Corner cube and method of manufacturing corner cube

Abstract

To provide a corner cube and its manufacturing method capable of improving productivity and reducing cost.SOLUTION: The corner cube 1 is a corner cube that reflects incident light in a direction parallel to and opposite to an incident direction, and includes a first resin-substrate 3A having a flat plate shape, a second resin-substrate 3A having a flat plate shape and connected to the first resin-substrate 5A at a right angle, and a third resin-substrate 3A having a flat plate shape and connected to each of the first resin-substrate 5A and the second resin-substrate 7A at a right angle, and the first resin-substrate 3A, the second resin-substrate 5A, and the third resin-substrate 7A are made of a resinous material.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] Corner cubes used in surveying instruments such as total stations have been known. For example, Patent Document 1 describes a corner cube reflector with 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 precision machining of optical glass by grinding and polishing, which requires a very long processing time, resulting in low productivity and high costs.

[0005] An object of the present invention is to provide a corner cube and a method for manufacturing the same that can improve productivity and reduce costs. [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 significantly shortening the time required for manufacturing. This results in improved productivity and reduced 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 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.

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

[0010] According to the present invention, productivity can be improved and costs can be reduced. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a top view of the corner cube according to the embodiment, seen from the opposite side to the light entrance. [Figure 2] FIG. 2 is a bottom view of the corner cube according to the embodiment, viewed from the light entrance side. [Figure 3] 3 is a side view of the corner cube according to the embodiment, as seen in the direction of arrow III in FIG. 1. FIG. [Figure 4] 4 is a front view of the corner cube according to the embodiment, as seen in the direction of arrow IV in FIG. 1. FIG. [Figure 5] 1A and 1B are explanatory diagrams illustrating the incident direction and reflection 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-sectional line VI-VI in FIG. 1. FIG. [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 corresponding to the cross-sectional line VI-VI in FIG. 1, showing the thickness of the corner cube cross section. [Figure 10] 1 is a flowchart showing a manufacturing procedure for a corner cube. [Figure 11] FIG. 2 is a top view showing the shape of a core of a mold into which a resin material is injected. [Figure 12] 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 FIG. 11. [Figure 13] FIG. 10 is a diagram showing the position of a gate through which a resin material is injected. [Figure 14] 10 is a cross-sectional view showing a state in which resin is injected between the core and the cavity of the mold. FIG. [Figure 15] FIG. 10 is a cross-sectional view showing a state in which the core is separated from the cavity. [Figure 16] FIG. 10 is a cross-sectional view showing the state in which the molded product has been released from the core by a stripper plate. [Figure 17]FIG. 10 is a top view of a corner cube according to a modified example, seen from the opposite side to the light entrance. [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. FIG. [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. FIG. [Figure 20] FIG. 10 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. [Figure 21] FIG. 10 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] 10 is a side view showing a corner cube according to a modified example being released by gripping a boss at a gate portion thereof. FIG. [Figure 23] 10 is a top view showing a corner cube according to a modified example being released by gripping the gate boss. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A corner cube according to this embodiment is used in surveying instruments such as total stations, theodolites, and transits. Corner cubes are also called corner cube reflectors or corner cube prisms.

[0013] <Corner cube exterior configuration> 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 an embodiment, seen from the side opposite to the light entrance, Figure 2 is a bottom view of the corner cube according to an embodiment, seen from the light entrance side, Figure 3 is a side view of the corner cube according to an embodiment, seen from the direction of arrow III in Figure 1, Figure 4 is a front view of the corner cube according to an 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, corner cube 1 includes a first substrate 3 having a substantially isosceles right-angled triangular shape, a second substrate 5 having a substantially isosceles right-angled triangular shape, and a third substrate 7 having a substantially isosceles right-angled triangular shape. Corner cube 1 is formed into a substantially triangular pyramid shape by connecting first substrate 3, second substrate 5, and third substrate 7 at right angles. In the example shown in FIGS. 1 to 5, corner cube 1 has a substantially equilateral triangular flat portion 9 at the apex of the triangular pyramid shape formed by removing gate marks left during resin molding. As a result, outer surfaces 3o, 5o, and 7o of first substrate 3, second substrate 5, and third substrate 7 are each formed into an isosceles trapezoid. The outer surfaces 3o, 5o, and 7o are free of ribs or grooves and are smooth except for inclined portions 25 and 27, which will be described later.

[0015] Although not shown, the corner cube 1 may be formed into a triangular pyramid shape with a pointed apex without forming the flat portion 9 at the apex. In this case, the outer surfaces 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] As will be described in detail later, the first substrate 3 is formed by depositing a metal film on the surface of a first resin substrate 3A, the second substrate 5 is formed by depositing a metal film on the surface of a second resin substrate 5A, and the third substrate 7 is formed by depositing a metal film on the surface of a third resin substrate 7A. The first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A are made of resin materials. Examples of resin materials that can be used include COC (cycloolefin copolymer) and COP (cycloolefin polymer), which have excellent dimensional stability even in high-temperature and high-humidity environments. Depending on the required precision, PC (polycarbonate) and PMMA (polymethyl methacrylate) may also be used. Resin materials other than those listed above may also 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 equilateral triangular opening surrounded by the ends 3e, 5e, and 7e of the first substrate 3, the second substrate 5, and the third substrate 7, opposite 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 from the entrance 11. The inner surfaces 3i, 5i, and 7i are each flat (planar) surfaces that form reflective surfaces that reflect 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 all right angles. That is, the inner surfaces 3i and 5i are connected at right angles, the inner surfaces 3i and 7i are also connected at right angles, and the inner surfaces 5i and 7i are also connected at right angles.

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

[0019] <Cross-sectional structure of each corner cube substrate> An example of the cross-sectional configuration of each substrate of a corner cube 1 according to an embodiment will be described with reference to Figures 6 to 9. Figure 6 is a cross-sectional view corresponding to the cross-sectional line VI-VI in Figure 1, illustrating the layer structure of the cross-section of the corner cube 1. Figure 7 is a conceptual diagram of the layer structure in region VII in Figure 6. Figure 8 is a conceptual diagram of another example of the layer structure in region VII in Figure 6. Figure 9 is a cross-sectional view corresponding to the cross-sectional line VI-VI in Figure 1, illustrating the plate thickness of the cross-section of the corner cube 1. Note that in Figure 6, the plate thickness is shown as constant to make the layer structure easier to understand. Also, in Figure 9, the metal film is omitted 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 incident aperture 11 and an outer surface 3Ao on the opposite side of the incident aperture 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 incident aperture 11 and an outer surface 5Ao on the opposite side of the incident aperture 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 includes a metal reflective film 19 formed on the surface of the resin substrate 3A, 5A and a protective film 21 formed on the surface of the metal reflective film 19. The metal reflective film 19 is formed by sputtering using a highly reflective metal material, such as aluminum, gold, or silver. In addition to the above metals, alloys with improved durability and secondary processability 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 (such as argon) is introduced. When a high voltage is applied between the resin substrate 3A, 5A and the metal material, argon electrons and ions move at high speed and collide with the metal material, causing a sputtering phenomenon, which repels particles of the metal material and adheres 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 vapor deposition using, for example, a glass material. The protective film 21 enhances heat resistance and abrasion resistance. In the vapor deposition process, the glass material and the resin substrates 3A and 5A on which the metal reflective film 19 has been 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, forming a protective film. Methods for heating the glass material include, for example, resistance heating, electron beam heating, high-frequency induction heating, and laser heating. The metal film 15 formed on the inner surfaces 3Ai, 5Ai, and 7Ai of the first resin substrate 3A, second resin substrate 5A, and 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 enhanced 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, allowing for desired optical characteristics to be obtained through 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 products such as surveying equipment in which the corner cube 1 is installed. The dielectric multilayer film 23 is formed by sputtering or vapor deposition.

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

[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, FIG. 9 illustrates a shape without an inclined portion (a shape with a constant thickness) with a dashed line. Although not shown in FIG. 9, the third resin substrate 7A is also formed to the same thickness as the first resin substrate 3A and the second resin substrate 5A. Although not shown in FIG. 9, the metal film 15 shown in FIGS. 6 to 8 is formed on both the inner and outer surfaces of each of the resin substrates 3A, 5A, and 7A formed to the above thickness. The inclined portions 25 and 27 of each of the resin substrates 3A, 5A, and 7A are realized by the shape of the mold into which the resin material is injected. The inclination of the inclined portions 25, 27, that is, the thickness of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A, is set to an appropriate value according to the pressure distribution when the resin material is injected into the mold.

[0026] <Corner cube manufacturing method> An example of a manufacturing method for a corner cube 1 according to an embodiment will be described with reference to Figures 10 to 16. Figure 10 is a flowchart 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 between the protrusion of the core and the recess of the cavity, taken along 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 where resin has been injected between the core and the cavity of the mold, Figure 15 is a cross-sectional view showing the state where the core has been separated from the cavity, and Figure 16 is a cross-sectional view showing the state where the resin-molded product has been released from the core by a stripper plate.

[0027] 10, in step S10, a molten resin material is poured into a mold, and a flat first resin substrate 3A, a flat second resin substrate 5A connected perpendicularly to the first resin substrate 3A, and a flat third resin substrate 7A connected perpendicularly 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, and 7Ai and the outer surfaces 3Ao, 5Ao, and 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 core 31 of mold 29 into which resin material is injected in step S10. As shown in FIG. 11, core 31 is, for example, substantially rectangular, and has a triangular pyramid-shaped protrusion 33 at its center for forming the inner surfaces 3Ai, 5Ai, and 7Ai of resin substrates 3A, 5A, and 7A, which serve as the reflective surfaces of corner cube 1. The surface of protrusion 33 is fabricated by ultra-fine machining using, for example, a very small end mill. The surface of 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] Furthermore, convex portions 35 are provided at the four corners of the core 31. Meanwhile, as shown in Fig. 12, concave portions 39 are provided in the cavity 37 of the mold 29 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 tapered portions, thereby positioning the core 31 and the cavity 37 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] 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 pyramidal 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 pyramidal shape of corner cube 1.

[0032] 14 to 16 show the cross-sectional structure of the mold 29 during resin molding (injection molding in this example) in step S10. First, as shown in Fig. 14, molten resin material is injected from a gate 41 into the space between a core 31 and a 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 port 11) of the triangular pyramidal resin molded product 1A made up of a first resin substrate 3A, a second resin substrate 5A, and a third resin substrate 7A.

[0033] The cavity 37 has a shape in which 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 having a shape in which 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 each of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A, respectively, are formed 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 (near the flat portion 9) of the triangular pyramid shape.

[0034] Next, as shown in Fig. 15, the core 31 is moved away from the cavity 37 together with the stripper plate 43. As a result, the resin molded product 1A made up 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 on the resin molded product 1A are not shown 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 (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 way, the resin molded product 1A can be released from the mold without affecting the surface precision of the reflective surface, as compared to when releasing the resin molded product 1A using an ejector pin, for example.

[0036] <Effects of the embodiment> As described above, the corner cube 1 according to this embodiment is made of a resin material. Because 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] Furthermore, metal films 15 are deposited on the inner surfaces 3Ai, 5Ai, and 7Ai of the first, second, and third resin substrates 3A, 5A, and 7A, respectively, forming reflective surfaces that reflect light. If the metal film 15 were deposited only on the inner surfaces, the reflective surfaces may deform slightly in response to temperature changes due to the difference in thermal expansion coefficients between the resin substrates 3A, 5A, and 7A and the metal film 15. In the corner cube 1 according to this embodiment, the metal film 15 is deposited on both the inner surfaces 3Ai, 5Ai, and 7Ai and the outer surfaces 3Ao, 5Ao, and 7Ao. This balances the forces generated by the difference in thermal expansion coefficients between the inside and outside of the resin substrates 3A, 5A, and 7A. Additionally, the formation of the metal film 15 on both surfaces improves the strength of the resin substrates 3A, 5A, and 7A. This prevents minute deformation and improves the flatness of the reflective surfaces.

[0038] In this embodiment, particularly, a molten resin material is injected into a mold 29, and a resin molded product 1A is formed by injection molding or compression molding. The resin material is injected through 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. When injection molding is performed by injecting the resin material through 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, the pressure is high near the gate 41 and low near the edge on the entrance 11 side. This pressure distribution can cause sink marks (surface depressions due to volumetric shrinkage) near the edge on the entrance 11 side. In the corner cube 1 according to this embodiment, the outer surfaces 3Ao, 5Ao, and 7Ao of the first resin substrate 3A, second resin substrate 5A, and third resin substrate 7A are formed with inclined portions 25 and 27 that are inclined relative to the inner surfaces 3Ai, 5Ai, and 7Ai, respectively, so that the thickness T1 near the end on the entrance 11 side is thinner than the thickness T2 near the gate 41. This reduces the effects of pressure drops near the end on the entrance 11 side and suppresses deformation due to sink marks. This improves the flatness of the reflecting surface.

[0039] Furthermore, in the manufacturing method of the corner cube 1 according to this embodiment, in step S10, molten resin material is injected into a mold 29, and a resin molded product 1A consisting of a first resin substrate 3A, a second resin substrate 5A, and a 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 reduces the time required for manufacturing. This improves productivity and reduces costs.

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

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

[0042] Furthermore, according to the manufacturing method of this embodiment, in step S10, a resin material is injected into a mold 29 shaped to form inclined portions 25, 27 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, that are inclined with respect to the inner surfaces 3Ai, 5Ai, 7Ai, so that the plate thickness T1 near the end on the incident port 11 side is thinner than the plate thickness T2 near the gate 41. This makes it possible to suppress the effects of a pressure drop near the end on the incident port 11 side and to suppress deformation due to sink marks. This therefore improves the flatness of the reflecting surface.

[0043] <Modification> The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of 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 in a direction perpendicular to the light entrance 11. This modification will be described in detail with reference to FIGS. 17 to 23. FIG. 17 is a top view of the corner cube according to the modification, seen from the side opposite the light entrance. FIG. 18 is a side view of the corner cube according to the modification, seen from the direction of arrow XVIII in FIG. 17. FIG. 19 is a front view of the corner cube according to the modification, seen from the direction of arrow XIX in FIG. 17. FIG. 20 is a cross-sectional view of the corner cube according to the modification, showing the state in which resin has been injected between the core and cavity of a mold. FIG. 21 is a cross-sectional view of the corner cube according to the modification attached to a holder. FIG. 22 is a side view of the corner cube according to the modification, showing the corner cube being released by gripping its gate boss. FIG. 23 is a top view of the corner cube according to the modification, showing the corner cube being released by gripping its gate boss. In FIGS. 17 to 23, components similar to those in the above-described embodiment are designated by the same reference numerals, and their description will be omitted where 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 (approximately 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 rest of the configuration of the corner cube 1 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 made up of the first resin substrate 3A, the second resin substrate 5A, and the third resin substrate 7A. A gate 41 is connected to the tip of the hollow portion for the boss 45, and molten resin material is injected through 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 near 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 in the above-described embodiment.

[0047] As shown in FIG. 21 , the corner cube 1 of this modified example is attached to a columnar holder 47 when mounted on a surveying instrument such as a total station, theodolite, or transit. The holder 47 has an insertion hole 49 into which a boss 45 can fit 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 precision by fitting the boss 45 into the insertion hole 49 and by the abutment of the flat portion 9 against the side surface of the holder 47. The holder 47 may be cylindrical or polygonal. The shape and size of the holder 47 are determined depending on the size and quantity 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 automated 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. Using boss 45 when attaching corner cube 1 to holder 47 facilitates positioning, and corner cube 1 can be fixed without contacting outer faces 3o, 5o, and 7o with holder 47, preventing any impact on the flatness of the reflecting surface. Furthermore, resin molded product 1A can be removed from mold 29 by gripping boss 45, making removal easy and enabling 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 within the scope of the 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 Third resin substrate 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 second resin substrate in a flat plate shape connected to the first resin substrate at a right angle; a third resin substrate in a flat plate shape connected to the first resin substrate and the second resin substrate at right angles, the first resin substrate, the second resin substrate, and the third resin substrate are made of a resin material; Corner cube.

2. 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; A metal film is formed on both the inner surface and the outer surface. The corner cube according to claim 1 .

3. 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 the plate thickness in the vicinity of the entrance 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; The corner cube according to claim 1 .

4. a cylindrical boss extending from near a vertex of a triangular pyramid formed by the first resin substrate, the second resin substrate, and the third resin substrate in a direction perpendicular to the light entrance; The corner cube according to claim 1 .

5. 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 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 to the first resin substrate at a right angle, and a flat third resin substrate connected to each of the first resin substrate and the second resin substrate at a right angle; A method for manufacturing corner cubes.

6. 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. The method for manufacturing the corner cube according to claim 5 .

7. 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; The method for manufacturing the corner cube according to claim 5 .

8. 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 thickness of the first resin substrate, the second resin substrate, and the third resin substrate, each having an inner surface on the light entrance side and an outer surface on the opposite side to the entrance, is thinner than the thickness of the outer surface near the entrance of a triangular pyramid 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 5 .

9. In the first step, Injecting the resin material into the mold having a shape in which 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 is formed in a direction perpendicular to the light entrance. The method for manufacturing the corner cube according to any one of claims 5 to 8.

10. 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 9 .

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