WO2022249607A1

WO2022249607A1 - Optical scanning device and optical scanning method

Info

Publication number: WO2022249607A1
Application number: PCT/JP2022/008111
Authority: WO
Inventors: 年賢難波
Original assignee: 株式会社フジクラ
Priority date: 2021-05-24
Filing date: 2022-02-28
Publication date: 2022-12-01
Also published as: JPWO2022249607A1; JP7526889B2

Abstract

This optical scanning device (2) increases the roundness of a trajectory drawn by an irradiation point when scanning a laser beam so as to draw a circular trajectory. An optical scanning device (2) equipped with a scanning unit (20), command waveform generation units (first command waveform generation unit 26a, second command waveform generation unit 26b) for generating a first command waveform and a second command waveform for controlling the scanning unit (20), a trajectory acquisition unit 28 for acquiring the trajectory of the laser beam, and command waveform correction units (first command waveform correction unit 23a, second command waveform correction unit 23b) for correcting the first command waveform and/or the second command waveform, wherein the command waveform correction units (first command waveform correction unit 23a, second command waveform correction unit 23b) correct the amplitude of the first command waveform and/or the amplitude of the second command waveform and the phase difference between the first command waveform and the second command waveform so as to increase the roundness of the trajectory.

Description

Optical scanning device and optical scanning method

The present invention relates to an optical scanning device and an optical scanning method for scanning an object with a laser beam.

In the field of laser processing, optical scanning devices that scan objects with laser light are widely used.

Japanese Patent Publication JP 2015-30011 Japanese Patent Publication JP 2014-217875

As an optical scanning device, for example, as described in Patent Document 1, a device using a galvanometer scanner as a scanning unit for scanning laser light is known. The galvanometer scanner includes a first mirror and a second mirror, which are a pair of mirrors that reflect laser light, a first motor that changes the tilt of the first mirror in the first direction, and a tilt of the second mirror in the second direction. a second motor for changing the tilt. The first motor is controlled by a first command waveform and the second motor is controlled by a second command waveform. As another type of optical scanning device, there is known a device using a two-axis tilt stage as a scanning unit, as described in Japanese Patent Application Laid-Open No. 2002-200022. The biaxial tilt stage has a function of tilting the mirror in a first direction according to a first command waveform (for example, slightly rotating the mirror with the x-axis as a rotation axis), and a function of tilting the mirror in a second direction according to a second command waveform. (for example, the mirror is slightly rotated with the y-axis as the rotation axis).

However, in an actual optical scanning device, the trajectory drawn by the irradiation point of the laser light is distorted, and the roundness of the trajectory is reduced.

An aspect of the present invention has been made in view of the above problems, and is an optical scanning device capable of increasing the roundness of a trajectory drawn by an irradiation point when scanning a laser beam in a circular trajectory. Alternatively, the object is to realize an optical scanning method.

In order to solve the above problems, an optical scanning device according to an aspect of the present invention includes a mirror that reflects a laser beam, a scanning unit that scans the laser beam by changing the inclination of the mirror; a command waveform generator that generates a first command waveform for controlling scanning of the part in a first direction and a second command waveform for controlling scanning of the scanning part in a second direction; and a command waveform correction unit for correcting at least one of the first command waveform and the second command waveform, wherein the command waveform correction unit increases the circularity of the trajectory. and at least one of a first amplitude that is the amplitude of the first command waveform and a second amplitude that is the amplitude of the second command waveform, and a phase difference between the first command waveform and the second command waveform. correct.

In order to solve the above problems, an optical scanning device according to an aspect of the present invention includes a mirror that reflects a laser beam, a scanning unit that scans the laser beam by changing the inclination of the mirror; a command waveform generator that generates a first command waveform for controlling scanning of the part in a first direction and a second command waveform for controlling scanning of the scanning part in a second direction; a trajectory acquisition unit that acquires the first command waveform and the second command waveform by a frequency common to each, a first amplitude and a second amplitude that are amplitudes of each, and a phase difference of each It is a prescribed sine wave, and the command waveform generation unit (1) determines the relationship between the frequency of scanning the laser light, the diameter of the trajectory, the first amplitude, the second amplitude, and the phase difference (2) said first command waveform having a desired frequency and having a first amplitude, a second amplitude and a phase difference corresponding to said desired frequency and a desired diameter and said generating a second command waveform, wherein the table is adapted to increase the circularity of the trajectory compared to when the first amplitude and the second amplitude are equal and the phase difference is 90°; is defined for the first amplitude, the second amplitude, and the phase difference.

In order to solve the above problems, an optical scanning method according to an aspect of the present invention includes a mirror that reflects a laser beam, and a scanning unit that scans the laser beam by changing the tilt of the mirror. In the scanning method, a command waveform generation step of generating a first command waveform for controlling scanning in a first direction of the scanning unit and a second command waveform for controlling scanning in a second direction by the scanning unit and a locus obtaining step of obtaining the locus of the laser beam, and a command waveform correcting step of correcting at least one of the first command waveform and the second command waveform, wherein the command waveform correcting step comprises the A first amplitude, which is the amplitude of the first command waveform; a second amplitude, which is the amplitude of the second command waveform; At least one of the phase differences is corrected.

According to one aspect of the present invention, it is possible to realize an optical scanning device or an optical scanning method capable of increasing the roundness of a trajectory drawn by an irradiation point when scanning laser light so as to draw a circular trajectory. .

1 is a block diagram showing the configuration of an optical scanning device according to a first embodiment of the present invention; FIG. 2 is a block diagram showing the configuration of a first correction value generation unit provided in the optical scanning device shown in FIG. 1; FIG. 2 is a graph showing command waveforms in the optical scanning device shown in FIG. 1; 2A and 2B are schematic diagrams for explaining the operation of a mirror included in the optical scanning device shown in FIG. 1; FIG. 4 is a graph showing command amplitude dependence of the center of amplitude in an example of the present invention and a comparative example thereof; 2 is a block diagram showing the configuration of an optical scanning device according to a second embodiment of the present invention; FIG. 7 is a Lissajous figure showing the trajectory of irradiation points obtained as a result of wobble scanning performed using the optical scanning device shown in FIG. 6; (a) shows a perfectly circular trajectory, and (b) shows an elliptical trajectory. 7 is a flowchart of an optical scanning method performed by the optical scanning device shown in FIG. 6; FIG. 7 is a schematic diagram showing a configuration of a modified example of a scanning unit included in the optical scanning device shown in FIG. 6; FIG. 4 shows the frequency dependence of the first amplitude, the second amplitude and the phase difference obtained according to one embodiment of the present invention; FIG. It is the frequency dependence of the 1st amplitude obtained by the comparative example of this invention, a 2nd amplitude, and a phase difference. 4 is a graph showing the frequency dependence of circularity of trajectories obtained by each of an example of the present invention and a comparative example.

[First embodiment]
A basic configuration of an optical scanning device 1 according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. FIG. 1 is a block diagram showing the configuration of the optical scanning device 1. As shown in FIG. FIG. 2 is a block diagram showing the configuration of the first correction value generator 13a provided in the optical scanning device 1. As shown in FIG. FIG. 3 is a graph showing command waveforms in the optical scanning device 1. As shown in FIG. 4A and 4B are schematic diagrams for explaining the operation of the mirror 11 included in the optical scanning device 1. FIG. 4, illustration of the biaxial tilt stage 12 provided in the optical scanning device 1 is omitted.

(Basic Configuration of Optical Scanning Device)
The optical scanning device 1 has, as a basic configuration, a mirror 11, a biaxial tilt stage 12, a first correction value generator 13a, a second correction value generator 13b, a first combined waveform generator 14a, a first A two-composite waveform generating section 14 b and a driving section 15 are provided. The optical scanning device 1 is incorporated in, for example, a laser processing machine, and is used to move an irradiation point of laser light on an object.

The mirror 11 is configured to reflect the laser light. For example, the laser beam reflected by the mirror 11 is directly applied to the object. Alternatively, the laser beam reflected by the mirror 11 is applied to the object through the galvanometer scanner.

The biaxial tilt stage 12 is configured to change the tilt of the mirror 11 using piezo elements. The biaxial tilt stage 12 includes a first columnar piezo element, a second columnar piezo element, a first displacement sensor 12a, and a second displacement sensor 12b. In FIG. 1, illustration of the first columnar piezoelectric element and the second columnar piezoelectric element is omitted.

In this embodiment, the two-axis tilt stage 12 is configured to (1) slightly rotate the stage on which the mirror 11 is mounted by expanding and contracting the first columnar piezoelectric element about the x-axis, and (2) A two-axis integral piezo stage is used, which allows the stage on which the mirror 11 is mounted to be slightly rotated about the y-axis by expanding and contracting two columnar piezo elements. The expansion and contraction of each of the first columnar piezo element and the second columnar piezo element changes the height of each of the first columnar piezo element and the second columnar piezo element. Hereinafter, the amount of change in height of the first columnar piezo element will be referred to as first displacement, and the amount of change in height of the second columnar piezo element will be referred to as second displacement. Note that each of the first columnar piezo element and the second columnar piezo element is an example of the first piezo element and the second piezo element, respectively.

Also, in this embodiment, the first displacement sensor 12a detects a first displacement in the first columnar piezo element, and the second displacement sensor 12b detects a second displacement in the second columnar piezo element.

The biaxial tilt stage 12 changes the tilt of the mirror 11 so that, for example, the irradiation point of the laser beam reflected by the mirror 11 draws a circular orbit on the object. In this case, by combining the translational movement of the object or the translational movement of the laser beam irradiation point by the galvanometer scanner, wobbling in which the laser beam irradiation point draws a spiral trajectory on the object can be realized.

It should be noted that, in this specification, slightly rotating the stage of the biaxial tilt stage 12 about the x-axis as the rotation axis _Ar is also described as tilting the biaxial tilt stage 12 with respect to the first direction. In this specification, the rotation angle of the stage from the first reference position _P0 with the x-axis as the rotation axis _Ar is also referred to as the tilt of the biaxial tilt stage 12 with respect to the first direction (FIG. 3 reference). The first reference position _P0 is the position of the stage in the first direction when the voltage applied to the first columnar piezoelectric element is 0V. That is, the first reference position _P0 is the position of the stage in the first direction when the first displacement is zero.

On the other hand, minutely rotating the stage about the y-axis is also described in this specification as tilting the biaxial tilt stage 12 in the second direction. In this specification, the rotation angle of the stage from the second reference position with the y-axis as the rotation axis is also referred to as the tilt of the biaxial tilt stage 12 with respect to the second direction. Here, the rotation axis when the stage is slightly rotated about the y-axis and the second reference position are not shown, but the rotation axis _Ar when the stage is slightly rotated about the x-axis is shown. and the first reference position _P0 . The second reference position is the position of the stage in the first direction when the voltage applied to the second columnar piezoelectric element is 0V. That is, the second reference position is the position of the stage in the first direction when the second displacement is zero.

(Command waveform and operation of 2-axis tilt stage)
The command waveform is the waveform of the control signal used to control the displacement of the piezo element. Since the piezoelectric element is displaced according to the applied voltage, the command waveform is preferably the waveform of the voltage signal.

As described above, the biaxial tilt stage 12 includes the first columnar piezoelectric element used to tilt the biaxial tilt stage 12 in the first direction and the first columnar piezoelectric element used to tilt the biaxial tilt stage 12 in the second direction. and a second columnar piezo element to be used. Therefore, the command waveform consists of a first command waveform used for controlling the first displacement of the first columnar piezoelectric element and a second command waveform used for controlling the second displacement of the second columnar piezoelectric element. include. In the following, using the first command waveform as an example, the operation of the mirror 11 when tilting the biaxial tilt stage 12 with respect to the first direction will be described with reference to FIGS. 3 and 4. FIG. Using the second command waveform, the operation of the mirror 11 when tilting the biaxial tilt stage 12 in the second direction is as follows, using the first command waveform as an example, except that the rotation axis differs between the x-axis and the y-axis. is used to tilt the biaxial tilt stage 12 with respect to the first direction. Therefore, detailed description of the operation of the mirror 11 when the two-axis tilt stage 12 is tilted in the second direction using the second command waveform is omitted here.

As shown in FIG. 3, the first command waveform is a voltage signal waveform represented by a time-varying positive voltage. In order to perform wobble scanning, the first command waveform has a waveform that oscillates periodically and is symmetrical with respect to the amplitude center voltage _Vc . The amplitude center voltage _Vc is the amplitude center when the command waveform is the waveform of the voltage signal. In this embodiment, the first command waveform has a sinusoidal shape defined by frequency f, amplitude center voltage _Vc , and amplitude _VI . Each of the maximum voltage V _W+ and minimum voltage V _W− of the first command waveform is given by V _W+ =V _c +V _I /2 and V _W− =V _c −V _I /2, respectively.

The first columnar piezoelectric element has a first displacement of zero when the applied voltage is 0V, that is, when the first command waveform is off. As a result, as shown in FIG. 4, the tilt of the biaxial tilt stage 12 with respect to the first direction is the first reference position _P0 , and the reflecting surface of the mirror 11 is parallel to the y-axis.

Also, when a positive voltage is applied to the first columnar piezoelectric element, it exhibits a first displacement according to the positive voltage. As a result, as shown in FIG. 4, the biaxial tilt stage 12 tilts in the first direction (the counterclockwise direction in FIG. 4).

In FIG. 4, (1) the position of the mirror 11 when the amplitude center voltage _Vc is applied is represented by the amplitude center position _Pc , and (2) the position of the mirror 11 when the maximum voltage Vw ₊ is applied is (3) The position of the mirror 11 when the minimum _{voltage VW-} _is applied is represented by the minimum amplitude position _PW- . Also, in FIG. 4, the angle formed by the mirror 11 at the amplitude center position _Pc and the mirror 11 at the first reference position _P0 is represented as the angle _θc . The angle formed by the mirror 11 at the amplitude maximum position PW ₊ and the mirror 11 at the amplitude center position _Pc is represented as an angle _θW .

As described above, the first command waveform is a sine wave and has a symmetrical waveform with respect to the amplitude center voltage _Vc . Therefore, the maximum amplitude position PW ₊ and the minimum amplitude position _PW- are symmetrical with respect to the center amplitude position _Pc . As a result, the angle formed by the mirror 11 at the amplitude minimum position P _W− and the mirror 11 at the amplitude center position P _c is also the angle θ _W .

By the way, the first columnar piezo element has hysteresis. Therefore, even when the same voltage (for example, the amplitude center voltage V _c ) is applied to the first columnar piezoelectric element, the values of the angle θ _c often differ. Due to the variation in the value of the angle θ _c in this manner, the position of the irradiation point of the laser beam reflected by the mirror 11 varies even when the same voltage is applied to the first columnar piezoelectric element. In the optical scanning device 1, by correcting the first command waveform using the first correction value generated by the first correction value generating section 13a, it is possible to suppress this variation in the irradiation point. Note that detailed functions of the first correction value generation unit 13a will be described later with reference to FIG.

(Correction of command waveform)
The first displacement sensor 12a generates a first monitor waveform representing a first displacement that changes over time.

The second displacement sensor 12b generates a second monitor waveform representing the temporally changing second displacement.

The first correction value generator 13a generates a first correction value based on a first monitor waveform and a first target value for controlling the tilt of the biaxial tilt stage 12 in the first direction. The first correction value is a correction value for correcting temporal drift that may occur in the amplitude center of the periodically vibrating first displacement (and thus the amplitude center position P _c in the first direction). This is a correction value for bringing the amplitude center closer to the first target value. The first correction value is obtained, for example, by calculating the difference between the first target value and the center of amplitude of the first displacement (first target value - center of amplitude of first displacement). If the center of amplitude of the first displacement is smaller than the first target value, the first correction value is positive, and if the center of amplitude of the first displacement is larger than the first target value, the first correction value is negative. The first correction value is provided to the first composite waveform generator 14a.

A configuration example of the first correction value generation unit 13a is shown in FIG. As shown in FIG. 2, the configuration example of the first correction value generation unit 13a includes a low-pass filter (LPF) 13a1, an averaging unit 13a2, a comparison unit 13a3, a PID control unit 13a4, and a limiter 13a5. there is

The LPF 13a1 has a passband defined by a predetermined center frequency and a predetermined band. The LPF 13a1 passes, as a signal, components included in the passband of the first monitor waveform, and blocks other components as noise. In this embodiment, the passband of the LPF 13a1 includes the frequency f of the first command waveform. The first monitor waveform that has passed through the LPF 13a1 is supplied to the averaging section 13a2.

The averaging unit 13a2 averages the components of the first monitor waveform passed by the LPF 13a1 to calculate the amplitude center of the first displacement, and supplies the amplitude center of the first displacement to the comparison unit 13a3.

The comparison unit 13a3 generates the first correction value by calculating the difference between the first target value and the amplitude center of the first displacement. In this embodiment, a subtraction circuit is used as the comparator 13a3. The first target value and the first correction value are supplied to the PID controller 13a4.

The PID control unit 13a4 performs PID (Proportional-Integral-Differential) control of the first correction value so that the amplitude center of the first displacement approaches (more preferably matches) the first target value. The PID-controlled first correction value is supplied to the limiter 13a5.

An upper limit value and a lower limit value are defined for the limiter 13a5. The limiter 13a5 refers to the first correction value, the upper limit value, and the lower limit value supplied from the PID control unit 13a4, and (1) if the first correction value is equal to or more than the lower limit value and less than the upper limit value, the first (2) if the first correction value is less than the lower limit, supply the lower limit as the first correction value to the first composite waveform generation unit 14a; 3) If the first correction value is greater than or equal to the upper limit value, the upper limit value is supplied to the first composite waveform generator 14a as the first correction value.

It should be noted that the PID control section 13a4 and the limiter 13a5 can be omitted from the first correction value generation section 13a.

The first synthetic waveform generator 14a is configured to generate a first synthetic waveform by synthesizing the first command waveform and the first correction value. In this embodiment, an adder circuit is used as the first combined waveform generator 14a. The first composite waveform generated by the first composite waveform generation section 14 a is provided to the driving section 15 .

The second correction value generator 13b generates a second correction value based on a second monitor waveform and a second target value for controlling the tilt of the biaxial tilt stage 12 with respect to the first direction. The second correction value is a correction value for correcting drift over time that can occur in the amplitude center of the second displacement that oscillates periodically (and thus the amplitude center position P _c in the second direction). This is a correction value for bringing the amplitude center closer to the second target value. The second correction value, like the first correction value, is obtained, for example, by calculating the difference between the second target value and the center of the amplitude of the second displacement (the second target value - the center of the amplitude of the second displacement). . The second correction value is provided to the second composite waveform generator 14b.

A configuration example of the second correction value generation unit 13b can be configured in the same manner as the configuration example of the first correction value generation unit 13a shown in FIG. Therefore, detailed description of the configuration example of the second correction value generation unit 13b is omitted here.

The second synthetic waveform generator 14b is configured to generate a second synthetic waveform by synthesizing the second command waveform and the second correction value. In this embodiment, an adder circuit is used as the second synthesized waveform generator 14b. The second composite waveform generated by the second composite waveform generator 14 b is supplied to the drive section 15 .

The drive unit 15 is configured to control the tilt of the biaxial tilt stage 12 with respect to the first direction by driving the biaxial tilt stage 12 according to the first synthesized waveform. Similarly, the driving section 15 is configured to control the tilt of the biaxial tilt stage 12 in the second direction by driving the biaxial tilt stage 12 according to the second synthesized waveform.

As described above, the first correction value generated by the first correction value generator 13a is determined so as to bring the center of amplitude of the first displacement closer to the first target value. The driving unit 15 controls the tilt of the two-axis tilt stage 12 with respect to the first direction according to the first synthesized waveform obtained by synthesizing the first command waveform and the first correction value. It can be brought close to the first target value. Similarly, the second correction value generated by the second correction value generator 13b is determined so as to bring the center of amplitude of the second displacement closer to the second target value. By controlling the tilt of the biaxial tilt stage 12 in the second direction using the second synthesized waveform obtained by synthesizing the second command waveform and the second correction value, the amplitude center of the second displacement is shifted to the second It is possible to approach the target value.

The drift over time that can occur in the amplitude center of the piezo element is a slow phenomenon compared to one cycle of the command waveform. This is for the following reasons. That is, in feedback control (correction), it is necessary to sample the angle and position of the controlled object at a sufficiently fast period (frequency) in response to changes in the controlled object, and output a correction value so as to match the target value. Here, since the drift of the piezo element gradually changes (for example, 0.1 mrad change in 10 minutes), the drift can be suppressed by performing feedback control with a period that is in time for the change (for example, if correction is performed with a 10 s period, feedback control On the other hand, if the command waveform is a sine wave with an amplitude of 0.1 mrad and a frequency of 1000 Hz, and the piezoelectric element is driven by angle feedback control (with angle correction), the cycle is sufficiently faster than the command waveform cycle of 1 ms. (For example, correction at a period of 1 μs or less).Since the drift period is sufficiently slower than the command waveform period, the drift correction frequency is much higher than the command waveform correction frequency. (For example, the drift correction frequency is 1/10000000 or less of the command waveform correction frequency.) Therefore, the drift can be suppressed by correcting the drift once every several hundred to several thousand cycles of the command waveform. , the frequency at which the first correction value generator 13a generates the first correction value can be determined without greatly depending on the frequency of the first command waveform, and the second correction value generator 13b generates the second correction value The generation frequency can be determined without greatly depending on the frequency of the command waveform, so that the optical scanning device 1 can speed up scanning while suppressing temporal drift that may occur in the displacement of the piezoelectric element. can.

(Effect obtained by basic configuration)
As described above, the optical scanning device 1 includes the mirror 11 that reflects laser light and the piezoelectric element (the first A tilt stage (two-axis tilt stage 12) that changes the tilt of the mirror 11 by means of a columnar piezoelectric element and a second columnar piezoelectric element), and displacement of the piezoelectric elements (the first columnar piezoelectric element and the second columnar piezoelectric element) (first displacement , second displacement), and displacements detected by the displacement sensors (first displacement sensor 12a, second displacement sensor 12b) (first displacement, second displacement). 2 displacement) to generate correction values (first correction value, second correction value) for correcting command waveforms (first command waveform, second command waveform) (first correction value generation unit 13a , second correction value generation unit 13b), and a composite waveform (first composite a composite waveform generator (first composite waveform generator 14a, second composite waveform generator 14b) for generating a waveform and a second composite waveform); and a driving unit 15 for driving (the first columnar piezoelectric element and the second columnar piezoelectric element), and the command waveforms (the first command waveform and the second command waveform) oscillate periodically and The correction value generator (first correction value generator 13a, second correction value generator 13b) sets the amplitude center of the periodically oscillating displacement to the target value (first target value, The correction values (first correction value, second correction value) are determined so as to approach the second target value).

A correction value generation unit (first correction value generation unit 13a, second correction value generation unit 13b) calculates the center of amplitude of the displacement that oscillates periodically, and then uses the center of amplitude to generate a correction value (first correction value, second correction value). The temporal drift that can occur in the center of amplitude of the piezo elements (the first columnar piezo element and the second columnar piezo element) is a slow phenomenon compared to one cycle of the command waveforms (the first command waveform and the second command waveform). be. Therefore, in the optical scanning device 1, the correction value generator (first correction value generator 13a, second correction value generator 13b) instructs the frequency of generating the correction values (first correction value, second correction value). It can be determined without greatly depending on the frequency f of the waveforms (first command waveform, second command waveform). Therefore, the optical scanning device 1 can further increase the operating frequency of wobble scanning while suppressing temporal drift that may occur in the displacement of the piezoelectric elements (the first columnar piezoelectric element and the second columnar piezoelectric element). That is, the optical scanning device 1 can speed up scanning while suppressing drift.

In the optical scanning device 1, the correction value generators (the first correction value generator 13a and the second correction value generator 13b) average the outputs of the displacement sensors (the first displacement sensor 12a and the second displacement sensor 12b). A configuration is adopted in which a value is calculated and the average value is used as the amplitude center.

Thus, the amplitude center of displacement (first displacement, second displacement) can be obtained, for example, by calculating the average value of the outputs of the displacement sensors (first displacement sensor 12a, second displacement sensor 12b). . As described above, the drift over time that can occur in the amplitude center of the piezo elements (the first columnar piezo element and the second columnar piezo element) is compared with one cycle of the command waveforms (the first command waveform and the second command waveform). It is a slow phenomenon. Therefore, the average value of the outputs of the displacement sensors (first displacement sensor 12a, second displacement sensor 12b) is used as the center of amplitude, and the correction value can be calculated by taking the difference between the target value and the center of amplitude. The first columnar piezoelectric element and the second columnar piezoelectric element) can be easily suppressed from drifting over time.

In the optical scanning device 1, the correction value generators (first correction value generator 13a, second correction value generator 13b) generate correction values (first correction value, second correction value) using PID control. The configuration of generating is adopted.

Thus, PID control is suitable as feedback control for bringing the amplitude center closer to the target value.

Further, in the optical scanning device 1, the piezo elements include a first piezo element that changes the tilt of the mirror with respect to the first direction and a second piezo element that changes the tilt of the mirror with respect to the second direction. The stage (two-axis tilt stage 12) is a two-axis tilt stage including the first piezo element (first columnar piezo element) and the second piezo element (second columnar piezo element), and is equipped with a displacement sensor. The (first displacement sensor 12a, second displacement sensor 12b) includes the first displacement sensor 12a for detecting the first displacement, which is the displacement of the first piezo element (first columnar piezo element), and the second piezo element (second and a second displacement sensor 12b for detecting a second displacement that is a displacement of a columnar piezoelectric element). and a first command waveform that is symmetrical with respect to the center of amplitude, and a second command waveform for controlling the second piezo element, which oscillates periodically and is symmetrical with respect to the center of amplitude and a second command waveform that is a symmetrical waveform, and the correction value generator (first correction value generator 13a, second correction value generator 13b) is configured such that the amplitude center of the first displacement that oscillates periodically is generating a first correction value so as to approach a first target value, and generating a second correction value such that the amplitude center of the second displacement that oscillates periodically approaches a second target value; drives the first piezoelectric element (first columnar piezoelectric element) according to a first composite waveform that is the sum of the first command waveform and the first correction value, and the second command waveform and the second correction value, A second piezo element (second columnar piezo element) is driven in accordance with a second composite waveform that is the sum of .

According to the above configuration, the irradiation point of the laser light can be scanned along the first direction and the second direction, which are two independent directions. Therefore, it is possible to increase the degree of freedom when setting the trajectory of the irradiation point to be drawn on the object. The optical scanning device 1 can, for example, draw a circular trajectory or a spiral trajectory on the object. Moreover, according to the above configuration, it is possible to speed up scanning while suppressing temporal drift that may occur in the displacements of the first piezoelectric element and the second piezoelectric element.

Also, in the optical scanning device 1, a configuration is adopted in which the frequency of the command waveforms (first command waveform, second command waveform) is 1000 Hz or more.

In the optical scanning device 1, the command waveform ( (first command waveform, second command waveform). Therefore, the optical scanning device 1 is effective when the frequency of the command waveform (first command waveform, second command waveform) is 1000 Hz or more.

(Modified example of optical scanning device)
In this embodiment, the case where the optical scanning device 1 includes two piezoelectric elements, the first columnar piezoelectric element and the second columnar piezoelectric element, has been described. However, in the optical scanning device 1, in the case of one-dimensional drawing (eg, straight line drawing) instead of two-dimensional drawing (eg, circular drawing), the second columnar piezo element can be omitted.

When the second columnar piezo element is omitted in the optical scanning device 1 (when only the first columnar piezo element is provided), the optical scanning device 1 tilts the biaxial tilt stage 12 only in the first direction. can be done. Therefore, the optical scanning device 1 can scan the irradiation point of the laser beam on the object along the direction corresponding to the first direction. Then, by using a galvanometer scanner to translate the irradiation point in a direction that intersects (preferably orthogonally) to the direction corresponding to the first direction, wobbling that the irradiation point draws a zigzag trajectory on the object is realized. can do.

(Additional Configuration of Optical Scanning Device)
An additional configuration of the optical scanning device 1 will be described with continued reference to FIG. In addition to the basic configuration described above, the optical scanning device 1 includes a first command waveform generator 16a, a second command waveform generator 16b, and a controller 17 as additional components.

The first command waveform generator 16a is configured to generate a first command waveform. For example, the first command waveform generator 16a generates a sine wave having a frequency f, an amplitude center voltage V _c , and an amplitude _VI specified by the controller 17 as the first command waveform. The first command waveform generated by the first command waveform generator 16a is supplied to the first composite waveform generator 14a.

The second command waveform generator 16b is configured to generate a second command waveform. For example, the second command waveform generator 16b generates a sine wave having a frequency f, an amplitude center voltage V _c , and an amplitude _VI specified by the controller 17 as the second command waveform. The second command waveform generated by the second command waveform generator 16b is provided to the second composite waveform generator 14b.

The control unit 17 acquires the first monitor waveform and the second monitor waveform from each of the first displacement sensor 12a and the second displacement sensor 12b. Further, the control unit 17 controls the frequency f, the amplitude center voltage V _c and the amplitude V _I of each of the first command waveform and the second command waveform, the first target value, and the A second target value and a phase difference between the first command waveform and the second command waveform are generated. For example, when the frequency f, the amplitude center voltage V _c , and the amplitude _VI are equal in each of the first command waveform and the second command waveform, and the phase difference between the first command waveform and the second command waveform is π/2. , the irradiation point of the laser beam can draw a circular trajectory on the object. In this case, for example, by combining the translational movement of the laser light irradiation point by the galvanometer scanner, wobbling in which the laser light irradiation point draws a spiral trajectory on the object can be realized.

The frequency f, the amplitude center voltage V _c , and the amplitude V _I of the first command waveform are supplied to the first command waveform generator 16a, and the first monitor waveform and the first target value are supplied to the first correction value generator 13a. supplied. Further, the frequency f, the amplitude center voltage V _c and the amplitude V _I of the second command waveform are supplied to the second command waveform generator 16b, and the second monitor waveform and the second target value are supplied to the second correction value generator 16b. 13b.

〔Example〕
An embodiment of the optical scanning device 1 and a comparative example for the embodiment will be described below. In this embodiment, f=3000 Hz, V _c =3.59 V, and V _I =0.68 V are adopted as the frequency f, amplitude center voltage V _c , and amplitude V _I of the first command waveform, respectively. V _c =3.59 V is the first target value θ _c =1.3 mrad. and V _I =0.68 V corresponds to θ _W =0.2 mrad. corresponds to

Note that the comparative example was obtained by omitting the first correction value generation unit 13a and the first synthetic waveform generation unit 14a based on the present embodiment. That is, in the comparative example, the first command waveform is not corrected.

Using each of the optical scanning device 1 of the example and the comparative example, the results of wobble scanning by continuously operating only the first piezo element for 10 minutes, and the results of the inclination with respect to the first direction are shown below. Table 1 shows. Note that the amplitude center voltage V _c of the comparative example is V _c =3.40V.

Referring to Table 1, in this example, when wobble scanning with a frequency of 3000 Hz is performed for 10 minutes, the time _- dependent It was found that the drift can be suppressed. In a conventional optical scanning device using angle feedback control, when the frequency of wobble scanning increases (for example, when it exceeds 1000 Hz), angle feedback control cannot keep up with the frequency of wobble scanning, and wobble scanning is disturbed. In this embodiment, angle feedback control is not used, so wobble scanning is not disturbed even at a frequency as high as 3000 Hz.

Next, in each of the present embodiment and the comparative example, the case where the amplitude V _I of the second command waveform is changed to V _I =0.70 V, 2.11 V, and 3.51 V will be described. Each of V _I =0.70 V, 2.11 V, and 3.51 V corresponds to θ _W =0.2 mrad, 0.6 mrad, 1.0 mrad. corresponds to In this embodiment, f=3000 Hz and Vc=3.50 V are used as the frequency f of the second command waveform and the amplitude center voltage Vc, respectively. Vc=3.50V is the second target value θc=1.225 mrad. corresponds to The results of performing wobble scanning using each of the example and the comparative example of the optical scanning device 1 as described above are the results when θw is changed sequentially to 0.2 mrad, 0.6 mrad, and 1.0 mrad. The tilt results for the two directions are shown in FIG. Note that the amplitude center voltage V _c of the comparative example is V _c =3.40V.

Referring to FIG. 5, in the comparative example, (1) θ _W =0.2 mrad. , θ _c =1.185 mrad. and (2) θ _W =0.6 mrad. , θ _c =1.225 mrad. and (3) θ _W =1.0 mrad. , θ _c =1.257 mrad. Met. On the other hand, in the present embodiment, the angle θ _c is θ _W =0.2 mrad, 0.6 mrad, 1.0 mrad. , the angle θ _c after 10 minutes is θ _c =1.225 mrad. was found to be almost unchanged.

From the results of FIG. 5, when wobble scanning is performed at a frequency of 3000 Hz while changing the angle θw, the present example shows that the angle _θ It was found that _W -dependent drift can be suppressed.

[Second embodiment]
A configuration of an optical scanning device 2 according to a second embodiment of the present invention will be described with reference to FIGS. 6 to 9. FIG. FIG. 6 is a block diagram showing the configuration of the optical scanning device 2. As shown in FIG. FIG. 7 is a Lissajous figure showing the trajectory of irradiation points obtained as a result of wobble scanning performed using the optical scanning device 2 . (a) of FIG. 7 shows a perfectly circular trajectory, and (b) of FIG. 7 shows an elliptical trajectory. FIG. 8 is a flowchart of the optical scanning method M10 performed by the optical scanning device 2. As shown in FIG. FIG. 9 is a schematic diagram showing the configuration of a scanning section 30 that is a modified example of the scanning section 20 provided in the optical scanning device 2. As shown in FIG.

(Configuration of Optical Scanning Device)
The optical scanning device 2 basically includes a mirror 21, a two-axis tilt stage 22, a first command waveform correction section 23a, a second command waveform correction section 23b, a drive section 25, and a trajectory acquisition section 28. , and a determination unit 29 . Note that the mirror 21 and the biaxial tilt stage 22 are an example of a scanning section. Similar to the optical scanning device 1, the optical scanning device 2 is incorporated in, for example, a laser processing machine, and is used to move the irradiation point of the laser beam on the object.

Each of the mirror 21 and the two-axis tilt stage 22 has the same configuration as the mirror 11 and the two-axis tilt stage 12 provided in the optical scanning device 1, and each of the first displacement sensor 22a and the second displacement sensor 22b is , have the same configurations as the first displacement sensor 12a and the second displacement sensor 12b provided in the biaxial tilt stage 12 (see FIGS. 1 and 6). Therefore, in this embodiment, description of the mirror 21 and the biaxial tilt stage 22 is omitted.

In addition to the basic configuration 2 described above, the optical scanning device 2 further includes a first command waveform generator 26a, a second command waveform generator 26b, and a controller 27 as additional components. The first command waveform generator 26a, the second command waveform generator 26b, and the controller 27 are provided as additional components of the optical scanning device 1. The first command waveform generator 16a, the second command waveform generator 16b, and the same configuration as the control unit 17 . Therefore, in the present embodiment, detailed descriptions of the first command waveform generator 26a, the second command waveform generator 26b, and the controller 27 are omitted.

(Lissajous figure of command waveform and trajectory)
In this embodiment, wobble scanning is performed using a sine wave as each of the first command waveform input to the first columnar piezoelectric element and the second command waveform input to the second columnar piezoelectric element. In a state where the first command waveform correction section 23a and the second command waveform correction section 23b, which will be described later, do not correct the first command waveform and the second command waveform, respectively (for example, the state immediately after the start of wobble scanning). , the first command waveform and the second command waveform have the same frequency f, the same first amplitude _I1 and the second amplitude _I2 , and the phase difference Δ of 90°. is. Note that the first amplitude _I1 and the second amplitude _I2 are hereinafter also simply referred to as the amplitude _I1 and the amplitude _I2 .

By the way, a problem called axial interference is known in an optical scanning device using a two-axis tilt stage. That is, when the tilt of the mirror 21 in the first direction is periodically changed according to the first command waveform, the tilt of the mirror 21 in the second direction is periodically changed in conjunction therewith. Therefore, the actual tilt of the mirror 21 in the second direction is the tilt represented by the second command waveform and the tilt caused by the periodic change in the tilt of the mirror 21 in the first direction. That is, the tilt of the mirror 21 with respect to the second direction is different from the tilt of the mirror 21 represented by the second command waveform. Similarly, if the tilt of the mirror 21 in the second direction is changed periodically according to the second command waveform, the tilt of the mirror 21 in the first direction will change periodically accordingly. Therefore, the actual tilt of the mirror 21 in the first direction is the tilt represented by the first command waveform superimposed with the tilt caused by the periodic change in the tilt of the mirror 21 in the second direction. That is, the tilt of the mirror 21 with respect to the first direction is different from the tilt of the mirror 21 represented by the first command waveform. Such a phenomenon is called axial interference.

For example, a sine wave is input to the biaxial tilt stage as the first command waveform so that the irradiation point of the laser beam draws a circular orbit, and two sine waves delayed by 90° from the first command waveform are input as the second command waveform. Even if it is input to the axis tilt stage, since mutual axis interference occurs, the trajectory drawn by the irradiation point of the laser light is distorted and the roundness of the trajectory is reduced.

In an ideal case where axial interference that may occur in the biaxial tilt stage 22 is not assumed, each of the above-described first command waveform and second command waveform is input to the first columnar piezo element and the second columnar piezo element, respectively. Thus, the irradiation point of the laser beam reflected by the mirror 21 draws a circular trajectory as shown in FIG. 7(a). In the trajectory shown in FIG. 7(a), the diameter is constant even when the angle for measuring the diameter is changed. Therefore, the trajectory shown in FIG. 7A has a roundness of 100%.

Note that the x-axis shown in FIG. 7 is determined to be parallel to the linear trajectory drawn by the irradiation point when the biaxial tilt stage 22 is tilted with respect to the first direction. Similarly, the y-axis shown in FIG. 7 is determined to be parallel to the linear trajectory drawn by the irradiation point when the biaxial tilt stage 22 is tilted with respect to the second direction.

On the other hand, when axial interference occurs in the biaxial tilt stage 22, by inputting each of the above-described first command waveform and second command waveform to the first columnar piezo element and the second columnar piezo element, respectively, The irradiation point draws an elliptical trajectory as shown in FIG. 7(b). In the trajectory shown in FIG. 7(b), the major and minor axes are tilted with respect to the x-axis and y-axis. Here, the diameter of the trajectory on the x-axis is called the x-axis diameter, and the diameter of the trajectory on the y-axis is called the y-axis diameter.

The purpose of the optical scanning device 2 is to make the elliptical trajectory as shown in FIG. 7B approach a circular trajectory as shown in FIG. 7A using a method different from conventional feedback control. I have to. The conventional feedback control means that the displacement of the columnar piezoelectric element or the tilt of the mirror is sequentially monitored, and the feedback continues to correct the first command waveform and the second command waveform so that the monitored tilt of the mirror becomes the desired tilt. It refers to control.

(Optical scanning method M10)
An optical scanning method M10 in which the optical scanning device 2 performs wobble scanning, and for bringing an elliptical trajectory closer to a circle will be described with reference to FIG. As shown in FIG. 8, the optical scanning method M10 includes steps S11 to S24.

Step S11 is a step of setting frequency f and diameter d in wobble scanning. In the optical scanning device 2, the frequency f and the diameter d may be set by the user, or automatically set by the optical scanning device 2 according to the material of the object, the thickness of the object, and the like. may be configured to In this embodiment, f=3000 Hz is adopted as the frequency f, and d=500 μm is adopted as the diameter d.

Step S12 is a step of performing wobble scanning with the center position of wobble scanning fixed, that is, with the irradiation point not translated. The control unit 27 supplies the frequency f set in step S11, the amplitude _I1 determined according to the diameter d, and the amplitude center voltage to the first command waveform generation unit 26a, and supplies the frequency f and the diameter d and the amplitude _center voltage are supplied to the second command waveform generator 26b. The first command waveform generator 26a generates a first command waveform according to the acquired frequency f, amplitude I ₁ , and amplitude center voltage. The second command waveform generator 26b generates a second command waveform according to the acquired frequency f, amplitude I ₂ , and amplitude center voltage. The drive unit 25 performs wobble scanning by controlling the biaxial tilt stage 22 according to the first command waveform and the second command waveform.

Step S13 is a step of measuring the x-axis diameter using the trajectory of the irradiation point. The trajectory acquisition unit 28 uses the first monitor waveform and the second monitor waveform acquired from the biaxial tilt stage 22 via the control unit 27 to create a Lissajous figure and obtain the trajectory of the irradiation point. The trajectory of the irradiation point is supplied to the determination section 29 . The determination unit 29 measures the x-axis diameter using the trajectory of the irradiation point.

Note that in the present embodiment, the trajectory acquisition unit 28 is configured to obtain a trajectory by creating a Lissajous figure. However, as in the modification shown in FIG. 9, when the optical scanning device 2 is provided with an imaging unit 34 (for example, a digital camera) that captures an image representing the trajectory (hereinafter referred to as a trajectory image), the trajectory acquisition The unit 28 may be configured to acquire a trajectory image via the control unit 27 and obtain a trajectory from the trajectory image by performing image processing on the trajectory image.

In step S14, the determination unit 29 determines whether or not the measured value of the x-axis diameter is equal to the set value of the x-axis diameter. In this embodiment, the set value of the x-axis diameter is 500 μm. In this determination, the number of significant digits is predetermined, for example, 3 digits, and the fourth digit is rounded off. If the measured value of the rounded x-axis diameter is equal to the set value, the determination unit 29 determines “Yes”.

If the measured value of the x-axis diameter is not equal to the set value, in step S15, the first command waveform correction unit 23a corrects the amplitude _I1 of the first command waveform so that the measured value of the x-axis diameter approaches the set value. do. The first command waveform whose amplitude _I1 has been corrected is supplied to the driving section 25 .

In step S16, the driving section 25 performs wobble scanning. At this time, the drive unit 25 controls the tilt of the biaxial tilt stage 22 in the first direction according to the first command waveform whose amplitude _I1 is corrected.

The biaxial tilt stage 22 changes the tilt of the mirror 21 with respect to the first direction according to the first command waveform whose amplitude _I1 is corrected. Then, the biaxial tilt stage 22 generates a first monitor waveform and a second monitor waveform and supplies them to the control section 27 .

Using the new first monitor waveform and second monitor waveform, the trajectory acquisition unit 28 creates a Lissajous figure and obtains a new trajectory of the irradiation point. A new trajectory of the irradiation point is supplied to the determination unit 29 .

Returning to step S13 again, the determination unit 29 measures the x-axis diameter using the new trajectory of the irradiation point, and determines whether or not the measured value of the x-axis diameter is equal to the set value, which is the desired diameter. In optical scanning method M10, steps S13-S16 are repeated until the measured x-axis diameter equals the desired diameter setting.

Step S17 is a step of measuring the y-axis diameter using the trajectory of the irradiated point with the x-axis diameter corrected. If the measured value of the x-axis diameter is equal to the set value, which is the desired diameter, in step S17, the determining unit 29 measures the y-axis diameter using the trajectory of the irradiation point with the corrected x-axis diameter.

In step S18, the determination unit 29 determines whether or not the measured value of the y-axis diameter is equal to the set value of the y-axis diameter. In this embodiment, the set value for the y-axis diameter is 500 μm. In this determination, the number of significant digits is predetermined, for example, 3 digits, and the fourth digit is rounded off. If the measured value of the rounded y-axis diameter is equal to the set value, the determination unit 29 determines “Yes”.

If the measured value of the y-axis diameter is not equal to the set value, in step S19, the second command waveform correction unit 23b corrects the amplitude _I2 of the second command waveform so that the measured value of the y-axis diameter approaches the set value. do. The second command waveform with corrected amplitude _I2 is supplied to the driving section 25 .

In step S20, the driving section 25 performs wobble scanning. At this time, the drive unit 25 controls the tilt of the biaxial tilt stage 22 in the second direction according to the second command waveform whose amplitude _I2 is corrected.

The biaxial tilt stage 22 changes the tilt of the mirror 21 with respect to the second direction according to the second command waveform whose amplitude _I2 is corrected. Then, the biaxial tilt stage 22 generates a first monitor waveform and a second monitor waveform and supplies them to the control section 27 .

Using the first monitor waveform and the new second monitor waveform, the trajectory acquisition unit 28 creates a Lissajous figure and obtains a new trajectory of the irradiation point. A new trajectory of the irradiation point is supplied to the determination unit 29 .

Returning to step S17 again, the determination unit 29 measures the y-axis diameter using the new trajectory of the irradiation point, and determines whether or not the measured value of the y-axis diameter is equal to the set value of the y-axis diameter. In optical scanning method M10, steps S17 to S20 are repeated until the measured value of the y-axis diameter is equal to the set value, which is the desired diameter.

Step S21 is a step of calculating the roundness of the trajectory using the trajectory of the irradiation point with the corrected x-axis diameter and y-axis diameter. If the measured value of the y-axis diameter is equal to the set value, which is the desired diameter, in step S21, the determination unit 29 calculates the roundness of the trajectory of the irradiation point with the corrected x-axis diameter and y-axis diameter.

In step S22, the determination unit 29 determines whether or not the calculated roundness is equal to or greater than the roundness set value. Roundness is obtained by dividing the minor axis length of the current trajectory by the major axis length. In this embodiment, 95% is adopted as the setting value for the roundness.

If the calculated roundness is less than the set value, which is the desired roundness, in step S23, the second command waveform correction unit 23b adjusts the first command waveform so that the calculated roundness approaches the set value. is corrected for the phase difference Δ of the second command waveform with respect to The second command waveform corrected for the phase difference Δ is supplied to the driving section 25 .

In step S24, the driving section 25 performs wobble scanning. At this time, the drive unit 25 controls the tilt of the biaxial tilt stage 22 in the second direction according to the second command waveform whose amplitude _I2 is corrected.

Returning to step S21 again, the determination unit 29 uses the new trajectory of the irradiation point to calculate the circularity of the trajectory, and determines whether the calculated circularity is equal to or greater than the set value. In the optical scanning method M10, steps S21 to S24 are repeated until the calculated roundness reaches or exceeds the set value.

(Correction using a table)
In the optical scanning method M10 shown in FIG. 8, (1) the x-axis diameter, y-axis diameter, and circularity of the trajectory obtained by performing wobble scanning are obtained using the trajectory of the irradiation point. , (2) a configuration in which steps S13 to S16, steps S17 to S20, and steps S21 to S24 are repeated. The optical scanning method M10 configured in this manner is such that the roundness of the trajectory after correction exceeds the set value of the roundness, and the x-axis diameter and the y-axis diameter of the trajectory after correction are each set. Correct the first command waveform and the second command waveform so as to approach the value.

However, in a modified example of the optical scanning device 2, a table representing the relationship between frequency f, diameter d, amplitude I ₁ , amplitude I ₂ , and phase difference Δ is created in advance with respect to typical frequency f and diameter d. Alternatively, the table may be stored in a storage unit provided in the optical scanning device 2 .

Table 2 illustrates tables for d=500 μm and f=100, 1000, 2000, 3000 and 4000 Hz. This table is obtained by performing the optical scanning method M10 shown in FIG. 8 for each of d=500 μm and f=100, 1000, 2000, 3000 and 4000 Hz. That is, in this table, in the first command waveform and the second command waveform, the circularity of the trajectory is improved as compared with the case where the amplitude _I1 and the amplitude _I2 are equal and the phase difference Δ is 90°. The phase difference Δ is set to increase, and the amplitudes I ₁ and I ₂ are set so that the diameter d approaches the set value of 500 μm.

The first command waveform generator 26a can easily generate the first command waveform having the amplitude _I1 and the phase difference Δ corresponding to the desired frequency f and diameter d by referring to Table 2. . Further, the second command waveform generator 26b can easily generate the second command waveform having the amplitude _I2 and the phase difference Δ corresponding to the desired frequency f and diameter d by referring to the table of Table 2. can be done. The first command waveform generator 26a and the second command waveform generator 26b together constitute an example of a command waveform generator.

Although the table in Table 2 is for d=500 μm, it is preferable to also create a table for diameter d, which is frequently used such as d=300, 400, and 600 μm.

When performing wobble scanning using frequencies f and diameters d not registered in these tables, amplitudes I ₁ and I ₂ corresponding to frequencies f and diameters d registered in one or more tables , and the phase difference Δ by linear interpolation.

For example, when f=3500 Hz and d=500 μm, the amplitude I ₁ , amplitude I ₂ , and phase difference , f=4000 Hz and d=500 μm rows.

Further, the amplitude I ₁ , the amplitude I ₂ , and the phase difference Δ when f = 3000 Hz and d = 450 µm are obtained from the row of f = 3000 Hz and d = 500 µm registered in the table of Table 2 and d = It can be obtained by linear interpolation using the row of f=3000 Hz and d=400 μm of the table in which the amplitude I ₁ , the amplitude I ₂ corresponding to 400 μm, and the phase difference Δ are registered.

(Modified example of scanning unit)
In the optical scanning device 2 shown in FIG. 6, wobble scanning is performed using the scanning section 20 including the biaxial tilt stage 22 . However, the optical scanning device 2 may be configured to perform wobble scanning using a scanning section 30 (see FIG. 9) instead of the scanning section 20 . The scanning unit 30 is provided with a galvanometer scanner after the mirror 21 and the two-axis tilt stage 22 that constitute the scanning unit 20 . 9, the objective lens OL provided in the optical scanning device 2, the object W, the table T on which the object W is placed, and the imaging unit 34 are shown in addition to the scanning unit 30. ing.

As shown in FIG. 9, the scanning unit 30 is a galvanometer scanner including a first mirror 31a, a second mirror 31b, a first galvanometer motor 32a, and a second galvanometer motor 32b. The first galvanometer motor 32a corresponds to the first columnar piezo element of the biaxial tilt stage 22 and is used to tilt the first mirror 31a in the first direction. The first galvanometer motor 32a is controlled by the first command waveform. Similarly, the second galvanometer motor 32b corresponds to the second columnar piezo element of the biaxial tilt stage 22 and is used to tilt the second mirror 31b in the second direction. In the scanning unit 30, the first galvanometer motor 32a and the second galvanometer motor 32b are not integrated, and the first mirror 31a and the second mirror 31b are provided independently.

In the scanning unit 30 configured in this way, since the first galvanometer motor 32a and the second galvanometer motor 32b are independent, axial interference is unlikely to occur. However, since the first mirror 31a and the second mirror 31b are larger than the mirror 21 of the scanning unit 20, the scanning unit 30 has a problem that it is difficult to increase the frequency f of wobble scanning.

In addition, in the galvanometer scanner, the arrangement of each of the first mirror 31a, the second mirror 31b, the first galvanomotor 32a, and the second galvanomotor 32b is restricted for the reason of space saving, for example. For example, a first rotation axis that is a rotation axis common to the first mirror 31a and the first galvanomotor 32a, and a second rotation axis that is a rotation axis common to the second mirror 31b and the second galvanomotor 32b. At least one of them may be arranged at an angle that deviates from the ideal angle. In this case, the first rotation axis and the second rotation axis of the galvanometer scanner are not orthogonal to each other. When each of the first mirror 31a, the second mirror 31b, the first galvano motor 32a, and the second galvano motor 32b is ideally arranged, a sine wave is input to the first galvano motor 32a as the first command waveform. By inputting a sine wave whose phase is delayed by 90° from the first command waveform as the second command waveform to the second galvano motor 32b, the irradiation point draws a circular orbit. When drawing a circle with the 2-axis tilt stage using a configuration in which a 2-axis galvano scanner whose first and second rotation axes are not perpendicular to each other is arranged after the 2-axis tilt stage, the roundness of the trajectory decreases. do.

Further, as described in the background art section of Japanese Patent Application Laid-Open No. 2009-06641, it is known that distortions called pincushion distortion and barrel distortion may occur in an optical system that constitutes a galvanometer scanner. there is Pincushion distortion is due to pincushion errors in the first mirror 31a and the second mirror 31b of the galvanometer scanner. Also, the barrel distortion is caused by the distortion aberration of the objective lens OL provided behind the first mirror 31a and the second mirror 31b. These pincushion and barrel distortions also distort the trajectory drawn by the illuminated point and reduce the circularity of the trajectory.

The optical scanning device 2 uses a configuration in which a two-axis galvanometer scanner having a first rotation axis and a second rotation axis that are not orthogonal to each other is arranged behind the two-axis tilt stage 22, and a circle is drawn by the two-axis tilt stage 22. , pincushion distortion, and barrel distortion can be suppressed.

(Effect obtained by the second embodiment)
As described above, the optical scanning device 2 includes mirrors that reflect laser light, and the

scanning units

20 and 30 that scan the laser light by changing the inclination of the mirrors. command waveform generators (first command waveform generator 26a, second command waveform generator 26a, second a command waveform generator 26b), a trajectory acquisition unit 28 that acquires the trajectory of the laser beam, and a command waveform correction unit that corrects at least one of the first command waveform and the second command waveform (first command waveform correction unit 23a, The command waveform correction unit (first command waveform correction unit 23a, second command waveform correction unit 23b) is provided with a second command waveform correction unit 23b), and the command waveform correction unit (first command waveform correction unit 23a, second command waveform correction unit 23b) adjusts the first amplitude I ₁ and/or the second amplitude _I2 and the phase difference Δ.

The scanning unit 20 includes a mirror 21, and the scanning unit 30 includes a first mirror 31a, a second mirror 31b, and a mirror 21.

According to the above configuration, the roundness of the trajectory drawn by the irradiation point of the laser light can be increased.

In the optical scanning device 2, the first command waveform and the second command waveform have the same frequency, the same first amplitude _I1 and the second amplitude _I2 , and a phase difference Δ of 90°. It is preferably a sine wave.

According to the above configuration, it is possible to easily realize drawing so that the irradiation point of the laser light draws a circular trajectory. As a result, it is possible to easily achieve a substantially constant processing width in any scanning direction.

In the optical scanning device 2, the scanning unit 20 further includes a biaxial tilt stage 22 that changes the tilt of the mirror 21 using piezoelectric elements (first and second columnar piezoelectric elements). A configuration is adopted in which each of the waveform and the second command waveform controls the tilt of the biaxial tilt stage 22 with respect to the first direction and the second direction, respectively.

According to the above configuration, by adopting the two-axis tilt stage as part of the scanning unit, even if axial interference may occur, the roundness of the trajectory drawn by the irradiation point of the laser beam can be improved. can.

In the optical scanning device 2, the scanning unit 30 includes a first mirror 31a and a second mirror 31b that reflect laser light, a first motor (first galvanometer motor 32a) that changes the inclination of the first mirror 31a, and a second motor (second galvanometer motor 32b) that changes the inclination of the second mirror 31b. The tilt of the first mirror 31a in the first direction is controlled, and the second command waveform controls the tilt of the second mirror 31b in the second direction by controlling the second motor (second galvanometer motor 32b). configuration is adopted.

According to the above configuration, by adopting the scanning unit 30 provided with the galvanometer scanner in the rear stage of the mirror 21 and the biaxial tilt stage 22, pincushion distortion and barrel distortion that may occur when drawing a circle are caused. It is possible to suppress the decrease in roundness that occurs.

A modified example of the optical scanning device 2 includes the

scanning units

20 and 30, a first command waveform for controlling the scanning of the

scanning units

20 and 30 in the first direction, and the

scanning units

20 and 30 in the second direction. A command waveform generation unit (first command waveform correction unit 23a, second command waveform correction unit 23b) that generates a second command waveform for controlling scanning, and a trajectory acquisition unit 28 that acquires the trajectory of the laser light. The first command waveform and the second command waveform are sine waves defined by a common frequency f, a first amplitude _I1 and a second amplitude _I2 , and a phase difference Δ. The command waveform generator (the first command waveform generator 26a and the second command waveform generator 26b) determines (1) the frequency f, the diameter d of the trajectory of the laser light, the first amplitude _I1 , ( ₂ ) having a desired frequency f and corresponding to the desired frequency and the desired diameter d to generate first and second command waveforms having a first amplitude I ₁ , a second amplitude I ₂ , and a phase difference Δ, wherein the table shows that the first amplitude I ₁ and the second amplitude I ₂ are equal, Also, the first amplitude I ₁ , the second amplitude I ₂ , and the phase difference Δ are determined so as to increase the circularity of the trajectory compared to when the phase difference Δ is 90°.

A modified example of the optical scanning device 2 has the same effects as the optical scanning device 2 . Furthermore, according to a modified example of the optical scanning device 2, the command waveform generators (the first command waveform generator 26a and the second command waveform generator 26b) obtain the desired frequency f and the desired frequency f by referring to the table. A first command waveform and a second command waveform having a first amplitude I ₁ , a second amplitude I ₂ , and a phase difference Δ corresponding to the diameter d of the can be generated. Therefore, the modified example of the optical scanning device 2 can easily improve the roundness of the trajectory drawn by the irradiation point of the laser light compared to the optical scanning device 2 .

Also, in the optical scanning device 2, a configuration is adopted in which the frequency f of the first command waveform and the second command waveform is 1000 Hz or more.

In order to eliminate axial interference caused by the biaxial tilt stage 22 and pincushion distortion and barrel distortion caused by the galvanometer scanner optical system, the displacement of the piezoelectric elements (the first columnar piezoelectric element and the second columnar piezoelectric element) is adjusted. Alternatively, feedback control is widely performed in which the tilt of the mirror is sequentially monitored and the first command waveform and the second command waveform are continuously corrected so that the monitored tilt of the mirror becomes a desired tilt. However, such feedback takes time. Therefore, when the frequency f of the wobble scanning is increased, the feedback control eventually cannot catch up with the frequency f of the wobble scanning. On the other hand, the optical scanning device 2 corrects at least one of the first amplitude _I.sub.1 , the second amplitude _I.sub.2 , and the phase difference .DELTA. Circularity can be increased. Therefore, the optical scanning device 2 is suitable for increasing the frequency of the first command waveform and the second command waveform.

The optical scanning device 2 further includes an imaging unit 34 that captures an image (trajectory image) representing the trajectory of the laser beam, and the trajectory acquisition unit 28 performs image processing on the image (trajectory image) to A configuration is employed in which the trajectory is obtained from (trajectory image).

In this way, the trajectory of the laser light can also be obtained by performing image processing on the image representing the trajectory captured by the imaging unit 34 (trajectory image).

Further, in the above-described embodiments, the present invention is expressed as an apparatus (optical scanning device), but the present invention can also be expressed as a method (optical scanning method). That is, "an optical scanning method using a scanning unit that includes a mirror that reflects a laser beam and scans the laser beam by changing the inclination of the mirror, wherein the scanning of the scanning unit in a first direction is controlled. a command waveform generating step of generating a first command waveform for controlling scanning of the scanning unit and a second command waveform for controlling scanning in a second direction of the scanning unit; a locus obtaining step of obtaining a locus of the laser light; and a command waveform correcting step of correcting at least one of the command waveform and the second command waveform, wherein the command waveform correcting step corrects the amplitude of the first command waveform so as to increase the circularity of the locus. correcting at least one of a certain first amplitude I ₁ and a second amplitude I ₂ that is the amplitude of the second command waveform, and a phase difference Δ between the first command waveform and the second command waveform; The scope of the present invention also includes an optical scanning method characterized by:

In this optical scanning method, the step of generating command waveforms is performed using sinusoidal waves having the same frequency, the same first amplitude _I1 and the second amplitude _I2 , and the phase difference of 90°. Preferably, a certain first command waveform and said second command waveform are generated. This point is the same as in the case of the optical scanning device 2 described above.

[Combination of First Embodiment and Second Embodiment]
In the optical scanning device according to one embodiment of the present invention, the configuration of the optical scanning device 1 (see FIG. 1) according to the first embodiment and the configuration of the optical scanning device 2 (see FIG. 6) according to the second embodiment A configuration that also has a configuration may be adopted. The optical scanning device configured as described above can increase the circularity of the trajectory drawn by the irradiation point of the laser beam, can bring the diameter d of the trajectory closer to the set value, and can and the drift over time that can occur in the first displacement and the second displacement, which are the displacements of the second columnar piezoelectric element, can be suppressed.

Further, in the optical scanning device according to the embodiment of the present invention, in the optical scanning device having both the configuration of the optical scanning device 1 and the configuration of the optical scanning device 2, the typical frequency f and the diameter d are: A table representing the relationship between the frequency f, the diameter d, the amplitude I ₁ , the amplitude I ₂ , and the phase difference Δ may be created in advance and stored in the storage unit provided in the optical scanning device. good. In addition to the effects described above, the optical scanning device configured in this way can easily improve the roundness of the trajectory drawn by the irradiation point of the laser light. This is because the command waveform generator can generate the first command waveform and the second command waveform by referring to the table.

〔Example〕
An embodiment of the optical scanning device in which the optical scanning device 1 is combined with the optical scanning device 2 and a comparative example for the embodiment will be described below. Each of FIGS. 10 and 11 shows the frequency dependence of amplitude I ₁ , amplitude I ₂ , and phase difference Δ obtained by the present example and comparative example, respectively. FIG. 12 is a graph showing the frequency dependence of the roundness of the trajectory obtained by each of the example and the comparative example.

In this embodiment, f = 3000 Hz, V _c = 4.27 V, and V _I = 5.54 V are adopted as the frequency f, the amplitude center voltage V _c , and the amplitude V _I of the first command waveform at startup, respectively. did. V _c =4.27 V is the first target value θ _c =1.55 mrad. and V _I =5.54 V corresponds to θ _W =1.63 mrad. corresponds to Further, in this embodiment, the frequency f, amplitude center voltage V _c and amplitude V _I of the second command waveform at startup are f=3000 Hz, V _c =5.16 V, and V _I =7.32 V, respectively. It was adopted. V _c =5.16 V is the second target value θ _c =1.82 mrad. and V _I =7.32 V corresponds to θ _W =2.09 mrad. corresponds to

Also, in this example, the optical scanning method M10 was performed. In this example, d=500 μm was used as each of the set value of the x-axis diameter and the set value of the y-axis diameter, and 95% was used as the set value of the roundness. As the frequency f, f=100, 1000, 2000, 3000 and 4000 Hz are adopted.

It should be noted that the comparative example was based on the present embodiment, and the first command waveform and the second command waveform were not corrected in the comparative example.

Referring to FIG. 10, in this example, by performing the optical scanning method M10, the corrected amplitude I ₁ , amplitude I ₂ , and phase difference Δ have different values depending on the frequency f. As a result, in any case, the roundness of the trajectory of the irradiation point was 95% or more.

On the other hand, referring to FIG. 11, since the optical scanning method M10 is not performed in the comparative example, the amplitude I ₁ , the amplitude _I ₂ , and the phase difference _Δ , and the phase difference Δ remained. Referring to FIG. 12, it was found that in the comparative example, there was a negative correlation between the frequency f and the roundness, and the higher the frequency f, the lower the roundness. This decrease in roundness is considered to be caused by axial interference. On the other hand, in this example, no correlation was observed between the frequency f and the circularity, and the circularity did not decrease even when the frequency f was changed.

[Additional notes]
The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. is also included in the technical scope of the present invention.

Also, in the above-described embodiments, the present invention is expressed as a device (optical scanning device). However, the present invention can also be expressed as a method (optical scanning method). That is, "an optical scanning method using a scanning unit that includes a mirror that reflects a laser beam and scans the laser beam by changing the inclination of the mirror, wherein the scanning of the scanning unit in a first direction is controlled. a command waveform generating step of generating a first command waveform for controlling scanning of the scanning unit and a second command waveform for controlling scanning in a second direction of the scanning unit; a locus obtaining step of obtaining a locus of the laser light; and a command waveform correcting step of correcting at least one of the command waveform and the second command waveform, wherein the command waveform correcting step corrects the amplitude of the first command waveform so as to increase the circularity of the locus. and correcting at least one of a certain first amplitude and a second amplitude that is the amplitude of the second command waveform, and a phase difference between the first command waveform and the second command waveform. A scanning method” is also included in the scope of the present invention.

In this optical scanning method, the command waveform generating step is a sine wave having the same frequency, the same first amplitude and the second amplitude, and a phase difference of 90°. Preferably, a first command waveform and said second command waveform are generated.

(summary)
An optical scanning device according to a first aspect of the present invention includes a mirror that reflects a laser beam, a scanning unit that scans the laser beam by changing the inclination of the mirror, and a scanning unit that scans the laser beam in a first direction. a command waveform generation unit that generates a first command waveform for controlling the scanning unit and a second command waveform for controlling the scanning in the second direction of the scanning unit; a trajectory acquisition unit that acquires the trajectory of the laser light; a command waveform correction unit that corrects at least one of the first command waveform and the second command waveform, wherein the command waveform correction unit corrects the first command waveform so as to increase the circularity of the trajectory. and at least one of the second amplitude, which is the amplitude of the second command waveform, and the phase difference between the first command waveform and the second command waveform.

In the optical scanning device according to the second aspect of the present invention, in addition to the configuration of the optical scanning device according to the first aspect, the first command waveform and the second command waveform have the same frequency, and , the first amplitude and the second amplitude are equal, and the phase difference is a sine wave of 90°.

In the optical scanning device according to the third aspect of the present invention, in addition to the configuration of the optical scanning device according to the first aspect or the second aspect, the scanning unit uses a piezo element to tilt the mirror. A variable 2-axis tilt stage is further provided, wherein each of the first command waveform and the second command waveform controls tilt of the 2-axis tilt stage with respect to the first direction and the second direction, respectively. , is adopted.

In the optical scanning device according to the fourth aspect of the present invention, in addition to the configuration of the optical scanning device according to the third aspect, the piezoelectric element is a first piezoelectric element that is displaced according to the first command waveform. and a second piezoelectric element that is displaced according to the second command waveform. A first displacement sensor that detects a first displacement that is the displacement of the first piezoelectric element; A second displacement sensor for detecting a second displacement, which is the displacement of an element, and correcting the first command waveform so that the center of amplitude of the first displacement detected by the first displacement sensor approaches a first target value. a first correction value generation unit that generates a first correction value; and a second correction value generation unit that corrects the second command waveform so that the center of amplitude of the second displacement detected by the second displacement sensor approaches a second target value. a second correction value generator that generates a correction value; a first combined waveform generator that generates a first composite waveform by combining the first command waveform and the first correction value; and the second command waveform. and the second correction value to generate a second composite waveform; a first drive section for driving the first piezo element according to the first composite waveform; and a second driving section for driving the second piezo element according to the two synthesized waveforms.

According to the above configuration, the first correction value generating section calculates the center of amplitude of the first displacement, generates the first correction value using the center of amplitude, and the second correction value generating section calculates the center of amplitude of the second displacement, and then uses the center of amplitude to generate a second correction value. The possible drift over time in the center of amplitude of the first and second displacements is a slow phenomenon compared to one period of the first and second command waveforms. Therefore, in the present optical scanning device, the frequency at which the first correction value generator generates the correction value and the frequency at which the second correction value generator generates the correction value are determined by the first command waveform and the second command waveform. It can be determined without greatly depending on the frequency. Therefore, the present optical scanning device can suppress temporal drift that may occur in the displacement of the piezoelectric element.

In the optical scanning device according to the fifth aspect of the present invention, in addition to the configuration of the optical scanning device according to the first aspect or the second aspect, the scanning unit is provided behind the mirror. A galvanometer scanner comprising a first mirror and a second mirror that reflect laser light, a first motor that changes the tilt of the first mirror, and a second motor that changes the tilt of the second mirror. the first command waveform controls the tilt of the first mirror in the first direction by controlling the first motor; and the second command waveform controls the second motor. A configuration is adopted in which the inclination of the second mirror in the second direction is controlled by controlling the tilt.

According to the above configuration, by adopting the galvanometer scanner as the scanning unit, even if distortions called pincushion distortion and barrel distortion may occur, the roundness of the trajectory drawn by the irradiation point of the laser light can be corrected. can be enhanced.

An optical scanning device according to a sixth aspect of the present invention is provided with a mirror that reflects a laser beam, a scanning unit that scans the laser beam by changing the inclination of the mirror, and a scanning unit that scans the laser beam in a first direction. a command waveform generation unit that generates a first command waveform for controlling the scanning unit and a second command waveform for controlling the scanning in the second direction of the scanning unit; a trajectory acquisition unit that acquires the trajectory of the laser light; wherein the first command waveform and the second command waveform are sine waves defined by a frequency common to each, a first amplitude and a second amplitude that are amplitudes of each, and a phase difference of each , the command waveform generator (1) refers to a table representing the relationship between the laser beam scanning frequency, the trajectory diameter, the first amplitude, the second amplitude, and the phase difference; (2) generating said first command waveform and said second command waveform having a desired frequency and having a first amplitude, a second amplitude and a phase difference corresponding to said desired frequency and desired diameter; , the table includes the first amplitude, the second amplitude, and the A second amplitude and the phase difference are defined.

The optical scanning device according to the sixth aspect has the same effect as the optical scanning device according to the first aspect. Furthermore, according to the above configuration, the command waveform generation section refers to the table to generate the first command waveform having the first amplitude, the second amplitude, and the phase difference corresponding to the desired frequency and the desired diameter. and the second command waveform. Therefore, the present optical scanning device can easily improve the circularity of the trajectory drawn by the irradiation point of the laser light, as compared with the optical scanning device according to the first aspect of the present invention.

In the optical scanning device according to the seventh aspect of the present invention, in addition to the configuration of the optical scanning device according to the sixth aspect, the scanning unit includes a two-axis tilting device that changes the tilt of the mirror using a piezo element. a stage, wherein each of the first command waveform and the second command waveform controls tilts of the two-axis tilt stage with respect to the first direction and the second direction, respectively; , a first piezo element that is displaced according to the first command waveform, and a second piezo element that is displaced according to the second command waveform, and the displacement of the first piezo element is the first a first displacement sensor that detects a displacement; a second displacement sensor that detects a second displacement that is the displacement of the second piezoelectric element; and a center of amplitude of the first displacement detected by the first displacement sensor as a first target. a first correction value generator for generating a first correction value for correcting the first command waveform so that the center of amplitude of the second displacement detected by the second displacement sensor approaches the second target value; A second correction value generation unit that generates a second correction value for correcting the second command waveform so as to approximate the second command waveform, and a first combined waveform that generates a first combined waveform by combining the first command waveform and the first correction value. a first composite waveform generation section that generates a second composite waveform by combining the second command waveform and the second correction value; and a second composite waveform generation section that generates a second composite waveform according to the first composite waveform. A configuration is adopted in which a first driving section for driving one piezoelectric element and a second driving section for driving the second piezoelectric element according to the second synthesized waveform are further provided.

The optical scanning device according to the seventh aspect has the same effects as the optical scanning device according to the fourth aspect. That is, according to the above configuration, even when the circularity of the trajectory of the laser beam is increased by referring to the table, it is possible to suppress temporal drift that may occur in the displacement of the piezoelectric element.

In an optical scanning device according to an eighth aspect of the present invention, in addition to the configuration of the optical scanning device according to any one of the first to seventh aspects, an image representing the locus is captured. A configuration is adopted in which an imaging unit is further provided, and the trajectory acquisition unit acquires the trajectory from the image by performing image processing on the image.

In this way, the trajectory of the laser light can also be obtained by performing image processing on the image representing the trajectory captured by the imaging unit.

An optical scanning method according to a ninth aspect of the present invention is an optical scanning method using a scanning unit that includes a mirror that reflects a laser beam and that scans the laser beam by changing the tilt of the mirror, a command waveform generating step of generating a first command waveform for controlling scanning of the scanning unit in the first direction and a second command waveform for controlling the scanning of the scanning unit in the second direction; and a trajectory of the laser beam. and a command waveform correction step of correcting at least one of the first command waveform and the second command waveform, wherein the command waveform correction step increases the circularity of the trajectory. at least one of a first amplitude that is the amplitude of the first command waveform, a second amplitude that is the amplitude of the second command waveform, and a phase difference between the first command waveform and the second command waveform correct.

The optical scanning method according to the ninth aspect has the same effects as the optical scanning device according to the first aspect.

In the optical scanning method according to the tenth aspect of the present invention, in addition to the configuration of the optical scanning method according to the ninth aspect described above, the command waveform generating step has equal frequencies and amplitudes and the first and second command waveforms, which are sinusoidal waves having equal first and second amplitudes and a phase difference of 90°, are employed.

Reference Signs List 1 optical scanning device 11 mirror 12 2-axis tilt stage 12a first displacement sensor 12b second displacement sensor 13a first correction value generator 13a1 low-pass filter (LPF)
13a2 averaging unit 13a3 comparison unit 13a4 PID control unit 13a5 limiter 13b second correction value generation unit 14a first synthetic waveform generation unit 14b second synthesis waveform generation unit 15 drive unit 16a first command waveform generation unit 16b second command waveform generation Part 17 Control part

Claims

a scanning unit that includes a mirror that reflects a laser beam and that scans the laser beam by changing the tilt of the mirror;
a command waveform generator that generates a first command waveform for controlling scanning of the scanning unit in a first direction and a second command waveform for controlling scanning of the scanning unit in a second direction;
a trajectory acquisition unit that acquires the trajectory of the laser light;
a command waveform correction unit that corrects at least one of the first command waveform and the second command waveform,
The command waveform correction unit is configured to increase the roundness of the trajectory, at least one of a first amplitude that is the amplitude of the first command waveform and a second amplitude that is the amplitude of the second command waveform, correcting a phase difference between the first command waveform and the second command waveform;
An optical scanning device characterized by:
The first command waveform and the second command waveform are sine waves having the same frequency, the same first amplitude and the second amplitude, and the phase difference of 90°.
2. The optical scanning device according to claim 1, wherein:
The scanning unit further includes a biaxial tilt stage that changes the tilt of the mirror using a piezo element,
each of the first command waveform and the second command waveform controls tilts of the two-axis tilt stage with respect to the first direction and the second direction, respectively;
3. The optical scanning device according to claim 1, wherein:
The piezo element is composed of a first piezo element displaced according to the first command waveform and a second piezo element displaced according to the second command waveform,
a first displacement sensor that detects a first displacement that is the displacement of the first piezo element;
a second displacement sensor that detects a second displacement that is the displacement of the second piezo element;
a first correction value generator that generates a first correction value for correcting the first command waveform so that the center of amplitude of the first displacement detected by the first displacement sensor approaches a first target value;
a second correction value generator for generating a second correction value for correcting the second command waveform so that the center of amplitude of the second displacement detected by the second displacement sensor approaches a second target value;
a first synthesized waveform generation unit that generates a first synthesized waveform by synthesizing the first command waveform and the first correction value;
a second synthesized waveform generation unit that generates a second synthesized waveform by synthesizing the second command waveform and the second correction value;
a first drive unit that drives the first piezo element according to the first composite waveform;
a second driving unit that drives the second piezo element according to the second composite waveform,
4. The optical scanning device according to claim 3, wherein:
The scanning unit is a galvanometer scanner provided after the mirror, and includes a first mirror and a second mirror that reflect laser light, a first motor that changes the inclination of the first mirror, and the second mirror. Further comprising a galvanometer scanner comprising a second motor that changes the tilt of the mirror,
the first command waveform controls the tilt of the first mirror in the first direction by controlling the first motor;
The second command waveform controls the tilt of the second mirror in the second direction by controlling the second motor.
3. The optical scanning device according to claim 1, wherein:
a scanning unit that includes a mirror that reflects a laser beam and that scans the laser beam by changing the tilt of the mirror;
a command waveform generator that generates a first command waveform for controlling scanning of the scanning unit in a first direction and a second command waveform for controlling scanning of the scanning unit in a second direction;
a trajectory acquisition unit that acquires the trajectory of the laser light,
The first command waveform and the second command waveform are sine waves defined by a frequency common to each, a first amplitude and a second amplitude that are amplitudes of each, and a phase difference of each,
The command waveform generator (1) refers to a table representing the relationship between the frequency of scanning the laser light, the diameter of the trajectory, the first amplitude, the second amplitude, and the phase difference, and ( 2) generating said first command waveform and said second command waveform having a desired frequency and having a first amplitude, a second amplitude and a phase difference corresponding to said desired frequency and desired diameter;
The table is arranged such that the first amplitude and the second amplitude are equal and the phase difference is 90 degrees, so as to increase the roundness of the trajectory. 2 amplitude and said phase difference are defined;
An optical scanning device characterized by:
The scanning unit further includes a biaxial tilt stage that changes the tilt of the mirror using a piezo element,
each of the first command waveform and the second command waveform controls the tilt of the two-axis tilt stage with respect to the first direction and the second direction, respectively;
The piezo element is composed of a first piezo element displaced according to the first command waveform and a second piezo element displaced according to the second command waveform,
a first displacement sensor that detects a first displacement that is the displacement of the first piezo element;
a second displacement sensor that detects a second displacement that is the displacement of the second piezo element;
a first correction value generator that generates a first correction value for correcting the first command waveform so that the center of amplitude of the first displacement detected by the first displacement sensor approaches a first target value;
a second correction value generator for generating a second correction value for correcting the second command waveform so that the center of amplitude of the second displacement detected by the second displacement sensor approaches a second target value;
a first synthesized waveform generation unit that generates a first synthesized waveform by synthesizing the first command waveform and the first correction value;
a second synthesized waveform generation unit that generates a second synthesized waveform by synthesizing the second command waveform and the second correction value;
a first drive unit that drives the first piezo element according to the first composite waveform;
a second driving unit that drives the second piezo element according to the second composite waveform,
7. The optical scanning device according to claim 6, wherein:
Further comprising an imaging unit that captures an image representing the trajectory,
The trajectory obtaining unit obtains the trajectory from the image by subjecting the image to image processing.
The optical scanning device according to any one of claims 1 to 7, characterized in that:
An optical scanning method using a scanning unit that includes a mirror that reflects a laser beam and that scans the laser beam by changing the tilt of the mirror,
a command waveform generating step of generating a first command waveform for controlling scanning of the scanning unit in a first direction and a second command waveform for controlling scanning of the scanning unit in a second direction;
a trajectory acquisition step of acquiring the trajectory of the laser light;
a command waveform correction step of correcting at least one of the first command waveform and the second command waveform;
The command waveform correcting step includes at least one of a first amplitude that is the amplitude of the first command waveform and a second amplitude that is the amplitude of the second command waveform so as to increase the circularity of the locus; correcting a phase difference between the first command waveform and the second command waveform;
An optical scanning method characterized by:
In the command waveform generating step, the first command waveform and the second command waveform are sinusoidal waves having the same frequency, the same first amplitude and the second amplitude, and a phase difference of 90°. generate a command waveform,
10. The optical scanning method according to claim 9, wherein: