Lens assembly for a LIDAR system
A LIDAR system may include a laser diode that emits a beam having a slow axis and a fast axis so that a cross-section of the beam has a width substantially greater than a height. A first three-element lens may be optically aligned with a photodetector of the LIDAR system. A second three-element lens may be optically aligned with the diode laser. The second three-element lens may include at least one lens having a predetermined astigmatism that reduces the width of the beam with respect to the height.
1. A lens assembly for a LIDAR system, the lens assembly comprising:
a first positive lens;
a second positive lens; and
a third negative lens interposed between the first positive lens and the second positive lens, wherein optical axes of the first positive lens, the second positive lens, and the third negative lens are aligned with an optical axis of a laser of the LIDAR system, and wherein at least one optical surface of the first positive lens, the second positive lens, or the third negative lens is a freeform surface.
2. The lens assembly of claim 1 , wherein the first positive lens, the second positive lens, and the third negative lens collectively comprise a Cooke triplet lens.
3. The lens assembly of claim 2 , wherein the freeform surface is configured to apply astigmatism to collimate a beam of the laser.
4. The lens assembly of claim 1 , wherein the first positive lens, the second positive lens, and the third negative lens collectively comprise a first three-element lens, the lens assembly further comprising:
a second three-element lens, wherein an optical axis of the second three-element lens is aligned with an optical axis of a sensor of the LIDAR system, and wherein the second three-element lens is adjacent to the first three-element lens such that the optical axis of the second three-element lens is substantially parallel to the optical axis of the first three-element lens.
5. The lens assembly of claim 4 , wherein a perimeter of the first three-element lens includes a truncated portion that is adjacent to the second three-element lens.
6. The lens assembly of claim 1 , wherein at least one of the first positive lens, the second positive lens, and the third negative lens is a biconic lens that includes the freeform surface.
7. The lens assembly of claim 1 , wherein at least one of the first positive lens, the second positive lens, or the third negative lens is a rotationally asymmetric lens that includes the freeform surface.
8. A LIDAR system comprising:
a laser configured to emit a beam having a slow axis and a fast axis so that a cross-section of the beam has a width substantially greater than a height;
a photodetector;
a first three-element lens optically aligned with the laser; and
a second three-element lens optically aligned with the photodetector,
wherein the first three-element lens includes at least one lens having a predetermined astigmatism that reduces the width of the beam with respect to the height.
9. The LIDAR system of claim 8 , wherein the at least one lens having the predetermined astigmatism is a lens having a freeform surface.
10. The LIDAR system of claim 8 , wherein the at least one lens having the predetermined astigmatism is a rotationally asymmetric lens.
11. The LIDAR system of claim 8 , wherein at least one of the first three-element lens and the second three-element lens is a Cooke triplet lens.
12. The LIDAR system of claim 8 , wherein the at least one lens having the predetermined astigmatism is a plastic lens.
13. The LIDAR system of claim 8 , wherein the laser is a laser diode.
14. The LIDAR system of claim 11 , wherein the first three-element lens is adjacent to the Cooke triplet lens and an optical axis of the first three-element lens is substantially parallel to an optical axis of the second three-element lens.
15. The LIDAR system of claim 14 , wherein the optical axis of the first three-element lens is folded by a first mirror between the first three-element lens and the laser, and wherein the optical axis of the second three-element lens is folded by a second mirror between the second three-element lens and the photodetector.
16. A method of fabricating a lens assembly for a LIDAR system, the method comprising:
placing a first three-lens group into a first portion of a lens holder so that the first three-lens group is optically aligned with a laser diode, wherein a beam of the laser diode diverges in an asymmetrical pattern; and
placing a second three-lens group into a second portion of the lens holder so that the second three-lens group is optically aligned with a photodetector,
wherein the first three-lens group includes at least one lens having a predetermined astigmatism that reduces asymmetry of the asymmetrical pattern of the beam.
17. The method of claim 16 , wherein the at least one lens having the predetermined astigmatism is a freeform lens.
18. The method of claim 16 , wherein the at least one lens having the predetermined astigmatism is a rotationally asymmetric lens.
19. The method of claim 16 , wherein the at least one lens having the predetermined astigmatism is a plastic lens.
20. The method of claim 16 , wherein placing the first three-lens group into the first portion of the lens holder and placing the second three-lens group into the second portion of the lens holder further comprises:
aligning the second three-lens group such that an optical axis of the second three-lens group is substantially parallel to an optical axis of the first three-lens group.