JP2013003526A - Optical scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanning device that can improve the scanning accuracy of an optical scanner.SOLUTION: An image projection device (optical scanning device) 100 includes an optical scanner 10 having two horizontal resonance modes in a horizontal direction, and a drive unit for driving the optical scanner 10. The drive unit selects one of the two resonance modes, and drives the optical scanner 10 in a horizontal direction using the selected resonance mode.

Description

  The present invention relates to an optical scanning device, and more particularly to an optical scanning device including an optical scanner.

  Optical scanners that polarize and scan light beams such as laser light are used in optical devices such as image projection devices and laser printers. Some of these optical scanners include a polygon mirror that scans reflected light by rotating a polygonal column mirror with a motor, and a galvano mirror that rotates and vibrates a plane mirror by an electromagnetic actuator. However, in such an optical scanner, a mechanical drive mechanism for driving the mirror with a motor or an electromagnetic actuator is required. However, since the drive mechanism is relatively large and expensive, There is a problem in that downsizing is hindered and the price is increased.

  Therefore, in order to reduce the size, cost, and productivity of optical scanners, component parts such as mirrors and elastic beams can be manufactured using micromachining technology that uses silicon manufacturing technology to finely process silicon and glass. Development of an integrally formed MEMS (Micro Electro Mechanical Systems) optical scanner (so-called MEMS mirror) is in progress.

  Conventionally known as such an optical scanner is a two-dimensional scanning optical scanner (two-dimensional MEMS) capable of horizontal scanning and vertical scanning. A two-dimensional scanning MEMS is generally designed so that raster scanning is possible. In raster scanning, two-dimensional scanning is realized by DC driving in the vertical direction (eg, triangular wave driving of about 60 Hz) and resonance driving in the horizontal direction. Note that the two-dimensional MEMS is applied to, for example, a laser projector. There are piezoelectric, electromagnetic, electrostatic, and other driving methods for MEMS. Most of the driving methods in the horizontal direction use resonance driving.

  An example of such a MEMS mirror (two-dimensional MEMS) is described in Patent Document 1, for example. In Patent Document 1, there is one resonance mode in the horizontal direction, and horizontal driving (resonance driving) is performed at the resonance frequency of the resonance mode.

Special table 2007-522529

  Here, in the horizontal direction drive to which the resonance drive is applied, the mirror displacement is affected by the variation of the resonance frequency and the variation of the Q value. When the resonance frequency varies, the horizontal scanning period varies. On the other hand, when the Q value varies, the horizontal scanning amplitude varies. For this reason, the conventional optical scanner drive has a problem that the scanning accuracy decreases due to variations in the period and amplitude.

  The amplitude variation can be dealt with by adjusting the amplitude by the drive signal, but in this case, there is a problem that the control unit for controlling the driving (scanning) of the optical scanner becomes large.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to provide an optical scanning device capable of improving the scanning accuracy of an optical scanner.

  Another object of the present invention is to provide an optical scanning device capable of controlling the driving of an optical scanner with high accuracy while reducing the size.

  In order to achieve the above object, an optical scanning device according to one aspect of the present invention includes an optical scanner having two resonance modes in a predetermined direction, and a drive device for driving the optical scanner. The driving device selects one of the two resonance modes and drives the optical scanner in a predetermined direction in the selected resonance mode.

  The optical scanning device according to this one aspect drives the optical scanner having two resonance modes in a predetermined direction as described above. In the optical scanner, by having two resonance modes in a predetermined direction, it is possible to reduce the frequency variation of the resonance frequency and the variation of the Q value in each resonance mode compared to the case of having one resonance mode in that direction. it can.

  Here, the variation in the resonance frequency and the Q value in the optical scanner is caused by the processing variation at the time of manufacture. Therefore, it is possible to reduce variations in the resonance frequency and the Q value by improving the processing accuracy. However, as described above, the configuration having two resonance modes in the horizontal direction can reduce variations in the resonance frequency and the Q value without improving the processing accuracy. In other words, manufacturing variations in solids can be reduced.

  Then, scanning is performed by selecting one of the two resonance modes in which the variation in the resonance frequency and the variation in the Q value are reduced, and driving the optical scanner in a predetermined direction in the selected resonance mode (resonance frequency). Accuracy can be improved.

  In addition, since it is not necessary to adjust the amplitude by the drive signal in order to suppress the amplitude variation due to the variation in the Q value, the drive device does not become large. Therefore, it is possible to improve the driving accuracy of the optical scanner while reducing the size.

  The optical scanning device according to the above aspect preferably includes a PLL (Phase Locked Loop) circuit unit that performs frequency tracking control on the resonance frequency of the selected resonance mode. With this configuration, the drive frequency can be locked to the resonance frequency of the selected resonance mode by the PLL circuit unit. That is, the drive frequency can be controlled by the PLL circuit unit so as to follow the resonance frequency. As a result, even when the resonance frequency varies depending on the solid variation or the environmental temperature, the optical scanner can always be driven at the resonance frequency of the selected resonance mode.

  The optical scanner can be formed of a structure including a mirror part that reflects light. Moreover, when it has two resonance modes, the resonance mode by the side of a high frequency among two resonance modes has the characteristics that the stress distortion to a structure is large. Therefore, in driving the optical scanner, it is preferable to set the resonance frequency of the resonance mode with the smaller stress strain to the structure as the drive frequency. That is, it is preferable to select a resonance mode on the low frequency side from the two resonance modes and set the resonance frequency as the drive frequency. If comprised in this way, the robustness of a system can be ensured easily. In addition, since the stress strain applied to the structure is small, the stability of the system can also be achieved.

  In the configuration including the PLL circuit unit, preferably, a resonance mode having a resonance frequency closer to a predetermined frequency is selected, and the resonance frequency is set as a drive frequency. With this configuration, for example, by selecting a resonance mode having a resonance frequency closer to the design value, the resonance frequency closer to the design value can be set as the drive frequency. Therefore, the deviation amount from the design value of the drive frequency can be suppressed as small as possible. For this reason, for example, even when the resonance frequency changes due to environmental changes or aging, the optical scanner can be driven to resonate at a resonance frequency closer to the design value.

  In the optical scanning device according to the above aspect, the optical scanner may include a mirror part that reflects light and a mirror frame that surrounds the mirror part. In this case, it is preferable to have a second distortion sensor for detecting the movement of the mirror frame in addition to the first distortion sensor for detecting the movement of the mirror section. In driving the optical scanner, it is preferable to select the resonance mode used for driving by comparing the output from the first strain sensor and the output from the second strain sensor. With this configuration, even if the phase relationship between the two resonance modes is complicated, the output from the first strain sensor and the output from the second strain sensor are compared to drive in either of the two resonance modes. Can be detected. For example, although there are two main resonance modes, even when other small resonance modes (resonance modes that are not in the horizontal direction) are mixed and mixed, the two resonance modes can be easily detected. Therefore, for example, it is possible to prevent the driving in the resonance mode in which the optical scanner is damaged, and thus it is possible to avoid a problem that leads to a system failure.

  Further, the optical scanning device can be an optical scanning device that performs two-dimensional scanning by two scannings in a first direction and a second direction, which are different directions. In this case, the optical scanner is preferably configured to have two resonance modes in the first direction. If comprised in this way, the optical scanning apparatus of the two-dimensional scanning which can improve the scanning precision of an optical scanner can be obtained easily.

  As described above, according to the present invention, an optical scanning device capable of improving the scanning accuracy of an optical scanner can be easily obtained.

  In addition, according to the present invention, it is possible to easily obtain an optical scanning device capable of controlling the driving of the optical scanner with high accuracy while reducing the size.

It is the perspective view which showed typically the principal part structure of the optical scanner by 1st Embodiment of this invention. It is the perspective view which expanded and showed a part of FIG. It is the schematic which shows the drive signal applied to the drive part (piezoelectric element) of an optical scanner. It is the schematic diagram which showed a mode that the scanning projection was carried out with the optical scanner of two-dimensional scanning. 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 scanner by 1st Embodiment of this invention. FIG. 7 is an enlarged cross-sectional view illustrating a part of the optical scanner illustrated in FIG. 6. 1 is a plan view (a diagram showing a part of an optical scanner) showing an example of an optical scanner according to a first embodiment of the present invention. FIG. It is the top view which expanded and showed a part (part enclosed with the broken line R) of FIG. It is a figure for demonstrating the horizontal direction drive of the optical scanner by the comparative example which has one resonance mode (The figure which showed the frequency characteristic of a horizontal direction). It is a block diagram of the system which carries out follow-up control of the resonant frequency by PLL. It is the block diagram which showed the specific example of the PLL circuit part. It is the figure which showed the relationship between the phase difference of two signals to compare in a comparative example, and an LPF output value. It is a figure for demonstrating the horizontal direction drive of the optical scanner by 1st Embodiment of this invention (The figure which showed the frequency characteristic of the horizontal direction in case there are two resonance modes). It is the figure which showed the relationship between the phase difference of two signals to compare and LPF output value in 1st Embodiment of this invention. The block diagram (The block diagram of the system which applies PLL only to either Mode1 or Mode2 out of two resonance modes) which showed the structure of the optical scanner control part (horizontal drive control part) by 1st Embodiment of this invention. is there. It is the block diagram (block diagram of the system which can select a mode) which showed the structure of the optical scanner control part (horizontal drive control part) by 2nd Embodiment of this invention. It is the perspective view which showed typically the principal part structure of the optical scanner by 3rd Embodiment of this invention. It is the top view which showed the principal part structure of the optical scanner by 3rd Embodiment of this invention. The block diagram (The block diagram of the system which incorporated the phase difference discrimination | determination of the distortion sensor for mirror frames, and the distortion sensor for mirrors) which showed the structure of the optical scanner control part (horizontal drive control part) in 3rd Embodiment of this invention. is there. It is the figure (schematic diagram showing the drive signal (drive waveform) applied to the drive part (piezoelectric element)) of the optical scanner by the optical scanner control part (drive circuit) by a 4th embodiment of the present invention. FIG. 10 is a diagram illustrating a configuration of an optical scanner control unit (drive circuit) according to a fourth embodiment of the present invention (a diagram illustrating a circuit configuration (V drive configuration) for generating a vertical scanning drive signal (vertical drive voltage)). . FIG. 10 is a diagram illustrating a configuration of an optical scanner control unit (drive circuit) according to a fourth embodiment of the present invention (a diagram illustrating a circuit configuration (H drive configuration) for generating a horizontal scanning drive signal (horizontal drive voltage)). .

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described in detail with reference to the drawings. In the following embodiments, an example in which the present invention is applied to an image projection apparatus that is an example of an optical scanning apparatus will be described.

(First embodiment)
FIG. 1 is a perspective view schematically showing an optical scanner according to a first embodiment of the present invention. FIG. 2 is an enlarged perspective view of a part of FIG. FIG. 3 is a schematic diagram showing a drive signal applied to the drive unit (piezoelectric element) of the optical scanner. FIG. 4 is a schematic diagram showing a state where scanning projection is performed by a two-dimensional scanning optical scanner. 5 to 9 are views showing an optical scanner according to the first embodiment of the present invention and an image projection apparatus equipped with the optical scanner. First, an optical scanner, an image projection apparatus, and a drive system for driving the optical scanner according to the first embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 4, the optical scanner 10 according to the first embodiment is mounted on an image projection apparatus 100 such as a projector apparatus, and functions as a scanning unit that scans light from the light source 30. 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.

  The light source 30 is provided in the image projection apparatus 100 together with the optical scanner 10, and emits a light beam (for example, laser light) LT toward the optical scanner 10.

  As shown in FIGS. 1 and 2, the optical scanner 10 includes a mirror unit 11 that reflects the light beam LT from the light source 30 (see FIG. 4) toward the projection surface 200 (see FIG. 4). The mirror unit 11 has a rotation centered on a first axis (horizontal torsion bar) parallel to the X axis and a second axis (vertical torsion bar) parallel to the Y axis and intersecting the first axis at a substantially right angle. It is configured to be able to move. 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.

  As shown in FIG. 5, in addition to the optical scanner 10 and the light source 30 described above, the image projection apparatus 100 drives the optical scanner control unit 40 that controls the driving of the optical scanner 10 and the light source 30, and the light beam LT. A light source driving circuit 70 capable of modulating the light source, and an image signal control unit 80 for controlling the light source driving circuit 70.

  The optical scanner 10 has a distortion sensor 18 as will be described later. The strain sensor 18 has a piezoresistive element as an angle detection sensor that detects the angle (rotation angle (deflection angle)) of the mirror unit 11.

  The optical scanner control unit 40 includes a horizontal drive control unit (drive circuit) 50 that controls rotation about the X axis with respect to the mirror unit 11, that is, driving in the horizontal direction (H direction), and a rotation about the Y axis with respect to the mirror unit 11. And a vertical drive control unit 60 that controls driving in the vertical direction (V direction). The optical scanner control unit 40 and the horizontal drive control unit 50 are examples of the “drive device” in the present invention.

  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 scanner control unit 40 receives a synchronization signal for synchronizing the driving timing of the mirror unit 11 with the image signal. Thus, appropriate image display based on the input image signal is performed on the projection plane 200 (see FIG. 4).

  The optical scanner 10 according to the first embodiment includes a structure (MEMS structure; a resonance structure including the mirror portion 11) obtained by performing an etching process on a silicon substrate, as shown in FIG. In addition to the mirror unit 11, the fixed frame 12, the drive unit 13, and the mirror frame (movable frame) 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. 6 (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 crosses the horizontal direction 6 (an axis that scans a video (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 scanner 10 and surrounds other parts (such as the mirror unit 11, the drive unit 13, and the mirror frame 14).

  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. . Further, as shown in FIG. 7, the unimorph structure as the driving 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 13 b within a range that does not cause polarization inversion (depolarization), the piezoelectric element 13 a sandwiched between the pair of electrodes 13 b Stretch or shrink. 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.

  As shown in FIG. 6, the mirror frame 14 is a substantially rhombus-shaped frame located inside the drive unit 13. A pair of vertical torsion bars 15 extending along the Y-axis direction are provided between the mirror frame 14 and the fixed frame 12. The pair of vertical torsion bars 15 are arranged so as to overlap with the Y axis and be symmetric with respect to the X axis. Further, one end of each of the pair of vertical torsion bars 15 is connected to an end portion of the fixed frame 12 on the Y axis. The mirror frame 14 is disposed between the other ends of the pair of vertical torsion bars 15 and is supported (clamped) by the other end (the pair of vertical torsion bars 15). For this reason, the mirror frame 14 can be rotated around the Y axis with the vertical torsion bar 15 as a rotation axis (center axis).

  The mirror frame 14 is a frame that surrounds the mirror unit 11, and in addition to the mirror unit 11, a pair of horizontal torsion bars 16 extending along the X-axis direction are provided inside the mirror frame 14. The pair of horizontal torsion bars 16 are arranged 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 horizontal torsion bars 16 is connected to an end portion on the X axis of the mirror frame 14. The mirror portion 11 is disposed between the other ends of the pair of horizontal torsion bars 16 and is supported (sandwiched) by the other end (the pair of horizontal torsion bars 16). For this reason, the mirror part 11 is rotated around the Y axis together with the mirror frame 14, and is also rotated around the X axis about the horizontal torsion bar 16 as a rotation axis (center axis).

  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 vertical torsion bar 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 vertical torsion bar 15.

  Further, a distortion sensor 18 a (18) for detecting the twist angle of the vertical torsion bar 15 is provided in the vicinity of the vertical torsion bar 15. Similarly, in the vicinity of the horizontal torsion bar 16, a strain sensor 18b (18) for detecting the twist angle of the horizontal torsion bar 16 is provided. Each of the strain sensors 18a and 18b has a piezoresistive element 20, and detects a shear stress generated when the vertical torsion bar 15 and the horizontal torsion bar 16 are deformed by a resistance value. The piezoresistive element 20 (strain sensors 18a and 18b) is generated by partially doping an impurity such as boron or arsenic into a silicon substrate. And based on the output from the distortion sensor 18a, while detecting the angle (deflection angle) of the mirror part 11 (mirror frame 14) around the Y-axis by the vertical torsion bar 15, based on the output from the distortion sensor 18b, The angle (deflection angle) of the mirror unit 11 around the X axis by the horizontal torsion bar 16 is detected.

  The strain sensor 18a is arranged on the axis of the vertical torsion bar 15 (on the Y axis) (the root portion of the vertical torsion bar 15), and the strain sensor 18b is on the axis of the horizontal torsion bar 16 (on the X axis). ) (The root portion of the horizontal torsion bar 16). The term “on the axis” includes not only on the vertical torsion bar 15 and the horizontal torsion bar 16 but also on the extension line of the vertical torsion bar 15 and the extension line of the horizontal torsion bar 16.

  The scanning operation (drive control) of the optical scanner 10 is performed by adjusting the timing for driving (stretching) the four drive units 13 and vibrating the mirror unit 11 about the X axis and the Y axis. For example, the frequency when vibrating around the Y axis is set to 60 Hz, and the frequency when vibrating around the X axis is set to 30 kHz. That is, it is driven at 60 Hz (design value) in the vertical direction V (see FIG. 4), and is driven at 30 kHz (design value) in the horizontal direction H (see FIG. 4). Further, the vertical direction is DC driven, and the horizontal direction is resonance driven. The movement of the mirror unit 11 is detected by the distortion sensor 18 in both the vertical direction and the horizontal direction. The horizontal direction H is an example of the “predetermined direction” and the “first direction” in the present invention, and the vertical direction V is an example of the “second direction” in the present invention.

  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 unit 11 vibrates around the Y axis together with the mirror frame 14, and the inclination (angle) of the mirror unit 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 mirror frame 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.

  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.

  Here, as shown in FIG. 3, by applying a voltage obtained by superimposing the horizontal scanning drive signal and the vertical scanning drive signal to the four drive units 13 (piezoelectric elements 13a), the horizontal torsion bar 16 is supported as described above. The horizontal resonance driving and the vertical driving (DC driving) for driving the entire mirror frame 14 are realized. The vertical drive signal is a 60 Hz triangular wave, and the horizontal drive signal is a sine wave. The frequency of the horizontal drive signal is the horizontal resonance frequency of the mirror unit 11. Therefore, as will be described later, the phase difference between the drive signal and the horizontal strain sensor detection signal is detected and the PLL is applied so that the horizontal drive frequency becomes the horizontal resonance frequency. Thus, even when the resonance frequency is shifted due to the environmental temperature or the like, the tracking control can be performed by the PLL.

  In the image projection apparatus 100 equipped with such an optical scanner 10, as shown in FIG. 4, a 60 Hz triangular wave scan is performed in the vertical direction (V direction), and a sine wave at the resonance frequency in the horizontal direction (H direction). A scan is performed. Since the vertical direction is DC drive, the scanning angle is determined by the drive signal. On the other hand, since the vertical direction is resonant driving, the number of scans per unit time and the scan angle vary. Therefore, the scanning angle corresponds by adjusting the amplitude of the drive signal based on the distortion sensor output.

  Here, in the horizontal direction drive to which the resonance drive is applied, the mirror displacement is affected by the variation of the resonance frequency and the variation of the Q value. When the resonance frequency varies, the horizontal scanning period varies. On the other hand, when the Q value varies, the horizontal scanning amplitude varies. Further, the variation in the resonance frequency and the Q value in the optical scanner is caused by the processing variation at the time of manufacture. Therefore, the inventors of the present application performed a TM (Taguy Methods) evaluation by simulation in order to reduce the influence of this processing variation. As a result, it has been found that it is desirable to create two resonance modes in the mirror horizontal direction. That is, it has been found that manufacturing robustness can be improved by having two resonance modes in the horizontal direction.

  Therefore, in the first embodiment, the optical scanner 10 is configured to have two resonance modes in the horizontal direction. In order to obtain a configuration having two resonance modes in the horizontal direction, in addition to the horizontal torsion bar 16 (see FIGS. 2 and 6), the mirror frame 14 (see FIGS. 2 and 6) also has a horizontal direction (horizontal scanning direction). ) To be twisted. As a result, two resonance modes are obtained: a resonance mode based on vibrations based on the horizontal torsion bar 16 and a resonance mode based on vibrations based on the mirror frame 14.

  The resonance frequency of the optical scanner 10 is clarified in terms of Young's modulus, Poisson's ratio, density in the substrate (silicon substrate), the shape of the mirror portion 11, the fixing condition, the piezoelectric constant of the piezoelectric element, and the like. For example, it can be calculated by commercially available simulation software. Therefore, a configuration having two resonance modes in the horizontal direction can be easily obtained by simulation.

  In this case, for example, as shown in FIGS. 8 and 9, the distance L (see FIG. 8) from the drive unit 13 to the mirror frame 14 is shortened, and the width of the displacement enlargement unit 21 provided in the vertical torsion bar 15. W (see FIG. 19) may be lengthened. The displacement enlarging unit 21 has a function of enlarging the displacement during DC driving. Then, by adjusting the distance L and the width W, the rigidity of the portion between the drive unit 13 and the mirror frame 14 can be adjusted. Thereby, it is possible to easily generate two or more resonance modes for resonantly driving the mirror unit 11 (driving body), and adjust the two resonance modes so as to approach each other (Δf in FIG. 4 becomes small). be able to. The above is one example in which the resonance mode can be adjusted by changing the rigidity of this portion, and the method for adjusting the resonance mode may be other than the above.

  As described above, since the optical scanner 10 is symmetric with respect to the X axis and the Y axis, only a part of the optical scanner 10 is shown in FIG. Further, in FIG. 8, the displacement enlarged portion 21 is formed in the drive portion 13 (region to be the drive portion 13 of the silicon substrate) and the vertical torsion bar 15. If comprised in this way, the deformation | transformation (bending deformation etc.) of the drive part 13 (area | region used as the drive part 13 of a silicon substrate) will be changed into a twist deformation | transformation (rotation torque), and a displacement will be expanded and transmitted to the vertical torsion bar 15. It is preferable because it can be made to occur. For this reason, such a configuration is preferably applied also to the optical scanner 10 according to the first embodiment. However, a configuration in which such a displacement enlarging portion 21 is not formed is also possible. The displacement enlarging portion 21 may be formed on either the holding portion 19 or the vertical torsion bar 15.

  In both of the two resonance modes, the frequency variation of the resonance frequency is reduced. The “horizontal direction” is a direction scanned by resonance driving as described above, and is also a direction in which the horizontal torsion bar 16 (first axis) is rotated as a central axis.

  In the first embodiment, one of the two resonance modes is selected by the optical scanner control unit 40 (horizontal drive control unit 50) (see FIG. 5), and the optical scanner 10 is horizontal in the selected resonance mode. Driven in the direction.

  Next, the horizontal driving of the optical scanner 10 by the optical scanner control unit 40 (horizontal drive control unit 50) of the first embodiment will be described. Before describing driving by the optical scanner control unit 40 of the first embodiment (driving the optical scanner 10 having two resonance modes in the horizontal direction), driving of the optical scanner according to the comparative example having one resonance mode is described. Will be described first.

  10 to 13 are diagrams for explaining horizontal driving of an optical scanner according to a comparative example having one resonance mode. As shown in FIG. 10A, the optical scanner according to the comparative example is a second-order lag system in which one resonance mode exists. In FIG. 10, one resonance mode is indicated as mode0. Further, the horizontal driving according to the comparative example is performed at this resonance frequency. In the second-order lag system, as shown in FIG. 10B, the phase difference between the drive signal and the mirror displacement is 90 degrees at the resonance frequency.

  Since the resonance frequency varies depending on individual variations and environmental temperature, it is preferable to perform PLL control in order to always drive at the resonance frequency.

  Further, as shown in FIG. 11, the optical scanner control unit 540 that controls driving of the optical scanner according to the comparative example has a detection circuit 51 that detects a signal from the distortion sensor 18 (18a), and performs frequency tracking control with respect to the resonance frequency. A PLL circuit unit 150, an amplitude control circuit 52, and a horizontal drive circuit 53 are provided. The PLL circuit unit 150 includes a phase comparison circuit 151, a loop filter 152, and a voltage controlled oscillator (VCO) 153.

  In the horizontal drive of the optical scanner according to the comparative example configured as described above, the horizontal displacement sensor 18b (18) detects the displacement operation in the mirror horizontal direction. Then, the output signal of the VCO 153 is controlled so that the phase difference between the detection signal of the strain sensor 18b and the drive signal output from the VCO 153 is 90 degrees. By this operation, the drive signal for driving the mirror part of the MEMS 500 (optical scanner) in the horizontal direction follows the resonance frequency. The horizontal swing angle of the mirror part depends on the Q value of resonance. Since the Q value also varies, the amplitude control circuit 52 controls the amplitude of the drive signal based on the output value from the distortion sensor 18b in order to obtain a predetermined mirror swing angle.

  FIG. 12 shows a specific example of the PLL circuit unit 150. In this specific example, the phase comparison circuit 151 (see FIG. 11) that compares the phase difference between the detection signal from the distortion sensor 18b (see FIG. 11) and the drive signal is configured by an ExOR circuit 151a. A pulse train corresponding to the phase difference is output from the ExOR circuit 151a. The loop filter 152 (see FIG. 11) includes a low-pass filter (LPF) 152a, and the pulse train output from the ExOR circuit 151a is smoothed by the LPF 152a. Then, based on the LPF output value, control for determining whether to increase or decrease the drive frequency is performed.

  The determination control for increasing or decreasing the drive frequency will be specifically described with reference to FIG. FIG. 13 shows the relationship between the phase difference between two signals to be compared and the LPF output value. As shown in FIG. 13, when the phase difference between two signals to be compared is 0 degree, the LPF output value is zero. When the phase difference is 180 degrees, the LPF output value is Vcc. Since the LPF output value with a phase difference of 0 to 180 degrees is linear, the LPF output value with a phase difference of 90 degrees is Vcc / 2. Therefore, when locking with a phase difference of 90 degrees, the target value of the LPF output value is Vcc / 2. When the LPF output value is smaller than Vcc / 2, control is performed to increase the drive frequency. On the other hand, when the LPF output value is larger than Vcc / 2, control is performed to increase the drive frequency.

  In this way, the optical scanner according to the comparative example is driven in the horizontal direction.

  14 to 16 are views for explaining horizontal driving of the optical scanner according to the first embodiment of the present invention. Subsequently, with reference to FIGS. 6, 12, and 14 to 16, driving by the optical scanner control unit 40 (horizontal drive control unit 50) of the first embodiment (an optical scanner having two resonance modes in the horizontal direction). 10 driving) will be described.

  As shown in FIG. 14A, the optical scanner 10 according to the first embodiment has two resonance modes. In FIG. 14, the two resonance modes are shown as Mode1 and Mode2, respectively. Further, the resonance mode of Mode 1 is a resonance mode due to vibration made with reference to the horizontal torsion bar 16 (see FIG. 6). On the other hand, the resonance mode of Mode 2 is a resonance mode due to vibration made with reference to the mirror frame 14 (see FIG. 6).

When the frequency of Mode 1 is fmode 1 and the frequency of Mode 2 is fmode 2, the relationship between Mode 1 and Mode 2 preferably satisfies the following expressions (1) and (2).
f _mode1 <f _mode 2 (1)
f _mode1 + 0.2 × f _mode1 ≧ f _mode2 (2)

  As shown in FIG. 14, in Mode 1, the phase difference between the drive signal and the detection signal of the distortion sensor 18b (see FIG. 6) is 90 degrees. In Mode 2, the phase difference between the drive signal and the detection signal of the distortion sensor 18b (see FIG. 6) is 270 degrees.

  In the first embodiment, the relationship between the phase difference between two signals to be compared and the LPF output value is as shown in FIG. Since the LPF output value with a phase difference of 0 to 180 degrees is linear, the LPF output value with a phase difference of 90 degrees is Vcc / 2. In addition, since the LPF output value from 180 degrees to 360 degrees is also linear, the LPF output value when the phase difference is 270 degrees is Vcc / 2. Note that the slope of the LPF output value when the phase difference is 0 degree to 180 degrees and the slope of the LPF output value when the phase difference is 180 degrees to 360 degrees are opposite to each other.

  Here, when the resonance frequency of Mode 1 is used as the drive frequency, the target value of the LPF output value is set to Vcc / 2, and when the output value is smaller than Vcc / 2, control is performed to increase the drive frequency. Conversely, when the output value is greater than Vcc / 2, control is performed to lower the drive frequency. On the other hand, when the resonance frequency of Mode 2 is used as the drive frequency, the target value of the LPF output value is set to Vcc / 2, and when the output value is smaller than Vcc / 2, the drive frequency is controlled to be lowered. Conversely, when the output value is greater than Vcc / 2, control is performed to increase the drive frequency.

  As the drive frequency, which resonance mode is used can be selected, and PLL is applied by the logic for the selected mode.

  Comparing the two resonance modes, the resonance mode on the high frequency side has a feature that the influence of stress strain on the MEMS structure is large. Therefore, in order to improve the robustness of the system, it is preferable to use a resonance mode (Mode 1) on the low frequency side that is less affected by stress strain on the MEMS structure. That is, it is preferable to select a resonance mode (Mode 1) on the low frequency side and set the resonance frequency as the driving frequency.

  Further, as shown in FIG. 16, the optical scanner control unit 40 (horizontal drive control unit 50) that controls the driving of the optical scanner 10 according to the first embodiment includes a detection circuit 51 that detects a signal from the distortion sensor 18b, and a resonance frequency. 1 has a PLL circuit unit 150 and a horizontal drive circuit 53 for performing frequency tracking control. The PLL circuit unit 150 includes a phase comparison circuit 151 and a frequency control circuit 154. The loop filter and voltage controlled oscillator (VCO) are included in the frequency control circuit 154, for example. Similarly to the comparative example shown in FIG. 12, the phase comparison circuit 151 is composed of an ExOR circuit, and the loop filter is composed of LPF. However, in the first embodiment, unlike the comparative example, the amplitude control circuit 52 (see FIG. 11) is not provided.

  In the frequency control circuit 154, logic for applying a PLL to either the resonance mode of Mode 1 or the resonance mode of Mode 2 is set in advance. In other words, in the frequency control circuit 154 of the first embodiment, the PLL logic is set for mode 1 locking for locking Mode 1 or mode 2 locking for locking Mode 2.

  As described above, when the two resonance modes are compared, the stress mode applied to the MEMS structure is smaller in the resonance mode (Mode 1) on the low frequency side. Therefore, in consideration of the stability of the system, it is preferable to drive with Mode1. For this reason, in the first embodiment, the logic is set so that the frequency control circuit 154 applies a PLL to the resonance mode of Mode1. However, the frequency control circuit 154 can also set the logic so as to apply a PLL to the resonance mode of Mode2.

  The remaining operations of the optical scanner 10 according to the first embodiment for driving in the horizontal direction are the same as those in the comparative example described above.

  In this manner, the optical scanner 10 is driven in the horizontal direction by the optical scanner control unit 40 (horizontal drive control unit 50) of the first embodiment.

  In the first embodiment, as described above, the optical scanner 10 having two horizontal resonance modes is driven. In the optical scanner 10, by having two horizontal resonance modes, the frequency variation of the resonance frequency and the Q value variation in each resonance mode can be reduced as compared with the case of having one horizontal resonance mode. Can do.

  Further, as described above, the variation in the resonance frequency and the Q value is caused by the processing variation at the time of manufacturing the optical scanner 10. Therefore, it is possible to reduce variations in the resonance frequency and the Q value by improving the processing accuracy. However, as described above, the optical scanner 10 having two horizontal resonance modes can reduce variations in the resonance frequency and the Q value without improving the processing accuracy. In other words, manufacturing variations in solids can be reduced.

  Then, the optical scanner control unit 40 (horizontal drive control unit 50) selects one of the two resonance modes in which the variation in the resonance frequency and the variation in the Q value are reduced, and the selected resonance mode (resonance frequency). ), The scanning accuracy can be improved by driving the optical scanner 10 (mirror unit 11) in the horizontal direction.

  In addition, since it is not necessary to perform amplitude adjustment by the drive signal in order to suppress amplitude variation due to Q value variation, an amplitude control circuit is not required. Therefore, the control unit (drive device) does not increase. Thereby, the drive accuracy of the optical scanner 10 can be improved while achieving miniaturization.

  In the first embodiment, the optical scanner control unit 40 (horizontal drive control unit 50) includes the PLL circuit unit 150 that performs frequency tracking control with respect to the resonance frequency of the selected resonance mode. Thus, the drive frequency can be locked to the resonance frequency of the selected resonance mode. That is, the drive frequency can be controlled by the PLL circuit unit 150 so as to follow the resonance frequency. As a result, even when the resonance frequency varies depending on the solid variation or the environmental temperature, the optical scanner can always be driven at the resonance frequency of the selected resonance mode.

  In the first embodiment, as described above, the optical scanner control unit 40 (horizontal drive control unit 50) uses the resonance frequency of the resonance mode (Mode 1) with the smaller stress strain on the MEMS structure as the drive frequency. The robustness of the system can be easily secured by horizontally driving the optical scanner 10 (mirror unit 11). In addition, since the stress strain applied to the structure is small, the stability of the system can also be achieved.

  Accordingly, the scanning accuracy can be improved by driving the optical scanner 10 according to the first embodiment by the optical scanner control unit 40 (horizontal drive control unit 50).

(Second Embodiment)
FIG. 17 is a block diagram (block diagram of a mode selectable system) showing the configuration of the optical scanner control unit (horizontal drive control unit) according to the second embodiment of the present invention. Next, with reference to FIG. 17, the drive system by 2nd Embodiment of this invention is demonstrated. Note that, in FIG. 17, corresponding components are denoted by the same reference numerals, and redundant description is omitted as appropriate.

  In the system according to the second embodiment, unlike the first embodiment, it is always selected whether to drive in the Mode 1 resonance mode or the Mode 2 resonance mode, out of the two resonance modes.

  In the second embodiment, a frequency discrimination circuit 54 is further provided in the configuration of the first embodiment. The frequency discriminating circuit 54 is connected to the frequency control circuit 154 and receives a signal from the frequency control circuit 154. Further, the frequency discriminating circuit 54 discriminates which one of the two resonance modes the resonance frequency of the resonance mode is closer to the design value at a predetermined timing, and sets the resonance frequency tracking setting of the frequency control circuit 154 based on the result. change. That is, in the second embodiment, the frequency discriminating circuit 54 discriminates which of the two resonance modes (resonance frequency) is closer to the design value of the drive frequency, and sets the setting of the frequency control circuit 154 to the design value. Switch to a closer resonance mode. The mirror is driven in the horizontal direction in the resonance mode (resonance frequency) closer to the design value of the drive frequency.

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

  In the second embodiment, as described above, the resonance mode having a resonance frequency closer to the design value of the drive frequency is selected, and the resonance frequency is set as the drive frequency. The amount of deviation can be kept as small as possible. Therefore, for example, even when the resonance frequency changes due to environmental changes or aging, the optical scanner can be driven to resonate at a resonance frequency closer to the design value.

  Note that when the resonance frequency of horizontal scanning changes (deviates from the design value), the number of scanning lines (scanning line density) scanned per unit time changes. Although the influence of the scanning line density can be adjusted by image processing, the processing becomes complicated in this case. Therefore, by configuring as described above, it is possible to reduce the influence of the scanning line density while suppressing complicated processing.

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

(Third embodiment)
18 and 19 are diagrams showing the main configuration of an optical scanner according to the third embodiment of the present invention. FIG. 20 is a block diagram (block diagram of the drive system) showing the configuration of the optical scanner control unit (horizontal drive control unit) in the third embodiment of the present invention. Next, with reference to FIGS. 18-20, the drive system by 3rd Embodiment of this invention is demonstrated. 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 FIGS. 18 and 19, the optical scanner 10 further includes a distortion sensor 18 c (18) for monitoring the movement of the mirror frame 14. Specifically, in the third embodiment, in addition to the distortion sensors 18a and 18b for monitoring the vertical movement and the horizontal movement of the mirror unit 11, the movement of the mirror frame 14 is monitored. A strain sensor 18c is added.

  Further, the added strain sensor 18c has a piezoresistive element 20 like the strain sensors 18a and 18b, and is generated by partially doping impurities such as boron and arsenic into silicon. Yes. Since this process does not depend on the number of strain sensors to be generated (the cost of generating strain sensors is not related to the number of strain sensors), even if the number of strain sensors is increased, the cost does not increase.

  The strain sensor 18c is disposed, for example, on an extension line (on the Y axis) of the vertical torsion bar 15 in the mirror frame 14.

  The strain sensor 18c detects a twist angle of the mirror frame 14 in the horizontal direction. In the case where the optical scanner 10 has two resonance modes, as described above, one of the two resonance modes is a resonance mode due to vibration made with the mirror frame 14 as a reference. That is, this is a resonance mode that occurs when the mirror frame 14 is twisted in the horizontal direction. For this reason, by providing the strain sensor 18c, the twist (movement) of the mirror frame 14 in which one of the two resonance modes occurs is detected.

  Then, based on phase difference information between the distortion sensor 18b (mirror distortion sensor 18b) for detecting the movement of the mirror unit 11 and the distortion sensor 18c (mirror distortion sensor 18c) for detecting the movement of the mirror frame 14, It is possible to detect which of the resonance modes is being driven. The strain sensor 18b (mirror strain sensor 18b) is an example of the “first strain sensor” in the present invention, and the strain sensor 18c (mirror frame strain sensor 18c) is the “second strain sensor” in the present invention. It is an example.

  Further, in the third embodiment, as shown in FIG. 20, in the configuration of the first embodiment, a resonance mode determination circuit 55 is further provided. The resonance mode discriminating circuit 55 receives a detection signal from the mirror distortion sensor 18b and a detection signal from the mirror frame distortion sensor 18c. The resonance mode discriminating circuit 55 discriminates the phase difference between the input mirror strain sensor output and the mirror frame strain sensor output, thereby performing horizontal resonance driving in either of the two resonance modes. Detect whether or not

  When the optical scanner 10 (see FIG. 19) is driven in the mode 1 resonance mode, the phases of the two detection signals are in phase and the phase difference is substantially zero. On the other hand, when the optical scanner 10 (see FIG. 19) is driven in the mode 2 resonance mode, the phase of the two detection signals is an intermediate value between the in-phase and anti-phase.

  Further, the resonance mode discrimination circuit 55 outputs the result to the frequency control circuit 154 in order to apply the phase difference discrimination between the mirror distortion sensor output and the mirror frame distortion sensor output to the drive frequency control.

  The frequency control circuit 154 selects (changes) a resonance mode to be used for driving based on the phase difference determination result output from the resonance mode determination circuit 55, and the mirror unit of the optical scanner 10 at the resonance frequency of the resonance mode. 11 is driven in the horizontal direction.

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

  In the third embodiment, as described above, the output (detection signal) from the distortion sensor 18b (mirror distortion sensor 18b) and the output (detection signal) from the distortion sensor 18c (mirror frame distortion sensor 18c). By performing the phase difference discrimination, it is possible to detect which of the two resonance modes is being driven. For this reason, even if the frequency characteristic becomes complicated by selecting the resonance mode to be used for driving based on the detected phase difference determination result, the optical scanner 10 can be operated in either the Mode 1 or Mode 2 resonance mode. The mirror unit 11 can be driven.

  For example, if there are two main resonance modes, but other small resonance modes (resonance modes that are not in the horizontal direction) are mixed and mixed, the phase delay is caused by the small resonance modes, so the drive signal and distortion It may be difficult to identify the resonance mode in the phase difference determination with the sensor 18b (mirror distortion sensor 18b). In that case, driving in a resonance mode in which the MEMS structure is damaged may lead to a system failure.

  However, by configuring as described above, even when the frequency characteristic becomes complicated, the two resonance modes can be easily detected, and the mirror unit 11 of the optical scanner 10 can be moved in either the Mode 1 or Mode 2 resonance mode. It can be driven. Therefore, since driving in a resonance mode that damages the MEMS structure is suppressed, the occurrence of a system failure can be suppressed.

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

(Fourth embodiment)
21 to 23 are diagrams showing the configuration of an optical scanner control unit (drive circuit) according to a fourth embodiment of the present invention. FIG. 21 is a schematic diagram showing a drive signal (drive waveform) applied to the drive unit (piezoelectric element) of the optical scanner. FIG. 22 is a diagram showing a circuit configuration (V drive configuration) for generating a vertical scan drive signal (vertical drive voltage), and FIG. 23 is for generating a horizontal scan drive signal (horizontal drive voltage). It is a figure which shows the circuit structure (H drive structure). Next, with reference to FIGS. 21 to 23, in the fourth embodiment, a circuit configuration of a drive circuit (generation circuit) that generates a drive voltage will be described.

  As shown in FIG. 21, the vertical drive voltages (V +, V−) are DC drive voltages. In order to drive the mirror unit 11 in the vertical direction by the DC drive voltage, the DC drive voltage requires a certain amount of high voltage (amplitude). Further, in order to prevent the negative voltage from exceeding the coercive electric field of the piezoelectric element, offset driving to the positive side is required.

  Here, since both V + and V- have the same waveform with an amplitude of 70 Vp-p, it is easy to input a common signal (voltage). However, in this case, as described above, the minus voltage exceeds the coercive electric field of the piezoelectric element, so that a problem of depolarization occurs. Therefore, in order to prevent the occurrence of depolarization, a signal having an offset in the DC level is input to the drive unit 13 of the optical scanner 10 so that the plus side is 50 V to -20 V and the minus side is 20 V to -50 V. Is done.

  Such a voltage (signal) is generated by the circuit shown in FIG. Specifically, a high voltage signal of −35V to 35V is generated from the basic signal (3.3V to 0V) by an amplifier, and a high voltage signal of 50V to −20V (V +) and a signal of 20V to −50V (V−) are generated. Level conversion. The basic signal is output with the phase changed by 180 degrees by the inverting amplifier circuit. The high voltage signal of −35V to 35V is level-converted by a constant current circuit in which a Zener diode and a constant current diode are connected in series.

  The horizontal drive voltages (H1, H2) are generated by the circuit shown in FIG. Specifically, the horizontal drive voltage H1 is generated by amplifying a basic signal by an amplifier. On the other hand, the horizontal drive voltage H2 is generated by amplifying the basic signal by changing its phase by 180 degrees by an inverting amplifier circuit. As a result, a horizontal drive voltage H2 that is a signal having an opposite phase to the horizontal drive voltage H1 is generated.

  Then, as shown in FIG. 21, a voltage in which the vertical drive voltage (V +, V−) and the horizontal drive voltage (H1, H2) are superimposed is applied to each drive unit 13 (piezoelectric element).

  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 above first to fourth embodiments, an example in which one distortion sensor is provided in the vicinity of the vertical torsion bar, in the vicinity of the horizontal torsion bar, and in the mirror frame is shown. A plurality of sensors can be provided.

  Moreover, although the example using the drive part of the unimorph structure was shown in the said 1st-3rd embodiment, such a piezoelectric-type drive part is not restricted to a unimorph, For example, a bimorph may be sufficient.

  In the first to third embodiments, an example of an optical scanner capable of two-dimensional scanning is shown as an example of an optical scanner. However, the present invention is not limited to this, and may be a one-dimensional optical scanner, for example. .

  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.

  The optical scanning device of the present invention can be applied to an image forming apparatus such as a copying machine or a printer in addition to the image projection apparatus.

10 Optical scanner (MEMS mirror)
DESCRIPTION OF SYMBOLS 11 Mirror part 12 Fixed frame 13 Drive part 13a Piezoelectric element 13b Electrode 14 Mirror frame (movable frame)
15 vertical torsion bar 16 horizontal torsion bar 17 connecting portion 18a strain sensor 18b strain sensor, mirror strain sensor (first strain sensor)
18c Strain sensor, strain sensor for mirror frame (second strain sensor)
20 Piezoresistive element 30 Light source 40 Optical scanner controller (drive device)
50 Horizontal drive controller (drive device)
DESCRIPTION OF SYMBOLS 51 Detection circuit 53 Horizontal drive circuit 54 Frequency discrimination circuit 55 Resonance mode discrimination circuit 60 Vertical drive control part 70 Light source drive circuit 80 Image signal control part 100 Image projection apparatus (optical scanning apparatus)
150 PLL circuit section 151 Phase comparison circuit 151a ExOR circuit 152 Loop filter 152a LPF
154 Frequency control circuit

Claims (6)

An optical scanner having two resonance modes in a predetermined direction;
A drive device for driving the optical scanner,
The driving device selects one of two resonance modes and drives the optical scanner in the predetermined direction in the selected resonance mode.   The optical scanning device according to claim 1, further comprising a PLL circuit unit that performs frequency tracking control with respect to a resonance frequency of the selected resonance mode. The optical scanner comprises a structure including a mirror part that reflects light,
3. The optical scanning device according to claim 2, wherein in driving the optical scanner, a resonance frequency of a resonance mode having a smaller stress strain on the structure is used as a driving frequency. 4.   3. The optical scanning device according to claim 2, wherein a resonance mode having a resonance frequency closer to a predetermined frequency is selected, and the resonance frequency is set as a drive frequency. The optical scanner includes a mirror part that reflects light and a mirror frame that surrounds the mirror part, and includes a first distortion sensor that detects movement of the mirror part and a second distortion sensor that detects movement of the mirror frame. ,
The resonance mode used for driving is selected by comparing the output from the first strain sensor and the output from the second strain sensor in driving the optical scanner. 5. The optical scanning device according to claim 1. An optical scanning device that performs two-dimensional scanning by two scanning in a first direction and a second direction, which are different directions,
The optical scanning device according to claim 1, wherein the optical scanner has two resonance modes in the first direction.