JP2015210451A - Vibration element, optical scanner, image forming apparatus, image projection device, and optical pattern reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration element that has a simpler configuration and can reduce manufacturing cost.SOLUTION: There are formed a power feeding path that includes a first torsion beam 101, second torsion beam 102, first conductive member 201, and first electrode 501, and a power feeding path that includes a third torsion beam 103, fourth torsion beam 104, second conductive member 202, and second electrode 502. A first magnet group is arranged that generates a magnetic field acting on a current flowing through the first torsion beam 101 and a current flowing through the fourth torsion beam 104. A second magnet group is arranged that generates a magnetic field acting on a current flowing through the second torsion beam 102 and a current flowing through the third torsion beam 103. With this configuration, a vibration part 21 causes torsional vibration.

Description

  The present invention relates to a vibration element used for light scanning and the like, and an optical scanning device, an image forming apparatus, an image projection apparatus, and an optical pattern reading apparatus using the vibration element.

  In recent years, MEMS (Micro Electro Mechanical Systems) type vibration elements have been put into practical use and applied to laser beam printers, laser projectors, and the like. The vibration element has a vibrator configured to support the mirror with a torsion bar (torsion beam), and is driven at a drive frequency near the resonance frequency determined by the moment of inertia of the mirror and the spring constant of the torsion beam. The In an optical scanning device using such an oscillating element, an arc sine lens or the like that corrects the focal length according to the scanning angle so that the beam waist of the laser beam is positioned on a predetermined projection surface without depending on the scanning angle This optical system is required.

  Focal length correction can also be realized by a variable focus mirror. According to Patent Document 1, an optical information reading device is proposed in which a variable focus mirror is arranged in an optical system of an optical scanning device and a beam waist scanning position can be changed.

Japanese Patent Laid-Open No. 07-121645

  If a variable focus mirror is arranged instead of an optical system such as an arc sine lens, the optical components related to the correction of the focal length can be simplified. However, if the variable focus mirror is simply arranged, the optical scanning device becomes large.

  In order to reduce the size of the optical scanning device, it is conceivable to integrate the scanning mirror and the variable focus mirror. That is, the mirror itself supported by the torsion beam of the vibration element is used as a variable focus mirror. However, this has the following problems.

  In order to use a mirror supported by a torsion beam as a variable focus mirror, it is necessary to dispose a driving source such as a piezoelectric element on the back surface or the periphery of the mirror member in order to deform the mirror. Furthermore, in order to drive the piezoelectric element, a wiring for supplying power to the drive source from the outside of the vibration element is required. However, in the case of wiring using a wire or the like, there is a problem of disconnection or separation of the joint due to high-speed vibration of the mirror. On the other hand, it is also conceivable to realize wiring by forming a conductive layer on the torsion beam. However, since the maximum stress is applied to the torsion beam at the time of vibration, peeling of the conductive layer can occur particularly in applications where the torsion angle per unit length of the torsion beam is large. When a wide scanning angle is required, it is necessary to lengthen the torsion beam. When it is necessary to reduce the size of the vibration element, it is necessary to narrow the scanning angle. That is, there is a problem that wide-angle scanning and miniaturization cannot be achieved. In addition, in a torsion beam with a wiring layer formed on the surface, the Q value of vibration decreases due to the presence of a layer with a large amount of internal friction on the surface with the largest amount of deformation, or abnormal vibration occurs due to deformation of the torsion beam due to film stress. May occur. A decrease in Q value leads to an increase in power consumption and a decrease in scanning angle. Abnormal vibrations cause fluctuations in the scanning speed of the light, fluctuations in the focal point in the sub-scanning direction, and the like. It cannot be formed accurately at the position.

  Aside from these problems, two drive means are required, such as a drive means for the variable focus mirror and a drive means for rotational vibration for optical scanning. This complicates the configuration of the optical scanning device and increases the manufacturing cost.

  Accordingly, an object of the present invention is to provide a vibration element that has a simpler configuration and can reduce manufacturing costs.

The present invention is, for example,
A piezoelectric material having a first electrode and a second electrode;
A first conductive member coupled to the first electrode;
A conductive first torsion beam and a second torsion beam coupled to the first conductive member;
A second conductive member coupled to the second electrode;
A conductive third torsion beam and a fourth torsion beam coupled to the second conductive member;
A mirror member fixed to the piezoelectric material or the first conductive member and having a curvature that varies with the deformation of the piezoelectric material;

Have
The piezoelectric material includes the first torsion beam, the second torsion beam, the power supply path including the first conductive member and the first electrode, the third torsion beam, and the fourth torsion beam. The vibrating element is deformed according to a voltage applied through the power supply path including the second conductive member and the second electrode.

  ADVANTAGE OF THE INVENTION According to this invention, the vibration element which can reduce manufacturing cost with a simpler structure is provided.

It is a figure which shows an example of a vibration element. It is a figure which shows an example of a vibration element. It is a figure which shows an example of a drive signal. It is a figure which shows an example of a vibration element. It is a figure which shows an example of a vibration element. It is a top view explaining operation | movement of an optical scanning device. It is a graph which shows the drive signal of an optical scanning device. It is a top view explaining operation | movement of an optical scanning device. It is a graph explaining operation | movement of an optical scanning device. It is a graph explaining operation | movement of an optical scanning device. 1 is a plan view illustrating an example of an image forming apparatus. It is a top view which shows an example of an image projector. It is a top view which shows an example of an optical pattern reader.

[Optical scanning device]
FIG. 1A illustrates the vibration element 11 constituting the optical scanning device. FIG. 1B shows a configuration example of the vibration element 11. The vibration element 11 includes a vibration portion 21 and a first torsion beam 101, a second torsion beam 102, a third torsion beam 103, and a fourth torsion having conductivity that support the vibration portion 21 so as to be able to swing (rotate and vibrate). A beam 104 is provided. The piezoelectric material 401 has at least a first electrode 501 and a second electrode 502. According to FIG. 1B, the first electrode 501 is provided on the first surface side of the piezoelectric material 401, and the second electrode 502 is provided on the second surface side of the piezoelectric material 401. A first conductive member 201 is coupled to the first electrode 501. The first conductive member 201 is, for example, a circular flat plate. A conductive first torsion beam 101 and a second torsion beam 102 are coupled to the first conductive member 201. In this example, the first torsion beam 101 is coupled to one end side of the first conductive member 201, and the second torsion beam 102 is coupled to the other end side of the first conductive member 201. .

  The second conductive member 202 is coupled to the second electrode 502. The second conductive member 202 is a frame having a space in the center, for example. Such a frame is advantageous in terms of weight reduction. Note that the second conductive member 202 may also be a circular flat plate. A conductive third torsion beam 103 and a fourth torsion beam 104 are coupled to the second conductive member 202. In this example, the third torsion beam 103 is coupled to one end side of the second conductive member 202, and the fourth torsion beam 104 is coupled to the other end side of the second conductive member 202. .

  The mirror member 301 is fixed to the piezoelectric material 401 via the first conductive member 201. The piezoelectric material 401 includes the first torsion beam 101, the second torsion beam 102, the first conductive member 201, and the first electrode 501, the third torsion beam 103, and the fourth torsion beam 104. And deformed according to the voltage applied through the power supply path including the second conductive member 202 and the second electrode 502. That is, the piezoelectric material 401 is deformed by applying a voltage between the first electrode 501 and the second electrode 502 of the piezoelectric material 401. The curvature of the mirror member 301 changes with the deformation of the piezoelectric material 401.

  The first magnet group includes a first magnet 601 disposed along the first torsion beam 101 and a fourth magnet 604 disposed along the fourth torsion beam 104. The first magnet group generates a magnetic field that acts on the current flowing through the first torsion beam 101 and the fourth torsion beam 104. The second magnet group includes a second magnet 602 disposed along the second torsion beam 102 and a third magnet 603 disposed along the third torsion beam 103. The second magnet group generates a magnetic field that acts on the current flowing through the third torsion beam 103 and the second torsion beam 102. The second magnet group includes a first magnet 601 and a second magnet 602. The Lorentz force that causes torsional vibration is generated by the action of the current and the magnetic field.

  One end of each of the first torsion beam 101, the second torsion beam 102, the third torsion beam 103, and the fourth torsion beam 104 is fixed to a housing or the like, and the other is fixed to a conductive member. Has been. The first torsion beam 101 and the fourth torsion beam 104 are arranged so as to be parallel to each other, and these are torsionally deformed as an integral torsion beam. Further, the second torsion beam 102 and the third torsion beam 103 are arranged so as to be parallel to each other, and these are torsionally deformed as an integral torsion beam. Thereby, the reflection direction of the mirror member 301 in the vibration part 21 is changed, and optical scanning is performed.

  FIG. 2 is a cross-sectional view of the optical scanning device 1. The drive signal generated by the drive circuit 801 is applied to the first torsion beam 101, the second torsion beam 102, the third torsion beam 103, and the fourth torsion beam 104. The voltage applied to the first torsion beam 101 is V1, the voltage applied to the second torsion beam 102 is V2, and the voltage applied to the third torsion beam 103 is V3. The voltage applied to the fourth torsion beam 104 is V4. A current I1 corresponding to the potential difference (V1-V2) is applied from the first twisted beam 101 to the second twisted beam 102 through the first conductive member 201. This is the first power supply path. Further, a current I2 corresponding to the potential difference (V3-V4) is supplied from the third twisted beam 103 to the fourth torsion beam 104 through the second conductive member 202. This is the second power supply path. A magnetic field H <b> 1 is generated by the first magnet 601 and the fourth magnet 604. The second magnet 602 and the fourth magnet 603 generate a magnetic field H2. Currents I1 and I2 act on the magnetic fields H1 and H2. As a result, a twisting torque is generated in the set of the first torsion beam 101 and the fourth torsion beam 104. Similarly, a torsion torque is generated in the set of the third torsion beam 103 and the second torsion beam 102. As a result, the rotational vibration of the vibration unit 21 is excited.

  The potential of the first conductive member 201 is (V1 + V2) / 2, respectively. The potential of the second conductive member 202 is (V3 + V4) / 2. These potential differences are generated between the first electrode 501 and the second electrode 502, and an electric field E is generated inside the piezoelectric material 401. The piezoelectric material 401 expands and contracts according to the magnitude of the electric field E, the curvature of the mirror member 301 changes, and the focus and curvature of the mirror member 301 become variable. That is, the vibration part 21 functions as a variable curvature mirror part. By controlling the curvature of the mirror member 301, the position of the scanning beam with respect to the beam waste can be adjusted.

  FIG. 3 shows an example of a drive signal generated by the drive circuit 801. A signal having a frequency twice that of a certain frequency signal S1 is defined as S2. Note that S1 also represents the amplitude of the signal S1. Similarly, S2 also represents the amplitude of the signal S2. The voltage V1 described above is (S1 + S2) / 2, the voltage V2 is (−S1 + S2) / 2, the voltage V3 is (S1−S2) / 2, and the voltage V4 is (−S1−S2) / 2. is there. At this time, the potential difference (V2-V1) or (V4-V3) becomes the signal S1, and the current I corresponding to the signal S1 is passed through the torsion beam. In addition, the potential difference between the first conductive member 201 and the second conductive member 202 is S2, and a signal having a frequency twice as high as the current passed through the torsion beam is applied to the piezoelectric material 401. With the drive signal shown in FIG. 3, the optical scanning device 1 can realize a change in curvature at a frequency twice as high as the optical scanning frequency.

  According to the present embodiment, the first torsion beam 101, the second torsion beam 102, the third torsion beam 103, the fourth torsion beam 104, the first conductive member 201, and the second conductive member 202. Functions as wiring. Therefore, no wiring is required, and there is no wiring disconnection problem. In addition, since there is no junction between the wiring and the electrode, there is no difference in physical characteristics between the junction and the surrounding area, and the curvature can be easily set stably.

[Vibration elements with other structures]
FIG. 4 shows the vibration element 12. A description of portions common to the vibration element 11 is omitted. Also in the vibration element 12, the first electrode 501 is provided on the first surface side of the piezoelectric material 401, and the second electrode 502 is provided on the second surface side of the piezoelectric material 401. The mirror member 301 is fixed to the first conductive member 201. The first conductive member 201 is electrically connected to the first electrode (that is, they are conductive). The second electrode 502 is electrically connected to the second conductive member 202 and fixed.

  The first torsion beam 101 is coupled to one end side of the first conductive member 201, and the second torsion beam 102 is also coupled to one end side of the first conductive member 201. Similarly, the third torsion beam 103 is coupled to one end side of the second conductive member 202, and the fourth torsion beam 104 is also coupled to one end side of the second conductive member 202. In this way, the first torsion beam 101 and the second torsion beam 102 are arranged in parallel. Further, the third torsion beam 103 and the fourth torsion beam 104 are arranged in parallel. That is, four parallel beams function as an integral torsion beam group.

  The first magnet 601 is disposed along the first torsion beam 101 and the third torsion beam 103. The second magnet 602 is disposed along the second torsion beam 102 and the fourth torsion beam 104. A current flowing through the first torsion beam 101 and the second torsion beam 102 acts on the magnetic field H generated by the first magnet 601 and the second magnet 602, and the third torsion beam 103 and the fourth torsion beam. The electric current which flows into 104 acts. This generates torsional vibration.

  The vibration element 12 has a configuration in which the vibration portion 21 is supported only on one side (cantilever support structure). However, since the torsion beam is composed of four parallel beams, the bending rigidity is high. In addition, the resonance frequency is also high in a mode in which bending vibration occurs in a direction perpendicular to the mirror member 301 and a mode in which bending vibration occurs in a parallel direction. Therefore, it is difficult for abnormal vibrations due to flexural vibrations to occur. In addition, there is an advantage that the overall size can be reduced and the number of magnets can be reduced.

  FIG. 5A is a perspective view showing the vibration element 13. FIG. 5B is a diagram illustrating a configuration example of the vibration element 13. FIG. 5C is a cross-sectional view illustrating a configuration example of the vibration unit 21. A description of portions common to the vibration element 11 or the vibration element 12 is omitted. As shown in FIG. 5B, the electrode provided on the first surface side of the piezoelectric material 401 is divided into a first electrode 501 and a second electrode 502. In accordance with the division of the electrodes, the conductive member provided on the first surface side of the piezoelectric material 401 is also divided into a first conductive member 201 and a second conductive member 202. It is assumed that the shape of the divided electrode and the shape of the conductive member are basically the same. The mirror member 301 is fixed to the first conductive member 201 and the second conductive member 202. A third electrode 503 is provided on the second surface side of the piezoelectric material 401.

  The first magnet group includes a first magnet 601 disposed along the first torsion beam 101 and a fourth magnet 604 disposed along the fourth torsion beam 104. The first magnet group generates a magnetic field that acts on the current flowing through the first torsion beam 101 and the fourth torsion beam 104. The second magnet group includes a second magnet 602 disposed along the second torsion beam 102 and a third magnet 603 disposed along the third torsion beam 103.

  As shown in FIG. 5C, a portion of the piezoelectric material 401 where the first electrode 501 and the third electrode 503 face each other, a portion where the second electrode 502 and the third electrode 503 face each other, Then, they are polarized in different directions. The first electrode 501 and the third electrode 503 form a first capacitor, and the second electrode 502 and the third electrode 503 form a second capacitor. These capacitors are connected in series. By applying a voltage between the first electrode 501 and the second electrode 502, an electric field E is generated between the electrode plates, and the piezoelectric material 401 expands and contracts to change the curvature of the mirror member 301. Such polarization is realized by applying an electric field higher than the coercive electric field of the piezoelectric material 401 between the first electrode 501 and the second electrode 502 formed separately when the piezoelectric material 401 is manufactured. In this configuration, there is nothing arranged on the second surface side of the piezoelectric material 401, and an ideal unimorph structure is realized by the piezoelectric material 401 and other members. Therefore, the optical scanning device 1 can be realized in which the curvature of the mirror member 301 is almost uniform and the beam shape of the reflected light is hardly distorted.

[Materials]
The material used for the torsion beam is not particularly limited as long as it is a conductive material such as a resin material mixed with carbon in addition to a metal material, but from the viewpoint of repeated durability and impact resistance, SUS301 and SUS631. Metal materials such as stainless steel, copper alloy, and Co (cobalt) -Ni (nickel) base alloy may be employed. Among these, age-hardening type Co-Ni based alloys such as Co-Ni-Cr (chromium) -Mo (molybdenum) alloys represented by SPRON (registered trademark) 510 have a particularly high fatigue limit and are subjected to repeated stress. Is convenient. In addition, since the Co—Ni-based alloy has high heat resistance and corrosion resistance, it is unlikely that energization or heat generated by it will affect the material characteristics, which is also appropriate for an optical scanning apparatus that energizes a torsion beam. Let's go. In addition, the Co—Ni base alloy has a feature that the internal friction is small, and has a high Q value when the vibration elements 11 to 13 are caused to resonate and rotationally vibrate. In the case of using a Co—Ni—Cr—Mo alloy, after a work hardening treatment is performed by rolling or drawing at a working rate of 50% or more, more preferably 90% or more, shape processing is performed, Age hardening treatment may be performed at a temperature of about 600 ° C. The final Young's modulus and hardness can be adjusted by the processing rate and the aging heat treatment temperature and time. For the shape processing, etching processing, press processing, laser processing, wire electric discharge processing or the like can be used. In work hardening processing and shape processing, depending on the finish, internal friction near the surface may increase and the Q value of the vibration element may decrease. In such a case, it is better to perform an etching process before age-hardening treatment, and after performing shape processing larger than the target dimension, finish shape processing is performed using a nitric acid-based etchant or the like. preferable. In addition, even when there are minute cracks or surface roughness that occur during work hardening or shape processing, problems such as a decrease in Q value and durability of the vibration element occur. In such a case, electropolishing is preferably performed before age hardening, and the surface is preferably smoothed by electropolishing using a phosphoric acid-based or ethylene glycol-based liquid.

  From the viewpoint of productivity, the conductive members 201 and 202 are preferably made of the same material as the torsion beam and have an integral structure. However, the present invention is not limited to this, and it may be formed of a conductive material such as a metal material and joined to the torsion beam. When joining, it is preferable to use a wire rod for the torsion beam because the shape processing can be simplified, and for the purpose of improving the durability of the joint portion, a joining surface is formed by forging etc. Is preferred.

  As the piezoelectric material 401, lead zirconate titanate (PZT) having a large piezoelectric constant is preferably used. However, the material is not limited to this, and any material having piezoelectric characteristics such as barium titanate, lead titanate, lead niobate, or the like may be used. As long as the piezoelectric material 401 has a shape in which a film can be formed in addition to a sintered body in which electrodes are formed on both surfaces, the film is formed on a composite structure of a conductive member and a mirror member such as conductive members 201 and 202 and a mirror member. It may be formed by. In the case of using a sintered body, the piezoelectric material 401 is held by direct bonding of the electrodes 501 and 502 and the conductive members 201 and 202 or by adhesion using an adhesive or the like. In the case of bonding, the facing area is increased as much as possible and the bonding layer is thinned so that the electric capacity between the conductive member and the electrode in the bonding portion is larger than the electric capacity between both electrodes of the piezoelectric material 401. Thus, it is preferable to bring the conductive member and the electrode close to each other. Moreover, conductivity may be imparted to the adhesive to ensure conductivity. In the case of forming by film formation, the film is formed directly on the conductive members 201 and 202, and no electrode is formed between them. As a film formation method, various film formation methods such as a sol-gel method can be used. Among them, an aerosol deposition method and a gas deposition method are used which are easy to form a thick film with a high film formation rate and good film quality. Is preferred. When PZT is used for the material of the piezoelectric material 401 and a metal material is used for the conductive members 201 and 202, an intermediate layer for preventing lead diffusion may be formed. In order to improve the piezoelectric characteristics, it is effective to increase the heat treatment temperature. Therefore, it is preferable that the conductive members 201 and 202 serving as a film formation base material be formed of a material having high heat resistance, and a Co—Ni base. An alloy or the like is preferably used.

  The mirror member 301 may be a reflection film directly formed on the conductive member 201 in addition to a reflection film or an increase reflection film formed on a base material with good surface flatness such as a silicon wafer or thin glass. Examples of the reflective film include films of Au, Ag, Al, etc. formed by vapor deposition. Further, a reflective reflection film is formed thereon as necessary. Further, a mirror surface can be formed by polishing the conductive member 201. In this case, the conductive member 201 also functions as the mirror member 301.

  The magnets 601 to 604 are not particularly limited, but are preferably as small and strong as possible in order to reduce the moment of inertia related to torsional vibration. Therefore, an Nd—Fe—B magnet or Sm—Co magnet having a strong magnetic force, an Fe—Cr—Co magnet excellent in workability capable of forming a small shape, or the like can be suitably used.

[Operation of optical scanning device]
Next, the operation of the optical scanning device will be described with reference to FIGS.

  FIG. 6A shows a state of laser beam scanning by an optical scanning device employing any of the vibrating elements 11 to 13. FIG. 6B shows a state of deformation of the mirror member 301 disposed in the vibration unit 21, and is a common deformation in the light scanning direction and the sub-scanning direction perpendicular thereto. When the mirror member 301 has a curvature as shown in (R1) of FIG. 6B by an electric signal applied to the piezoelectric material 401, the beam waist of the projection surface P1 whose distance is R1 from the scanning center is shown. Assume that it is located in the center. When the vibrating portion 21 is rotated by the torsional vibration of the torsion beam to reach the state of (R1 ′) in FIG. The beam waist is positioned at the right end of the projection plane P1 at a distance R1 ′ from the scanning center. If the curvature does not change from the state (R1), the beam waist is at the position R1 in the scanning end direction, and the beam diameter expands at the right end of the projection plane P1. Similarly, at the left end of the scan, the beam waist is held on the projection plane P1 by changing the curvature in the state of (R ″) in FIG. 6B. Without using a lens optical system such as an arc sine lens, by controlling the mirror curvature using a signal including a frequency twice as high as the scanning frequency 6 (c) similarly holds the beam waist on the projection surface P2 having a longer projection distance than the surface P1. FIG. 6 shows a deformed state of the mirror member 301, and the beam waist position is (R2) → (R2 ′) → (R2) → ( R2 ") → (R ) When you move. As described above, the surface holding the beam waist can be changed by controlling the drive signal of the piezoelectric material 401.

  FIG. 7 is an example of a drive signal for performing scanning as shown in FIG. The drive circuit 801 applies a drive signal S2 generated by adding an offset voltage ΔV to a drive signal S1 having a frequency f1 and a signal having a frequency f2 that is twice the frequency f1 to the twisted beam. Thereby, rotational vibration is generated and curvature deformation of the mirror member 301 is induced.

  The drive signal S2 having the frequency f2 is a drive signal for maintaining the beam waist on the scan plane within one scan, and ΔV is an offset for changing the plane holding the beam waist. When the vibration unit 21 is rotationally vibrated by resonance, the drive signal S1 having the frequency f1 and the rotation angle of the vibration unit 21 are shifted by 90 degrees. Therefore, the phase of the drive signal S2 is also shifted from the phase of the drive signal S1 so that the curvature deformation of the mirror member 301 of the vibration unit 21 is controlled in accordance with the rotation angle.

  Next, the moving speed of the beam spot formed on the projection surface will be described. The optical scanning device changes the beam intensity based on the time series data while scanning the beam, or detects the change in the intensity of the reflected light during the beam scanning as the time series data. Read the optical pattern. At this time, if the moving speed of the beam changes greatly, image distortion and variation in reading resolution occur. A method of correcting the time-series data so that the change in the beam intensity corresponds to the change in the moving speed of the beam or a method in which the reading speed corresponds to the change in the moving speed can be considered, but this requires expensive high-speed control means. It becomes. It is preferable that the movement of the beam spot on the projection surface is as constant as possible, and within a range in which constant velocity on the projection surface can be obtained with respect to the beam scanning angle of the vibrating elements 11 to 13 whose angle changes in a sine wave shape. It is preferred to use.

  FIG. 8 shows the optical scanning state as in FIG. Projection plane located at a distance L from the scanning center, with θo being the maximum scanning angle of the beam due to rotational vibration of the mirror member 301 with reference to the center of scanning, and θeff being the effective range in which scanning light is actually used. A range corresponding to θeff on P is Xeff. Assuming that the projection plane P is P1 in FIG. 6A, the position of Xeff corresponds to the position of R1 'at the end of the projection plane P1. When the beam direction is the direction of the angle θ and the moving speed of the beam spot formed on the projection plane P is V, the moving speed V with respect to the angle θ is based on the moving speed Vo when the angle θ = 0. The rate of change V / Vo is as shown in FIG. In FIG. 9A, the horizontal axis represents the angle θ indicating the beam direction, and the vertical axis represents the rate of change V / Vo of the moving speed V. As the maximum scanning angle θo is increased, the moving speed V with respect to the angle θ changes as shown in (i) to (v) of the figure. At this time, if the allowable error of the spot moving speed is Δv, the angle within this range in the graph of (iii), that is, the effective scanning angle θeff is Θ3. In the graph (iv) in which the maximum scanning angle is increased, the effective scanning angle is expanded to Θ4. However, in the graph (v) in which the maximum scanning angle is further increased, the effective scanning angle becomes Θ5 and narrows conversely. Even if the maximum scanning angle is increased further, the effective scanning angle cannot be expanded. FIG. 9B shows the relationship between the maximum scanning angle θo and the effective scanning angle θeff, and the maximum scanning angle at which the effective scanning angle is widest differs depending on the size of the allowable error. FIG. 9C shows the maximum effective scanning angle with respect to the size of the allowable error and the maximum scanning angle necessary for obtaining the effective scanning angle. Although there is a difference due to an allowable error, a maximum scanning angle of 40 degrees or more is required to obtain the maximum effective scanning angle. In an optical scanning device, it is desirable that a wide range of image formation and reading can be performed with a short projection distance, and the effective scanning angle is preferably as wide as possible. In addition, the maximum scanning angle is preferably as narrow as possible from the viewpoints of downsizing the vibration elements 11 to 13 and power consumption. For these reasons, it is preferable to operate the vibration element at the maximum scanning angle at which the effective scanning angle reaches a peak. For this purpose, the maximum vibration angle is ± 40 degrees or more with respect to the center of the scanning, and the rotational vibration amplitude of the vibration element. Is preferably ± 20 degrees or more. In order to achieve this amplitude with a small vibration element, the torsion beam supporting the mirror member 301 needs to have high strength and durability, and the torsion beam using the age-hardening type Co—Ni based alloy is from this point. Is also highly preferred.

  Next, changes in the beam spot diameter projected onto the projection surface during optical scanning will be described. In an optical scanning device, the beam spot diameter greatly affects the definition of an image formed or projected by optical scanning and the resolution of optical pattern reading. For this reason, it is preferable that the variation of the beam spot diameter within the effective scanning region is as small as possible.

  FIG. 10A shows an example of a change in the beam spot diameter depending on the position on the projection surface. 8 shows the change in the beam spot diameter when the projection distance L shown in FIG. 8 is set to 174 mm and the beam spot is moved in the x-axis direction from the center O of the projection surface by the rotational vibration of the vibrating elements 11 to 13. The horizontal axis in FIG. 10A is the distance x from the center of the projection surface, and the vertical axis is the beam spot diameter φ. FIG. 10B shows an example of a drive signal applied to the piezoelectric material 401 in order to change the curvature of the mirror member 301. The drive signal having the frequency f2 is a drive signal having a frequency f2 that is twice the frequency of the rotation vibration of the vibration elements 11 to 13, that is, the scanning frequency (rotation vibration frequency) f1, and the drive signal having the frequency f2 shown in FIG. Is the same. The drive signal of frequency f4 is a signal having a frequency f4 that is four times the frequency f1, and the drive signal of frequency f2 + f4 is a signal obtained by superimposing the drive signal of frequency f2 and the drive signal of frequency f4 at an appropriate ratio. The change of the beam spot diameter depending on the position on the scanning plane is shown in the graph of “no f2” in FIG. 10A when the mirror deformation synchronized with the scanning frequency is not performed. The spot diameter increases rapidly. On the other hand, when the curvature of the mirror member 301 is changed by the drive signal of the frequency f2, it is as shown in the graph of “only f2” in FIG. 10A, and within the effective scanning range of Xeff. The fluctuation of the beam spot diameter can be greatly suppressed. Further, when the curvature of the mirror member 301 is changed by a drive signal in which the frequencies f2 and f4 are superimposed, the graph is shown in the graph “f2 + f4” in FIG. 10A, and is almost independent of the position. A constant beam spot diameter can be obtained.

  The above-described effects of constant velocity and stabilization of the beam spot diameter can be obtained only when the vibrating elements 11 to 13 can perform stable optical scanning without causing abnormal vibration or the like. By appropriately setting the maximum scanning angle using the vibration elements 11 to 13 and controlling the curvature of the vibration unit 21 with a signal having a frequency twice and four times the scanning frequency, image formation and projection, An optical scanning device capable of reading an optical pattern with high accuracy can be realized.

[Image forming apparatus]
FIG. 11 shows an image forming apparatus 7 which is an embodiment of an optical scanning device. The vibration element 10 is any one of the vibration elements 11 to 13 described above, and the configuration around the vibration unit is omitted. The light source 971 emits light whose intensity is modulated based on the drive signal output from the control circuit 970 according to the image data. The emitted light is reflected by the mirror member 301 of the vibration element 10 through the emission optical system 972, and scans on the photoconductor 975 which is an example of an image carrier. The scanned light is detected by BD sensors 973 and 974. The control circuit 970 generates and outputs a control signal for controlling the scanning angle based on detection signals output from the BD sensors 973 and 974. The control signal is fed back to the drive circuit 801 of the drive circuit 870 of the vibration element 10. As a result, the drive circuit 801 stably maintains the maximum scanning angle of the vibration element 10 at an appropriate value. A drive circuit 801 included in the drive circuit 870 outputs a control signal for controlling the mirror curvature based on the detection signal. Thereby, the beam spot diameter on the photosensitive member 975 is maintained at a substantially constant size.

  The image forming apparatus 7 using the vibration elements 11 to 13 is less likely to cause disconnection or abnormal vibration, and can perform stable optical scanning and mirror curvature control. For this reason, the effects of constant speed and stabilization of the beam spot diameter are exhibited by optimizing the maximum scanning angle and optimizing the mirror curvature control signal. That is, highly accurate and reliable image formation is possible. Further, in the image forming apparatus 7 using the vibration elements 11 to 13, the lens optical system that corrects the variation in the scanning speed can be simplified. In addition, it is not necessary to correct the image data or the intensity modulation signal of the laser beam in order to cope with fluctuations in the scanning speed. Thereby, a small and inexpensive image forming apparatus can be realized.

[Image forming apparatus]
FIG. 12A shows an image projection apparatus 8 which is an embodiment of the optical scanning apparatus. The vibration element 10 is any one of the vibration elements 11 to 13 described above. The light source device 981 including the three primary colors of RGB emits light whose intensity is modulated in accordance with a signal output from the control circuit 980 based on the image data. The light is two-dimensionally scanned by the vibration element 10 and the vertical scanning device 982 and projected onto the screen 983 as an image. The scanning speed of the vertical scanning device 982 is slower than that of the vibration element 10. For the vertical scanning device 982, for example, a galvanometer mirror that can perform positioning with high accuracy by non-resonant driving is used. Based on the control signal output from the control circuit 980, the drive circuit 801 included in the drive circuit 880 controls the scanning angle of the vibration element 10. Similarly, the scanning angle of the vertical scanning device 982 is controlled based on the output from the control circuit 980. Further, the drive circuit 801 of the drive circuit 880 outputs a mirror curvature control signal (drive signal), whereby the beam spot diameter on the screen 983 is maintained at a substantially constant size. Further, when the trapezoidal correction of the image is set through the input unit 984, the control circuit 980 changes the mirror curvature control signal in accordance with the change in the drive signal of the vertical scanning device 982. As a result, even when oblique projection is performed as shown in FIG. 12B, the focal length is increased in the scanning of the upper portion of the screen, and the focal length is decreased in the lower portion, so that the beam spot diameter on the screen is set to a substantially constant size. Can be maintained.

  As described above, the image projection apparatus 8 using any of the vibration elements 11 to 13 can perform stable optical scanning and mirror curvature control without causing disconnection or abnormal vibration. For this reason, it is possible to exhibit the effects of constant speed and stabilization of the beam spot diameter by optimizing the maximum scanning angle and optimizing the mirror curvature control signal. As a result, highly accurate and reliable image projection is possible. Further, in the image projection device 8, the beam spot diameter can be made substantially constant on the screen even by oblique projection by adjusting the mirror curvature control signal. Thereby, the high-definition image projector 8 that can be used in a limited space can be realized.

[Optical pattern reader]
FIG. 13 shows an optical pattern reading device 9 which is an embodiment of an optical scanning device. The vibration element 10 is any one of the vibration elements 11 to 13. The light emitted from the light source 991 is reflected by the mirror member 301 of the vibration element 10 through the emission optical system 992, and scans the optical pattern. The reflected light whose intensity changes in accordance with the optical pattern is reflected again by the vibration element 10, collected by the detection optical system 994, and detected by the optical sensor 995. The decoder 996 binarizes the detection signal output from the optical sensor 995. Thereby, the information of the optical pattern is read. The drive circuit 890 outputs a drive signal for rotational vibration of the vibration element 10 and a mirror curvature control signal based on the signal from the control circuit 990. Thereby, the beam spot diameter is maintained at a substantially constant size on the projection surface having the optical pattern.

  The optical pattern reader 9 using any of the vibration elements 11 to 13 can perform stable optical scanning and mirror curvature control without causing disconnection or abnormal vibration. For this reason, it is possible to exhibit the effects of constant speed and stabilization of the beam spot diameter by optimizing the maximum scanning angle and optimizing the mirror curvature control signal. As a result, highly accurate and reliable reading is possible.

[Summary]
According to the present embodiment, the first conductive member 201 is coupled to the first electrode 501 of the piezoelectric material 401, and the first conductive member 201 includes the conductive first twisted beam 101 and the second twisted beam. The beams 102 are joined. The second conductive member 202 is coupled to the second electrode 502 of the piezoelectric material 401, and the conductive third torsion beam 103 and the fourth torsion beam 104 are coupled to the second conductive member 202. Accordingly, the first feeding path including the first torsion beam 101, the second torsion beam 102, the first conductive member 201, and the first electrode 501, the third torsion beam 103, and the fourth torsion beam 104. A second power supply path including the second conductive member 202 and the second electrode 502 is formed. The mirror member 301 may be fixed to the piezoelectric material 401 or may be fixed to the first conductive member 201. Furthermore, a first magnet group that generates a magnetic field that acts on the current flowing in the first torsion beam 101 and the current flowing in the fourth torsion beam 104 is disposed. In addition, a second magnet group that generates a magnetic field acting on the current flowing in the second torsion beam 102 and the current flowing in the third torsion beam 103 is disposed. Thereby, these torsion beams generate torsional vibration, and the mirror member 301 can scan light. Each magnet group may include one magnet or a plurality of magnets. Furthermore, the piezoelectric material 401 is deformed according to the voltages applied through the two power supply paths, and the curvature of the mirror member 301 changes as the piezoelectric material 401 is deformed. Thus, in this embodiment, it is possible to simultaneously supply power for vibrating the vibrating elements 11 to 14 and power for changing the curvature of the mirror member 301 through the torsion beam. Therefore, the number of driving circuits and wiring can be reduced. That is, the present embodiment can provide a vibration element that has a simpler configuration and can reduce manufacturing costs. Further, electric power can be supplied to the piezoelectric material 401 without using wiring, and defects such as disconnection are less likely to occur, and stable rotational vibration (swing) can be realized. Further, since the scanning mirror and the variable focus mirror are integrated, the optical scanning device can be expected to be downsized. Further, in this embodiment, since it is not necessary to arrange a magnet in the vibration part 21, it is easy to realize weight reduction of the vibration part 21 and a reduction in manufacturing cost. Furthermore, the four torsion beams are less likely to fluctuate even when an impact is applied from the outside, and even if fluctuated, the effect of attenuating the fluctuation in a short time will be brought about.

  As described with reference to FIGS. 1, 2, and 5, the first torsion beam 101 is coupled to one end side of the first conductive member 201, and the second torsion beam 102 is connected to the first conductive member 201. It may be coupled to the other end side of the adhesive member 201. The third torsion beam 103 may be coupled to one end side of the second conductive member 202, and the fourth torsion beam 104 may be coupled to the other end side of the second conductive member 202. . Since the double-sided support structure can be realized in this way, the bending rigidity is higher than that of the cantilevered support structure, and the fluctuation of the scanning line in the sub-scanning direction can be easily suppressed.

  As described with reference to FIGS. 1, 2, and 5, the first magnet group is disposed along the first magnet 601 disposed along the first torsion beam 101 and the fourth torsion beam 104. The fourth magnet 604 may be included. The second magnet group may include a third magnet 603 disposed along the third twisted beam 103 and a second magnet 602 disposed along the second twisted beam 102. The magnetic field generated by these magnets acts on the current flowing in the torsion beam and generates a force that causes torsional vibration. Therefore, it is not necessary to arrange a magnet in the vibration part 21. The magnet may be a permanent magnet or an electromagnet.

  As described with reference to FIG. 4, the first torsion beam 101 is coupled to one end side of the first conductive member 201, and the second torsion beam 102 is one end side of the first conductive member 201. May be bonded to. The third torsion beam 103 may be coupled to one end side of the second conductive member 202, and the fourth torsion beam 104 may be coupled to one end side of the second conductive member 202. As a result, a cantilevered support structure can be realized, which is advantageous in terms of downsizing the vibration element as compared to the double-supported support structure. The cantilevered support structure is disadvantageous in terms of vibration stability compared to the double-supported support structure. However, since the present embodiment has four torsion beams arranged in parallel, the vibration can be stabilized more than the vibration element that supports the vibration part with two torsion beams. As described with reference to FIG. 4, the first magnet group includes magnets arranged along the first torsion beam 101 and the second torsion beam 102, and the second magnet group includes the third torsion beam 101. You may have the magnet arrange | positioned along the beam 103 and the 4th torsion beam 104. FIG. Thereby, the number of magnets can be reduced.

  As described with reference to FIGS. 1, 2, and 4, the first electrode 501 is provided on the first surface side of the piezoelectric material 401, and the second electrode 502 is provided on the second surface side of the piezoelectric material 401. It may be done. As described with reference to FIG. 5, the first electrode 501 may be provided on the first surface side of the piezoelectric material 401, and the second electrode 502 may also be provided on the first surface side of the piezoelectric material 401. . In the latter case, the third electrode 503 is provided on the second surface side of the piezoelectric material 401. Three electrodes form a series circuit of two capacitors. Further, the portion of the piezoelectric material 401 where the first electrode 501 and the third electrode 503 face each other and the portion where the second electrode 502 and the third electrode 503 face each other are polarized in different directions. May be. This is useful for setting the first electrode 501 and the second electrode 502 as voltage application target electrodes.

  As shown in FIG. 1 and the like, the second conductive member 202 may have a frame such as a frame. Compared with the flat plate structure, the frame structure is advantageous in terms of weight reduction.

  Note that a drive circuit 801 that supplies a drive signal to the piezoelectric material 401 via any one of the vibration elements 11 to 13, the first torsion beam 101 and the second torsion beam 102 of the vibration element 11, and a mirror of the vibration element 11 There may be further provided an optical scanning device that includes a magnetic field generation unit 700 that generates a magnetic field that swings the unit, and that scans light from the light source by the mirror member 301. By employing the vibrating elements 11 to 13, stable light scanning can be realized.

  The drive circuit may generate a drive signal by superimposing a signal having a frequency f2 that is twice the rotational vibration frequency f1 of the mirror member 301 and a signal having a frequency f4 that is four times. Thereby, a substantially constant beam spot diameter can be obtained regardless of the position.

  The rotation angle of the mirror member 301 may be ± 20 degrees or more. This is effective in reducing power consumption while widening the scanning angle of the mirror section.

  As described with reference to FIG. 11, an image forming apparatus 7 includes an optical scanning device and an image carrier, and forms an image on the image carrier with light scanned by the optical scanning device. May be provided. The image forming apparatus 7 using the vibration elements 11 to 13 is less likely to cause disconnection or abnormal vibration, and can perform stable optical scanning and mirror curvature control. For this reason, the effects of constant speed and stabilization of the beam spot diameter are exhibited by optimizing the maximum scanning angle and optimizing the mirror curvature control signal. That is, highly accurate and reliable image formation is possible. Further, in the image forming apparatus 7 using the vibration elements 11 to 13, the lens optical system that corrects the variation in the scanning speed can be simplified. In addition, it is not necessary to correct the image data or the intensity modulation signal of the laser beam in order to cope with fluctuations in the scanning speed. Thereby, a small and inexpensive image forming apparatus can be realized.

As described with reference to FIG. 12, an image projection apparatus 8 may be provided that projects an image on a screen with light scanned by the optical scanning apparatus. The image projection device 8 using any of the vibration elements 11 to 13 can perform stable optical scanning and mirror curvature control without causing disconnection or abnormal vibration. For this reason, it is possible to exhibit the effects of constant speed and stabilization of the beam spot diameter by optimizing the maximum scanning angle and optimizing the mirror curvature control signal. As a result, highly accurate and reliable image projection is possible. Further, in the image projection device 8, the beam spot diameter can be made substantially constant on the screen even by oblique projection by adjusting the mirror curvature control signal. As a result, a high-definition image projection device 8 that can be used in a limited space can be realized. As described with reference to FIG. 13, an optical pattern reading device 9 including an optical scanning device is provided. May be. The optical pattern reader 9 using any of the vibration elements 11 to 13 can perform stable optical scanning and mirror curvature control without causing disconnection or abnormal vibration. For this reason, it is possible to exhibit the effects of constant speed and stabilization of the beam spot diameter by optimizing the maximum scanning angle and optimizing the mirror curvature control signal. As a result, highly accurate and reliable reading is possible.

Claims (17)

A piezoelectric material having a first electrode and a second electrode;
A first conductive member coupled to the first electrode;
A conductive first torsion beam and a second torsion beam coupled to the first conductive member;
A second conductive member coupled to the second electrode;
A conductive third torsion beam and a fourth torsion beam coupled to the second conductive member;
A mirror member fixed to the piezoelectric material or the first conductive member and having a curvature that varies with the deformation of the piezoelectric material;

Have
The piezoelectric material includes the first torsion beam, the second torsion beam, the power supply path including the first conductive member and the first electrode, the third torsion beam, and the fourth torsion beam. The vibrating element is deformed according to a voltage applied through a power supply path including the second conductive member and the second electrode.   The first torsion beam is coupled to one end side of the first conductive member, and the second torsion beam is coupled to the other end side of the first conductive member. The vibrating element according to claim 1.   The third torsion beam is coupled to one end side of the second conductive member, and the fourth torsion beam is coupled to the other end side of the second conductive member. The vibrating element according to claim 1. A first magnet group that generates a magnetic field that acts on a current flowing in the first torsion beam and a current flowing in the fourth torsion beam;
A second magnet group for generating a magnetic field acting on the current flowing in the second torsion beam and the current flowing in the third torsion beam;
The first magnet group includes a first magnet disposed along the first torsion beam, and a fourth magnet disposed along the fourth torsion beam.
The second magnet group includes a third magnet disposed along the third torsion beam and a second magnet disposed along the second torsion beam. Or the vibration element of 3.   The first torsion beam is coupled to one end side of the first conductive member, and the second torsion beam is coupled to the one end side of the first conductive member. The vibrating element according to claim 1.   The third torsion beam is coupled to one end side of the second conductive member, and the fourth torsion beam is coupled to the one end side of the second conductive member. The vibrating element according to claim 1 or 5. A first magnet group that generates a magnetic field that acts on a current flowing in the first torsion beam and a current flowing in the fourth torsion beam;
A second magnet group for generating a magnetic field acting on the current flowing in the second torsion beam and the current flowing in the third torsion beam;
The first magnet group includes magnets arranged along the first torsion beam and the second torsion beam,
The vibrating element according to claim 5, wherein the second magnet group includes magnets arranged along the third torsion beam and the fourth torsion beam.   The first electrode is provided on a first surface side of the piezoelectric material, and the second electrode is provided on a second surface side of the piezoelectric material. The vibration element according to item 1.   The first electrode is provided on a first surface side of the piezoelectric material, and the second electrode is also provided on a first surface side of the piezoelectric material. The vibration element according to item 1.   The vibration element according to claim 9, further comprising a third electrode provided on the second surface side of the piezoelectric material.   Of the piezoelectric material, the portion where the first electrode and the third electrode face each other and the portion where the second electrode and the third electrode face each other are polarized in different directions. The vibration element according to claim 10. The vibration element according to any one of claims 1 to 11,
A drive circuit for supplying a drive signal to the piezoelectric material via the first torsion beam, the second torsion beam, the third torsion beam, and the fourth torsion beam of the vibration element;
And a magnetic field generation unit that generates a magnetic field for oscillating the mirror unit of the vibration element, and scans light from a light source with the mirror unit.   13. The optical scanning according to claim 12, wherein the drive circuit generates the drive signal by superimposing a signal having a frequency twice as high as a rotational vibration frequency of the mirror unit and a signal having a frequency four times as high as that of the mirror unit. apparatus.   14. The optical scanning device according to claim 12, wherein a rotation angle of the mirror unit is ± 20 degrees or more.   An image projection apparatus comprising the optical scanning device according to claim 12, wherein an image is projected onto a screen by light scanned by the optical scanning device.   15. An image forming apparatus comprising: the optical scanning device according to claim 12; and an image carrier, wherein an image is formed on the image carrier by light scanned by the optical scanning device. apparatus.   An optical pattern reading device comprising the optical scanning device according to claim 12.

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