Optical deflector device for deflection in two dimensions, which uses curved sawtooth drive voltages

Abstract

Optical deflector device for deflection in two dimensions, comprising an optical deflector and a driver for driving the optical deflector, wherein the optical deflector comprises: a mirror (1); a first piezoelectric actuating device (4a-1, 4b-1, 4a-2, 4b-2; 7a-1~7a-4, 7b-1~7b-4) for pivoting the mirror (1) with respect to a first axis of the mirror (1); a second piezoelectric actuating device (6a-1~6a~4, 6b-1~6b-4) of a meandering design for pivoting the mirror (1) with respect to a second axis of the mirror (1) which is perpendicular to the first axis, a movable frame (2) for supporting the mirror (1); and a support body (5) surrounding the movable frame (2), wherein the driver has a curved sawtooth drive voltage (V) Y1 , V Y2 ) generated and the curved sawtooth drive voltage (V Y1 , V Y2) to the second piezoelectric actuating device (6a-1~6a~4, 6b-1~6b-4); wherein the second piezoelectric actuating device (6a-1~6a~4, 6b-1~6b-4) comprises a pair of third piezoelectric actuating devices, each positioned opposite to the other with respect to the mirror (1), and connected between the support body (5) and the movable frame (2); wherein each of the third piezoelectric actuating devices has the following: a first group of piezoelectric actuating elements (6a-1, 6a-3, 6b-1, 6b-3) serving as cantilevers, and a second group of piezoelectric actuators (6a-2, 6a-4, 6b-2, 6b-4) serving as cantilevers alternating with the first group of piezoelectric actuators (6a-1, 6a-3, 6b-1, 6b-3); wherein the piezoelectric actuating elements (6a-1, 6a-2, 6a-3, 6a-4, 6b-1, 6b-2, 6b-3, 6b-4) are folded at each actuating element and are connected between the support body (5) and the movable frame (2), wherein each of the piezoelectric actuating elements (6a-1, 6a-2, 6a-3, 6a-4, 6b-1, 6b-2, 6b-3, 6b-4) is parallel with the first axis of the mirror (1); where the driver supplies the curved sawtooth drive voltage (V Y1 ) applied to the first group of piezoelectric actuators (6a-1, 6a-3, 6b-1, 6b-3); where the driver provides another curved sawtooth drive voltage (V) Y2 ) in phase opposite to the curved sawtooth drive voltage (V Y1 ) generated and the further curved sawtooth drive voltage (V Y2 ) to the second group of piezoelectric actuating elements (6a-2, 6a-4, 6b-2, 6b-4).

Description

BACKGROUND area

[0001] The subject matter disclosed herein relates to an optical deflector device which can be applied, for example, to a vehicle headlight. Description of related technology

[0002] A prior art optical deflector for deflection in two dimensions or directions is constituted by a mirror, a movable frame surrounding the mirror for supporting the mirror by a pair of torsion bars, by inner piezoelectric actuators (first piezoelectric actuators) of a torsion bar type which are fixed between the movable frame and the torsion bars and serve as cantilevers or levers for pivoting the mirrors by the torsion bars with respect to an X-axis of the mirror, a supporting body surrounding the movable frame, and by outer piezoelectric actuators (second piezoelectric actuators) of a meander type or serpentine type which are fixed between the supporting body and the movable frame and serve as cantilevers or levers.Levers for pivoting the mirror through the movable frame with respect to a Y-axis of the mirror perpendicular to the X-axis (see; JP 2009 - 223 165 A).

[0003] In general, the mirror is swung with respect to the X-axis for horizontal deflection at a high frequency by the inner piezoelectric actuators using sinusoidal waves, while the mirror is swung with respect to the Y-axis for vertical deflection at a low frequency by the other piezoelectric actuators using straight sawtooth waves.

[0004] If the above-described prior art two-dimensional deflection optical deflector is used in a vehicle headlight to distribute light, a light source must be turned off to stop the horizontal deflection for the falling period of each of the sawtooth waves. This would make control difficult because not each of the sawtooth waves is symmetrical about its center—that is, a rising period or a falling period of each of the sawtooth waves is much longer than a falling period or a rising period thereof. Since the sawtooth waves are straight, irregularity in the illumination would also occur. This will be discussed in more detail later.

[0005] US 2008 / 0 239 252 A1 discloses an image projector capable of projecting a high-quality image while maintaining a compact size. In the image projector, a luminous flux is deflected two-dimensionally by rotating a reflector for reflecting a luminous flux emitted by a light source around a second axis, which is nearly orthogonal to a first axis as the center, using resonant drive, while the reflector is rotated around the first axis as the center using non-resonant drive.The shape of one or more optical surfaces of an optical projection system for projecting an image onto a projection plane by directing light onto the projection plane includes a shape for performing a correction to maintain a nearly constant scanning speed of the light flux along one scanning direction on the projection plane and a shape for performing a correction to suppress distortion in an image along the other scanning direction, which is nearly orthogonal to the one scanning direction on the projection plane. The controlled rotation of the reflector performs at least one correction to maintain a nearly constant scanning speed of the light flux along the other scanning direction on the projection plane and one correction to suppress distortion in an image along the one scanning direction on the projection plane.

[0006] DE 697 34 132 T2 discloses an inertial positioner comprising a base plate and a carrier plate slidably connected to each other via a bearing assembly to enable relative movement of the plates in a positioning direction. The bearing assembly comprises two sets of cage ball bearings seated in respective pairs of V-grooves formed in the opposing surfaces of the base and carriage plates, the V-groove pairs being spaced apart in the positioning direction. Extending between the plates is an actuator comprising a piezoelectric element and a rod. The piezoelectric element is attached to the carrier plate, and the rod forms a frictional engagement connection with the base plate via a collar attached to the base plate via biasing means. In operation, a periodic sawtooth voltage is applied to the piezoelectric element to generate movement.

[0007] US 2011 / 0 032 590 A1 discloses a meander-shaped oscillator comprising: a plurality of vibrating plates bent and coupled in predetermined directions, and piezoelectric actuators each comprising a lower electrode, a piezoelectric body, and an upper electrode stacked in this order on the vibrating plate, and wherein the piezoelectric actuators are alternately arranged on the vibrating plates. SUMMARY

[0008] The subject matter disclosed herein seeks to solve one or more of the problems described above.

[0009] According to the present invention, an optical deflector device is provided having the features of claim 1. Preferred embodiments of the invention are set forth in the subclaims.

[0010] Since the sawtooth drive voltage applied to the second piezoelectric actuator is curved, the downward angle rate (tilt cosine angle) of the mirror can be curved. As a result, when the two-dimensional deflection optical deflector device according to the subject matter disclosed herein is applied to a vehicle headlight, illumination irregularity can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above and other advantages and features of the subject matter disclosed herein will become more apparent from the following description of certain embodiments when taken in conjunction with the accompanying drawings and compared with the prior art, in which figures: Fig. 1 is a diagram for explaining the swivel angle of a mirror of a vehicle headlight with respect to the horizontal direction to which the prior art two-dimensional deflection optical deflector is applied; Fig. 2 is an image showing scan lines of reflected light in Fig. 1 illustrates; Fig. 3A, Fig. 3B, Fig. 3C, Fig. 3D, Fig. 3E and Fig. 3F are timing diagrams for explaining the operation of the optical deflector of the Fig. 1; Fig. Figure 4 is a figure showing the relationship between the scan line and the distance of the Fig. 2 illustrates; Fig. Figure 5 is a figure showing the density of scan lines of the Fig. 2 illustrates; Fig. 6 is a diagram illustrating a first embodiment of the optical deflector device for deflection in two dimensions according to the subject matter disclosed herein; Fig. Figure 7 is a cross-sectional view of the optical deflector of the Fig. 6; Fig. 8A, Fig. 8B, Fig. 8C, Fig. 8D, Fig. 8E and Fig. 8F are timing charts for explaining the operation of the optical deflector device of the Fig. 6; Fig. Fig. 9 is a diagram for explaining the operation of the external piezoelectric actuators of the Fig. 6; Fig. Fig. 10 is a diagram for explaining the tilt angle of the mirror of a vehicle headlight with respect to a horizontal direction in which the optical deflector device is used for deflection in two dimensions of the Fig. 6 is applied; Fig. 11 is a figure showing scan lines of reflected light in Fig. 10 illustrates; Fig. Figure 12 is a figure showing the relationship between the scan line and the distance of the Fig. 11 illustrates; Fig. Figure 13 is a figure showing the density of scan lines of the Fig. 11 illustrates; Fig. 14A; Fig. 14B, Fig. 14C, Fig. 14D, Fig. 14E and Fig. 14F are other timing charts for explaining the operation of the optical deflector device of the Fig. 6; Fig. 15 is a diagram illustrating a second embodiment of the optical deflector device according to the subject matter disclosed herein; Fig. 16 is a cross-sectional view of the optical deflector of the Fig. 15; Fig. 17A, Fig. 17B, Fig. 17C, Fig. 17D, Fig. 17E and Fig. 17F are timing charts for explaining the operation of the optical deflector device of the Fig. 15; and Fig. 18A, Fig. 18B, Fig. 18C, Fig. 18D, Fig. 18E and Fig. 18F are other timing charts for explaining the operation of the optical deflector device of the Fig. 15. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0012] Before describing exemplary embodiments, an optical deflector for deflection in two dimensions of the prior art will be described with reference to Fig. 1, 2, 3A to 3F, 4 and 5.

[0013] In Fig. 1, which is a diagram for explaining the tilt angle of a mirror of a vehicle headlight with respect to the horizontal direction, in which the optical deflector 100 for deflection in two dimensions of the prior art is applied, the optical deflector 100 associated with its driver 200 is located at a height H of 0.75 m, and reflected light R of light L from a laser diode 300 reflected by a mirror 100a ranges from 5 m to 100 m in front of the optical deflector 100. If a downward angle or downward angle (tilt cosine angle) β is defined by β=0° for the vertical direction and β=90° for the horizontal direction, here the distance of 5 m corresponds to an angle β=81.47°, and the distance of 100 m corresponds to β=89.57°, so that the deflection angle Δβ of the reflected light R is equal to 8.10° (= 89.57° - 81.47°).In this case, the elevation angle α for the optical deflector 100 is 8.53° when β=81.47°, and the angle α is 0.43° when β=89.57°.

[0014] In Fig. 2, which are the scanning or guide lines of the reflected light R of the Fig. 1, the reflected light R is obtained by reflecting the light L from the laser diode at the mirror 100a, which is pivoted with respect to a first axis, such as an X-axis, by sinusoidal voltages V Xa and V Xb from the driver 200 opposite in phase to each other, as shown in the Fig. 3A and Fig. 3B, and is defined with respect to a second axis, such as a Y-axis, perpendicular to the X-axis by straight sawtooth voltages V Y1 and V Y2 by the driver 200 in opposite phase to each other, as shown in the Fig. 3C and Fig. 3D. If the frequency of the sinusoidal voltages V Xa and V Xb equal to 480 times that of the straight sawtooth voltages V Y1 and V Y2 In this case, the reflected light R has 480 scan lines SL1, SL2, ... , SL 480 The uppermost scan line SL1 corresponds to the furthest distance of 100m at β=89.57°, and the lowermost scan line SL 480 corresponds to the closest distance of 5 m at β=81.47°. Note that each scan line is actually formed by a pair of scan lines in a rightward direction and a leftward direction.

[0015] As in the Fig. 3C and Fig. 3D, a rise period Ta of the straight sawtooth voltage V Y1 (a decay period T b the straight sawtooth voltage V Y2 ) much longer than a decay period T bthe straight sawtooth voltage V Y1 (a rise period T b the straight sawtooth voltage V Y2 ). Here Ta+Tb=T where T is a period. In this case, for the period T a the straight sawtooth voltage V Y1 linearly at a fixed rate, while the straight sawtooth voltage V Y2 is reduced linearly at the specified rate. As in Fig. 3E, the downward angle β is therefore linear at a fixed rate for the period T a In this case, the peak values ​​of the straight sawtooth voltages V Y1 and V Y2 strongly shifted towards the end of their period, ie T a >>T b , so that the angle of fall β for the period T b is greatly enlarged. Since it is difficult to determine the horizontal deflection for the period T bTherefore, the laser diode 300 is turned off to stop the horizontal scanning operation, as shown in Fig. Figure 3F illustrates what would complicate the control. On the other hand, the sweep rate of the mirror 100a is zero at dead centers, where β=89.57° and β=81.47°, and it is uniform between the dead centers and reversal points, respectively. Therefore, the scan lines SL1, SL2, ..., SL 480 uniform only for the period T a available.

[0016] Fig. 4 is a figure showing the relationship between the scan lines SL i and the illumination distance through the scan line SL i (i = 1, 2, ... , 480) in Fig. 2 illustrates, and Fig. Figure 5 is a graph showing the density of scan lines SL i in the horizontal direction of the Fig. 2. As in Fig. 4 and Fig. 5, the greater the distance from the optical deflector, the smaller the density of the scan lines in the horizontal direction, since the scanning time period of each of the scan lines SL1, SL2, ..., SL 480 For example, the number of scan lines within the distance of 40 m to 100 m from the optical deflector 100 is 20 scan lines, while the number of scan lines within the distance of 5 m to 40 m from the optical deflector 100 is 460. Therefore, each of the scan lines SL1, SL2, ..., SL 20 clearly see as lines.

[0017] Thus, an irregularity of the illumination would occur depending on the distance from the optical deflector 100.

[0018] In Fig. 6, which illustrates a first embodiment of the optical deflector device according to the subject matter disclosed herein, an optical deflector 10 and its driver 20 are provided.

[0019] The optical deflector 10 is constructed by a circular mirror 1 for reflecting an incident light, a movable frame 2 surrounding the mirror 1 to support the mirror 1 through a pair of torsion bars 3a and 3b, inner piezoelectric actuators (first piezoelectric actuators) 4a-1, 4a-2, 4b-1 and 4b-2 of a torsion bar type fixed between the movable frame 2 and the torsion bars 3a and 3b and serving as cantilevers for swinging the mirror 1 through the torsion bars 3a and 3b with respect to an X-axis of the mirror 1, and a support body 5 surrounding the movable frame 2, and outer piezoelectric actuators (second piezoelectric actuators) 6a-1, 6a-2, 6a-3 and 6a-4, 6b-1, 6b-2, 6b-3 and 6b-4 of a meander-shaped design, which are attached between the support body 5 and the movable frame 2 and serve as cantilevers,to pivot the mirror 1 through the movable frame 2 with respect to a Y-axis of the mirror 1 perpendicular to the X-axis. Each of the piezoelectric actuators 4a-1, 4a-2, 4b-1 and 4b-2, 6a-1, 6a-2, 6a-3 and 6a-4, 6b-1, 6b-2, 6b-3 and 6b-4 is also referred to as a piezoelectric actuator.

[0020] The torsion bars 3a and 3b are arranged along the X-axis and have ends coupled to the inner periphery of the movable frame 2 and other ends coupled to the outer periphery of the mirror 1. Therefore, the torsion bars 3a and 3b are twisted by the internal piezoelectric actuators 4a-1, 4a-2, 4b-1, and 4b-2 to pivot the mirror 1 with respect to the X-axis.

[0021] The inner piezoelectric actuators 4a-1 and 4b-1 oppose each other along the Y axis and sandwich the torsion bar 3a between them. The inner piezoelectric actuators 4a-1 and 4b-1 have ends coupled to the inner periphery of the movable frame 2 and other ends coupled to the torsion bar 2a. In this case, the bending direction of the inner piezoelectric actuator 4a-1 is opposite to that of the inner piezoelectric actuator 4b-1.

[0022] Similarly, the inner piezoelectric actuators 4a-2 and 4b-2 oppose each other along the Y-axis and sandwich the torsion bar 3b between them. The inner piezoelectric actuators 4a-2 and 4b-2 have ends coupled to the inner periphery of the movable frame 2 and other ends coupled to the torsion bar 3b. In this case, the bending direction of the inner piezoelectric actuator 4a-2 is opposite to that of the inner piezoelectric actuator 4b-2.

[0023] The support body 5 has a rectangular frame that surrounds the movable frame 2.

[0024] The outer piezoelectric actuators 6a-1, 6a-2, 6a-3 and 6a-4, 6b-1, 6b-2, 6b-3 and 6b-4 are connected between the inner periphery of the support body 5 and the outer periphery of the movable frame 2 to pivot the movable frame 2 associated with the mirror 1 with respect to the support body 5, ie, the mirror 1, with respect to the Y-axis.

[0025] The outer piezoelectric actuators 6a-1, 6a-2, 6a-3, and 6a-4 are serially coupled from the support body 5 to the movable frame 2, or arranged one behind the other. Likewise, each of the outer piezoelectric actuators 6a-1, 6a-2, 6a-3, and 6a-4 is parallel to the X-axis of the mirror 1. Therefore, the outer piezoelectric actuators 6a-1, 6a-2, 6a-3, and 6a-4 are folded or arranged in a meandering shape between the support body 5 and the movable frame 2, so that the amplitudes of the outer piezoelectric actuators 6a-1, 6a-2, 6a-3, and 6a-4 can be varied along the directions perpendicular to the Y-axis of the mirror 1.

[0026] Similarly, the outer piezoelectric actuators 6b-1, 6b-2, 6b-3, and 6b-4 are serially coupled or arranged one behind the other from the support body 5 to the movable frame 2. Likewise, each of the outer piezoelectric actuators 6b-2, 6b-3, and 6b-4 is parallel to the X-axis of the mirror 1. Therefore, the outer piezoelectric actuators 6b-1, 6b-2, 6b-3, and 6b-4 are folded or arranged in a meandering shape between the support body 5 and the movable frame 2 in each actuator, so that the amplitudes of the outer piezoelectric actuators 6b-1, 6b-2, 6b-3, and 6b-4 can be varied along the directions perpendicular to the Y-axis of the mirror 1.

[0027] On the optical deflector 10 there are contact fields P a1 , P a2 , P a3 , P a4 and P a5 , P b1 , P b2 , P b3 , P b4 and P b5which are connected to the driver 20.

[0028] The contact field P a1 is connected to the upper electrode layer 707 (it Fig. 7) of each of the inner piezoelectric actuators 4a-1 and 4a-2, and the contact pad P a2 is connected to the lower electrode layer 705 (see Fig. 7) of each of the inner piezoelectric actuators 4a-1 and 4a-2. Likewise, the contact pad P a3 with the upper electrode layer 707 (see Fig. 7) of each of the outer piezoelectric actuators 6a-1 and 6a-3 and the contact pad P a4 is connected to the upper electrode layer 707 (see Fig. 7) of each of the outer piezoelectric actuators 6a-2 and 6a-4. Furthermore, the contact pad P a5 with the lower electrode layer 705 (see Fig. 7) of each of the outer piezoelectric actuators 6a-1, 6a-2, 6a-3 and 6a-4.

[0029] On the other side is the contact field P b1 with the upper electrode layer 707 (see Fig. 7) of each of the inner piezoelectric actuators 4b-1 and 4b-2, and the contact pad P b2 is connected to the lower electrode layer 705 (see Fig. 7) of each of the inner piezoelectric actuators 4b-1 and 4b-2. Likewise, the contact pad P b3 with the upper electrode layer 707 (see Fig. 7) of each of the outer piezoelectric actuators 6b-1 and 6b-3, and the contact pad P b4 is connected to the upper electrode layer 707 (see Fig. 7) of each of the outer piezoelectric actuators 6b-2 and 6b-4. Furthermore, the contact pad P b5 with the lower electrode layer 705 (see Fig. 7) of each of the outer piezoelectric actuators 6b-1, 6b-2, 6b-3 and 6b-4.

[0030] The driver 20 is constructed by a control circuit 21, such as a microcomputer, which has a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), an input / output interface (I / O interface), and so on.

[0031] The driver 20 further comprises a non-volatile memory 221 for storing drive data Xa for driving the upper electrode layers of the inner piezoelectric actuators 4a-1 and 4a-2, a digital-to-analog converter (DAC) 231 for converting the drive data Xa into a sinusoidal drive voltage V Xa and a driver circuit 241 for generating the sinusoidal drive voltage V Xaon the contact field P a1 to create.

[0032] The driver 20 further comprises a non-volatile memory 222 for storing drive data Xb for driving the upper electrode layers of the inner piezoelectric actuators 4b-1 and 4b-2, a digital-to-analog converter (DAC) 231 for converting the drive data Xa into a sinusoidal drive voltage V Xb and a driver circuit 242 for generating the sinusoidal drive voltage V Xb on the contact field P b1 to create.

[0033] The driver 20 further comprises a non-volatile memory 223 for storing reference data Xr for driving the lower electrode layers of the inner piezoelectric actuators 4a-1, 4a-2, 4b-1 and 4b-2, a digital-to-analog converter (DAC) 232 for converting the reference data Xr into a reference voltage V Xrand a driver circuit 243 to generate the reference voltage V Xr to the contact fields P a2 and P b2 to create.

[0034] The driver 20 further comprises a non-volatile memory 224 for storing the drive data Y1 for driving the upper electrode layers of the outer piezoelectric actuators 6a-1, 6a-3, 6b-1 and 6b-3, a digital-to-analog converter (DAC) 234 for converting the drive data Y1 into a curved sawtooth drive voltage V Y1 , and a driver circuit 244 to generate the curved sawtooth drive voltage V Y1 to the contact fields P a3 and P b3 to create.

[0035] The driver 20 further comprises a non-volatile memory 225 for storing the drive data Y2 for driving the upper electrode layers of the outer piezoelectric actuators 6a-2, 6a-4, 6b-2 and 6b-4, a digital-to-analog converter (DAC) 235 for converting the drive data Y2 into a curved sawtooth drive voltage V Y2 , and a driver circuit 245 to generate the curved sawtooth drive voltage V Y2 to the contact fields P a4 and P b4 to create.

[0036] The driver 20 further comprises a non-volatile memory 226 for storing reference data Yr for driving the lower electrode layers of the outer piezoelectric actuators 6a-1, 6a-2, 6a-3 and 6a-4, 6b-1, 6b-2, 6b-3 and 6b-4, a digital-to-analog converter (DAC) 236 for converting the reference data Yr into a reference voltage V yrand a driver circuit 246 to generate the reference voltage V Yr to the contact fields P a5 and P b5 to create.

[0037] It should be noted that the number of outer piezoelectric actuators 6a-1, 6a-2, 6a-3 and 6a-4 and the number of outer piezoelectric actuators 6b-1, 6b-2, 6b-3 and 6b-4 may have other values, such as 2, 6, 8, ...

[0038] The structure of each element of the optical deflector 10 will be described next with reference to Fig. 7 explained.

[0039] In Fig. 7, a monocrystalline silicon support layer 701, a silicon oxide intermediate layer 702, and a monocrystalline silicon active layer 703 are formed by a silicon-on-insulator (SOI) substrate. Furthermore, reference numeral 704 denotes a silicon oxide layer, reference numeral 705 denotes a lower electrode layer made of Pt, Au, or the like, reference numeral 706 denotes a lead zirconate titanate (PZT) layer, reference numeral 707 denotes an upper electrode layer made of Pt, Au, or the like, reference numeral 708 denotes a metal layer made of Al, Ag, or the like, and 709 denotes a hard mask layer made of silicon oxide or the like.

[0040] The mirror 1 is constructed by the monocrystalline silicon support layer 701 serving as a vibration plate, the metal layer 708 serving as a reflector, and the hard mask layer 709.

[0041] The movable frame 2 and the torsion bars 3a and 3b are constructed by the monocrystalline silicon active layer 703 and the silicon oxide layer 704.

[0042] The inner piezoelectric actuators 4a-1, 4a-2, 4b-1 and 4b-2 and the outer piezoelectric actuators 6a-1 to 6a-4 and 6b-1 to 6b-4 are constructed by the monocrystalline silicon active layer 703, the silicon oxide layer 704, the lower electrode layer 705, the PZT layer 706 and the upper electrode layer 707.

[0043] The support body 5 is constructed by the monocrystalline silicon layer 701, the silicon intermediate layer 702, the monocrystalline active silicon layer 703, the silicon oxide layer 704 and the hard mask layer 709.

[0044] The contact fields P a1 , P a2 , P a3 , P a4 and P a5 , P b1 , P b2 , P b3 , P b4 and Pb5 are formed by the lower electrode layer 705.

[0045] First, an optical deflection or horizontal scanning operation by swiveling the mirror with respect to the X-axis is explained below.

[0046] As in the Fig. 8A and Fig. As illustrated in Figure 8B, the sinusoidal drive voltage Vx a , based on the drive data Xa previously stored in the non-volatile memory 221 and the sinusoidal drive voltage V Xb , based on the drive data Xb previously stored in the non-volatile memory 222, sinusoidally at a predetermined frequency and symmetrically or oppositely in phase with each other with the reference voltage V Xr, based on the reference data Xr previously stored in the non-volatile memory 223, in the same manner as in the prior art. As a result, the inner piezoelectric actuators 4a-1 and 4a-2 and the inner piezoelectric actuators 4b-1 and 4b-2 perform bending operations in opposite directions to each other, so that the torsion bars 3a and 3b are twisted to pivot the mirror 1 with respect to the X-axis.

[0047] In the optical deflection or horizontal guidance operation by pivoting the mirror 1 with respect to the X-axis, the deflection angle of the mirror 1 can be increased if the frequency of the sinusoidal drive voltage V Xa and V Xb , oscillates in resonance with the natural frequency of a mechanically oscillating system of the mirror 1 with respect to the X-axis, depending on the internal piezoelectric actuators 4a-1, 4a-2, 4b-1 and 4b-2.

[0048] Next, an optical deflection or horizontal scanning or guiding operation by pivoting the mirror 1 with respect to the Y-axis is explained below.

[0049] The outer piezoelectric actuators 6a-1, 6a-2, 6a-3 and 6a-4, 6b-1, 6b-2, 6b-3 and 6b-4 are divided into an odd-numbered group of outer piezoelectric actuators 6a-1 and 6a-3, 6b-1 and 6b-3 and an even-numbered group of outer piezoelectric actuators 6a-2 and 6a-4, 6b-2 and 6b-4, which alternates with the odd-numbered group of outer piezoelectric actuators 6a-1 and 6a-3, 6b-1 and 6b-3.

[0050] As in Fig. 9, which shows only the outer piezoelectric actuators 6b-1, 6b-2, 6b-3, and 6b-4, when the odd-numbered group of the outer piezoelectric actuators 6a-1, 6a-3, 6b-1, and 6b-3 is bent in one direction, for example, in a downward direction, the even-numbered group of the outer piezoelectric actuators 6a-2, 6a-4, 6b-2, and 6b-4 is bent in the other direction, that is, in the upward direction. On the other hand, when the odd-numbered group of outer piezoelectric actuators 6a-1, 6a-3, 6b-1, and 6b-3 is bent in the upward direction, the even-numbered group of outer piezoelectric actuators 6a-2, 6a-4, 6b-2, and 6b-4 is bent in the downward direction. Thus, the mirror 1 is pivoted with respect to the Y-axis.

[0051] It should be noted that the frequency of the curved sawtooth drive voltages V Y1 and V Y2is sufficiently small so as not to cause resonance with the natural frequency of a mechanically oscillating system of the mirror 1 with respect to the Y-axis depending on the external piezoelectric actuators 6a-1, 6a-2, 6a-3 and 6a-4, 6b-1, 6b-2, 6b-3 and 6b-4.

[0052] That is, as in the Fig. 8C and Fig. 8D illustrates the curved sawtooth drive voltages V Y1 based on the drive data Y1 previously stored in the non-volatile memory 224 and the curved sawtooth drive voltages V Y2 based on the drive data Y2 previously stored in the non-volatile memory 225 are curved and sawtooth-shaped with a predetermined frequency and they are symmetrical or opposite in phase with each other with the reference voltage V Yr, based on the drive data previously stored in non-volatile memory 226. The curved sawtooth drive voltages V Y1 , like her Fig. 8C is applied to the odd-numbered group of the outer piezoelectric actuators 6a-1, 6a-3, 6b-1 and 6b-3, and the curved sawtooth drive voltages V Y2 , as in Fig. 8D is applied to the even-numbered group of outer piezoelectric actuators 6a-2, 6a-4, 6b-2 and 6b-4.

[0053] For each of the half periods T a and T b (= T / 2) are the curved sawtooth drive voltages V Y1 and V Y2 curved, ie the curved sawtooth drive voltages V Y1 and V Y2 are first changed gradually and then changed rapidly, or the curved sawtooth drive voltages V Y1 and V Y2are first changed rapidly and then gradually. That is, for the first half-period T a the curved sawtooth drive voltage V Y1 first gradually increased and then rapidly increased, and the curved sawtooth drive voltage V Y2 is first gradually reduced and then rapidly reduced. On the other hand, for the last half-period T b the curved sawtooth drive voltage V Y1 first rapidly decreased and then gradually decreased, and the curved sawtooth drive voltages V Y2 is first enlarged rapidly and then gradually enlarged. As in Fig. 8E, as a consequence, the rate of the downward angle β is curved, that is, the downward angle β is first changed gradually and then changed rapidly, or the downward angle β is first changed rapidly and then changed gradually. That is, for the first half-period T athe downward angle β is first gradually reduced from β=89.57° and then rapidly reduced to β=81.47°. On the other hand, the downward angle β for the latter half-period T b first rapidly increased from β=81.47° and then gradually increased to β=89.57°.

[0054] The rise and fall rates of the curved sawtooth drive voltages V Y1 and V Y2 , ie the fall rates and rise rates of the downward angle β are determined in such a way that the scan lines SL1, SL2, ..., SL 480 are uniform in the horizontal direction, as in the Fig. 10 and Fig. 11. More specifically, in order to obtain a uniform illumination depending on the distance from the optical deflector 10, the scan lines SL1, SL2, ..., SL 480 uniform in the horizontal direction for the first half period T a (=T / 2) is raised or enlarged, while the scan lines SL 480 , SL479 , ..., SL1 uniformly in the horizontal direction for the latter half period T b reduced or lowered.

[0055] Regarding the state of the art, it should be noted that in order to maintain a regular illumination, depending on the distance from the optical deflector, the periods of the scan lines SL1, SL2, ..., SL 480 must differ from each other, which would be difficult to control.

[0056] Since the scan lines SL1, SL2, ..., SL 480 ; SL 480 , SL 479 , ..., SL1 are uniform in the horizontal distribution throughout the entire period T, the laser diode 30 does not need to be turned off, so the horizontal scanning process is not stopped. This would simplify the control.

[0057] Fig. 12 is a figure showing the relationship between the scan lines SL i and the illumination distance through the scan line SL i(i = 1, 2, ..., 480) of the Fig. 11 illustrates, and Fig. 13 is a figure showing the density of scan lines SL i in the horizontal direction of the Fig. 11. As shown in the Fig. 12 and Fig. As illustrated in Figure 13, the density of the scan lines in the horizontal direction is accurate or uniform, regardless of the distance from the optical deflector 10.

[0058] Thus, an irregularity of the illumination depending on the distance from the optical deflector 10 would not occur.

[0059] In the example described above, a ratio of the frequency of the sinusoidal drive voltages V Xa and V Xb to that of the curved drive voltages V Y1 and V Y2 greater than 1, although the frequency of the sinusoidal drive voltages V Xa and V Xb 960 times as large as that of the curved drive voltages V Y1 and VY2 . The frequency of the sinusoidal drive voltages V Xa and V Xb for the first half period T a different from the frequency of the sinusoidal drive voltages V Xa and V Xb for the last half-period T b be.

[0060] In the example described above, the first half period T a the same as the last half-period T b , however, the first half period T a be longer than the last half-period T b , for example T a : T b = 9 : 1, as in Fig. 14A to 14F. In this case, the scan lines SL1, SL2, ..., SL 480 uniform in the horizontal direction for the first half period T a raised, and the laser diode is switched on for the last half period T b turned off to stop the horizontal scanning process, which would make control a bit more complicated.

[0061] In Fig. 15, which illustrates a second embodiment of the optical deflector device according to the subject matter disclosed herein, inner piezoelectric actuators (first piezoelectric actuators) 7a-1, 7a-2, 7a-3 and 7a-4, 7b-1, 7b-2, 7b-3 and 7b-4 are of a meander type instead of the torsion bars 3a and 3b and the inner piezoelectric actuators (first piezoelectric actuators) 4a-1, 4a-2, 4b-1 and 4b-2 of the Fig. 6. Each of the inner piezoelectric actuators 7a-1, 7a-2, 7a-3 and 7a-4, 7b-1, 7b-2, 7b-3 and 7b-4 is called a piezoelectric actuator.

[0062] The inner piezoelectric actuators 7a-1, 7a-2, 7a-3 and 7a-4, 7b-1, 7b-2, 7b-3 and 7b-4 are coupled or fixed between the inner circumference of the movable frame 2 and the mirror 1 in order to pivot the mirror 1 with respect to the X-axis.

[0063] The inner piezoelectric actuators 7a-1, 7a-2, 7a-3, and 7a-4 are serially coupled or arranged in series from the movable frame 2 to the mirror 1. Likewise, each of the inner piezoelectric actuators 7a-1, 7a-2, 7a-3, and 7a-4 is parallel to the Y-axis of the mirror 1. Therefore, the inner piezoelectric actuators 7a-1, 7a-2, 7a-3, and 7a-4 are folded or meander-shaped in each actuator from the support body 5 to the mirror 1, so that the amplitudes of the inner piezoelectric actuators 7a-1, 7a-2, 7a-3, and 7a-4 can be changed along directions perpendicular to the X-axis of the mirror 1.

[0064] Similarly, the inner piezoelectric actuators 7b-1, 7b-2, 7b-3, and 7b-4 are serially coupled from the movable frame 2 to the mirror 1. Likewise, the inner piezoelectric actuators 7b-1, 7b-2, 7b-3, and 7b-4 are parallel to the Y-axis of the mirror 1. Therefore, the inner piezoelectric actuators 7b-1, 7b-2, 7b-3, and 7b-4 are folded or meander-shaped in each actuator from the support body 5 to the mirror 1, so that the amplitudes of the inner piezoelectric actuators 7b-1, 7b-2, 7b-3, and 7b-4 can be changed along directions perpendicular to the X-axis of the mirror 1.

[0065] Likewise, in Fig. 15 contact fields P a0 ', P a1 ', P a2 ', P b0 ', P b1 ' and P b2 ' instead of the contact fields P a1 , P a2 , P b1 , P b2 , P b3 , P b4 and Pb5 the Fig. 6 provided

[0066] The contact field P a0 ' is connected to the upper electrode layer 707 (see Fig. 16) of each of the inner piezoelectric actuators 7a-1 and 7a-3, and the contact pad P a2 ' is connected to the upper electrode layer 707 (see Fig. 16) of each of the inner piezoelectric actuators 7a-2 and 7a-4. Furthermore, the contact pad P a2 ' with the lower electrode layer 705 (see Fig. 7) of each of the outer piezoelectric actuators 6a-1 and 6a-3 and the contact pad P a4 is connected to the upper electrode layer 707 (see Fig. 16) of each of the outer piezoelectric actuators 6a-2 and 6a-4. Furthermore, the contact pad P a5 with the lower electrode layer 705 (see Fig. 7) of each of the outer piezoelectric actuators 7a-1, 7a-2, 7a-3 and 7a-4.

[0067] On the other hand, the contact field P b0 ' with the upper electrode layer 707 (see Fig. 16) of each of the inner piezoelectric actuators 7b-1 and 7b-3, and the contact pad P b1 ' is connected to the upper electrode layer 707 (see Fig. 16) of each of the inner piezoelectric actuators 7b-2 and 7b-4. Furthermore, the contact pad P b2 ' with the lower electrode layer 705 (see Fig. 16) of each of the inner piezoelectric actuators 7b-1, 7b-2, 7b-3 and 7b-4.

[0068] The drive circuit 241 applies a straight sawtooth drive voltage V Xa ' to the contact fields P a0 ' and P b0'. Likewise, the drive circuit 242 applies a straight sawtooth drive voltage V Xb ' to the contact fields P a1 ' and P b1 '. Furthermore, the drive circuit 243 applies a reference voltage V Xr ' based on reference data Xr' stored in the non-volatile memory 223 to the contact pads P a2 ' and P b2 ' on.

[0069] It should be noted that the frequency of the straight sawtooth drive voltages V Xa ' and V Xb ' is sufficiently small so that no resonance with the natural frequency of a mechanically oscillating system of the mirror 1 with respect to the X-axis depending on the internal piezoelectric actuators 7a-1, 7a-2, 7a-3 and 7a-4, 7b-1, 7b-2, 7b-3 and 7b-4 occurs.

[0070] As in Fig. 16, which is a cross-sectional view of the optical deflector of the Fig. As illustrated in Fig. 15, the inner piezoelectric actuators 7a-1, 7a-2, 7a-3 and 7a-4, 7b-1, 7b-2, 7b-3 and 7b-4 are constructed by the monocrystalline silicon active layer 703, the silicon oxide layer 704, the lower electrode layer 705, the PZT layer 706 and the upper electrode layer 707.

[0071] An optical deflection or horizontal scanning operation by pivoting the mirror 1 with respect to the X-axis is similar to the optical deflection or vertical guiding operation by pivoting the mirror 1 with respect to the Y-axis below.

[0072] The inner piezoelectric actuators 7a-1, 7a-2, 7a-3 and 7a-4, 7b-1, 7b-2, 7b-3 and 7b-4 are divided into an odd-numbered group of the inner piezoelectric actuators 7a-1 and 7a-3, 7b-1 and 7b-3 and an even-numbered group of the inner piezoelectric actuators 7a-2 and 7a-4, 7b-2 and 7b-4, which alternate with the odd-numbered group of the inner piezoelectric actuators 7a-1 and 7a-3, 7b-1 and 7b-3.

[0073] In the same manner as the outer piezoelectric actuators 6a-1, 6a-2, 6a-3 and 6a-4, 6b-1, 6b-2, 6b-3 and 6b-4, when the odd-numbered group of the inner piezoelectric actuators 7a-1, 7a-3, 7b-1 and 7b-3 is bent in one direction, for example, in a downward direction, the even-numbered group of the inner piezoelectric actuators 7a-2, 7a-4, 7b-2 and 7b-4 is bent in the other direction, that is, in the upward direction. On the other hand, when the odd-numbered group of inner piezoelectric actuators 7a-1, 7a-3, 7b-1, and 7b-3 is bent in the upward direction, the even-numbered group of inner piezoelectric actuators 7a-2, 7a-4, 7b-2, and 7b-4 is bent in the downward direction. Thus, the mirror 1 is pivoted with respect to the X-axis.

[0074] The operation of the optical deflector device for deflection in two dimensions or directions is based on the timing diagrams of the Fig. 17A; Fig. 17B, Fig. 17C, Fig. 17D, Fig. 17E and Fig. 17 F and the Fig. 18A, Fig. 18B, Fig. 18C, Fig. 18D, Fig. 18E and Fig. 18F corresponding to those of Fig. 9A, Fig. 9B, Fig. 9C, Fig. 9D, Fig. 9E and Fig. 9F and the Fig. 14A, Fig. 14B, Fig. 14C, Fig. 14D, Fig. 14 E and Fig. 14F executed.

[0075] That is, as in the Fig. 17A, Fig. 17B, Fig. 18A and Fig. 18B, the drive voltage V Xa ' based on the drive data Xa' previously stored in the non-volatile memory 221 and the drive voltage V Xb' based on the drive data Xb' previously stored in the non-volatile memory 222, straight and sawtooth at a predetermined frequency and symmetrical or opposite in phase with each other with the reference voltage V Xr ' based on the reference data Xr' previously stored in the non-volatile memory 223. As a result, the inner piezoelectric actuators 7a-1, 7a-3, 7b-1, and 7b-3 and the inner piezoelectric actuators 7a-2, 7a-4, 7b-2, and 7b-4 perform bending operations in opposite directions to each other to pivot the mirror 1 with respect to the X-axis.

[0076] It should be noted that the frequency of the straight sawtooth drive voltages V Xa ' and V Xb' is sufficiently small so that no resonance with the natural frequency of a mechanically oscillating system of the mirror 1 with respect to the X-axis depending on the internal piezoelectric actuators 7a-1, 7a-2, 7a-3 and 7a-4, 7b-1, 7b-2, 7b-3 and 7b-4 occurs.

[0077] It should be noted that the curved sawtooth drive voltage V Y1 , as in the Fig. 9C and Fig. 14C, can be applied to the even-numbered group of the inner piezoelectric actuators 6a-2 and 6a-4, 6b-2 and 6b-4 and that the curved sawtooth drive voltage V Y2 , as they are in the Fig. 9D and Fig. 14D, can be applied to the odd-numbered group of the inner piezoelectric actuators 6a-1 and 6a-3, 6b-1 and 6b-3.

[0078] Likewise, the straight sawtooth drive voltage V Xa ', as they are in the Fig. 17C and Fig. 18C, to which even-numbered group of outer piezoelectric actuators 7a-2, 7a-4, 7b-2 and 7b-4 are applied, and the straight sawtooth drive voltage V Xb ', as they are in the Fig. 17D and Fig. 18 D can be applied to the odd-numbered group of outer piezoelectric actuators 7a-1, 7a-3, 7b-1 and 7b-3.

[0079] The subject matter disclosed herein may be applied to devices other than vehicle headlights, where irregular illumination would occur depending on the distance from the device.

[0080] It will be apparent to those skilled in the art that various modifications and variations may be made to the subject matter disclosed herein without departing from the scope of the invention as defined by the appended claims.

Claims

[1] An optical deflector device for deflection in two dimensions, comprising an optical deflector and a driver for driving the optical deflector, the optical deflector comprising: a mirror (1); a first piezoelectric actuator (4a-1, 4b-1, 4a-2, 4b-2; 7a-1~7a-4, 7b-1~7b-4) for pivoting the mirror (1) with respect to a first axis of the mirror (1); a second piezoelectric actuator (6a-1~6a~4, 6b-1~6b-4) of a meander type for pivoting the mirror (1) with respect to a second axis of the mirror (1) which is perpendicular to the first axis, a movable frame (2) for supporting the mirror (1); and a support body (5) surrounding the movable frame (2), wherein the driver has a curved sawtooth drive voltage (V Y1 , V Y2 ) and the curved sawtooth drive voltage (V Y1 , V Y2) to the second piezoelectric actuator (6a-1~6a~4, 6b-1~6b-4); wherein the second piezoelectric actuator (6a-1~6a~4, 6b-1~6b-4) comprises a pair of third piezoelectric actuators each located opposite to each other with respect to the mirror (1), connected between the support body (5) and the movable frame (2); wherein each of the third piezoelectric actuators comprises: a first group of piezoelectric actuators (6a-1, 6a-3, 6b-1, 6b-3) serving as cantilevers, and a second group of piezoelectric actuators (6a-2, 6a-4, 6b-2, 6b-4) serving as cantilevers alternating with the first group of piezoelectric actuators (6a-1, 6a-3, 6b-1, 6b-3); wherein the piezoelectric actuators (6a-1, 6a-2, 6a-3, 6a-4, 6b-1, 6b-2, 6b-3, 6b-4) are folded at each actuator and connected between the support body (5) and the movable frame (2), each of the piezoelectric actuators (6a-1, 6a-2, 6a-3, 6a-4, 6b-1, 6b-2, 6b-3, 6b-4) being parallel to the first axis of the mirror (1); where the driver provides the curved sawtooth drive voltage (V Y1 ) to the first group of piezoelectric actuators (6a-1, 6a-3, 6b-1, 6b-3); where the driver provides a further curved sawtooth drive voltage (V Y2 ) in phase opposite to the curved sawtooth drive voltage (V Y1 ) and the further curved sawtooth drive voltage (V Y2 ) to the second group of piezoelectric actuators (6a-2, 6a-4, 6b-2, 6b-4). [2] An optical deflector device for deflection in two dimensions according to claim 1, wherein the curved sawtooth drive voltage (V Y1 , V Y2 ) has a period (T) which is separated by a rise period (T a ) and a decay period (T b ) is formed, where the curved sawtooth drive voltage (V Y1 , V Y2 ) for the rise period (T a ) or the decay period (T b ) first gradually changed and then rapidly changed, where the curved sawtooth drive voltage (V Y1 , V Y2 ) for the other of the rise period (T a ) or waste period (T b ) first changed rapidly and then changed gradually. [3] An optical deflector device for deflection in two dimensions according to claim 2, wherein the rise period (T a ) and the decay period (T b) are each half of the period (T), where the curved sawtooth drive voltage (V Y1 , V Y2 ) symmetrical with respect to the rise period (T a ) and the decay period (T b ) is. [4] An optical deflector device for deflection in two dimensions according to claim 1, wherein the curved sawtooth drive voltage (V Y1 , V Y2 ) has a period (T) which is separated by a rise period (T a ) and a decay period (T b ) is formed, where the curved sawtooth drive voltage (V Y1 , V Y2 ) for the rise period (T a ) or the decay period (T b ) first changed rapidly and then gradually changed, where the curved sawtooth drive voltage (V Y1 , V Y2 ) for the other of the rise period (T a ) or waste period (T b) first changed gradually and then changed rapidly. [5] An optical deflector device for deflection in two dimensions according to claim 4, wherein the rise period (T a ) and the decay period (T b ) are each half of the period (T), where the curved sawtooth drive voltage (V Y1 , V Y2 ) is symmetrical with respect to the rise period (Ta) and the fall period (Tb). [6] An optical deflector device for deflection in two dimensions according to claim 1, wherein the curved sawtooth drive voltage (V Y1 , V Y2 ) has a period (T) which is separated by a rise period (T a ) and a decay period (T b ), where the rise period (T a ) or the decay period (T b ) is longer than the other period, where the curved sawtooth drive voltage (V Y1 , V Y2) for the mentioned one of the rising periods (T a ) or the waste period (T b ) first gradually changed and then rapidly changed, where the curved sawtooth drive voltage (V Y1 , V Y2 ) for the other of the rise period (T a ) or the decay period (T b ) has changed rapidly. [7] An optical deflector device for deflection in two dimensions according to claim 1, wherein the first piezoelectric actuator (4a-1, 4b-1, 4a-2, 4b-2; 7a-1~7a-4, 7b-1~7b-4) is of a torsion bar type, wherein the driver supplies a sinusoidal drive voltage (V Xa , V Xb ) and the sinusoidal drive voltage (V Xa , V Xb ) to the first piezoelectric actuator (4a-1, 4b-1, 4a-2, 4b-2; 7a-1~7a-4, 7b-1-7b-4) [8] An optical deflector device for deflection in two dimensions according to claim 7, wherein a frequency of the sinusoidal drive voltage (V Xa , V Xb ) is greater than a frequency of the curved sawtooth drive voltage (V Y1 , V Y2 ). [9] An optical deflector device for deflection in two dimensions according to claim 1, wherein the first piezoelectric actuator (4a-1, 4b-1, 4a-2, 4b-2; 7a-1~7a-4, 7b-1~7b-4) has a meander type, wherein the driver supplies a straight sawtooth drive voltage (V Xa ' , V Xb ') is generated, and the straight sawtooth drive voltage (V Xa ' , V Xb ') to the first piezoelectric actuator (4a-1, 4b-1, 4a-2, 4b-2; 7a-1~7a-4, 7b-1-7b-4). [10] An optical deflector device for deflection in two dimensions according to claim 9, wherein a frequency of the straight sawtooth drive voltage (VXa ' , V Xb ') is greater than a frequency of the curved sawtooth drive voltage (V Y1 , V Y2 ).

Images