Shape measurement probe, three-dimensional shape measurement method using same, and non-contact optical measurement device

Abstract

Provided are: a shape measurement probe that can perform measurement without malfunction even after collision with an object to be measured; and a three-dimensional shape measurement device that comprises the shape measurement probe.　The shape measurement probe comprises a probe shaft that rotates and emits measurement light, a rotation mechanism that rotates the probe shaft, a probe base that supports the probe shaft, a probe holder for mechanically connecting the probe base and the rotation mechanism, and a pressing mechanism that presses the probe base and the probe holder at prescribed force and thereby mechanically connects the probe base and the probe holder. The shape measurement probe is configured such that, when force that is equal to or greater than a certain force is applied to the probe shaft, the mechanical connection produced by the pressing mechanism is released, and the tip position of the probe shaft is thereby shifted from a prescribed position.

Description

Shape measurement probe, three-dimensional shape measurement method using the same, and non-contact optical measurement device

[0001] The present invention relates to a shape measuring probe, a three-dimensional shape measuring method using the same, and a non-contact optical measuring device.

[0002] Patent Document 1 discloses a technology that allows the probe to be replaced depending on the purpose of the measurement in an apparatus that emits measurement light and irradiates the measurement light onto the object to be measured (workpiece) via a probe attached to a rotary motor.

[0003] Special Publication No. 2022-549181

[0004] When measuring the shape of a workpiece by bringing a probe close to the workpiece, there is a possibility that the probe may come into contact with the workpiece. If the rotating probe comes into contact with the workpiece, there is a possibility that the workpiece and the probe may be damaged. The technology described in Patent Document 1 provides a function that allows the probe to be easily attached and detached by attaching the probe to a rotary motor using a magnet, but the purpose is to replace the probe depending on the purpose of the measurement, and there is a concern that if the probe collides with the workpiece, the probe may fall off, or if the collision occurs in the axial direction of the probe, a large force may be applied to the probe and motor, causing them to break down.

[0005] The present invention has been made in consideration of the above points, and aims to provide a shape measurement probe that can prevent equipment failure even when the probe collides with a workpiece, a three-dimensional shape measurement method using the same, and a non-contact optical measurement device.

[0006] The present invention achieves the above object by providing the following configuration: A shape measurement probe that emits measurement light from a light source toward a measurement object and receives the measurement light reflected by the measurement object, the shape measurement probe including: a probe shaft that rotates to emit the measurement light; a rotation mechanism that rotates the probe shaft; a probe base that supports the probe shaft; a probe holder for mechanically connecting the probe base to the rotation mechanism; and a pressing mechanism that mechanically connects the probe base to the probe holder by pressing the probe base to the probe holder with a predetermined force, wherein the mechanical connection by the pressing mechanism is released when a force equal to or greater than the predetermined force is applied to the probe shaft, thereby displacing the tip position of the probe shaft from the predetermined position; a three-dimensional shape measurement method using the shape measurement probe; and a non-contact optical measurement device.

[0007] According to the present invention, it is possible to provide a non-contact optical measuring device that is robust against contact and collision with a workpiece.

[0008] Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

[0009] FIG. 1 is a schematic diagram showing an example of a non-contact optical measurement device. FIG. 2 is an enlarged view of the inclinable part of FIG. 1. FIG. 3 is a diagram showing another example of a configuration in which a pressurizing mechanism is realized using a spring. FIG. 4 is a diagram showing the state of the inclinable part when a probe comes into contact with a measurement workpiece. FIG. 5 is a diagram showing another example of a configuration of a kinematic mount. FIG. 6 is a diagram showing yet another example of a configuration of a kinematic mount. FIG. 7 is a diagram showing an embodiment of a mechanism for reproducing the position of a measurement probe shaft other than a kinematic mount mechanism. FIG. 8 is a diagram showing an example of a method for estimating not only the presence or absence of contact but also the method of contact from the outputs of four displacement detectors. FIG. 9 is a schematic diagram showing an example of a non-contact optical measurement device when a robot is used. FIG. 10 is a schematic diagram showing an example of a pressurizing mechanism for a probe holding mechanism realized using magnets. FIG. 11 is a schematic diagram showing a method for increasing the range of motion of a probe holding mechanism by elastically holding a target ring for a displacement sensor against a deforming part of the probe holding mechanism. FIG. 12 is a diagram showing an example of a configuration in which a reflective mirror / optical path switching element is rotated by a small rotating mechanism at the tip of a probe shaft.

[0010] Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

[0011] 1 is a schematic diagram showing an example of a non-contact optical measurement device according to the first embodiment. The non-contact optical measurement device 290 according to the present embodiment includes a probe control mechanism 200, connection cables 150, 151, and 152, a measurement head 160, and a measurement probe 180.

[0012] Hereinafter, an example of a three-dimensional shape measuring device configured as a non-contact optical measuring device will be described. The probe control mechanism 200 controls a distance measurement light source built into the measuring head 160 to output measurement light to the measuring probe 180. The connection cable 150 has an optical fiber and guides the measurement light to the measuring probe 180. The measuring probe 180 is a device that irradiates a measurement workpiece 301 with the measurement light 300, detects reflected light from the measurement workpiece 301 with a detector 173, and guides the detected signal to the probe control mechanism 200 via the cable 151.

[0013] Here, a wavelength-swept laser is used as the measurement light, and the measurement light is separated into measurement light and reference light by coupler 171. The measurement light is guided to circulator 170, passes through it, and a laser is emitted from lens 161 to irradiate the measurement work 301. The light reflected by the measurement work 301 is again focused by lens 161 and returned to the optical fiber, where it is redirected by circulator 170 and combined with the initially separated reference light by coupler 172 to cause interference, which is detected by detector 173, resulting in an interference beat with a frequency proportional to the difference between the distance to the measurement work and the length of the reference optical path. This can be analyzed by probe control mechanism 200 to measure the distance.

[0014] Alternatively, if broadband light is used as the measurement light, the same optical path as above is used, and a spectroscope is used as the detector 173, an interference spectrum can be obtained at the detector. The period of this interference spectrum is proportional to the difference between the distance to the measurement workpiece 301 and the length of the reference optical path, so by processing this with the probe control mechanism 200, it is possible to measure the distance.

[0015] The measurement head 160 and the measurement probe 180 have a lens 161, a rotation mechanism 162, an optical path switching element 163, a measurement probe shaft 164, a polarization state control unit 165, a fixed quarter-wave plate 166, and a rotating quarter-wave plate 167. The lens 161 narrows the measurement light output from the probe control mechanism 200 and guided to the connection cable 150, and guides the light to the measurement probe shaft 164. Under the control of a distance calculation unit (described later), the rotation mechanism 162 uses a driving device such as a motor to rotate the optical path switching element 163 around a rotation axis parallel to the measurement light output from the lens 161.

[0016] The measurement light emitted from the lens 161 is converted into circularly polarized light by a fixed quarter-wave plate 166. The rotation direction of the circularly polarized light is selected by the linear direction controlled by a polarization state control unit 165. This circularly polarized light is converted back into linearly polarized light by a quarter-wave plate 167 that rotates together with the measurement probe shaft 164, and the direction of the axis of the plate 167 relative to the optical path switching element 163 is adjusted in advance so that the direction of the linearly polarized light can be selected to be perpendicular or parallel to the reflecting surface of the optical path switching element 163 depending on the rotation direction of the circularly polarized light.

[0017] The optical path switching element 163 selectively emits light using measurement light whose polarization direction is controlled by the polarization state control unit 165 and quarter-wave plates 166 and 167. The optical path switching element 163 has an optical path switching function, and emits light in at least one of a first direction 300 a, which is the same traveling direction as the traveling direction of the measurement light output from the lens 161, and a second direction 300 b, which is approximately perpendicular to the first direction 300 a. The optical path switching element 163 is, for example, a polarizing beam splitter that selectively emits light depending on, for example, a change in the polarization direction.

[0018] The measurement probe shaft 164 holds the optical path switching element 163 and passes the light emitted from the lens 161. The measurement probe shaft 164 is, for example, cylindrical with an opening facing downward (first direction 300a) as shown in FIG. 1 , and holds the optical path switching element 163 at its tip. The measurement probe shaft 164 rotates around a rotation axis parallel to the measurement light output from the lens 161, and the rotation of the tip of the measurement probe 164 causes the optical path switching element 163 to rotate.

[0019] As another example, if it is not necessary to switch the measurement direction and only measurement in the lateral direction indicated by 300b is required, a simple reflecting mirror may be used instead of the optical path switching element 163. In this case, if fluctuations in the reflection characteristics of the reflecting mirror due to the polarization direction do not pose a problem, the polarization state control unit 165 and the quarter-wave plates 166 and 167 may be omitted.

[0020] The polarization state control unit 165 controls the polarization of the measurement light output from the distance measurement control mechanism (not shown) under the control of the probe control mechanism 200. The polarization state control unit 165 changes the polarization direction of the measurement light, for example.

[0021] As shown in Figure 1, when the measurement target portion of the measurement workpiece 301 has a cylindrical hole shape, the bottom depth of the hole shape can be measured by using measurement light emitted in a first direction 300a by controlling the polarization state of the polarization state control unit 165.

[0022] Furthermore, the light emitted from the light path switching element 163 in the second direction 300b due to polarization control by the polarization state control unit 165 rotates in accordance with the rotation of the light path switching element 163, passes through an opening or wall surface on the side of the tip of the measurement probe shaft 164, and is irradiated onto the measurement work 301. The light reflected or scattered by the measurement work 301 travels the same path as the light emitted in the first direction 300a and reaches the probe control mechanism 200, and the distance to the measurement work 301 is calculated. By rotating the measurement probe 180 using the measurement light emitted in the second direction 300b, it is possible to measure the shape of the side surface of, for example, a cylindrical shape.

[0023] Next, we will explain the three-dimensional shape measuring device equipped with the measurement head 160. The measurement workpiece 301 is mounted on a moving mechanism 500 (an XYZ stage in this figure), which allows the measurement workpiece 301 to approach the measurement probe shaft 164 of the measurement head 160 from various positions and directions, and measurement light 300 is emitted from the measurement probe shaft 164 to measure the shape of the measurement workpiece 301.

[0024] FIG. 1 illustrates an example of a state in which the shape of a hole 311 formed in a measurement workpiece 301 is being measured. In this state, the depth of the hole's bottom can be measured by controlling the measurement light to be emitted in the direction 300a, and the inner diameter shape of the hole can be measured by controlling the measurement light to be emitted in the direction 300b and rotating the rotation mechanism 162. To achieve this, the overall control device 225 issues commands to the movement mechanism control device 215, which may be an XYZ stage controller, a CMM (Coordinate Measurement Machine), a robot controller, or the like, to drive the movement mechanism 500 and control the desired positional relationship between the measurement probe shaft 164 and the measurement workpiece 301. Next, the overall control device 225 issues commands to the probe control mechanism 200, which then uses the measurement head 160 to measure the shape as described above.

[0025] In this explanation, the measurement workpiece 301 is described as being mounted on the moving mechanism 500 (XYZ stage), but various other configurations are possible as long as it is possible to change the relative positional relationship between the measurement probe shaft 164 and the measurement workpiece 301. For example, the moving mechanism 500 may be an XY stage instead of an XYZ stage, and the relative movement in the vertical direction between the measurement probe shaft 164 and the measurement workpiece 301 may be achieved by mounting the measurement head 160 on a Z stage (not shown) and driving this.

[0026] It is also possible to use a stage mechanism of a five-axis machining center as the moving mechanism 500, or to grip the measuring head 160 instead of the machining tool of the five-axis machining center and measure the shape of the workpiece before and after machining on the machining device. In this case, the measuring head 160 is mounted on an XYZ stage (not shown), and the measurement workpiece 301 is mounted on the XYZ stage. In this case, the stage is a two-axis rotating stage. This makes it possible to approach the measurement probe shaft 164 to any position on the measurement workpiece 301 in any orientation.

[0027] When the relative positions of the measurement probe shaft 164 and the measurement workpiece 301 are moved, contact between the measurement probe shaft 164 and the measurement workpiece 301 or the movement mechanism 500 may occur due to an installation error of the measurement workpiece 301, an error in the shape of the measurement workpiece 301, an error in the program of the movement mechanism 500, or other errors. Conventionally, when such contact occurs, serious damage occurs to the measurement probe shaft 164 and the measurement head 160, particularly the rotation mechanism 162, making it necessary to replace or repair the entire measurement head 160, which can result in high costs and the inability to perform measurements for a long period of time.

[0028] In view of these problems, the present invention provides a function in which, when contact occurs, a part of the measurement probe 180 reversibly deforms to deflect the force caused by contact between the measurement probe shaft 164 and the workpiece 301, and at the same time detects the contact and stops the movement mechanism 500, thereby keeping the deformation within the range of reversible deformation of the measurement probe 180 and preventing damage to the measurement probe 180, the main body of the measurement head 160, the workpiece 301, etc. Furthermore, even if the deformation is large and damage remains in the components of the measurement probe 180, the present invention provides a function that allows repairs to be carried out easily, at low cost, and with short downtime, by replacing the measurement probe 180 with a spare one.

[0029] The measurement probe 180 of the present invention is formed by the following configuration shown in FIG. 1 in addition to the measurement probe shaft 164, the rotating quarter-wave plate 167, and the reflecting mirror / optical path switching element 163 already described.

[0030] To explain this part, FIG. 2, which is an enlarged view of the relevant part of FIG. 1, will also be used.

[0031] First, we will explain the part consisting of the probe mounting part 187 attached to the rotation mechanism flange part 189 of the rotation mechanism 162 inside the measurement head 160, the pillars 185 that support the disk-shaped part of the probe base 181 relative to the probe mounting part 187, and the mounting screws 186 that fix the measurement head 160 to the rotation mechanism flange part 189. These parts rotate integrally with the rotation mechanism 162 via the mounting screws 186 and are parts that do not deform when the measurement workpiece 301 comes into contact with the measurement probe shaft 164. The probe shaft part reversibly displaces relative to this part, thereby realizing the function of deflecting the force caused by contact. Note that although the example in Figure 1 shows three pillars 185, the number of pillars can be one or any number greater than one as long as sufficient strength is maintained.

[0032] Next, the probe shaft portion will be described. The probe base 181 is pressed against the probe holder 184 by a pressure mechanism 183 such as a spring. The center of the probe base 181 is hollow, and the measurement probe shaft 164 is firmly fixed thereto. With this configuration, the measurement probe shaft 164 normally rotates integrally with the rotation mechanism 162. However, when a force due to contact with the measurement probe shaft 164 is applied to the measurement probe shaft 164, such as the workpiece 301, the force acting on the pressure mechanism 183 exceeds the applied pressure, causing the probe base 181 to float up from the probe holder 184 and deflect the force due to contact between the measurement probe shaft 164 and the workpiece 301. When the force due to contact is released, the probe base 181 is pressed against the probe holder 184 again, thereby restoring the unity of the rotation mechanism 162 and the measurement probe shaft 164. In FIG. 1, the pressure applying mechanisms are provided at three locations indicated by circles, but the number of locations is not limited to three. For example, as shown in FIG. 3, even if the probe base 181 is pressed against the probe holder 184 by a single spring 183′ arranged so that the coil surrounds the center of rotation through which the optical path of the measurement light 300 passes, it is possible to apply pressure stably without blocking the optical path of the measurement light 300.

[0033] Here, since it is necessary to be able to reproduce the positional relationship between the probe base 181 and the probe holder 184 when they are pressed against each other, the embodiment shown in FIG. 1 employs a kinematic mount mechanism. A kinematic mount is a mechanism that uniquely determines the six degrees of freedom of the position and orientation of an object by pressing against it. There are various variations, but in FIG. 1 , a kinematic mount is configured in three locations: two approximately parallel rods 182 b attached to the probe holder 184 and one sphere 182 a attached to the probe base 181 (this pair forms one component of the kinematic mount 182). By pressing the sphere against the parallel rods, the center position of the sphere is constrained to a straight line, determining two degrees of freedom. By using three sets of these pairs, all six degrees of freedom are determined, allowing stable reproduction of position and orientation with sub-micrometer accuracy.

[0034] The operation of the probe when it comes into contact will be further explained using Figure 4. Figure 4(a) is a reprint of the same view as the enlarged view of the tiltable portion of the measurement probe 180 in Figure 3. In contrast to this, Figure 4(b) shows the state in which the tip of the measurement probe 180 comes into contact with the measurement workpiece 301 from the side, and a force is applied to the right in the figure. In this way, one of the three spheres 182a that make up the kinematic mount (the sphere on the right in the figure) floats relative to the rod 182b, and the measurement probe shaft 164 and probe base 181 rotate counterclockwise, deflecting the force applied to the tip of the measurement probe shaft 164 (not shown) from the left.

[0035] 4(c) is a diagram showing a state in which the workpiece 301 to be measured comes into contact with the tip of the measurement probe 180 from below in the figure, and an upward force is applied to the measurement probe shaft 164. In this way, the three spheres 182a that make up the kinematic mount float relative to the rod 182b, and the measurement probe shaft 164 and probe base 181 move upward, deflecting the force applied from below to the tip, not shown, of the measurement probe shaft 164.

[0036] In either case of Figures 4(a) or (b), when the external force acting on the measurement probe shaft 164 is released, the force of the pressure mechanism 183 (a spring is used in this figure) presses the probe base 181 against the probe holder 184, thereby restoring the constraint provided by the kinematic mount and returning the probe to its original position in Figure 4(a).

[0037] There are other possible configurations for the kinematic mount as described using Figure 3. First, a rod pair may be used on the probe base 181 side and a sphere on the probe holder 184 side. Furthermore, as shown in Figure 5, the same purpose can be achieved by configuring one pair from two adjacent spheres 182a' and one rod 182b'. Also, a V-shaped groove may be used instead of two rods. It goes without saying that the same purpose can be achieved by configuring each pair with any combination of two rods and a sphere, two spheres and one rod, or one sphere and a V-shaped groove.

[0038] Furthermore, instead of assigning the same type of constraint to each of the three pairs, for example, as shown in FIG. 6, a configuration can be used in which the first pair is composed of a sphere and a bowl-shaped cone shape 182a-1 to constrain the position of three degrees of freedom, the second pair is composed of a sphere 182b and a V-shaped groove shape 182a-2 to constrain two degrees of freedom on a straight line, and the third pair is composed of a sphere and a plane 182a-3 to constrain one degree of freedom on a plane.

[0039] Configurations other than the kinematic mount mechanism include a combination of a mating cylinder and a flat portion, or a combination of a conical shape and a mortar shape, which are described in Figures 7(a) and 7(b), respectively. In Figure 7(a), a low-height protrusion 193 with a slanted end is formed at the center of the probe base 181. The outer diameter of this protrusion 193 is specified with a fit tolerance relative to the inner diameter of the center hole of the probe holder 184, so that the rotation center is aligned with an accuracy of approximately 10 micrometers. The vertical height of the page is determined by the contact plane between the probe holder 184 and the probe base 181, so five degrees of freedom other than the probe rotation direction by the rotation mechanism 162 are accurately reproduced. Since precision in the probe rotation direction is not required, this can be left as is, or a key groove and key-like portion can be formed between the probe holder 184 and the probe base 181 to accurately constrain the rotational degree of freedom.

[0040] 7(b), the contact surface between the probe holder 184 and the probe base 181 is made conical and pressed by the pressure mechanism 183, thereby making it possible to constrain five degrees of freedom other than the direction of probe rotation by the rotation mechanism 162. Since precision in the direction of probe rotation is not required to be very high, this may be left as is, or a key groove and a key-like portion may be formed between the probe holder 184 and the probe base 181 to accurately constrain the degree of freedom in the direction of rotation.

[0041] Finally, the contact detection mechanism of the present invention will be described. The probe base 181 is disk-shaped, and contact is detected by a displacement sensor 190 detecting displacement of the disk-shaped portion of the probe base 181 caused by contact of the measurement probe shaft 164 with the measurement workpiece 301. Displacement detection can be performed non-contact by any of the following methods: (1) detecting changes in eddy currents induced in the target disk by electromagnetic induction; (2) detecting changes in capacitance between the target disk and the displacement sensor 190; (3) magnetizing the target and detecting changes in the magnetic field using the displacement sensor 190; (4) irradiating the target disk with light and detecting the intensity of reflected or scattered light; (5) triangulation, in which light is irradiated onto the target disk and a sensor detects changes in the reflection position due to target displacement; or (6) measuring the distance to the target using laser interference. Multiple displacement sensors 190 are arranged so that the distance can be measured at one, two, or preferably three or more locations.

[0042] As will be described in detail later using Figure 8, when the distance between any of the multiple sensors and the probe base 181 approaches and falls below a threshold, contact is detected, causing the contact detection mechanism 199 to issue an alarm and the movement mechanism control device 215 to stop. If three or more displacement sensors 190 are provided here, the direction of contact can be detected, as will be described later. Even if only one displacement sensor 190 is provided, as long as it is positioned so that it can detect the distance close to the center of the probe base 181, no matter in which direction the measurement probe shaft 164 is tilted or displaced in the Z direction, the probe base 181 will always displace in a direction approaching the sensor, making it possible to detect contact of the measurement probe shaft 164.

[0043] Alternatively, as another configuration example, if a sensor that can detect tilt simultaneously with displacement is used as the displacement sensor 190, it is possible to detect contact in various directions with a single displacement sensor with high accuracy. For example, the sensor may be a sensor that has three built-in laser interferometers and detects tilt and displacement from the difference between these, or a sensor that detects tilt by irradiating a laser and detecting the direction of the laser reflected from a target.

[0044] As described above, the operation when the contact detection mechanism 199 issues a contact detection alarm and the movement mechanism control device 215 stops will be described. To release the contact, the operator issues an instruction to the movement mechanism control device 215 via the overall control device 225, changing the relative position of the measurement workpiece 301 and the measurement probe 180. Depending on the device configuration, an interlock function may be activated and the movement mechanism control device 215 may not respond while the contact detection mechanism 199 is issuing an alarm. In such a device configuration, a switch (not shown) that disables the interlock function may be provided in the movement mechanism control device 215, or an interlock release button may be provided on the GUI (graphic user interface) of the overall control device 225, providing a function to disable the interlock during the contact release operation.

[0045] Since the probe shaft 164 may have been damaged during contact, in a desirable configuration, after the contact is released, the overall control device 225 automatically performs an operation check and recalibration, or prompts the operator to perform an operation check and recalibration. Using a calibration workpiece (not shown) placed by the operator on the moving mechanism 500, or a calibration workpiece (not shown) that is always fixed to a part of the moving mechanism 500, the relative positions of the measurement probe 180 and the calibration workpiece are changed, and the calibration workpiece is measured with the measurement probe 180. If the contact speed between the probe and the workpiece is excessive and a large force is applied to the probe shaft 164 before the moving mechanism control device 215 stops, causing irreversible deformation due to plastic deformation or the like, if the deformation is large, the optical path of the measurement light 300 may be blocked, making it impossible to obtain a correct signal. This is determined by the probe control mechanism 200, and the operator is prompted to replace the probe unit 180 via the overall control device 225.

[0046] If the irreversible deformation is minor, for example, on the order of a few micrometers, there is no problem with the measurement function, but the measured radius value changes by the amount of change in the position of the reflecting mirror / optical path switching element 163 at the tip of the probe shaft 164, resulting in errors in the shape and diameter value of the measurement target portion 311 of the workpiece 301 being measured. By measuring a calibration workpiece whose shape is known in advance, it is possible to determine the calibration offset to be added to the radius value to be measured, and to always measure the shape of the measurement workpiece 301 accurately.

[0047] As yet another configuration example, a contact sensor may be used instead of the displacement sensor as the displacement sensor 190 to detect contact between the probe base 181 and the contact sensor due to contact with the measurement probe shaft 164. For example, a strain gauge or piezoelectric element may be used to detect the strain inside the displacement sensor due to contact, or a contact sensor may be used that excites vibration on the surface of the displacement sensor and detects a decrease in the vibration amplitude due to contact as a change in current. Alternatively, a microswitch whose conduction state changes upon contact may be used as the contact sensor. Alternatively, an electrode may be exposed on the surface of the contact sensor, and contact may be detected by a change in electrical resistance due to contact with the probe base 181.

[0048] Furthermore, the rotation mechanism flange portion 189 and the probe mounting portion 187 are formed so that the cylindrical protrusion of the probe mounting portion 187 fits into a cylindrical recess in the rotation mechanism flange portion 189. If the diameters of this cylindrical protrusion and recess are formed with a fit tolerance, it becomes possible to assemble the measurement probe 180 to the rotation mechanism 162 with a variation of around 10 micrometers. In this state, by tightening the mounting screw 186, the rotation mechanism flange portion 189 and the probe mounting portion 187 of the measurement probe 180 are firmly fixed. With this configuration, even if the measurement probe 180 is damaged, it can be easily replaced with a spare measurement probe 180 that has been prepared in advance.

[0049] Alternatively, instead of a fitting structure, a kinematic mount structure may be formed on the contact surface between the rotation mechanism flange portion 189 and the probe attachment portion 187, and a magnet may be incorporated into either the rotation mechanism flange portion 189 or the probe attachment portion 187, with the other being made of a ferromagnetic material, or magnets may be incorporated into both the rotation mechanism flange portion 189 and the probe attachment portion 187, with the opposing magnetic poles forming a pair. In this way, no attachment screw 186 is required when replacing the measurement probe, and it becomes possible to attach and detach it with a single touch using magnetic attraction.

[0050] The above-described embodiment makes it possible to provide a function in an apparatus for measuring the three-dimensional shape of a measurement workpiece that can prevent damage to the measurement head by stopping the moving mechanism while variably deflecting contact between the measurement probe shaft 164 and the measurement workpiece 301.

[0051] As another example, an apparatus can be configured that inspects the appearance of the surface of a three-dimensional workpiece (e.g., scratches on the surface) rather than measuring its three-dimensional shape. A laser or a high-intensity broadband light source is used as the measurement light, and the measurement light is irradiated onto the measurement workpiece 301 through the lens 161 in FIG. 1 . The light reflected and scattered by the workpiece is again focused by the lens 161 and detected by the detector 173 through the circulator 170. In this case, since interference detection is not performed, the couplers 171 and 172 used to split and combine the reference light are not required. By detecting the intensity of the reflection and scattering of the workpiece with the detector 173, the probe control mechanism 200 can obtain and analyze an appearance image of the measurement workpiece, thereby detecting defects in the measurement workpiece. Alternatively, if a spectrometer is used as the detector 173, the spectrum of the reflected light can be obtained by the probe control mechanism 200. This data can be analyzed by the overall control device 225 to analyze the distribution of material on the surface of the measurement workpiece.

[0052] An embodiment in which a robot is used as the measuring head movement mechanism 500 will be described using Figure 9. In the example shown in this figure, the robot 500' is a six-axis articulated robot having six rotary joints, A1 to A6. The measuring head 160 is attached to the tip of this robot via a measuring head attachment 501. The overall control device 225 in Figure 1 then controls the robot 500' via the movement mechanism control device 215 to change the relative position and orientation of the measuring probe shaft 164 extending from the measuring head 160 and the workpiece 301, making it possible to measure any portion of the workpiece 301. The example in Figure 9 shows a state in which an oblique hole 311 formed in the workpiece 301 is being measured.

[0053] In this way, by utilizing the robot's flexible position and orientation control capabilities, it becomes possible to move the measuring head to various locations on the workpiece and perform measurements flexibly. Although a six-axis articulated robot is shown in the diagram of this embodiment, it goes without saying that other types of robots, such as SCARA robots and gantry robots, may also be used.

[0054] An embodiment in which a magnet is used instead of a spring as a pressure mechanism for applying pressure to the probe base is shown in Figure 10. Figure 10 shows the measurement head 160 and measurement probe 180 extracted from Figure 1. Only the parts that differ from Figure 1 will be explained here.

[0055] The probe base 181 is attracted to the probe holder 184 by a magnetic pressure applying mechanism 183a. In this embodiment, the probe holder 184 is made of a ferromagnetic material. The center of the probe base 181 is hollow, and the measurement probe shaft 164 is firmly fixed thereto. With this configuration, the measurement probe shaft 164 normally rotates integrally with the rotation mechanism 162, but when a force is applied to the measurement probe shaft 164 due to contact with the measurement workpiece 301 or the like, the force acting on the magnet part of the pressure applying mechanism 183a exceeds the magnetic attraction force, causing the probe base 181 to float from the probe holder 184 and deflect the force due to contact between the measurement probe shaft 164 and the measurement workpiece 301 or the like.

[0056] When the contact force is released, the probe base 181 is attracted to the probe holder 184 again by the attractive force of the magnet, thereby restoring the unity of the rotation mechanism 162 and the measurement probe shaft 164. Note that if the probe base 181 is far away from the probe holder 184, the attractive force of the magnet 183a on the probe holder 184 becomes weaker, and the probe base 181 may not be attracted again stably. In such a case, it is advisable to provide an auxiliary weak spring 183b to push the probe base 181 back toward the probe holder 184.

[0057] Although three pressure mechanisms are provided in FIG. 10, the number of locations is not limited to three. For example, the probe base 181 may be attached to the probe holder 184 by a single annular magnet that surrounds the measurement light 300, i.e., the center of rotation of the rotation mechanism 162, thereby enabling stable pressure application without blocking the optical path of the measurement light 300.

[0058] With this configuration, it is possible to provide a function that prevents damage to the measuring head in an apparatus for measuring the three-dimensional shape of a measurement workpiece by stopping the moving mechanism while variably deflecting contact between the measurement probe shaft 164 and the measurement workpiece 301. The attractive force of the magnet 183a increases rapidly when the distance to the probe holder 184, which is the object to be attracted, is short, so it is possible to apply a stable pressure only when the measurement probe shaft 164 is not in contact with the measurement workpiece or the like, and to reduce the pressure when contact occurs.

[0059] 11 shows an embodiment in which the tiltable range of the measurement probe shaft 164 can be extended by compensating for the operating range of the displacement sensor 190. In FIG. 1, when the measurement probe shaft 164 comes into contact with a measurement workpiece or the like, the contact detection mechanism 199 detects the contact and stops the movement mechanism 500 via the movement mechanism control device 215, but if the movement speed of the movement mechanism 500 is high, it may not be able to stop in time and the tiltable range of the measurement probe shaft 164 may be exceeded. In this case, the measurement probe shaft undergoes elastic deformation, and if the elastic deformation range is exceeded, the measurement probe shaft 164 may become irreversibly deformed or break.

[0060] If a small sensor using, for example, eddy current is used as the displacement sensor 190, the detectable range of the displacement of the probe base 181 is, for example, about 1.5 mm. Therefore, if the amount of displacement of the probe base 181 from when the displacement sensor 190 detects contact until the movement mechanism stops exceeds 1.5 mm, the range in which the measurement probe shaft 164 can be tilted will be exceeded.

[0061] Furthermore, when a contact sensor is used as the displacement sensor 190, the measurement probe shaft 164 has already begun to elastically deform when contact is detected, and it is necessary to stop the moving mechanism 500 before this deformation enters the range of plastic deformation or breakage.

[0062] An embodiment that addresses this issue is shown in Figure 11. The measurement head 160 and measurement probe 180 portions of Figure 1 are extracted, and only the portions that differ from Figure 1 will be explained.

[0063] In the embodiment of FIG. 11 , the displacement of the probe base 181 is not measured by the displacement sensor / contact sensor 190, but is instead measured by measuring the displacement of an annular target ring 191. The target ring 191 is held relative to the probe base 181 via a target ring elastic holding mechanism 192. Normally, the target ring 191 moves integrally with the probe base 181. When the target ring 191 is displaced and comes into contact with the displacement sensor 190 or the surrounding components of the measurement head 160, the target ring elastic holding mechanism 192 elastically deforms and absorbs the large displacement applied to the measurement probe shaft 164. This makes it possible to compensate for the operating range of the proximity sensor 190 and extend the tiltable range of the measurement probe shaft 164. Desirably, three or more target ring elastic holding mechanisms 192 are provided to normally hold the target ring 191 integrally with the probe base 181.

[0064] For example, a rubber member or a spring may be used as the target ring elastic holding mechanism 192. In particular, when a spring is used, if the measurement head 160 is moved at high speed, the spring may vibrate, causing unnecessary movement of the target ring 191 and possibly causing the displacement sensor 190 to malfunction.

[0065] A desirable embodiment that can solve this problem is to effectively configure the target ring elastic holding mechanism 192 with three types of members: a hole 194, a pillar 195, and a spring 196. The pillar 195, which has a flared end, is passed through the hole 194 drilled in the target ring 191 and then through the spring 196, and then fixed to the probe base 181 with the spring compressed. Then, the target ring 191 is pressed against the flared part at the end of the pillar 195 by the pressure of the spring 196, and the target ring 191 will not separate from the flared part at the end of the pillar 195 unless the inertial force acting on the target ring 191 due to the movement of the measurement head 160 exceeds this pressure. Furthermore, the target ring 191 will not shift sideways unless the inertial force acting on the target ring 191 due to the left-right movement of the measurement head 160 exceeds the static friction force obtained by multiplying the static friction coefficient between the expanded portion at the end of the pillar 195 and the target ring 191 and the pressure applied by the spring 196.

[0066] In the diagram of this embodiment, the pillars 195 are fixed to the probe base 181 and the target ring 191 has holes 194 through which the pillars 195 pass. However, it should be noted that the same effect can be obtained by conversely fixing the pillars 195 to the target ring 191 and opening holes 194 through which the pillars 195 pass in the probe base 181.

[0067] Furthermore, in a configuration that uses a target ring 191 in addition to the probe base 181 in this way, there is no need to make the probe base 181 disk-shaped in order to use it as a target for the proximity sensor / contact sensor 190 as in Figure 1, so the probe base 181 may be shaped with arms extending in three directions, and a target ring elastic holding mechanism 192 may be attached to the tip of each arm, as shown in the A-A cross-sectional view of Figure 11. In that case, the shape of the pillar 185 is not cylindrical, but can be made to have a larger cross-sectional area, for example a fan shape, as shown in the A-A cross-sectional view, to increase strength.

[0068] The configuration of the embodiment described above makes it possible to compensate for the operating range of the proximity sensor 190 and widen the tiltable range of the measurement probe shaft 164.

[0069] 12, an embodiment will be described in which the rotation mechanism 162 is provided on the measurement probe 180 side, rather than on the measurement head 160 side. Only the parts that differ from FIG.

[0070] As shown in Figure 12, a small rotation mechanism 162 is disposed at the tip of a measurement probe shaft 164. A reflecting mirror / optical path switching element 163 and, if necessary, a quarter-wave plate 167 are mounted on the hollow rotation shaft of the rotation mechanism 162, and these are rotated by the rotation mechanism 162. A probe mounting portion 187 of the measurement probe 180 configured in this manner is attached with a mounting screw 186 to a non-rotating, fixed flange portion 189' provided on the measurement head 160 side. The measurement light emitted from the lens 161 passes through the quarter-wave plate 166 and the rotating quarter-wave plate 167 if necessary, and then reaches the rotating reflecting mirror / optical path switching element 163, thereby changing the measurement direction.

[0071] Even with this configuration, in an apparatus for measuring the three-dimensional shape of a measurement workpiece, it is possible to provide a function that can stop the moving mechanism while variably deflecting contact between the measurement probe shaft 164 and the measurement workpiece 301, thereby preventing damage to the measurement head.

[0072] Figure 8 shows an embodiment in which not only the presence or absence of contact but also the direction of contact is detected and reflected in the control of the device. As already explained, when using proximity sensors / contact sensors 190 that simply measure distance or contact without detecting the tilt of the target ring 191 or probe base 181, it is preferable to use sensors in three or more locations, but Figure 8 shows an example in which sensors are used in four locations. In this way, four proximity sensors / contact sensors are arranged at 90-degree intervals around the measurement probe shaft 164 relative to the target ring 191 or the disk-shaped probe base 181.

[0073] These sensors are named x+, x-, y+, and y- in accordance with the coordinate system shown in the figure. These outputs are received by a contact detection mechanism 199. In a basic configuration, if any of the x+, x-, y+, and y- sensors detects proximity or contact, the contact detection mechanism 199 determines that the measurement probe shaft 164 has come into contact with a workpiece or the like. In addition, the contact detection mechanism 199 can further determine the direction of contact by analyzing which sensor is making the detection. The table in Figure 8 is an example of a judgment table when there are four sensors.

[0074] In the table, 1 indicates that the respective sensor has detected proximity / contact, and 0 indicates that it has not detected proximity / contact. By referring to this table and reading the corresponding collision direction column, the direction of contact of the measurement probe shaft 164 with the measurement workpiece or the like can be determined. In this way, when four sensors are used, in addition to contact in the Z direction, the lateral contact direction can also be determined with a resolution of 45°. For example, doubling the number of sensors doubles the angular resolution.

[0075] Furthermore, if the proximity sensor is capable of measuring the distance to the target 181 / 191, rather than simply whether the target is farther than a reference distance, by using three or more proximity sensors 190, the amount of tilt, direction of tilt, and displacement in the Z direction of the target 181 / 191 can be quantitatively determined by calculation within the contact detection mechanism 199.

[0076] As described above, the contact direction of the measurement probe shaft 164 can be detected by the contact detection mechanism 199, allowing the movement mechanism control device 215 to automatically drive the movement mechanism 500 in a direction that will resolve the contact. Alternatively, this information can be displayed to the operator by the overall control device 225, allowing the operator to manually perform the operation to resolve the contact. <Note> A force is applied to the probe base by a spring or magnet in the direction that moves the probe away from the probe rotation motor, pressing the probe base against a holding surface such as a kinematic mount. The holding surface rotates with the rotation motor. As a result, if a force is applied to the probe tip due to a collision with the workpiece, the force is released by separating the holding surface from the probe base. When the force is released, the probe base is pressed against the holding surface again, thereby reversibly returning to its original position with good reproducibility. Furthermore, a collision can be detected by detecting the displacement of the probe with a sensor, and the operation of the movement mechanism for the relative position of the probe and workpiece can be stopped, preventing device failure. This makes it possible to provide a non-contact optical measurement device that is robust against contact and collision with the workpiece.

[0077] 150: optical fiber connection cable, 151: detector connection cable, 152: proximity sensor connection cable, 160: measurement head, 161: lens, 162: rotation mechanism, 163: reflecting mirror / light path switching element, 164: measurement probe shaft, 165: polarization state control section, 166: fixed quarter-wave plate, 167: rotating quarter-wave plate, 170: circulator, 171: coupler, 172: coupler, 173: detector, 180: measurement probe, 181: probe base, 182: kinematic mount, 183: pressure mechanism (spring), 183a: pressure mechanism (magnet), 183b: pressure mechanism (auxiliary spring), 184: probe holder , 185: Pillar, 186: Mounting screw, 187: Probe mounting portion, 189: Rotation mechanism flange portion, 190: Displacement sensor / contact sensor, 191: Target ring, 192: Target ring elastic holding mechanism, 193: Fitting protrusion portion of probe base, 194: Hole, 195: Pillar, 196: Spring, 199: Contact detection mechanism, 200: Probe control mechanism, 215: Moving mechanism control device, 225: Overall control device, 300: Measurement light, 300a: Measurement light facing in first direction, 300b: Measurement light facing in second direction, 301: Measurement workpiece, 311: Narrow portion / hole portion, 500: Moving mechanism, 500': Robot, 501: Measurement head attachment.

Claims

1. A shape measuring probe that emits measurement light emitted from a light source towards a measurement object and receives reflected light of the measurement light reflected by the measurement object, comprising: a probe shaft that rotates to emit the measurement light; and a rotation mechanism that rotates the probe shaft; a probe base that supports the probe shaft; a probe holder for mechanically connecting the probe base and the rotation mechanism; and a pressing mechanism that mechanically connects the probe base and the probe holder by pressing the probe base and the probe holder with a predetermined force, wherein the shape measuring probe is configured such that when a force equal to or greater than the predetermined force is applied to the probe shaft, the mechanical connection by the pressing mechanism is released, causing the tip position of the probe shaft to shift from a predetermined position.

2. A shape measuring probe according to claim 1, characterized in that the pressure exerted by said pressure mechanism is due to at least either the elastic force of an elastic body or the attractive force of a magnet.

3. A shape measuring probe as claimed in claim 1, characterized in that the rotation mechanism and the probe holder are mechanically connected by at least one of a kinematic mounting mechanism, a combination of a mating cylinder and a flat portion, or a combination of a conical shape and a mortar shape.

4. A shape measuring probe as claimed in claim 1, characterized in that the probe holder is attached to the rotation mechanism by screw fastening, or by being pressed by elastic force or magnetic force via a fitting structure or a kinematic mounting mechanism.

5. A shape measuring probe according to claim 1, further comprising a detection mechanism for detecting that a force equal to or greater than the predetermined value has been applied to the probe shaft.

6. A shape measuring probe according to claim 5, wherein said detection mechanism is a displacement detection sensor which detects the displacement of the relative position between said probe shaft and said rotation mechanism.

7. A shape measuring probe according to claim 6, characterized in that the displacement detection sensor detects the displacement of the rotating probe shaft by a non-rotating displacement detection sensor.

8. A shape measuring probe as claimed in claim 6, characterized in that the displacement detection sensor is either (a) a sensor which detects distance or inclination without contact using any of the following: electromagnetic induction, capacitance, magnetic field, light intensity, laser triangulation or laser interference, or (b) a contact sensor which detects contact due to displacement as a change in current, detects strain due to contact with a strain gauge or piezoelectric element, or captures it as a decrease in vibration amplitude.

9. A shape measuring probe as claimed in any one of claims 1 to 8, characterized in that the measurement light is a wavelength swept laser, and the distance between the tip of the probe shaft and the object to be measured is measured based on an interference beat between the measurement light and the reflected light, and the three-dimensional shape of the object to be measured is measured.

10. A shape measuring probe according to any one of claims 1 to 8, wherein the measurement light is broadband light, and the shape measuring probe measures the distance between the tip of the probe shaft and the object to be measured based on the interference spectrum of the measurement light and the reflected light, and measures the three-dimensional shape of the object to be measured.

11. A shape measuring probe as claimed in any one of claims 1 to 8, characterized in that the measurement light is a laser or a high-brightness broadband light source, and the shape measuring probe is provided with a defect detection mechanism which obtains an external image of the object to be measured based on the intensity of reflection / scattering of the reflected light, and detects defects in the object to be measured.

12. A non-contact optical measuring device equipped with a shape measuring probe as defined in any one of claims 6 to 8, characterized in that the non-contact optical measuring device has a plurality of the displacement detection sensors, and is equipped with a display mechanism for detecting the contact direction between the measurement object and the probe shaft by comparing detection values ​​of the plurality of displacement detection sensors, and displaying the movement direction of the probe shaft to prevent the probe shaft from contacting the measurement object.

13. A non-contact optical measuring device equipped with a shape measuring probe according to any one of claims 6 to 8, characterized in that the non-contact optical measuring device has a plurality of the displacement detection sensors, detects the contact direction between the measurement object and the probe shaft by comparing the detection values ​​of the plurality of displacement detection sensors, and further comprises a moving mechanism for moving the probe shaft so that the probe shaft does not come into contact with the measurement object.

14. A non-contact optical measuring device according to claim 13, wherein the moving mechanism can be any one of a CMM (Coordinate Measurement Machine), a multi-axis robot, and a multi-axis stage.

15. A method for measuring the three-dimensional shape of an object, comprising using a shape measuring probe according to any one of claims 1 to 8.

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