JP2018151496A - Actuator driver, image projector, and temperature detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator driver, an image projector and a temperature detector with which it is possible to detect the temperature of an actuator at low cost with high accuracy.SOLUTION: A V drive generation circuit 22 and an H drive generation circuit 23 output drive signals for cyclically driving an MEMS mirror device 20 equipped with strain gauges 7V, 7H for measuring the displacement of a mirror unit 3. Each of constant current sources 64, 65 supplies a constant current to the strain gauges 7V, 7H. An averaging processing unit 29 detects an average value based on the output voltages of the constant current sources 64, 65 within a prescribed period as temperature information pertaining to the strain gauges 7V, 7H. A vertical scanning speed correction unit 26, an amplitude adjustment unit 27 and a phase adjustment unit 28 adjust the drive signals of the V drive generation circuit 22 and H drive generation circuit 23 on the basis of the temperature information detected by the averaging processing unit 29.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a drive device that drives an actuator.

  2. Description of the Related Art Conventionally, a MEMS (Micro Electro Mechanical System) device manufactured by a semiconductor process technology is known. A MEMS actuator such as a MEMS mirror used in a laser projector is characterized by a small and high-speed response, but a desired performance may not be obtained depending on the operating temperature. For this reason, the temperature of the MEMS actuator is detected, and the signal for driving the MEMS actuator is corrected according to the detected temperature. For example, Patent Document 1 discloses a drive for driving a resonance type deflection element in order to maintain the deflection surface at a constant oscillation amplitude even when the resonance frequency of the resonance type deflection element changes due to a change in ambient temperature or the like. An optical scanning device is disclosed in which the signal frequency is driven by a drive signal having a frequency that is shifted from the resonance frequency inherent to the resonance type deflection element by a frequency corresponding to the temperature of the resonance type deflection element.

JP 2011-180450 A

  When correcting the temperature of the drive signal of the MEMS actuator, in order to accurately measure the temperature of the MEMS actuator, it is preferable to arrange a temperature sensor in the MEMS actuator itself, but it requires an arrangement space, an increase in cost, etc. Problem arises.

  Examples of the problem to be solved by the present invention are as described above. The main object of the present invention is to provide an actuator driving device, an image projecting device, and a temperature detecting device capable of detecting the temperature of an actuator accurately at low cost.

  The invention described in claim is an actuator driving device, wherein a driving circuit for outputting a driving signal for periodically driving an actuator having a strain gauge for measuring displacement of a movable portion, and a constant for the strain gauge A power supply unit that supplies current, a temperature detection unit that detects an average value of output voltage values within a predetermined period of the power supply unit as temperature information of the strain gauge, and the temperature detection unit And an adjustment unit that adjusts a drive signal of the drive circuit based on temperature information.

  The invention described in claim 1 is an actuator driving device, wherein a driving circuit that outputs a driving signal for periodically driving an actuator including a strain gauge that measures the displacement of the movable portion, and the strain gauge A power supply unit that supplies a constant voltage, a temperature detection unit that detects, as temperature information of the strain gauge, an average value based on an output current value within a predetermined period of the power supply unit, and the temperature detection unit An adjustment unit that adjusts a drive signal of the drive circuit based on the detected temperature information.

  The invention described in claim 1 is a temperature detection device, wherein a power supply unit that supplies a constant current to a strain gauge that measures displacement of a movable part of an actuator, and an output within a predetermined period of the power supply unit And a temperature detector that detects an average value of the voltage value as temperature information of the strain gauge.

  The invention described in claim 1 is a temperature detection device, wherein a power supply unit that supplies a constant voltage to a strain gauge that measures the displacement of the movable part of the actuator, and an output within a predetermined period of the power supply unit And a temperature detector that detects an average value of current values as temperature information of the strain gauge.

The structure of an image projector is shown. It is a top view of a MEMS mirror device. The structural example of a strain gauge and the table regarding the temperature characteristic of a strain gauge are shown. The 1st structural example regarding the temperature detection of a strain gauge vicinity is shown. The 2nd structural example regarding the temperature detection of a strain gauge vicinity is shown.

  In one preferred embodiment of the present invention, the actuator driving device includes a driving circuit that outputs a driving signal for periodically driving an actuator including a strain gauge that measures the displacement of the movable portion, and a constant for the strain gauge. Detected by the temperature detection unit, a temperature detection unit for detecting an average value of the output voltage value of the power supply unit within a predetermined period as temperature information of the strain gauge, and the temperature detection unit. And an adjustment unit that adjusts a drive signal of the drive circuit based on the temperature information.

  Here, the “average value” includes not only the average value but also a value according to an average value such as an intermediate value between the maximum value and the minimum value. In this configuration, the actuator driving device can suitably detect the temperature information of the strain gauge from the strain gauge and can suitably adjust the driving signal of the driving circuit.

  In another preferred embodiment of the present invention, the actuator drive device includes a drive circuit that outputs a drive signal for periodically driving an actuator including a strain gauge that measures the displacement of the movable portion, and a constant for the strain gauge. A power supply unit that supplies the voltage of the power supply unit, a temperature detection unit that detects an average value based on an output current value of the power supply unit within a predetermined period as temperature information of the strain gauge, and the temperature detection unit And an adjustment unit that adjusts a drive signal of the drive circuit based on the temperature information. Also with this configuration, the actuator driving device can suitably detect the temperature information of the strain gauge from the strain gauge and can suitably adjust the driving signal of the driving circuit. In a preferred example of the actuator driving device, the strain gauge may include a piezoresistor.

  In one aspect of the actuator driving device, the temperature detecting unit calculates the average value with a period of one cycle or more of the driving signal as the predetermined period. According to this aspect, the actuator driving device can detect accurate temperature information by suitably extracting the direct current component of the output voltage value or the output current value. The “predetermined period” is, for example, an integral multiple of the period of the drive signal.

  In another aspect of the actuator driving device, the actuator driving device includes a correction circuit that corrects the output of the strain gauge in accordance with an output voltage value of the power supply unit, and the adjustment unit corrects by the correction circuit. The drive signal of the drive circuit is adjusted based on the output of the strain gauge and the temperature information detected by the temperature detector. According to this aspect, the actuator driving device can appropriately detect the temperature information and the displacement information of the movable part from the strain gauge, and suitably execute the adjustment of the driving signal by the driving circuit.

  In another preferred embodiment of the present invention, the image projection apparatus includes: the actuator having a mirror disposed on the movable part; the light source unit that emits light corresponding to an image signal toward the mirror; And the actuator driving device described. According to this aspect, the image projection apparatus can suitably execute the drive adjustment of the mirror necessary for displaying the image indicated by the image signal based on the temperature information detected from the strain gauge.

  In another preferred embodiment of the present invention, the temperature detection device includes a power supply unit that supplies a constant current to a strain gauge that measures the displacement of the movable part of the actuator, and an output voltage within a predetermined period of the power supply unit. And a temperature detection unit that detects an average value as temperature information of the strain gauge. With this configuration, the temperature detection device can preferably detect the temperature information of the strain gauge.

  In another preferred embodiment of the present invention, the temperature detection device includes a power supply unit that supplies a constant voltage to a strain gauge that measures the displacement of the movable part of the actuator, and an output current within a predetermined period of the power supply unit. And a temperature detection unit that detects an average value as temperature information of the strain gauge. Even with this configuration, the temperature detection device can preferably detect the temperature information of the strain gauge.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[Configuration of image projection apparatus]
FIG. 1 shows the configuration of the image projection apparatus 100. The image projection device 100 controls the drive of the light source unit 10 that emits the projection light “L1” that constitutes the image, the MEMS mirror device 20 that reflects the projection light L1 emitted from the light source unit 10, and the MEMS mirror device 20. And a MEMS driving circuit 30 to be performed. The image projection apparatus shown in FIG. 1 is configured so that the temperature of the MEMS mirror device 20 can be detected by a strain sensor provided in the MEMS mirror device 20.

  FIG. 2 is a top view of the MEMS mirror device 20. As shown in FIG. 2, the MEMS mirror device 20 mainly includes a fixed frame 1, a frame part 2, a mirror part 3, magnets 4 </ b> A to 4 </ b> D, X-axis torsion bars 5 </ b> A and 5 </ b> B, and a Y-axis torsion bar. 6A, 6B and strain gauges 7V, 7H.

  The fixed frame 1 is a structure for supporting the frame portion 2 and is formed of a metal material or a semiconductor material such as silicon. The fixed frame 1 has a frame shape with a gap inside. The frame part 2 has a frame shape with a gap inside. The frame portion 2 is connected to the fixed frame 1 via X-axis torsion bars 5A and 5B, and can swing (rotate) with respect to the fixed frame 1 using the X-axis torsion bars 5A and 5B as rotation axes. . Further, convex patterns are formed on the surfaces of the fixed frame 1 and the frame part 2, and the wiring pattern extending from the fixed frame 1 via the X-axis torsion bars 5 </ b> A and 5 </ b> B follows the frame shape of the frame part 2. Thus, the coil 8 is formed on the surface of the frame portion 2. The mirror unit 3 is a disk-shaped member having a reflection film formed on the surface thereof that reflects the incident projection light L1, and is connected to the frame unit 2 via Y-axis torsion bars 6A and 6B. The mirror unit 3 is swingable with respect to the frame unit 2 with the Y-axis torsion bars 6A and 6B as rotation axes. The magnets 4 </ b> A to 4 </ b> D are arranged around the frame portion 2 and generate a magnetic field in the horizontal (H) direction and the vertical (V) direction in a region where the coil 8 formed in the frame portion 2 exists. The mirror unit 3 is an example of the “movable unit” in the present invention, and the MEMS mirror device 20 is an example of the “actuator” in the present invention.

  A strain gauge 7V is provided near the X-axis torsion bar 5B, and a strain gauge 7H is provided near the Y-axis torsion bar 6B. The strain gauge 7V is a sensor that detects the position of the mirror unit 3 in the vertical (V) direction, and outputs a voltage corresponding to the twist amount and twist direction of the X-axis torsion bar 5B. The strain gauge 7H is a sensor that detects the position of the mirror unit 3 in the horizontal (H) direction, and outputs a voltage corresponding to the twist amount and twist direction of the Y-axis torsion bar 6B.

  FIG. 3A shows a configuration example of the strain gauge 7V. 3A shows only the strain gauge 7V, the strain gauge 7H has the same configuration as the strain gauge 7V. As shown in FIG. 3A, the strain gauge 7V is configured by bridge-connecting four piezo resistances R1 to R4. The strain gauge 7V inputs a constant voltage to a pair of opposing connection points (for example, P1 and P3), and measures a potential difference generated between another pair of connection points (for example, P2 and P4). Thus, the strain on the surface on which the strain gauge 7V is disposed can be measured.

  Here, the piezo resistances R1 to R4 have temperature characteristics, and the resistance value increases as the temperature increases. FIG. 3B is a table showing an example of temperature characteristics of the piezo resistances R1 to R4. In FIG. 3B, the resistance values of the piezo resistances R1 to R4 are shown for each combination of the temperature environment of each piezo resistance R1 to R4 and the displacement state of the mirror unit 3. Here, the temperature environment is divided into three types of “low temperature”, “normal temperature”, and “high temperature”, and the displacement state of the mirror unit 3 is such that the piezo resistances R1 and R4 are maximized. The state in which the amplitude is maximum (when the amplitude is at the upper MAX), the state where the amplitude of the mirror unit 3 is 0 (when the amplitude is zero), and the amplitude of the mirror unit 3 is maximized in the direction in which the piezoresistors R2 and R3 are maximum. There are three types of states (amplitude lower side MAX).

  As shown in FIG. 3B, the piezo resistance R1 to R4 has a higher resistance value as the temperature is higher, regardless of the displacement state of the mirror unit 3. In this embodiment, the MEMS drive circuit 30 uses the temperature characteristics of the piezo resistances R1 to R4 to change the output current of the constant voltage source connected to the connection point P1 or the output voltage of the constant current source. Based on this, the temperature is preferably estimated. The MEMS drive circuit 30 is an example of the “actuator drive device” and the “temperature detection device” in the present invention.

[Temperature detection configuration]
(First configuration example)
FIG. 4 shows a first configuration example relating to temperature detection using strain gauges 7V and 7H. As shown in FIG. 4, the MEMS drive circuit 30 mainly includes a thermistor 21, a V drive generation circuit 22, an H drive generation circuit 23, a drive synthesis circuit 24, a drive amplifier 25, and a vertical scanning speed correction unit. 26, amplitude adjustment unit 27, phase adjustment unit 28, averaging processing unit 29, constant current source 31, constant voltage sources 32 and 33, current detection resistors 35 and 36, and operational amplifiers 41 to 44. , LPF (Low-Pass Filter) 48, 49 and ADC (Analog to Digital Converter) 51-55.

  The connection point P1 of the strain gauge 7V is connected to the constant voltage source 32. Between the constant voltage source 32 and the connection point P1, a current detection element having a sufficiently small resistance value with respect to the piezoresistor of the strain gauge 7V. A resistor 35 is provided. The operational amplifier 42 is connected to both ends of the current detection resistor 35, and supplies a signal corresponding to the potential difference between both ends of the current detection resistor 35 to the averaging processing unit 29 via the ADC 52. In this configuration, when the piezoresistance of the strain gauge 7V changes based on the temperature characteristics, the value of the current flowing through the current detection resistor 35 changes, and the potential difference between both ends of the current detection resistor 35 changes. Therefore, the temperature near the strain gauge 7V (that is, the temperature of the MEMS mirror device 20) can be estimated from the output of the ADC 52 by grasping in advance the correspondence between the potential difference between both ends of the current detection resistor 35 and the temperature. It is possible. Note that the piezoresistance of the strain gauge 7V changes with the displacement of the mirror unit 3 (see FIG. 3B), and the output of the ADC 52 changes with the displacement of the mirror unit 3, so that the averaging processing unit 29 described later performs time averaging. Is done.

  Similarly, the connection point P1 of the strain gauge 7H is connected to the constant voltage source 33. Between the constant voltage source 33 and the connection point P1, the resistance value is sufficiently small with respect to the piezoresistance of the strain gauge 7H. A current detection resistor 36 is provided. The operational amplifier 44 is connected to both ends of the current detection resistor 36, and supplies a signal corresponding to the potential difference between both ends of the current detection resistor 36 to the averaging processing unit 29 via the ADC 54. The constant voltage sources 32 and 33 are an example of the “power supply unit” in the present invention.

  Further, the connection points P2 and P4 of the strain gauge 7V are connected to the operational amplifier 43, and a signal corresponding to the potential difference “V_SENSP−V_SENSN” at the connection points P2 and P4 from the operational amplifier 43 passes through the LPF 48 and the ADC 53. It is supplied to the drive generation circuit 22. Here, the amplitude of the mirror unit 3 in the V direction has a predetermined correlation with the potential difference “V_SENSP−V_SENSN”. Therefore, the V drive generation circuit 22 specifies the amplitude of the mirror unit 3 in the V direction based on the output signal of the ADC 53. Similarly, the connection points P2 and P4 of the strain gauge 7H are connected to the operational amplifier 45, and a signal corresponding to the potential difference “H_SENSP−H_SENSN” at the connection points P2 and P4 from the operational amplifier 45 passes through the LPF 49 and the ADC 55. It is supplied to the H drive generation circuit 23.

  The averaging processing unit 29 performs time averaging of the signals supplied from the ADCs 52 and 54, thereby generating temperature information of the strain gauges 7V and 7H (that is, the MEMS mirror device 20) independent of the displacement state of the mirror unit 3. . For example, the averaging processing unit 29 time-averages one period of horizontal scanning of signals supplied from the ADCs 52 and 54 or one frame of an image to be displayed. Thereby, the averaging processing unit 29 extracts only the DC component from the output signals of the ADCs 52 and 54 including the DC component and the AC component. Then, the averaging processing unit 29 uses, for example, an intermediate value of values obtained by averaging the outputs of the ADCs 52 and 54 as time information as temperature information of the MEMS mirror device 20, the vertical scanning speed correction unit 26, the amplitude adjustment unit 27, and the phase. It supplies to the adjustment part 28, respectively. As described above, in the example of FIG. 4, the averaging processing unit 29 uses the vertical scanning speed correction unit 26, the amplitude adjustment unit 27, and the phase adjustment unit as temperature information considering the temperatures of both the strain gauge 7 </ b> V and the strain gauge 7 </ b> H. 28 respectively. The averaging processing unit 29 is an example of the “temperature detection unit” in the present invention.

  The thermistor 21 is provided in the MEMS drive circuit 30, and the resistance value changes according to the temperature. In the example of FIG. 4, a voltage corresponding to the resistance value of the thermistor 21 is input to the operational amplifier 41 by the constant current source 31, and a signal corresponding to a voltage difference from the reference voltage is supplied to the ADC 51. As a result, the temperature information detected by the thermistor 21 is supplied to the vertical scanning speed correction unit 26, the amplitude adjustment unit 27, and the phase adjustment unit 28.

  The V drive generation circuit 22 generates a drive signal in the V direction of the mirror unit 3. In this embodiment, the V drive generation circuit 22 controls the signal indicating the amplitude in the V direction of the mirror unit 3 supplied from the ADC 53 and the vertical scanning speed of the mirror unit 3 received from the vertical scanning speed correction unit 26 described later. Based on the signal and a control signal related to the amplitude in the V direction of the mirror unit 3 received from the amplitude adjusting unit 27 described later, the above-described drive signal is generated.

  The H drive generation circuit 23 generates a drive signal for the mirror unit 3 in the H direction. In this embodiment, the H drive generation circuit 23 is based on a control signal related to the amplitude in the H direction of the mirror unit 3 received from an amplitude adjusting unit 27 described later and a control signal related to timing received from a phase adjusting unit 28 described later. The above-mentioned drive signal is generated.

  The drive synthesis circuit 24 synthesizes the triangular wave drive signal generated by the V drive generation circuit 22 and the sine wave drive signal generated by the H drive generation circuit 23 and supplies them to the drive amplifier 25. The drive amplifier 25 amplifies the synthesized drive signal and supplies it to the coil 8. The V drive generation circuit 22, the H drive generation circuit 23, the drive synthesis circuit 24, and the drive amplifier 25 are examples of the “drive circuit” in the present invention.

  The vertical scanning speed correction unit 26 determines a parameter for adjusting the waveform of the drive signal generated by the V drive generation circuit 22 so that the vertical scanning speed unevenness of the mirror unit 3 does not appear, and a control signal that specifies the parameter is determined. , Supplied to the V drive generation circuit 22. In this case, the vertical scanning speed correction unit 26 has information on the detected temperature of the thermistor 21 supplied from the ADC 51 (that is, the temperature of the MEMS drive circuit 30) and the strain gauges 7V and 7H supplied from the averaging processing unit 29. A parameter for adjusting the waveform of the drive signal is selected based on the information on the temperature (that is, the temperature of the MEMS mirror device 20). Accordingly, the vertical scanning speed correction unit 26 takes into consideration the temperature characteristics of the MEMS mirror device 20 and the temperature characteristics of the MEMS drive circuit 30, and causes the V drive generation circuit 22 to generate a waveform pattern corresponding to these temperatures. In this case, for example, the vertical scanning speed correction unit 26 sets the above parameters to be set for each combination of the temperature of the strain gauges 7V and 7H (that is, the MEMS mirror device 20) and the temperature of the thermistor 21 (that is, the MEMS drive circuit 30). The specified table is stored in advance, and the above-described parameters are selected with reference to the table.

  The amplitude adjustment unit 27 adjusts the intensity of the drive signal of the mirror unit 3 based on the temperature information of the thermistor 21 supplied from the ADC 51 and the temperature information of the strain gauges 7V and 7H supplied from the averaging processing unit 29. Control signal for generating. As a result, the amplitude adjusting unit 27 makes the angle of view in the H direction and the V direction (that is, the deflection width of the mirror unit 3) constant. In this case, for example, the amplitude adjustment unit 27 defines the strength of the drive signal to be set for each combination of the temperature of the strain gauges 7V and 7H (that is, the MEMS mirror device 20) and the temperature of the thermistor 21 (that is, the MEMS drive circuit 30). The table is stored in advance, and the strength of the drive signal is determined with reference to the table. Then, the amplitude adjustment unit 27 transmits a control signal for adjusting the intensity of the drive signal of the mirror unit 3 to the V drive generation circuit 22 and the H drive generation circuit 23, respectively.

  Based on the temperature information of the thermistor 21 supplied from the ADC 51 and the temperature information of the strain gauges 7V and 7H supplied from the averaging processor 29, the phase adjustment unit 28 outputs the output timing of the projection light L1 of the light source unit 10 and A parameter for adjusting the phase of horizontal scanning is determined so as to match the timing of horizontal scanning. In this case, for example, the phase adjustment unit 28 defines the above-described parameters to be set for each combination of the temperature of the strain gauges 7V and 7H (that is, the MEMS mirror device 20) and the temperature of the thermistor 21 (that is, the MEMS drive circuit 30). A table is stored in advance, and the above parameters are selected with reference to the table. Then, the phase adjustment unit 28 supplies a control signal designating the above parameters to the H drive generation circuit 23. The vertical scanning speed correction unit 26, the amplitude adjustment unit 27, and the phase adjustment unit 28 are examples of the “adjustment unit” in the present invention.

  As described above, the MEMS drive circuit 30 according to the first configuration example mainly includes the V drive generation circuit 22, the H drive generation circuit 23, the vertical scanning speed correction unit 26, the amplitude adjustment unit 27, and the phase. An adjustment unit 28, an averaging processing unit 29, and constant voltage sources 32 and 33 are provided. The V drive generation circuit 22 and the H drive generation circuit 23 output drive signals for periodically driving the MEMS mirror device 20 including the strain gauges 7 </ b> V and 7 </ b> H that measure the displacement of the mirror unit 3. The constant voltage sources 32 and 33 supply constant voltages to the strain gauges 7V and 7H, respectively. The averaging processing unit 29 detects an average value based on the output current within a predetermined period of the constant voltage sources 32 and 33 as temperature information of the strain gauges 7V and 7H. The vertical scanning speed correction unit 26, the amplitude adjustment unit 27, and the phase adjustment unit 28 adjust the drive signals of the V drive generation circuit 22 and the H drive generation circuit 23 based on the temperature information detected by the averaging processing unit 29. According to this aspect, the MEMS drive circuit 30 preferably estimates the temperatures of the strain gauges 7V and 7H using the strain gauges 7V and 7H, and preferably uses the drive signals output by the V drive generation circuit 22 and the H drive generation circuit 23. Can be adjusted.

(Second configuration example)
FIG. 5 shows a second configuration example relating to temperature detection near the strain gauges 7V and 7H. In the second configuration example, the MEMS drive circuit 30 mainly includes a thermistor 21, a V drive generation circuit 22, an H drive generation circuit 23, a drive synthesis circuit 24, a drive amplifier 25, and a vertical scanning speed correction unit 26. The amplitude adjusting unit 27, the phase adjusting unit 28, the averaging processing unit 29, the constant current sources 31, 64, 65, the operational amplifiers 41 to 44, the LPFs 48 and 49, the ADCs 51 to 55, and the variable amplifier 60. , 61 and DC voltmeters 62, 63. The V drive generation circuit 22, the H drive generation circuit 23, the drive synthesis circuit 24, the drive amplifier 25, the vertical scanning speed correction unit 26, the amplitude adjustment unit 27, the phase adjustment unit 28, and the averaging processing unit according to the second configuration example. The processing executed by 29 and the like is the same as the processing of the first configuration example, and thus the description of the processing executed by these will be omitted as appropriate.

  Since a constant current is supplied from the constant current source 64 to the connection point P1 of the strain gauge 7V, the voltage “V_PZB” at the connection point P1 according to the resistance value of the piezoresistor of the strain gauge 7V that changes depending on the temperature characteristics. Changes. The operational amplifier 42 supplies a signal corresponding to the voltage “V_PZB” corresponding to the temperature of the strain gauge 7V to the averaging processing unit 29 via the ADC 52.

  In the second configuration example, since the voltage “V_PZB” at the connection point P1 is variable, the potential difference “V_SENSP−V_SENSN” also changes in proportion to the voltage “V_PZB”. Therefore, in the second configuration example, the DC voltmeter 62 detects the voltage “V_PZB”, and the variable amplifier 60 changes the gain according to the voltage “V_PZB” detected by the DC voltmeter 62. Thereby, a signal corresponding to the amplitude of the mirror unit 3 in the V direction is suitably supplied to the V drive generation circuit 22 via the LPF 48 and the ADC 53.

  Here, the relationship between the voltage “V_PZB” and the potential difference “V_SENSP−V_SENSN” will be supplementarily described with reference to FIG. FIG. 3C shows the voltage “V_PZB” and the potential difference “V_SENSP” for each temperature environment when a constant current of 0.1 [mA] is supplied from the constant current source 64 when the amplitude of the mirror unit 3 is constant. -V_SENSN ”combination. In this case, the piezoresistors R1 to R4 have the temperature characteristics shown in FIG.

  As shown in FIGS. 3B and 3C, the resistance value of the piezoresistors R1 to R4 increases as the temperature increases, and the voltage “V_PZB” and the potential difference “V_SENSP” are proportional to the resistance values of the piezoresistors R1 to R4. -V_SENSN "increases. Therefore, in order to prevent a change in potential difference “V_SENSP−V_SENSN” due to a temperature change, in the second configuration example, the variable amplifier 60 changes the gain according to the voltage “V_PZB” detected by the DC voltmeter 62.

  A second configuration example will be described with reference to FIG. 5 again. Since a constant current is supplied from the constant current source 65 to the connection point P1 of the strain gauge 7H, the voltage “H_PZB” at the connection point P1 according to the resistance value of the piezoresistor of the strain gauge 7H that varies depending on the temperature characteristics. Changes. The operational amplifier 44 supplies a signal corresponding to the voltage “H_PZB” corresponding to the temperature of the strain gauge 7 </ b> H to the averaging processing unit 29 via the ADC 54. The constant current sources 64 and 65 are an example of the “power supply unit” in the present invention.

  Further, since the potential difference “H_SENSP−H_SENSN” also changes in proportion to the voltage “H_PZB”, the DC voltmeter 63 detects the voltage “H_PZB”, and the variable amplifier 61 gains according to the detected voltage “H_PZB”. Is changed to cancel the fluctuation of the voltage “H_PZB”. Accordingly, the variable amplifier 61 supplies an output signal corresponding to the amplitude of the mirror portion 3 in the H direction to the H drive generation circuit 23 via the LPF 49 and the ADC 55 without depending on the fluctuation of the voltage “H_PZB”. The variable amplifiers 60 and 61 and the DC voltmeters 62 and 63 are examples of the “correction circuit” in the present invention.

  As described above, the MEMS drive circuit 30 according to the second configuration example mainly includes the V drive generation circuit 22, the H drive generation circuit 23, the constant current sources 64 and 65, the averaging processing unit 29, A vertical scanning speed correction unit 26, an amplitude adjustment unit 27, and a phase adjustment unit 28 are provided. The V drive generation circuit 22 and the H drive generation circuit 23 output drive signals for periodically driving the MEMS mirror device 20 including the strain gauges 7 </ b> V and 7 </ b> H that measure the displacement of the mirror unit 3. The constant current sources 64 and 65 supply constant currents to the strain gauges 7V and 7H, respectively. The averaging processing unit 29 detects an average value based on the output voltage of the constant current sources 64 and 65 within a predetermined period as temperature information of the strain gauges 7V and 7H. The vertical scanning speed correction unit 26, the amplitude adjustment unit 27, and the phase adjustment unit 28 adjust the drive signals of the V drive generation circuit 22 and the H drive generation circuit 23 based on the temperature information detected by the averaging processing unit 29. As described above, also in the second configuration example, the MEMS drive circuit 30 preferably estimates the temperatures of the strain gauges 7V and 7H using the strain gauges 7V and 7H, similarly to the first configuration example, and the V drive generation circuit. 22 and the drive signal output by the H drive generation circuit 23 can be suitably adjusted.

[Modification]
Next, a modified example suitable for the above embodiment will be described. The following modifications may be applied to the above-described embodiments in combination.

(Modification 1)
In the first configuration example shown in FIG. 4, the MEMS drive circuit 30 has a configuration for supplying a signal corresponding to the temperature for each of the strain gauge 7 </ b> V and the strain gauge 7 </ b> H to the averaging processing unit 29. Instead, the MEMS drive circuit 30 may have a configuration in which a signal corresponding to the temperature for one of the strain gauge 7V and the strain gauge 7H is supplied to the averaging processing unit 29. Even in this case, the averaging processing unit 29 uses the temperature detected from either the strain gauge 7V or the strain gauge 7H as the temperature of the MEMS mirror device 20, and the vertical scanning speed correction unit 26 and the amplitude adjustment unit 27. , And can be supplied to the phase adjustment unit 28, respectively. Similarly, in the second configuration example shown in FIG. 5, the MEMS drive circuit 30 has a configuration in which a signal corresponding to the temperature for one of the strain gauge 7V and the strain gauge 7H is supplied to the averaging processing unit 29. Also good.

(Modification 2)
In the first and second configuration examples, the thermistor 21 is provided in the MEMS mirror device 20. Instead of or in addition to this, for example, the thermistor 21 may be provided in the vicinity of the coil 8 so that the temperature of the coil 8 can be accurately detected. In this case, the vertical scanning speed correction unit 26 and the like can generate a control signal to be supplied to the V drive generation circuit 22 and the like in consideration of the temperature characteristics of the coil 8. In another example, the thermistor 21 may not be provided in the MEMS drive circuit 30. In this case, for example, the vertical scanning speed correction unit 26 or the like regards the temperature estimated from the output of the strain gauge 7V or / and the strain gauge 7H as the temperature of the MEMS drive circuit 30, and generates a control signal as in the embodiment. In yet another example, the thermistor 21 may be provided near the laser element of the light source unit 10. In this case, the phase adjustment unit 28 determines a parameter for adjusting the phase of horizontal scanning, for example, further taking into account the temperature indicated by the detection signal of the temperature sensor provided in the vicinity of the laser element of the light source unit 10.

(Modification 3)
Although the light source unit 10 is an electromagnetic drive type MEMS mirror having magnets 4A to 4D, the drive method of the MEMS mirror applicable to the present invention is not limited to this. Instead of this, even in a MEMS mirror that employs other driving methods such as an electrostatic driving method using an electrostatic force acting between electrode plates, a piezoelectric driving method using a deformation force of a piezoelectric material, the present invention is similar to the embodiment. Can be suitably applied.

(Modification 4)
The configuration for detecting the temperature based on the temperature characteristic of the piezoresistor included in the strain gauge 7 (7A, 7B) is not limited to the image projector 100 shown in FIG. 1, and may be applied to any actuator having a movable part. .

  In this case, the actuator is provided with a strain gauge for measuring the displacement of the movable part. Similar to the configuration example of FIG. 4 or FIG. 5, the constant voltage source or the constant current source connected to the strain gauge, the output of the constant voltage source. An averaging processing unit that averages the output voltage of the current or the constant current source over a predetermined period of time, a drive generation circuit that adjusts the drive signal of the movable unit based on temperature information output by the averaging processing unit, and the like are provided. Thus, the configuration of the present invention that detects the temperature based on the temperature characteristics of the strain sensor is preferably applied to any actuator having a movable part.

DESCRIPTION OF SYMBOLS 1 Fixed frame 2 Frame part 3 Mirror part 4A-4D Magnet 5A, 5B X-axis torsion bar 6A, 6B Y-axis torsion bar 10 Light source part 20 MEMS mirror device 30 MEMS drive circuit 100 Image projector

Claims (8)

A drive circuit for outputting a drive signal for periodically driving an actuator having a strain gauge for measuring the displacement of the movable part;
A power supply for supplying a constant current to the strain gauge;
A temperature detection unit that detects an average value of the output voltage value within a predetermined period of the power supply unit as temperature information of the strain gauge;
An adjustment unit that adjusts a drive signal of the drive circuit based on temperature information detected by the temperature detection unit;
An actuator driving device comprising: A drive circuit for outputting a drive signal for periodically driving an actuator having a strain gauge for measuring the displacement of the movable part;
A power supply for supplying a constant voltage to the strain gauge;
A temperature detection unit that detects, as temperature information of the strain gauge, an average value based on an output current value within a predetermined period of the power supply unit;
An adjustment unit that adjusts a drive signal of the drive circuit based on temperature information detected by the temperature detection unit;
An actuator driving device comprising:   The actuator driving apparatus according to claim 1, wherein the strain gauge includes a piezoresistor.   4. The actuator driving apparatus according to claim 1, wherein the temperature detection unit calculates the average value by setting a period of one cycle or more of the driving signal as the predetermined period. 5. A correction circuit for correcting the output of the strain gauge according to the output voltage value of the power supply unit;
2. The actuator drive according to claim 1, wherein the adjustment unit adjusts a drive signal of the drive circuit based on an output of the strain gauge corrected by the correction circuit and temperature information detected by the temperature detection unit. apparatus. The actuator having a mirror disposed on the movable part;
A light source unit that emits light corresponding to an image signal toward the mirror;
The actuator driving device according to any one of claims 1 to 5,
An image projection apparatus comprising: A power supply that supplies a constant current to the strain gauge that measures the displacement of the movable part of the actuator;
A temperature detection unit that detects an average value of the output voltage value within a predetermined period of the power supply unit as temperature information of the strain gauge;
A temperature detecting device comprising: A power supply unit that supplies a constant voltage to a strain gauge that measures the displacement of the movable part of the actuator;
A temperature detection unit that detects an average value of output current values within a predetermined period of the power supply unit as temperature information of the strain gauge;
A temperature detecting device comprising: