Laser length calibration device and laser length calibration method.

Abstract

This invention provides a laser measurement length calibration device that can perform highly accurate length calibration when used in conjunction with a reflective optical displacement meter that utilizes laser light. [Solution] The laser measurement length calibration device (1) comprises a base portion (1A) having a reference plane (PR) extending in the calibration length direction (C), and a pair of V-shaped projections (1B) projecting from the base portion (1A) toward the opposite side of the reference plane (PR). Each V-shaped projection (1B) has a pair of inclined planes (P1, P2) that intersect with the reference plane (PR) at a line of intersection (L) parallel to the reference plane (PR), forming a predetermined interior angle (θ). In each V-shaped projection (1B), the interior angle (θ) formed by the pair of inclined planes (P1, P2) is between 100 degrees and 140 degrees. Furthermore, the distance (D1) between the line of intersection (L1) of the first V-shaped projection (1B1) and the reference plane (PR) is equal to the distance (D1) between the line of intersection (L2) of the second V-shaped projection (1B2) and the reference plane (PR).

Description

Technical Field

[0001] The present disclosure relates to a length calibration instrument for laser measurement and a laser measurement length calibration method.

Background Art

[0002] To measure the shape of a workpiece to be measured, a contact measurement device as disclosed in Patent Document 1 below is known. The contact measurement device disclosed in Patent Document 1 includes a probe with a ruby ball attached to its tip, and measures the shape by bringing the ruby ball into contact with the surface of the workpiece. Such a contact measurement method takes time for measurement because it is necessary to move the ruby ball to the measurement point. Also, attention must be paid to how the ruby ball at the tip of the probe contacts the workpiece surface from which direction. Therefore, measurement of the shape of a workpiece is also performed using a reflection type optical displacement meter that utilizes the reflection of laser light.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such measurement using laser light, calibration is required in advance. In particular, calibration of the distance between two points, that is, the length is required. In the contact measurement method having the probe described above, length calibration is performed using a gauge block or the like. A gauge block is a block having a predetermined reference length and usually has a rectangular parallelepiped shape. When the lengths of the four side surfaces of the gauge block have the reference length, length calibration can be performed by bringing the ruby ball at the tip of the probe into contact with a pair of end surfaces located at both ends of those side surfaces.

[0005] However, reflective optical displacement meters, which use reflected laser light for measurement, have difficulty detecting edges that intersect at right angles. When a laser beam is shone at a right angle onto a side surface having the aforementioned reference length, the distance to that side surface can be measured with a reflective optical displacement meter, but it is difficult to accurately detect the position of the edge from the reflected light at its end. Therefore, it is difficult to calibrate the length of a reflective optical displacement meter using the edges at both ends of a side surface having a reference length, utilizing the reflection of laser light.

[0006] Next, let's consider detecting edges by changing the direction of the laser beam so that the laser beam can be irradiated onto both the side and end faces from a direction that allows for irradiation of both surfaces. In this case, the angle of incidence of the laser beam onto the side or end face becomes about 45 degrees, and the intensity of the reflected light becomes weak, making edge detection still difficult. Furthermore, the direction of the laser beam irradiation must be changed for one edge and the opposite edge.

[0007] The purpose of this disclosure is to provide a laser measurement length calibration device that enables highly accurate length calibration when used with a reflective optical displacement meter that utilizes laser light, and a laser measurement length calibration method using this length calibration device. [Means for solving the problem]

[0008] The laser length calibration instrument according to this disclosure comprises a base portion having a reference plane extending in the calibration length direction, and a pair of first and second V-shaped projections projecting from the base portion toward the opposite side of the reference plane, wherein each of the pair of first and second V-shaped projections has a pair of first and second inclined planes that intersect with the reference plane at a line of intersection parallel to the reference plane, forming a predetermined interior angle, the interior angle formed by the first and second inclined planes in each of the pair of first and second V-shaped projections is 100 degrees or more and 140 degrees or less, and the distance between the line of intersection of the first V-shaped projection and the reference plane is equal to the distance between the line of intersection of the second V-shaped projection and the reference plane.

[0009] The length calibration device described above may further include a third plane that intersects at a right angle with the respective lines of intersection of the pair of first and second V-shaped projections.

[0010] In addition, the length calibration device may further include a fourth plane that is parallel to the third plane and is opposite to the third plane.

[0011] Furthermore, the surface roughness of at least the first and second inclined planes may be 0.2 μm or more and 1.6 μm or less.

[0012] Furthermore, in each of the pair of first and second V-shaped protrusions, the virtual plane that bisects the interior angle θ may intersect the reference plane at an angle of 70 degrees or more and 90 degrees or less.

[0013] In the laser measurement length calibration method using the laser measurement length calibration device described above, a reflective optical displacement meter using laser light is scanned and moved in the calibration length direction so as to sequentially straddle the two intersection lines of the pair of first and second V-shaped protrusions, and the distance between the two intersection lines in the calibration length direction of the length calibration device is measured with the reflective optical displacement meter, and length calibration is performed in the measurement of the reflective optical displacement meter based on the measured distance between the intersection lines. [Effects of the Invention]

[0014] The laser length calibration device described in this disclosure can be used in conjunction with a reflective optical displacement meter that utilizes laser light to perform highly accurate length calibration. The laser length calibration method described in this disclosure, using the above-mentioned length calibration device, can perform highly accurate length calibration. [Brief explanation of the drawing]

[0015] [Figure 1] This is a perspective view showing the length calibration device according to the embodiment together with a laser displacement meter. [Figure 2] This is a perspective view showing a typical gauge block together with a laser displacement meter. [Figure 3]It is a schematic side view for explaining edge detection of a gauge block using a laser displacement meter. [Figure 4] It is a schematic perspective view showing a three - dimensional measuring machine used in the length calibration method according to the embodiment. [Figure 5] It is a block diagram of the above three - dimensional measuring machine. [Figure 6] It is a perspective view for explaining the scanning measurement of the chevron protrusion of the above length calibration instrument. [Figure 7] It is a figure for explaining the above scanning measurement result. [Figure 8] It is a schematic configuration diagram showing the configuration of a laser displacement meter. [Figure 9] It is a partially enlarged side view showing a modification example of the above embodiment.

Mode for Carrying Out the Invention

[0016] The length calibration instrument for laser measurement according to the embodiment will be described with reference to FIGS. 1 and 2.

[0017] When using a reflection - type optical displacement meter using laser light to measure the shape or posture of a workpiece to be measured, calibration is performed in advance to ensure the measurement results by this reflection - type optical displacement meter. The length calibration instrument 1 of the present embodiment shown in FIG. 1 is manufactured so that the length calibration can be appropriately performed. When calibrating the length measurement by measuring the distance between two points, the length calibration instrument 1 is used.

[0018] The length calibration instrument 1 of this embodiment is made of metal, but it may be made of other materials such as ceramics or resins. As shown in FIG. 1, the length calibration instrument 1 includes a base portion 1A and a pair of first chevron-shaped protruding portions 1B1 and second chevron-shaped protruding portions 1B2. When there is no need to distinguish between the first chevron-shaped protruding portion 1B1 and the second chevron-shaped protruding portion 1B2 for description, it is simply referred to as the chevron-shaped protruding portion 1B. The base portion 1A has a reference plane PR extending in the calibration length C direction. The first chevron-shaped protruding portion 1B1 protrudes integrally from the side surface of the base portion 1A toward the side opposite to the reference plane PR from one end of the base portion 1A, that is, the upper end in FIG. 1. Similarly, the second chevron-shaped protruding portion 1B2 protrudes integrally from the side surface of the base portion 1A toward the side opposite to the reference plane PR from the other end of the base portion 1A, that is, the lower end in FIG. 1. The first chevron-shaped protruding portion 1B1 and the second chevron-shaped protruding portion 1B2 have the same shape.

[0019] Each chevron-shaped protruding portion 1B includes a pair of first inclined planes P1 and second inclined planes P2 that intersect at an intersection line L parallel to the reference plane PR. The first inclined plane P1 and the second inclined plane P2 form a predetermined interior angle θ. In the length calibration instrument 1 shown in FIG. 1, the inclined plane facing obliquely upward in each chevron-shaped protruding portion 1B is defined as the first inclined plane P1. When distinguishing between the intersection line L of the first chevron-shaped protruding portion 1B1 and the intersection line L of the second chevron-shaped protruding portion 1B2, the intersection line L of the first chevron-shaped protruding portion 1B1 is also referred to as the first intersection line L1, and the intersection line L of the second chevron-shaped protruding portion 1B2 is also referred to as the second intersection line L2. The distance D1 between the first intersection line L1 and the reference plane PR is equal to the distance D1 between the second intersection line L2 and the reference plane PR.

[0020] In this embodiment, the first inclined plane P1 and the second inclined plane P2 have the same shape. The intersection line L is a ridge line, and it can also be said that it is formed by the intersection of the first inclined plane P1 and the second inclined plane P2. The first inclined plane P1 and the second inclined plane P2 including the intersection line L serve as the measurement surface. The distance D2 between the pair of intersection lines L becomes the reference length when performing length calibration. Therefore, the first intersection line L1 and the second intersection line L2 are parallel with a distance D2 therebetween.

[0021] The length calibration device 1 further includes a third plane P3 that intersects the two intersection lines L at a right angle. In this embodiment, the third plane P3 intersects the first inclined plane P1 and the second inclined plane P2 at a right angle. The length calibration device 1 further includes a fourth plane P4 that is the opposite side of the third plane P3 and is parallel to the third plane P3. The fourth plane P4 also intersects the first inclined plane P1 and the second inclined plane at a right angle, similar to the third plane P3. The third plane P3 is formed as a continuous plane from the base portion 1A to the pair of V-shaped protrusions 1B. The fourth plane P4 is also formed as a continuous plane from the base portion 1A to the pair of V-shaped protrusions 1B.

[0022] A recess 1C is formed between a pair of V-shaped protrusions 1B of the length calibration device 1. The surface of the recess 1C is a plane parallel to the reference plane PR. A pair of mounting holes 1D are formed in the base portion 1A, penetrating from the surface of the recess 1C to the reference plane PR. The length calibration device 1 is fixed to a jig or the like by bolts inserted through 1D.

[0023] The interior angle θ formed between the first inclined plane P1 and the second inclined plane P2 is set to be between 100 degrees and 140 degrees, taking into consideration measurement by a laser displacement meter 2 (see Figure 8), which is a reflective optical displacement meter using laser light, as described later. In this embodiment, the interior angle θ is specifically set to 120 degrees. Here, α1 is the angle between the first inclined plane P1 and the plane that includes the first intersection line L1 and is parallel to the reference plane PR. Similarly, α2 is the angle between the second inclined plane P2 and the plane that includes the second intersection line L2 and is parallel to the reference plane PR. In this embodiment, angles α1 and α2 are both 30 degrees.

[0024] Therefore, in this embodiment, the virtual plane PV (see Figure 7) that includes the line of intersection L and bisects the interior angle θ is perpendicular to the reference plane PR. However, the inclination lengths of the first inclined plane P1 and the second inclined plane P2 may be made different so that the virtual plane PV is not perpendicular to the reference plane PR. In other words, the angles α1 and α2 described above may be made different, and this will be explained later with reference to Figure 9 as an example of a modified configuration. However, even in such a case, the interior angle θ is set to be between 100 degrees and 140 degrees.

[0025] The laser displacement meter 2 used in this embodiment is a diffuse reflection type that uses triangulation. As shown in Figure 8, the laser displacement meter 2 is a sensor that measures distance by triangulation using laser light 4. The laser displacement meter 2 has a light-emitting element 5 for the laser light 4, a photodetector 6 for the laser light 4, and an optical system 7 associated with them. The light-emitting element 5 is, for example, a laser diode (LD). The photodetector 6 is, for example, a position-sensitive detector (PSD), a charge-coupled device (CCD), a complementary metal-oxide-semiconductor (CMOS), a linear array, etc. The configuration of the laser displacement meter 2 is well known, and commercially available products can be used.

[0026] The laser displacement meter 2 emits a single-wavelength laser beam 4 toward the length calibration instrument 1 and detects the reflected light reflected from the surface of the length calibration instrument 1. In other words, this laser displacement meter 2 does not use multi-wavelength laser beams such as white lasers, and does not require a spectrometer. Therefore, among the wide variety of laser displacement meters, the laser displacement meter 2 of this embodiment has a relatively simple configuration and is inexpensive. The laser beam 4 from the light-emitting element 5 is focused by the optical system 7 and irradiated onto the object to be measured, such as the length calibration instrument 1. The emitted laser beam 4 is diffusely reflected at the irradiation position 8 on the surface of the object to be measured, and a portion of the reflected light 9 is received by the photodetector 6 via the optical system 7. Based on the intensity distribution of the reflected light 9 detected by the photodetector 6, the distance to the irradiation position 8 is measured using triangulation.

[0027] Therefore, if reflected light does not return from the object to be measured, such as the length calibration device 1, or if the intensity of the reflected light is low, the distance to the object to be measured cannot be measured. Or, even if it can be measured, the accuracy will be low. In this embodiment, by using the length calibration device 1 described above, such constraints are eliminated and accurate length calibration is achieved. Here, a case in which the length calibration of the laser displacement meter 2 is attempted using a gauge block 1X, which is used in general, instead of the length calibration device 1 described above, will be briefly explained with reference to Figures 2 and 3. In the following, with respect to the laser light 4 irradiated onto the surface of the length calibration device 1, β1 in Figure 8 is defined as the angle of incidence, and β2 is defined as the angle of emission of the reflected light 9 from the photodetector 6.

[0028] The gauge block 1X is typically a rectangular parallelepiped. As shown in Figure 2, the length of the gauge block 1X is the reference length D2 described above. If the laser displacement meter 2 can accurately detect the edges at both ends of the gauge block 1X, the upper and lower ends in Figure 2, then length calibration can be performed. However, in reality, as shown in Figure 3, even when the optical axis 4a of the laser beam 4 emitted from the laser displacement meter 2 coincides with the edge, a portion of the laser beam 4 is diffusely reflected from the surface of the gauge block 1X. Therefore, a portion of the reflected light 9 can be detected by the photodetector 6. Note that in Figure 3, the thickness of the laser beam 4 is shown large for clarity. The intensity distribution of the reflected light 9 is shown in the upper part of Figure 3. As can be seen from this intensity distribution, the centroid of the intensity distribution of the reflected light 9 is detected to be offset from the edge. Therefore, accurate length calibration cannot be performed with a general-purpose gauge block 1X.

[0029] By using the length calibration device 1 of this embodiment shown in Figure 1 and performing length calibration using the distance D2 between a pair of intersecting lines L, the limitations that exist when using the general-purpose gauge block 1X shown in Figures 2 and 3 can be eliminated. Furthermore, the surface of the general-purpose gauge block 1X is usually polished, and the reflection of laser light 4 on its surface is close to specular reflection. In this embodiment, as described above, a diffuse reflection type laser displacement meter 2 is used. In the diffuse reflection type laser displacement meter 2, measurement is performed by the intensity distribution of reflected light 9, so if it is specular reflection, limitations such as a narrower measurable range will arise. Therefore, the surface roughness of the length calibration device 1 of this embodiment is set to 0.2 μm or more and 1.6 μm or less.

[0030] To detect the intersection line L located at both ends of the reference length D2 of the length calibration device 1, the first inclined plane P1 and the second inclined plane P2 are measured. Therefore, the surface roughness of the first inclined plane P1 and the second inclined plane P2 must be at least 0.2 μm or more and 1.6 μm or less. The surface roughness referred to here is the centerline average roughness Ra as defined in JIS B 0601:2001. If the surface roughness is less than 0.2 μm, it approaches specular reflection, resulting in limitations such as a narrower measurable range. On the other hand, if the surface roughness exceeds 1.6 μm, the reflected light 9 at the irradiation position 8 is diffused too much, resulting in insufficient intensity of the reflected light 9.

[0031] Next, a length calibration method according to an embodiment using the length calibration device 1 described above will be explained. First, the three-dimensional measuring machine 10 used for calibration will be explained with reference to Figures 4 and 5. The three-dimensional measuring machine 10 comprises a triaxial stage 11, a measurement stage 12, and a laser displacement meter 2. The triaxial stage 11 and the measurement stage 12 are installed on a surface plate 13. Normally, the workpiece to be measured is placed on the measurement stage 12, but during length calibration, the length calibration device 1 described above is placed on it, and the three-dimensional measuring machine 10 measures the length calibration device 1 installed on the measurement stage 12. In other words, the three-dimensional measuring machine 10 performs length calibration by measuring the three-dimensional coordinates of a pair of intersection lines L of the length calibration device 1 and measuring the reference length D2 between them.

[0032] The triaxial stage 11 movably supports the laser displacement meter 2. The triaxial stage 11 consists of linear guides for the X, Y, and Z axes (in the X, Y, and Z directions) that define a Cartesian coordinate system, and the laser displacement meter 2 moves along each axis. The X and Y axes are two axes extending horizontally and perpendicular to each other. The Z axis is an axis extending vertically and perpendicular to the X and Y axes. In the following description, the direction of extension of the X axis will be referred to as the X direction, the direction of extension of the Y axis as the Y direction, and the direction of extension of the Z axis as the Z direction. The measurement stage 12 has a mounting surface 12a on which a workpiece or a measurement target such as a length calibration device 1 is placed.

[0033] In this embodiment, the length calibration device 1 is fixed to the base 3. The base 3 is attached to the length calibration device 1 so that the calibration length direction C of the length calibration device 1 coincides with the Z direction when placed on the mounting surface 12a. Alternatively, the length calibration device 1 may be attached to a jig placed on the mounting surface 12a using the mounting holes 1D, without attaching the base 3 to the length calibration device 1. In this case, it is necessary to align the calibration length direction C of the length calibration device 1 with the X direction or the Z direction. In such cases, the adjustment work can be easily performed by attaching a dial gauge to the triaxial stage 11 and moving the triaxial stage 11 in the X direction or the Z direction while the tip of the measuring probe is in contact with the third plane P3 or the fourth plane P4.

[0034] The measurement stage 12 is connected to a motor (not shown) and rotates around the rotational axis R. The object to be measured operated by the three-dimensional measuring machine 10 has four degrees of freedom (three translational degrees of freedom + one rotational degree of freedom). The three-axis stage 11 is calibrated so that the rotational axis R of the measurement stage 12 is parallel to the Z-axis. Because the three-dimensional measuring machine 10 has four degrees of freedom, the movement mechanism of the three-dimensional measuring machine 10 can reduce the mechanical errors caused by the movement of the laser displacement meter 2 and the object to be measured, and its configuration is simpler compared to other movement mechanisms that have more than four degrees of freedom by incorporating joints.

[0035] The optical axis 4a of the laser beam 4 emitted from the laser displacement meter 2 shown in Figure 8 is parallel to the Y-axis. The optical axis 4a of the laser beam 4 and the optical axis 9a of the reflected light 9 from the irradiation position 8 on the surface of the length calibration instrument 1 to the light receiver 6 define a plane containing these optical axes 4a and 9a, and this plane is approximately parallel to the XZ plane. On this plane are the emission point on the light-emitting element 5, the irradiation position 8, and the centroid of the reflected light 9 determined from the intensity distribution of the reflected light 9 incident on the detection surface of the light receiver 6, and the distance to the irradiation position 8 can be triangulated.

[0036] Figure 5 is a block diagram showing the configuration of the three-dimensional measuring machine 10. As shown in this figure, the three-dimensional measuring machine 10 includes a control unit 14. The control unit 14 includes a calculation unit 15 such as a CPU, a storage unit 16 for storing data and control programs, and an input / output unit 17 for inputting and outputting signals between the three-axis stage 11, the measurement stage 12, and external devices such as the laser displacement meter 2. The control unit 14 controls the three-axis stage 11, the measurement stage 12, and the laser displacement meter 2. For example, the control unit 14 moves the laser displacement meter 2 to a desired coordinate by operating the three-axis stage 11. The control unit 14 also knows the information of each of the four degrees of freedom of the three-dimensional measuring machine 10, and together with the signal of the detection result from the laser displacement meter 2, measures the three-dimensional coordinate of the intersection line L of the length calibration device 1, i.e., the reference length D2.

[0037] To measure the three-dimensional coordinates of the pair of intersection lines L of the length calibration device 1, the laser displacement meter 2 is scanned and moved in the calibration length direction C, i.e., the Z direction, so as to sequentially straddle the pair of first and second intersection lines L1 and L2, as shown in Figure 1, while measuring the length calibration device 1 with the laser displacement meter 2. This scanning measurement allows the pair of intersection lines L to be detected, and the distance between them, i.e., the reference length D2, can be accurately measured. In the state shown in Figure 1, the length calibration device 1 is set up so that its calibration length direction C is the Z direction, and length calibration is performed in the Z direction. However, it is also possible to set up the length calibration device 1 so that the calibration length direction C is the X direction and perform length calibration in the X direction.

[0038] Figures 6 and 7 show the measurement state of the first inclined plane P1 and the second inclined plane P2, including the intersection line L, with the scanning movement described above. In these figures, the laser beam 4 is scanned from the first inclined plane P1 to the second inclined plane P2, but the laser beam 4 may also be scanned from the second inclined plane P2 to the first inclined plane P1. Also, in Figures 6 and 7, the boundary between the first inclined plane P1 and the second inclined plane P2 is shown in an enlarged view, and the boundary is curved. This curved shape is drawn to account for the manufacturing constraints of the length calibration instrument 1 and wear due to use. Even in this case, the intersection line L of the first inclined plane P1 and the second inclined plane P2 is measured by the method described below.

[0039] The laser displacement meter 2 is moved in the Z direction, and measurements are taken while scanning the irradiation position 8 of the laser beam 4 from the first inclined plane P1 to the second inclined plane P2. Since the interior angle θ between the first inclined plane P1 and the second inclined plane P2 is set within the angle range described above, both planes can be accurately measured with a single scanning movement. Through this scanning movement of the laser displacement meter 2, the distance d1 from the laser displacement meter 2 to the first inclined plane P1, or the distance d2 from the laser displacement meter 2 to the second inclined plane P2, can be obtained at each position along the Z direction. A plot of these distances d1 and d2 is shown at the bottom of Figure 7. The data for each distance is stored in the storage unit 16 of the control unit 14.

[0040] The distances d1 and d2 at each position along the Z direction are two-dimensional data distributed on the YZ plane at a predetermined X coordinate on the X axis. The control unit 14 approximates each of the distances d1 and d2 stored in the storage unit 16 with a linear function. The intersection point of the linear function f1 of distance d1 and the linear function f2 of distance d2 is calculated as the three-dimensional coordinate of the intersection line L. In this way, the three-dimensional coordinates of a pair of intersection lines L, i.e., the first intersection line L1 and the second intersection line L2, are obtained on the YZ plane described above. From these coordinates, the distance between the pair of intersection lines L, i.e., the reference length D2, is calculated. The three-dimensional measuring machine 10, including the laser displacement meter 2, is calibrated so that the calculated reference length D2 becomes the actual reference length D2 of the length calibration device 1.

[0041] In the length calibration device 1 of the embodiment described above, at each V-shaped projection 1B, the angle α1 formed between the plane PQ (see Figure 9), which includes the intersection line L and is parallel to the reference plane PR, and the first inclined plane P1, and the angle α2 formed between the aforementioned plane PQ and the second inclined plane P2, are set to be equal. However, as described above, angles α1 and α2 may be different, and a modified example when they are different is shown in Figure 9. However, even in this case, the interior angle θ is set to be between 100 degrees and 140 degrees.

[0042] In the modified length calibration device 1Y shown in Figure 9, the angle α2Y between the surface PQ and the second inclined plane P2 is set to be smaller than the angle α1 between the surface PQ and the first inclined plane P1. The laser beam 4 emitted by the laser displacement meter 2 and the reflected light 9 from the laser beam 4 are also shown in Figure 9. As shown in Figure 8, since the laser displacement meter 2 uses triangulation, the optical axis 4a of the laser beam 4 and the optical axis 9a of the reflected light 9 reflected to the receiver 6 do not coincide. For this reason, as shown in Figure 9, the intensity of the reflected light 9 to the receiver 6 from a surface inclined in the opposite direction to the receiver 6, such as the second inclined plane P2, is weaker. On the other hand, the intensity of the reflected light 9 to the receiver 6 from a surface directed towards the receiver 6, such as the first inclined plane P1, is not weaker.

[0043] Therefore, in this modified example, a V-shaped projection 1B is formed so that the second inclined plane P2 is directed more toward the light receiver 6. In the embodiment described above, the virtual plane PV that bisects the interior angle θ intersects the reference plane PR at a right angle. In this modified example, the angle γ between the virtual plane PV that bisects the interior angle θ and the reference plane PR is less than 90 degrees. That is, in the embodiment described above, this angle γ is 90 degrees. If the angle γ is 90 degrees, the length calibration device 1 can be used without worrying about the orientation of the laser displacement meter 2, making it easier to handle. On the other hand, if the angle γ is less than 90 degrees as in this modified example, it becomes necessary to pay attention to the orientation of the laser displacement meter 2, but the measurement accuracy can be improved. The angle γ between the virtual plane PV and the reference plane PR is defined on the obtuse angle side and takes a value of 90 degrees or less.

[0044] However, if the internal angle θ is set within the optimal range described above, and the angle γ is too small, the orientation of the first inclined plane P1 will not be suitable for reflection to the light receiver 6, so it is preferable that the angle γ be 70 degrees or more. In this way, the entire pair of first inclined planes P1 and second inclined planes P2 may be inclined with respect to the reference plane PR. The length calibration instrument 1,1Y has a pair of V-shaped protrusions 1B, and the side on which the entire first inclined plane P1 and second inclined plane P2 are inclined is the same for both V-shaped protrusions 1B. In the above embodiment and the above modification, the angle γ formed by the two V-shaped protrusions 1B is the same, but it may be different.

[0045] The length calibration instruments 1 and 1Y according to the above embodiment include a base portion 1A having a reference plane PR extending in the calibration length direction C, and a pair of first V-shaped projections 1B1 and second V-shaped projections 1B2 projecting from the base portion 1A toward the opposite side of the reference plane PR. Each of the pair of first V-shaped projections 1B1 and second V-shaped projections 1B2 has a pair of first inclined planes P1 and second inclined planes P2 that intersect with each other at an intersection line L parallel to the reference plane PR, forming a predetermined interior angle θ. In each of the pair of first V-shaped projections 1B1 and second V-shaped projections 1B2, the interior angle θ formed by the first inclined plane P1 and second inclined plane P2 is between 100 degrees and 140 degrees. Furthermore, the distance D1 between the intersection line L1 of the first V-shaped projection 1B1 and the reference plane PR is equal to the distance D1 between the intersection line L2 of the second V-shaped projection 1B2 and the reference plane PR.

[0046] Therefore, the length calibration devices 1 and 1Y according to the above embodiment are equipped with a pair of intersection lines L spaced apart by a distance D2 that serves as a reference for length calibration. The pair of intersection lines L are arranged along the calibration length direction C parallel to the reference plane PR, spaced apart by a distance D2, and their distance D1 from the reference plane PR is the same. On both sides of each intersection line L, a pair of inclined planes P1 and P2 are formed to form an interior angle θ suitable for easy and accurate detection by a reflective optical displacement meter using laser light 4, i.e., the laser displacement meter 2 in the above embodiment. Specifically, the interior angle θ is set to be between 100 degrees and 140 degrees. For calibration, it is only necessary to scan the laser light 4 of the reflective optical displacement meter 2 along the calibration length direction C, and according to the length calibration devices 1 and 1Y according to the above embodiment, length calibration can be performed quickly and accurately.

[0047] The length calibration devices 1 and 1Y according to the above embodiment also include a third plane P3 that intersects at a right angle with the intersection line L of the pair of first and second V-shaped projections 1B1 and 1B2. Therefore, when setting up the length calibration device 1 for calibration, it is easier to adjust the orientation of the length calibration device 1. For example, when it is desired to align the third plane P3 of the length calibration device 1 with the scanning direction of the reflective optical displacement meter 2, the orientation of the length calibration device 1 can be adjusted while bringing the tip of the dial gauge probe into contact with the third plane P3. As a result, calibration accuracy can be improved.

[0048] Furthermore, the length calibration devices 1 and 1Y according to the above embodiment also include a fourth plane P4 that is parallel to the third plane P3 and is the opposite surface of the third plane P3. Therefore, the length calibration device 1 can be used without distinguishing between the third plane P3 and the fourth plane P4, improving the versatility of the length calibration device 1.

[0049] Furthermore, according to the length calibration devices 1 and 1Y of the above embodiment, the surface roughness of at least the first inclined plane P1 and the second inclined plane P2 is 0.2 μm or more and 1.6 μm or less. Since each intersection line L is measured by measuring these two planes, these two surfaces can be measured accurately by the diffuse reflection type laser displacement meter 2. As a result, calibration accuracy can be improved.

[0050] Furthermore, according to the length calibration devices 1 and 1Y of the above embodiment, in each of the pair of first V-shaped projections 1B1 and second V-shaped projections 1B2, the virtual plane PV that bisects the interior angle θ intersects the reference plane PR at an angle of 70 degrees or more and 90 degrees or less. The embodiment shown in Figure 1, etc., has an angle γ between the virtual plane PV and the reference plane PR of 90 degrees, while the modified example shown in Figure 9 has an angle γ of less than 90 degrees. The upper limit of the angle γ is 90 degrees. It is preferable that the angle γ be 70 degrees or more, because if it is less than 70 degrees, even if the measurement accuracy of one of the pair of inclined planes P1 and P2 (the second inclined plane P2 in the modified example) is improved, there is a risk that the measurement accuracy of the other (the first inclined plane P1 in the modified example) will decrease.

[0051] According to the laser measurement length calibration method of the above embodiment, first, a reflective optical displacement meter using laser light, i.e., a laser displacement meter 2 in the above embodiment, measures the distance D2 between two intersection lines L in the calibration length direction C of the length calibration device 1. At this time, the laser displacement meter 2 is scanned and moved in the calibration length direction C so as to sequentially straddle the two intersection lines L of the pair of first and second V-shaped protrusions 1B1 and 2B2, and the distance D2 is measured. Based on the measured distance D2 between the intersection lines L, length calibration is performed in the measurement of the reflective optical displacement meter 2. According to the laser measurement length calibration method of the above embodiment, the above advantages of the length calibration device 1 can be realized while performing length calibration with high accuracy.

[0052] Although several embodiments have been described, it is possible to modify or transform the embodiments based on the above disclosure. All components of the above embodiments, and all features described in the claims, may be individually selected and combined, provided that they do not contradict each other. For example, in the above embodiments, the reflective optical displacement meter using laser light was a diffuse reflection type laser displacement meter 2, but it may also be a confocal sensor or the like.

[0053] Furthermore, in the above embodiment, a recess 1C was formed between the second inclined plane P2 of the first V-shaped projection 1B1 and the first inclined plane P1 of the second V-shaped projection 1B2. However, the second inclined plane of the first V-shaped projection and the first inclined plane of the second V-shaped projection may be formed on a single continuous plane. For example, a single continuous plane including the intersection lines of the first V-shaped projection and the intersection lines of the second V-shaped projection may be formed between these two intersection lines. The second inclined plane of the first V-shaped projection and the first inclined plane of the second V-shaped projection may then be provided on this continuous plane. That is, in such a case, the second inclined plane of the first V-shaped projection and the first inclined plane of the second V-shaped projection can be considered to be the same continuous plane. Alternatively, a part of this continuous plane can be considered to form the second inclined plane of the first V-shaped projection, and another part can be considered to form the first inclined plane of the second V-shaped projection.

[0054] Alternatively, a continuous concave surface containing the intersection lines of the first V-shaped projection and the second V-shaped projection may be formed between these two intersection lines. The second inclined plane of the first V-shaped projection and the first inclined plane of the second V-shaped projection may be provided on this continuous concave surface. In other words, in such a case, the second inclined plane of the first V-shaped projection and the first inclined plane of the second V-shaped projection can be considered to be the same continuous concave surface. Alternatively, a part of this continuous concave surface can be considered to form the second inclined plane of the first V-shaped projection, and another part can be considered to form the first inclined plane of the second V-shaped projection.

[0055] Furthermore, according to this disclosure, measurements using laser light can be performed quickly and accurately. Therefore, for example, it can contribute to United Nations Sustainable Development Goal (SDG) 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster technological innovation." [Explanation of Symbols]

[0056] 1,1Y calibration equipment 1A Base section 1B Chevron protrusion 1B1 1st chevron protrusion 1B2 2nd chevron protrusion 2. Laser displacement sensor 4. Laser light 9 Reflected light C Calibration in the length direction D2 (distance between a pair of intersecting lines L) L(L1,L2) intersection line P1 1st inclined plane P2 2nd inclined plane P3 3rd plane P4 4th plane PR reference plane PV (virtual plane that bisects the interior angle θ) γ (angle between the reference plane PR and the virtual plane PV) θ interior angle

Claims

1. A length calibration device for laser measurement, A base portion having a reference plane extending in the calibration length direction, It comprises a pair of first and second V-shaped projections that protrude from the base portion toward the opposite side of the reference plane, Each of the pair of first and second V-shaped projections is provided with a pair of first and second inclined planes that intersect with the reference plane at a predetermined interior angle on an intersection line parallel to the reference plane, In each of the pair of first and second V-shaped protrusions, the interior angle formed by the first and second inclined planes is 100 degrees or more and 140 degrees or less. A laser length calibration device in which the distance between the intersection line of the first V-shaped projection and the reference plane is equal to the distance between the intersection line of the second V-shaped projection and the reference plane.

2. A laser length calibration device according to claim 1, A laser length calibration device further comprising a third plane that intersects at a right angle with the respective lines of intersection of the pair of first and second V-shaped protrusions.

3. A laser length calibration device according to claim 2, A laser length calibration device further comprising a fourth plane parallel to the third plane and opposite to the third plane.

4. A laser length calibration device according to any one of claims 1 to 3, A laser length calibration device having a surface roughness of at least 0.2 μm or more and 1.6 μm or less for the first and second inclined planes.

5. A laser length calibration device according to any one of claims 1 to 3, A laser length calibration device wherein, in each of the pair of first and second V-shaped protrusions, a virtual plane that bisects the interior angle θ intersects the reference plane at an angle of 70 degrees or more and 90 degrees or less.

6. A laser measurement length calibration method using a laser measurement length calibration device according to any one of claims 1 to 3, While scanning a reflective optical displacement meter using laser light in the calibration length direction so as to sequentially straddle the two intersection lines of the pair of first and second V-shaped protrusions, the distance between the two intersection lines of the length calibration device in the calibration length direction is measured with the reflective optical displacement meter. A laser measurement length calibration method for performing length calibration in the measurement of the reflective optical displacement meter based on the measured distance between the intersection lines.

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