JP2009217207A - Optical reflection element - Google Patents

Abstract

The present invention relates to an optical reflecting element used in a laser scanning unit of a laser printer, an electrophotographic apparatus, etc., and an object thereof is to realize an optical reflecting element for realizing a small laser scanning unit.
A support body, a first support section having one end supported by the support body, a first arm supported by a tip portion of the first support section, and a second support section. A tuning fork vibrator 6 composed of an arm 4, a second support part 11 supported by the vibration center 9 of the tuning fork vibrator 6, and a mirror part 12 supported by the tip of the second support part 11 The first arm 3 and the second arm 4 are provided with protrusions 7a and 7b.
[Selection] Figure 1

Description

  The present invention relates to an optical reflection element used in a laser scan unit or the like.

Conventionally, as a laser scanning unit that sweeps light emitted from a laser used in a laser printer or the like, a polygon mirror provided with a mirror on the side surface of a polygonal rotating body has been used. A laser beam was swept onto the scanning surface of the body drum (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 11-281908

  With such widespread use of color laser printers and miniaturization of printers, miniaturization of optical reflecting elements used in laser scan units has become a proposition. However, in a laser scanning unit using a polygon mirror, in addition to downsizing the polygon mirror, a separate drive device for driving the polygon mirror is required, and thus downsizing is very difficult. It was.

  Therefore, the present invention aims to solve such problems and realize an optical reflecting element capable of reducing the size of the laser scan unit.

  In order to achieve this object, the present invention provides an optical reflecting element supported by a support, a first support part having one end supported by the support, and the other end of the first support part. A tuning fork vibrator having a first arm and a second arm, a second support part supported at one end at the vibration center of the tuning fork vibrator, and supported at the other end of the second support part. And a projection provided on the first arm and the second arm.

  By adopting a vibrator configuration that vibrates flexural vibrations generated by two tuning fork vibrators having such protrusions as torsional vibrations of the mirror part, it is possible to control repeated rotational vibrations with high accuracy and at a large deflection angle. A small optical reflecting element for sweeping light can be realized.

(Embodiment 1)
Hereinafter, the configuration of the optical reflecting element according to Embodiment 1 of the present invention will be described with reference to the drawings.

  FIG. 1 is a plan view of the optical reflecting element according to the first embodiment, and FIG. 2 is a cross-sectional view taken along the line AA in FIG. FIG. 3 is a conceptual diagram for explaining the operating principle of the optical reflecting element.

  1 to 3, the optical reflecting element according to the first embodiment includes a tuning fork vibrator 6 including a first support portion 2, a first arm 3, a second arm 4, and a connecting portion 5. The first arm 3 and the second arm 4 have projections 7 a and 7 b, one end of the first support portion 2 is fixed to the support 1, and the vibration center 9 of the tuning fork vibrator 6 is One end of the second support part 11 is fixed, and the other end of the second support part 11 has a mirror part 12 for reflecting light such as a laser beam, and the first arm 3 and the second arm 4 have Is basically provided with a protrusion 7a, 7b. By setting it as such a structure, a resonant frequency can be reduced and a small optical reflection element can be implement | achieved as a result.

  And since the 1st arm 3 and the 2nd arm 4 make bending vibration, the amount of amplitude becomes the largest at the free end of the 1st arm 3 and the 2nd arm 4, and the said projection parts 7a and 7b are It is most effective to provide at the free ends of the first arm 3 and the second arm 4.

  In addition, when it cannot provide in a free end, it is also possible to arrange | position in the predetermined location in the middle of the 1st arm 3 and the 2nd arm 4.

  As described above, by providing the projections 7a and 7b at the free ends of the first arm 3 and the second arm 4, the free end of the tuning fork vibrator 6 becomes a fulcrum of the additional mass, and the tuning fork with the fulcrum as an axis. It acts so as to move in the thickness direction of the vibrator 6, and the moment of inertia of the tuning fork vibrator 6 leads to an increase in the amount of movable amplitude, and the amplitude quantity of the tuning fork vibrator 6 can be increased. As a result, the mirror section 12 Thus, it is possible to realize an optical reflecting element that can increase the amplitude amount of the repetitive rotational vibration and can increase the deflection angle of the mirror portion 12 with a small shape.

  More preferably, the protrusions 7a and 7b are provided so that the first arm 3 and the second arm 4 are orthogonal to each other and arranged inside the tuning fork vibrator 6, so that the tuning fork vibrator 6 can be twisted more efficiently. Can be generated well. The protrusions 7a and 7b are preferably symmetrical from the viewpoint of vibration characteristics, and the shape of the protrusions 7a and 7b at that time is not particularly limited, and is appropriately selected from the viewpoint of vibration characteristics and productivity. Can do.

  In addition, it is desirable that the mass of the projections 7a and 7b is large, and when the large shape cannot be provided by design, it is possible to add a weight to the projections 7a and 7b, thereby further increasing the effect. Can be made.

  In addition, as a substrate material constituting the optical reflecting element, it is preferable from the viewpoint of productivity that an elastic member having elasticity, mechanical strength and high Young's modulus such as a metal material or an inorganic material is used as the base material 20. As such an elastic member, it is preferable to use a metal, quartz, glass or quartz material from the viewpoint of mechanical characteristics and availability. Further, by using silicon, titanium, stainless steel, Elinvar or brass alloy as the metal, it is possible to realize an optical reflecting element having excellent vibration characteristics and workability.

  A piezoelectric actuator 10 for causing flexural vibration is formed on at least one surface of the first arm 3 and the second arm 4 made of a base material 20 such as silicon. The piezoelectric actuator 10 is preferably a thin film laminated piezoelectric actuator having a laminated structure of a first electrode layer 21, a piezoelectric layer 22 and a second electrode layer 23. Thus, a thin tuning fork vibrator 6 can be designed. Further, by making the thickness of the tuning fork vibrator 6 smaller than the width dimension of the first arm 3 and the second arm 4, a small optical reflecting element can be realized.

  The first electrode layer 21, the piezoelectric layer 22, and the second electrode layer 23 can be sequentially formed on the base material 20 on which the tuning fork vibrator 6 is formed by a thin film process such as a sputtering technique. Therefore, the piezoelectric actuator 10 is preferably formed on the same surface of the tuning fork vibrator 6 from the viewpoint of productivity.

  It is more effective to form the piezoelectric actuator 10 on the first arm 3, the second arm 4, and the connecting portion 5. As a result, an optical reflecting element capable of exciting torsional vibration more efficiently can be obtained.

  The piezoelectric material used for the piezoelectric layer 22 is preferably a piezoelectric material having a high piezoelectric constant such as lead zirconate titanate (PZT).

  Further, the mirror part 12 can be efficiently designed by vibration design so that the resonance frequency of the tuning fork vibrator 6 and the resonance frequency of the torsional vibrator constituted by the mirror part 12 and the second support part 11 are substantially the same frequency. It is possible to realize an optical reflecting element that repeatedly rotates and vibrates.

  Furthermore, by making the widths of the first arm 3, the second arm 4 and the connecting portion 5 equal, it is possible to provide an optical reflecting element that suppresses unnecessary vibration modes, and the tuning fork vibrator 6 can be The optical reflection element having the same effect can be obtained by forming the letter shape. The effect can be exhibited more by combining these.

  Further, by using the same material for the base material 20 of the first support part 2, the tuning fork vibrator 6, the second support part 11 and the mirror part 12, an optical reflection element having stable vibration characteristics and excellent productivity is realized. can do.

  Moreover, it is preferable that the cross-sectional shape of the 1st support part 2 and the 2nd support part 11 is circular. As a result, the vibration mode of torsional vibration is stabilized, unnecessary resonance can be suppressed, and an optical reflection element that is hardly affected by disturbance vibration can be realized.

  The mirror portion 12 can also be formed by mirror polishing the surface of the substrate 20, and more preferably, can be formed as a mirror film of a metal thin film of gold or aluminum having excellent light reflection characteristics. It is. The mirror film made of these metal thin films can be formed by a sputtering technique in the same manner as described above in the process of manufacturing the piezoelectric actuator 10.

  The optical reflecting element having such a configuration can be manufactured in a lump with high accuracy by applying a semiconductor process such as a thin film process or a photolithography technique on the base material 20 such as a silicon wafer. Therefore, it is possible to realize an optical reflecting element that is small in size, high in accuracy, and excellent in production efficiency.

  Further, by utilizing the torsional vibration of the torsional vibrator composed of the second support part 11 and the mirror part 12, it is possible to increase the deflection angle of the mirror part 12 while having a small device structure. A reflective element can be realized.

  Further, the configuration of the torsional vibrator formed by the flexural vibration of the first arm 3 and the second arm 4 constituting the tuning fork vibrator 6 which is a vibration driving part, the second support part 11 and the mirror part 12. Therefore, it is possible to realize an optical reflection element capable of designing and responding to a wide range of drive frequencies, deflection angles, and the like of the mirror unit 12 by devising each dimension and shape. it can.

  The lead electrodes of the first electrode layer 21 and the second electrode layer 23 of the piezoelectric actuator 10 formed on the first arm 3 and the second arm 4 are individually provided with lead lines (not shown). While forming, it is connected to the connection terminal 25. As a result, opposite electrical signals can be applied to each piezoelectric actuator 10.

  Next, the operation principle of the optical reflecting element having such a configuration will be described. FIG. 3 is a conceptual diagram for explaining the operation principle, and illustration of the protrusions 7a and 7b is omitted.

  As shown in FIGS. 1 to 3, by applying an alternating drive voltage between the first electrode layer 21 and the second electrode layer 23 constituting the piezoelectric actuator 10, Expansion and contraction occur, and deformation of the piezoelectric actuator 10 causes flexural vibration in directions in which the phases of the first arm 3 and the second arm 4 differ by 180 degrees (in the directions of arrows 8a and 8b).

  In addition, the first arm 3 and the second arm 4 are opposite by applying oppositely the positive and negative of the drive signal applied to the respective piezoelectric actuators 10 formed on the first arm 3 and the second arm 4. It will bend and vibrate in the direction (arrow 8a, 8b direction). At this time, since the projections 7 a and 7 b are added to the free ends of the first arm 3 and the second arm 4, they serve as weights, and the first arm 3 and the second arm 4 The resonance frequency can be reduced and the torsional vibration of the tuning fork vibrator 6 can be efficiently vibrated.

  By providing the protrusions 7 a and 7 b, the vibration energy of the first arm 3 and the second arm 4 oscillated at a lower frequency is propagated to the connecting portion 5 of the tuning fork vibrator 6. As a result, the tuning fork vibrator 6 repeats rotational vibration (torsional vibration) at a lower frequency with the vibration center 9 of the tuning fork vibrator 6 as a vibration axis (rotation axis 14).

  Next, the vibration energy of this repetitive rotational vibration is transmitted to the second support part 11 joined to the connecting part 5, and the second support part 11 and the mirror part 12 are centered around the rotation shaft 14. As a torsional vibrator, a torsional vibration is generated. As a result, repetitive rotational vibration is caused in the mirror portion 12 in the direction indicated by the arrow 13 with the rotation shaft 14 as the axis.

  At this time, the direction of the repetitive rotational vibration of the tuning fork vibrator 6 and the direction of the repetitive rotational vibration of the torsional vibrator composed of the second support part 11 and the mirror part 12 vibrate in opposite directions that are 180 degrees different in phase. It becomes.

  By constructing a vibrator having such a vibration mode and inputting a light beam generated from a laser light source or an LED light source to the mirror part 12, a small optical reflection element capable of increasing the deflection angle of the mirror part 12 is realized. can do. By designing the vibration of these vibration parts, a small optical reflection element that can largely change the reflection angle of the output light and can sweep the input light such as a laser beam to a predetermined design value. Can be realized.

  In this way, the vibration source is the tuning fork vibrator 6 having a high Q value, and this stable vibration energy is supplied as excitation energy for generating torsional vibration to the torsional vibrator composed of the second support portion 11 and the mirror portion 12. By doing so, the stable repetitive rotational vibration can be generated in the mirror unit 12.

  Note that the optical reflecting element in the case where the piezoelectric actuator 10 is formed on one surface of the first arm 3 and the second arm 4 in order to cause repetitive rotational vibration of the tuning fork vibrator 6 has been described as an example. By forming the piezoelectric actuator 10 on only one of them, it is possible to realize the same operation of the optical reflecting element as described above. This utilizes the vibration characteristics of the tuning fork, and applied the property that when one of the arms is excited, it can be vibrated by propagation of kinetic energy to the other arm via the connecting portion 5. Is.

  As an application of the optical reflecting element having the above-described configuration, a laser beam printer can be cited as an example. The photosensitive unit used in this laser beam printer or the like is a laser that is a light source, a photosensitive drum that is irradiated with a laser beam emitted from this laser, and reflects the laser beam and changes its reflection direction, thereby changing the laser beam. The optical reflecting element for sweeping the scanning surface of the photosensitive drum is used, and the optical reflecting element used in the photosensitive unit is a small laser beam printer by using the optical reflecting element having the configuration shown in FIGS. Can be realized.

  Next, a method for manufacturing the optical reflecting element in the first embodiment will be described.

  First, a silicon substrate 20 having a thickness of 0.3 mm is prepared, and a first electrode layer 21 made of a platinum electrode is formed thereon using a thin film process such as sputtering or vapor deposition. At this time, the thickness of the silicon substrate 20 may be thick. As a result, a silicon substrate 20 having a large wafer shape can be used, and since warpage and the like are small, a highly accurate optical reflecting element can be efficiently manufactured.

  Thereafter, a piezoelectric layer 22 is formed on the first electrode layer 21 by a sputtering method or the like using a piezoelectric material such as lead zirconate titanate (PZT). At this time, it is preferable to use an oxide dielectric containing Pb and Ti as the orientation control layer between the piezoelectric layer 22 and the first electrode layer 21, and it is more preferable to form an orientation control layer made of PLMT. . Thereby, the crystal orientation of the piezoelectric layer 22 is further improved, and the piezoelectric actuator 10 having excellent piezoelectric characteristics can be realized.

  Next, a second electrode layer 23 made of titanium / gold is formed on the piezoelectric layer 22.

  At this time, titanium under the gold electrode is formed in order to increase the adhesion with the piezoelectric layer 22 such as a PZT thin film, and a metal such as chromium can be used in addition to titanium.

  As a result, the piezoelectric actuator 10 having excellent adhesion with the piezoelectric layer 22 and having a strong diffusion strength with the gold electrode can be formed. At this time, the platinum electrode is 0.2 μm thick, the PZT thin film is 3.5 μm, the titanium electrode is 0.01 μm, and the gold electrode is 0.3 μm.

  Next, a patterned first electrode layer 21, piezoelectric layer 22 and second electrode layer 23 are formed by etching using a photolithographic technique. At this time, a predetermined electrode pattern was formed using an etchant composed of an iodine / potassium iodide mixed solution, ammonium hydroxide, and hydrogen peroxide mixed solution as an etchant for the second electrode layer 23.

Moreover, as an etching method used for the first electrode layer 21 and the piezoelectric layer 22, any one of a dry etching method and a wet etching method, or a combination of these methods can be used. For example, in the case of a dry etching method, a fluorocarbon-based etching gas or SF ₆ gas can be used. The piezoelectric thin film layer is wet-etched using an etching solution made of a mixed solution of hydrofluoric acid, nitric acid, acetic acid, and hydrogen peroxide to form a patterned piezoelectric layer 22. Thereafter, by further forming the patterned first electrode layer 21 by etching the lower electrode thin film layer by dry etching, the piezoelectric actuator 10 as shown in FIG. 2 can be formed.

Next, unnecessary silicon is removed by isotropically dry-etching the silicon substrate 20 using XeF ₂ gas, and an optical reflecting element having a shape as shown in FIG. 2 can be formed. .

When a silicon substrate or the like is etched with high accuracy by utilizing anisotropy by dry etching, SF ₆ gas that promotes etching and C ₄ F ₈ gas that suppresses etching are more linear. Etching is preferably performed. In the etching, a mixed gas using the gas can be used, or an etching method in which the gas is alternately switched to perform dry etching is possible, and these methods are matched to the dimensional shape and processing accuracy. It is possible to select and perform etching appropriately.

  By the manufacturing method as described above, it is possible to efficiently produce a small and highly accurate optical reflecting element collectively.

  By the manufacturing process as described above, the length of the first and second arms 3 and 4; 1.0 mm, the width; 0.3 mm, the length of the protrusions 7a and 7b; 0.55mm, the width; Length of the first support portion 2; 0.2 mm, width: 0.1 mm, length of the second support portion 11; 0.4 mm, width; 0.1 mm, mirror portion 12; 1.0 × 1. When the thickness was 0 mm, an optical reflection element having characteristics of a drive frequency: 15 kHz and a deflection angle of the mirror portion 12: ± 10 degrees could be produced.

(Embodiment 2)
Hereinafter, the configuration of the optical reflecting element according to Embodiment 2 of the present invention will be described with reference to the drawings.

  FIG. 4 is a plan view of the optical reflecting element according to the second embodiment.

  The basic configuration of the optical reflecting element in the second embodiment is substantially the same as that of the first embodiment, and detailed description thereof is omitted. The optical reflecting element in the second embodiment is the same as that of the first embodiment. A greatly different configuration will be described with reference to the drawings.

  In FIG. 4, a third support portion 30 is provided between an intermediate portion of the first arm 3 and the second arm 4 and the second support portion 11. As a result, the energy of the repetitive rotational vibration of the tuning fork vibrator 6 can be efficiently transmitted to the second support portion 11, and a further compact optical reflecting element can be realized. In FIG. 4, the third support portion 30 is a vibration of a higher-order standing wave having a resonance frequency of the torsional vibrator formed of the second support portion 11 and the mirror portion 12 generated in the second support portion 11. It is characterized by being provided at the node. This standing wave appears as a fraction of an integer as shown by 1/2, 1/3, and 1/4, and the third support portion 30 is added to the vibration node of the predetermined standing wave. Is preferably provided. In addition, the third support portion 30 is preferably disposed between the intermediate portion of the second support portion 11 and the connecting portion 5.

  The third support portion 30 is preferably disposed at a position close to the vibration center 9 of the tuning fork vibrator 6. As a result, it is possible to efficiently cause the mirror unit 12 to repeatedly rotate and vibrate while suppressing the attenuation of the flexural vibration of the first arm 3 and the second arm 4.

  As described above, the third support portion 30 is an optical reflection element provided at the vibration node portion of the higher-order standing wave having the resonance frequency of the torsional vibrator generated in the second support portion 11. Thus, an optical reflecting element that is smaller and has a large deflection angle can be realized.

  The present invention has an effect that the optical reflecting element can be miniaturized, and is particularly useful for electrophotographic copying machines, laser printers, and optical scanners.

The top view of the optical reflection element in Embodiment 1 of this invention Sectional view in the AA part of FIG. Conceptual diagram for explaining the operating principle of the optical reflection element The top view of the optical reflective element in Embodiment 2 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support body 2 1st support part 3 1st arm 4 2nd arm 5 Connection part 6 Tuning fork vibrator 7a, 7b Projection part 8a, 8b Arrow 9 Vibration center 10 Piezoelectric actuator 11 2nd support part 12 Mirror part 13 Arrow 14 Rotating shaft 20 Base material 21 First electrode layer 22 Piezoelectric layer 23 Second electrode layer 25 Connection terminal 30 Third support portion

Claims (15)

A support, a first support having one end supported by the support, a tuning fork vibrator having a first arm and a second arm supported by the other end of the first support, and A second support part having one end supported at the vibration center of the tuning fork vibrator, and a mirror part supported by the other end of the second support part, and protruding from the first arm and the second arm. An optical reflecting element provided with a portion. The optical reflection element according to claim 1, wherein the protrusions are provided at the free ends of the first arm and the second arm. The optical reflecting element according to claim 1, wherein the protrusions are provided symmetrically with respect to the tuning fork vibrator. The optical reflecting element according to claim 1, wherein the protrusion is provided inside the tuning fork vibrator. 2. The optical reflecting element according to claim 1, wherein the first arm and the second arm bend and vibrate in directions in which the phases of the first arm and the second arm differ by 180 degrees, and the tuning fork vibrator vibrates such that the tuning fork vibrator torsionally vibrates about the rotation axis. . The optical reflection element according to claim 1, wherein the resonance frequency of the tuning fork vibrator and the resonance frequency of the torsional vibrator formed of the mirror part and the second support part are substantially the same frequency. The optical reflective element according to claim 1, wherein the base material of the optical reflective element is an elastic member. The optical reflecting element according to claim 7, wherein the elastic member is made of metal, quartz, glass, or quartz. The optical reflective element according to claim 8, wherein the metal is silicon, titanium, stainless steel, elimbar, or a brass alloy. The optical reflecting element according to claim 7, wherein the first support part, the tuning fork vibrator, the second support part, the protrusion part, and the mirror part are made of the same base material. The optical reflective element according to claim 1, wherein a piezoelectric actuator is provided on at least one surface of the first arm and / or the second arm. The optical reflective element according to claim 11, wherein the piezoelectric actuator is a laminated piezoelectric thin film comprising a first electrode layer, a piezoelectric layer, and a second electrode layer. The optical reflecting element according to claim 12, wherein a piezoelectric actuator is provided on the same surface of the tuning fork vibrator. The optical reflective element according to claim 1, wherein a third support portion is provided between the first arm and the second arm, and the second support portion. The optical reflection element according to claim 14, wherein the third support portion is provided in a vibration node portion of a standing wave of a higher order having a resonance frequency of the torsional vibrator.

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