LIDAR system calibration
AssigneeOffice National d'Etudes et de Recherches Aerospatiales
InventorsDavid Tomline Michel, François Gustave
Life of this patent
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Abstract
A method for calibrating a LIDAR system proposes incorporating in the LIDAR system a reference optical path which is formed from an optical fiber. The length of the optical fiber determines a measurement reference value, which can then be used to evaluate distances of targets to be characterized using the LIDAR system. The calibration method is simple and economical to implement. It may be used in particular for a LIDAR system which is designed to perform air speed measurements, in particular on board an aircraft.
Claims17
A method for calibrating a LIDAR system, in order to provide a measurement reference value, which corresponds to a free-space propagation distance reference value, said measurement and free-space propagation distance reference values being intended to be used for calibration of the LIDAR system in order to evaluate a separating distance of at least one target to be characterized using said LIDAR system, the method comprising the following steps:
- /0/ determining a distance limit value such that portions of the radiation emitted by the LIDAR system which are reflected by components internal to said LIDAR system, correspond to times between emission and detection which are equivalent to those of targets located at less than this distance limit value in front of an output optical aperture of the LIDAR system, the length of the reference optical path being selected such that the free-space propagation distance value is greater than the distance limit value determined in step /0/
- /1/ coupling the LIDAR system to a reference optical path which is formed from at least one optical fiber efficient for guiding radiation emitted by the LIDAR system during an operation of said LIDAR system, so that at least a portion of the radiation travels the reference optical path between an emission channel and a detection channel of the LIDAR system, the reference optical path having a known length;
- /2/ carrying out a distance measurement sequence using the LIDAR system coupled to the reference optical path as resulting from step /1/, in order to obtain a measurement value which is representative of a time of radiation propagation in the reference optical path, and which is intended to constitute the measurement reference value;
- then
- /3/ converting the known length of the reference optical path into a free-space propagation distance value for the radiation, according to a principle of propagation time equality, to form the free-space propagation distance reference value, and associating said free-space propagation distance reference value with the measurement reference value in order to constitute the calibration of the LIDAR system,
- wherein the reference optical path formed from the at least one optical fiber is incorporated within the LIDAR system,
- wherein the LIDAR system is of a monostatic type, whereby optical output and detection apertures of the LIDAR system are coincident.
A method for calibrating a LIDAR system, in order to provide a measurement reference value, which corresponds to a free-space propagation distance reference value, said measurement and free-space propagation distance reference values being intended to be used for calibration of the LIDAR system in order to evaluate a separating distance of at least one target to be characterized using said LIDAR system, the method comprising the following steps:
- /1/ coupling the LIDAR system to a reference optical path which is formed from at least one optical fiber efficient for guiding radiation emitted by the LIDAR system during an operation of said LIDAR system, so that at least a portion of the radiation travels the reference optical path between an emission channel and a detection channel of the LIDAR system, the reference optical path having a known length;
- /2/ carrying out a distance measurement sequence using the LIDAR system coupled to the reference optical path as resulting from step /1/, in order to obtain a measurement value which is representative of a time of radiation propagation in the reference optical path, and which is intended to constitute the measurement reference value;
- then
- /3/ converting the known length of the reference optical path into a free-space propagation distance value for the radiation, according to a principle of propagation time equality, to form the free-space propagation distance reference value, and associating said free-space propagation distance reference value with the measurement reference value in order to constitute the calibration of the LIDAR system,
- wherein the reference optical path formed from the at least one optical fiber is incorporated within the LIDAR system,
- wherein the reference optical path which is formed from said at least one optical fiber is adapted to be reversibly coupled to the LIDAR system in step /1/, so as to be able to be optically decoupled from said LIDAR system during measurement sequences useful for characterizing targets.
Dependencies are inferred from the claim text.