Patent ID: 6618132
Filing Date: 2003-09-09
Classification: G01S

Abstract:
A laser tracker for detecting a retroreflective target on an object, comprising:a laser which produces an output beam; a linear polarizer tilted at an angle with respect to the laser beam which passes a beam having a first linear polarization; a quarter wave plate positioned after the polarizer which passes the beam and converts the beam to a circular polarization; a reflector affixed to a target; a scanning optical system for directing the circularly polarized beam into a field of view wherein the beam will illuminate said retroreflective target which is present in the field of view, thereby producing a reflected beam which is directed back to the quarter wave plate which converts the beam to a beam having a second linear polarization orthogonal to the first linear polarization, and then to the linear polarizer which reflects the beam; a photodetector positioned to receive the reflected beam which is also focused onto the detector by the optical system, and producing a detector signal; a signal processing system connected to the detector to obtain information about the target from the detector signal, wherein said scanning optical system comprises: a first cylindrical lens between the laser and polarizer to diverge the beam in one dimension to produce an expanding planar beam; a scanning mirror assembly after the quarter wave plate to scan the beam over a scanning plane; and a second cylindrical lens before the photodetector to focus the reflected beam onto the photodetector.