Metrology of Visibly Transparent Large Aspheric Optics

There is a growing need to fabricate high-optical-quality optics that conform to an aircraft’s outer moldline shape to reduce drag. However, fabrication of such free-form and aspheric optics has proven challenging. The current fabrication bottleneck is in the speed and precision of performing metrology of the optical surfaces because traditional interferometric techniques are not applicable. To meet the established technology and market gap, Bridger Photonics, Inc. proposes developing a length metrology system capable of interferometric-level precision, but with absolute length and thickness measurement capabilities (i.e. not merely displacement). Bridger’s metrology system will be coupled with precise, multi-axis stages to rapidly scan and characterize free-form optical surfaces and thicknesses during or after fabrication. The system will be based on Bridger’s proprietary high-resolution coherent measurement techniques and will achieve nanometer-scale precision, >1 kHz update rates, and up to 100 mm measurement ranges for specular surfaces. Because of the thickness measurement capabilities, Bridger’s system will be capable of measuring the transmitted wavefront of large aspheric optics.