Optical scanning device, driving method for optical scanning device, and image drawing system

Abstract

To provide an optical scanner, a driving method of the optical scanner and an image drawing system which can keep a frequency ratio of a frequency of a first drive signal to a frequency of a second drive signal at a constant level when changing the frequency of the first drive signal and the frequency of the second drive signal.SOLUTION: A drive control unit applies a first drive signal having a first drive frequency according to a first set value to a first actuator, applies a second drive signal having a second drive frequency according to a second set value to a second actuator, changes the first drive frequency by changing the first set value in a first number unit obtained by dividing the first set value by the greatest common factor of the first set value and the second set value, and changes the second drive frequency by changing the second set value in a second number unit obtained by dividing the second set value by the greatest common factor.SELECTED DRAWING: Figure 17

Description

[Technical Field]

[0001] The present disclosure relates to an optical scanning device, a driving method for an optical scanning device, and an image drawing system. [Background technology]

[0002] Micromirror devices (also called microscanners) are known as one of the microelectromechanical systems (MEMS) devices fabricated using silicon (Si) microfabrication technology. Optical scanning devices equipped with these micromirror devices are small and consume low power, and are therefore expected to be applied to image drawing systems such as laser displays and laser projectors.

[0003] In a micromirror device, a mirror portion is formed so as to be able to swing around a first axis and a second axis that are orthogonal to each other, and the light reflected by the mirror portion is scanned two-dimensionally by swinging the mirror portion around each axis. Also, a micromirror device is known that enables Lissajous scanning of light by resonating the mirror portion around each axis.

[0004] Patent Document 1 discloses a technique for selecting the drive frequency of a MEMS mirror and the frame rate, which is the rate at which the MEMS mirror completes one rotation of the scan, based on the amplitude and phase of the MEMS mirror. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-184018 Summary of the Invention [Problem to be solved by the invention]

[0006] If the frequency ratio between the frequency of the first drive signal for oscillating the mirror unit around the first axis and the frequency of the second drive signal for oscillating the mirror unit around the second axis fluctuates, the scanning trajectory of the light fluctuates. As a result, blurring occurs in the image that is drawn. The technology described in Patent Document 1 does not take into consideration maintaining a constant frequency ratio between the frequency of the first drive signal and the frequency of the second drive signal when changing the frequencies of the first drive signal and the second drive signal.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide an optical scanning device, a driving method for an optical scanning device, and an image drawing system that can maintain a constant frequency ratio between the frequency of a first drive signal and the frequency of a second drive signal when the frequency of the first drive signal and the frequency of the second drive signal are changed. [Means for solving the problem]

[0008] The optical scanning device of the present disclosure includes a mirror unit having a reflective surface that reflects incident light, a first actuator that oscillates the mirror unit around a first axis that is in a plane that includes the reflective surface of the mirror unit when it is stationary, a second actuator that oscillates the mirror unit around a second axis that is in the plane that includes the reflective surface of the mirror unit when it is stationary and that intersects the first axis, and at least one processor, wherein the processor applies a first drive signal to the first actuator having a first drive frequency that corresponds to a first set value, applies a second drive signal to the second actuator having a second drive frequency that corresponds to a second set value, and when changing the first drive frequency and the second drive frequency, derives a greatest common divisor of the first and second set values, and changes the first drive frequency by changing the first set value by a first number unit obtained by dividing the first set value by the greatest common divisor, and changes the second drive frequency by changing the second set value by a second number unit obtained by dividing the second set value by the greatest common divisor. The first number and the second number are relatively prime.

[0009] In the optical scanning device of the present disclosure, the processor may simultaneously change the first drive frequency and the second drive frequency at the same timing based on a common clock signal.

[0010] In addition, in the optical scanning device of the present disclosure, the common clock signal may be a clock signal in which the clock rises according to a value obtained by multiplying a first setting value by a second number, or a clock signal in which the clock rises according to a value obtained by multiplying a second setting value by a first number.

[0011] In addition, the optical scanning device of the present disclosure may be configured such that the processor applies to the first actuator a first drive signal having a first drive frequency changed at the timing when the clock of a first clock signal rises in accordance with a value obtained by multiplying a first setting value by a second number, and applies to the second actuator a second drive signal having a second drive frequency changed at the timing when the clock of a second clock signal rises in accordance with a value obtained by multiplying a second setting value by the first number.

[0012] In addition, the optical scanning device of the present disclosure may have a processor that changes the first drive frequency and the second drive frequency, changes the first setting value and second number, and the second setting value and first number to values ​​corresponding to the changed first drive frequency and second drive frequency, generates a first clock signal based on the changed first setting value and second number, and generates a second clock signal based on the changed second setting value and first number.

[0013] In addition, the optical scanning device of the present disclosure may have a processor that changes the first drive frequency and the second drive frequency, and also changes the phase difference between the first clock signal and the second clock signal before the first drive frequency and the second drive frequency are changed to a phase difference obtained by multiplying that phase difference by the ratio of the first drive frequency before the change to the first drive frequency after the change.

[0014] In addition, the driving method for an optical scanning device disclosed herein is a driving method for an optical scanning device that includes a mirror unit having a reflective surface that reflects incident light, a first actuator that oscillates the mirror unit around a first axis that is located in a plane that includes the reflective surface of the mirror unit when it is stationary, and a second actuator that oscillates the mirror unit around a second axis that is located in a plane that includes the reflective surface of the mirror unit when it is stationary and that intersects the first axis, wherein the driving method includes applying a first drive signal having a first drive frequency corresponding to a first set value to the first actuator, and applying a second drive signal having a second drive frequency corresponding to a second set value to the second actuator, and when changing the first drive frequency and the second drive frequency, deriving the greatest common divisor of the first set value and the second set value, changing the first drive frequency by changing the first set value by a first number unit obtained by dividing the first set value by the greatest common divisor, and changing the second drive frequency by changing the second set value by a second number unit obtained by dividing the second set value by the greatest common divisor.

[0015] An image drawing system according to the present disclosure includes any one of the optical scanning devices described above and a light source that irradiates the mirror portion with light. [Effects of the Invention]

[0016] According to the present disclosure, when the frequency of the first drive signal and the frequency of the second drive signal are changed, the frequency ratio between the frequency of the first drive signal and the frequency of the second drive signal can be kept constant. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram of an image drawing system. [Figure 2] FIG. 1 is a perspective view of the appearance of a micromirror device. [Figure 3] 4 is a graph showing an example of a first drive signal. [Figure 4] 10 is a graph showing an example of a second drive signal. [Figure 5] FIG. 2 is a block diagram showing an example of the functional configuration of a drive control unit according to the first embodiment. [Figure 6]4A and 4B are diagrams illustrating an example of signals output from a pair of first angle detection sensors. [Figure 7] 10A and 10B are diagrams illustrating an example of signals output from a pair of second angle detection sensors. [Figure 8] 3 is a circuit diagram showing an example of the configuration of a first signal processing unit. FIG. [Figure 9] FIG. 10 is a diagram illustrating an example of first signal processing. [Figure 10] FIG. 10 is a diagram illustrating an example of second signal processing. [Figure 11] FIG. 4 is a diagram for explaining a process for generating a first zero-cross pulse. [Figure 12] 10A and 10B are diagrams for explaining a process of generating a second zero-cross pulse. [Figure 13] 10 is a graph showing an example of the relationship between a first drive frequency and a first deflection angle. [Figure 14] 10 is a graph showing an example of the relationship between a second drive frequency and a second deflection angle. [Figure 15] FIG. 10 is a diagram for explaining a process for determining a target first drive frequency. [Figure 16] FIG. 2 is a diagram for explaining a common clock signal. [Figure 17] 5A and 5B are diagrams for explaining timings for changing the first drive frequency and the second drive frequency. [Figure 18] 5 is a flowchart showing an example of a drive frequency change process according to the first embodiment. [Figure 19] 10A and 10B are diagrams for explaining timings for changing the first drive frequency and the second drive frequency according to a modified example. [Figure 20] FIG. 10 is a block diagram showing an example of the functional configuration of a drive control unit according to a second embodiment. [Figure 21] FIG. 3 is a diagram for explaining a first clock signal and a second clock signal. [Figure 22] 5A and 5B are diagrams for explaining a process of changing the phase difference between a first clock signal and a second clock signal. [Figure 23] 10 is a flowchart showing an example of a drive frequency change process according to the second embodiment. [Figure 24] FIG. 10 is a plan view of a micromirror device according to a modified example. [Figure 25] FIG. 10 is a circuit diagram showing a configuration of a first signal processing unit according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, examples of embodiments for carrying out the technology of the present disclosure will be described in detail with reference to the drawings.

[0019] [First embodiment] First, the configuration of an image drawing system 10 according to this embodiment will be described with reference to Fig. 1. As shown in Fig. 1, the image drawing system 10 includes an optical scanning device 2 and a light source 3. The optical scanning device 2 includes a micro mirror device (hereinafter referred to as "MMD (Micro Mirror Device)") 4, a drive control unit 5, and a temperature sensor 7. The drive control unit 5 is an example of a processor according to the disclosed technology.

[0020] The image drawing system 10 draws an image by optically scanning a surface 6 to be scanned with a light beam L emitted from a light source 3, which is reflected by an MMD 4, under the control of a drive control unit 5. The surface 6 to be scanned is, for example, a screen for projecting an image or the retina of a human eye.

[0021] The image rendering system 10 is applicable to, for example, a Lissajous scanning laser display. Specifically, the image rendering system 10 is applicable to a laser scan display such as AR (Augmented Reality) glasses or VR (Virtual Reality) glasses.

[0022] The MMD4 is a piezoelectric biaxial drive micromirror device that can oscillate a mirror portion 20 (see FIG. 2) around a first axis a1 and a second axis a2 perpendicular to the first axis a1. Hereinafter, the direction parallel to the second axis a2 will be referred to as the X-direction, the direction parallel to the first axis a1 as the Y-direction, and the direction perpendicular to the first axis a1 and the second axis a2 as the Z-direction. While this embodiment illustrates an example in which the first axis a1 and the second axis a2 are perpendicular to each other (i.e., intersect perpendicularly), the first axis a1 and the second axis a2 may intersect at an angle other than 90°. Here, "intersect" refers to an angle within a certain range of angles, including an allowable error, centered on 90°.

[0023] The light source 3 is a laser device that emits, for example, laser light as the light beam L. The light source 3 outputs, for example, three-color laser light of R (Red), G (Green), and B (Blue). When the mirror unit 20 of the MMD 4 is stationary, the light source 3 preferably irradiates the light beam L perpendicularly to a reflecting surface 20A (see FIG. 2) of the mirror unit 20. Note that if the light beam L is irradiated perpendicularly to the reflecting surface 20A from the light source 3, there is a possibility that the light source 3 may become an obstacle when the light beam L is scanned and drawn on the scanned surface 6. For this reason, it is preferable to control the light beam L emitted from the light source 3 using an optical system such as a beam splitter so that the light beam L is irradiated perpendicularly to the reflecting surface 20A. The optical system may or may not include a lens. Furthermore, the angle at which the light beam L emitted from the light source 3 is irradiated onto the reflecting surface 20A is not limited to being perpendicular, and the light beam L may be irradiated obliquely with respect to the reflecting surface 20A.

[0024] Based on the optical scanning information, the drive control unit 5 outputs drive signals to the light source 3 and the MMD 4. Based on the input drive signal, the light source 3 generates a light beam L and irradiates it onto the MMD 4. Based on the input drive signal, the MMD 4 oscillates the mirror unit 20 around the first axis a1 and the second axis a2.

[0025] The temperature sensor 7 is provided near the MMD 4. The temperature sensor 7 detects the temperature of the environment in which the MMD 4 is installed, and outputs a signal to the drive control unit 5 according to the detected temperature.

[0026] The drive control unit 5 causes the mirror unit 20 to resonate around the first axis a1 and the second axis a2, so that the light beam L reflected by the mirror unit 20 scans the surface to be scanned 6 so as to trace a Lissajous waveform. This optical scanning method is called a Lissajous scanning method.

[0027] Next, the configuration of the MMD 4 according to this embodiment will be described with reference to Fig. 2. As shown in Fig. 2, the MMD 4 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 connection section 25, and a fixed frame 26. The MMD 4 is a so-called MEMS scanner.

[0028] The mirror section 20 has a reflecting surface 20A that reflects incident light. The reflecting surface 20A is provided on one surface of the mirror section 20 and is formed of a metal thin film such as gold (Au), aluminum (Al), silver (Ag), or a silver alloy. The shape of the reflecting surface 20A is, for example, a circular shape centered on the intersection of the first axis a1 and the second axis a2.

[0029] The first axis a1 and the second axis a2 exist in a plane including the reflecting surface 20A when the mirror section 20 is stationary. The planar shape of the MMD 4 is rectangular and is line-symmetric with respect to the first axis a1 and line-symmetric with respect to the second axis a2.

[0030] The first support parts 21 are arranged outside the mirror part 20 at positions facing each other across the second axis a2. The first support parts 21 are connected to the mirror part 20 on the first axis a1 and support the mirror part 20 so that it can swing around the first axis a1. In this embodiment, the first support parts 21 are torsion bars extending along the first axis a1.

[0031] The first movable frame 22 is a rectangular frame body that surrounds the mirror section 20 and is connected to the mirror section 20 on the first axis a1 via the first support section 21. Piezoelectric elements 30 are formed on the first movable frame 22 at positions facing each other across the first axis a1. In this way, by forming two piezoelectric elements 30 on the first movable frame 22, a pair of first actuators 31 are configured.

[0032] The pair of first actuators 31 are arranged at positions facing each other across the first axis a1. The first actuators 31 apply a rotational torque around the first axis a1 to the mirror section 20, causing the mirror section 20 to swing around the first axis a1.

[0033] The second support parts 23 are arranged on the outside of the first movable frame 22 at positions facing each other across the first axis a1. The second support parts 23 are connected to the first movable frame 22 on the second axis a2, and support the first movable frame 22 and the mirror part 20 so that they can swing around the second axis a2. In this embodiment, the second support parts 23 are torsion bars extending along the second axis a2.

[0034] The second movable frame 24 is a rectangular frame body that surrounds the first movable frame 22 and is connected to the first movable frame 22 on the second axis a2 via the second support portion 23. Piezoelectric elements 30 are formed on the second movable frame 24 at positions facing each other across the second axis a2. In this way, by forming two piezoelectric elements 30 on the second movable frame 24, a pair of second actuators 32 are configured.

[0035] The pair of second actuators 32 are disposed at positions facing each other across the second axis a2. The second actuators 32 apply a rotational torque around the second axis a2 to the mirror section 20 and the first movable frame 22, thereby causing the mirror section 20 to swing around the second axis a2.

[0036] The connection portions 25 are arranged on the outside of the second movable frame 24 at positions facing each other across the first axis a1. The connection portions 25 are connected to the second movable frame 24 on the second axis a2.

[0037] The fixed frame 26 is a rectangular frame body that surrounds the second movable frame 24, and is connected to the second movable frame 24 via a connection portion 25 on the second axis a2.

[0038] Furthermore, a pair of first angle detection sensors 11A and 11B are provided on the first movable frame 22 near the first support portion 21 at positions facing each other across the first axis a1. Each of the pair of first angle detection sensors 11A and 11B is configured with a piezoelectric element. Each of the first angle detection sensors 11A and 11B converts a force applied by deformation of the first support portion 21 accompanying rotation of the mirror portion 20 about the first axis a1 into a voltage and outputs a signal. In other words, the first angle detection sensors 11A and 11B output a signal corresponding to the angle of the mirror portion 20 about the first axis a1.

[0039] Additionally, a pair of second angle detection sensors 12A and 12B are provided on the second movable frame 24 near the second support portion 23 at positions facing each other across the second axis a2. Each of the pair of second angle detection sensors 12A and 12B is configured with a piezoelectric element. Each of the second angle detection sensors 12A and 12B converts a force applied by deformation of the second support portion 23 accompanying rotation of the mirror portion 20 about the second axis a2 into a voltage and outputs a signal. That is, the second angle detection sensors 12A and 12B output a signal corresponding to the angle of the mirror portion 20 about the second axis a2.

[0040] 2 does not show wiring and electrode pads for supplying drive signals to the first actuator 31 and the second actuator 32. Also, in FIG. 2, wiring and electrode pads for outputting signals from the first angle detection sensors 11A, 11B and the second angle detection sensors 12A, 12B are not shown. A plurality of electrode pads are provided on the fixed frame 26.

[0041] The deflection angle θ1 of the mirror section 20 around the first axis a1 (hereinafter referred to as the "first deflection angle") is controlled by a drive signal (hereinafter referred to as the "first drive signal") that the drive control section 5 provides to the first actuator 31. The first drive signal is, for example, a sinusoidal AC voltage. The first drive signal is a drive voltage waveform V applied to one of the pair of first actuators 31. 1A (t) and the driving voltage waveform V applied to the other 1B (t) and the driving voltage waveform V 1A (t) and the drive voltage waveform V 1B (t) are in opposite phase to each other (i.e., a phase difference of 180°).

[0042] The first deflection angle θ1 is the angle at which the normal to the reflecting surface 20A is inclined with respect to the Z direction on the XZ plane.

[0043] The deflection angle θ2 of the mirror section 20 around the second axis a2 (hereinafter referred to as the "second deflection angle") is controlled by a drive signal (hereinafter referred to as the "second drive signal") that the drive control section 5 provides to the second actuator 32. The second drive signal is, for example, a sinusoidal AC voltage. The second drive signal is a drive voltage waveform V applied to one of the pair of second actuators 32. 2A (t) and the driving voltage waveform V applied to the other 2B (t) and the driving voltage waveform V 2A (t) and the drive voltage waveform V 2B (t) are in opposite phase to each other (i.e., a phase difference of 180°).

[0044] The second deflection angle θ2 is the angle at which the normal to the reflecting surface 20A is inclined with respect to the Z direction in the YZ plane.

[0045] Fig. 3 shows an example of the first drive signal, and Fig. 4 shows an example of the second drive signal. Fig. 3 shows the drive voltage waveform V 1A (t) and V 1B FIG. 4 shows the drive voltage waveform V included in the second drive signal. 2A (t) and V 2B (t) is shown.

[0046] Drive voltage waveform V 1A (t) and V 1B (t) are expressed as follows: V 1A (t)=V off1 +V1sin(2πf d1 t) V 1B (t)=V off1 +V1sin(2πf d1 t+α)

[0047] where V1 is the amplitude voltage. off1 is the bias voltage. V off1 f may be zero. d1 is the drive frequency (hereinafter referred to as the "first drive frequency"); t is time; α is the drive voltage waveform V 1A (t) and V 1B In this embodiment, for example, α=180°.

[0048] Drive voltage waveform V 1A (t) and V 1B When the first drive frequency f (t) is applied to the pair of first actuators 31, the mirror section 20 is driven at a first drive frequency f d1 It oscillates around the first axis a1.

[0049] Drive voltage waveform V 2A (t) and V 2B (t) are expressed as follows: V 2A (t)=V off2 +V2sin(2πf d2 t+φ) V 2B (t)=V off2 +V2sin(2πf d2 t+β+φ)

[0050] where V2 is the amplitude voltage. off2 is the bias voltage. V off2 f may be zero. d2 is the drive frequency (hereinafter referred to as the "second drive frequency"); t is time; β is the drive voltage waveform V 2A (t) and V2B In this embodiment, for example, β is set to 180°. Also, φ is the phase difference of the driving voltage waveform V 1A (t) and V 1B (t) and the driving voltage waveform V 2A (t) and V 2B (t) is the phase difference with (t).

[0051] Drive voltage waveform V 2A (t) and V 2B When the second drive frequency f (t) is applied to the pair of second actuators 32, the mirror section 20 is driven at a second drive frequency f d2 It oscillates around the second axis a2.

[0052] In this embodiment, the first driving frequency f d1 is set to coincide with the resonance frequency around the first axis a1 of the mirror portion 20. d2 is the first driving frequency f d1 and the first driving frequency f d1 and the second driving frequency f d2 The frequency ratio H is set based on the scanning density of light according to the drawing pattern. d2 MMD4 is set so that the resonance frequency of the mirror section 20 around the second axis a2 coincides with the resonance frequency of the mirror section 20 around the second axis a2. d1 >f d2 That is, the oscillation frequency of the mirror section 20 around the first axis a1 is higher than the oscillation frequency of the mirror section 20 around the second axis a2. d1 and the second driving frequency f d2 does not necessarily have to coincide with the resonance frequency. For example, the first driving frequency f d1 and the second driving frequency f d2 and may be frequencies within a frequency range near the resonant frequency (for example, the range of the half-width of the frequency distribution with the resonant frequency as the peak value). This frequency range is, for example, within the range of the so-called Q value.

[0053] Next, the functional configuration of the drive control unit 5 will be described with reference to Fig. 5. As shown in Fig. 5, the drive control unit 5 has a first drive signal generation unit 60A, a second drive signal generation unit 60B, a first signal processing unit 61A, a second signal processing unit 61B, a first phase shift unit 62A, a second phase shift unit 62B, a first zero-cross pulse output unit 63A, a second zero-cross pulse output unit 63B, a derivation unit 64, a clock signal generation unit 65, and a light source drive unit 66.

[0054] The first drive signal generation unit 60A, the first signal processing unit 61A, and the first phase shift unit 62A may perform feedback control so that the oscillation of the mirror unit 20 about the first axis a1 maintains a vibration state of a specified frequency. The second drive signal generation unit 60B, the second signal processing unit 61B, and the second phase shift unit 62B may perform feedback control so that the oscillation of the mirror unit 20 about the second axis a2 maintains a vibration state of a specified frequency.

[0055] The first drive signal generating section 60A generates the above-mentioned drive voltage waveform V 1A (t) and V 1B The first drive signal including (t) is generated, and the generated first drive signal is applied to the pair of first actuators 31 via the first phase shift unit 62A. This causes the mirror unit 20 to oscillate around the first axis a1.

[0056] The second drive signal generating section 60B generates the above-mentioned drive voltage waveform V 2A (t) and V 2B The second drive signal including (t) is generated, and the generated second drive signal is applied to the pair of second actuators 32 via the second phase shift unit 62B. This causes the mirror unit 20 to oscillate around the second axis a2.

[0057] The first drive signal generated by the first drive signal generating section 60A and the second drive signal generated by the second drive signal generating section 60B have a drive voltage waveform V 2A (t) and V 2B In the equation for (t), the phases are synchronized as indicated by φ.

[0058] The first angle detection sensors 11A and 11B output signals corresponding to the angle of the mirror section 20 about the first axis a1. The second angle detection sensors 12A and 12B output signals corresponding to the angle of the mirror section 20 about the second axis a2.

[0059] 6 shows an example of signals output from the pair of first angle detection sensors 11A and 11B. In FIG. 6, S1a1 and S1a2 represent signals output from the pair of first angle detection sensors 11A and 11B when the mirror unit 20 is swung only around the first axis a1 without swung around the second axis a2. The signals S1a1 and S1a2 are output at a first drive frequency f d1 are waveform signals that approximate sine waves and have opposite phases to each other.

[0060] When the mirror unit 20 is swung simultaneously around the first axis a1 and the second axis a2, vibration noise RN1 caused by the swinging of the mirror unit 20 around the second axis a2 is superimposed on the output signals of the pair of first angle detection sensors 11A, 11B. S1b1 represents a signal in which the vibration noise RN1 is superimposed on the signal S1a1. S1b2 represents a signal in which the vibration noise RN1 is superimposed on the signal S1a2. In the example of FIG. 6, the vibration noise RN1 is emphasized for the purpose of explaining this embodiment.

[0061] 7 shows an example of signals output from the pair of second angle detection sensors 12A and 12B. In FIG. 7, S2a1 and S2a2 represent signals output from the pair of second angle detection sensors 12A and 12B when the mirror unit 20 is not swung around the first axis a1 but is swung only around the second axis a2. The signals S2a1 and S2a2 are output at a second drive frequency f d2 are waveform signals that approximate sine waves and have opposite phases to each other.

[0062] When the mirror unit 20 is swung simultaneously around the first axis a1 and the second axis a2, vibration noise RN2 caused by the swinging of the mirror unit 20 around the first axis a1 is superimposed on the output signals of the pair of second angle detection sensors 12A, 12B. S2b1 represents a signal in which the vibration noise RN2 is superimposed on the signal S2a1. S2b2 represents a signal in which the vibration noise RN2 is superimposed on the signal S2a2. Note that in the example of FIG. 7, the vibration noise RN2 is emphasized for the purpose of explaining this embodiment.

[0063] The first signal processing unit 61A generates a signal S1c (hereinafter referred to as a "first angle detection signal") from which vibration noise RN1 has been removed, based on signals S1a1 and S1a2 output from the pair of first angle detection sensors 11A and 11B. The second signal processing unit 61B generates a signal S2c (hereinafter referred to as a "second angle detection signal") from which vibration noise RN2 has been removed, based on signals S2a1 and S2a2 output from the pair of second angle detection sensors 12A and 12B.

[0064] The first signal processing unit 61A can be realized, for example, by a circuit having the configuration shown in Fig. 8. As shown in Fig. 8, the first signal processing unit 61A is made up of a buffer amplifier 71, a variable gain amplifier 72, a subtraction circuit 73, and a gain adjustment circuit 74. The gain adjustment circuit 74 is made up of a first BPF (Band Pass Filter) circuit 75A, a second BPF circuit 75B, a first detection circuit 76A, a second detection circuit 76B, and a subtraction circuit 77. The subtraction circuits 73 and 77 are differential amplifier circuits made up of operational amplifiers.

[0065] The signal S1b1 output from the first angle detection sensor 11A is input to the positive input terminal (non-inverting input terminal) of the subtraction circuit 73 via the buffer amplifier 71. The signal output from the buffer amplifier 71 is branched on the way to be input to the subtraction circuit 73, and is input to a first BPF circuit 75A in the gain adjustment circuit 74.

[0066] The signal S1b2 output from the first angle detection sensor 11B is input to the negative input terminal (inverting input terminal) of the subtraction circuit 73 via the variable gain amplifier 72. The signal output from the variable gain amplifier 72 is branched on the way to be input to the subtraction circuit 73, and is input to a second BPF circuit 75B in the gain adjustment circuit 74.

[0067] The first BPF circuit 75A and the second BPF circuit 75B each have a second drive frequency f d2 The passband B1 has a center frequency of, for example, f d2 The vibration noise RN1 is in the frequency band of ±5 kHz. d2 , the first BPF circuit 75A passes through the passband B1. Therefore, the first BPF circuit 75A extracts and outputs the vibration noise RN1 from the signal input from the buffer amplifier 71. The second BPF circuit 75B extracts and outputs the vibration noise RN1 from the signal input from the variable gain amplifier 72.

[0068] The first detection circuit 76A and the second detection circuit 76B are each configured by, for example, an RMS-DC converter (Root Mean Squared value to Direct Current converter). The first detection circuit 76A converts the amplitude of the vibration noise RN1 input from the first BPF circuit 75A into a DC voltage signal and inputs it to the positive input terminal of the subtraction circuit 77. The second detection circuit 76B converts the amplitude of the vibration noise RN1 input from the second BPF circuit 75B into a DC voltage signal and inputs it to the negative input terminal of the subtraction circuit 77.

[0069] The subtraction circuit 77 outputs a value d1 obtained by subtracting the DC voltage signal input from the second detection circuit 76B from the DC voltage signal input from the first detection circuit 76A. The value d1 corresponds to the difference between the amplitude of the vibration noise RN1 included in the signal S1b1 output from the first angle detection sensor 11A and the amplitude of the vibration noise RN1 included in the signal S1b2 output from the first angle detection sensor 11B. The subtraction circuit 77 inputs the value d1 to a gain adjustment terminal of the variable gain amplifier 72 as a gain adjustment value.

[0070] The variable gain amplifier 72 adjusts the amplitude level of the signal S1b2 input from the first angle detection sensor 11B by multiplying the signal S1b2 by the value d1 input as the gain adjustment value. In this way, feedback control is performed by the gain adjustment circuit 74, so that the amplitude of the vibration noise RN1 contained in the signal S1b2 after passing through the variable gain amplifier 72 is adjusted to match the amplitude of the vibration noise RN1 contained in the signal S1b1 after passing through the buffer amplifier 71.

[0071] The subtraction circuit 73 outputs a value obtained by subtracting the signal S1b2 input to its negative input terminal from the signal S1b1 input to its positive input terminal. Because the amplitudes of the vibration noise RN1 contained in both signals match due to the above-mentioned feedback control, the vibration noise RN1 contained in both signals is cancelled out by the subtraction process performed by the subtraction circuit 73. Therefore, the subtraction circuit 73 outputs a first angle detection signal S1c (see FIG. 9), which is a signal from which the vibration noise RN1 has been removed.

[0072] 9 shows how the first angle detection signal S1c is generated based on the outputs S1b1 and S1b2 from the pair of first angle detection sensors 11A and 11B. The first angle detection signal S1c corresponds to a signal obtained by removing the vibration noise RN1 from the signal S1b1 and doubling the amplitude of the signal.

[0073] When the oscillation of the mirror section 20 around the first axis a1 is maintained in a resonant state, as shown in FIG. 9, the first angle detection signal S1c output from the first signal processing section 61A has a waveform V 1A There is a 90° phase delay relative to (t).

[0074] The second signal processing unit 61B can be realized by a configuration similar to that of the first signal processing unit 61A, and therefore a description thereof will be omitted.

[0075] 10 shows how the second angle detection signal S2c is generated based on the outputs S2b1 and S2b2 from the pair of second angle detection sensors 12A and 12B. The second angle detection signal S2c corresponds to a signal obtained by removing the vibration noise RN2 from the signal S2b1 and doubling its amplitude.

[0076] When the oscillation of the mirror section 20 around the second axis a2 is maintained in a resonant state, as shown in FIG. 10, the second angle detection signal S2c output from the second signal processing section 61B has a waveform V 2A There is a 90° phase delay relative to (t).

[0077] The first angle detection signal S1c generated by the first signal processing unit 61A is fed back to the first drive signal generating unit 60A. The first phase shifting unit 62A shifts the phase of the drive voltage waveform output from the first drive signal generating unit 60A. The first phase shifting unit 62A shifts the phase by, for example, 90°. The first angle detection signal S1c generated by the first signal processing unit 61A is also input to the first zero-crossing pulse outputting unit 63A.

[0078] The second angle detection signal S2c generated by the second signal processing unit 61B is fed back to the second drive signal generating unit 60B. The second phase shifting unit 62B shifts the phase of the drive voltage waveform output from the second drive signal generating unit 60B. The second phase shifting unit 62B shifts the phase by, for example, 90°. The second angle detection signal S2c generated by the second signal processing unit 61B is also input to a second zero-crossing pulse outputting unit 63B.

[0079] The first zero-cross pulse output unit 63A generates a zero-cross pulse (hereinafter referred to as a "first zero-cross pulse") ZC1 based on the first angle detection signal S1c input from the first signal processing unit 61A. The first zero-cross pulse output unit 63A is configured with a zero-cross detection circuit.

[0080] 11, the first zero-cross pulse output unit 63A generates a first zero-cross pulse ZC1 at the timing when the first angle detection signal S1c, which is an AC signal, crosses zero volts. The first zero-cross pulse output unit 63A inputs the generated first zero-cross pulse ZC1 to the light source drive unit 66.

[0081] The second zero-cross pulse output unit 63B generates a zero-cross pulse (hereinafter referred to as a "second zero-cross pulse") ZC2 based on the second angle detection signal S2c input from the second signal processing unit 61B. The second zero-cross pulse output unit 63B is configured by a zero-cross detection circuit.

[0082] 12, the second zero-cross pulse output unit 63B generates a second zero-cross pulse ZC2 at the timing when the second angle detection signal S2c, which is an AC signal, crosses zero volts. The second zero-cross pulse output unit 63B inputs the generated second zero-cross pulse ZC2 to the light source drive unit 66.

[0083] Although the first zero-cross pulse output unit 63A and the second zero-cross pulse output unit 63B output zero-cross pulses using both the time points when the sine wave changes from negative to positive and the time points when the sine wave changes from positive to negative, the present invention is not limited to this. For example, the first zero-cross pulse output unit 63A and the second zero-cross pulse output unit 63B may output zero-cross pulses using either the time points when the sine wave changes from negative to positive and the time points when the sine wave changes from positive to negative.

[0084] The light source driving unit 66 drives the light source 3 based on, for example, drawing data supplied from outside the image drawing system 10. The light source driving unit 66 also controls the irradiation timing of the laser light from the light source 3 so that the irradiation timing is synchronized with the first zero-cross pulse ZC1 and the second zero-cross pulse ZC2.

[0085] As described above, the first drive frequency f d1 , second drive frequency f d2 , and the first driving frequency fd1 and the second driving frequency f d2 The light source 3 is driven and the mirror section 20 oscillates around the first axis a1 and the second axis a2 in accordance with the initial setting value of the frequency ratio H. As a result, the light beam L reflected by the mirror section 20 scans the scanned surface 6 so as to draw a Lissajous waveform.

[0086] Incidentally, the resonance frequency around the first axis a1 and the resonance frequency around the second axis a2 of the mirror portion 20 may vary depending on the environmental conditions. In this embodiment, an example will be described in which the environmental condition is the environmental temperature. FIG. 13 shows the first drive frequency f at each of four environmental temperatures. d1 13 shows an example of the relationship between the second drive frequency f and the first deflection angle θ1. As shown in FIG. 13, when the environmental temperature changes, the resonance frequency f changes, and as a result, the first deflection angle θ1 also fluctuates. FIG. 14 shows the relationship between the second drive frequency f and the first deflection angle θ1 at each of four environmental temperatures. d2 14 shows an example of the relationship between the resonance frequency and the second deflection angle θ2. As shown in FIG. 14, when the environmental temperature changes, the resonance frequency changes, and as a result, the second deflection angle θ2 also changes.

[0087] Therefore, the optical scanning device 2 according to this embodiment adjusts the first driving frequency f in response to fluctuations in the environmental temperature. d1 , and the second driving frequency f d2 At this time, if the frequency ratio H changes, the scanning density of the light on the surface 6 to be scanned also changes. Therefore, the optical scanning device 2 changes the first driving frequency f while maintaining the frequency ratio H. d1 , and the second driving frequency f d2 While maintaining the frequency ratio H, the first drive frequency f d1 , and the second driving frequency f d2 The functions of the first drive signal generating unit 60A, the second drive signal generating unit 60B, the derivation unit 64, and the clock signal generating unit 65 when changing the first drive frequency f for each environmental temperature shown in FIG. 13 are described below. d1 and the first deflection angle θ1 (hereinafter referred to as "temperature characteristic information") is stored in advance in a storage device such as a nonvolatile memory provided in the drive control unit 5. The temperature characteristic information is used to calculate the relationship between the first driving frequency f for each environmental temperature. d1Alternatively, when the environmental temperature is input, the first drive frequency f at which the first deflection angle θ1 becomes maximum may be calculated. d1 It can also be a function that outputs

[0088] In this embodiment, a case where a DDS (Direct Digital Synthesizer) is used to generate the first drive signal by the first drive signal generating unit 60A and the second drive signal by the second drive signal generating unit 60B will be taken as an example. In addition, in the following, the first drive frequency f d1 "f d1A " and the changed first drive frequency f d1 "f d1B In the following, the second driving frequency before the change will be expressed as f d2 "f d2A " and the second drive frequency f d2 "f d2B " should be written as ".

[0089] The output frequency of the DDS is expressed by the following equation (1).

[0090]

number

[0091] where f out is the output frequency of the DDS. f c is the system clock frequency, N is the length of the phase accumulator, and M is the tuning word value. The system clock frequency and the length of the phase accumulator are known. Therefore, the first drive signal generating unit 60A calculates f in equation (1). out is the target first driving frequency f d1 By setting the tuning word value M so that d1 Furthermore, the second drive signal generating section 60B can generate a first drive signal having f out is the target second driving frequency f d2By setting the tuning word value M so that d2 A second drive signal having the following can be generated.

[0092] Hereinafter, the tuning word value M set in the DDS to generate the first drive signal will be referred to as "M1," and the tuning word value M set in the DDS to generate the second drive signal will be referred to as "M2." The tuning word value M1 is an example of a first set value according to the disclosed technology, and d1 is proportional to M1. The tuning word value M2 is an example of a second setting value according to the disclosed technology, and f d2 is proportional to M2. In the following, the first driving frequency f d1A The tuning word value M corresponding to 1A " and the changed first drive frequency f d1B The tuning word value M corresponding to 1B In the following, the second driving frequency before the change will be expressed as f d2A The tuning word value M corresponding to 2A " and the second drive frequency f d2B The tuning word value M corresponding to 2B " should be written as ".

[0093] The derivation unit 64 acquires the temperature detected by the temperature sensor 7, and calculates the first driving frequency f based on the acquired temperature. d1 and the second driving frequency f d2 Specifically, for example, the derivation unit 64 determines whether to change the first driving frequency f when the absolute value of the difference between the temperature at which the tuning word values ​​M1 and M2 were most recently set and the acquired temperature is equal to or greater than a certain value (for example, 1°C). d1 and the second driving frequency f d2 It is determined that the value is to be changed.

[0094] The derivation unit 64 calculates the first driving frequency f d1 and the second driving frequency f d2 If it is determined that M 1A and M2A Next, the derivation unit 64 derives the greatest common divisor G of M 1A The deriving unit 64 derives a first number Q1, which is a quotient obtained by dividing M by the greatest common divisor G. 2A A second number Q2 is derived by dividing by the greatest common divisor G.

[0095] Furthermore, the derivation unit 64 calculates the target first driving frequency f based on the acquired temperature and temperature characteristic information. d1 As an example, as shown in FIG. 15, when the environmental temperature changes from 25° C. to 35° C., the target first driving frequency f d1 In this way, the derivation unit 64 determines the first driving frequency f at which the first swing angle θ1 becomes the target angle (the maximum angle in this embodiment) in accordance with the acquired temperature. d1 The first driving frequency f d1 Let's say.

[0096] The derivation unit 64 calculates the target first driving frequency f according to equation (1). d1 The derivation unit 64 derives a tuning word value M1 that satisfies M 1A +n (n is an integer) × Q1 is determined so that the value obtained is closest to the derived tuning word value M1. Then, the derivation unit 64 determines the tuning word value M 1B is derived. M 1B =M 1A +n×Q1 (2) That is, M 1B is M 1A can be said to be a value changed in units of the first number Q1.

[0097] Furthermore, the derivation unit 64 calculates the tuning word value M 2B is derived. M 2B =M 2A +n×Q2 (3) That is, M 2B is M 2A can be said to be a value changed by the second number Q2.

[0098] (1) M in Eq. 1B By substituting f d1B M in equation (1) is obtained. 2B By substituting f d2B where M 1A = G × Q1, and M 2A = G × Q2, so the first drive frequency f d1 and the second driving frequency f d2 The frequency ratio H before the change is f d2A / f d1A =M 2A / M 1A = (G × Q2) / (G × Q1) = Q2 / Q1. Also, the first drive frequency f d1 and the second driving frequency f d2 The frequency ratio H after the change is f d2B / f d1B =M 2B / M 1B =(M 2A +n×Q2) / (M 1A +n×Q1)=(G×Q2+n×Q2) / (G×Q1+n×Q1)=((G+n)×Q2) / ((G+n)×Q1)=Q2 / Q1. In this way, M 1A is changed by the first number Q1, and M 2A By changing the second number Q2, the changed frequency ratio H, f d1B and f d2B The ratio of f is the frequency ratio H before the change d1A and f d2A This is exactly the ratio of

[0099] The clock signal generating unit 65 generates a clock signal at a first drive frequency f d1 When the second drive signal generating unit 60B changes the second drive frequency f d2 As an example, as shown in FIG. 16, the common clock signal is generated to change M 1A The clock signal rises according to the value obtained by multiplying Q2 by Q1. Specifically, the common clock signal is the clock signal that rises according to the value obtained by multiplying Q1 by Q2. 1A×Q2) times. One cycle of the common clock signal corresponds to the Q2 cycle of the first drive signal and the Q1 cycle of the second drive signal. The period corresponding to one cycle of the common clock signal may be the period of one frame when drawing a moving image.

[0100] In addition, M 1A ×Q2=M 2A ×Q1, the common clock signal is 2A It may be a clock signal in which the clock rises every Q×Q1) times.

[0101] The first drive signal generating section 60A and the second drive signal generating section 60B generate a first drive frequency f d1 and the second driving frequency f d2 Change the

[0102] Specifically, as shown in FIG. 17 as an example, the first drive signal generating section 60A converts the tuning word value M1 of the DDS into the M derived by the deriving section 64 at the timing when the clock of the common clock signal rises. 1B As a result, the first drive signal generation section 60A changes the first drive frequency f d1 is f d1B The first drive signal thus generated is applied to the pair of first actuators 31 via the first phase shift unit 62A.

[0103] 17, the second drive signal generating section 60B generates the tuning word value M2 of the DDS at the timing when the same clock as the clock used by the first drive signal generating section 60A rises, and the tuning word value M2 is calculated based on the M derived by the deriving section 64. 2B As a result, the second drive signal generation section 60B changes the second drive frequency f d2 is f d2B and applies the generated second drive signal to the pair of second actuators 32 via the second phase shift section 62B.

[0104] First drive frequency f d1 and the second driving frequency f d2 Along with the change, the clock signal generated by the clock signal generating unit 65 is also changed to (M 1B × Q2) times. In this case, Q2 is M 2B M 1B and M 2B is the quotient obtained by dividing by the greatest common divisor G.

[0105] Next, the flow of the drive frequency change process will be described with reference to Fig. 18. The flow of the drive frequency change process is executed, for example, while the image drawing system 10 is drawing an image.

[0106] In step S10 of FIG. 18, the derivation unit 64 acquires the temperature detected by the temperature sensor 7, as described above, and calculates the first driving frequency f d1 and the second driving frequency f d2 If the determination is negative, step S10 is executed again, and if the determination is positive, the process proceeds to step S12.

[0107] In step S12, the derivation unit 64 calculates M 1A and M 2A In step S14, the derivation unit 64 derives the greatest common divisor G of M 1A The derivation unit 64 derives a first number Q1, which is a quotient obtained by dividing M by the greatest common divisor G derived in step S12. 2A by the greatest common divisor G derived in step S12 to derive a second number Q2.

[0108] In step S16, the derivation unit 64 calculates the target first driving frequency f based on the temperature and temperature characteristic information acquired in step S10. d1 Furthermore, the derivation unit 64 determines the target first driving frequency f d1 The derivation unit 64 derives a tuning word value M1 that satisfies M1A +n×Q1 is determined so that the value obtained is closest to the derived tuning word value M1. Then, the derivation unit 64 determines the tuning word value M 1B The derivation unit 64 also derives the tuning word value M 2B is derived.

[0109] In step S18, the first drive signal generation unit 60A and the second drive signal generation unit 60B wait until the common clock signal generated by the clock signal generation unit 65 rises. When the common clock signal generated by the clock signal generation unit 65 rises, the determination in step S18 becomes positive, and the process proceeds to step S20.

[0110] In step S20, the first drive signal generation unit 60A calculates the tuning word value M1 of the DDS based on the M derived in step S16. 1B As a result, the first drive signal generation section 60A changes the first drive frequency f d1 is f d1B The second drive signal generator 60B generates a first drive signal that has been changed to the first drive signal M2 derived in step S16, and applies the generated first drive signal to the pair of first actuators 31 via the first phase shifter 62A. 2B As a result, the second drive signal generation section 60B changes the second drive frequency f d2 is f d2B The second drive signal is then applied to the pair of second actuators 32 via the second phase shift unit 62B. When the process of step S20 is completed, the process returns to step S10. When the image drawing process by the image drawing system 10 is completed, the drive frequency change process is completed.

[0111] As described above, according to this embodiment, the first driving frequency f d1 and the second driving frequency f d2 When changing the first drive frequency f d1 and the second driving frequency f d2The frequency ratio H of the first driving frequency f d1 and the second driving frequency f d2 are changed to the same timing, the phase difference φ between the first drive signal and the second drive signal can be maintained.

[0112] In the first embodiment, as shown in FIG. 19, the first drive signal generation section 60A and the second drive signal generation section 60B generate the first drive frequency f at the timing when the system clock rises, which is the same timing as the timing when the binarized first drive signal and second drive signal rise. d1 and the second driving frequency f d2 In this case, the system clock becomes a common clock signal. In addition, in this case, the clock signal generating unit 65 in the first embodiment is not required.

[0113] [Second embodiment] A second embodiment of the disclosed technology will be described. Note that the configuration of the image rendering system 10 (see FIG. 1) and the configuration of the MMD 4 (see FIG. 2) according to this embodiment are the same as those of the first embodiment, and therefore their description will be omitted.

[0114] The functional configuration of the drive control unit 5 according to this embodiment will be described with reference to Fig. 20. Functional units having the same functions as those in the first embodiment are assigned the same reference numerals as those in the first embodiment, and their description will be omitted. The drive control unit 5 has a first drive signal generation unit 60C, a second drive signal generation unit 60D, a first signal processing unit 61A, a second signal processing unit 61B, a first phase shift unit 62A, a second phase shift unit 62B, a first zero-cross pulse output unit 63A, a second zero-cross pulse output unit 63B, a derivation unit 64, a first clock signal generation unit 65A, a second clock signal generation unit 65B, and a light source drive unit 66.

[0115] The first clock signal generating unit 65A is M 1A Specifically, as shown in FIG. 21, for example, the first clock signal generating unit 65A generates a first clock signal whose clock rises in accordance with the value obtained by multiplying Q1 by Q2.1A ×Q2) rises.

[0116] The second clock signal generating unit 65B is M 2A Specifically, as shown in FIG. 21, for example, the second clock signal generating unit 65B generates a second clock signal whose clock rises in accordance with the value obtained by multiplying Q1 by Q2. 2A ×Q1) rises.

[0117] In this embodiment, a case where there is a phase difference between the first clock signal and the second clock signal will be described. This phase difference is equal to the phase difference between the first drive signal and the second drive signal, and is therefore represented as "φ". The initial value of the phase difference φ is set according to the phase difference between the first angle detection signal S1c and the second angle detection signal S2c. In the following, the first drive frequency f d1 and the second driving frequency f d2 The phase difference φ before the change is "φ c1 " and the phase difference φ after the change is expressed as "φ c2 " should be written as ".

[0118] As shown in FIG. 22, the second clock signal generating unit 65B generates a clock signal having a first driving frequency f d1 and the second driving frequency f d2 At the same time as the timing of the change of φ c1 φ c1 to f d1B f for d1A The phase difference φ obtained by multiplying the ratio of c2 Change to.

[0119]

number

[0120] The first clock signal generating unit 65A generates a first driving frequency f d1 At the same time as the timing of changing the tuning word value M1 and the second number Q2, d1Band f d2B Change the value according to the 1B and Q2 to generate a first clock signal whose clock rises according to the value obtained by multiplying Q2 by Q1.

[0121] The second clock signal generating unit 65B generates a second driving frequency f d2 At the same time as the timing of changing the tuning word value M2 and the first number Q1, d1B and f d2B Change the value according to the 2B and Q1 to generate a second clock signal whose clock rises according to the value obtained by multiplying Q1 by Q2.

[0122] The first drive signal generation unit 60C generates a first drive frequency f d1 The functions other than the function for changing the first drive frequency f are the same as those of the first drive signal generation unit 60A according to the first embodiment. d1 This section explains the functions for changing the

[0123] The first drive signal generating section 60C converts the tuning word value M1 of the DDS into the M derived by the deriving section 64 at the timing when the clock of the first clock signal generated by the first clock signal generating section 65A rises. 1B As a result, the first drive signal generation section 60C changes the first drive frequency f d1 is f d1B The first drive signal having the first drive frequency f is generated, and the generated first drive signal is applied to the pair of first actuators 31 via the first phase shift unit 62A. d1 The timing of this change is indicated by t1 in the upper part of FIG.

[0124] The second drive signal generation unit 60D generates a second drive frequency f d2 The functions other than the function for changing the second drive frequency f are the same as those of the second drive signal generation unit 60B according to the first embodiment. d2 This section explains the functions for changing the

[0125] The second drive signal generating section 60D calculates the tuning word value M2 of the DDS based on the M derived by the deriving section 64 at the timing when the clock of the second clock signal generated by the second clock signal generating section 65B rises. 2B As a result, the second drive signal generation section 60D changes to the second drive frequency f d2 is f d2B The second drive signal having the second drive frequency f is generated, and the generated second drive signal is applied to the pair of second actuators 32 via the second phase shift unit 62B. d2 The timing of this change is indicated by t2 in the upper part of FIG.

[0126] Next, the flow of the drive frequency change process according to this embodiment will be described with reference to Fig. 23. The flow of the drive frequency change process is executed, for example, while an image is being drawn by the image drawing system 10. Steps in Fig. 23 that execute the same processes as those in Fig. 18 are assigned the same step numbers and their descriptions will be omitted.

[0127] 23 is completed, the process proceeds to step S30. In step S30, the first drive signal generating unit 60C determines whether or not it is time for the clock of the first clock signal generated by the first clock signal generating unit 65A to rise. If this determination is affirmative, the process proceeds to step S32.

[0128] In step S32, the first drive signal generation unit 60C calculates the tuning word value M1 of the DDS based on the M derived in step S16. 1B As a result, the first drive signal generation section 60C changes the first drive frequency f d1 is f d1B The first drive signal thus generated is applied to the pair of first actuators 31 via the first phase shift unit 62A.

[0129] In step S34, the first clock signal generating unit 65A calculates the tuning word value M1 and the second number Q2 as d1B and fd2B Change the value according to the 1B A first clock signal is generated, the clock of which rises in accordance with the value obtained by multiplying Q2 by Q. When the process of step S34 ends, the process proceeds to step S42.

[0130] On the other hand, if the determination in step S30 is negative, the process proceeds to step S36. In step S36, the second drive signal generation unit 60D determines whether it is time for the clock of the second clock signal generated by the second clock signal generation unit 65B to rise. If this determination is negative, the process returns to step S30, and if the determination is positive, the process proceeds to step S38.

[0131] In step S38, the second drive signal generation unit 60D calculates the tuning word value M2 of the DDS by the M derived in step S16. 2B As a result, the second drive signal generation section 60D changes to the second drive frequency f d2 is f d2B and applies the generated second drive signal to the pair of second actuators 32 via the second phase shift section 62B.

[0132] In step S40, the second clock signal generating unit 65B calculates the tuning word value M2 and the first number Q1 as d1B and f d2B Change the value according to the 2B At this time, the second clock signal generating unit 65B generates a second clock signal whose clock rises in accordance with the value obtained by multiplying Q1 by Q2. c1 φ c1 to f d1B f for d1A The phase difference φ obtained by multiplying the ratio of c2 When the process of step S34 ends, the process proceeds to step S42.

[0133] In step S42, the derivation unit 64 calculates the first driving frequency f d1and the second driving frequency f d2 If the determination is negative, the process returns to step S30, and if the determination is positive, the process returns to step S10. When the image drawing process by the image drawing system 10 is completed, the drive frequency change process ends.

[0134] As described above, according to this embodiment, it is possible to achieve the same effects as in the first embodiment. d1 and the second driving frequency f d2 Even if the phase difference φ between the first drive signal and the second drive signal is changed based on a different clock signal, the phase difference φ between the first drive signal and the second drive signal can be maintained.

[0135] In the above embodiments, the first driving frequency f d1 After determining the first driving frequency f d1 and the second driving frequency f based on the frequency ratio H d2 However, the present invention is not limited to this. d2 After determining the second driving frequency f d2 and the first drive frequency f based on the frequency ratio H d1 The above may be determined.

[0136] Furthermore, the configuration of the MMD 4 shown in each of the above embodiments is merely an example. Various modifications are possible to the configuration of the MMD 4. For example, a first actuator 31 that oscillates the mirror section 20 about the first axis a1 may be disposed on the second movable frame 24, and a second actuator 32 that oscillates the mirror section 20 about the second axis a2 may be disposed on the first movable frame 22.

[0137] Furthermore, in the above-described embodiments, the pair of first angle detection sensors 11A, 11B are disposed at positions facing each other across the first axis a1. However, this is not limiting. For example, as shown in FIG. 24, the pair of first angle detection sensors 11A, 11B may be disposed at positions facing each other across the second axis a2. In the example of FIG. 24, the pair of first angle detection sensors 11A, 11B are disposed near the first support portions 21 on the first movable frame 22. The first angle detection sensor 11A is disposed near the first support portion 21 connected to one side of the mirror portion 20. The first angle detection sensor 11B is disposed near the first support portion 21 connected to the other side of the mirror portion 20. Therefore, the pair of first angle detection sensors 11A, 11B are disposed at positions facing each other across the second axis a2 and across the mirror portion 20. The pair of first angle detection sensors 11A and 11B are disposed at positions shifted in the same direction (the -X direction in the example of FIG. 24) from the first axis a1.

[0138] When the pair of first angle detection sensors 11A, 11B are arranged at positions facing each other across the first axis a1 as in the above-described embodiments, vibration noise can be eliminated by subtracting one of their output signals from the other. In contrast, when the pair of first angle detection sensors 11A, 11B are arranged at positions facing each other across the second axis a2 as in this embodiment, vibration noise can be eliminated by adding the output signals of both.

[0139] An example of the configuration of the first signal processing unit 61A in this embodiment is shown in Fig. 25. As shown in Fig. 25, in this embodiment, the first signal processing unit 61A has an adder circuit 73A instead of the subtractor circuit 73. The adder circuit 73A outputs a value obtained by adding together a signal S1b1 input from the first angle detection sensor 11A via a buffer amplifier 71 and a signal S1b2 input from the first angle detection sensor 11B via a variable gain amplifier 72.

[0140] Furthermore, in the above-described embodiments, the pair of second angle detection sensors 12A and 12B are disposed at positions facing each other across the second axis a2. However, this is not limiting. For example, as shown in FIG. 24, the pair of second angle detection sensors 12A and 12B may be disposed at positions facing each other across the first axis a1. In the example of FIG. 24, the pair of second angle detection sensors 12A and 12B are disposed near the second support portions 23 on the second movable frame 24. The second angle detection sensor 12A is disposed near the second support portion 23 connected to one side of the first movable frame 22. The second angle detection sensor 12B is disposed near the second support portion 23 connected to the other side of the first movable frame 22. Therefore, the pair of second angle detection sensors 12A and 12B are disposed at positions facing each other across the first axis a1 and across the mirror unit 20 and the first movable frame 22. The pair of second angle detection sensors 12A and 12B are disposed at positions shifted in the same direction (+Y direction in the example of FIG. 24) from the second axis a2.

[0141] When a pair of second angle detection sensors 12A, 12B are arranged at positions opposite each other across the second axis a2 as in the above-described embodiments, vibration noise can be eliminated by subtracting one of the output signals from the other. In contrast, when a pair of second angle detection sensors 12A, 12B are arranged at positions opposite each other across the first axis a1 as in this embodiment, vibration noise can be eliminated by adding the output signals of the two. The configuration of the second signal processing unit 61B in this embodiment can be realized by a configuration similar to that of the first signal processing unit 61A shown in FIG. 25, and therefore description thereof will be omitted.

[0142] In each of the above embodiments, any one of the pair of first angle detection sensors 11A, 11B may be provided on the MMD 4. Similarly, any one of the pair of second angle detection sensors 12A, 12B may be provided on the MMD 4.

[0143] Furthermore, the hardware configuration of the drive control unit 5 can be modified in various ways. The drive control unit 5 can be configured using at least one of an analog arithmetic circuit and a digital arithmetic circuit. The drive control unit 5 may be configured with a single processor, or may be configured with a combination of two or more processors of the same or different types. Processors include a central processing unit (CPU), a programmable logic device (PLD), and a dedicated electrical circuit. As is well known, a CPU is a general-purpose processor that executes software (programs) and functions as various processing units. A PLD is a processor, such as a field programmable gate array (FPGA), whose circuit configuration can be changed after manufacturing. A dedicated electrical circuit is a processor, such as an application specific integrated circuit (ASIC), having a circuit configuration designed specifically to execute specific processing. [Explanation of symbols]

[0144] 2 Optical scanning device 3 light source 4 Micromirror Device (MMD) 5 Drive control unit 6 Scanned surface 7 Temperature Sensor 10 Image drawing system 11A, 11B First angle detection sensor 12A, 12B Second angle detection sensor 20 Mirror section 20A reflective surface 21 1st support part 22 First movable frame 23 Second support part 24 Second movable frame 25 Connection 26 Fixed Frame 30 Piezoelectric element 31 First Actuator 32 Second actuator 60A, 60C First drive signal generating unit 60B, 60D Second drive signal generating unit 61A First signal processing section 61B Second signal processing section 62A First Phase Shift Section 62B Second phase shift section 63A 1st zero cross pulse output section 63B Second zero-cross pulse output section 64 Derivation part 65 Clock signal generation unit 65A First clock signal generator 65B Second clock signal generator 66 Light source driver 71 Buffer amplifier 72 Variable Gain Amplifier 73, 77 Subtraction circuit 73A Adding circuit 74 Gain adjustment circuit 75A 1st BPF circuit 75B 2nd BPF circuit 76A 1st detection circuit 76B Second detection circuit L Light beam RN1, RN2 vibration noise S1c First angle detection signal S2c Second angle detection signal ZC1 1st zero cross pulse ZC2 Second zero cross pulse a1 First axis a2 2nd axis f d1 First drive frequency f d2 Second Drive Frequency

Claims

1. a mirror portion having a reflective surface that reflects incident light; a first actuator that swings the mirror unit around a first axis that is in a plane that includes the reflecting surface of the mirror unit when the mirror unit is stationary; a second actuator that oscillates the mirror unit around a second axis that intersects with the first axis and is within a plane that includes the reflecting surface of the mirror unit when the mirror unit is stationary; at least one processor; An optical scanning device comprising: The processor: applying a first drive signal having a first drive frequency according to a first set value to the first actuator; applying a second drive signal having a second drive frequency according to a second set value to the second actuator; When the first drive frequency and the second drive frequency are changed, controlling the phase difference between the first drive signal and the second drive signal to maintain a predetermined value; deriving the greatest common divisor of the first set value and the second set value; changing the first drive frequency by changing the first setting value by adding an integer multiple of a first number obtained by dividing the first setting value by the greatest common divisor; The second drive frequency is changed by changing the second setting value by adding an integer multiple of a second number obtained by dividing the second setting value by the greatest common divisor. Optical scanning device.

2. The processor changes the first drive frequency and the second drive frequency at the same timing based on a common clock signal.

2. The optical scanning device according to claim 1.

3. The common clock signal is a clock signal whose clock rises in response to a value obtained by multiplying the first set value by the second number, or a clock signal whose clock rises in response to a value obtained by multiplying the second set value by the first number.

3. The optical scanning device according to claim 2.

4. The processor: applying to the first actuator the first drive signal, the first drive frequency of which is changed at a timing when a clock of a first clock signal rises in accordance with a value obtained by multiplying the first set value and the second number; The second drive signal, the second drive frequency of which is changed, is applied to the second actuator at a timing when a clock of a second clock signal rises in accordance with a value obtained by multiplying the second set value and the first number.

2. The optical scanning device according to claim 1.

5. The processor: changing the first drive frequency and the second drive frequency, and changing the first set value and the second number, and the second set value and the first number to values ​​according to the changed first drive frequency and the changed second drive frequency, generating the first clock signal based on the changed first set value and the changed second number, and generating the second clock signal based on the changed second set value and the changed first number.

5. The optical scanning device according to claim 4.

6. The processor: The first drive frequency and the second drive frequency are changed, and the first drive frequency and changing the phase difference between the first clock signal and the second clock signal before the second drive frequency is changed to a phase difference obtained by multiplying the phase difference by a ratio of the first drive frequency before the change to the first drive frequency after the change.

6. The optical scanning device according to claim 4 or claim 5.

7. a mirror portion having a reflective surface that reflects incident light; a first actuator that swings the mirror unit around a first axis that is in a plane that includes the reflecting surface of the mirror unit when the mirror unit is stationary; a second actuator that oscillates the mirror unit around a second axis that intersects with the first axis and is within a plane that includes the reflecting surface of the mirror unit when the mirror unit is stationary; A method for driving an optical scanning device comprising: applying a first drive signal having a first drive frequency according to a first set value to the first actuator; applying a second drive signal having a second drive frequency according to a second set value to the second actuator; When the first drive frequency and the second drive frequency are changed, controlling the phase difference between the first drive signal and the second drive signal to maintain a predetermined value; deriving the greatest common divisor of the first set value and the second set value; changing the first drive frequency by changing the first setting value by adding an integer multiple of a first number obtained by dividing the first setting value by the greatest common divisor; The second drive frequency is changed by changing the second setting value by adding an integer multiple of a second number obtained by dividing the second setting value by the greatest common divisor. A method for driving an optical scanning device.

8. An optical scanning device according to any one of claims 1 to 6; a light source that irradiates the mirror portion with light; An image drawing system comprising:

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