Reflector and target device

Abstract

The present invention provides a reflector and target device that prevent offset between the reflector's measurement reference point and the measurement point when the reflector is installed at the measurement point. [Solution] A reflector 3 comprising an optical member 7 having at least four reflective surfaces that internally reflect incident measurement light, wherein the optical member includes a retroreflector composed of three retroreflective surfaces among the reflective surfaces, and at least one of the reflective surfaces constitutes a deflection optical section that deflects the incident measurement light to guide it to the retroreflector and deflects the measurement light retroreflected by the retroreflector to emit it in the exact opposite direction to the incident measurement light, and further the optical member is configured such that a virtual image of the optical center of the reflector is formed on the extension of the incident optical axis.

Description

Technical Field

[0001] The present invention relates to a reflector used as a target when performing measurement and a target device including the reflector.

Background Art

[0002] When performing light wave distance measurement with a measuring device, a reflector as a target is provided at the measurement point.

[0003] The reflector includes a corner cube prism, the corner cube prism retroreflects the distance measuring light, the measuring device receives the reflected light, and distance measurement is performed based on the time difference between the emission timing of the distance measuring light and the reception timing of the reflected distance measuring light and the speed of light.

[0004] In the case of a corner cube prism, the optical center, which is the measurement reference point, exists inside the corner cube prism. Also, in order to accurately measure the measurement point using the reflector, it is necessary to install the reflector so that the position of the optical center of the corner cube prism coincides with the measurement point.

[0005] Usually, the reflector is held by a holding device, and the holding device has a housing of the reflector, a pole to which the housing is attached, and a rock pier installed at the measurement point.

[0006] The corner cube prism has an optical center as the measurement reference point, and the optical center is inside the corner cube prism. Therefore, when the rock pier is provided at the lower end of the pole, the optical center is offset from the axis of the pole (see Patent Document 2). In this case, an error due to the offset occurs when the reflector is not facing the measuring device.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

[0008] The present invention provides a reflector and target device that prevent offset from occurring between the measurement reference point and the measurement point when the reflector is installed at the measurement point. [Means for solving the problem]

[0009] The present invention relates to a reflector comprising an optical member having at least four reflective surfaces that internally reflect incident measurement light, wherein the optical member includes a retroreflector composed of three retroreflective surfaces, at least one of the reflective surfaces being deflected to guide the incident measurement light to the retroreflector and a deflecting optical section being deflected to emit the retroreflected measurement light in the direction opposite to the incident measurement light, and further relating to a reflector configured such that a virtual image of the optical center of the reflector is formed on the extension of the incident optical axis.

[0010] Furthermore, the present invention relates to a reflector in which the deflection optical unit is composed of a plurality of reflective surfaces, one of which is the incident surface of the measurement light, and the incident angle of the internal reflection of the measurement light deflected by the incident surface onto the incident surface is greater than or equal to a critical angle.

[0011] Furthermore, the present invention relates to a reflector configured such that one of the three surfaces constituting the retroreflector is the incident surface of the measurement light, and the incident angle of internal reflection to the incident surface is greater than or equal to the critical angle.

[0012] Furthermore, the present invention relates to a reflector in which the deflection optical unit is composed of a reflective surface other than the incident surface of the measurement light.

[0013] Furthermore, the present invention relates to a reflector in which the optical element is a prism.

[0014] Furthermore, the present invention relates to a reflector in which the optical member consists of a corner cube prism as a retroreflector composed of three surfaces capable of retroreflection and a prism as a deflecting optical section for deflecting the measurement light, and the corner cube prism and the prism are integrated.

[0015] Furthermore, the present invention relates to a reflector in which the optical element is composed of multiple mirrors.

[0016] Furthermore, the present invention relates to a reflector with a beveled structure that suppresses the generation of stray light.

[0017] Furthermore, the present invention relates to a reflector formed on the edge portion of the three surfaces capable of retroreflection, as described above.

[0018] Furthermore, the present invention relates to a reflector in which an anti-reflective coating is provided near the edges of the three ridges of the prism that are capable of retroreflection.

[0019] Furthermore, the present invention relates to a reflector in which a light-shielding material is provided on the measurement light incident surface of the deflection optical unit to suppress the incidence of stray light.

[0020] Furthermore, the present invention relates to a reflector in which two sets of deflection optical units are arranged symmetrically so that their virtual image formation positions coincide and integrated into a single unit.

[0021] Furthermore, the present invention relates to a reflector in which the reflector includes a housing for housing the prism, and the housing has an indicator portion for indicating the virtual image formation position of the reflector.

[0022] The present invention also relates to a target device comprising any one of the above reflectors and a pole for supporting the reflector, wherein the virtual image formation position of the reflector is located on the axis of the pole.

[0023] Furthermore, the present invention relates to a target device in which the reflector is configured to be slidable and fixed with respect to the pole.

Effect of the Invention

[0024] According to the present invention, there is provided a reflector comprising an optical member having at least four reflecting surfaces for internally reflecting incident measurement light, the optical member including a retroreflector composed of three surfaces capable of retroreflection among the reflecting surfaces, at least one of the reflecting surfaces deflects the incident measurement light so as to guide it to the retroreflector, and a deflection optical portion that deflects the measurement light retroreflected by the retroreflector so as to emit it in a direction exactly opposite to the incident measurement light. Further, the optical member is configured such that a virtual image of the optical center of the reflector is formed on the extension of the incident light axis. Therefore, the measurement reference point of the reflector can be set as the virtual image position, and the measurement reference position can be installed at the measurement point without offset, exhibiting an excellent effect.

Brief Description of the Drawings

[0025] [[ID=1�]] [Figure 1] It is an explanatory diagram of the measurement of a measurement point using the target device according to this embodiment. [Figure 2] (A) and (B) show the optical member included in the reflector and the relationship between the optical member and the pole. (A) is an elevation view, and (B) is a view taken along the A-A arrow of (A). [Figure 3] It is a perspective view showing the relationship between the optical member and the pole. [Figure 4] It is an explanatory diagram of the reflector according to the second embodiment. [Figure 5] (A) is a perspective view of the reflector according to the third embodiment, and (B) is a view taken along the C arrow of (A). [Figure 6] It is an explanatory diagram of the reflector according to the fourth embodiment. [Figure 7] (A), (B), and (C) are diagrams illustrating reflectors that guide incident light to a retroreflector through a single internal reflection. [Figure 8] (A), (B), (C), and (D) are diagrams illustrating reflectors that guide incident light to a retroreflector through two internal reflections. [Figure 9] (A), (B), (C), and (D) are diagrams illustrating reflectors that guide incident light to a retroreflector through three internal reflections. [Figure 10] (A) and (B) are explanatory diagrams of reflectors that guide incident light to a retroreflector through four internal reflections, respectively. [Figure 11] This is a perspective view of a prism. [Figure 12] (A) is an explanatory diagram showing an example of a normal light path, and (B) is an explanatory diagram showing an example of a stray light path. [Figure 13] (A), (B), (C), and (D) are explanatory diagrams showing examples of structural chamfering in prisms. [Figure 14] (A) and (B) are diagrams illustrating other examples of stray light suppression means in the prism. [Figure 15] An example of widening the field of view of the reflector is shown, where (A) is a front view and (B) is a view taken along arrow E in (A). [Figure 16] This is an explanatory diagram of a reflector according to the fifth embodiment. [Modes for carrying out the invention]

[0026] The embodiments of the present invention will be described below with reference to the drawings.

[0027] Figure 1 is an explanatory diagram of the measurement of a measurement point using a target device 1 according to the first embodiment of the present invention, and Figures 2(A) and 2(B) are explanatory diagrams of the target device 1.

[0028] The target device 1 comprises a pole 2 having a tip at its lower end and a reflector 3 provided on the pole 2. In the figure, 4 indicates a measuring device.

[0029] The target device 1 is installed at the measurement point P. The target device 1 has a horizontal detector 5 (see Figure 2), such as a bubble tube, at the required position, and the measurement operator supports the target device 1 in a vertical position based on the detection result of the horizontal detector 5. The measurement operator also positions the reflector 3 facing the measurement device 4.

[0030] The measuring device 4 emits measuring light 6, the reflector 3 retroreflects the measuring light 6, the measuring device 4 receives the reflected light, and the necessary measurements such as distance measurement, angle measurement, and tracking are performed. Here, the measuring light 6 includes distance measuring light for distance measurement, angle measuring light for angle measurement, and tracking light for tracking.

[0031] In this embodiment, as shown in Figures 2(A) and 2(B), the reflector 3 has an optical member 7, and the optical member 7 is configured such that the measurement reference point O' is formed outside the optical member 7. Furthermore, the reflector 3 is provided on the pole 2 such that the measurement reference point O' coincides with the axis of the pole 2. In Figure 2(B), O indicates the optical center of the optical member 7, and O' indicates the position of the virtual image formed on the extension of the incident optical axis 11 at a position symmetric to the optical center O, and is the measurement reference point.

[0032] Therefore, accurate measurements can be taken even if there is no offset between the measurement point P and the measurement reference point, the reflector 3 is not precisely facing the measuring device 4, or there is a difference in height between the measuring device 4 and the reflector 3.

[0033] Furthermore, the reflector 3 is slidable relative to the pole 2 and can be fixed to the pole 2 at any position using a fastener 10 such as a screw. Additionally, the pole 2 may have markings indicating the fixing position of the reflector 3.

[0034] Therefore, even if there is a height difference between the reflector 3 and the measuring device 4 that causes measurement errors, accurate measurements can be performed by adjusting the height of the reflector 3.

[0035] Figures 2(A), 2(B), and 3 illustrate the reflector according to the first embodiment.

[0036] Figures 2(A) and 2(B) show the relationship between the reflector 3 and the optical element 7, and between the optical element 7 and the pole 2. Figure 2(A) is a side view, and Figure 2(B) is a view taken along arrow AA in Figure 2(A) (plan view). Note that the optical element 7 is shown in a simplified manner.

[0037] In Figures 2(A) and 2(B), a prism 8 is used as the optical element 7. The prism 8 has the function of a deflecting optical element that deflects the optical axis of the measurement light 6, as well as the function of retroreflecting the measurement light 6, and is configured to function as a corner cube.

[0038] As shown in Figure 3, the prism 8 is a tetrahedron composed of four faces: the first face 8a, the second face 8b, the third face 8c, and the fourth face 8d, with three of the four faces being orthogonal. In the illustration, the first face 8a, the second face 8b, and the third face 8c are orthogonal, and the point where these three faces intersect is vertex 9.

[0039] As shown in Figure 2(B), the first surface 8a of the prism 8 is the incident surface, and the reference optical axis of the measurement light incident from the first surface 8a is shown as the incident optical axis 11. The incident measurement light is deflected in the direction of the vertex 9 by internal reflection of the fourth surface 8d. Here, internal reflection means that the measurement light is reflected inside the optical member 7. Also, in Figure 2(B), R indicates the reflection point of the incident optical axis 11 on the fourth surface 8d.

[0040] In the example shown in Figure 3, the measurement light reflected internally by the fourth surface 8d (#1) is sequentially reflected internally by #2 of the first surface 8a, #3 of the third surface 8c, and #4 of the second surface 8b, and then further reflected internally by #5 of the fourth surface 8d.

[0041] The measurement light is deflected by internal reflection on the fourth surface 8d (#1), retroreflected by internal reflection on the orthogonal first surface 8a, second surface 8b, and third surface 8c, and the retroreflected measurement light is deflected by internal reflection on the fourth surface 8d and emitted from the first surface 8a in the exact opposite direction to the incident direction of the measurement light.

[0042] Therefore, the first surface 8a, the second surface 8b, and the third surface 8c (hereinafter also referred to as the three surfaces or three reflective surfaces) constitute a corner cube as a retroreflector (the angle formed by the three reflective surfaces is 90°90°90°), and the fourth surface 8d deflects the incident measurement light toward the retroreflector and further deflects the retroreflected measurement light so that it is emitted, thus functioning as a deflection optical unit.

[0043] Thus, the prism 8 has the function of both a deflection optical unit and a corner cube.

[0044] In addition to corner cubes, retroreflective prisms can also be used as retroreflectors. For example, prisms with an angle of 90°90°90° / n (a natural number) between their three reflective surfaces, or prisms with an angle of 90°60°45° between their three reflective surfaces, can retroreflect the measurement light using their three reflective surfaces and can be used as retroreflectors. In this case, the prism 8 has the function of both a deflection optical unit and a retroreflective prism or retroreflective mirror. In the following description, when it is stated that a device has three retroreflective surfaces, it may also include the case where the three surfaces are orthogonal.

[0045] Furthermore, in order to increase the reflection efficiency due to internal reflection on the second surface 8b, the third surface 8c, and the fourth surface 8d, a reflective film may be formed on the second surface 8b, the third surface 8c, and the fourth surface 8d.

[0046] Furthermore, in order to increase the reflection efficiency at the first surface 8a, the angle of the fourth surface 8d may be selected such that the angle of incidence to #2 is greater than or equal to the critical angle of total internal reflection defined by the prism 8, so that the internal reflection at #2 of the first surface 8a becomes total internal reflection. Alternatively, a beam splitter film may be deposited on the first surface 8a to increase the usable angle at the first surface 8a, thereby increasing the internal reflection efficiency at the increased angle. The optical properties of the beam splitter film may be, for example, transmission:reflection = 2:1. It goes without saying that the optical properties of the beam splitter film are not limited to transmission:reflection = 2:1, but may be appropriately selected in accordance with the optical properties required of the prism 8.

[0047] Figure 4 shows a reflector 13 according to a second embodiment. The optical element 14 included in the reflector 13 may be composed of four mirrors 14a, 14b, 14c, and 14d. Although only three mirrors 14a, 14c, and 14d are shown in Figure 4, the reflector is composed of four mirrors in the shape shown in Figure 3, with the inner surface of each mirror being a reflective surface (first surface 8a, second surface 8b, third surface 8c, and fourth surface 8d), so that the measurement light incident on the optical element 14 is internally reflected by each mirror.

[0048] Furthermore, as in the first embodiment, in order to increase the reflection efficiency due to internal reflection on the second surface 8b, the third surface 8c, and the fourth surface 8d, reflective films may be formed on the second surface 8b, the third surface 8c, and the fourth surface 8d. In addition, a beam splitter film capable of transmission and reflection may be formed on the mirror 14a. For example, the optical properties of the beam splitter film are set to transmission:reflection = 2:1. It goes without saying that the optical properties of the beam splitter film are not limited to transmission:reflection = 2:1, but can be selected as appropriate.

[0049] The three orthogonal surfaces (the first surface 8a, the second surface 8b, and the third surface 8c forming an angle of 90°90°90°) constitute a retroreflector, and the fourth surface 8d constitutes a deflection optical section.

[0050] In the optical member 14 of the second embodiment, similar to the optical member 7 (prism 8) of the first embodiment, the mirrors 14a, 14b, 14c, and 14d, in which the angles formed by the three reflective surfaces (first surface 8a, second surface 8b, and third surface 8c) are 90°90°90° / n (natural number) and the angles formed by the three reflective surfaces are 90°60°45°, can also retroreflect the measurement light using the three reflective surfaces and can be used as retroreflectors. Alternatively, the mirror shown in Patent Document 5 may be used as a retroreflector.

[0051] In the second embodiment, the measurement light incident from the mirror 14a is reflected (blinded) by the fourth surface 8d, incident on the retroreflector, and retroreflected by the retroreflector. The retroreflected measurement light is reflected and deflected by the fourth surface 8d and emitted in a direction directly opposite to the incident direction of the measurement light.

[0052] Figures 5(A) and 5(B) show a prism 17 included in the reflector 16 according to the third embodiment. Figure 5(A) is a perspective view of the prism 17, and Figure 5(B) is a view taken along arrow C in Figure 5(A).

[0053] The prism 17, as an optical component, includes a corner cube composed of three orthogonal surfaces and a reflective surface as a deflection optical section that internally reflects the incident measurement light toward the corner cube. In the third embodiment, as in the first embodiment, other prisms capable of retroreflection on three surfaces can be used in addition to the corner cube.

[0054] In this third embodiment, the incident measurement light is guided to the corner cube by two internal reflections.

[0055] In the third embodiment of the prism 17, the vertex angle of the prism 17 (the angle at the top end formed by the first face 8a and the fourth face 8d in Figure 5(B)) is made smaller than the vertex angle of the prism 8 in the first embodiment, so that the corner cube is composed of the orthogonal second face 8b, third face 8c, and fourth face 8d.

[0056] The measurement light (incident optical axis 11) incident from the first surface 8a is internally reflected by the fourth surface 8d, then internally reflected a second time by the incident surface (first surface 8a), and then incident on the corner cube. The measurement light is retroreflective by the corner cube.

[0057] In the third embodiment, the fourth surface 8d and the first surface 8a deflect the measurement light through internal reflection and guide it to the corner cube. Therefore, in the third embodiment, the fourth surface 8d and the first surface 8a function as a deflection optical unit.

[0058] Here, the first surface 8a, which is the incident surface, also serves as the second internal reflection, and the prism 17 may be configured such that the angle of incidence when the measurement light internally reflected by the fourth surface 8d enters the first surface 8a is greater than or equal to the critical angle, and the internal reflection of the measurement light at the first surface 8a is total internal reflection. Alternatively, a beam splitter film may be deposited on the first surface 8a, as in the first embodiment.

[0059] In the third embodiment, the optical center O is located on the reflected optical axis 11' which is deflected for the second time on the first surface 8a, and the position where the virtual image O' is formed is on the extension of the incident optical axis 11 and is equal to the physical distance from the first reflection point to the optical center O.

[0060] Figure 6 shows a reflector 19 according to the fourth embodiment. In the fourth embodiment, an optical element 20 equivalent to the prism 17 according to the third embodiment is composed of four mirrors 14a, 14b, 14c, and 14d, and a retroreflector is further composed of three orthogonal mirrors among the four mirrors. Note that mirror 14b is not shown.

[0061] The inner surfaces of each mirror are reflective surfaces 8a, 8b, 8c, and 8d, and the retroreflector is formed by the orthogonal second surface 8b, third surface 8c, and fourth surface 8d. In the fourth embodiment, as in the second embodiment, mirrors with different angles can be used as retroreflectors as long as retroreflection is possible on the three surfaces of the second surface 8b, third surface 8c, and fourth surface 8d.

[0062] The measurement light incident on the mirror 14a is internally reflected twice by the fourth surface 8d and the first surface 8a, incident on the retroreflector, retroreflected by the retroreflector, and further deflected by the first surface 8a and the fourth surface 8d, and emitted in a direction directly opposite to the incident direction of the measurement light.

[0063] Various modifications are possible for the reflector, which is configured so that the optical components include a deflection optical unit and a retroreflector. The following describes some modified examples.

[0064] Furthermore, as mentioned above, the optical component can be composed of either a prism or a mirror. The following explanation will describe the case where the optical component is a prism.

[0065] In the modified examples shown in Figures 7(A), 7(B), and 7(C), the prism is configured such that the measurement light is guided to a retroreflector composed of three orthogonal surfaces by a single internal reflection. Note that the prism in Figure 7(C) is a single unit formed by integrating two prisms 7a and 7b.

[0066] In the modified examples shown in Figures 8(A), 8(B), 8(C), and 8(D), the prism is configured such that the measurement light is guided to a retroreflector composed of three orthogonal surfaces by two internal reflections.

[0067] In the modified examples shown in Figures 9(A), 9(B), 9(C), and 9(D), the prism is configured such that the measurement light is guided to a retroreflector composed of three orthogonal surfaces through three internal reflections.

[0068] In the modified examples shown in Figures 10(A) and 10(B), the prism is configured such that the measurement light is guided to a retroreflector composed of three orthogonal surfaces through four internal reflections.

[0069] In addition, in Figures 7(A), 7(B), 7(C), 8(A), 8(B), 8(C), 8(D), 9(A), 9(B), 9(C), 9(D), 10(A), and 10(B), components equivalent to those shown in Figure 3 are denoted by the same reference numerals. Furthermore, in the above modified examples, as in the first embodiment, in addition to the corner cube, a prism capable of retroreflection on three faces can be used.

[0070] The optical center of the prism moves symmetrically from each reflective surface in accordance with the number of reflections, and finally lies on the optical axis toward the retroreflector. Furthermore, the position where the virtual image O' is formed is equal to the physical distance from the first reflection point to the optical center O on the extension of the incident optical axis 11. Therefore, as the number of reflections increases, the position where the virtual image O' is formed moves further away from the first reflection point.

[0071] Furthermore, while the above-described modifications illustrate the case where the reflected light path is coplanar (two-dimensional), the prism may also be configured to have a three-dimensional reflected light path. The choice of which modification of the prism to select should be determined by considering the performance and shape required of the reflector.

[0072] Next, the reflector may cause the measurement light to have a retroreflective optical path that differs from the normal optical path. In this case, if the measuring device 4 receives the reflected light and performs the measurement, a measurement error will occur.

[0073] The following explains how to suppress retroreflection of light other than normal light (hereinafter referred to as stray light).

[0074] First, let's explain stray light with reference to the prism 8 shown in Figure 11.

[0075] The prism 8 is composed of four surfaces: the first surface 8a, the second surface 8b, the third surface 8c, and the fourth surface 8d. Note that the fourth surface 8d is not shown. In Figures 11, 12(A), and 12(B), the prism 8 is shown as a corner cube prism, but other prisms can be used as long as retroreflection is possible with three surfaces.

[0076] The normal light incident on the prism 8 is the measurement light 6 that is incident in the same or parallel optical path as the incident optical axis (reference optical axis) 11, as shown in Figure 12(A) (see Figure 3), and retroreflected.

[0077] In Figure 12(A), the measurement light 6 (normal light) incident from the first surface 8a is sequentially reflected internally by the fourth surface 8d (#1), the first surface 8a (#2), the third surface 8c (#3), the second surface 8b (#4), and the fourth surface 8d (#5), and then emitted from the first surface 8a.

[0078] Here, the first surface 8a(#2), the third surface 8c(#3), and the second surface 8b(#4) are three orthogonal reflective surfaces that constitute a retroreflector, and the measurement light 6 is retroreflected by the first surface 8a(#2), the third surface 8c(#3), and the second surface 8b(#4).

[0079] In Figure 12(B), the ray N is stray light with a retroreflective path different from that of the normal ray. When the ray N (stray light) enters the prism 8 from #1 of the first surface 8a, it is reflected sequentially by the third surface 8b (#2), the fourth surface 8d (#3), the second surface 8b (#4), the first surface 8a (#5), the third surface 8c (#6), the fourth surface 8d (#7), and the second surface 8b (#8), and the reflected light is emitted from #9 of the first surface 8a in the exact opposite direction to the incident ray N.

[0080] Here, the second surface 8b(#4), the first surface 8a(#5), and the third surface 8c(#6) are three orthogonal reflective surfaces that constitute the retroreflector, and the light ray N becomes stray light retroreflected by the retroreflector (the second surface 8b(#4), the first surface 8a(#5), and the third surface 8c(#6)).

[0081] One measure to combat stray light is to perform structural chamfering. Structural chamfering limits the reflective surface so that light rays N are not retroreflected by repeated internal reflections.

[0082] Figures 13(A), 13(B), 13(C), and 13(D) show examples of structural chamfering. The dashed lines in the figures indicate that the prism 8 is structurally chamfered at the positions indicated by the dashed lines. In Figures 13(A), 13(B), 13(C), and 13(D), the prism 8 is shown as a corner cube prism, but other prisms can be used as long as retroreflection is possible on three faces.

[0083] In Figures 13(A), 13(B), 13(C), and 13(D), 11 indicates the incident optical axis (particularly the reference optical axis) of the measurement light 6 (normal light). Structural chamfering is achieved by removing corners and edges and chamfering them in order to minimize the influence on the optical path of the normal light.

[0084] Figures 13(A) and 13(B) show structural chamfering by cutting off the corners 22b that are not vertices 9 of the prism 8 and the edges 22a of the prism 8; Figure 13(C) shows structural chamfering by removing both vertices 22c of the base that appear in the isosceles triangle of the prism 8; and Figure 13(D) shows structural chamfering by removing both edge portions 22a that appear in the isosceles triangle of the prism 8.

[0085] Furthermore, although not specifically shown in the illustration, the edges of the three orthogonal surfaces may be structurally chamfered.

[0086] Furthermore, instead of structural chamfering, the edges of the three orthogonal surfaces may be coated with an anti-reflective coating near the edges of the three surfaces. The area coated with the anti-reflective coating shall be the same as that of the structural chamfering described above, in order to minimize the impact on the optical path of normal light.

[0087] Similarly, the prism 17 shown in Figure 5 is also subjected to measures such as removal of corners and edges, structural chamfering, and application of an anti-reflective coating, in order to minimize its influence on the optical path of the normal light.

[0088] By performing structural chamfering, the incidence of non-normal light rays and retroreflection (stray light) after incidence can be suppressed or reduced.

[0089] Furthermore, when a prism is used as the optical element, the optical element may consist of one prism, or it may consist of two or more prisms. For example, Figure 7(C) above shows an example consisting of two prisms. The optical element shown in Figure 7(C) consists of a retroreflective portion 7a (retroreflector portion) including the vertex 9 and a deflection portion 7b, and the retroreflective portion 7a and the deflection portion 7b are integrated so that no optical effect occurs at the boundary portion, and is an optical element equivalent to that in Figure 7(B).

[0090] Figures 14(A) and 14(B) show other means of suppressing the generation of stray light.

[0091] Figure 14(A) shows the prism 8 shown in Figure 3, and a light-shielding material 23a is provided on the upper part of the incident surface (first surface 8a) of the prism 8. The light-shielding material 23a blocks the incidence of light from the portion of the light-shielding material 23a, suppressing the generation of stray light. Various materials and materials such as opaque sheets, plates, paints, and films can be used for the light-shielding material 23a.

[0092] Figure 14(B) shows the case where a light-shielding material 23b is provided on the lower part of the incident surface (first surface 8a) of the prism 17 shown in Figure 5. The light-shielding material 23b also similarly blocks the incidence of light from the portion of the light-shielding material 23b, suppressing the generation of stray light. In addition, the edge portion 22a is structurally chamfered.

[0093] Next, by combining multiple optical elements 7, retroreflection of measurement light over a wide area (wide field of view) becomes possible. Figure 15 shows an example in which a reflector 26 is constructed using two sets of the optical elements 7 described above.

[0094] Figure 15(A) is a front view, and Figure 15(B) is a view taken along arrow EE in Figure 15(A).

[0095] Two sets of optical elements 7 are symmetrically arranged around a pole 2, and the virtual image O' positions of the two sets of optical elements 7 are combined such that they coincide at a single point on the axis of the pole 2.

[0096] Furthermore, the two sets of optical elements 7 are integrated by a retaining member 25 to form a reflector 26. The reflector 26 is attached to the pole 2 via the retaining member 25, and is also slidable relative to the pole 2 and can be fixed in any position by a fixing device 10.

[0097] By integrating two sets of optical elements 7 to form the reflector 26, measurement light can be retroreflected with approximately twice the field of view of the optical element 7 alone. Therefore, by equipping the target device 1 with the reflector 26, work efficiency is improved when measuring in situations where the orientation of the target device 1 relative to the measuring device is unstable, such as when the measuring device tracks the target device 1 during measurement.

[0098] Furthermore, a wide-angle reflector can also be constructed by combining the optical components shown in Figures 4 to 10.

[0099] Although each of the reflectors 3 described above is configured to be installed at the measurement point via the pole 2, it is also possible to install the reflector 3 at the measurement point by itself.

[0100] Figure 16 shows a reflector 27 according to the fifth embodiment. The reflector 27 will be described with reference to Figure 16.

[0101] The reflector 27 has a housing 28 that houses a prism 8, and the housing 28 is configured such that the first surface 8a (incident surface of the measurement light) of the prism 8 is open.

[0102] Furthermore, the basic shape of the prism 8 shown in the fifth embodiment is the same as that shown in Figures 2 and 12, but a structural chamfer 8e is implemented to suppress stray light.

[0103] In the figure, O indicates the optical center of the prism 8, and the virtual image O' of the optical center O is formed at a position symmetrical with respect to the fourth surface 8d on the extension of the incident optical axis 11. The position of the virtual image O' serves as the measurement reference point.

[0104] The rear wall (opposite the incident surface) of the housing 28 has an indicator portion 29 that protrudes along the extension of the incident optical axis 11. The indicator portion 29 indicates a measurement point with its tip, and is configured so that its tip coincides with the formation position of the virtual image O'.

[0105] The shape of the indicator portion 29 may be conical or rod-shaped, and the tip of the indicator portion 29 may be pointed or spherical to facilitate the indication of the measurement point. The indicator portion 29 functions as a probe to indicate the measurement point in position measurement.

[0106] The indicator portion 29 may be formed integrally with the housing 28, or it may be manufactured separately from the housing 28 and attached to the housing 28, and furthermore, the indicator portion 29 may be detachable from the housing 28.

[0107] When performing measurements using the reflector 27, the operator sets the tip of the indicator unit 29 at the measurement point and points the first surface 8a towards the measuring device, thereby enabling measurement of the measurement point.

[0108] Furthermore, the shape of the housing 28 can be appropriately modified to match the shape of the prism 8, and any prism within the aforementioned prism can be used as a prism constituting the reflector 27.

[0109] In this embodiment, the reflector 27 is easy to carry and does not require a pole, thus improving work efficiency. [Explanation of Symbols]

[0110] 1. Target device 2 poles 3 Reflectors 4. Measuring device 6. Measurement light 7 Optical components 8 prisms 11 Incident optical axis 11′ Reflected optical axis 13 Reflectors 14 Optical components 16 reflectors 17 Prism 19 Reflector 20 Optical components 27 Reflector 28 Housing 29 Instruction section

Claims

1. A reflector comprising an optical member having at least four reflective surfaces that internally reflect incident measurement light, wherein the optical member includes a retroreflector composed of three retroreflecting surfaces among the reflective surfaces, at least one of the reflective surfaces is configured as a deflecting optical section that deflects the incident measurement light to guide it to the retroreflector and deflects the measurement light retroreflected by the retroreflector to emit it in the direction opposite to the incident measurement light, and further comprises an optical member configured such that a virtual image of the optical center of the reflector is formed on the extension of the incident optical axis.

2. The reflector according to claim 1, wherein the deflection optical unit is composed of a plurality of reflective surfaces, one of which is the incident surface of the measurement light, and the incident angle of the internal reflection of the measurement light deflected by the incident surface onto the incident surface is greater than or equal to the critical angle.

3. The reflector according to claim 1, wherein one of the three surfaces constituting the retroreflector is the incident surface of the measurement light, and is configured such that the incident angle of internal reflection to the incident surface is greater than or equal to the critical angle.

4. The reflector according to claim 1, wherein the deflection optical unit is composed of a reflective surface other than the incident surface of the measurement light.

5. The reflector according to claim 1, wherein the optical element is a prism.

6. The optical component comprises a corner cube prism as a retroreflector composed of three surfaces capable of retroreflection and a prism as a deflection optical unit for deflecting measurement light, wherein the corner cube prism and the prism are integrated into one, as described in claim 1.

7. The reflector according to claim 1, wherein the optical element is composed of a plurality of mirrors.

8. The reflector according to claim 5 or 6, wherein the prism has a structure that suppresses the generation of stray light and is chamfered.

9. The reflector according to claim 8, wherein the structural chamfer is formed on the ridges of the three surfaces capable of retroreflection.

10. The reflector according to claim 5 or claim 6, wherein an anti-reflective coating is provided near the edges of the three ridges of the prism that are capable of retroreflection.

11. The reflector according to claim 1, wherein a light-shielding material that suppresses the incidence of stray light is provided on the measurement light incident surface of the deflection optical unit.

12. The reflector according to claim 1, wherein two sets of deflection optical units are symmetrically arranged and integrated so that their virtual image formation positions coincide.

13. The reflector according to claim 5 or 6, wherein the reflector includes a housing for housing the prism, and the housing has an indicator portion for indicating the virtual image formation position of the reflector.

14. A target device comprising a reflector according to any one of claims 1 to 12 and a pole supporting the reflector, wherein the virtual image formation position of the reflector is located on the axis of the pole.

15. The target device according to claim 14, wherein the reflector is configured to be slidable and fixable with respect to the pole.

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