Comparison of contact and non-contact asphere surface metrology devices

Scott DeFisher; Edward M. Fess

doi:10.1117/12.2029349

15 October 2013 Comparison of contact and non-contact asphere surface metrology devices

Scott DeFisher, Edward M. Fess

Proceedings Volume 8884, Optifab 2013; 88840U (2013) https://doi.org/10.1117/12.2029349
Event: SPIE Optifab, 2013, Rochester, New York, United States

Abstract

Metrology of asphere surfaces is critical in the precision optics industry. Surface metrology serves as feedback into deterministic grinding and polishing platforms. Many different techniques and devices are used to qualify an asphere surface during fabrication. A contact profilometer is one of the most common measurement technologies used in asphere manufacturing. A profilometer uses a fine stylus to drag a diamond or ruby tip over the surface, resulting in a high resolution curved profile. Coordinate measuring machines (CMM) apply a similar concept by touching the optic with a ruby or silicon carbine sphere. A CMM is able to move in three dimensions while collecting data points along the asphere surface. Optical interferometers use a helium-neon laser with transmission spheres to compare a reflected wavefront from an asphere surface to a reference spherical wavefront. Large departure aspheres can be measured when a computer generated hologram (CGH) is introduced between the interferometer and the optic. OptiPro Systems has developed a non-contact CMM called UltraSurf. It utilizes a single point non-contact sensor, and high accuracy air bearings. Several different commercial non-contact sensors have been integrated, allowing for the flexibility to measure a variety of surfaces and materials. Metrology of a sphere and an asphere using a profilometer, CMM, Interferometer with a CGH, and the UltraSurf will be presented. Cross-correlation of the measured surface error magnitude and shape will be demonstrated. Comparisons between the techniques and devices will be also presented with attention to accuracy, repeatability, and overall measurement time.

Citation Download Citation

Scott DeFisher and Edward M. Fess "Comparison of contact and non-contact asphere surface metrology devices", Proc. SPIE 8884, Optifab 2013, 88840U (15 October 2013); https://doi.org/10.1117/12.2029349

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