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

Abstract

To provide an optical scanner, a method for driving an optical scanner, and an image drawing system that can suppress reduction of the accuracy of detecting an angle around a first axis and an angle around a second axis of a mirror part.SOLUTION: A driving control unit derives a first integration value by integrating a first phase delay time of an output signal of a first angular detection sensor corresponding to a first reference signal according to a first driving signal natural-number times of the number in one frame of a dynamic image as a drawing target, and derives a second integration value by integrating a second phase delay time of an output signal of a second angular detection sensor corresponding to a second reference signal according to a second driving signal natural-number times of the number in one frame of a dynamic image as a drawing target.SELECTED DRAWING: Figure 13

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 rate at which the MEMS mirror completes one rotation 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] The output signal of the angle detection sensor that detects the angle of the mirror unit about the first axis contains noise and the like caused by the oscillation of the mirror unit about the second axis, which may reduce the detection accuracy of the angle of the mirror unit about the first axis.Similarly, the output signal of the angle detection sensor that detects the angle of the mirror unit about the second axis contains noise and the like caused by the oscillation of the mirror unit about the first axis, which may reduce the detection accuracy of the angle of the mirror unit about the second axis.

[0007] The technique described in Patent Document 1 does not take into consideration the accuracy of detecting the angle of the mirror portion about the first axis and the angle of the mirror portion about the second axis.

[0008] 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 suppress a decrease in the detection accuracy of the angle around the first axis and the angle around the second axis of the mirror part. [Means for solving the problem]

[0009] The optical scanning device of the present disclosure is an optical scanning device including: 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 with the first axis; a first angle detection sensor that outputs a signal corresponding to the angle of the mirror unit about the first axis; a second angle detection sensor that outputs a signal corresponding to the angle of the mirror unit about the second axis; and at least one processor, wherein the processor A first drive signal having a first drive frequency is applied to the actuator, a second drive signal having a second drive frequency is applied to the second actuator, and a first integrated value is derived by integrating a first phase delay time of an output signal of a first angle detection sensor relative to a first reference signal corresponding to the first drive signal a natural number multiple of a number of times corresponding to the period of one frame of a moving image to be drawn, and a second integrated value is derived by integrating a second phase delay time of an output signal of a second angle detection sensor relative to a second reference signal corresponding to the second drive signal a natural number multiple of a number of times corresponding to the period of one frame.

[0010] In the optical scanning device of the present disclosure, the first reference signal may be the first drive signal, and the second reference signal may be the second drive signal.

[0011] In addition, the optical scanning device of the present disclosure may have a processor that derives a first integrated value after binarizing the first drive signal and the output signal of the first angle detection sensor, and that derives a second integrated value after binarizing the second drive signal and the output signal of the second angle detection sensor.

[0012] In addition, the optical scanning device of the present disclosure may have a processor that derives a first average phase delay time, which is the average value of the first phase delay times, by dividing the first integrated value by the number of integrations, derives a second average phase delay time, which is the average value of the second phase delay times, by dividing the second integrated value by the number of integrations, outputs a first reference signal indicating that the angle of the mirror unit about the first axis has become the first reference angle when the first average phase delay time has elapsed since the time when the first drive signal indicates that the angle of the mirror unit about the first axis has become the first reference angle, and outputs a second reference signal indicating that the angle of the mirror unit about the second axis has become the second reference angle when the second average phase delay time has elapsed since the time when the second drive signal indicates that the angle of the mirror unit about the second axis has become the second reference angle.

[0013] In the optical scanning device of the present disclosure, the first reference angle and the second reference angle may be zero.

[0014] Further, a driving method of an optical scanning device according to the present disclosure is a driving method of an optical scanning device including: a mirror section having a reflective surface that reflects incident light; a first actuator that oscillates the mirror section around a first axis that is in a plane that includes the reflective surface of the mirror section when stationary; a second actuator that oscillates the mirror section around a second axis that is in the plane that includes the reflective surface of the mirror section when stationary and that intersects with the first axis; a first angle detection sensor that outputs a signal according to the angle of the mirror section about the first axis; and a second angle detection sensor that outputs a signal according to the angle of the mirror section about the second axis, a first drive signal having a first drive frequency is applied to the first actuator, a second drive signal having a second drive frequency is applied to the second actuator, a first integrated value is derived by integrating a first phase delay time of an output signal of the first angle detection sensor with respect to a first reference signal corresponding to the first drive signal a natural number multiple of a number of times corresponding to the period of one frame of a moving image to be drawn, and a second integrated value is derived by integrating a second phase delay time of an output signal of the second angle detection sensor with respect to a second reference signal corresponding to the second drive signal a natural number multiple of a number of times corresponding to the period of one frame.

[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, it is possible to suppress a decrease in the detection accuracy of the angle of the mirror section about the first axis and the angle of the mirror section about the second axis. [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 a functional configuration of a drive control unit. [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] 10A and 10B are diagrams for explaining deviations in output signals of angle detection sensors; [Figure 12] FIG. 1 is a diagram for explaining one frame. [Figure 13] FIG. 10 is a diagram for explaining a process for deriving a first integrated value. [Figure 14] FIG. 10 is a diagram for explaining a process for deriving a second integrated value. [Figure 15] FIG. 4 is a diagram for explaining a process for generating a first zero-cross pulse. [Figure 16]10A and 10B are diagrams for explaining a process of generating a second zero-cross pulse. [Figure 17] 10 is a flowchart illustrating an example of a first average phase delay time derivation process. [Figure 18] 10 is a flowchart illustrating an example of a second average phase delay time derivation process. [Figure 19] 10 is a graph showing an example of the relationship between the standard deviation of the first integrated value and the number of integrations. [Figure 20] 10 is a graph showing an example of the relationship between the standard deviation of the second integrated value and the number of integrations. [Figure 21] FIG. 10 is a plan view of a micromirror device according to a modified example. [Figure 22] 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, 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 and a drive control unit 5. 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 applied 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 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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°).

[0041] 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.

[0042] 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°).

[0043] 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.

[0044] 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.

[0045] 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)

[0046] 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°.

[0047] 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 swings around the first axis a1.

[0048] 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)

[0049] 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).

[0050] 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.

[0051] 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.

[0052] 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 derivation unit 63A, a second derivation unit 63B, a first zero-cross pulse output unit 65A, a second zero-cross pulse output unit 65B, and a light source drive unit 66.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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 As indicated by φ in the equation for (t), they are phase-synchronized.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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).

[0073] 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.

[0074] 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.

[0075] 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).

[0076] The first angle detection signal S1c generated by the second 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°.

[0077] 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 degrees.

[0078] The first angle detection signal S1c generated by the first signal processing unit 61A is ideally a sine wave, but in many cases it is not a smooth sine wave. This is because the processing by the first signal processing unit 61A cannot completely remove the influence of the oscillation of the mirror unit 20 about the second axis a2. Similarly, the second angle detection signal S2c generated by the second signal processing unit 61B is ideally a sine wave, but in many cases it is not a smooth sine wave because the influence of the oscillation of the mirror unit 20 about the first axis a1 remains.

[0079] In this case, as shown in FIG. 11 as an example, the timing at which the second angle detection signal S2c crosses zero is slightly shifted from the timing at which the second deflection angle θ2 actually becomes 0°. In the example of FIG. 11, the dashed-dotted line indicates an ideal sine wave waveform representing the oscillation of the mirror section 20 about the second axis a2, and the dashed-two-dotted line indicates a waveform affected by the oscillation of the mirror section 20 about the first axis a1. Also in the example of FIG. 11, the solid line represents the second angle detection signal S2c. Although FIG. 11 has been described using the second angle detection signal S2c as an example, the first angle detection signal S1c also similarly includes the influence of the oscillation of the mirror section 20 about the second axis a2.

[0080] The applicant has found that the first timing at which the second angle detection signal S2c crosses zero repeatedly shifts before and after the second timing at which the second swing angle θ2 actually becomes 0°. Furthermore, the applicant has found that within the period of one frame of the moving image to be drawn, the total amount of shift when the first timing shifts before the second timing is approximately equal to the total amount of shift when the first timing shifts after the second timing.

[0081] Therefore, the first derivation unit 63A reduces the influence of the oscillation of the mirror unit 20 about the second axis a2 by integrating the phase delay time of the first angle detection signal S1c relative to the first drive signal within one frame period (hereinafter referred to as the "first phase delay time"). Similarly, the second derivation unit 63B reduces the influence of the oscillation of the mirror unit 20 about the first axis a1 by integrating the phase delay time of the second angle detection signal S2c relative to the second drive signal within one frame period (hereinafter referred to as the "second phase delay time"). The first drive signal is an example of a first reference signal according to the disclosed technology, and the second drive signal is an example of a second reference signal according to the disclosed technology.

[0082] Here, an example will be described in which a DDS (Direct Digital Synthesizer) is used to generate the first drive signal and the second drive signal for one frame period of a moving image. The output frequency of the DDS is expressed by the following equation (1).

[0083]

number

[0084] 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. M is the tuning word value.

[0085] As mentioned above, the target first drive frequency f d1 is set to coincide with the resonance frequency around the first axis a1 of the mirror section 20. In addition, the target second driving frequency f 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. The system clock frequency and the length of the phase accumulator are known.

[0086] Therefore, using equation (1), the first driving frequency f d1 Similarly, using equation (1), the tuning word value M1 that gives the second driving frequency f d2 Assuming that the greatest common divisor of the tuning word value M1 and the tuning word value M2 is G, the following equation (2) is established. M1×Q2=M2×Q1 (2) Here, Q1 is the quotient obtained by dividing the tuning word value M1 by the greatest common divisor G. Q2 is the quotient obtained by dividing the tuning word value M2 by the greatest common divisor G.

[0087] That is, as shown in FIG. 12, the first driving frequency f d1 and a period of Q2 cycles of the first drive signal having a second drive frequency f d2 In this embodiment, this period is set to the period of one frame.

[0088] The first derivation unit 63A derives a first integrated value by integrating the first phase delay time of the first angle detection signal S1c relative to the first drive signal n times the number of times corresponding to the period of one frame of the moving image to be drawn. n is a natural number, and in this embodiment, n=1. Note that n may be 2 or more.

[0089] 13, the first derivation unit 63A binarizes the first drive signal and the first angle detection signal S1c. For example, the first derivation unit 63A binarizes the first drive signal and the first angle detection signal S1c by setting values ​​equal to or greater than the average value of the minimum and maximum values ​​of the first drive signal and the first angle detection signal S1c to 1 and values ​​less than the average value to 0.

[0090] The first derivation unit 63A derives the first integrated value by continuously integrating the first phase delay time of the first angle detection signal S1c with respect to the binarized first drive signal a number of times corresponding to the period of one frame of the moving image to be drawn. In this case, the number of integrations is Q2 as described above. In the example of FIG. 13, the first phase delay time of the corresponding period is C i (i is an integer from 0 to Q2-1) In addition, in the example of Fig. 13, the difference in the timing of the rise of the first drive signal and the first angle detection signal S1c after binarization is used, but the difference in the timing of the fall of the first drive signal and the first angle detection signal S1c after binarization may also be used.

[0091] Next, the first derivation unit 63A derives a first average phase delay time, which is the average value of the first phase delay times, by dividing the first integrated value by the number of integrations.

[0092] The second derivation unit 63B derives a second integrated value by integrating the second phase delay time of the second angle detection signal S2c relative to the second drive signal n times the number of times corresponding to the period of one frame of the moving image to be drawn.

[0093] 14, the second derivation unit 63B binarizes the second drive signal and the second angle detection signal S2c. For example, the second derivation unit 63B binarizes the second drive signal and the second angle detection signal S2c by setting values ​​equal to or greater than the average value of the minimum and maximum values ​​of the second drive signal and the second angle detection signal S2c to 1 and values ​​less than the average value to 0.

[0094] The second derivation unit 63B derives the second integrated value by continuously integrating the second phase delay time of the second angle detection signal S2c with respect to the binarized second drive signal a number of times corresponding to the period of one frame of the moving image to be drawn. In this case, the number of integrations is Q1 as described above. In the example of FIG. 14, the second phase delay time of the corresponding period is C j (j is an integer between 0 and Q1-1.) In the example of Fig. 14, the difference in the timing of the rise of the binarized second drive signal and second angle detection signal S2c is used, but the difference in the timing of the fall of the binarized second drive signal and second angle detection signal S2c may also be used.

[0095] Next, the second derivation unit 63B derives a second average phase delay time, which is the average value of the second phase delay times, by dividing the second integrated value by the number of integrations.

[0096] The first zero-cross pulse output unit 65A generates a reference signal (hereinafter referred to as the "first reference signal") based on the first drive signal and the first average phase delay time derived by the first derivation unit 63A. The first reference signal is a signal indicating that the angle of the mirror unit 20 about the first axis a1 has reached a reference angle (hereinafter referred to as the "first reference angle"). In this embodiment, an example in which zero is used as the first reference angle will be described. That is, the first zero-cross pulse output unit 65A generates a zero-cross pulse (hereinafter referred to as the "first zero-cross pulse") ZC1 as an example of the first reference signal based on the first drive signal and the first average phase delay time derived by the first derivation unit 63A. The first zero-cross pulse output unit 65A is configured by a zero-cross detection circuit. The first zero-cross pulse is a zero-cross signal indicating that the angle of the mirror unit 20 about the first axis a1 has reached zero.

[0097] As shown in FIG. 15, the first zero-cross pulse output section 65A receives the first drive signal when the angle of the mirror section 20 around the first axis a1 reaches the first reference angle (V off1 The first zero-cross pulse output unit 65A generates a first zero-cross pulse ZC1 when a first average phase delay time has elapsed since the time when the light source crosses the zero-cross pulse ZC1. The first zero-cross pulse output unit 65A outputs the generated first zero-cross pulse ZC1 to the light source drive unit 66.

[0098] The second zero-cross pulse output unit 65B generates a reference signal (hereinafter referred to as the "second reference signal") based on the second drive signal and the second average phase delay time derived by the second derivation unit 63B. The second reference signal is a signal indicating that the angle of the mirror unit 20 about the second axis a2 has reached a reference angle (hereinafter referred to as the "second reference angle"). In this embodiment, an example in which zero is used as the second reference angle will be described. That is, the second zero-cross pulse output unit 65B generates a zero-cross pulse (hereinafter referred to as the "second zero-cross pulse") ZC2 as an example of the second reference signal based on the second drive signal and the second average phase delay time derived by the second derivation unit 63B. The second zero-cross pulse output unit 65B is configured by a zero-cross detection circuit. The second zero-cross pulse is a zero-cross signal indicating that the angle of the mirror unit 20 about the second axis a2 has reached zero.

[0099] As shown in FIG. 16, the second zero-cross pulse output section 65B receives the second drive signal when the second drive signal indicates that the angle of the mirror section 20 around the second axis a2 has reached the second reference angle (V off2 The second zero-cross pulse output unit 65B generates a second zero-cross pulse ZC2 when the second average phase delay time has elapsed since the time when the light source crosses the zero-cross pulse ZC1. The second zero-cross pulse output unit 65B outputs the generated second zero-cross pulse ZC2 to the light source drive unit 66.

[0100] Although the first zero-cross pulse output unit 65A and the second zero-cross pulse output unit 65B 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 65A and the second zero-cross pulse output unit 65B 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.

[0101] 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.

[0102] Next, the flow of the first average phase delay time derivation process will be described with reference to Fig. 17. The first average phase delay time derivation process is executed at predetermined time intervals, for example, while the image rendering system 10 is rendering an image. This time interval may be, for example, a time interval corresponding to the period of one frame or a time interval corresponding to the period of multiple frames.

[0103] 17, the first derivation unit 63A binarizes the first drive signal and the first angle detection signal S1c, as described above. In step S12, the first derivation unit 63A derives a first integrated value by continuously integrating the first phase delay time of the first angle detection signal S1c with respect to the first drive signal after binarization by the processing of step S10 a number of times equivalent to the period of one frame of the moving image to be drawn, as described above.

[0104] In step S14, the first derivation unit 63A derives a first average phase delay time, which is the average value of the first phase delay times, by dividing the first integrated value derived in step S12 by the number of integrations. When the processing of step S14 ends, the first average phase delay time derivation processing ends. The first average phase delay time derivation processing is periodically executed while the image is being drawn, thereby updating the first average phase delay time.

[0105] Next, the flow of the second average phase delay time derivation process will be described with reference to Fig. 18. The second average phase delay time derivation process is executed at predetermined time intervals, for example, while the image rendering system 10 is rendering an image. This time interval may be, for example, a time interval corresponding to the period of one frame or a time interval corresponding to the period of multiple frames. Furthermore, the second average phase delay time derivation process may be executed simultaneously with the first average phase delay time derivation process described above.

[0106] 18, the second derivation unit 63B binarizes the second drive signal and the second angle detection signal S2c, as described above. In step S22, the second derivation unit 63B derives a second integrated value by continuously integrating the second phase delay time of the second angle detection signal S2c with respect to the second drive signal after binarization by the processing of step S20 a number of times equivalent to the period of one frame of the moving image to be drawn, as described above.

[0107] In step S24, the second derivation unit 63B derives a second average phase delay time, which is the average value of the second phase delay times, by dividing the second integrated value derived in step S22 by the number of integrations, as described above. When the processing of step S24 ends, the second average phase delay time derivation processing ends. The second average phase delay time derivation processing is periodically executed while the image is being drawn, thereby updating the second average phase delay time.

[0108] Next, the flow of the first zero-cross pulse generation process will be described. For example, the first zero-cross pulse generation process is executed while the image drawing system 10 is drawing an image.

[0109] The first zero-cross pulse output unit 65A generates a binarized signal by binarizing the first drive signal generated by the first drive signal generation unit 60A. The binarization method may be a method using a comparator or a method using a one-bit register in an FPGA (Field Programmable Gate Array). The first zero-cross pulse output unit 65A delays the binarized signal by a first average phase delay time and outputs the resulting binarized signal to the light source drive unit 66 as a first zero-cross pulse ZC1, thereby completing the first zero-cross pulse generation process.

[0110] Next, the flow of the second zero-cross pulse generation process will be described. For example, the second zero-cross pulse generation process is executed while the image drawing system 10 is drawing an image.

[0111] The second zero-cross pulse output unit 65B generates a binarized signal by binarizing the second drive signal generated by the second drive signal generation unit 60B. The binarization may be performed using a comparator or by providing a one-bit register within the FPGA. The second zero-cross pulse output unit 65B delays the binarized signal by the second average phase delay time and outputs the resulting binarized signal to the light source drive unit 66 as a second zero-cross pulse ZC2, thereby completing the second zero-cross pulse generation process.

[0112] 19 shows an example of the relationship between the standard deviation of the first integrated value derived a certain number of times (e.g., 1000 times) and the number of integrations, and FIG. 20 shows an example of the relationship between the standard deviation of the second integrated value derived a certain number of times and the number of integrations. Also, the smaller the standard deviation of the first integrated value, i.e., the smaller the variation in the first integrated value, the more the influence of the oscillation of the mirror unit 20 about the second axis a2 has been removed from the first angle detection signal S1c. The smaller the standard deviation of the second integrated value, i.e., the smaller the variation in the second integrated value, the more the influence of the oscillation of the mirror unit 20 about the first axis a1 has been removed from the second angle detection signal S2c.

[0113] The upper part of Fig. 19 shows the standard deviation of the first integrated value when the process of deriving the first integrated value is performed a certain number of times while changing the number of integrations from 1 to 100. The lower part of Fig. 19 is an enlarged view of the portion of the upper part of Fig. 19 where the number of integrations is from 40 to 60 (the portion surrounded by the dashed rectangle). The solid line in Fig. 19 represents the standard deviation of the first integrated value when the first phase delay time is continuously integrated, as in the above embodiment. The dashed-dotted line in Fig. 19 represents the standard deviation of the first integrated value when the first phase delay time is randomly selected and integrated, as a comparative example.

[0114] The upper part of Fig. 20 shows the standard deviation of the second integrated value when the process of deriving the second integrated value is performed a certain number of times while changing the number of integrations from 1 to 100. The lower part of Fig. 20 is an enlarged view of the portion of the upper part of Fig. 20 where the number of integrations is from 20 to 30 (the portion surrounded by the dashed rectangle). The solid line in Fig. 20 represents the standard deviation of the second integrated value when the second phase delay time is continuously integrated, as in the above embodiment. The dashed-dotted line in Fig. 20 represents the standard deviation of the second integrated value when the second phase delay time is randomly selected and integrated, as a comparative example.

[0115] 19 and 20 show the results when the first and second phase delay times are expressed in terms of the number of clocks of the system clock. Also, Fig. 19 and 20 show the results when the optical scanning device 2 is driven with the aforementioned Q1 set to 25 and Q2 set to 51.

[0116] 19, in the comparative example, the more the number of integrations, the smaller the standard deviation of the first integrated value, but once the number of integrations reaches a certain number, the degree to which the standard deviation of the first integrated value decreases decreases. In other words, in the comparative example, the number of integrations must be increased in order to further reduce the standard deviation of the first integrated value.

[0117] 19, even when the first phase delay time is continuously accumulated, the standard deviation of the first accumulated value tends to decrease as the number of accumulations increases, but the standard deviation of the first accumulated value is smallest when the number of accumulations is Q2 (here, 51). As described above, when the number of accumulations is Q2, this is the time when the number of accumulations corresponds to the period of one frame of the moving image to be drawn.

[0118] 20, in the comparative example, the standard deviation of the second integrated value decreases as the number of integrations increases, but once the number of integrations reaches a certain number, the degree to which the standard deviation of the second integrated value decreases decreases. In other words, in the comparative example, the number of integrations must be increased in order to further reduce the standard deviation of the second integrated value.

[0119] As shown by the solid line in Figure 20, even when the second phase delay time is continuously integrated, the standard deviation of the second integrated value tends to decrease as the number of integrations increases, but the standard deviation of the second integrated value is smallest when the number of integrations is Q1 (25 in this case). As mentioned above, when the number of integrations is Q1, this is the number of integrations corresponding to the period of one frame of the moving image to be drawn. In this case, the standard deviation of the second integrated value is also smallest when the number of integrations is twice (50 in this case), three times (75 in this case), and four times (100 in this case) Q1.

[0120] As described above, according to this embodiment, the first integrated value is derived by integrating the first phase delay time a number of times corresponding to the period of one frame of the moving image to be drawn. This first integrated value is obtained by reducing the influence of the oscillation of the mirror unit 20 about the second axis a2 from the first angle detection signal S1c. Furthermore, according to this embodiment, the second integrated value is derived by integrating the second phase delay time a number of times corresponding to the period of one frame of the moving image to be drawn. This second integrated value is obtained by reducing the influence of the oscillation of the mirror unit 20 about the first axis a1 from the second angle detection signal S2c.

[0121] Therefore, by using the first integrated value and the second integrated value derived in this manner, it is possible to suppress a decrease in the detection accuracy of the angle around the first axis a1 and the angle around the second axis a2 of the mirror section 20. Furthermore, it is possible to reduce the number of integrations required when deriving the first integrated value and the second integrated value.

[0122] In the above embodiment, the first derivation unit 63A derives the first integrated value by integrating the first phase delay time of the first angle detection signal S1c with respect to the first drive signal. However, the present invention is not limited to this. For example, the first derivation unit 63A may derive the first integrated value by integrating the first phase delay time of the first angle detection signal S1c with respect to a first reference signal, which is a reference signal corresponding to the first drive signal, such as a signal obtained by duplicating the first drive signal.

[0123] In the above embodiment, the second derivation unit 63B derives the second integrated value by integrating the second phase delay time of the second angle detection signal S2c with respect to the second drive signal, but this is not limiting. For example, the second derivation unit 63B may derive the second integrated value by integrating the second phase delay time of the second angle detection signal S2c with respect to a second reference signal, which is a reference signal corresponding to the second drive signal, such as a signal obtained by duplicating the second drive signal.

[0124] Furthermore, the configuration of the MMD 4 shown in the above embodiment is just one 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.

[0125] Furthermore, in the above embodiment, 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. 21 , 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. 21 , 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. 21) from the first axis a1.

[0126] 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 embodiment, vibration noise can be eliminated by subtracting one of the output signals from the other. On the other hand, 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 the two.

[0127] An example of the configuration of the first signal processing unit 61A in this embodiment is shown in Fig. 22. As shown in Fig. 22, 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.

[0128] Furthermore, in the above embodiment, the pair of second angle detection sensors 12A, 12B are disposed at positions facing each other across the second axis a2. However, this is not limiting. For example, as shown in FIG. 21 , the pair of second angle detection sensors 12A, 12B may be disposed at positions facing each other across the first axis a1. In the example of FIG. 21 , the pair of second angle detection sensors 12A, 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, 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. 21) from the second axis a2.

[0129] When the pair of second angle detection sensors 12A, 12B are arranged at positions opposite each other across the second axis a2 as in the above embodiment, vibration noise can be eliminated by subtracting one of the output signals from the other. In contrast, when the 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. 22, so a description thereof will be omitted.

[0130] In the above embodiment, either one of the pair of first angle detection sensors 11A, 11B may be provided on the MMD 4. Similarly, either one of the pair of second angle detection sensors 12A, 12B may be provided on the MMD 4.

[0131] 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 an 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]

[0132] 2 Optical scanning device 3 light source 4 Micromirror Device (MMD) 5 Drive control unit 6 Scanned surface 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 First drive signal generating unit 60B 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 derivation part 63B 2nd derived part 65A 1st zero cross pulse output section 65B Second zero-cross pulse output section 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; a first angle detection sensor that outputs a signal corresponding to an angle of the mirror portion around the first axis; a second angle detection sensor that outputs a signal corresponding to an angle of the mirror portion around the second axis; at least one processor; An optical scanning device comprising: The processor: applying a first drive signal having a first drive frequency to the first actuator; applying a second drive signal having a second drive frequency to the second actuator; deriving a first integrated value by integrating a first phase delay time of an output signal of the first angle detection sensor with respect to a first reference signal corresponding to the first drive signal a number of times equal to a natural number multiple of a number of times corresponding to a period of one frame of a moving image to be drawn; deriving a second integrated value by integrating a second phase delay time of an output signal of the second angle detection sensor with respect to a second reference signal corresponding to the second drive signal a number of times equal to a natural number multiple of a number of times corresponding to a period of one frame; deriving a first average phase delay time, which is an average value of the first phase delay time, by dividing the first integrated value by the number of integrations; deriving a second average phase delay time, which is an average value of the second phase delay time, by dividing the second integrated value by the number of integrations; outputting a first reference signal indicating that the angle of the mirror section about the first axis has reached a first reference angle at a time when the first average phase delay time has elapsed since the time when the first drive signal crossed a DC bias component; a second reference signal indicating that the angle of the mirror section about the second axis has reached a second reference angle when the second average phase delay time has elapsed since the second drive signal crossed the DC bias component; Optical scanning device.

2. the first reference signal is the first drive signal, The second reference signal is the second drive signal.

2. The optical scanning device according to claim 1.

3. The processor: deriving the first integrated value after binarizing the first drive signal and the output signal of the first angle detection sensor; The second drive signal and the output signal of the second angle detection sensor are binarized, and then the second integrated value is derived.

3. The optical scanning device according to claim 2.

4. The first reference angle and the second reference angle are zero.

2. The optical scanning device according to claim 1.

5. 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 first angle detection sensor that outputs a signal corresponding to an angle of the mirror portion around the first axis; a second angle detection sensor that outputs a signal corresponding to an angle of the mirror portion around the second axis; A method for driving an optical scanning device comprising: applying a first drive signal having a first drive frequency to the first actuator; applying a second drive signal having a second drive frequency to the second actuator; deriving a first integrated value by integrating a first phase delay time of an output signal of the first angle detection sensor with respect to a first reference signal corresponding to the first drive signal a number of times equal to a natural number multiple of a number of times corresponding to a period of one frame of a moving image to be drawn; deriving a second integrated value by integrating a second phase delay time of an output signal of the second angle detection sensor with respect to a second reference signal corresponding to the second drive signal a number of times equal to a natural number multiple of a number of times corresponding to a period of one frame; deriving a first average phase delay time, which is an average value of the first phase delay time, by dividing the first integrated value by the number of integrations; deriving a second average phase delay time, which is an average value of the second phase delay time, by dividing the second integrated value by the number of integrations; outputting a first reference signal indicating that the angle of the mirror section about the first axis has reached a first reference angle at a time when the first average phase delay time has elapsed since the time when the first drive signal crossed a DC bias component; a second reference signal indicating that the angle of the mirror section about the second axis has reached a second reference angle when the second average phase delay time has elapsed since the second drive signal crossed the DC bias component; A method for driving an optical scanning device.

6. An optical scanning device according to any one of claims 1 to 4; a light source that irradiates the mirror portion with light; An image drawing system comprising:

Images