As optical designs require increasingly more aspheric elements to achieve high-resolution, high-quality imaging fromsmaller, more cost-effective systems, active alignment solutions to center and de-tilt aspheres in-situ during assembly arebecoming paramount. Traditional active alignment systems, i.e. autocollimators, determine lens orientation from center ofcurvature (CC) positions of each surface and are consequently limited when measuring aspheres. Such tools measure theparaxial CC; therefore, measurement is inherently blind to orientation of the aspheric edge, leading to centered yet tiltedaspheric surfaces and, thus, degraded image quality from the final optical assembly.Current market solutions to measure aspheric tilt consist of external probes directly measuring the aspheric edge; however,this approach involves addition and alignment of multiple precision stages and secondary sensors, adding to the complexityand cost of alignment systems.This paper demonstrates a novel solution for accurately measuring aspheric tilt during the assembly process utilizing theexisting capabilities of the Lens Alignment Station (LAS). The LAS is an active alignment tool whose specialized designextends measurement ability beyond the requirement of confocal reflection. Aspheric measurement begins with standardvertex centration using the LAS at confocal position, but for tilt, we image away from confocal position and flood thesurface with a high NA objective sampling the aspheric edge. Beyond confocal reflection, the LAS detects retroreflectedconcentric fringes that trace an orbit as a tilted asphere rotates. The orbit radius is proportional to tilt magnitude, such thatsimple software calculations accurately yield aspheric tilt measurements without requiring expensive external hardware.
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