Lidar system including multifaceted deflector
A system and method for scanning of coherent LIDAR. The system includes a motor, a laser source configured to generate an optical beam, and a deflector. A first facet of the plurality of facets has a facet normal direction. The deflector is coupled to the motor and is configured to rotate about a rotation axis to deflect the optical beam from the laser source. The laser source is configured to direct the optical beam such that the optical beam is incident on the deflector at a first incident angle in a first plane, wherein the first plane includes the rotation axis, wherein the first incident angle is spaced apart from the facet normal direction for the first facet. A second facet of the plurality of facets includes an optical element configured to deflect the optical beam at the first incident angle into a deflected angle.
1. A light detection and ranging (LIDAR) system comprising:
a motor;
a laser source configured to generate an optical beam; and
a deflector including a plurality of facets, wherein:
a first facet of the plurality of facets has a facet normal direction and is covered with a first optical element having a first spacing (i) that is less than ten times an operating wavelength and (ii) that is in a range of 0.8 microns to 10 microns;
the deflector is coupled to the motor and is configured to rotate about a rotation axis to deflect the optical beam from the laser source;
the laser source is configured to direct the optical beam such that the optical beam is incident on the deflector at a first incident angle in a first plane, wherein the first plane includes the rotation axis, wherein the first incident angle is spaced apart from the facet normal direction for the first facet; and
a second facet of the plurality of facets includes a second optical element configured to deflect the optical beam at the first incident angle into a deflected angle.
2. The LIDAR system as recited in claim 1 , wherein the second optical element has a facet ruling normal direction equal to or nearly equal to half the first incident angle for each ruling on the first facet.
3. The LIDAR system as recited in claim 2 , wherein the deflected angle is within ten degrees of the facet normal direction.
4. The LIDAR system as recited in claim 1 , further comprising a stepping motor that is configured to change an attack angle for the optical beam at the first facet of the deflector.
5. The LIDAR system as recited in claim 1 , wherein the second optical element include a second spacing, and wherein the first spacing of the first optical element differs from the second spacing of the second optical element.
6. The LIDAR system as recited in claim 1 , wherein a second facet of the deflector includes a second optical element, the second optical element configured to deflect the optical beam at the first incident angle into a second deflected angle that is different than the deflected angle.
7. The LIDAR system as recited in claim 1 , wherein each facet of the deflector has a normal direction perpendicular to the rotation axis, and wherein the second optical element is a reflective blazed grating.
8. The LIDAR system as recited in claim 1 , wherein a cross-section of the deflector perpendicular to the rotation axis has a polygonal shape.
9. The LIDAR system as recited in claim 1 , wherein a cross-section of the optical element has a triangular shape or a sawtooth shape.
10. The LIDAR system as recited in claim 1 , wherein the laser source is a source of multiple optical beams and is configured such that the multiple optical beams approach the axis of rotation at multiple different incident angles.
11. The LIDAR system as recited in claim 10 , wherein the multiple different incident angles are within 40 degrees of the first incident angle.
12. The LIDAR system as recited in claim 1 , wherein a cross-section of the deflector perpendicular to the rotation axis has maximum diameter in a range from 0.5 centimeter to 5.0 centimeter.
13. The LIDAR system as recited in claim 1 , wherein the deflected angle is horizontal or nearly horizontal to the facet normal direction.
14. A deflector including a plurality of facets for an optical scanning system comprising:
a body including a plurality of outward facing facets relative to an axis of the body;
wherein a facet of the plurality of outward facing facets has a facet normal direction and is covered with an optical element having a spacing (i) that is less than ten times an operating wavelength and (ii) that is in a range of 0.8 microns to 10 microns.
15. The deflector as recited in claim 14 , wherein the optical element is a reflective blazed grating with a facet ruling normal direction in a range from 10 degrees to 40 degrees.
16. The deflector as recited in claim 14 , wherein a first facet of the deflector has a different spacing from a different second facet of the deflector.
17. The deflector as recited in claim 14 , wherein each facet of the deflector has a different spacing than every other facet of the deflector.
18. The deflector as recited in claim 14 , wherein each facet of the deflector has a normal direction perpendicular to the central axis.
19. The deflector as recited in claim 14 , wherein a cross-section of the deflector perpendicular to the central axis has a polygonal shape.
20. The deflector as recited in claim 14 , wherein a cross-section of the optical element has a triangular shape or sawtooth shape.