Purchasing a laser tracker is no small matter. Most advanced systems are a sizable capital investment. The full potential of a laser tracker can be realized in the targets that a user chooses for the application. Some basic questions need to be asked when selecting a target: • Are you measuring simple distance, or do you want to measure in multiple axes? • What is the environment in which the target will be used? • Will the target be fixed or is mobility an issue? • What is the complexity of the part you want measure? MOST CHOSEN The most often used target is the spherically mounted reflector (SMR). Typically, these are configured in one of two ways—prismatic or hollow. Prismatic SMRs have a solid glass prism corner cube inside a machined steel sphere. This configuration provides the longest linear range of measurement. A robust, hollow SMR is constructed using a hollow aluminum optic coated with golden reflective surfaces. This construction endures harsh environments and treatment more readily, as well as lending itself to highly precise measurements. BEING ‘ACTIVE’ In some applications, where the object to be measured is in motion, an “automated SMR” is needed. The “motorized SMR” solution should lock on to the laser tracker and positions itself so as not to lose the laser beam. The reflector faces the laser tracker, regardless of movement. With these attributes an operator has opened up the possibility of a new range of laser tracker applications that include measuring, • the compound actions of robots, • long rails, • moving vehicles, and • CMM and CNC positioning, In more advanced applications, such a motorized device helps deliver volumetric error compensation on multiaxis CNC machining centers. A SMART TARGET If a laser tracker needs to be used in large-scale measurement applications, the customary solution may to use three separate trackers. However, automation in a “smart” sensor—one that can determine position in the x, y and z axes, as well as pitch, yaw and roll—can save a user considerable time, expense and ensure great accuracy. A “smart” target gets its identification as such because it uses a motorized receiver that tracks the laser beam in real time, providing object pitch and yaw. It also uses roll detection technology to provide the object’s roll angle. HANDHELD PART PROBING A handheld probe and/or scanner combination uses a target similar to an SMR in a sensor head, but it also Incorporates a probe to access hidden points and/or a scanner to do dynamic noncontact scanning. The more degrees of freedom that the sensor head possesses, the more easily it can be used in measurement applications such as: • tooling, fixtures and jigs • automotive body parts • mold and die cavities • surface contours • part inspection • compare-to-CAD • gap and flush measurement • in-process inspection Earlier probes, which rely on photogrammetry techniques are limited in distance and their orientation on a 2-D plane. More advanced solutions use a rotating sensor head instead of photogrammetry. In this technology, the advanced sensors located inside the target allow the system to be used over the full range of the laser tracker, thus maximizing that investment. In addition, the advanced solution technology permits a user to both scan and probe with a single target unit. Thus the user has an economical and flexible solution. A wireless version of these advanced targets provides even greater targeting versatility. For more information regarding targeting and laser tracker solutions, contact: Automated Precision Inc. 15000 Johns Hopkins Dr. Rockville, MD 20850 PH: (800) 537-2720 www.apisensor.com firstname.lastname@example.org
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