Driving device for movable body and movable body deflection device

Abstract

[Purpose] To provide a driving device for a movable body, the driving device being capable of reliably reducing the amplitude of ringing occurring when driving a swingable movable body. [Constitution] A driving device according to the present invention generates a driving signal for driving a movable part of an actuator having the movable part swingably fixed thereto. The driving device includes: a waveform generation circuit that generates a sawtooth wave signal which has a sawtooth waveform of a predetermined frequency and each cycle of which comprises a rise period in which voltage gradually rises and a fall period in which voltage gradually falls; and an amplifier that generates, as the driving signal, a signal obtained by amplifying the sawtooth wave signal. When the shorter period of the rise period and the fall period is divided into a first section and a second section following the first section, the voltage change rate of the sawtooth wave signal in the second section is lower than the voltage change rate of the sawtooth wave signal in the first section.

Description

Movable body drive device and movable body deflection device

[0001] The present invention relates to a drive device for driving a movable body, particularly a movable body that is fixed in a swingable state, and a movable body deflection device.

[0002] As such a movable body deflection device, a drive device that drives a MEMS (Micro Electro Mechanical Systems) mirror that has a mirror unit and can oscillate the mirror unit in a rotational direction around at least one axis is known. The drive device oscillates the mirror unit by supplying a drive signal having, for example, a sawtooth or rectangular waveform to the MEMS mirror.

[0003] Incidentally, when a device having a resonant characteristic such as a MEMS mirror is driven by a signal having a sawtooth or rectangular waveform so that the amplitude changes sharply in a short period of time, ringing occurs at the resonant frequency of the MEMS mirror.

[0004] Therefore, a driving device has been proposed that generates a driving signal in which the ringing superimposed on both signals is cancelled out by combining two identical sawtooth wave signals that serve as the source of the driving signal with a phase shift of half a cycle of the resonant frequency (see, for example, Patent Document 1).

[0005] Patent No. 5659056

[0006] However, the amplitude of the ringing (high frequency component) decays over time. Therefore, during a half cycle of the resonant frequency, there is a difference in amplitude between the ringing that occurs first and the ringing that occurs after the half cycle of the resonant frequency has elapsed. Therefore, even if the two are combined, it is not possible to completely cancel out the ringing.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a drive device for a movable body that can reliably reduce the amplitude of ringing when driving a swingable movable body with a drive signal.

[0008] A driving device for a movable body according to the present invention is a driving device that generates a driving signal for driving an actuator having a movable part that is fixed so as to be able to swing, so as to swing the movable part, and includes: a waveform generating circuit that generates a sawtooth wave signal having a sawtooth waveform of a predetermined frequency, each cycle consisting of a rise period in which the voltage gradually rises and a fall period in which the voltage gradually falls; and an amplifier that generates a signal by amplifying the sawtooth wave signal as the driving signal, and is characterized in that when one of the rise period and fall period, which has a shorter duration, is divided into a first section and a second section following the first section at a boundary point, the voltage change rate of the sawtooth wave signal in the second section is lower than the voltage change rate of the sawtooth wave signal in the first section.

[0009] A movable body deflection device according to the present invention includes a waveform generating circuit that generates a sawtooth wave signal having a sawtooth waveform of a predetermined frequency, each cycle consisting of a rise period in which voltage gradually increases and a fall period in which the voltage gradually decreases; an amplifier that generates a signal by amplifying the sawtooth wave signal as a drive signal; a movable part that is fixed so as to be able to swing; and a drive part that drives the movable part to swing in accordance with the drive signal, wherein when one of the rise period and fall period, which has a shorter period length, is divided into a first section and a second section subsequent to the first section, the voltage change rate of the sawtooth wave signal in the second section is lower than the voltage change rate of the sawtooth wave signal in the first section.

[0010] In the present invention, the shorter of the rise period and fall period of each cycle of a sawtooth wave signal serving as a drive signal for oscillating a movable body is divided into a first section and a subsequent second section, and the voltage change rate in the second section is set lower than the voltage change rate in the first section, thereby making it possible to reliably reduce ringing.

[0011] FIG. 1 is a diagram showing a schematic configuration of a mirror deflection device 100 as a first embodiment of a movable body deflection device according to the present invention. FIG. 2 is a waveform diagram showing an example of a sawtooth wave signal generated by the driving device 10. FIG. 3 is a waveform diagram showing another example of a sawtooth wave signal generated by the driving device 10. FIG. 4 is a block diagram showing an example of the internal configuration of the driving device 10. FIG. 5 is a diagram showing an example of a memory map of a waveform memory 101. FIG. 6 is a waveform diagram showing one period of waveforms of sample data d1 to dr and a sawtooth wave signal WVS included in waveform data WD1 stored in the waveform memory 101. FIG. 7 is a waveform diagram showing one period of waveforms of sample data d1 to dr and a sawtooth wave signal WVS included in waveform data WD2 stored in the waveform memory 101. FIG. 8 is a waveform diagram showing one period of waveforms of sample data d1 to dr and a sawtooth wave signal WVS included in waveform data WD3 stored in the waveform memory 101. FIG. 9 is a block diagram showing another example of the internal configuration of the driving device 10. FIG. 10 is a diagram showing a schematic configuration of a mirror deflection device 100A as a second embodiment of a movable body deflection device according to the present invention. It is a block diagram showing an example of the internal configuration of the drive device 10A.It is a flowchart showing a ringing initial correction routine.It is a flowchart showing a ringing correction routine.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0013] FIG. 1 is a diagram showing a schematic configuration of a mirror deflection device 100 as a first embodiment of a movable body deflection device according to the present invention.

[0014] As shown in FIG. 1, a mirror deflection device 100 includes a driving device 10 according to the present invention and a MEMS (Micro Electro Mechanical System) mirror 20 as an actuator.

[0015] The MEMS mirror 20 includes a frame 21 in which a mirror portion MR having a reflective surface is arranged at the center, bases 22a and 22b, and magnets 23a and 23b.

[0016] The frame 21 is provided with torsion bars T1a and T1b at two opposing locations on its outer periphery, each extending in the direction of the axis J1 shown in Figure 1. One end of each of the torsion bars T1a and T1b is fixed to bases 22a and 22b. The magnets 23a and 23b are installed at opposing positions on an axis perpendicular to the axis J1, with the frame 21 sandwiched between them.

[0017] That is, the mirror portion MR is a movable portion that is fixed to the bases 22a and 22b via the torsion bars T1a and T1b in a state that allows it to swing in the rotational direction around the axis J1.

[0018] A coil LC wired in a loop or spiral shape is disposed on the surface of the frame 21. One end of the wire constituting the coil LC is connected to an electrode pad Pa provided on the base 22a, and the other end of the wire is connected to an electrode pad Pb provided on the base 22b.

[0019] With this configuration, in the MEMS mirror 20, a driving unit consisting of a coil LC and magnets 23a and 23b drives the mirror portion MR, which serves as a movable portion, to oscillate in a rotational direction around the axis J1 in accordance with a driving signal VG supplied to the pads Pa and Pb.

[0020] The driving device 10 generates a sawtooth wave signal having a predetermined frequency and a sawtooth waveform, and supplies the amplified signal to the electrode pads Pa and Pb of the MEMS mirror 20 as the driving signal VG.

[0021] FIG. 2A is a waveform diagram showing an example of a sawtooth wave signal generated by the driving device 10. As shown in FIG.

[0022] As shown in FIG. 2A, the sawtooth wave signal is a sawtooth oscillation signal having an amplitude A, each cycle of which is made up of a rising period Pr in which the voltage gradually rises and a falling period Pf in which the voltage gradually falls.

[0023] In this case, in the sawtooth wave signal shown in FIG. 2A, the length of the rise period Pr during which the voltage gradually rises to the peak voltage Vp is shorter than the fall period Pf during which the voltage gradually falls from the peak voltage Vp state.

[0024] In the sawtooth wave signal shown in FIG. 2A, the shorter of the rising period Pr and the falling period Pf, i.e., the length of the rising period Pr, is equal to the period of the resonance frequency when the mirror portion MR oscillates (hereinafter referred to as the resonance period T0).

[0025] Furthermore, in the sawtooth wave signal shown in FIG. 2A, when the rising period Pr is divided into a first section f1 and a subsequent second section f2 with a boundary time tx as the boundary, the voltage change rate in the second section f2 is set lower than the voltage change rate in the first section f1.

[0026] This makes it possible to reduce the amplitude of ringing during the rising period Pr compared to when the voltage is raised to the peak voltage Vp at the same voltage change rate as in the first section f1.

[0027] FIG. 2B is a waveform diagram showing another example of a sawtooth wave signal generated by the driving device 10. In FIG.

[0028] As shown in FIG. 2B, the sawtooth wave signal is a sawtooth oscillation signal having an amplitude A, each cycle of which is made up of a rising period Pr in which the voltage gradually rises and a falling period Pf in which the voltage gradually falls.

[0029] In this case, in the sawtooth wave signal shown in FIG. 2B, the length of the rise period Pr during which the voltage gradually rises to the peak voltage Vp is longer than the fall period Pf during which the voltage gradually falls from the peak voltage Vp state.

[0030] In the sawtooth wave signal shown in FIG. 2B, the shorter of the rising period Pr and the falling period Pf, that is, the length of the falling period Pf, is equal to the resonance period T0 when the mirror part MR oscillates.

[0031] Furthermore, in the sawtooth wave signal shown in FIG. 2B, when the falling period Pf is divided into a first section f1 and a subsequent second section f2 with the boundary time tx as the boundary, the voltage change rate in the second section f2 is set lower than the voltage change rate in the first section f1.

[0032] This makes it possible to reduce the amplitude of ringing during the falling period Pf, compared to when the voltage is decreased uniformly at the voltage change rate in the second section f2.

[0033] However, if variations occur in the resonant frequency and Q value of the mirror portion MR due to manufacturing variations, etc., the ringing state (frequency, amplitude, attenuation characteristics) may also deviate from the expected state, which may result in incomplete ringing suppression.

[0034] To address this issue, the driving device 10 has the function of adjusting the phase (position) of the boundary time tx between the first section f1 and the second section f2 shown in Figure 2A or 2B, as well as the voltage change rate of each of the first section f1 and the second section f2, in accordance with the waveform adjustment signal WAJ.

[0035] As a result, by adjusting the position (phase) of the boundary time tx, the ringing frequency deviation caused by the above-mentioned variation in the resonant frequency is fine-tuned. Furthermore, by adjusting the voltage change rate in this way, the change in the amount of attenuation of the ringing over time caused by the above-mentioned variation in the Q factor is corrected. Furthermore, even if the resonant frequency of the mirror portion MR becomes an integer multiple of the frequency of the sawtooth wave signal and the spectrum of the integer multiple of the sawtooth wave signal is lost due to attenuation associated with the notch characteristic, the linearity of the sawtooth waveform can be maintained by adjusting both the position (phase) of the boundary time tx and the voltage change rate to generate a resonant spectrum.

[0036] FIG. 3 is a block diagram showing an example of the internal configuration of the drive device 10.

[0037] In the example shown in FIG. 3 , the driving device 10 includes a waveform generating circuit 11 and an output amplifier 12 .

[0038] The waveform generating circuit 11 includes a waveform memory 101 , a read control circuit 102 , and a DA (digital to analog) converter 103 .

[0039] The waveform memory 101 stores in advance a plurality of waveform data pieces representing one period of the signal waveform of the sawtooth wave signal shown in FIG. 2A or 2B.

[0040] FIG. 4 is a diagram showing an outline of the memory map of the waveform memory 101. As shown in FIG.

[0041] As shown in FIG. 4, the waveform memory 101 stores waveform data WD1 to WDj that represent the waveform of one cycle of a sawtooth wave signal, in which the position (phase) of the boundary time point tx shown in FIG. 2A or 2B and the voltage change rate in the first section f1 and the second section f2 are different.

[0042] Each of the waveform data WD1 to WDj includes sample data d1 to dr, which respectively represent, for example, in 8 bits, each sample value when one period of the sawtooth wave signal described above is sampled r times (r is an integer of 2 or more) at a predetermined sampling interval SP.

[0043] In this case, the sampling interval SP is 1 / n (n is an integer greater than or equal to 2) of the resonance period T0 of the mirror portion MR, and "n" is the number of samples within the rise period Pr shown in FIG. 2A or the fall period Pf shown in FIG. 2B.

[0044] The read control circuit 102 receives a waveform adjustment signal WAJ that specifies one of the waveform data WD1 to WDj, and performs read control on the waveform memory 101 to repeatedly read out the one waveform data piece specified by the waveform adjustment signal WAJ.

[0045] In response to this read control, the waveform memory 101 repeatedly reads out the sequence of sample data d1 to dr included in one of the waveform data WD1 to WDj. Specifically, the waveform memory 101 repeatedly performs a series of read processes in which each of the sample data d1 to dr is read out in turn at each sampling interval SP, and supplies the read sequence of sample data d1 to dr to the DA converter 103.

[0046] The DA converter 103 converts each of the sample data d1 to dr read out from the waveform memory 101 into an analog voltage corresponding to the sample value indicated by the sample data piece, thereby generating a sawtooth wave signal WVS, and supplies this to the output amplifier 12.

[0047] The output amplifier 12 amplifies the sawtooth wave signal WVS and supplies the amplified signal as a drive signal VG to the MEMS mirror 20. The output amplifier 12 may be built in the DA converter 103.

[0048] The operation of generating and adjusting the sawtooth wave signal WVS by the driving device 10 configured as shown in FIG. 3 will be described below with reference to an example shown in FIGS. 5A to 5C.

[0049] 5A, 5B, and 5C are waveform diagrams showing sample data d1-dr included in waveform data WD1, WD2, and WD3, respectively, and the waveform of one cycle of sawtooth wave signal WVS based on the sample data d1-dr. Note that in FIGS. 5A-5C, the number of samples n within the rising period Pr is set to "8," and the associated sampling interval SP is set to (resonance period T0 / 8). Also, in FIGS. 5A-5C, the form of sample data d9-dr during the falling period Pf and the waveform of sawtooth wave signal WVS based on the sample data d9-dr are the same.

[0050] Here, when the driving device 10 receives a waveform adjustment signal WAJ that specifies, for example, waveform data WD1, first, the sample data d1 to dr included in the waveform data WD1 is read from the waveform memory 101 and supplied to the DA converter 103. As a result, the driving device 10 outputs a sawtooth wave signal WVS having a sawtooth waveform corresponding to the series of sample data d1 to dr shown in FIG.

[0051] According to the waveform data WD1, as shown in FIG. 5A, the rising period Pr is divided into a first section f1 and a second section f2 of the same length, with a boundary time t1 as the boundary.

[0052] 5A, the number of sample data pieces in the first interval f1 (four pieces, d1 to d4) is the same as the number of sample data pieces in the second interval f2 (four pieces, d5 to d8). However, the amplitude difference P2 between adjacent pieces of sample data d4 to d8 is smaller than the amplitude difference P1 between adjacent pieces of sample data d1 to d4.

[0053] For example, the amplitude difference P1 is expressed as follows: P1=(A / 8)+α, where A is the amplitude of the sawtooth wave signal WVS and α is a positive predetermined number, and the amplitude difference P2 is expressed as follows: P2=(A / 8)-α.

[0054] As a result, in the first section f1 within the rising period Pr of the sawtooth wave signal WVS generated based on the waveform data WD1, the voltage of the sawtooth wave signal WVS rises at a voltage change rate of f1:(A+8α) / T0, and in the next second section f2, the voltage of the sawtooth wave signal WVS rises at a voltage change rate of f2:(A-8α) / T0, which is lower than that of the first section f1.

[0055] Furthermore, when the driving device 10 receives a waveform adjustment signal WAJ that specifies the waveform data WD2, first, the sample data d1 to dr included in the waveform data WD2 is read from the waveform memory 101 and supplied to the DA converter 103. As a result, the driving device 10 generates a sawtooth wave signal WVS having a sawtooth waveform corresponding to the series of sample data d1 to dr shown in FIG.

[0056] According to the waveform data WD2, as shown in Figure 5B, the rise period Pr is divided into a first section f1 and a second section f2 that is shorter than the first section f1, with the boundary being a boundary time t2 that is one sampling interval SP later than the boundary time t1 shown in Figure 5A.

[0057] Therefore, as shown in FIG. 5B, the number of sample data pieces in the first section f1 (five pieces: d1 to d5) is greater than the number of sample data pieces in the second section f2 (three pieces: d6 to d8).

[0058] In this case, in the waveform data WD2, the first sample data d1 among the sample data d1 to d5 in the first section f1 has a sample value with the amplitude difference P2 described above, and the amplitude difference between adjacent pieces of sample data d1 to d5 in the series is the amplitude difference P1 described above. Also, the amplitude difference between adjacent pieces of sample data d5 to d8 in the series in the second section f2 is the amplitude difference P2 described above.

[0059] Therefore, in the first section f1 within the rising period Pr of the sawtooth wave signal WVS generated based on the waveform data WD2, the voltage of the sawtooth wave signal WVS increases at a voltage change rate of f1:(A+4.8α) / T0, and in the next second section f2, the voltage of the sawtooth wave signal WVS increases at a voltage change rate of f2:(A-8α) / T0, which is lower than that of the first section f1.

[0060] That is, the voltage change rate in the first section f1 shown in Fig. 5B is lower than the voltage change rate in the first section f1 shown in Fig. 5A. Note that the voltage change rate in the second section f2 is the same in both Fig. 5A and Fig. 5B, but the section length of the second section f2 shown in Fig. 5B is shorter than the second section f2 shown in Fig. 5A, and therefore the time during which the state of the voltage change rate (A-8α) / T0 described above is maintained is also shorter.

[0061] Furthermore, when the driving device 10 receives a waveform adjustment signal WAJ that specifies the waveform data WD3, first, the sample data d1 to dr included in the waveform data WD3 is read from the waveform memory 101 and supplied to the DA converter 103. As a result, the driving device 10 generates a sawtooth wave signal WVS having a sawtooth waveform corresponding to the series of sample data d1 to dr shown in FIG.

[0062] According to the waveform data WD3, as shown in Figure 5C, the rise period Pr is divided into a first section f1 and a second section f2 that is shorter than the first section f1, with the boundary being a boundary time t3 that is two sampling intervals SP later than the boundary time t1 shown in Figure 5 as the boundary.

[0063] Therefore, as shown in FIG. 5C, the number of sample data pieces in the first section f1 (six pieces: d1 to d6) is greater than the number of sample data pieces in the second section f2 (two pieces: d7 and d8).

[0064] In this case, in the waveform data WD3, the amplitude difference between adjacent pieces of sample data d1 and d2 in the series of sample data d1 to d6 in the first section f1 is the amplitude difference P2 described above, and the amplitude difference between adjacent pieces of sample data d2 to d6 in the series is the amplitude difference P1 described above. Also, the amplitude difference between adjacent pieces of sample data d6 to d8 in the series of sample data d6 to d8 in the second section f2 is the amplitude difference P2 described above.

[0065] Therefore, in the first section f1 within the rising period Pr of the sawtooth wave signal WVS generated based on the waveform data WD3, the voltage of the sawtooth wave signal WVS increases at a voltage change rate of f1: (A + 2.66α) / T0, and in the second section f2, the voltage of the sawtooth wave signal WVS increases at a voltage change rate of f2: (A - 8α) / T0, which is lower than that of the first section f1.

[0066] That is, the voltage change rate in the first section f1 shown in Fig. 5C is lower than the voltage change rate in the first section f1 shown in Fig. 5B. Note that the voltage change rate in the second section f2 is the same in both Fig. 5B and Fig. 5C, but the section length of the second section f2 shown in Fig. 5C is shorter than the second section f2 shown in Fig. 5B, and therefore the time during which the state of the voltage change rate (A-8α) / T0 described above is maintained is also shorter.

[0067] 3, the waveform data WD1 to WDj, which indicate the position of the boundary time point tx at which the voltage change rate is switched within the shorter of the falling period Pf and the rising period Pr, and which indicate different voltage change rates in the first section f1 and the second section f2, are stored in advance in the waveform memory 101. The driving device 10 then reads out one waveform data segment indicated by the waveform adjustment signal WAJ from among the waveform data WD1 to WDj, and performs digital-to-analog conversion on this to obtain a sawtooth wave signal WVS in which the position of the boundary time point tx and the voltage change rates in the first section f1 and the second section f2 have been adjusted.

[0068] As a result, by adjusting the position (phase) of the boundary time point tx described above, a fine adjustment is made to the ringing frequency deviation caused by variations in the resonant frequency of the mirror section MR. Furthermore, by adjusting the voltage change rate, a correction is made to the change in the amount of attenuation of the ringing over time caused by variations in the Q value of the mirror section MR. Furthermore, even if the resonant frequency of the mirror section MR becomes an integer multiple of the frequency of the sawtooth wave signal and the spectrum of the integer multiple of the sawtooth wave signal is lost due to attenuation associated with the notch characteristic, the linearity of the sawtooth waveform can be maintained by adjusting both the position (phase) of the boundary time point tx and the voltage change rate to generate a resonant spectrum.

[0069] In the configuration shown in FIG. 3, waveform data WD1 to WDj are prepared in advance, each adjusted to a different degree of adjustment (the position of the boundary time point tx, and the voltage change rate at each of f1 and f2). Alternatively, the driving device 10 may generate basic waveform data itself including sample data d1 to dr, and then adjust this data based on the waveform adjustment signal WAJ.

[0070] FIG. 6 is a block diagram showing an example of another internal configuration of the drive device 10 that has been designed in consideration of the above points.

[0071] In the configuration shown in FIG. 6, a waveform generating circuit 11A is used in place of the waveform generating circuit 11 shown in FIG.

[0072] The waveform generating circuit 11A includes a microcontroller (hereinafter also referred to as MCU) 110 equipped with a CPU, memory, etc., and a DA converter 103 .

[0073] The MCU 110 includes a non-volatile memory 111 that stores a waveform data generation program for generating waveform data that is the basis of the sawtooth wave signal WVS, as well as basic parameters for generating the sawtooth wave signal, etc. The basic parameters include the frequency, amplitude, resonance period of the mirror part MR, number of samplings n, boundary time tx, and initial voltage change rates in each of the first section f1 and the second section f2.

[0074] The waveform data generating program includes a rising waveform data generating step, a falling waveform data generating step, and a ringing adjustment step.

[0075] By executing the rising waveform data generation process, the MCU 110 generates a series of sample data d1 to d8, each consisting of, for example, 8 bits, that represent the signal waveform during the rising period Pr in Figure 5A, based on the above-mentioned basic parameters, for example, amplitude: A, resonance period: T0, number of samples n: 8, initial position of boundary time point tx: t1, initial voltage change rates at f1 and f2, respectively: Q1 and Q2.

[0076] Next, the MCU 110 executes a falling waveform data generating step to generate a series of sample data d9 to dr, each consisting of, for example, 8 bits, which represents the signal waveform in the falling period Pf of FIG. 5A.

[0077] Next, the MCU 110 executes a ringing adjustment process to adjust the series of sample data d1 to d8 generated based on the above-described basic parameters in accordance with the waveform adjustment signal WAJ that specifies the position of the boundary time tx between the first interval f1 and the second interval f2 and the voltage change rates in each of the first interval f1 and the second interval f2. For example, when the MCU 110 receives the waveform adjustment signal WAJ that specifies the boundary time t2 and the voltage change rates in each of the first interval f1 and the second interval f2 as shown in FIG. 5B, the MCU 110 adjusts the sample data d1 to d8 shown in FIG. 5A, which were generated based on the above-described basic parameters, to the form of the sample data d1 to d8 shown in FIG. 5B.

[0078] The MCU 110 then connects the adjusted series of sample data d1 to d8 with the series of sample data d9 to dr generated based on the basic parameters, and supplies the result to the DA converter 103.

[0079] The DA converter 103 and the output amplifier 12 are the same as those shown in FIG. 3, and therefore a description thereof will be omitted.

[0080] FIG. 7 is a diagram showing a schematic configuration of a mirror deflection device 100A as a second embodiment of a movable body deflection device according to the present invention.

[0081] A mirror deflection device 100A shown in FIG. 7 includes a driving device 10A according to the present invention and a MEMS mirror 20A as an actuator.

[0082] The MEMS mirror 20A has the same configuration as that shown in FIG. 1 except for the newly provided swing angle sensor 25, and therefore a description of the other configuration will be omitted.

[0083] The swing angle sensor 25 is, for example, a piezoelectric sensor or the like, and is installed on the surface of the torsion bar T1a. The swing angle sensor 25 detects the swing angle when the mirror part MR swings around the axis J1, and supplies a swing angle detection signal SA indicating the swing angle to the drive device 10A.

[0084] Similar to the driving device 10 shown in FIG. 1, the driving device 10A generates a sawtooth wave signal WVS having a sawtooth waveform as shown in FIG. 2A or 2B, amplifies this signal, and supplies the amplified signal as a driving signal VG to the electrode pads Pa and Pb of the MEMS mirror 20A.

[0085] Therefore, in the drive device 10A, as in the drive device 10, when generating a sawtooth wave signal, ringing is suppressed by making the voltage change rate in the latter section f2 of the first section f1 and second section f2, which are obtained by dividing the shorter of the voltage rise period and fall period into two sections at the boundary time tx, lower than in the first section f1.

[0086] Furthermore, the drive unit 10A does not adjust ringing in accordance with the waveform adjustment signal WAJ supplied from the outside, but has a self-correction function that corrects ringing suppression to an optimal state based on the swing angle detection signal SA supplied from the swing angle sensor 25.

[0087] FIG. 8 is a block diagram showing an example of the internal configuration of such a driving device 10A.

[0088] As shown in FIG. 8, a driving device 10A employs a waveform generating circuit 11B instead of the waveform generating circuit 11A shown in FIG.

[0089] The waveform generating circuit 11B includes an AD converter 109, an MCU (microcontroller) 110A, and a DA converter 103.

[0090] The AD converter 109 converts the swing angle represented by an analog voltage value in the swing angle detection signal SA supplied from the swing angle sensor 25 into a swing angle data signal DSA represented by a digital value, and supplies the swing angle data signal DSA to the MCU 110A.

[0091] The MCU 110A includes a waveform data generation program for generating waveform data that forms the basis of a sawtooth wave signal, a non-volatile memory 111A that stores basic parameters for generating a sawtooth wave signal, and a ringing detector 112.

[0092] The basic parameters include the frequency, amplitude, resonance period of the mirror portion MR, number of samplings n, boundary time tx, initial voltage change rates in each of the first interval f1 and the second interval f2, etc. The waveform data generation program also includes a rising waveform data generation step, a falling waveform data generation step, and a ringing correction step.

[0093] The ringing detector 112 is composed of, for example, a frequency analyzer that performs FFT (fast Fourier transform), detects ringing based on the swing angle data signal DSA, and generates ringing information that indicates the frequency and amplitude of the detected ringing.

[0094] The MCU 110A executes a rising waveform data generating step, a falling waveform data generating step, and a ringing correction step in accordance with a waveform data generating program stored in the memory 111A.

[0095] The following describes the operations performed by the MCU 110A in each of the rising waveform data generating step, the falling waveform data generating step, and the ringing correction step, assuming that the driving device 10A generates the driving signal VG shown in FIG. 2A.

[0096] First, the MCU 110A executes the rising waveform data generation process to generate a series of sample data d1 to d8, each consisting of, for example, 8 bits, representing the signal waveform during the rising period Pr in Figure 5A, based on the above-mentioned basic parameters, for example, amplitude: A, resonance period: T0, number of samples n: 8, initial position of boundary time point tx: t1, initial voltage change rates at f1 and f2: Q1 and Q2.

[0097] Next, the MCU 110A executes a falling waveform data generating step to generate a series of sample data d9 to dr, each consisting of, for example, 8 bits, which represents the signal waveform in the falling period Pf of FIG. 5A.

[0098] Next, the MCU 110A executes a ringing correction process.

[0099] In the ringing correction process, the MCU 110A first performs an operation according to a ringing (hereinafter also referred to as RG) initial correction routine shown in FIG.

[0100] That is, in the RG initial correction process, the MCU 110A first resets the correction values ​​(amplitude, phase) for ringing correction to predetermined initial values ​​(step S11).

[0101] Next, the MCU 110A takes in the ringing information generated by the ringing detector 112, and sets the frequency and amplitude of the currently occurring ringing in an internal register (not shown) (step S12).

[0102] Next, since the period of the above-mentioned ringing frequency is the resonance period T0 of the mirror portion MR, the MCU 110A sets this as the period length of the rise period Pr (step S13).

[0103] Next, the MCU 110A sets the length of the falling period Pf by subtracting the length of the rising period Pr from the length of one cycle of the sawtooth wave signal.

[0104] Next, the MCU 110A corrects the magnitude of the amplitude difference P1 due to each of the sample data d1 to d4 in the first section f1 shown in FIG. 5A to a value that is one step larger (a predetermined amount), and corrects the amplitude difference P2 (P1 > P2) due to each of the sample data d5 to d8 in the second section f2 to a value that is one step smaller (a predetermined amount) (step S15). As a result, the MEMS mirror 20A is driven by the drive signal VG generated in accordance with the series of sample data d1 to dr, including the corrected sample data d1 to d8. At this time, the ringing detector 112 generates ringing information indicating the frequency and amplitude of the ringing detected in this driving state.

[0105] Here, the MCU 110A detects the amplitude of the ringing currently occurring by taking in the ringing information generated by the ringing detector 112 (step S16).

[0106] Next, the MCU 110A determines whether the amplitude of the ringing detected in step S16 has decreased from the amplitude of the ringing acquired in step S12 (step S17).

[0107] If it is determined in step S17 that the amplitude difference P1 has decreased, the MCU 110A corrects the magnitude of the amplitude difference P1 due to each of the sample data d1 to d4 in the first section f1 at the current time to a value that is one step larger (a predetermined amount), and corrects the amplitude difference P2 due to each of the sample data d5 to d8 in the second section f2 to a value that is one step smaller (a predetermined amount) (step S18). As a result, the MEMS mirror 20A is driven by the drive signal VG generated in accordance with the series of sample data d1 to dr including the corrected sample data d1 to d8. At this time, the ringing detector 112 generates ringing information indicating the frequency and amplitude of the ringing detected in this driving state.

[0108] Here, the MCU 110A detects the amplitude of the ringing currently occurring by taking in the ringing information generated by the ringing detector 112 (step S19).

[0109] Next, the MCU 110A determines whether the amplitude of the ringing detected in step S19 has decreased from the amplitude of the ringing previously acquired (step S20). If it is determined in step S20 that the amplitude has decreased, the MCU 110A returns to execution of step S18 and executes the series of operations from step S18 to S20 again.

[0110] If it is determined in step S17 that the amplitude of the ringing detected in step S16 has not decreased from the amplitude of the previously acquired ringing, the MCU 110A corrects the boundary time tx between the first interval f1 and the second interval f2 by one step, i.e., by one sampling interval, to a phase that is advanced by one step (step S21). This increases the number of sampled data pieces in the first interval f1, each having an amplitude difference P1, by one, and decreases the number of sampled data pieces in the second interval f2, each having an amplitude difference P2, by one. The MEMS mirror 20A is then driven by the drive signal VG generated in accordance with the series of sample data d1-dr, including the corrected sample data d1-d8. At this time, the ringing detector 112 generates ringing information indicating the frequency and amplitude of the ringing detected in this driving state.

[0111] Here, the MCU 110A detects the amplitude of the ringing currently occurring by taking in the ringing information generated by the ringing detector 112 (step S22).

[0112] Next, the MCU 110A determines whether the amplitude of the ringing detected in step S22 has decreased from the amplitude of the ringing previously acquired (step S23). If it is determined in step S23 that the amplitude has decreased, the MCU 110A returns to execution of step S21 and executes the series of operations from step S21 to S23 again.

[0113] On the other hand, if it is determined in step S23 that the amplitude difference has not decreased, the MCU 110A corrects the boundary time tx between the first interval f1 and the second interval f2 by one stage, i.e., to a phase delayed by one sampling interval (step S24). As a result, the number of sampled data pieces each having an amplitude difference P1 included in the first interval f1 decreases by one, and the number of sampled data pieces each having an amplitude difference P2 included in the second interval f2 increases by one.

[0114] After step S24, the MCU 110A proceeds to execute step S18, and again executes the series of operations from steps S18 to S20.

[0115] During this time, if it is determined in step S20 that the amplitude of the ringing detected in step S19 has not decreased from the amplitude of the ringing obtained last time, MCU 110A corrects the magnitude of the amplitude difference P1 due to each of the sample data d1 to d4 in the first section f1 at the current time to a value that is one step smaller (a predetermined amount), and corrects the amplitude difference P2 due to each of the sample data d5 to d8 in the second section f2 to a value that is one step larger (a predetermined amount) (step S25).

[0116] At this time, by executing step S25, the ringing is corrected to be suppressed as much as possible.

[0117] Therefore, after executing step S25, the MCU 110A exits the RG initial correction routine shown in FIG. 9 and returns to the execution of the main routine (not explained).

[0118] During the execution of the main routine, the MCU 110A executes an RG correction routine shown in FIG. 10 at predetermined intervals.

[0119] First, the MCU 110A corrects the magnitude of the amplitude difference P1 due to each of the sample data d1 to d4 in the first section f1 at the current time by one step (predetermined amount) to a value larger (or smaller), and also corrects the amplitude difference P2 due to each of the sample data d5 to d8 in the second section f2 by one step (predetermined amount) to a value larger (or smaller) (step S31). As a result, the MEMS mirror 20A is driven by the drive signal VG generated in accordance with the series of sample data d1 to dr including the corrected sample data d1 to d8. At this time, the ringing detector 112 generates ringing information indicating the frequency and amplitude of the ringing detected in this driving state.

[0120] Here, the MCU 110A detects the amplitude of the ringing currently occurring by taking in the ringing information generated by the ringing detector 112 (step S32).

[0121] Next, the MCU 110A determines whether the amplitude of the ringing detected in step S32 has decreased from the amplitude of the ringing previously acquired (step S33). If it is determined in step S33 that the amplitude has not decreased, the MCU 110A performs phase correction to return the boundary time tx between the first interval f1 and the second interval f2 to the previous state by one stage (step S34).

[0122] After step S34 is executed, or if it is determined in step S33 that the amplitude of the ringing has decreased, the ringing is suppressed to the maximum extent possible, so MCU 110A exits this RG correction routine and returns to executing the main routine (not described).

[0123] The MCU 110A then supplies to the DA converter 103 the series of sample data d1 to d8 that has been corrected as described above and the series of sample data d9 to dr that has been generated in the falling waveform data generating step.

[0124] The DA converter 103 converts each of the sample data d1 to dr into an analog voltage corresponding to the sample value indicated by the sample data piece, thereby generating a sawtooth wave signal WVS, and supplies this to the output amplifier 12.

[0125] The output amplifier 12 amplifies the sawtooth signal WVS and supplies the amplified signal to the MEMS mirror 20A as a drive signal VG.

[0126] In this way, in the drive device 10A shown in Figure 8, as in the drive device 10 shown in Figure 3 or Figure 6, the shorter of the rise period Pr and fall period Pf of the voltage of the sawtooth wave signal is divided into a first section f1 and a second section f2 at the boundary time tx, and ringing is suppressed by making the voltage change rate in the latter section f2 of these two sections lower than in the first section f1.

[0127] That is, the driving device (10) that generates a driving signal (VG) that drives the actuator (20) having a movable part (MR) that is fixed so as to be able to swing, so as to swing the movable part, may include the following waveform generating circuit and amplifier.

[0128] First, when generating a drive signal having a sawtooth waveform as shown in FIG. 2A , a waveform generating circuit (11, 11A, 11B) generates a sawtooth wave signal (WVS) having a sawtooth waveform of a predetermined frequency, with each period consisting of a rise period (Pr) in which the voltage gradually rises and a fall period (Pf) in which the voltage gradually falls. An amplifier (12) amplifies the sawtooth wave signal and outputs the amplified signal as a drive signal (VG). In this case, when the sawtooth wave signal generated by the waveform generating circuit has the shorter of the rise period (Pr) and the fall period (Pf), i.e., when the rise period is divided into a first period (f1) and a second period (f2) following the first period, the voltage change rate of the sawtooth wave signal in the second period (f2) is lower than the voltage change rate of the sawtooth wave signal in the first period (f1).

[0129] Furthermore, when generating a drive signal having a sawtooth waveform as shown in FIG. 2B , the waveform generating circuit (11, 11A, 11B) generates a sawtooth wave signal (WVS) having a sawtooth waveform of a predetermined frequency, with each period consisting of a rising period (Pr) in which the voltage gradually rises and a falling period (Pf) in which the voltage gradually falls. The amplifier (12) amplifies the sawtooth wave signal and outputs the amplified signal as the drive signal (VG). In this case, when the sawtooth wave signal generated by the waveform generating circuit has the shorter of the falling period (Pf) and the rising period (Pr), i.e., when the falling period is divided into a first period (f1) and a second period (f2) following the first period, the voltage change rate of the sawtooth wave signal in the second period (f2) is lower than the voltage change rate of the sawtooth wave signal in the first period (f1).

[0130] 10, 10A Driver 11, 11A Waveform generating circuit 20, 20A MEMS mirror 101 Waveform memory 103 DA converter 110, 110A MCU

Claims

1. A drive device that generates a drive signal to drive an actuator having a movable part that is fixed so as to be able to swing, so as to swing the movable part, comprising: a waveform generation circuit that generates a sawtooth wave signal having a predetermined frequency, each cycle consisting of a rise period in which the voltage gradually rises and a fall period in which the voltage gradually falls; and an amplifier that generates a signal by amplifying the sawtooth wave signal as the drive signal, wherein when one of the rise period and the fall period, which has a shorter duration, is divided into a first section and a second section following the first section, the voltage change rate of the sawtooth wave signal in the second section is lower than the voltage change rate of the sawtooth wave signal in the first section.

2. The drive device according to claim 1, wherein the length of said one period is equal to the resonance period of said actuator.

3. The drive device described in claim 1, wherein the waveform generating circuit includes a DA converter that receives waveform data including a series of multiple sample data pieces and generates the sawtooth wave signal by converting each of the sample data pieces into an analog signal at a predetermined sampling interval, and the predetermined sampling interval is expressed as 1 / n of the resonance period of the actuator (n is the number of samples in one of the periods).

4. A drive device as described in any one of claims 1 to 3, characterized in that the waveform generating circuit has an adjustment function that receives a waveform adjustment signal and adjusts the voltage change rate in the first section and the voltage change rate in the second section in accordance with the waveform adjustment signal.

5. The drive device according to claim 4, wherein the first section and the second section have the same length.

6. The drive device according to claim 4, wherein the waveform generating circuit has an adjustment function for adjusting the phase at the boundary between the first section and the second section within one of the periods in accordance with the waveform adjustment signal.

7. A drive device as described in any one of claims 1 to 3, characterized in that it includes a swing angle sensor that detects the swing angle of the swing of the movable part and generates a swing angle detection signal indicative of the swing angle, and the waveform generation circuit includes a ringing correction unit that detects the amplitude of ringing occurring in the sawtooth wave signal in accordance with the swing angle detection signal, and adjusts the voltage change rate in the first interval and the voltage change rate in the second interval, or the phase at the boundary point between the first interval and the second interval within one of the periods, so as to reduce the amplitude of the ringing.

8. A movable body deflection device comprising: a waveform generating circuit that generates a sawtooth wave signal having a sawtooth waveform of a predetermined frequency, each cycle consisting of a rise period in which the voltage gradually rises and a fall period in which the voltage gradually falls; an amplifier that generates a signal by amplifying the sawtooth wave signal as a drive signal; an actuator having a movable part that is fixed so as to be able to swing; and a drive part that drives the movable part to swing in accordance with the drive signal, wherein when one of the rise period and the fall period, which has a shorter period length, is divided into a first section and a second section subsequent to the first section, the voltage change rate of the sawtooth wave signal in the second section is lower than the voltage change rate of the sawtooth wave signal in the first section.

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