Corner cube and method for manufacturing corner cube

Abstract

To provide a corner cube capable of improving productivity and reducing costs, and a method for manufacturing the same. [Solution] The corner cube 1 is a corner cube that reflects incident light in a direction parallel to and opposite to the incident direction, and has a flat first resin substrate 3A, a flat second resin substrate 5A connected at right angles to the first resin substrate 3A, and a flat third resin substrate 7A connected at right angles to each of the first resin substrate 3A and the second resin substrate 5A, and the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A are made of a resin material.

Description

[Technical field]

[0001] The present invention relates to a corner cube and a method for manufacturing the same. [Background technology]

[0002] Conventionally, corner cubes used in surveying instruments such as total stations have been known. For example, Patent Document 1 describes a corner cube reflector that has a triangular pyramid shape with one corner of a regular hexahedron as its apex. This corner cube reflector is manufactured by molding optical glass such as BK7 or transparent quartz glass. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-315561 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional corner cube reflectors require a very long processing time because they require precision machining of optical glass through grinding and polishing, resulting in low productivity and high costs.

[0005] An object of the present invention is to provide a corner cube that can improve productivity and reduce costs, and a method for manufacturing the same. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a corner cube that reflects incident light in a direction parallel to and opposite to the incident direction, comprising a flat first resin substrate, a flat second resin substrate connected perpendicularly to the first resin substrate, and a flat third resin substrate connected perpendicularly to each of the first resin substrate and the second resin substrate, wherein the first resin substrate, the second resin substrate, and the third resin substrate are made of a resin material.

[0007] The corner cube of the present invention is made of a resin material. Therefore, the base shape can be formed by resin molding, eliminating the need for precision machining such as grinding and polishing that is required when optical glass is used, and the time required for manufacturing can be significantly reduced. This improves productivity and reduces costs. Furthermore, the weight can be reduced.

[0008] In addition, in order to achieve the above-mentioned object, the present invention provides a method for manufacturing a corner cube that reflects incident light in a direction parallel to and opposite to the incident direction, comprising a first step of injecting molten resin material into a mold and forming, by injection molding or compression molding, a flat first resin substrate, a flat second resin substrate connected at right angles to the first resin substrate, and a flat third resin substrate connected at right angles to each of the first resin substrate and the second resin substrate.

[0009] According to the present invention, a molten resin material is injected into a mold, and a first resin substrate, a second resin substrate, and a third resin substrate are formed by injection molding or compression molding. This eliminates the need for precision machining by grinding and polishing as in the case of using optical glass, and can significantly reduce the time required for manufacturing. This can improve productivity and reduce costs. Furthermore, the weight can be reduced. Effect of the Invention

[0010] According to the present invention, it is possible to improve productivity and reduce costs. [Brief description of the drawings]

[0011] [Figure 1] 1 is a top view of a corner cube according to an embodiment, seen from the opposite side to the light entrance. FIG. [Diagram 2] 4 is a bottom view of the corner cube according to the embodiment, seen from the light entrance side. FIG. [Diagram 3] 3 is a side view of the corner cube according to the embodiment as viewed in the direction of arrow III in FIG. [Figure 4] 4 is a front view of the corner cube according to the embodiment as viewed in the direction of arrow IV in FIG. [Diagram 5] 1A and 1B are diagrams illustrating the incident direction and the reflected direction of light in a corner cube. [Figure 6] 6 is a cross-sectional view showing the layer structure of the corner cube along the cross-section line VI-VI in FIG. 1. [Figure 7] FIG. 7 is a diagram conceptually showing a layer structure in region VII of FIG. 6. [Figure 8] FIG. 7 is a diagram conceptually illustrating another example of the layer structure in region VII of FIG. 6. [Figure 9] 6 is a cross-sectional view showing the thickness of the corner cube in cross section along the line VI-VI in FIG. 1. FIG. [Figure 10] 1 is a flowchart showing a manufacturing procedure for a corner cube. [Figure 11] 4 is a top view showing the shape of a core of a mold for injecting a resin material. FIG. [Figure 12] 12 is a cross-sectional view showing a fitting structure formed by a protrusion of a core and a recess of a cavity, the cross-sectional view corresponding to the cross-sectional line XII-XII in FIG. 11. [Figure 13] FIG. 13 is a diagram showing the position of a gate through which a resin material is injected. [Figure 14] 1 is a cross-sectional view showing a state in which resin is injected between a core and a cavity of a mold. [Figure 15] FIG. 4 is a cross-sectional view showing a state in which the core is separated from the cavity. [Figure 16] 4 is a cross-sectional view showing the state in which the molded product has been released from the core by a stripper plate. FIG. [Figure 17]13 is a top view of a corner cube according to a modified example, seen from the opposite side to the light entrance. FIG. [Figure 18] 18 is a side view of a corner cube according to a modified example, as viewed in the direction of arrow XVIII in FIG. 17. [Figure 19] 18 is a front view of a corner cube according to a modified example, as viewed in the direction of arrow XIX in FIG. 17. [Figure 20] 13 is a cross-sectional view showing a state in which resin is injected between a core and a cavity of a mold according to a modified example. FIG. [Figure 21] FIG. 11 is a cross-sectional view showing a state in which a corner cube according to a modified example is attached to a holder. [Figure 22] 13 is a side view showing a state in which a gate boss of a corner cube according to a modified example is gripped and released from a mold. FIG. [Diagram 23] 13 is a top view showing a state in which a gate boss of a corner cube according to a modified example is gripped and released from the mold. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A corner cube according to the present embodiment is used in surveying instruments such as a total station, a theodolite, a transit, etc. The corner cube is also called a corner cube reflector, a corner cube prism, etc.

[0013] <External appearance of corner cube> An example of the external configuration of a corner cube according to an embodiment will be described with reference to Figures 1 to 5. Figure 1 is a top view of the corner cube according to the embodiment, seen from the side opposite to the light entrance, Figure 2 is a bottom view of the corner cube according to the embodiment, seen from the light entrance side, Figure 3 is a side view of the corner cube according to the embodiment, seen from the direction of arrow III in Figure 1, Figure 4 is a front view of the corner cube according to the embodiment, seen from the direction of arrow IV in Figure 1, and Figure 5 is an explanatory diagram for explaining the incident direction and reflection direction of light in the corner cube.

[0014] As shown in Figs. 1 to 5, the corner cube 1 has a first substrate 3 having a substantially isosceles right-angled triangular flat plate shape, a second substrate 5 having a substantially isosceles right-angled triangular flat plate shape, and a third substrate 7 having a substantially isosceles right-angled triangular flat plate shape. The corner cube 1 is formed into a substantially triangular pyramid shape by connecting the first substrate 3, the second substrate 5, and the third substrate 7 at right angles. In the example shown in Figs. 1 to 5, the corner cube 1 has a substantially equilateral triangular flat portion 9 formed at the apex of the triangular pyramid shape by removing the gate marks during resin molding. As a result, the outer surfaces 3o, 5o, and 7o of the first substrate 3, the second substrate 5, and the third substrate 7 are each formed into an isosceles trapezoid shape. The outer surfaces 3o, 5o, and 7o are not formed with ribs or grooves, and are formed as surfaces without irregularities except for inclined portions 25 and 27 described later.

[0015] Although not shown in the drawings, the apex of the corner cube 1 may be formed into a triangular pyramid shape with a pointed apex without forming the flat portion 9. In this case, the outer faces 3o, 5o, and 7o of the first substrate 3, second substrate 5, and third substrate 7 are each formed into the shape of an isosceles right triangle.

[0016] Although details will be described later, the first substrate 3 is formed by forming a metal film on the surface of the first resin substrate 3A, the second substrate 5 is formed by forming a metal film on the surface of the second resin substrate 5A, and the third substrate 7 is formed by forming a metal film on the surface of the third resin substrate 7A. The first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A are made of a resin material. For example, COC (cycloolefin copolymer), COP (cycloolefin polymer), etc., which have excellent dimensional stability even under high temperature and high humidity environments, may be used as the resin material, or PC (polycarbonate), PMMA (polymethylmethacrylate), etc. may be used depending on the required accuracy. In addition, resin materials other than the above may be used.

[0017] As shown in FIG. 2, the corner cube 1 has an entrance 11 through which light is incident. The entrance 11 is an opening in the shape of an equilateral triangle surrounded by the ends 3e, 5e, and 7e of the first substrate 3, the second substrate 5, and the third substrate 7 on the opposite side to the flat portion 9. The first substrate 3, the second substrate 5, and the third substrate 7 each have an inner surface 3i, 5i, and 7i on the entrance 11 side, and an outer surface 3o, 5o, and 7i on the opposite side to the entrance 11. The inner surfaces 3i, 5i, and 7i are each flat surfaces (planes) and form a reflecting surface that reflects light. The inner surfaces 3i, 5i, and 7i are each formed in the shape of a right-angled isosceles triangle, and the angles formed by the three surfaces 3i, 5i, and 7i are each a right angle. That is, the inner surfaces 3i and 5i are connected at a right angle, the inner surfaces 3i and 7i are also connected at a right angle, and the inner surfaces 5i and 7i are also connected at a right angle.

[0018] Corner cube 1 reflects light incident from light entrance 11 in a direction parallel to and opposite to the direction of incidence by reflecting the light from any two or three of its inner faces, 3i, 5i, and 7i. In the example shown in Fig. 5, corner cube 1 reflects light 13 incident from light entrance 11 in a direction parallel to and opposite to the direction of incidence by reflecting the light from each of three faces, 7i, 5i, and 3i, in that order.

[0019] <Cross-sectional structure of each corner cube substrate> An example of the cross-sectional configuration of each substrate of the corner cube 1 according to the embodiment will be described with reference to Figs. 6 to 9. Fig. 6 is a cross-sectional view corresponding to the cross-sectional line VI-VI in Fig. 1 for illustrating the layer structure of the cross-section of the corner cube 1, Fig. 7 is a diagram conceptually illustrating the layer structure in the region VII in Fig. 6, Fig. 8 is a diagram conceptually illustrating another example of the layer structure in the region VII in Fig. 6, and Fig. 9 is a cross-sectional view corresponding to the cross-sectional line VI-VI in Fig. 1 for illustrating the plate thickness of the cross-section of the corner cube 1. Note that in Fig. 6, the plate thickness is shown as being constant in order to make the layer structure easier to understand. Also, in Fig. 9, the metal film is omitted in order to make the plate thickness easier to understand.

[0020] As shown in FIG. 6, the first resin substrate 3A of the first substrate 3 has an inner surface 3Ai on the side of the entrance 11 and an outer surface 3Ao on the opposite side to the entrance 11. A metal film 15 is formed on both the inner surface 3Ai and the outer surface 3Ao of the first resin substrate 3A. Similarly, the second resin substrate 5A of the second substrate 5 has an inner surface 5Ai on the side of the entrance 11 and an outer surface 5Ao on the opposite side to the entrance 11. A metal film 15 is formed on both the inner surface 5Ai and the outer surface 5Ao of the second resin substrate 5A. The metal film 15 formed on the inner surface and the metal film 15 formed on the outer surface have the same layer structure and approximately the same thickness. Although not shown in FIG. 6, the third resin substrate 7A of the third substrate 7 also has a layer structure similar to that of the first resin substrate 3A and the second resin substrate 5A.

[0021] As shown in FIG. 7, the metal film 15 has a metal reflection film 19 formed on the surface of the resin substrate 3A, 5A made of resin, and a protective film 21 formed on the surface of the metal reflection film 19. The metal reflection film 19 is formed by sputtering using a metal material with high reflectivity, such as aluminum, gold, silver, etc. In addition to the above metals, alloys with improved durability and secondary workability may also be used. Sputtering is also called a sputtering method. In sputtering, the metal material and the resin substrate 3A, 5A are placed in a container, the container is evacuated, and an inert gas (argon, etc.) is introduced. When a high voltage is applied between the resin substrate 3A, 5A and the metal material, the electrons and ions of argon move at high speed and collide with the metal material, causing a sputtering phenomenon, which causes particles of the metal material to be repelled and adhere to the surface of the resin substrate 3A, 5A. In this way, a thin film of the metal material is formed on the surface of the resin substrate 3A, 5A.

[0022] The protective film 21 is formed by deposition using, for example, a glass material. The protective film 21 enhances heat resistance and abrasion resistance. In the deposition, the glass material and the resin substrates 3A and 5A on which the metal reflective film 19 is formed are placed in a container, the container is evacuated, and the glass material is heated. The glass material evaporated (vaporized) by heating adheres to the surface of the metal reflective film 19 of the resin substrates 3A and 5A to form a protective film. Methods for heating the glass material include, for example, a resistance heating method, an electron beam method, a high-frequency induction method, and a laser method. The metal film 15 formed on the inner surfaces 3Ai, 5Ai, and 7Ai of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A constitute a reflective surface that reflects light.

[0023] As shown in FIG. 8, a dielectric multilayer film 23 may be formed on the metal reflective film 19 instead of the protective film 21. The dielectric multilayer film 23 is provided as an increased reflection film to achieve higher reflectance and required optical characteristics. The dielectric multilayer film 23 is formed by stacking two or more types of dielectric films with different refractive indices, and can obtain any optical characteristics by the interference of light. For example, it is possible to change optical characteristics such as the wavelength of the reflected light, reflectance, and incidence angle dependency. The dielectric multilayer film 23 is customized according to the functions required for a product such as a surveying instrument in which the corner cube 1 is mounted. The dielectric multilayer film 23 is formed by sputtering or deposition.

[0024] As shown in FIG. 9, the outer surface 3Ao of the first resin substrate 3 has inclined portions 25 and 27 inclined with respect to the inner surface 3Ai. In the example shown in FIG. 9, two inclinations are provided: an inclined portion 25 with a relatively small inclination with respect to the inner surface 3Ai, and an inclined portion 27 with a relatively large inclination with respect to the inner surface 3Ai. Similarly, the outer surface 5Ao of the second resin substrate 5A has inclined portions 25 and 27 inclined with respect to the inner surface 5Ai. As in the above, the inclined portion 25 has a relatively small inclination with respect to the inner surface 5Ai, and the inclined portion 27 has a relatively large inclination with respect to the inner surface 5Ai. The inclination may be one step or three or more steps. The inclination is not limited to a linear inclination, and may be a curved inclination.

[0025] As a result, the thickness T1 of each of the first resin substrate 3A and the second resin substrate 5A near the entrance 11 is thinner than the thickness T2 (the thickness near the flat portion 9) near the apex of the triangular pyramid shape of the corner cube 1. For comparison, a shape without an inclined portion (a shape with a constant thickness) is illustrated by a dashed line in FIG. 9. Although not illustrated in FIG. 9, the third resin substrate 7A is also formed to have the same thickness as the first resin substrate 3A and the second resin substrate 5A. Although not illustrated in FIG. 9, the metal film 15 shown in FIG. 6 to FIG. 8 is formed on both the inner and outer surfaces of each of the resin substrates 3A, 5A, 7A formed to have the above thickness. The inclined portions 25, 27 of each of the resin substrates 3A, 5A, 7A are realized by the shape of a mold into which the resin material is injected. The inclination of the inclined portions 25, 27, ie, the plate thicknesses of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A, are set to appropriate values ​​according to the pressure distribution when the resin material is injected into the mold.

[0026] <Manufacturing method of corner cubes> An example of a method for manufacturing a corner cube 1 according to an embodiment will be described with reference to Figures 10 to 16. Figure 10 is a flow chart showing the manufacturing procedure for the corner cube 1, Figure 11 is a top view showing the shape of the core of a mold into which a resin material is injected, Figure 12 is a cross-sectional view showing the fitting structure of the protrusion of the core and the recess of the cavity, corresponding to the cross-sectional line XII-XII in Figure 11, Figure 13 is a diagram showing the position of the gate through which the resin material is injected, Figure 14 is a cross-sectional view showing the state in which resin is injected between the core and the cavity of the mold, Figure 15 is a cross-sectional view showing the state in which the core is separated from the cavity, and Figure 16 is a cross-sectional view showing the state in which the resin molded product is released from the core by a stripper plate.

[0027] 10, in step S10, a molten resin material is injected into a mold, and a flat first resin substrate 3A, a flat second resin substrate 5A connected at right angles to the first resin substrate 3A, and a flat third resin substrate 7A connected at right angles to each of the first resin substrate 3A and the second resin substrate 5A are formed by injection molding or compression molding. Step S10 is an example of the first step.

[0028] In step S20, a metal reflective film 19 and a protective film 21 are formed on both the inner surfaces 3Ai, 5Ai, 7Ai and the outer surfaces 3Ao, 5Ao, 7Ao of each of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A formed in step S10. Step S20 is an example of the second step.

[0029] 11 shows the shape of the core 31 of the mold 29 into which the resin material is injected in step S10. As shown in FIG. 11, the core 31 is, for example, substantially rectangular, and a triangular pyramid-shaped protrusion 33 is provided at the center thereof for forming the inner surfaces 3Ai, 5Ai, and 7Ai of the resin substrates 3A, 5A, and 7A that become the reflective surfaces of the corner cube 1. The surface of the protrusion 33 is fabricated by ultra-fine machining using, for example, a very small end mill. The surface of the protrusion 33 is fabricated so that, for example, the flatness is 1 μm or less and the surface roughness Ra is 0.05 μm or less.

[0030] Moreover, convex portions 35 are provided at the four corners of the core 31. Meanwhile, as shown in Fig. 12, the cavity 37 of the mold 29 is provided with concave portions 39 at positions corresponding to the four convex portions 35 of the core 31. As shown in Fig. 12, the sides of the convex portions 35 and the concave portions 39 are tapered, and the convex portions 35 fit into the concave portions 39 via the tapers, so that the core 31 and the cavity 37 are positioned by spigot fitting. This makes it possible to evenly balance the thicknesses of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A.

[0031] Fig. 13 shows the position of gate 41 provided in cavity 37 of mold 29. As shown in Fig. 13, gate 41 is located near the apex (approximately the center of flat portion 9) of triangular pyramid-shaped resin molded product 1A made up of first resin substrate 3A, second resin substrate 5A, and third resin substrate 7A. That is, in step S10, resin material is injected into mold 29 from gate 41 located near the apex (approximately the center of flat portion 9) of the triangular pyramid shape of corner cube 1.

[0032] 14 to 16 show the cross-sectional structure of the mold 29 when resin molding (injection molding in this example) is performed in step S10. First, as shown in Fig. 14, molten resin material is injected from a gate 41 into the space between the core 31 and the cavity 37 of the mold 29. At this time, a stripper plate 43 is provided on the core 31. The stripper plate 43 is formed in the shape of an equilateral triangle frame, and supports the lower end (edge ​​of the entrance 11) of the triangular pyramid-shaped resin molded product 1A made up of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A.

[0033] The cavity 37 is shaped so that the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A have the aforementioned inclined portions 25, 27. That is, in the above step S10, a resin material is injected into a mold 29 shaped so that the inclined portions 25, 27 inclined with respect to the inner surfaces 3Ai, 5Ai, 7Ai are formed on the outer surfaces 3Ao, 5Ao, 7Ao of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A, respectively, so that the plate thickness T1 in the vicinity of the entrance 11 is thinner than the plate thickness T2 in the vicinity of the apex (in the vicinity of the flat portion 9) of the triangular pyramid shape.

[0034] Next, as shown in Fig. 15, the core 31 is separated from the cavity 37 together with the stripper plate 43. As a result, the resin molded product 1A consisting of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A is released from the cavity 37. Note that gate marks in the resin molded product 1A are omitted from illustration in Figs. 15 and 16.

[0035] 16, the stripper plate 43 is protruded from the core 31, whereby the stripper plate 43 lifts the lower end (the edge of the entrance port 11) of the resin molded product 1A, thereby releasing the resin molded product 1A from the core 31. By using the stripper plate 43 in this manner, the resin molded product 1A can be released from the mold without affecting the surface accuracy of the reflective surface, as compared to the case where the resin molded product 1A is released from the mold using, for example, an ejector pin.

[0036] <Effects of the embodiment> As described above, the corner cube 1 according to this embodiment is made of a resin material. Since the base shape of the corner cube 1 can be formed by resin molding, precision machining such as grinding and polishing, which is required when optical glass is used, is not required, and the time required for manufacturing can be significantly reduced. This improves productivity and reduces costs.

[0037] Moreover, a metal film 15 is formed on the inner surfaces 3Ai, 5Ai, and 7Ai of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A constituting the corner cube 1, forming a reflective surface that reflects light. In this case, if the metal film 15 is formed only on the inner surfaces, the reflective surface may be slightly deformed in response to temperature changes due to the difference in thermal expansion coefficient between the resin substrates 3A, 5A, and 7A and the metal film 15. In the corner cube 1 according to the embodiment, the metal film 15 is formed on both the inner surfaces 3Ai, 5Ai, and 7Ai and the outer surfaces 3Ao, 5Ao, and 7Ao in the same manner, so that the force generated by the difference in thermal expansion coefficient can be balanced between the inside and outside of the resin substrates 3A, 5A, and 7A. In addition, since the metal film 15 is formed on both sides, the strength of the resin substrates 3A, 5A, and 7A can be improved. This prevents minute deformation and improves the flatness of the reflective surface.

[0038] Particularly in this embodiment, a molten resin material is injected into a mold 29, and a resin molded product 1A made of a first resin substrate 3A, a second resin substrate 5A, and a third resin substrate 7A, which form the base shape of the corner cube 1, is formed by injection molding or compression molding. In this case, when the resin material is injected from a gate 41 located near the apex of the triangular pyramid shape formed by the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A for injection molding, the pressure is high near the gate 41 and low near the end on the entrance 11 side. Due to such pressure distribution, a sink mark (a depression on the surface due to volumetric shrinkage) may occur near the end on the entrance 11 side. In the corner cube 1 according to this embodiment, the outer surfaces 3Ao, 5Ao, 7Ao of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A are each provided with inclined portions 25, 27 inclined with respect to the inner surfaces 3Ai, 5Ai, 7Ai, so that the thickness T1 near the end on the entrance 11 side is thinner than the thickness T2 near the gate 41. This makes it possible to suppress the effect of a pressure drop near the end on the entrance 11 side and to suppress deformation due to sink marks. This improves the flatness of the reflecting surface.

[0039] According to the method for manufacturing the corner cube 1 of this embodiment, in step S10, molten resin material is injected into the mold 29, and the resin molded product 1A consisting of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A is formed by injection molding or compression molding. This eliminates the need for precision machining such as grinding and polishing, as is required when optical glass is used, and significantly shortens the time required for manufacturing. This improves productivity and reduces costs.

[0040] Particularly in this embodiment, gate 41 for injecting resin material provided in cavity 37 of mold 29 is located at the center of corner cube 1 (resin molded product 1A). This makes it possible to equalize the pressure of the resin material at the position farthest from gate 41 in mold 29 (end on the entrance port 11 side), improving the balance of pressure distribution in first resin substrate 3A, second resin substrate 5A, and third resin substrate 7A. Therefore, first resin substrate 3A, second resin substrate 5A, and third resin substrate 7A can be molded with uniform accuracy.

[0041] Furthermore, according to the manufacturing method of this embodiment, in step S20, the metal film 15 is formed on both the inner surfaces 3Ai, 5Ai, 7Ai and the outer surfaces 3Ao, 5Ao, 7Ao of each of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A. This allows the force generated by the difference in thermal expansion coefficient to be balanced between the inside and outside of the resin substrates 3A, 5A, 7A. In addition, since the metal film 15 is formed on both sides, the strength of the resin substrates 3A, 5A, 7A can be improved. This prevents minute deformation and improves the flatness of the reflecting surface.

[0042] According to the manufacturing method of this embodiment, in step S10, a resin material is injected into a mold 29 having a shape in which inclined portions 25, 27 inclined with respect to the inner surfaces 3Ai, 5Ai, 7Ai are formed on the outer surfaces 3Ao, 5Ao, 7Ao of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A, respectively, so that the plate thickness T1 near the end on the entrance 11 side is thinner than the plate thickness T2 near the gate 41. This makes it possible to suppress the influence of a pressure drop near the end on the entrance 11 side, and to suppress deformation due to sink marks. Therefore, the flatness of the reflecting surface can be improved.

[0043] <Modification> The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit and technical concept of the present invention.

[0044] For example, the corner cube 1 may be provided with a cylindrical boss extending from near the apex of the triangular pyramid shape in a direction perpendicular to the entrance 11. The details of this modification will be described with reference to Figs. 17 to 23. Fig. 17 is a top view of the corner cube according to the modification seen from the opposite side to the entrance of light, Fig. 18 is a side view of the corner cube according to the modification seen from the direction of the arrow XVIII in Fig. 17, Fig. 19 is a front view of the corner cube according to the modification seen from the direction of the arrow XIX in Fig. 17, Fig. 20 is a cross-sectional view showing a state in which resin is injected between the core and the cavity of the mold according to the modification, Fig. 21 is a cross-sectional view showing a state in which the corner cube according to the modification is attached to a holder, Fig. 22 is a side view showing a state in which the gate boss of the corner cube according to the modification is gripped and released from the mold, and Fig. 23 is a top view showing a state in which the gate boss of the corner cube according to the modification is gripped and released from the mold. In Figs. 17 to 23, the same reference numerals are used for the same configurations as those in the above-mentioned embodiment, and the description will be omitted as appropriate.

[0045] As shown in FIGS. 17 to 19, the corner cube 1 has a first substrate 3, a second substrate 5, and a third substrate 7, similar to the previously described embodiment. The corner cube 1 of this modification has a cylindrical boss 45 that extends from near the apex of the triangular pyramid shape (substantially the center of the flat portion 9) in a direction perpendicular to the entrance 11. The boss 45 is integrally formed by resin molding together with the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A. In other words, the boss 45 is made of the same resin material as the resin substrates 3A, 5A, and 7A. Note that no metal film 15 is formed on the surface of the boss 45. The configuration of the corner cube 1 other than the above is the same as that of the previously described embodiment.

[0046] As shown in FIG. 20, the cavity 37 of the mold 29 is shaped to form a boss 45 together with the resin molded product 1A consisting of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A. The gate 41 is connected to the tip of the hollow portion for the boss 45, and the molten resin material is injected from the gate 41. That is, in this modification, in step S10 of FIG. 10, the resin material is injected into the mold 29 shaped to form a cylindrical boss 45 extending from the vicinity of the apex (approximately the center of the flat portion 9) of the triangular pyramid shape formed by the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A in a direction perpendicular to the entrance 11. The configuration of the mold 29 other than the above is the same as that of the above embodiment.

[0047] As shown in FIG. 21, the corner cube 1 of this modification is attached to a columnar holder 47 when it is mounted on a surveying instrument such as a total station, a theodolite, or a transit. The holder 47 is provided with an insertion hole 49 into which the boss 45 can be fitted at the mounting position of the corner cube 1. The corner cube 1 is fixed to the holder 47 by fitting the boss 45 into the insertion hole 49. The corner cube 1 is positioned with high accuracy by fitting the boss 45 into the insertion hole 49 and by the flat portion 9 abutting against the side surface of the holder 47. The holder 47 may be cylindrical or polygonal columnar. The shape and size of the holder 47 are determined according to the size and number of the corner cubes 1.

[0048] 22 and 23, the corner cube 1 or resin molded product 1A of this modification can be lifted by gripping the boss 45 with a jig 51. The jig 51 may be, for example, a robot hand provided in an automatic machine such as a robot, or a tool held by a user. For example, in step S10 of FIG. 10, the resin molded product 1A including the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A may be removed from the mold 29 by gripping the boss 45.

[0049] As described above, corner cube 1 of this modified example has cylindrical boss 45 that extends from near the apex of the triangular pyramid shape (approximately the center of flat portion 9) in a direction perpendicular to entrance 11. By using boss 45 when attaching corner cube 1 to holder 47, positioning is facilitated and outer faces 3o, 5o, 7o of corner cube 1 can be fixed without contacting holder 47, preventing any effect on the flatness of the reflecting surface. Furthermore, when resin molded product 1A is removed from mold 29, boss 45 can be grasped for removal, making removal easy and allowing resin molded product 1A to be removed from mold 29 without affecting the precision of the reflecting surface.

[0050] In addition to the above, the methods according to the above-described embodiments and the methods according to the modifications may be used in appropriate combination.

[0051] Although not specifically illustrated, the present invention can be implemented with various modifications without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0052] 1 Corner Cube 1A Resin molded products 3 First board 3A 1st resin board 3Ai Inner surface 3Ao Outer surface 5 Second board 5A Second resin board 5Ai Inner surface 5Ao Outer surface 7 Third board 7A 3rd resin board 7Ai Inner surface 7Ao Outer surface 9 Flat area 11 Inlet 13 light 15 Metal Film 19 Metal reflective film 21 Protective film 23 Dielectric multilayer film 25 Slope 27 Slope 29 Molds 31 cores 37 Cavity Gate 41 43 Stripper plate 45 Boss T1 Plate thickness T2 plate thickness

Claims

1. A corner cube that reflects incident light in a direction parallel to and opposite to the incident direction, A first resin substrate having a flat plate shape; A flat second resin substrate connected at right angles to the first resin substrate; a third resin substrate having a flat plate shape connected at right angles to the first resin substrate and the second resin substrate, the first resin substrate, the second resin substrate, and the third resin substrate are made of a resin material; Each of the first resin substrate, the second resin substrate, and the third resin substrate is An inner surface on the light entrance side; an outer surface opposite the entrance, an inclined portion inclined with respect to the inner surface is formed on the outer surface so that a plate thickness in the vicinity of the entrance is thinner than a plate thickness in the vicinity of a vertex of a triangular pyramid shape formed by the first resin substrate, the second resin substrate, and the third resin substrate; Corner cube.

2. A corner cube that reflects incident light in a direction parallel to and opposite to the direction of incidence, A first resin substrate having a flat plate shape; A flat second resin substrate connected at right angles to the first resin substrate; a third resin substrate having a flat plate shape connected at right angles to the first resin substrate and the second resin substrate, the first resin substrate, the second resin substrate, and the third resin substrate are made of a resin material; a cylindrical boss extending from near a vertex of a triangular pyramid shape formed by the first resin substrate, the second resin substrate, and the third resin substrate in a direction perpendicular to the light entrance; Corner cube.

3. A method for manufacturing a corner cube that reflects incident light in a direction parallel to and opposite to the incident direction, comprising the steps of: a first step of injecting a molten resin material into a mold and forming, by injection molding or compression molding, a flat first resin substrate, a flat second resin substrate connected at right angles to the first resin substrate, and a flat third resin substrate connected at right angles to each of the first resin substrate and the second resin substrate; A method for manufacturing a corner cube.

4. In the first step, injecting the resin material into the mold from a gate located near a vertex of a triangular pyramid shape formed by the first resin substrate, the second resin substrate, and the third resin substrate; A method for manufacturing the corner cube according to claim 3.

5. The method further includes a second step of forming a metal film on both an inner surface on the light entrance side and an outer surface on the opposite side to the light entrance of each of the first resin substrate, the second resin substrate, and the third resin substrate formed in the first step. A method for manufacturing the corner cube according to claim 3.

6. In the first step, the resin material is injected into the mold having a shape in which an inclined portion is formed on the outer surface that is inclined with respect to the inner surface, such that the plate thickness in the vicinity of the incident port is thinner than the plate thickness in the vicinity of the apex of a triangular pyramid shape formed by the first resin substrate, the second resin substrate, and the third resin substrate, for each of the first resin substrate, the second resin substrate, and the third resin substrate, which have an inner surface on the light incident port side and an outer surface on the opposite side to the incident port; A method for manufacturing the corner cube according to claim 3.

7. In the first step, Injecting the resin material into the mold having a shape in which a cylindrical boss is formed, the cylindrical boss extending in a direction perpendicular to the light entrance from near a vertex of a triangular pyramid shape formed by the first resin substrate, the second resin substrate, and the third resin substrate; The method for manufacturing the corner cube according to claim 3 .

8. In the first step, a molded product including the first resin substrate, the second resin substrate, and the third resin substrate is removed from the mold by gripping the boss; The method for manufacturing the corner cube according to claim 7 .

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