JP5797346B2 - Laser tracker shared with a 6-DOF probe having a separable spherical reflector - Google Patents

Description

This application claims the benefit of US Provisional Patent Application No. 61 / 592,049, filed Jan. 30, 2012, the contents of which are hereby incorporated by reference. This application also claims the benefit of US Patent Application No. 13 / 407,983, filed February 29, 2012, which claims the benefit of US Provisional Patent Application No. 61 / 448,823, filed March 3, 2011. The contents of which are incorporated herein by reference. U.S. Patent Application No. 13 / 407,983 also claims U.S. Patent Application No. 61 / 442,452, filed Feb. 14, 2011, which claims the benefit of U.S. Provisional Patent Application No. 61 / 442,452. The benefit of 13 / 370,339 is also claimed, the contents of which are incorporated herein by reference. U.S. Patent Application No. 13 / 407,983 is also incorporated in U.S. Provisional Patent Application No. 61 / 475,703, filed Apr. 15, 2011, and U.S. Provisional Patent Application No. 61/592, filed on Jan. 30, 2012. The benefit of No. 049 is also claimed, the contents of which are incorporated herein by reference.

  The present application relates to a coordinate measuring apparatus. One type of coordinate measuring device belongs to the category of equipment that measures the three-dimensional (3D) coordinates of a point by sending a laser beam to that point. The laser beam may collide directly with the point, or impinge on a retro-reflector target that contacts the point. In either case, the instrument determines the coordinates of the point by measuring the distance to the target and two angles. The distance is measured by a distance measuring device such as an absolute distance meter or an interferometer. The angle is measured by an angle measuring device such as an angle encoder. A gimbal beam steering mechanism in the instrument guides the laser beam to the point of interest.

  A laser tracker is a specific type of coordinate measuring device that tracks a retro-reflector with one or more laser beams it generates. Coordinate measuring devices closely related to the laser tracker are a laser scanner and a total station. Laser scanners irradiate a point on a surface with one or more laser beams in a stepwise fashion. Then, the scattered light from the surface is picked up, and the distance from this light to each point and two angles are determined. Total stations are most often used for surveying, but can also be used to measure the coordinates of diffusely scattered or retroreflective targets. Hereinafter, the term laser tracker is used in a broad sense including a laser scanner and a total station.

  Usually, a laser tracker sends a laser beam to a retro-reflector target. A common type of retroreflector target is a spherically mounted retroreflector (SMR), which includes a corner cube retroreflector embedded in a metal sphere. The corner cube retro reflector includes three mirrors that are perpendicular to each other. The vertex that is the common intersection of the three mirrors is located at the center of the sphere. By positioning the corner cube in this way in the sphere, the vertical distance from the apex to the surface on which the SMR rests remains constant even when the SMR rotates. As a result, the laser tracker can measure the 3D coordinates of a surface by following its position as the SMR moves on the surface. In other words, a laser tracker can fully characterize the 3D coordinates of a surface if it only measures three degrees of freedom (one radial distance and two angles).

  One type of laser tracker has only an interferometer (IFM) and no absolute distance meter (ADM). If an object blocks the path of the laser beam from one of these trackers, the IFM loses its distance criteria. The operator must then reset the reference distance by tracking the retroreflector to a known position before continuing the measurement. A way to circumvent this restriction is to put the ADM in a tracker. ADM can measure distance in a point-and-shoot manner, which will be described in more detail later. Some laser trackers do not have an interferometer and contain only ADMs. US Patent No. 7,352,446 to Bridges et al. (Hereinafter "the '446 patent"), the contents of which are incorporated herein by reference, has only an ADM capable of accurately scanning a moving target ( A laser tracker that does not have an IFM is disclosed. Prior to the '446 patent, the absolute rangefinder had a slow response speed and could not accurately locate the moving target.

  A gimbal mechanism in the laser tracker can be used to guide the laser beam from the tracker to the SMR. Part of the light that is retro-reflected by the SMR enters the laser tracker and currency to the position detector. The control system in the laser tracker can maintain the laser beam at the center of the SMR by adjusting the rotation angle of the mechanical axis of the laser tracker using the position of the light on the position detector. In this way, the tracker can follow (track) the SMR moving on the surface of the object of interest. The gimbal mechanism used in the laser tracker may be used for various other applications. As a simple example, a laser tracker is used in a gimbal steering system with a visible pointer beam but no rangefinder to guide the light beam to a series of retro-reflector targets and measure the angle of each of the targets May be.

  An angle measuring device such as an angle encoder is attached to the mechanical shaft of the tracker. One distance measurement and two angle measurements made by the laser tracker are sufficient to fully identify the three-dimensional position of the SMR.

  Several laser trackers are available or have been proposed so far for measuring 6 degrees of freedom rather than the usual 3 degrees of freedom. An exemplary 6-degree-of-freedom (6-DOF) system is disclosed in US Pat. No. 7,800,758 to Bridges et al. (Hereinafter “'758”), the contents of which are incorporated herein by reference. No. Patent No. 2010/0128259 by Bridges et al., The contents of which are incorporated herein by reference.

US Pat. No. 7,352,446 US Patent No. 7,800,758 US Patent Application Publication No. 2010/0128259

  In the past, the 6-DOF probe and SMR were separate accessories that were relatively expensive. What is needed is an accessory that is relatively inexpensive and combines the functionality of SMR and 6-DOF probes.

  A method for measuring three-dimensional coordinates of a probe center includes providing a steel ball integrated retroreflector, the steel ball integrated retroreflector including a retro reflector attached to the retroreflector body, wherein the retroreflector body is The first portion of the outer surface has a first sphere, the first portion has a target center, and the retroreflector is configured to receive the first light beam and return the second light beam. The second light beam is part of the first light beam, and the second light beam travels in a direction substantially opposite to the direction of the first light beam. The method also includes providing a probe assembly, the probe assembly including a probe stylus and a probe head, the probe stylus including a probe tip, and the probe tip is a second portion of the surface thereof. The second part has a probe center, the probe head receives a steel ball integrated retroreflector and allows the steel ball integrated retroreflector to rotate around the target center while the target It is configured to keep the center in a substantially constant position with respect to the probe assembly. The method further includes providing an orientation sensor, wherein the orientation sensor is configured to perform a three orientation degree of freedom measurement of the probe assembly, and providing a coordinate measurement device; The coordinate measuring device includes a first motor, a second motor, a first angle measuring device, a second angle measuring device, a distance meter, a position detector, a control system, and a processor, The first motor and the second motor are configured to cooperate to guide the first light beam in the first direction, the first direction being a first rotation angle about the first axis and Determined by a second rotation angle about a second axis, the first rotation angle is generated by the first motor, the second rotation angle is generated by the second motor, and the first angle measurement The device is configured to measure the first rotation angle The second angle measuring device is configured to measure a second rotation angle, and the distance meter includes, at least in part, a first distance from the coordinate measuring device to the steel ball integrated retroreflector. The photodetector is configured to measure based on the third portion of the second light beam received, and the position detector is responsive to the position of the fourth portion of the second light beam on the position detector. And the control system is configured to transmit the second signal to the first motor and the third signal to the second motor, and The signal and the third signal are based at least in part on the first signal, and the control system directs the first direction of the first light beam to a position in the space of the steel ball integrated retroreflector. Configured to adjust to match, the processor is centered on the probe It is configured to determine dimension coordinates, three-dimensional coordinates, on at least a portion, a first distance, the first rotation angle, the second angle of rotation, based on the 3 orientation degrees of freedom. The method also includes installing a steel ball integrated retroreflector on the probe head, guiding a first light beam from the coordinate measuring device to the steel ball integrated retroreflector, and measuring a first distance. Measuring a first rotation angle; measuring a second rotation angle; performing a three azimuth degree of freedom measurement based at least in part on information provided by an azimuth sensor; Calculate the probe center three-dimensional coordinates based at least in part on the first distance, the first rotation angle, the second rotation angle, and the three degrees of freedom, and store the probe center three-dimensional coordinates Including the steps of:

  Referring now to the drawings, there are shown exemplary embodiments, which should not be construed as limiting with respect to the overall scope of the disclosure, and that through the drawings, The numbers were the same.

1 is a perspective view of a laser tracker system comprising a retro reflector target according to an embodiment of the present invention. FIG. 1 is a perspective view of a laser tracker system comprising a 6-DOF target according to an embodiment of the present invention. FIG. It is a block diagram explaining the optical system of the laser tracker by one embodiment of this invention, and the element of an electronic component. It is a figure which shows the afocal beam expander by a prior art. It is a figure which shows the afocal beam expander by a prior art. It is a figure which shows the optical fiber beam incident emission part by a prior art. 1 is a schematic diagram of a prior art detector assembly. FIG. 1 is a schematic diagram of a prior art detector assembly. FIG. 1 is a schematic diagram of a prior art detector assembly. FIG. 1 is a schematic diagram of a prior art detector assembly. FIG. 1 is a schematic diagram illustrating a position detector assembly according to an embodiment of the present invention. 1 is a schematic diagram illustrating a position detector assembly according to an embodiment of the present invention. 1 is a block diagram of electrical and electro-optic elements in a prior art ADM. FIG. 1 is a schematic diagram showing optical fiber elements in a prior art optical fiber network. FIG. 1 is a schematic diagram showing optical fiber elements in a prior art optical fiber network. FIG. 1 is a schematic diagram illustrating optical fiber elements in an optical fiber network according to an embodiment of the present invention. FIG. 1 is an exploded view of a prior art laser tracker. FIG. 1 is a cross-sectional view of a prior art laser tracker. FIG. 3 is a block diagram of the operation and communication elements of a laser tracker according to an embodiment of the invention. FIG. 3 is a block diagram of elements of a laser tracker that utilizes a single wavelength, according to an embodiment of the invention. FIG. 3 is a block diagram of elements of a laser tracker that utilizes a single wavelength, according to an embodiment of the invention. FIG. 2 is a block diagram of elements of a laser track having 6-DOF functionality according to an embodiment of the present invention. 6 is a front view of a 6-DOF SMR magnetically attached to a 6-DOF probe base, in accordance with an embodiment of the present invention. FIG. 6 is a front view of a 6-DOF SMR clamped and secured to a 6-DOF probe base, in accordance with an embodiment of the present invention. FIG. FIG. 6 is a front view of a probe assembly and 6-DOF SMR installed on a correction fixture. 1 is a cross-sectional view of a correction fixture according to an embodiment of the present invention. FIG. 6 is a front view illustrating a yaw motion of a 6-DOF probe to obtain a correction parameter according to an embodiment of the present invention. FIG. 6 is a front view illustrating pitch motion of a 6-DOF probe to obtain correction parameters according to an embodiment of the present invention. FIG. 6 is a front view illustrating the roll motion of a 6-DOF probe to obtain correction parameters according to an embodiment of the present invention. FIG. 4 is a front view of a probe assembly and 6-DOF SMR with intermittent rotational position indexing and mating functions, in accordance with an embodiment of the present invention. It is a flowchart of the measuring method of the three-dimensional coordinate by one embodiment of this invention. FIG. 19 is a flow diagram of a method beginning with reference symbol A of FIG. 18 according to an embodiment of the present invention. FIG. 20 is a flow diagram of a method beginning with reference symbol B of FIG. 19 according to an embodiment of the present invention. FIG. 19 is a flow diagram of a method beginning with reference symbol A of FIG. 18 according to an embodiment of the present invention. FIG. 22 is a flow diagram of a method beginning with reference C in FIG. 21 according to an embodiment of the present invention. FIG. 19 is a flow diagram of a method beginning with reference symbol A of FIG. 18 according to an embodiment of the present invention.

  The exemplary laser tracker system 5 shown in FIG. 1 includes a laser tracker 10, a retroreflector target 26, an optional auxiliary unit processor 50, and an optional auxiliary computer 60. The exemplary gimbal beam steering mechanism 12 of the laser tracker 10 includes a zenith carriage 14 that is attached to an azimuth base 16 and rotates about an azimuth axis 20. The payload 15 is mounted on the zenith carriage 14 and rotates around the zenith shaft 18. The zenith axis 18 and the azimuth axis 20 are orthogonal to each other at the gimbal point 22 in the tracker 10, and this is generally the origin of distance measurement. The laser beam 46 effectively passes through the gimbal point 22 and is oriented perpendicular to the zenith axis 18. In other words, the laser beam 46 is substantially perpendicular to the zenith axis 18 and in a plane that passes through the azimuth axis 20. The emitted laser beam 46 is directed in a desired direction by rotation of the payload 15 around the zenith axis 18 and rotation of the zenith carriage 14 around the azimuth axis 20. The zenith angle encoder is internal to the tracker and is attached to a zenith machine shaft that is aligned with the zenith shaft 18. The azimuth angle encoder is internal to the tracker and is attached to an azimuth machine axis that is aligned with the azimuth axis 20. Zenith and azimuth angle encoders measure senis rotation and azimuth rotation angles with relatively high accuracy. The emitted laser beam 46 travels to a steel ball integrated retroreflector target 26, which may be, for example, a steel ball integrated retroreflector (SMR) as described above. By measuring the radial distance between the gimbal point 22 and the retroreflector 26, the rotation angle around the zenith axis 18 and the rotation angle around the azimuth axis 20, the position of the retroreflector 26 is determined by the spherical coordinates of the tracker. Specified in the system.

  The emitted laser beam 46 may include one or more laser wavelengths, which will be described later. For clarity and simplicity, the following description assumes a steering mechanism of the type shown in FIG. However, other types of steering mechanisms can be used. For example, the laser beam can be reflected by a mirror that rotates about the azimuth and sennis axes. The technology described in this specification can be applied regardless of the type of the steering mechanism.

  A magnetic nest 17 may be included in the laser tracker, for resetting the laser tracker to the “home” position of different sized SMRs, eg 1, 5, 7/8, 1/2 inch SMR. . A retro reflector 19 on the tracker may be used to reset the tracker to a reference distance. In addition, a mirror on the tracker that is not visible in the diagram of FIG. 1 may be shared with a retro-reflector on the tracker to enable a self-correction function, which is described in US Pat. No. 7,327,446. The contents of which are incorporated herein by reference.

  FIG. 2 shows an exemplary laser tracker system 7 that is similar to the laser tracker system 5 of FIG. 1 except that a 6-DOF probe 1000 is used instead of the retroreflector target 26. . In FIG. 1, other types of retro-reflector targets may be used. For example, a cat-eye retro-reflector, which is a glass retro-reflector that focuses light on a small spot of light on the reflective back of the glass structure, may be used.

  FIG. 3 is a block diagram illustrating optical and electrical elements in an embodiment of a laser tracker. This shows an element of a laser tracker that emits light of two wavelengths: a first wavelength for ADM and a visible pointer and a second wavelength for tracking. The visible pointer allows the user to see the position of the laser beam spot emitted by the tracker. The two types of wavelengths are combined using a free space beam splitter. The electro-optic (EO) system 100 includes a visible light source 110, an isolator 115, an optional first fiber exit 170, an optional interferometer (IFM) 120, a beam expander 140, and a first beam. It includes a splitter 145, a position detection assembly 150, a second beam splitter 155, an ADM 160, and a second fiber entrance / exit section 170.

  The visible light source 110 may be a laser, a superluminescent diode, or other light emitting device. The isolator 115 may be a Faraday isolator, attenuator, or other device that can reduce light reflected back to the light source. The optional IFM can be configured in various ways. As an example of a possible implementation, the IFM may include a beam splitter 122, a retroreflector 126, quarter wave plates 124, 130, and a phase analyzer 128. Visible light source 110 may emit light into free space, which then travels through free space through isolator 115 and optional IFM 120. Alternatively, the isolator 115 may be connected to the visible light source 110 by an optical fiber cable. In this case, the light from the isolator may be emitted into the free space through the first optical fiber entrance / exit part 170, which will be described later with reference to FIG.

  Although beam expander 140 can be constructed using various lens configurations, two commonly used prior art configurations are shown in FIGS. 4A and 4B. FIG. 4A shows a configuration 140A based on the use of a minus lens 141A and a plus lens 142A. The collimated light beam 220A incident on the minus lens 141A exits as a larger collimated light beam 230A from the plus lens 142A. FIG. 4B shows a configuration 140B based on the use of two plus lenses 141B, 142B. The collimated light beam 220B incident on the first plus lens 141B exits from the second plus lens 142B as a larger collimated light beam 230B. A small amount of light emitted from the beam expander 140 is lost by being reflected by the beam splitters 145 and 155 on the way to the tracker. The portion of the light that has passed through the beam splitter 155 is combined with the light from the ADM 160 to form a composite light beam 188 that exits the laser tracker and proceeds to the retro-reflector 90.

  The ADM 160 includes a light source 162, ADM electronics 164, a fiber network 166, an interconnect electrical cable 165, and interconnect optical fibers 168, 169, 184, 186. The ADM electronics transmits electrical modulation and bias voltage to the light source 162, which may be a distributed feedback laser operating at a wavelength of about 1550 nm, for example. In some embodiments, the fiber network 166 may be the prior art fiber optic network 420A shown in FIG. 8A. In this embodiment, light from light source 162 in FIG. 3 travels on optical fiber 184, which is equivalent to optical fiber 432 in FIG. 8A.

  The fiber network of FIG. 8A includes a first fiber coupler 430, a second fiber coupler 436, and low transmission reflectors 435, 440. Light passes through the first fiber coupler 430 and is divided into two paths: a first path through the optical fiber 433 to the second fiber coupler 436, and a second path through the optical fiber 433 and the fiber length equalizer 423. . The fiber length equalizer 423 leads to the fiber length 168 of FIG. 3, which proceeds to the reference channel of the ADM electronics 164. The purpose of the fiber length equalizer 423 is to match the length of the optical fiber in which light travels in the reference channel with the length of the optical fiber in which light travels in the measurement channel. By matching the fiber lengths in this manner, ADM errors caused by ambient temperature changes are reduced. Such an error may occur because the effective optical path length of the optical fiber is equal to the average refractive index of the optical fiber multiplied by the fiber length. Since the refractive index of an optical fiber depends on the temperature of the fiber, changes in the temperature of the optical fiber change the effective optical path length of the measurement and reference channels. When the effective optical path length of the measurement channel optical fiber changes with respect to the effective optical path length of the reference channel optical fiber, the retro-reflector position will obviously change even if the retro-reflector target 90 remains stationary. . To avoid this problem, two steps are taken. First, the fiber length of the reference channel is matched as closely as possible to the fiber length of the measurement channel. Second, the measurement and reference fibers are routed side by side as much as possible to ensure that the temperature changes of the optical fibers in these two channels are almost the same.

  The light passes through the second optical fiber coupler 436 and is split into two paths, a first optical path to the low reflection fiber terminator 440 and a second path to the optical fiber 438, from which the light is shown in FIG. Proceed to optical fiber 186. The light on the optical fiber 186 travels through the second fiber entrance / exit section 170.

  In one embodiment, the fiber entrance and exit 170 is shown in prior art FIG. Light from optical fiber 186 in FIG. 3 travels to fiber 172 in FIG. The fiber incidence / emission unit 170 includes an optical fiber 172, a ferrule 174, and a lens 176. The optical fiber 172 is attached to the ferrule 174, which is stably attached to the structure in the laser tracker 10. If desired, the end of the optical fiber may be polished at an angle to reduce back reflection. The light 250 is emitted from the core of the fiber, and the fiber may be a single mode optical fiber whose diameter is 4-12 micrometers depending on the wavelength of light used and the specific type of optical fiber. Light 250 diverges at an angle and enters lens 176, thereby being collimated. A method for transmitting and receiving optical signals over a single optical fiber in an ADM system is described in the '758 patent with respect to FIG.

  Referring to FIG. 3, the beam splitter 155 may be a dichroic beam splitter, which transmits different wavelengths than it reflects. In some embodiments, light from ADM 160 is reflected by dichroic beam splitter 155 and combined with light from visible laser 110 that has passed through dichroic beam splitter 155. The combined light beam 188 exits the laser tracker as a first beam and travels to the retroreflector 90, which returns a portion of the light as a second beam. Of the second beam, the ADM wavelength portion is reflected by the dichroic beam splitter 155 and returns to the second fiber entrance / exit section 170, which couples the light back into the optical fiber 186.

  In certain embodiments, the optical fiber 186 corresponds to the optical fiber 438 of FIG. 8A. The returning light passes from the optical fiber 438 through the second fiber coupler 436 and is split into two paths. The first path leads to optical fiber 424, which in one embodiment corresponds to optical fiber 169 leading to the measurement channel of ADM electronics 164 of FIG. The second path leads to the optical fiber 433 and then to the first fiber coupler 430. The light emitted from the first fiber coupler 430 is divided into two paths, that is, a first path to the optical fiber 432 and a second path to the low reflection termination 435. In some embodiments, the optical fiber 432 corresponds to the optical fiber 184, which leads to the light source 162 of FIG. In most cases, the light source 162 includes a built-in Faraday isolator, which minimizes the amount of light that enters the light source from the optical fiber 432. If too much light is supplied to the laser in the opposite direction, the laser can become unstable.

Light from the fiber network 166 enters the ADM electronics 164 through optical fibers 168 and 169. One embodiment of a prior art ADM electronic component is shown in FIG. The optical fiber 168 in FIG. 3 corresponds to the optical fiber 3232 in FIG. 7, and the optical fiber 169 in FIG. 3 corresponds to the optical fiber 3230 in FIG. Referring now to FIG. 7, the ADM electronics 3300 includes a frequency reference 3302, a synthesizer 3304, a measurement detector 3306, a reference detector 3308, a measurement mixer 3310, a reference mixer 3312, and a conditioning electronics 3314. 3316, 3318, 3320, an N-dividing prescaler 3324, and an analog-to-digital converter (ADC) 3322. The frequency reference may be, for example, a constant-temperature bath crystal oscillator (OCXO), and a reference frequency f _REF that can be 10 MHz is transmitted to, for example, a synthesizer, and this is one of two types of electrical signals, that is, one signal of frequency f _RF Two signals of frequency f _LO are generated. The signal f _RF is supplied to the light source 3102, which corresponds to the light source 162 in FIG. The two signals having the frequency f _LO are supplied to the measurement mixer 1110 and the reference mixer 3312. Light from optical fibers 168 and 169 of FIG. 3 appears on fibers 3232 and 3230 of FIG. 7, respectively, and enters the reference and measurement channels, respectively. The reference detector 3308 and the measurement detector 3306 convert the optical signal into an electrical signal. These signals are conditioned by electrical components 3316 and 3314, respectively, and transmitted to mixers 3312 and 3310, respectively. The mixer generates a frequency f _IF equal to the absolute value of f _LO −f _RF . The signal f _RF may be a relatively high frequency, for example 2 GH, while the signal f _IF may be a relatively low frequency, for example 10 kHz.

The reference frequency f _REF is transmitted to the prescaler 3324, which divides the frequency by an integer value. For example, a frequency of 10 MHz is divided by 40 to obtain an output frequency of 250 kHz. In this example, the 10 kHz signal entering ADC 3322 is sampled at a rate of 250 kHz, thereby producing 25 samples per cycle. The signal from the ADC 3322 is sent to the data processor 3400, which may be one or more digital signal processor (DSP) units installed, for example, in the ADM electronics 164 of FIG.

  The method of extracting a distance is based on the calculation of the phase of the ADC signal for the reference and measurement channels. This method is described in detail in US Pat. No. 7,701,559 (hereinafter referred to as the “'559 patent”) by Bridges et al., The contents of which are incorporated herein by reference. The calculation includes the use of equations (1)-(8) of the '559 patent. In addition to this, when the ADM first starts measuring the retro-reflector, the frequency generated by the synthesizer is changed several times (eg, three times) and the possible ADM distance is calculated each time. By comparing the possible ADM distances for each of the selected frequencies, the ambiguity of the ADM measurement is eliminated. By combining the formulas (1)-(8) of the '599 patent with the synchronization method described with respect to FIG. 5 of the' 559 patent and the Kalman filter scheme described in the '559 patent, the ADM moves the moving target. It can be measured. In other embodiments, absolute distance measurements may be obtained by other methods, such as using pulsed time of flight rather than phase difference.

  A portion of the return light beam 190 that passes through the beam splitter 155 reaches the beam splitter 145, which transmits a portion of the light to the beam splitter 140 and another portion of the light to the position detector assembly 150. The light emitted from the laser tracker 10 or the EO system 100 may be considered as the first beam, and the portion of the light reflected by the retroreflector 90 or 26 may be considered as the second beam. Some of the reflected beams are sent to different functional elements of the EO system 100. For example, the first portion may be sent to a distance meter such as ADM 160 of FIG. The second portion may be sent to the position detector assembly 150. In some cases, the third portion may be transmitted to other functional units such as the optional interferometer 120. Significantly, in the example of FIG. 3, the first and second portions of the second beam are reflected by beam splitters 155 and 145, respectively, and then transmitted to the distance meter and position detector. Rather, it should be understood that light can be transmitted to a rangefinder or position detector.

  Four examples of prior art position detector assemblies 150A-150D are shown in FIGS. FIG. 6A shows the simplest example, where the position detector assembly includes a position sensor 151, which is mounted on a circuit board 152, which obtains power from the electronic box 350 and returns signals to it. This may represent an electronic processing function at any location within the laser tracker 10, auxiliary unit 50, or external computer 60. FIG. 6B includes an optical filter 154 that blocks unwanted light wavelengths from reaching the position sensor 151. Unwanted light wavelengths may also be blocked, for example, by coating the surface of beam splitter 145 or position sensor 151 with a suitable film. FIG. 6C includes a lens 153 that reduces the size of the light beam. FIG. 6D includes both an optical filter 154 and a lens 153.

  FIG. 6E illustrates a position sensing assembly according to an embodiment of the present invention, which includes an optical conditioner 149E. The optical conditioner includes a lens 153 and may also include an optional wavelength filter 154. In addition, at least one of the diffusion plate 156 and the spatial filter 157 is included. As mentioned above, a common type of retro-reflector is a corner cube retro-reflector. One corner cube retroreflector is composed of three mirrors, each connected at right angles to the remaining two mirrors. The intersection line where these three mirrors are connected may have a finite thickness, and the light is not completely reflected by the tracker. Lines with finite thickness diffract as they propagate and when they reach the position detector, they may not look exactly the same as when they are in the position detector. However, the diffracted light pattern generally deviates from perfect symmetry. As a result, the light hitting the position detector 151 may have an increase or decrease in optical power (hot spot), for example, near the diffracted line. Because the light uniformity from the retro-reflector can vary from one retro-reflector and the light dispersion on the position detector can change with the rotation or tilt of the retro-reflector, By including 156, it may be advantageous to improve the smoothness of the light striking the position detector 151. The ideal position detector should respond to the center of gravity and the ideal diffuser should spread the spot symmetrically, so the position detector should not affect the resulting position. Can argue. In practice, however, the diffuser plate has been observed to improve the performance of the position detector assembly, possibly due to the non-linearity (imperfection) effect of the position detector 151 and lens 153. A glass corner cube retro-reflector may also generate a non-uniform light spot at the position detector 151. The variation in the spot of light in the position detector may be particularly noticeable from the light reflected from the corner cube in the 6-DOF target, which was assigned to the common assignee of this application, February 2012. No. 13 / 370,339 (hereinafter referred to as “'339 application”) filed on the 10th and 13 / 407,983 (hereinafter referred to as “the' 983 application”) filed on February 29, 2012. The content of which is incorporated herein by reference. In some embodiments, the diffuser plate 156 is a holographic diffuser. A holographic diffuser provides controlled homogeneous light at a specified diffusion angle. In other embodiments, other types of diffuser plates are used, such as ground glass or “opal” diffuser plates.

  The purpose of the spatial filter 157 of the position detector assembly 150E is to block the ghost beam, which may be caused by unwanted reflections in the optical plane, from hitting the position detector 151, for example. The spatial filter includes a plate 157 having an aperture. By placing the spatial filter 157 away from the lens by a distance approximately equal to the focal length of the lens, the return light 243E passes through the spatial filter when it is near its narrowest beam waist. For example, a beam traveling at a different angle as a result of reflection of the optical element hits the spatial filter at a position away from the aperture and is blocked from reaching the position detector 151. An example is shown in FIG. 6E, in which unwanted ghost beam 244E is reflected off the surface of beam splitter 145 and travels to spatial filter 157 where it is blocked. Without a spatial filter, the ghost beam 244E would have reached the position detector 151, which would inaccurately determine the position of the beam 243E on the position detector 151. Even a weak ghost beam may significantly change the position of the center of gravity on the position detector 151 if the ghost beam is a relatively large distance away from the main light spot.

  Retroreflectors of the type described herein, such as corner cubes or cat eye retroreflectors, have the property of reflecting light incident on the retroreflector in a direction parallel to the incident light. In addition, incident and reflected rays may be placed symmetrically around the symmetry point of the retroreflector. For example, in the case of an open air corner cube retroreflector, the symmetry point of the retroreflector is the vertex of the corner cube. In a glass corner cube retroreflector, the symmetry point is also the apex, but in this case it is necessary to consider that light bends at the glass-air interface. In a cat-eye retroreflector with a refractive index of 2.0, the symmetry point is at the center of the sphere. In a cat-eye retroreflector made of two glass hemispheres placed symmetrically on a common plane, the symmetry point is a point located at the center of each hemisphere on that plane. Importantly, with respect to the type of retroreflector normally used with laser trackers, the light returned by the retroreflector to the tracker is shifted to the opposite side of the apex with respect to the incident laser beam.

  This behavior of the retroreflector 90 of FIG. 3 is the basis for tracking the retroreflector by the laser tracker. The position sensor has an ideal turn point on its surface. The ideal turn-back point is the point where the laser beam sent to the retroreflector symmetry point (eg, the apex of the corner cube retroreflector in the SMR) returns. Usually, the turning point is near the center of the position sensor. When the laser beam is sent to one side of the retroreflector, it reflects back to the other side and appears to be offset from the return point of the position sensor. By knowing the position of the light return beam on the position sensor, the control system of the laser tracker 10 can cause the motor to move the light beam toward the point of symmetry of the retroreflector.

  As the retroreflector traverses the tracker at a constant speed, the beam at the retroreflector (after the transient response has settled) strikes the retroreflector a certain distance away from the retroreflector's symmetry point. The laser tracker performs a correction considering the distance of this deviation based on the scale factor obtained from the controlled measurement and based on the distance from the light beam on the position sensor to the ideal return point.

  As explained above, the position detector performs two important functions. That is, enabling tracking and correcting the measured value in consideration of the movement of the retroreflector. The position sensor in the position detector may be any kind of device as long as the position can be measured. For example, the position sensor may be a position sensitive detector or a photosensitive element array. The position sensitive detector may be, for example, a lateral effect detector or a quadrant detector. The photosensitive element array may be, for example, a CMOS or CCD array.

  In some embodiments, the regressed light that is not reflected by the beam splitter 145 passes through the beam expander 140 and thereby becomes smaller. In other embodiments, the positions of the position detector and rangefinder are reversed so that the light reflected by the beam splitter 145 travels to the rangefinder and the light transmitted through the beam splitter travels to the position detector.

  The light passes through the optional IFM, through the isolator, and enters the visible light source 110. At this stage, the optical power is sufficiently small so that the visible light source 110 is not unstable.

  In an embodiment, the light from the visible light source 110 is emitted through the beam incident emission unit 170 of FIG. The fiber entrance / exit section may be attached to the output of the light source 110 or the optical fiber output of the isolator 115.

  In some embodiments, the fiber network 166 of FIG. 3 is the prior art fiber network 420B of FIG. 8B. Here, the optical fibers 184, 186, 168, 169 in FIG. 3 correspond to the optical fibers 443, 444, 424, 422 in FIG. 8B. The fiber network of FIG. 8B is similar to the fiber network of FIG. 8A, but the fiber network of FIG. 8B has one fiber coupler instead of two fiber couplers. The advantage of FIG. 8B compared to FIG. 8A is simplicity, but FIG. 8B is more likely to cause unwanted back reflections of light into the optical fibers 422 and 424.

  In some embodiments, the fiber network 166 of FIG. 3 is the fiber network 420C of FIG. 8C. Here, the optical fibers 184, 186, 168, and 169 in FIG. 3 correspond to the optical fibers 447, 455, 423, and 424 in FIG. 8C. The fiber network 420 </ b> C includes a first fiber coupler 445 and a second fiber coupler 451. The first fiber coupler 445 is a 2 × 2 coupler and has two input ports and two output ports. This type of coupler is usually manufactured by placing two fiber cores in close proximity and then drawing while heating. In this way, the desired portion of light can be separated into adjacent fibers by evanescent coupling between the fibers. The second fiber coupler 451 is of a type called a circulator. It has three ports, each of which can transmit or receive light, but only in specified directions. For example, light on optical fiber 448 enters port 453 and is carried to port 454 as indicated by the arrow. At port 454, light may be transmitted over optical fiber 455. Similarly, light sent over optical fiber 455 may enter port 454 and be transmitted toward port 456 in the direction of the arrow, where some light may be transmitted to optical fiber 424. If only three ports are required, the optical power loss of the circulator 451 may be smaller than in the case of a 2 × 2 coupler. On the other hand, the circulator 451 can be more expensive than a 2 × 2 coupler, and polarization mode dispersion can occur, which can be problematic in some circumstances.

  FIGS. 9 and 10 show an exploded view and a cross-sectional view, respectively, of the prior art laser tracker 2100 shown in FIGS. 2 and 3 of Bridge et al. US 2010/0128259, incorporated herein by reference. The azimuth assembly 2110 includes a column housing 2112, an azimuth encoder assembly 2120, lower and upper azimuth bearings 2114 A, 2114 B, an azimuth motor assembly 2125, an azimuth slip ring assembly 2130, and an azimuth circuit board 2135.

  The purpose of the azimuth encoder assembly 2120 is to accurately measure the rotation angle of the yoke 2142 relative to the column housing 2112. The azimuth encoder assembly 2120 includes an encoder disk 2121 and a read head assembly 2122. The encoder disk 2121 is attached to the shaft of the yoke housing 2142, and the read head assembly 2122 is attached to the post assembly 2110. Read head assembly 2122 includes a circuit board on which one or more read heads are secured. The laser beam sent from the reading head is reflected by the fine grid lines of the encoder disk 2121. The reflected light picked up by the detector on the encoder read head is processed to determine the angle of the encoder disk that rotates with respect to the fixed read head.

  The azimuth motor assembly 2125 includes an azimuth motor rotor 2126 and an azimuth motor stator 2127. The azimuth motor rotor includes a permanent magnet attached directly to the shaft of the yoke housing 2142. The azimuth motor stator 2127 includes magnetic field windings that generate a predetermined magnetic field. This magnetic field interacts with the magnets of the azimuth motor rotor 2126 to produce the desired rotational motion. The azimuth motor stator 2127 is attached to the support frame 2112.

  The azimuth circuit board 2135 represents one or more circuit boards that provide the electrical functions required by azimuth components such as encoders and motors. The azimuth slip ring assembly 2130 includes an outer portion 2131 and an inner portion 2132. In some embodiments, the wire bundle 2138 exits the auxiliary unit processor 50. Wire bundle 2138 may transmit power to or from the tracker. A part of the wires of the wire bundle 2138 may be guided to a connector on the circuit board. In the example shown in FIG. 10, the wire is routed to the azimuth circuit board 2135, the encoder read head assembly 2122, and the azimuth motor assembly 2125. Another wire is routed to the inner portion 2132 of the slip ring assembly 2130. Inner portion 2132 is attached to post assembly 2110 so that it remains stationary. Outer portion 2131 is attached to yoke housing 2140 and thus rotates relative to inner portion 2132. Slip ring assembly 2130 is designed to allow low impedance electrical contact as outer portion 2131 rotates relative to inner portion 2132.

  The zenith assembly 2140 includes a yoke housing 2142, a zenith encoder assembly 2150, left and right zenith bearings 2144A, 2144B, a zenith motor assembly 2155, a senis slip ring assembly 2160, and a zenith circuit board 2165. .

  The purpose of the Zenith encoder assembly 2150 is to accurately measure the rotation angle of the payload frame 2172 relative to the yoke housing 2142. Zenith encoder assembly 2150 includes a Zenith encoder disk 2151 and a Zenith readhead assembly 2152. The encoder disk 2151 is attached to the payload housing 2142 and the read head assembly 2152 is attached to the yoke housing 2142. Zenith readhead assembly 2152 includes a circuit board on which one or more readheads are secured. The laser beam sent from the reading head is reflected by the fine lattice lines on the encoder disk 2151. The reflected light picked up by the detector on the encoder read head is processed to determine the angle of the encoder disk that rotates with respect to the fixed read head.

  Zenith motor assembly 2155 includes a Zenith motor rotor 2156 and a Zenith motor stator 2157. Zenith motor rotor 2156 includes a permanent magnet attached directly to the shaft of payload frame 2172. Zenith motor stator 2157 includes magnetic field windings that generate a predetermined magnetic field. This magnetic field interacts with the rotor magnet to produce the desired rotational motion. Zenith motor stator 2157 is attached to yoke frame 2142.

  Zenith circuit board 2165 represents one or more circuit boards, which provide the electrical functions required by Zenith components such as encoders and motors. Zenith slip ring assembly 2160 includes an outer portion 2161 and an inner portion 2162. The wire bundle 2168 may exit the azimuth outer slip ring 2131 and carry power or signals. A portion of the wires of wire bundle 2168 may be guided to a connector on the circuit board. In the example shown in FIG. 10, the wire is routed to the Zenith circuit board 2165, the Zenith motor assembly 2150, and the encoder readhead assembly 2152. The other wires are routed to the inner portion 2162 of the slip ring assembly 2160. Inner portion 2162 is attached to yoke frame 2142 so that it rotates only at the azimuth angle and not at the senis angle. Outer portion 2161 is attached to payload frame 2172 so that it rotates to both zenith and azimuth angles. The slip ring assembly 2160 is designed to allow low impedance electrical contact when the outer portion 2161 rotates with respect to the inner portion 2162. Payload assembly 2170 includes a primary optics assembly 2180 and a secondary optics assembly 2190.

  FIG. 11 is a block diagram illustrating a dimensioning electronic component processing system 1500, which is a laser tracker electronic component processing system 1510, a processing system for peripheral elements 1582, 1584, 1586, a computer 1590, and here illustrated by a cloud. Other networked components 1600 that are connected. An exemplary laser tracker electronics processing system 1510 includes a master processor 1520, payload function electronics 1530, azimuth encoder electronics 1540, Zenith encoder electronics 1550, display and user interface (UI) electronics 1560, Removable storage hardware 1565, radio frequency identification (RFID) electronics, and antenna 1572 are included. Payload functional electronic component 1530 includes a number of sub-functions including 6-DOF electronic component 1531, camera electronic component 1532, ADM electronic component 1533, position detector (PSD) electronic component 1534, and level electronic component. 1535. Most of the subfunctions have at least one processor unit, which may be, for example, a digital signal processor (DSP) or a field programmable gate array (FPGA). The electronic component units 1530, 1540, 1550 are separated as shown, depending on their position in the laser tracker. In some embodiments, the payload function 1530 is in the payload 2170 of FIGS. 9 and 10, the azimuth encoder electronics 1540 is in the azimuth assembly 2110, and the zenith encoder electronics 1550 is in the zenith assembly 2140.

  Many types of peripheral devices are possible, but three such devices are shown here. That is, a temperature sensor 1582, a 6-DOF probe 1584, and a portable information terminal 1586 that may be a smartphone, for example. The laser tracker may communicate with peripheral devices in a variety of ways, including wireless communication through antenna 1572, a visual system such as a camera, and the distance and angle to a collaborative target such as a 6-DOF probe 1584. A method based on a reading value is included. The peripheral device may include a processor. The 6-DOF accessory may include a 6-DOF probe assembly, a 6-DOF scanner, a 6-DOF projector, a 6-DOS sensor, a 6-DOF indicator, and the like. The processors of these 6-DOF devices may be shared with processing devices in the laser tracker and external computers and cloud processing resources. In general, where the term laser tracker processor or measurement instrument processor is used, this shall include possible external computers and cloud support functions.

  In some embodiments, another communication bus extends from the master processor 1520 to each of the electronic component units 1530, 1540, 1550, 1560, 1565, 1570. Each communication line may have, for example, three serial lines, including a data line, a clock line, and a frame line. The frame line indicates whether the electronic device unit should pay attention to the clock line. If it indicates that care should be taken, the electronic component unit reads the current value of the data line at each clock signal. The clock signal may correspond to, for example, a rising edge of a clock pulse. In certain embodiments, information is transmitted over data lines in the form of packets. In some embodiments, each packet includes an address, a numeric value, a data message, and a checksum. The address indicates a location to which the data message is to be transmitted in the electronic component unit. The position may correspond to, for example, a processor subroutine in the electronic component unit. The numerical value indicates the length of the data message. The data message includes data or instructions to be transmitted by the electronic component unit. The checksum is a numerical value that is used to minimize the chance that an error is transmitted over the communication line.

  In some embodiments, the master processor 1520 may include the payload function electronics 1530 on the bus 1610, the azimuth encoder electronics 1540 on the bus 1611, the Zenith encoder electronics 1550 on the bus 1612, and the display and UI on the bus 1613. Information packets are sent to electronic component 1560, removable storage hardware 1565 on bus 1614, and RFID and wireless electronic component 1570 on bus 1616.

  In some embodiments, the master processor 1520 also transmits a sync pulse on each of the electronic component units simultaneously on the sync bus 1630. The sync pulse allows the numerical values collected by the laser tracker measurement function to be synchronized. For example, azimuth encoder electronics 1540 and Zenith electronics 1550 latch their encoder values as soon as a sync pulse is received. Similarly, the payload function electronic component 1530 latches data collected by the electronic component included in the payload. 6-DOF, ADM, and position detectors all latch data when a sync pulse is applied. In most cases, the camera and inclinometer collect data at a slower rate than the sync pulse repetition rate, but data may be latched at multiples of the sync pulse period.

  Azimuth encoder electronics 1540 and Zenith encoder electronics 1550 are separated from each other and from payload electronics 1530 by slip rings 2130, 2160 shown in FIGS. Therefore, in FIG. 11, the bus lines 1610, 1611 and 1612 are depicted as separate bus lines.

  The laser tracker electronic component processing system 1510 may communicate with the external computer 1590 or provide the calculation, display, and UI functions in the laser tracker. The laser tracker may communicate with the computer 1590 over a communication link 1606, which may be, for example, an Ethernet line or wireless communication. The laser tracker may also communicate with other elements 1600 indicated by clouds and a communication link 1602 such as an Ethernet cable, one or more wireless connections. An example of element 1600 is other three-dimensional test equipment, such as an articulated arm CMM, which may be moved by a laser tracker. Communication link 1604 between computer 1590 and element 1600 may be wired (eg, Ethernet) or wireless. An operator sitting in front of remote computer 1590 may connect to the Internet, indicated by cloud 1600, via Ethernet or wireless, which is connected to master processor 1520 via Ethernet or wireless. In this way, the user can control the operation of the remote laser tracker.

  Laser trackers today use one visible wavelength (usually red) and one infrared wavelength for ADM. The red wavelength may be supplied by a frequency stabilized helium neon (HeNe) laser suitable for use in an interferometer and for providing a red pointer beam. Alternatively, the red wavelength may be supplied by a diode laser that serves as a pointer beam. The disadvantage of using two light sources is the extra space and cost required by the additional light sources, beam splitters, isolators, and other components. Another drawback when using two light sources is that it is difficult to perfectly align the two light beams over the entire path they travel. This can cause various problems, for example, good performance cannot be obtained simultaneously from different subsystems operating at different wavelengths. A system that uses one light source and thereby eliminates the above disadvantages is shown in the optoelectronic system 500 of FIG. 12A.

  FIG. 12A includes a visible light source 110, an isolator 115, a fiber network 420, an ADM electronic component 530, a fiber incidence / emission unit 170, a beam splitter 145, and a position detector 150. Visible light source 110 may be, for example, a red or green diode laser or a vertical cavity surface emitting laser (VCSEL). The isolator may be a Faraday isolator, an attenuator, or any other device that can sufficiently reduce the amount of light returned to the light source. The light from the isolator 115 travels to the fiber network 420, which in one embodiment is the fiber network 420A of FIG. 8A.

  FIG. 12B shows an embodiment of an optoelectronic system 400 in which single wavelength light is used, but the modulation is not by direct modulation of the light source but by electro-optic modulation of the light. . The optoelectronic system 400 includes a visible light source 110, an isolator 115, an electro-optic modulator 410, an ADM electronic component 475, a fiber network 420, a fiber entrance / exit unit 170, a beam splitter 145, and a position detector 150. ,including. The visible light source 110 may be, for example, a red or green laser diode. The laser light is sent through an isolator 115, which may be, for example, a Faraday isolator or an attenuator. The isolator 115 may be a fiber that is coupled at its input and output ports. The isolator 115 sends the light to the electro-optic modulator 410, which modulates the light up to a selected frequency up to 10 GHz or as desired. The electrical signal 476 from the ADM electronics 475 drives the modulation in the electro-optic modulator 410. The modulated light from electro-optic modulator 410 travels to fiber network 420, which may be network 420A, 420B, 420C or 420D as described above. Part of the light travels through the optical fiber 422 to the reference channel of the ADM electronic component 475. Another part of the light exits the tracker, is reflected by the retro-reflector 90, returns to the tracker and reaches the beam splitter 145. A small amount of light is reflected by the beam splitter and travels to position detector 150, which was described above with respect to FIGS. Part of the light enters the fiber entrance and exit 170 through the beam splitter 145, enters the optical fiber 424 through the fiber network 420, and enters the measurement channel of the ADM electronic component 475. In general, the system 500 of FIG. 12A can be manufactured less expensively than the system 400 of FIG. 12B, but the electro-optic modulator 410 may be able to achieve higher modulation frequencies, which may be advantageous in some cases.

  FIG. 13 shows an embodiment of a locator camera system 950 and an optoelectronic system 900, in which an orientation camera 910 is combined with the high electronic capabilities of a 3D laser tracker to make a six degree of freedom measurement. The optoelectronic system 900 includes a visible light source 905, an isolator 910, an optional electro-optic modulator 410, an ADM electronic component 715, a fiber network 420, a fiber entrance and exit 170, a beam splitter 145, and position detection. Instrument 150, beam splitter 922, and orientation camera 910. Light from the visible light source is generated in optical fiber 980 and travels through isolator 910, which may be an optical fiber coupled to input and output ports. The light travels through electro-optic modulator 410 and is modulated by electrical signal 716 from ADM electronics 715. Alternatively, the ADM electronic component 715 transmits an electrical signal on the cable 717 and modulates the visible light source 905. Some of the light entering the fiber network travels through the fiber length equalizer 423 and the optical fiber 422 and enters the reference channel of the ADM electronics 715. Electrical signal 469 may optionally be provided to fiber network 420, which provides a switching signal to fiber optic switches in fiber network 420. Part of the light travels from the fiber network to the fiber entrance and exit 170, which sends the light over the optical fiber to free space as a light beam 982. A small amount of light is reflected by the beam splitter 145 and lost. Part of the light passes through beam splitter 145, beam splitter 922, exits the tracker, and proceeds to a six degree of freedom (DOF) device 4000. The 6-DOF device 4000 may be a probe, scanner, projector, sensor, or other device.

  Light from the 6-DOF device 4000 enters the optoelectronic system 900 on its return path and reaches the beam splitter 922. Part of the light is reflected by the beam splitter 922 and enters the orientation camera 910. An orientation camera 910 records the position of several marks provided on the retro-reflector target. From these marks, the azimuth angle (ie, three degrees of freedom) of the 6-DOF probe is specified. The principle of the orientation camera is described below in this application and also in the '58 patent. In the beam splitter 145, part of the light travels through the beam splitter and is placed on the optical fiber by the fiber incident / emission unit 170. Light travels to the fiber network 420. Part of this light travels to the optical fiber 424 from which it enters the measurement channel of the ADM electronics 715.

  Locator camera system 950 includes a camera 960 and one or more light sources 970. The locator camera system is also shown in FIG. 1, where the camera is element 52 and the light source is element 54. The camera includes a lens system 962, a photosensitive element array 964, and a body 966. One application of the locator camera system 950 is to locate a retro reflector target in the workspace. It is done by blinking the light source 970 and the camera picks it up as a bright spot on the photosensitive element array 964. A second use of the locator camera system 950 is to determine the approximate orientation of the 6-DOF device 4000 based on the reflector spot on the 6-DOF device 4000 or the observation position of the LED. If two or more locator camera systems are available on the laser tracker, the orientation of each retroreflector target in the workspace may be calculated using the principle of angular surveying. When one locator camera is installed so as to pick up the light reflected along the optical axis of the laser tracker, the direction to each retro reflector can be specified. When one camera is installed off the optical axis of the laser tracker, the general direction from the image on the photosensitive element array to the retroreflector target can be obtained immediately. In this case, the more accurate direction to the target can be specified by rotating the mechanical axis of the laser in a plurality of directions and observing changes in the spot position on the photosensitive element array.

  FIG. 14A shows an embodiment of a 6-DOF probe 4400. The probe 4400 includes a 6-DOF SMR 4434 installed on a magnetic nest 4432 having a strong magnet 44433. The 6-DOF probe 4400 includes a stylus 4410, a main body 4420, and a head 4430. The stylus 4410 includes a probe tip 4414 and a probe shaft 4412. The head 4430 includes a magnetic nest 4432 that is configured to rotate the 6-DOF SMR 4434 around the SMR center but not translate the SMR center. 6-DOF SMR 4434 may be advantageously used as a free-standing target. In this way, both 6-DOF SMR 4434 and 6-DOF probe 4400 can be obtained at almost the same price as with 6-DOF SMR alone. In some embodiments, the 6-DOF SMR includes a line of intersection between the reflective surfaces that is visible by an orientation camera, such as camera 910. The 6-DOF SMR aspect is described in more detail in the '339 and' 983 patent applications. In general, 6-DOF laser trackers have the six-degree-of-freedom measurement capability of probes with retro-reflector targets. One way to obtain such 6-DOF measurements is to incorporate marks into a corner cube retro-reflector, as described above, and observe these marks with a azimuth camera to obtain a 6-DOF SMR or 6-DOF probe. This is to determine the degree of freedom in three directions.

  Other methods for making a three azimuth degree of freedom determination may also be used. In the present application, the term azimuth sensor is used in common with a laser tracker and refers to all devices capable of performing a three azimuth degree of freedom determination. A first example of another method for making a three azimuth degree of freedom determination is to place at least three points of light on a probe that includes a retroreflector. By observing the point of light, it is possible to determine the degree of freedom in three directions with a certain configuration. A second example of an alternative method for determining three orientation degrees of freedom uses a combination of two sensor methods. The first sensor method is to allow a small amount of light impinging on the corner cube retroreflector to pass through the retroreflector and hit the position detector, which can be a CMOS array or a position sensitive detector, for example. There may be. In this way, in some embodiments, the pitch and yaw angle of the retro reflector attached to the probe assembly can be determined. The second sensor method is to measure the orientation of the probe with respect to the gravity vector using a mechanical pendulum coupled to an angle encoder. This measurement provides an angle closely related to the probe roll angle. By combining the results of the first sensor and the second sensor, three degrees of freedom can be obtained. Regardless of which method is used, the idea of incorporating an SMR that is separable from the measuring device is applicable. In any case, the term azimuth sensor refers to the device required for measuring three azimuth degrees of freedom.

  FIG. 14B shows an embodiment of a 6-DOF probe 4450. This is similar to the 6-DOF probe 4400, except that it includes restraining means 4460. The restraining means includes an element that contacts 6-DOF SMR 4434, which is, for example, a machined metal piece, a plastic cover, a strap. The restraining means 4460 is brought into physical contact with the 6-DOF SMR 4434 by the fixing mechanism 4464. Examples of suitable fixing mechanisms include hook type clamps and screw clamps. Two possible advantages of including a clamping mechanism are that the 6-DOF SMR has less chance to move, which will result in the need to repeat the correction procedure described below, and that the SMR hits the probe to the floor. The chance of falling is reduced. The magnet 4433 shown in FIG. 14B may be optionally installed.

  An advantage of the probe embodiment shown in FIGS. 14A-B is that a 6-DOF search function can be added to the 6-DOF SMR function at a very low cost. Another advantage is that these embodiments do not require a power supply because 6-DOF SMR can be used completely passively if desired.

  One embodiment of a 6-DOF probe 4200 is shown in FIG. 15A. The probe includes a probe head 4240, a probe body 4220, and a probe stylus 4210. The 6-DOF SMR 4234 is held in place by the restraining means 4260. The restraining means 4260 includes an element 4262 that contacts the 6-DOF SMR 4234. Element 4262 may be, for example, a machined metal piece, a plastic cover, or a strap. The restraining means 4260 is in physical contact with the 6-DOF SMR 4234 by the securing mechanism 4264. Examples of suitable fixing mechanisms include hook type clamps and screw type clamps. The 6-DOF SMR 4234 is installed on a nest base 4332, which in one embodiment is magnetic. The probe body 4220 includes a housing 4224, optional actuator buttons 4226, 4227, and an optional nest accommodating portion 4228. The probe housing 4224 has a contour shape that is easy to hold by hand. Probe stylus 4210 includes a probe tip 4214, a probe shaft 4212, a probe connector 4216, and a probe clamp 4218. The probe clamp allows various styluses with different lengths, angles and shapes to be attached to the 6-DOF probe.

  In certain embodiments, the 6-DOF SMR 4480 of FIG. 17 includes an intermittent rotational position indexing function 4471 and the probe head 4475 includes a mating structure 4772 that includes a mating function 4473. The intermittent rotational position indexing and mating functions are configured so that the orientation of the 6-DOF SMR is fixed within the nest 4432 and the SMR sphere center does not move relative to the 6-DOF probe assembly. The purpose of the intermittent rotational position indexing and mating function of FIG. 17 is to enable them to be used immediately based on probe correction parameters obtained from the factory or from previously performed correction procedures. .

  In other embodiments, the angle of the light beam from the tracker to the probe body 4420 is changed by rotating the 6-DOF SMR 4434, 4234 relative to the body. This can be done by rotating the 6-DOF SMR 4434, 4234 over the nests 4432, 4232. To determine the rotation angle of the 6-DOF SMR, a correction procedure may be performed quickly, with the probe placed in a fixed nest 4250 as shown in FIG. 15A. The probes of FIGS. 14A and 14B are equally well utilized for the correction procedures described herein. In FIG. 15A, the probe tip 4214 is placed over a fixed nest 4250. The operator may move the 6-DOF probe 4200 with the opposite hand while placing the fixed nest on a convenient surface and holding it in place with one hand, this movement according to the method described below. Done.

  The fixed nest can be any of several types. One type of fixed nest 4250 is shown in cross-sectional view 4280 of FIG. 15B and includes a body 4255 on which are embedded three small spheres, two of which are 4251A and 4251B, Located 120 degrees apart, supports the probe tip 4214 or 4414. A small magnet 4249 may be placed in the fixed nest 4250, which provides downward force to the probe tips 4214, 4414. The three small spheres hold the center of the spherical probe tip fixed in space so that the 6-DOF probe 4200, 4400 or 4450 can rotate to any desired angle. Since the center of the probe tip remains fixed, the calculated value of the probe tip should remain constant regardless of the rotation angle of the 6-DOF probe. This makes it possible to determine the 6-DOF SMR orientation for the remaining portion of the probe. Another name for a nest containing three small spheres that are 120 degrees apart is “trihedal hollow”.

  Other types of nested configurations may be used. In some embodiments, small protrusions are used instead of small spheres. Such a protrusion is used, for example, in the nest 17 of FIG. In other embodiments, the fixed nest includes a conical seat. As the name suggests, the conical seat includes a cone, and generally the conical region is adapted to contact the probe tip. If designed correctly, a nest of the type shown in FIG. 17 or a nest formed as a conical seat can provide high performance. Usually, the best performance is obtained by a three-sided recess.

  The 6-DOF SMR does not have translational freedom at that position in FIG. 14A, 14B, or 15A, but has three degrees of freedom. In one embodiment, the probe is rotated around three different axes to obtain the information necessary to determine the numerical value of the three azimuth degrees of freedom. For convenience, the three angular degrees of freedom can be a yaw angle, a pitch angle, and a roll angle. The yaw angle 4263 is a rotation angle around the axis 4261 that passes through the reference direction of the 6-DOF probe. In certain embodiments, the reference axis passes through the center of the body 4220 and the center of the stylus 4210. However, the stylus need not be arranged in this manner and may instead be placed at any desired angle. The pitch angle is an angle 4266 around the axis 4265, as shown in FIG. 16B. The roll angle is an angle 4270 around a point through 4268 and is perpendicular to axes 4261 and 4265. The roll angle in this case is not a roll angle of 6-DOF SMR but a system level roll angle. However, the information obtained from rotating as in FIGS. 16A, 16B, 16C is sufficient to determine the orientation of the 6-DOF SMR with respect to the remainder of the probe assembly. In general, it is important to get enough information to determine the orientation of the 6-DOF SMR on the probe assembly by rotating it to cover three angles such as yaw, pitch, roll angle, and so on. This is necessary to determine the coordinates of the probe when it moves to a point on the surface of the workpiece.

  The probe assembly may conveniently be attached and housed in the 6-DOS body while the 6-DOF probe is used to perform measurements. FIG. 15A shows a fixed nest 4250B magnetically attached to position 4228 on the probe book 4220. It is also possible to attach the probe body to the probe with a tether or mechanical snap. Of course, the fixed nest 4250 may simply be held near the fixed nest 4250 and used as necessary.

  FIG. 18 is a flow diagram of a method 4900 for measuring the three-dimensional coordinates of the probe center. Step 4905 provides a steel ball integrated retroreflector, the steel ball integrated retroreflector includes a retroreflector mounted to the retroreflector body, the retroreflector body having a first spherical shape on a first portion of the outer surface thereof. The first portion has a target center, the retroreflector is configured to receive a first light beam and return a second light beam, the second light beam being a first light beam. Being part of the beam, the second light beam travels substantially opposite to the direction of the first light beam.

  Step 4910 provides a probe assembly, the probe assembly including a probe stylus and a probe head, the probe stylus including a probe tip, the probe tip having a second sphere on a second portion of the surface thereof. And the second portion has a probe center, and the probe head receives the steel ball integrated retroreflector and rotates the steel ball integrated retroreflector about the target center while the target center is in relation to the probe assembly. It is configured to hold in a substantially constant position.

  Step 4915 provides an orientation sensor, which is configured to make a three orientation degree of freedom measurement of the probe assembly.

  Step 4920 provides a coordinate measuring device that includes a first motor, a second motor, a first angle measuring device, a second angle measuring device, a distance meter, and position detection. A first motor and a second motor are configured to cooperate to guide the first light beam in the first direction, wherein the first direction is Determined by a first rotation angle around the first axis and a second rotation angle around the second axis, the first rotation angle being generated by the first motor and the second rotation angle being the first rotation angle. The first angle measuring device is configured to measure the first rotation angle, the second angle measuring device is configured to measure the second rotation angle, and the distance meter Reduce the first distance from the coordinate measuring device to the steel ball integrated retro-reflector Also configured to measure based on a third portion of the second light beam received by the first light detector, wherein the position detector is configured to measure the second light beam to the position detector. The control system is configured to generate a first signal in response to the position of the fourth portion, and the control system transmits a second signal to the first motor and a third signal to the second motor. The second signal and the third signal are based at least in part on the first signal, and the control system is configured to control the first light beam to the spatial position of the steel ball integrated retroreflector. And the processor is configured to determine a three-dimensional coordinate of the probe center, wherein the three-dimensional coordinate is at least in part a first distance, a first rotation angle, a second Based on the rotation angle and three degrees of freedom.

  Step 4925 installs the steel ball integrated retro-reflector on the probe head.

  Step 4930 guides the first light beam of the coordinate measuring device to the steel ball integrated retro-reflector.

  Step 4935 measures a first distance.

  Step 4940 measures a first rotation angle.

  Step 4945 measures a second rotation angle.

  Step 4950 performs a three azimuth degree of freedom measurement based at least in part on information provided by the azimuth sensor.

  Step 4955 calculates three-dimensional coordinates of the probe center based at least in part on the first distance, the first rotation angle, the second rotation angle, and the three azimuth degrees of freedom.

  Step 4960 stores the three-dimensional coordinates of the probe center. Method 4900 ends with reference symbol A.

  FIG. 19 is a flowchart of a method 5000 beginning with reference A in FIG. 18 and further comprising measuring a probe correction parameter, the probe correction parameter being information indicating at least the orientation of the steel ball integrated retroreflector with respect to the probe assembly. including.

  FIG. 20 is a flow diagram of a method 5100 starting with reference symbol B of FIG. 19, where step 5105 provides a nest configured to receive a probe tip, the nest further extending the probe tip around the probe center. Configured to rotate, the probe center is held at a substantially fixed spatial point. Step 5110 places the probe tip in the nest. Step 5115 rotates the probe tip. Step 5120 measures a quantity group, the quantity group includes a first distance, a first rotation angle, a second rotation angle, and three azimuth degrees of freedom, each of which is a plurality of different rotations of the probe tip. Obtained with respect to. Step 5125 calculates probe correction parameters based at least in part on the quantity group.

  FIG. 21 is a flow diagram of a method 5200 that begins with reference A in FIG. Step 5205 removes the steel ball integrated retroreflector from the probe head. Step 5210 guides the first light beam from the coordinate measuring device to the steel ball integrated retroreflector. Step 5215 measures the first distance. Step 5220 measures a first rotation angle. Step 5225 measures a second rotation angle. Step 5230 measures the three-dimensional coordinates of the target center.

  FIG. 22 is a flow diagram of a method 5300 that begins with reference C in FIG. Step 5305 installs a steel ball integrated retro reflector on the probe head. Step 5310 guides the first light beam from the coordinate measuring device to the steel ball integrated retroreflector. Step 5315 measures the first distance. Step 5320 measures a first rotation angle. Step 5325 measures the second rotation angle. Step 5330 performs a three azimuth degree of freedom measurement. Step 5335 calculates the three-dimensional coordinates of the probe center based at least in part on the first distance, the first rotation angle, the second rotation angle, and the three degrees of freedom.

  FIG. 23 is a flow diagram of a method 5400 that begins with reference A in FIG. Step 5405 incorporates the pattern into the retro-reflector. Step 5410 provides an optical system including a lens and a photosensitive element array, wherein the lens is configured to form an image of at least a portion of at least a patterned retroreflector on the photosensitive array. Step 5415 converts the image into a digital data set. Step 5420 performs a three azimuth degree of freedom calculation based at least in part on the digital data set.

  Although the invention has been described with reference to exemplary embodiments, it will be appreciated by those skilled in the art that various changes may be made and equivalents substituted for the elements without departing from the scope of the invention. In addition, many modifications may be made and specific circumstances and materials may be employed in accordance with the teachings of the present invention without departing from the basic scope thereof. Accordingly, the present invention is disclosed as the best mode for carrying out the invention and is not intended to be limited to particular embodiments, but the invention includes all embodiments that fall within the scope of the appended claims. . Furthermore, the use of terms such as first, second, etc. does not imply any order or significance, and terms such as first, second, etc. distinguish one element from another. Used for. Furthermore, the use of certain terms such as (a, an) does not limit the quantity, but indicates that there is at least one item shown.

Claims (13)

In the method (4900) of measuring the three-dimensional coordinates of the first point and the second point,
Providing a steel ball integrated retroreflector (4234, 4434), the steel ball integrated retroreflector including a retroreflector attached to the retroreflector body, wherein the retroreflector body is a first of the outer surfaces thereof. The part has a first sphere, the first part has a target center, and the retroreflector receives the first light beam (46,984) and receives the second light beam (47,986). Step (4905), wherein the second light beam is part of the first light beam and the second light beam travels in a direction substantially opposite to the direction of the first light beam. )When,
Providing a probe assembly (4200, 4400, 4450, 4480), the probe assembly comprising a probe stylus (4210, 4410) and a probe head (4240, 4430, 4440, 4475), wherein the probe stylus comprises Including a probe tip (4214, 4414), the probe tip having a second sphere on a second portion of its surface, the second portion having a probe center, and a probe head having a steel ball integrated retro Receiving the reflector and allowing the steel ball integrated retroreflector to rotate about the target center, while being configured to maintain the target center in a substantially constant position with respect to the probe assembly; (4910);
Providing a coordinate measuring device (10), the coordinate measuring device comprising a first motor (2125), a second motor (2155), a first angle measuring device (2120), and a second Angle measuring device (2150), distance meter (120, 160), position detector (151), control system (1520, 1530, 1540, 1550), direction sensor (910), and processor (1520, 1530) 1531, 1532, 1533, 1534, 1535, 1540, 1550, 1560, 1565, 1570, 1590),
The first motor and the second motor are configured to cooperate to guide the first light beam in the first direction, the first direction being the first around the first axis (20). And the second rotation angle around the second axis (18), the first rotation angle is generated by the first motor and the second rotation angle is generated by the second motor And
The first angle measuring device is configured to measure the first rotation angle, the second angle measuring device is configured to measure the second rotation angle, and
A rangefinder measures a first distance from the coordinate measuring device to the steel ball integrated retroreflector based at least in part on the third portion of the second light beam received by the first photodetector. Configured to
A position detector is configured to generate a first signal in response to the position of the fourth portion of the second light beam on the position detector;
The control system is configured to send a second signal to the first motor and a third signal to the second motor, wherein the second signal and the third signal are at least in part, And the control system is configured to adjust the first direction of the first light beam to the position in the space of the steel ball integrated retroreflector,
An azimuth sensor is configured (4915) to perform three orientation degrees of freedom (4263, 4265, 4270) measurement of the probe assembly
A processor is configured to determine a three-dimensional coordinate of the probe center, the three-dimensional coordinate based at least in part on the first distance, the first rotation angle, the second rotation angle, and the three azimuth degrees of freedom. Such step (4920),
Installing a steel ball integrated machining retro-reflector on the probe head (4925);
Moving the probe center to the first point;
Guiding the first light beam from the coordinate measuring device to the steel ball integrated retroreflector (4930);
Measuring a first distance (4935);
Measuring a first rotation angle (4940);
Measuring a second rotation angle (4945);
Performing 3 orientation degrees of freedom measurement based at least in part on information provided by the orientation sensor (4950);
Calculating (4955) a first set of three-dimensional coordinates of the probe center based, at least in part, on a first distance, a first rotation angle, a second rotation angle, and three azimuth degrees of freedom;
Storing (4960) a first set of three-dimensional coordinates of the probe center;
Removing the steel ball integrated retro reflector from the probe head (5205);
Moving the target center to a second point after removing the steel ball integrated retroreflector from the probe head;
Guiding the first light beam from the coordinate measuring device to the steel ball integrated retroreflector at the second point (5210);
Measuring a second distance of the target center of the second point (5215);
Measuring (5220) a third rotation angle of the target center at the second point;
Measuring a fourth rotation angle of the center of the target at the second point (5225);
Determining (5230) a second set of three-dimensional coordinates of the target center based at least in part on the second distance, the third rotation angle, and the fourth rotation angle;
Storing a second set of three-dimensional coordinates of the target center;
A method comprising the steps of: The method of claim 1, wherein
The method of installing the steel ball integrated retroreflector on the probe head further comprises installing the steel ball integrated retroreflector at the index position. The method of claim 2, wherein
Providing the steel ball integrated retro-reflector further includes providing a collar on the steel ball integrated retro-reflector, the collar including an intermittent rotational position indexing function (4471);
Providing the probe assembly further comprises providing a mating structure (4472) on the probe head, the mating structure having a mating function (4473);
The step of installing the steel ball integrated retro-reflector on the probe head further includes the step of moving the steel ball integrated retro-reflector to the indexing position by aligning the intermittent rotational position indexing function with the mating function. A method characterized by that. The method of claim 1, wherein
The method of installing the steel ball integrated retroreflector on the probe head further comprises rotating the steel ball integrated retroreflector in a desired orientation relative to the probe head without shifting the target center. The method of claim 4, wherein
Providing the probe assembly further comprises providing a clamping device (4461) on the probe head, the clamping device configured to hold the steel ball integrated retroreflector in a fixed orientation;
The method of installing the steel ball integrated retro reflector further comprises the step of clamping and fixing the steel ball integrated retro reflector in a desired orientation. The method (5000) of claim 4,
Determining a probe correction parameter (5005), wherein the probe correction parameter includes at least information indicative of the orientation of the steel ball integrated retroreflector with respect to the probe assembly. The method (5100) of claim 6, wherein:
Determining the probe correction parameter further comprises:
Providing a nest (4250, 4280) configured to receive a probe tip, wherein the nest is further configured to rotate the probe tip about the probe center, wherein the probe center is substantially fixed. A step (5105) to be held at the designated spatial point;
Placing the probe tip into the nest (5110);
Rotating the probe tip (5115);
Measuring a quantity group, wherein the quantity group includes a first distance, a first rotation angle, a second rotation angle, and three azimuth degrees of freedom, each of which is a plurality of different rotations of the probe tip A step (5120) as obtained with respect to
Calculating (5125) a probe correction parameter based at least in part on the quantity group;
A method comprising the steps of: The method (5400) of claim 1, further comprising:
Incorporating a pattern into the retro-reflector (5405);
Providing an optical system including a lens and a photosensitive element array, wherein the lens is configured to form an image of at least a portion of at least a patterned retroreflector on the photosensitive array (5410); ,
Converting the image into a digital data set (5415);
Performing at least in part a calculation of 5 degrees of freedom based on the digital data set (5420);
A method comprising the steps of: The method of claim 8, wherein
A method of providing a steel ball integrated retroreflector, wherein the retroreflector is a glass corner cube retroreflector. The method of claim 1, wherein
Providing the probe assembly, wherein the probe assembly operates without using power. The method of claim 1, wherein
The method wherein the probe assembly includes an actuator button (4226, 4227). The method of claim 1, wherein
Providing the probe assembly, wherein the probe stylus is removed and replaced with a second probe stylus. The method of claim 1, wherein
Installing the hard ball integrated retro-reflector on the probe head comprises magnetically coupling the hard ball integrated retro-reflector to the probe head.

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