Optical scanning device, drive method for optical scanning device, and image rendering system

Abstract

An optical scanning device according to the present invention comprises a mirror part, a first actuator that swings the mirror part around a first axis, a second actuator that swings the mirror part around a second axis, a first angle sensor that outputs a signal that corresponds to the angle of the mirror part around the first axis, a second angle sensor that outputs a signal that corresponds to the angle of the mirror part around the second axis, and a processor. The processor gives a first drive signal to the first actuator, gives a second drive signal to the second actuator, and adjusts the phase of at least one of the first drive signal and the second drive signal on the basis of the difference between a target phase difference and a phase difference to be adjusted that is the phase difference between the output signal of the first angle sensor relative to a first reference signal that corresponds to the first drive signal and the output signal of the second angle sensor relative to a second reference signal that corresponds to the second drive signal.

Description

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

[0001] The technology disclosed herein relates to an optical scanning device, a method for driving an optical scanning device, and an image rendering system.

[0002] Micromirror devices (also known as microscanners) are a type of micro-electromechanical system (MEMS) device fabricated using silicon (Si) microfabrication technology. Due to their small size and low power consumption, these micromirror devices are expected to have a wide range of applications, including laser displays, laser projectors, and optical coherence tomography (OCT) systems.

[0003] A micromirror device is formed in which the mirror portion is rotatable around a first axis and a second axis that are orthogonal to each other. By rotating the mirror portion around each axis, the light reflected by the mirror portion is scanned two-dimensionally. Furthermore, a micromirror device is known that enables Lissajous scanning of light by resonating the mirror portion around each axis (see, for example, Japanese Patent Application Publication No. 2012-141462).

[0004] However, when the micromirror device is being driven, if the phase difference between the oscillation of the mirror around the first axis and the oscillation around the second axis fluctuates from frame to frame, the drawing trajectory of the moving image will shift from frame to frame, resulting in a problem where the desired moving image is not accurately drawn. Specifically, if the phase difference is unstable, not only will the spacing between adjacent drawing trajectories fluctuate, but multiple drawing trajectories will overlap, causing a significant degradation in image quality.

[0005] The present invention aims to provide an optical scanning device, a method for driving the optical scanning device, and an image rendering system that can suppress the degradation of image quality of the rendering of moving images.

[0006] To achieve the above objective, the optical scanning apparatus of the present disclosure comprises a mirror portion that reflects incident light, a first actuator that swings the mirror portion around a first axis, a second actuator that swings the mirror portion around a second axis intersecting the first axis, a first angle sensor that outputs a signal corresponding to the angle of the mirror portion around the first axis, a second angle sensor that outputs a signal corresponding to the angle of the mirror portion around the second axis, and a processor, wherein the processor provides a first drive signal having a first frequency to the first actuator, provides a second drive signal having a second frequency to the second actuator, calculates an adjustment target phase difference which is the phase difference between the output signal of the first angle sensor with respect to a first reference signal corresponding to the first drive signal and the output signal of the second angle sensor with respect to a second reference signal corresponding to the second drive signal, and adjusts the phase of at least one of the first drive signal and the second drive signal based on the difference between the adjustment target phase difference and the target phase difference.

[0007] The processor may calculate the phase difference to be adjusted based on the first phase delay time of the output signal of the first angle sensor and the second phase delay time of the output signal of the second angle sensor.

[0008] The processor may measure the first phase delay time and the second phase delay time using both the rising and falling edges of the clock signal.

[0009] The processor may calculate the first phase delay time and the second phase delay time, respectively, based on the first number of clock cycles measured using the rising edge timing of the clock signal and the second number of clock cycles measured using the falling edge timing of the clock signal.

[0010] If the first clock speed and the second clock speed are the same, the processor may calculate based on the first clock speed; if the first clock speed and the second clock speed are different, it may calculate based on the larger clock speed minus half.

[0011] The processor may calculate a first integrated value by accumulating the first phase delay time a number of times that is an integer multiple of the number of times corresponding to one frame duration of the moving image to be drawn, and calculate a second integrated value by accumulating the second phase delay time a number of times that is an integer multiple of the number of times corresponding to one frame duration.

[0012] The processor may calculate a first integrated value after binarizing the output signal of the first angle sensor, and then calculate a second integrated value after binarizing the output signal of the second angle sensor.

[0013] The processor may calculate a first average phase delay time, which is the average of the first phase delay time, by dividing the first integrated value by the number of integrations, and calculate a second average phase delay time, which is the average of the second phase delay time, by dividing the second integrated value by the number of integrations. It may also generate a first reference signal indicating that the angle around the first axis of the mirror unit has become the first reference angle when the first average phase delay time has elapsed from the point in time when the first drive signal indicates that the angle around the second axis of the mirror unit has become the second reference angle, and generate a second reference signal indicating that the angle around the second axis of the mirror unit has become the second reference angle when the second average phase delay time has elapsed from the point in time when the second drive signal indicates that the angle around the second axis of the mirror unit has become the second reference angle.

[0014] The first and second reference angles may be zero.

[0015] The processor may calculate the phase difference to be adjusted based on the time difference between the first reference signal and the second reference signal.

[0016] The processor may calculate the first average phase delay time each time a new first phase delay time is obtained through FIFO processing, and calculate the second average phase delay time each time a new second phase delay time is obtained.

[0017] The first reference signal may be the first drive signal, and the second reference signal may be the second drive signal.

[0018] The first frequency and the second frequency may be two values ​​obtained by integer multiples of two relatively prime integers.

[0019] The present disclosure provides a method for driving an optical scanning device, comprising: a mirror portion that reflects incident light; a first actuator that swings the mirror portion around a first axis; a second actuator that swings the mirror portion around a second axis intersecting the first axis; a first angle sensor that outputs a signal corresponding to the angle of the mirror portion around the first axis; and a second angle sensor that outputs a signal corresponding to the angle of the mirror portion around the second axis. The method includes: applying a first drive signal having a first frequency to the first actuator; applying a second drive signal having a second frequency to the second actuator; calculating an adjustment target phase difference, which is the phase difference between the output signal of the first angle sensor with respect to a first reference signal corresponding to the first drive signal and the output signal of the second angle sensor with respect to a second reference signal corresponding to the second drive signal; and adjusting the phase of at least one of the first drive signal and the second drive signal based on the difference between the adjustment target phase difference and the target phase difference.

[0020] The image rendering system disclosed herein comprises the above-mentioned optical scanning device and a light source that irradiates light onto the mirror portion.

[0021] The technology disclosed herein provides an optical scanning device, a method for driving the optical scanning device, and an image rendering system that can suppress the degradation of image quality of the rendering motion.

[0022] This is a schematic diagram showing the configuration of the image drawing system. This is a perspective view of the micromirror device. This diagram shows an example of the first drive signal and the second drive signal, where (A) is a diagram showing the first drive signal and (B) is a diagram showing the second drive signal. This is a block diagram showing the configuration of the drive control device. This is a block diagram showing the configuration of the first basic signal generation unit and the second basic signal generation unit. This is a diagram showing the generation process of the first basic signal by the first basic signal generation unit. This is an explanatory diagram showing the relationship between the period of the first drive signal and the period of the second drive signal. This is a diagram showing an example of the output signal of the first angle sensor. This is a diagram showing an example of the output signal of the second angle sensor. This is a conceptual diagram showing the signal processing by the first signal processing unit. This is a conceptual diagram showing the signal processing by the second signal processing unit. This is a diagram showing the integration process of the first phase delay time by the first reference signal generation unit. This is an explanatory diagram showing the generation timing of the first reference signal. This is a diagram showing the integration process of the second phase delay time by the second reference signal generation unit. This is an explanatory diagram showing the generation timing of the second reference signal. This is a diagram explaining the details of the measurement method for the first phase delay time. This is a diagram explaining PL control by the DDS control unit. This figure shows an example of the processing flow in PL control. This figure conceptually shows the drawing trajectory. This figure explains the FIFO process when determining the first average phase delay time. This figure explains the FIFO process when determining the second average phase delay time.

[0023] An example of an embodiment relating to the technology of this disclosure will be described with reference to the attached drawings.

[0024] Figure 1 schematically shows an image drawing system 10 according to one embodiment. The image drawing system 10 includes an optical scanning device 2 and a light source 3. The optical scanning device 2 consists of a micromirror device (hereinafter referred to as MMD (Micro Mirror Device)) 4 and a drive control device 5. The drive control device 5 is an example of a "processor" according to the disclosed technology.

[0025] The image drawing system 10, in accordance with the control of the drive control device 5, draws a moving image by reflecting the light beam LB irradiated from the light source 3 with the MMD 4 and optically scanning the surface to be scanned 6. The surface to be scanned 6 can be a screen, the retina of a human eye, etc.

[0026] The image rendering system 10 is applied, for example, to a Lissajous scanning laser display. Specifically, the image rendering system 10 is applicable to laser scanning displays such as AR (Augmented Reality) glasses and VR (Virtual Reality) glasses.

[0027] MMD4 is the first axis a １ and the first axis a １ The second axis a intersects with ２ This is a piezoelectric two-axis driven micromirror device that enables the mirror portion 20 (see Figure 2) to swing around the first axis a １ The direction parallel to the second axis is the X direction, and the second axis a ２ The direction parallel to this is the Y direction, and the first axis a １ and second axis a ２ The direction perpendicular to the X and Y directions is called the Z direction. In this embodiment, the X and Y directions are perpendicular to each other.

[0028] Light source 3 is a laser device that emits, for example, laser light as an optical beam LB. For example, light source 3 outputs laser light of three colors: R (Red), G (Green), and B (Blue). Light source 3 may irradiate the optical beam LB perpendicularly onto the reflective surface 20A (see Figure 2) of the mirror section 20 of the MMD 4 when the mirror section 20 is stationary.

[0029] Furthermore, if the light source 3 irradiates the light beam LB perpendicularly to the reflective surface 20A, the light source 3 may become an obstacle when scanning the light beam LB across the scanned surface 6. For this reason, it is preferable to control the light beam LB emitted from the light source 3 with an optical system to irradiate the reflective surface 20A perpendicularly. The optical system may or may not include lenses. Also, the angle at which the light beam LB emitted from the light source 3 irradiates the reflective surface 20A is not limited to perpendicular; the light beam LB may be irradiated at an angle to the reflective surface 20A.

[0030] The drive control device 5 outputs drive signals to the light source 3 and the MMD 4 based on the optical scanning information. The light source 3 generates a light beam LB based on the input drive signal and irradiates the MMD 4 with the light beam LB. Based on the input drive signal, the MMD 4 causes the mirror unit 20 to swing around a first axis a １ and a second axis a ２ .

[0031] The drive control device 5 resonates the mirror unit 20 around the first axis a １ and the second axis a ２ respectively, whereby the light beam LB reflected by the mirror unit 20 is scanned to draw a Lissajous pattern on the scanned surface 6. This optical scanning method is called a Lissajous scanning method.

[0032] Next, an example of the MMD 4 will be described with reference to FIG. 2. FIG. 2 is an external perspective view of the MMD 4. As shown in FIG. 2, the MMD 4 includes a mirror unit 20, a first support portion 21, a first movable frame 22, a second support portion 23, a second movable frame 24, a connection portion 25, and a fixed frame 26. The MMD 4 is a so-called MEMS scanner.

[0033] The mirror unit 20 has a reflection surface 20A that reflects incident light. The reflection surface 20A is provided on one surface of the mirror unit 20 and is formed of, for example, a thin metal film of gold (Au), aluminum (Al), silver (Ag), a silver alloy, or the like. The shape of the reflection surface 20A is, for example, a circular shape centered on the intersection of a first axis a １ and a second axis a ２ .

[0034] The first axis a １ and the second axis a ２ lie within a plane including the reflection surface 20A when the mirror unit 20 is stationary. The planar shape of the MMD 4 is rectangular, and is line-symmetric with respect to the first axis a １ and line-symmetric with respect to the second axis a ２ .

[0035] The first support portions 21 are each disposed at positions facing each other on the outer side of the mirror unit 20 across the second axis a ２ therebetween. The first support portion 21 extends along the first axis a １It is connected to the mirror section 20 above, and the mirror section 20 is connected to the first axis a １ It is supported so as to be able to swing around. In this embodiment, the first support part 21 is the first axis a １ It is a torsion bar that extends along the curve.

[0036] The first movable frame 22 is a rectangular frame surrounding the mirror portion 20, and the first axis a １ It is connected to the mirror section 20 via the first support section 21 above. The first axis a is located on the first movable frame 22. １ Two piezoelectric elements 30 are formed at opposing positions, with the first movable frame 22 in between. In this way, the first actuator 31 is constructed by forming two piezoelectric elements 30 on the first movable frame 22.

[0037] The two piezoelectric elements 30 constituting the first actuator 31 are located on the first axis a １ They are positioned opposite each other, with the first axis a in between. The first actuator 31 is located on the mirror portion 20, along the first axis a １ By applying rotational torque to the surrounding area, the mirror portion 20 is moved to the first axis a １ To shake it around.

[0038] The second support part 23 is located outside the first movable frame 22, with the first axis a １ They are positioned opposite each other, with the second support portion 23 on the second axis a ２ It is connected to the first movable frame 22 above, and the first movable frame 22 and the mirror part 20 are connected to the second axis a ２ It is supported so as to be able to swing around. In this embodiment, the second support part 23 is the second axis a ２ It is a torsion bar that extends along the curve.

[0039] The second movable frame 24 is a rectangular frame surrounding the first movable frame 22, and the second axis a ２ It is connected to the first movable frame 22 via the second support part 23 above. The second shaft a is located on the second movable frame 24. ２ Two piezoelectric elements 30 are formed at opposing positions, with the second movable frame 24 in between. In this way, the second actuator 32 is constructed by forming two piezoelectric elements 30 on the second movable frame 24.

[0040] The two piezoelectric elements 30 that constitute the second actuator 32 are located on the second axis a ２ The second actuator 32 is positioned opposite each other, with the mirror portion 20 and the first movable frame 22 on the second axis a ２ By applying rotational torque around the second shaft a ２ The mirror section 20 is oscillated around it.

[0041] The connecting portion 25 is located on the outside of the second movable frame 24, with the first axis a １ They are positioned opposite each other, with the second axis a in between. The connecting part 25 is located on the second axis a ２ It is connected to the second movable frame 24 above.

[0042] The fixed frame 26 is a rectangular frame surrounding the second movable frame 24, and the second axis a ２ It is connected to the second movable frame 24 via the connection part 25 above.

[0043] Furthermore, the first movable frame 22 is provided with a first angle sensor 11A near the first support portion 21. The first angle sensor 11A is located on the first axis a １ It is composed of two piezoelectric elements 12 positioned opposite each other with respect to the mirror portion 20. Each of the piezoelectric elements 12 is on the first axis a of the mirror portion 20 １ The force applied due to the deformation of the first support portion 21 accompanying the rotation is converted into a voltage and a signal is output. In other words, the first angle sensor 11A controls the first axis a of the mirror portion 20. １ It outputs a signal that corresponds to the surrounding angle.

[0044] Furthermore, the second movable frame 24 is provided with a second angle sensor 11B near the second support portion 23. The second angle sensor 11B is located on the second axis a ２ It is composed of two piezoelectric elements 13 positioned opposite each other across the mirror portion 20. Each of the piezoelectric elements 13 is on the second axis a of the mirror portion 20 ２ The force applied due to the deformation of the second support portion 23 accompanying the rotation is converted into a voltage and a signal is output. In other words, the second angle sensor 11B controls the second axis a of the mirror portion 20. ２ It outputs a signal that corresponds to the surrounding angle.

[0045] In Figure 2, the wiring and electrode pads for supplying drive signals to the first actuator 31 and the second actuator 32 are omitted from the illustration. Similarly, in Figure 2, the wiring and electrode pads for outputting signals from the first angle sensor 11A and the second angle sensor 11B are also omitted from the illustration. Multiple electrode pads are provided on the fixed frame 26.

[0046] First axis a of the mirror section 20 １ The surrounding oscillation amplitude (hereinafter referred to as the first oscillation amplitude) A １ This is controlled by a drive signal (hereinafter referred to as the first drive signal) that the drive control device 5 applies to the first actuator 31. The first drive signal is a drive voltage waveform V applied to one of the two piezoelectric elements 30 that constitute the first actuator 31. １Ａ (t) and the drive voltage waveform V applied to the other side １Ｂ (t) and the drive voltage waveform V １Ａ (t) and drive voltage waveform V １Ｂ (t) are in opposite phases to each other (i.e., phase difference of 180°).

[0047] Note that the first oscillation amplitude A １ This is the maximum angle at which the normal of the reflective surface 20A is inclined with respect to the Z direction in the XZ plane.

[0048] Second axis a of the mirror section 20 ２ The surrounding oscillation amplitude (hereinafter referred to as the second oscillation amplitude) A ２ This is controlled by a drive signal (hereinafter referred to as the second drive signal) that the drive control device 5 applies to the second actuator 32. The second drive signal is a drive voltage waveform V applied to one of the two piezoelectric elements 30 that constitute the second actuator 32. ２Ａ (t) and the drive voltage waveform V applied to the other side ２Ｂ (t) and the drive voltage waveform V ２Ａ (t) and drive voltage waveform V ２Ｂ (t) are in opposite phases to each other (i.e., phase difference of 180°).

[0049] Note that the second oscillation amplitude A ２ This is the maximum angle at which the normal of the reflective surface 20A is inclined with respect to the Z direction in the YZ plane.

[0050] FIG. 3 shows an example of a first drive signal and a second drive signal. (A) of FIG. 3 shows a drive voltage waveform V included in the first drive signal １Ａ (t) and V １Ｂ (t). (B) of FIG. 3 shows a drive voltage waveform V included in the second drive signal ２Ａ (t) and V ２Ｂ (t).

[0051] The drive voltage waveforms V １Ａ (t) and V １Ｂ (t) are respectively expressed as follows. V １Ａ (t) = V ｏｆｆ１ + V １ sin(2πf ｄ１ t) V １Ｂ (t) = V ｏｆｆ１ + V １ sin(2πf ｄ１ t + α)

[0052] Here, V １ is an amplitude voltage. V ｏｆｆ１ is a bias voltage. V ｏｆｆ１ may be zero. f ｄ１ is a first frequency. t is time. α is the phase difference between the drive voltage waveforms V １Ａ (t) and V １Ｂ (t). In the present embodiment, for example, α = 180°.

[0053] When the drive voltage waveforms V １Ａ (t) and V １Ｂ (t) are applied to the two piezoelectric elements 30 constituting the first actuator 31, the mirror section 20 swings about the first axis a ｄ１ at the first frequency f １ .

[0054] The drive voltage waveforms V ２Ａ (t) and V ２Ｂ (t) are respectively expressed as follows. V ２Ａ (t) = V ｏｆｆ２ + V ２ sin(2πf ｄ２ t + φ) V ２Ｂ (t) = V ｏｆｆ２ + V ２ sin(2πf ｄ２t + β + φ)

[0055] Here, V ２ is an amplitude voltage. V ｏｆｆ２ is a bias voltage. V ｏｆｆ２ may be zero. f ｄ２ is the second frequency. t is time. β is a phase difference between driving voltage waveforms V ２Ａ (t) and V ２Ｂ (t). In the present embodiment, for example, β = 180°. Further, φ is a phase difference between a first driving signal and a second driving signal.

[0056] When the driving voltage waveforms V ２Ａ (t) and V ２Ｂ (t) are applied to the two piezoelectric elements constituting the second actuator 32, the mirror portion 20 swings around the second axis a ｄ２ at the second frequency f ２ .

[0057] The first frequency f ｄ１ is set so as to match a resonance frequency when the mirror portion 20 is swung around the first axis a １ . The second frequency f ｄ２ is set so as to match a resonance frequency when the mirror portion 20 is swung around the second axis a ２ . In the present embodiment, f ｄ１ > f ｄ２ is satisfied. That is, for the mirror portion 20, a swing frequency around the first axis a １ is higher than a swing frequency around the second axis a ２ . Note that the first frequency f ｄ１ and the second frequency f ｄ２ do not necessarily need to match the resonance frequencies. For example, the first frequency f ｄ１ and the second frequency f ｄ２ may each be a frequency within a frequency range near the resonance frequency. Examples of this frequency range include a half-width range of a frequency distribution having the resonance frequency as a peak value, and also include, for example, a range within a so-called Q value.

[0058] Figure 4 shows an example of the configuration of the drive control device 5. The drive control device 5 includes a mirror drive device 4A and a light source drive device 3A. The mirror drive device 4A includes a first basic signal generation unit 40A, a second basic signal generation unit 40B, a first signal output unit 41A, a second signal output unit 41B, a first signal processing unit 42A, a second signal processing unit 42B, a first reference signal generation unit 43A, a second reference signal generation unit 43B, a DDS (Direct Digital Synthesizer) control unit 44, and an oscillator 45.

[0059] The first basic signal generation unit 40A, the second basic signal generation unit 40B, the first reference signal generation unit 43A, the second reference signal generation unit 43B, and the DDS control unit 44 are each digital circuits, and are composed of, for example, FPGA (Field Programmable Gate Array) circuits 46. The oscillator 45 generates and supplies a system clock signal CLK (hereinafter simply referred to as the clock signal CLK) to each part of the system including the FPGA circuit 46.

[0060] The first basic signal generation unit 40A and the second basic signal generation unit 40B are each composed of DDS. The first basic signal generation unit 40A generates a sinusoidal first basic signal BS1 based on the clock signal CLK. The second basic signal generation unit 40B generates a sinusoidal second basic signal BS2 based on the clock signal CLK.

[0061] The first signal output unit 41A outputs the above-mentioned drive voltage waveform V based on the first basic signal BS1. １Ａ (t) and V １Ｂ A first drive signal including (t) is generated and output to the first actuator 31. As a result, the mirror unit 20 controls the first axis a １ It sways around.

[0062] The second signal output unit 41B outputs the above-mentioned drive voltage waveform V based on the second basic signal BS2. ２Ａ (t) and V ２Ｂ A second drive signal including (t) is generated and output to the second actuator 32. As a result, the mirror unit 20 controls the second axis a ２ It sways around.

[0063] The first drive signal and the second drive signal are defined as the drive voltage waveform V included in the second drive signal. ２Ａ (t) and V ２Ｂ As shown by φ in the equation for (t), the phase is synchronized.

[0064] The first signal processing unit 42A generates a binarized first sensor signal by processing the output signal from the first angle sensor 11A. The second signal processing unit 42B generates a binarized second sensor signal by processing the output signal from the second angle sensor 11B.

[0065] The first reference signal generation unit 43A generates the first axis a of the mirror unit 20 based on the first sensor signal. １ A first reference signal ZC1 is generated and output, indicating the timing when the surrounding angle becomes the first reference angle. In this embodiment, the first reference angle is 0°, and the first reference signal ZC1 is a so-called zero-crossing signal.

[0066] The second reference signal generation unit 43B generates the second axis a of the mirror unit 20 based on the second sensor signal. ２ A second reference signal ZC2 is generated and output, indicating the timing when the surrounding angle becomes the second reference angle. In this embodiment, the second reference angle is 0°, and the second reference signal ZC2 is a so-called zero-crossing signal.

[0067] The first reference signal ZC1 and the second reference signal ZC2 are supplied to the DDS control unit 44 and the light source drive device 3A.

[0068] The DDS control unit 44 controls the first basic signal generation unit 40A and the second basic signal generation unit 40B. For example, the DDS control unit 44 sets the tuning word value (described later), adjusts the cumulative value of the phase accumulator (also called the counter value), and resets the phase accumulator. In this embodiment, the DDS control unit 44 performs PL (Phase Lock) control, which is a control that maintains the phase difference between the first drive signal and the second drive signal at a target phase difference.

[0069] Figure 5 shows the configuration of the first basic signal generation unit 40A and the second basic signal generation unit 40B. The first basic signal generation unit 40A is a DDS composed of a phase accumulator 50A and a waveform ROM (Read Only Memory) 51A.

[0070] The phase accumulator 50A operates between 0 and 2π radians. Ｎ This is an N-bit modulo N counter having n steps. N is the number of bits in the phase accumulator, for example, 64. The phase accumulator 50A has a first frequency f ｄ１ The corresponding tuning word value M1 is set. Specifically, the tuning word value M1 is set to satisfy the following equation. Here, f ｃ f is the frequency of the clock signal CLK. ｄ１ = f ｃ ×M1 / 2 Ｎ

[0071] The phase accumulator 50A accumulates a first phase amount Δ1 corresponding to the tuning word value M1 in synchronization with the clock signal CLK, and sequentially outputs the accumulated values ​​to the waveform ROM 51A. The phase accumulator 50A starts accumulating from 0, and when the accumulated value reaches 2π, it resets the accumulated value to 0 and starts accumulating again.

[0072] The first phase quantity Δ1 satisfies the following equation: Δ1 = 2π × M1 / 2 Ｎ

[0073] The waveform ROM 51A stores one period of sine wave data as reference wave data. The waveform ROM 51A receives the accumulated value from the phase accumulator 50A as its address. By reading the data from the beginning address (corresponding to 0) to the end address (corresponding to 2π) of the waveform ROM 51A, one period of the first fundamental signal BS1 is output.

[0074] The first signal output unit 41A includes a digital-to-analog converter (DAC) and a phase shift circuit. The DAC converts the first basic signal BS1 into an analog signal. The phase shift circuit shifts the phase of the first basic signal BS1 converted into an analog signal, thereby creating the drive voltage waveform V that constitutes the first drive signal described above. １Ａ(t) and V １Ｂ Generate (t).

[0075] The second basic signal generation unit 40B is a DDS composed of a phase accumulator 50B and a waveform ROM 51B.

[0076] The phase accumulator 50B operates between 0 and 2π radians. Ｎ It is an N-bit modulo N counter with a step of n. The phase accumulator 50B has a second frequency f ｄ２ The corresponding tuning word value M2 is set. Specifically, the tuning word value M2 is set to satisfy the following equation: f ｄ２ = f ｃ ×M2 / 2 Ｎ

[0077] The phase accumulator 50B, in synchronization with the clock signal CLK, accumulates a second phase amount Δ2 corresponding to the tuning word value M2, and sequentially outputs the accumulated values ​​to the waveform ROM 51B. The phase accumulator 50B starts accumulating from 0, and when the accumulated value reaches 2π, it resets the accumulated value to 0 and starts accumulating again.

[0078] The second phase quantity Δ2 satisfies the following equation: Δ2 = 2π × M² / 2 Ｎ

[0079] The waveform ROM 51B stores one period of sine wave data as reference wave data. The waveform ROM 51B receives the accumulated value from the phase accumulator 50B as its address. By reading the data from the beginning address to the end address of the waveform ROM 51B, one period of the second fundamental signal BS2 is output.

[0080] The second signal output section 41B includes a DAC and a phase shift circuit. The DAC converts the second fundamental signal BS2 into an analog signal. The phase shift circuit shifts the phase of the second fundamental signal BS2 converted into an analog signal, thereby creating the drive voltage waveform V that constitutes the second drive signal described above. ２Ａ (t) and V ２Ｂ Generate (t).

[0081] Figure 6 schematically shows the generation process of the first basic signal BS1 by the first basic signal generation unit 40A. Figure 6 shows a comparison between the case where M1 = 1 and the case where M1 = 3. The period T of the first basic signal BS1 changes as the first phase amount Δ1 changes according to the tuning word value M1. １ It changes. Period T １ is the first frequency f ｄ１ And, T １ = 1 / f ｄ１ The relationship is as follows. The same applies to the generation process of the second basic signal BS2 by the second basic signal generation unit 40B. The period T of the second basic signal BS2 ２ The second frequency f ｄ２ And, T ２ = 1 / f ｄ２ They have a relationship.

[0082] first frequency f ｄ１ and the second frequency f ｄ２ The frequency ratio H is set based on the density of the Lissajous pattern being scanned by light. First frequency f ｄ１ and the second frequency f ｄ２ These are two values ​​obtained by multiplying two relatively prime integers by an integer.

[0083] Specifically, the first frequency f ｄ１ and the second frequency f ｄ２ This is set by tuning word values ​​M1 and M2. If G is the greatest common divisor of tuning word value M1 and tuning word value M2, then the first frequency f satisfies the following equation. ｄ１ and the second frequency f ｄ２ The following is set: M1 × Q2 = M2 × Q1

[0084] 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.

[0085] As shown in Figure 7, the period T of the first drive signal １ The period of Q1 and the period T of the second drive signal. ２ The period of Q2 coincides. This period is the duration of one frame FT of the moving image being drawn.

[0086] Figure 8 shows an example of the output signal of the first angle sensor 11A. In Figure 8, S1a １ and S1a ２ The mirror portion 20 is on the second axis a ２ Without causing any movement around it, the first axis a １ This represents the signal output from the two piezoelectric elements 12 when they are oscillated only in the rotational direction. Signal S1a １ S1a ２ is the first frequency f ｄ１ These are waveform signals that approximate a sine wave, and are in opposite phase to each other.

[0087] The mirror section 20 is on the first axis a １ and second axis a ２ If it is simultaneously oscillated around it, signal S1a １ S1a ２ The second axis a of the mirror section 20 ２ Vibration noise RN1, caused by surrounding fluctuations, is superimposed. S1b １ This is signal S1a １ This represents a signal with vibration noise RN1 superimposed. S1b ２ This is signal S1a ２ This represents a signal with vibration noise RN1 superimposed on it. In the example shown in Figure 8, the vibration noise RN1 is emphasized for the purpose of explaining this embodiment.

[0088] Figure 9 shows an example of the output signal of the second angle sensor 11B. In Figure 9, S2a １ and S2a ２ The mirror portion 20 is on the first axis a １ Without causing any movement around it, the second axis a ２ This represents the signal output from the two piezoelectric elements 13 when they are oscillated only in the rotational direction. Signal S2a １ S2a ２ The second frequency f ｄ２ These are waveform signals that approximate a sine wave, and are in opposite phase to each other.

[0089] The mirror section 20 is on the first axis a １ and second axis a ２ If it is simultaneously oscillated around it, signal S2a １ S2a ２ The first axis a of the mirror section 20１ Vibration noise RN2, caused by surrounding oscillations, is superimposed. S2b １ This is signal S2a １ This represents a signal with vibration noise RN2 superimposed. S2b ２ This is signal S2a ２ This represents a signal with vibration noise RN2 superimposed on it. In the example shown in Figure 9, the vibration noise RN2 is emphasized for the purpose of explaining this embodiment.

[0090] Figure 10 conceptually illustrates the signal processing by the first signal processing unit 42A. The first signal processing unit 42A processes signal S1b １ From signal S1b ２ The first sensor signal S1c is generated by subtracting from signal S1b. １ This corresponds to a signal with twice the amplitude of the signal from which vibration noise RN1 has been removed.

[0091] First axis a of the mirror section 20 １ If the surrounding oscillations maintain a resonant state, ideally the first sensor signal S1c will have a 90° phase delay relative to the first drive signal.

[0092] Furthermore, the first signal processing unit 42A binarizes the first sensor signal S1c using a comparator to obtain a rectangular waveform. For example, the first signal output unit 41A binarizes the first sensor signal S1c using 0V as the comparison voltage.

[0093] Figure 11 conceptually illustrates the signal processing by the second signal processing unit 42B. The second signal processing unit 42B processes signal S2b １ Signal S2b ２ The second sensor signal S2c is generated by subtracting from signal S2b. １ This corresponds to a signal with twice the amplitude of the signal from which vibration noise RN2 has been removed.

[0094] Second axis a of the mirror section 20 ２ If the surrounding oscillations maintain a resonant state, ideally the second sensor signal S2c will have a 90° phase delay relative to the second drive signal.

[0095] Furthermore, the second signal processing unit 42B binarizes the second sensor signal S2c using a comparator to obtain a rectangular waveform. For example, the second signal output unit 41B binarizes the second sensor signal S2c using 0V as the comparison voltage.

[0096] The first signal processing unit 42A and the second signal processing unit 42B input the binarized first sensor signal S1c and second sensor signal S2c to the first reference signal generation unit 43A and the second reference signal generation unit 43B, respectively. This is because the first reference signal generation unit 43A and the second reference signal generation unit 43B are digital circuits and cannot process analog signals.

[0097] The first sensor signal S1c before binarization is ideally a sine wave, but it is often not a smooth sine wave. This is because, in the processing by the first signal processing unit 42A, the second axis a of the mirror unit 20 ２ This is because the influence of surrounding fluctuations cannot be completely eliminated. Similarly, the second sensor signal S2c before binarization is ideally a sine wave, but the first axis a of the mirror unit 20 １ Because the effects of surrounding fluctuations remain, the resulting waveform is often not a smooth sine wave.

[0098] As known in Japanese Patent Publication No. 2023-143439, the timing at which the second sensor signal S2c crosses zero is actually the second axis a of the mirror unit 20. ２ The timing is slightly off from when the surrounding angle becomes 0°. As a result, the first timing when the second sensor signal S2c crosses zero is actually off from the second axis a of the mirror unit 20. ２ In some cases, the timing may shift both before and after the second timing, when the surrounding angle becomes 0°. In this case, within one frame period (FT), the total amount of shift when the first timing is before the second timing will be approximately equal to the total amount of shift when it is after the second timing.

[0099] In this embodiment, the first reference signal generation unit 43A calculates the phase delay time of the first sensor signal S1c with respect to the first drive signal within one frame period FT (hereinafter referred to as "first phase delay time") for one period T. １By measuring and accumulating each value and calculating the average of the accumulated values, the second axis a of the mirror section 20 is determined. ２ The influence of surrounding oscillations is reduced. Specifically, the first reference signal generation unit 43A measures the phase delay time of the first sensor signal S1c with respect to the first basic signal BS1, which is the source of the first drive signal, as the first phase delay time. The first basic signal BS1 is an example of the "first reference signal corresponding to the first drive signal" according to the technology of this disclosure. The first reference signal may also be the first drive signal.

[0100] Similarly, the second reference signal generation unit 43B calculates the phase delay time of the second sensor signal S2c with respect to the second drive signal within one frame period FT (hereinafter referred to as "second phase delay time") for one period T. ２ By measuring and accumulating each value and calculating the average of the accumulated values, the first axis a of the mirror section 20 is determined. １ The influence of surrounding oscillations is reduced. Specifically, the second reference signal generation unit 43B measures the phase delay time of the second sensor signal S2c with respect to the second basic signal BS2, which is the source of the second drive signal, as the second phase delay time. The second basic signal BS2 is an example of a "second reference signal corresponding to the second drive signal" according to the technology of this disclosure. The second reference signal may be the second drive signal.

[0101] As shown in Figure 12, the first reference signal generation unit 43A calculates a first integrated value by accumulating the first phase delay time n times, which corresponds to the number of times equivalent to one frame period FT. n is an integer of 1 or more, and in this embodiment, n = 1.

[0102] The number of times the first phase delay time is accumulated within one frame period FT is Q1 as described above. In the example shown in Figure 12, the first phase delay time is C ｉ (where i is an integer from 1 to Q1) is used to represent this. In the example shown in Figure 12, the difference between the rising edge timing of the first basic signal BS1 and the rising edge timing of the first sensor signal S1c is measured, but the difference between the falling edge timing of the first basic signal BS1 and the falling edge timing of the first sensor signal S1c may also be measured.

[0103] Furthermore, the first reference signal generation unit 43A calculates the first average phase delay time CA1, which is the average value of the first phase delay time, by dividing the first integrated value by the number of integrations. Then, the first reference signal generation unit 43A generates the first reference signal ZC1 based on the first average phase delay time CA1.

[0104] Specifically, as shown in Figure 13, the first reference signal generation unit 43A generates the first drive signal for the first axis a of the mirror unit 20. １ The point in time (V in this embodiment) indicates that the surrounding angle has become the first reference angle. ｏｆｆ１ A first reference signal ZC1 is generated and output to the light source drive device 3A when the first average phase delay time CA1 has elapsed from the point in time when the signal crosses the line.

[0105] As shown in Figure 14, the second reference signal generation unit 43B calculates the second integrated value by accumulating the second phase delay time n times, which corresponds to the number of times equivalent to one frame period FT. n is an integer of 1 or more, and in this embodiment, n = 1.

[0106] The number of times the second phase delay time is accumulated within one frame period FT is Q2 as described above. In the example shown in Figure 14, the second phase delay time is C ｊ (where j is an integer from 1 to Q2) is used to represent this. In the example shown in Figure 14, the difference between the rising edge timing of the second basic signal BS2 and the rising edge timing of the second sensor signal S2c is measured, but the difference between the falling edge timing of the second basic signal BS2 and the falling edge timing of the second sensor signal S2c may also be measured.

[0107] Furthermore, the second reference signal generation unit 43B calculates the second average phase delay time CA2, which is the average value of the second phase delay time, by dividing the second integrated value by the number of integrations. Then, the second reference signal generation unit 43B generates the second reference signal ZC2 based on the second average phase delay time CA2.

[0108] Specifically, as shown in Figure 15, the second reference signal generation unit 43B generates the second drive signal for the second axis a of the mirror unit 20. ２ The point in time (V in this embodiment) indicates that the surrounding angle has become the second reference angle. ｏｆｆ２A second reference signal ZC2 is generated and output to the light source drive device 3A when the second average phase delay time CA2 has elapsed from the point in time when the signal crosses the line.

[0109] Furthermore, the DDS control unit 44 adjusts the timing of the first drive signal based on the first average phase delay time CA1 and adjusts the timing of the second drive signal based on the second average phase delay time CA2. Specifically, the DDS control unit 44 calculates the phase difference (corresponding to the first average phase delay time CA1) between the timing at which the cumulative value of the phase accumulator 50A reaches a reference value (e.g., 0) and the rising edge timing of the first sensor signal S1c, and corrects the tuning word value M1 or the cumulative value based on the calculated phase difference. Similarly, the DDS control unit 44 calculates the phase difference (corresponding to the second average phase delay time CA2) between the timing at which the cumulative value of the phase accumulator 50B reaches a reference value (e.g., 0) and the rising edge timing of the second sensor signal S2c, and corrects the tuning word value M2 or the cumulative value based on the calculated phase difference. This improves the synchronization accuracy between the first drive signal, the second drive signal, and the oscillation of the mirror unit 20.

[0110] Furthermore, the DDS control unit 44 performs the PL control described above based on the first reference signal ZC1 and the second reference signal ZC2. This PL control will be described later.

[0111] Next, with reference to Figures 16 and 17, the method for measuring the first phase delay time by the first reference signal generation unit 43A will be described in detail. In this embodiment, the first reference signal generation unit 43A measures the first phase delay time using both the rising and falling timings of the clock signal CLK.

[0112] Specifically, as shown in Figures 16 and 17, the first reference signal generation unit 43A measures the rising edge timing of the first sensor signal S1c using both the rising edge timing and the falling edge timing of the clock signal CLK. Specifically, it detects the rising edge of the first sensor signal S1c using a comparator at the rising edge timing and falling edge timing of the clock signal CLK. Next, the first reference signal generation unit 43A counts the number of clock cycles from the rising edge timing of the first basic signal BS1 to the measured rising edge timing of the first sensor signal S1c.

[0113] Furthermore, since the first basic signal BS1 is a digital signal generated based on the clock signal CLK, its timing is known in advance and does not need to be measured. When the first reference signal is used as the first drive signal, the first drive signal can be binarized, and the rising edge timing of the first drive signal can be measured using both the rising and falling edge timings of the clock signal CLK.

[0114] In Figures 16 and 17, NC1 is the number of clocks counted using the rising edge timing of the clock signal CLK (hereinafter referred to as the first clock count), and NC2 is the number of clocks counted using the falling edge timing of the clock signal CLK (hereinafter referred to as the second clock count).

[0115] The first reference signal generation unit 43A calculates the first phase delay time based on the first clock number NC1 and the second clock number NC2. As shown in Figure 16, when the first clock number NC1 and the second clock number NC2 are the same, the first phase delay time is calculated based on the first clock number NC1. Specifically, the first phase delay time is the time obtained by multiplying the first clock number NC1 by the clock period. On the other hand, as shown in Figure 17, when the first clock number NC1 and the second clock number NC2 are different, the first phase delay time is calculated based on the value obtained by subtracting 1 / 2 from the larger first clock number NC1. Specifically, the first phase delay time is the time obtained by multiplying the value obtained by subtracting 1 / 2 from the larger first clock number NC1 by the clock period. Here, 1 / 2 of one clock corresponds to half a period of the clock signal CLK.

[0116] If the rising edge timing of the first sensor signal S1c is measured using only the rising edge timing of the clock signal CLK, the measured value will be the same in both the cases shown in Figure 16 and Figure 17. In contrast, as in this embodiment, by measuring using both the rising and falling edge timings of the clock signal CLK, it is possible to double the measurement accuracy.

[0117] Similarly, the second reference signal generation unit 43B measures the second phase delay time using both the rising and falling timings of the clock signal CLK. The detailed processing is the same as that of the first reference signal generation unit 43A, so the explanation is omitted.

[0118] By using both the rising and falling edges of the clock signal CLK in this way, it is possible to determine the phase delay time with high accuracy without increasing power consumption.

[0119] Furthermore, this allows for highly accurate determination of the phase delay time, enabling a more precise understanding of the mirror's oscillation state and reducing synchronization errors with the drive signal. This allows for more precise control of the light irradiation timing, suppressing deviations in the drawing position and enabling high-definition rendering with less image distortion and blur. In addition, the reduced error in the phase delay time minimizes variations between frames, improving the stability and image quality of moving images.

[0120] Next, with reference to Figure 18, the PL control by the DDS control unit 44 will be explained. In PL control, the phase difference PDT between the first sensor signal S1 and the second sensor signal S2 is adjusted. This phase difference PDT is the phase difference to be adjusted, which is obtained by the following formula: PDT = PD2 + PD3 - PD1

[0121] Here, PD1 is the phase difference between the first basic signal BS1 and the second sensor signal S2, that is, the phase difference between the first drive signal and the first sensor signal S1. The phase difference PD1 is equal to the first phase delay time C ｉAlternatively, it corresponds to the first average phase delay time CA1. Furthermore, PD2 is the phase difference between the second basic signal BS2 and the second sensor signal S2, i.e., the phase difference between the second drive signal and the second sensor signal S2. The phase difference PD2 corresponds to the second phase delay time C ｊ Alternatively, it corresponds to the second mean phase delay time CA2.

[0122] Furthermore, PD3 is the phase difference between the first fundamental signal BS1 and the second fundamental signal BS2, that is, the phase difference between the first drive signal and the second drive signal. The phase difference PD3 is a known value determined by the Lissajous pattern being drawn. First frequency f ｄ１ and the second frequency f ｄ２ Because they are different, the phase difference PD3 changes over time within the FT period of one frame.

[0123] The DDS control unit 44 adjusts the phase difference PD3 so that the phase difference PDT is maintained at the target phase difference. The phase difference PDT corresponds to the time difference between the first reference signal ZC1 and the second reference signal ZC2. That is, the phase difference PDT corresponds to the first phase delay time C ｉ and the second phase delay time C ｊ The value obtained from these, more specifically, is the value calculated from the first average phase delay time CA1 and the second average phase delay time CA2. Note that the target phase difference data is stored in memory (not shown).

[0124] The DDS control unit 44 adjusts the phase of the first basic signal BS1, i.e., the phase of the first drive signal, in order to adjust the phase difference PD3. Alternatively, the phase of the second basic signal BS2, i.e., the phase of the second drive signal, may also be adjusted in order to adjust the phase difference PD3. The phase of the first basic signal BS1 is adjusted by correcting it by adding or subtracting the accumulated value of the phase accumulator 50A. The phase of the second basic signal BS2 is adjusted by correcting it by adding or subtracting the accumulated value of the phase accumulator 50B.

[0125] Figure 19 shows an example of the processing flow in PL control. First, the DDS control unit 44 obtains the first reference signal ZC1 and the second reference signal ZC2 from the first reference signal generation unit 43A and the second reference signal generation unit 43B (step S10). Next, the DDS control unit 44 calculates the phase difference PDT between the first sensor signal S1 and the second sensor signal S2 based on the time difference between the first reference signal ZC1 and the second reference signal ZC2 (step S11).

[0126] Next, the DDS control unit 44 obtains the target phase difference from memory (step S12) and calculates an adjustment amount representing the difference between the obtained target phase difference and the calculated phase difference PDT (step S13). Then, the DDS control unit 44 adjusts the phase of, for example, the first drive signal based on the calculated adjustment amount (step S14). As a result, the phase difference PDT approaches the target phase difference. The DDS control unit 44 has previously obtained the current setting value of the phase difference PD3 and adjusts the phase of at least one of the first drive signal and the second drive signal based on this setting value.

[0127] In this embodiment, the first reference signal ZC1 and the second reference signal ZC2 are generated using the first average phase delay time CA1 and the second average phase delay time CA2. As described above, the first average phase delay time CA1 and the second average phase delay time CA2 are obtained for each frame period FT, so the DDS control unit 44 performs phase adjustment by PL control for each frame period FT. For example, as shown in Figure 20, the DDS control unit 44 performs phase adjustment by PL control at the timing when the drawing trajectory coincides with the center C of the Lissajous waveform.

[0128] As described above, in this embodiment, PL control is performed to adjust the phase of at least one of the first drive signal and the second drive signal so that the phase difference PDT between the first sensor signal S1 and the second sensor signal S2 approaches the target phase difference. This suppresses fluctuations between frames in the drawing trajectory of the moving image being drawn, thereby suppressing degradation of image quality. Furthermore, in this embodiment, the phase difference PDT between the first sensor signal S1 and the second sensor signal S2 is calculated using the first average phase delay time CA1 and the second average phase delay time CA2. This improves the accuracy of the calculation of the phase difference PDT and further suppresses degradation of image quality. Moreover, in this embodiment, as described above, the first phase delay time C is calculated using both the rising and falling timings of the clock signal CLK. ｉ and the second phase delay time C ｊ Because the values ​​are calculated with high precision, image quality degradation is further suppressed.

[0129] Next, a modified example of the above embodiment will be described. In the above embodiment, the first basic signal generation unit 40A generates a plurality of first phase delay times C included within the frame period FT for each frame period FT. １ ~C Ｑ１ The first average phase delay time CA1 is obtained by accumulating these values ​​and calculating the average of the accumulated values. Alternatively, as shown in Figure 21, the first basic signal generation unit 40A generates a new first phase delay time C ｉ Each time this is calculated, that is, one period T １ For each of these, multiple first phase delay times C １ ~C Ｑ１ The first average phase delay time CA1 may be obtained by accumulating these values ​​and calculating the average of the accumulated values. For example, a new first phase delay time C １ When calculated, the first phase delay time C used in the previous integration is １ ~C Ｑ１ Excluding the first phase delay time C １ In addition, multiple first phase delay times C １ ~C Ｑ１ This process, known as FIFO (First In First Out), is used to accumulate the results.

[0130] Similarly, in the above embodiment, the second basic signal generation unit 40B generates a plurality of second phase delay times C included within each frame period FT for each frame period FT. １ ~C Ｑ２ The second average phase delay time CA2 is obtained by accumulating these values ​​and calculating the average of the accumulated values. Alternatively, as shown in Figure 22, the second basic signal generation unit 40B generates a new second phase delay time C ｉ Each time this is calculated, that is, one period T ２ For each of these, multiple second phase delay times C １ ~C Ｑ２ The second mean phase delay time CA2 can also be obtained by accumulating these values ​​and calculating the average of the accumulated values. For example, a new second phase delay time C １ When this is calculated, the second phase delay time C used in the previous integration is used. １ ~C Ｑ２ Excluding the first phase delay time, a new second phase delay time C is defined. １ In addition, multiple second phase delay times C １ ~C Ｑ２ This process involves accumulating the values, known as FIFO processing.

[0131] This improves the accuracy of the first reference signal ZC1 and the second reference signal ZC2. Furthermore, in this case, the DDS control unit 44 can perform phase adjustment by PL control multiple times within one frame period FT. For example, the DDS control unit 44 performs phase adjustment by PL control each time a new first average phase delay time CA1 and a second average phase delay time CA2 are obtained, that is, each time a new first reference signal ZC1 and a second reference signal ZC2 are obtained. As a result, fluctuations in the phase difference are quickly corrected, so disturbances in the drawing trajectory are suppressed and image quality degradation is further reduced.

[0132] Note that the configuration of MMD4 shown in the above embodiment is just one example. The configuration of MMD4 can be modified in various ways. For example, the mirror portion 20 can be positioned along the first axis a １ The first actuator 31 that causes the surrounding oscillation is positioned on the second movable frame 24, and the mirror section 20 is on the second axis a ２ A second actuator 32 that causes the surrounding area to oscillate may be placed on the first movable frame 22.

[0133] Furthermore, in the above embodiment, the first angle sensor 11A is the first axis a １ It is composed of two piezoelectric elements 12 positioned opposite each other across the first axis a １ It may also consist of a single piezoelectric element 12 located in the vicinity of the second axis a. Similarly, in the above embodiment, the second angle sensor 11B is located on the second axis a ２ It is composed of two piezoelectric elements 13 positioned opposite each other across the second axis a ２ It may also consist of a single piezoelectric element 13 located in the vicinity of it.

[0134] The hardware configuration of the drive control device 5 can be modified in various ways. The drive control device 5 may consist of a single processor, or it may consist of a combination of two or more processors of the same or different types. Processors include a CPU (Central Processing Unit), a Programmable Logic Device (PLD), and dedicated electrical circuits. 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 whose circuit configuration can be changed after manufacturing, such as an FPGA. A dedicated electrical circuit is a processor with a circuit configuration specifically designed to execute a particular process, such as an ASIC (Application Specific Integrated Circuit).

[0135] The following technology can be understood from the above description. [Note 1] An optical scanning device comprising: a mirror portion that reflects incident light; a first actuator that swings the mirror portion around a first axis; a second actuator that swings the mirror portion around a second axis intersecting the first axis; a first angle sensor that outputs a signal corresponding to the angle of the mirror portion around the first axis; a second angle sensor that outputs a signal corresponding to the angle of the mirror portion around the second axis; and a processor, wherein the processor provides the first actuator with a first drive signal having a first frequency; provides the second actuator with a second drive signal having a second frequency; calculates an adjustable phase difference which is the phase difference between the output signal of the first angle sensor with respect to a first reference signal corresponding to the first drive signal and the output signal of the second angle sensor with respect to a second reference signal corresponding to the second drive signal; and adjusts the phase of at least one of the first drive signal and the second drive signal based on the difference between the adjustable phase difference and the target phase difference. [Note 2] The optical scanning apparatus according to Note 1, wherein the processor calculates the phase difference to be adjusted based on the first phase delay time of the output signal of the first angle sensor and the second phase delay time of the output signal of the second angle sensor. [Note 3] The optical scanning apparatus according to Note 2, wherein the processor measures the first phase delay time and the second phase delay time using both the rising edge timing and the falling edge timing of the clock signal. [Note 4] The optical scanning apparatus according to Note 3, wherein the processor calculates each of the first phase delay time and the second phase delay time based on the first number of clocks measured using the rising edge timing of the clock signal and the second number of clocks measured using the falling edge timing of the clock signal. [Note 5] The optical scanning apparatus according to Note 4, wherein if the first number of clocks and the second number of clocks are the same, the processor calculates based on the first number of clocks, and if the first number of clocks and the second number of clocks are different, the processor calculates based on the larger number of clocks minus 1 / 2.[Note 6] The optical scanning apparatus according to any one of Notes 2 to 5, wherein the processor calculates a first integrated value by accumulating the first phase delay time a number of times that is an integer multiple of the number of times corresponding to the duration of one frame of the moving image to be drawn, and calculates a second integrated value by accumulating the second phase delay time a number of times that is an integer multiple of the number of times corresponding to the duration of one frame. [Note 7] The optical scanning apparatus according to Note 6, wherein the processor calculates the first integrated value after binarizing the output signal of the first angle sensor, and calculates the second integrated value after binarizing the output signal of the second angle sensor. [Note 8] The optical scanning apparatus according to Note 6 or Note 7, wherein the processor calculates a first average phase delay time, which is the average value of the first phase delay time, by dividing the first integrated value by the number of integrations; calculates a second average phase delay time, which is the average value of the second phase delay time, by dividing the second integrated value by the number of integrations; generates a first reference signal indicating that the angle around the first axis of the mirror portion has become the first reference angle when the first average phase delay time has elapsed from the time the first drive signal indicates that the angle around the second axis of the mirror portion has become the second reference angle when the second average phase delay time has elapsed from the time the second drive signal indicates that the angle around the second axis of the mirror portion has become the second reference angle. [Note 9] The optical scanning apparatus according to Note 8, wherein the first reference angle and the second reference angle are zero. [Addendum 10] The optical scanning apparatus according to Addendum 8 or Addendum 9, wherein the processor calculates the phase difference to be adjusted based on the time difference between the first reference signal and the second reference signal. [Addendum 11] The optical scanning apparatus according to any one of Addendum 8 to Addendum 10, wherein the processor calculates the first average phase delay time each time a new first phase delay time is acquired by FIFO processing, and calculates the second average phase delay time each time a new second phase delay time is acquired.[Note 12] The optical scanning device according to any one of Note 1 to Note 11, wherein the first reference signal is the first drive signal and the second reference signal is the second drive signal. [Note 13] The optical scanning device according to any one of Note 1 to Note 12, wherein the first frequency and the second frequency are two values ​​obtained by integer multiples of two relatively prime integers.

Claims

1. An optical scanning device comprising: a mirror portion that reflects incident light; a first actuator that swings the mirror portion around a first axis; a second actuator that swings the mirror portion around a second axis intersecting the first axis; a first angle sensor that outputs a signal corresponding to the angle of the mirror portion around the first axis; a second angle sensor that outputs a signal corresponding to the angle of the mirror portion around the second axis; and a processor, wherein the processor applies a first drive signal having a first frequency to the first actuator, applies a second drive signal having a second frequency to the second actuator, calculates an adjustment target phase difference which is the phase difference between the output signal of the first angle sensor with respect to a first reference signal corresponding to the first drive signal and the output signal of the second angle sensor with respect to a second reference signal corresponding to the second drive signal, and adjusts the phase of at least one of the first drive signal and the second drive signal based on the difference between the adjustment target phase difference and the target phase difference.

2. The optical scanning apparatus according to claim 1, wherein the processor calculates the phase difference to be adjusted based on the first phase delay time of the output signal of the first angle sensor and the second phase delay time of the output signal of the second angle sensor.

3. The optical scanning apparatus according to claim 2, wherein the processor measures the first phase delay time and the second phase delay time using both the rising edge timing and the falling edge timing of the clock signal.

4. The optical scanning apparatus according to claim 3, wherein the processor calculates each of the first phase delay time and the second phase delay time based on a first number of clocks measured using the rising edge timing of the clock signal and a second number of clocks measured using the falling edge timing of the clock signal.

5. The optical scanning apparatus according to claim 4, wherein the processor calculates based on the first clock number if the first clock number and the second clock number are the same, and calculates based on a value obtained by subtracting 1 / 2 from the larger clock number if the first clock number and the second clock number are different.

6. The optical scanning apparatus according to any one of claims 2 to 5, wherein the processor calculates a first integrated value by accumulating the first phase delay time a number of times that is an integer multiple of the number of times corresponding to one frame period of the moving image to be drawn, and calculates a second integrated value by accumulating the second phase delay time a number of times that is an integer multiple of the number of times corresponding to one frame period.

7. The optical scanning apparatus according to claim 6, wherein the processor calculates the first integrated value after binarizing the output signal of the first angle sensor, and calculates the second integrated value after binarizing the output signal of the second angle sensor.

8. The optical scanning apparatus according to claim 6, wherein the processor calculates a first average phase delay time, which is the average value of the first phase delay time, by dividing the first integrated value by the number of integrations; calculates a second average phase delay time, which is the average value of the second phase delay time, by dividing the second integrated value by the number of integrations; generates a first reference signal indicating that the angle around the first axis of the mirror portion has become the first reference angle when the first average phase delay time has elapsed from the time the first drive signal indicates that the angle around the second axis of the mirror portion has become the second reference angle when the second average phase delay time has elapsed from the time the second drive signal indicates that the angle around the second axis of the mirror portion has become the second reference angle.

9. The optical scanning apparatus according to claim 8, wherein the first reference angle and the second reference angle are zero.

10. The optical scanning apparatus according to claim 8, wherein the processor calculates the phase difference to be adjusted based on the time difference between the first reference signal and the second reference signal.

11. The optical scanning apparatus according to claim 8, wherein the processor calculates the first average phase delay time each time a new first phase delay time is obtained by FIFO processing, and calculates the second average phase delay time each time a new second phase delay time is obtained.

12. The optical scanning apparatus according to claim 1, wherein the first reference signal is the first drive signal and the second reference signal is the second drive signal.

13. The optical scanning apparatus according to claim 1, wherein the first frequency and the second frequency are two values ​​obtained by integer multiples of two relatively prime integers, respectively.

14. A method for driving an optical scanning device comprising: a mirror portion that reflects incident light; a first actuator that swings the mirror portion around a first axis; a second actuator that swings the mirror portion around a second axis intersecting the first axis; a first angle sensor that outputs a signal corresponding to the angle of the mirror portion around the first axis; and a second angle sensor that outputs a signal corresponding to the angle of the mirror portion around the second axis, wherein the method involves applying a first drive signal having a first frequency to the first actuator, applying a second drive signal having a second frequency to the second actuator, calculating an adjustment target phase difference which is the phase difference between the output signal of the first angle sensor with respect to a first reference signal corresponding to the first drive signal and the output signal of the second angle sensor with respect to a second reference signal corresponding to the second drive signal, and adjusting the phase of at least one of the first drive signal and the second drive signal based on the difference between the adjustment target phase difference and the target phase difference.

15. An image drawing system comprising: an optical scanning device according to claim 1; and a light source for irradiating the mirror portion with light.

Images