Measuring with an Optical Diverter
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APPLICATION NOTE Measuring with an Optical Diverter on a 3D Profiler Zygo’s Optical Diverter is an accessory that makes it possible to enhance the flexibility of many of the profilers by making it easy to measure internal surfaces and the sidewalls of very large parts. Introduction NewView™ optical profilers are well-suited to measuring surface finish non-destructively. This is easily accomplished on a variety of materials that have undergone a variety of manufacturing processes. Certain types of parts pose challenges to the established measurement method because of size—those that are too large to be easily positioned beneath the objective—or have internal surfaces, such as those found in cylinder bore walls. These surfaces require a direct line-of-sight perpendicular to the surface being measured—something the Optical Diverter provides. How the Optical Diverter works The Optical Diverter combines a long working distance objective with a slim 45 degree mirror mounted on the end of a probe. The probe redirects the microscope illumination making it possible to acquire data from internal as well as external surfaces. An easy-to-attach fixture secures the diverter to the profiler head and ensures rapid transition between operation modes. In many measurement situations, the diverter is used with a 5-axis encoded motion stage. Other mounts and staging configurations can be used to accommodate a variety of part sizes. In addition, the diverter can be used with a specialized software feature which makes it possible to stitch several frames of a sidewall together to form a picture of surface characteristics. The stitching feature is available in Mx software. Usually stitching can only be done in the X/Y axes, but the Stitching feature provides the flexibility to stitch in X/Z, Y/Z, and theta axes (with the addition of a theta stage). Stitching Multiple Measurements When it is not possible to measure an entire sidewall surface with a single measurement due to part size, Mx software takes several different measurements and integrates them into one data set. Once the test area is defined, a stage pattern is created that breaks the larger view into a number of smaller subregions. Each sub-region is equal to the field of view of the profiler’s objective and zoom setting, minus a small percentage for overlap. And with just a few software control settings, processing is automatic. Conclusion The Optical Diverter accessory makes it possible to obtain data from surfaces previously not accessible with a standard profiler. It is particularly suited to internal surfaces of cylinder bore walls or for large parts that would not otherwise fit within the form factor of the profiler. And, when a test part is too large to capture all of the data in one measurement, the Stitching feature can be used to generate a data set that tells the whole story of surface characterization. For More Information… Please contact your Zygo representative for more information, or visit us at: www.zygo.com and click Contact. ZYGO Corporation 21 Laurel Brook Road Middlefield, CT 06455 USA ©Zygo Corporation and the Zygo logo are registered trademarks of Zygo Corporation. A