A non-contact surface measurement system for freeform and conformal optics

Abstract

OptiPro Systems has been developing the UltraSurf, a non-contact measuring system using state of the art, precision motion control. The goal is to precisely scan standard optical shapes such as concave and convex spherical surfaces, as well as the complex geometries of aspheric, ogive, and freeform shapes without the limitations associated with other measurement methods. Common optical measurement methods have limitations with surface roughness, slope error, and deviation from best-fit sphere. Optipro designed the UltraSurf to further the manufacturing capabilities of companies generating complex precision optics. The UltraSurf measures with sub-micrometer non-contact point sensors to collect surface information. Various sensors are commercially available from multiple companies, each with their own distinct optical measuring technology. One optical sensor uses white light confocal chromatic imaging to measure individual optical surfaces. Another optical sensor uses low-coherence interferometry with a near infrared laser, and is able to measure the inside, outside, and thickness of optical materials at a single point. The UltraSurf scans the optical sensors over the surface of the part under test, keeping it normal to the surface. The single point measuring method coupled with computer-controlled motion gives the UltraSurf flexibility to measure greatly varied geometries. Ultimately, a point cloud of the measured surface is generated. The cloud can be used to calculate deviation from the desired shape, as well as various surface parameters. Applications, definitions, and measurement results of freeform and conformal shapes using UltraSurf will be presented.