Chromatic Range Sensor System

Abstract

To provide a system for calibrating an optical probe of a chromatic range sensor connected to a coordinate measurement machine.SOLUTION: A calibration system for a chromatic range sensor (CRS) optical probe of a coordinate measurement machine (CMM) includes a cylindrical calibration member and a spherical calibration member. The cylindrical calibration member has at least a first cylindrical calibration surface. A central axis of the first cylindrical calibration surface extends along a Z direction, and is aligned so as to be substantially parallel to a rotational axis of a CRS optical probe. A spherical calibration member has a spherical calibration surface having a plurality of first surface parts. The CMM is operated to obtain a radial distance measurement value of the cylindrical calibration member and determine cylindrical calibration data using the radial distance measurement value. The CMM is also operated to determine spherical calibration data using the radial distance measurement value of the spherical calibration member.SELECTED DRAWING: Figure 20

Description

[Technical field]

[0001] The present invention relates generally to precision measurement equipment, and more particularly to chromatic range sensor optical probes for coordinate measuring machines (CMMs) used to determine measurements of workpieces. [Background technology]

[0002] One type of coordinate measuring machine scans the surface of a workpiece with a probe and calculates the 3D profile of the workpiece after the scan. One type of scanning probe measures the workpiece directly by mechanically contacting the probe with various points along the workpiece surface, often with balls.

[0003] Other CMMs use optical probes to measure the workpiece without contacting the workpiece surface. Some optical probes (e.g. triangulation probes) use light to measure points on the workpiece surface and are coupled with a video camera (e.g. stereo vision or structured light systems) for imaging two-dimensional (2D) cross-sections of the workpiece surface. Some systems use image processing software to determine the coordinates of geometrical parts of the workpiece.

[0004] Also known are "hybrid" coordinate measuring machines that use both optical and mechanical measurement detectors. One such machine is described in U.S. Pat. No. 4,908,951 and has two spindles. One spindle is for carrying a mechanical contact probe and the other spindle is for holding a video camera. The optical path of the video camera is set up so that the laser probe can measure simultaneously with the video camera along the Z axis, i.e. the optical axis of the video camera.

[0005] US Patent No. 5,825,666 (Patent Document 2) describes an optical three-dimensional coordinate measuring machine, in which an optical contact probe of the machine sets the distal end of a contact of a standard probe to a first target. The standard probe is attached to a video camera, which images the target on the camera. The movement and position of the target in the XY coordinate system are displayed on a computer image processing device of the machine. A second target is attached to the proximal end of the probe, which displays the movement and position of the Z coordinate. The second target may obscure the photodetector, but can be focused on the camera by a light beam parallel to the XY plane. Here, the two second targets can be illuminated by beams parallel to the XY plane and orthogonal to each other. And, when using star probes, the rotation about the Z axis is calculated by a computer. Also disclosed is an automatic exchange rack for holding multiple probes, a probe holder, and multiple lenses for selective attachment to the camera, respectively. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 4,908,951 [Patent Document 2] U.S. Patent No. 5,825,666 [Patent Document 3] U.S. Patent No. 7,876,456 [Patent Document 4] U.S. Patent No. 7,990,522 [Patent Document 5] US Patent Publication No. 20120050723 Summary of the Invention [Problem to be solved by the invention]

[0007] The optical probe and / or coordinate measuring machine may include, for example, a rotation mechanism for rotating an optical pen of the optical probe about an axis. In addition, the optical pen may include a reflective element disposed in the light path of the light source, which directs the measurement light in a different direction than the light source light.

[0008] Problems in this regard include errors in measurements taken with a rotating optical pen coordinate measuring machine, which may have nonlinear components, such as radius errors, rotation angle errors, and z-position errors. Conventionally, interferometric calibrations are used to deal with such errors. However, interferometric calibrations are difficult to perform accurately, especially for rotating probes. In addition, such calibrations are difficult to perform at the measurement site, such as in a manufacturing plant.

[0009] What is needed is a system and method that can address these issues, one for calibrating the optical probe of a chromatic range sensor connected to a coordinate measuring machine. [Means for solving the problem]

[0010] A calibration system according to the present invention is for providing calibration data for a coordinate measuring machine (CMM). The calibration system includes a CMM having a light generating circuit, a wavelength detecting circuit, and a CMM control circuit, and a chromatic range sensor (CRS) optical probe configured to be connectable to the CMM. The CRS optical probe includes an optical pen having a confocal optical path including at least a confocal aperture and a chromatic dispersion optical element. The optical pen is configured to direct a radial distance detection beam along a radial direction relative to an axis of rotation and to rotate the radial distance detection beam about the axis of rotation such that different wavelengths of light are focused at different distances near a measured surface of a workpiece along the measurement axis. The calibration system includes a cylindrical calibration member and a spherical calibration member.

[0011] The cylindrical calibration member is for providing cylindrical calibration data for correcting misalignment errors of the CRS optical probe and has at least a first cylindrical calibration surface having a central axis extending along a Z-axis. The CRS optical probe is configured to rotate the radial distance detection beam about a rotation axis at a first Z coordinate position along the Z direction relative to the cylindrical calibration member to provide a first cylindrical radial distance data set acquired during the rotational movement. The cylindrical radial distance data set is referenced to a detection rotation angle of the radial distance detection beam about the rotation axis. The first cylindrical radial distance data set referenced to the detection rotation angle is processed to determine the cylindrical calibration data.

[0012] The spherical calibration member has a spherical calibration surface and is used to provide spherical calibration data for correcting misalignment errors of the CRS optical probe. For each of a plurality of first surface portions on the spherical calibration surface, the CRS optical probe is configured to rotate the radial distance detection beam about a rotation axis with the optical pen at a position approximately at a first standoff distance from the spherical calibration member to provide a spherical radial distance data set corresponding to each surface portion, the spherical radial distance data set being acquired during the rotational movement. The optical pen is also moved in a scanning axis direction (i.e., the radial distance detection beam is moved in response to the scanning axis direction) to acquire the spherical radial distance data set. Each set of radial distance data corresponding to each of the detected surface portions is processed to determine a closest detected surface point representative of a point closest to the optical pen. The spherical calibration data is determined based at least in part on the closest detected surface points corresponding to the plurality of surface portions.

[0013] In some embodiments, a method is presented for providing calibration data to correct misalignment errors in a rotating chromatic range sensor configured to direct a radial distance sensing beam along a radial direction relative to an axis of rotation and rotate the radial distance sensing beam about the axis of rotation, and a cylindrical calibration member and a spherical calibration member are provided.

[0014] The cylindrical calibration member has at least a first cylindrical calibration surface with a central axis along a Z direction. The cylindrical calibration member is disposed in a relationship to a rotating chromatic range sensor. The rotating chromatic range sensor is operative to rotate a radial distance detection beam about a rotation axis at a first Z coordinate position along the Z direction relative to the cylindrical calibration member to provide a first cylindrical radial distance data set acquired during the rotation. The cylindrical radial distance data set references a detection rotation angle about the rotation axis of the radial distance detection beam. The first cylindrical radial distance data set referenced to the detection rotation angle is processed to determine a first set of cylindrical calibration data.

[0015] The spherical calibration member has a spherical calibration surface with a plurality of first surface portions and is positioned in a relationship to the rotating chromatic range sensor. For the plurality of first surface portions, the rotating chromatic range sensor is operative to rotate a radial distance detection beam about the axis of rotation with an optical pen of the rotating chromatic range sensor at approximately a first standoff distance from the spherical calibration member to provide a spherical radial distance data set corresponding to each surface portion acquired during the rotation. Each set of radial distance data corresponding to each detected surface portion is processed to determine a closest detected surface point for each set, the closest point representing the closest to the optical pen of the rotating chromatic range sensor. The spherical calibration data is determined based at least in part on the closest detected surface points corresponding to the plurality of surface portions.

[0016] In some embodiments, a calibration system for a chromatic range sensor (CRS) including a CRS optical probe is provided, the calibration system comprising a cylindrical calibration member capable of providing cylindrical calibration data for correcting misalignment errors of the CRS optical probe, a spherical calibration member capable of providing spherical calibration data for correcting misalignment errors of the CRS optical probe, and a stage (e.g., a surface plate) for positioning the cylindrical calibration member and the spherical calibration member relative to the CRS optical probe.

[0017] In some embodiments, the calibration system includes a controller (e.g., one or more controllers, control circuits, etc.) configured to compute each set of radial distance data corresponding to each of the detected surface portions to determine a closest detected surface point (a point representing closest to the optical pen) for each surface portion, and to determine spherical calibration data based at least in part on the closest detected surface points corresponding to the plurality of surface portions. The controller may also be configured to reference the cylindrical radial distance data to a detected rotation angle about an axis of rotation of the radial distance detection beam, and may be configured to compute a first cylindrical radial distance data set that references the detected rotation angle to determine the cylindrical calibration data. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a block diagram of an exemplary chromatic range sensor (CRS) system having an optical pen. [Diagram 2] FIG. 1 is a block diagram of a coordinate measurement system including a coordinate measuring machine, a CRS optical probe including an optical pen, a controller, and a user interface. [Diagram 3] 3A and 3B are diagrams showing the internal structure of the CRS optical probe of FIG. 2 according to the first embodiment. [Figure 4] 4A and 4B are diagrams illustrating the structure of an optical pen including the exchange mount and replaceable optical mechanism of FIGS. 3A and 3B. [Diagram 5] FIG. 3 is a block diagram showing the structure of the probe controller of FIG. 2. [Figure 6] FIG. 1 is a block diagram illustrating one embodiment of an optical pen that includes a rotor of interchangeable optical mechanisms and an encoder for measuring and reporting position information. [Figure 7] 7A-7C are cross-sectional views showing representative calibration components of the optical pen of FIG. [Figure 8] 8A-8C are conceptual diagrams showing examples of misalignments that can cause measurement errors when using a rotating optical pen, and examples of parameters that may be taken into account to compensate for such errors. [Figure 9] 9A to 9D are diagrams showing a calibration member in the shape of a ring gauge according to one embodiment. [Figure 10] FIG. 2 illustrates a calibration member in the form of a stepped ring gauge according to one embodiment. [Figure 11] 11A to 11C are cross-sectional views and conceptual diagrams showing a calibration member in the shape of a stepped ring gauge according to another embodiment. [Figure 12] 12A-12C are diagrams showing calibration members in the form of one or more precision glass tubes according to an embodiment. [Figure 13] 13A to 13E are diagrams showing a calibration member in which a plurality of precision metal tubes are nested together according to the embodiment. [Figure 14] 1 is a graph of an example radius measurement data set associated with an optical pen. [Figure 15] 15 is a graph of corrected slope and offset determined based on the example radial distance measurement data set of FIG. 14. [Figure 16] 13A-13C are graphical illustrations of radial distance data obtained at gauge distance (at multiple locations) and at multiple locations of offset of the rotation axis of the optical pen relative to the central axis of the calibration member according to one embodiment. [Figure 17] FIG. 1 illustrates the calibration procedure for the rotating chromatic range sensor structure of a CMM. [Figure 18] FIG. 1 illustrates a typical configuration of a coordinate measuring system including a CMM and typical calibration components. [Figure 19] 1A-1C illustrate an embodiment of a calibration member in the form of a spherical calibration member. [Figure 20] FIG. 1 is a flow diagram illustrating one embodiment of an exemplary calibration procedure for a rotating chromatic range sensor of a CMM. [Figure 21] FIG. 2 is a flow diagram illustrating one embodiment of an exemplary procedure for obtaining spherical calibration data from radial distance measurements of a spherical calibration member. [Figure 22]1 is a conceptual diagram illustrating a method for measuring the radial distances of multiple surface portions of a spherical calibration member with an optical pen at a first orientation and standoff distance relative to the spherical calibration member. [Diagram 23] FIG. 13 is a conceptual diagram illustrating the processing of radial distance data to determine the closest surface point on each of a plurality of surface portions of a spherical calibration surface, and using the closest point to generate spherical calibration data. [Figure 24] FIG. 13 is a conceptual diagram illustrating the processing of radial distance data to determine the closest surface point on each of a plurality of surface portions of a spherical calibration surface, and using the closest point to generate spherical calibration data. [Diagram 25] 25A and 25B are explanatory diagrams of a method for acquiring spherical radial distance data for a surface portion of a spherical calibration member. [Figure 26] 13 is a conceptual diagram illustrating a method for measuring the radial distances of multiple surface portions of a spherical calibration member by positioning the optical pen at a second orientation and standoff distance relative to the spherical calibration member. [Figure 27] Figure 27A is a conceptual diagram showing one ideal alignment of a CMM with an optical pen to obtain radial distance measurements of a spherical calibration member, and Figures 27B and 27C are conceptual diagrams showing various misalignment errors when using a CMM with an optical pen to measure radial distance measurements of a spherical calibration member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] FIG. 1 is a block diagram showing the basic components of a representative chromatic range sensor (CRS) system 100 with a desired operating principle for a coordinate measuring machine. The CRS system 100 has some similarities to the devices described in U.S. Pat. No. 7,876,456 and U.S. Pat. No. 7,990,522. The CRS system 100 shown in FIG. 1 is a chromatic point sensor system including an optical mechanism 120 and electronics 160, which may measure one point at a time. Hereinafter, the optical mechanism 120 of FIG. 1 is also referred to as an optical pen. However, various embodiments may utilize alternative chromatic range systems, such as a chromatic line sensor.

[0020] The optical pen 120 includes a fiber optic connector 109, a housing 131 (e.g., an assembly hollow tube), and a color dispersive optical element 150. The fiber optic connector 109 is attached to an end of the housing 131. In various embodiments, the fiber optic connector 109 may be oriented at an angle relative to the housing 131. The fiber optic connector 109 carries input and output optical fibers (not shown in detail) through an integrated input and output fiber optic cable 112. The input and output optical fibers output measurement light from a light source through a fiber aperture 195 and receive reflected measurement signal light through the fiber aperture 195.

[0021] During the measurement operation, broadband source light (e.g., white light) emitted from the end of the fiber through a fiber aperture 195 is collected by a chromatic dispersion optical element 150, which may include a simple or compound lens that promotes axial chromatic dispersion, so that the focus along the optical axis OA is at a different distance depending on the wavelength of the light, as is well known in confocal chromatic sensor devices. The source light forms a measurement light 196 that includes wavelengths of light that are focused on the work surface 190 at a position Z from the optical pen 120 (which may, for example, function as a radial distance detection beam). The reflected light from the work surface 190 is again focused on the fiber aperture 195 by the chromatic dispersion optical element 150. The measurable measurement light and reflected light are bounded by limiting rays LR1, LR2. Due to the axial chromatic dispersion, only one wavelength exhibits a forward focal length FF that corresponds to the measurement distance from the optical pen 120 to the work surface 190. The optical pen 120 is configured such that the wavelength that is best focused on the work surface 190 is the wavelength that is best focused on the fiber aperture 195. The fiber aperture 195 spatially filters the reflected light so that the best focused light passes through the aperture 195 and into the core of the fiber optic cable 112. As described in more detail below, the fiber optic cable 112 conveys the reflected signal light to a wavelength detector 162 that is used to determine the wavelength of predominant intensity that corresponds to the measured distance to the work surface 190.

[0022] FIG. 1 also shows a schematic representation of an optional reflective element 155, shown in dashed lines. A reflective element, as described in detail in U.S. Patent Publication No. 20120050723, may be disposed in the path of the source light SB of the present invention. In such an embodiment, rather than a measurement axis MA that is coaxial with the optical axis OA, the reflective element may reflect the measurement light 196' in a different direction along the measurement axis MA' (e.g., orthogonal to the optical axis) as required by the measurement application. Such an orthogonal direction is used in the embodiments shown in the other figures, as described in more detail below.

[0023] The electronics 160 includes a fiber coupler 161, a wavelength detector 162, a light source 164, a signal processor 166, and a memory 168. In various embodiments, the wavelength detector 162 includes a spectrometer or spectrometer arrangement. A dispersive optical element, such as a diffraction grating, in the wavelength detector 162 receives the reflected light through the fiber optic cable 112 and communicates the resulting spectral intensity profile to a detector array 163. The wavelength detector 162 may also include associated signal processing functionality, such as functionality provided by the signal processor 166 in some embodiments, such as removing detector-specific error components from the profile data or compensating the profile data. Thus, certain aspects of the wavelength detector 162 and the signal processor 166 may be integrated or may be indistinguishable.

[0024] The white light source 164 is controlled by a signal calculator 166 and is connected to the fiber cable 112 via an optical coupler 161 (e.g., a 2×1 optical coupler). As described above, light travels through the optical pen 120 which generates axial chromatic aberration, the focal length of which varies depending on the wavelength of the light. The wavelength of light that is most efficiently transmitted when passing backward through the fiber is the wavelength that is focused on the work surface 190 at position Z. The wavelength-dependent reflected light intensity then passes again through the fiber coupler 161 such that approximately 50% of the light is directed to a wavelength detector 162 which operates to receive the spectral intensity profile distributed on the pixel array along the measurement axis of the detector array 163 and provide corresponding profile data. In brief, the sub pixel-resolution distance indicating coordinates of the profile data, e.g., peak position coordinates, are calculated by the signal calculator 166. The distance indicating coordinates (DIC) corresponding to the wavelength peaks then determine the measured distance to the surface via a distance calibration look-up table. The calibration look-up table is stored in memory 168. The distance indicating coordinate (DIC) may be determined in a variety of ways, such as by determining the center of gravity of the profile data within a peak region of the profile data. The rotational systems described herein may also utilize calibration data (e.g., stored in memory 168 or other storage) to provide an indication or adjustment of a measured distance based at least in part on the angular orientation of the optical pen 120.

[0025] Typically, the optical pen 120 has a measurement range R defined by a minimum and maximum distance ZMIN and ZMAX in the Z-axis direction. In some known examples of optical pens, the measurement range R is preferably approximately 1 / 10 of the nominal standoff or operable distance from the end of the pen (e.g., in the range of tens of microns to a few millimeters). Figure 1 shows that when a reflective element 155 is used, the measurement range R' is determined along a measurement axis MA' defined by the location of the reflective element 155 (e.g., the x-axis). In this case, the measurement range R' is defined by a minimum and maximum distance XMIN and XMAX in the X-axis direction.

[0026] In some embodiments, the electronics 160 is separate from the optical pen 120. It is known to mount an optical pen similar to the optical pen 120 of FIG. 1 to a CMM using a custom designed bracket and to route optical fibers similar to the fiber optic cable 112 along temporary paths external to the CMM machine to remote electronics similar to the electronics 160.

[0027] 2, 3A, and 3B, a group of light source / wavelength detector components 160A (e.g., including wavelength detector 162 and light source 164) may be included in the CRS optical probe assembly in some embodiments. A group of components in measurement signal processing control circuit 160B (e.g., including signal processor 166 and memory unit 168) may be located external to the CRS optical probe assembly if necessary (e.g., to maintain a lightweight probe and compact size).

[0028] FIG. 2 is a block diagram of a three-dimensional coordinate measuring system 200 and a CRS optical probe device 215 that can be automatically connected and replaced. That is, the CRS optical probe device 215 can be automatically replaced with another type of CMM probe. Here, the CRS optical probe device is simply called a CRS optical probe. Unless otherwise specified in the specification, a reference numeral having a similar suffix in a plurality of drawings (for example, a reference numeral 2XX having the same suffix XX as a reference numeral 1XX) basically has a similar configuration. And, a change to a configuration 2XX based on a description of a similar configuration 1XX is generally easily inferred from a well-known technique. However, despite such an inference, it is obvious that different aspects of various configurations naturally exist in different embodiments, so the configuration of the present invention should not be interpreted as being limited to one of the well-known techniques.

[0029] The three-dimensional coordinate measuring system 200 includes a three-dimensional coordinate measuring machine (CMM) controller 202, a computer and user interface 206, a probe signal processing and control circuitry 207, and a three-dimensional coordinate measuring machine (CMM) 210. The CMM controller 202 includes a probe head controller 203, a position latch 204, and a motion controller 205. The CRS optical probe 215 includes an auto-exchange joint element 236 and is connected to the CMM 210 via a mating joint element of an auto-exchange joint connection mechanism 230 (also referred to as an auto-joint connection).

[0030] The CMM 210 communicates with all of the other components through a data transfer line 201 (e.g., a bus). The data transfer line 201 is connected by a connector 208 (e.g., a "micro-D" connector) to a probe head cable 211 which carries input and output signals to the CRS optical probe 215. The CRS optical probe 215 is controlled by a probe signal processing control circuit 207 which includes a measurement signal processing control circuit 260B, as described for example for the measurement signal processing control circuit 160B in FIG. 1, and exchanges data with this control circuit 207, but the CMM 210 is controlled by a CMM controller 202. A user can control all of the components through a computer and user interface 206.

[0031] 2, the CRS optical probe 215 includes a probe electronics 275 including a light source / wavelength detector component 260A (e.g., a light source and a wavelength detector as described for component 160A in FIG. 1) and an optical pen 220 for projecting a measurement light 296 onto a surface 290 to be measured. In one particular embodiment, the surface 290 to be measured is the inner surface of a screw hole. Such surfaces are difficult or impossible to measure completely and reliably using known CMM probes (e.g., contact probes). The CRS optical probe of the present invention can scan and measure such surfaces with improved measurement completeness, accuracy, and versatility.

[0032] 5, in one embodiment, data relating to the optical pen 220 and / or replaceable optical mechanism 280 (e.g., identification data, calibration data, compensation data, etc.) is preferably stored external to the CRS optical probe 215 (e.g., in the probe signal processing and control circuitry 207). Alternatively, some of such data may be stored within the CRS optical probe 215 or as other coded data.

[0033] Figures 3A and 3B are schematic diagrams of a CMM 210 and a CRS optical probe 215', which is similar to the CRS optical probe 215 of Figure 2. Figure 3A is a front view, and Figure 3B is a view of the CMM 210 and the CRS optical probe 215 from different angles. As shown in Figures 3A and 3B, the CMM 210 includes a probe head 213. The probe head 213 transmits and receives probe signals through a probe head cable 211. The probe head 213 is fixed to the spindle 217 of the CMM. A probe 215' is connected to the probe head 213 using a probe automatic joint connection mechanism 230.

[0034] In one embodiment, the probe head 213 rotates 360 degrees in a horizontal plane and includes a U-shaped joint. The probe automatic joint connection mechanism 230 is an electromechanical connection mechanism that mechanically clamps and secures the CRS optical probe 215' to the probe head 213, allowing the probe to be removed and another probe to be attached. In one embodiment, the probe automatic joint connection mechanism 230 includes first and second automatic exchange joint elements 234, 236, where the first automatic exchange joint element 234 is attached to the probe head 213 and the second automatic exchange joint element 236 is attached to the CRS optical probe 215'. In one embodiment, the probe automatic joint connection mechanism 230 includes a mating electrical contact or electrical connection portion 235, where the electrical contacts are automatically connected when the probe is attached to the probe head 213 and an electrical connection is established.

[0035] The CRS optical probe 215' receives power and control signals through an automatic joint connection mechanism 230. Signals sent to the CRS optical probe 215' through the automatic joint connection mechanism 230 pass through an electrical connection 235. As shown in Figures 3A and 3B, the CRS optical probe 215' includes a probe assembly 216 and an automatic exchange joint element 236 attached to the probe assembly 216 for automatically connecting the probe to the CMM using the probe automatic joint connection mechanism 230. The probe 215' may also include a protective cover or probe housing 269 (shown diagrammatically). The probe assembly 216 includes an optical pen 220 and a probe electronics section 275 having a light source 264 and a wavelength detector 262, all of which are supported by various structural members of the probe assembly 216.

[0036] In the embodiment shown in Figures 3A and 3B, the structural members extend from a base member 218 that is secured to an auto-interchange joint element 236. An optical pen 220 (or an optical mechanism similar to the optical pen 120) includes a fiber optic connector 209 and a confocal optical path having an aperture 295 and a chromatic dispersion optical element 250, and outputs a measurement light 296 (which may function as a radial distance detection beam, for example). In some embodiments, the optical pen 220 may include a repeatable, rapid-interchangeable interchange mount 285 to allow for interchangeability of the chromatic dispersion optical element 250. A powered light source 264 (e.g., a broad spectrum LED light source) may be powered through the auto-interchange joint element and interfaced with known circuitry (e.g., circuitry used in commercially available chromatic distance measurement systems) included in a probe power and signal control circuit portion 276 of the probe electronics section 275. In several embodiments, the probe electronics unit 275 includes a serial converter 277S that serializes various data signals and transmits them to a parallel converter (e.g., included in the probe signal processing control circuit 207) over a relatively small number of wires in the automatic joint connection mechanism 230.

[0037] 3A, the serializer 277S is included in the probe power supply and signal control circuitry 276. However, in other configurations, where most of the serialized data to be transmitted is measured spectral profile data generated in the CRS wavelength detector 262, it is better to include the serializer 277S in the CRS wavelength detector 262. In general, the serializer 277S should be located in a desired position in the probe electronics section 275, i.e., a position that can provide sufficiently low noise levels and crosstalk characteristics.

[0038] The light source 264 generates the light required by the CRS optical probe assembly 216. The light has an input spectral profile in the wavelength range that is transmitted to the optical pen 220 through the fiber optic cable 212. The CRS wavelength detector 262 may include known circuitry (such as that used in commercially available chromatic distance measurement systems) that interfaces with the spectrometer arrangement 262' and the detector array 263. The detector array 263 is comprised of a number of pixels distributed along the detection axis of the CRS wavelength detector 262 that are illuminated with the respective wavelengths of light reflected from the surface to be measured back into the confocal optical path, allowing the CRS wavelength detector 262 to provide output spectral profile data.

[0039] As described above, the configuration of the present invention allows the CRS optical probe assembly 216 to perform the functions of generating measurement light and processing reflected light from the workpiece, thereby enabling self-contained and automatic replacement of the CRS optical probe assembly 216. Such a CRS optical probe device does not require or include an optical fiber connection from the CRS optical probe assembly through the automatic joint connector to an external element, or an optical fiber connection along any other temporary path, such as parallel to the automatic joint connector. In other words, such a CRS optical probe assembly is not connected to or does not include an optical fiber extending from the CRS optical probe assembly to the outside.

[0040] In various embodiments, the CRS optical probe assembly 216 is configured by mounting an optical pen 220 to a distal end of the CRS optical probe assembly 216 relative to the probe head 213. In the embodiment of Figures 3A and 3B, the CRS optical probe 215' includes a base member 218, a wavelength detector mounting member 219A coupled to the base member 218, and an optical pen mounting member 219B coupled to the base member 218. The optical pen mounting member 219B holds the optical pen 220 without holding the wavelength detector 262. This allows heat and mass associated with flexing and vibration to be isolated from the optical pen 220. In some embodiments, one or both of the mounting members 219A and 219B may include a hollow tube (e.g., a carbon fiber tube) extending from the base member 218 toward the distal end of the CRS optical probe assembly 216.

[0041] In one embodiment, the center of mass of the optical pen 220 is located on or near an axis defined by the center of mass CMPA of the rest of the CRS optical probe 215' and the central axis CAJ of the probe automatic joint connection mechanism 230. Using this configuration, the CRS optical probe 215' can be moved to allow smooth operation of the probe head 213 (e.g., avoidance of unnecessary additional torque, vibration, deflection, etc.). In one aspect of the invention, the optical pen 220 is mounted relative to the probe automatic joint connection mechanism 230 such that the central axis CAOP (e.g., reference axis for measurement) of the optical pen 220 is coaxial with the central axis CAJ of the automatic exchange joint connection mechanism 230. In such a configuration, when the CMM rotates the probe automatic joint connection mechanism 230 about its axis, the optical pen 220 can be rotated about its axis without lateral movement of the measurement reference axis in the XY plane. Such a configuration provides advantages such as improved mechanical stability and simplified calculation of the measurement position of the optical pen 220 relative to the positioning by the CMM.

[0042] 4A and 4B are diagrams specifically illustrating the configuration of the optical pen 220 of FIGS. 3A and 3B described above, and will be used to explain an embodiment including a representative replacement mount 285. In the embodiment illustrated in FIGS. 4A and 4B, the optical pen 220 includes a base member 282 and a replaceable optical mechanism 280. The replaceable optical mechanism 280 includes a front plate 286, a hollow tube 231, and a color dispersion optical member 250. The base member 282 of the optical pen includes a base housing 282A including a surface that becomes a first engagement half member 285A of the replacement mount 285. Corresponding to this surface, the front plate 286 also includes a surface that becomes a second engagement half member 285B of the replacement mount 285. In one embodiment, the second engagement piece 285B is forcibly attached to the first engagement piece 285A by a retention arrangement formed by a permanent magnet 285C attached to one or both of the first and second engagement pieces 285A, 285B. More generally, the retention arrangement may be a spring-loaded mechanical tab or other known mechanism. Such an arrangement allows the second engagement piece 285B to be automatically connected to and disconnected from the first engagement piece 285A under program control (e.g., under control of the computer and user interface 206).

[0043] For example, in one embodiment, the optical pen 220 may be provided with a collar 232 guided by program control. This allows the optical pen 220 to be inserted into an arm of an engagement fork provided on a probe rack within the movable range of the CMM. The CMM then moves the CRS optical probe 215' so that the arm of the engagement fork hooks the collar 232, hooking the exchangeable optical mechanism 280 onto the probe rack, and the two engagement half members 285A, 285B of the exchange mount 285 can be separated. Also, by performing the reverse operation, the exchangeable optical mechanism 280 can be attached again to the base member 282. Furthermore, with such a configuration, in the event of a side collision with the workpiece, the exchangeable optical mechanism 280 is separated from the base member 282, preventing damage to the exchangeable optical mechanism 280.

[0044] In one embodiment, the exchange mount 285 may include three spheres or balls 285D fixed to the first engagement piece 285A in a first triangular pattern (e.g., an equilateral triangle). The exchange mount 285 may also include three radial V-grooves 285E formed in the same engagement pattern to the second engagement piece 285B. With this configuration of the exchange mount 285, the exchangeable optical mechanism 280 can be mounted so that the measurement light 296 directed horizontally from the exchangeable optical mechanism 280 is oriented in a direction selected from three directions spaced 120 degrees apart around the axis. The above embodiment is a representative configuration, but the present invention is not limited thereto. Various other known exchange mount configurations may be employed to provide an exchange mount with suitable mounting and dismounting repeatability.

[0045] The interchangeable optical mechanism 280 includes a color dispersive optical element 250 (e.g., similar to the color dispersive optical element 150 of FIG. 1). In one embodiment, the base member 282 includes an end of an optical fiber 212 that is connected to an LED light source 264 and a spectrometer arrangement 262′ through a fiber connector 261. The end of the optical fiber is typically located near the confocal aperture 295, fixed relative to a first mating half 285A of an exchange mount 285 that is positioned around the confocal aperture 295. In some embodiments, the end of the optical fiber forms the confocal aperture 295. In some embodiments, the confocal aperture 295 can be a thin aperture that is glued in close proximity to the end of the optical fiber (e.g., on a holder or connector that supports the optical fiber) or a thin aperture adjacent to the end of the optical fiber. 4A, the base member 282 includes a fiber optic end positioning mechanism 283 having a fiber optic holding member 283A (such as a fiber optic connector that mates with the connector 209 in this embodiment) and a fiber optic end positioning arrangement 283B that is secured (e.g., glued) to the base member 282 in a position adjacent to a first mating half member 285A of an exchange mount 285.

[0046] In this embodiment, the optical fiber end positioning mechanism 283 has an optical fiber holding member that holds an optical fiber (e.g., an optical fiber passing through the connector 209). The optical fiber holding member fixes the optical fiber end and the confocal aperture 295 in a position relative to the first engagement half member 285A of the exchange mount 285. However, in other embodiments, the confocal aperture 295 may be fixed to the base member 282, and the end of the optical fiber may be fixed in a position adjacent to the confocal aperture 295 separately by an appropriate optical fiber end positioning mechanism 283 as needed.

[0047] The interchangeable optical mechanism 280 receives measurement light from the confocal aperture 295 and reflects the measurement light back to the confocal aperture 295. It provides axial chromatic dispersion of the measurement light at each measurement distance along the measurement axis. In one embodiment, the chromatic dispersion optical member 250 also includes a reflective element 294 for irradiating the measurement light in a direction perpendicular to the axis of the optical pen 220 (e.g., transverse to the central axis of the hollow tube 231).

[0048] Fig. 5 is a block diagram of the computer and user interface 206 and the probe signal processing control circuit 207 shown in Fig. 2. As shown in Fig. 5, the probe signal processing control circuit 207 includes a parallel converter 277D, a position latch 515, a CRS optical probe ID 520, and an optical pen ID 525. Each component of the probe signal processing control circuit 207 is connected to each other and also to the computer and user interface 206 by a data transfer line 201.

[0049] The deserializer 277D works in conjunction with the serializer 277S of FIG. 3A to serialize various data signals and transmit them through the auto-joint connection mechanism 230, which consists of a relatively small number of wires. The serializer 277S and the deserializer 277D are related to the use of low voltage differential signaling (LVDS) for use in several embodiments. In brief, a synchronization signal is provided between the serializer and the deserializer to ensure synchronization between the serializer and the deserializer. After the relevant data signal is provided to the signal line, a clock signal (e.g., a clock signal that is the exact opposite of the previous clock signal) is sent to the corresponding signal line until the deserializer operation is completed, at the point where the synchronization signal is turned on.

[0050] The position latch 515 is associated with the XYZ latch signals. Briefly, the XYZ latch signals are provided to synchronize the measurement positioning operations of the CRS optical probe with the measurement positioning operations of the CMM controller 202. In one embodiment, the position latch 515 communicates with the position latch 204 of the CMM controller 202 to ensure that the coordinate positions of the CMM 210 are properly synchronized. In other words, the position latch 515 and the position latch 204 are coupled to ensure that all of the derived measurements have their measurement accuracy. This ensures that the CMM machine coordinates (which reflect the position of the CRS optical probe during a particular measurement) are properly coupled to the CRS optical probe measurements (measurements related to the CRS optical probe position).

[0051] The CRS optical probe ID 520 is utilized to identify the CRS optical probe 215' (e.g., by reading and processing an identification signal obtained from an identification element included in the CRS optical probe 215'), and the optical pen ID 525 is utilized to identify the replaceable optical mechanism 280 (e.g., by reading and processing an identification signal obtained from an identification element included in the replaceable optical mechanism 280). Proper identification of the CRS optical probe 215' and the replaceable optical mechanism 280 allows for the use of appropriate configuration and calibration data to verify correct operation and resulting measurements from the CRS optical probe 215' and the replaceable optical mechanism 280.

[0052] FIG. 6 is a structural diagram of an optical pen 220A according to an embodiment. The optical pen 220A includes a non-rotating or fixed part 605, a rotation mechanism 610 for rotating the direction of the replaceable optical mechanism 280A and the measurement light 296, and an encoder 630 for measuring and reporting position information. The position information is, for example, a rotation angle and Z-axis position information about the optical pen, and position information of the calibration member, and is described in detail with reference to, for example, FIGS. 7A to 13E, 16, and 20 to 27C. As shown in FIG. 6, the base member 282A includes components of the non-rotating part 605, the rotation mechanism 610, and the encoder 630.

[0053] FIG. 6 shows some representative "bounding" confocal rays (or ray segments). In particular, rays R1 and R2 are shown between the transfer lens 251 and the aperture 295, and rays R3 and R4 are shown between the transfer lens 251 and the chromatic dispersion optics 250. In some embodiments, the transfer lens 251 is a collimating lens or a lens similar to a collimating lens. The rays R3 and R4 are then approximately parallel or collimated, which provides benefits in some embodiments, as described in more detail below. Rays R5 and R6 are shown within the chromatic dispersion optics 250, which provide rays R7 and R8 as the measurement light 296. Here, the operating position 297 of the confocal aperture can be positioned close to or at the best focus position of the lenses of the optical pen 220. In particular, in this embodiment, it can be positioned close to or at the focus position of the transfer lens 251. The transfer lens 251 may be disposed within the range of the extension portion 282AX of the base member 282A.

[0054] As shown in FIG. 6, the rotation mechanism 610 includes a rotating portion 612. In this embodiment, the rotating portion 612 includes a surface that is to be the first half of the exchange mount 285. The first half can be coupled to the second half of the exchange mount 285 located on the front plate 286 in a similar configuration as described in FIG. 4A and 4B. The rotation mechanism 610 also includes a bearing 614 as well as a motor 616 and a gear 618 for rotational drive to rotate the rotating portion 612. Alternatively, a motor and a rotation actuator (e.g., a motor sleeve mechanism, etc.) may be used. When the transfer lens 251 is located on the base member 282A, the error / effect due to rotation is small. This is because the transmission of the large diameter parallel light shown as parallel light R3 and R4 through the rotation joint is less sensitive to changes in alignment.

[0055] The encoder 630 detects configuration position information (eg, rotational position information, Z-axis position information) of the optical pen 220A and reports the position information, for example, via one or more cables (eg, the probe head cable 211 of FIG. 2).

[0056] In one embodiment, the replaceable optical mechanism 280A may include an ID element 233 (e.g., mounted on the front plate 286). A corresponding reader 233R is disposed in the optical pen base member 282A. The ID element 233 may be encoded with a specific identification information representative of the replaceable optical mechanism 280. In one embodiment, the ID element 233 may include a radio frequency identification device (RFID), which may be a passive RFID. The reader 233R (e.g., an RFID reader) is positioned close enough to the ID element 233 to read data from it. If the reader 233R is not positioned adjacent to the ID element 233, a hole may be provided in the base member 282A. This allows the material of the base member to not block signal exchange (e.g., radio signals, optical signals, optical images, etc.) between the ID element 233 and the reader 233R. The ID element 233 may include an identifying mark (e.g., a simple bar code) or color, and the reader 233R may include a photodetector that provides a signal corresponding to the identifying mark or color. The ID element 233 may also include a passive resonant circuit at a specific frequency, and the reader 233R may include an exciter / detector that provides a signal responsive to the specific frequency. The reader 233R reports identification information based on the response signal, for example, through one or more cables (see probe head cable 211 in FIG. 2).

[0057] For ease of illustration, the rotation mechanism 610 and the encoder 630 are shown in functional block form. The arrangement of the rotation mechanism 610 and the encoding element 630 is exemplary only and not limiting. Various configurations may be modified to similar configurations for rotating and telescoping interchangeable optical mechanisms and reporting position information with minor adaptations that are obvious from this disclosure.

[0058] For calibration and accuracy purposes, the optical pen may be characterized by calibration data or information that includes or is based on radial distance data, and that may be associated with, for example, the following values: Multiple rotation positions of interchangeable optical mechanisms, Various focal lengths and measurement distances for the optical pen 220A, the interchangeable optical mechanism 280, the chromatic dispersion optical element 250, and the exchange mount 285, etc. Such calibration data or information compensates for various misalignments, which may be functions of rotational position, Z-axis position, and CRS measurement distance, as well as other errors (rotary encoder error, Z stage error, etc.).

[0059] 7A-7C are diagrams illustrating an exemplary calibration component 740 for the optical pen 220A of FIG. 6 that can be used to obtain radial distance and other data for use in calibrating the optical pen 220A. FIG. 7A is a conceptual diagram showing an overview of an optical pen configuration including a calibration component, and FIGS. 7B-7C are detailed diagrams of an embodiment. The optical pen 220A of FIG. 7A has a non-rotating or fixed portion 605 and a rotating portion 610. The calibration component 740 includes a calibration gauge extension 744 that moves and is attached to the non-rotating portion 605, and a calibration gauge or calibration member 746. As shown, the calibration gauge 746 is a cylindrical calibration member that is held in place relative to the rotating portion 610 of the optical pen 220A by the calibration gauge extension 744. As the rotation mechanism 610 rotates around the central axis of the optical pen 220A (the reference axis for obtaining measurements), a measurement of the calibration member (e.g., using the measurement light 296 shown in FIG. 7C) is performed to obtain a radial distance measurement for calibration of the optical pen 220A.

[0060] The retention force of the calibration gauge extension 744 can be variously arranged to hold the calibration member 746 in place relative to the rotating chromatic range sensor structure of the optical pen 220A. For example, a similar mechanism can be used for the exchange mount 285. With this arrangement, the calibration member 746 can be automatically connected, positioned, and disconnected from the calibration extension 744 under program control (e.g., under control of the computer and user interface 206).

[0061] As shown in Figures 7B and 7C, the calibration component 740 includes an extended actuator 742. The extended actuator 742 may include bearings, motors, and gears (not shown for ease of illustration, but similar to the bearings 614, motors 616, and gears 618 of the rotation mechanism 610 in Figure 6). The extended actuator 742 facilitates positioning of the calibration gauge extension 744 between the stowed position (Figure 7B) and the extended calibration position (Figures 7A and 7C). Figure 7B shows an example of a structure in which the calibration gauge extension 744 is in the stowed position and is not connected to the calibration member 746'. During a calibration operation using the calibration gauge or the calibration member 746', the calibration gauge extension 744 moves and extends to the calibration position. Alternatively, the calibration gauge extension 744 is stowed in the stowed position to avoid interference with other measurements using the optical pen 220A (e.g., measuring the inner surface of the screw hole shown in Figure 2). As discussed above, in one embodiment, when the calibration gauge extension 744 is moved to the calibration position and extended, the calibration gauge extension 744 connects with the calibration member 746', as shown in FIG. 7C.

[0062] In some embodiments, the optical pen 220A and the calibration member 746' are configured such that the calibration member 746' is held by the optical pen. For example, the calibration member 746' may be held by the calibration gauge extension in its retracted position during the retracted period. This ensures that the calibration gauge extension 744 and the calibration member 746' do not block or interfere with the radial distance detection beam (i.e., the measurement light 296) during normal measurement operations during the retracted period. During the calibration period, the calibration member 746' moves and is held by the calibration gauge extension in its calibration position.

[0063] The calibration gauge extension 744 may be positioned by the extension actuator 742 at one of a number of calibration positions in its extension direction, facilitating collection of calibration radial distance data at different CRS measurement distances or focal lengths. In such a situation, the encoder reports Z-axis position information of the optical pen 220A relative to the position of the calibration member. In a manner similar to the interchangeable optical mechanism 280A described above, the calibration member 746' may include an ID element and the calibration gauge extension 744 may include a reader corresponding to the ID element.

[0064] Alternative configurations for the extension actuator 742 may be utilized (e.g., a motor sleeve mechanism, etc.) The calibration gauge extension 744 also positions the calibration gauge or calibration member 746' in a constrained relationship with respect to the rotating CRS structure of the optical pen 220A.

[0065] As shown in FIG. 7C, the calibration gauge or member 746' comprises a cylindrical ring gauge having an inner circumferential surface 748 and an outer circumferential surface 750. Other calibration members may be used, and various materials (e.g., metal, glass, etc.) may be used for the calibration member. One or more of the inner circumferential surface 748 and the outer circumferential surface 750 may include a printed texture or patterned surface (see, e.g., FIGS. 9A-9D) or various combinations thereof, thereby providing calibration data that may be used to generate calibration information for the optical pen 220A upon scanning with the measurement beam 296.

[0066] The conceptual diagrams shown in Figures 8A-8C show, in an exaggerated manner, examples of some misalignments that result in measurement errors when measuring with an optical pen, and examples of parameters that may be taken into account to compensate for such errors. As shown in Figure 8A, in the ideal case, an optical pen (see optical pen 220A in Figure 6) has a reference central axis 820. When measuring the surface of an ideal cylinder 830, the reference central axis 820 is aligned with the central axis of the cylinder 830. The angle of incidence of the measurement light (see measurement light 296 in Figure 7C) with respect to the normal to the surface of the ideal cylinder 830 is ideally constant. An ideal measurement represents the distance from the ideal center C to an ideal point along an ideal trace 870 of the cylinder 830. An example of an ideal point along the ideal trace 870 is shown in Figures 8A and 8B. This includes the ideal point Pideal 850 at a rotation angle ω = 0.

[0067] However, misalignment of the optical pen or other components can cause measurement errors (due to a variety of factors, such as misalignment of the exchange mount 285). For example, the optical pen's optical axis may have an xy offset 810 from the nominal central axis 820, and the optical pen's axis of rotation 860 along the optical pen length L may be misaligned with respect to the nominal central axis 820 of the optical pen 220A. In addition, the reflective element 294 (see Figs. 2, 7B) may be misaligned from the optical pen's optical axis. As a result, measurements taken of the measurement points are measured from positions S that pivot about a non-ideal center S', as shown in detail in Fig. 8B. These, along with other possible misalignments, can result in the measurement points being on a non-ideal or erroneous trace 890, as shown in Fig. 8B. An example of a measurement point associated with a misalignment error is shown in Figs. 8A and 8B, including a measurement point 840 at a rotation angle ω=0. It should be noted that the illustrated examples contain geometric exaggeration (e.g., the Z axis is reduced to scale to better illustrate potential misalignments and errors).

[0068] FIG. 8B shows an example of misalignment that causes harmonic errors. Here, the reference central axis m (i.e., the mount axis) corresponds to the reference central axis 820 in FIG. 8A. The rotation axis r corresponds to the rotation axis 860 in FIG. 8A. The optical axis o is collinear with the optical axis of the pen along the optical length L of the pen. The axis designations m, r, and o are used in subscripts of the various misalignment parameters, some of which are shown in FIG. 8B. The mount axis misalignment angle θm represents the misalignment angle of the mount axis m with respect to the rotation axis r, occurring in a plane that contains the rotation axis and is oriented by the mount axis misalignment rotational orientation angle φm (not shown). The rotation axis misalignment angle θr represents the misalignment angle of the optical axis o with respect to the rotation axis r, occurring in a plane that contains the rotation axis and is oriented by the rotational misalignment orientation angle φr (not shown). The measurement light emitted by the pen also has a pointing error. The pointing error is represented by the output normal elevation angle error δθo (in the vertical direction) and by the output normal rotation axis error δφo (in the horizontal direction).

[0069] FIG. 8C uses the same exaggerated geometry as FIG. 8B to show an example of first harmonic error caused by various misalignments of the optical pen. As shown in the table, in this example the optical pen has an X-axis offset δx of 50 μm and a Y-axis offset δy of −40 μm, which constitute the x and y components of the xy offset 810 of FIG. 8A. The other parameters shown in the table are defined in the description of FIG. 8B above, with (exaggerated) values ​​as an example. For example, The mount axis misalignment angle θm is 6 degrees, The mount axis misalignment rotation orientation angle φm is 240 μm, The mount axis clock error δφm (not shown) is 5 degrees, The ideal optical pen length L is 2000 μm (shortened in FIG. 8B to exaggerate the error), The rotation axis misalignment angle θr is 8 degrees, The rotation axis misalignment orientation angle φr is 40 degrees, The output normal rotation axis error δφo is 10 degrees, The output normal elevation error δθo is 5 degrees, The ideal calibration measurement distance is 1000 μm. To some extent, the rotation related error (symbol φ) is coupled to the phase of the rotation offset error and the harmonic error. The axial misalignment and elevation error (symbol θ) are coupled to the radial offset, Z offset and harmonic amplitude errors. As shown, the radial error is primarily a first harmonic oscillating about a radial offset error of about -180. The Z error is primarily a first harmonic oscillating about a constant Z error offset, which is an offset constant of about 180 μm. The rotation error is primarily a first harmonic oscillating about a rotation offset constant of about -50 μm. All three curves have slight but higher order harmonic content. In this example, various points are exaggerated to better illustrate the potential misalignments and the errors they introduce. The actual misalignments in one embodiment are on the order of 0.1 to 1 degree, and the actual errors (other than xy offsets) are on the order of sub-single micrometers.

[0070] As described elsewhere, radial distance measurements obtained by measuring a calibration member at a given rotation angle ω and a given Z position are used to generate calibration data. The calibration data can similarly be used to adjust measurement data (e.g. radial distance data) obtained by measuring a workpiece with an optical pen of a coordinate measuring machine. The calibration data added to the radial distance data generated using the calibration member can be used as part of the calibration information or can be used to generate the calibration information. For example, measurements obtained using an interferometer (e.g. distances measured at various light wave frequencies) or measurements of the calibration member can be used to determine the CRS distances relative to the optical pen. In another example, the Z axis information of the optical pen relative to the position of the calibration member can be used. In another example, Measurements taken from a plurality of cylindrical calibration members; Measurements taken from a plurality of spherical calibration elements; or Such as measurements taken from multiple types of calibration members (e.g., measurements taken from a cylindrical calibration member and measurements taken from a spherical calibration member). Radial distance measurements from multiple calibration members may be used.

[0071] 9A-9D show a calibration member 946 in the form of a ring gauge according to a first embodiment. FIG. 9A shows a perspective view of the cylindrical ring gauge 946, and FIG. 9B shows a cross-sectional view thereof. The inner peripheral surface 904 of the cylindrical ring gauge 946 has a number of known features, such as a printed or machined pattern 906, in a known positional relationship to one another. The inner peripheral surface 904 is a cylindrical calibration surface, and a central axis 905 of the inner peripheral surface 904 along the Z direction is aligned to be approximately parallel to the rotation axis of the CRS optical pen during calibration measurements (see, for example, reference central axis 820 and rotation axis 860 in FIG. 8A). The illustrated first cylindrical calibration surface 904 is located at a known distance of a first radius Rc from the central axis 905 along the Z axis.

[0072] 9C and 9D conceptually show an example of a pattern, and show a printed or processed pattern applied (printed) or formed on the inner peripheral surface 904 in a flat printed or processed view. The printed or processed pattern 906 may include a first set of angular reference features (e.g., reference lines, etc.). The angular reference features are formed on or within the first cylindrical calibration surface. That is, the angular reference features are configured to be detectable by a radial distance detection beam on or within the first cylindrical calibration surface, and are arranged at known angles or angular intervals from each other around the central axis. The features of the pattern are configured to be detectable by an optical pen, such as the optical pen 220A in FIGS. 7A to 7C. For example, a printed pattern may be black and white, grayscale, or multicolored, and a processed pattern may be changed in depth or shape. Various combinations of these may also be used.

[0073] 9C, pattern 906 has rotation indicia or vertical reference lines 908 spaced at known intervals that may be regular or irregular. Pattern 906 also has Z axis indicia or tilt reference lines 910 spaced at known intervals that may be regular or irregular. The vertical lines 908 provide calibration information for the rotational position. The inclined lines 910 provide calibration information for the Z-axis position relative to the rotational indicator or vertical reference line 908. The lines 908, 910 may be formed with a constant thickness or with a variable thickness. For example, as shown, one of the vertical lines 908 may be a reference line with a different thickness than the other vertical lines to indicate a specific rotational position on the calibration gauge 946. Multiple reference lines may be used to indicate multiple specific positions (e.g., intermediate points) on the calibration gauge. In the case of a machining pattern, the pattern 906 in FIG. 9C represents a machining diagram showing the location of a depression or protrusion to be formed on the inner peripheral surface 904 of the calibration member. In other embodiments, the inner peripheral surface 904 is flat.

[0074] For ease of illustration, the vertical lines 908 of the pattern 906 in Fig. 9C are shown as white bars and the inclined lines 910 as black bars. In the case of a printed pattern, in practice the two types of bars can be the same color (e.g. black) or different colors (e.g. indicating an angular position relative to the bars), or various combinations of these are also possible. As mentioned above, in the case of an engineered pattern, depressions of different widths and depths can be used to facilitate measuring the calibration information.

[0075] Also shown in Figure 9C is an example of a calibration measurement trace 920. Position information of the trace 920 acquired by the optical pen 220A (e.g., position information provided by the encoder 630 in Figure 6 as a measurement on the trace 920) may be used as calibration data or information together with the measurement results on the trace 920 (e.g., radial distance measurement data and Z position measurement data), or may be used to create calibration data or information based on, for example, a difference between the measurement results for each measurement position and an ideal result.

[0076] Pattern 906' in Figure 9D is similar to pattern 906 in Figure 9C, except that it does not include the slanted lines 910, and trace 920' measures calibration information for the calibration member using only the vertical lines 908. If Z-axis calibration information is required, it can be obtained in other ways, such as by detecting the top or bottom edges of calibration member 946 as the calibration member is moved into position. Other patterns may also be used in conjunction with or substituted for the calibration (e.g., a slanted grid, horizontal and slanted lines, etc.).

[0077] FIG. 10 is a cross-sectional view of a calibration member 1046 having a central axis 1005 according to the second embodiment. The calibration member 1046 is a ring gauge having a stepped diameter, and has a first inner peripheral surface 1048 having a first diameter and a second inner peripheral surface 1048' having a second diameter smaller than the first diameter. One or both of the first and second inner peripheral surfaces 1048, 1048' may be provided with a pattern surface for calibration measurement (e.g., a printed or machined pattern surface, see FIGS. 9C and 9D). The use of the ring gauge 1046 having a stepped diameter facilitates calibration measurements at multiple measurement distances simultaneously with calibration measurements regarding the Z axis. The calibration gauge extension 744 (see FIGS. 7A to 7C) can position the calibration gauge 1046 relative to the measurement light 296 in a first extended position, which facilitates calibration reading of the first inner peripheral surface 1048. Additionally, the calibration gauge extension 744 can position the calibration gauge 1046 relative to the measurement beam 296 in a second extended position, which can facilitate a calibration reading of the second inner circumferential surface 1048'. Additionally, in other embodiments, detection of the change from the first inner circumferential surface 1048 to the second inner circumferential surface 1048' can be used to obtain Z-axis calibration information.

[0078] FIG. 11A is a perspective view of a calibration member 1146 in the shape of a ring gauge according to another embodiment. FIGS. 11B and 11C are conceptual diagrams showing an embodiment of a calibration member 1146' in the shape of a ring gauge similar to that of FIG. 11A. The calibration member 1146 in FIG. 11A has a plurality of cylindrical inner circumferential surfaces 1148i to 1148n, the diameters of which change stepwise from 1149i to 1149n. Similarly, the calibration member 1146' in FIGS. 11B and 11C has a plurality of cylindrical inner circumferential surfaces 1148i' to 1148n' having diameters 1149i' to 1149n' which change stepwise. A pattern surface for calibration measurement may be provided on one or more of the cylindrical inner circumferential surfaces 1148i to 1148n or 1148i' to 1148n' (for example, a printed or processed pattern surface, see FIGS. 9C, 9D, 13D, and 13E). In FIG. 11A, seven steps of the inner peripheral surface are provided, while in FIGS. 11B and 11C, ten steps of the inner peripheral surface are provided. FIG. 11B shows a processing diagram of the ten steps of the inner peripheral surface of the ring gauge 1146'. FIG. 11C shows a 3D plot of representative measurement data of stepped inner diameters 1149i'-1149n' of the cylindrical inner peripheral surface 1148i'-1148n' of the ring gauge 1146' collected during a spiral scan in the Z direction with a rotating optical pen. This facilitates a calibration read of the first inner peripheral surface 1048. The stepped surfaces of the calibration members 1146, 1146' facilitate the acquisition of measurements over the entire measurement range for distance (e.g., radial distance measurements) simultaneously with the acquisition of Z-axis calibration data. The acquired measurements can be used to generate calibration information for the measurement range of CRS distances of the optical pen.

[0079] As shown in FIG. 11A, the outer peripheral surface 1150 of the ring gauge 1146 includes a flat surface 1152 with a recess 1154. The flat surface 1152 and recess 1154 facilitate the positioning of the ring gauge 1146 in a constrained relationship with respect to the rotational CRS structure of the optical pen by the calibration gauge extension (see calibration gauge extension 744 of optical pen 220A in FIGS. 7A-7C). Specifically, when the optical pen is mounted on a measurement platform (set for rotation angle ω=0), the flat surface 1152 provides a reference surface for the rotation angle ω of the optical pen. Additionally, the orthogonal surface of the recess 1154 provides a reference for alignment in the Z-axis direction. For example, the flat surface 1152 and recess 1154 are sized and shaped to receive a corresponding tab or protrusion (not shown) on the calibration gauge extension. This allows the calibration gauge extension to hold the ring gauge 1146 in a constrained relationship with respect to the rotational CRS structure. Other positioning schemes may be used (eg, flat surfaces on opposite sides of the ring gauge, differently shaped recesses, tabs on the calibration member and corresponding recesses on the calibration gauge extension, etc., as well as various combinations thereof).

[0080] FIG. 12A shows a perspective view of a calibration member 1246 in the form of a precision glass tube according to another embodiment, and FIG. 12B shows a cross-sectional view thereof. According to FIG. 12B, the precision glass tube 1246 has a cylindrical inner circumferential surface 1204 and a cylindrical outer circumferential surface 1250. One or both of the inner circumferential surface 1204 and the outer circumferential surface 1250 may be provided with a pattern surface for calibration measurement (e.g., a printed or machined pattern surface, see FIGS. 9C, 9D, 13D and 13E). The pattern of the cylindrical surface may include non-patterned portions (e.g., gaps or windows between reference lines), which facilitates the measurement of the pattern of the other cylindrical surface. For example, the pattern of the cylindrical inner circumferential surface 1204 may have gaps or windows (see window 1374 in FIG. 13D) through which features of the pattern of the cylindrical surface 1250 may be observed, measured or otherwise detected.

[0081] The inner and outer circumferential surfaces 1204 and 1205 are cylindrical calibration surfaces with a central axis 1205 along the Z direction. During calibration measurements, the central axis 1205 is aligned as parallel as possible to the rotation axis of the CRS optical pen (see, for example, reference central axis 820 and rotation axis 860 in FIG. 8A). The first cylindrical calibration surface 1204 is located at a first known radius Ri from the central axis 1205 in the Z direction as shown. The second cylindrical calibration surface 1250 is located at a second known radius Ro from the central axis 1205 in the Z direction as shown.

[0082] In some embodiments, the inner circumferential surface 1204 has a pattern for measuring one type of calibration information (e.g., a pattern that facilitates measuring angular position information), and the outer circumferential surface 1250 has a pattern for facilitating measuring another type of calibration information (e.g., a pattern that facilitates measuring Z-axis position information). In some embodiments, the outer circumferential surface 1250 may have a patterned surface, while the inner circumferential surface 1204 may be unpatterned and may be a transparent or semi-transparent surface. Distance measurements (radial distance) are obtained by sensing the inner circumferential surface 1204 and the outer circumferential surface 1250 (e.g., a known or measured refractive index for the material may be used to convert from optical thickness to physical thickness, if necessary). Angular position and Z-axis position measurements are obtained by sensing features of the pattern on the outer circumferential surface 1250.

[0083] FIG. 12C illustrates a calibration member 1246′ comprising two nested precision glass tubes, an inner tube 1258 and an outer tube 1260, according to an embodiment. The inner tube 1258 has a calibration surface 1262 formed of a cylindrical inner circumferential surface and a calibration surface 1264 formed of a cylindrical outer circumferential surface. The outer tube 1260 has a calibration surface 1266 formed of a cylindrical inner circumferential surface and a calibration surface 1268 formed of a cylindrical outer circumferential surface. The calibration surfaces 1262, 1264, 1266, and 1268 have a central axis 1205 along the Z direction. During the calibration measurement, the central axis 1205 is aligned as parallel as possible to the rotation axis of the CRS optical pen (see, for example, the reference central axis 820 and the rotation axis 860 in FIG. 8A). The calibration surface 1262 is located at a known radius R1i from the central axis 1205 in the Z direction, as shown. As shown, the calibration surfaces 1264 and 1266 are each disposed at a distance of approximately known radius R2i from the central axis 1205 in the Z direction (for simplicity of explanation, it is assumed that the difference in radius between the two calibration surfaces 1264 and 1266 is negligible). The calibration surface 1268 is disposed at a position of known radius R2o from the central axis 1205 in the Z direction, as shown.

[0084] A pattern surface for calibration measurements may be provided on one or more of the cylindrical inner surface 1262 of the inner tube 1258, the cylindrical outer surface 1264 of the inner tube 1258, the cylindrical inner surface 1266 of the outer tube 1260, and the cylindrical outer surface 1268 of the outer tube 1260 (e.g., a printed or machined pattern surface, see Figures 9C, 9D, 13D, and 13E).

[0085] A cylindrical surface pattern may include non-patterned portions (e.g., gaps or windows between reference lines) that facilitate measuring patterns on other cylindrical surfaces. For example, the pattern on the cylindrical inner circumferential surface 1262 of inner tube 1258 may have gaps or windows through which features of the pattern on the cylindrical inner circumferential surface 1266 of outer tube 1260 may be viewed, measured, or otherwise detected, similar to the description of FIG. 12B.

[0086] In some embodiments, the outer periphery 1268 of the outer tube 1260 is patterned, while the remaining surfaces of the inner tube 1258 and outer tube 1260 are unpatterned and transparent or semi-transparent. Distance measurements (radial distance) are obtained by detecting one or more of the inner periphery 1262 of the inner tube 1258, the outer periphery 1264 of the inner tube 1258, the inner periphery 1266 of the outer tube 1260, and the outer periphery 1268 of the outer tube 1260. Rotational and Z-axis position measurements are obtained by detecting pattern features on the outer periphery 1268 of the outer tube 1260. Various combinations of patterned and non-patterned surfaces and / or types of patterns may be used. Nested tubes may also be added. A bottom cap or other retaining structure may be used to hold the nested tubes 1258, 1260 in place relative to one another. The nested glass tube embodiment facilitates acquisition of calibration information covering the full measurement range of the optical pen CRS measurement distances simultaneously with acquisition of Z-axis calibration data, allowing multiple gauge distance measurements without repositioning the calibration member. As described in FIG. 12B, optical distances or optical thicknesses may be converted to physical distances, if desired.

[0087] Figures 13A-13E show an embodiment of a nested calibration member 1346 made of multiple precision metal tubes 1358, 1360, 1370. In Figures 13A-13E, for ease of illustration, the nested metal tubes 1358, 1360, 1370 are exaggerated in size and the spacing between the metal tubes is negligible or exaggerated. More than three nested metal tubes can also be used (e.g., seven or more tubes).

[0088] FIG. 13A is a longitudinal cross-sectional view of the calibration member 1346. Precision metal tube 1358 has an inner circumferential surface 1362, precision metal tube 1360 has an inner circumferential surface 1366, and precision metal tube 1370 has an inner circumferential surface 1372. The inner circumferential surfaces 1362, 1366, and 1372 have a central axis 1305 extending in the Z direction that is aligned to be approximately parallel to the rotation axis of the CRS optical pen during calibration measurements (see, for example, reference central axis 820 and rotation axis 860 in FIG. 8A). The cylindrical calibration surfaces 1362, 1366, and 1372 are located at known radial distances (such as R1, R2, and R3 shown) from the central axis 1205 in the Z direction.

[0089] 13B is a cross-sectional view of an embodiment of nested metal tubes 1358, 1360, 1370 having different lengths L1, L2, L3 along the Z-axis 1305. A portion of one or more of the inner circumferential surface 1362 of metal tube 1358, the inner circumferential surface 1366 of metal tube 1360, and the inner circumferential surface 1372 of metal tube 1370 may be provided with a patterned surface for calibration measurements (e.g., a printed or machined patterned surface, see FIGS. 9C and 9D). Calibration measurements are performed in a similar manner as described for graduated diameter ring gauge 1046 of FIG. 10 and graduated diameter ring gauges 1146, 1146' of FIGS. 11A-11C.

[0090] The calibration gauge extension 744 (see FIGS. 7A-7C) can position the calibration gauge 1346 at a first extended position relative to the measurement beam 296 to facilitate taking a calibration reading of the inner circumferential surface 1362. The calibration gauge extension 744 can also position the calibration gauge 1346 at a second extended position relative to the measurement beam 296 to facilitate taking a calibration reading of the inner circumferential surface 1366. The calibration gauge extension 744 can also position the calibration gauge 1346 at a third extended position relative to the measurement beam 296 to facilitate taking a calibration reading of the inner circumferential surface 1372. Detection of changes in the inner circumferential surfaces 1362, 1366, 1372 can be used to obtain Z-axis calibration information in addition to or instead of Z-axis calibration information based on the surface patterns of one or more of the inner circumferential surfaces 1362, 1366, 1372. Other configurations may also be used in conjunction with or substituted for the calibration (e.g., including a pattern on the inner surface of the outer tube and viewing the pattern through an opening or window in the inner tube, as detailed in FIG. 13D).

[0091] 13C-13E show an embodiment of a calibration gauge 1346 that includes nested metal tubes 1358, 1360, 1370 that generally have the same length L1 along the Z axis 1305. These may be tapered slightly in the length direction (not shown) to help provide a calibration gauge with good concentricity and alignment. The side surface of the inner tube (such as the metal tubes 1358, 1360 shown) is provided with a pattern in the form of windows or segments that penetrate the side wall of the tube, as shown conceptually in FIGS. 13D-13E below. Measurement light 296 can pass through these windows or segments to reach the larger diameter tube wall. At least a portion of the remaining portions of inner surface 1362 of tube 1358, inner surface 1366 of tube 1360, and inner surface 1372 of tube 1370 may be provided with a patterned surface (e.g., a printed or machined patterned surface; see Figures 9C and 9D) for calibration measurements in a manner similar to that described above.

[0092] The illustrated calibration member 1346 includes a cap 1380 that holds the tubes 1358, 1360, and 1370 in place relative to one another. A calibration gauge extension 744 (see FIGS. 7A-7C) can engage the cap 1380 to position the calibration gauge 1346 in a constrained relationship to the rotating CRS structure. The nested metal tube embodiment shown in Figures 13D and 13E allows calibration information over the measurement range of the optical pen's CRS distances to be easily obtained simultaneously with obtaining Z-axis calibration information without having to reposition the calibration member at each of the gauge distances R1, R2, and R3.

[0093] FIGURE 13D conceptually illustrates calibration member 1346. A nested inner tube 1358 of calibration member 1346 has a pattern in the shape of a window 1374 extending therethrough. A nested central tube 1360 has a pattern in the shape of a window 1376 extending therethrough. FIGURE 13D illustrates example patterns shown as printed / machined views of the windows, which are planar developments of one or more patterns applied (printed) or formed on the inner surfaces 1362, 1366, 1372 of tubes 1358, 1360, 1370.

[0094] The window 1374 of inner tube 1358 and the window 1376 of central tube 1360 are sized and the inner and central tubes 1358, 1360 are positioned such that, during a measurement operation, the rotating CRS structure (see FIGS. 7A-7C) can sense the window 1376 of tube 1360 through the opening of window 1374 in tube 1358 and can also sense a portion of the inner surface 1372 of outer tube 1370. Sensing of the windows 1374, 1376 and inner surfaces 1362, 1366, 1372 by the rotating CRS structure (see FIGS. 7A-7C) provides calibration measurement data or is used to generate calibration data or information.

[0095] Additionally, one or more of the inner surfaces 1362, 1366, 1372 may have a patterned surface (e.g., a printed or machined patterned surface, see FIGS. 9C and 9D) that can also be used for calibration measurements. The inner surface 1362 of the illustrated tube 1358 includes vertical patterned lines 1308, the inner surface 1366 of the tube 1360 includes slanted lines 1310, and the inner surface 1372 of the tube 1370 includes slanted lines 1310. The illustrated windows 1374, 1376 are rectangular, but some or all of the windows may have slanted sides. The slanted sides may provide Z-axis calibration measurement data (e.g., instead of or in addition to the slanted lines 1310).

[0096] The embodiment of Figure 13E is similar to the embodiment of Figure 13D, except that nested inner tube 1358 has a pattern in the shape of a segment 1382 passing through tube 1358 instead of a window, and nested central tube 1360 has a pattern in the shape of a segment 1384 passing through tube 1360 instead of a window. Figure 13E shows example patterns shown as printed / machined views of segments that are flattened out from one or more patterns printed or formed on inner surfaces 1362, 1366, 1372 of tubes 1358, 1360, 1370.

[0097] In a measurement operation, the segment 1382 of the inner tube 1358 and the segment 1384 of the central tube 1360 are sized and the inner and central tubes 1358, 1360 are positioned relative to each other such that the rotating CRS structure (see FIGS. 7A-7C) can detect segment 1384 of tube 1360 through the opening of segment 1382 of tube 1358 and detect a portion of the inner surface 1372 of the outer tube 1370 through the openings of segments 1382, 1384 in at least partial alignment. Detection of segments 1382, 1384 and inner surfaces 1362, 1366, 1372 by the rotating CRS structure (see FIGS. 7A-7C) can provide calibration measurement (distance) data that can be used as or to generate calibration data or information. Additionally, as described above, one or more of the inner circumferential surfaces 1362, 1366, 1372 may be provided with a patterned surface (eg, a printed or machined patterned surface such as the sloping lines 1310) that can also be used for calibration measurements.

[0098] 14 shows a graph of calibration test data collected using a cylindrical calibration member to measure seven calibration steps and plotted in a cylindrical coordinate system (Z axis in the plane of the paper). For example, a calibration ring gauge with seven or more concentric calibration surfaces may be used, such as a stepped calibration surface (see, e.g., Figs. 11A-11C, 13B) and / or multiple calibration surfaces generally aligned perpendicular to the Z axis of the rotating CRS device (see, e.g., Figs. 12C, 13C-13E). The vertical axis represents radial distance measurements and the horizontal axis represents the rotation angle of the optical pen plotted in units of rotation cycles. Measurements under different radial distance conditions are repositioning the calibration member in the Z-axis direction (e.g., using the calibration gauge extension 744 of FIGS. 7A-7C to align a calibration member having a stepped surface, such as in the embodiment of FIGS. 11A-11C and 13B); adjusting control parameters of a probe signal processing control circuit (see probe signal processing control circuit 207 in Figs. 2 and 5) as much as possible; and / or and scanning a Z-axis stage incorporated in the telescopic section or the base section to perform a spiral scan.

[0099] Table 1 illustrates the error sources in a rotated CRS structure. See also Figure 8C above.

[0100] [Table 1]

[0101] The errors due to misalignment may also be expressed by a set of mathematical equations. The errors may be compared to measurement data collected from the calibration components to generate calibration data or information for correcting the errors (e.g., adjusting test measurement results). For example, curve fitting to the measurement data may be used to determine coefficients in the equations that represent the errors.

[0102] As an example, the error of the measurement value is expressed by the following relational expression (1).

[0103]

number

[0104] Here, D C ,ω C (,Z C ) is the data variable for the measured input value (Z C is a third measurement input that is not in the equation above but can be collected. ΔR, Δφ, and ΔZ are the measurement errors. The fitting coefficients up to the second harmonic are the remaining symbols, all defined below. D C represents the corrected distance measurement data from an optical pen and is calibrated to be non-rotational and linear, but may have offset and scaling errors as a result of various mechanical misalignments of the measurement device during rotational measurements. ω C represents the corrected rotation angle output value of the optical pen's rotary encoder. ZC represents the corrected Z-axis stage position output value of the optical pen rotary encoder platform.

[0105] ΔR represents the radial distance measurement error and includes terms with coefficients: Ro represents the constant term of the radial offset. R L represents the coefficient of the radial linear (scaling) term. C R1 represents the amplitude coefficient of the radial first harmonic term. θ R1 represents the phase coefficient of the radial first harmonic term. C R2 represents the amplitude coefficient of the radial second harmonic term. θ R2 represents the phase coefficient of the radial second harmonic term.

[0106] Δφ represents the rotation measurement error and includes terms with coefficients: φo represents the constant term of the rotation offset. φ L represents the coefficient of the rotational linear (scaling) term. Cφ1 represents the amplitude coefficient of the rotational first harmonic term. θφ1 represents the phase coefficient of the rotational first harmonic term. Cφ2 represents the amplitude coefficient of the rotational second harmonic term. θφ2 represents the phase coefficient of the rotational second harmonic term.

[0107] ΔZ represents the Z-axis measurement error and includes terms with coefficients: Zo represents the constant term for the Z-axis offset. Z L represents the coefficient of the Z-axis linear (scaling) term. C Z1 represents the amplitude coefficient of the Z-axis first harmonic term. θ Z1 represents the phase coefficient of the Z-axis first harmonic term. C Z2 represents the amplitude coefficient of the Z-axis second harmonic term. θ Z2represents the phase coefficient of the Z-axis second harmonic term. In some embodiments, the second harmonic term here is treated as negligible, while other embodiments may include second and higher order harmonic terms.

[0108] The fully corrected measurements of the rotational CRS measurement device are expressed in a cylindrical coordinate system according to the relationship in equation (2).

number

[0109] The terms on the right are as defined above. R RCPS,c represents the fully corrected radial distance measurement. φ RCPS,c represents the fully corrected measurement of the rotation angle. Z RCPS,c represents the Z-axis distance measurement. Figure 14 shows an example of the Z-axis projection of the corrected data for the calibration element of Figure 11B plotted in a cylindrical coordinate system, where the data has been corrected for at least the radial offset.

[0110] The data is transformed from cylindrical to Cartesian coordinates using equation (3).

number

[0111] Transformations are useful for visualizing data. Figure 11C is an example of the data from Figure 14 transformed and plotted in a Cartesian coordinate system. Transformations can also be used to normalize the data. For example, the data may be transformed into a Cartesian coordinate system, and then a rotation and translation transformation may be performed to align the data with the Z axis, and then a transformation back to a cylindrical coordinate system may be performed.

[0112] In some cases, measurements of small radii are of interest, and calibration to the radius measurement of one calibration element is sufficient. In these cases, the linear coefficient R L ,φL ,Z L are set to zero and the fit only needs to include the constant offset terms Ro, φo, Zo, together with harmonic terms if necessary (e.g. only the first and second harmonic terms for radius are needed). In other cases, measurements are performed over the entire radius range of the optical pen, and the entire range of radius measurements is calibrated using separate ring gauges, or preferably one multi-stage ring gauge. If necessary, potential rotational and Z-axis errors at different radii can be calibrated out using a calibration member having marks or shapes necessary for rotational and Z-axis calibration. In such cases, the linear fit is performed using the linear coefficients R L ,φ L ,Z L and constant offset terms Ro, φo, and Zo. The fit is done simultaneously to these parameters as well as the harmonic coefficients. In some cases it may be desirable to average the radial data over a regular integer number of rotation cycles (which averages out the harmonic content) (see Figure 14, labelled "Average Radial Distance"). The linear and offset terms are then fitted only to the average radial data over multiple gauge radii Ri to obtain the linear correction coefficients R L ,φ L ,Z L and determine the constant offset correction terms Ro, φo, and Zo.

[0113] As an example, FIG. 15 shows a graph of the calibration test data of FIG. 14 along with an indication of the traceable tolerances. The vertical axis of FIG. 15 represents the mean radial distance and the horizontal axis represents the gage number (step number in the case of a stepped gage) of the calibration member. At a given radial distance or step, the difference between the test data and the traceable tolerance corresponds to the radial error ΔR at that distance or step. A straight line fit to the test data shows good linearity, but some offset and slope errors from the traceable tolerances of the multi-step calibration member. A linear fit of the measured mean radial distance (dashed line) and its relationship to the traceable tolerances for each step radius (i.e., ΔR=Ro+R from Equation (1)) is shown. L DC ) to obtain the corrected slope R L A method for calibrating the measurements to the trace tolerance is derived using the calibration coefficients for slope and offset Ro. By using the corrected slope and offset to calibrate the rotating CRS structure, the radius measurements can be performed with high accuracy in the entire measurement range. Similar corrections are preferably applied to the Z axis and rotation angle as well, using Z axis or rotation angle reference patterns of the calibration member at different radial positions.

[0114] FIG. 16 graphically illustrates obtaining more consecutive calibration distance measurements at a range of different distances (four different gauge distance locations shown) and at a range of different offsets (N offset locations shown). By comparing measurements at different gauge distances and offset locations, e.g., by performing simultaneous curve fitting, errors due to mechanical rotation (errors that have a common mode with respect to the rotation angle) can be separated from errors due to CRS pen calibration (errors that have a common mode with respect to the CRS distance measurements).

[0115] The use of XY offsets from the axis of the gauge (e.g., multiple distance gauges) and multiple gauge distance steps provides measured distance data for each CRS distance within the CRS measurement range. This facilitates continuous calibration of the CRS distances as opposed to piecewise linear calibrations based solely on the radius of each ring gauge distance or step. For example, a first calibration performed with the ideal axis of the optical pen centered on the calibration member can remove harmonic errors. As shown in FIG. 16, at the first offset, the ideal axis of the optical pen is aligned with the central axis of the calibration member. This data can be used to correct specific radius measurements with small deviations. Calibrated distance measurements are then performed at multiple offsets from the central axis of the calibration member to the ideal axis of the optical pen (e.g., offsets 2 through N). The generated data may include measurements at successive radial distances. The XY offsets introduce small vibration deviations in the alignment of the sensor with respect to the ring gauge or similar work surface. Depending on the type of surface of the calibration member, such deviations may result in radius measurement errors. In such an embodiment, if the surface type is known and the angular deviation is deterministic, a look-up table or similar calculation can be used to correct for such errors.

[0116] The ring gauge (i.e., calibration member) described herein is particularly advantageous for calibrating the optical pen when the axis of the optical pen can be aligned to the axis of the ring gauge and subsequent workpiece measurements are performed in that aligned state (e.g., the same alignment). These configurations can be realized on a variety of platforms (e.g., SCARA-type assembly robots, image processing systems, CMMs, etc., each with a fixed automatic joint). For example, in these configurations, the probe is held in a fixed orientation (e.g., vertical) (i.e., the probe can be used for the calibration process as well as for performing workpiece measurements), and the ring gauge can be mounted on the platform in a corresponding fixed orientation (e.g., vertical) for the calibration process.

[0117] 17 is a flow diagram illustrating a calibration procedure 1700 according to one embodiment of a rotating CRS structure of a CMM. The procedure 1700 may be performed, for example, using one or more embodiments of a CMM with a calibration member described herein. The procedure provides calibration data or information for correcting misalignment errors of the rotating CRS structure. The rotating CRS structure is configured to project a radial distance sensing beam along a radial direction about an axis of rotation and to rotate the radial distance sensing beam about the axis of rotation.

[0118] The procedure 1700 begins in step 1702 by the probe signal processing control circuit (e.g., probe signal processing control circuit 207 of FIGS. 2 and 5) invoking the procedure. The procedure 1700 includes steps 1702 through 1710. In step 1710, a calibration member (see, e.g., cylindrical calibration member 746 of FIGS. 7A-7C, cylindrical calibration member 946 of FIGS. 9A-9D, cylindrical calibration member 1046 of FIG. 10, cylindrical calibration members 1146, 1146' of FIGS. 11A-11C, cylindrical calibration member 1246 of FIGS. 12A-12B, cylindrical calibration member 1246' of FIG. 12C, and cylindrical calibration member 1346 of FIGS. 13A-13E) is positioned with respect to the rotating CRS structure of the CMM (see, e.g., FIGS. 6, 7A-7C). The calibration member has at least a first cylindrical calibration surface (see, for example, surfaces 1148i-1148n and 1148i'-1148n' in Figures 11A-11C), which has a central axis aligned substantially parallel to the rotational axis of the CMM, with the central axis oriented along the Z direction.

[0119] The first cylindrical calibration surface may include one or more reference features formed on or within the first cylindrical calibration surface, such as a first set of vertical reference features (e.g., see vertical lines 908 in FIG. 9C ) and / or a first set of tilted reference features (e.g., see tilted lines 910 in FIG. 9C ). The reference features may be configured to be detectable by the radial distance detection beam and may be at predetermined locations relative to one another (e.g., the tilted reference features may be located on or within the first cylindrical calibration surface at a known angle or angular spacing relative to one another about a central axis).

[0120] The calibration member may be arranged in a constrained relationship with respect to the rotating CRS structure. Here, the direction of the rotation axis and the direction of the central axis have a certain angular relationship with each other, and the parallelism between the two is within a certain threshold, for example, within 5 degrees. The calibration member may be held in a constrained state by, for example, a calibration gauge extension of the rotating CRS structure (see, for example, calibration gauge extension 744 in FIGS. 7A-7C). Procedure 1700 proceeds from step 1710 to step 1720.

[0121] In step 1720, the rotating CRS structure is operated to provide a first set of radial distance measurement data acquired at a first Z coordinate position in the Z direction relative to the calibration member while rotating the radial distance detection beam about the rotation axis and references a sensed rotation angle of the radial distance detection beam about the rotation axis. For example, an encoder (see encoder 630 in FIG. 6) can provide the sensed value of the rotation angle information. Procedure 1700 proceeds from step 1720 to step 1730.

[0122] At step 1730, the procedure 1700 determines whether to obtain an additional set of radial distance measurement data. If at step 1730, it is determined that an additional set of measurement data is to be obtained, then the procedure 1700 proceeds from step 1730 to step 1740.

[0123] In step 1740, optical adjustments are performed to facilitate acquisition of additional sets of radial distance data, such as repositioning a stepped calibration member (e.g., calibration member 1146 of FIGS. 11A-11C) using a calibration gauge extension (e.g., calibration gauge extension 744 of FIGS. 7A-7C), or otherwise adjusting the relative positions of the calibration member and / or the CRS probe, adjusting signal processing routines, etc. From step 1740, procedure 1700 returns to step 1720 to operate the CRS probe to acquire additional sets of radial distance measurement data.

[0124] If, at step 1730, an additional set of radial distance measurement data is not acquired, the procedure proceeds from step 1730 to step 1750. At step 1750, procedure 1700 processes the acquired set of radial distance measurement data referenced to a sensed rotation angle to determine calibration data that is configured for use in characterizing or compensating for radial distance measurement errors as a function of a sensed rotation angle of the radial distance detection beam about the rotation axis. Procedure 1700 proceeds from step 1750 to step 1760 to end or to perform additional processing (e.g., storing the calibration data and / or determining additional calibration data).

[0125] More or fewer operations may be performed in procedure 1700 than those shown, and operations may be performed in various orders. For example, in one embodiment, procedure 1700 may simultaneously acquire sets of radial distance data for multiple measurement distances (e.g., when measuring a calibration member having multiple calibration surfaces generally aligned in a direction perpendicular to the Z axis of a rotating CRS device (see FIGS. 12C, 13C-13E)). Procedure 1700 may process one or more sets of radial distance measurement data before completing acquisition of the sets of radial distance measurement data. In another example, calibration information may include data acquired using an interferometer, such as ideal CRS distance data for an optical pen, radii of one or more cylindrical calibration surfaces, etc. Procedure 1700 may be modified to include operations of retrieving interferometrically acquired data and / or performing interferometric measurements.

[0126] As noted above, other calibration members may be employed in addition to or in place of the cylindrical calibration members, for example spherical calibration members.

[0127] FIG. 18 shows a representative configuration of a coordinate measuring system 1800 including a CMM 210 and a number of calibration members. The coordinate measuring system 1800 is configured similarly to the coordinate measuring system 200 of FIG. 2, and here, detailed examples of specific components included in the system will be described in addition, and examples of its operation will be described. These are indicated with similar or identical reference numerals to those in FIG. 2. The coordinate measuring system 1800 includes a manual operation unit 1810, and a host equipment system including an interface equipment 202′ and a host computer 206 (e.g., including a computer and a user interface). The interface equipment 202′ includes, for example, a motion controller 205 for controlling the operation of the CMM 210, a probe signal processing and control circuit 207 (e.g., may be included in other configurations, or may be included in other configurations as an alternative), and an interface circuit (not shown) connected to the CRS optical probe 215 (e.g., via a signal control line 201A).

[0128] The manual operation unit 1810 may be connected to and / or part of the interface device 202′ (e.g., via a signal control line 201C) and may include a joystick 1811 for manual operation of the CMM 210. The host computer 206 is connected to the interface device 202′ (e.g., via a signal control line 201B). The host computer 206 may execute the operation of the CMM 210 by user input or program control and process measurement data of a workpiece W having a measured surface 290 (e.g., the measured surface 290 may be the inner surface of a screw hole in the workpiece W). The host computer 206 includes an input means 1812 (e.g., a keyboard, etc.) for inputting, for example, measurement conditions and measurement procedures, and an output means 1813 (e.g., a display, a printer, etc.) for outputting, for example, measurement results. The host computer 206 and the interface device 202′ may be integrated and / or do not need to be distinguished from each other. Moreover, the signal control lines 201A to 201C may be part of a general data transfer line / bus configuration 201.

[0129] The CMM 210 includes a drive mechanism 1851 disposed on a base plate 1852 and a mount 236 (e.g., the mount 236 may include an auto-exchange joint element attached to an articulated probe head 213) for mounting the CRS optical probe 215 to the drive mechanism 1851. The drive mechanism 1851 includes x-axis, y-axis, and z-axis slide mechanisms 1851X, 1851Y, 1851Z for moving the CRS optical probe 215 in three dimensions. The CRS optical probe 215 may be automatically stored in a storage rack (not shown) and automatically removed from the storage rack and mounted on the mount 236 (e.g., under control of an inspection program) at the auto-joint connection mechanism 230. The auto-joint connection mechanism 230 may include precision kinematic mounting means, fiber optic connections, electrical connections, etc., which provide a common physical interface for a variety of interchangeable CMM probes and sensors according to established principles. As part of a measurement or calibration operation, the CRS optical probe 215 is positioned by the CMM 210 relative to a surface (e.g., a measured surface 290 of a workpiece or a measured surface of a calibration part) and irradiates the surface with a measurement light 296 (e.g., a radial distance detection beam).

[0130] As shown in FIG. 18, a base plate 1852 (e.g., serving as a stage for CMM 210) has various calibration members disposed thereon (e.g., the calibration members may be fixed to base plate 1852 or may be located at known coordinate locations). In the example of FIG. 18, a spherical calibration member 1898, a cylindrical calibration member 1846A, and a cylindrical calibration member 1846B are disposed on base plate 1852 for use in various calibration processes. Cylindrical calibration members 1846A, 1846B have different radii to their respective cylindrical calibration surfaces. As discussed above, rather than having two cylindrical calibration members of different radii, a single cylindrical calibration member including two cylindrical calibration surfaces of different radii may be used.

[0131] A first embodiment of a calibration member is shown in Figure 19. The calibration member is a spherical calibration member 1998 that is used to obtain spherical calibration data to correct misalignment errors of a CMM's CRS optical probe (see, for example, optical probe arrangement 215 of CMM 210 in Figure 18). The spherical calibration member 1998 has a spherical calibration surface 1904 and is typically supported on (e.g., may be part of or located on) base plate 1852 by support structure 1906.

[0132] The radius Rs (or diameter) and reference center Cs of the spherical calibration member 1998 are assumed to be known. As will be described in more detail with reference to Figures 20-27C, radial distances measured using this spherical calibration member are used to determine spherical calibration data, such as spherical calibration information of radius, rotation angle, and Z position.

[0133] One or more spherical calibration members, such as calibration member 1898 of FIGURE 18 or calibration member 1998 of FIGURE 19, may be used in conjunction with one or more cylindrical calibration members (e.g., see cylindrical calibration members 1846A, 1846B of FIGURE 18) to obtain radial distance measurements for determining calibration data, such as cylindrical and spherical calibration data. For example, radial distance measurements of one or more cylindrical calibration members may be obtained to obtain calibration data for cylindrical radius, and radial distance measurements of one or more spherical calibration members may be obtained to obtain spherical calibration data for rotation angle and Z position.

[0134] Using a cylindrical calibration member to obtain the radius calibration data and a spherical calibration member to obtain the rotation angle and Z position calibration data tends to simplify the cylindrical calibration member used. This is because the radial distance measurement value of the spherical calibration member is substituted for the rotation angle and Z position calibration data to obtain the rotation angle and Z position calibration data, and it is not necessary to provide a pattern on the cylindrical calibration member for obtaining the rotation angle and Z position calibration data. Of course, various combinations of radius, rotation angle, and Z position calibration data may be obtained from the radial distance measurement values ​​of various calibration members, such as cylindrical and spherical calibration members.

[0135] FIG. 20 illustrates a procedure 2000 for calibrating a rotating CRS device of a CMM. The procedure may be used, for example, with a CMM equipped with one or more calibration features as described herein. The procedure 2000 provides calibration data or information for correcting misalignment errors of the rotating CRS device. The rotating CRS device is configured to irradiate a radial distance detection beam in a radial direction of its rotation axis and rotate the radial distance detection beam about the rotation axis. The procedure 2000 may be called, for example, by a probe signal processing control circuit (probe signal processing control circuit 207 in FIGS. 2, 5 and 18) or a basic calibration routine circuit.

[0136] As shown, procedure 2000 starts with a base calibration 2002 of the CMM. The base calibration may be performed (e.g., along with other steps of procedure 2000 that are performed later) at the manufacturing factory and / or at other times (e.g., at the measurement site). A "base calibration" is also referred to as a "factory calibration" and / or an "initial calibration." A base calibration may utilize a measurement calibration surface (e.g., a reflective surface such as a mirror) that moves through a series of distance positions from an optical pen. Each actual distance is known and has been measured and / or otherwise determined (e.g., using an interferometer). The distances are also measured with the optical pen.

[0137] The difference between the actual distance and the distance measured by the optical pen is used to determine a correction value for each distance, which may be used to create a correction table to obtain each corrected distance Dc (e.g., distances between the distances recorded in the correction table may be interpolated).

[0138] The basic calibration 2002 may include obtaining other calibration data, such as, for example, obtaining radial distance measurements to determine calibration offset information (see, e.g., FIGS. 14-19, 21-29 and their respective description), registering one or more calibration members for the optical pen (e.g., cylindrical calibration members, spherical calibration members, etc. For example, with reference to FIGS. 18 and 19, determining the radius and reference center value of cylindrical calibration members 1846a, 1846b, and determining the radius value Rs and reference center value Cs of spherical calibration members 1898, 1998 on base plate 1852), or any combination thereof.

[0139] From step 2002, procedure 2000 proceeds to step 2004. In step 2004, procedure 2000 acquires cylindrical calibration data using one or more cylindrical calibration members. For example, step 2004 is performed as described above with respect to Figs. 14-17. For example, calibration data for radius correction may be acquired using a cylindrical calibration member registered to the pen. The cylindrical calibration member may have, for example, two or more stepped radii that can be used with or without Z-stage scanning (e.g., three ring gauges of different radii stacked and measured in one Z-scan, or two measurements are taken without Z-stage scanning using two ring gauges), and at least radius offset and linear correction coefficient data can be acquired to correct for mechanical misalignment errors of the rotary pen.

[0140] In this step, error calibration information for rotation angle, Z position, first and second harmonic may be acquired to establish a reference origin. A cylindrical calibration element may provide more accurate radial correction information for an optical pen, e.g., offset, linear, rotational second harmonic correction information, meaning more accurate than the typical acquisition method using a spherical calibration element (e.g., in step 2006 below), since the cylindrical calibration element has fewer translational motion axes, reducing calibration errors.

[0141] Procedure 2000 proceeds from step 2004 to step 2006. In step 2006, procedure 2000 measures radial distance measurements using one or more spherical calibration members to obtain calibration data. FIG. 21 is an exemplary flow diagram of procedure 2100 for measuring a spherical calibration member for use with a CMM having one or more calibration members, for example, and obtaining calibration data. Procedure 2100 may be invoked, for example, in step 2006 of procedure 2000 of FIG. 20. FIGS. 22-28 are conceptual diagrams illustrating the process of determining calibration data by obtaining radial distance measurement data of a spherical calibration member, as well as examples of types of errors that may be subjected to compensation routines using the obtained calibration data. For convenience, the description of procedure 2100 refers to FIGS. 22-25.

[0142] As shown, the procedure 2100 starts at step 2112 by operating the rotating CRS device to provide a spherical radial distance data set corresponding to a first surface portion (e.g., a section) of the surface of the spherical calibration member 1998 (see, e.g., FIG. 25A). The data set is acquired while rotating a radial distance detection beam about a rotation axis with the optical pen of the rotating CRS device located at approximately a first standoff position or first distance D1 from the spherical calibration member 1998 according to a first orientation of the optical pen 220. The radial distance data is acquired while the probe measurement beam (e.g., the radial distance detection beam) rotates and moves along the Z axis of the probe / pen coordinate system (the Z axis of the spherical calibration member coordinate system and the orientation in FIG. 22 corresponding to the scan axis direction SA), making a measurement corresponding to a section of the cylindrical calibration member closest to the optical pen.

[0143] As the optical pen 220 (and corresponding radial distance detection beam 296) moves in the scanning axis direction SA relative to the spherical calibration member 1998, the radial distance detection beam 296 rotates (e.g., according to a rotation angle ω) about the rotation axis PA of the optical pen 220 (e.g., an axis corresponding to the Z axis of the optical pen / probe coordinate system) at multiple positions. Figures 25A and 25B show the position of a surface portion (e.g., a region) and corresponding measurement data (e.g., data corresponding to the detected radial distance R).

[0144] The movement of the optical pen 220 along the scanning axis direction SA with respect to the spherical calibration member 1998 may be at least partially relative movement. For example (optionally), the spherical calibration member 1998 may be placed on a stage or other mechanism (e.g., placed on a base plate or part of a base plate, etc.) that allows the spherical calibration member 1998 to move in one or more dimensions (e.g., 1D, 2D, or 3D), thereby causing the optical pen 220 to move relative to the spherical calibration member 1998 (i.e., the spherical calibration member 1998 is moved relative to the optical pen 220 by the stage or other mechanism).

[0145] 22, the optical pen 220 may be positioned at a first standoff distance D1 from the surface 1904 of the spherical calibration member 1998 and may be operative to obtain radial distance data corresponding to a first surface portion (e.g., a section) of the spherical calibration member 1998 and determine a closest point P1 relative to the first surface portion. Data corresponding to the first surface portion is obtained at multiple positions along the scan axis direction SA (see, e.g., FIGS. 25A and 25B).

[0146] Acquiring radial distance data corresponding to the first surface portion may include moving the CRS optical probe having the optical pen 220 to a series of positions along the scanning axis SA (i.e., while maintaining the standoff distance D1), and acquiring radial distance data corresponding to a portion of the first surface portion (i.e., data corresponding to a current position along the scanning axis SA) at each position to which the radial distance detection beam of the optical pen 220 is rotated. By following such operations, radial distance data corresponding to one surface portion can be obtained (see, for example, FIG. 25A for a graphical representation of example radial distance data for one surface portion).

[0147] In step 2114, the procedure 2100 determines the closest point of approach (e.g., CP or Pi, see P1-P4 in FIG. 22, CP in FIGS. 23, 25A, 27A-27C, and P1'-P4' in FIG. 26) of the optical pen 220 to a surface portion (e.g., a region) of the surface 1904 of the spherical calibration member based on the spherical radius distance data set acquired for the region. With reference to FIG. 25A, the closest point of approach CP is related to a normal vector at a rotation angle φi and a distance Zi. For example, the closest point of approach CP can be obtained using a smoothing process, a sphere fitting algorithm based on a known radius (see radius Rs in FIG. 19), or other fitting functions. The size of the surface portion or region (e.g., the range of the Z-axis scan along the scan axis direction SA) may be selected within a range such that the closest point of approach can be determined with sufficient accuracy (e.g., using a sphere fitting algorithm based on a known radius). Procedure 2100 proceeds from step 2114 to step 2116.

[0148] In step 2116, the procedure 2100 determines whether to obtain radial distance data sets corresponding to other surface portions (e.g., zones) of the spherical calibration member 1998 at the standoff distance D1 and the same first orientation. Typically, radial distance data sets are obtained from at least two zones of the spherical calibration member for a given standoff distance and orientation. As shown in FIG. 22, radial distance data sets are obtained for four zones to determine four corresponding closest points of approach P1, P2, P3, and P4, respectively (i.e., one for each zone). For ease of illustration, the closest points of approach (i.e., each corresponding to one zone) are shown spaced apart along an equator EQ portion of the spherical calibration member 1998 (where equator EQ may be defined by the closest points of approach P1-P4 determined for the zones). Typically, the zones and / or their corresponding closest points of approach may be uniformly distributed and / or equidistant from one another on the spherical calibration surface 1904 of the spherical calibration member 1998. For example, the areas and / or their corresponding points of closest approach may be uniformly distributed along the equator EQ of the spherical calibration member 1998.

[0149] 22, the Z axis of the coordinate system of the optical pen 220 (i.e. the axis corresponding to the optical pen axis PA) is aligned (or parallel) to the reference axis Zs of the spherical calibration member 1998. The reference axis Zs of the spherical calibration member 1998 is typically aligned with the direction of gravity and / or parallel to the Z axis direction of the CMM coordinate system.

[0150] A threshold may be used to determine whether to acquire radial distance data sets corresponding to other surface portions or regions of surface 1904 (e.g., radial distance data sets corresponding to a threshold number of regions (4, 6, etc.) may be acquired until a threshold number of data sets are acquired). The threshold may be determined based on various factors, such as the desired compensation accuracy, the type of calibration error to be compensated for based on the spherical calibration data, whether data at multiple standoff distances or orientations has been acquired, and available data processing resources.

[0151] If it is determined in step 2116 that radial distance data sets corresponding to other surface portions (e.g., areas) of the spherical calibration member are to be acquired under the standoff distance and first orientation conditions, the procedure proceeds from step 2116 to step 2118, where the optical pen is repositioned to another position (e.g., another position around the equator EQ) (the orientation conditions are unchanged in the example of FIG. 22) and another radial distance data set corresponding to the other surface portion (e.g., the area including the corresponding closest point of approach P2) of the spherical calibration member is acquired at approximately the first standoff distance or first distance D1 from the spherical calibration member. The location may be along the equator EQ of the spherical calibration member (e.g., in one ideal configuration, in a plane perpendicular to the probe axis PA). If it is desired to acquire multiple sets of radial distance data using the spherical calibration member, the corresponding locations may be equally spaced from each other along the equator. For example, if data for two surface portions (e.g., two areas) is to be acquired, the areas may be spaced 180 degrees apart along the equator EQ. From step 2118, the procedure 2100 proceeds to step 2112 to obtain data for another surface portion of the spherical calibration member.

[0152] If, in step 2116, it is determined that radial distance data sets corresponding to other surfaces of the spherical calibration member are not to be acquired at the same distance and orientation conditions as the current situation (e.g., first, second orientation, etc.), the procedure proceeds from step 2116 to step 2120. In step 2120, the procedure calculates radial distance data, approach point information, or both, for the surface data sets acquired at the standoff distance and current orientation conditions (e.g., first, second orientation, etc.) to generate or determine spherical calibration data (e.g., spherical calibration data of radius, Z position and rotation angle) at the current standoff distance and current orientation conditions.

[0153] For example, referring to Figs. 23 and 24, in the example considered in Fig. 22, five closest points CP of the optical pen 220 to the area of ​​the surface 1904 of the spherical calibration member 1998 along the equator are determined. The five points can be fitted to a sphere using the radius Rs or diameter of the calibration member (see Fig. 19), both of which are known. The coordinates of the five points can be transformed to the CMM coordinate system and averaged, for example, to determine the reference position RP, which is the centre of the spherical calibration member 1998. Information about the deviation of the five points along the optical pen axis PA and / or the scanning axis SA (e.g., at the current probe orientation, some of the five points are off the equatorial plane) can also be used to generate Z position calibration information. Rotary encoder information (see, for example, encoder 630 in Fig. 6) can also be used to generate rotation calibration information. Referring to Fig. 24, the difference between the nominal and measured points can be used as calibration data or can be used to generate the calibration data. Such differences can be expressed as (ΔR(φ,XYZ), Δφ(φ,XYZ), Δz(φ,XYZ)), where φ is the rotation angle and z is the Z-axis position on the optical pen axis PA (i.e., the Z-axis of the probe / pen coordinate system corresponds to the optical pen axis PA). In this way, data corresponding to the position error of each point can be obtained as a function of the rotation angle φ and the position z on the optical pen axis PA.

[0154] Obtaining calibration data by measuring the radial distance of multiple surface portions (e.g., areas) of a spherical calibration member large enough to accurately determine the approach point helps to avoid distortions in the measurement of large surface slopes and helps to avoid errors due to extrapolating the fitting of one surface area in finding the reference center. The spherical calibration member may be a standard size for the CMM, which facilitates obtaining spherical calibration data in multiple orientation conditions (e.g., see Figs. 22 and 26, where the optical pen 220 is oriented differently relative to the CMM coordinate system). Procedure 2100 returns to the procedure called from step 2120, e.g., returning to procedure 2000 of Fig. 20 to provide the generated spherical calibration data.

[0155] Referring again to FIG. 20, the procedure 2000 proceeds from step 2006 to step 2008, which determines whether to acquire additional calibration data at other orientation conditions of the optical pen 220 with respect to the spherical calibration member 1998 at the first standoff distance. At different orientation conditions of the optical pen with respect to the spherical calibration member, gravity induces different errors in the measurements acquired using the rotating measurement beam. Acquiring calibration measurements at various orientation conditions of the optical pen 220 facilitates acquisition of more accurate calibration data. Such calibration data is useful when measurements are desired with the Z-axis of the optical pen positioned at an orientation different from gravity. In other words, spherical calibration data for compensating for the effects of gravity on the configuration of the CMM 210 and the optical pen 220 can be acquired by acquiring radial distance data at multiple orientation conditions of the optical pen with respect to the spherical calibration member.

[0156] If in step 2008 it is determined to obtain additional calibration data at the first standoff distance and at other orientation conditions of the optical pen relative to the spherical calibration member, procedure 2000 proceeds from step 2008 to step 2010, where the orientation condition of the optical pen 220 relative to the spherical calibration member 1998 is changed.

[0157] 22 and 26 are conceptual diagrams showing different orientations of the optical pen 220 with respect to the spherical calibration member 1998. In FIGS. 22 and 26, the reference axis Zs of the coordinate system of the spherical calibration member 1998 is shown vertically oriented (e.g., aligned with the gravity vector) and parallel to the Z axis of the CMM coordinate system. In FIG. 22, the optical pen axis PA and the scanning axis direction SA along the direction of movement of the optical pen 220 (e.g., for scanning an area of ​​the surface 1904 of the spherical calibration member 1998) are parallel to the Z axis and the reference axis Zs of the CMM coordinate system. In FIG. 26, the optical pen axis PA and the scanning axis direction SA along the direction of movement of the optical pen 220 are not parallel to the Z axis of the CMM coordinate system (i.e., tilted with respect to the Z axis of the CMM coordinate system). Therefore, the optical pen of FIG. 22 has a different orientation condition with respect to the spherical calibration member 1998 than the optical pen of FIG. 26.

[0158] After changing the orientation of the optical pen relative to the spherical calibration member in step 2010 (e.g., from the orientation of FIG. 22 to the orientation of FIG. 26), the procedure 2000 returns to step 2006 to acquire spherical calibration data with the changed orientation of the optical pen relative to the spherical calibration member. For example, with reference to FIG. 26, radial distance data sets may be acquired in four zones corresponding to closest points of approach P1', P2', P3', and P4', which, as shown, are along an equatorial EQ' portion of the spherical calibration member 1998, which is different from the equator EQ shown in FIG.

[0159] If in step 2008 it is determined not to acquire additional calibration data at other orientation conditions of the optical pen 220 relative to the spherical calibration member 1998 at the first standoff distance, then procedure 2000 proceeds from step 2008 to step 2012 to determine whether to acquire additional calibration data at other standoff position or distance conditions of the optical pen 220 relative to the spherical calibration member 1998. Similar to the method described above with reference to Figures 14-17, acquiring spherical calibration data at multiple standoff or distance conditions, within the chromatic dispersion of the optical probe, allows calibration offset and linear scaling data to be readily generated as a function of measurement distance or measurement radius to compensate for various misalignment errors.

[0160] If it is determined in step 2012 that additional calibration data should be acquired under other standoff position or distance conditions of the optical pen 220 relative to the spherical calibration member 1998, the procedure 2000 proceeds from step 2012 to step 2014, where the standoff position or distance of the optical pen 220 relative to the spherical calibration member 1998 is changed. The procedure proceeds from step 2014 to step 2006, where spherical calibration data is acquired under a changed standoff position or distance condition different from the standoff distance D1 in Figures 22 and 26 (for example, the changed standoff distance D2 may be larger or smaller than D1). Note that Figures 27B and 27C show examples of measurements under different standoff distance conditions.

[0161] Figure 27A is a conceptual diagram showing an ideal arrangement of a CMM with an optical pen 220 to obtain radial distance measurements for a spherical calibration member 1998. Figures 27B and 27C are conceptual diagrams showing various misalignment errors in the process of obtaining radial distance measurements for a spherical calibration member 1998 at various standoff distance conditions.

[0162] In the ideal arrangement of Figure 27A, the CRS optical probe with the optical pen moves in a scanning axis direction SA (e.g., up and down in the orientation shown), which is parallel to the axis PA of the optical pen 220, and the radial distance detection beam 296 from the optical pen is perpendicular to the axis PA of the optical pen. CMM reference point (X,Y,Z) CMM (e.g., the point at which a CRS optical probe with an optical pen is attached to a CMM or other mechanism) and the measurement data (ΔX, ΔY, ΔZ) CRS Using and , the position of the measurement point (which as shown is a point on a spherical calibration member 1998 having a reference center (X,Y,Z) ref and supported by a support structure 1906) can be precisely determined. In the ideal arrangement of FIG. 27A, the ΔZ component is the reference point (X, Y, Z) CMM and the radial distance detection beam. The trigonometric function component ΔX / ΔY corresponds to the horizontal standoff distance D1 (e.g., along the radial distance detection beam from the optical pen axis PA to the closest point CP on the surface of the spherical calibration member 1998). In contrast to the ideal arrangement of FIG. 27A, measurement conditions are often not ideal (e.g., including non-ideal arrangements) and measurement errors (e.g., those listed in Table 1 above) arise, for example, due to misalignment of various configurations (e.g., probe, optical pen, CMM, etc.).

[0163] FIG. 27B shows an exaggerated Z position error ΔZ and rotation axis misalignment angle error θr that may occur when the optical probe / optical pen axis PA is not aligned with the scanning axis SA, which is the direction of movement of the optical pen 220. Ideally, the radial distance detection beam 296 of the optical pen 220 is perpendicular to the surface of the spherical calibration member 1998 at the closest point CP in a section of the surface of the spherical calibration member 1998 when acquiring radial distance data (see, for example, FIG. 27A). However, if the scanning axis SA is not aligned with the axis PA of the optical pen 220, the radial distance detection beam 296 will not be perpendicular to the surface of the spherical calibration member 1998 at the closest point CP. This results in errors in the acquired radial distance data, such as the Z position error ΔZ and the misalignment angle error θr. The magnitude and signal of these errors are a function of standoff distance, rotational position, etc. In the example of FIG. 27B, determination and / or knowledge of the distances (e.g., D1B, D2B) and distance errors (e.g., ΔZ1B, ΔZ2B) allows for the determination of the misalignment angle error θr and / or other errors (e.g., by following certain trigonometric functions and / or other calculations and relationships, etc.).

[0164] As shown in FIG. 27B, radial distance measurements can be taken at different standoff distance conditions. As shown, on either side of the spherical calibration member 1998, respective closest points of approach CP RB ,CP LBFor example, radial distance measurements may be obtained at a first standoff distance (corresponding to distance D1B) as shown by the solid optical pen 220 and at a second standoff distance (corresponding to distance D2B) as shown by the dashed optical pen 220. For example, the magnitude of the Z position error ΔZ as shown in FIG. 27B may be expressed as a function of standoff distance. Specifically, as shown in FIG. 27B, the first standoff distance corresponds to distance D1B, and the Z position error changes as the optical pen 220 moves around the equator EQ1B of the spherical calibration member 1998 (e.g., to obtain data sets for different zones spaced apart around the spherical calibration member 1998). A peak in the Z position error corresponds to a first Z position error ΔZ1B (e.g., at the closest point of approach CP RB The second standoff distance corresponds to a distance D2B, and the peak Z position error associated with moving the optical pen about the equator EQ1B corresponds to a second Z position error ΔZ2B (e.g., the closest point of approach CP RB (relative to the position of

[0165] Ideally, the radial distance sensing beam 296 of the optical pen 220 is perpendicular to the axis PA and the scanning axis direction SA of the optical pen 220 (see, for example, FIG. 27A). FIG. 27C shows an example of errors that can occur when the angle of the radial distance sensing beam is not perpendicular to the optical pen axis PA. For example, in the case of misalignment of the reflective member 294 (see FIG. 4A), the radial distance sensing beam is not perpendicular to the axis PA and the scanning axis direction SA of the optical pen 220. This results in errors in the radial distance measurement, such as the output normal elevation error δθo described above. The magnitude and signal of these errors may be relatively constant or may be a function of standoff distance, rotational position, etc.

[0166] As shown in FIG. 27C, measurements can be taken at different standoff distances. On either side of the spherical calibration member 1998, the closest point of approach CP RC ,CP LC27B. Radial distance measurements may be taken, for example, at a first standoff distance, as indicated by the solid optical pen 220, and at a second standoff distance, as indicated by the dashed optical pen 220. Specifically in FIG. 27C, the first standoff distance corresponds to distance D1C. As the optical pen moves around the equator EQ1C of the spherical calibration member 1998 (e.g., to obtain data sets for different zones spaced apart around the circumference of the spherical calibration member 1998), the Z position error will be relatively constant (as opposed to the large variations in Z position error of FIG. 27B). The relatively constant (or peaking) Z position error may be observed (e.g., at the closest point of approach CP as shown). RC The second standoff distance corresponds to a distance D2C. And the Z position error that is relatively constant (or exhibits a peak) while the optical pen moves about the equator EQ1C (e.g., the closest point of approach CP RC 27C , determining and / or knowing the distances (e.g., D1C, D2C) and distance errors (e.g., ΔZ1C, ΔZ2C) may allow for determining (e.g., according to certain trigonometric functions and / or other calculations and relationships, etc.) errors in the radial distance measurements, such as the illustrated output normal elevation error δθo (which is relatively constant in the example of FIG. 27C ), and / or other errors.

[0167] If in step 2012 it is determined not to obtain additional calibration data at other standoff distances or distance conditions of the optical pen 220 relative to the spherical calibration member 1998, then procedure 2000 proceeds from step 2012 to step 2016 to determine whether to obtain additional calibration data (e.g., using another calibration member or calibration mechanism). If, in step 2016, it is determined to acquire additional calibration data, then procedure 2000 proceeds to step 2004. If, in step 2016, it is determined not to acquire additional calibration data, then procedure 2000 ends or performs additional processing (generating additional calibration data based on acquired calibration data, stored calibration data, etc.).

[0168] Embodiments of procedures 2000 and 2100 may perform more or fewer operations than those shown, may perform operations in various orders or sequences, may combine procedures 2000 and 2100, may omit a base calibration (e.g., a factory calibration) (e.g., when this procedure is invoked for calibration at the measurement site), and may instead retrieve pre-determined base calibration data (e.g., from a factory or other location).

[0169] In other examples, adjustments to obtain spherical calibration data for different zones, orientations, standoff positions or distances are performed in different orders. For example, procedure 2000 may perform steps 2012 / 2014 before or in parallel with steps 2008 / 2010. In the illustration of FIG. 20, steps 2012 / 2014 are relatively outside and steps 2008 / 2010 are relatively inside in this loop of procedure 2000. In the case of including only the XYZ axes of the CMM, this order may be reversed (e.g., steps 2012 / 2014 are moved to the inner loop and steps 2008 / 2010 are moved to the outer loop) since it is preferable to perform additional standoff data in the inner loop. The orientation operation of the automatic joint, which is not as repeatable as the XYZ operation, is desired to be relatively slow. Also, due to effects of temperature drift or other factors, when calibrating all standoff conditions for all XYZ axis motion, it is required that the calibration at one orientation condition is performed in the inner loop, while the calibration at a different standoff condition can be separated and included in the outer loop.

[0170] For multiple data sets collected at different radii using a cylindrical calibration member, multiple data sets of radial distances collected at different standoff distances from a spherical calibration member can be used to obtain offset and linear scaling correction data in a similar manner as described above. A set of radial distance measurements taken at different standoff distances of a surface portion (e.g., area) of the circumference of a cylindrical calibration member is similar to a data set of radial distance measurements of different ring gauges, or radial distance measurements of steps at different radii on a ring gauge. Offset and linear scaling correction data may be obtained based on radial distance data sets collected at different radii using a cylindrical calibration member, radial distance data sets collected at different standoff distances from a spherical calibration member, and / or various combinations thereof.

[0171] For example, with reference to equation (1) (reproduced below for convenience), a set of relationships can be used to express the error in radial distance measurements, where the terms in the relationships are determined based on cylindrical calibration data sets, spherical calibration data sets, and / or combinations thereof (e.g., a term determined using cylindrical calibration data is refined or confirmed based on spherical calibration data).

[0172]

number

[0173] For example, correction of radial distance error ΔR is based on cylindrical factory calibration data, and correction of rotational error Δφ and Z position error ΔZ is based on spherical calibration data.

[0174] For example, offset Ro, linear correction factor R L D C , and the second harmonic (C R2 cos(4πφc+θ R2 The first harmonic (C R1 cos(2πφc+θR1 The term (X,Y,Z) is the reference coordinate system of the CMM. CMM ), measurements taken with a cylindrical calibration member, or a combination of these. Depending on the required accuracy, probe stiffness, and other aspects, these factors are determined from measurements taken with the probe in a vertical orientation and applied to the correction for all orientation conditions or for the same orientation condition. Alternatively, these factors are determined for each orientation condition from measurements taken at each orientation condition (see description of equation (4) below).

[0175] The errors in the rotation angle offset φo and the Z offset Zo are determined based on measurements at the closest points in multiple zones of the spherical calibration member at standoff distances as a function of the rotation angle φc (see FIG. 27B). Determination or adjustment may be performed using measurements taken at additional standoff distances. Higher order harmonic correction factors (e.g., C φ1 D C sin(2πφc+θ φ1 );C φ2 D C sin(4πφc+θ φ2 );C Z1 D C sin(2πφc+θ Z1 );C Z2 D C sin(4πφc+θ Z2 )) as well as the linear correction factor φ L D C , and a linear correction factor for Z position error, Z L D Lis preferably determined using radial distance measurements of the spherical calibration member taken at different standoff distances depending on the measurement range of the optical pen. If higher harmonic correction factors are desired, additional zone radial distance measurements are taken. (For example, four or more zone measurements at one or more standoff distances are taken if first harmonic correction is desired, and eight or more zone measurements at one or more standoff distances are taken if first and second harmonic correction is desired.) In some implementations, the Dc term may be set to zero (e.g., because rotation with a digital rotary encoder capable of 0 to 360 degrees rotation provides relatively little or no linear scaling error).

[0176] As described above, by obtaining radial distance measurements of the spherical calibration member under multiple optical probe / pen orientations relative to the gravity direction, spherical calibration data for gravity compensation corresponding to different orientation conditions can be determined. Gravity compensation for different orientations of the Z-axis of the optical pen 220 of the rotational CRS measurement device under a certain standoff distance condition can be expressed in a Cartesian coordinate system by the following relationship (4).

[0177]

number

[0178]

number

[0179]

number

[0180] Additionally, the above terms represent an average of measurement data taken at the N closest points of a number of equally spaced zones along the equator of the spherical calibration member at that orientation.

[0181]

number

[0182] The above terms represent the coordinates of the center of an accepted spherical calibration member. Using the relationship in equation (4), compensation for gravity under different orientation conditions can be performed.

[0183] As stated above, a calibration system for providing calibration data for a coordinate measuring machine (CMM) is provided. The calibration system includes a CMM having a light generating circuit, a wavelength detecting circuit, and a CMM control circuit, and a chromatic range sensor (CRS) optical probe configured to be connectable to the CMM. The CRS optical probe includes an optical pen having a confocal optical path including at least a confocal aperture and a chromatic dispersion optical element. The optical pen is configured to direct a radial distance detection beam along a radial direction relative to an axis of rotation and to rotate the radial distance detection beam about the axis of rotation such that different wavelengths of light are focused at different distances near a measured surface of the workpiece along the measurement axis. The calibration system includes a cylindrical calibration member and a spherical calibration member.

[0184] The cylindrical calibration member is for providing cylindrical calibration data for correcting misalignment errors of the CRS optical probe, and has at least a first cylindrical calibration surface, a central axis of the cylindrical calibration surface extending along a Z direction. The CRS optical probe is configured to rotate the radial distance detection beam about a rotation axis at a first Z coordinate position in the Z direction relative to the cylindrical calibration member to provide a first cylindrical radial distance data set acquired during the rotational movement. The cylindrical radial distance data set references a detection rotation angle about the rotation axis of the radial distance detection beam. The first cylindrical radial distance data set referenced to the detection rotation angle is processed to determine the cylindrical calibration data.

[0185] The spherical calibration member has a spherical calibration surface and is used to provide spherical calibration data for correcting misalignment errors of the CRS optical probe. For each of a plurality of first surface portions on the spherical calibration surface, the CRS optical probe is configured to rotate the radial distance detection beam about a rotation axis with an optical pen at a position approximately a first standoff distance from the spherical calibration member to provide a spherical radial distance data set corresponding to each surface portion acquired during the rotational movement. The optical pen is also moved in a scan axis direction to acquire the spherical radial distance data set, and each set of radial distance data corresponding to each of the detected surface portions is processed to determine a closest detected surface point representative of a point closest to the optical pen. The spherical calibration data is determined based at least in part on the closest detected surface points corresponding to the plurality of surface portions.

[0186] In some embodiments, the cylindrical calibration member comprises a first set of angular reference features formed on or within a first cylindrical calibration surface, the first set of angular reference features configured to be detectable by a radial distance detection beam and positioned on or within the first cylindrical calibration surface at a known angle or angular spacing from one another about the central axis.

[0187] In some embodiments, the cylindrical calibration member is a ring gauge. In some embodiments, the cylindrical calibration member is a first cylindrical calibration member, the first cylindrical calibration surface is disposed at a known first radius R1 from the central axis along a Z direction, and the calibration system further comprises a second cylindrical calibration surface. The second cylindrical calibration surface is at least one of (i) a portion of the first cylindrical calibration member and (ii) a portion of a second cylindrical calibration member having a second central axis extending in a Z direction, the second cylindrical calibration surface is disposed at a known second radius R2 from the central axis along the Z direction, the second radius R2 being different from the first radius R2. The CRS optical probe is configured to rotate a radial distance detection beam about a rotation axis at a Z coordinate position along the Z direction relative to the second cylindrical calibration surface to provide a second cylindrical radial distance data set acquired during the rotational movement. The second cylindrical radial distance data set is referenced to a sensed rotation angle of the radial distance detection beam about the rotation axis and is added to the first cylindrical radial distance data set for processing to determine the cylindrical calibration data.

[0188] In embodiments, the calibration system is configured to determine calibration data for the CRS optical probe by computing the cylindrical calibration data and the spherical calibration data.

[0189] In some embodiments, the spherical calibration surface includes a plurality of points that are the same radial distance from a common center point of the spherical calibration surface.

[0190] In some embodiments, the plurality of first surface portions on the spherical calibration surface include a plurality of zones on the spherical calibration surface, the plurality of zones being equidistant from one another around an equator of the spherical calibration member, and the optical probe is moved along a Z-axis of the probe when acquiring spherical radial distance data corresponding to one of the plurality of zones.

[0191] In some embodiments, the spherical calibration surface includes a plurality of second surface portions, and for each surface portion of the plurality of second surface portions, the CRS optical probe is configured to rotate the radial distance detection beam about the axis of rotation with the optical pen at approximately the first standoff distance from the spherical calibration member to provide a spherical radial distance data set acquired during the rotational movement. Each set of radial distance data corresponding to each detected surface portion of the plurality of second surface portions is processed to determine a closest detected surface point representative of the point closest to the optical pen. The spherical calibration data is determined based at least in part on the closest detected surface points corresponding to the plurality of second surface portions. In some embodiments, the plurality of first surface portions on the spherical calibration surface include a plurality of first regions on the spherical calibration surface, the plurality of first regions being equidistant from one another around a first equator of the spherical calibration member; The plurality of second surface portions on the spherical calibration surface include a plurality of second regions on the spherical calibration surface, the plurality of second regions being equidistant from one another around a second equator of the spherical calibration member.

[0192] In some embodiments, for each of the first surface portions on the spherical calibration surface, the CRS optical probe is configured to rotate the radial distance detection beam about the axis of rotation with the optical pen at approximately a second standoff distance from the spherical calibration member to provide a spherical radial distance data set acquired during the rotational movement. Each set of radial distance data corresponding to each surface portion detected at the second standoff distance is processed to determine a closest detected surface point representative of the point closest to the optical pen. The spherical calibration data is determined based at least in part on the closest detected surface point corresponding to the second standoff distance.

[0193] In embodiments, the calibration system includes a platen configured to position the cylindrical calibration member and the spherical calibration member relative to the CRS optical probe.

[0194] In some embodiments, the CRS optical probe is configured to rotate the radial distance detection beam about the axis of rotation for each of the first surface portions while the optical pen is in a first orientation relative to the spherical calibration member to provide a spherical radial distance data set acquired during the rotational movement, and to rotate the radial distance detection beam about the axis of rotation for each of the second surface portions on the spherical calibration surface while the optical pen is in a second orientation different from the first orientation relative to the spherical calibration member to provide a spherical radial distance data set acquired during the rotational movement.

[0195] A method is provided for providing calibration data to correct misalignment errors in a rotary chromatic range sensor configured to direct a radial distance sensing beam along a radial direction relative to an axis of rotation and to rotate the radial distance sensing beam about the axis of rotation. A cylindrical calibration member and a spherical calibration member are provided.

[0196] The cylindrical calibration member has at least a first cylindrical calibration surface having a central axis along the Z direction and is positioned in a relationship to the rotating chromatic range sensor. The rotating chromatic range sensor is operative to rotate a radial distance detection beam about the rotation axis at a first Z coordinate position along the Z direction relative to the cylindrical calibration member to provide a first cylindrical radial distance data set acquired during the rotation. The cylindrical radial distance data set references a detection rotation angle about the rotation axis of the radial distance detection beam. The first cylindrical radial distance data set referenced to the detection rotation angle is processed to determine a first cylindrical calibration data set.

[0197] The spherical calibration member has a spherical calibration surface with a plurality of first surface portions and is positioned in a relationship to the rotating chromatic range sensor. For the plurality of first surface portions, the rotating chromatic range sensor is operative to rotate a radial distance detection beam about the axis of rotation with an optical pen of the rotating chromatic range sensor at approximately a first standoff distance from the spherical calibration member to provide a spherical radial distance data set corresponding to each surface portion acquired during the rotation. Each set of radial distance data corresponding to each detected surface portion is processed to determine a closest detected surface point, which point represents the closest to the optical pen of the rotating chromatic range sensor. The spherical calibration data is determined based at least in part on the closest detected surface points corresponding to the plurality of surface portions.

[0198] In some embodiments, the cylindrical calibration member includes a first set of angular reference features formed on or within the first cylindrical calibration surface, the first set of angular reference features disposed on or within the first cylindrical calibration surface at a known angle or angular spacing from one another about the central axis, and the method includes operating the rotating chromatic range sensor to sense the first set of angular reference features.

[0199] In some embodiments, the cylindrical calibration member is a ring gauge. In some embodiments, the cylindrical calibration member is a first cylindrical calibration member, and the first cylindrical calibration surface is located at a known distance of a first radius R1 from the central axis in a Z direction. The method includes providing a second cylindrical calibration surface, the second cylindrical calibration surface being at least one of (i) a portion of the first cylindrical calibration member and (ii) a portion of a second cylindrical calibration member, the second cylindrical calibration surface having a second central axis in a Z direction, the second cylindrical calibration surface being located at a known distance of a second radius R2 from the central axis in a Z direction, the second radius R2 being different from the first radius R2. The method includes operating the chromatic range sensor to rotate the radial distance detection beam about the rotation axis at a Z coordinate position in the Z direction relative to the second cylindrical calibration surface, and providing a second cylindrical radial distance data set acquired during the rotation operation, the second cylindrical radial distance data set being referenced to a sensed rotation angle of the radial distance detection beam about the rotation axis. The second cylinder radius distance data set, which references the sensed rotation angle, is added to the first cylinder radius distance data set and processed to determine the cylinder calibration data.

[0200] In embodiments, the cylindrical calibration data and the spherical calibration data are processed to generate calibration data for the chromatic range sensor.

[0201] In some embodiments, the spherical calibration surface has a plurality of second surface portions, and the method includes operating the chromatic range sensor to rotate the radial distance detection beam about the axis of rotation with the optical pen at approximately a first standoff distance from the spherical calibration member for each of the plurality of second surface portions to provide a spherical radial distance data set acquired during the rotational movement. Each set of radial distance data corresponding to each of the detected surface portions of the plurality of second surface portions is processed to determine a closest detected surface point representative of the point closest to the optical pen. The spherical calibration data is determined based at least in part on the closest detected surface points corresponding to the plurality of surface portions.

[0202] In some embodiments, the method includes operating the rotating chromatic range sensor to rotate the radial distance detection beam about the axis of rotation with the optical pen of the rotating chromatic range sensor at approximately the second standoff distance from the spherical calibration member relative to the first plurality of surface portions to provide a spherical radial distance data set acquired during the rotational movement. Each set of radial distance data corresponding to each surface portion detected at the second standoff distance is processed to determine a closest detected surface point representative of the point closest to the optical pen of the rotating chromatic range sensor. The spherical calibration data is determined based at least in part on the closest detected surface points corresponding to the plurality of surface portions at the second standoff distance.

[0203] A calibration system for a chromatic range sensor (CRS) including a CRS optical probe is provided, the calibration system comprising a cylindrical calibration member capable of providing cylindrical calibration data for correcting misalignment errors of the CRS optical probe, a spherical calibration member capable of providing spherical calibration data for correcting misalignment errors of the CRS optical probe, and a base configured to position the cylindrical calibration member and the spherical calibration member relative to the CRS optical probe.

[0204] The cylindrical calibration member has at least a first cylindrical calibration surface having a central axis in a Z direction. The CRS optical probe is configured to rotate a radial distance detection beam about a rotation axis at a first Z coordinate position in a Z direction relative to the cylindrical calibration member to provide a first cylindrical radial distance data set acquired during the rotation. The cylindrical radial distance data set references a detection rotation angle of the radial distance detection beam about the rotation axis. The first cylindrical radial distance data set referenced to the detection rotation angle is processed to determine cylindrical calibration data.

[0205] The spherical calibration member has a spherical calibration surface. For each of a plurality of first surface portions on the spherical calibration surface, the CRS optical probe is configured to rotate a radial distance detection beam about the axis of rotation with the optical pen at approximately a first standoff distance from the spherical calibration member to provide a spherical radial distance data set corresponding to the respective surface portion acquired during the rotation. Each set of radial distance data corresponding to each detected surface portion is processed to determine a closest detected surface point representative of a point closest to the optical pen. The spherical calibration data is determined based at least in part on the closest detected surface points corresponding to the plurality of surface portions.

[0206] In some embodiments, a cylindrical calibration member and a spherical calibration member are mounted on the platen.

[0207] Although preferred embodiments of the present invention have been described, many variations on the configurations and operational procedures shown herein will be apparent to one of ordinary skill in the art based on this disclosure. For example, the CMMs disclosed herein may be any type of conventional CMM and / or any other type of machine that utilizes an optical probe to determine coordinate values ​​(e.g., a robotic platform that utilizes an optical probe, etc.). As another example, in addition to the CRS optical probes disclosed herein, other types of optical probes may be used with the system arrangements and configurations disclosed herein (e.g., if other non-contact white light optical probes are used, light may be similarly transmitted to the optical probes via the free space fiber optic couplings disclosed herein, etc.).

Claims

1. A light generating circuit, A wavelength detection circuit; and CMM control circuit, A coordinate measuring machine (CMM) having a chromatic range sensor (CRS) optical probe configured to be connectable to the CMM; a cylindrical calibration member used to provide cylindrical calibration data for correcting misalignment errors of the CRS optical probe; a spherical calibration member used to provide spherical calibration data for correcting misalignment errors of the CRS optical probe; A system comprising: The CRS optical probe includes an optical pen having a confocal optical path including at least a confocal aperture and a chromatic dispersion optical element, the optical pen is configured to direct a radial distance detection beam along a radial direction relative to a rotation axis and rotate the radial distance detection beam about the rotation axis so that different wavelengths of light are focused at different distances near a measured surface of the workpiece along a measurement axis; the cylindrical calibration member has at least a first cylindrical calibration surface having a central axis extending along a Z-axis; the CRS optical probe is configured to rotate the radial distance detection beam about the axis of rotation at a first Z coordinate position along the Z direction relative to the cylindrical calibration member to provide a first cylindrical radial distance data set acquired during the rotational movement; the cylinder radial distance data set references a sensed rotation angle of the radial distance detection beam about the rotation axis, and the first cylinder radial distance data set references the sensed rotation angle and is processed to determine the cylinder calibration data; the spherical calibration member has a spherical calibration surface; the CRS optical probe is configured to rotate the radial distance detection beam about the axis of rotation with the optical pen at approximately a first standoff distance from the spherical calibration member for each of a plurality of first surface portions on the spherical calibration surface to provide a spherical radial distance data set acquired during the rotational movement; the optical pen is moved along a scan axis to acquire the spherical radial distance data set, and each set of radial distance data corresponding to each of the detected surface portions is processed to determine a closest detected surface point representative of a point closest to the optical pen, and the spherical calibration data is determined based at least in part on the closest detected surface points corresponding to the plurality of surface portions. A system characterized by:

2. The system according to claim 1 comprises: a system configured to determine calibration data for the CRS optical probe by calculation of the cylindrical calibration data and the spherical calibration data.

3. 2. The system of claim 1, The system according to claim 1, wherein the spherical calibration surface includes a plurality of points each of which is the same radial distance from a common center point of the spherical calibration surface.

4. 2. The system of claim 1, wherein the plurality of first surface portions on the spherical calibration surface include a plurality of areas on the spherical calibration surface, the plurality of areas being equidistant from one another around an equator of the spherical calibration member.

5. 2. The system of claim 1, the spherical calibration surface having a plurality of second surface portions; the CRS optical probe is configured to rotate the radial distance detection beam about the axis of rotation with the optical pen at approximately the first standoff distance from the spherical calibration member for each of the plurality of second surfaces to provide a spherical radial distance data set acquired during the rotational movement; Each set of radial distance data corresponding to each of the detected surface portions of the plurality of second surface portions is processed to determine a detected closest surface point representative of the point closest to the optical pen; The system is configured to determine the spherical calibration data based at least in part on the detected closest surface points corresponding to the plurality of second surface portions.

6. 2. The system of claim 1, the plurality of first surface portions on the spherical calibration surface include a plurality of first regions on the spherical calibration surface, the plurality of first regions being equidistant from one another around a first equator of the spherical calibration member; the plurality of second surface portions on the spherical calibration surface include a plurality of second regions on the spherical calibration surface, the plurality of second regions being equidistant from one another around a second equator of the spherical calibration member. A system characterized by:

7. 2. The system of claim 1, wherein for each of the first surface portions on the spherical calibration surface, the CRS optical probe is configured to rotate the radial distance detection beam about the axis of rotation with the optical pen at approximately a second standoff distance from the spherical calibration member to provide a spherical radial distance data set acquired during the rotational movement; a system configured to process each set of radial distance data corresponding to each detected surface portion to determine a closest detected surface point representing the point closest to the optical pen, and to determine the spherical calibration data based at least in part on the closest detected surface point corresponding to the second standoff distance.

8. 2. The system of claim 1, further comprising a base configured to position the cylindrical calibration member and the spherical calibration member relative to the CRS optical probe.

9. 2. The system of claim 1, The CRS optical probe comprises: rotating the radial distance detection beam about the axis of rotation for each of the first plurality of surfaces with the optical pen in a first orientation relative to the spherical calibration member to provide a spherical radial distance data set acquired during the rotational movement; a system configured to rotate the radial distance detection beam about the rotation axis for each of a plurality of second surface portions on the spherical calibration surface while the optical pen is in a second orientation relative to the spherical calibration member that is different from the first orientation, to provide a spherical radial distance data set acquired during the rotational movement.

10. 2. The system of claim 1, wherein the cylindrical calibration member comprises a first set of angular reference features formed on or within the first cylindrical calibration surface; the first set of angular reference features are configured to be detectable by the radial distance detection beam and are disposed on or within the first cylindrical calibration surface at a known angle or angular spacing from one another about the central axis.

11. 2. The system of claim 1, The system according to claim 1, wherein the cylindrical calibration member is a ring gauge.

12. 2. The system of claim 1, the cylindrical calibration member is a first cylindrical calibration member, and the first cylindrical calibration surface is disposed at a distance of a known first radius R1 from the central axis along the Z direction; The system further includes a second cylindrical calibration surface, the second cylindrical calibration surface comprising: A portion of the first cylindrical calibration member; and A portion of the second cylindrical calibration member At least one of the second cylindrical calibration surface has a second central axis extending in the Z direction, and the second cylindrical calibration surface is provided at a distance of a known second radius R2 different from the central axis along the Z direction; the CRS optical probe is configured to rotate the radial distance detection beam about the axis of rotation at a Z coordinate position along the Z direction relative to the second cylindrical calibration surface to provide a second cylindrical radial distance data set acquired during the rotational movement; the second cylindrical radial distance data set references a detection rotation angle about the rotation axis of the radial distance detection beam, the second cylindrical radial distance data set referenced to the detection rotation angle being configured to be added to the first cylindrical radial distance data set and processed to determine the cylindrical calibration data.

13. 1. A method for providing calibration data for correcting misalignment errors in a rotating chromatic range sensor, comprising: The rotary chromatic range sensor is configured to direct a radial distance detection beam along a radial direction relative to a rotation axis and rotate the radial distance detection beam about the rotation axis so that different wavelengths of light are focused at different distances near a measured surface of a workpiece along a measurement axis; The method comprises: providing a cylindrical calibration member having at least a first cylindrical calibration surface with a central axis along the Z direction; positioning said cylindrical calibration member in a relationship to said rotating chromatic range sensor; operating the rotating chromatic range sensor to rotate the radial distance detection beam about the axis of rotation at a first Z coordinate position along the Z direction relative to the cylindrical calibration member to provide a first cylindrical radial distance data set acquired during the rotation, wherein the cylindrical radial distance data set references a sensed rotation angle of the radial distance detection beam about the axis of rotation; processing the first cylinder radius distance data set referenced to the sensed rotation angle to determine a first cylinder calibration data set; providing a spherical calibration member having a spherical calibration surface with a plurality of first surface portions; positioning the spherical calibration member in a relationship to the rotating chromatic range sensor; operating the rotary chromatic range sensor relative to the first plurality of surface portions and rotating the radial distance detection beam about the axis of rotation with an optical pen of the rotary chromatic range sensor at approximately a first standoff distance from the spherical calibration member to provide a spherical radial distance data set corresponding to each of the surface portions acquired during the rotation, and also moving the radial distance detection beam in a scan axis direction to acquire the spherical radial distance data set; processing each set of radial distance data corresponding to each detected surface portion to determine a closest detected surface point representative of the point of said rotating chromatic range sensor closest to said optical pen; determining spherical calibration data based at least in part on the detected closest surface points according to the plurality of surface portions.

14. The method of claim 13 further comprises: processing the cylindrical calibration data and the spherical calibration data to generate calibration data for the chromatic range sensor.

15. 14. The method of claim 13, the spherical calibration surface having a plurality of second surface portions; The method comprises: operating the chromatic range sensor to rotate the radial distance detection beam about the axis of rotation with the optical pen at approximately the first standoff distance from the spherical calibration member for each of the plurality of second surfaces to provide spherical radial distance data acquired during the rotational movement; processing each set of radial distance data corresponding to each detected surface portion of the plurality of second surface portions to determine a detected closest surface point representative of the point closest to the optical pen; determining the spherical calibration data based at least in part on the detected closest surface points corresponding to the plurality of surface portions.

16. The method of claim 13 further comprises: operating the rotating chromatic range sensor to rotate the radial distance detection beam about the axis of rotation with the optical pen of the rotating chromatic range sensor at approximately the second standoff distance from the spherical calibration member relative to the first plurality of surface portions to provide a spherical radial distance data set acquired during the rotational movement; processing each set of radial distance data corresponding to each surface portion detected at the second standoff distance to determine a closest detected surface point representing the point of the rotating chromatic range sensor closest to the optical pen; determining the spherical calibration data based at least in part on the detected closest surface points corresponding to the plurality of surface portions at the second standoff distance.

17. The method of claim 13 further comprises: operating the rotating chromatic range sensor with the optical pen in a first orientation relative to the spherical calibration member to rotate the radial distance sensing beam about the axis of rotation relative to the first plurality of surface portions to provide a spherical radial distance data set acquired during the rotational movement; operating the rotating chromatic range sensor with the optical pen in a second orientation relative to the spherical calibration member, the second orientation being different from the first orientation, to rotate the radial distance detection beam about the axis of rotation for each of a plurality of second surface portions on the spherical calibration surface, and providing a spherical radial distance data set acquired during the rotational movement; The method according to claim 1, further comprising:

18. a chromatic range sensor (CRS) including a CRS optical probe; a cylindrical calibration member capable of providing cylindrical calibration data for correcting misalignment errors of the CRS optical probe; a spherical calibration member capable of providing spherical calibration data for correcting misalignment errors of the CRS optical probe; a stage configured to position the cylindrical calibration member and the spherical calibration member relative to the CRS optical probe; the cylindrical calibration member has at least a first cylindrical calibration surface having a central axis in a Z direction, and the CRS optical probe is configured to rotate a radial distance detection beam about the rotation axis at a first Z coordinate position in the Z direction relative to the cylindrical calibration member to provide a first cylindrical radial distance data set acquired during the rotation, the cylindrical radial distance data set being configured to reference a detection rotation angle of the radial distance detection beam about the rotation axis, and the first cylindrical radial distance data set referenced to the detection rotation angle being processed to determine the cylindrical calibration data; the spherical calibration member has a spherical calibration surface, and for each of a plurality of first surface portions on the spherical calibration surface, the CRS optical probe is configured to rotate the radial distance detection beam about the rotation axis using an optical pen at approximately a first standoff distance from the spherical calibration member to provide a corresponding spherical radial distance data set acquired during the rotation, and also move the optical pen in a scanning axis direction to acquire the spherical radial distance data set, each set of radial distance data corresponding to each detected surface portion is processed to determine a detected closest surface point representing a point closest to the optical pen, and the spherical calibration data is determined based at least in part on the detected closest surface points responsive to the plurality of surface portions. A calibration system comprising:

19. 20. The calibration system according to claim 18, wherein the stage comprises a base, and the cylindrical calibration member and the spherical calibration member are placed on the base.

20. The calibration system of claim 18 further comprising a control unit configured to calculate each set of radial distance data corresponding to each detected surface portion to determine the closest detected surface point representing the closest to the optical pen, and to determine the spherical calibration data based at least in part on the closest detected surface points corresponding to the plurality of surface portions.

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