JP5400636B2 - Optical deflector and optical apparatus using the same - Google Patents

Description

  The present invention relates to a piezoelectric drive type optical deflector and an optical apparatus using the same. For example, as an optical device, there are a laser printer, a barcode reader, a projector, and the like.

  Recently, as a piezoelectric drive type optical deflector, a semiconductor manufacturing process technology, a micro electromechanical system (MEMS) technology is used to support a semiconductor substrate having a cavity and a mirror and a pair of mirrors that can be oscillated. There are known elastic beams, that is, a torsion bar, and two pairs of piezoelectric actuators acting on the torsion bar (see Patent Documents 1, 2, and 3). In this case, the mirror has a rectangular reflecting surface located at the center of the cavity of the support. Each torsion bar has a proximal end coupled to the support and a distal end coupled to the mirror. Each piezoelectric actuator acts as a cantilever, its proximal end is fixed to the support, and its distal end is connected to a torsion bar. Therefore, applying a driving voltage to the piezoelectric actuator causes the piezoelectric actuator to bend and deform torsionally the torsion bar, thereby rotating the mirror. As a result, the reflected light of the light incident on the rectangular reflecting surface of the mirror can be scanned one-dimensionally. Patent Documents 1 and 2 disclose a two-dimensional optical deflector.

  In the above-described piezoelectric drive type optical deflector, a piezoelectric type angle detection sensor (hereinafter referred to as a piezoelectric sensor) is a torsion bar in order to detect the angle of the rectangular reflecting surface of the mirror and feedback control the deflection angle and scan speed. (See Patent Document 3). In this case, since the piezoelectric sensor acts as a cantilever and is fixed to the side of the mirror and its base end is connected to the torsion bar, the angle of the mirror is detected without phase shift. Therefore, the mirror swing can be feedback controlled in real time.

JP 2005-148459 A JP 2008-20701 A JP 2009-169325 A JP 2001-234331 A JP 2002-177765 A JP 2003-81694 A

  In the conventional piezoelectric drive type optical deflector described above, since the mirror and the piezoelectric sensor are coupled, the mirror and the piezoelectric sensor act as one moment of inertia. Therefore, when the mirror and the piezoelectric sensor are operated in the atmosphere, the stress from the piezoelectric actuator is distributed to the mirror and the piezoelectric sensor according to the mass due to the viscous resistance of the atmosphere.

  The stress from the piezoelectric actuator dispersed in the piezoelectric sensor is relatively small for the piezoelectric sensor. Therefore, the displacement amount of the piezoelectric sensor is minute compared to the displacement amount of the piezoelectric actuator. As a result, there is a problem that it is difficult to detect a torsional displacement having a good signal-to-noise (S / N) ratio as a piezoelectric electromotive force.

  Here, the moment of inertia is defined as the moment of inertia around an axis connecting a pair of torsion bars.

In order to solve the above-described problems, an optical deflector according to the present invention includes a support body in which a cavity portion is formed, a mirror having a reflecting surface located in the cavity portion of the support body, and a base end connected to the support body. An elastic beam having a distal end coupled to the mirror, an actuator having a proximal end coupled to the support and a distal end coupled to the elastic beam, and an elastic beam coupled between the elastic beams and positioned on the outer peripheral side of the mirror via a slit. A piezoelectric sensor for detecting the angle, the actuator causes the mirror and the piezoelectric sensor to rotate and vibrate in the same direction via the elastic beam, and the slit changes the vibration frequency of the mirror to the frequency of rotation of the piezoelectric sensor. It is provided so that it may correspond . Thereby, since the mirror and the piezoelectric sensor are separated by the slit, the moment of inertia of the mirror and the moment of inertia of the piezoelectric sensor are different. In addition, the moment of inertia of the piezoelectric sensor becomes relatively large because the piezoelectric sensor is located on the outer peripheral side of the mirror via the slit.

  An optical device according to the present invention detects the angle signal of the above-described optical deflector, a light source for irradiating the optical deflector with light, a light source driving circuit for driving the light source, and a mirror of the piezoelectric sensor. A mirror angle detection circuit that performs correction, a storage circuit that stores correction data for correcting the detected angle signal of the mirror, a control circuit that corrects the detected angle signal of the mirror using the correction data, and a correction mirror An actuator driving circuit for driving the actuator by an angle signal.

  According to the present invention, the stress from the actuator is more distributed to the piezoelectric sensor having a large moment of inertia than the mirror having a small moment of inertia.

  The stress of the actuator dispersed in the piezoelectric sensor is relatively large. Accordingly, the piezoelectric sensor can be positively deformed. As a result, the displacement amount of the piezoelectric sensor can be increased, and therefore, a torsional displacement having a high S / N ratio can be detected as the piezoelectric electromotive force.

1 is a perspective view showing an embodiment of a piezoelectric drive type optical deflector according to the present invention. FIG. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1 for illustrating deformation of the piezoelectric actuator in FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1 for explaining deformation of the mirror and the piezoelectric sensor in FIG. 1. FIG. 2 is a timing diagram illustrating an input voltage, a mirror angle, and an output voltage of a piezoelectric sensor of the piezoelectric actuator of FIG. 1. FIG. 5 is a cross-sectional view taken along the line VV in FIG. 1 for explaining a method of manufacturing the optical deflector of the piezoelectric drive type in FIG. 1. FIG. 5 is a cross-sectional view taken along the line VV in FIG. 1 for explaining a method of manufacturing the optical deflector of the piezoelectric drive type in FIG. 1. FIG. 5 is a cross-sectional view taken along the line VV in FIG. 1 for explaining a method of manufacturing the optical deflector of the piezoelectric drive type in FIG. 1. It is a figure which shows the example of the optical apparatus using the optical deflector of the piezoelectric drive system of FIG. It is a flowchart for demonstrating operation | movement of the control circuit of FIG.

  FIG. 1 is a perspective view showing an embodiment of a piezoelectric drive type optical deflector according to the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1 for explaining the deformation of the piezoelectric actuator of FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1 for explaining deformation of the mirror and the piezoelectric sensor in FIG. 1.

As shown in FIG. 1, the optical deflector of the piezoelectric driving method, for example, have a size of 3 mm × 3 mm, the support 1 empty sinus portion 1a is formed, the radius 1mm located in the center of the air-dong portion 1a A mirror 2 having a circular reflecting surface, a pair of elastic beams having a width of about 30 μm and a length of about 300 μm for supporting the mirror 2 in a swingable manner, ie, torsion bars 3 and 4, and a torsion bar 3 acting as a cantilever 1 A pair of piezoelectric actuators 5, 6, a pair of piezoelectric actuators 7, 8 acting as a cantilever on the torsion bar 4, and a pair of piezoelectric sensors 9, 10 having a width of about 100 μm on which the torsion bars 3, 4 act. ing. The piezoelectric sensors 9 and 10 have a semi-annular shape, are connected to the roots of the torsion bars 3 and 4 on the mirror 2 side, and are provided on the outer peripheral side of the mirror 2 via slits SL . Since the piezoelectric sensors 9 and 10 need to bend, the thickness is 100 μm or less. The width SW of the slit SL (shown in FIG. 3) is about 10 μm to 100 μm, for example 20 μm. This is because if the width SW of the slit SL exceeds 100 μm, the phase shift between the piezoelectric sensors 9 and 10 and the mirror 2 increases, and the detection accuracy decreases. That is, the width SW of the slit SL is provided so that the vibration frequency of the swing (rotational vibration) of the mirror 2 matches the vibration frequency of the swing (rotational vibration) of the piezoelectric sensors 9 and 10. The maximum amplitudes 9 and 10 are set to be larger than the maximum amplitude of the mirror 2.

  The mirror 2 comprises a diaphragm 2a and a lower electrode 2b (shown in FIG. 3) that acts as a reflector.

  The torsion bar 3 comprises a diaphragm 3a and a lower electrode 3b (shown in FIG. 2), and the torsion bar 4 comprises a diaphragm 4a and a lower electrode 4b (not shown).

  The piezoelectric actuator 5 is a piezoelectric unimorph diaphragm, and includes a diaphragm 5a, a lower electrode 5b, a piezoelectric layer 5c and an upper electrode 5d (see also FIG. 2), and the piezoelectric actuator 6 is also a piezoelectric unimorph diaphragm. The diaphragm 6a, the lower electrode 6b, the piezoelectric layer 6c, and the upper electrode 6d (see also FIG. 2). In this case, as described above, the piezoelectric actuators 5 and 6 make a pair and act on the torsion bar 3.

  The piezoelectric actuator 7 is a piezoelectric unimorph diaphragm, and includes a diaphragm 7a, a lower electrode 7b, a piezoelectric layer 7c and an upper electrode 7d (only 7b and 7d are shown), and the piezoelectric actuator 8 is also a piezoelectric unimorph diaphragm. The diaphragm 8a, the lower electrode 8b, the piezoelectric layer 8c, and the upper electrode 8d (only 8b and 8d are shown). In this case, as described above, the piezoelectric actuators 7 and 8 make a pair and act on the torsion bar 4.

  The piezoelectric sensor 9 is a piezoelectric unimorph diaphragm, and includes a diaphragm 9a, a lower electrode 9b, a piezoelectric layer 9c and an upper electrode 9d (see also FIG. 3), and the piezoelectric sensor 10 is also a piezoelectric unimorph diaphragm. The diaphragm 10a, the lower electrode 10b, the piezoelectric layer 10c, and the upper electrode 10d (see also FIG. 3). In this case, as described above, the torsion bars 3 and 4 act on the piezoelectric sensors 9 and 10.

  In FIGS. 1, 2 and 3, the lower electrodes 2b, 3b, 4b, 5b, 6b, 7b, 8b, 9b and 10b are connected in common and are grounded, for example.

  Although not shown in FIGS. 1, 2 and 3, an etching stopper is provided between the support 1 and the diaphragms 2a, 3a, 4a, 5a, 6a, 7a, 8a, 9a and 10a in the manufacturing process. A working insulating layer, for example, a silicon oxide layer 1012 (shown in FIGS. 5, 6, and 7) is provided.

  Further, although not shown in FIGS. 1, 2 and 3, the diaphragms 2a, 3a, 4a, 5a, 6a, 7a, 8a, 9a, 10a and the lower electrodes 2b, 3b, 4b, 5b, 6b, 7b, 8b, 9b and 10b are electrically insulated by an insulating layer such as a silicon oxide layer 1022 (shown in FIGS. 5, 6 and 7).

  In FIGS. 1, 2 and 3, the mirror 2 is separated from the piezoelectric sensors 9 and 10 and becomes circular, so that the moment of inertia is relatively small. On the other hand, although the piezoelectric sensors 9 and 10 are separated from the mirror 2, the moment of inertia becomes relatively large because the piezoelectric sensors 9 and 10 are separated from the outer peripheral side of the mirror 2. As a result, the stress of the torsion bars 3 and 4 due to the piezoelectric actuators 5, 6, 7 and 8 is more dispersed in the piezoelectric sensors 9 and 10 than in the mirror 2. Accordingly, deformation of the center portion of the mirror 2 is suppressed, and the piezoelectric sensors 9 and 10 are positively deformed.

  Next, the operation of the piezoelectric drive type optical deflector of FIGS. 1, 2, and 3 will be described with reference to the timing chart of FIG. Note that the lower electrodes 2b, 3b, 4b, 5b, 6b, 7b, 8b, 9b, and 10b are grounded. The lower electrode and the peripheral part of the upper electrode act as pads for bonding wires.

  4A is applied as the input voltage of the upper electrodes 5d and 7d of the piezoelectric actuators 5 and 7, and the input voltage of the upper electrodes 6d and 8d of the piezoelectric actuators 6 and 8 is applied as shown in FIG. A sine wave AC voltage shown in B) is applied. In this case, the sine wave AC voltage shown in FIG. 4A and the sine wave AC voltage shown in FIG. As a result, as shown in FIG. 2, the piezoelectric layer 5c (7c) of the piezoelectric actuator 5 (7) and the piezoelectric layer 6c (8c) of the piezoelectric actuator 6 (8) are curved to the opposite sides, and accordingly, the piezoelectric actuator The vibration plate 5a (7a) of 5 (7) and the vibration plate 6a (8a) of the piezoelectric actuator 6 (8) are rotated in an S shape. At this time, since the base ends of the diaphragm 5a (7a) and the diaphragm 6a (8a) are connected to the support 1, the tips of the diaphragm 5a (7a) and the diaphragm 6a (8a) are connected to the support 1. Vibrates up and down in the thickness direction. In this case, since there is a phase difference of 180 ° between the input voltage of the upper electrode 5d (7d) of the piezoelectric actuator 5 (7) and the input voltage of the upper electrode 6d (8d) of the piezoelectric actuator 6 (8), the diaphragm 5a When the tip of (7a) vibrates up or down, the tip of diaphragm 6a (8a) vibrates down or up. Accordingly, the torsion bar 3 (4) swings or rotates.

  When the torsion bar 3 (4) swings, that is, rotates and oscillates, as shown in FIG. 3, rotational torque about the torsion bar 3 (4) is generated in the mirror 2 and the piezoelectric sensors 9 and 10, and the mirror 2 and piezoelectric The sensors 9 and 10 are inclined with the torsion bar 3 (4) as the central axis. In this case, as described above, due to the difference in the moment of inertia, the piezoelectric sensors 9 and 10 oscillate or rotate more greatly than the mirror 2 as indicated by arrows in FIG. That is, the maximum vibration width of the piezoelectric sensors 9 and 10 is larger than the maximum amplitude of the mirror 2. However, the slit width SW of the slit SL is set so that the oscillation frequency of the mirror 2 and the oscillation frequency of the piezoelectric sensors 9 and 10 are kept the same. At this time, the diaphragm 5a (7a) and the diaphragm 6a (8a) vibrate up and down following the AC voltage, so that a seesaw-like rotational torque is generated in the mirror 2 and the piezoelectric sensors 9, 10. 4 (C) and 4 (D), the angle of the mirror 2 swings sinusoidally and the outputs of the piezoelectric sensors 9 and 10 also change sinusoidally. In this case, the angle change of the mirror 2 and the outputs of the piezoelectric sensors 9 and 10 are input to the upper electrode 5d (7d) of the piezoelectric actuator 5 (7) shown in FIG. Compared to the voltage and the input voltage of the upper electrode 6d (8d) of the piezoelectric actuator 6 (8) shown in FIG.

The diaphragms 9a and 10a of the piezoelectric sensors 9 and 10 are swung, that is, rotationally oscillated around the torsion bar 3 (4) in synchronization with the mirror 2. At this time, the piezoelectric sensors 9 and 10 operate on the reverse principle of the piezoelectric actuators 5, 6, 7 and 8. Accordingly, since the diaphragms 9a and 10a of the piezoelectric sensors 9 and 10 are curved in the same direction, the piezoelectric layers 9c and 10c of the piezoelectric sensors 9 and 10 generate piezoelectric electromotive forces having the same polarity. As a result, as shown in FIG. As shown in (D), the output voltages of the piezoelectric sensors 9 and 10 change in the same sine wave with the same phase as the angle change of the mirror 2.

  As described above, in the present invention as well, since the piezoelectric sensors 9 and 10 are separated from the piezoelectric actuators 5, 6, 7, and 8, the crossing with the input voltage of the piezoelectric actuators 5, 6, 7 and 8 is performed. There is no talk. Further, since the piezoelectric sensors 9 and 10 are provided in the vicinity of the mirror 2, the piezoelectric sensors 9 and 10 can detect the oscillation vibration of the mirror 2 without phase shift, and accordingly, the deflection angle and scan speed of the mirror 2 can be detected in real time. Can be controlled.

  The phase difference between the input voltage of the upper electrode 5d (7d) of the piezoelectric actuator 5 (7) and the input voltage of the upper electrode 6d (8d) of the piezoelectric actuator 6 (8) may be slightly shifted from 180 °.

  1 will be described with reference to FIGS. 5, 6, and 7. FIG. 5, 6, and 7 are cross-sectional views taken along line VV in FIG. 1.

  First, referring to FIG. 5A, a silicon-on-insulator (SOI) substrate is prepared. The SOI substrate has a single crystal silicon support layer (also called a handling layer) 1011 having a thickness of about 100 to 600 μm, for example 525 μm, an intermediate silicon oxide layer (also called a BOX layer) 1012 having a thickness of about 0.5 to 2 μm, for example 2 μm, and a thickness of about It consists of a single crystal silicon active layer 1013 of 5-100 μm, for example 50 μm.

  Next, referring to FIG. 5B, the SOI substrate is thermally oxidized to form silicon oxide layers 1021 and 1022 having a thickness of about 0.1 to 1.0 μm, for example, 0.5 μm on the front and back surfaces.

  Next, referring to FIG. 5C, a thickness of about 30 to 100 μm, for example 50 nm, and a thickness of about 100 to 300 μm, for example, 150 nm are formed on the silicon oxide layer 1022 by sputtering, electron beam (EB) deposition, or the like. The Pt films are sequentially formed, whereby the lower electrode layer 1031 is formed. Next, a piezoelectric layer 1032 made of lead zirconate titanate (PZT) having a thickness of about 1 to 10 μm, for example, 3 μm, is formed on the lower electrode layer 1031 by a reactive arc discharge ion plating method. For the reactive arc discharge ion plating method, see Patent Documents 4, 5, and 6. Next, an upper electrode layer 1033 made of Pt having a thickness of 10 to 200 nm, for example, about 150 nm is formed on the piezoelectric layer 1032 by sputtering, EB vapor deposition, or the like.

Referring now to FIG. 6 (A), to pattern the upper electrode layer 1033 and the piezoelectric layer 1032 using photolithography and dry etching. Next, the lower electrode layer 1031 is patterned using photolithography and dry etching. At this time, the lower electrode layer 1031 in the region of the mirror 2 is covered with the photoresist layer, and remains as a reflective layer. In order to increase the light reflectivity of the mirror 2, after that, Al and Au having a thickness of about 100 to 500 nm are formed by sputtering, EB evaporation, etc., and the lower part is formed by using photolithography and dry etching. A reflective layer having a high reflectance is formed on the electrode layer 1031.

  Thus, the patterned lower electrode layer 1031 forms the lower electrodes 2b, 3b, 4b, 5b, 6b, 7b, 8b, 9b, 10b, and the patterned piezoelectric layer 1032 is the piezoelectric layers 3c, 4c. 5c, 6c, 7c, 8c, 9c, and 10c are formed, and the patterned upper electrode layer 1033 forms upper electrodes 3d, 4d, 5d, 6d, 7d, 8d, 9d, and 10d.

  Next, referring to FIG. 6B, the silicon oxide layer 1021 is removed, and a hard mask layer 104 for high frequency coupled plasma reactive ion etching (ICP-RIE) is formed in a region corresponding to the support 1. To do. That is, a thick resist layer is formed on the surface by photolithography, and the silicon oxide layer 1021 is removed by wet etching using buffered hydrofluoric acid (BHF) using the thick resist layer as an etching mask. Next, Al is formed over the single crystal silicon support layer 1011 by a sputtering method, an EB vapor deposition method, or the like, and patterned by photolithography and an etching method to form the hard mask layer 104.

  Next, referring to FIG. 6C, patterned lower electrodes 2b, 3b, 4b, 5b, 6b, 7b, 8b, 9b, 10b, piezoelectric layers 3c, 4c, 5c, After forming resist patterns covering 6c, 7c, 8c, 9c, 10c and upper electrodes 3d, 4d, 5d, 6d, 7d, 8d, 9d, 10d, silicon oxide layer 1022 and single crystal silicon active in ICP-RIE apparatus Layer 1013 is etched away.

  Thus, the patterned single crystal silicon active layer 1013 forms the diaphragms 2a, 3a, 4a, 5a, 6a, 7a, 8a, 9a and 10a.

  At the same time, as shown in FIG. 6C, in the ICP-RIE apparatus, the single crystal silicon support layer 1011 is removed using the hard mask layer 104 as an etching mask to form the cavity 1 a of the support 1. Note that there is no problem even if the hard mask layer 104 remains attached to the support 1.

  Further, the ICP-RIE method is an etching method suitable for anisotropically etching single crystal silicon. Therefore, the single crystal silicon support layer 1011 and the single crystal silicon active layer 1013 can be etched vertically.

  Finally, referring to FIG. 7, the intermediate silicon oxide layer 1012 is etched away using buffered hydrofluoric acid (BHF). Thereby, rotation of the mirror 2, torsional deformation of the torsion bars 3 and 4, bending of the piezoelectric actuators 5, 6, 7 and 8, and bending of the piezoelectric sensors 9 and 10 are possible. Then, each device is separated (chip) from the wafer by a dicing process and mounted on a transistor outline (TO) type package by die bonding and wire bonding.

  FIG. 8 is a view showing an optical device such as a laser printer including the optical deflector of FIG.

  In FIG. 8, the optical deflector 801 shown in FIG. 1 reflects the laser light from the laser light source 802 and projects it in the scanning direction S of the projection object 803. The optical deflector 801 and the laser light source 802 are controlled by the control unit 804.

  The control unit 804 detects the output of the piezoelectric actuator drive circuit 8041 for driving the piezoelectric actuators 5 (7) and 6 (8) of the optical deflector 801 and the outputs of the piezoelectric sensors 9 and 10 of the optical deflector 801, that is, the mirror angle. It comprises a mirror angle detection circuit 8042, a laser light source drive circuit 8043 for driving the laser light source 802, a storage circuit 8044, and a control circuit (for example, a microcomputer) 8045 for controlling these.

  The control circuit 8045 receives data D from the outside, and sends a laser modulation signal corresponding to the data D to the laser light source driving circuit 8043 of the laser light source 802 in synchronization with the scanning of the projection object 803. In addition, since the piezoelectric sensor output from the optical deflector 801 does not completely match the actual mirror angle, it is necessary to previously store the angle correction data measured in advance in the storage circuit 8044 as a table. The angle correction data changes in accordance with the slit width SW between the mirror of the optical deflector 801 and the piezoelectric sensor.

FIG. 9 is a flowchart for explaining the operation of the control circuit 8045 of FIG. In the optical device of FIG. 8, when the resonance frequency of the mirror of the optical deflector 801 is 25 k Hz, the peak-to-peak voltage V _pp and a frequency of the piezoelectric actuator sinusoidal input signal and 20V and 25 kHz, the mirror swing angle ( The maximum deflection angle) was ± 5 °. At this time, the detection mirror deflection angle of the piezoelectric sensor had a variation of ± 0.05 ° (equivalent to 1%) with respect to the target value ± 5 °. Therefore, in the optical apparatus of FIG. 8, assuming that the mirror deflection angle is θ (only a positive value is defined), the target value θ _aim is 5 °, and the allowable value is 0.05 °, the mirror deflection angle is allowed. The range can be 4.95 ° to 5.05 °.

  First, in step 901, the mirror angle θ is detected by the mirror angle detection circuit 8042. In this case, outputs of the same polarity from the piezoelectric sensors 9 and 10 are added to obtain a mirror angle.

  Next, in step 902, it is determined whether or not the mirror angle θ detected in step 901 is larger than the previous value θ0. That is, it is determined whether or not θ is a mirror deflection angle (maximum deflection angle). Note that the mirror deflection angle is assumed to have the same positive and negative values centered on 0 °, and only positive values are considered. When the detected mirror angle θ is not the mirror deflection angle, the process proceeds to step 903, the previous value θ 0 is replaced with θ, and the process returns to 901. When it is determined that the mirror angle θ is the mirror deflection angle, the process proceeds to step 904.

  In step 904, the mirror shake angle θ ′ is calculated by correcting the mirror angle determined as the mirror shake angle in step 902 with reference to the angle correction data in the storage circuit 8044.

  In step 905, it is determined whether or not the allowable range of the mirror deflection angle θ ′ of the target value 5 ° is 4.95 ° to 5.05 °. As a result, if θ ′ <4.95 °, the process proceeds to step 906, where the parameter of the sine wave input signal of the piezoelectric actuator is updated and set in the piezoelectric actuator drive circuit 8041, and feedback is performed so as to increase the mirror deflection angle θ ′. . On the other hand, if θ ′> 5.05 °, the process proceeds to step 907 where the parameter of the sine wave input signal of the piezoelectric actuator is updated and set in the piezoelectric actuator drive circuit 8041 and fed back so as to reduce the mirror deflection angle θ ′. Thereafter, the process proceeds to step 908. If θ ′ is 4.95 ° ≦ θ ′ <5.05 °, the process proceeds directly to step 908.

In steps 906 and 907, at least one of the parameter amplitude A, the phase difference φ, and the frequency f of the two sine wave input signals of the piezoelectric actuator is updated. For example, in step 906,
A ← A + ΔA (constant value)
φ ← φ + Δφ (constant value)
f ← f−Δf (constant value)
On the other hand, in step 907,
A ← A-ΔA (constant value)
φ ← φ−Δφ (constant value)
f ← f + Δf (constant value)
And Thereby, the allowable range of the mirror deflection angle θ ′ with the target value of 5 ° is made close to 4.95 ° to 5.05 °.

  In step 908, θ0 is initialized (= 0), and the process returns to step 901.

  On the other hand, the control circuit 8045 performs laser signal modulation according to data D in synchronization with the phase of the sine wave input signal of the piezoelectric actuator drive circuit 8041 by a routine (not shown) executed in parallel with the control routine of FIG. Occur. As a result, the laser light source driving circuit 8043 drives the laser light source 802 using the laser modulation signal.

  A first operation example of the control routine of FIG. 9 will be described. Consider a case in which the temperature of the external environment deviates during operation and the resonance frequency of the mirror deviates from 25 kHz. As a result, the fluctuation of the detection mirror deflection angle of the piezoelectric sensor is ± 2 °. Also in this case, the above fluctuations converged to ± 1 ° instantaneously by feedback control of the amplitude, phase difference or frequency of the sine wave input signal of the piezoelectric actuator by the control routine of FIG. Thus, the optical apparatus can be stably operated by accurately detecting the mirror swing angle by the piezoelectric sensor of the present invention.

A second operation example of the control routine of FIG. 9 will be described. When a plurality of the optical deflectors shown in FIG. 8 were manufactured, the resonance frequency of half of the mirrors was 25 kHz, but the resonance frequency of the remaining mirrors was slightly shifted to 24.997 to 25.003 kHz. At this time, if the peak-to-peak voltage V _pp and the frequency of the sine wave input signal of the piezoelectric actuator of the optical deflector having the mirrors with resonance frequencies of 24.997 kHz and 25.003 kHz are 20 V and 5 kHz, the mirror deflection angle is ± 4 due to the decrease in frequency. Consider the case. Also in this case, the deflection angle becomes ± 5 ° by feedback control of the amplitude, phase difference or frequency of the sine wave input signal of the piezoelectric actuator by the control routine of FIG. As described above, even when maintaining the mirror deflection angle has priority over the operation speed, the optical device can be stably operated by accurately detecting the mirror deflection angle by the piezoelectric sensor of the present invention.

A third operation example of the control routine of FIG. 9 will be described. When the resonance frequency of the mirror of the optical deflector 801 is 25 kHz, the peak-to-peak voltage V _pp and the frequency of the sine wave input signal of the piezoelectric actuator are 20 V and 25 kHz. As a result, the mirror deflection angle reaches the target value ± 5 °. Let us consider the case of applying external vibration of 25kHz and 500G. Even in this case, the increase in the abnormal amplitude of the mirror due to the external vibration can be instantaneously controlled by feedback control of the amplitude, phase difference or frequency of the sine wave input signal of the piezoelectric actuator by the control routine of FIG. Note that the connection between the torsion bar and the mirror of the optical deflector was damaged without the feedback control according to the present invention for the above-described external vibration of 25 kHz and 500 G. As described above, the optical device can be stably operated by accurately detecting the mirror deflection angle by the piezoelectric sensor of the present invention without using the acceleration sensor, and thus the manufacturing cost can be reduced.

1: support 1a: Check-dong 2: Mirror 3,4: elastic beam (torsion bar)
5, 6, 7, 8: Piezoelectric actuator 9, 10: Piezoelectric sensors 2a, 3a, 4a, 5a, 6a, 7a, 8a, 9a, 10a: Diaphragms 2b, 3b, 4b, 5b, 6b, 7b, 8b, 9b, 10b: Lower electrodes 3c, 4c, 5c, 6c, 7c, 8c, 9c, 10c: Piezoelectric layers 3d, 4d, 5d, 6d, 7d, 8d, 9d, 10d: Upper electrodes
SW: slit width 1011: single crystal silicon layer 1012: intermediate silicon oxide layer 1013: single crystal silicon active layer 1021, 1022: silicon oxide layer 1031: lower electrode layer 1032: piezoelectric layer 1033: upper electrode layer 104: hard mask layer
SL: Slit

Claims (5)

A support formed with a cavity,
A mirror having a reflective surface located within the cavity of the support;
An elastic beam having a proximal end coupled to the support and a distal end coupled to the mirror;
An actuator having a proximal end coupled to the support and a distal end coupled to the elastic beam;
A piezoelectric sensor connected to the elastic beam and positioned on the outer peripheral side of the mirror through a slit to detect the angle of the mirror;
The actuator rotates and vibrates the mirror and the piezoelectric sensor in the same direction via the elastic beam ,
The slit is an optical deflector provided so that the vibration frequency of the rotational vibration of the mirror matches the frequency of the rotational vibration of the piezoelectric sensor.   The optical deflector according to claim 1, wherein the slit is provided so that a maximum vibration width of the piezoelectric sensor is larger than a maximum vibration width of the mirror.   The optical deflector according to claim 1, wherein the actuator is a piezoelectric actuator.   The optical deflector according to claim 1, wherein the reflection surface of the mirror is circular, and the piezoelectric sensor is semi-annular. An optical deflector according to any one of claims 1 to 4 ,
A light source for irradiating the light deflector with light;
A light source driving circuit for driving the light source;
A mirror angle detection circuit for detecting an angle signal of a mirror of the piezoelectric sensor;
A storage circuit for storing correction data for correcting the detected angle signal of the mirror;
A control circuit for correcting the detected angle signal of the mirror by the correction data;
And an actuator driving circuit for driving the actuator by the corrected mirror angle signal.

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