JP2017102412A - Optical deflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical deflector which offers increased output of a sensor for detecting a swing angle of a mirror unit without causing a reduction in driving force for swinging motion of the mirror unit.SOLUTION: An optical deflector 1 includes: a mirror unit 2; sub-actuators 11c, 11d configured to work together to cause a torsion bar 5b extending from the mirror unit 2 to swing back and forth; piezoelectric sensors 13c, 13d, each being configured to output voltage between two surfaces of a second piezoelectric film layer formed away from a first piezoelectric film layer for generating actuator force in the respective sub-actuator 11c, 11d; and sensor wiring lines 24a, 24b that respectively connect one surface and the other surface of the second piezoelectric film layer of the piezoelectric sensor 13c to the other surface and one surface of the second piezoelectric film layer of the piezoelectric sensor 13d.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical deflector that emits reflected light by reflecting incident light by a mirror portion while reciprocatingly rotating a mirror portion around a predetermined rotation axis.

  In recent years, it has been known that an optical deflector manufactured using a manufacturing technology of MEMS (Micro Electro Mechanical Systems) is used in a vehicle headlamp, an image display device, or the like.

  A general optical deflector which is a kind of MEMS emits reflected light by reflecting incident light by a mirror part while reciprocating a mirror part around a predetermined rotation axis. The reflected light scans a predetermined scanning area as scanning light, but in order to appropriately control the irradiation point of the scanning light in the scanning area, the mirror unit that determines the irradiation destination of the reflected light is rotated. It is necessary to detect the corner.

  Patent Document 1 discloses an optical deflector that includes a torsion bar that protrudes from a mirror unit along a rotation axis set for the mirror unit, and a pair of piezoelectric actuators that reciprocally rotate the torsion bar around the rotation axis. To do. In the optical deflector, one piezoelectric actuator is provided with a piezoelectric sensor for detecting the rotation angle of the mirror portion. This piezoelectric sensor has a piezoelectric film layer formed separately from the piezoelectric film layer that generates the actuator force, and outputs a voltage generated according to the deformation of the piezoelectric actuator to the piezoelectric film layer.

JP 2014-56015 A

  Since the area of the piezoelectric actuator in the MEMS optical deflector is small, the area of the piezoelectric film layer of the piezoelectric sensor when a part of the piezoelectric film layer of the piezoelectric actuator is used for the piezoelectric sensor is also limited. The output will be small. Further, when the area of the piezoelectric film layer for the piezoelectric sensor is increased in order to increase the output of the piezoelectric sensor, the area of the piezoelectric film layer for generating the actuator force is reduced correspondingly, and as a result, the actuator force is weakened. This hinders the reciprocating rotation of the mirror part.

  An object of the present invention is to provide an optical deflector that increases the detection output of the rotation angle of the mirror portion without causing any trouble in the reciprocating rotation of the mirror portion.

The optical deflector of the present invention is
A mirror that reflects incident light and emits reflected light; and
A torsion bar projecting from the mirror portion along a rotation axis set for the mirror portion;
A first piezoelectric film layer, coupled to the torsion bar at both ends with respect to the rotational axis, and deformed in accordance with an applied voltage between both surfaces of the first piezoelectric film layer; A pair of piezoelectric actuators that reciprocally rotate the coupling portion with the bar around the rotation axis;
A support portion for supporting a base end portion of the pair of piezoelectric actuators;
A pair of piezoelectric sensors that are individually provided for the pair of piezoelectric actuators and that output a voltage generated between both surfaces of the second piezoelectric film layer according to deformation of the corresponding piezoelectric actuator;
One surface of the second piezoelectric film layer of one piezoelectric sensor of the pair of piezoelectric sensors is connected to the other surface of the second piezoelectric film layer of the other piezoelectric sensor, and the first piezoelectric sensor of the one piezoelectric sensor is connected. And an inter-sensor wiring connecting the other surface side of the second piezoelectric film layer to the one surface side of the second piezoelectric film layer of the other piezoelectric sensor.

  According to the present invention, the inter-sensor wiring for mutually connecting the pair of piezoelectric sensors in the piezoelectric actuators on both sides to the torsion bar is connected to the one surface of the second piezoelectric film layer of one of the piezoelectric sensors. The other piezoelectric film layer is connected to the other surface side, and the other piezoelectric film layer of one piezoelectric sensor is connected to the other surface side of the second piezoelectric film layer. Therefore, although the direction of deformation is reversed in the piezoelectric actuators on both sides, the generated voltage of the same phase is output from the pair of piezoelectric sensors in the piezoelectric actuators on both sides to the torsion bar, and the rotation of the mirror unit is performed. The detection output of the moving angle can be increased almost twice as compared with the case where there is one piezoelectric sensor.

  In order to stabilize the reciprocating rotation of the mirror around the rotation axis, it is necessary to balance the rotational driving force of the piezoelectric actuators on both sides, and the rotational driving force of the piezoelectric actuators on both sides is the maximum rotational driving force. It is necessary to match the rotational driving force of the smaller piezoelectric actuator. When the output of the piezoelectric sensor is increased by increasing the area of the second piezoelectric film layer of one of the piezoelectric actuators on both sides, only the maximum rotational driving force of the one piezoelectric actuator is greatly reduced. When the piezoelectric actuator cooperates, the rotational driving force when the mirror portion is stably reciprocally rotated is greatly reduced.

  According to the present invention, in order to increase the detection output of the rotation angle of the mirror unit, the area of the second piezoelectric film layer in one piezoelectric actuator is not increased, but the piezoelectric actuators on both sides with respect to the rotation axis are not increased. In each case, a second piezoelectric film layer is formed to increase the area of the second piezoelectric film layer as a whole of the optical deflector, thereby increasing the detection output of the rotation angle of the mirror section. Accordingly, it is possible to suppress a decrease in rotational driving force when the piezoelectric actuators on both sides work together to stably reciprocate the mirror portion.

  In the present invention, a pair of signal output wirings for guiding a voltage generated between both surfaces of the second piezoelectric film layer of the one piezoelectric sensor to the support portion is provided, and the inter-sensor wiring is disposed on the torsion bar. It is preferably formed across the bar.

  According to this configuration, the inter-sensor wiring is formed on the torsion bar so as to cross the torsion bar, so that a total of two signal output wirings for the pair of piezoelectric sensors can be used. As a result, a pair of signal output wirings are provided for each piezoelectric sensor, and two signal output wirings can be reduced compared to a total of four signal output wirings in the entire pair of piezoelectric sensors. .

  In the present invention, the torsion bar is coupled to the support portion at an end opposite to the mirror portion, and one surface of the second piezoelectric film layer of the one piezoelectric sensor among the pair of signal output wirings. It is preferable that the signal output wiring connected to the side reaches the support portion via an end portion of the torsion bar opposite to the mirror portion.

  According to this configuration, the signal output wiring connected to the one surface side of the second piezoelectric film layer of one of the piezoelectric sensors reaches the support portion via the end of the torsion bar opposite to the mirror portion. Yes. The piezoelectric actuator has a voltage application wiring for applying a voltage to one surface side of the first piezoelectric film layer, and the voltage application wiring generally reaches the support portion via the base end portion of the piezoelectric actuator. The signal output wiring connected to the one surface side of the second piezoelectric film layer of one of the piezoelectric sensors reaches the support portion via the torsion bar without passing through the base end portion of the piezoelectric actuator. An increase in wiring density at the base end can be avoided.

  In the present invention, the one piezoelectric actuator in which the second piezoelectric film layer of the one piezoelectric sensor is formed is provided on both the other surface side of the first piezoelectric film layer and the other surface side of the second piezoelectric film layer. Preferably, the ground electrode layer is in contact with the ground electrode layer, and the ground electrode layer is preferably connected to the ground wiring of the support portion via the base end portion of the one piezoelectric actuator.

  According to this configuration, one piezoelectric actuator has the ground electrode layer in contact with both the other surface side of the first piezoelectric film layer and the other surface side of the second piezoelectric film layer. As a result, the number of ground lines can be reduced by combining the ground lines on the other side of the first piezoelectric film layer and the other side of the second piezoelectric film layer in one piezoelectric actuator.

  In the present invention, the first piezoelectric film layer and the second piezoelectric film layer may include a region opposite to the mirror portion side in the direction of the rotation axis and the mirror in the range of the end portion on the tip side of each piezoelectric actuator. It is preferable to occupy the region on the part side.

  According to this configuration, the end range on the tip side of each piezoelectric actuator is not entirely occupied by the second piezoelectric film layer, and the first piezoelectric film layer is located on the side opposite to the mirror portion side in the direction of the rotation axis. Occupy. By leaving a part of the end range on the tip side of each piezoelectric actuator as the first piezoelectric film layer, it is possible to minimize a decrease in desired actuator force despite an increase in the output of the piezoelectric sensor.

  Furthermore, since the second piezoelectric film layer occupies the mirror part side in the direction of the rotation axis in the end range on the tip side of each piezoelectric actuator, it approaches the mirror part rather than occupying the opposite side of the mirror part. Thus, the detection accuracy of the rotation angle of the mirror portion by the piezoelectric sensor can be increased.

It is a schematic block diagram of an optical deflector. It is an enlarged view of a torsion bar and its periphery. It is sectional drawing of the laminated structure of an optical deflector. FIG. 4A is a cross-sectional view in which the range including the torsion bar and the tip portions of the sub-actuators on both sides thereof is cut along the lateral direction at respective positions in the axial direction of the torsion bar. FIG. FIG. 4B is a cross-sectional view cut at the location of the inter-sensor wiring farther from the mirror part, and FIG. 4C is a signal output from one sensor film region in the vertical direction. It is the lamination | stacking sectional drawing cut | disconnected by the extraction | drawer location of the wiring for operation. The figure which shows the output of each piezoelectric sensor.

  FIG. 1 is a schematic configuration diagram of the optical deflector 1. Note that the laser device 14 illustrated as the light source in FIG. 1 is not included in the components of the optical deflector 1. The optical deflector 1 is manufactured using a MEMS manufacturing technique. The optical deflector 1 includes a mirror part 2 that is rotatably arranged at the center, an inner rectangular frame 3 that surrounds the mirror part 2 from the outside, and an outer rectangular frame 4 that surrounds the inner rectangular frame 3 from the outside. .

  In FIG. 1, the mirror part 2 is shown in a state of facing directly in front. In addition, the direction in front is the direction in which the normal line of the mirror surface 2a of the mirror unit 2 is in the same direction as the stacking direction in the SOI (Silicon on Insulator) substrate 35 (FIG. 3) constituting the optical deflector 1. It is.

  For convenience of describing the configuration of the optical deflector 1, directions parallel to the long side direction and the short side direction of the outer rectangular frame 4 are defined as a horizontal direction Q and a vertical direction R, respectively. The stacking direction in the SOI substrate 35 is perpendicular to both the horizontal direction Q and the vertical direction R. Further, for both surfaces in the thickness direction of the optical deflector 1, the surface on the side on which the incident light La from the laser device 14 is incident is defined as the front surface, and the surface opposite to the front surface is defined as the back surface. The surface of the mirror part 2 on which the mirror surface 2 a is formed is the surface side of the mirror part 2.

  The optical deflector 1 includes an element that moves or displaces when the optical deflector 1 is actuated (for example, the mirror unit 2 or the like). The configuration of the optical deflector 1 is the same as when the mirror surface 2a is facing directly in front. explain.

  The pair of torsion bars (elastic beams) 5 a and 5 b protrude from both sides of the mirror portion 2 in the vertical direction R, and are connected to the inner peripheral edge of the inner rectangular frame 3 at the protruding ends. Hereinafter, the torsion bars 5a and 5b are collectively referred to as “torsion bar 5” unless otherwise distinguished.

  When the two rotation axes of the mirror unit 2 are referred to as the first and second rotation axes, the axis of the torsion bar 5 coincides with the first rotation axis. The second rotation axis is orthogonal to the first rotation axis. The first and second rotation axes are both orthogonal to the normal line of the mirror surface 2a.

  The inner actuators 6a and 6b have a symmetrical shape with respect to the first rotation axis, and are disposed in the circular hole 10 that defines the inner peripheral edge of the inner rectangular frame 3 together with the mirror portion 2 and the torsion bar 5. ing. The inner actuator 6a has subactuators 11a and 11c and a handle portion 12a, and the inner actuator 6b has subactuators 11b and 11d and a handle portion 12b.

  The handle portions 12a and 12b are formed in the circular hole 10 along the second rotation axis. Both the handle portions 12a and 12b are coupled to the inner peripheral edge of the inner rectangular frame 3 on the proximal end side, and on the distal end side, the handle portion 12a is coupled to the boundary portion of the subactuators 11a and 11c, and the handle portion 12b is coupled to the subactuator. 11b and 11d are connected to the boundary.

  The subactuators 11a to 11d have a circular arc shape that is ¼ of the circumference, and constitute a circumferential shape as a whole. The subactuators 11a and 11b reciprocately rotate the torsion bar 5a around the first rotation axis, and the subactuators 11c and 11d reciprocately rotate the torsion bar 5b around the first rotation axis.

  The piezoelectric film layer 45 (FIG. 3) of the subactuators 11a and 11b constitutes a first piezoelectric film layer for actuator function. The piezoelectric film layer 45 (FIG. 3) of the subactuators 11c and 11d is divided into a first piezoelectric film layer as a piezoelectric film layer for an actuator function and a second piezoelectric film layer for a piezoelectric sensor.

  In the reciprocating rotation of the mirror unit 2, the coupling part between the inner actuator 6a and the torsion bars 5a and 5b and the coupling part between the inner actuator 6b and the torsion bars 5a and 5b are mutually in the thickness direction of the optical deflector 1. Must be displaced in the opposite direction. Therefore, the voltage applied to the first piezoelectric film layer of the inner actuator 6a and the voltage applied to the first piezoelectric film layer of the inner actuator 6b increase or decrease with a phase difference of 180 °. The applied voltage is typically a sine waveform.

  Hereinafter, the inner actuators 6a and 6b are collectively referred to as “inner actuator 6” unless otherwise distinguished. The sub-actuators 11a to 11d are collectively referred to as “sub-actuators 11” unless otherwise distinguished. When the pattern parts 12a and 12b are not particularly distinguished, they are collectively referred to as the "pattern part 12". The piezoelectric sensors 13c and 13d are collectively referred to as “piezoelectric sensor 13” unless otherwise distinguished.

  The outer actuators 7 a and 7 b are disposed on both sides of the inner rectangular frame 3 in the lateral direction Q, and are interposed between the inner rectangular frame 3 and the outer rectangular frame 4 so as to be interposed between the inner rectangular frame 3 and the outer rectangular frame 4. And When the outer actuators 7a and 7b are not particularly distinguished, they are collectively referred to as “outer actuators 7”. The outer actuator 7 is formed by connecting a plurality of unimorph piezoelectric cantilevers in series along a meander line (bellows-like line).

  In the illustrated optical deflector 1, the outer actuators 7 a and 7 b on both sides in the lateral direction Q with respect to the inner rectangular frame 3 are both coupled to the lower end portion in the longitudinal direction R of the inner rectangular frame 3 on the tip side. Accordingly, the outer actuators 7a and 7b vibrate the lower end portion of the inner rectangular frame 3 in the same direction in the front and back directions in order to rotate the mirror portion 2 around the second rotation axis.

  Therefore, in each outer actuator 7, the odd-numbered cantilevers and the even-numbered cantilevers need to bend in the opposite directions in the front and back directions of the optical deflector 1 in the order of arrangement in the lateral direction Q. Therefore, the piezoelectric film layer of the odd-numbered cantilever and the piezoelectric film layer of the even-numbered cantilever are applied with a voltage having the same waveform (eg, sine wave) and frequency and having an opposite phase.

  The electrode pads 8 a and 8 b are formed on the surface of each short side portion of the outer rectangular frame 4, respectively, and wiring (not shown) formed along the surface of the optical deflector 1 or an embedded wiring layer of the optical deflector 1. (The buried wiring layer is connected to each electrode such as the inner actuator 6 via a lower electrode layer 44 of FIG. 3 described later as a ground wiring.)

  When the optical deflector 1 is installed in a product such as a projector or a vehicle headlamp, the optical deflector 1 is incorporated in the product together with the laser device 14. Incident light La from the laser device 14 enters the mirror unit 2 through the same optical path regardless of the rotation angle of the mirror unit 2. The mirror unit 2 reflects the incident light La incident on the same optical path in a direction corresponding to the rotation angle of the mirror unit 2 and emits the reflected light Lb. For example, when the optical deflector 1 is equipped in an optical scanning device (optical scanner), the reflected light Lb is used as scanning light for scanning a predetermined irradiation area.

  The operation of the mirror unit 2 will be schematically described. The mirror unit 2 reciprocally rotates around the axis (first rotation axis) of the torsion bar 5 by the operation of the inner actuator 6. The mirror unit 2 is also reciprocally rotated around the second rotation axis that is included in the mirror surface 2a of the mirror unit 2 and orthogonal to the first rotation axis by the operation of the outer actuator 7 at the center of the mirror surface 2a.

  For example, the reciprocating frequency of the mirror part 2 around the first rotation axis is 15 kHz, and the reciprocating frequency of the mirror part 2 around the second rotation axis is 60 Hz.

  The reflected light Lb is directed directly to the scanning area to which the reflected light Lb is irradiated, or is directed to the scanning area after passing through an optical system (not shown). When the light deflector 1 is installed in a vehicle headlamp (an example of a scanning light device), in a typical vehicle headlamp, the reflected light Lb is reciprocally rotated by the mirror unit 2 around the first rotation axis. Thus, the irradiation area in front of the vehicle is scanned in the left-right direction. The reflected light Lb scans the irradiation area in front of the vehicle in the front-rear direction by the reciprocating rotation of the mirror unit 2 around the second rotation axis.

  FIG. 2 is an enlarged view of the torsion bar 5b and its surroundings. The sub-actuator 11c of the inner actuator 6a and the sub-actuator 11d of the inner actuator 6b are coupled to the intermediate portion of the torsion bar 5b from both sides in the lateral direction Q at the tip (end on the torsion bar 5b side).

  Since the subactuators 11c and 11d have a symmetric structure with respect to the axis of the torsion bar 5b except for the wiring, the structure of the subactuator 11c will be described, and the description of the structure of the subactuator 11d will be omitted.

  The sensor film region 17c occupies a region on the mirror portion 2 side in the direction of the axis of the torsion bar 5 in the end portion range (end portion range on the torsion bar 5b side) of the sub-actuator 11c. The actuator film region 16c occupies a region closer to the base end side (the handle portion 12a side) than the sensor film region 17c in the subactuator 11c, and extends in the direction of the axis of the torsion bar 5 in the end region on the distal end side of the subactuator 11c. It occupies a region on the inner rectangular frame 3 side (the side opposite to the mirror portion 2 side). The length of the actuator film region 16c and the sensor film region 17c in the axial direction of the torsion bar 5 is longer in the actuator film region 16c.

  The laminated structure portion from the lower electrode layer 44 to the upper electrode layer 46 in the actuator film region 16c generates an actuator force as a main function portion of the subactuator 11c. On the other hand, the laminated structure part from the lower electrode layer 44 to the upper electrode layer 46 in the sensor film region 17c constitutes the piezoelectric sensor 13c as an additional function part of the subactuator 11c. The structures of the actuator film region 16d, the piezoelectric sensor 13d, and the sensor film region 17d of the subactuator 11d correspond to the structures of the actuator film region 16c, the piezoelectric sensor 13c, and the sensor film region 17c of the subactuator 11c, respectively.

  The slit 53c is formed at the boundary between the actuator film region 16c and the sensor film region 17c in the subactuator 11c, and separates the piezoelectric film layer of the actuator film region 16c of the subactuator 11c from the piezoelectric film layer of the sensor film region 17c. Yes. The slit 53d is formed at the boundary between the actuator film region 16d and the sensor film region 17d in the subactuator 11d, and separates the piezoelectric film layer of the actuator film region 16d of the subactuator 11d from the piezoelectric film layer of the sensor film region 17d. Yes. Details of the separation structure will be described later with reference to FIG.

  Hereinafter, the slits 53c and 53d are collectively referred to as “slits 53” unless otherwise distinguished.

  The signal output wirings 21a and 21b extend from the position of the sensor film regions 17c and 17d to the position of the inner rectangular frame 3 in the axial direction of the torsion bar 5b on the surface. The extension wires 28a and 28b serve as extensions of the signal output wires 21a and 21b, are formed on the surface of the inner rectangular frame 3, and are connected to the ends of the signal output wires 21a and 21b at one end, respectively. . The extension wires 28a and 28b are connected to predetermined electrode pads 8a and 8b from the inner rectangular frame 3 through the surfaces of the outer actuators 7a and 7b, respectively, at the other end.

  Refer to FIG. 4 for details of connections between the signal output wirings 21a and 21b, the inter-sensor wirings 24a and 24b, and the electrical connection points 25a, 25b, 26a and 26b, and the sensor film regions 17c and 17d. It will be described later.

  It is sectional drawing of the laminated structure of the optical deflector 1 of FIG. The optical deflector 1 has a laminated structure of a thermal silicon oxide film 39, an SOI 35, a thermal silicon oxide film 40, a lower electrode layer 44, a piezoelectric film layer 45, and an upper electrode layer 46 in order from the bottom. The SOI substrate 35 further has a laminated structure of a Si support layer 31, an intermediate oxide film layer 32, and a Si active layer 33 from the bottom to the top. The thickness of the thermally oxidized silicon films 39 and 40 is, for example, 0.1 to 2.0 μm.

  The interlayer insulating film 50 covers the thermally oxidized silicon film 40 and the portion above the thermally oxidized silicon film 40 in the inner actuator 6 and the outer actuator 7. The interlayer insulating film 50 is also formed on the surface side of the outer rectangular frame 4 so as to insulate at least between the electrode pad 8 and the active layer 33. The material of the support layer 31 and the active layer 33 is Si (silicon). The intermediate oxide film layer 32 is silicon dioxide. A wiring 54 is further formed on the surface side of the interlayer insulating film 50.

Specifically, the lower electrode layer 44 is composed of two upper and lower metal thin films. Titanium (Ti) is used for the lower metal thin film, and platinum (Pt) is used for the upper metal thin film. Further, strontium ruthenium oxide (SrRuO ₃ ) may be formed on Pt as a diffusion preventing layer. Each metal thin film is formed by, for example, a sputtering method or an electron beam evaporation method.

  The piezoelectric film layer 45 is made of lead zirconate titanate (PZT) as a piezoelectric material. The thickness of the piezoelectric film layer 45 is, for example, about 1 to 10 μm.

As a material of the upper electrode layer 46, Pt or Au is used. The upper electrode layer 46 is formed by, for example, sputtering or electron beam evaporation. SrRuO ₃ can also be formed as a diffusion preventing layer between the piezoelectric film layer 45 and the lower electrode layer. Further, Ti can be formed on the upper surface of Pt as an adhesion layer with the wiring 54.

As a material of the interlayer insulating film 50, silicon oxide (SiO ₂ ) or silicon nitride (SiN) can be used. Further, aluminum (Al) can be used as the material of the wiring 54. The film thickness of each layer may be appropriately set with reference to already known documents such as Japanese Patent Application Laid-Open No. 2005-148459.

  In FIG. 3, the cross section of the laminated structure of the inner rectangular frame 3 and the torsion bar 5 is omitted. The laminated structure of the inner rectangular frame 3 (not shown) includes a laminated range from the intermediate oxide film layer 32 to the lower electrode layer 44, and an interlayer insulating film 50 is further coated thereon. The lower electrode layer 44 of the inner rectangular frame 3 is integrated with the lower electrode layer 44 of the inner actuator 6 and plays a role as wiring for maintaining the lower electrode layer 44 of the inner actuator 6 at the ground potential. The laminated structure of the torsion bar 5 includes a laminated range from the intermediate oxide film layer 32 to the thermally oxidized silicon film 40, and an interlayer insulating film 50 is further coated thereon.

  FIG. 4 is a cross-sectional view in which the range including the torsion bar 5b and the tip portions of the subactuators 11c and 11d is cut along the lateral direction Q at respective positions in the axial direction (vertical direction R) of the torsion bar 5b. FIG. 4A is a cross-sectional view taken along the longitudinal direction R at the location of the inter-sensor wiring 24b closer to the mirror section 2. FIG. 4B is a cross-sectional view taken in the longitudinal direction R and cut in the longitudinal direction R at a location of the inter-sensor wiring 24a far from the mirror unit 2. FIG. 4C is a stacked cross-sectional view taken along the vertical direction R at the location where the signal output wiring 21a is drawn from the sensor film region 17c.

  In FIG. 4, the lower electrode layer 44, the piezoelectric film layer 45 and the upper electrode layer 46 in the actuator film regions 16c and 16d, and the lower electrode layer 44, the piezoelectric film layer 45 and the upper electrode layer 46 in the sensor film regions 17c and 17d are shown. And is divided by a slit 53. Further, after dividing by the slit 53, the surface side of the subactuators 11 c and 11 d is covered with the interlayer insulating film 50.

  The signal output wirings 21 a and 21 b are formed by patterning the lower electrode layer 44 and then performing etching processing before coating with the interlayer insulating film 50. Typically, the signal output wirings 21a and 21b are formed by etching together when the lower electrode layer 44 of the inner actuator 6 and the outer actuator 7 is formed by etching.

  The inter-sensor wires 24a and 24b and the electrical connection points 25a, 25b, 26a, and 26b are formed on the surface of the interlayer insulating film 50 by patterning after the interlayer insulating film 50 is formed. Regarding the electrical connection points 25a, 25b, 26a, and 26b, contact holes are formed in advance in corresponding portions of the interlayer insulating film 50 before the formation thereof.

  In the interlayer insulating film 50, the corresponding portions of the electrical connection points 25a and 25b are in the sensor film regions 17c and 17d, respectively. The portion corresponding to the electrical connection point 26a in the interlayer insulating film 50 is located at the end of the extension portion on the torsion bar 5 side of the lower electrode layer 44 of the sensor film region 17d (FIG. 4B described later). The portion corresponding to the electrical connection point 26b in the interlayer insulating film 50 is located at the end of the extension portion on the torsion bar 5 side of the lower electrode layer 44 in the sensor film region 17c (FIG. 4A described later).

  As illustrated in FIG. 4B, the inter-sensor wiring 24a connects the electrical connection point 25a and the lower electrode layer 44 of the sensor film region 17d via the electrical connection point 25a. As illustrated in FIG. 4A, the inter-sensor wiring 24b connects the electrical connection point 25b and the lower electrode layer 44 of the sensor film region 17c via the electrical connection point 26a. The inter-sensor wires 24a and 24b are formed so as to cross the torsion bar 5b.

  Hereinafter, the signal output wirings 21a and 21b are collectively referred to as “signal output wiring 21” unless otherwise distinguished. The inter-sensor wirings 24a and 24b are collectively referred to as “inter-sensor wiring 24” unless otherwise distinguished. The electrical connection points 25a and 25b are collectively referred to as “electric connection point 25” unless otherwise distinguished. The electrical connection points 26a and 26b are collectively referred to as “electrical connection point 26” unless otherwise distinguished.

  FIG. 4C shows a cross section at a longitudinal position (position in the longitudinal direction R) where the signal output wiring 21a is connected to the lower electrode layer 44 of the sensor film region 17c at one end. The signal output wiring 21a extends from the lower electrode layer 44 of the sensor film region 17c toward the torsion bar 5 at one end.

  4C and FIG. 2 described above, the signal output wiring 21a extends in the vertical direction R from the position farther from the mirror portion 2 than the inter-sensor wiring 24a toward the inner rectangular frame 3. On the other hand, the signal output wiring 21 b extends from the electrical connection point 26 a toward the inner rectangular frame 3. The signal output wirings 21 a and 21 b are formed as remaining portions of the lower electrode layer 44 by etching the lower electrode layer 44 before the formation of the interlayer insulating film 50.

  The signal output wirings 21 a and 21 b can be formed without using the lower electrode layer 44. For example, the signal output wiring 21 a can be formed by forming a contact hole in the interlayer insulating film 50 and adding additional wiring such as Al from the lower electrode layer 44. The signal output wiring 21b can also be formed by an additional wiring such as Al from the electrical connection point 26a or the inter-sensor wiring 24a.

  FIG. 5 shows the outputs of the piezoelectric sensors 13c and 13d. In FIG. 5, the output V1 of the first-stage piezoelectric sensor 13c from the top indicates the potential of the upper electrode layer 46 with respect to the lower electrode layer 44 in the sensor film region 17c.

  The output V3 of the second-stage piezoelectric sensor 13d from the top when there is no reverse connection indicates the potential of the upper electrode layer 46 with respect to the lower electrode layer 44 in the sensor film region 17d without the inter-sensor wires 24a and 24b. Since the subactuator 11d is deformed in the opposite direction to the thickness direction of the optical deflector 1 with respect to the subactuator 11c, V3 is 180 ° out of phase with V1.

  The output V2 of the third-stage piezoelectric sensor 13d from the top is the potential of the lower electrode layer 44 with respect to the upper electrode layer 46 in the piezoelectric sensor 13d when the inter-sensor wiring 24 is added. In this case, the upper electrode layer 46 of the piezoelectric sensor 13d is the same as the ground potential of the lower electrode layer 44 of the piezoelectric sensor 13c, and the direction of V2 is reversed from the direction of V3, so the output V2 is in phase with V1. Become.

  In the optical deflector 1, the lower electrode layer 44 of the piezoelectric sensor 13c and the upper electrode layer 46 of the piezoelectric sensor 13d are drawn out from the signal output wiring 21a, connected to the electrode pad 8a, and the upper electrode layer of the piezoelectric sensor 13c. 46 and the lower electrode layer 44 of the piezoelectric sensor 13d are drawn out from the signal output wiring 21b and connected to the electrode pad 8b. As a result, the output V1 of the piezoelectric sensor 13c and the output V2 of the piezoelectric sensor 13d are summed, and an output (output power) that is twice the output (output power) when there is only one piezoelectric sensor is output from the electrode pad 8. Can be output.

  If there is an imbalance in the rotational driving force of the torsion bar 5b by the subactuators 11c and 11d, the reciprocating rotation of the mirror part 2 around the first rotation axis will become unstable. Therefore, the rotational driving force of the torsion bar 5b by the subactuators 11c and 11d needs to match the rotational driving force of the subactuator having the smaller maximum rotational driving force among the subactuators 11c and 11d.

  In this optical deflector 1, in order to double the output of the piezoelectric sensor, the area of one sensor film region of the subactuators 11c and 11d is not increased, but the piezoelectric sensor 13c is applied to both the subactuators 11c and 11d. , 13d are provided to increase the area of the piezoelectric film layer of the piezoelectric sensor of the entire optical deflector 1 so as to increase the detection output of the rotation angle of the mirror unit 2. Therefore, despite the increase in the area of the piezoelectric film layer of the piezoelectric sensor of the entire optical deflector 1, the imbalance in the maximum rotational driving force of the subactuators 11c and 11d is eliminated, and the subactuators 11c and 11d work together. And the fall of the rotational drive force when rotating the mirror part 2 stably reciprocatingly is suppressed.

  Also, the end range on the tip side of the subactuators 11c and 11d is not entirely occupied by the sensor film regions 17c and 17d, and the side of the inner rectangular frame 3 in the direction of the axis of the torsion bar 5b is the actuator film region 16c. , 16d. In order to increase the output of the piezoelectric sensor, there is a way to use the entire end range on the tip side of only one of the subactuators 11c and 11d as the sensor film region, but the tip end side of each of the subactuators 11c and 11d. By leaving a part of the partial area in the actuator film regions 16c and 16d, it is possible to suppress the decrease in the area of the actuator film regions 16c and 16d and to minimize the decrease in the actuator force.

  Further, since the sensor film regions 17c and 17d occupy the mirror portion 2 side in the axial direction of the torsion bar 5 in the end portion range of each sub-actuator, the mirror portion is more than when the inner rectangular frame 3 side is occupied. 2 and the detection accuracy of the rotation angle of the mirror unit 2 can be increased.

  Although the embodiment of the present invention has been described, the present invention is not limited to the embodiment and can be implemented with various modifications.

  For example, in the embodiment shown in FIGS. 2 and 4, the signal output wiring 21a is drawn from the lower electrode layer 44 of the sensor film region 17c. However, in FIG. 4, the lower end of the slit 53c extends to the lower surface of the piezoelectric film layer 45, and the lower electrode layer 44 remains integral with the actuator film region 16c and the sensor film region 17c without being divided by the slit 53c. You can also In a typical optical deflector, the lower electrode layer 44 may be used in common with a ground electrode layer common to electrical elements of the optical deflector. In that case, the lower electrode layer 44 as the ground electrode layer is not divided in the middle, but is finally integrated with the lower electrode layer 44 as the ground wiring of the outer rectangular frame 4, so that the electrode pad 8 a having the ground potential is formed. It is connected to the.

  Therefore, by integrating the lower electrode layer 44 of the actuator film region 16c and the sensor film region 17c in the subactuator 11c, the lower electrode layer 44 of the sensor film region 17c is set to the ground potential. As a result, an increase in wiring density in the outer actuator 7a is avoided.

  In the subactuator 11c, by integrating the lower electrode layer 44 of the actuator film region 16c and the sensor film region 17c, the signal output wiring 21a in the torsion bar 5b can be omitted, whereas the signal output wiring 21b. Cannot be omitted. Therefore, even when the signal output wiring 21a is omitted, the signal output wiring 21b is formed on the torsion bar 5b as in the embodiment, or via the sub-actuator 11c and the handle portion 12b instead of the torsion bar 5b. Thus, it is necessary to form and connect to the corresponding electrode pad 8b.

  In the embodiment, the torsion bar 5 is coupled to the inner rectangular frame 3 as a support portion at the end opposite to the mirror portion 2, but the opposite end is separated from the inner rectangular frame 3. It may be. In that case, the signal output wiring 21 is formed on the surface of the actuator film region 16 of the subactuators 11c and 11d without reaching the inner rectangular frame 3 from the opposite end of the torsion bar 5, and From the base end portion, the handle portion 12 is reached to the inner rectangular frame 3.

  In the embodiment, the material of the piezoelectric film layer 45 of the actuator film regions 16c and 16d as the first piezoelectric film layer and the material of the piezoelectric film layer 45 of the sensor film regions 17c and 17d as the second piezoelectric film layer are both Although it is PZT, other materials can be used.

  In the embodiment, the voltage between the front surface and the back surface of the piezoelectric film layer 45 is an applied voltage or a generated voltage between both surfaces of the piezoelectric film layer, and the front surface side and the back surface side of the piezoelectric film layer 45 are respectively One side and the other side. However, the back surface side and the front surface side of the piezoelectric film layer 45 can also be the one surface side and the other surface side of the piezoelectric film layer, respectively.

  In the embodiment, the piezoelectric sensors 13c and 13d are one piezoelectric sensor and the other piezoelectric sensor, respectively. However, each of the piezoelectric sensors 13c and 13d may be the other piezoelectric sensor and one piezoelectric sensor.

  Since the optical deflector 1 of the embodiment uses the reflected light Lb reflected by the mirror surface 2a as a two-dimensional scanning light, the mirror unit 2 is respectively rotated around the first and second rotation axes orthogonal to each other. It is designed to reciprocate at a frequency of. The optical deflector of the present invention can also be applied to a one-dimensional scanning optical deflector. In that case, the inner rectangular frame 3 constitutes a support portion that supports the base end portions of the subactuators 11c and 11d as a pair of actuators. Further, the first and second rotation axes may intersect at a predetermined angle other than 90 ° without being orthogonal to each other.

  In the illustrated example, the inter-sensor wires 24a and 24b that traverse the torsion bar 5b (extending in the width direction of the torsion bar 5b) and the signal output wires 21a and 21b extending in the longitudinal direction of the torsion bar 5b are: Although exposed on the surface, these wirings may be coated with a passivation film.

DESCRIPTION OF SYMBOLS 1 ... Optical deflector, 2 ... Mirror part, 2a ... Mirror surface, 3 ... Inner side rectangular frame (support part), 4 ... Outer side rectangular frame (support part), 5a, 5b .. Torsion bar, 6a, 6b ... inner actuator (actuator), 11c, 11d ... subactuator, 13c, 13d ... piezoelectric sensor, 16c, 16d ... actuator film region, 17c, 17d ... Sensor film region, 21a, 21b ... signal output wiring, 24a, 24b ... sensor wiring, 44 ... lower electrode layer, 45 ... piezoelectric film layer (first piezoelectric film layer and second piezoelectric film layer) Piezoelectric film layer), 46... Upper electrode layer, 53c, 53d.

Claims (5)

A mirror that reflects incident light and emits reflected light; and
A torsion bar projecting from the mirror portion along a rotation axis set for the mirror portion;
A first piezoelectric film layer, coupled to the torsion bar at both ends with respect to the rotational axis, and deformed in accordance with an applied voltage between both surfaces of the first piezoelectric film layer; A pair of piezoelectric actuators that reciprocally rotate the coupling portion with the bar around the rotation axis;
A support portion for supporting a base end portion of the pair of piezoelectric actuators;
A pair of piezoelectric sensors that are individually provided for the pair of piezoelectric actuators and that output a voltage generated between both surfaces of the second piezoelectric film layer according to deformation of the corresponding piezoelectric actuator;
One surface of the second piezoelectric film layer of one piezoelectric sensor of the pair of piezoelectric sensors is connected to the other surface of the second piezoelectric film layer of the other piezoelectric sensor, and the first piezoelectric sensor of the one piezoelectric sensor is connected. An optical deflector comprising: an inter-sensor wiring connecting the other surface side of the second piezoelectric film layer to the one surface side of the second piezoelectric film layer of the other piezoelectric sensor. The optical deflector according to claim 1.
A pair of signal output wirings for guiding a voltage generated between both surfaces of the second piezoelectric film layer of the one piezoelectric sensor to the support portion;
The inter-sensor wiring is formed on the torsion bar so as to cross the torsion bar. The optical deflector according to claim 2, wherein
The torsion bar is coupled to the support portion at an end opposite to the mirror portion,
Of the pair of signal output wirings, the signal output wiring connected to one surface side of the second piezoelectric film layer of the one piezoelectric sensor has an end portion on the opposite side of the mirror portion of the torsion bar. An optical deflector characterized in that the optical deflector reaches the support portion via a via. The optical deflector according to claim 2 or 3,
One piezoelectric actuator in which the second piezoelectric film layer of the one piezoelectric sensor is formed is in contact with both the other surface side of the first piezoelectric film layer and the other surface side of the second piezoelectric film layer. A ground electrode layer,
The optical deflector, wherein the ground electrode layer is connected to the ground wiring of the support portion via a base end portion of the one piezoelectric actuator. In the optical deflector according to any one of claims 1 to 4,
The first piezoelectric film layer and the second piezoelectric film layer include a region on the side opposite to the mirror unit side and a region on the mirror unit side in the direction of the rotation axis in the end range on the tip side of each piezoelectric actuator. An optical deflector characterized by occupying.