Control device for optical deflector, control method for optical deflector, and projection system

Abstract

The present invention facilitates identification of the cause of an operation abnormality in a system comprising an optical deflector.　Provided is an abnormality detection method implemented by a control device in a system comprising an optical deflector provided with a mirror having a resonant axis and a non-resonant axis, and a control device that is connected to the optical deflector, the abnormality detection method comprising: (a) detecting an abnormality relating to driving of the mirror on the basis of a sensor signal output from the optical deflector in a state in which the resonant axis of the mirror is driven and the non-resonant axis is not driven; and (b) detecting, after (a), an abnormality relating to driving of the mirror on the basis of a sensor signal output from the optical deflector in a state in which both the resonant axis and the non-resonant axis of the mirror are driven.

Description

Control device for optical deflector, control method for optical deflector, projection system

[0001] The present disclosure relates to a control device for an optical deflector, a control method for an optical deflector, and a projection system.

[0002] Japanese Patent Application Laid-Open No. 2021-117273 (Patent Document 1) describes an illumination device including an optical deflector. This illumination device projects an image by scanning laser light emitted from a semiconductor light source onto a screen using the optical deflector.

[0003] By the way, generally, such a device is provided with a configuration for detecting an abnormal operation. As causes of the abnormal operation, various causes such as, for example, a failure of the optical deflector and a failure of a circuit for driving the optical deflector can be considered. However, conventionally, it has been difficult to specify the cause (location where the abnormality occurs) of the abnormal operation.

[0004] Japanese Patent Application Laid-Open No. 2021-117273

[0005] One of the objects of the specific aspect according to the present disclosure is to provide a technology that makes it easy to specify the cause of an abnormal operation in a system including an optical deflector.

[0006] [1] An anomaly detection method according to one embodiment of the present disclosure is an anomaly detection method performed by a control device in a system comprising an optical deflector having a mirror having a resonant axis and a non-resonant axis and a control device connected to the optical deflector, the method comprising: (a) detecting an anomaly related to the driving of the mirror based on a sensor signal output from the optical deflector while the resonant axis of the mirror is driven and the non-resonant axis is not driven; and (b) detecting an anomaly related to the driving of the mirror based on the sensor signal output from the optical deflector while both the resonant axis and the non-resonant axis of the mirror are driven, after (a). [2] A control device according to one aspect of the present disclosure is a control device used in connection with an optical deflector having a mirror having a resonant axis and a non-resonant axis, comprising: a controller; a resonant drive signal generation unit that supplies a resonant drive signal to the optical deflector for driving the resonant axis of the mirror based on data provided by the controller; a non-resonant drive signal generation unit that supplies a non-resonant drive signal to the optical deflector for driving the non-resonant axis of the mirror based on data provided by the controller; and a resonant sensor signal processing unit that calculates the phase difference between the resonant drive signal and the sensor signal and the amplitude of the sensor signal based on a sensor signal acquired from the optical deflector and supplies the phase difference and amplitude to the controller, wherein the controller (a) detects an abnormality related to the driving of the mirror based on the sensor signal output from the optical deflector in a state in which the resonant axis of the mirror is driven and the non-resonant axis is not driven, (b) A control device for an optical deflector that, after (a), detects an abnormality related to the driving of the mirror based on the sensor signal output from the optical deflector while both the resonant axis and the non-resonant axis of the mirror are driven. [3] An optical scanning system according to one embodiment of the present disclosure is an optical scanning system comprising the control device of [1] and an optical deflector controlled by the control device.

[0007] The above configuration makes it easier to identify the cause of malfunctions in systems equipped with optical deflectors.

[0008] Figure 1 is a diagram showing the overall configuration of a projection system according to one embodiment. Figure 2 is a block diagram illustrating the detailed configuration of the system control unit. Figure 3 is a diagram conceptually illustrating the driving state and projection state of the optical deflector 30 in the projection system 100. Figure 4 is a flowchart showing the overall flow of the abnormality detection process performed in the control unit. Figure 5 is a flowchart showing the processing content of step S3 in detail. Figure 6 is a flowchart showing the processing content of step S4 in detail. Figure 7 is a graph showing an example of the correspondence between the phase difference of the resonant drive signal and the resonant sensor signal and the phase of the non-resonant drive signal. Figure 8(A) is a graph showing an example of the waveform of the non-resonant axis drive signal with the phase of the non-resonant axis drive signal on the horizontal axis, and the change in the phase difference between the resonant drive signal and the resonant sensor signal with the same phase on the horizontal axis. Figure 8(B) is a diagram schematically showing the relationship between the movement of each even-numbered and odd-numbered torsion bar and the movement of the mirror. Figure 9(A) shows an example of the correspondence between the phase difference of the non-resonant axis drive signal and the voltage value of the non-resonant axis drive signal when the phase of the non-resonant axis drive signal is at a certain value, for odd-numbered sets of torsion bars. Figure 9(B) shows an example of the correspondence between the phase difference of the non-resonant axis drive signal and the voltage value of the non-resonant axis drive signal when the phase of the non-resonant axis drive signal is at a certain value, for even-numbered sets of torsion bars. Figure 10 is a flowchart that shows the processing details of step S5.

[0009] Figure 1 shows the overall configuration of an image projection system according to one embodiment. The illustrated image projection system 100 projects an image onto a screen S by scanning light, and includes a control device 10, a laser light source 20, and an optical deflector 30.

[0010] The control device 10 controls the operation of the laser light source 20 and the optical deflector 30 in order to project an image onto the screen S. This control device 10 can be realized by combining a computer system equipped with, for example, a CPU, ROM, RAM, etc., which can perform various functions by executing an operating program, with various digital circuits.

[0011] To make the functions of the control device 10 easier to understand, the control device 10 will be explained using functional blocks. The control device 10 is composed of a system control unit 11, a light source drive unit 12, a resonant drive signal generation unit 13, a non-resonant drive signal generation unit 14, and a resonant sensor signal processing unit 15.

[0012] The system control unit 11 is a controller that controls the overall operation of the control device 10. Specifically, the system control unit 11 generates image data by performing predetermined information processing on image signals input from an external device (e.g., a personal computer) and supplies it to the light source drive unit 12.

[0013] Furthermore, the system control unit 11 receives a resonant sensor signal, which is a sensor signal corresponding to the deflection angle (i.e., fluctuation) of the optical deflector 30, from the optical deflector 30, calculates the phase difference with the resonant drive signal based on this resonant sensor signal, and monitors the abnormal state of the resonant drive signal, resonant sensor signal, and non-resonant drive signal based on this phase difference.

[0014] If the system control unit 11 detects an abnormality in the optical deflector 30 or other abnormalities (such as a temperature anomaly), it outputs an abnormality detection signal to forcibly stop the operation of the light source drive unit 12 and the optical deflector 30 (for example, by cutting off the power supply). The system control unit 11 also outputs a resonant drive signal and a non-resonant drive signal to the optical deflector 30.

[0015] The light source drive unit 12 controls the operation of the laser light source 20. Specifically, the light source drive unit 12 converts image data (digital signals) supplied from the system control unit 11 into analog signals and outputs them to the laser light source 20. The light source drive unit 12 also performs control such as overcurrent prevention.

[0016] The resonant drive signal generation unit 13 primarily converts the resonant drive signal data (digital signal) supplied from the system control unit 11 into an analog signal, performs processing such as increasing the voltage to the magnitude required to drive the optical deflector 30 (amplification), and outputs it to the optical deflector 30.

[0017] The non-resonant drive signal generation unit 14 mainly converts the non-resonant drive signal data (digital signal) supplied from the system control unit 11 into an analog signal, performs processing such as increasing the voltage to the size required to drive the optical deflector 30 (amplifying it), and outputs it to the optical deflector 30.

[0018] The resonance sensor signal processing unit 15 primarily acquires the resonance sensor signal from the optical deflector 30, converts it into digital data (digital signal), and outputs it to the system control unit 11.

[0019] The laser light source 20 is a semiconductor light source such as a laser diode, and is controlled by a control signal supplied from the light source drive unit 12 of the control device 10 to output laser light to the optical deflector 30.

[0020] The optical deflector 30 is, for example, a MEMS device equipped with mirrors, which projects light incident from the laser light source 20 onto the screen S by reflecting and scanning it. The optical deflector 30 is controlled by a resonant drive signal for the horizontal axis direction (H axis direction) and by a non-resonant drive signal for the vertical axis direction (V axis direction). The optical deflector 30 also outputs a voltage that changes according to the deflection angle in the horizontal axis direction as a resonant sensor signal to the control device 10.

[0021] Figure 2 is a block diagram illustrating the detailed configuration (function) of the system control unit. The system control unit 11 in this embodiment is composed of an overall control block 50, an image processing block 51, a light source control block 52, a first processing block 53, a second processing block 54, a third processing block 55, a test block 56, enable circuits 60-63, and selectors 64 and 65.

[0022] The overall control block 50 controls the entire system control unit 11. Specifically, the overall control block 50 outputs setting parameters for generating resonant drive signal data to the first processing block 53 and setting parameters for generating non-resonant drive signal data to the second processing block 54. The overall control block 50 also receives control signals and error signals from the first processing block 53, the second processing block 54, and the third processing block 55, and stores their values ​​as registers. Furthermore, if the overall control block 50 receives an error signal, it outputs the error signal to the outside.

[0023] The image processing block 51 generates image data based on an image signal input from an external source and scanning position information from the optical deflector 30. The scanning position information is output from the first processing block 53 and the second processing block 54, respectively.

[0024] The light source control block 52 performs interface control for outputting image data to the light source drive unit 12, specifically by performing operation timing conversion and data conversion, and outputs image data for driving the light source to the light source drive unit 12.

[0025] The first processing block 53 is a functional block that processes resonant drive signal data. Specifically, the first processing block 53 generates resonant drive signal data (generally a sine wave) based on the resonant drive frequency and amplitude set by the overall control block 50. The first processing block 53 then outputs a digital-to-analog conversion request to the resonant drive signal generation unit 13 for outputting the resonant drive signal data to the optical deflector 30.

[0026] Furthermore, the first processing block 53 detects if the resonant drive frequency of the resonant drive signal deviates from a predetermined range and outputs a frequency abnormality signal to the overall control block 50. The predetermined range is determined in advance by the characteristics of the optical deflector 30 and is set by a threshold value provided by the overall control block 50.

[0027] The second processing block 54 is a functional block that processes non-resonant drive signal data. Specifically, the second processing block 54 outputs non-resonant drive signal data (generally a sawtooth wave) based on the drive waveform, amplitude, and offset set by the overall control block 50. The second processing block 54 then outputs a digital-to-analog conversion request to the non-resonant drive signal generation unit 14 for outputting non-resonant drive signal data to the optical deflector 30.

[0028] The third processing block 55 is a functional block for processing resonance sensor signal data. Specifically, the third processing block 55 outputs an analog-to-digital conversion request (acquisition request) to the resonance sensor signal processing unit 15 for acquiring resonance sensor data. This analog-to-digital conversion request is made at regular intervals to periodically acquire resonance sensor data.

[0029] Furthermore, the third processing block 55 performs quadrature detection using the resonant drive signal and the resonant sensor signal to obtain the amplitude of the resonant sensor signal and the phase difference between the resonant drive signal and the resonant sensor signal. Quadrature detection is basically performed each time resonant sensor data is acquired (each time data acquisition by analog-to-digital conversion is completed), but it may also be performed every two or more times resonant sensor data is acquired. If the amplitude of the resonant sensor signal is smaller than a certain expected value, the third processing block 55 detects this as an abnormality and outputs an amplitude abnormality signal to the overall control block 50. The certain value is determined by the characteristics of the optical deflector 30 and is set based on a threshold value provided by the overall control block 50.

[0030] When the test block 56 receives a test mode command for abnormality detection from the overall control block 50, it performs processing to detect abnormalities in the control device 10 itself. Specifically, the test block 56 generates test data and test acquisition completion data used for abnormality detection and outputs them to selectors 64 and 65, respectively. Furthermore, if the test block 56 identifies the cause of the abnormality as being in the control device 10 as a result of the abnormality detection, it outputs an abnormality signal (test abnormality signal) to the overall control block 50.

[0031] The enable circuits 60-63 are digital circuits that can switch between a state in which input data is passed through and a state in which data indicating a predetermined value (for example, 0) is output without passing the input data. In test mode, the test is performed using the test data of the test block 56 itself as pseudo-data, so the predetermined value is set to a value that does not activate the optical deflector 30 or the laser light source 20 due to the output of data or signals from the control device 10.

[0032] The enable circuit 60 is connected between the light source control block 52 and the light source control unit 12. The enable circuit 60 switches between allowing the image data to pass through as is or outputting a predetermined value based on the control of the overall control block 50 (whether or not a test mode command is given).

[0033] The enable circuit 61 is connected between the first processing block 53 and the resonant drive signal generation unit 13. Based on the control of the overall control block 50 (whether or not a test mode command is given), the enable circuit 61 switches between passing the resonant drive signal data as is or outputting a predetermined value.

[0034] The enable circuit 62 is connected between the second processing block 54 and the non-resonant drive signal generation unit 14. Based on the control of the overall control block 50 (whether or not a test mode command is given), the enable circuit 62 switches between passing the non-resonant drive signal data as is or outputting a predetermined value.

[0035] The enable circuit 63 is connected between the third processing block 55 and the resonance sensor signal processing unit 15. Based on the control of the overall control block 50 (whether or not a test mode command is given), the enable circuit 63 switches between letting the data indicating the acquisition request output from the third processing block 55 pass through as is or outputting a predetermined value.

[0036] Selectors 64 and 65 are digital circuits capable of selectively passing one of multiple input data. Selectors 64 and 65 are connected between the resonance sensor signal processing unit 15 and the third processing block 55, respectively.

[0037] Based on the control of the overall control block 50 (whether or not a test mode command is given), the selector 64 selectively outputs either the resonance sensor signal data output from the resonance sensor signal generation unit 15 or the test resonance sensor signal data (pseudo-data) output from the test block 56 to the third processing block 55.

[0038] Based on the control of the overall control block 50 (whether or not a test mode command is given), the selector 65 selectively outputs to the third processing block 55 either data indicating completion of data acquisition output from the resonance sensor signal generation unit 15 or test acquisition completion data (pseudo-data) output from the test block 56.

[0039] Figure 3 is a schematic plan view showing an example of the configuration of an optical deflector. The optical deflector 30 is configured to be rotatable on two axes (the X-axis and Y-axis in the figure) and includes a mirror 70 that reflects light, and actuators 76, 77, 80, and 90 for driving the mirror 70. Actuators 76 and 77 generate a driving force to rotate the mirror 70 around the Y-axis. Actuators 80 and 90 generate a driving force to rotate the mirror 70 around the X-axis.

[0040] The actuator 80 is composed of seven interconnected torsion bars 81 to 87. Each torsion bar 81 to 87 is connected in a serpentine shape in plan view along the X-axis. For example, torsion bars 81 and 82 are connected relatively above each other in the figure, and torsion bars 82 and 83 are connected relatively below each other in the figure. The other torsion bars 83 to 87 are connected in a similar manner. The torsion bars 81 to 86 are configured so that the closer they are to the mirror 70, the longer they are in the vertical direction in the figure. Each torsion bar 81, etc., is wired (not shown) so that a separate drive voltage can be applied to the odd-numbered torsion bars 81, 83, 85, and 87, and the even-numbered torsion bars 82, 84, and 86, counting from the side closest to the mirror 70.

[0041] Similarly, the actuator 90 is configured to have seven interconnected torsion bars 91 to 97. Each torsion bar 91 to 97 is connected in a serpentine shape in plan view along the X-axis. For example, torsion bars 91 and 92 are connected relatively above each other in the figure, and torsion bars 92 and 93 are connected relatively below each other in the figure. The other torsion bars 93 to 97 are connected in the same manner. The torsion bars 91 to 96 are configured to be longer in the vertical direction in the figure the closer they are to the mirror 70. Each torsion bar 91, etc., is provided with wiring (not shown) that allows for the application of separate drive voltages to the odd-numbered torsion bars 91, 93, 95, and 97, and the even-numbered torsion bars 92, 94, and 96, counting from the side closest to the mirror 70.

[0042] Figure 4 is a flowchart showing the overall flow of the abnormality detection process performed in the control device. The control device 10 performs the abnormality detection process, outlined below, when the projection system 100 is powered on or at other appropriately set timings. The control device 10 continues to drive the optical deflector 30 if no abnormality is detected, and stops driving the optical deflector 30 if an abnormality is detected.

[0043] First, the control device 10 performs abnormality detection related to its own functions (step S1). Specifically, the control device 10 detects whether there are any abnormalities in the function of searching for the resonant frequency and the function of resonant feedback control. The control device 10 also detects whether these abnormality detection functions are operating normally. If there is an abnormality in any of the functions, it can be determined that some kind of failure / malfunction has occurred in the electronic circuits of the control device 10 itself.

[0044] Next, the control device 10 executes resonance frequency search (step S2). Specifically, the control device 10 variably sets the drive frequency of the resonance drive signal and searches for the frequency at which the resonance sensor signal becomes maximum. Then, the control device 10 specifies the frequency at which the resonance sensor signal becomes maximum as the resonance frequency. Here, the control device 10 operates the optical deflector 30 about the resonance axis (X-axis) and performs resonance frequency search without operating about the non-resonance axis (Y-axis). This is because if the non-resonance axis is operated, the resonance frequency fluctuates due to its amplitude and phase. The control device 10 records the phase difference between the resonance drive signal and the resonance sensor signal at this time (for example, stores it in a memory not shown). Also, during the period until this search period is completed, the phase difference and amplitude are observed, and it is confirmed that both the phase difference and amplitude are within the specified range. The specified range is defined from the resonance frequency search range, the clock frequency of the control device, and the like.

[0045] Next, the control device 10 executes abnormality detection of the resonance axis (step S3). Specifically, the control device 10 drives the resonance axis of the optical deflector 30 with the resonance drive signal based on the resonance frequency obtained in step S2. Then, the control device 10 respectively detects whether the amplitude of the resonance sensor signal is greater than or equal to a specified value, whether the phase difference between the resonance drive signal and the resonance sensor signal is within the specified range, and whether the resonance frequency is within the specified range. If any of the cases where the amplitude is not greater than the specified value, the phase difference is not within the specified range, or the resonance frequency is not within the specified range is detected, it can be specified that some failure / malfunction has occurred in the resonance axis of the optical deflector 30. Specifically, it can be specified that it is due to an abnormal operation of the actuator corresponding to the resonance axis of the optical deflector 30 or an abnormal operation of the resonance drive signal generation unit 13 in the control device 10.

[0046] Next, the control device 10 executes abnormality detection for the resonance axis and the non-resonance axis (step S4). Specifically, the control device 10 drives the resonance axis of the optical deflector 30 with a resonance drive signal having the resonance frequency obtained in step S2, and also drives the non-resonance axis with a non-resonance drive signal set as appropriate. Then, the control device 10 detects whether the amplitude of the resonance sensor signal is greater than or equal to a specified value, whether the phase difference between the resonance drive signal and the resonance sensor signal is within a specified range, and whether the resonance frequency is within a specified range. However, since the phase difference fluctuates because the non-resonance axis is also being driven, the specified range for detecting the normality of the phase difference is set to a range different from that in the case of step S3 and is a predetermined range.

[0047] When any one of the cases where the amplitude is not greater than or equal to the specified value, the phase difference is not within the specified range, or the resonance frequency is not within the specified range is detected, it can be specified that some kind of failure / malfunction has occurred in the non-resonance axis of the optical deflector 30. Since the abnormality detection of the resonance axis was executed in step S3 earlier, if no abnormality was detected in step S3, the abnormality detected in step S4 can be specified as being caused by the non-resonance axis. Specifically, it can be specified as being due to an abnormal operation of the actuator corresponding to the non-resonance axis of the optical deflector 30 or an abnormal operation of the non-resonance drive signal generation unit 14 in the control device 10.

[0048] Next, the control device 10 executes adjustment of the drive signal for the non-resonance axis (step S5). When the non-resonance axis is operated for one cycle, the phase difference between the resonance drive signal and the resonance sensor signal shifts with respect to the deflection angle of the mirror 70 by the odd-numbered torsion bars and the even-numbered torsion bars in the actuators 80 and 90 of the optical polarizer 30. Therefore, the magnitude of the voltage of the non-resonance drive signal can be adjusted (corrected) using this phenomenon (shift of the phase difference). Also, a failure determination can be made based on the shift of the phase difference.

[0049] Next, each of the above-described processes of steps S1, S3, S4, and S5 will be described in more detail.

[0050] (Processing details of step S1) In step S1, the system control unit 11 confirms the normality of its own function by internally looping a signal generated for testing without driving the optical deflector 30. Specifically, in the circuit shown in Figure 2, the overall control block 50 outputs a test mode signal to each enable circuit 60 to 63 and each selector 64, 65, thereby controlling each enable circuit 60 to 63 to output a predetermined value (for example, 0 data), and also controls each selector 64, 65 to receive data from the test block 56 instead of data from the resonance sensor signal processing unit 15.

[0051] Upon receiving a test mode command from the overall control block 50, the test block 56 sets a virtual resonant frequency and generates a test resonant drive signal (virtual resonant drive signal). The test block 56 also inputs a test resonant sensor signal (virtual sensor signal) for the resonant axis to the selector 65. The test block 56 virtually searches for the resonant frequency and observes the phase difference and amplitude during the search period. This creates a state similar to when the resonant frequency of the resonant drive signal is actually set and searched.

[0052] Furthermore, after the test block 56 transitions to a virtual resonance state in test mode, it checks the phase difference between the virtual resonance drive signal and the virtual sensor signal, and checks the amplitude of the virtual sensor signal. If all of these check results are within expectations, the control circuit is considered to be in a normal state and the next test is performed. If any of the results are unexpected, it is considered that there is a malfunction in the control circuit, and the test block 56 outputs test abnormality data to the overall control block 50.

[0053] Furthermore, test block 56 verifies the normality of the flag set. Test block 56 intentionally creates an abnormality in the control device using a virtual resonant drive signal and a virtual sensor signal, and verifies that the control device 10 correctly detects the abnormality when it occurs. Test block 56 also verifies the behavior when the search for the resonant frequency does not complete successfully. For example, by intentionally reducing the amplitude of the virtual sensor signal, it verifies that an amplitude abnormality from the third processing block 55 is output to the overall control block 50, and tests that the amplitude verification function of the resonant sensor signal in the control device 10 is functioning correctly.

[0054] If the test block 56 detects an "abnormality" as a result of the above, it does not output an abnormality signal to the overall control block 50. This is because a condition in which an "abnormality" occurs has been intentionally created, and this "abnormality" has been correctly detected, which is normal operation for the system control unit 11. On the other hand, if no "abnormality" is detected as a result of the above, it means that the detection of the "abnormality" has not been performed correctly, so it outputs test abnormality data indicating that the test result is "abnormal" to the overall control block 50.

[0055] Test block 56 also verifies the normality of abnormality detection related to the driving of the resonant axis, and abnormality detection related to the driving of both the resonant axis and the non-resonant axis. Specifically, test block 56 verifies the normality of the feedback control operation of the resonant frequency and makes abnormality judgments regarding amplitude and phase difference.

[0056] (Processing details of step S3) Figure 5 is a flowchart showing the processing details of step S3. The overall control block 50 sets the amplitude of the resonant axis by controlling the first processing block 53 (step S20). Resonant drive signal data is generated by the first processing block 53 under the control of the overall control block 50. This resonant drive signal data is output to the resonant drive signal generation unit 13 via the enable circuit 61, converted into an analog signal, the resonant drive signal, and output to the optical deflector 30, thereby starting the driving of the mirror 70 of the optical deflector 30 (step S21). At this stage, only the resonant axis is driven. The driving of the mirror 70 continues until the amplitude of the resonant axis reaches a specified value (step S22; NO).

[0057] When the amplitude of the resonant axis reaches a specified value (step S22; YES), the third processing block 55 calculates the phase difference between the resonant drive signal and the resonant sensor signal for each scanning period (step S23).

[0058] If the resonant drive state is not stable (step S24; NO), the overall control block 50 returns to step S23. If the resonant drive state is stable (step S24; YES), the overall control block 50 records the time information, drive information, and diagnostic information in a memory (not shown) (step S25). The determination of whether or not the resonant drive state is stable is made based on the amplitude change of the resonant sensor signal and the elapsed time.

[0059] If the phase difference output from the third processing block 55 is within the specified range and the amplitude of the resonance sensor signal output from the third processing block 55 is greater than or equal to the specified value (step S26; YES), the overall control block 50, if it wishes to continue the diagnosis further (step S27; YES), changes the setting value of the resonance axis amplitude (step S28) and returns to step 22. On the other hand, if it does not wish to continue the diagnosis (step S27; NO), it terminates the series of processes.

[0060] Furthermore, if the phase difference is not within the specified range or the amplitude is not equal to or greater than the specified value (step S26; NO), the overall control block 50 performs abnormality processing (step S29) and terminates the series of processes. Abnormality processing refers to, for example, outputting a signal or data indicating an abnormality to an external device (not shown) or stopping the drive of the optical deflector 30.

[0061] (Processing details of step S4) Figure 6 is a flowchart showing the processing details of step S4. The overall control block 50 sets the amplitude of the non-resonant axis by controlling the second processing block 54 (step S40). The second processing block 54, under the control of the overall control block 50, generates non-resonant drive signal data. This non-resonant drive signal data is output to the non-resonant drive signal generation unit 14 via the enable circuit 62, converted into an analog non-resonant drive signal, and output to the optical deflector 30. The amplitude of the resonant axis is set in step S20 or changed in step S28. As a result, the driving of the mirror 70 of the optical deflector 30 begins (step S41). Here, both the resonant axis and the non-resonant axis are driven. The driving of the mirror 70 continues until the amplitude of the non-resonant axis reaches a specified value (step S42; NO).

[0062] When the amplitude of the non-resonant axis reaches a specified value (step S42; YES), the third processing block 55 calculates the phase difference between the resonant drive signal and the resonant sensor signal for each scanning period (step S43).

[0063] If the resonant drive state is not stable (step S44; NO), the overall control block 50 returns to step S43. If the resonant drive state is stable (step S44; YES), the overall control block 50 sets the expected value of the phase difference (step S45). The overall control block 50 also records the time information, drive information, and diagnostic information into a memory (not shown) (step S46).

[0064] Figure 7 is a graph showing an example of the correspondence between the phase difference of the resonant drive signal and the resonant sensor signal and the phase of the non-resonant drive signal. The phase difference between the resonant drive signal and the resonant sensor signal varies depending on the amplitude and phase of the non-resonant drive signal. This is because the rigidity of the actuator of the optical deflector 30 changes. In step S45 described above, the overall control block 50 can set the expected value of the phase difference with respect to the phase of the non-resonant drive signal by using a data table or approximation formula that shows the correspondence between phase difference and phase as shown in Figure 7.

[0065] If the actual phase difference is within the specified range when compared with the set expected phase difference, and the amplitude of the resonant sensor signal output from the third processing block 55 is greater than or equal to the specified value (step S47; YES), the overall control block 50, if it wishes to continue the diagnosis further (step S48; YES), changes the setting value of the non-resonant axis amplitude (step S49) and returns to step 42. On the other hand, if it does not wish to continue the diagnosis (step S48; NO), it terminates the series of processes.

[0066] Furthermore, if the phase difference is not within the specified range or the amplitude is not equal to or greater than the specified value (step S47; NO), the overall control block 50 performs abnormality processing (step S50) and terminates the series of processes. Abnormality processing refers to, for example, outputting a signal or data indicating an abnormality to an external device (not shown) or stopping the drive of the optical deflector 30.

[0067] (Processing details of step S5) As illustrated in Figure 3 above, the optical deflector 30 of this embodiment is configured such that the length of the torsion bars decreases as they get closer to the mirror 70 (excluding the one furthest from the mirror 70). Therefore, when comparing the odd-numbered sets of torsion bars 81, 83, and 85 with the even-numbered sets of torsion bars 82, 84, and 86, a difference in the total length of each set results in a difference in the generated driving force. This difference in driving force results in a difference in the deflection angle when the mirror 70 is moved one cycle in the Y-axis direction (non-resonant axis direction). This difference in deflection angle then causes a phase difference between the resonant drive signal and the resonant sensor signal.

[0068] Figure 8(A) is a graph showing an example of the change in phase difference between the waveform of the non-resonant axis drive signal, with the phase of the non-resonant axis drive signal plotted on the horizontal axis, and the resonant drive signal and resonant sensor signal, with the same phase plotted on the horizontal axis. Figure 8(B) is a schematic diagram showing the relationship between the movement of the even-numbered and odd-numbered torsion bars and the movement of the mirror. The waveform of the non-resonant axis drive signal changes with respect to the phase (0 to 2π) within the scanning period as shown in the figure. Furthermore, the change in phase difference with respect to the phase of the non-resonant axis drive signal fluctuates depending on the magnitude of the voltage peak Vpp of the non-resonant axis drive signal, as shown in the figure.

[0069] Here, range a shown in the figure indicates the specified range of phase difference corresponding to odd-numbered sets of torsion bars 81, etc. If the phase difference falls within the specified range a, the operation of the odd-numbered sets of torsion bars 81, etc. can be said to be normal. In the illustrated example, the operation can be said to be generally normal when the voltage peak value is 48Vpp, but not normal at other voltage peak values. Similarly, range b shown in the figure indicates the specified range of phase difference corresponding to even-numbered sets of torsion bars 82, etc. If the phase difference falls within the specified range b, the operation of the even-numbered sets of torsion bars 82, etc. can be said to be normal. In the illustrated example, the operation can be said to be generally normal when the voltage peak value is 48Vpp, but not normal at other voltage peak values.

[0070] Figure 9(A) shows an example of the correspondence between the phase difference of the non-resonant axis drive signal and the voltage value of the non-resonant axis drive signal when the phase of the non-resonant axis drive signal is at a certain value, for odd-numbered sets of torsion bars. Figure 9(B) shows an example of the correspondence between the phase difference of the non-resonant axis drive signal and the voltage value of the non-resonant axis drive signal when the phase of the non-resonant axis drive signal is at a certain value, for even-numbered sets of torsion bars. In this way, by pre-determining or defining an appropriate voltage value of the non-resonant axis drive signal for a given phase difference, the voltage of the non-resonant axis drive signal can be corrected based on the difference between the actual voltage value and the appropriate voltage value.

[0071] Figure 10 is a flowchart showing in detail the processing content of step S5. The overall control block 50 detects the phase difference between the resonant drive signal and the resonant sensor signal at the phase of a specific non-resonant shaft drive signal for each of the odd-numbered and even-numbered torsion bars (step S70). If the overall control block 50 determines that the phase difference for each of the odd-numbered and even-numbered groups is within a predetermined range (the specified ranges a and b described above) (step S71; YES), no adjustment is necessary and the process is terminated.

[0072] If the phase difference is not within the specified range (step S71; NO), the overall control block 50 corrects the voltage (i.e., amplitude) of the non-resonant shaft drive signal used for the even-numbered torsion bars 82, etc., based on the difference between the actual voltage value and the appropriate voltage value described above (step S73), if the phase difference corresponding to the even-numbered set exceeds the specified range (step S72; YES). Then, the process returns to step S71.

[0073] If the phase difference is not within the specified range (step S71; NO), the overall control block 50 corrects the voltage (i.e., amplitude) of the non-resonant shaft drive signal used for the odd-numbered torsion bars 81, etc., based on the difference between the actual voltage value and the appropriate voltage value described above (step S73), if the phase difference corresponding to the odd-numbered set exceeds the specified range (step S72; NO). Then, the process returns to step S71. The process from step S71 to step S73, or from step S71 to step S74, is performed until the phase difference between the resonant drive signal and the resonant sensor signal falls within the specified range.

[0074] According to the embodiments described above, it becomes easier to identify the cause of operational abnormalities in a system equipped with an optical deflector. In other words, it becomes possible to realize a fault diagnosis function with a simple configuration in a projection system equipped with a laser light source and an optical deflector. Furthermore, it becomes possible to adjust the amplitude (voltage value) of the non-resonant axis drive signal. In addition, it is expected that the degradation trend and failure pattern of the optical deflector can be analyzed based on the behavior and operating conditions before and after the occurrence of the abnormality. For example, if the amplitude of the resonant sensor signal at the time of abnormality is lower than the initial value (value at the time of shipment of the device), it can be identified as degradation of the optical deflector.

[0075] This disclosure is not limited to the embodiments described above, and can be modified and implemented in various ways within the scope of the gist of this disclosure. For example, the anomaly detection operation according to the embodiments described above can be performed both when light is being scanned and when it is not, so it may be performed during a test period when light is not being scanned, or it may be performed as a pre-operation immediately before starting to scan light. Furthermore, when applied to a projection system, the anomaly detection operation may be performed using invisible light.

[0076] Furthermore, the systems to which this disclosure can be applied are not limited to image projection systems, but can be applied to any optical scanning system that has a configuration for scanning light (visible light, invisible light). For example, this disclosure can be applied to optical distance measuring systems (such as LiDAR).

[0077] This disclosure has the following features: (Note 1) An anomaly detection method performed by a control device in a system comprising an optical deflector having a mirror having a resonant axis and a non-resonant axis, the method comprising: (a) detecting an anomaly related to the driving of the mirror based on a sensor signal output from the optical deflector while the resonant axis of the mirror is driven and the non-resonant axis is not driven; and (b) detecting an anomaly related to the driving of the mirror based on the sensor signal output from the optical deflector while both the resonant axis and the non-resonant axis of the mirror are driven, after (a). (Note 2) The anomaly detection method according to Note 1, wherein (a) detects an anomaly related to the driving of the resonant axis when the amplitude of the sensor signal is not greater than or equal to a first specified value, and / or when the phase difference between the resonant drive signal provided from the control device to the optical deflector for driving the resonant axis and the sensor signal is not within a first specified range. (Note 3) The abnormality detection method according to Note 1 or 2, wherein (b) above detects an abnormality related to the driving of the non-resonant axis when the amplitude of the sensor signal is not greater than or equal to a second specified value, and / or when the phase difference between the non-resonant drive signal provided from the control device to the optical deflector for driving the non-resonant axis and the sensor signal is not within a second range which is an expected value determined based on the phase of the non-resonant drive signal. (Note 4) The abnormality detection method according to any one of Notes 1 to 3, wherein the sensor signal is a signal that changes in accordance with the fluctuation of the resonant axis. (Note 5) The abnormality detection method according to any one of Notes 1 to 4, further comprising (c) the control device detecting an abnormality in the operation of the control device itself before (a) above. (Note 6) The abnormality detection method described in Note 5, wherein the control device internally loops a virtual resonant drive signal, which is a resonant drive signal virtually generated for driving the optical polarizer, and a virtual sensor signal, which is a pseudo-generated sensor signal obtained from the optical polarizer, and detects an abnormality related to the driving of the mirror based on the virtual resonant drive signal and the virtual sensor signal.(Note 7) The abnormality detection method described in Note 6, wherein (c) above is a method in which the virtual resonant drive signal and the virtual sensor signal, which are set to conditions under which an abnormality related to the driving of the mirror should be detected, are internally looped within the control device, and when the abnormality is detected, the operation of the control device itself is deemed to be normal. (Note 8) (d) The abnormality detection method described in any of Notes 1 to 7, wherein, after (b) above, the amplitude of the non-resonant drive signal is corrected if the phase difference is not within the third specified range, based on the correspondence between the phase of the non-resonant drive signal within the driving period of the non-resonant drive signal provided from the control device to the optical deflector for driving the non-resonant axis and the phase difference between the non-resonant drive signal and the sensor signal. (Note 9) A control device used in connection with an optical deflector equipped with a mirror having a resonant axis and a non-resonant axis, comprising: a controller; a resonant drive signal generation unit that supplies a resonant drive signal to the optical deflector for driving the resonant axis of the mirror based on data provided by the controller; a non-resonant drive signal generation unit that supplies a non-resonant drive signal to the optical deflector for driving the non-resonant axis of the mirror based on data provided by the controller; and a resonant sensor signal processing unit that calculates the phase difference between the resonant drive signal and the sensor signal and the amplitude of the sensor signal based on a sensor signal acquired from the optical deflector and supplies the phase difference and amplitude to the controller, wherein the controller (a) detects an abnormality related to the driving of the mirror based on the sensor signal output from the optical deflector when the resonant axis of the mirror is driven but the non-resonant axis is not driven; and (b) detects an abnormality related to the driving of the mirror based on the sensor signal output from the optical deflector when both the resonant axis and the non-resonant axis of the mirror are driven, after (a), A control device for an optical deflector that performs the following: (Appendix 10) An optical scanning system comprising the control device described in Appendix 9, and an optical deflector controlled by the control device.

[0078] 10: Control device, 11: System control unit, 12: Light source drive unit, 13: Resonant drive signal generation unit, 14: Non-resonant drive signal generation unit, 15: Resonant sensor signal generation unit, 20: Light source, 30: Optical deflector, 50: Overall control block, 51: Image processing block, 52: Light source drive control block, 53: First processing block, 54: Second processing block, 55: Third processing block, 56: Test block, 60-63: Enable circuit, 64, 65: Selector, 70: Mirror, 76, 77, 80, 90: Actuator, 81-87, 91-97: Torsion bar

Claims

1. An anomaly detection method performed by the control device in a system comprising an optical deflector equipped with a mirror having a resonant axis and a non-resonant axis, and a control device connected to the optical deflector, the method comprising: (a) detecting an anomaly related to the driving of the mirror based on a sensor signal output from the optical deflector while the resonant axis of the mirror is driven and the non-resonant axis is not driven; and (b) detecting an anomaly related to the driving of the mirror based on the sensor signal output from the optical deflector while both the resonant axis and the non-resonant axis of the mirror are driven, after (a).

2. The abnormality detection method according to claim 1, wherein (a) detects an abnormality related to the driving of the resonant axis when the amplitude of the sensor signal is not greater than or equal to a first specified value, and / or when the phase difference between the resonant drive signal provided from the control device to the optical deflector for driving the resonant axis and the sensor signal is not within the first specified range.

3. The abnormality detection method according to claim 1, wherein (b) detects an abnormality related to the driving of the non-resonant axis when the amplitude of the sensor signal is not greater than or equal to a second specified value, and / or when the phase difference between the non-resonant drive signal provided from the control device to the optical deflector for driving the non-resonant axis and the sensor signal is not within a second range which is an expected value determined based on the phase of the non-resonant drive signal.

4. The abnormality detection method according to claim 1, wherein the sensor signal is a signal that changes in accordance with the fluctuation of the resonant axis.

5. (c) The abnormality detection method according to claim 1, further comprising the control device detecting an abnormality in the operation of the control device itself before the action described in (a).

6. The abnormality detection method according to claim 5, wherein the control device internally loops a virtual resonant drive signal, which is a virtual resonant drive signal used to drive the optical polarizer, and a virtual sensor signal, which is a virtual sensor signal obtained from the optical polarizer, and detects an abnormality related to the driving of the mirror based on the virtual resonant drive signal and the virtual sensor signal.

7. The abnormality detection method according to claim 6, wherein (c) is configured such that the virtual resonant drive signal and the virtual sensor signal, which are set to conditions under which an abnormality related to the driving of the mirror should be detected, are internally looped within the control device, and when the abnormality is detected, the control device itself is deemed to be functioning normally.

8. (d) After (b) above, correcting the amplitude of the non-resonant drive signal if the phase difference is not within a third specified range, based on the correspondence between the phase of the non-resonant drive signal within the drive period of the non-resonant drive signal provided from the control device to the optical deflector for driving the non-resonant axis and the phase difference between the non-resonant drive signal and the sensor signal. This is the abnormality detection method according to claim 1.

9. A control device used in connection with an optical deflector equipped with a mirror having a resonant axis and a non-resonant axis, comprising: a controller; a resonant drive signal generation unit that supplies a resonant drive signal to the optical deflector for driving the resonant axis of the mirror based on data provided by the controller; a non-resonant drive signal generation unit that supplies a non-resonant drive signal to the optical deflector for driving the non-resonant axis of the mirror based on data provided by the controller; and a resonant sensor signal processing unit that calculates the phase difference between the resonant drive signal and the sensor signal and the amplitude of the sensor signal based on a sensor signal acquired from the optical deflector and supplies the phase difference and amplitude to the controller, wherein the controller (a) detects an abnormality related to the driving of the mirror based on the sensor signal output from the optical deflector when the resonant axis of the mirror is driven but the non-resonant axis is not driven; and (b) detects an abnormality related to the driving of the mirror based on the sensor signal output from the optical deflector when both the resonant axis and the non-resonant axis of the mirror are driven, after (a). A control device for optical deflectors that performs the following operation.

10. An optical scanning system comprising: a control device according to claim 9; and an optical deflector controlled by the control device.

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