JP2012118125A - Optical scanning apparatus and driving method thereof - Google Patents

Abstract

The present invention provides an optical scanning apparatus and a driving method thereof capable of causing the resonance frequency of a mirror to follow the driving frequency of the mirror in both the main scanning direction and the sub-scanning direction.
The optical scanning device is driven in a first direction or a second direction orthogonal to the first direction with a predetermined driving waveform and emits light emitted from the light source in a first direction. A vibrating mirror that reflects on the first surface and scans in the first direction or the second direction; and a second surface that is a back surface of the first surface of the vibrating mirror; A two-dimensional photo reflector that irradiates a surface with light and detects a swing angle of the vibrating mirror in the first direction and the second direction based on reflected light from the second surface; The phase difference between the actual phase of the oscillating mirror in the first direction and the drive waveform in the first direction obtained based on the deflection angle, and the actual phase of the oscillating mirror in the second direction and the A phase controller that calculates a phase difference from the driving waveform in the second direction.
[Selection] Figure 1

Description

  The present invention relates to an optical scanning device that scans light emitted from a light source in a predetermined direction, and a driving method thereof.

  2. Description of the Related Art Conventionally, there is known an optical scanning device that scans light modulated according to input image data on a screen to form an image. In order for such an optical scanning device to project an image, the mirror must be driven in the main scanning direction and the sub-scanning direction. In the case of the raster scanning method, although there are differences depending on the image resolution, the difference in scanning frequency is that the sub-scanning frequency is 60 Hz (progressive scanning frame frequency) and the main scanning frequency is about 30 KHz (when the screen resolution is VGA) or more. Arise. For this reason, a configuration in which the main scanning system and the sub-scanning system are provided separately is common. For example, horizontal scanning (main scanning) is performed by a polygon mirror, and vertical scanning (sub-scanning) is performed by a galvanometer mirror.

  However, providing the main scanning system and the sub scanning system separately causes an increase in size and cost due to a complicated structure. Therefore, in recent years, a microfabrication technique has been developed, and a two-dimensional scanning integrated MEMS mirror is being sought for a compact information device that is easy to carry.

  By the way, the MEMS mirror is generally driven by utilizing the resonance frequency of the mirror. However, since the resonance frequency differs (varies) for each individual MEMS mirror, in the conventional optical scanning device, either the drive frequency or the resonance frequency of the mirror is changed in order to drive each MEMS mirror efficiently. Both frequencies are matched (for example, see Patent Documents 1 and 2).

  For example, in Patent Document 1, with respect to the main scanning direction, the mirror resonance frequency is detected by detecting the mirror position (angle) using reflection of light on the back side of the mirror, and the detected resonance frequency of the mirror is close to the detected resonance frequency. A technique for adjusting the driving frequency is disclosed. In Patent Document 2, with respect to the main scanning direction, the mirror resonance frequency is detected by detecting the mirror position (angle) using reflection of light on the mirror front side, and the detected resonance frequency of the mirror is in the vicinity. A technique for adjusting the driving frequency is disclosed.

  However, in both techniques disclosed in Patent Documents 1 and 2, the driving frequency in the main scanning direction is adjusted to the vicinity of the resonance frequency of the mirror, but the sub-scanning direction is not considered.

  The present invention has been made in view of the above points, and an optical scanning device capable of causing the resonance frequency of the mirror to follow the mirror driving frequency in both the main scanning direction and the sub-scanning direction, and the driving thereof. It is an object to provide a method.

  The optical scanning device is driven in a first direction or a second direction orthogonal to the first direction with a predetermined driving waveform, and the emitted light emitted from the light source is reflected by the first surface. And a vibration mirror that scans in the first direction or the second direction, and a second surface that is a back surface of the first surface of the vibration mirror, and emits light to the second surface. A two-dimensional photoreflector that irradiates and detects a swing angle of the vibrating mirror in the first direction and the second direction based on reflected light from the second surface; and based on a swing angle of the vibrating mirror The phase difference between the actual phase of the oscillating mirror in the first direction and the drive waveform in the first direction obtained in the above, and the actual phase of the oscillating mirror in the second direction and the second direction And a phase controller for calculating a phase difference with the drive waveform of .

  In the driving method of the present optical scanning device, the oscillating mirror is driven in a first direction or a second direction orthogonal to the first direction with a predetermined driving waveform, and the emitted light emitted from the light source is transmitted to the oscillating mirror. A first step of reflecting on the first surface and scanning in the first direction or the second direction, and irradiating light to a second surface which is the back surface of the first surface of the vibrating mirror; A second step of detecting a swing angle of the vibrating mirror in the first direction and the second direction based on reflected light from the second surface; and obtained based on a swing angle of the vibrating mirror. The phase difference between the actual phase of the oscillating mirror in the first direction and the driving waveform in the first direction, and the actual phase of the oscillating mirror in the second direction and the driving waveform in the second direction. And a third step of calculating a phase difference between the first and second phases.

  According to the disclosed technology, it is possible to provide an optical scanning apparatus and a driving method thereof that can cause the resonance frequency of the mirror to follow the driving frequency of the mirror in both the main scanning direction and the sub-scanning direction.

It is a figure which illustrates the optical scanning device concerning this embodiment. It is a figure which illustrates the projector provided with the optical scanning device concerning this embodiment. It is a figure which illustrates the optical scanning part and two-dimensional photo reflector which concern on this Embodiment. It is a top view which illustrates the vibration mirror vicinity of FIG. 3, and a two-dimensional photo reflector. FIG. 4 is a right side view illustrating the vicinity of the vibrating mirror and the two-dimensional photo reflector in FIG. 3. It is FIG. (1) for demonstrating operation | movement of a two-dimensional photo reflector. It is FIG. (2) for demonstrating operation | movement of a two-dimensional photo reflector. It is an example of the block diagram of the control system which drives a vibration mirror. It is an example of the block diagram of the input-output transfer function of a vibration mirror. It is a figure which illustrates the frequency transfer characteristic of the input / output of the block diagram shown in FIG. FIG. 6 is a diagram (part 1) illustrating the relationship between the phase of the driving waveform of the vibrating mirror and the phase of the deflection angle waveform of the vibrating mirror. FIG. 10 is a diagram (part 2) illustrating the relationship between the phase of the driving waveform of the vibrating mirror and the phase of the deflection angle waveform of the vibrating mirror. FIG. 10 is a diagram (part 3) illustrating the relationship between the phase of the driving waveform of the vibrating mirror and the phase of the deflection angle waveform of the vibrating mirror;

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

  FIG. 1 is a diagram illustrating an optical scanning device according to this embodiment. FIG. 2 is a diagram illustrating a projector provided with the optical scanning device according to this embodiment. Referring to FIG. 1 and FIG. 2, the optical scanning device 10 generally includes a first light source 20a, a second light source 20b, a third light source 20c, a first lens 30a, a second lens 30b, It has a three lens 30c, a first mirror 40a, a second mirror 40b, a third mirror 40c, an optical scanning unit 50, a two-dimensional photo reflector 59, and a scanning lens 60. The optical scanning device 10 is built in the projector 80, scans light in two dimensions according to an image signal, and projects the light onto a screen 90.

  In the optical scanning device 10, the first light source 20a, the second light source 20b, and the third light source 20c are light sources that emit green (G), red (R), and blue (B) light, respectively. As the 1st light source 20a, the 2nd light source 20b, and the 3rd light source 20c, a laser diode etc. can be used, for example. The first light source 20a, the second light source 20b, and the third light source 20c are controlled in emission power, emission timing, and the like by a light source control means (not shown). The light source control means (not shown) may be provided inside the optical scanning device 10 or may be provided outside.

  Each light (diverging light) emitted from the first light source 20a, the second light source 20b, and the third light source 20c in accordance with the content of the image signal is respectively the first lens 30a, the second lens 30b, and the third lens 30c. Is converted into substantially parallel light and enters the first mirror 40a, the second mirror 40b, and the third mirror 40c. As the first lens 30a, the second lens 30b, and the third lens 30c, for example, a convex glass lens, a plastic lens, or the like can be used. As the 1st mirror 40a, the 2nd mirror 40b, and the 3rd mirror 40c, a plane mirror etc. can be used, for example.

  The light that has entered the first mirror 40 a, the second mirror 40 b, and the third mirror 40 c is converted into an optical path, mixed, and incident on the optical scanning unit 50. The optical scanning unit 50 has a function of reflecting incident light and scanning in two-dimensional directions orthogonal to each other. One of the orthogonal directions is called a main scanning direction, and the other is called a sub-scanning direction. For example, in FIG. 2, the longitudinal direction (X direction) of the screen 90 can be the main scanning direction, and the short direction (Y direction) can be the sub scanning direction. The light scanned in the predetermined direction by the optical scanning unit 50 is projected onto the screen 90 after the optical path is adjusted by the scanning lens 60.

  FIG. 3 is a diagram illustrating an optical scanning unit and a two-dimensional photo reflector according to this embodiment. Referring to FIG. 3, the optical scanning unit 50 includes a substantially rectangular outer frame portion 51, a substantially rectangular inner frame portion 52 provided on the inside thereof, and a substantially circular vibration provided on the inside thereof. For example, it is integrally formed with a single crystal silicon substrate. The two-dimensional photo reflector 59 is provided on the back side (opposite to the optical scanning direction) of the vibrating mirror 53 in order to detect the swing angle of the vibrating mirror 53 in the main scanning direction and the sub-scanning direction.

  The inner frame portion 52 is rotatably supported by the outer frame portion 51 by a pair of elastically deformable support portions 54. The support part 54 includes a support part 54a provided on the outer frame part 51, and a support part 54b extending in a direction substantially orthogonal to the support part 54a from a substantially central part of the support part 54a. The vibrating mirror 53 is rotatably supported by the inner frame portion 52 by a pair of elastically deformable support portions 55. The support part 55 includes a support part 55a provided in the inner frame part 52, and a support part 55b extending in a direction substantially orthogonal to the support part 55a from a substantially central part of the support part 55a. The support part 54b and the support part 55b have a torsion beam structure.

  The vibrating mirror 53 is, for example, a MEMS mirror. The vibrating mirror 53 is configured to be rotatable by an actuator that uses the deformation force of the piezoelectric element as a driving force. In other words, each support portion 54a is provided with two piezoelectric elements 56 at positions that are substantially line-symmetric with respect to an axis connecting the support portions 54b (referred to as a first support shaft). Each support portion 55a is provided with two piezoelectric elements 57 at positions substantially symmetrical with respect to an axis connecting the support portions 55b (referred to as a second support shaft).

  The first support shaft and the second support shaft are orthogonal to each other, and when the piezoelectric element 56 is driven by a drive unit (not shown), the vibration mirror 53 rotates with respect to the first support shaft. Thereby, the light incident on the vibrating mirror 53 is scanned in the sub-scanning direction. When the piezoelectric element 57 is driven by a drive unit (not shown), the vibrating mirror 53 rotates with respect to the second support shaft. Thereby, the light incident on the vibrating mirror 53 is scanned in the main scanning direction. Note that a reflective film made of a metal thin film such as gold (Au) or aluminum (Al) is formed on the front and back surfaces of the vibrating mirror 53, and reflects incident light. The vibrating mirror 53 has a predetermined resonance frequency.

  4A is a plan view illustrating the vicinity of the vibrating mirror and the two-dimensional photo reflector in FIG. 4B is a right side view illustrating the vicinity of the vibrating mirror and the two-dimensional photo reflector in FIG. Referring to FIGS. 3, 4A, and 4B, the two-dimensional photo reflector 59 includes a light source 59a and four light receiving sensors 59b to 59e, and the back side of the vibrating mirror 53 (the side opposite to the light scanning direction). Are provided at a predetermined distance. Note that A schematically shows light emitted from the light source 59a.

  The light source 59 a is, for example, a light emitting diode or the like, and is provided at the center of the two-dimensional photo reflector 59. The light receiving sensors 59b to 59e are, for example, photodetectors and are provided concentrically at regular intervals around the light source 59a. The light receiving sensors 59b and 59c are provided in the sub-scanning direction, and the light receiving sensors 59d and 59e are provided in the main scanning direction. The light source 59a is disposed at a position corresponding to the vicinity of the center of the vibrating mirror 53 in plan view. The four light receiving sensors 59b to 59e are arranged at positions corresponding to the vicinity of the outer edge portion of the vibrating mirror 53 in plan view.

  5A and 5B are diagrams for explaining the operation of the two-dimensional photo reflector. FIG. 5A schematically shows the vicinity of the vibrating mirror 53 and the two-dimensional photo reflector 59 in FIG. 3 as viewed from the front. Note that A schematically shows the emitted light from the light source 59 a, and B schematically shows the reflected light that is reflected from the back surface of the vibrating mirror 53. FIG. 5B schematically shows the vicinity of the vibrating mirror 53 and the two-dimensional photo reflector 59 of FIG. 3 as viewed from above. Reference numeral 59x denotes a light spot when the outgoing light A from the light source 59a is reflected by the back surface of the vibrating mirror 53 and the reflected light B reaches the two-dimensional photo reflector 59.

  As shown in FIG. 5A, the vibrating mirror 53 is tilted so that the right side of the paper is lowered, the vibrating mirror 53 is horizontal, and the vibrating mirror 53 is tilted so that the left side of the paper is lowered (the vibrating mirror 53 is moved in the main scanning direction). ) When the oscillating mirror 53 is horizontal as shown in the center of FIG. 5A, the emitted light A is reflected in the opposite direction on the back surface of the oscillating mirror 53 and returns toward the light source 59a as shown in the center of FIG. The amount of light received by the light receiving sensor 59d is equal to the amount of light received by the light receiving sensor 59e, and it can be determined that the vibrating mirror 53 is in a horizontal state.

  When the oscillating mirror 53 is tilted so that the right side of the sheet is lowered as shown on the left side of FIG. 5A, the emitted light A is reflected according to the tilt of the back surface of the oscillating mirror 53 as shown on the left side of FIG. The amount of light received by the light receiving sensor 59d is greater than the amount of light received by the light receiving sensor 59e, and it can be determined that the vibrating mirror 53 is tilted so that the right side of the sheet is lowered. Similarly, when the oscillating mirror 53 is tilted so that the left side of the paper is lowered as shown on the right side of FIG. 5A, the emitted light A is reflected according to the inclination of the back surface of the oscillating mirror 53 as shown on the right side of FIG. Therefore, it is possible to determine that the amount of light received by the light receiving sensor 59d is smaller than the amount of light received by the light receiving sensor 59e, and the vibrating mirror 53 is tilted so that the left side of the paper surface is lowered.

  FIG. 6 is an example of a block diagram of a control system for driving the oscillating mirror. Although FIG. 6 illustrates driving in the sub-scanning direction of the vibrating mirror 53 of the optical scanning unit 50, the same block diagram can be used for the main scanning direction. However, in FIG. 6, it is necessary to replace the sub-scanning system reference phase clock with the main scanning system reference phase clock and the light receiving sensors 59b and 59c with the light receiving sensors 59d and 59e.

  In the phase control loop shown in FIG. 6, the light emitted from the light source 59a provided at the center of the two-dimensional photo reflector 59 vibrates according to the inclination (deflection angle) of the vibration mirror 53 of the optical scanning unit 50 in the sub-scanning direction. The light is reflected by the back side of the mirror 53 and received by the light receiving sensors 59b and 59c of the phase detector 103. The light received by the light receiving sensors 59b and 59c is converted into an electric signal and input to the signal processing unit 104 of the phase detection unit 103. The signal processing unit 104 determines the actual phase signal based on the light receiving ratio of the light receiving sensors 59b and 59c. (Pulse signal) is generated and output. In this way, the actual phase of the vibrating mirror 53 in the sub-scanning direction is obtained based on the deflection angle of the vibrating mirror 53 in the sub-scanning direction. The same applies to the main scanning direction.

  The phase controller 100 compares the reference phase clock on the system side with the actual phase signal output from the signal processing unit 104 to calculate the phase difference. Then, based on the phase difference calculated by the phase controller 100, the drive waveform generator 101 generates a drive waveform (for example, a sine wave), is amplified by the drive circuit 102, and is input to the piezoelectric element 56. To drive. Here, the phase difference calculated by the phase controller 100 is a phase difference between the actual phase of the oscillating mirror 53 and the drive waveform generated by the drive waveform generator 101. The frequency controller 105, the drive circuit 106, and the resonance frequency variable unit 107 will be described later.

  FIG. 7 is an example of a block diagram of an input / output transfer function of a vibrating mirror of a controlled object model used for control design. In FIG. 7, the input is the drive torque and the output is the deflection angle of the vibrating mirror. Jm in block 110 represents inertia of the vibrating mirror 53, s in blocks 111 and 112 represents Laplace operator, Dm in block 113 represents viscous resistance of the vibrating mirror 53, and Km in block 114 represents a torsion beam portion of the optical scanning unit 50. The torsional constant is shown. In the main scanning direction, the support portion 55b is a torsion beam portion, and in the sub scanning direction, the support portion 54b is a torsion beam portion.

  FIG. 8 is a diagram illustrating the input / output frequency transfer characteristics of the block diagram shown in FIG. 7, and shows the gain characteristics and phase characteristics of the optical scanning unit 50. In other words, the relationship between the amplitude of the driving waveform of the vibrating mirror 53 and the amplitude of the swing angle waveform of the vibrating mirror 53 and the relationship between the phase of the driving waveform of the vibrating mirror 53 and the phase of the swing angle waveform of the vibrating mirror 53 are shown. . As shown in FIG. 8, the frequency transfer characteristic of the optical scanning unit 50 is a secondary system characteristic, and the phase delay is 90 deg at the resonance frequency C. In the frequency region lower than the resonance frequency C, the phase delay is smaller than 90 deg, and in the frequency region higher than the resonance frequency C, the phase delay is larger than 90 deg. The driving waveform of the vibrating mirror 53 is a waveform for driving the piezoelectric element 56 or 57.

  The resonance frequency of the oscillating mirror 53 can be detected using the characteristics shown in FIG. Hereinafter, a method for detecting the resonance frequency of the vibrating mirror 53 will be described. 9A to 9C are diagrams illustrating the relationship between the phase of the driving waveform of the vibrating mirror and the phase of the deflection angle waveform of the vibrating mirror. 9A to 9C, D indicates a driving waveform of the oscillating mirror 53, and E indicates a deflection angle waveform of the oscillating mirror 53. FIG. 9A illustrates a case where there is a 45 degree delay in the phase of the deflection angle waveform E of the oscillating mirror 53 with reference to the phase of the drive waveform D of the oscillating mirror 53. In this case, as shown in FIG. The frequency of the driving waveform D of the mirror 53 is smaller than the resonance frequency of the vibrating mirror 53.

  FIG. 9B illustrates a case where there is a delay of 90 degrees in the phase of the deflection angle waveform E of the oscillating mirror 53 with reference to the phase of the driving waveform D of the oscillating mirror 53. In this case, as can be seen from FIG. The frequency of the driving waveform D of the oscillating mirror 53 is equal to the resonance frequency of the oscillating mirror 53. Further, FIG. 9C illustrates a case where the phase of the deflection angle waveform E of the oscillating mirror 53 has a delay of 135 degrees with reference to the phase of the driving waveform D of the oscillating mirror 53. In this case, as can be seen from FIG. The frequency of the driving waveform D of the oscillating mirror 53 is greater than the resonance frequency of the oscillating mirror 53. Accordingly, if the phase difference between the drive waveform D of the vibration mirror 53 and the deflection angle waveform E of the vibration mirror 53 can be detected, a quantitative deviation between the frequency of the drive waveform D of the vibration mirror 53 and the resonance frequency of the vibration mirror 53 can be determined. It is.

The relationship between the resonance frequency f = ω / (2π) of the oscillating mirror 53, the inertia Jm of the oscillating mirror 53, and the torsion constant Km of the torsion beam portion of the optical scanning unit 50 is ω ² = Km / Jm. Here, ω is an angular frequency. That is, by electrically changing either the torsional constant of the torsion beam or the inertia of the vibrating mirror 53 itself, the resonance frequency of the vibrating mirror 53 can be matched with a desired value.

  Here, returning to FIG. 6, the frequency controller 105, the drive circuit 106, and the resonance frequency variable unit 107 will be described. The frequency controller 105 compares the target phase difference with the phase difference calculated by the phase controller 100 to generate a frequency control signal. The frequency control signal generated by the frequency controller 105 is amplified by the drive circuit 106 and drives the resonance frequency variable unit 107 having a function of changing the resonance frequency of the oscillating mirror 53. That is, the frequency controller 105 controls the resonance frequency variable unit 107 based on the phase difference calculated by the phase controller 100 so that the resonance frequency of the oscillating mirror 53 follows the frequency of the drive waveform of the oscillating mirror 53.

  The resonance frequency variable unit 107 is, for example, a heat generating element provided via an insulating layer in a part where the piezoelectric elements 56 and 57 of the support part 54a and the support part 55a are not provided. As the heating element, for example, a platinum (Pt) thin film heater or the like can be used. A platinum (Pt) thin film heater or the like can be formed by, for example, a sputtering method or the like. By driving the resonance frequency variable unit 107 based on the frequency control signal generated by the frequency controller 105, a current flows through the heating element to generate heat. Since the resonance frequency variable portion 107 is provided in the vicinity of the support portion 54b and the support portion 55b, the support portion 54b and the support portion 55b are heated by the radiant heat of the resonance frequency variable portion 107, and the torsional constant changes. As a result, the resonance frequency of the vibrating mirror 53 changes.

  In FIG. 6, since the phase difference between the drive waveform of the oscillating mirror 53 and the deflection angle waveform of the oscillating mirror 53 can be detected by the phase controller 100, the target phase difference is set to 90 deg, and the resonance frequency variable unit 107 is driven. By controlling the phase difference signal generated by the controller 100 to be 90 deg which is the target phase difference, the resonance frequency of the oscillating mirror 53 can be made to follow the frequency of the driving waveform of the oscillating mirror 53.

  Note that the phase controller 100 and the frequency controller 105 shown in FIG. 6 are built in the optical scanning device 10 and include, for example, a CPU, a ROM, a main memory, and the like. Various functions of the phase controller 100 and the frequency controller 105 are realized by a control program recorded in a ROM or the like being read into the main memory and executed by the CPU. However, part or all of the phase controller 100 and the frequency controller 105 may be realized only by hardware. Further, the phase controller 100 and the frequency controller 105 may be physically configured by a plurality of devices.

  As described above, in the present application, the phase difference between the drive waveform of the oscillating mirror 53 and the deflection angle waveform of the oscillating mirror 53 can be directly detected from the phase controller 100 while the phase control operation is in the target tracking state. Easy.

  In this embodiment, the piezoelectric drive type vibration mirror is used. However, instead of the piezoelectric drive type vibration mirror, an electromagnetic drive type vibration mirror is used, and a drive coil provided on the electromagnetic drive type vibration mirror side is provided. The torsional constant of the torsion beam may be changed by heating the coil by superimposing a high frequency current for coil overheating in addition to the drive current and transmitting this heat to the torsion beam. Further, instead of the piezoelectric drive type vibration mirror, an electrostatic drive type vibration mirror is used, and a heating element is provided in the vicinity of the torsion beam supporting the electrostatic drive type vibration mirror. The torsional constant of the torsion beam may be changed by heating the torsion beam with radiant heat.

  As described above, in the optical scanning device used for two-dimensional optical scanning, when the two-dimensional scanning integrated type oscillating mirror is driven at the resonance frequency, the oscillating mirror is separated from the front side of the oscillating mirror that reflects the screen projection light. A two-dimensional photo reflector is provided in the back space. Then, the light of the light source of the two-dimensional photo reflector is reflected on the back surface of the vibration mirror, and the phase of the swing angle (main scanning and sub-scanning) of the vibration mirror is detected by the plurality of light receiving sensors of the two-dimensional photo reflector. It is possible to determine the direction of the resonance point as seen from FIG.

  Also, in the drive control system of the oscillating mirror, frequency control is executed in addition to the phase control of the oscillating motion of the oscillating mirror, so that the resonance frequency of the oscillating mirror is set to a desired drive frequency (fixed) using the phase detection result. Can be followed. As a result, it is possible to suppress individual variations in the resonance frequency of the vibrating mirror, and it is possible to realize cost reduction during mass production.

  The preferred embodiment has been described in detail above. However, the present invention is not limited to the above-described embodiment, and various modifications and replacements are made to the above-described embodiment without departing from the scope described in the claims. Can be added.

DESCRIPTION OF SYMBOLS 10 Optical scanning device 20a 1st light source 20b 2nd light source 20c 3rd light source 30a 1st lens 30b 2nd lens 30c 3rd lens 40a 1st mirror 40b 2nd mirror 40c 3rd mirror 50 Optical scanning part 51 Outer frame part 52 Inside Frame part 53 Vibration mirror 54, 54a, 54b, 55, 55a, 55b Support part 56, 57 Piezoelectric element 59 Two-dimensional photo reflector 59a Light source 59b, 59c, 59d, 59e Light receiving sensor 59x Light spot 60 Scan lens 80 Projector 90 Screen 100 Phase controller 101 Drive waveform generator 102 Drive circuit 103 Phase detection unit 104 Signal processing unit 105 Frequency controller 106 Drive circuit 107 Resonance frequency variable unit A Output light B Reflected light C Resonance frequency D Drive waveform E Deflection angle waveform of vibration mirror

JP 2009-009093 A JP 2009-198988 A

Claims (7)

A light source;
Driven in a first direction or a second direction orthogonal to the first direction with a predetermined driving waveform, the emitted light emitted from the light source is reflected by a first surface, and the first direction or the A vibrating mirror that scans in a second direction;
Provided on the second surface side that is the back surface of the first surface of the vibrating mirror, irradiates the second surface with light, and based on the reflected light from the second surface, the first direction And a two-dimensional photo reflector for detecting a swing angle of the vibrating mirror in the second direction;
The phase difference between the actual phase of the oscillating mirror in the first direction and the drive waveform in the first direction obtained based on the deflection angle of the oscillating mirror, and the oscillating mirror in the second direction. An optical scanning device comprising: a phase controller that calculates a phase difference between an actual phase and the driving waveform in the second direction. A resonance frequency variable section that varies the resonance frequency of the vibrating mirror;
The frequency controller further controls the resonance frequency variable unit based on the phase difference in the first direction and the second direction, and causes the resonance frequency to follow the frequency of the drive waveform. 1. The optical scanning device according to 1. The resonance frequency variable portion is a heating element,
The optical scanning device according to claim 2, wherein the frequency controller changes the resonance frequency by causing a current to flow through the heat generating element to generate heat. The two-dimensional photo reflector is
An irradiation light source for irradiating light on the second surface;
Four light receiving sensors provided concentrically and equidistantly around the irradiation light source,
Of the four light receiving sensors, two light receiving sensors arranged in point symmetry with respect to the irradiation light source detect a deflection angle of the vibrating mirror in the first direction,
The other two light receiving sensors arranged in point symmetry with respect to the irradiation light source among the four light receiving sensors detect a deflection angle of the vibrating mirror in the second direction. An optical scanning device according to claim 1. The vibrating mirror is driven in a first direction or a second direction orthogonal to the first direction with a predetermined driving waveform, and the emitted light emitted from the light source is reflected by the first surface of the vibrating mirror and A first step of scanning in a first direction or the second direction;
The oscillating mirror in the first direction and the second direction is irradiated with light on a second surface which is the back surface of the first surface of the oscillating mirror, and based on the reflected light from the second surface. A second step of detecting the deflection angle of
The phase difference between the actual phase of the oscillating mirror in the first direction and the drive waveform in the first direction obtained based on the deflection angle of the oscillating mirror, and the oscillating mirror in the second direction. And a third step of calculating a phase difference between the actual phase and the driving waveform in the second direction.   6. The driving of the optical scanning device according to claim 5, further comprising a fourth step of causing the resonance frequency of the oscillating mirror to follow the frequency of the driving waveform based on the phase difference in the first direction and the second direction. Method.   7. The method of driving an optical scanning device according to claim 6, wherein in the fourth step, the resonance frequency is varied by causing a current to flow through the heat generating element to generate heat.

Images