Optical deflector drive device, optical deflector drive method, optical scanning device

Abstract

To detect malfunctions in optical deflectors with greater precision. [Solution] A device for driving an optical polarizer equipped with a mirror, comprising: a controller for controlling the operation of the mirror; a driver that outputs a first drive signal to the optical polarizer for resonantly driving the mirror on the first axis and a second drive signal for non-resonantly driving the mirror on the second axis based on data output from the controller; and a sensor processing unit for acquiring a sensor signal output from the mirror, wherein the controller determines the phase difference between the first drive signal and the sensor signal, determines that the operation of the optical polarizer is normal if the phase difference with respect to the phase of the second drive signal at the time the phase difference is determined to be within a predetermined range, and determines that the operation of the optical polarizer is abnormal if the phase difference is not within the predetermined range.

Description

Technical Field

[0001] The present disclosure relates to a driving device for an optical deflector, a driving method for an optical deflector, and an optical scanning device.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2021-117273 (Patent Document 1) discloses a control unit that generates a resonance drive signal for resonantly driving a mirror of an optical deflector and a non-resonance drive signal for non-resonantly driving the mirror, a resonance sensor that detects the resonant drive of the mirror and generates a resonance sensor signal, and a signal processing unit that obtains the phase difference between the resonance drive signal generated by the control unit and the resonance sensor signal when the mirror is scanned by resonant drive and non-resonant drive. An illumination device configured to determine whether the amplitude of the non-resonance drive signal is normal (i.e., detect an operation abnormality) based on the phase difference is described.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One of the objectives of the specific aspect according to the present disclosure is to provide a technology that enables more accurate detection of operation abnormalities of an optical deflector.

Means for Solving the Problems

[0005] [1] A driving device for an optical deflector according to an aspect of the present disclosure is a device for driving an optical deflector including a mirror that rotates about each of a first axis and a second axis, a controller for controlling the operation of the mirror, A driver connected to the controller outputs to the optical deflector a first drive signal for resonantly driving the mirror on the first axis and a second drive signal for non-resonantly driving the mirror on the second axis, based on data output from the controller. A sensor processing unit connected to the controller for acquiring sensor signals output from the mirror, Includes, The controller determines the phase difference between the first drive signal and the sensor signal, and determines that the operation of the optical polarizer is normal if the phase difference with respect to the phase of the second drive signal at the time the phase difference is determined to fall within a predetermined range, and determines that the operation of the optical polarizer is abnormal if the phase difference does not fall within the predetermined range. This is the drive mechanism for the optical deflector. [2] A method for driving an optical deflector according to one embodiment of the present disclosure is: A method for driving an optical deflector equipped with mirrors that rotate in each of the first and second axes, A first drive signal is provided to the mirror to cause it to resonantly drive on the first axis, and a second drive signal is provided to cause it to non-resonantly drive on the second axis. To acquire the sensor signal output from the aforementioned mirror, This includes determining the phase difference between the first drive signal and the sensor signal, determining that the operation of the optical polarizer is normal if the phase difference with respect to the phase of the second drive signal at the time the phase difference is determined falls within a predetermined range, and determining that the operation of the optical polarizer is abnormal if the phase difference does not fall within the predetermined range. This is a method for driving an optical deflector. [3] A drive device for an optical deflector according to one embodiment of the present disclosure is The drive device described in [1] above, The optical deflector connected to the drive unit, It is an optical scanning device that includes [a specific component].

[0006] The above configuration provides a technology that enables more precise detection of malfunctions in the optical deflector. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows a schematic configuration of an optical scanning device according to one embodiment. [Figure 2] Figure 2 is a schematic diagram showing an example of the configuration of an optical deflector. [Figure 3] Figure 3 is a diagram illustrating the timing of phase difference acquisition. [Figure 4] Figures 4(A) to 4(D) are diagrams illustrating the principle for determining whether or not there is an operational abnormality. [Figure 5] Figure 5(A) is a diagram illustrating an example of a certain range. Figure 5(B) is a diagram illustrating another example of a certain range. [Figure 6] Figure 6 is a flowchart showing the operation procedure of the controller in the drive unit. [Modes for carrying out the invention]

[0008] Figure 1 is a diagram showing the schematic configuration of an optical scanning device according to one embodiment. The optical scanning device 100 of this embodiment is for scanning light such as laser light incident from a light source, and is composed of a drive unit 1 and an optical deflector 2. The drive unit 1 is connected to the optical deflector 2 and controls the operation of the optical deflector 2. The optical deflector 2 has a rotatable mirror, and the direction of light reflection can be freely changed by causing light such as laser light to be incident on this mirror. The optical scanning device 100 according to this embodiment can be used, for example, to configure an image projection device (projector) that forms an image on a screen by scanning laser light incident from a light source (not shown) in two directions (H direction and V direction).

[0009] The drive device 1 is configured to include a controller 10, a driver 14, a sensor processing unit 15, and a memory 16. The controller 10 controls the overall operation of the drive device 1 and has a drive signal generation unit 11, an arithmetic unit 12, and an abnormality determination unit 13 as functional blocks. Each functional block in the controller 10 can be realized by, for example, executing a predetermined program in a microcomputer.

[0010] The drive signal generation unit 11 generates data (drive data) for generating a drive signal and supplies the drive data to the driver 14. The drive data includes at least data for generating each of the horizontal drive signal and the vertical drive signal, and hereinafter, each is referred to as "horizontal drive data" and "vertical drive data".

[0011] The arithmetic unit 12 acquires horizontal drive data from the drive signal generation unit 11 and acquires digital data (hereinafter referred to as "sensor data") of the sensor signal output from the sensor processing unit 15, and based on these, calculates the phase difference between the horizontal drive signal and the sensor signal.

[0012] The abnormality determination unit 13 acquires data indicating the amplitude and phase of the vertical drive signal from the drive signal generation unit 11 and acquires data indicating the phase difference between the horizontal drive signal and the sensor signal from the arithmetic unit 12, and determines the presence or absence of an operation abnormality of the optical deflector 2 based on these amplitude, phase, and phase difference. Data indicating the presence or absence of an operation abnormality is stored in the memory 16.

[0013] The driver 14 mainly performs processes such as performing digital-to-analog conversion on the horizontal drive data and the vertical drive data output from the drive signal generation unit 11 and amplifying them to the drive voltage level of the optical deflector 2, thereby generating the horizontal drive signal and the vertical drive signal. Further, these signals are output to the optical deflector 2.

[0014] The sensor processing unit 15 amplifies the sensor signal output from the optical deflector 2 to an appropriate voltage level suitable for mainly performing analog-digital conversion, and then performs analog-digital conversion to convert it into sensor data which is digital data. The sensor data is output to the arithmetic unit 12 of the controller 10.

[0015] The memory 16 stores data indicating the determination result of the presence or absence of an operation abnormality by the abnormality determination unit 13. Also, the memory 16 can store data necessary for the abnormality determination in the abnormality determination unit 13.

[0016] FIG. 2 is a schematic diagram showing a configuration example of an optical deflector. The illustrated optical deflector 2 mainly includes a mirror 30, first actuators 31, 32, second actuators 33, 34, and sensors 35, 36. The mirror 20 has a reflecting surface for reflecting incident light, and is configured to be rotatable about two axes of the X-axis and Y-axis shown in the figure. The first actuators 31, 32 generate a driving force for rotating the mirror 30 about the Y-axis. The second actuators 33, 34 generate a driving force for rotating the mirror 30 about the X-axis. As each of the first actuators 31, 32, and the second actuators 33, 34, for example, piezoelectric, electrostatic, or electromagnetic actuators can be used. The displacement amounts of each of the first actuators 31, 32, and the second actuators 33, 34 are detected by the sensors 35, 36.

[0017] FIG. 3 is a diagram for exemplifying the acquisition timing of the phase difference. Here, a trajectory L when scanning light on the screen is schematically shown. The vertical direction in the figure corresponds to the V direction, and the horizontal direction corresponds to the H direction. In the illustrated example, within one cycle of the scanning period in the V direction, the phase difference is acquired at three timings: a timing T1 close to the start of the scanning period, an intermediate timing T2, and a timing T3 close to the end of the scanning period. Note that these are just examples, and the number of times the phase difference is acquired within one cycle may be increased or decreased.

[0018] Figures 4(A) to 4(D) are diagrams illustrating the principle for determining the presence or absence of operational abnormalities. In detail, from top to bottom, Figure 4(A) is a waveform diagram of the horizontal drive signal, Figure 4(B) is a waveform diagram of the sensor signal, Figure 4(C) is a diagram showing the correspondence between phase θ and the vertical drive signal, and Figure 4(D) is a diagram showing the correspondence between phase θn and phase difference φn. The temporal relative relationships of each of these figures are shown using dotted lines in a format similar to a timing chart.

[0019] The horizontal drive signal illustrated in Figure 4(A) is a sinusoidal signal with a predetermined period. When the optical deflector 2 is operated by this horizontal drive signal, the sensor signal becomes a sinusoidal signal with approximately the same period as the horizontal drive signal, as illustrated in Figure 4(B). The three black dots shown on the waveform in Figure 4(A) represent the respective time periods T1 to T3 shown in Figure 3 above. As can be seen from the comparison between Figure 4(A) and Figure 4(B), a phase difference occurs between the horizontal drive signal and the sensor signal. The phase differences φn in each time period T1, T2, and T3 are denoted as φ1, φ2, and φ3, respectively.

[0020] As shown in Figure 4(C), the relationship between the amplitude (the magnitude of the vertical drive signal) and the phase θn is not constant at each time point T1 to T3. Therefore, as shown in Figure 4(D), the phase difference φn can vary not only with respect to the amplitude A of the vertical drive signal but also with respect to the phase θn of the vertical drive signal. When the optical deflector 2 is driven, the tilt of the vertical drive is usually controlled linearly, but the rigidity of the horizontal resonance movement around the mirror 30 during this process changes depending on the tilt of the vertical drive.

[0021] Therefore, as shown in Figure 4(D), if the phase difference φn with respect to the phase θn falls within a predetermined range, it can be determined that there is no operational abnormality; if it falls outside this range, it can be determined that there is an operational abnormality. This predetermined range can be determined in advance, for example, by methods such as experiments or simulations.

[0022] Figure 5(A) is a diagram illustrating an example of a certain range. The range between the upper and lower limits, which are shown by thick lines in the figure (indicated by patterns in the figure), can be defined as a certain range. In this case, the upper and lower limits are predetermined based on experiments or simulations, for example. Alternatively, as illustrated in Figure 5(B), an approximate straight line or curve may be determined based on multiple data of phase θn and phase difference φn obtained in advance through experiments, etc., and the upper and lower limits of the threshold can be determined by changing the intercept based on this approximate curve, etc., and the range between these upper and lower limits (indicated by patterns in the figure) can be defined as a certain range. Data for identifying the certain range is stored in memory 16 in advance, read by the anomaly determination unit 13, and used for determination.

[0023] Figure 6 is a flowchart showing the operation procedure of the controller in the drive unit. Note that the order of the processes shown here can be changed as long as it does not cause inconsistencies or contradictions in the results of the information processing, and it is also possible to add other processes that are not explicitly shown here.

[0024] The controller 10 starts driving the mirror 20 of the optical deflector 2 (step S11). Specifically, the drive signal generation unit 11 generates horizontal drive data and vertical drive data, which are input to the driver 14. Based on this data, the driver 14 inputs horizontal drive signals and vertical drive signals to the optical deflector 2, thereby driving the mirror 30. Here, with the mirror 30 resonantly driven in the main scanning direction (Y-axis direction), non-resonant driving in the sub-scanning direction (X-axis direction) is then started.

[0025] The calculation unit 12 of the controller 10 calculates the phase difference for each scanning period of the Y-axis, which is the resonant axis (step S12). Specifically, the calculation unit 12 calculates the phase difference between the digital data of the sensor signal input from the sensor processing unit 15 and the horizontal drive data (digital data of the horizontal drive signal) input from the drive signal generation unit 11.

[0026] Next, the calculation unit 12 of the controller 10 determines whether the resonant drive state is stable or not (step S13). Specifically, the calculation unit 12 determines whether the resonant drive state is stable or not based on the amplitude change and elapsed time of the sensor signal acquired by the calculation unit 12. If the resonant drive state is not stable (step S13; NO), the process returns to step S12.

[0027] If the resonant drive state is stable (step S13; YES), the abnormality determination unit 13 determines whether the phase difference obtained in step S12 falls within a certain range set based on the amplitude and phase of the vertical drive signal, that is, whether it is within the acceptable range. If it is within the acceptable range (step S14; YES), the abnormality determination unit 13 stores data indicating "no operational abnormality (normal)" in the memory 16. Then, the process returns to step S12 and the subsequent processing is repeated.

[0028] If the phase difference is outside the acceptable range (step S14: NO), the abnormality determination unit 13 performs a predetermined abnormality processing (step S15). Specifically, the abnormality determination unit 13 stores data indicating "abnormal operation" in the memory 16. The abnormality determination unit 13 may also output a signal or data indicating an abnormal operation to a higher-level device (not shown), or it may instruct the drive signal generation unit 11 to stop driving the optical deflector.

[0029] According to the above embodiment, it becomes possible to detect malfunctions in the optical deflector with greater precision.

[0030] This disclosure is not limited to the embodiments described above, and can be implemented in various modified forms within the scope of the gist of this disclosure. For example, the specific structure of the optical deflector to be controlled is not limited to that illustrated in Figure 2 above.

[0031] Furthermore, the setting of the specified range described above may be calculated each time from the amplitude and phase fluctuations of the vertical drive signal. More specifically, for example, data showing the relationship between amplitude and phase can be obtained for each phase period of the vertical drive signal (for example, the period from θ1 to θ2, the period from θ2 to θ3, and the period from θ3 to θ4 as shown in the figure), and based on this data, linear approximation or the like can be performed (see Figure 5(B)), and based on the obtained approximation formula, the specified range can be determined by setting the upper and lower limits of the threshold as, for example, a range of ±10%. In this case, a step to determine the specified range should be added between step S13 and step S14 in the flowchart described above (see Figure 6).

[0032] This disclosure has the following features:

[0033] (Note 1) A device for driving an optical deflector equipped with mirrors that rotate in each of the first and second axes, A controller for controlling the operation of the aforementioned mirror, A driver connected to the controller outputs to the optical deflector a first drive signal for resonantly driving the mirror on the first axis and a second drive signal for non-resonantly driving the mirror on the second axis, based on data output from the controller. A sensor processing unit connected to the controller for acquiring sensor signals output from the mirror, Includes, The controller determines the phase difference between the first drive signal and the sensor signal, and determines that the operation of the optical polarizer is normal if the phase difference with respect to the phase of the second drive signal at the time the phase difference is determined to fall within a predetermined range, and determines that the operation of the optical polarizer is abnormal if the phase difference does not fall within the predetermined range. A drive mechanism for an optical deflector. (Note 2) The controller is connected to a memory that has pre-stored determination data capable of identifying a certain range, The controller identifies the certain range by reading the determination data from the memory. The drive device for the optical deflector described in Appendix 1. (Note 3) The controller writes determination result data indicating whether the operation of the optical deflector is normal or abnormal to the memory. The drive device for the optical deflector described in Appendix 2. (Note 4) The first drive signal is a horizontal drive signal, and the second drive signal is a vertical drive signal. A drive device for the optical deflector described in any of the appendices 1 to 3. (Note 5) The controller determines whether the operation of the optical deflector is normal or abnormal when the resonant drive state of the optical deflector is stable. A drive device for the optical deflector described in any of the appendices 1 to 4. (Note 6) A method for driving an optical deflector equipped with mirrors that rotate in each of the first and second axes, A first drive signal is provided to the mirror to cause it to resonantly drive on the first axis, and a second drive signal is provided to cause it to non-resonantly drive on the second axis. To acquire the sensor signal output from the aforementioned mirror, This includes determining the phase difference between the first drive signal and the sensor signal, determining that the operation of the optical polarizer is normal if the phase difference with respect to the phase of the second drive signal at the time the phase difference is determined falls within a predetermined range, and determining that the operation of the optical polarizer is abnormal if the phase difference does not fall within the predetermined range. A method for driving an optical deflector. (Note 7) The drive unit described in any of the appendices 1 to 5, The optical deflector connected to the drive unit, An optical scanning device, including one. [Explanation of Symbols]

[0034] 1: Drive unit, 2: Optical deflector 2, 10: Controller, 11: Drive signal generation unit, 12: Calculation unit, 13: Anomaly detection unit, 14: Driver, 15: Sensor processing unit, 16: Memory

Claims

1. A device for driving an optical deflector equipped with mirrors that rotate on each of the first and second axes, A controller for controlling the operation of the aforementioned mirror, A driver connected to the controller outputs to the optical deflector a first drive signal for resonantly driving the mirror on the first axis and a second drive signal for non-resonantly driving the mirror on the second axis, based on data output from the controller. A sensor processing unit connected to the controller for acquiring sensor signals output from the mirror, Includes, The controller determines the phase difference between the first drive signal and the sensor signal, and determines that the operation of the optical polarizer is normal if the phase difference with respect to the phase of the second drive signal at the time the phase difference is determined to fall within a predetermined range, and determines that the operation of the optical polarizer is abnormal if the phase difference does not fall within the predetermined range. A drive mechanism for an optical deflector.

2. The controller is connected to a memory that has pre-stored determination data capable of identifying a certain range, The controller identifies the certain range by reading the determination data from the memory. A drive device for an optical deflector according to claim 1.

3. The controller writes determination result data indicating whether the operation of the optical deflector is normal or abnormal to the memory. A drive device for an optical deflector according to claim 2.

4. The first drive signal is a horizontal drive signal, and the second drive signal is a vertical drive signal. A drive device for an optical deflector according to claim 1.

5. The controller determines whether the operation of the optical deflector is normal or abnormal when the resonant drive state of the optical deflector is stable. A drive device for an optical deflector according to claim 1.

6. A method for driving an optical deflector equipped with mirrors that rotate on a first axis and a second axis, A first drive signal is provided to the mirror to cause it to resonantly drive on the first axis, and a second drive signal is provided to cause it to non-resonantly drive on the second axis. To acquire the sensor signal output from the aforementioned mirror, This includes determining the phase difference between the first drive signal and the sensor signal, determining that the operation of the optical polarizer is normal if the phase difference with respect to the phase of the second drive signal at the time the phase difference is determined falls within a predetermined range, and determining that the operation of the optical polarizer is abnormal if the phase difference does not fall within the predetermined range. A method for driving an optical deflector.

7. The drive device according to claim 1, The optical deflector connected to the drive unit, An optical scanning device, including one.

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