Systems and methods for refractive beam-steering

1. A light detection and ranging (LIDAR) apparatus, comprising:

a polygon deflector comprising a plurality of facets;

a motor rotatably coupled to the polygon deflector, the motor configured to rotate the polygon deflector about a first axis orthogonal to a first plane; and

an optic positioned within an interior of the polygon deflector, the optic configured to collimate a first beam incident on a particular facet of the plurality of facets, the particular facet of the plurality of facets configured to refract the first beam in the first plane between a first angle and a second angle as the polygon deflector rotates about the first axis to output a second beam, the polygon deflector has a duty cycle greater than fifty percent, the duty cycle based on a duration that the polygon deflector refracts the first beam relative to a duration that the polygon deflector is rotated.

2. The LIDAR apparatus of claim 1 , wherein the plurality of facets form a non-orthogonal angle with one of a top or a bottom of the polygon deflector such that each facet of the plurality of facets is configured to refract the first beam in a second plane orthogonal to the first plane.

3. The LIDAR apparatus of claim 1 , wherein:

a plurality of first beams in the first plane includes the first beam;

the LIDAR apparatus comprises a planar fiber array configured to transmit the plurality of first beams within the interior of the polygon deflector; and

the optic is configured to shape the plurality of beams with an angular spread in a second plane orthogonal to the first plane.

4. The LIDAR apparatus of claim 3 , wherein the planar fiber array is mounted in a focal plane of the optic.

5. The LIDAR apparatus of claim 3 , wherein the angular spread is based on a transverse spacing of fibers in the fiber array.

6. The LIDAR apparatus of claim 3 , wherein:

the optic comprises a first lens configured to collimate the first beam and a second lens configured to deflect the collimated first beam to provide a deflected first beam; and

an inner surface of the polygon deflector is configured to collimate the deflected first beam within the polygon deflector.

7. The LIDAR apparatus of claim 6 , wherein the first lens is an aspheric lens and wherein the second lens is a positive cylindrical lens that has a same curvature as the inner surface.

8. The LIDAR apparatus of claim 6 , wherein the optic further comprises a pair of mirrors positioned with respect to each other such that a first mirror of the pair of mirrors is configured to reflect the first beam from the planar fiber array to a second mirror of the pair of the mirrors and wherein the second mirror is configured to reflect the first beam to the first lens.

9. The LIDAR apparatus of claim 3 , wherein the optic is a free form toric single lens.

10. The LIDAR apparatus of claim 3 , wherein each facet is configured to increase the angular spread of the first beam in the second plane based on a ratio of an index of refraction of the polygon deflector to an index of refraction of a medium surrounding the polygon deflector.

11. The LIDAR apparatus of claim 1 , wherein the motor is a brushless DC motor comprising:

a plurality of bearings rotatably coupled to an inner surface of the polygon deflector that defines the interior;

a rotor actuated by coils to rotate the polygon deflector about the first axis; and

a stator positioned in the interior of the polygon deflector, the stator defining a cavity where the optic is positioned.

12. The LIDAR apparatus of claim 1 , wherein the polygon deflector is transmissive at a wavelength of the first beam.

13. A LIDAR system, comprising:

a polygon deflector comprising a plurality of facets;

a detector array; and

a processing circuit configured to:

cause the polygon deflector to rotate about a first axis at a rotational frequency;

cause a laser source to transmit a first beam in an interior of the polygon deflector so that the polygon deflector refracts the first beam in a first plane between a first angle and a second angle, the first plane orthogonal to the first axis, the polygon deflector has a duty cycle greater than fifty percent, the duty cycle based on a duration that the polygon deflector refracts the first beam relative to a duration that the polygon deflector is rotated;

receive a signal from the detector array based on a second beam received at the detector array from an object responsive to the first beam; and

determine a range to the object based on the signal received from the detector array.

14. The LIDAR system of claim 13 , wherein:

a plurality of first beams in the first plane include the first beam;

the LIDAR apparatus comprises a planar fiber array to transmit the plurality of first beams within the interior of the polygon deflector; and

the optic is configured to shape the plurality of first beams with an angular spread in a second plane orthogonal to the first plane.

15. The LIDAR system of claim 14 , wherein:

the optic comprises a first lens configured to collimate the first beam and a second lens configured to deflect the collimated first beam to provide a deflected first beam; and

an inner surface of the polygon deflector is configured to collimate the deflected first beam within the polygon deflector.

16. An autonomous vehicle comprising:

a light detection and ranging (LIDAR) apparatus that comprises:

a polygon deflector comprising a plurality of facets;

a motor rotatably coupled to the polygon deflector, the motor configured to rotate the polygon deflector about a first axis orthogonal to a first plane; and

an optic positioned within an interior of the polygon deflector, the optic configured to collimate a first beam incident on a particular facet of the plurality of facets, the particular facet of the plurality of facets configured to refract the first beam in the first plane between a first angle and a second angle as the polygon deflector rotates about the first axis to output a second beam, the polygon deflector has a duty cycle greater than fifty percent, the duty cycle based on a duration that the polygon deflector refracts the first beam relative to a duration that the polygon deflector is rotated.

17. The autonomous vehicle of claim 16 , wherein the plurality of facets form a non-orthogonal angle with one of a top or a bottom of the polygon deflector such that each facet of the plurality of facets is configured to refract the beam in a second plane orthogonal to the first plane.

18. The autonomous vehicle of claim 16 , wherein:

a plurality of first beams in the first plane include the first beam;

the LIDAR apparatus comprises a planar fiber array configured to transmit the plurality of first beams within the interior of the polygon deflector; and

the optic is configured to shape the plurality of beams with an angular spread in a second plane orthogonal to the first plane;

wherein the planar fiber array is mounted in a focal plane of the optic.

19. The autonomous vehicle of claim 18 , wherein:

the optic comprises a first lens configured to collimate the first beam and a second lens configured to deflect the collimated first beam to provide a deflected first beam; and

an inner surface of the polygon deflector is configured to collimate the deflected first beam within the polygon deflector;

wherein the first lens is an aspheric lens and the second lens is a positive cylindrical lens that has a same curvature as the inner surface.