Reflecting mirror

Abstract

A reflecting mirror according to the present disclosure comprises a base body having a first surface, which is a reflecting surface, and a second surface positioned opposite to the first surface. The base body has a plurality of recesses positioned on the second surface, and a plurality of ribs extending along the edges of the plurality of recesses. When a part of the outer peripheral part of the base body in a plan view viewed from a direction orthogonal to the second surface is defined as a first end part and the other part of the outer peripheral part of the base body is defined as a second end part, the thickness of the base body decreases from the first end part toward the second end part. The plurality of ribs include a plurality of first ribs and a second rib. The width of the second rib, which is the dimension thereof in the direction orthogonal to the extension direction thereof, is larger than the width of the first ribs. The second rib is positioned on the second end part.

Description

Mirror

[0001] This disclosure relates to a mirror.

[0002] Astronomical telescopes and the like are equipped with mirrors for reflecting light from an object. As an example of such a mirror, Patent Document 1 discloses a lightweight mirror having a front surface with a reflecting surface for reflecting light and a back surface having a core formed by performing a plurality of perforations and a support portion through which bolts and the like are inserted and supported.

[0003] In order to achieve weight reduction while maintaining appropriate strength, the back surface shape of the outer peripheral portion of the lightweight mirror described in Patent Document 1 is configured as a curved surface from the support points.

[0004] Japanese Unexamined Patent Application Publication No. 2004-163803

[0005] The mirror according to one aspect of the present disclosure includes a substrate having a first surface that is a reflecting surface and a second surface located opposite to the first surface. The substrate has a plurality of recesses located on the second surface and a plurality of ribs extending along the edges of the plurality of recesses. When a part of the outer peripheral portion of the substrate in a plan view seen from a direction orthogonal to the second surface is defined as a first end portion and another part of the outer peripheral portion of the substrate is defined as a second end portion, the thickness of the substrate decreases from the first end portion toward the second end portion. The plurality of ribs includes a plurality of first ribs and a second rib. The second rib has a width, which is a dimension in a direction orthogonal to the extending direction, larger than the width of the first rib. The second rib is located at the second end portion.

[0006] FIG. 1 is a diagram showing a simple configuration of an astronomical telescope including the mirror according to the embodiment. FIG. 2 is a plan view of the mirror according to the embodiment seen from the first surface side. FIG. 3 is a plan view of the mirror according to the embodiment seen from the second surface side. FIG. 4 is a cross-sectional view taken along line IV-IV shown in FIG. 3. FIG. 5 is an enlarged plan view of the mirror according to the embodiment seen from the second surface side.

[0007] The embodiments for implementing the reflecting mirror according to this disclosure (hereinafter referred to as "Embodiments") will be described in detail below with reference to the drawings. However, this disclosure is not limited by these embodiments. Furthermore, each embodiment can be combined as appropriate, provided that the processing content is not inconsistent. Also, the same parts are denoted by the same reference numerals in each of the following embodiments, and redundant descriptions are omitted.

[0008] Furthermore, in the embodiments described below, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not require strict adherence to "constant," "orthogonal," "perpendicular," or "parallel" conditions. In other words, each of the above expressions allows for deviations such as manufacturing accuracy or installation accuracy.

[0009] The lightweight mirror described in Patent Document 1 may warp due to thermal expansion or contraction when used in environments with large temperature changes. For example, when changing from a high-temperature environment to a low-temperature environment, axial force may be generated in bolts inserted into the support part, pulling it towards the back side. In this case, a localized force is applied around the support part, which may cause warping of the reflective surface. In particular, if the back surface has curvature, as in the lightweight mirror described in Patent Document 1, that is, if the thickness of the lightweight mirror is not uniform, the thinner parts have lower rigidity compared to the thicker parts, making the reflective surface more prone to warping. If warping occurs on the reflective surface, the reflection accuracy of the lightweight mirror may deteriorate.

[0010] This disclosure provides a lightweight reflecting mirror that is less prone to warping.

[0011] <Reflector Configuration> The configuration of the reflector 1 according to this embodiment will be described with reference to Figures 1 to 5. Figure 1 is a diagram showing a simplified configuration of an astronomical telescope equipped with the reflector 1 according to this embodiment. Figure 2 is a plan view of the reflector 1 according to this embodiment as seen from the first surface 3 side. Figure 3 is a plan view of the reflector 1 according to this embodiment as seen from the second surface 4 side. Figure 4 is a cross-sectional view taken along the line IV-IV shown in Figure 3. Figure 5 is an enlarged plan view of the reflector 1 according to this embodiment as seen from the second surface 4 side. Note that the arrows in Figure 1 indicate the direction of light propagation.

[0012] The reflector 1 receives light emitted from an object and reflects the light to the secondary mirror 10. One embodiment of the reflector 1 is, for example, an offset reflector. An offset reflector is a reflector used in an axially symmetric aspherical shape where the axis of the shape and the optical axis do not coincide. The advantage of using an offset reflector is that, in the capture of incident light, the incident light is not obscured by the secondary mirror 10.

[0013] In this disclosure, a reflecting mirror 1 used in an astronomical telescope is described, but the apparatus to which the reflecting mirror 1 according to the first embodiment is applied is not limited to astronomical telescopes. For example, the reflecting mirror 1 may be used in telescopes or antennas used for targets or applications other than celestial bodies. In this case, the reflecting mirror 1 may have an offset shape.

[0014] Furthermore, while Figure 1 shows an example of using the reflecting mirror 1 and the secondary mirror 10 in combination, the method is not limited to this, and the reflecting mirror 1 may also be used alone.

[0015] As shown in Figures 2 to 5, the reflecting mirror 1 according to this embodiment comprises a base body 2 made of ceramic. The base body 2 has a first surface 3 and a second surface 4 which is the back surface of the first surface 3. The first surface 3 is a curved surface (for example, a quadratic surface) reflective surface 3a. In this disclosure, the entire first surface 3 may be the reflective surface 3a.

[0016] The reflective surface 3a is formed, for example, by mirror-finishing the entire first surface 3 and then applying a light-reflecting coating to the mirror surface. The reflecting mirror 1 according to this embodiment can reflect light from the object being observed with this reflective surface 3a.

[0017] Although this disclosure describes the case where the reflective surface 3a is concave, the reflective surface 3a is not limited to a concave shape, and may be planar or convex. Furthermore, the reflective surface 3a may be spherical or aspherical.

[0018] The base body 2 has a first end portion 21 and a second end portion 22. As shown in Figure 3, in a plan view from a direction perpendicular to the second surface 4 (in this case, the negative Z-axis direction), the first end portion 21 is part of the outer periphery of the base body 2, and the second end portion 22 is the other part of the outer periphery of the base body 2.

[0019] Specifically, the second end portion 22 may be located opposite the first end portion 21, with the center of the second surface 4 in between. In the example shown in Figure 3, the first end portion 21 is located on the positive Y-axis side of the outer periphery of the base 2. The second end portion 22 is located on the negative Y-axis side of the outer periphery of the base 2.

[0020] As shown in Figure 4, the thickness of the base 2 decreases from the first end 21 to the second end 22. A reflecting mirror 1 with a base 2 of varying thickness in this way can be used as an offset reflecting mirror.

[0021] Note that Figure 4 shows an example where the thickness of the base 2 differs from the first end 21 to the second end 22, but the thickness of the base 2 is not limited to this. For example, the base 2 may have a region where the thickness of the base 2 does not change from the first end 21 to the second end 22.

[0022] As shown in Figures 3 and 4, the second surface 4 of the base body 2 may be provided with a plurality of recesses 6. Furthermore, the bottom surface 6a of the recesses 6 may be a curved surface that conforms to the shape of the reflective surface 3a. In this way, by making the thickness of the reflective surface 3a and the bottom surface 6a of the recesses 6 constant, the weight of the reflector 1 can be reduced.

[0023] Furthermore, the second surface 4 of the base body 2 is provided with a plurality of ribs 7 extending along the edge of the recess 6. The side surfaces 71 of these ribs 7 are provided substantially perpendicular to the second surface 4, as shown in Figure 4, but are not limited to this. As another example, the side surfaces 71 of the ribs 7 may be inclined with respect to the direction perpendicular to the second surface 4.

[0024] Furthermore, as shown in Figure 3, the multiple ribs 7 include multiple first ribs 7a and multiple second ribs 7b. At least one of the multiple first ribs 7a may be connected to the second rib 7b. In the example in Figure 3, four first ribs 7a are connected to the second rib 7b.

[0025] The width of each first rib 7a, in other words, the dimension in the direction perpendicular to the extension direction, may be constant along the extension direction. The width of the first rib 7a referred to here may be the width of the first rib 7a excluding the portion that intersects with other first ribs 7a or second ribs 7b.

[0026] The width of the second rib 7b, in other words, the dimension in the direction perpendicular to the extension direction, is greater than the width of the first rib 7a. Here, the extension direction of the second rib 7b is the direction along the shape of the second rib 7b in a plan view from the direction perpendicular to the second surface 4 (here, the negative Z-axis direction), in other words, the direction in which the second rib 7b extends. The width of the second rib 7b may also be the average dimension in the direction perpendicular to the extension direction of the second rib 7b. The width of the second rib 7b may also be the maximum dimension in the direction perpendicular to the extension direction of the second rib 7b.

[0027] As described above, by forming multiple recesses 6 in the base 2, the volume of the reflector 1 can be reduced, thereby making the reflector 1 lighter. Furthermore, by forming ribs 7 along the edges of the recesses 6, the strength of the reflector 1, which has been lightened by the recesses 6, can be ensured.

[0028] The second surface 4 of the base 2 may be provided with three or more support parts 8. The reflector 1 may be supported by the support parts 8 on a support body (not shown). For example, the support parts 8 may be provided with through holes (not shown) for inserting support members such as bolts. The reflector 1 may be supported on the support body via such support members.

[0029] As shown in Figure 3, the support portion 8 may be circular in shape when viewed in a plan view from a direction perpendicular to the second surface 4 (in this case, the negative Z-axis direction). Alternatively, the support portion 8 may be elliptical or polygonal in shape when viewed in a plan view from a direction perpendicular to the second surface 4.

[0030] As described above, the thickness of the reflector 1 decreases from the first end 21 to the second end 22, resulting in lower rigidity at the thinner second end 22. Therefore, when the reflector 1 is used in an environment with large temperature fluctuations, there is a risk of warping occurring on the reflective surface 3a due to thermal expansion or contraction.

[0031] Therefore, in the reflector 1 according to this embodiment, the second rib 7b, which is wider than the width of the first rib 7a, is located at the second end 22. This improves the rigidity of the thin second end 22, and even when the reflector 1 is used in an environment with large temperature changes, warping of the reflective surface 3a is less likely to occur. Furthermore, as described above, by forming a plurality of recesses 6 in the base 2, the reflector 1 can be made lighter. Thus, the reflector 1 according to the first embodiment is lightweight and less prone to warping.

[0032] As shown in Figure 3, in a plan view from a direction perpendicular to the second surface 4 (in this case, the negative Z-axis direction), the second rib 7b may extend along the outer circumference of the base body 2, including the second end portion 22. In this case, for example, the second end portion 22 may be located at the center of the second rib 7b in the direction of extension.

[0033] Furthermore, when the dimension in the extending direction is defined as the length, the length M1 of the second rib 7b may be greater than, for example, the width of the second rib 7b.

[0034] With this configuration, the rigidity of the outer periphery of the base 2, including the second end portion 22 which has a small thickness, can be improved, and warping of the reflective surface 3a, especially warping in the direction along the outer periphery including the second end portion 22, is less likely to occur.

[0035] As shown in Figure 3, the width W1 of the second rib 7b at the second end 22 may be greater than the width W2 of the second rib 7b at a position away from the second end 22. Here, the second rib 7b at the second end 22 is the central part in the extending direction of the second rib 7b, and the second rib 7b at a position away from the second end 22 may be the end of the second rib 7b.

[0036] Specifically, the width of the second rib 7b may increase from the end of the second rib 7b toward the center in the direction of extension of the second rib 7b. In other words, in a plan view from a direction perpendicular to the second surface 4 (here, the negative Z-axis direction), the second rib 7b may have a roughly crescent shape. The width of the second rib 7b may be greatest at the center in the direction of extension of the second rib 7b.

[0037] The second end portion 22 is thin in the base 2 and is prone to warping when the reflector 1 undergoes thermal contraction due to temperature changes. Therefore, by increasing the width of the second rib 7b at the second end portion 22, the rigidity of the second end portion 22 can be improved, making it less likely for the reflector 1 to warp.

[0038] Note that the shape of the second rib 7b is not limited to the example shown in Figure 3. For example, the second rib 7b may have a portion in its extending direction that is narrower than the first rib 7a. In this case, if the width of the second rib 7b is the average dimension in the direction perpendicular to the extending direction of the second rib 7b or the maximum dimension in the direction perpendicular to the extending direction of the second rib 7b, then the width of the second rib 7b is greater than the width of the first rib 7a.

[0039] As shown in Figure 5, the connection between the first rib 7a and the second rib 7b may have a curved shape in a plan view taken from a direction perpendicular to the second surface 4 (in this case, the negative Z-axis direction). Specifically, the corner 72 formed by the first rib 7a and the second rib 7b at the connection between the first rib 7a and the second rib 7b may have a curved shape in a plan view taken from a direction perpendicular to the second surface 4.

[0040] With this configuration, the concentration of stress at the connection point between the first rib 7a and the second rib 7b can be reduced, thereby improving the strength of the area near the connection point between the first rib 7a and the second rib 7b in the reflector 1.

[0041] As shown in FIG. 3, in a plan view seen from a direction orthogonal to the second surface 4, the direction from the first end portion 21 toward the second end portion 22 is defined as the first direction (here, the negative Y-axis direction). When there are three support portions 8, a virtual line passing through the center S of the support portions 8 and orthogonal to the first direction is defined as the first virtual line L1. When there are four or more support portions 8, it is set based on three points from which the center point can be calculated. Here, the center S of three or more support portions 8 means the center of the figure surrounded by the three or more support portions 8 in a plan view seen from the direction orthogonal to the second surface 4 (here, the negative Z-axis direction).

[0042] In this case, the second surface 4 has a first region R1 which is a region on the first end portion 21 side with respect to the first virtual line L1, and a second region R2 which is a region on the second end portion 22 side with respect to the first virtual line L1. The number N2 of the support portions 8 located in the second region R2 may be larger than the number N1 of the support portions 8 located in the first region R1. In the example of FIG. 3, since there is one support portion 8 located in the first region R1 and two support portions 8 located in the second region R2, the number N2 of the support portions 8 located in the second region R2 is larger than the number N1 of the support portions 8 located in the first region R1.

[0043] Generally, a portion with a small thickness in a member has lower rigidity than a portion with a large thickness and is likely to resonate in a low-frequency region with respect to vibrations from the outside. In the present embodiment, by arranging more support portions 8 in the second region R2 which is relatively thinner than the first region R1 which is relatively thicker in the base body 2, vibrations with a large amplitude in the low-frequency range can be reduced. As a result, there is a tendency to improve the environmental resistance of the mirror.

[0044] The support portion 8 may be located at the central portion in the extending direction of the first rib 7a. The central portion of the first rib 7a referred to here may be a portion other than the end portions of the first rib 7a. The end portion of the first rib 7a may be, for example, a portion intersecting with another first rib 7a or the second rib 7b. In the present embodiment, as shown in FIG. 3, the support portion 8 may be located in the middle in the extending direction of the first rib 7a.

[0045] If the support portion 8 is located at the end of the first rib 7a, that is, at a portion intersecting with another first rib 7a or the second rib 7b, when the mirror 1 thermally contracts due to a temperature change, the support portion 8 may be subjected to stress from three or more directions. On the other hand, by positioning the support portion 8 at the central portion in the extending direction of the first rib 7a, when the mirror 1 thermally expands or thermally contracts due to a temperature change, the directions in which the support portion 8 receives stress can be reduced to two directions. Therefore, the mirror 1 according to the first embodiment tends to be excellent in resistance to deformation. Further, as shown in FIG. 3, the extending direction of the first rib 7a where the support portion 8 is located may be a direction toward the center S of three or more support portions 8, respectively. Thereby, since the directions in which the support portions 8 receive stress are directions that cancel each other out, it tends to be excellent in resistance to deformation.

[0046] Incidentally, when the support portion 8 is located on the first rib 7a, the width of the first rib 7a described above may be the width of the first rib 7a other than the support portion 8.

[0047] As shown in FIG. 3, in a plan view seen from a direction orthogonal to the second surface 4 (here, the negative Z-axis direction), the diameter T1 of the support portion 8 may be larger than the width of the first rib 7a. Here, the diameter T1 of the support portion 8 means, for example, the maximum length of a line segment connecting two points on the contour of the support portion 8 in a plan view seen from a direction orthogonal to the second surface 4.

[0048] Thus, since the support portion 8 is thicker than the first rib 7a, the strength around the support portion 8 can be improved as compared with the case where the diameter of the support portion 8 is the same as the width of the first rib 7a. Further, since the first rib 7a can be made thinner, the mirror 1 can be lightened.

[0049] As shown in FIG. 3, in a plan view seen from a direction orthogonal to the second surface 4 (here, the negative Z-axis direction), the distance D1 between the center S of three or more support portions 8 and the center of gravity C of the mirror 1 may be smaller than the distance D2 between the center S and the support portion 8.

[0050] Here, the center of gravity C of the mirror 1 means the center of gravity (center of mass) of the mirror 1 itself. Note that the position of the center of gravity C is not limited to the position shown in FIG. 3.

[0051] Thus, because distance D1 is smaller than distance D2, the center S of the support portion 8 approaches the center of gravity C of the reflecting mirror 1. This reduces the rotational moment around the center S of the reflecting mirror 1 as the axis of rotation, making it less susceptible to vibrations during use. Therefore, the reflecting mirror 1 becomes structurally stable. Consequently, the reflecting mirror 1 according to the first embodiment can stably maintain high optical performance.

[0052] Furthermore, the support portion 8 in the thinner portion tends to be more susceptible to stress, making it highly likely that the reflector 1 will warp. Therefore, when arranging multiple support portions 8, compared to the case in Figure 3 where three support portions 8 are tentatively placed at the three intersections where the outer edge of the circular region R3 intersects with the first rib 7a where no support portion 8 is placed, the arrangement of the three support portions 8 in Figure 3 in this embodiment allows more of the support portions 8 to be placed in the thicker portion, thus tending to reduce the occurrence of warping of the reflector 1.

[0053] In a plan view from a direction perpendicular to the second surface 4 (in this case, the negative Z-axis direction), the centroid C of the reflecting mirror 1 may be located in a region surrounded by three or more support parts 8. In the example in Figure 3, the centroid C is located in a circular region R3 where the three support parts 8 are located on the circumference. Note that the region surrounded by three or more support parts 8 is not limited to the circular region R3, but may also be a polygonal region with each support part 8 as its vertex.

[0054] Thus, because the center of gravity C is located in a region surrounded by three or more support parts 8, the reflector 1 is structurally stable, and therefore the reflector 1 is less likely to deform even when used for a long period of time. Consequently, the reflector 1 according to the first embodiment has excellent reflection accuracy.

[0055] In this offset reflecting mirror, where the second surface 4 is supported on a plane, the difference in thickness between the first end 21 and the second end 22 of the reflecting mirror 1 increases as the optical axis of the telescope and the axis of symmetry with respect to the shape of the secondary mirror 10 move further apart. A larger difference in thickness results in a larger difference in the rigidity of the reflecting mirror 1, making it more susceptible to deformation due to thermal expansion or contraction when used in environments with large temperature changes. Therefore, the support portion 8 may be positioned according to the size of the offset angle. Specifically, when the offset angle is large, it is desirable to position the support portion 8 on the side of the first end 21, which has greater thickness.

[0056] Therefore, as shown in Figures 3 and 4, for example, the intersection point I between the reflected light axis (principal ray axis) of incident light perpendicular to the second surface 4 and the second surface 4 may be located in a region surrounded by three or more support parts 8. In other words, the three or more support parts 8 may be positioned such that the intersection point I is located in a region surrounded by three or more support parts 8. In the example of Figure 3, the intersection point I is located in a circular region R3 where the three support parts 8 are located on the circumference.

[0057] In this way, because the intersection point I is located in a region surrounded by three or more support parts 8, the reflecting mirror 1 is less likely to deform.

[0058] Furthermore, this technology can also take the following configuration: (1) A reflector comprising a base having a first surface which is a reflective surface and a second surface located opposite to the first surface, wherein the base has a plurality of recesses located on the second surface and a plurality of ribs extending along the edges of the plurality of recesses, and when a part of the outer periphery of the base is defined as the first end and another part of the outer periphery of the base is defined as the second end, the thickness of the base decreases from the first end toward the second end, the plurality of ribs include a plurality of first ribs and a second rib, the width of the second rib, which is a dimension in the direction perpendicular to the extending direction, is greater than the width of the first rib, and the second rib is located at the second end. (2) The base has three or more support parts located on the second surface, and in a plan view taken from a direction perpendicular to the second surface, when the direction from the first end toward the second end is defined as the first direction, and a virtual line passing through the centers of the three or more support parts and perpendicular to the first direction is defined as the first virtual line, the second surface has a first region located on the first end side of the first virtual line and a second region located on the second end side of the first virtual line, and the number of support parts located in the second region is greater than the number of support parts located in the first region, the reflector according to (1). (3) In a plan view taken from a direction perpendicular to the second surface, the second rib extends along the outer circumference of the base including the second end, and when the dimension in the extension direction is defined as the length, the length of the second rib is greater than the width of the second rib, the reflector according to (1) or (2). (4) The reflector according to (3), wherein the width of the second rib at the second end is greater than the width of the second rib at a position away from the second end. (5) The reflector according to any one of (1) to (4), wherein at least one of the plurality of first ribs is connected to the second rib, and the connection between the first rib and the second rib has a curved shape in a plan view taken from a direction perpendicular to the second surface. (6) The reflector according to (2), wherein the support portion is located at the center in the extending direction of the first rib.(7) The reflector according to (2), wherein in a plan view taken from a direction perpendicular to the second surface, the diameter of the support portion is greater than the width of the first rib. (8) The reflector according to (2), wherein in a plan view taken from a direction perpendicular to the second surface, the distance between the centers of the three or more support portions and the center of gravity of the reflector is less than the distance between the center and the support portion. (9) The reflector according to (2), wherein in a plan view taken from a direction perpendicular to the second surface, the center of gravity of the reflector is located in the region surrounded by the three or more support portions.

[0059] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. Indeed, the embodiments described above can be embodied in a variety of forms. Furthermore, the embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.

[0060] 1 Reflector 2 Base 3 First surface 3a Reflecting surface 4 Second surface 6 Recess 7 Rib 7a First rib 7b Second rib 8 Support part 21 First end 22 Second end 71 Side surface 72 Corner R1 First region R2 Second region R3 Circular region

Claims

1. A reflecting mirror comprising a base having a first surface which is a reflective surface and a second surface located opposite the first surface, wherein the base has a plurality of recesses located on the second surface and a plurality of ribs extending along the edges of the plurality of recesses, and when a part of the outer periphery of the base is defined as a first end and another part of the outer periphery of the base is defined as a second end in a plan view taken from a direction perpendicular to the second surface, the thickness of the base decreases from the first end toward the second end, the plurality of ribs include a plurality of first ribs and a second rib, the width of the second rib, which is a dimension in a direction perpendicular to the extending direction, is greater than the width of the first rib, and the second rib is located at the second end.

2. The reflector according to claim 1, wherein the base has three or more support parts located on the second surface, and in a plan view taken from a direction perpendicular to the second surface, when the direction from the first end toward the second end is defined as the first direction, and a virtual line passing through the centers of the three or more support parts and perpendicular to the first direction is defined as the first virtual line, the second surface has a first region located on the first end side of the first virtual line and a second region located on the second end side of the first virtual line, and the number of support parts located in the second region is greater than the number of support parts located in the first region.

3. In a plan view taken from a direction perpendicular to the second surface, the second rib extends along the outer circumference of the base body including the second end, and when the dimension in the extending direction is defined as the length, the length of the second rib is greater than the width of the second rib, as described in claim 1 or 2.

4. The reflector according to claim 3, wherein the width of the second rib at the second end is greater than the width of the second rib at a position away from the second end.

5. The reflector according to any one of claims 1 to 4, wherein at least one of the plurality of first ribs is connected to the second rib, and the connection portion between the first rib and the second rib has a curved shape in a plan view taken from a direction perpendicular to the second surface.

6. The reflector according to claim 2, wherein the support portion is located at the center of the first rib in the extending direction.

7. The reflector according to claim 2, wherein, in a plan view taken from a direction perpendicular to the second surface, the diameter of the support portion is greater than the width of the first rib.

8. In a plan view taken from a direction perpendicular to the second surface, the distance between the centers of the three or more support parts and the centroid of the reflector is smaller than the distance between the center and the support parts, as described in claim 2.

9. The reflector according to claim 2, wherein, in a plan view taken from a direction perpendicular to the second surface, the center of gravity of the reflector is located in the region surrounded by the three or more support parts.

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