Position Reference System and Method for Positioning and Tracking One or More Objects
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Accused Products
Abstract
Position reference system and method for positioning and tracking one or more objects which in addition to range and azimuth also provides the elevation angle of the target relative to the instrument axes of the sensor platform. The system and method is based on a near IR laser radar transceiver and one or more active or passive retroreflectors placed on the objects to be positioned. The present invention further includes an internal beam stabilization mechanism protected from the environment and utilize a cylindrical window which is transparent for the near IR laser radiation, but absorbs all visible and UV radiation and thus protects the optical parts from ambient solar radiation. In addition, the cylindrical window protects all internal mechanical parts, notably the rotating and moving parts, from a corrosive and freezing/icing environment.
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Citations
38 Claims
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1-19. -19. (canceled)
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20. A method for positioning and tracking one or more objects using a transceiver unit fixed to a sensor platform and one or more active or passive retroreflector arranged at each of said one or more objects to be positioned, comprising:
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(a) emitting a fan-shaped pulsed laser beam with predefined vertical and horizontal beam widths by controlling a mirror (34) for emitting the laser beam in a plane in the vertical direction and stabilizing the fan-shaped beam relative to a plane in the horizontal direction and overlapping Instantaneous Field-of-View of a receiver relative to the horizontal plane, (b) detecting reflected or returned light from said at least one retroreflector located at an object to be positioned and tracked by the controllable mirror (34) and an optical receiver lens (37) focusing the reflected or returned light onto a photodiode array (38), (c) calculating elevation angle to the object by measuring mirror angle and interpolation of illuminated photodiodes in the photodiode array (38), measuring azimuth angle and measuring time-of-flight for laser light pulses from transmission to reception, and (d) calculating range and bearing to the object relative to instrument-axes of the sensor platform based on information from step (c). - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
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28. A system for positioning and tracking one or more objects provided with active or passive retroreflectors, comprising a transceiver unit (11) having a housing (12) with a window (13) through which light can be transmitted and received, a stationary part (20) and rotating part (30) in one unit enclosed and sealed within the housing (12), the rotating part (30) including a transmitter assembly with a laser source (32) and optical collimator (33), a receiver assembly including an optical receiver lens assembly (37), and a mirror (34) for transmitting and receiving reflected or returned light from a retroreflector, wherein
the laser source (32) and optical collimator (33) are arranged to generate a pulsed fan-shaped laser beam with predefined vertical and horizontal beam widths, the mirror (34) is controllable and arranged for emitting the laser beam in a plane of the vertical direction and stabilizing the fan-shaped beam and an overlapping Instantaneous Field-of-View of the receiver relative to a plane in the horizontal direction, the receiver assembly includes a photodiode array (38) and that the optical receiver lens (37) is arranged to focus returned or reflected light from a retroreflector on one of the at least one objects via the mirror (34) onto the photodiode array (38), and a unit for calculating range, bearing and elevation to the at least one object relative to the instrument-axes of the sensor platform.
Specification