JP6480784B2 - Optical scanning actuator evaluation system - Google Patents

Description

  The present invention relates to an evaluation apparatus for an optical scanning actuator that two-dimensionally scans irradiation light such as laser light, and more particularly to a technique for evaluating the oscillation characteristics of a light reflecting surface of the optical scanning actuator.

  2. Description of the Related Art Conventionally, an optical scanning device that two-dimensionally scans irradiation light (for example, laser light) from a light source is known. This type of optical scanning device has an optical scanning actuator composed of a galvanometer mirror or the like, and a drive unit that drives the optical scanning actuator. The optical scanning actuator includes a light reflecting surface, and the light reflecting surface is configured to be swingable about two axes (for example, x axis and y axis) orthogonal to each other. The drive unit supplies two drive signals (for example, sine wave signals) having frequencies corresponding to resonance frequencies around the two axes of the light reflecting surface to the optical scanning actuator. As a result, the light reflecting surface of the optical scanning actuator is driven to swing around the x axis and the y axis, and the light applied to the light reflecting surface is two-dimensionally scanned.

Japanese Patent Application Laid-Open No. 07-175005

  By the way, since the optical scanning actuator has a solid variation, it is necessary to grasp the characteristics of each optical scanning actuator, particularly the resonance frequency around the x axis and the resonance frequency around the y axis of the light reflecting surface. For this reason, conventionally, for example, the resonance frequency of the light reflecting surface is obtained as follows. That is, when obtaining the resonance frequency around the x-axis of the light reflecting surface, only the first drive signal for swinging the light reflecting surface around the x-axis is supplied to the light scanning actuator. The frequency of the first drive signal is changed. Then, the swing angle of the light reflecting surface around the x axis at each frequency is detected, and the frequency of the first drive signal that maximizes the swing angle of the light reflecting surface around the x axis is reflected by the light. The resonance frequency around the x-axis of the surface is used. Similarly, when obtaining the resonance frequency of the light reflecting surface around the y axis, only the second drive signal for driving the light reflecting surface to swing around the y axis is supplied to the optical scanning actuator. At the same time, the frequency of the second drive signal is changed. Then, the swing angle of the light reflecting surface around the y axis at each frequency is detected, and the frequency of the second drive signal that maximizes the swing angle of the light reflecting surface around the y axis is reflected by the light. The resonance frequency around the y-axis of the surface is used.

  However, in the above-described method, the swing angle of the light reflecting surface around the x axis and the swing angle around the y axis are detected in a state where the light reflecting surface is swung only around one axis. . For this reason, the swing angle around the x axis and the swing angle around the y axis of the detected light reflection surface may be different from the actual swing angle when the optical scanning actuator is operating. There is. As a result, the resonance frequency around the x-axis and the resonance frequency around the y-axis of the light reflecting surface may deviate from the actual resonance frequency. In order to efficiently operate the optical scanning actuator, it is desirable to accurately grasp the resonance frequency around the x axis and the resonance frequency around the y axis of the light reflecting surface.

  Accordingly, the present invention provides a rocking angle of the light reflecting surface around the first axis and a rocking around the second axis in a state where the light reflecting surface is swung around the first axis and the second axis. An apparatus for evaluating an optical scanning actuator capable of detecting (calculating) an angle and accurately grasping the resonance frequency around the first axis and the resonance frequency around the second axis of the light reflecting surface is provided. The purpose is to do.

  According to an aspect of the present invention, the light reflecting surface is driven to swing around the first axis and the second axis orthogonal to each other by the first sine wave signal and the second sine wave signal, thereby irradiating the light reflecting surface. An apparatus for evaluating an optical scanning actuator for two-dimensionally scanning the emitted light is provided. The optical scanning actuator evaluation apparatus includes a light source unit that irradiates light to the light reflecting surface, a driving unit that supplies the first sine wave signal and the second sine wave signal to the optical scanning actuator, and a light receiving surface. An optical position detector that detects an incident position of the scanning light on the light receiving surface by the optical scanning actuator, a first incident position and a second incident position of the scanning light on the light receiving surface, and the first Based on the detection time difference between the incident position and the second incident position, and the distance between the light reflecting surface and the light receiving surface, the light reflecting surface swings around the first axis and swings around the second axis. An arithmetic processing unit for calculating a moving angle.

  The evaluation apparatus for the optical scanning actuator is configured so that the light reflecting surface is swung around the first axis and the second axis while the light reflecting surface is swung around the first axis and the second axis. Since the swing angle around the axis can be calculated, the deviation between the calculated swing angle and the actual swing angle is suppressed. As a result, it is possible to accurately grasp the resonance frequency around the first axis and the resonance frequency around the second axis of the light reflecting surface.

It is a figure which shows the structure of the two-dimensional scanning type semiconductor galvanometer mirror which is an example of an optical scanning actuator. It is a figure which shows schematic structure of the evaluation apparatus of the optical scanning actuator by one Embodiment of this invention. It is a flowchart which shows the calculation process of the rocking | fluctuation angle of the light reflection surface of the said optical scanning actuator which the control part of the said evaluation apparatus performs. It is a flowchart which shows the detection process of the resonant frequency around the x-axis (1st axis | shaft) of the said light reflection surface which the said control part performs. It is a flowchart which shows the detection process of the resonant frequency around the y-axis (2nd axis | shaft) of the said light reflection surface which the said control part performs.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The present invention provides an evaluation apparatus for an optical scanning actuator. The light scanning actuator is driven to swing around a first axis (x-axis) and a second axis (y-axis) whose light reflecting surfaces are orthogonal to each other, thereby irradiating the light reflecting surface (for example, Laser light) is two-dimensionally scanned (for example, Lissajous scanning). Such an optical scanning actuator is mounted on an optical distance measuring device that measures the distance to an object existing in a target area, a laser scanning projector, or the like.

  FIG. 1 shows a configuration of a two-dimensional scanning type semiconductor galvanometer mirror (hereinafter simply referred to as “galvanometer mirror”) as an example of the optical scanning actuator. The galvanometer mirror 10 includes a frame-shaped fixed portion 11, an outer movable portion 12a disposed inside the fixed portion 11, and an inner movable portion 12b disposed inside the outer movable portion 12a. The outer movable portion 12a is supported by a pair of first torsion bars 13 and 13 so as to be swingable, and the inner movable portion 12b is supported by a pair of second torsion bars 14 and 14 so as to be swingable. The first torsion bars 13 and 13 and the second torsion bars 14 and 14 are orthogonal to each other in the axial direction. In the following description, the central axis of the first torsion bars 13 and 13 is the x axis, and the central axis of the second torsion bars 14 and 14 is the y axis (see FIG. 2).

  A light reflecting surface (mirror) 15 is formed at the center of the inner movable portion 12b. A first drive coil 16 and a second drive coil 17 are formed on the peripheral portions of the outer movable portion 12a and the inner movable portion 12b, respectively. The end of the first drive coil 16 is connected to the first electrode terminals 18 and 18 formed on the fixed portion 11, and the end of the second drive coil 17 is the second electrode terminal 19 formed on the fixed portion 11. , 19. In addition, the pair of first permanent magnets 20 and 20 that mainly apply a magnetic field to the first drive coil 16 and the pair of second permanent magnets 21 and 21 that mainly apply a magnetic field to the second drive coil 17 serve as the fixed portion 11. They are arranged opposite to each other. In the present embodiment, the fixed portion 11, the outer movable portion 12a, the inner movable portion 12b, the first torsion bars 13 and 13, and the second torsion bars 14 and 14 are integrally formed from a semiconductor substrate.

  In the galvanometer mirror 10, when alternating currents flow through the first drive coil 16 and the second drive coil 17, these alternating currents, the magnetic field generated by the first permanent magnets 20, 20, and the magnetic field generated by the second permanent magnets 21, 21 As a result, Lorentz force acts on the movable parts 12a and 12b. Then, the entire movable part including the outer movable part 12a and the inner movable part 12b swings around the x axis, and the inner movable part 12b swings around the y axis. That is, the light reflecting surface 15 swings around the x axis and the y axis, and thereby the light irradiated on the light reflecting surface 15 is two-dimensionally scanned. For this reason, the galvanometer mirror 10 is configured such that an alternating current (for example, a sine wave signal) having a predetermined frequency is supplied as a drive signal to each of the first drive coil 16 and the second drive coil 17.

  Here, in order to efficiently swing and drive the light reflecting surface 15, the first drive signal supplied to the first drive coil 16 has a frequency corresponding to the resonance frequency around the x axis of the light reflecting surface 15. In addition, the second drive signal supplied to the second drive coil 17 needs to have a frequency corresponding to the resonance frequency of the light reflecting surface 15 around the y axis. The resonance frequency around the x-axis of the light reflecting surface 15 is the resonance frequency around the x-axis of the entire movable part including the outer movable part 12a and the inner movable part 12b. The resonance frequency around the y-axis of the light reflecting surface 15 is the resonance frequency around the y-axis of the inner movable portion 12b.

  On the other hand, the galvanometer mirror 10 has solid variations, and it is difficult to set the frequency of the first drive signal and the frequency of the second drive signal uniformly for all the galvanometer mirrors 10. Therefore, in the present embodiment, the light reflection surface 15 including the resonance frequency around the x axis and the resonance frequency around the y axis of the light reflection surface 15 is measured for each galvano mirror by a galvano mirror evaluation device described below. The swing characteristics of the are grasped.

  FIG. 2 shows a schematic configuration of the galvanometer mirror evaluation apparatus. As shown in FIG. 2, the galvanometer mirror evaluation apparatus 1 includes a light source unit 2 that supplies a laser beam to a galvanometer mirror 10 to be evaluated, and a drive unit 3 that swings and drives a light reflecting surface 15 of the galvanometer mirror 10. The optical position detector 4 that mainly detects the position of the scanning light of the galvanometer mirror 10 and the controller 5 that controls the overall operation of the evaluation apparatus 1 are included.

  The light source unit 2 includes a polarization beam splitter 2 a and irradiates the light reflecting surface 15 of the galvanometer mirror 10 with laser light. The drive unit 3 supplies the first drive signal and the second drive signal to the galvanometer mirror 10. Specifically, in the present embodiment, the drive unit 3 supplies the first sine wave signal to the first drive coil 16 of the galvano mirror 10 and the second sine wave signal to the second drive coil 17. The drive unit 3 is configured to be able to change the frequency and amplitude of the first sine wave signal and the frequency and amplitude of the second sine wave signal, respectively.

  The light position detection unit 4 has a light receiving surface 4a on which the light reflected by the light reflection surface 15 of the laser light irradiated from the light source unit 2 to the light reflection surface 15 is incident, and the reflected light to the light reception surface 4a The incident position P can be detected as two-dimensional coordinates (X, Y). Here, as shown in FIG. 2, the light receiving surface 4a of the light position detecting unit 4 is not driven, that is, parallel to the light reflecting surface 15 in a stopped state and separated by a predetermined distance L. Be placed. The light position detection unit 4 is not particularly limited as long as it can detect the light receiving position as a two-dimensional coordinate. For example, a two-dimensional PSD (Position Sensitive Detector) element may be used.

  The control unit 5 controls the light source unit 2 and the driving unit 3, and the incident position P = (X, Y) of the reflected light from the light reflection surface 15 from the light position detection unit 4, that is, the scanning light of the galvano mirror 10 Enter. Then, the control unit 5 performs a predetermined calculation process based on the incident position P = (X, Y) input from the light position detection unit 4 to swing the light reflecting surface 15 of the galvano mirror 10 around the x axis. The angle θx and the swing angle θy around the y axis are calculated.

  Further, the control unit 5 controls the driving unit 3 so as to change the frequency of the first sine wave signal and calculates the swing angle θx around the x of the light reflecting surface 15 at each frequency before and after the change, The resonance frequency around the x axis of the light reflecting surface 15 is obtained based on the swing angle θx around the x axis of the light reflecting surface 15 at each calculated frequency.

  Further, the control unit 5 controls the driving unit 3 so as to change the frequency of the second sine wave signal, and calculates the swing angle θy around the y axis of the light reflecting surface 15 at each frequency before and after the change. The second resonance frequency of the light reflecting surface 15 is obtained based on the rocking angle θy about the y axis of the light reflecting surface 15 at each calculated frequency. Therefore, in the present embodiment, the control unit 5 has a function as the “arithmetic processing unit” of the present invention.

  Next, the operation of the evaluation apparatus 1, particularly the processing executed by the control unit 5 will be specifically described. First, as an advance preparation, the operator sets the galvanometer mirror 10 to be evaluated on the sample mounting table (not shown) of the evaluation apparatus 1. At this time, the operator operates the evaluation device 1 to irradiate the light reflecting surface 15 of the galvanometer mirror 10 with laser light, and the incident position of the reflected light by the light reflecting surface 15 on the light receiving surface 4a of the detection unit 4 is received. The position of the galvanometer mirror 10 and / or the light receiving surface 4a is adjusted as appropriate so that the origin position O of the surface 4a = (0, 0). Of course, the operator may set the incident position of the reflected light on the light receiving surface 4a of the detection unit 4 to the origin position O of the light receiving surface 4a. Then, after the preliminary preparation is completed, when the operator performs a predetermined operation on the evaluation device 1, the evaluation device 1 (particularly the control unit 5) executes the following processing.

[Calculation of rocking angle of light reflecting surface 15]
FIG. 3 is a flowchart illustrating a calculation process of the swing angle (the swing angle about the x axis and the swing angle about the y axis) of the light reflecting surface 15 executed by the control unit 5 of the evaluation apparatus 1.

  In step S <b> 1, an irradiation command is output to the light source unit 2. As a result, laser light is irradiated from the light source unit 2 to the light reflecting surface 15 of the galvanometer mirror 10. In this state, the reflected light of the laser beam from the light reflecting surface 15 is incident on the origin position O of the light receiving surface 4 a of the detection unit 4.

  In step S <b> 2, the drive signal supply command is output to the drive unit 3. The supply command includes the frequency fx and amplitude Dx of the first sine wave signal and the frequency fy and amplitude Dy of the second sine wave signal. When the supply unit 3 receives the supply command, the drive unit 3 supplies the first sine wave signal having the frequency fx and the amplitude Dx to the first drive coil 16 of the galvano mirror 10 and also the second sine wave having the frequency fy and the amplitude Dy. The signal is supplied to the second drive coil 17 of the galvanometer mirror 10. As a result, the light reflecting surface 15 of the galvanometer mirror 10 swings around the x axis and the y axis, and the scanning light of the galvanometer mirror 10 is incident on the light receiving surface 4 a of the light position detector 4.

  In step S3, it is determined whether or not the time t has elapsed since the start of the swinging of the light reflecting surface 15. If the time t has elapsed, the process proceeds to step S4. The time t can be arbitrarily set.

In step S <b> 4, the first incident position P (t) = (X ₁ , Y ₁ ) of the scanning light of the galvano mirror 10 on the light receiving surface 4 a is input from the detection unit 4. The first incident position P (t) = (X ₁ , Y ₁ ) input in step S3 corresponds to the “first incident position of the scanning light on the light receiving surface at time t” in the present invention.

In step S5, the first incident position P (t) = (X ₁ , Y ₁ ) input in step S4 is subjected to coordinate conversion, and the first angle A1 about the x-axis and the y-axis about the light reflecting surface 15 are converted. The first angle B1 is calculated. Specifically, the first angle A1 around the x axis and the first angle B1 around the y axis of the light reflecting surface 15 are calculated as follows.

The normal line of the light reflecting surface 15 coincides with the Z axis in FIG. 2 when the light reflecting surface 15 is in a stopped state, but when the light reflecting surface 15 is driven to swing, the angle φx around the x axis and the The direction changes according to the angle φy around the y axis. The normal vector ( _nx , _ny , _nz ) of the light reflecting surface 15 is the rotation matrix around the y axis, the rotation matrix around the x axis, and the unit normal of the light reflecting surface 15 when in the stopped state. It is expressed by equation (1) using a vector.

The unit vector (b _x , b _y , b _z ) of the light reflected by the light reflecting surface 15, that is, the scanning light of the galvanometer mirror 10 is the normal vector (n _x , n _y , n _z ) of the light reflecting surface 15. Using the unit vector (b _x , b _y , b _z ) of the scanning light of the galvanometer mirror 10, the position on the light receiving surface 4 a of the optical position detection unit 4 is expressed by the equation (3). Represented by

  Therefore, the first angle A1 around the x-axis of the light reflecting surface 15 is represented by Expression (4), and the first angle B1 around the y-axis of the light reflecting surface 15 is represented by Expression (5).

  In step S6, it is determined whether or not a predetermined time Δt has elapsed since the first incident position P (t) was input in step S4. When the predetermined time Δt has elapsed, the process proceeds to step S7.

In step S7, as in step S4, the second incident position P (t + ΔT) = (X ₂ , X ₂ ) of the scanning light of the galvano mirror 10 on the light receiving surface 4a is input from the detection unit 4. The incident position P (t + Δt) = (X ₂ , Y ₂ ) input in step S6 corresponds to the “second incident position of the scanning light on the light receiving surface at time t + Δ” in the present invention.

In step S8, as in step S5, the second incident position P (t + Δt) = (X ₂ , Y ₂ ) input in step S7 is subjected to coordinate conversion, and the _{second of} the light reflecting surface 15 around the x-th axis. The angle A2 and the second angle B2 around the second axis are calculated (see equations (6) and (7)).

  In step S9, the light reflecting surface 15 is calculated from the first angle (A1, B1) of the light reflecting surface 15 calculated in step S5 and the second angle (A2, B2) of the light reflecting surface 15 calculated in step S8. The swing angle θx around the x axis and the swing angle θy around the y axis are calculated. Specifically, the control unit 5 calculates the swing angle θx around the x axis and the swing angle θy around the y axis of the light reflecting surface 15 as follows.

  When the maximum touch angle around the x-axis and the maximum touch angle around the y-axis of the light reflecting surface 15 are A0 and B0, respectively, the first angle A1 around the x axis of the light reflecting surface 15 is expressed by equation (8). The first angle B1 around the y-axis of the light reflecting surface 15 is expressed by Expression (9).

  Further, the second angle A2 around the x-axis of the light reflecting surface 15 is represented by Expression (10), and the second angle B2 around the y-axis of the light reflecting surface 15 is represented by Expression (11).

  By substituting equation (8) into equation (10) and substituting equation (9) into equation (11), equations (12) and (13) are obtained. Therefore, the maximum touch angle A0 around the x-axis of the light reflecting surface 15 is expressed by Expression (14), and the maximum touch angle B0 around the y-axis of the light reflecting surface 15 is expressed by Expression (15).

  Then, by substituting Expression (4) and Expression (5) into Expression (14) and Expression (15), respectively, and doubling them, the light reflection surface 15 has an oscillation angle θx (= 2 × A0) and the swing angle θy (= 2 × B0) about the y-axis. In this way, the evaluation apparatus 1 calculates the swing angle θx around the x axis and the θy around the y axis of the light reflecting surface 15.

[Detection of Resonant Frequency of Light Reflecting Surface 15 Around X-Axis]
FIG. 4 is a flowchart showing a resonance frequency detection process around the x-axis of the light reflecting surface 15 executed by the control unit 5 of the evaluation apparatus 1.

  In step S <b> 11, an irradiation command is output to the light source unit 2. As a result, laser light is irradiated from the light source unit 2 to the light reflecting surface 15 of the galvanometer mirror 10.

  In step S <b> 12, the drive signal supply command is output to the drive unit 3. The supply command output in step S12 includes the frequency fx1 (initial value) and amplitude Dx of the first sine wave signal, and the frequency fy1 (initial value) and amplitude Dy of the second sine wave signal. In the present embodiment, the frequency fx1 (initial value) of the first sine wave signal and the frequency fy1 (initial value) of the second sine wave signal are set to respective design values, for example, and the first sine wave The amplitude Dx of the signal and the amplitude Dy of the second sine wave signal are not particularly limited, but are set to, for example, ½ of the respective design values.

  In step S13, a first swing angle θx1 around the x axis of the light reflecting surface 15 when the frequency of the first sine wave signal is fx1 (initial value) is calculated (see FIG. 3).

  In step S14, a frequency change command for the first sine wave signal is output to the drive unit 3. When receiving the frequency change command, the drive unit 3 changes the frequency of the first sine wave signal from fx1 (initial value) to fx2 (= fx1 + Δfx). Δfx can be set arbitrarily. The frequency of the second sine wave signal remains fy1 (initial value).

  In step S15, a second swing angle θx2 about the x axis of the light reflecting surface 15 when the frequency of the first sine wave signal is fx2 is calculated (see FIG. 3).

  In step S16, the first swing angle θx1 around the x axis of the light reflecting surface 15 calculated in step S13 and the second swing around the x axis of the light reflecting surface 15 calculated in step S15. The angle θx2 is compared. If the second swing angle θx2> the first swing angle θx1, the process proceeds to step S17. If the second swing angle θx2 <the first swing angle θx1, the process proceeds to step S18.

  In step S17, the resonance frequency of the light reflecting surface 15 around the x axis is detected by changing the frequency of the first sine wave signal in the same direction as in step S14. Specifically, a frequency change command for the first sine wave signal is output to the drive unit 3 to add the frequency of the first sine wave signal by Δfx, and each frequency fxn after addition (n = 3,4). ,...), The rocking angle θxn (n = 3, 4,...) Around the x axis of the light reflecting surface 15 is calculated. Then, the frequency fxn of the first sine wave signal at which the rocking angle θxn around the x axis of the light reflecting surface 15 is maximum is detected as the resonance frequency around the x axis of the light reflecting surface 15.

  In step S18, the resonance frequency around the x axis of the light reflecting surface 15 is detected by changing the frequency of the first sine wave signal in the direction opposite to that in step S14. Specifically, a frequency change command for the first sine wave signal is output to the drive unit 3 to subtract the frequency of the first sine wave signal by Δfx, and each frequency fxn after subtraction (n = 3,4). ,...), The rocking angle θxn (n = 3, 4,...) Around the x axis of the light reflecting surface 15 is calculated. Then, the frequency fxn of the first sine wave signal at which the rocking angle θxn around the x axis of the light reflecting surface 15 is maximum is detected as the resonance frequency around the x axis of the light reflecting surface 15.

[Detection of Resonant Frequency of Light Reflecting Surface 15 Around Y Axis]
FIG. 5 is a flowchart showing a resonance frequency detection process around the y-axis of the light reflecting surface 15 executed by the control unit 5 of the evaluation apparatus 1.

  In step S <b> 21, an irradiation command is output to the light source unit 2. As a result, laser light is irradiated from the light source unit 2 to the light reflecting surface 15 of the galvanometer mirror 10.

  In step S <b> 22, the drive signal supply command is output to the drive unit 3. The supply command output in step S22 includes the frequency fxn and amplitude Dx of the first sine wave signal, and the frequency fy1 (initial value) and amplitude Dy of the second sine wave signal. The frequency fxn of the first sine wave signal is a resonance frequency around the x axis of the light reflecting surface 15 detected by the detection processing shown in FIG.

  In step S23, a first swing angle θy1 around the y axis of the light reflecting surface 15 when the frequency of the second sine wave signal is fy1 (initial value) is calculated (see FIG. 3).

  In step S24, a frequency change command for the second sine wave signal is output to the drive unit 3. When receiving the frequency change command, the drive unit 3 changes the frequency of the second sine wave signal from fy1 (initial value) to fy2 (= fy1 + Δfy). Δfy can be arbitrarily set. The frequency of the first sine wave signal remains fxn (resonance frequency around the x axis of the light reflecting surface 15).

  In step S25, a second swing angle θy2 about the y-axis of the light reflecting surface 15 when the frequency of the second sine wave signal is fy2 is calculated (see FIG. 3).

  In step S26, the first swing angle θy1 about the y axis of the light reflecting surface 15 calculated in step S23 and the second swing of the light reflecting surface 15 about the y axis calculated in step S25. Compare the angle θy2. If the second swing angle θy2> the first swing angle θy1, the process proceeds to step S27. If the second swing angle θy2 <the first swing angle θy1, the process proceeds to step S28.

  In step S27, the frequency of the second sine wave signal is changed in the same direction as in step S24, and the resonance frequency around the y-axis of the light reflecting surface 15 is detected. Specifically, a frequency change command for the second sine wave signal is output to the drive unit 3 to add the frequency of the second sine wave signal by Δfy, and each frequency fyn after the addition (n = 3, 4). ,...), The rocking angle θyn (n = 3, 4,...) Around the y-axis of the light reflecting surface 15 is calculated. Then, the frequency fyn of the second sine wave signal at which the rocking angle θyn around the y-axis of the light reflecting surface 15 is maximized is detected as the resonance frequency around the y-axis of the light reflecting surface 15.

  In step S28, the frequency of the second sine wave signal is changed in the direction opposite to that in step S24, and the resonance frequency around the y-axis of the light reflecting surface 15 is detected. Specifically, a frequency change command for the second sine wave signal is output to the drive unit 3 to subtract the frequency of the second sine wave signal by Δfy and each frequency fyn (n = 3,4) after the subtraction. ,...), The rocking angle θxn (n = 3, 4,...) Around the y-axis of the light reflecting surface 15 is calculated. Then, the frequency fyn of the second sine wave signal at which the rocking angle θyn around the y-axis of the light reflecting surface 15 is maximized is detected as the resonance frequency around the y-axis of the light reflecting surface 15.

  In step S29, the resonance frequency around the x axis and the resonance frequency around the y axis of the light reflecting surface 15 are output to a display unit (not shown).

  As described above, according to the evaluation apparatus 1 according to the present embodiment, the light reflecting surface 15 of the galvanometer mirror 10 is swung around the x axis and the y axis, and the x of the light reflecting surface 15 is. The swing angle θx about the axis and the swing angle θy about the y axis can be obtained. Therefore, it is possible to accurately grasp the resonance frequency around the x axis and the resonance frequency around the y axis of the light reflecting surface 15 in each galvanometer mirror 10. Therefore, an appropriate drive signal can be set for each galvanometer mirror 10, and the galvanometer mirror 10 can be driven efficiently.

  In the above-described embodiment, the control unit 5 of the evaluation apparatus 1 executes the detection process of the resonance frequency around the x-axis of the light reflecting surface 15 illustrated in FIG. The process of detecting the resonance frequency around the y-axis is executed. However, the present invention is not limited to this, and the control unit 5 may execute the detection process shown in FIG. 4 after the detection process shown in FIG. 5 is executed. In this case, a step corresponding to step S29 in FIG. 5 is added to FIG.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Evaluation apparatus of galvanometer mirror (optical scanning actuator) 2 ... Light source part 2a ... Polarization beam splitter 3 ... Drive part 4 ... Optical position detection part 4a ... Light-receiving surface 5 ... Control part 10 ... Galvano mirror 11 ... Fixed part 12a ... Outer side Movable part 12b ... inner movable part 13 ... first torsion bar 14 ... second torsion bar 15 ... light reflecting surface 16 ... first drive coil 17 ... second drive coil 20, 21 ... permanent magnet

Claims (5)

The light reflecting surface is driven to swing around the first axis and the second axis orthogonal to each other by the first sine wave signal and the second sine wave signal, thereby two-dimensionally scanning the light applied to the light reflecting surface. An optical scanning actuator evaluation device comprising:
A light source unit for irradiating the light reflecting surface with light;
A drive unit for supplying the first sine wave signal and the second sine wave signal to the optical scanning actuator;
An optical position detector that has a light receiving surface and detects an incident position of scanning light by the optical scanning actuator on the light receiving surface;
A first incident position and a second incident position of the scanning light on the light receiving surface, a detection time difference between the first incident position and the second incident position, and a distance between the light reflecting surface and the light receiving surface; An arithmetic processing unit that calculates a swing angle around the first axis and a swing angle around the second axis of the light reflecting surface,
A device for evaluating an optical scanning actuator. The drive unit is configured to be able to change the frequency of the first sine wave signal and the frequency of the second sine wave signal,
The arithmetic processing unit calculates a swing angle around the first axis of the light reflecting surface at each frequency before and after the change of the first sine wave signal, and swings the light reflecting surface around the first axis. Obtaining the frequency of the first sine wave signal with the maximum angle as the resonance frequency around the first axis of the light reflecting surface;
The rocking angle of the light reflecting surface around the second axis at each frequency before and after the change of the second sine wave signal is calculated, and the rocking angle of the light reflecting surface around the second axis is maximized. The frequency of the second sine wave signal is obtained as a resonance frequency around the second axis of the light reflecting surface.
The apparatus for evaluating an optical scanning actuator according to claim 1. The optical position detector includes a two-dimensional PSD (Position Sensitive Detector) element,
The apparatus for evaluating an optical scanning actuator according to claim 1. The light receiving surface is parallel to the light reflecting surface in a stopped state;
The light position detecting unit receives the first incident position and the second incident position when the light reflected from the light reflecting surface of the light irradiated from the light source unit when the light reflecting surface is in a stopped state receives the light. Detect as a two-dimensional coordinate with the position incident on the surface as the origin,
The evaluation apparatus of the optical scanning actuator as described in any one of Claims 1-3. The arithmetic processing unit is configured such that the frequency of the first sine wave signal is fx, the frequency of the second sine wave signal is fy, the distance between the light reflecting surface and the light receiving surface is L, and the first incident position is (X ₁ , Y ₂ ), the second incident position is (X ₂ , Y ₂ ), and the detection time difference between the first incident position and the second incident position is Δt, Calculating a swing angle θx about the first axis and a swing angle θy about the second axis of the light reflecting surface;
The apparatus for evaluating an optical scanning actuator according to claim 4.