COHERENT LIDAR SYSTEM FOR AUTOMATED VEHICLES
A coherent lidar system suitable for use on an automated vehicle includes a laser-unit, a lens, a coupler, and a polarized-beam-splitter. The laser-unit is used to provide a laser-beam directed toward a target-area and generate a local-oscillator. The local-oscillator is characterized by a reference-polarization. The lens is used to collect reflected-light that is a reflection of the laser-beam by a target present in the target-area. The coupler is used to combine the reflected-light collected by the lens and the local-oscillator to form a composite-beam. The polarized-beam-splitter used to provide a first-beam that corresponds to the composite-beam polarized to a first-polarization, and a second-beam that corresponds to the composite-beam polarized to a second-polarization different from the first-polarization.
1 . A coherent lidar system suitable for use on an automated vehicle, said system comprising:
a laser-unit used to provide a laser-beam directed toward a target-area and generate a local-oscillator, wherein the local-oscillator is characterized by a reference-polarization;
a lens used to collect reflected-light that is a reflection of the laser-beam by a target present in the target-area;
a coupler used to combine the reflected-light collected by the lens and the local-oscillator to form a composite-beam; and
a polarized-beam-splitter used to provide a first-beam that corresponds to the composite-beam polarized to a first-polarization, and a second-beam that corresponds to the composite-beam polarized to a second-polarization different from the first-polarization.
2 . The system in accordance with claim 1 , wherein the first-polarization and the second-polarization are selected so a first-power of the local-oscillator present in the first-beam is substantially equal to a second-power of the local-oscillator present in the second-beam.
3 . The system in accordance with claim 1 , wherein the reference-polarization of the local-oscillator is characterized as linear-polarization to a reference-angel, the first-polarization is characterized as linear-polarization to a first-angle measured relative to the reference-angle, and the second-polarization is characterized as linear-polarization to a second-angle measured relative to the reference-angle.
4 . The system in accordance with claim 3 , wherein the second-angle is perpendicular to the first-angle.
5 . The system in accordance with claim 4 , wherein the first-angle is minus forty-five degrees relative to the reference-angle, and the second-angle is plus forty-five degrees relative to the reference-angle.
6 . The system in accordance with claim 1 , wherein the reference-polarization of the local-oscillator is characterized as linear-polarization to a reference-angel, the first-polarization is characterized as clockwise-polarization, and the second-polarization is characterized as counter-clockwise-polarization.
7 . The system in accordance with claim 1 , wherein the laser-unit is configured to frequency-modulate the laser-beam and the local-oscillator.
8 . The system in accordance with claim 1 , wherein the system includes a first-detector used to provide a first-signal indicative of the first-beam, and a second-detector used to provide a second-signal indicative of the second-beam.
9 . The system in accordance with claim 4 , wherein the system includes a processor configured to combine the first-signal and the second-signal using a sum-of-squares process to provide a ranging-signal indicate of a distance to the target.