Patent ID: 8115925
Filing Date: 2012-02-14
Classification: G01N,G01S,Y02A

Abstract:
1. A polarization switching lidar device for remote detection and characterization of at least one airborne aggregation of particulates comprising: a source of a polarized pulsed laser light beam; a first actively controlled retarder arranged to intersect the polarized pulsed laser light beam, to transmit a portion of the polarized pulsed laser light beam, and to be controllably alternated between a zero retardation state and a quarter-wave retardation state such that the transmitted portion of the polarized pulsed laser light beam exiting the first actively controlled retarder is linearly polarized in a predetermined direction when the actively controlled retarder is in the zero retardation state, while the transmitted portion of the polarized pulsed laser light beam exiting the first actively controlled retarder is circularly polarized in a predetermined rotational sense when the first actively controlled retarder is in the quarter-wave retardation state; a first directable telescoping assembly arranged to intersect the transmitted portion of the polarized pulsed laser light beam exiting the first actively controlled retarder and to controllably redirect the intersected polarized pulsed laser light beam into a predetermined space angle; a second directable telescoping assembly arranged to collect at least a portion of backscattered photons from the scanned polarized pulse laser light beam backscattered by the at least one airborne aggregations of particulates, and to redirect the collected portion of backscattered photons along a detection optical path; a second actively controlled retarder arranged along the detection optical path to intersect the collected portion of backscattered photons, to transmit a fraction of the collected portion of backscattered photons, and to be controllably alternated between a zero retardation state and a quarter-wave retardation state such that the transmitted fraction of the collected portion of backscattered photons exiting the second actively controlled retarder is linearly polarized when the first actively controlled retarder is in the zero retardation state, while the transmitted fraction of the collected portion of backscattered photons exiting the second actively controlled retarder is linearly polarized in a direction perpendicular to the predetermined direction when the first actively controlled retarder is in the quarter-wave retardation state; a polarizer arranged to intersect the backscattered photons exiting the second actively controlled retarder and to selectively transmit only a part of the backscattered photons exiting the second actively controlled retarder which is linearly polarized in the direction perpendicular to the predetermined direction; an optical matcher arranged to collect the transmitted part of the backscattered photons exiting the polarizer and to focus the transmitted part of the backscattered photons exiting the polarizer onto a photodetector arranged to generate at least one electronic signal proportional to the collected part of the backscattered photons exiting the polarizer which is linearly polarized in the direction perpendicular to the predetermined direction.