Model of a burst imaging lidar through the atmosphere

Abstract

This paper presents a model used to predict the performances of a burst illumination imaging lidar propagating through the atmosphere. The laser beam propagates near the ground on a long distance and undergoes strong perturbations due to atmospheric turbulences. This model takes into account both propagating paths: forward propagation as the wavefront progresses towards the observed object and backward propagation as the light is reflected back to the receiver.

SimBIL: appearance-based simulation of burst-illumination laser sequences

“…To simulate the pulsed coherent BIL imaging system, illustrated schematically in Fig. 5, we use models of laser propagation similar to those described in [5,7,25]. In general, there are two principal degrading effects that we can include in physical simulation of BIL imagery: speckle induced by the interaction of the rough surface with the laser source, and the effect of turbulence introduced by the atmospheric propagation path, usually modelled by a refractive index structure constant, conventionally indicated as C n 2 .…”

Detecting and characterising returns in a pulsed ladar system

“…Further, the difference between the adjoining exponentials f a (i, P), f c (i, P) and the central Gaussian f b (i, P) only deviates far from the breakpoints i 1 and i 2 . Then, from (1) and (5) we have sði; h; PÞ ¼ X iþW l¼iÀW f ðl; PÞG 00 ði À l; hÞ…”

“…In the latter context, the ladar has the ability to acquire both reflectance and geometric data simultaneously from the target, thus providing potentially a more powerful classification tool than a purely passive source in the visible or infrared wavebands. To produce a full three-dimensional (3D) image [4], such ladars can be built either using a single detector with a scanning mechanism in two dimensions, a linear array of detectors with a scanning mechanism in one dimension or a focal plane array of either integrating sensor elements combined with a gated source (burst illumination, flash ladar) [5] or of 3D range sensing elements such as avalanche photodiodes [6] or PIN devices [7]. If a multi-spectral capability is included, that is, the ability to acquire images of the target at several different wavelengths [4,7], then it is possible to combine the 3D geometry of the laser ranging with the spectral signature of the response to provide very informative data about the nature of the target.…”