Optical deflectors, laser scanners

Abstract

To reduce in-plane distortion of mirrors in optical deflectors. [Solution] An optical deflector configured using a substrate having a first layer and a second layer, comprising: a mirror plate configured using the first layer; a mirror having ribs disposed on the back side of the mirror plate and configured using the second layer; an actuator spaced apart from the mirror and disposed around the mirror; and a torsion bar configured using the second layer and connecting the ribs of the mirror and the actuator.

Description

Technical Field

[0001] The present disclosure relates to an optical deflector and a laser scanner.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2016-170376 (Patent Document 1) describes an optical deflector including a mirror portion, a support portion, a pair of torsion bars that couple the mirror portion and the support portion on the rotation axis of the mirror portion, and ribs formed on the back surface of the mirror portion. In this optical deflector, each torsion bar has a pair of auxiliary portions extending from each torsion bar. The rib has a pair of rib extension portions extending from the outer edge of the mirror portion, and the pair of rib extension portions are formed to extend and join on the auxiliary portion. However, this optical deflector has room for improvement in that the in-plane distortion of the mirror is large.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One object of a specific aspect according to the present disclosure is to provide a technique capable of reducing the in-plane distortion of a mirror.

Means for Solving the Problems

[0005] [1] An optical deflector according to one aspect of the present disclosure is an optical deflector configured using a substrate having a first layer and a second layer, a mirror having a mirror plate configured using the first layer and ribs configured using the second layer and disposed on the back surface side of the mirror plate, an actuator disposed around the mirror and spaced apart from the mirror, It is constructed using the second layer, and includes a torsion bar connecting the rib of the mirror and the actuator, It is an optical deflector that includes [a specific component]. [2] A laser scanner in one aspect relating to this disclosure is: The optical deflector [1] and, A light source that directs laser light into the optical deflector, A drive circuit that controls the operation of the light deflector and the light source, It is a laser scanner that includes [a specific feature / feature].

[0006] The above configuration makes it possible to reduce the in-plane distortion of the mirror in the optical deflector. Furthermore, a high-quality laser scanner equipped with a mirror with reduced in-plane distortion can be obtained. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram showing the configuration of a laser scanner according to one embodiment. [Figure 2] Figure 2 is a perspective view showing the configuration of an optical deflector according to one embodiment. [Figure 3] Figure 3 is an enlarged perspective view of the main part of the optical deflector. [Figure 4] Figure 4A is an enlarged perspective view of the main part of the optical deflector, seen from the back side. Figure 4B is an enlarged view of the cross-section along line AA shown in Figure 4A. [Figure 5] Figure 5A is a diagram illustrating an example of the size of the mirror plate and ribs. Figure 5B is a diagram illustrating an example of the size of the connection between the torsion bar and the actuator. [Figure 6] Figure 6 shows the names of the various parts of the mirror plate and ribs. [Figure 7] Figure 7 shows the various parts of the torsion bar. [Figure 8] Figure 8A is a plan view illustrating the rib shape of the optical deflector in the first comparative example. Figure 8B is a cross-sectional view along line BB in Figure 8A. [Figure 9]Figure 9A is a plan view illustrating the rib shape of the optical deflector in the second comparative example. Figure 9B is a cross-sectional view along the CC line in Figure 9A. [Figure 10] Figure 10A is a plan view illustrating the rib shape of the optical deflector in a simplified form of this embodiment. Figure 10B is a cross-sectional view along line CC in Figure 10A. [Figure 11] Figures 11A to 11D show the manufacturing process of an optical deflector according to one embodiment. [Figure 12] Figures 12A to 12D show the manufacturing process of an optical deflector according to one embodiment. [Modes for carrying out the invention]

[0008] Figure 1 is a schematic diagram showing the configuration of a laser scanner according to one embodiment. The laser scanner of this embodiment includes an optical deflector 1, a light source 2, and a control circuit 3. Laser light emitted from the light source 2 is incident on the optical deflector 1. The optical deflector 1 freely changes the reflection direction of the laser light when it is reflected by a mirror that operates under the control of the control circuit 3. As a result, the laser light reflected by the optical deflector 1 can be scanned on the screen 4 to draw a desired image.

[0009] Figure 2 is a perspective view showing the configuration of an optical deflector in one embodiment. Figure 3 is an enlarged perspective view of the main part of the optical deflector. Figure 4A is an enlarged perspective view of the main part of the optical deflector viewed from the back side. The optical deflector 1 in this embodiment is composed of a mirror 5, torsion bars 6a and 6b, actuators 7a and 7b, an inner frame 8, and actuators 9a and 9b.

[0010] Mirror 5 reflects the incident laser light and is configured to be rotatable about each of the X-axis and Y-axis, which are two mutually perpendicular axes shown in FIG. 2. In the present embodiment, the mirror 5 is configured to have a substantially circular shape in plan view, but the plan view shape is not limited thereto. As shown in FIG. 4A, the mirror 5 includes a mirror plate 9 and ribs 10. The optical deflector 1 of the present embodiment is configured using a semiconductor substrate having an active layer, a support layer, and an insulating layer interposed therebetween. Specifically, the mirror plate 9 is configured using the active layer of a SOI (Silicon on Insulator) wafer, and the ribs 10 are configured using the support layer of the SOI wafer. As is well known to those skilled in the art, a SOI wafer is a semiconductor substrate having a configuration in which a SiO2 film (BOX layer), which is a thin insulating film, is interposed between a Si substrate (support layer) and a surface Si layer (active layer).

[0011] The rib 10 includes a circular portion (annular portion) 11 disposed on the back side of the mirror plate 9, and semi-elliptical portions (first connection portions) 12a and 12b each having a part extending and protruding to the outside of the mirror plate 9 (toward the actuators 7a and 7b). The rib 10 functions to suppress in-plane distortion of the mirror plate 9. Each of the semi-elliptical portions 12a and 12b functions to share the stress by the torsion bars 6a and 6b and relieve the stress applied to the mirror plate 9. The circular portion 11 and the semi-elliptical portions 12a and 12b are connected and integrally formed.

[0012] As shown in FIG. 3 and the like, one end side portion (first end portion) of the torsion bar 6a is connected to the rib 10 (specifically, the semi-elliptical portion 12a) of the mirror 5, and the other end side portion (second end portion) is connected to the actuator 7a. As shown in FIG. 4A, the torsion bar 6a includes a portion 13a, which is the other end side portion connected to the actuator 7a, and a columnar portion connecting between the first end portion and the second end portion.

[0013] Similarly, as shown in FIG. 4A and the like, one end portion (first end) of the torsion bar 6b is connected to the rib 10 (specifically, the semi-elliptical portion 12b) of the mirror 5, and the other end portion (second end) is connected to the actuator 7b. As shown in FIG. 4A, the torsion bar 6b includes a portion 13b which is the other end portion connected to the actuator 7b, and a columnar portion connecting between the first end and the second end.

[0014] The actuators 7a and 7b are arranged around the mirror 5 so as to annularly surround the mirror 5 in plan view as a whole. Each of the actuators 7a and 7b is connected to each of the torsion bars 6a and 6b on the back side. Each of the actuators 7a and 7b is configured by arranging a piezoelectric element using a piezoelectric material such as PZT (lead zirconate titanate) on a surface not facing the support layer of the active layer. By alternately applying voltages of opposite phases to each of the actuators 7a and 7b, the piezoelectric material can be deformed. When this deformation is transmitted to the mirror 5 via each of the torsion bars 6a and 6b, the mirror 5 can be rotated about the X axis.

[0015] The actuators 9a and 9b are arranged spaced apart from each other with the mirror 5 and the like interposed therebetween in the Y-axis direction. Each of the actuators 9a and 9b is connected to each of the actuators 7a and 7b via an inner frame 8 arranged around each of the actuators 7a and 7b. Each of the actuators 9a and 9b is configured by arranging a piezoelectric element using a piezoelectric material such as PZT on a surface not facing the support layer of the active layer. By alternately applying voltages to each of the actuators 9a and 9b, the piezoelectric material can be deformed. When this deformation is transmitted to the mirror 5 via the inner frame 8 and each of the torsion bars 6a and 6b, the mirror 5 can be rotated about the Y axis.

[0016] Figure 4B is an enlarged view of the cross-section along line AA shown in Figure 4A. As described above, the mirror plate 9 is constructed using the active layer of the SOI wafer, and the ribs 10 are constructed using the support layer of the SOI wafer. Note that because the thickness of the BOX layer is extremely thin compared to the active layer and the support layer, the BOX layer located between the active layer and the support layer is omitted from the illustration in Figure 4B. As shown in the illustration, the ribs 10 are positioned to support the back side of the mirror plate 9. As an example of size, the thickness T1 of the mirror plate 9 can be 42.5 μm, the thickness T2 of the ribs 10 can be 130 μm, and the width d0 of the ribs 10 in plan view (width in the cross-section along line AA) can be 50 μm.

[0017] Figure 5A is a diagram illustrating an example of the sizes of the mirror plate and ribs. Figure 5A shows a plan view of the mirror plate 9 and rib 10 as seen from the back side. Figure 5B is a diagram illustrating an example of the sizes of the connection part between the torsion bar and the actuator. Figure 5B shows a plan view of the torsion bar, etc., as seen from the back side. Figure 6 is a diagram showing the names of each part of the mirror plate and ribs. Figure 7 is a diagram showing the parts of the torsion bar.

[0018] As shown in Figures 5A and 6, the rib 10 has a circular portion 11, which is an annular portion provided in a vertically elongated, approximately elliptical shape in the figures. The circular portion 11 is positioned so that its center substantially coincides with the center of the mirror plate 9. The circular portion 11 has an opening cut out in the inside, which is a horizontally elongated, elliptical shape in the figures. The contour of this opening (the inner contour of the annular portion) will be referred to as the "inner ellipse" below. In addition, the outer edge of the circular portion 11 of the rib 10 in a plan view is a vertically elongated ellipse in the figures, and the contour of this part (the outer contour of the annular portion) will be referred to as the "outer ellipse" below.

[0019] As shown in Figure 6, the inner and outer ellipses each have a major axis and a minor axis. Furthermore, each of the semi-elliptical portions 12a and 12b has a planar shape that approximates an ellipse cut in half along its major axis. These semi-elliptical portions 12a and 12b also each have a major axis and a minor axis, as shown in Figure 6.

[0020] As shown in Figure 5A, the diameter of the mirror plate 9 can be 1120 μm as an example. In the rib 10, the major and minor axes of the outer ellipse can be 854 μm and 710 μm, respectively, as an example, and the major and minor axes of the inner ellipse can be 610 μm and 554 μm, respectively, as an example.

[0021] 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 150 μm. The distance between the two ends of the semi-elliptical portions 12a and 12b can be 246 μm.

[0022] In the figure, the width of a portion of the torsion bar 6a connected to the lower side of the semi-elliptical section 12a, specifically the portion extending horizontally (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 section 12b, specifically the portion extending horizontally (first end) 131g, can be set to 35 μm as an example. Furthermore, the semi-elliptical sections 12a and 12b can be extended to a position 45 μm away from the outer edge of the mirror plate 9, as an example.

[0023] The semi-elliptical sections 12a and 12b are annular in shape, consisting of a curved section that follows the shape of an ellipse and extends to a position where it does not overlap with the mirror plate 9, connecting with the circular section 11 at a position where it overlaps with the mirror plate 9 in a plan view, and a straight section extending in the direction of the major axis. In this embodiment, the semi-elliptical sections 12a and 12b are thicker from the connection point with the circular section 11 to the end position of the mirror plate 9, and thinner where they do not overlap with the mirror plate 9. The sections are thicker where they overlap with the mirror plate 9 to suppress distortion of the mirror plate 9. The sections are thinner where they do not overlap with the mirror plate 9 to relieve stress with flexible movement.

[0024] As shown in Figure 7, the portion of the torsion bar 6a connected to the actuator 7a (second end portion) 13a has a portion located on the inner ellipse side that extends laterally in a rod shape (second connecting portion) 131a, portions 131b and 131c connected to both sides of portion 131a, each having a roughly U-shape (roughly inverted U-shape) in plan view and extending inward from the actuator 7a (protruding portions), and portions 131d connected to each of the roughly U-shaped portions 131b and 131c and located on the outer ellipse side (base portion). Although not shown, portion 13b has a similar configuration. Portions 131a, 131b, and 131c together constitute a concave portion that is concave and annular in plan view.

[0025] As shown in Figure 5B, the width of part 131a can be set to 50 μm as an example. The radius of the circular outer edge of parts 131b and 131c can be set to 70 μm as an example. The width of part 131d can be set to 100 μm as an example. The width of the notch 140 (see Figure 7) can be set to 85 μm as an example. The notch 140 is the part of actuator 7a (7b) from which the part 131a, which is the bifurcated portion of the rod-shaped part 131e of part 13a (13b), and parts of each part 131b and 131c overlap in a plan view have been removed.

[0026] Next, the effects of the ribs 10 of the optical deflector 1 in this embodiment will be explained. Figure 8A is a plan view illustrating the rib shape of the optical deflector in the first comparative example. Figure 8B is a cross-sectional view along line BB in Figure 8A. Figure 9A is a plan view illustrating the rib shape of the optical deflector in the second comparative example. Figure 9B is a cross-sectional view along line CC in Figure 9A. Figure 10A is a plan view illustrating the rib shape of the optical deflector in a simplified form of this embodiment. Figure 10B is a cross-sectional view along line CC in Figure 10A. Each figure shows the parts relating to the mirror (mirror plate and ribs) and the torsion bar.

[0027] In the first comparative example, the mirror plate 1009 and torsion bars 1006a and 1006b are constructed using an active layer. As shown in Figures 8A and 8B, a circular rib 1010 is constructed in plan view using a support layer located below the active layer in the figures. The rib 1010 is provided only on the back side of the mirror plate 1009, and not on the back side of the torsion bars 1006a and 1006b.

[0028] Similar to the first comparative example, the second comparative example also uses an active layer to construct the mirror plate 2009 and the torsion bars 2006a and 2006b. In the second comparative example, as shown in Figures 9A and 9B, the rib 2010 and each of the ribs 2010a and 2010b are constructed using a support layer located below the active layer in the figures. Specifically, the rib 2010 is a circular portion in plan view provided on the back side of the mirror plate 2009, and each of the ribs 2010a and 2010b is a rectangular portion in plan view provided on the back side of each of the torsion bars 2006a and 2006b.

[0029] In this simplified embodiment, the mirror plate 9 is constructed using an active layer, but the torsion bars 6a and 6b are constructed using a support layer instead of an active layer. The ribs 10 are also constructed using a support layer, and each torsion bar 6a and 6b is connected to the ribs 10. The mirror plate 9 is not connected to the surrounding actuators and inner plate by an active layer, but is separated in an island-like manner. That is, the mirror plate 9 is supported by each torsion bar 6a and 6b and the ribs 10, which are made of support layers, and is indirectly connected to the surrounding actuators, etc. In this simplified embodiment, each torsion bar 6a and 6b, which connects the ribs 10 to the actuators 7a and 7b respectively, has a first end that connects to the rib 10 and a second end that connects to the actuators 7a and 7b, and is configured as an elongated rectangle in plan view between the first and second ends.

[0030] The dynamic surface deformation in the first comparative example, the second comparative example, and this embodiment (simplified form) described above was compared using RMS values. For this embodiment (simplified form), the size based on the numerical example described above was assumed, and simulations were performed assuming similar sizes for the first comparative example and the second comparative example. As a result, the RMS value for the structure of this embodiment (simplified form) was the lowest at 0.144λ, followed by the second comparative example at a low RMS value of 0.268λ, and the first comparative example at a high RMS value of 0.525λ. In other words, 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, which is thought to mitigate the effects of twisting of the torsion bars 6a and 6b, and as a result, the dynamic surface deformation, i.e., the in-plane strain of the mirror plate 9, is mitigated.

[0031] Next, the effects of the structure of the rib 10 in this embodiment will be explained with reference to Figure 6. As described above, in this embodiment, the rib 10, which is made of a support layer, is arranged on the back side of the mirror plate 9, which is made of an active layer. The rib 10 is provided in an annular shape with a relatively wide width in a plan view in the portion located near the center of the mirror plate 9, and is arranged to surround the center of the circular mirror plate 9 in a plan view. This makes it possible to suppress distortion of the edges of the mirror plate 9, thereby suppressing dynamic surface deformation. In addition, since the rib 10 and the mirror plate 9 are made 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 relaxed while maintaining the resonant frequency. As a result, the swing angle of the mirror plate 9 can be increased.

[0032] Here, the resonant frequency f can be expressed as f = (1 / 2π) × √(k / J). As can be seen from this relationship, the resonant frequency f depends on the moment of inertia J of the mirror 5 and the spring constant k of the torsion bar 6a, etc. The resonant frequency f decreases with increasing moment of inertia. 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., and increases with increasing width or thickness, while decreases with increasing length.

[0033] Furthermore, the rib 10 has a semi-elliptical portion 12a (12b) that connects to the torsion bar 6a (6b), which is split into two branches from the circular portion 11. As a result, when the deformation of the torsion bar 6a, etc. is transmitted to the mirror plate 9, one branch of the semi-elliptical portion 12a acts to push the mirror plate 9 upward from the back side, and the other branch acts to pull the mirror plate 9 from the back side, thus distributing the deformation transmitted from the torsion bar 6a, etc. to the mirror plate 9. This configuration can provide a solution to the problem of wanting to alleviate stress at the connection point between the mirror plate 9 and the rib 10.

[0034] Herein, more preferred embodiments of the rib 10 of this embodiment, which is arranged on the back surface of the mirror plate 9, are listed below. Note that one or more of the following embodiments can be adopted at will, and multiple embodiments can be adopted in any combination.

[0035] (1) The major axis of the outer ellipse and the minor axis of the inner ellipse coincide (are in the same direction). (2) The minor axis of the outer ellipse and the major axis of the inner ellipse coincide (are in the same direction). (3) The major axis of the outer ellipse coincides with (is in the same direction as) the Y-axis of the mirror plate. (4) The minor axis of the outer ellipse coincides with (is in the same direction as) the X-axis of the mirror plate. (5) The minor axis of the semi-ellipse coincides with (is in the same direction as) the major axis of the outer ellipse. (6) The longitudinal direction of the lateral portion of the torsion bar 6a, etc., is aligned with the minor axis of the semi-ellipse. (7) The major axis of the outer ellipse is greater than the radius of the mirror plate and less than the diameter. (8) The minor axis of the outer ellipse is greater than the radius of the mirror plate and less than the diameter. (9) The major axis of the inner ellipse is smaller than the minor axis of the outer ellipse. (10) The minor axis of the inner ellipse is smaller than the major axis of the outer ellipse. (11) The major axis of the semi-ellipse is greater than the minor axis of the semi-ellipse and smaller than the diameter of the mirror plate. (12) The minor axis of the semi-ellipse is set such that d1 > 10 μm. However, d1 is the distance between the lateral portion such as the torsion bar 6a and the outer edge of the mirror plate 9.

[0036] Next, the effects of the torsion bars 6a and 6b of the optical deflector 1 in this embodiment will be explained with reference to Figure 7. As described above, in this embodiment, the torsion bars 6a and 6b are also composed of an active layer and are continuously connected to the rib 10 on the back side of the mirror plate 9. In other words, the torsion bars 6a and 6b and the rib 10 are integrally constructed. The torsion bars 6a and 6b have portions 13a and 13b that are connected to the actuators 7a and 7b on the back side of the inner frame 8.

[0037] In part 13a, parts 131b and 131c, which are connected to both sides of part 131a and are roughly U-shaped (roughly inverted U-shaped), have their bottom ends protruding inward from the actuator 7a in a plan view. As shown in Figure 7, part 13a of the torsion bar 6a that is connected to the actuator 7a has a part (second connecting part) 131a located on the inner ellipse side and extending in a roughly rectangular shape horizontally in the figure in a plan view, parts (protruding parts) 131b and 131c connected by part 131a, and a part 131d (base part) connected to each of parts 131b and 131c. Part 131d is connected to the actuator 7a. Part 13b has a similar configuration.

[0038] With this configuration, when displacement from the actuator 7a is transmitted to the columnar portion 131e, which connects the first and second ends of the torsion bar 6a, etc., it becomes possible to distribute and transmit the displacement to the respective portions 131b and 131c, which are separated from the actuator 7a, etc. Therefore, it is possible to provide a solution to the problem of wanting to alleviate (reduce) the stress on the insulating film of SOI interposed between the respective portions 131b and 131c and the actuator 7a, etc.

[0039] Herein, more preferred embodiments of the torsion bar 6a and other parts 13 of this embodiment are listed below. Note that one or more of the following embodiments can be adopted at will, and multiple embodiments can be adopted in any combination.

[0040] (1) The width of each part 131b and 131c is greater than the width of the columnar part 131e of the torsion bar 6a. (2) The radius R1 of the inner curve of each section 131b and 131c is greater than four times the width of each section 131b and 131c. (3) The width d2 of part 131d is 20% to 40% of the width d4 of the support. (4) The maximum width d3 of part 13a is greater than 6 times the radius R1 of the inner curve.

[0041] Figures 11A to 11D and 12A to 12D show the manufacturing process of an optical deflector according to one embodiment. Here, a portion of the optical deflector 1 is schematically shown. Note that, due to the need to illustrate the oxide film of the SOI substrate, etc., the representation of the thickness of each layer differs from the schematic cross-sectional view of the optical deflector 1 described above.

[0042] As shown in Figure 11A, an SOI substrate 31 is prepared. The SOI substrate 31 has an active layer 31a, a support layer 31c, and an oxide film 31b interposed between them.

[0043] As shown in Figure 11B, the surface (active layer 31a side) and back surface (support layer 31c side) of the SOI substrate 31 are oxidized in 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, for example, 0.1 to 1 μm.

[0044] Next, as shown in Figure 11C, a lower electrode layer 33, a piezoelectric layer 34, and an upper electrode layer 35 are sequentially formed on the surface (active layer 31a side) of the SOI substrate 31. Specifically, a lower electrode layer 33 consisting of, for example, two layers of metal thin films is formed on the thermal silicon oxide film 32a. For the materials of the lower electrode layer 33, titanium can be used for the first layer (lower layer) of the metal thin film, and platinum can be used for the second layer (upper layer) of the metal thin film. The thickness of each metal thin film can be, for example, 30 to 100 nm for the first layer of titanium and 100 to 300 nm for the second layer of platinum. Next, a piezoelectric layer 34 consisting of, for example, one layer of piezoelectric film is formed on the lower electrode layer 33. For example, PZT, a piezoelectric material, can be used as the material for the piezoelectric layer 34. The thickness of the piezoelectric film can be, for example, 0.3 μm to 15 μm. Next, an upper electrode layer 35 consisting of, for example, one layer of metal thin film is formed on the piezoelectric layer 34. For the upper electrode layer 35, for example, platinum or gold may be used. The thickness of the upper electrode layer 35 should be, for example, about 10 to 200 nm.

[0045] Next, as shown in Figure 11D, the upper electrode layer 35 and the piezoelectric layer 34 are patterned to form the parts that will become piezoelectric elements such as the actuator 7a. Specifically, first, a resist material is patterned on the upper electrode layer 35 using photolithography technology. Next, using the patterned resist material as a mask, dry etching is performed on the upper electrode layer 35 and the piezoelectric layer 34 using an RIE (Reactive Ion Etching) apparatus.

[0046] Next, as shown in Figure 12A, the 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, the resist material is patterned using photolithography technology. Next, using the patterned resist material as a mask, the lower electrode layer 33, the thermal oxide film 32a, the active layer 31a of the SOI substrate 31, and the oxide film 31b are dry-etched using an RIE apparatus.

[0047] The metal thin film of mirror 5 may be provided separately from the lower electrode layer 35, and in that case, materials such as gold, platinum, silver, and aluminum can be used. The thickness of the metal thin film can be, for example, about 100 to 500 nm.

[0048] Next, as shown in Figure 12B, the ribs 10, torsion bars 6a, 6b, and parts 13a, 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 technology. Next, the patterned resist material is used as a mask to dry etch the thermal oxide film 32b and the support layer 31c of the SOI substrate 31 using a RIE apparatus.

[0049] Next, as shown in Figure 12C, the thermal oxide film 32b used for dry etching with an ICP (Inductively Coupled Plasma)-RIE apparatus is removed at the rib 10, torsion bars 6a and 6b, and areas 13a and 13b.

[0050] Materials that can be used for the thin metal film include, for example, gold, platinum, silver, and aluminum. The thickness of the thin metal film can be, for example, about 100 to 500 nm.

[0051] Next, as shown in Figure 12D, the support layer 31c of the SOI substrate 31 is etched using a RIE apparatus until the thickness of the ribs 10 and the thickness of the torsion bars 6a and 6b reach predetermined values. Although the above manufacturing process exemplifies the use of a dry etching method, a wet etching method can also be used.

[0052] Through the above process, the optical deflector 1 is obtained. In this way, the optical deflector 1 can be integrally formed using semiconductor planar processes and MEMS processes, making it easy to manufacture and enabling miniaturization, mass production, and improved yield. Furthermore, when incorporating the optical deflector 1 into various devices, it is also possible to integrally form the entire device using semiconductor planar processes and MEMS processes, making it easy to incorporate the optical deflector 1 into other devices.

[0053] According to the embodiments described above, the in-plane distortion of the mirror in the optical deflector can be reduced. Furthermore, a high-quality laser scanner equipped with a mirror with reduced in-plane distortion can be obtained.

[0054] This disclosure is not limited to the embodiments described above, and can be implemented in various ways within the scope of the gist 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.

[0055] This disclosure has the following features as an example: (Note 1) An optical deflector configured using a substrate having a first layer and a second layer, A mirror having a mirror plate made of the first layer and a rib disposed on the back side of the mirror plate and made of the second layer, An actuator is positioned around the mirror, spaced apart from the mirror, It is constructed using the second layer, and includes a torsion bar connecting the rib of the mirror and the actuator, A light deflector, including one. (Note 2) The actuator has a piezoelectric element disposed on a surface of the first layer that does not face the second layer. The optical deflector described in Appendix 1. (Note 3) The substrate is a semiconductor substrate having an active layer, a support layer, and an insulating layer interposed between the active layer and the support layer, The first layer is the active layer, The second layer is the support layer. The optical deflector described in Appendix 1 or 2. (Note 4) The torsion bar has a first end that connects to the rib and a second end that connects to the actuator, and is configured in a rectangular shape in plan view between the first end and the second end. An optical deflector as described in any of the appendices 1-3. (Note 5) The rib has an annular portion, The annular portion is positioned such that its center substantially coincides with the center of the mirror plate. An optical deflector as described in any of the appendices 1-4. (Note 6) The rib further has two first connecting portions that extend outward from the annular portion to the mirror plate in a plan view, and which extend in different directions from each other. The torsion bar has a first end connecting the two first connecting portions, a second end connecting to the actuator, and a columnar portion connecting the first end and the second end. The optical deflector described in Appendix 5. (Note 7) The torsion bar has a first end that connects to the rib, a second end that connects to the actuator, and a columnar portion that connects the first end and the second end. The second end has a base portion in contact with the actuator and a concave portion that is concave in plan view and connected to the columnar portion. An optical deflector as described in any of the appendices 1-6. (Note 8) The concave portion has a substantially U-shape in plan view and two protruding portions extending inward from the actuator, and a substantially rectangular second connecting portion connecting the two protruding portions in plan view. The columnar portion is connected to the second connecting portion. The optical deflector described in Appendix 7. (Note 9) The actuator has a notch that overlaps with the concave portion in a plan view. The optical deflector described in Appendix 8. (Note 10) The aforementioned annular portion has an elliptical outer and inner contour in plan view. The major axis of the outer ellipse corresponding to the outer contour coincides with the minor axis of the inner ellipse corresponding to the inner contour, and the minor axis of the outer ellipse coincides with the major axis of the inner ellipse. The optical deflector described in Appendix 5. (Note 11) The major axis of the outer ellipse is greater than the radius of the mirror plate and less than the diameter. The optical deflector described in Appendix 10. (Note 12) An optical deflector as described in any of the appendices 1 to 11, A light source that directs laser light into the optical deflector, A drive circuit that controls the operation of the light deflector and the light source, Laser scanners, including... [Explanation of Symbols]

[0056] 1: Light deflector, 2: Light source, 3: Drive circuit, 4: Screen, 5: Mirror, 6a, 6b: Torsion bar, 7a, 7b: Actuator, 8: Inner frame, 9a, 9b: Actuator, 11: Circular section, 12a, 12b: Semi-elliptical section

Claims

1. An optical deflector configured using a substrate having a first layer and a second layer, A mirror having a mirror plate made of the first layer and a rib disposed on the back side of the mirror plate and made of the second layer, An actuator is positioned around the mirror, spaced apart from the mirror, It is constructed using the second layer, and includes a torsion bar connecting the rib of the mirror and the actuator, A light deflector, including one.

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

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

4. The torsion bar has a first end that connects to the rib and a second end that connects to the actuator, and is configured in a rectangular shape in plan view between the first end and the second end. The optical deflector according to claim 1.

5. The rib has an annular portion, The annular portion is positioned such that its center substantially coincides with the center of the mirror plate. The optical deflector according to claim 1.

6. The rib further has two first connecting portions that extend outward from the annular portion to the mirror plate in a plan view, and which extend in different directions from each other. The torsion bar has a first end connecting the two first connecting portions, a second end connecting to the actuator, and a columnar portion connecting the first end and the second end. The optical deflector according to claim 5.

7. The torsion bar has a first end that connects to the rib, a second end that connects to the actuator, and a columnar portion that connects the first end and the second end. The second end portion has a base portion in contact with the actuator and a concave portion that is concave in plan view and connected to the columnar portion. The optical deflector according to claim 1.

8. The concave portion has a substantially U-shape in plan view and two protruding portions extending inward from the actuator, and a substantially rectangular second connecting portion connecting the two protruding portions in plan view. The columnar portion is connected to the second connecting portion. The optical deflector according to claim 7.

9. The actuator has a notch that overlaps with the concave portion in a plan view. The optical deflector according to claim 8.

10. The aforementioned annular portion has an elliptical outer and inner contour in plan view. The major axis of the outer ellipse corresponding to the outer contour coincides with the minor axis of the inner ellipse corresponding to the inner contour, and the minor axis of the outer ellipse coincides with the major axis of the inner ellipse. The optical deflector according to claim 5.

11. The major axis of the outer ellipse is greater than the radius of the mirror plate and less than the diameter. The optical deflector according to claim 10.

12. The optical deflector according to claim 1, A light source that directs laser light into the optical deflector, A drive circuit that controls the operation of the light deflector and the light source, Laser scanners, including...

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