Light deflector, laser scanner

Abstract

The present application provides a light deflector, a laser scanner, and reduces in-plane distortion of a mirror in the light deflector. A light deflector is provided, which is configured using a substrate having a first layer and a second layer, the light deflector including: a mirror having a mirror plate configured using the first layer and a rib configured on a back surface side of the mirror plate and configured using the second layer; an actuator configured separately from the mirror around the mirror; and a torsion bar configured using the second layer, connecting the rib of the mirror and the actuator.

Description

Technical Field

[0001] This disclosure relates to optical deflectors and laser scanners. Background Technology

[0002] Japanese Patent Application Publication No. 2016-170376 (Patent Document 1) discloses an optical deflector comprising a mirror portion, a support portion, a pair of torsion bars coupled to the mirror portion and the support portion along the rotation axis of the mirror portion, and a rib formed on the back surface of the mirror portion. In this optical deflector, each torsion bar has a pair of auxiliary portions extending from it. The rib has a pair of rib extensions extending from the outer edge of the mirror portion, and the pair of rib extensions are formed to extend and engage with the auxiliary portions. However, this optical deflector has room for improvement regarding the large in-plane distortion of the mirror.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-170376 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] One of the purposes of the specific methods disclosed herein is to provide a technique that can reduce in-plane distortion of a mirror.

[0008] Methods for solving problems

[0009] [1] One aspect of the optical deflector of the present invention is constructed using a substrate having a first layer and a second layer, the optical deflector comprising:

[0010] A reflector having a mirror plate formed using the first layer and a rib disposed on the back side of the mirror plate and formed using the second layer;

[0011] An actuator, which is disposed separately from the reflector around the reflector; and

[0012] A torsion bar, constructed using the second layer, connects the rib of the reflector to the actuator.

[0013] [2] One type of laser scanner disclosed herein includes:

[0014] The optical deflector described in [1];

[0015] A light source that directs laser light toward the light deflector; and

[0016] The driving circuit controls the operation of the light deflector and the light source respectively.

[0017] Based on the above structure, in-plane distortion of the mirrors in the optical deflector can be reduced. Furthermore, a high-quality laser scanner equipped with mirrors that reduce in-plane distortion can be obtained. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the structure of a laser scanner according to one embodiment.

[0019] Figure 2 This is a perspective view showing the structure of an optical deflector according to one embodiment.

[0020] Figure 3 This is an enlarged 3D view of the main part of the optical deflector.

[0021] Figure 4A This is an enlarged stereoscopic view of the main part of the optical deflector as seen from the back side. Figure 4B It is an enlarged representation Figure 4A The diagram shows the cross-section at line AA.

[0022] Figure 5A This is an example diagram used to illustrate the dimensions of the mirror plate and ribs. Figure 5B This is a diagram illustrating an example of the dimensions of the connection between the torsion bar and the actuator.

[0023] Figure 6 This is a diagram showing the names of the various parts of the mirror plate and ribs.

[0024] Figure 7 This is a diagram showing the various parts of a torsion bar.

[0025] Figure 8A This is a top view used to illustrate the rib shape of the optical deflector in the first comparative example. Figure 8B yes Figure 8A A sectional view at line BB in the diagram.

[0026] Figure 9A This is a top view used to illustrate the rib shape of the optical deflector in the second comparative example. Figure 9B yes Figure 9A A sectional view at the CC line.

[0027] Figure 10A This is a top view of the rib shape of the optical deflector used to illustrate a simplified embodiment of this invention. Figure 10B yes Figure 10A A sectional view at the CC line.

[0028] Figures 11A-11D This is a diagram illustrating the manufacturing process of an optical deflector according to one embodiment.

[0029] Figures 12A-12DThis is a diagram illustrating the manufacturing process of an optical deflector according to one embodiment.

[0030] Explanation of reference numerals in the attached figures

[0031] 1: Light deflector; 2: Light source; 3: Drive circuit; 4: Screen; 5: Reflector; 6a, 6b: Torsion bar; 7a, 7b: Actuator; 8: Inner frame; 9a, 9b: Actuator; 11: Circular part; 12a, 12b: Semi-elliptical part. Detailed Implementation

[0032] Figure 1 This diagram schematically illustrates the structure of a laser scanner according to one embodiment. The laser scanner of this embodiment is configured to include a light deflector 1, a light source 2, and a control circuit 3. A laser beam emitted from the light source 2 is incident on the light deflector 1. The light deflector 1, via a reflector controlled by the control circuit 3, allows for flexible changes in the direction of laser reflection. Therefore, the laser beam reflected by the light deflector 1 can be scanned on the screen 4 to depict a desired image.

[0033] Figure 2 This is a perspective view showing the structure of an optical deflector according to one embodiment. Figure 3 This is an enlarged 3D view of the main part of the optical deflector. Figure 4A This is an enlarged perspective view of the main parts of the optical deflector as seen from the rear side. The optical deflector 1 in this embodiment is configured to include a reflector 5, torsion bars 6a and 6b, actuators 7a and 7b, an inner frame 8, and actuators 9a and 9b.

[0034] Reflector 5 reflects the incident laser light, thus enabling it to reflect the incident laser light separately. Figure 2 The mirror rotates along two mutually orthogonal axes, namely the X-axis and Y-axis. In this embodiment, the reflector 5 is roughly circular when viewed from above, but its shape is not limited to this. Figure 4A As shown, the reflector 5 is configured to include a mirror plate 9 and a rib 10. The light deflector 1 of this embodiment is constructed using a semiconductor substrate having an active layer, a support layer, and an insulating layer between them. Specifically, the mirror plate 9 is constructed using the active layer of an SOI (Silicon on Insulator) wafer, and the rib 10 is constructed using the support layer of an SOI wafer. An SOI wafer refers to a semiconductor substrate, as known to those skilled in the art, having a structure in which a SiO2 film (BOX layer) as a thin insulating film is sandwiched between a Si substrate (support layer) and a surface Si layer (active layer).

[0035] Rib 10 includes: a circular portion (annular portion) 11 disposed on the back side of mirror plate 9; and semi-elliptical portions (first connecting portions) 12a and 12b, each extending and protruding outward from the mirror plate 9 (actuator 7a, 7b side). Rib 10 functions to suppress in-plane distortion of mirror plate 9. Each semi-elliptical portion 12a and 12b shares the stress of torsion bars 6a and 6b, thus mitigating the stress applied to mirror plate 9. The circular portion 11 is integrally formed with each semi-elliptical portion 12a and 12b.

[0036] like Figure 3 As shown, one end (first end) of the torsion bar 6a is connected to the rib 10 (specifically, the semi-elliptical portion 12a) of the reflector 5, and the other end (second end) is connected to the actuator 7a. Figure 4A As shown, the torsion bar 6a has a portion 13a that serves as the other end portion connected to the actuator 7a, and a columnar portion that connects the first end portion and the second end portion.

[0037] Similarly, as Figure 4A As shown, one end (first end) of the torsion bar 6b ​​is connected to the rib 10 (specifically, the semi-elliptical portion 12b) of the reflector 5, and the other end (second end) is connected to the actuator 7b. Figure 4A As shown, the torsion bar 6b ​​has a portion 13b that serves as the other end portion connected to the actuator 7b, and a columnar portion that connects the first end portion and the second end portion.

[0038] Actuators 7a and 7b are arranged around the reflector 5 in a ring shape when viewed from above. Each actuator 7a and 7b is connected to a torsion bar 6a and 6b on its back side. Each actuator 7a and 7b is constructed by placing a piezoelectric element on the surface of the active layer that is not opposite to the support layer; the piezoelectric element is made of a piezoelectric material such as PZT (lead zirconate titanate). By alternately applying voltages of opposite phases to each actuator 7a and 7b, the piezoelectric material can be deformed. This deformation is transmitted to the reflector 5 via the torsion bars 6a and 6b, thereby enabling the reflector 5 to rotate about the X-axis.

[0039] Actuators 9a and 9b are arranged separately along the Y-axis, separated by a reflector 5. Each actuator 9a and 9b is connected to the other actuator 7a and 7b via an inner frame 8 arranged around them. Each actuator 9a and 9b is constructed by placing a piezoelectric element on the surface of the active layer that is not opposite to the support layer; the piezoelectric element is made of a piezoelectric material such as PZT. By alternately applying voltage to each actuator 9a and 9b, the piezoelectric material can be deformed. This deformation is transmitted to the reflector 5 via the inner frame 8 and the torsion bars 6a and 6b, thereby enabling the reflector 5 to rotate about the Y-axis.

[0040] Figure 4B It is an enlarged representation Figure 4A The diagram shows a cross-section at line AA. As described above, mirror plate 9 is constructed using the active layer of an SOI wafer, and rib 10 is constructed using the support layer of an SOI wafer. Furthermore, compared to the active layer and support layer, the BOX layer is extremely thin, therefore... Figure 4B The diagram of the BOX layer existing between the active layer and the support layer is omitted. As shown in the figure, the rib 10 is arranged to support the back side of the mirror plate 9. In one example of the dimensions, the thickness T1 of the mirror plate 9 can be set to 42.5 μm, the thickness T2 of the rib 10 can be set to 130 μm, and the width d0 of the rib 10 in top view (width in the AA line section) can be set to 50 μm.

[0041] Figure 5A This is an example diagram used to illustrate the dimensions of the mirror plate and ribs. In Figure 5A The image shows a top view of the mirror plate 9 and rib 10 viewed from the rear side. Figure 5B This is an example diagram illustrating the dimensions of the connection between the torsion bar and the actuator. Figure 5B The image shows a top view of the torsion bar and other components viewed from the rear side. Figure 6 This is a diagram showing the names of the various parts of the mirror plate and ribs. Figure 7 This is a diagram showing the various parts of a torsion bar.

[0042] like Figure 5A and Figure 6 As shown, rib 10 has a circular portion 11, which is a roughly elliptical annular portion that is longitudinally elongated. The circular portion 11 is positioned such that its center is approximately aligned with the center of mirror plate 9. The circular portion 11 has an opening on its inner side that is cut out into a horizontally elongated elliptical shape in the figure. The outline of this opening (the inner outline of the annular portion) will be referred to as the "inner ellipse" below. In addition, the outer edge of the circular portion 11 of rib 10 when viewed from above is a longitudinally elongated ellipse in the figure, and the outline of this part (the outer outline of the annular portion) will be referred to as the "outer ellipse" below.

[0043] like Figure 6 As shown, the inner and outer ellipses have major and minor axes, respectively. Furthermore, the semi-elliptical portions 12a and 12b each have a top-view shape that approximates a shape formed by halving the major axis of the ellipse. These semi-elliptical portions 12a and 12b are also as shown... Figure 6 The figure shown has a major axis and a minor axis.

[0044] like Figure 5A As shown, for example, the diameter of mirror plate 9 can be set to 1120 μm. In rib 10, for example, the major and minor axes of the outer ellipse can be set to 854 μm and 710 μm, respectively, and for example, the major and minor axes of the inner ellipse can be set to 610 μm and 554 μm, respectively.

[0045] The distance between the upper outer edge of the inner ellipse and the upper outer edge of the outer ellipse in the figure can be 150 μm. Similarly, the distance between the lower outer edge of the inner ellipse and the lower outer edge of the outer ellipse in the figure can be set to 150 μm. The distance between the two ends of the semi-elliptical portions 12a and 12b can be 246 μm.

[0046] In the figure, the width of a portion of the torsion bar 6a connected to the lower side of the semi-elliptical portion 12a, specifically the portion extending in the left-right direction (first end) 131f, can be set to 35 μm as an example. Similarly, the width of a portion of the torsion bar 6b ​​connected to the upper side of the semi-elliptical portion 12b, specifically the portion extending in the left-right direction (first end) 131g, can be set to 35 μm as an example. Furthermore, as an example, the semi-elliptical portions 12a and 12b can be configured to extend to a position 45 μm from the outer edge of the mirror plate 9.

[0047] The semi-elliptical portions 12a and 12b, when viewed from above, connect to the circular portion 11 at the point where they overlap with the mirror plate 9. They form an annular shape consisting of a curved portion extending along an ellipse to a point where they do not overlap with the mirror plate 9, and a straight portion extending along the major axis. Furthermore, in this embodiment, the semi-elliptical portions 12a and 12b thicken from the connection point with the circular portion 11 to the end of the mirror plate 9, and taper at the point where they do not overlap with the mirror plate 9. At the point where they overlap with the mirror plate 9, they are thickened to suppress distortion of the mirror plate 9. At the point where they do not overlap with the mirror plate 9, they are thinned to alleviate stress with smooth movement.

[0048] like Figure 7 As shown, the portion (second end) 13a of the torsion bar 6a connected to the actuator 7a has: a portion (second connecting portion) 131a disposed on the inner elliptical side and extending laterally in the figure in a rod-like shape; portions (protruding portions) 131b and 131c connected to both sides of the portion 131a and respectively in a roughly U-shape (roughly inverted U-shape) extending towards the inside of the actuator 7a in top view; and a portion (base) 131d connected to the roughly U-shaped portions 131b and 131c respectively and disposed on the outer elliptical side. Additionally, although not shown in the figure, portion 13b also has the same structure. Portions 131a, 131b, and 131c together form a concave portion that is concave and annular in top view.

[0049] like Figure 5B As shown, as an example, the width of portion 131a can be set to 50 μm. As an example, the radius of the outer edge of each of portions 131b and 131c can be set to 70 μm. Furthermore, as an example, the width of portion 131d can be set to 100 μm. Additionally, as an example, the notch 140 (refer to...) Figure 7The width of the notch 140 can be set to 85 μm. The notch 140 refers to the portion formed by removing a local portion in the actuator 7a (7b), which overlaps with the portion that is divided into two strands from the rod-shaped portion 131e of the portion 13a (13b), namely portion 131a and a portion of each portion 131b, 131c when viewed from above.

[0050] Next, the effect of the rib 10 of the optical deflector 1 in this embodiment will be explained.

[0051] Figure 8A This is a top view used to illustrate the rib shape of the optical deflector in the first comparative example. Figure 8B yes Figure 8A A sectional view at line BB in the diagram. Figure 9A This is a top view used to illustrate the rib shape of the optical deflector in the second comparative example. Figure 9B yes Figure 9A A sectional view at the CC line. Figure 10A This is a top view illustrating the rib shape of the optical deflector in a simplified embodiment of this invention. Figure 10B yes Figure 10A A sectional view at the CC line. The figures show the parts related to the reflector (mirror plate and ribs) and torsion bar.

[0052] In the first comparative example, an active layer was used to construct the mirror plate 1009 and the torsion bars 1006a and 1006b. Furthermore, as... Figure 8A and Figure 8B As shown, a support layer located on the lower side of the active layer forms a circular rib 1010 when viewed from above. The rib 1010 is only provided on the back side of the mirror plate 1009, and no rib 1010 is provided on the back side of the torsion bars 1006a and 1006b.

[0053] Similar to the first comparative example, in the second comparative example, an active layer is also used to construct the mirror plate 2009 and the torsion bars 2006a and 2006b. In the second comparative example, as... Figure 9A and Figure 9B As shown, a support layer located on the lower side of the active layer is used to form ribs 2010 and ribs 2010a and 2010b. Specifically, rib 2010 is a circular portion on the back side of mirror plate 2009 in plan view, and each rib 2010a and 2010b is a rectangular portion on the back side of torsion bars 2006a and 2006b in plan view.

[0054] In this simplified embodiment, an active layer is used to construct the mirror plate 9, but the torsion bars 6a and 6b are constructed using support layers instead of active layers. Furthermore, the ribs 10 are also constructed using support layers, and each torsion bar 6a and 6b is connected to the rib 10. The mirror plate 9 is separated from the surrounding actuators and inner plate by an island shape, rather than being connected via an active layer. That is, the mirror plate 9 is supported by the torsion bars 6a and 6b and the ribs 10, which are constructed using support layers, and is indirectly connected to the surrounding actuators, etc. In this simplified embodiment, each torsion bar 6a and 6b that connects the ribs 10 to the actuators 7a and 7b has a first end connected to the rib 10 and a second end connected to the actuators 7a and 7b, and each torsion bar 6a and 6b forms an elongated rectangle when viewed from above between the first and second ends.

[0055] The dynamic surface deformation in the first comparative example, the second comparative example, and this embodiment (simplified method) was compared using RMS values. Regarding this embodiment (simplified method), the dimensions of the numerical examples described above were assumed, and simulations were also performed for the first and second comparative examples based on these dimensions. The results showed that the RMS value in the structure of this embodiment (simplified method) was the lowest at 0.144λ, the second lowest at 0.268λ, and the highest at 0.525λ for the first comparative example. That is, as in this embodiment, the torsion bars 6a and 6b and the rib 10 are composed of a support layer, and the mirror plate 9 is composed of an active layer. Therefore, the torsional effect of the torsion bars 6a and 6b is mitigated, and as a result, the dynamic surface deformation, i.e., the in-plane distortion of the mirror plate 9, is mitigated.

[0056] Next, refer to Figure 6 The effects of the rib 10 structure in this embodiment will be explained. As described above, in this embodiment, a rib 10 composed of a support layer is disposed on the back side of the mirror plate 9, which is composed of an active layer. The portion of the rib 10 disposed near the center of the mirror plate 9 is arranged in a ring shape with a relatively thick width when viewed from above, so as to surround the center of the circular mirror plate 9 when viewed from above. As a result, the distortion of the edge of the mirror plate 9 can be suppressed, and thus dynamic surface deformation can be suppressed. In addition, since the rib 10 and the mirror plate 9 are composed of different layers (support layer / active layer), it is easy to increase the size and thickness of the rib 10. As the thickness of the rib 10 is increased, the thickness of the torsion bar 6a, etc., can also be increased. Therefore, the spring constant of the torsion bar 6a, etc., can be increased, and stress can be mitigated while maintaining the resonant frequency. As a result, the deflection angle of the mirror plate 9 can be increased.

[0057] Here, from this relationship, it can be seen that the resonant frequency f depends on the inertial torque J of the reflector 5, the spring constant k of the torsion bar 6a, etc. The resonant frequency f decreases with increasing inertial torque. The resonant frequency f increases with increasing spring constant. The spring constant depends on the width, thickness, and length of the torsion bar 6a, etc.; the spring constant increases with increasing width or thickness, and decreases with increasing length.

[0058] Furthermore, the semi-elliptical portion 12a (12b) of the rib 10, which connects to the torsion bar 6a (6b), is divided into two branches from the circular portion 11. Thus, when deformation of the torsion bar 6a, etc., is transmitted to the mirror plate 9, one of the two branches of the semi-elliptical portion 12a functions to push the mirror plate 9 upwards from the back, while the other branch functions to attract the mirror plate 9 from the back side. Therefore, the deformation transmitted from the torsion bar 6a, etc., can be distributed and transmitted to the mirror plate 9. This structure provides a solution to the problem of mitigating stress at the connection between the mirror plate 9 and the rib 10.

[0059] Here, in the rib 10 of this embodiment disposed on the back side of the mirror plate 9, more preferred embodiments are listed below. Furthermore, any one or more of the following embodiments can be used, and multiple embodiments can be used in combination.

[0060] (1) The major axis of the outer ellipse is the same as the minor axis of the inner ellipse (in the same direction).

[0061] (2) The minor axis of the outer ellipse is the same as the major axis of the inner ellipse (in the same direction).

[0062] (3) The major axis of the external ellipse is in the same direction as the Y-axis of the mirror plate.

[0063] (4) The minor axis of the external ellipse is in the same direction as the X-axis of the mirror plate.

[0064] (5) The minor axis of the semiellipse is the same as the major axis of the external ellipse (in the same direction).

[0065] (6) The length direction of the transverse portion of the torsion bar 6a, etc., is along the minor axis of the semi-ellipse.

[0066] (7) The major axis of the outer ellipse is greater than the radius of the mirror plate and less than the diameter of the mirror plate.

[0067] (8) The minor axis of the outer ellipse is greater than the radius of the mirror plate and less than the diameter of the mirror plate.

[0068] (9) The major axis of the inner ellipse is smaller than the minor axis of the outer ellipse.

[0069] (10) The minor axis of the inner ellipse is smaller than the major axis of the outer ellipse.

[0070] (11) The major axis of the semiellipse is greater than the minor axis of the semiellipse, and smaller than the diameter of the mirror plate.

[0071] (12) The minor axis of the semi-ellipse is set to d1 > 10 μm

[0072] Wherein, d1 is the distance between the lateral portion of the torsion bar 6a and the outer edge of the mirror plate 9.

[0073] Next, refer to Figure 7 The effects of the torsion bars 6a and 6b of the optical deflector 1 in this embodiment will be explained. As described above, in this embodiment, the torsion bars 6a and 6b are also made of active layers and are continuously formed with the rib 10 on the back side of the mirror plate 9. That is, the torsion bars 6a and 6b are integrally formed with the rib 10. Moreover, the torsion bars 6a and 6b have portions 13a and 13b that connect to the actuators 7a and 7b on the back side of the inner frame 8.

[0074] At part 13a, the bottom sides of the U-shapes of parts 131b and 131c, which are connected to both sides of part 131a and respectively form a roughly U-shape (roughly inverted U-shape), protrude inwards from the actuator 7a when viewed from above. For example... Figure 7 As shown, the portion 13a in the torsion bar 6a connected to the actuator 7a has: a portion (second connecting portion) 131a disposed on the inner elliptical side and extending in a generally rectangular shape laterally in the figure when viewed from above; portions (protruding portions) 131b and 131c connected through portion 131a; and a portion 131d (base) connected to portions 131b and 131c respectively. Portion 131d is connected to the actuator 7a. Portion 13b also has the same structure.

[0075] With this structure, when displacement from the actuator 7a, etc., is transmitted to the columnar portion 131e, which connects the first and second ends of the torsion bar 6a, etc., the displacement can be distributed and transmitted to portions 131b, 131c, which are separated from the actuator 7a, etc. Therefore, a solution can be provided for the problem of mitigating (reducing) the stress applied to the insulating film of the SOI between the portions 131b, 131c and the actuator 7a, etc.

[0076] Here, a more preferred embodiment is described below for the torsion bar 6a and other parts 13 in this embodiment. Furthermore, any one or more of the following embodiments can be used, and multiple embodiments can be used in combination.

[0077] (1) The widths of each part 131b and 131c are greater than the width of the columnar part 131e of the torsion bar 6a.

[0078] (2) The radius R1 of the inner curve of each part 131b and 131c is more than 4 times the width of each part 131b and 131c.

[0079] (3) The ratio of the width d2 of part 131d to the width d4 of the support is 20%~40%.

[0080] (4) The maximum width d3 of part 13a is greater than 6 times the radius R1 of the inner curve.

[0081] Figures 11A-11D , Figures 12A-12D This diagram illustrates the manufacturing process of an optical deflector according to one embodiment. Here, a portion corresponding to optical deflector 1 is shown schematically. Furthermore, since it is necessary to illustrate the oxide film, etc., of the SOI substrate here, the thicknesses of each layer differ from the schematic cross-sectional view of optical deflector 1 described above.

[0082] like Figure 11A As shown, an SOI substrate 31 is prepared. The SOI substrate 31 has an active layer 31a, a support layer 31c, and an oxide film 31b between them.

[0083] like Figure 11B As shown, the surface (active layer 31a side) and back side (support layer 31c side) of the SOI substrate 31 are oxidized by a thermal oxidation furnace (diffusion furnace) to form thermal oxide films 32a and 32b. The thickness of the thermal oxide films 32a and 32b can be set to, for example, 0.1 to 1 μm.

[0084] Next, as Figure 11C As shown, a lower electrode layer 33, a piezoelectric layer 34, and an upper electrode layer 35 are sequentially formed on the surface of the SOI substrate 31 (on the active layer 31a side). Specifically, a lower electrode layer 33, for example, composed of two metal thin films, is formed on the thermal oxide film 32a. The first (lower) metal thin film can be titanium, and the second (upper) metal thin film can be platinum. The thickness of each metal thin film can be, for example, about 30-100 nm for the first titanium layer and about 100-300 nm for the second platinum layer. Next, a piezoelectric layer 34, for example, composed of a single piezoelectric film, is formed on the lower electrode layer 33. PZT, as a piezoelectric material, can be used as the material for the piezoelectric layer 34. The thickness of the piezoelectric film can be, for example, about 0.3 μm to 15 μm. Next, an upper electrode layer 35, for example, composed of a single metal thin film, is formed on the piezoelectric layer 34. The material used for the upper electrode layer 35 is, for example, platinum or gold. The thickness of the upper electrode layer 35 is, for example, about 10 to 200 nm.

[0085] Next, as Figure 11DAs shown, the upper electrode layer 35 and the piezoelectric layer 34 are patterned to form a portion that will become a piezoelectric element such as the actuator 7a. Specifically, firstly, a photolithography technique is used to pattern a resist material on the upper electrode layer 35. Next, using the patterned resist material as a mask, a Reactive Ion Etching (RIE) device is used to dry etch the upper electrode layer 35 and the piezoelectric layer 34.

[0086] Next, as Figure 12A As shown, a mirror plate 9 and actuators 7a and 7b are formed by patterning the lower electrode layer 33, the thermal oxide film 32a, the active layer 31a of the SOI substrate 31, and the oxide film 31b. First, a photolithography technique is used to pattern the resist material. Then, using the patterned resist material as a mask, a refining etching apparatus is used to dry etch the lower electrode layer 33, the thermal oxide film 32a, the active layer 31a of the SOI substrate 31, and the oxide film 31b.

[0087] Furthermore, the metal thin film of the reflector 5 can be disposed separately from the lower electrode layer 35. In this case, materials such as gold, platinum, silver, and aluminum can be used. The thickness of the metal thin film can be set to approximately 100-500 nm.

[0088] Next, as Figure 12B As shown, ribs 10, torsion bars 6a and 6b, and portions 13a and 13b are formed by patterning the thermal oxide film 32b and the support layer 31c of the SOI substrate 31. First, the resist material is patterned using photolithography. Then, using the patterned resist material as a mask, the thermal oxide film 32b and the support layer 31c of the SOI substrate 31 are dry etched using a RIE device.

[0089] Next, as Figure 12C As shown, the thermal oxide film 32b used in the dry etching based on the ICP (Inductively Coupled Plasma)-RIE device is removed at rib 10, torsion bars 6a, 6b, and locations 13a, 13b.

[0090] Materials used for metal thin films include, for example, gold, platinum, silver, and aluminum. The thickness of the metal thin film can be set to, for example, around 100 to 500 nm.

[0091] Next, as Figure 12D As shown, the support layer 31c of the SOI substrate 31 is etched using a RIE device until the thickness of the rib 10 and the thicknesses of the torsion bars 6a and 6b reach the specified values. Furthermore, the above manufacturing process illustrates the use of a dry etching method, but a wet etching method can also be used.

[0092] Through the above processes, the optical deflector 1 is obtained. Thus, the optical deflector 1 can be integrally formed using both semiconductor planar technology and MEMS technology, making manufacturing easy and enabling miniaturization, mass production, and improved yield. Furthermore, when assembling the optical deflector 1 into various devices, it can also be integrally formed as a whole using both semiconductor planar technology and MEMS technology, making it easy to assemble the optical deflector 1 into other devices.

[0093] According to the above-described implementation, in-plane distortion of the mirrors in the optical deflector can be reduced. Furthermore, a high-quality laser scanner equipped with mirrors that reduce in-plane distortion can be obtained.

[0094] Furthermore, this disclosure is not limited to the embodiments described above, and various modifications can be made within the scope of the spirit of this disclosure. For example, the shape, thickness, and other conditions of the optical deflector 1 are not limited to those exemplified in the above embodiments.

Claims

1. An optical deflector constructed using a substrate having a first layer and a second layer, wherein, The optical deflector includes: A reflector having a mirror plate formed using the first layer and a rib disposed on the back side of the mirror plate and formed using the second layer; An actuator, which is disposed separately from the reflector around the reflector; and A torsion bar, constructed using the second layer, connects the rib of the reflector to the actuator.

2. The optical deflector according to claim 1, wherein, The actuator has a piezoelectric element disposed on the surface of the first layer that is not opposite to the second layer.

3. The optical deflector according to claim 1, wherein, The substrate is a semiconductor substrate having an active layer, a support layer, and an insulating layer between the active layer and the support layer. The first layer is the active layer. The second layer is the support layer.

4. The optical deflector according to claim 1, wherein, The torsion bar has a first end connected to the rib and a second end connected to the actuator, and the torsion bar is rectangular in shape when viewed from above between the first end and the second end.

5. The optical deflector according to claim 1, wherein, The rib has a ring-shaped portion. The annular portion is configured such that its center is approximately aligned with the center of the mirror plate.

6. The optical deflector according to claim 5, wherein, The rib also has two first connecting portions, which are portions extending from the annular portion towards the outer side of the mirror plate when viewed from above, and extending in opposite directions to each other. The torsion bar has a first end connecting the two first connecting portions, a second end connected to the actuator, and a columnar portion connecting the first end and the second end.

7. The optical deflector according to claim 1, wherein, The torsion bar has a first end connected to the rib, a second end connected to the actuator, and a columnar portion connecting the first end and the second end. The second end has a base that contacts the actuator and a concave portion that is concave when viewed from above and is connected to the columnar portion.

8. The optical deflector according to claim 7, wherein, The concave portion has: two protruding portions, which are generally U-shaped when viewed from above, extending inwards towards the actuator; and a second connecting portion, which is generally rectangular when viewed from above, connecting the two protruding portions. The columnar portion is connected to the second connecting portion.

9. The optical deflector according to claim 8, wherein, The actuator has a notch at the position where it overlaps with the concave portion when viewed from above.

10. The optical deflector according to claim 5, wherein, The outer and inner contours of the annular portion are both elliptical when viewed from above. The major axis of the outer ellipse corresponding to the outer contour is the same as the minor axis of the inner ellipse corresponding to the inner contour, and the minor axis of the outer ellipse is the same as the major axis of the inner ellipse.

11. The optical deflector according to claim 10, wherein, The major axis of the outer ellipse is larger than the radius of the mirror plate but smaller than the diameter of the mirror plate.

12. A laser scanner, wherein, The laser scanner includes: The optical deflector as described in claim 1; A light source that directs laser light toward the light deflector; and The driving circuit controls the operation of the light deflector and the light source respectively.

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