Design and fabrication of a compact lidar telescope

A prototype compact off-axis reflective lidar telescope has been designed and fabricated for remote sensing of atmospheric winds from space and airborne platforms. The 250 mm aperture telescope consists of two mirrors and a collimating lens to achieve a very compact size, without any central obscuration.It has no internal focal point to prevent air breakdown, and the pupil relay optics has also been eliminated. This paper presents the results of optical design and sensitivity analysis along with the predicted performance. The major design issues for lidar systems, particularly the one that utilizes coherent detection for higher sensitivity and Doppler frequency extraction, are the wavefront quality, polarization purity, and a minimum backscattering off the reflective surfaces. These design issues along with the other optical characteristics of this lidar telescope are presented. The effect on the wavefront quality of the tilt, decentration and axial spacing tolerances for the mirrors, collimating lens and quarter wave plate is discussed.