MEMS mirror driving circuit, scanning projection system, and MEMS mirror driving method

Abstract

To minimize, even if an abnormal event, such as the inability to receive MEMS driving data, occurs, the impact of the abnormal event.SOLUTION: An MEMS mirror driving circuit includes: a driving circuit 120 that receives MEMS driving data from a control circuit 210 and outputs a driving signal generated based on the MEMS driving data to an MEMS mirror device 260; and a safety circuit 110 that receives status information and the MEMS driving data from the control circuit 210, determines whether data communication with the control circuit 210 is normal or not, obtains driving signal information for generating an alternative driving signal to replace the driving signal based on the status information and the MEMS driving data if the data communication is normal, and outputs the alternative driving signal generated based on the driving signal information to the MEMS mirror device 260 instead of the driving signal if the data communication is not normal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a MEMS mirror driving circuit, a scanning projection system, and a MEMS mirror driving method. [Background technology]

[0002] There are known lighting devices and image projection devices that project images by scanning light emitted from a light source with a MEMS (Micro Electro Mechanical Systems) mirror. In such devices, it is necessary to check whether the MEMS mirror is operating properly. For example, Patent Document 1 describes a lighting device equipped with an optical deflector that can detect the operation of the MEMS mirror with a simple configuration. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7343410 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional devices such as those described in Patent Document 1 are designed on the assumption that the MEMS driver that drives the MEMS mirror can reliably receive MEMS drive data from the control circuit, which can lead to problems if an abnormal event occurs, such as the MEMS driver being unable to receive MEMS drive data from the control circuit.

[0005] The present invention has been made in view of the above, and aims to provide a MEMS mirror drive circuit, a scanning projection system, and a MEMS mirror drive method that can minimize the effects of an abnormal event, such as an inability to receive MEMS drive data, even if such an abnormal event occurs. [Means for solving the problem]

[0006] The MEMS mirror driving circuit according to the present invention comprises: a drive circuit that receives MEMS drive data from the control circuit and outputs a drive signal generated based on the MEMS drive data to the MEMS mirror device; a safety circuit that receives status information and the MEMS drive data from the control circuit, determines whether data communication with the control circuit is normal, acquires drive signal information for generating an alternative drive signal to replace the drive signal based on the status information and the MEMS drive data if the data communication is normal, and outputs the alternative drive signal generated based on the drive signal information to the MEMS mirror device instead of the drive signal if the data communication is not normal; Equipped with. [Effects of the Invention]

[0007] According to the present invention, even if an abnormal event occurs, such as the inability to receive MEMS drive data, the influence of the abnormal event can be minimized. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing an example of the configuration of a scanning projection system according to a first embodiment. [Figure 2] 2 is a diagram showing an example of the configuration of an internal block of a safety circuit according to the first embodiment. FIG. [Figure 3] 10A and 10B are diagrams showing an example of waveforms of drive voltage signals for MEMS mirrors when a laser is scanned in the horizontal direction. [Figure 4] FIG. 10 is a diagram showing an example of the waveform of a drive voltage signal for a MEMS mirror when a laser is scanned in the vertical direction. [Figure 5] 10 is an example of a flowchart of a status information reception process according to the first embodiment. [Figure 6] 10 is an example of a flowchart of a timeout process according to the first embodiment. [Figure 7] 10 is an example of a flowchart of a process to be performed when data is interrupted according to the first embodiment. [Figure 8] 10A and 10B are diagrams for explaining a stopping sequence of the MEMS mirror. [Figure 9] FIG. 10 is a diagram for explaining upper and lower peak values ​​in the case of bipolar driving. [Figure 10] FIG. 10 is a diagram for explaining an upper peak value in the case of unipolar driving. [Figure 11] 10 is a flowchart illustrating an example of a drive data saving process according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings, in which the same or corresponding parts are designated by the same reference numerals.

[0010] (Embodiment 1) As shown in FIG. 1, the scanning projection system 1000 according to the first embodiment of the present invention includes a MEMS driver 100, a control circuit 210, an LDD (Laser Diode Driver) 220, an LD (Laser Diode) 230, a beam splitter 240, a PD (Photo-Diode) module 250, and a MEMS mirror device 260.

[0011] The MEMS driver 100 is a MEMS mirror drive circuit that drives a MEMS mirror device 260 by converting MEMS drive data received from a control circuit 210 into a drive voltage signal through D / A (Digital to Analog) conversion and outputting the drive voltage signal. More specifically, as shown in Fig. 1, the MEMS driver 100 includes a safety circuit 110, a drive circuit 120, a changeover switch 130, and a sensor circuit 140. The MEMS drive data is digital data obtained by sampling the drive voltage signal that oscillates the MEMS mirror at a predetermined sampling frequency, and is output from the control circuit 210 at each sampling period.

[0012] The safety circuit 110 is a circuit that outputs an alternative drive voltage signal (alternative drive signal) that replaces the drive voltage signal (drive signal) of the drive circuit 120 when MEMS drive data cannot be received normally from the control circuit 210, and details will be described later.

[0013] The drive circuit 120 performs D / A conversion on the MEMS drive data received from the control circuit 210 to generate a drive voltage signal, and outputs the generated drive voltage signal to the MEMS mirror device 260 .

[0014] The changeover switch 130 is a switch that switches whether to output the drive voltage signal from the drive circuit 120 or the alternative drive voltage signal from the safety circuit 110 to the MEMS mirror device 260 .

[0015] The sensor circuit 140 receives a sensor voltage signal output from the MEMS mirror device 260 and outputs MEMS sensor data to the control circuit 210. The sensor circuit 140 is a circuit corresponding to the sensor signal processing unit 103 described in Patent Document 1, and is not an essential circuit for the MEMS driver 100. However, the output of the MEMS sensor data by the sensor circuit 140 allows the control circuit 210 to correct the drive timing of the MEMS mirror device 260.

[0016] The control circuit 210 controls the operation of the entire scanning projection system 1000 and synchronizes the drive timing of the MEMS mirror device 260 and the LD 230. Specifically, based on data of the image to be projected, the control circuit 210 outputs MEMS drive data to the MEMS driver 100 and outputs LD drive data to the LDD 220. The control circuit 210 also outputs status information to the MEMS driver 100, which is used to determine whether data communication between the control circuit 210 and the MEMS driver 100 is normal. The status information will be described later. As described above, the control circuit 210 may correct the drive timing of the MEMS mirror device 260 using MEMS sensor data received from the MEMS driver 100.

[0017] The LDD 220 outputs a drive current signal for driving the LD 230 based on the LD drive data received from the control circuit 210 .

[0018] The LD 230 emits visible light laser of one or more colors of RGB (Red, Green, Blue). The output level of the laser emitted by the LD 230 changes based on the drive current signal received from the LDD 220.

[0019] The beam splitter 240 splits the laser beam output from the LD 230 into two beams. This allows the laser beam output from the LD 230 to enter not only the MEMS mirror device 260 but also the PD module 250.

[0020] The PD module 250 measures the amount of light of the laser output by the LD 230, and outputs the amount of light (light emission state) of the laser as laser state information (light emission state data) to the control circuit 210 and the MEMS driver 100. Note that, although the LD 230 is used as the light source in this embodiment, the light source is not limited to the LD 230, and the PD module 250 may measure the amount of light of any light source and output the light emission state data to the control circuit 210 and the MEMS driver 100.

[0021] The MEMS mirror device 260 includes an actuator made of a piezoelectric element and a MEMS mirror that is oscillated by the actuator. The magnitude of the oscillation (rotation angle) of the MEMS mirror is based on the magnitude of the drive voltage signal received from the MEMS driver 100. The MEMS mirror device 260 projects an image onto a predetermined projection surface by oscillating the mirror while reflecting the laser output by the LD 230 on the mirror, thereby performing a raster scan.

[0022] Typically, this raster scanning involves parallel main scanning, which is performed by resonantly driving the MEMS mirror to oscillate in the horizontal direction, and sub-scanning, which is performed by non-resonantly driving the MEMS mirror to oscillate in the vertical direction. The drive voltage signal for oscillating the MEMS mirror is obtained by D / A converting the MEMS drive data, so control circuit 210 outputs, in parallel, horizontal MEMS drive data for generating a drive voltage signal for oscillating the MEMS mirror in the horizontal direction and vertical MEMS drive data for generating a drive voltage signal for oscillating the MEMS mirror in the vertical direction.

[0023] In order for the above-mentioned control circuit 210 to perform the process of correcting the drive timing of the MEMS mirror device 260 using the MEMS sensor data, the MEMS mirror device 260 must be equipped with a sensor that detects the movement of the MEMS mirror, and in this case, a sensor voltage signal is output based on the value detected by this sensor.

[0024] Next, details of the safety circuit 110 will be described. The safety circuit 110 is a circuit that stores MEMS drive data when it is being received correctly from the control circuit 210, and outputs a drive voltage signal (alternative drive voltage signal) based on the stored data when it is no longer able to receive the data correctly. The stored data may be the MEMS drive data itself, but in this embodiment, the peak values ​​(upper peak value and lower peak value) and periods (rise period and fall period) are stored, and the waveform of the drive voltage signal is reproduced based on these.

[0025] As shown in FIG. 2, the safety circuit 110 includes a state determination unit 111, a drive data control unit 112, a drive voltage output unit 113, and a memory 114.

[0026] The state determination unit 111 monitors the reception state of data (MEMS drive data and status information) from the control circuit 210 by a timeout process (FIG. 6) described later or the like, and determines whether data communication with the control circuit 210 is normal. Then, if the state determination unit 111 determines that there is an abnormality in the data communication with the control circuit 210, it instructs the drive data control unit 112 to output MEMS drive data (by a data interruption process (FIG. 7) described later), issues a switching instruction to the changeover switch 130 to output an alternative drive voltage signal from the safety circuit 110, and further outputs an LD drive stop signal to the LDD 220 to stop driving of the LD 230.

[0027] The drive data control unit 112 stores drive characteristic data (peak value and period) indicating the characteristics of the MEMS drive data received from the control circuit 210 in memory 114 through a status information reception process (FIG. 5) described later. In addition, while the drive state information in the status information indicates that the drive is in progress, the drive data control unit 112 stores the MEMS drive data and lift state information in the status information that have been successfully received in memory 114, thereby enabling reference to the latest values ​​of the MEMS drive data and lift state information.

[0028] 3 shows an example of a waveform 300 (an example of a sine wave) of a drive voltage signal when the MEMS mirror device 260 is resonantly driven to horizontally scan the output of the LD 230. The MEMS drive data for driving the MEMS mirror in this way is a value obtained by sampling this waveform 300 at a predetermined sampling frequency, but because this sampling frequency is very high, plotting the MEMS drive data results in a waveform 300 that is almost identical to that obtained when the drive voltage signal is plotted.

[0029] As can be seen from Figure 3, waveform 300 of the MEMS drive data has lower peak values ​​370 and 372 and upper peak value 371. The period (time) from timing 310 when the MEMS drive data reaches lower peak value 370 to timing 320 when the MEMS drive data reaches upper peak value 371 is the rising period, and the period (time) from timing 320 when the MEMS drive data reaches upper peak value 371 to timing 330 when the MEMS drive data reaches lower peak value 372 is the falling period. Note that the MEMS mirror device 260 can be driven by bipolar drive (drive in which the drive voltage signal takes positive and negative values) or unipolar drive (drive in which the drive voltage signal is always 0V or higher). The lower peak values ​​370 and 372 and upper peak value 371 shown in Figure 3 represent the case of bipolar drive (dotted line 350 is at 0V). In the case of unipolar drive (dotted line 360 ​​is at 0V), the lower peak value is 0V.

[0030] 4 also shows an example of a waveform 301 (an example of a ramp wave) of a drive voltage signal when the MEMS mirror device 260 is non-resonantly driven to scan the output of the LD 230 in the vertical and horizontal directions. As described above, when the MEMS drive data for driving the MEMS mirror in this way is plotted, a waveform 301 that is almost the same as when the drive voltage signal is plotted is obtained.

[0031] As can be seen from Figure 4, even in the case of non-resonant driving, waveform 301 of MEMS drive data has lower peak values ​​370 and 372 and upper peak value 371. The period (time) from timing 311 when the MEMS drive data reaches lower peak value 370 to timing 321 when the MEMS drive data reaches upper peak value 371 is the rising period, and the period (time) from timing 321 when the MEMS drive data reaches upper peak value 371 to timing 331 when the MEMS drive data reaches lower peak value 372 is the falling period. Note that lower peak values ​​370 and 372 and upper peak value 371 shown in Figure 4 also represent the case of bipolar driving (dotted line 350 is at 0 V). In the case of unipolar driving (dotted line 360 ​​is at 0 V), the lower peak value is 0 V.

[0032] 3 as horizontal direction drive data peak values, and stores the rising period and falling period shown in FIG. 3 as horizontal direction waveform cycle counter values ​​in memory 114 as drive characteristic data indicating the characteristics of the MEMS drive data in the horizontal direction through a status information reception process (FIG. 5) described later. Similarly, the drive data control unit 112 stores the upper peak value 371 and the lower peak value 372 shown in FIG. 4 as vertical direction drive data peak values ​​in memory 114 as drive characteristic data indicating the characteristics of the MEMS drive data in the vertical direction, and stores the rising period and falling period shown in FIG. 4 as vertical direction waveform cycle counter values ​​in memory 114. The drive characteristic data is data necessary for the safety circuit 110 to generate an alternative drive voltage signal, and is also called drive signal information.

[0033] Then, the drive data control unit 112 generates alternative MEMS drive data (alternative drive data) based on the drive characteristic data stored in memory 114. The drive data control unit 112 also refers to the laser state, and if the laser is not being output, changes the alternative drive data so that the amplitude of the oscillation of the MEMS mirror is gradually reduced and stopped in accordance with an attenuation amount that matches the characteristics of the MEMS mirror. If the laser is being output, the drive data control unit 112 outputs the generated alternative drive data as is, thereby maintaining the oscillation of the MEMS mirror.

[0034] The drive voltage output unit 113 outputs an alternative drive voltage signal based on the value of the alternative drive data output by the drive data control unit 112. In practice, the drive voltage output unit 113 may be the same circuit as the drive circuit 120. Therefore, instead of including the drive voltage output unit 113 (outputting an alternative drive voltage signal), the safety circuit 110 may output alternative drive data (without including the drive voltage output unit 113), and in FIG. 1 the changeover switch 130 may be disposed on the input side of the drive circuit 120 instead of the output side, so that the data input to the drive circuit 120 can be switched between the MEMS drive data from the control circuit 210 and the alternative drive data from the safety circuit 110 in response to a switching instruction.

[0035] In this embodiment, the drive characteristic data includes information regarding the peak value and period of the MEMS drive data, and from this information the drive data control unit 112 can generate and output MEMS drive data (alternative drive data) of any waveform shape (sine wave, rectangular wave, ramp wave (triangular wave, sawtooth wave), etc.) depending on the application, etc. Furthermore, as will be described later in a second embodiment, if it is desired to reproduce the MEMS drive data more accurately, the drive data control unit 112 may store in the memory 114 one period of MEMS drive data in each of the horizontal and vertical directions (horizontal periodic drive data and vertical periodic drive data).

[0036] That is, the safety circuit 110 according to the first embodiment acquires drive characteristic data (peak value and period) as drive signal information, and the safety circuit 110 according to a second embodiment described below acquires period drive data, which is one period of MEMS drive data, as drive signal information. When the MEMS driver 100 cannot normally receive the MEMS drive data from the control circuit 210, the safety circuit 110 generates an alternative drive voltage signal from the alternative drive data generated based on the drive signal information and outputs the alternative drive voltage signal to the MEMS mirror device 260.

[0037] The status information is data indicating the state of control by the control circuit 210, and includes lift / lower status information and drive status information. The lift / lower status information indicates whether the MEMS drive data is rising or falling (rising or falling). For example, in FIG. 3, if it is in the rising period, the lift / lower status information is rising, and if it is in the falling period, the lift / lower status information is falling. The drive status information also indicates the drive status (driving or stopped) of the MEMS mirror. For example, if the control circuit 210 is outputting MEMS drive data at every sampling period, the drive status information is driving, and if it is not outputting MEMS drive data, the drive status information is stopped.

[0038] Since both the elevation status information and the drive status information can be represented by one bit each, the status information can be represented by two bits. However, since status information exists for each type of MEMS drive data, in this embodiment, there is status information corresponding to the horizontal MEMS drive data (horizontal status information) and status information corresponding to the vertical MEMS drive data (vertical status information). In this embodiment, the control circuit 210 outputs the status information at the same timing (predetermined sampling period) as the MEMS drive data. However, the status information may be output only when the value changes.

[0039] Although not shown, as described above, while the driving status information in the status information indicates that the drive is in operation, every time the drive data control unit 112 normally receives MEMS driving data and lift status information in the status information, it stores the latest MEMS driving data and the latest lift status information in the memory 114. However, since there are two types of MEMS driving data and status information, one for the horizontal direction and one for the vertical direction, as described above, the memory 114 stores the latest horizontal MEMS driving data, the latest horizontal lift status information, the latest vertical MEMS driving data, and the latest vertical lift status information, respectively, as shown in FIG.

[0040] Next, the status information reception process executed when the safety circuit 110 receives status information will be described with reference to Fig. 5. However, since there are two types of status information, horizontal direction status information and vertical direction status information, as described above, in reality, two processes are executed: status information reception process when horizontal direction status information is received (horizontal direction status information reception process) and status information reception process when vertical direction status information is received (vertical direction status information reception process).

[0041] First, the safety circuit 110 determines whether the drive of the MEMS mirror is stopped, i.e., whether the drive status information included in the status information indicates that the mirror is stopped (step S101). If the mirror is stopped (step S101; Yes), the status information reception process ends. If the mirror is not stopped (step S101; No), the safety circuit 110 determines whether the elevation status information included in the status information has changed, i.e., whether the elevation status information has changed from up to down or from down to up (step S102).

[0042] If the lifting / lowering status information has not changed (step S102; No), the status information reception process ends. If the lifting / lowering status information has changed (step S102; Yes), the safety circuit 110 determines whether the lifting / lowering status information is descent (step S103).

[0043] If the lift status information is down (step S103; Yes), the safety circuit 110 records the most recently acquired MEMS drive data as an upper peak value (upper horizontal peak value or upper vertical peak value) in the memory 114 (step S104). Then, counting of the down cycle is started (step S105). Specifically, a counter that counts the down cycle (down counter) is reset to 0. Then, the up cycle count is ended (step S106). Specifically, the value (horizontal up counter value or vertical up counter value) of the counter that has been counting the up cycle (up counter) is recorded in the memory 114. Then, the safety circuit 110 ends the status information reception process.

[0044] On the other hand, if the lift status information is rising (step S103; No), the safety circuit 110 records the most recently acquired MEMS drive data as a lower peak value (horizontal lower peak value or vertical lower peak value) in the memory 114 (step S107). Then, counting of the rise period is started (step S108). Specifically, a counter that counts the rise period (rise counter) is reset to 0. Then, the fall period count is ended (step S109). Specifically, the value (horizontal fall counter value or vertical fall counter value) of the counter that has been counting the fall period (fall counter) is recorded in the memory 114. Then, the safety circuit 110 ends the status information reception process.

[0045] By the above status information reception process, the latest drive characteristic data (peak value and period) is stored in the memory 114.

[0046] Next, the timeout process executed when the safety circuit 110 detects a timeout of the MEMS drive data will be described with reference to Fig. 6. Here, a timeout of the MEMS drive data occurs when the MEMS drive data cannot be received within a set period (for example, a period twice the sampling period of the MEMS drive data). The timer for detecting the timeout is reset when the MEMS drive data is received, and the timeout process is not executed as long as the MEMS drive data is being received normally.

[0047] As described above, there are two types of MEMS drive data: horizontal MEMS drive data and vertical MEMS drive data, and therefore, in reality, two processes are executed: a timeout process when horizontal MEMS drive data times out (horizontal timeout process), and a timeout process when vertical MEMS drive data times out (vertical timeout process). However, when a timeout occurs, it is considered that data communication between the control circuit 210 and the MEMS driver 100 is no longer normal (an abnormality has occurred), so when one timeout process is executed, it is considered that the other timeout process is also executed in most cases.

[0048] First, the safety circuit 110 adds 1 to the number of times that drive data has not been received (step S201). Note that the number of times that drive data has not been received is reset to 0 when the MEMS driver 100 is started. Then, the safety circuit 110 determines whether the number of times that drive data has not been received is equal to or greater than a specified value (for example, 3 times) (step S202).

[0049] If the number of times drive data has not been received is less than the specified value (step S202; No), the timeout process ends. If the number of times drive data has not been received is equal to or greater than the specified value (step S202; Yes), the safety circuit 110 executes the data interruption process described below (step S203), resets the number of times drive data has not been received to 0 (step S204), and ends the timeout process.

[0050] By the above-described timeout processing, it is monitored whether or not the data communication between the control circuit 210 and the safety circuit 110 is normal, and if it is not normal (abnormal), the data interruption processing described below is executed.

[0051] Next, the data interruption processing will be described with reference to Fig. 7. This processing is called from step S203 of the timeout processing (Fig. 6), and so, similarly to the timeout processing, two types of processing are executed: data interruption processing when horizontal MEMS drive data times out (horizontal data interruption processing), and data interruption processing when vertical MEMS drive data times out (vertical data interruption processing).

[0052] First, the safety circuit 110 switches the output source circuit of the drive voltage signal that the MEMS driver 100 outputs to the MEMS mirror device 260 from the drive circuit 120 to the safety circuit 110 (step S211). Specifically, the state determination unit 111 instructs the drive data control unit 112 to output alternative drive data, and issues a switching instruction to the changeover switch 130 to output an alternative drive voltage signal. At that time, the drive data control unit 112 determines the timing when data communication with the control circuit 210 became abnormal based on the latest MEMS drive data and elevation state information that were successfully received, and generates the alternative drive data by matching this timing with the output start timing within one cycle of the waveform of the alternative drive data generated from the drive characteristic data.

[0053] Then, the safety circuit 110 stops the light emission of the LD 230 (step S212). Specifically, the state determination unit 111 outputs an LD drive stop signal to the LDD 220. The LDD 220, which has received the LD drive stop signal, stops the light emission of the LD 230 by outputting a drive current signal to the LD 230, causing the LD 230 to stop light emission, regardless of the LD drive data received from the control circuit 210.

[0054] Then, the safety circuit 110 acquires light emission state data from the PD module 250 and determines whether the LD 230 is still emitting light (step S213). This is because the laser continues to be emitted from the LD 230 for a while even if the LD drive stop signal is output to the LDD 220.

[0055] If the LD 230 is still emitting light (step S213; Yes), the safety circuit 110 outputs an alternative drive voltage signal based on the value of the drive characteristic data stored in the memory 114 (step S214), and the process returns to step S213.

[0056] If the LD 230 is turned off (does not emit light) (step S213; No), the safety circuit 110 determines whether the elevation status information is rising or not (step S215). If the elevation status information is rising (step S215; Yes), the safety circuit 110 reduces the upper peak value and outputs an alternative drive voltage signal (step S216), and proceeds to step S218. If the elevation status information is falling (step S215; No), the safety circuit 110 reduces the lower peak value and outputs an alternative drive voltage signal (step S217), and proceeds to step S218. Note that the reduction of the upper peak value in step S216 may be performed at predetermined intervals rather than every cycle. Furthermore, the reduction of the lower peak value in step S217 may also be performed at predetermined intervals rather than every cycle.

[0057] In step S218, the safety circuit 110 determines whether both the upper peak value and the lower peak value are below the specified values. If they are not below the specified values ​​(step S218; No), the process returns to step S215. If they are below the specified values ​​(step S218; Yes), the safety circuit 110 outputs 0 V as the alternative drive voltage signal (step S219), and ends the data interruption process.

[0058] In the processing from step S215 to step S219, the safety circuit 110, as a stop sequence for the MEMS mirror, reduces the upper peak value and the lower peak value so that the amplitude of waveform 300 of the alternative drive voltage signal gradually decreases for each predetermined period according to an attenuation amount that matches the characteristics of the MEMS mirror (for example, the thickness, area, etc. of the MEMS mirror), as shown in Fig. 8. Then, when the amplitude falls below the stop allowable range (i.e., when both the upper peak value and the lower peak value fall below the specified value), the safety circuit 110 sets the amplitude to 0 (i.e., outputs 0 V) ​​to stop the MEMS mirror.

[0059] However, as mentioned above, the MEMS mirror device 260 can be driven by bipolar driving or unipolar driving. Therefore, in the case of bipolar driving, the absolute values ​​of both the positive upper peak value 371 and the negative lower peak value 372 shown in FIG. 9 are reduced to approach 0V. In the case of unipolar driving, the positive upper peak value 373 shown in FIG. 10 is reduced to approach 0V. Note that, although unipolar driving here is defined as "driving in which the drive voltage signal is always 0V or higher," unipolar driving in which the drive voltage signal is always 0V or lower is also possible, in which case the absolute value of the negative lower peak value is reduced to approach 0V.

[0060] The above-described data interruption processing allows the safety circuit 110 to output an alternative drive voltage signal in the event of an abnormality, thereby maintaining the oscillation of the MEMS mirror. This prevents the MEMS mirror from suddenly stopping its oscillation and prevents the laser irradiation from the LD 230 from remaining at a single point and causing harm to nearby people. Furthermore, if the MEMS mirror's oscillation suddenly stops, an unexpected load may be applied to the actuator of the MEMS mirror, potentially causing device failure such as breakage, disconnection, or short circuit. Therefore, maintaining the oscillation of the MEMS mirror prevents such device failure. Furthermore, by gradually reducing the amplitude of the reciprocating motion of the MEMS mirror after the laser output from the LD 230 is stopped, the MEMS mirror can be safely stopped without applying excessive load to the MEMS mirror.

[0061] (Embodiment 2) In the first embodiment, the drive data control unit 112 stores the peak value and cycle counter value of the MEMS drive data as drive characteristic data in the memory 114, and generates alternative drive data from these. This saves the memory capacity required to store the drive characteristic data, but there are cases where the waveform of the MEMS drive data cannot be faithfully reproduced. In order to reproduce the waveform of the MEMS drive data as faithfully as possible, a second embodiment will be described in which one cycle of MEMS drive data is stored.

[0062] As shown by the dotted lines in FIG. 2 , the drive data control unit 112 according to the second embodiment stores MEMS drive data for one horizontal cycle (horizontal cycle drive data) and MEMS drive data for one vertical cycle (vertical cycle drive data) in the memory 114. Although not shown, the memory 114 has two independent memory banks (memory bank A and memory bank B) for storing horizontal cycle drive data and two independent memory banks (memory bank A and memory bank B) for storing vertical cycle drive data. A timing counter (initial value is the starting address of the memory bank) is also provided as a variable for specifying the address in the memory bank where the MEMS drive data is stored. When the MEMS drive data is stored in the memory banks, the two memory banks are alternately updated by one cycle at a time. This ensures that the memory bank that is not currently being updated stores the complete MEMS drive data for one cycle.

[0063] 11, a drive data saving process in which the drive data control unit 112 saves one cycle's worth of MEMS drive data in a memory bank in the memory 114 will be described. This process is executed every time one piece of MEMS drive data is received (i.e., for each MEMS drive data sampling period). However, since there are two types of MEMS drive data, horizontal MEMS drive data and vertical MEMS drive data, as described above, in reality, two processes are executed: a drive data saving process for saving horizontal MEMS drive data (horizontal drive data saving process) and a drive data saving process for saving vertical MEMS drive data (vertical drive data saving process).

[0064] First, the safety circuit 110 determines whether the received MEMS drive data is the first data of the cycle (step S301). This determination can be made based on whether the lift status information in the status information has switched from lift to lower (or lower to lift).

[0065] If it is the first data of the cycle (step S301; Yes), the timing counter is reset (step S302), the memory bank to be updated is alternately switched (if memory bank A had been updated up until then, it is switched to memory bank B, and if memory bank B had been updated, it is switched to memory bank A) (step S303), and the process proceeds to step S304.

[0066] If it is not the first data of the cycle (step S301; No), the process proceeds to step S304.

[0067] In step S304, the safety circuit 110 determines whether the memory bank currently being updated is memory bank A. If the memory bank currently being updated is memory bank A (step S304; Yes), the safety circuit 110 stores the MEMS drive data at the timing counter position (address) of memory bank A (step S305) and proceeds to step S307. If the memory bank currently being updated is not memory bank A (step S304; No), the safety circuit 110 stores the MEMS drive data at the timing counter position (address) of memory bank B (step S306) and proceeds to step S307.

[0068] In step S307, the safety circuit 110 updates the timing counter (to the address where the MEMS drive data is to be written next), and ends the drive data storage process.

[0069] By the above drive data storage process, the MEMS drive data for one cycle is stored in the memory 114.

[0070] In the second embodiment, the MEMS drive data itself is stored in memory 114 as drive signal information by the drive data storage process (FIG. 11), so there is no need to execute the status information reception process (FIG. 5) of the first embodiment. Furthermore, the timeout process (FIG. 6) and data interruption process (FIG. 7) are also executed in the second embodiment, but in step S211 of the data interruption process (FIG. 7), the drive data control unit 112 determines the timing at which data communication with the control circuit 210 became abnormal based on the latest MEMS drive data and elevation status information that were successfully received, and generates substitute drive data based on this timing to match the output start timing within one cycle of the waveform of one cycle of MEMS drive data acquired by referring to the memory bank that is not currently being updated in the drive data storage process (FIG. 11).

[0071] Other than the above, the processing in embodiment 2 is the same as the processing in embodiment 1. In embodiment 2, the amount of data that must be stored in memory 114 increases compared to embodiment 1, but the waveform of the drive voltage signal that drives MEMS mirror device 260 can be made closer to the normal waveform. Embodiment 2 is effective in cases where the drive voltage signal that drives MEMS mirror device 260 needs to be substantially the same as the normal signal even if an abnormality occurs in data communication between control circuit 210 and MEMS driver 100.

[0072] (Variation) Although various embodiments have been described above, the present invention can be applied to any system that emits a laser (whether a visible light laser or an invisible light laser) and reflects the light while driving a single MEMS mirror, thereby scanning and irradiating the laser.

[0073] For example, a noise condition (e.g., SN (Signal Noise) ratio) on the communication path between the control circuit 210 and the MEMS driver 100 may be acquired, and instead of (or in addition to) the timeout processing described above, a process (reliability determination process) may be performed to determine whether the influence of noise is significant and the reliability of the data is low (e.g., the SN ratio is equal to or less than a predetermined reference value). If it is determined that the reliability of the data is low, the above-described data interruption process may be performed to switch the output source of the drive voltage signal from the drive circuit 120 to the safety circuit 110, thereby preventing abnormal oscillation of the MEMS mirror due to garbled data.

[0074] Furthermore, an error detection code may be added to the data used in communication between the control circuit 210 and the MEMS driver 100, and a process for detecting whether or not there is an error in the data (error detection process) may be performed instead of (or in addition to) the timeout process described above. If an error is detected in the data, the data interruption process described above may be performed to switch the output source of the drive voltage signal from the drive circuit 120 to the safety circuit 110, thereby preventing abnormal oscillation of the MEMS mirror due to a data error.

[0075] Furthermore, in the above embodiment, MEMS mirror device 260 is described as being voltage-driven, having a MEMS mirror that oscillates using an actuator made of a piezoelectric element, and the drive signal is described as being a drive voltage signal, but MEMS mirror device 260 is not limited to being voltage-driven. For example, if MEMS mirror device 260 is current-driven, safety circuit 110 and drive circuit 120 may generate and output a drive current signal from MEMS drive data as the drive signal.

[0076] Furthermore, in the above-described data interruption processing (FIG. 7), when the state determination unit 111 outputs the LD drive stop signal to the LDD 220 in step S212, it is assumed that the light emission of the LD 230 will always stop thereafter. However, there is a possibility that the emission of the LD 230 will not stop due to some cause (for example, a break in the signal line for the LD drive stop signal from the safety circuit 110 to the LDD 220). In preparation for such a case, a timer may be counted in the loop of steps S213 to S214 of the data interruption processing (FIG. 7), and if the LD 230 continues to emit light after a predetermined time (for example, 5 seconds) has elapsed, a message notifying the user of the abnormality (for example, lighting up an LED for error display, outputting an error sound, or issuing a voice announcement such as "An internal circuit communication error has occurred and we have tried to stop the laser light emission, but the light emission cannot be stopped. Please turn off the power to the main unit and contact manufacturer support.") may be output.

[0077] Since the control flow of each of the above-mentioned processes is simple, the MEMS driver 100 (MEMS mirror driving circuit) can be realized as a digital circuit described in a hardware description language such as VHDL (Verilog Hardware Description Language). However, not all of the processes executed by the MEMS driver 100 have to be realized as a digital circuit. For example, the MEMS driver 100 may include a processor such as a CPU (Central Processing Unit), and this processor may execute a program to execute all or part of the above-mentioned processes.

[0078] The scanning projection system 1000 shown in each of the above-described embodiments can be used, for example, in a laser scanning projection device equipped with a MEMS scanning mirror device, a laser scanning illumination device incorporating a MEMS scanning mirror device, etc.

[0079] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to the above-described embodiments, but includes the scope of the invention described in the claims and its equivalents. [Explanation of symbols]

[0080] 100...MEMS driver, 110...safety circuit, 111...state determination unit, 112...driving data control unit, 113...driving voltage output unit, 114...memory, 120...driving circuit, 130...changeover switch, 140...sensor circuit, 210...control circuit, 220...LDD, 230...LD, 240...beam splitter, 250...PD module, 260...MEMS mirror device, 300, 301...waveform, 310, 311, 320, 321, 330, 331...timing, 350, 360...dotted line, 370, 372...lower peak value, 371, 373...upper peak value, 1000...scanning projection system

Claims

1. a drive circuit that receives MEMS drive data from the control circuit and outputs a drive signal generated based on the MEMS drive data to the MEMS mirror device; a safety circuit that receives status information and the MEMS drive data from the control circuit, determines whether data communication with the control circuit is normal, acquires drive signal information for generating an alternative drive signal to replace the drive signal based on the status information and the MEMS drive data if the data communication is normal, and outputs the alternative drive signal generated based on the drive signal information to the MEMS mirror device instead of the drive signal if the data communication is not normal; Equipped with MEMS mirror drive circuit.

2. the status information includes elevation status information indicating an elevation status of the value of the MEMS drive data; The MEMS mirror driving circuit according to claim 1 .

3. The safety circuit comprises: As the drive signal information, an increase period during which the value of the MEMS drive data increases and a decrease period during which the value of the MEMS drive data decreases are acquired based on the elevation state information; generating the alternative drive signal based on the timing when data communication with the control circuit becomes abnormal and the rising period and the falling period; The MEMS mirror driving circuit according to claim 2 .

4. The safety circuit comprises: As the drive signal information, periodic drive data, which is data for one period of the MEMS drive data, is acquired based on the lifting state information and the MEMS drive data; generating the alternative drive signal based on the timing when data communication with the control circuit becomes abnormal and the cycle of drive data; The MEMS mirror driving circuit according to claim 2 .

5. The safety circuit comprises: receiving light emission status data indicating a light emission status of the light source; If the light emission state data indicates that the light is off, gradually reducing the amplitude of the alternative drive signal to 0 at each predetermined period in accordance with an attenuation amount that matches the characteristics of the MEMS mirror included in the MEMS mirror device; The MEMS mirror driving circuit according to claim 3 or 4.

6. a light source that emits light; a MEMS mirror device including a MEMS mirror that reflects light emitted from the light source and irradiates the light onto a projection surface, and an actuator that oscillates the MEMS mirror; a control circuit that outputs MEMS drive data for generating a drive signal that drives the actuator; a MEMS mirror drive circuit that receives the MEMS drive data from the control circuit and outputs the drive signal; 1. A scanning projection system comprising: The MEMS mirror driving circuit includes: a drive circuit that receives the MEMS drive data from the control circuit and outputs the drive signal generated based on the MEMS drive data to the MEMS mirror device; a safety circuit that receives status information and the MEMS drive data from the control circuit, determines whether data communication with the control circuit is normal, acquires drive signal information for generating an alternative drive signal to replace the drive signal based on the status information and the MEMS drive data if the data communication is normal, and outputs the alternative drive signal generated based on the drive signal information to the MEMS mirror device instead of the drive signal if the data communication is not normal; Equipped with Scanning projection system.

7. receiving status information and MEMS drive data from the control circuit and determining whether data communication with the control circuit is normal; If the data communication is normal, a drive signal generated based on the MEMS drive data is output to the MEMS mirror device, and drive signal information for generating a substitute drive signal that substitutes for the drive signal is acquired based on the status information and the MEMS drive data. If the data communication is not normal, the alternative drive signal generated based on the drive signal information is output to the MEMS mirror device instead of the drive signal. MEMS mirror driving method.

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