Catadioptric optics for laser Doppler velocimeter applications

This paper examines the adaptation of low-cost Schmidt-Cassegrain astronomical telescopes to perform the laser-beam-focusing and scattered-light collection tasks associated with dual-beam laser Doppler velocimetry. A generic telescope design is analyzed using ray-tracing methods and Gaussian beam-propagation theory. A straightforward modification procedure to convert from infinite to near unity conjugate-ratio operation with very low residual aberration is identified and tested with a 200-mm-aperture telescope modified for f/10 operation. Performance data for this modified telescope configuration are near the diffraction limit and agree well with predictions.