Non-contact metrology of aspheres and windows of large departure

The measurement of large departure aspheres and windows is a challenge for the optics community. OptiPro systems has developed a non-contact measuring system called UltraSurf to overcome these difficulties. The UltraSurf system utilizes a single point non-contact sensor coupled with high accuracy air bearings to scan optical surfaces. Five air bearing axes allow for the optical probe to maintain normal angles with the surface under test, and provide a smooth and accurate scan. The axes of motion allow scanning of rotationally symmetric parts such as spheres and aspheres, but also give it the freedom to perform areal surface scanning and freeform metrology. By maintaining a tangent angle with the surface, this technique allows for large surface slopes and deviation from best fit sphere to easily be measured. Several commercial non-contact sensors have been integrated into UltraSurf. The sensors operate with different optical principles, allowing for greater flexibility of the types of surfaces to be measured. One sensor applies white-light confocal chromatic aberration for high resolution, single surface measurement. Another sensor that uses low-coherence interferometry with a 1310 nanometer light source is able to see through materials, enabling multiple surface and thickness measurements simultaneously. Measurement of large departure aspheres and windows will be demonstrated. Cross comparison of UltraSurf data with current metrology techniques will be shown on surfaces that can be measured with multiple methods.