Modeling of collection efficiency in lidar spectroscopy

We performed a calibration experiment on a Spectralon Target using a wavelength of 0.532 µm and a 60 cm lidar system coupled to a photon counter via a Triax 190 monochrometer. The complete system optics, including the telescope and monchromator, were modeled using a commercial ray-tracing program. Energy efficiency was calculated by generating large numbers of equal-area rays on the telescope input pupil from points in the plane of the target. The number of these rays received by the PMT cathode was then used to estimate the optical efficiency. Comparison of the calculated and observed signals gave agreement to within 30%. We discuss the possible sources of disagreement between the calculated and observed signals.