Patent Publication Number: US-2023136366-A1

Title: Three-dimensional-measuring-apparatus inspection gauges, three-dimensional-measuring-apparatus inspection methods and three-dimensional measuring apparatuses

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to Japanese Patent Applications number 2021-177083, filed on Oct. 29, 2021. The contents of this application are incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     There is a conventionally known inspection gauge used when the motion precision of a three-dimensional measuring apparatus is inspected. The inspection gauge has spheres that are provided at positions corresponding to vertices of a triangular pyramid, and are connected by rod-like members provided at positions corresponding to sides of the triangular pyramid (e.g. see the specification of Germany Patent Application Publication No. 19720883). 
     When a three-dimensional measuring apparatus is inspected by causing a probe of the three-dimensional measuring apparatus to come into contact with spheres of the inspection gauge arranged at vertices of a triangular pyramid of the inspection gauge to thereby measure distances between the spheres. For example, there are three-dimensional measuring apparatuses that perform measurement of an object by using a probe caused to assume such a position that it points vertically downward or such a position that it points a horizontal direction. In the conventional configuration, indicators of the inspections are motion errors of a three-dimensional measuring apparatus that performs measurement with different probe positions, there is problem that the inspection cannot be carried out with high precision with a single three-dimensional-measuring-apparatus inspection gauge. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention has been made in view of these points, and an objective thereof is to enhance the precision of inspection of a three-dimensional measuring apparatus using an inspection gauge. 
     A three-dimensional-measuring-apparatus inspection gauge according to the present inventions comprises: a plurality of targets to be measured with which a tip of a probe of a three-dimensional measuring apparatus comes into contact; and a frame member that supports the plurality of targets, wherein the plurality of targets are arranged in positions corresponding to each vertex of a triangular prism. 
     A three-dimensional-measuring-apparatus inspection method according to the present invention, comprises: a step of placing, on mounting surface of a three-dimensional measuring apparatus on which a work is placed, a three-dimensional-measuring-apparatus inspection gauge comprising a plurality of targets to be measured with which a tip of a probe of a three-dimensional measuring apparatus comes into contact; and a frame member that supports the plurality of targets, wherein the plurality of targets are arranged in positions corresponding to each vertex of a triangular prism; a step at which a processor causes the three-dimensional measuring apparatus to measure to-be-measured distances which are distances between a plurality of targets of the three-dimensional-measuring-apparatus inspection gauge; and a step at which the processor determines whether or not there is an anomaly of the three-dimensional measuring apparatus on a basis of whether or not the to-be-measured distances are in a predetermined appropriate range. 
     A three-dimensional measuring apparatus according to the present invention, comprises: a table; a probe provided to assume variable positions; a moving mechanism that moves the probe; a position indication part that formed on the table, and indicates a placement position for the above three-dimensional-measuring-apparatus inspection gauge; and a control unit that controls a position of the probe, and operation of the moving mechanism so as to measure to-be-measured distances which are distances between a plurality of targets of the three-dimensional-measuring-apparatus inspection gauge placed at the placement position, wherein the control unit performs on a basis of selecting operation for selecting a first inspection mode or a second inspection mode either: first-mode inspection operation in which the to-be-measured distances are measured by causing the probe of the three-dimensional measuring apparatus to come into contact with the plurality of targets while the probe is at a constant position; or second-mode inspection operation in which the to-be-measured distances are measured by causing the probe of the three-dimensional measuring apparatus to come into contact with contact the plurality of targets while the probe is at a plurality of positions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a three-dimensional measuring apparatus. 
         FIG.  2    is a perspective view showing configuration around a probe. 
         FIG.  3    is a block diagram of a control unit. 
         FIG.  4    is a perspective view showing the appearance of an inspection gauge. 
         FIG.  5    is a figure for explaining a sphere. 
         FIG.  6    is a front view of the inspection gauge. 
         FIG.  7    is a left side view of the inspection gauge. 
         FIG.  8    is a plan view of the inspection gauge. 
         FIG.  9    is a figure for explaining a relationship between the shape of the inspection gauge and a space where the probe moves. 
         FIG.  10    is a figure for explaining a relationship between the shape of the inspection gauge and a space where the probe moves. 
         FIG.  11    is a figure for explaining a relationship between the shape of the inspection gauge and a space where the probe moves. 
         FIG.  12    is a figure for explaining a relationship between the shape of the inspection gauge and a space where the probe moves. 
         FIG.  13    is a flowchart of a three-dimensional-measuring-apparatus inspection method using the inspection gauge. 
         FIG.  14    is a figure showing one modified example of a three-dimensional-measuring-apparatus inspection gauge. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present inventions will be described below through embodiments of the invention. However, the following embodiments do not limit the claimed invention, and not all combinations of features described in the embodiments are essential to the solution of the invention. 
     A three-dimensional measuring apparatus and a three-dimensional-measuring-apparatus inspection gauge according to aspects of the present inventions are explained with reference to the figures.  FIG.  1    is a perspective view of a three-dimensional measuring apparatus  1 .  FIG.  2    is a perspective view showing configuration around a probe  25 . Although terms representing directions like “upper,” “lower,” “right” and “left” are used below in accordance with the position of a subject drawn in the figures, these terms are not used with the intension to limit the present inventions. 
     (Three-Dimensional Measuring Apparatus) 
     The three-dimensional measuring apparatus  1  includes a table  2 , a moving mechanism  10 , a probe unit  20  and a control unit  30 . 
     The three-dimensional measuring apparatus  1  is an apparatus that causes the tip of the probe  25  of the probe unit  20  to contact an object to be measured, and measures the shape of the object. When the three-dimensional measuring apparatus  1  performs an inspection, a three-dimensional-measuring-apparatus inspection gauge  50  (hereinafter, referred to as an “inspection gauge  50 ”) is used. Details of the inspection gauge  50  are mentioned later with reference to  FIG.  4    and the like. 
     The table  2  is a table on which a work which is an object is placed, and has a horizontal mounting surface. The mounting surface of the table  2  is provided with a position indication part representing a placement position of the inspection gauge  50 . 
     The moving mechanism  10  has a column  11 , a supporter  12 , a beam  13 , a Y-axis-direction driving section  14  and a slider  15 . 
     The moving mechanism  10  causes each section to operate in accordance with a control signal from the control unit  30 . Specifically, the moving mechanism  10  moves the probe unit  20  supported by the slider  15  to thereby move the probe  25  in certain direction in the X-axis direction, the Y-axis direction, and the Z-axis direction in a space above the table  2 . 
     The column  11  and the supporter  12  are support members provided such that they extend upward in the Z-axis direction from the table  2 . The beam  13  extends between the column  11  and the supporter  12  in the horizontal direction (the X-axis direction in  FIG.  1   ). The beam  13  has a guide (not shown) for moving the slider  15  in the X-axis direction. 
     The Y-axis-direction driving section  14  operates in accordance with a control signal from the control unit  30  to move the column  11 , the supporter  12  and the beam  13  integrally in the Y-axis direction. The slider  15  is a member supported by the beam  13 , and the probe unit  20  is provided at the lower end of the slider  15 . 
     The probe unit  20  has a Z-axis spindle  23 , a position changing mechanism  24  and the probe  25 . 
     The Z-axis spindle  23  is configured to move in the Z-axis direction. The Z-axis spindle  23  moves the probe  25  along the Z-axis direction. As shown in  FIG.  2   , the position changing mechanism  24  is a mechanism for changing the position of the probe  25 . The position changing mechanism  24  causes the probe  25  to assume a predetermined position in accordance with a control signal from the control unit  30 . 
     For example, the position changing mechanism  24  causes the probe  25  to assume a position with (A) an elevation angle of 90°, (B) an elevation angle of 45° and (C) an elevation angle of 0°. When the probe  25  is at the position with the elevation angle of 90°, the probe  25  is perpendicular to the Z-axis direction. When the probe  25  is at the position with the elevation angle of 45°, the probe  25  is inclined at an angle of 450 to the Z-axis direction. When the probe  25  is at the position with the elevation angle of 0°, the probe  25  is parallel to the Z-axis direction. For example, the position changing mechanism  24  causes the probe  25  to assume positions at predetermined azimuths relative to the Z axis. For example, 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315° are set as the predetermined azimuths, and the position changing mechanism  24  is configured to cause the probe  25  to be at any of the azimuths. In the present embodiment, as an example, the probe  25  is at the azimuth of 0° when the probe  25  is at a position to point the negative direction of the Y axis as in  FIG.  2   . 
     (Control Unit) 
       FIG.  3    is a block diagram of the control unit  30 . The control unit  30  is a unit for controlling operation of each section of the three-dimensional measuring apparatus  1 . The control unit  30  has an interface section  31 , a storage section  32  and a control section  33 . 
     The interface section  31  is an interface for acquiring data obtained by measurement by the probe  25 , outputting measurement results to an external display section (not shown), and receiving predetermined operation input from an operator, and so on. For example, the interface section  31  receives an instruction by selecting operation of an operator for selecting an inspection mode of the three-dimensional measuring apparatus  1 . 
     The storage section  32  is a storage medium that stores various types of data, and has a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk and the like. The storage section  32  has stored thereon various types of operating program for causing the three-dimensional measuring apparatus  1  to operate. The storage section  32  has stored thereon information about a first inspection mode and a second inspection mode. 
     The “first inspection mode” is a mode for a simple inspection of the three-dimensional measuring apparatus  1 , and this inspection is implemented in a state where the probe  25  is at a position with the elevation angle of 0°, for example. The storage section  32  has stored thereon data, as information about the first inspection mode, representing in which order and along which path the probe  25  is moved relative to a plurality of spheres T1 to T6 (details are mentioned later) of the inspection gauge  50 . 
     In the simple inspection, the three-dimensional measuring apparatus  1  moves the probe  25  at a position with the elevation angle of 0° (pointing downward in the Z-axis direction), and measurement is performed by causing the tip of the probe  25  to contact the spheres T of the inspection gauge  50 . Specifically, the three-dimensional measuring apparatus  1  measures representative points of the spheres T (e.g. the center coordinates of the sphere T). The simple inspection can be implemented in a shorter time than a detailed inspection described below, and so is used as a daily inspection. 
     The “second inspection mode” is a mode for a detailed inspection of the three-dimensional measuring apparatus  1 , this inspection is implemented while the position of the probe  25  is changed to several positions, and the motion error precision of the three-dimensional measuring apparatus  1  is measured. For example, scale errors, and motion errors related to squareness, rolling, pitching and yawing are measured. The storage section  32  has stored thereon data, as information about the second inspection mode, representing at which position, in which order and along which path the probe  25  is moved relative to the spheres T1 to T6 of the inspection gauge  50 . 
     For example, in the detailed inspection, measurement of the six spheres T1 to T6 is performed while the probe  25  is at a predetermined direction, thereafter the of the probe  25  is changed to another direction, and measurement of the six spheres T1 to T6 is performed again in that state. In this manner, in the detailed inspection, measurement of the spheres T is performed with a plurality of directions of the probe  25 . If the number of directions of the probe  25  is too small, inspections with high precision cannot be implemented, whereas if the number directions of the probe  25  is too large, inspections take a long time. It is possible to set the number of set directions of the probe  25  freely. For example, the set directions may include all three directions, the elevation angle of 0°, the elevation angle of 45° and the elevation angle of 90°, and the directions with the elevation angle of 45° and the elevation angle of 90° may include positions with two azimuths or more. 
     For example, the control section  33  is a processor which is a CPU (Central Processing Unit). By executing an operating program stored on the storage section  32 , the control section  33  functions as an operation control section  331 , a measurement data processing section  332  and a display processing section  333 . 
     The operation control section  331  has a functionality of causing the three-dimensional measuring apparatus  1  to perform a normal measurement mode of causing each section of the three-dimensional measuring apparatus  1  to operate and performing measurement of an object placed on the table  2 . On the basis of the information about the first inspection mode stored on the storage section  32 , the operation control section  331  causes the three-dimensional measuring apparatus  1  to perform inspection operation in the first inspection mode for the simple inspection. The operation control section  331  causes the three-dimensional measuring apparatus  1  to perform inspection operation in the second inspection mode for the detailed inspection on the basis of the information about the second inspection mode stored on the storage section  32 . 
     The measurement data processing section  332  has a functionality of processing data obtained by the measurement using the probe  25 , and of generating coordinate information and distance information about an object. For example, the measurement data processing section  332  determines whether or not to-be-measured distances which are distances between the plurality of spheres T are within a predetermined appropriate range. 
     In a case that it is determined as a result of the measurement in the first inspection mode (simple inspection) that the to-be-measured distances are not within the predetermined appropriate range, for example, the operation control section  331  may control operation of each section of the three-dimensional measuring apparatus  1  such that the inspection mode automatically switches to the second inspection mode (detailed inspection). 
     For example, the display processing section  333  causes the display section which is not shown to display a user interface for an operator to perform predetermined input operation. In addition, for example, the display processing section  333  causes the display section to display information about measurement results. Specifically, in inspection, the display processing section  333  provides a user interface for an operator to select either the “first inspection mode (simple inspection)” or the “second inspection mode (detailed inspection).” For example, if the to-be-measured distances, which are the measurement results, are not within the predetermined appropriate range, the display processing section  333  causes the display section to display information to that effect. 
     The three-dimensional measuring apparatus  1  configured as above implements measurement operation in a conventional manner for measuring an object. On the other hand, when performing an inspection, the three-dimensional measuring apparatus  1  uses the inspection gauge  50  according to the present embodiment and implements inspection operation in either inspection mode in accordance with an instruction for the “first inspection mode (simple inspection)” or the “second inspection mode (detailed inspection)” input from an operator. 
     (Three-Dimensional-Measuring-Apparatus Inspection Gauge) 
     The three-dimensional-measuring-apparatus inspection gauge  50  according to one embodiment of the present invention is explained below.  FIG.  4    is a perspective view showing the appearance of the inspection gauge  50 .  FIG.  5    is a figure for explaining a sphere T.  FIG.  6    is a front view of the inspection gauge  50 .  FIG.  7    is a left side view of the inspection gauge  50 .  FIG.  8    is a plan view of the inspection gauge  50 . 
     The inspection gauge  50  includes the plurality of spheres T1 to T6 (also referred to as “spheres T”), and a frame member  51 . In this embodiment, the spheres T1-T6 are placed at each vertex of a triangular prism in which one of the side surfaces of the triangular prism faces to a lower surface side of the frame member  51  (triangular prism in the state shown in  FIG.  4   ). The frame member  51  is a member supporting the spheres T. The inspection gauge  50  is a tool that is used in a state where it is arranged on the table  2  of the three-dimensional measuring apparatus  1  when an inspection of the three-dimensional measuring apparatus  1  is performed. The inspection gauge  50  can be used for both the simple inspection in which measurement of the spheres T is performed in a state where the probe  25  is caused to point a predetermined direction, whereas the detailed inspection in which measurement of the spheres T is performed while the position of the probe  25  is changed to point a plurality of directions. 
     As shown in  FIG.  5   , the plurality of spheres T are to-be-measured members with which the tip of the probe  25  of the three-dimensional measuring apparatus  1  comes into contact. The three-dimensional measuring apparatus  1  performs operation of measuring a sphere T in a state where the probe  25  is caused to assume a position in which it points downward in the Z-axis direction ((i) in the figure), and operation of measuring a sphere T in a state where the probe  25  is caused to assume a position in which it is inclined to the Z-axis direction ((ii) in the figure). For example, each sphere T is formed of the same material and in the same shape. Although a sphere T is described as an example below, the target is not necessarily limited to a sphere, but can be any three-dimensional shape that enables a representative point to be measured. 
     Each sphere T may be supported directly by the frame member  51 , but, in the present embodiment, is supported by the frame member  51  via a support member  41 . As an example, the support member  41  is a rod-like member that extends upward in the Z-axis direction in a state where the inspection gauge  50  is placed on the table  2 . In this example, the support member  41  has a shaft section  41   a  having a diameter which is smaller than the diameter of the sphere T, and supporting the lower part of the sphere T. 
     Each sphere T is supported by the support member  41  in such a manner that its surface area C 1  including an area above a horizontal plane H passing through the center of the sphere T and an area below the horizontal plane H does not contact other members. In this example, the area C 1  is an area other than a portion which is part of the sphere T and is supported by the shaft section  41   a . The sphere T supported by the support member  41  as described above allows the tip of the probe  25  to touch the entire area C 1 . 
     As shown in  FIG.  4   , the frame member  51  supports a first sphere T1, a second sphere T2, a third sphere T3, a fourth sphere T4, a fifth sphere T5 and a sixth sphere T6 as the plurality of spheres T. The frame member  51  having the six spheres T1 to T6 allows the three-dimensional measuring apparatus  1  to measure a large number of parameters for estimating motion error precision at a time of inspection of the three-dimensional measuring apparatus  1 . 
     The first sphere T1, the second sphere T2 and the third sphere T3 are positioned at positions corresponding to the vertices of a triangle  100   a  forming one bottom surface of a triangular prism  100  (in  FIG.  4   , the triangular prism  100  is drawn in a state where the triangular prism lies down). The fourth sphere T4, the fifth sphere T5 and the sixth sphere T6 are positioned at positions corresponding to the vertices of a triangle  100   b  forming the other bottom surface of the triangular prism  100  corresponding to the spheres T1 to T3. Specifically, in this example, the spheres T1, T3, T4 and T6 are provided at the same height, whereas the spheres T2 and T5 are provided at the same height at position which is apart upward from the other spheres by a predetermined distance. In this example, the bottom surfaces of the triangular prism  100 , corresponding to triangles  100   a  and  100   b , are perpendicular to the mounting surface. 
     For example, the triangular prism  100  may be a regular triangular prism whose triangles  100   a  and  100   b  have equal side lengths. Specifically, the triangular prism  100  may have a shape in which the triangles  100   a  and  100   b  have equal side lengths, and the height of the triangular prism (Y-axis length in the figure) also is equal to the side lengths of the triangles  100   a  and  100   b . In this configuration, the plurality of spheres T are located at equal intervals from each other. 
     (Details of Structure of Frame Member) 
     As shown in  FIG.  4   , the frame member  51  has a first frame  53 - 1 , a second frame  53 - 2  and coupling members  56 - 1  to  56 - 3 . In the example of  FIG.  4   , the frame member  51  is composed of multiple members, however the frame member  51  may be a single member integrally formed of a first frame portion corresponding to the first frame  53 - 1 , a second frame portion corresponding to the second frame  53 - 2  and connecting member portions that connects the frame portions. Such a member may be formed for example by a three-dimensional printer. 
     The first frame  53 - 1  is positioned at a position corresponding to the triangle  100   a  which is one bottom surface of the triangular prism  100 . The second frame  53 - 2  is positioned at a position corresponding to the triangle  100   b  which is the other bottom surface of the triangular prism  100 . For example, each of the first frame  53 - 1  and the second frame  53 - 2  is a single member formed of a metal material and has substantially identical shape. The first frame  53 - 1  is explained mainly below, and the same explanation about the second frame  53 - 2  is omitted. 
     As shown in  FIG.  7   , the first frame  53 - 1  has a base section  54  and an upright section  55 . For example, the first frame  53 - 1  has a left-right symmetric shape about a central axis CL in the Z-axis direction. 
     As an example, the base section  54  is a rod-like portion extending straight in the horizontal direction and having a rectangular cross-sectional shape. For example, the base section  54  has, at its both ends, support sections that support spheres T. As an example, the lower surface of the base section  54  is a flat surface. Specifically, the base section  54  supports the first sphere T1 on the upper surface of one end and the second sphere T2 on the upper surface of the other end. 
     The upright section  55  extends from the base section  54  upward in the Z-axis direction. As shown in  FIG.  7   , the upright section  55  has an isosceles triangle shape in which oblique sides  55   a  and  55   a  are left-right symmetric about the central axis CL. 
     As shown in  FIG.  8   , each oblique side  55   a  has inclined surfaces  55   a ′. Each inclined surface  55   a ′ is a flat surface facing upward from the three-dimensional-measuring-apparatus inspection gauge  50 . In a case that the inclined surface  55   a ′ is formed as a flat surface in this manner, there is an advantage that the probe  25  of the three-dimensional measuring apparatus  1  is less likely to be damaged even if the probe  25  moves downward in the Z-axis direction toward the inspection gauge  50  with momentum for some cause and hits the inclined surface  55   a ′. In one example, a distance d 50  from the sphere T1 to the lower end of the oblique side  55   a  of the upright section  55  is longer than 10%, and more specifically is longer than 15%, of the distance between the centers of the sphere T1 and sphere T3. 
     For example, all of the first coupling member  56 - 1 , the second coupling member  56 - 2  and the third coupling member  56 - 3  (also referred to as coupling members  56 ) are formed of a metal material and have identical shapes. The coupling members  56  are members for coupling the first frame  53 - 1  and the second frame  53 - 2 . As an example, the coupling members  56  are rod-like members extending straight in the Y-axis direction. For example, the lower surfaces of the coupling members  56  are flat surfaces, and the lower surfaces of the coupling members  56  may be positioned flush with the lower surfaces of the base sections  54  or may be positioned above the lower surfaces of the base sections  54 . 
     The first coupling member  56 - 1  couples a portion near a first-sphere-T1 support section of the first frame  53 - 1  and a portion near a fourth-sphere-T4 support section of the second frame  53 - 2 . The second coupling member  56 - 2  couples a portion near a second-sphere-T2 support section of the first frame  53 - 1  and a portion near a fifth-sphere-T5 support section of the second frame  53 - 2 . The third coupling member  56 - 3  couples a portion near a third-sphere-T3 support section of the first frame  53 - 1  and a portion near a sixth-sphere-T6 support section of the second frame  53 - 2 . According to such configuration, the pair of the frames  53 - 1  and  53 - 2  are coupled by the three coupling members  56  at portions near the support sections supporting the spheres T, and so the frame member  51  can support the spheres T with high positional precision. Note that, in a configuration for example in which two spheres are supported on the ends of the elongated member respectively, “portion near a support section” mean not a central section but a portion near an end of the member in the lengthwise direction. Specifically, as an example, a “portion near the support section” also includes an area which is apart from a sphere support section by a length which is equal to 20% of the distance between spheres. 
     (Relationship Between Shape of Inspection Gauge  50  and Space where Probe  25  Moves) 
       FIG.  9    and  FIG.  10    are figures for explaining a relationship between the shape of the inspection gauge  50  and a space where the probe unit  20  moves (simple inspection). Similarly,  FIG.  11    and  FIG.  12    are figures for explaining a relationship between the shape of the inspection gauge  50  and a space where the probe  25  moves (detailed inspection). 
     The inspection gauge  50  formed in a shape like the one mentioned above forms a first space SP 1  in an area above spheres T as shown in  FIG.  9    and  FIG.  10    (only a space above the spheres T1 and T4 is depicted in the figures). 
     The first space SP 1  is a space for allowing the probe unit  20  to approach the spheres T in a state where the probe  25  is caused to assume a position in which it points the direction of the elevation angle of 0°, and no member of the frame member  51  is present in the first space SP 1 . Such a first space SP 1  being formed above the spheres T allows the three-dimensional measuring apparatus  1  to perform the simple inspection with the inspection gauge  50 . 
     Regarding details of the shape of the first space SP 1 , the first space SP 1  has an X-axis length (see  FIG.  9   ) which is longer than the outer shape of the probe unit  20  in the X-axis direction, for example. 
     The first space SP 1  is formed to have a Y-axis length (see  FIG.  10   ) which is longer than a distance from the first sphere T1 to the fourth sphere T4 (in one example, the distance between the farthest points of the first sphere T1 and fourth sphere T4). The first space SP 1  being formed in an area from the first sphere T1 to the fourth sphere T4 in this manner allows the probe unit  20  to move in the Y-axis direction in the first space SP 1  and perform measurement of the fourth sphere T4 directly after performing measurement of the first sphere T1, for example. 
     Note that although the first space SP 1  corresponding to the first sphere T1 and the fourth sphere T4 is described as an example, first spaces SP 1  similar to the one described above are also formed in an area from the second sphere T2 to the fifth sphere T5 and an area from the third sphere T3 to the sixth sphere T6. 
     Next, as shown in  FIG.  11    and  FIG.  12   , the inspection gauge  50  forms a second space SP 2  in an area above spheres T (only a space above the spheres T1 and T4 is shown in the figures). 
     As an example, the second space SP 2  is a space that allows the probe unit  20  to approach the spheres T and the like from above and from a lateral side in a state where the probe  25  is caused to assume a position in which it points the direction of the elevation angle of 45° or 90°. No members of the frame member  51  is present in the second space SP 2 . 
     As shown in  FIG.  11   , the second space SP 2  is formed in such a shape that the probe unit  20  can approach the sphere T1 from the inner-space side of the triangular prism  100 . Specifically, in this example, the upright section  55  of the first frame  53 - 1  is formed such that the X-axis direction width ofthe upright section  55  is slightly smaller than the width of the triangle  100   a  of the triangular prism  100 . Accordingly, the second space SP 2  is formed not only in the area directly above the sphere T1, but also in an area inside the triangular prism  100 . As a result, it is possible to allow the probe unit  20  to move in the X-axis direction relative to the sphere T1 from the inner-space side of the triangular prism  100  to thereby cause the tip of the probe  25  to contact the sphere T1. 
     More specifically, the second space SP 2  has an X-axis length (a length “di” between the sphere T1 and a triangular-prism-100-side plane of the second space SP 2 ) which is longer than the outer shape of the probe unit  20  in the X-axis direction, for example. The second space SP 2  configured as above allows the probe unit  20  to move in the X-axis direction from the inner-space side of the triangular prism  100  toward the sphere T1. 
     The second space SP 2  is formed to have a Y-axis length (see  FIG.  12   ) which is longer than a distance from the first sphere T1 to the fourth sphere T4, similarly to the first space SP 1 . The second space SP 2  being formed in an area from the first sphere T1 to the fourth sphere T4 in this manner allows the probe unit  20  to move in the Y-axis direction in the second space SP 2 , and perform measurement of the fourth sphere T4 directly after performing measurement of the first sphere T1 in a state where the probe  25  is at the elevation angle of 45° or 90°, for example. 
     Although the second space SP 2  for the first sphere T1 and the fourth sphere T4 is described as an example, second spaces SP 2  similar to the one described above are also formed in an area from the second sphere T2 to the fifth sphere T5 and an area from the third sphere T3 to the sixth sphere T6. 
     (Three-Dimensional-Measuring-Apparatus-1 Inspection Method) 
       FIG.  13    is a flowchart of a three-dimensional-measuring-apparatus-1 inspection method using the inspection gauge  50 . One example of inspection operation of the three-dimensional measuring apparatus  1  is explained below. 
     First, at Step S 1 , an operator who inspects the three-dimensional measuring apparatus  1  places the inspection gauge  50  at a predetermined position on the table  2 . Specifically, the operator places the inspection gauge  50  at the predetermined position on the table  2  referring to a position indication part formed on the table  2  as a reference point. For example, the inspection gauge  50  is arranged on the table  2  of the three-dimensional measuring apparatus  1  in such a direction that the extending direction of the coupling members  56  of the inspection gauge  50  coincides with the Y-axis direction in the coordinate system of the three-dimensional measuring apparatus  1 . 
     Basically, the inspection gauge  50  may be placed at any position on the table  2 . Since measurement is performed in a state where the direction of the probe  25  has been changed to different positions in the second inspection mode, as an example, the inspection gauge  50  is preferably placed at the center of the coordinate system of the three-dimensional measuring apparatus  1 . In some case, a user might place a work in an end area of the measurement space of the three-dimensional measuring apparatus  1  when the measurement is carried out. In such a case, the user may place the inspection gauge  50  at a position where she/he usually places a work for inspection. 
     At Step S 2 , for example, the operator inputs to the three-dimensional measuring apparatus  1  an instruction as to which type of inspection operation is to be implemented via a user interface displayed on the display section of the three-dimensional measuring apparatus  1 . For example, the operator selects the simple inspection, which is an inspection in the first inspection mode, or the detailed inspection, which is an inspection in the second inspection mode. 
     At Step S 3 , the operation control section  331  of the three-dimensional measuring apparatus  1  causes the three-dimensional measuring apparatus  1  to perform either the first-mode inspection operation or the second-mode inspection operation based on a selection for the inspection mode by the operator. The three-dimensional measuring apparatus  1  measures the to-be-measured distances, which are the distances between the spheres T1 to T6 of the inspection gauge  50  by causing the tip of the probe  25  to contact the six spheres T1 to T6 of the inspection gauge  50 . Specifically, for example, in a case that an instruction for selecting the first inspection mode is received, the three-dimensional measuring apparatus  1  measures the to-be-measured distances, which are the distances between the plurality of spheres T by causing the probe  25  to contact the spheres T while the probe  25  is at a predetermined position (pointing downward in the Z-axis direction). 
     At Step S 4 , the measurement data processing section  332  of the three-dimensional measuring apparatus  1  determines whether or not the measured to-be-measured distances are within the predetermined appropriate range, and determines whether or not there is an anomaly of the three-dimensional measuring apparatus  1 . In a case that it is determined that there is an anomaly, the display processing section  333  causes the display section which is not shown to display information to that effect. In addition, in a case that it is determined that there is an anomaly, the operation control section  331  may automatically switch the inspection mode from the first inspection mode to the second inspection mode, and cause the three-dimensional measuring apparatus  1  to perform operation of the detailed inspection. 
     Although measurement of the six spheres T1 to T6 can be performed in any order in the second inspection mode (detailed inspection), for example the operation control section  331  may move the probe  25  such that measurement is performed in the order of the first sphere T1, the fourth sphere T4, the second sphere T2, the fifth sphere T5, the third sphere T3 and the sixth sphere T6 at a certain probe position. Thereafter, the three-dimensional measuring apparatus  1  may perform measurement of the all spheres T1 to T6 continuously in the same order as that described above at another probe position. In a case that the spheres T1 to T6 are measured continuously, influence of positioning errors of the probe  25  can be reduced. 
     In addition, regarding the position of the probe  25 , for example in a case that measurement of a sphere T is performed in a state where the probe  25  is caused to assume a position with the elevation angle of 45° and the azimuth of 90° (e.g. the positive direction along the X axis in  FIG.  4   ), measurement of the sphere T may also be carried out at a position with the elevation angle of 45° and the azimuth of −90° (e.g. the negative direction along the X axis in  FIG.  4   ) corresponding to the angles of 45° and the azimuth of 90°. 
     Advantageous Effects 
     Although conventional gauges cannot be used for both the simple inspection, which is a daily inspection, and the detailed inspection of the three-dimensional measuring apparatus  1 , the inspection gauge  50  according to present embodiment can be used for both the simple inspection and the detailed inspection for the three-dimensional measuring apparatus  1 . In addition, the inspection gauge  50  according to the present embodiment enables the probe  25  to approach the spheres T from the inner-space side of the triangular prism. Accordingly, for example, measurement of the spheres T on the same plane in the three-dimensional measuring apparatus space (for example, the spheres T1 and T4) can be performed with the probe  25  at different positions; therefore, high motion error estimation precision can be achieved. Accordingly, the precision of inspection of the three-dimensional measuring apparatus using the inspection gauge (particularly, inspections using motion errors as an indicator) can be enhanced. 
     According to the configuration of the present embodiment, the first frame  53 - 1  supports the three spheres T1 to T3. It is conceivable that the spheres T are supported not only by the first frame  53 - 1  but also by the coupling members  56 . It should be noted that according to configuration like the one in the present embodiment, the spheres T can be supported with high positional precision without being influenced by assembly-related dimensional errors of the first frame  53 - 1  and the coupling members  56 . Similar advantageous effects can also be achieved with the second frame  53 - 2 . Furthermore, assembly-related dimensional errors of a plurality of members do not occur in a case that the first frame  53 - 1  and the second frame  53 - 2  are formed of a single member, and so the positional precision of the spheres T is enhanced further. 
     Although the present inventions have been explained referring to an embodiment thus far, the technical scope of the present invention is not limited by the scope described in the embodiment described above, but various modifications and changes are possible within the scope of the gist of the present invention. For example, the frame member is not limited to the specific shape shown in the drawings of the above embodiment. The frame member is not limited to a frame configuration but may be any supporting structure. 
     Instead of configuration like the one mentioned above having the base sections  54  and the upright sections  55  having isosceles triangle shapes, the frames  53 - 1  and  53 - 2  of the frame member  51  may be configured such that they have the base sections  54  and rod-like members extending vertically upward out from the base sections  54 . As an example, the rod-like members may extend perpendicularly upward from the base sections  54 . 
     Although the three-dimensional measuring apparatus  1  including the table  2  is described as an example in the embodiment described above, the three-dimensional-measuring-apparatus inspection gauge  50  of the present invention can be used in a three-dimensional measuring apparatus having no table  2  is, where a work is placed on a predetermined mounting surface such as the ground, for example. An inspection gauge for three-dimensional measuring apparatus according to the embodiments of the present invention may include a plurality of the targets to be measured that are disposed at each vertex of a triangular prism with one of the side surfaces facing the bottom surface of the frame member. This configuration enables inspection of three-dimensional measuring apparatus with greater precision than conventional triangular pyramid-type gauges. In one embodiment of this configuration, it is preferable that a space in which the probe unit  20  can move is formed between a certain target (e.g., sphere T2) on one bottom surface of the triangular prism and a corresponding target (e.g., sphere T5) on the other bottom surface. The same applies to the spaces between spheres T1 and T4 and between spheres T3 and T6. 
       FIG.  14    is a figure showing one modified example of a three-dimensional-measuring-apparatus inspection gauge. As shown in  FIG.  14   , the frame member  51  may have three supporting parts  58  that support the three-dimensional-measuring-apparatus inspection gauge  50  for the three-dimensional measuring apparatus when the the inspection guage  50  is placed on the table of the three-dimensional measuring apparatus  1 . The supporting part  58  may be any shape having a tip end that makes point contact with the surface of the table. The supporting parts  58  may be provided on the lower surface of the base section  54 . As an example, two supporting parts  58  may be provided on one base portion  54  and one support  58  is provided on the other base section  54 . The three supporting parts  58  may be positioned at the corners of an equilateral triangle. 
     Regarding changes and modifications of the present invention, for example, an apparatus can be entirely or partially configured in a functionally or physically distributed/integrated manner in any units. In addition, new embodiments generated by any combinations of a plurality of embodiments are also included in embodiments of the present invention. Advantageous effects of the new embodiments generated by the combinations have combinations of advantageous effects of the original embodiments. 
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
           1 : Three-dimensional measuring apparatus 
           2 : Table 
           10 : Moving mechanism 
           11 : Column 
           12 : Supporter 
           13 : Beam 
           14 : Y-axis-direction driving section 
           15 : Slider 
           20 : Probe unit 
           23 : Z-axis spindle 
           24 : Position changing mechanism 
           25 : Probe 
           30 : Control unit 
           31 : Interface section 
           32 : Storage section 
           33 : Control section 
           41 : Support member 
           41   a : Shaft section 
           50 : Three-dimensional-measuring-apparatus inspection gauge 
           51 : Frame member 
           53 - 1 : First frame 
           53 - 2 : Second frame 
           54 : Base section 
           55 : Upright section 
           55   a : Oblique side 
           55   a ′: Inclined surface 
           56 : Coupling member 
           100 : Triangular prism 
           100   a : Triangle 
           100   b : Triangle 
           331 : Operation control section 
           332 : Measurement data processing section 
           333 : Display processing section 
         SP 1 : First space 
         SP 2 : Second space 
         T: Sphere