Optical scanning device and method for driving optical scanning device

Abstract

This optical scanning device is provided with a mirror unit, a first actuator, a second actuator, a first angle sensor, and a processor. The processor: derives a first phase difference between the first drive signal and the output signal of the first angle sensor on the basis of the output signal of the first angle sensor; and changing the first drive frequency and the second drive frequency along a preset frequency ratio line while maintaining the ratio between the first drive frequency and the second drive frequency so that the first phase difference is within the first target range. The frequency ratio line is a line indicating a frequency ratio corrected on the basis of the amount of change in the ratio between a first resonance frequency when the mirror unit is swung around the first axis and a second resonance frequency when the mirror unit is swung around the second axis.

Description

Technical Field

[0001] The present invention relates to an optical scanning device and a driving method for the optical scanning device. Background Technology

[0002] Micro-mirror devices (also known as micro-scanners) are a type of micro-electro-mechanical system (MEMS) device fabricated using silicon (Si) microfabrication technology. These micro-mirror devices are small and consume little power, and are therefore expected to have wide applications in laser displays, laser projectors, optical coherence tomography (OCT) scanners, and the like.

[0003] The mirror portion of a micromirror device is configured to oscillate around a first orthogonal axis and a second orthogonal axis. This oscillation of the mirror portion around these axes allows the reflected laser light to undergo two-dimensional scanning. Furthermore, a known micromirror device enables Lissajous scanning of the laser light by resonating the mirror portion around these axes. Lissajous scanning refers to setting the scanning trajectory of the laser light on the scanning surface as a Lissajous pattern.

[0004] The Lissajous pattern is determined based on the frequency ratio and phase difference between a first drive signal used to oscillate the mirror portion around a first axis and a second drive signal used to oscillate the mirror portion around a second axis. Therefore, in optical scanning devices, the frequency ratio and phase difference are usually fixed to constant values ​​so that the Lissajous pattern does not change (for example, see Japanese Patent Application Publication No. 2012-068349).

[0005] Furthermore, in a drawing apparatus using an optical scanning device, it is required to expand the scanning range of the laser on the scanning surface in order to draw a large image. In order to increase the scanning range and increase the swing amplitude of the mirror section, the frequency of the first driving signal (hereinafter referred to as the "first driving frequency") and the frequency of the second driving signal (hereinafter referred to as the "second driving frequency") are respectively set to values ​​close to the resonant frequency of the micromirror device for resonant driving.

[0006] The resonant frequency of micromirror devices varies due to individual differences such as manufacturing deviations or external environmental changes such as temperature variations. Therefore, it is necessary to consider the variation of the resonant frequency when changing the first and second driving frequencies. However, if the first and second driving frequencies are changed, the frequency ratio changes, thereby changing the scanning trajectory. Therefore, Japanese Patent Application Publication No. 2012-068349 proposes a method to change the first and second driving frequencies while maintaining the frequency ratio without changing the scanning trajectory. Summary of the Invention

[0007] The technical problem to be solved by the invention However, the resonant frequencies of micromirror devices differ around the first axis and around the second axis. Therefore, the resonant frequencies around the first and second axes vary due to individual differences in the micromirror devices or changes in the external environment. Consequently, the optimal frequency ratio for achieving the required scan range varies due to individual differences in the micromirror devices or changes in the external environment. For example, even if the first and second drive frequencies are set in a manner that provides the optimal frequency ratio for the required scan range, changes in the resonant frequencies due to subsequent external factors can alter the optimal frequency ratio and sometimes change the size of the scan range.

[0008] Therefore, when the resonant frequency changes, even if the first driving frequency and the second driving frequency are changed while maintaining the frequency ratio, as described in Japanese Patent Application Publication No. 2012-068349, it is sometimes impossible to meet the required scanning range when the resonant frequency changes.

[0009] The technical objective of this invention is to provide an optical scanning device and a driving method for the optical scanning device, wherein the optical scanning device can still meet the required scanning range even when the resonant frequency changes due to external environmental changes.

[0010] means for solving technical problems To achieve the above objectives, the optical scanning apparatus of the present invention comprises: a mirror portion having a reflective surface for reflecting incident light; a first actuator for oscillating the mirror portion around a first axis; a second actuator for oscillating the mirror portion around a second axis intersecting the first axis; a first angle sensor outputting a signal corresponding to the angle of the mirror portion around the first axis; and a processor for supplying a first drive signal having a first drive frequency to the first actuator and a second drive signal having a second drive frequency to the second actuator, wherein the processor performs the following processing: deriving a first phase difference between the first drive signal and the output signal of the first angle sensor based on the output signal of the first angle sensor; and changing the first drive frequency and the second drive frequency along a predetermined frequency ratio line while maintaining the ratio of the first drive frequency to the second drive frequency, such that the first phase difference is within a first target range, wherein the frequency ratio line is a line representing a frequency ratio corrected based on the change in the ratio of the first resonant frequency when the mirror portion oscillates around the first axis to the second resonant frequency when the mirror portion oscillates around the second axis.

[0011] The first target range is preferably determined based on the phase difference between the first driving signal and the output signal of the first angle sensor when the mirror part oscillates around the first axis at the first driving frequency as the resonant frequency.

[0012] The amplitude voltages of the first and second drive signals are preferably preset values.

[0013] The amplitude voltages of the first and second drive signals can be values ​​corrected based on the changes in the Q values ​​of the first and second axes, respectively.

[0014] The amplitude voltages of the first driving signal and the second driving signal can be values ​​corrected based on the changes in amplitude voltages of the first axis and the second axis, respectively.

[0015] The processor preferably performs the following processing: derives a first cumulative value by accumulating the first phase delay time of the output signal of the first angle sensor relative to the first drive signal by multiplying the number of times equivalent to the period of one frame by an integer multiple; and uses the average value obtained by dividing the derived first cumulative value by the first cumulative number as the first phase difference.

[0016] Preferably, a second angle sensor is also provided, the second angle sensor outputs a signal corresponding to the angle of the reflector portion around the second axis, and the processor performs the following processing: based on the output signal of the second angle sensor, derives a second phase difference between the second drive signal and the output signal of the second angle sensor; and changes the first drive frequency and the second drive frequency in such a way that the first phase difference is within a first target range and the second phase difference is within a second target range.

[0017] The second target range is preferably determined based on the phase difference between the second driving signal and the output signal of the second angle sensor when the mirror part oscillates around the second axis at the second driving frequency as the resonant frequency.

[0018] The processor preferably performs the following processing: derives a second cumulative value by accumulating the second phase delay time of the output signal of the second angle sensor relative to the second drive signal by multiplying the number of times equivalent to the period of 1 frame by an integer multiple; and uses the average value obtained by dividing the derived second cumulative value by the second cumulative number as the second phase difference.

[0019] In the driving method of the optical scanning device of the present invention, the optical scanning device comprises: a mirror portion having a reflective surface for reflecting incident light; a first actuator for oscillating the mirror portion about a first axis; a second actuator for oscillating the mirror portion about a second axis intersecting the first axis; a first angle sensor for outputting a signal corresponding to the angle of the mirror portion about the first axis; and a processor for assigning a first driving signal having a first driving frequency to the first actuator and a second driving signal having a second driving frequency to the second actuator. The driving method includes the following steps: The processor derives a first phase difference between the first drive signal and the first angle sensor output signal based on the output signal of the first angle sensor; and changes the first drive frequency and the second drive frequency along a preset frequency ratio line while maintaining the ratio of the first drive frequency to the second drive frequency, in a manner that keeps the first phase difference within a first target range. The frequency ratio line is a line that represents the frequency ratio corrected based on the change in the ratio of the first resonant frequency when the mirror part swings around the first axis to the second resonant frequency when the mirror part swings around the second axis.

[0020] Invention Effects According to the technology of the present invention, an optical scanning device and a driving method for the optical scanning device can be provided, wherein the optical scanning device can still meet the required scanning range even when the resonant frequency changes due to changes in the external environment. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of an optical scanning device.

[0022] Figure 2 This is a three-dimensional view of the micromirror device.

[0023] Figure 3 This is a diagram illustrating an example of the first drive signal and the second drive signal.

[0024] Figure 4 This is a block diagram illustrating an example of the structure of the drive control unit.

[0025] Figure 5 This is a diagram illustrating the processing of the first signal processing unit.

[0026] Figure 6 This diagram illustrates the processing of the second signal processing unit.

[0027] Figure 7 This diagram illustrates the processing of the first phase difference derivation section.

[0028] Figure 8 This diagram illustrates the processing of the second phase difference derivation section.

[0029] Figure 9This is a diagram illustrating the correction of the frequency ratio line.

[0030] Figure 10 This is a diagram illustrating frequency change processing.

[0031] Figure 11 This is a diagram illustrating the method for determining the first target range.

[0032] Figure 12 This is a flowchart illustrating the process of frequency change handling.

[0033] Figure 13 This is a block diagram illustrating an example of the structure of the drive control unit involved in the modified example.

[0034] Figure 14 This is a flowchart illustrating the frequency change processing involved in the variant example. Detailed Implementation

[0035] An example of an embodiment of the technology of the present invention will be described with reference to the accompanying drawings.

[0036] Figure 1 A schematic diagram of an image drawing system 10 according to one embodiment is shown. The image drawing system 10 includes a light scanning device 2 and a light source 3. The light scanning device 2 is composed of a micro mirror device (hereinafter referred to as "MMD (Micro Mirror Device)") 4 and a drive control unit 5. The drive control unit 5 is an example of a processor according to the technology of the present invention.

[0037] The image drawing system 10, under the control of the drive control unit 5, reflects the light beam LB emitted from the light source 3 via the MMD4 and performs light scanning on the scanned surface 6, thereby drawing an image. The scanned surface 6 may be a screen or the retina of the human eye, etc.

[0038] The image rendering system 10 is suitable, for example, for use in a Lissajous laser display. Specifically, the image rendering system 10 can be used in laser scanning displays such as AR (Augmented Reality) glasses or VR (Virtual Reality) glasses.

[0039] MMD4 is capable of making the mirror section 20 (reference) Figure 2 This is a piezoelectric two-axis driven micromirror device that oscillates around a first axis a1 and a second axis a2 intersecting the first axis a1. Hereinafter, the direction parallel to the second axis a2 is referred to as the X direction, the direction parallel to the first axis a1 is referred to as the Y direction, and the direction orthogonal to both the first axis a1 and the second axis a2 is referred to as the Z direction. In this embodiment, the X direction is orthogonal to the Y direction.

[0040] Light source 3 is, for example, a laser device that emits laser light as a beam LB. For example, light source 3 outputs laser light of three colors: R (Red), G (Green), and B (Blue). Preferably, light source 3 emits laser light towards the reflecting surface 20A (see reference) of the mirror section 20 of the MMD4 when the mirror section 20 is stationary. Figure 2 The light beam LB is illuminated perpendicularly from the light source 3 to the reflecting surface 20A. However, when the light beam LB is illuminated perpendicularly from the light source 3 to the reflecting surface 20A, the light source 3 may become an obstacle when scanning and mapping the surface 6. Therefore, it is preferable to control the light beam LB emitted from the light source 3 to illuminate the reflecting surface 20A perpendicularly using an optical system. The optical system can be either a lens-containing system or a lensless system. Furthermore, the angle at which the light beam LB from the light source 3 illuminates the reflecting surface 20A is not limited to perpendicular; the light beam LB can also be illuminated at an angle relative to the reflecting surface 20A.

[0041] The drive control unit 5 outputs drive signals to the light source 3 and MMD4 based on the light scanning information. The light source 3 generates a light beam LB based on the input drive signal and illuminates the MMD4. The MMD4 causes the reflector unit 20 to oscillate around the first axis a1 and the second axis a2 based on the input drive signal.

[0042] The drive control unit 5 causes the reflector unit 20 to resonate around the first axis a1 and the second axis a2, respectively, thereby causing the light beam LB reflected by the reflector unit 20 to scan the surface 6 in a manner that depicts a Lissajous pattern. This optical scanning method is called the Lissajous scanning method.

[0043] Next, use Figure 2 Here is an example of MMD4. Figure 2 This is a 3D rendering of the MMD4's appearance. (Example:) Figure 2 As shown, the MMD4 has a mirror section 20, a first support section 21, a first movable frame 22, a second support section 23, a second movable frame 24, a connecting section 25, and a fixing frame 26. The MMD4 is a so-called MEMS scanner.

[0044] The mirror section 20 has a reflective surface 20A for reflecting incident light. The reflective surface 20A is formed of a thin metal film, such as gold (Au), aluminum (Al), silver (Ag), or a silver alloy, disposed on one side of the mirror section 20. The shape of the reflective surface 20A is, for example, a circle centered on the intersection of the first axis a1 and the second axis a2.

[0045] When the reflector section 20 is stationary, the first axis a1 and the second axis a2 exist in the plane containing the reflecting surface 20A. The planar shape of the MMD4 is rectangular and is linearly symmetrical about the first axis a1 and also about the second axis a2.

[0046] The first support portion 21 is disposed on the outer side of the reflector portion 20 at a position opposite each other across the second axis a2. The first support portion 21 is connected to the reflector portion 20 on the first axis a1 and can swing around the first axis a1 to support the reflector portion 20. In this embodiment, the first support portion 21 is a torsion bar extending along the first axis a1.

[0047] The first movable frame 22 is a rectangular frame surrounding the reflector section 20, and is connected to the reflector section 20 via the first support section 21 on the first axis a1. Piezoelectric elements 30 are formed on the first movable frame 22 at positions opposite each other across the first axis a1. Thus, two piezoelectric elements 30 are formed on the first movable frame 22, thereby constituting the first actuator 31.

[0048] Two piezoelectric elements 30 constituting the first actuator 31 are positioned opposite each other across the first axis a1. The first actuator 31 applies a rotational torque about the first axis a1 to the mirror section 20, thereby causing the mirror section 20 to oscillate about the first axis a1.

[0049] The second support portion 23 is disposed on the outer side of the first movable frame 22 at a position opposite to it across the first axis a1. The second support portion 23 is connected to the first movable frame 22 on the second axis a2, and supports the first movable frame 22 and the reflector portion 20 in a manner that allows it to swing around the second axis a2. In this embodiment, the second support portion 23 is a torsion bar extending along the second axis a2.

[0050] The second movable frame 24 is a rectangular frame surrounding the first movable frame 22, and is connected to the first movable frame 22 via the second support 23 on the second axis a2. Piezoelectric elements 30 are formed on the second movable frame 24 at positions opposite each other across the second axis a2. Thus, the second actuator 32 is constructed by forming two piezoelectric elements 30 on the second movable frame 24.

[0051] Two piezoelectric elements 30 constituting the second actuator 32 are positioned opposite each other across the second axis a2. The second actuator 32 applies a rotational torque about the second axis a2 to the mirror section 20 and the first movable frame 22, thereby causing the mirror section 20 to oscillate about the second axis a2.

[0052] The connecting parts 25 are respectively disposed on the outer side of the second movable frame 24 at positions opposite each other across the first axis a1. The connecting parts 25 are connected to the second movable frame 24 on the second axis a2.

[0053] The fixed frame 26 is a rectangular frame that surrounds the second movable frame 24, and is connected to the second movable frame 24 via the connecting part 25 on the second axis a2.

[0054] Furthermore, a first angle sensor 11A is provided near the first support portion 21 in the first movable frame 22. The first angle sensor 11A is composed of two piezoelectric elements 12 positioned opposite each other across the first axis a1. The piezoelectric elements 12 convert the force applied due to the deformation of the first support portion 21 caused by the rotation of the reflector portion 20 around the first axis a1 into a voltage and output a signal. That is, the first angle sensor 11A outputs a signal corresponding to the angle of the reflector portion 20 around the first axis a1.

[0055] Furthermore, a second angle sensor 11B is provided near the second support portion 23 within the second movable frame 24. The second angle sensor 11B is composed of two piezoelectric elements 13 positioned opposite each other across the second axis a2. Each piezoelectric element 13 converts the force applied due to the deformation of the second support portion 23 accompanying the rotation of the reflector portion 20 around the second axis a2 into a voltage and outputs a signal. That is, the second angle sensor 11B outputs a signal corresponding to the angle of the reflector portion 20 around the second axis a2.

[0056] exist Figure 2 In the diagram, the wiring and electrode pads used to provide drive signals to the first actuator 31 and the second actuator 32 are omitted. Furthermore, in... Figure 2 The wiring and electrode pads used for outputting signals from the first angle sensor 11A and the second angle sensor 11B are also omitted from the illustration. Multiple electrode pads are provided on the mounting frame 26.

[0057] The oscillation amplitude (hereinafter referred to as the first oscillation amplitude) A1 of the reflector section 20 around the first axis a1 is controlled by a drive signal (hereinafter referred to as the first drive signal) supplied to the first actuator 31 by the drive control section 5. The first drive signal includes a drive voltage waveform V applied to one of the two piezoelectric elements 30 constituting the first actuator 31. 1A (t) and the driving voltage waveform V applied to the other. 1B (t). Driving voltage waveform V 1A (t) and driving voltage waveform V 1B (t) are out of phase (i.e., 180° phase difference).

[0058] In addition, the first oscillation amplitude A1 is the maximum value of the angle at which the normal of the reflecting surface 20A is tilted relative to the Z direction in the XZ plane.

[0059] The oscillation amplitude (hereinafter referred to as the second oscillation amplitude) A2 of the reflector section 20 around the second axis a2 is controlled by a drive signal (hereinafter referred to as the second drive signal) supplied to the second actuator 32 by the drive control section 5. The second drive signal includes a drive voltage waveform V applied to one of the two piezoelectric elements 30 constituting the second actuator 32.2A (t) and the driving voltage waveform V applied to the other. 2B (t). Driving voltage waveform V 2A (t) and driving voltage waveform V 2B (t) are out of phase (i.e., 180° phase difference).

[0060] In addition, the second oscillation amplitude A2 is the maximum value of the angle at which the normal of the reflecting surface 20A is tilted relative to the Z direction in the YZ plane.

[0061] Figure 3 This represents an example of the first drive signal and the second drive signal. Figure 3 (A) represents the driving voltage waveform V contained in the first driving signal. 1A (t) and V 1B (t) and bias voltage V off1 . Figure 3 (B) represents the driving voltage waveform V contained in the second driving signal. 2A (t) and V 2B (t) and bias voltage V off2 .

[0062] Drive voltage waveform V 1A (t) and V 1B (t) are represented as follows.

[0063] V 1A (t) = V off1 +V1sin(2πf d1 t) V 1B (t) = V off1 +V1sin(2πf d1 t+α) Here, V1 is the amplitude voltage. off1 This is the bias voltage. V off1 It can be zero. f d1 α is the driving frequency (hereinafter referred to as the first driving frequency). t is time. α is the driving voltage waveform V. 1A (t) and V 1B The phase difference (t). In this embodiment, for example, it is α = 180°.

[0064] By applying a driving voltage waveform V to the two piezoelectric elements 30 constituting the first actuator 31 1A (t) and V 1B (t), the reflector section 20 drives at the first driving frequency f d1 It oscillates around the first axis a1.

[0065] Drive voltage waveform V 2A (t) and V2B (t) are represented as follows.

[0066] V 2A (t) = V off2 +V2sin(2πf d2 t+ ) V 2B (t) = V off2 +V2sin(2πf d2 t+β+ ) Here, V2 is the amplitude voltage. off2 This is the bias voltage. V off2 It can be zero. f d2 t is the driving frequency (hereinafter referred to as the second driving frequency). β is the driving voltage waveform V. 2A (t) and V 2B The phase difference (t). In this embodiment, for example, it is set to β = 180°. And, The driving voltage waveform V 1A (t) and V 1B (t) and driving voltage waveform V 2A (t) and V 2B The phase difference of (t). In addition, the amplitude voltage V1 and the amplitude voltage V2 can be different.

[0067] By applying a driving voltage waveform V to the two piezoelectric elements 30 constituting the second actuator 32 2A (t) and V 2B (t), the reflector section 20 drives at the second frequency f d2 It oscillates around the second axis a2.

[0068] First driving frequency f d1 The second driving frequency is set to match the resonant frequency (hereinafter referred to as the first resonant frequency) when the reflector 20 oscillates around the first axis a1. d2 The frequency is set to match the resonant frequency (hereinafter referred to as the second resonant frequency) when the mirror section 20 oscillates around the second axis a2. In this embodiment, it is set to f. d1 >f d2 That is, the oscillation frequency of the reflector section 20 around the first axis a1 is higher than the oscillation frequency around the second axis a2. Additionally, the first driving frequency f... d1 It does not necessarily need to be the same as the first resonant frequency; the second driving frequency f d2 It does not necessarily need to be the same as the second resonant frequency. For example, the first driving frequency f d1 It can be a frequency in the frequency range near the first resonant frequency, and the second driving frequency f. d2This can be a frequency range near the second resonant frequency. For example, the frequency range is the range where the oscillation amplitude reaches more than 1 / √2 times the peak value (the so-called Q value range).

[0069] Figure 4 This illustrates an example of the structure of the drive control unit 5. The drive control unit 5 includes a mirror drive unit 4A and a light source drive unit 3A. The mirror drive unit 4A includes a first drive voltage waveform generation unit 60A, a first signal processing unit 61A, a first phase shift unit 62A, a first phase difference derivation unit 63A, a first zero-crossing pulse output unit 64A, a second drive voltage waveform generation unit 60B, a second signal processing unit 61B, a second phase shift unit 62B, a second phase difference derivation unit 63B, a second zero-crossing pulse output unit 64B, a frequency changing unit 65, and a memory 66.

[0070] The first drive voltage waveform generation unit 60A, the first signal processing unit 61A, and the first phase shifting unit 62A perform feedback control to maintain the resonant state of the oscillation of the reflector 20 around the first axis a1. The second drive voltage waveform generation unit 60B, the second signal processing unit 61B, and the second phase shifting unit 62B perform feedback control to maintain the resonant state of the oscillation of the reflector 20 around the second axis a2.

[0071] The first drive voltage waveform generation unit 60A generates the aforementioned drive voltage waveform V based on a reference waveform. 1A (t) and V 1B (t), and the generated driving voltage waveform V 1A (t) and V 1B (t) The first phase shifter 62A applies a signal to the two piezoelectric elements 30 constituting the first actuator 31. As a result, the mirror section 20 oscillates about the first axis a1. The first angle sensor 11A outputs a signal corresponding to the angle of the mirror section 20 about the first axis a1.

[0072] The second drive voltage waveform generation unit 60B generates the aforementioned drive voltage waveform V based on a reference waveform. 2A (t) and V 2B (t), and the generated driving voltage waveform V 2A (t) and V 2B (t) is applied to the two piezoelectric elements 30 constituting the second actuator 32 via the second phase shifter 62B. As a result, the mirror section 20 oscillates around the second axis a2. The second angle sensor 11B outputs a signal corresponding to the angle of the mirror section 20 around the second axis a2.

[0073] The first signal processing unit 61A generates a first sensor signal S1 based on the signal output from the first angle sensor 11A. Specifically, as follows: Figure 5As shown, the first signal processing unit 61A subtracts one of the two signals output by the two piezoelectric elements 12 constituting the first angle sensor 11A from the other, thereby generating a first sensor signal S1 that removes vibration noise caused by oscillation around the second axis a2. Furthermore, the first sensor signal S1 is an example of the "output signal of the first angle sensor" according to the technology of this invention.

[0074] The second signal processing unit 61B generates a second sensor signal S2 based on the signal output from the second angle sensor 11B. Specifically, as follows: Figure 6 As shown, the second signal processing unit 61B subtracts one of the two signals output by the two piezoelectric elements 13 constituting the second angle sensor 11B from the other, thereby generating a second sensor signal S2 that removes vibration noise caused by oscillation around the first axis a1. Furthermore, the second sensor signal S2 is an example of the "output signal of the second angle sensor" according to the technology of this invention.

[0075] The first phase difference derivation unit 63A derives a cumulative value by multiplying the phase delay time of the sensor signal S1 relative to the first drive signal by n times the number of times N corresponding to TF in one frame, and derives the average value obtained by dividing the derived cumulative value by the first cumulative number as the first phase difference PD1. The first phase difference PD1 is the average phase delay time of the sensor signal S1 relative to the first drive signal. Here, n is an integer. In this embodiment, n is set to 1. n can be an integer of 2 or more. Furthermore, TF in one frame is one cycle of the optical scanning of the scanning beam LB on the scanned surface 6, specifically, the time for drawing a Lissajous pattern once on the scanned surface 6. Furthermore, the number of times N corresponding to TF in one frame is TF in one frame multiplied by the first drive frequency f. d1 The value obtained.

[0076] Specifically, such as Figure 7 As shown, the first phase difference derivation unit 63A binarizes the first drive signal and the sensor signal S1. Here, for example, the drive voltage waveform V is used as the first drive signal. 1A (t). The first phase difference derivation unit 63A calculates the phase delay time δ1~δ1~δ1~δ1~δ1~δ2~δ3~δ1~δ2~δ3~δ4~δ5 ...3~δ5~δ1~δ1~δ2~δ3~δ1~ N And by calculating the phase delay time δ1~δ N The accumulated value is derived by performing accumulation. The first phase difference derivation unit 63A derives the first phase difference PD1 by dividing the derived accumulated value by the first accumulation number N.

[0077] The second phase difference derivation unit 63B derives a cumulative value by multiplying the phase delay time of the sensor signal S2 relative to the second drive signal by n times (equivalent to the number of times M equal to TF during one frame). It then derives the average value obtained by dividing the derived cumulative value by the second cumulative number as the second phase difference PD2. The second phase difference PD2 is the average phase delay time of the sensor signal S2 relative to the second drive signal. Here, the number of times M equal to TF during one frame is TF during one frame multiplied by the second drive frequency f. d2 The value obtained.

[0078] Specifically, such as Figure 8 As shown, the second phase difference derivation unit 63B binarizes the second drive signal and the sensor signal S2. Here, for example, the drive voltage waveform V is used as the second drive signal. 2A (t). The second phase difference derivation unit 63B calculates the phase delay time δ1 to δ2 of the sensor signal S2 relative to the binarized second drive signal. M And by calculating the phase delay time δ1~δ M The cumulative value is derived by accumulating the data. The second phase difference derivation unit 63B derives the second phase difference PD2 by dividing the derived cumulative value by the second accumulation number M.

[0079] The first zero-crossing pulse output unit 64A generates the first zero-crossing pulse ZC1 based on the first driving signal and the first phase difference PD1 derived by the first phase difference derivation unit 63A. The first zero-crossing pulse ZC1 is a signal indicating that the angle of the reflector unit 20 around the first axis a1 is zero.

[0080] The second zero-crossing pulse output unit 64B generates a second zero-crossing pulse ZC2 based on the second driving signal and the second phase difference PD2 derived from the second phase difference derivation unit 63B. The second zero-crossing pulse ZC2 is a signal indicating that the angle of the reflector unit 20 around the second axis a2 is zero.

[0081] The light source driving unit 3A drives the light source 3 based, for example, on drawing data supplied externally from the image drawing system 10. Furthermore, the light source driving unit 3A controls the irradiation timing in a manner that synchronizes the laser irradiation timing with the first zero-crossing pulse ZC1 and the second zero-crossing pulse ZC2 input from the mirror driving unit 4A. Additionally, when the driving frequency ratio described later is changed, the scanning trajectory (i.e., the Lissajous pattern) of the beam LB changes, and therefore the emission pattern of the light source 3 is corrected according to the change in the scanning trajectory.

[0082] When the optical scanning device 2 is started, the drive control unit 5 performs the following processing (hereinafter referred to as frequency change processing): while the mirror unit 20 is swinging around the first axis a1 and the second axis a2, the first drive frequency f is changed by increasing the swing amplitude of the mirror unit 20. d1 and the second driving frequency f d2 When the optical scanning device 2 is started, in addition to the above-mentioned parts, the frequency changing unit 65 is activated.

[0083] In this embodiment, the frequency changing unit 65 adjusts the first driving frequency f along a predetermined frequency ratio line so that the first phase difference PD1 derived by the first phase difference deriving unit 63A is within the first target range. d1 With the second driving frequency f d2 While maintaining a constant frequency ratio (hereinafter referred to as the drive frequency ratio R), the above frequency change process is performed. The frequency ratio line is contained in the startup condition data stored in memory 66.

[0084] The frequency ratio line is a line representing the driving frequency ratio R, corrected based on the change in the ratio of the first resonant frequency to the second resonant frequency (hereinafter referred to as the resonant frequency ratio). The first and second resonant frequencies vary due to external factors applied to the MMD4, and therefore the resonant frequency ratio changes due to these external factors. Therefore, the frequency ratio line is corrected based on the change in the resonant frequency ratio. For example, external factors are those caused by the mounting fixture used to mount the MMD4 to a substrate, etc. Even with the same MMD4, if the mounting fixture changes, the resonant frequency ratio will change.

[0085] Figure 9 The correction of the frequency ratio line is explained. Figure 9 In this diagram, L0 represents the frequency ratio line indicating the resonant frequency ratio before external factors are applied to MMD4. L1 represents the frequency ratio line indicating the resonant frequency ratio after external factors are applied to MMD4. The frequency ratio line L1 is obtained by correcting the frequency ratio line L0 based on the amount of change in the resonant frequency ratio caused by external factors. For example, the drive control unit 5 generates the frequency ratio line L1 by measuring the resonant frequency ratio and correcting the frequency ratio line L0 at a predetermined time before the optical scanning device 2 is activated. Here, the frequency ratio line L1 is an example of a "pre-set frequency ratio line" according to the technology of this invention.

[0086] Figure 10 This represents an example of frequency change processing. For example... Figure 10 As shown, the frequency changing unit 65 changes the first driving frequency f along the frequency ratio line L1 in a manner that brings the first phase difference PD1 within the first target range. d1 and the second driving frequency f d2 Additionally, when changing the first driving frequency f...d1 and the second driving frequency f d2 At that time, the amplitude voltages V1 and V2 of the first and second drive signals are not changed but are set to preset values.

[0087] In principle, the first oscillation amplitude A1 reaches its maximum when PD1 = 90°, so the first target range can be considered as a range centered at 90°. However, in reality, the first oscillation amplitude A1 does not necessarily reach its maximum when PD1 = 90°. Therefore, in this embodiment, it is set based on the first driving frequency f. d1 The range is determined by the first phase difference PD1 when the first resonant frequency causes the reflector 20 to swing around the first axis a1.

[0088] Specifically, such as Figure 11 As shown, at the first driving frequency f d1 When the first resonant frequency causes the reflector 20 to oscillate around the first axis a1, the first phase difference PD1 at which the first oscillation amplitude A1 reaches its maximum is determined, and the first target range is determined with the determined first phase difference PD1 as the center. Figure 11 f shown c1 This is the first resonant frequency. A 1P This represents the maximum value of the first oscillation amplitude A1. The first target range needs to be determined to achieve the maximum value A. 1P The first oscillation amplitude A1 is above the specified ratio.

[0089] Figure 12 The process of frequency change processing is described. In the frequency change processing, firstly, the frequency change unit 65 reads the start-up condition data from the memory 66 and obtains the corrected frequency ratio line L1 (step S10). Next, the frequency change unit 65 obtains the first phase difference PD1 derived by the first phase difference derivation unit 63A (step S11).

[0090] The frequency conversion unit 65 determines whether the acquired first phase difference PD1 is within the first target range (step S12). If the acquired first phase difference PD1 is not within the first target range (step S12: No), the frequency conversion unit 65 adjusts the first driving frequency f along the frequency ratio line L1. d1 and the second driving frequency f d2 Only the specified amount is changed (step S13). After that, the frequency change unit 65 returns to step S11 and obtains the first phase difference PD1 derived by the first phase difference deriving unit 63A again.

[0091] The frequency change unit 65 repeats steps S11 to S13 until the first phase difference PD1 is within the first target range. When the first phase difference PD1 is within the first target range (step S12: Yes), the frequency change unit 65 ends the frequency change process.

[0092] As described above, in this embodiment, even when the resonant frequency ratio changes due to external environmental variations, the first phase difference PD1 is brought within the first target range by frequency change processing performed at startup, thereby increasing the first oscillation amplitude A1 (i.e., increasing the scanning range of the beam LB in the X direction). Furthermore, in this embodiment, the frequency change processing is performed based on the drive frequency ratio R, which is corrected for the amount of change in the resonant frequency ratio caused by external environmental variations, etc. Therefore, as the first oscillation amplitude A1 increases, the second oscillation amplitude A2 also increases (i.e., increasing the scanning range of the beam LB in both the X and Y directions).

[0093] Previously, when the resonant frequency ratio changed due to external environmental changes, the first oscillation amplitude A1 or the second oscillation amplitude A2 decreased, which sometimes prevented the required scanning range from being met. According to this embodiment, by performing the above-described frequency change processing, the required scanning range can be met.

[0094] Furthermore, the applicant discovered that the change in the resonant frequency ratio when the mirror section 20 oscillates around the first axis a1 and the second axis a2 is equal to the change in the ratio of the first resonant frequency when the mirror section 20 oscillates around the first axis a1 to the second resonant frequency when it oscillates around the second axis a2. Therefore, by performing single-axis drive on the mirror section 20 before activating the optical scanning device 2 and measuring the first and second resonant frequencies respectively, the change in the resonant frequency ratio can be determined. When the mirror section 20 is driven in a single axis, the first and second resonant frequencies can be easily and accurately determined separately, thus allowing for easy and high-precision correction of the frequency ratio line.

[0095] For example, frequency ratio line L1 is measured by the first driving frequency f. d1 (i.e., the first resonant frequency) and the second driving frequency f d2 (i.e., the second resonant frequency), and obtain the first driving frequency f by calculating the change in the ratio of the two. d1 In order for the amplitude (e.g., Vpp value) of the first sensor signal S1 to reach a preset value (e.g., maximum value) when the mirror section 20 is driven in a single axis around the first axis a1, the second driving frequency f d2To ensure that the amplitude (e.g., Vpp value) of the second sensor signal S2 reaches a preset value (e.g., maximum value) when the mirror section 20 is driven in a single axis around the second axis a2, the frequency ratio line L0 is corrected as described above based on the change in the ratio of the two, thereby obtaining the frequency ratio line L1.

[0096] Additionally, the frequency ratio line L1 (reference) is measured by performing single-axis drive on the reflector section 20. Figure 9 When the first and second resonant frequencies are reached, the drive control unit 5 preferably sets the amplitude voltage V. 1S V 2S Set to a preset value. Here, the amplitude voltage V 1S This represents the amplitude voltage of the first drive signal when the mirror section 20 is driven in a single-axis manner around the first axis a1. Amplitude voltage V 2S This represents the amplitude voltage of the second drive signal when the mirror section 20 is driven in a single axis around the second axis a2. Furthermore, the preset value refers to the amplitude voltage V set when measuring the first and second resonant frequencies to obtain the frequency ratio line L0 before correction. 1S V 2S This is because the first and second resonant frequencies in the MMD4 exhibit nonlinearity, varying depending on the deflection angle of the reflector 20. If the amplitude voltage V is significantly changed during measurement... 1S V 2S Then, the effects caused by nonlinearity will appear, and the first and second resonant frequencies may change.

[0097] Furthermore, the first swing amplitude A1 and the second swing amplitude A2 also vary depending on the amplitude voltages V1 and V2. Therefore, it is also possible to change the amplitude voltages V1 and V2 to meet the required scanning range. However, as in this embodiment, the first driving frequency f is changed based on the first phase difference PD1. d1 and the second driving frequency f d2 It can maintain a resonant state, thus enabling low power consumption.

[0098] Furthermore, in the above embodiment, the frequency changing unit 65 changes the first driving frequency f such that the first phase difference PD1 derived by the first phase difference derivation unit 63A is within the first target range. d1 and the second driving frequency f d2 Alternatively, the first driving frequency f can be changed such that the second phase difference PD2 derived from the second phase difference derivation unit 63B is within the second target range. d1 and the second driving frequency f d2 When the second driving frequency f is... d2When the mirror section 20 oscillates around the second axis a2 at the second resonant frequency, the second phase difference PD2 at which the second oscillation amplitude A2 reaches its maximum is determined, and the second target range is determined with the determined second phase difference PD2 as the center. Similar to the first target range, the second target range is determined by obtaining a second oscillation amplitude A2 that is at least a predetermined proportion of the maximum value of the second oscillation amplitude A2. The specific method for determining the second target range is the same as the method for determining the first target range (see reference). Figure 11 ).

[0099] Furthermore, in the above embodiment, let f be... d1 >f d2 However, it can also be set to f. d1 <f d2 That is, the first resonant frequency can be less than the second resonant frequency.

[0100] The larger the Q value, the greater the change in oscillation amplitude relative to the frequency change. Therefore, the frequency changing unit 65 is preferably based on the phase difference around the axis with a large Q value (in f). d1 <f d2 In the case of the first phase difference PD1, at f d1 >f d2 In the case of the second phase difference (PD2), frequency change processing is performed.

[0101] Figure 13 This illustrates the structure of the drive control unit 5 involved in the modified example. In this modified example, the frequency changing unit 65 performs frequency changing processing based on both the first phase difference PD1 and the second phase difference PD2. Specifically, the frequency changing unit 65 changes the first drive frequency f in such a way that the first phase difference PD1 derived by the first phase difference deriving unit 63A is within a first target range and the second phase difference PD2 derived by the second phase difference deriving unit 63B is within a second target range. d1 and the second driving frequency f d2 .

[0102] Figure 14 The flowchart illustrates the frequency change processing involved in the modified example. In the frequency change processing involved in the modified example, firstly, the frequency change unit 65 reads the start-up condition data from the memory 66 and obtains the corrected frequency ratio line L1 (step S20). Next, the frequency change unit 65 obtains the first phase difference PD1 derived by the first phase difference deriving unit 63A and the second phase difference PD2 derived by the second phase difference deriving unit 63B (step S21).

[0103] The frequency change unit 65 determines whether the acquired first phase difference PD1 is within the first target range (step S22). If the acquired first phase difference PD1 is within the first target range (step S22: yes), the frequency change unit 65 determines whether the acquired second phase difference PD2 is within the second target range (step S23).

[0104] If the acquired first phase difference PD1 is not within the first target range (step S22: No) or if the acquired second phase difference PD2 is not within the second target range (step S23: No), the frequency changing unit 65 changes the first driving frequency f along the frequency ratio line L1. d1 and the second driving frequency f d2 Only the specified amount is changed (step S24). After that, the frequency change unit 65 returns the process to step S21 and obtains the first phase difference PD1 and the second phase difference PD2 again.

[0105] During the period when the first phase difference PD1 is within the first target range and the second phase difference PD2 is within the second target range, the frequency changing unit 65 repeats steps S21 to S24. When the second phase difference PD2 is within the second target range (step S23: Yes), the frequency changing unit 65 ends the frequency changing process.

[0106] In this modified example, frequency changing is performed based on the first phase difference PD1 and the second phase difference PD2, thus enabling a more accurate measurement of the required scanning range.

[0107] Furthermore, in the above embodiment, the amplitude voltages V1 and V2 are set to preset values ​​during frequency change processing. However, before frequency change processing, the amplitude voltages V1 and V2 can also be corrected based on the resonance characteristics of MMD4. For example, the drive control unit 5 can correct the amplitude voltage V1 based on the change in the Q value with respect to the first axis a1, and can correct the amplitude voltage V2 based on the change in the Q value with respect to the second axis a2. Here, the change in the Q value refers to the change caused by changes in the external environment, etc.

[0108] Furthermore, in the above embodiment, the amplitude voltages V1 and V2 are set to preset values, but preferably, the amplitude voltages V1 and V2 are corrected according to the preset values ​​in a way that keeps the area and shape of the image drawn on the scanned surface 6 by the beam LB constant. The correction amount of the amplitude voltages V1 and V2 when the mirror section 20 oscillates around the first axis a1 and the second axis a2 can be calculated based on the Q value, which is obtained from the frequency characteristics when the mirror section 20 is driven in a single axis. Therefore, before starting the optical scanning device 2, the mirror section 20 can be driven in a single axis and the first Q value and the second Q value can be measured respectively. The dissipated energy (energy leaked from MMD4 to the surrounding environment) can be calculated based on the change in the first Q value and the second Q value, and the correction amount of the amplitude voltages V1 and V2 can be obtained based on the calculated dissipated energy. Here, the first Q value is the Q value with respect to the first axis a1. The second Q value is the Q value with respect to the second axis a2. Specifically, the correction amounts of amplitude voltages V1 and V2 required to reduce energy dissipation are determined, and the amplitude voltages V1 and V2 are corrected based on the determined correction amounts, thereby ensuring that the area and shape of the image remain constant. When the mirror section 20 is driven in a single axis, the first Q value and the second Q value can be easily and accurately determined respectively, thus enabling easy and high-precision correction of amplitude voltages V1 and V2.

[0109] Furthermore, when the drive control unit 5 performs single-axis drive on the reflector unit 20 to measure the first Q value and the second Q value, it is preferable to use the amplitude voltage V. 1S V 2S Set to a preset value. Here, the preset value refers to the amplitude voltage V set when measuring the first and second resonant frequencies to obtain the frequency ratio line L0 before correction. 1S V 2S .

[0110] Furthermore, the drive control unit 5 can adjust the amplitude voltage V during single-axis drive of the first axis a1 and the second axis a2 according to their respective single-axis drives. 1S V 2S The amplitude voltages V1 and V2 during 2-axis drive are corrected by adjusting the change in amplitude voltage V. For example, the drive control unit 5 corrects the amplitude voltages V1 and V2 during 2-axis drive by adjusting the change in amplitude voltage V1 and V2. 1S V 2S The change ratio is calculated separately, and then multiplied by the amplitude voltages V1 and V2 to correct the amplitude voltages V1 and V2. The change ratio is the value obtained by dividing the changed value by the original value. Specifically, the drive control unit 5 measures the amplitude voltage V1. 1S and amplitude voltage V 2S The amplitude voltage V 1SIn order to make the amplitude (e.g., Vpp value) of the first sensor signal S1 reach a preset value (e.g., maximum value) when the mirror section 20 is driven in a single axis around the first axis a1, the amplitude voltage V 2S To ensure that the amplitude (e.g., Vpp value) of the second sensor signal S2 reaches a preset value (e.g., maximum value) when the mirror unit 20 is driven in a single-axis configuration around the second axis a2, the drive control unit 5 acquires the amplitude voltage V at the frequency ratio line L0 before correction. 1S V 2S The measured value and the newly measured amplitude voltage V 1S V 2S By comparing the measured values, the amplitude voltage V can be calculated. 1S V 2S Each of the respective change rates. Furthermore, even in either the case before or after the change, it is preferable to measure the amplitude voltage V at a predetermined value when the amplitude of the first sensor signal S1 reaches the measured value. 1S At that time, the first driving frequency f d1 The first resonant frequency is defined as the amplitude voltage V at which the amplitude of the second sensor signal S2 reaches a preset value. 2S At that time, the second driving frequency f d2 Set it as the second resonant frequency.

[0111] Furthermore, in order to obtain the frequency ratio line L0, the first driving frequency f when performing two-axis driving on the mirror unit 20 can be determined based on the ratio of the first resonant frequency to the second resonant frequency measured by performing single-axis driving on the mirror unit 20. d1 With the second driving frequency f d2 The frequency ratio.

[0112] Furthermore, the structure of the MMD4 shown in the above embodiment is an example. The structure of the MMD4 can be modified in various ways. For example, the first actuator 31 that causes the mirror part 20 to swing about the first axis a1 can be disposed in the second movable frame 24, and the second actuator 32 that causes the mirror part 20 to swing about the second axis a2 can be disposed in the first movable frame 22.

[0113] Furthermore, in the above embodiment, the first angle sensor 11A is composed of two piezoelectric elements 12 positioned opposite each other across the first axis a1, but it may also be composed of one piezoelectric element 12 positioned near the first axis a1. Similarly, in the above embodiment, the second angle sensor 11B is composed of two piezoelectric elements 13 positioned opposite each other across the second axis a2, but it may also be composed of one piezoelectric element 13 positioned near the second axis a2.

[0114] Furthermore, the hardware structure of the drive control unit 5 can be varied. The drive control unit 5 can be composed of either analog circuits or digital circuits, or both. The drive control unit 5 can be composed of a single processor, or a combination of two or more processors of the same or different types. The processor includes a CPU (Central Processing Unit), a programmable logic device (PLD), and dedicated circuits. As is well known, a CPU is a general-purpose processor that executes software (programs) and functions as a processing unit for various tasks. A PLD is a processor such as an FPGA (Field Programmable Gate Array) whose circuit structure can be modified after manufacturing. Dedicated circuits are processors such as ASICs (Application Specific Integrated Circuits) that have circuit structures specifically designed for performing specific processes.

[0115] All documents, patent applications and technical standards described in this specification are incorporated herein by reference to the same extent as the specific documents, patent applications and technical standards described therein.

[0116] Through the above explanation, you will be able to master the following techniques.

[0117] [Additional Item 1] An optical scanning device comprising: The reflecting mirror section has a reflecting surface that reflects incident light; The first actuator causes the mirror section to oscillate about the first axis; The second actuator causes the mirror portion to oscillate about a second axis that intersects the first axis; The first angle sensor outputs a signal corresponding to the angle of the reflector portion around the first axis; and The processor applies a first drive signal having a first drive frequency to the first actuator and a second drive signal having a second drive frequency to the second actuator. The processor performs the following processing: Based on the output signal of the first angle sensor, the first phase difference between the first driving signal and the output signal of the first angle sensor is derived; and To keep the first phase difference within a first target range, along a pre-defined frequency ratio line, while maintaining the ratio of the first driving frequency to the second driving frequency, the first driving frequency and the second driving frequency are changed. The frequency ratio line is a line that represents a frequency ratio corrected for the change in the ratio of the first resonant frequency when the mirror part oscillates around the first axis to the second resonant frequency when the mirror part oscillates around the second axis.

[0118] [Additional Item 2] According to the optical scanning device described in Addendum 1, wherein... The first target range is determined based on the phase difference between the first driving signal and the output signal of the first angle sensor when the mirror portion oscillates around the first axis at the first driving frequency as the resonant frequency.

[0119] [Additional Item 3] According to the optical scanning device described in addition item 1 or 2, wherein, The amplitude voltages of the first driving signal and the second driving signal are preset values.

[0120] [Additional Item 4] According to the optical scanning device described in Addendum 1, wherein... The amplitude voltages of the first driving signal and the second driving signal are values ​​obtained by correcting for the changes in the Q values ​​of the first axis and the second axis, respectively.

[0121] [Note 5] According to the optical scanning device described in Appendix 1, wherein... The amplitude voltages of the first drive signal and the second drive signal are values ​​obtained by correcting for the changes in amplitude voltages of the first axis and the second axis, respectively.

[0122] [Note 6] The optical scanning apparatus according to any one of appendices 1 to 5, wherein... The processor performs the following processing: The first accumulated value is derived by accumulating the first phase delay time of the output signal of the first angle sensor relative to the first drive signal by multiplying the number of times equivalent to one frame by an integer multiple; and The first phase difference is the average value obtained by dividing the derived first cumulative value by the first cumulative number of times.

[0123] [Additional Item 7] The optical scanning apparatus according to any one of appendices 1 to 6 further comprises a second angle sensor, the second angle sensor outputting a signal corresponding to the angle of the reflector portion around the second axis. The processor performs the following processing: Based on the output signal of the second angle sensor, the second phase difference between the second driving signal and the output signal of the second angle sensor is derived; and The first driving frequency and the second driving frequency are changed in such a way that the first phase difference is within the first target range and the second phase difference is within the second target range.

[0124] [Additional Item 8] According to the optical scanning device described in Addendum 7, wherein... The second target range is determined based on the phase difference between the second driving signal and the output signal of the second angle sensor when the mirror portion oscillates around the second axis at the second driving frequency as the resonant frequency.

[0125] [Note 9] According to the optical scanning apparatus described in Appendix 7 or 8, wherein... The processor performs the following processing: The second accumulated value is derived by accumulating the second phase delay time of the output signal of the second angle sensor relative to the second drive signal by multiplying the number of times equivalent to one frame by an integer multiple; and The average value obtained by dividing the derived second cumulative value by the second cumulative number is taken as the second phase difference.

Claims

1. An optical scanning device, comprising: The reflecting mirror section has a reflecting surface that reflects incident light; The first actuator causes the mirror section to oscillate about the first axis; The second actuator causes the mirror portion to oscillate about a second axis that intersects the first axis; The first angle sensor outputs a signal corresponding to the angle of the reflector portion around the first axis; and The processor applies a first drive signal having a first drive frequency to the first actuator and a second drive signal having a second drive frequency to the second actuator. The processor performs the following processing: Based on the output signal of the first angle sensor, the first phase difference between the first driving signal and the output signal of the first angle sensor is derived; and Along a pre-defined frequency ratio line, while maintaining the ratio of the first driving frequency to the second driving frequency, the first driving frequency and the second driving frequency are changed to ensure that the first phase difference is within a first target range. The frequency ratio line is a line that represents a frequency ratio corrected for the change in the ratio of the first resonant frequency when the mirror part oscillates around the first axis to the second resonant frequency when the mirror part oscillates around the second axis.

2. The optical scanning device according to claim 1, wherein, The first target range is determined based on the phase difference between the first driving signal and the output signal of the first angle sensor when the mirror portion oscillates around the first axis at the first driving frequency as the resonant frequency.

3. The optical scanning device according to claim 1, wherein, The amplitude voltages of the first driving signal and the second driving signal are preset values.

4. The optical scanning device according to claim 1, wherein, The amplitude voltages of the first drive signal and the second drive signal are values ​​obtained by correcting for the changes in the Q values ​​of the first axis and the second axis, respectively.

5. The optical scanning device according to claim 1, wherein, The amplitude voltages of the first drive signal and the second drive signal are values ​​obtained by correcting for the changes in amplitude voltages of the first axis and the second axis, respectively.

6. The optical scanning device according to claim 1, wherein, The processor performs the following processing: The first accumulated value is derived by accumulating the first phase delay time of the output signal of the first angle sensor relative to the first drive signal for a first number of accumulations, wherein the first number of accumulations is an integer multiple of the number equivalent to one frame period; and The first phase difference is the average value obtained by dividing the derived first cumulative value by the first cumulative number of times.

7. The optical scanning device according to claim 1, wherein, It also includes a second angle sensor, which outputs a signal corresponding to the angle of the reflector portion around the second axis. The processor performs the following processing: Based on the output signal of the second angle sensor, the second phase difference between the second driving signal and the output signal of the second angle sensor is derived; and The first driving frequency and the second driving frequency are changed so that the first phase difference is within the first target range and the second phase difference is within the second target range.

8. The optical scanning device according to claim 7, wherein, The second target range is determined based on the phase difference between the second driving signal and the output signal of the second angle sensor when the mirror portion oscillates around the second axis at the second driving frequency as the resonant frequency.

9. The optical scanning device according to claim 8, wherein, The processor performs the following processing: The second cumulative value is derived by accumulating the output signal of the second angle sensor relative to the second phase delay time of the second drive signal for a second number of times, which is an integer multiple of the number of times equivalent to 1 frame. and The average value obtained by dividing the derived second cumulative value by the second cumulative number is taken as the second phase difference.

10. A driving method for an optical scanning device, the optical scanning device comprising: The reflecting mirror section has a reflecting surface that reflects incident light; The first actuator causes the mirror section to oscillate about the first axis; The second actuator causes the mirror portion to oscillate about a second axis that intersects the first axis; The first angle sensor outputs a signal corresponding to the angle of the reflector portion around the first axis; and The processor applies a first drive signal having a first drive frequency to the first actuator and a second drive signal having a second drive frequency to the second actuator. The driving method includes the following steps: The processor performs the following processing: Based on the output signal of the first angle sensor, the first phase difference between the first driving signal and the output signal of the first angle sensor is derived; and Along a pre-defined frequency ratio line, while maintaining the ratio of the first driving frequency to the second driving frequency, the first driving frequency and the second driving frequency are changed to ensure that the first phase difference is within a first target range. The frequency ratio line is a line that represents a frequency ratio corrected for the change in the ratio of the first resonant frequency when the mirror part oscillates around the first axis to the second resonant frequency when the mirror part oscillates around the second axis.

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