair of first torsion beam members 3a and 3b as torsion rotation axes. Have. Both end sides of the first torsion beam members 3 a and 3 b are connected to the outer frame member 5. The outer frame member 5 is connected to the frame-shaped frame member 7 via second torsion beam members 6a and 6b provided on the same straight line as the first torsion beam members 3a and 3b. Thus, the mirror substrate 2 is held by the outer frame member 5 by the first torsion beam members 3a and 3b, and the outer frame member 5 is held by the frame member 7 by the second torsion beam members 6a and 6b. Yes.

  The mirror substrate (deflecting mirror 4 and first torsion beam members 3a and 3b) 2 is composed of a Si substrate, and the outer frame member 5, the second torsion beam members 6a and 6b, and the frame member 7 are metal members. It is comprised by. The outer frame member 5 is connected to an external force generating means 8 such as a piezoelectric element that applies a vibration force for reciprocally vibrating the outer frame member 5.

  The optical deflector 1 according to this embodiment is configured as described above, and drives the external force generating means 8 such as a piezoelectric element to generate vibrations in the outer frame member 5. A vibration force M is applied to the second torsion beam members 6 a and 6 b by the generated vibration, thereby causing the outer frame member 5 to reciprocate (reciprocate). The reciprocating vibration causes the deflecting mirror 4 to reciprocate (reciprocate and swing) using the first torsion beam members 3a and 3b as the torsion rotation shaft.

  In the optical deflector 1 of FIG. 1, when the resonance frequency of the deflecting mirror 4 has two resonance points and the resonance frequencies of the resonance points are f1 and f2, f1 is about 1.5 kHz and f2 is about 3 kHz. In this case, the shape dimensions of the mirror substrate (deflection mirror 4 and first torsion beam members 3a and 3b) 2 and outer frame member 5 are a1 = 7.5 mm, a2 = 5.5 mm, a3 = 4.5 mm, b1 = 10 mm, b2 = 8 mm, b3 = 1 mm.

  The length, width, thickness, and material of the deflection mirror 4, the first torsion beam members 3a and 3b, and the second torsion beam members 6a and 6b were set as shown in Table 1 below.

  In the optical deflector 1 shown in FIG. 1, the deflection angular frequency characteristic of the deflection mirror 4 was calculated as follows.

  FIG. 2 is a diagram obtained by modeling and approximating the optical deflector 1 shown in FIG. 1 as a two-degree-of-freedom system.

  In FIG. 2, K1 is the torsional rigidity of the pair of second torsion beam members 6a and 6b connected to the frame member 7, I1 is the moment of inertia of the outer frame member 5, and C1 is acting on the outer frame member 5. Viscosity resistance coefficient K2 is the torsional rigidity of the first torsion beam members 3a and 3b, I2 is the moment of inertia of the movable mirror 4, and C2 is the viscosity resistance coefficient acting on the deflection mirror 4.

  In the model shown in FIG. 2, the equations of motion are obtained by setting the angular displacements (deflection angles) of the outer frame member 5 and the deflection mirror 4 as θ1 and θ2, respectively. From the balance of forces, the following equations (1) and (2) are obtained. However, the torsional moment Mx acting on the fixed ends of the second torsion beam members 6a and 6b was considered as the excitation force.

I1 * θ1 + C1 * (θ1−θ2) + K1 * (θ1) = Mx (t) (1)
I2 * θ2 + C2 * (θ2−θ1) + K2 * (θ2−θ1) = 0 Equation (2)

  By solving the equations (1) and (2), each resonance frequency (f1, f2) of the deflection mirror 4 is obtained. Since the influence of the viscous resistance coefficients C1 and C2 on the resonance frequencies f1 and f2 is small, it is ignored and the displacement angles (running angles) θ1 and θ2 are obtained from the equations (1) and (2).

  Since equations (1) and (2) cannot be solved analytically, a solution is obtained by numerical calculation using numerical calculation software or the like.

  Then, with respect to the optical deflector 1 set to the dimensions as described above, when the excitation force M changing in a sine wave shape is applied from the external force generating means 8 to the outer frame member 5, the expression (1) , (2), displacement angles (runout angles) θ1 and θ2 were obtained.

  FIG. 3A is a diagram showing measurement results of the frequency characteristics of the obtained displacement angles (deflection angles) θ1 and θ2 of the deflection mirror 4. FIG. 3B is a diagram showing the measurement results of the deflection angle phase characteristics of the obtained displacement angles (deflection angles) θ1 and θ2 of the deflection mirror 4.

  As is clear from the measurement results shown in FIGS. 3A and 3B, the deflection mirror 4 of the optical deflector 1 shown in FIG. 1 has two resonance points, and the first resonance frequency of the deflection mirror 4. f1 was about 1.86 kHz, and the second resonance frequency f2 was 2.92 kHz.

  Thus, the optical deflector 1 of the present embodiment configured as described above includes the mirror substrate (deflection mirror 4 and first torsion beam members 3a and 3b) 2, the outer frame member 5, and the second torsion beam. By appropriately setting the shape dimensions of the members 6a and 6b, the two resonance frequencies of the deflecting mirror 4 have two resonance points, and f1 is approximately f2 / 2 with respect to the resonance frequencies f1 and f2. Can be set to

  Therefore, when this optical deflector 1 is used in an optical scanning device (optical writing device) of an image forming apparatus such as a printer or a copying machine, the image forming speed (process speed) is set to a normal 1 depending on the type of recording medium such as paper. Even in the case of an image forming apparatus that can be switched to the second speed, in the case of a normal image forming speed (process speed), the deflection mirror 4 is set to reciprocate at the second resonance frequency f2, and cardboard or the like is used. The normal half-speed image forming speed (process speed) to be fed can be dealt with by setting the deflection mirror 4 to reciprocately vibrate at the first resonance frequency f1.

  Further, in the optical deflector 1 of this embodiment, the mirror substrate (deflection mirror 4 and first torsion beam members 3a and 3b) 2 is composed of an Si substrate, and the outer frame member 5 and the second torsion beam member 6a. 6b and the frame member 7 are made of a metal member. Thereby, since the mirror substrate 2 and the outer frame member 5 having the second torsion beam members 6a and 6b can be separated, the shape of the mirror substrate 2 constituted by the Si substrate can be reduced. Therefore, the overall size of the optical deflector 1 can be reduced.

  Further, a plurality of mirror substrates 2 made of Si substrate can be cut out from one wafer by a semiconductor manufacturing process, and the outer frame member 5, the second torsion beam members 6a and 6b, and the frame member 7 are made of an inexpensive metal. By forming with a member, cost reduction can be achieved.

<Embodiment 2>
FIG. 4 is a schematic diagram showing the configuration of an optical deflector according to Embodiment 2 of the present invention.

  As shown in FIG. 4, the optical deflector 1 a according to this embodiment includes an outer frame member 11 provided with a mirror substrate 10 and external force generation means 13 a and 13 b, and these members are on the base substrate 14. Is installed.

  As shown in FIG. 5, the mirror substrate 10 includes a deflection mirror 15, a pair of first torsion beam members 16a and 16b integrally connected to both sides of the deflection mirror 15, and the first torsion beam member 16a. , 16b has a pair of holding members 17a, 17b integrally connected to both sides.

  The frame member 12 is integrally formed with a pair of second torsion beam members 18a and 18b connected so as to hold both sides of the outer frame member 11, and both end sides of the second torsion beam members 18a and 18b. A pair of arm members 19a, 19b connected and extending in both directions orthogonal to the second torsion beam members 18a, 18b, and a pair of fixing members 20a, formed at both ends of the second torsion beam members 18a, 18b, 20b.

  Each fixing member 20 a and 20 b is fixed on the base substrate 14. External force generating means 13a and 13b, which will be described later, are fixed to the lower surfaces of the arm members 19a and 19b, respectively.

  In addition, as shown in FIG. 6, you may connect a pair of arm member 19a, 19b so that it may extend to the one direction side of the orthogonal direction with respect to 2nd torsion beam member 18a, 18b.

  The outer frame member 11, the second torsion beam members 18a and 18b, the arm members 19a and 19b, and the fixing members 20a and 20b, which are integrally formed, are configured as shown in FIG.

  As shown in FIG. 7, in the present embodiment, these integral members have a four-layer structure of first to fourth frame members 12a, 12b, 12c, and 12d, and each of the first to fourth frame members 12a. ˜12d is made of a 0.05 mm thick metal plate made of SUS304.

  The outer frame member 11, the second torsion beam members 18a and 18b, the arm members 19a and 19b, and the fixing members 20a and 20b are integrally joined to the first to fourth frame members 12a to 12d, respectively. ing. The lowermost first frame member 12a is the first layer, and the uppermost fourth frame member 12d is the fourth layer. Openings 11a, 11b, 11c, and 11d are formed in the outer frame members 11 located in the first to fourth layers to secure a swinging space for the deflecting mirror 15 that swings back and forth.

  The outer frame member 11 in the third layer is formed with concave grooves 11e and 11f for positioning the holding members 17a and 17b of the mirror substrate 10. The outer frame member 11 in the fourth layer has a large opening 11d for weight reduction.

  Each of the first to fourth frame members 12a to 12d and each outer frame member 11 is first formed in each layer (in the figure, the first frame member 12d and the outer frame member in the fourth layer, for example, as shown in FIG. 8). 11) are sequentially formed by etching on the metal sheet member 21 so as to be connected to each other by the connecting member 22, and then the metal sheet member 21 of each layer is laminated and bonded to form the above-described four-layer frame member. 12 and the outer frame member 11 can be obtained.

  When the width and thickness dimensions of the second torsion beam members 18a and 18b are set to, for example, a width of 0.3 mm and a thickness of 0.2 mm, the aspect ratio (width / thickness) in this case is 1. 5 Although it is difficult to realize such a shape having a high aspect ratio with a single metal plate having a thickness of 0.2 mm, it can be realized by forming a thin metal plate with a laminated structure as in this embodiment. it can.

  In order to laminate and bond the metal sheet members 21 of each layer, for example, a diffusion bonding apparatus can be used as shown in FIG.

  As shown in FIG. 9, the metal sheet member 21 (first to fourth layers) constituting the first to fourth layers in the diffusion bonding apparatus 23 whose interior is evacuated (or filled with inert gas). 4 frame members 12a-12d) are positioned and laminated. And the metal sheet member 21 of each layer is joined by heating and pressurizing in this atmosphere, and utilizing the spreading | diffusion of the electron which arises on the joint surface of each layer.

  In this diffusion bonding, voids in the bonding surface disappear as the bonding proceeds. Diffusion bonding is a kind of solid phase bonding, and the bonding surfaces are brought into close contact with each other while removing the coating on the bonding surfaces at the time of bonding. As a result, the bonding members are in close contact with each other, and there is no gap. Therefore, the material properties such as fatigue strength show almost the same strength as the base material strength. Therefore, the second torsion beam members 18a and 18b having a four-layer structure manufactured by diffusion bonding are excellent in fatigue strength characteristics against vibration.

  As shown in FIG. 10, the external force generating means 13a, 13b of the present embodiment includes first piezoelectric elements 25a, 25b arranged on one end side of the upper surface of each piezoelectric element holding member 24a, 24b and the other end of the upper surface. The second piezoelectric elements 25c and 25d are arranged on the side. The first piezoelectric elements 25a and 25b and the second piezoelectric elements 25c and 25d are fixed to both sides of the lower surfaces of the arm members 19a and 19b, respectively.

  Each of the first and second piezoelectric elements 25a, 25b, 25c, and 25d is formed by stacking, for example, 10 to 20 layers of bulk PZT, and contracts in the thickness direction corresponding to the applied voltage. To do.

  An A-phase drive pulse signal is applied to the first piezoelectric elements 25a and 25b on one side from the common lead terminal 26a, and a common lead terminal is applied to the second piezoelectric elements 25c and 25d on the other side. The B-phase drive pulse signal is applied from 26b. The A-phase and B-phase drive pulse signals are 180 degrees out of phase with each other. Thus, the first piezoelectric elements 25a and 25b on one side driven by the A-phase driving pulse signal and the second piezoelectric elements 25c and 25d on the other side driven by the B-phase driving pulse signal are The phase of vibration is shifted 180 degrees.

  In this way, the first piezoelectric elements 25a and 25b on one side and the second piezoelectric elements 25c and 25d on the other side vibrate with a phase difference of 180 degrees, so that each first piezoelectric element on one side is vibrated. When the elements 25a and 25b are extended, the second piezoelectric elements 25c and 25d on the other side are displaced in the contracting direction. As a result, each of the first piezoelectric elements 25a, 25b on one side and each of the second piezoelectric elements 25c, 25d on the other side alternately expand and contract, so that the fixed arm members 19a, 19b The torsion beam members 18a and 18b are reciprocally oscillated (reciprocally oscillated).

  Then, the reciprocating vibration (reciprocating swing) of the second torsion beam members 18a and 18b causes the outer frame members 17a and 17b to generate reciprocating vibration. The reciprocating vibration causes the deflection mirror 15 to reciprocate (reciprocate and swing) using the first torsion beam members 16a and 16b as the torsional rotation shaft.

  Also in the optical deflector 1a of the present embodiment described above, similarly to the first embodiment, the mirror substrate (deflecting mirror 15 and first torsion beam members 16a and 16b) 10, the outer frame member 11, and the second torsion beam. By appropriately setting the shape dimensions of the members 18a and 18b, the two resonance frequencies of the deflecting mirror 15 have two resonance points, and f1 is approximately f2 / 2 with respect to the resonance frequencies f1 and f2. Can be set to

  Therefore, when this optical deflector 1a is used in an optical scanning device (optical writing device) of an image forming apparatus such as a printer or a copying machine, the image forming speed (process speed) is set to a normal 1 depending on the type of recording medium such as paper. Even in an image forming apparatus that can be switched to the second speed, in the case of a normal image forming speed (process speed), the deflection mirror 15 is set to reciprocate at the second resonance frequency f2, and cardboard or the like is used. The normal half-speed image forming speed (process speed) to be fed can be dealt with by setting the deflecting mirror 15 to reciprocately vibrate at the first resonance frequency f1.

  Further, in the optical deflector 1a of the present embodiment, the mirror substrate (deflection mirror 15 and first torsion beam members 16a and 16b) 10 is composed of an Si substrate, and the outer frame member 11 and the second torsion beam member 18a. 18b, arm members 19a and 19b, and fixing members 20a and 20b are formed by laminating thin metal plates. Thereby, since the mirror substrate 10 and the outer frame member 11 having the second torsion beam members 18a and 18b can be separated, the shape of the mirror substrate 10 constituted by the Si substrate can be reduced. Therefore, the overall size of the optical deflector 1a can be reduced.

<Embodiment 3>
In the second embodiment, as shown in FIG. 5, the pair of linear first torsion beam members 16 a and 16 b are connected to both sides of the deflection mirror 15. In the present embodiment, for example, FIG. As shown in FIG. 11, both sides of the deflection mirror 15 may be held by a pair of first torsion beam members 27 a and 27 b having a plurality of linear portions and bent portions. Other configurations are the same as those of the optical deflector of the second embodiment shown in FIG.

  As shown in FIGS. 11 and 12A, the first torsion beam members 27a and 27b are formed in a spring shape by being folded by a plurality of straight portions and bent portions, and are symmetrical with respect to the central axis A. It has become. As shown in FIG. 12B, the first torsion beam members 27a and 27b have three long beam portions 27a1, 27a2, and 27a3 and two short beam portions 27a4 and 27a5 along the central axis A direction. In addition, four middle beam portions 27a6, 27a7, 27a8, and 27a9 are provided in a direction orthogonal to the direction of the central axis A. One short beam portion 27a4 is connected to the mirror holding member 17a, and the other short beam portion 27a5 is connected to the deflection mirror 15. In addition, although FIG.12 (b) has shown the 1st torsion beam member 23a, the other 1st torsion beam member 23b is also comprised similarly.

  In the first torsion beam member 27a shown in FIG. 12B, for example, the length a of the two long beam portions 27a1 and 27a3 on both outer sides is 1 mm, and the length b of the central long beam portion 27a2 is 0. When the lengths c and d of the 8 mm and the two short beam portions 27a4 and 27a5 are set to 0.2 mm, it can be regarded as being substantially equivalent to a linear torsion beam member having a length of about 3 mm along the central axis A direction. it can. Thus, by forming the first torsion beam members 27a and 27b so as to have a plurality of straight portions and bent portions, the length is shortened compared to the case where the first torsion beam members 27a and 27b are formed in a straight shape. Miniaturization can be achieved.

<Embodiment 4>
FIG. 13 is a schematic diagram illustrating a configuration of an optical deflector according to Embodiment 4 of the present invention.

  In the optical deflector of the second embodiment, a piezoelectric element is used as the external force generating means. However, in the optical deflector 1b of the present embodiment, a pair of permanent magnets and a current are applied as shown in FIG. The external force generating means is constituted by the coil. Other configurations are the same as those of the optical deflector according to the second embodiment, and redundant description is omitted.

  As shown in FIG. 13, the optical deflector 1b of the present embodiment is disposed on both end sides of the mirror frame member 11 in the direction orthogonal to the second torsion beam members 18a and 18b (on both ends in the longitudinal direction of the outer frame member 11). Are arranged with a pair of permanent magnets 30a, 30b constituting external force generating means. Each permanent magnet 30a, 30b is fixed on the base substrate 14 so that the S pole and the N pole face each other. Thereby, the magnetic field from the permanent magnet 30a to the permanent magnet 30b is formed.

  Further, as shown in FIG. 14, on the back side of the outer frame member 11, a coil 31 constituting external force generating means is provided along the periphery of the opening edge portion 11 g for forming the swinging space of the deflection mirror 15. It arrange | positions so that it may go around in multiple times. Lead wires 32a and 32b are connected to the coil 31 along the longitudinal direction of the second torsion beam members 18a and 18b. A drive circuit 40 (see FIG. 16) is connected to one side of the terminals 33a and 33b of the lead wires 32a and 32b.

  Then, as shown in FIG. 15, by applying a sinusoidal drive current I to the coil 31, Lorentz forces F1 and F2 are generated by the interaction between the generated magnetic field and the sinusoidal drive current I flowing in the coil 31. Each acts in the direction of the arrow. Then, when the direction of the drive current I is reversed, the directions of the Lorentz forces F1 and F2 are reversed, thereby causing the outer frame member 11 to reciprocate with the second torsion beam members 18a and 18b as the oscillation center. The reciprocating vibration causes the deflection mirror 15 to reciprocate (reciprocate and swing) using the first torsion beam members 16a and 16b as the torsional rotation shaft.

  As shown in FIG. 16, the drive circuit 40 that applies the drive current I to the coil 31 includes a control unit 41, a D / A converter 42, an OA amplifier 43, and the like.

  In the present embodiment, as shown in FIG. 17, the coil 31 is integrated with the flexible wiring board 44 joined around the opening edge 11 g on the back side of the outer frame member 11 so as to circulate a plurality of times. It may be provided. The flexible wiring board 44 is provided with lead wires 32a and 32b from the coil 31 and terminals 33a and 33b.

  As described above, by using the flexible wiring board 44 integrally provided with the coil 31, it is easy to attach the outer frame member 11 to the back surface, and the efficiency of the attaching work can be improved.

<Embodiment 5>
FIG. 18 is a schematic diagram illustrating a configuration of an optical scanning device according to the fifth embodiment of the present invention. The optical scanning device 50 according to the present embodiment includes, for example, the optical deflector 1b according to the fourth embodiment. The optical deflector 1b has the same configuration as that of the optical deflector of the fourth embodiment shown in FIG.

  As shown in FIG. 18, in the optical scanning device 50 of the present embodiment, the laser light beam emitted from the semiconductor laser 11 as the light source passes through the optical system including the coupling lens 52, the cylinder lens 53, and the incident mirror 54. Then, it enters the surface of the movable mirror 15 of the optical deflector 1b. The incident laser light beam is reflected on the surface of the movable mirror 15 and imaged in a spot shape as a scanning spot on the scanning surface 56 by an imaging optical system (correction optical system) 55 including an fθ lens.

  Then, the scanning spot moves in the main scanning direction X in accordance with the reciprocal vibration (reciprocal rocking) of the deflection mirror 15 by the Lorentz forces F1 and F2 whose directions are reversed as described above. The frequency of the sinusoidal drive current I flowing in the coil 31 can be switched by inputting a frequency switching signal to the control unit 41 of the drive circuit 40 shown in FIG. Thereby, the optical scanning device 40 can switch to one of the scanning frequencies f1 and f2 selected in advance.

<Embodiment 6>
FIG. 19 is a schematic diagram illustrating a configuration of an image forming apparatus (in this embodiment, a color laser printer) including an optical scanning device according to Embodiment 6 of the present invention.

  As shown in FIG. 19, the image forming apparatus (laser printer) 60 according to the present embodiment includes image forming sections 61, 62, 63, and 64 of four colors of cyan, magenta, yellow, and black. Then, in each of the image forming units 61 to 64, for example, the laser light beams modulated by the recording signals on the photosensitive drums 65 of the corresponding image forming units 61 to 64 by the respective optical scanning devices 40 described in the fifth embodiment. An electrostatic latent image is formed by performing optical writing scanning according to, and the electrostatic latent images formed on the respective photosensitive drums 65 are developed into toner images of different colors, and the toner images are superimposed on the transfer belt 66. It is a tandem method of transferring.

  The optical scanning device 40 has the same configuration as that of the optical scanning device according to the fifth embodiment illustrated in FIG.

  The transfer belt 66 is supported and moved by a driving roller 67 and two driven rollers 68 and 69. The photosensitive drums 65 of the image forming units 61 to 64 are arranged at equal intervals along the moving direction. ing.

  Around each photosensitive drum 65, there are a charger 70 that charges the surface of the photosensitive drum 65, a developing device 71 that replenishes toner corresponding to each color of yellow, magenta, cyan, and black, and the photosensitive drum 65. A cleaning device 72 is provided for scraping and storing the residual toner after transfer of the toner with a blade.

  During an image forming operation, each optical scanning device 40 as a writing device is shifted by using a signal from a sensor 73 that detects a registration mark (not shown) formed at the end of the transfer belt 66 as a trigger to shift the writing timing in the sub-scanning direction. As a result, the electrostatic latent images of the respective colors are written, and the developing device 71 puts toner on the transfer belt 66 and sequentially superimposes the images.

  The paper P is supplied from the paper supply tray 74 by the paper supply roller 75, is sent out by the registration roller 76 in accordance with the timing of image formation of the fourth color, and is simultaneously transferred from the transfer belt 66 by the transfer unit 77. The sheet on which the toner image is transferred is sent to the fixing nip between the fixing roller 79 and the pressure roller 80 by the conveying belt 78, and after the toner image is fixed, the sheet is discharged to the discharge tray 82 by the discharge roller 81.

  In the image forming apparatus 60 of the present embodiment, a recording medium detection sensor 83 that detects the type of paper to be fed is disposed adjacent to the registration roller 76, and is detected by the recording medium detection sensor 83. The process speed can be switched according to the paper type of the paper. The image forming apparatus 60 of this embodiment can select a normal process speed and a normal 1/2 speed process speed.

  The process speed switching selection operation will be described below with reference to the flowchart shown in FIG.

  In the initial state, the process speed of the image forming apparatus 60 is set to the standard speed (1/1 speed), and the fixing temperature by heating the fixing roller 79 is set to 180 ° C. in accordance with the standard speed (step). S1, S2).

  In the image forming operation described above, the paper type fed by the recording medium detection sensor 83 is determined. At this time, if it is determined that the recording medium being fed is thick paper (step S3: YES), the heater of the fixing roller 79 is heated based on a control signal from a control unit (not shown) of the image forming apparatus 60. The energization to (not shown) is turned off, and at the same time, the energization to each optical scanning device 40 is simultaneously turned off (steps S4 and S5). When it is determined in step S3 that the recording medium being fed is a normal sheet (step S3: NO), the standard process speed set in steps S1 and S2 and the fixing temperature of 180 ° C. Then, the image forming operation is performed.

  As shown in FIG. 21A, when the energization to the heater (not shown) of the optical scanning device 40 and the fixing roller 79 is turned off at time T1, the deflection mirror 15 of the optical scanning device 40 (see FIG. 18). The vibration amplitude of dampens with time. Further, as shown in FIG. 21B, the temperature of the fixing roller 79 (fixing temperature) also decreases from a2 (180 ° C.).

  Then, as shown in FIGS. 21A and 21B, at the time T0 when the fixing temperature approaches a1 (150 ° C.), the process speed is set to 1 at the standard speed from the control unit (not shown) of the image forming apparatus 60. A command to set to / 2 and a command to set the scanning speed of the optical scanning device 40 (reciprocating vibration of the deflecting mirror 15 (see FIG. 18)) to 1/2 of the standard speed are issued (steps S6 and S7). By this command, the moving speeds of the photosensitive drum 65, the transfer belt 66, the conveyance belt 78, and the like are set to 1/2 the standard speed. Since the inertia of the drive system such as the photosensitive drum 65, the transfer belt 66, and the conveyance belt 78 is large, a predetermined time is required until the speed becomes 1/2 of the standard speed.

  When the process speed is switched to 1/2 of the standard speed at time T0 after a predetermined time has elapsed (step S8: YES), the fixing temperature is controlled to be set to a1 (150 ° C.) (step S9). ), The image forming operation is performed in a state where the process speed and the scanning speed of the optical scanning device 40 (reciprocating vibration of the deflection mirror 15 (see FIG. 18)) are switched to 1/2 of the standard speed.

  Note that the time constant of the deflecting mirror 15 (see FIG. 18) of the optical scanning device is approximately 0.1 (seconds), which is the time constant of the driving system such as the photosensitive drum 65, the transfer belt 66, and the conveying belt 78. Small enough compared. Therefore, at time T1, the vibration of the deflection mirror 15 (see FIG. 18) of the optical scanning device 40 is a steady vibration.

  As described above, the image forming apparatus 60 of the present embodiment includes the optical scanning device 40 described in the fifth embodiment, for example. Therefore, when the process speed is switched to 1/2 of the standard speed, the light is accordingly generated. The reciprocating vibration (reciprocating rocking) of the deflection mirror 15 (see FIG. 18) of the scanning device 40 can be switched to 1/2 of the standard speed to perform the image forming operation.

  In addition, since the entire optical deflector can be reduced in size as described in the above-described embodiment, the entire image forming apparatus 60 can also be reduced in size.

<Embodiment 7>
FIG. 22 is a schematic diagram illustrating a configuration of an image projection apparatus including the optical scanning device according to the seventh embodiment of the present invention.

  As shown in FIG. 22, the image projection apparatus 90 according to the present embodiment has different wavelengths emitted from a light source 91a made of a red semiconductor laser, a light source 91b made of a blue semiconductor laser, and a light source 91c made of a green semiconductor laser. Are made incident from different surfaces of the color synthesizing element 92 and concentrated on one optical path.

  The multiple interference film surfaces of the color combining element 92 are surfaces through which only the oscillation wavelengths of the respective light sources 91a to 91c are transmitted or reflected, and are combined. Then, the beam waist of the light beam emitted from the color synthesizing element 92 is collimated through the collimator lens 93 so as to come near the projection surface 96 by the optical scanning devices 94 and 95. As the optical scanning devices 94 and 95, for example, the optical scanning device of the fifth embodiment shown in FIG. 18 can be used.

  That is, after applying light to the optical scanning device 94 that performs optical scanning in the horizontal direction, a light beam is applied to the optical scanning device 95 in charge of vertical scanning to perform two-dimensional scanning. As a result, a color image is displayed in which pixels 97 in which light pulses of three colors overlap each other on the projection surface 96.

1, 1a, 1b Optical deflector 2, 10 Mirror substrate 3a, 3b, 16a, 16b, 27a, 27b First torsion beam member 4, 15 Deflection mirror 5, 11 Outer frame member 6a, 6b, 18a, 18b Second Torsion beam member 7 frame member 25a, 25b first piezoelectric element 25c, 25d second piezoelectric element 30a, 30b permanent magnet 31 coil 40 drive circuit 50 optical scanning device 60 image forming apparatus (laser printer)
90 Image projection device

Special table 2008-505367 JP 2005-181394 A

Claims (13)

A mirror substrate having a deflecting mirror for deflecting a light beam from a light source by reciprocally vibrating a pair of first torsion beam members joined to both sides as a torsional rotation axis; and an outer frame member for holding the mirror substrate; A pair of second torsion beam members provided on the same straight line as the first torsion beam member, both outer sides being fixedly held and both inner sides being joined to both sides of the outer frame member, and the outer frame An external force generating means for vibrating the member or the pair of second torsion beam members,
By applying an oscillating force from the external force generating means to the outer frame member or the pair of second torsion beam members, the pair of second torsion beam members and the first torsion beam member are twisted and rotated. An optical deflector for reciprocally vibrating the deflection mirror,
During the reciprocating vibration of the deflection mirror, the first resonance frequency determined approximately by the inertia of the outer frame member and the torsional rigidity of the pair of second torsion beam members is the inertia of the deflection mirror and the first torsion beam member. An optical deflection characterized in that the shape and dimensions of the deflection mirror and the first and second torsion beam members are set so as to be approximately ½ of the second resonance frequency which is generally determined by the torsional rigidity of vessel.   The mirror substrate is made of an Si substrate, the outer frame member and the second torsion beam member are made of a metal material, and the mirror substrate is bonded to the outer frame member. The optical deflector according to claim 1.   3. The optical deflector according to claim 2, wherein the outer frame member and the pair of second torsion beam members are configured by laminating metal plate materials.   4. The optical deflector according to claim 3, wherein the outer frame member and the pair of second torsion beam members are formed by laminating and joining metal plate materials by diffusion bonding.   The optical deflector according to claim 1, wherein the pair of first torsion beam members are formed in a folding spring shape having a plurality of linear portions and bent portions.   A pair of arm members extending in a direction orthogonal to the second torsion beam member are provided in the vicinity of both outer sides where the pair of second torsion beam members are fixedly held, and the external force generating means is provided on the pair of arm members. The optical deflector according to claim 1, wherein the optical deflector is provided.   The external force generation means is a piezoelectric element that expands and contracts in the thickness direction corresponding to an applied voltage, and the piezoelectric elements are provided at both ends of the pair of arm members, respectively. Light deflector.   A drive signal having a phase difference of 180 degrees is applied to each piezoelectric element provided at both ends of the one arm member and each piezoelectric element provided at both ends of the other arm member. 8. The optical deflector according to claim 7, wherein   The external force generating means includes a coil disposed on the outer frame member and a pair of permanent magnets disposed on both sides of the outer frame member in a direction orthogonal to the pair of first torsion beam members, 2. The outer frame member is vibrated by a Lorentz force generated by an interaction with a magnetic field formed between the pair of permanent magnets when a sinusoidal current is applied to the coil. An optical deflector as described in 1.   The optical deflector according to claim 9, wherein the coil is integrally formed on a flexible substrate fixed to a back surface of the outer frame member.   An optical scanning device comprising the optical deflector according to claim 1.   An image forming apparatus comprising the optical scanning device according to claim 11.   An image projection apparatus comprising the optical scanning device according to claim 11.

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