SMALL APERTURE OPTICAL PERISCOPE FOR LIDAR
A LiDAR system includes a first mirror positioned to receive the outgoing light beam from the laser; a second mirror positioned to receive a reflected light beam from the first mirror and to redirect the reflected light beam onto a target, and a detector that detects return light reflected off of the target. The second mirror of the optical periscope includes a cross-sectional area sized and shaped to substantially match a cross-sectional area of the reflected light beam to improve a quality of signal detected by the detector.
1 . A LiDAR system including:
a laser positioned to transmit an outgoing light beam;
an optical periscope including:
a first mirror positioned to receive the outgoing light beam from the laser;
a second mirror positioned to receive a reflected light beam from the first mirror and to redirect the reflected light beam onto a target, the second mirror having a cross-sectional area sized and shaped to substantially match a cross-sectional area of the reflected light beam; and
a detector that detects return light reflected off of the target.
2 . The LiDAR system of claim 1 , wherein the second mirror is a reflective patch on a transparent substrate.
3 . The LiDAR system of claim 2 , wherein the transparent substrate includes a coating that is anti-reflective to light emitted by the laser.
4 . The LiDAR system of claim 2 , wherein the transparent substrate includes a band-pass optical filter that (i) transmits light over a pass-band wavelength range that includes a wavelength of light emitted by the laser and (ii) blocks light outside of the pass-band wavelength range.
5 . The LiDAR system of claim 2 , where the return light travels in a direction antiparallel to the outgoing light beam.
6 . The LiDAR system of claim 2 , wherein the return light passes through the transparent substrate in route to the detector.
7 . The LiDAR system of claim 1 , wherein the second mirror prevents a portion of the return light from reaching the detector.
8 . The LiDAR system of claim 1 , wherein the laser and the first mirror are aligned along a first axis and the detector and the target are aligned along a second axis, the second axis being parallel to the first axis.
9 . The LiDAR system of claim 8 , further comprising collection optics positioned to intersect the second axis between the second mirror and the detector, the return light passing through the collection optics in route to the detector.
10 . The LiDAR system of claim 1 , wherein the optical periscope further includes an aperture located between the first and second mirrors, wherein the aperture is positioned to receive the reflected light beam from the first mirror, and the aperture is sized to block a predefined portion of the light from edges of the reflected light beam.
11 . A method for improving signal quality in a LiDAR system, the method comprising:
directing an outgoing light beam onto a first mirror of an optical periscope;
redirecting, by a second mirror or the optical periscope, a reflected light beam received from the first mirror onto a target, the second mirror having a cross-sectional area sized and shaped to substantially match a cross-sectional area of the reflected light beam; and
detecting, by a detector, return light reflected off the target.
12 . The method of claim 11 , wherein the second mirror is a reflective patch on a transparent substrate.
13 . The method of claim 12 , wherein the transparent substrate includes a coating that is anti-reflective to a wavelength of the outgoing light beam.
14 . The method of claim 13 , wherein the return light travels in a direction antiparallel to the outgoing light beam.
15 . The method of claim 12 , wherein the return light passes through the transparent substrate in route to the detector.
16 . The method of claim 12 , wherein the second mirror prevents a portion of the return light from reaching the detector.
17 . The method of claim 12 , wherein a laser and the first mirror are aligned along a first axis and the detector and the target are aligned along a second axis, the second axis being parallel to the first axis.
18 . The method of claim 17 , wherein the return light passes through collection optics positioned to intersect the second axis between the second mirror and the detector.
19 . A method for assembling a LiDAR device, the method comprising:
forming, on a transparent substrate, a reflective area having a cross-sectional profile substantially matching a cross-sectional profile of a light beam emitted from a laser;
assembling an optical periscope relative to the laser, the optical periscope including a first mirror positioned to receive an outgoing light beam emitted from the laser and further including the reflective area positioned to redirect a light beam reflected from the first mirror onto a target; and
positioning a detector to receive return light reflected off of the target.
20 . The method of claim 19 , wherein the laser and the first mirror are aligned along a first axis and the detector and the target are aligned along a second axis, the second axis being parallel to the first axis.
21 . The method of claim 19 , further comprising: coating the transparent substrate with a coating that is anti-reflective to a wavelength of light emitted by the laser.
22 . The method of claim 19 , wherein the return light passes through the transparent substrate in route to the detector the return light and travels in a direction antiparallel to a direction of the outgoing light beam.