JP2012237788A - Optical scanner and image projection device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner of two-dimentional scanning, which improves the detection accuracy of a mirror scanning angle.SOLUTION: An optical scanner 10 includes a mirror shaft portion 16 and a frame shaft portion 15 having different shaft directions from each other; a mirror portion 11 rotated by the rotations of the mirror shaft portion 16, and rotated by the rotations of the frame shaft portion 15; a moving frame portion 14 surrounding the mirror portion 11 and the mirror shaft portion 16, and rotated by the rotations of the frame shaft portion 15; and a driving portion 13 driving the mirror portion 11 while using the mirror shaft portion 16 and the frame shaft portion 15 as a center axis, by vibrating the moving frame portion 14 through the frame shaft portion 15. On an axis of the frame shaft portion 15, at a symmetrical position which becomes an opposite phase to the rotations of the mirror shaft portion 16, a first angle detecting portion 18a and a second angle detecting portion 18b for detecting an angle of the moving frame portion 14 are provided.

Description

  The present invention relates to an optical scanning device and an image projection device, and more particularly, to a two-dimensional scanning optical scanning device and an image projection device including the same.

  An optical scanning device that polarizes and scans a light beam such as a laser beam is used in an optical apparatus such as an image projection device or a laser printer. Some of these optical scanning devices include a polygon mirror that scans reflected light by rotating a polygonal column mirror with a motor, a galvano mirror that rotates and vibrates a plane mirror by an electromagnetic actuator, and the like. However, in such an optical scanning device, a mechanical drive mechanism for driving the mirror by a motor or an electromagnetic actuator is required. However, since the drive mechanism is relatively large and expensive, the optical scanning is performed. There is a problem that downsizing of the apparatus is hindered and the price is increased.

  Therefore, in order to reduce the size, cost and productivity of optical scanning devices, components such as mirrors and elastic beams using micromachining technology that microfabricates silicon and glass using semiconductor manufacturing technology. Development of an optical scanning device (so-called MEMS mirror) of MEMS (Micro Electro Mechanical Systems) in which is integrally formed.

  There is an image projection apparatus in which two sets of one-dimensional scanning optical scanning apparatuses are arranged, and light rays reflected by the respective mirrors are respectively set to horizontal scanning and vertical scanning to display a two-dimensional image on a projection surface. In addition, if a two-dimensional scanning optical scanning device capable of horizontal scanning and vertical scanning is used, raster scanning (horizontal scanning and vertical scanning) can be performed in one set, which leads to reduction in size and cost.

  Here, one of the factors that determine the quality of the image projection apparatus is to control the positions of the output image and the input image with high accuracy. For this control, it is necessary to accurately detect the angle of the mirror. Therefore, conventionally, an optical scanning device using a piezoresistive element for detecting the angle of the mirror is known (see, for example, Patent Document 1).

  Patent Document 1 discloses a two-dimensional scanning optical scanning device using a piezoresistive element. This optical scanning device includes a fixed frame portion, a movable frame portion, and a mirror portion. The mirror portion is supported by the movable frame portion so as to be rotatable in the horizontal direction by the first elastic beam, and the movable frame portion is supported by the fixed frame portion so as to be rotatable in the vertical direction by the second elastic beam. ing. With such a configuration, the mirror part swings in a two-dimensional direction with respect to the fixed frame part as the first and second elastic beams vibrate in the torsional direction. Thereby, the light reflected by the mirror unit is scanned in a two-dimensional direction. In addition, one piezoresistive element for detecting the torsion angle of the elastic beam is provided in the vicinity of each elastic beam, and the deflection angle of the mirror portion is detected based on the output from the piezoresistive element.

Japanese Patent No. 4147947

  However, the conventional optical scanning device described in Patent Document 1 has a disadvantage in that, in the two-dimensional scanning, the detection signal generated by driving the movable frame unit overlaps the detection signal generated by the driving of the mirror unit. Therefore, there is a problem that the detection accuracy is lowered due to the influence of the crosstalk.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical scanning device for two-dimensional scanning with improved detection accuracy of a mirror scanning angle. It is.

  Another object of the present invention is to provide an image projection apparatus capable of projecting a high-quality image by including an optical scanning apparatus with improved scanning angle detection accuracy.

  In order to achieve the above object, an optical scanning device according to a first aspect of the present invention rotates by rotating a first shaft portion and a second shaft portion having different axial directions, and the first shaft portion. , A mirror portion that is rotated by the rotation of the second shaft portion, a movable frame portion that surrounds the mirror portion and the first shaft portion and is rotated by the rotation of the second shaft portion, and is movable through the second shaft portion. A drive unit that drives the mirror unit with the first shaft unit and the second shaft unit as the central axes is provided by vibrating the frame unit. A first angle detection unit and a second angle that detect the angle of the movable frame portion at a symmetrical position on the axis of the second shaft portion and in an opposite phase to the rotation of the first shaft portion. A detection unit is provided.

  In the optical scanning device according to the first aspect, as described above, the first and second angle detection units that detect the angle of the movable frame unit are symmetrical positions that are in reverse phase with respect to the rotation of the first shaft unit. Therefore, the influence of the rotation of the first shaft portion can be removed by using the signals from the first and second angle detectors. For this reason, it is possible to extract only the signal due to the rotation of the second shaft portion that is not affected by the rotation of the first shaft portion. Thereby, the scanning angle of the mirror part can be detected with high accuracy.

  Also, with this configuration, it is not necessary to provide a filter or the like in the drive circuit, for example, in order to remove the influence of the rotation of the first shaft portion. Therefore, since a filter etc. can be reduced from a drive circuit, the simplification (miniaturization) of a drive circuit can also be achieved.

  In the optical scanning device according to the first aspect, it is preferable that the first angle detection unit and the second angle detection unit are arranged at positions that are axially symmetric with respect to the first shaft portion. If comprised in this way, the influence of rotation (crosstalk) of a 1st axial part can be easily removed by the detection signal in the symmetrical position used as an antiphase.

  Further, in the optical scanning device according to the first aspect, the first angle detection unit and the second angle detection unit may be arranged at positions symmetrical with respect to the mirror surface. Even in such a configuration, a detection signal at a symmetrical position having an opposite phase can be obtained, so that the influence of the rotation (crosstalk) of the first shaft portion can be easily removed.

  The optical scanning device according to the first aspect includes an arithmetic unit that detects the angle of the movable frame unit using the first detection signal from the first angle detection unit and the second detection signal from the second angle detection unit. It is preferable. If comprised in this way, the influence of the rotation (crosstalk) of a 1st axial part will be eliminated by calculating in a calculating part using the detection signal in the symmetrical position used as an antiphase (for example, taking a sum). Only the signal generated by the rotation of the second shaft portion can be easily taken out.

  In the optical scanning device according to the first aspect, each of the first angle detection unit and the second angle detection unit may include a piezoresistive element. If comprised in this way, the shear stress which generate | occur | produces by rotation of a 2nd axial part can be detected as a change of the resistance value of a piezoresistive element. Thereby, the angle of the movable frame portion can be detected with high accuracy. In addition, the optical scanning device can be easily reduced in size.

  In this case, the piezoresistive element is preferably arranged in the vicinity of the position where the shear stress generated by the rotation of the second shaft portion is the largest. If comprised in this way, the angle of a mirror part can be detected with high sensitivity.

  In the case where the first angle detection unit and the second angle detection unit have a piezoresistive element, it is preferable that the optical scanning device is made of an n-type single crystal silicon material and the piezoresistive element is formed in a p-type region. . In this case, the piezoresistive element is arranged so that the direction connecting the pair of detection electrodes is substantially parallel or substantially perpendicular to the <100> axis on the (100) plane of the n-type single crystal silicon material. Is preferred. If comprised in this way, the angle of a mirror part can be detected with high sensitivity easily.

  In this case, the second shaft portion is preferably arranged so as to be substantially parallel or substantially perpendicular to the <100> axis. If comprised in this way, the angle of a mirror part can be detected with high sensitivity more easily.

  Note that the optical scanning device may be made of a p-type single crystal silicon material, and the piezoresistive element may be formed of an n-type region. In this case, the piezoresistive element is arranged so that the direction connecting the pair of detection electrodes is substantially parallel or substantially perpendicular to the <110> axis in the (100) plane of the p-type single crystal silicon material. Is preferred. Even in such a configuration, the angle of the mirror portion can be easily detected with high sensitivity.

  In this case, the second shaft portion is preferably arranged so as to be substantially parallel or substantially perpendicular to the <110> axis. If comprised in this way, the angle of a mirror part can be detected with high sensitivity more easily.

  Here, “substantially parallel to the <100> axis” can be within a range of −10 degrees to +10 degrees. Further, “substantially perpendicular to the <100> axis” can be in the range of 80 to 100 degrees. Within such a range, the angle of the mirror part can be detected with high sensitivity.

  When the first angle detection unit and the second angle detection unit have a piezoresistive element, the piezoresistive element has a plane cross shape, and a pair of application electrodes and a pair of pairs are opposed to each other at its four tip portions. A detection electrode is preferably arranged. If comprised in this way, the angle of a mirror part can be detected with higher sensitivity.

  Further, the piezoresistive element may have a planar O-ring shape other than the planar cross shape. In this case, it is preferable that a pair of application electrodes and a pair of detection electrodes are disposed opposite to each other at four portions that are 90 degrees from the center of the plane O-ring shape. If comprised in this way, the angle of a mirror part can be detected with higher sensitivity.

  The optical scanning device according to the first aspect preferably includes a third angle detection unit that detects the angle of the mirror unit in the vicinity of the first shaft unit. If comprised in this way, while being able to detect the shear stress of a 1st axial part by resistance value, it is small and can detect the angle of a mirror part with high precision.

  An image projection device according to a second aspect of the present invention irradiates light to the optical scanning device according to the first aspect, an optical scanning device control unit that performs drive control of the optical scanning device, and a mirror unit of the optical scanning device. A light source, a light source driving circuit that drives the light source, and an image signal control unit that controls the light source via the light source driving circuit based on the image signal.

  In the image projection apparatus according to the second aspect, as described above, the optical scanning apparatus according to the first aspect is provided, so that mirror scanning can be performed with high accuracy with a small size and a compact size. For this reason, it is possible to project an image with high quality.

  As described above, according to the present invention, it is possible to easily obtain a two-dimensional scanning optical scanning device with improved detection accuracy of the mirror scanning angle.

  In addition, according to the present invention, it is possible to easily obtain an image projection apparatus capable of projecting a high-quality image by including an optical scanning device with improved scanning angle detection accuracy.

It is the schematic diagram which showed the mode of projection of the image projector by 1st Embodiment of this invention. It is the schematic diagram which showed the positional relationship of the optical scanning device and light source of the image projector by 1st Embodiment of this invention. 1 is a block diagram illustrating a configuration of an image projection apparatus according to a first embodiment of the present invention. It is the top view which showed the principal part structure of the optical scanning device by 1st Embodiment of this invention. FIG. 5 is an enlarged cross-sectional view illustrating a part of the optical scanning device illustrated in FIG. 4. FIG. 5 is an enlarged plan view showing a part of the optical scanning device shown in FIG. 4. It is the figure which showed the ideal motion (drive waveform) of the vertical direction of the mirror part at the time of two-dimensional drive. It is the figure which showed the state (actual sensor detection waveform (output waveform)) which the vertical resonance of the mirror part at the time of a two-dimensional drive and the crosstalk by the scanning of a perpendicular direction affected the scanning of a perpendicular direction. It is a block diagram of a vertical drive control unit for driving the optical scanning device according to the first embodiment in the vertical direction. It is the figure which showed the sensor output waveform in the optical scanning device by 1st Embodiment, and the waveform from which the horizontal direction crosstalk by the control circuit was removed. It is a block diagram of the vertical drive control part for driving the optical scanning device by a comparative example to a perpendicular direction. It is a top view of the optical scanning device by a 2nd embodiment of the present invention. It is sectional drawing which showed a part of optical scanning device by 2nd Embodiment of this invention. It is the top view which showed the piezoresistive element of the optical scanning device by 3rd Embodiment of this invention. It is the top view which showed the piezoresistive element of the optical scanning device by the modification of this invention. It is the top view (figure which showed the other example) which showed the piezoresistive element of the optical scanning device by the modification of this invention. It is the top view (figure which showed the other example) which showed the piezoresistive element of the optical scanning device by the modification of this invention. It is the top view (figure which showed the other example) which showed the piezoresistive element of the optical scanning device by the modification of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram showing a projection state of the image projection apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic diagram showing the positional relationship between the light scanning device and the light source of the image projection device according to the first embodiment of the present invention. FIG. 3 is a block diagram showing the configuration of the image projection apparatus according to the first embodiment of the present invention. 4 to 10 are views for explaining the optical scanning device according to the first embodiment of the present invention. First, an optical scanning device according to a first embodiment of the present invention and an image projection device including the optical scanning device will be described with reference to FIGS.

  As shown in FIG. 1, the image projection apparatus 100 according to the first embodiment has a substantially box shape, for example, and is configured as a projector apparatus that projects an image (image) onto a projection surface 200 such as a screen. Yes. In the image projection apparatus 100, a two-dimensional image can be displayed on the projection plane 200 by performing raster scanning of the light rays emitted toward the projection plane 200. In this raster scanning, for example, the light beam is continuously scanned from the start position Qa at the upper end of the display image to the end position Qb at the lower end of the display image, whereby one image display is completed. When the light beam is scanned to the end position Qb, vertical scanning (and horizontal scanning) for returning to the start position Qa is performed during a vertical blanking period without image display for the next image display.

  As shown in FIG. 2, the image projector 100 includes an optical scanning device 10 and a light source 30 that emits a light beam (for example, laser light) LT toward the optical scanning device 10.

  The optical scanning device 10 includes a mirror unit 11 that reflects the light beam LT from the light source 30 toward the projection surface 200 (see FIG. 1). The mirror unit 11 rotates around a first axis (mirror shaft unit) parallel to the X axis and a second axis (frame shaft unit) parallel to the Y axis and intersecting the first axis at a substantially right angle. Is configured to be possible. The mirror unit 11 is two-dimensionally rotated about the first axis and the second axis, so that the light beam LT from the light source 30 reflected by the mirror unit 11 is raster-scanned.

  In addition to the optical scanning device 10 and the light source 30 described above, the image projection device 100 drives the optical scanning device control unit 40 that controls the driving of the optical scanning device 10 and the light source 30 as shown in FIG. A light source driving circuit 70 capable of modulating the light beam LT and an image signal control unit 80 for controlling the light source driving circuit 70 are provided.

  The optical scanning device 10 includes angle detection units 18 and 19. The angle detection units 18 and 19 have a piezoresistive element as an angle detection sensor for detecting the angle (rotation angle (deflection angle)) of the mirror unit 11.

  The optical scanning device control unit 40 rotates about the X axis with respect to the mirror unit 11, that is, a horizontal drive control unit 50 that controls driving in the horizontal direction (H direction), and rotates about the Y axis with respect to the mirror unit 11, that is, And a vertical drive control unit 60 that controls driving in the vertical direction (V direction).

  The image signal control unit 80 generates a control signal for controlling the light source 30 based on, for example, an image signal input from the outside of the image projector 100. Based on this control signal, the light source 30 is controlled (for example, lighting / extinguishing control or emission intensity control) via the light source driving circuit 70. The optical scanning device controller 40 receives a synchronization signal for synchronizing the driving timing of the mirror unit 11 with the image signal. Thereby, appropriate image display based on the input image signal is performed on the projection plane 200 (see FIG. 1).

  Further, the optical scanning device 10 (10a) according to the first embodiment includes a structure (MEMS structure) obtained by performing an etching process or the like on a silicon substrate. As shown in FIG. In addition, the fixed frame 12, the drive unit 13, and the movable frame unit 14 are integrally provided. In the following description, an axis that traverses the center of the mirror unit 11 in the vertical direction in FIG. 4 (an axis that scans an image (image) in the X direction (left and right direction)) is an X axis, and the center of the mirror unit 11 is illustrated. An axis that traverses the horizontal direction 4 (an axis that scans an image (image) in the Y direction (vertical direction)) is defined as a Y axis. In other words, the point where the X axis and the Y axis are orthogonal to each other is the center of the mirror unit 11.

  The fixed frame 12 is a part corresponding to the outer edge of the optical scanning device 10 and surrounds other parts (the mirror part 11, the drive part 13, the movable frame part 14 and the like).

  The drive unit 13 is connected to the fixed frame 12 in the X-axis direction and is separated from the fixed frame 12 in the Y-axis direction. Furthermore, the drive unit 13 includes four unimorph structures, and the four unimorph structures are arranged so as to be symmetric with respect to the X axis and the Y axis, respectively, and separated from each other. . In addition, as shown in FIG. 5, the unimorph structure as the drive unit 13 includes a piezoelectric element 13a (for example, a material obtained by polarizing a sintered body made of PZT or the like) sandwiched between a pair of electrodes 13b. It is formed by affixing on the area | region used as the drive part 13 of a silicon substrate.

  In such a drive unit 13, when a ± voltage (AC voltage) is applied to the pair of electrodes 13b within a range that does not cause polarization inversion, the piezoelectric element 13a sandwiched between the pair of electrodes 13b expands or contracts. . Accordingly, the region that becomes the driving unit 13 of the silicon substrate is deformed (bending deformation / bending deformation). That is, the drive unit 13 is driven by being supplied with electric power.

  Further, as shown in FIG. 4, the movable frame portion 14 is a substantially rhombus-shaped frame located inside the drive portion 13. A pair of frame shaft portions (vertical torsion bars) 15 extending along the Y-axis direction are provided between the movable frame portion 14 and the fixed frame 12. The pair of frame shaft portions 15 are arranged so as to overlap with the Y axis and be symmetric with respect to the X axis. Furthermore, one end of each of the pair of frame shaft portions 15 is connected to an end portion on the Y axis of the fixed frame 12. The movable frame portion 14 is disposed between the other ends of the pair of frame shaft portions 15 and is supported (clamped) by the other end (the pair of frame shaft portions 15). For this reason, the movable frame portion 14 can be rotated around the Y axis with the frame shaft portion 15 as a rotation axis (center axis).

  The movable frame portion 14 is a frame surrounding the mirror portion 11, and in addition to the mirror portion 11, a pair of mirror shaft portions (horizontal torsion bars) 16 extending along the X-axis direction are provided inside thereof. . The pair of mirror shaft portions 16 are disposed so as to overlap the X axis and be symmetric with respect to the X axis. Further, one end of each of the pair of mirror shaft portions 16 is connected to an end portion on the X axis of the movable frame portion 14. The mirror portion 11 is disposed between the other ends of the pair of mirror shaft portions 16 and is supported (clamped) by the other end (the pair of mirror shaft portions 16). For this reason, the mirror part 11 is rotated around the Y axis together with the movable frame part 14, and is also rotated around the X axis with the mirror shaft part 16 as a rotation axis (center axis). The frame shaft portion 15 is an example of the “second shaft portion” in the present invention, and the mirror shaft portion 16 is an example of the “first shaft portion” in the present invention.

  Moreover, the said mirror part 11 is formed, for example in the substantially circular shape, and is obtained by sticking the reflecting film which consists of gold | metal | money, aluminum, etc. on the area | region used as the mirror part 11 of a silicon substrate. In addition to this, for example, a reflective film such as gold or aluminum can be formed on a part of the silicon substrate by vapor deposition or sputtering. It is also possible to improve the reflectivity by forming a dielectric multilayer film on gold or aluminum.

  Further, a part of the four drive units 13 is coupled to the frame shaft unit 15 by a coupling unit 17. The connecting portion 17 is formed integrally with the region serving as the driving portion 13 of the silicon substrate and the frame shaft portion 15. Then, the driving force generated by the driving unit 13 is transmitted to the frame shaft unit 15 through the connecting unit 17 to scan the mirror unit 11.

  Further, an angle detection unit 18 for detecting a twist angle of the frame shaft portion 15 is provided in the vicinity of the frame shaft portion 15. Similarly, an angle detection unit 19 for detecting the twist angle of the mirror shaft portion 16 is provided in the vicinity of the mirror shaft portion 16. Each of the angle detectors 18 and 19 has a piezoresistive element 20 and detects a shear stress generated when the frame shaft portion 15 and the mirror shaft portion 16 are deformed by a resistance value. Based on the output from the angle detection unit 18, the angle (deflection angle) of the mirror unit 11 (movable frame unit 14) around the Y axis by the frame shaft unit 15 is detected and output from the angle detection unit 19. Based on this, the angle (deflection angle) of the mirror part 11 around the X axis by the mirror shaft part 16 is detected.

  The angle detection unit 18 is disposed on the axis of the frame shaft unit 15 (on the Y axis), and the angle detection unit 19 is disposed on the axis of the mirror shaft unit 16 (on the X axis). The term “on-axis” includes not only on the frame shaft portion 15 and the mirror shaft portion 16 but also on the extension line of the frame shaft portion 15 and the extension line of the mirror shaft portion 16. The angle detector 19 is an example of the “third angle detector” in the present invention.

  Here, in the first embodiment, the angle detection unit 18 includes two angle detection units (a first angle detection unit 18a and a second angle detection unit 18b). The first angle detector 18 a and the second angle detector 18 b are provided at symmetrical positions that are in opposite phases with respect to the rotation of the mirror shaft 16. Specifically, in the first embodiment, the first angle detector 18 a and the second angle detector 18 b are provided at positions that are axially symmetric with respect to the mirror shaft 16.

  Further, as shown in FIG. 6, the angle detection unit 18 (piezoresistive element 20) is disposed in the vicinity of a position where the shear stress generated by the rotation of the frame shaft unit 15 is the largest. Specifically, the angle detection unit is on the axis of the frame shaft part 15 and at the root part of the frame shaft part 15 (the root part (connecting part) of the frame shaft part 15 on the fixed frame 12 side) or in the vicinity of the root part. 18 (piezoresistive element 20) is formed.

  Further, the angle detection unit 18 (piezoresistive element 20) is arranged on the side of the frame shaft portion 15 with respect to the edge portion 12a along the X axis inside the fixed frame 12 (a virtual line P connecting the edge portion 12a in the X axis direction). Is arranged.

The optical scanning device 10 of the first embodiment is made of an n-type single crystal silicon material, and the piezoresistive element 20 is formed of a p-type region doped (ion-implanted) with p ⁺ impurities (for example, boron). Has been. As shown in FIG. 6, the piezoresistive element 20 (ion-implanted region) has a planar cross shape, and one electrode 21 is formed at each of the four tip portions thereof. These electrodes 21 are made of a metal layer formed on the ion-implanted region (on the doped region). Of the four electrodes 21, a pair of electrodes 21 a facing each other is an applied electrode 21 a to which a current is applied, and another pair of electrodes 21 b facing each other is a detection electrode 21 b that detects a voltage. It has become. A signal line (wiring) 22 is connected to each electrode 21.

  Here, since the sensitivity of the piezoresistive element 20 is greatly influenced by the crystal orientation of the silicon single crystal, the piezoresistive element 20 has a pair of detections in order to detect the shearing force of the shaft portion with higher sensitivity. The direction connecting the electrodes 21b is preferably arranged so as to be substantially parallel or substantially perpendicular to the <100> axis in the (100) plane of the n-type single crystal silicon material. By configuring in this way, the sensitivity of the piezoresistive element 20 can be increased, so that the angle of the mirror portion 11 can be detected with high sensitivity. Further, the frame shaft portion 15 is preferably arranged so as to be substantially parallel or substantially perpendicular to the <100> axis. Also in this case, the angle of the mirror unit 11 can be detected with high sensitivity. Note that “substantially parallel to the <100> axis” can be within a range of −10 degrees to +10 degrees, for example. Further, “substantially perpendicular to the <100> axis” can be, for example, within a range of 80 degrees to 100 degrees. Within such a range, the angle of the mirror part 11 can be detected with high sensitivity. The resistance value is detected by the piezoresistive element 20 by, for example, applying a constant current to the electrodes parallel to the frame shaft portion 15 (between cd) and detecting the voltage of the electrodes perpendicular to the frame shaft portion 15 (between ab). It is done by doing.

  Note that the angle detector 19 (piezoresistive element 20) (see FIG. 4) that detects the angle around the X axis is also configured similarly to the first angle detector 18a and the second angle detector 18b. preferable.

  The scanning operation of the optical scanning device 10 is performed by adjusting the timing for driving (extending and contracting) the four driving units 13 and vibrating the mirror unit 11 around the X axis and the Y axis. For example, the frequency when vibrating around the Y axis is set to about 60 Hz, and the frequency when vibrating around the X axis is set to about 30 kHz. Note that the vertical drive signal when oscillating around the Y axis is, for example, a triangular wave, and the horizontal drive signal when oscillating around the X axis is, for example, a sine wave.

  Each of the four driving units 13 is specifically described with reference numerals 13-1 to 13-4. When the mirror unit 11 is vibrated around the Y axis, the drive units 13-1 and 13-3 are set as one set, the drive units 13-2 and 13-4 are set as the other set, The sign of the voltage applied to each of the other set is reversed. In this case, when the driving units 13-1 and 13-3 as one set are deformed in the extending direction, the driving units 13-2 and 13-4 as the other set are deformed in a contracting direction. Further, when the driving units 13-1 and 13-3 that are one set are deformed in a contracting direction, the driving units 13-2 and 13-4 that are the other set are deformed in a extending direction. Thereby, the mirror part 11 vibrates around the Y axis together with the movable frame part 14, and the inclination (angle) of the mirror part 11 varies around the Y axis.

  When the mirror unit 11 is vibrated around the X axis, the drive units 13-1 and 13-2 are set as one set, and the drive units 13-3 and 13-4 are set as the other set. The polarity of the voltage applied to each of the set and the other set is reversed. In this case, when the driving units 13-1 and 13-2 as one set are deformed in the extending direction, the driving units 13-3 and 13-4 as the other set are deformed in a contracting direction. Further, when the driving units 13-1 and 13-2 that are one set are deformed in a contracting direction, the driving units 13-3 and 13-4 that are the other set are deformed in a extending direction. Thereby, the mirror part 11 vibrates around the X axis together with the movable frame part 14, and the inclination (angle) of the mirror part 11 varies around the X axis.

  At this time, if the mirror unit 11 is rotated about the X axis only by deforming the driving unit 13, the variation in the inclination (angle) of the mirror unit 11 about the X axis becomes small. For this reason, when the scanning operation is actually performed, the frequency of the applied voltage to the drive unit 13 is set so that the mirror unit 11 resonates with the frequency of the voltage applied to the drive unit 13. That is, the vibration around the X axis of the mirror part 11 is made with reference to the mirror shaft part 16.

  By operating the mirror unit 11 as described above, the mirror unit 11 can be rotated around two axes that are orthogonal to each other, and two-dimensional scanning can be performed by the single mirror unit 11. A voltage obtained by superimposing a drive signal (sine wave) in the horizontal direction (H direction) and a drive signal (triangular wave) in the vertical direction (V direction) is applied to the four drive units (piezoelectric elements) 13-1 to 13-4. In addition, it is possible to realize horizontal resonance driving using the mirror shaft portion 16 as a fulcrum and vertical driving for driving the entire movable frame portion 14 as described above.

  Here, FIG. 7 shows an ideal vertical movement (drive waveform) of the mirror unit 11 during the two-dimensional drive. The vertical axis in FIG. 7 indicates the V direction angle of the mirror, and the horizontal axis indicates time. As shown in FIG. 7, the drive in the vertical direction of the mirror unit 11 (see FIG. 4) preferably has a drive waveform corresponding to the vertical drive signal (triangular wave).

  However, in the vertical driving, since the turn-back at the moment when the scanning direction changes (the portion surrounded by the broken line R) is steep, resonance occurs in the vertical scanning as shown in FIG. The frequency at this time is about 1 kHz to 2 kHz. Due to the influence of this resonance, it becomes difficult to scan at a constant speed in the vertical direction, and bright and dark horizontal stripes are generated in the projected image. FIG. 8 shows a state (actual detection waveform (output waveform) of the actual sensor (angle detection unit 18)) in which the vertical resonance of the mirror unit 11 during the two-dimensional driving affects the vertical scanning. .

  Furthermore, since the optical scanning device 10 also scans in the horizontal direction (H direction) by rotating the mirror unit 11 around the X axis, it is affected by the crosstalk. In other words, the detection signal generated by driving the movable frame portion 14 is detected due to the influence of crosstalk generated by driving the mirror portion 11. Specifically, as shown in the enlarged view of a part of the detection waveform in FIG. 8, the detection waveform in the vertical scanning finely vibrates in the vertical direction at a horizontal frequency (near 30 kHz). This crosstalk adversely affects the vertical control of the mirror unit 11 (movable frame unit 14). In FIG. 8, the influence of crosstalk noise is expressed by displaying the detection waveform line thickly. Further, since the horizontal drive of the mirror unit 11 is a resonance operation, the frequency varies.

  Therefore, in the first embodiment, the angle detection unit 18 that detects the angle of the movable frame unit 14 is configured to include the first angle detection unit 18a and the second angle detection unit 18b, and the first angle detection unit 18a and The second angle detection unit 18 b is disposed at a symmetrical position that is in reverse phase with respect to the rotation of the mirror shaft unit 16. Therefore, the crosstalk is obtained by adding (adding) the detection signal (first detection signal) from the first angle detection unit 18a and the detection signal (second detection signal) from the second angle detection unit 18b. Is removed. The detection signal from which the crosstalk has been removed is fed back to the vertical drive control unit 60 (see FIG. 3), so that the influence of resonance is removed. As a result, the mirror unit 11 can be scanned in the vertical direction at a constant speed.

  Specifically, as shown in FIG. 9, in the first embodiment, the vertical drive control unit 60 includes preamplifiers 61 and 62, a calculation unit 63, a phase compensator 64, a gain compensator 65, and a power amplifier 66. It is configured. In the first embodiment, the angle detection unit 18 that detects the angle of the movable frame unit 14 includes the first angle detection unit 18a and the second angle detection unit 18b. The sensor 2 corresponds to the first angle detection unit 18a, and the sensor 2 corresponds to the second angle detection unit 18b. The detection signal (output waveform) from the sensor 1 is amplified by the preamplifier 61 and input to the calculation unit 63. On the other hand, the detection signal (output waveform) from the sensor 2 is amplified by the preamplifier 62 and input to the calculation unit 63. The calculation unit 63 calculates (adds) the input signals by analog processing or digital processing, and outputs the calculated (added) signals.

  Further, the output (amplified output) from the sensor 1 has a waveform as shown in FIG. 10A, for example, and the output (amplified output) from the sensor 2 is, for example, (B in FIG. ). As described above, the sensor 1 (first angle detection unit 18a) and the sensor 2 (second angle detection unit 18b) are symmetrical with respect to the rotation of the mirror shaft unit 16 (see FIG. 4). Placed in position. Therefore, the phase of the crosstalk waveform applied to the detection signal (output waveform) of the sensor 1 and the waveform of crosstalk applied to the detection signal (output waveform) of the sensor 2 are 180 degrees different from each other. That is, they are in opposite phases. Therefore, the calculation unit 63 calculates (adds) the detection signal (output waveform) from the sensor 1 (first angle detection unit 18a) and the detection signal (output waveform) from the sensor 2 (second angle detection unit 18b). As a result, the crosstalk is canceled as shown in FIG. Thereby, only the signal by the rotation of the frame shaft portion 15 (see FIG. 4) that is not affected by the rotation of the mirror shaft portion 16 (see FIG. 4) is taken out. In FIGS. 10A and 10B, the detection waveform line is displayed thick to express the influence of crosstalk noise. In FIG. 10C, the waveform line is narrowed. By displaying, the state where the influence of the noise of the crosstalk is removed is expressed.

  As shown in FIG. 9, the signal from which the influence of crosstalk has been removed is subjected to phase compensation by the phase compensator 64 and then fed back to the vertical drive signal. Specifically, the feedback signal is subtracted from the vertical drive signal. The vertical drive signal from which the feedback signal has been subtracted is input to the gain compensator 65, and gain compensation is performed by the gain compensator 65. The gain-compensated signal is input to the power amplifier 66, power amplified, and supplied to the vertical drive actuator 90 (drive unit 13). Thereby, the drive part 13 (refer FIG. 4) of the optical scanning device 10 is driven.

  Thus, in the first embodiment, the detection signal (output waveform) from the sensor 1 (first angle detection unit 18a) and the detection signal (output waveform) from the sensor 2 (second angle detection unit 18b) are calculated. (Addition) cancels the crosstalk. Then, the resonance in the vertical direction of the mirror portion 11 is removed by feeding back the signal due to the rotation of the frame shaft portion 15 in which the crosstalk is canceled to the vertical drive signal. As a result, the angle of the movable frame portion 14 can be controlled with high accuracy, so that high-quality video projection is possible.

  Note that, unlike the first embodiment, a case where one angle detector 18 for detecting the twist angle of the frame shaft portion 15 is disposed (arranged in one place) will be described as a comparative example. FIG. 11 is a block diagram of a vertical drive control unit for driving the optical scanning device according to the comparative example in the vertical direction. Referring to FIG. 11, the optical scanning device according to the comparative example includes a band pass filter (BPF) 503 for removing the influence of crosstalk. In the comparative example, the detection signal (output waveform) from the angle detection unit (sensor 501) that detects the angle of the movable frame is amplified by the preamplifier 502 and input to the BPF 503. Then, the BPF 503 removes the influence of crosstalk. The detection signal from which the influence of the crosstalk has been removed is subjected to phase compensation by the phase compensator 504 and then fed back to the vertical drive signal. The gain compensator 505 performs gain compensation. The gain-compensated signal is input to the power amplifier 506, amplified, and supplied to the vertical drive actuator 507 (drive unit).

  However, the BPF 503 in this case has a disadvantage that the scale is large and adjustment is necessary. On the other hand, in the first embodiment, as described above, the BPF 503 can be deleted by using the sensor 1 (first angle detection unit 18a) and the sensor 2 (second angle detection unit 18b). Become. Therefore, simplification (downsizing) of the drive circuit and the like can be achieved. Note that only one angle detector 19 (see FIG. 4) that detects the angle of the mirror 11 around the X axis is not affected by the rotation around the Y axis.

  In the first embodiment, as described above, the angle detection unit 18 that detects the angle (deflection angle) of the movable frame unit 14 is configured to include the first angle detection unit 18a and the second angle detection unit 18b. By providing the first angle detection unit 18a and the second angle detection unit 18b at symmetrical positions that are in opposite phases with respect to the rotation of the mirror shaft unit 16, the first angle detection unit 18a and the second angle detection unit 18b are provided. By using the signal from, the influence of the rotation (crosstalk) of the mirror shaft portion 16 can be removed. For this reason, it is possible to extract only a signal due to the rotation of the frame shaft portion 15 that is not affected by the rotation of the mirror shaft portion 16. Thereby, the scanning angle of the mirror unit 11 can be detected with high accuracy.

  Further, in the first embodiment, in order to remove the influence of the rotation (crosstalk) of the mirror shaft portion 16, for example, it is not necessary to provide a filter (BPF) or the like in the drive circuit. Therefore, the filter (BPF) and the like can be reduced from the drive circuit (vertical drive control unit 60), so that the drive circuit can be simplified (downsized).

  In the first embodiment, the first angle detection unit 18 a and the second angle detection unit 18 b are arranged at positions that are axially symmetric with respect to the mirror shaft portion 16, so that detection is performed at a symmetric position that has an opposite phase. The influence of the rotation (crosstalk) of the mirror shaft portion 16 can be easily removed by the signal.

  Further, in the first embodiment, by providing the calculation unit 63 that detects the angle of the movable frame unit 14 using the detection signal from the first angle detection unit 18a and the detection signal from the second angle detection unit, the phase is reversed. Only the signal due to the rotation of the frame shaft portion 15 from which the influence of the rotation (crosstalk) of the mirror shaft portion 16 is removed is calculated by using the detection signal at the symmetrical position. It can be easily taken out.

  In the first embodiment, the first angle detection unit 18 a and the second angle detection unit 18 b each include the piezoresistive element 20, so that shear stress generated by the rotation of the frame shaft unit 15 is generated. This can be detected as a change in the resistance value of the piezoresistive element 20. Therefore, the angle of the movable frame portion 14 can be detected with high accuracy. In addition, the optical scanning device 10 can be easily reduced in size.

  In the first embodiment, the angle of the mirror portion 11 can be detected with high sensitivity by arranging the piezoresistive element 20 in the vicinity of the position where the shear stress of the frame shaft portion 15 becomes the largest. Even if the number of piezoresistive elements used for angle detection is increased, the silicon processing process for manufacturing the MEMS mirror can be simultaneously formed in the same process, and thus does not cause an increase in cost.

  Furthermore, in the first embodiment, by providing an angle detection unit 19 that detects the angle of the mirror unit 11 (the rotation angle around the X axis) in the vicinity of the mirror shaft unit 16, the shear stress of the mirror shaft unit 16 is reduced. In addition to being able to be detected by the resistance value, the angle of the mirror unit 11 (the rotation angle around the X axis) can be detected with high accuracy and a small size.

  In the first embodiment, by configuring the image projection apparatus 100 using the optical scanning apparatus 10, the image projection apparatus 100 can be configured to be small, compact, and to perform mirror scanning with high accuracy. can do. For this reason, the image projection apparatus 100 configured as described above can project a video with high quality. For example, image quality improvement effects such as horizontal stripe reduction can be obtained.

(Second Embodiment)
FIG. 12 is a plan view of an optical scanning device according to a second embodiment of the present invention. FIG. 13 is a cross-sectional view showing a part of an optical scanning device according to the second embodiment of the present invention. Next, an optical scanning device according to a second embodiment of the present invention will be described with reference to FIGS. In addition, in each figure, the same code | symbol is attached | subjected to a corresponding component, and the overlapping description is abbreviate | omitted suitably.

  In the optical scanning device 10 (10b) according to the second embodiment, the first angle detection unit 18a and the second angle detection unit 18b are opposite to each other with respect to the rotation of the mirror shaft unit 16, as in the first embodiment. It is provided at a symmetrical position as a phase. However, in the second embodiment, unlike the first embodiment, the first angle detection unit 18a and the second angle detection unit 18b are arranged at positions symmetrical with respect to the mirror surface. Specifically, as shown in FIGS. 12 and 13, the first angle detection unit 18 a and the second angle detection unit 18 b are arranged on the surface side of the optical scanning device 10 (silicon substrate) so as to be plane-symmetric with each other. It is formed on the back side.

  Other configurations of the second embodiment are the same as those of the first embodiment.

  In the second embodiment, as described above, the first angle detection unit 18a and the second angle detection unit 18b are arranged in a plane-symmetrical position with respect to the mirror surface, as in the first embodiment. Since a detection signal at a symmetrical position as a phase is obtained, the influence of the rotation (crosstalk) of the mirror shaft portion 16 can be easily removed.

  Further, by configuring the image projection device using the optical scanning device 10 (10b), it is possible to perform mirror scanning of the image projection device with a small size, compactness, and high accuracy, as in the first embodiment. Can be configured.

  Other effects of the second embodiment are the same as those of the first embodiment.

(Third embodiment)
FIG. 14 is a plan view showing a piezoresistive element of the optical scanning device according to the third embodiment of the present invention. Next, an optical scanning device according to a third embodiment of the present invention will be described with reference to FIGS. In addition, in each figure, the same code | symbol is attached | subjected to a corresponding component, and the overlapping description is abbreviate | omitted suitably.

  In the third embodiment, as shown in FIG. 14, the piezoresistive element 20 of the angle detector 18 (the ion-implanted region has a planar O-ring shape, and directions of 90 degrees from the ring center. One electrode 21 is formed on each of the four parts, which are formed of a metal layer formed on the ion-implanted region (on the doped region). Among them, a pair of electrodes 21a facing each other serves as an applied electrode 21a to which a current is applied, and another pair of electrodes 21b facing each other serves as a detection electrode 21b for detecting a voltage. A signal line (wiring) 22 is connected to each electrode 21.

  In this case as well, in the piezoresistive element 20, the direction connecting the pair of detection electrodes 21b is substantially parallel or substantially perpendicular to the <100> axis on the (100) plane of the n-type single crystal silicon material. It is preferable that they are arranged. By configuring in this way, the sensitivity of the piezoresistive element 20 can be increased, so that the angle of the mirror unit 11 (see FIG. 4) can be detected with high sensitivity.

  Further, the angle detector 19 (piezoresistive element 20) (see FIG. 4) for detecting the angle around the X axis is preferably configured similarly to the angle detector 18.

  Other configurations of the third embodiment are the same as those of the first and second embodiments. The effects of the third embodiment are the same as those of the first and second embodiments.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the first to third embodiments, an example in which one each of the first angle detection unit and the second angle detection unit is provided has been described. However, the present invention is not limited thereto, and the first angle detection unit and A plurality of second angle detection units may be provided. If comprised in this way, the detection sensitivity of an angle can be improved.

  In the first to third embodiments, the example in which the driving unit that drives the mirror unit is configured as a piezoelectric driving method including a piezoelectric element has been described. However, the present invention is not limited to this, and the mirror unit is driven. The drive actuator may be other than the piezoelectric drive system. For example, it may be electrostatic or electromagnetic.

  In the first to third embodiments, the example in which the angle detection unit is configured to include a piezoresistive element has been described. However, the present invention is not limited to this, and the angle detection unit may be other than the piezoresistive element. You may be set as the structure which has a photo sensor, another distortion sensor, etc. However, it is preferable that the angle detection unit has a piezoresistive element because it has a small configuration and can be detected with high accuracy.

  In the first to third embodiments, the example in which the optical scanning device is formed of an n-type single crystal silicon material and the piezoresistive element is formed in a p-type region is shown, but the present invention is not limited thereto, For example, the optical scanning device can be made of a p-type single crystal silicon material, and the piezoresistive element can be formed of an n-type region. In this case, the piezoresistive element is arranged so that the direction connecting the pair of detection electrodes is substantially parallel or substantially perpendicular to the <110> axis in the (100) plane of the p-type single crystal silicon material. Is preferred. Even in such a configuration, the angle of the mirror portion can be easily detected with high sensitivity. In this case, the frame shaft portion is preferably disposed so as to be substantially parallel or substantially perpendicular to the <110> axis. Note that “substantially parallel to the <110> axis” can be within a range of −10 degrees to +10 degrees, for example, as in the above embodiment. Further, “substantially perpendicular to the <110> axis” can be, for example, within a range of 80 degrees to 100 degrees.

  In the first to third embodiments, the example in which the crosstalk is canceled by adding the detection signal from the first angle detection unit and the detection signal from the second angle detection unit by the calculation unit has been described. The calculation in the calculation unit may be a calculation other than addition (calculation including addition) as long as the calculation can cancel the crosstalk. In this case, it is good also as a structure which provides a calculating part separately.

  Furthermore, in the said embodiment, the example which has arrange | positioned the piezoresistive element of the 1st, 2nd angle detection part at the frame axial part side with respect to the edge part (imaginary line P) along the X-axis inside a fixed frame. In this case, the angle detection unit 18 (piezoresistive element 20) may be arranged so as not to cover the virtual line P, or may be applied to the virtual line P as shown in FIGS. May be arranged. Further, as shown in FIGS. 17 and 18, the angle detection unit 18 (piezoresistive element 20) may be arranged on the fixed frame 12 side with respect to the virtual line P. Also in this case, the angle detection unit 18 (piezoresistive element 20) may be arranged so as not to cover the virtual line P or may be arranged so as to cover the virtual line P. However, if the angle detector 18 (piezoresistive element 20) is too far from the imaginary line P, especially if it is too far away from the fixed frame side, the detection sensitivity is lowered and it becomes difficult to detect the angle. The element 20) is preferably arranged in the vicinity of the virtual line P.

  Embodiments obtained by appropriately combining the techniques (configurations) disclosed above are also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Optical scanning device 11 Mirror part 12 Fixed frame 12a Edge part 13 Drive part 13a Piezoelectric element 13b Electrode 14 Movable frame part 15 Frame axial part (2nd axial part)
16 Mirror shaft (first shaft)
17 connecting part 18 angle detecting part 18a first angle detecting part 18b second angle detecting part 19 angle detecting part (third angle detecting part)
20 piezoresistive element 21 electrode 21a electrode, application electrode 21b electrode, detection electrode 30 light source 40 optical scanning device control unit 50 horizontal drive control unit 60 vertical drive control unit 61, 62 preamplifier 63 arithmetic unit 64 phase compensator 65 gain compensator 66 Power amplifier 70 Light source drive circuit 80 Image signal control unit 90 Vertical direction drive actuator 100 Image projection device

Claims (15)

A first shaft portion and a second shaft portion having different axial directions;
A mirror portion that is rotated by rotation of the first shaft portion and rotated by rotation of the second shaft portion;
A movable frame portion that surrounds the mirror portion and the first shaft portion and is rotated by the rotation of the second shaft portion;
A drive unit that drives the mirror unit around the first shaft unit and the second shaft unit by vibrating the movable frame unit via the second shaft unit;
A first angle detection unit and a second angle that detect an angle of the movable frame unit at a symmetrical position on the axis of the second shaft unit and in an opposite phase to the rotation of the first shaft unit. An optical scanning device comprising a detection unit.   2. The optical scanning device according to claim 1, wherein the first angle detection unit and the second angle detection unit are arranged at positions symmetrical with respect to the first shaft portion.   2. The optical scanning device according to claim 1, wherein the first angle detection unit and the second angle detection unit are arranged in plane symmetry with respect to a mirror surface.   The arithmetic unit for detecting the angle of the movable frame part using the first detection signal from the first angle detection part and the second detection signal from the second angle detection part. The optical scanning device according to any one of 1 to 3.   The optical scanning device according to claim 1, wherein each of the first angle detection unit and the second angle detection unit includes a piezoresistive element.   The optical scanning device according to claim 5, wherein the piezoresistive element is arranged in the vicinity of a position where the shear stress generated by the rotation of the second shaft portion is maximized. The first angle detection unit and the second angle detection unit include a piezoresistive element, and is an optical scanning device configured of an n-type single crystal silicon material,
The piezoresistive element is formed of a p-type region, and the direction connecting the pair of detection electrodes is substantially parallel or substantially perpendicular to the <100> axis on the (100) plane of the n-type single crystal silicon material. It arrange | positions so that it may become. The optical scanning device of any one of Claims 1-6 characterized by the above-mentioned.   The optical scanning device according to claim 7, wherein the second shaft portion is disposed so as to be substantially parallel or substantially perpendicular to the <100> axis. The first angle detection unit and the second angle detection unit have a piezoresistive element, and is an optical scanning device configured of a p-type single crystal silicon material,
The piezoresistive element is formed of an n-type region, and the direction connecting the pair of detection electrodes is substantially parallel or substantially perpendicular to the <110> axis in the (100) plane of the p-type single crystal silicon material. It arrange | positions so that it may become. The optical scanning device of any one of Claims 1-6 characterized by the above-mentioned.   The optical scanning device according to claim 9, wherein the second shaft portion is disposed so as to be substantially parallel or substantially perpendicular to the <110> axis.   The said substantially parallel is in the range of -10 degrees to +10 degrees, and the said substantially perpendicular is in the range of 80 degrees to 100 degrees, The any one of Claims 7-10 characterized by the above-mentioned. The optical scanning device according to 1. The first angle detector and the second angle detector have a piezoresistive element,
The piezoresistive element has a planar cross shape, and a pair of application electrodes and a pair of detection electrodes are arranged at four tip portions thereof so as to face each other. The optical scanning device according to any one of the above. The first angle detector and the second angle detector have a piezoresistive element,
The piezoresistive element has a planar O-ring shape, and a pair of application electrodes and a pair of detection electrodes are arranged opposite to each other at four portions that are 90 degrees from the center of the ring. The optical scanning device according to claim 1, wherein:   The optical scanning device according to claim 1, further comprising a third angle detection unit that detects an angle of the mirror unit in the vicinity of the first shaft unit. The optical scanning device according to any one of claims 1 to 14,
An optical scanning device controller for controlling the driving of the optical scanning device;
A light source for irradiating light to the mirror part of the optical scanning device;
A light source driving circuit for driving the light source;
An image projection apparatus comprising: an image signal control unit configured to control the light source via the light source driving circuit based on an image signal.

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