REMOTE MEASUREMENT OF SHALLOW DEPTHS IN SEMI-TRANSPARENT MEDIA

• US 20140146303A1
• Filed: 06/29/2012
• Published: 05/29/2014
• Est. Priority Date: 06/30/2011
• Status: Active Grant

• Current Assignee: The Board of Regents of the University of Colorado (University of Colorado System)
• Original Assignee: The Board of Regents of the University of Colorado (University of Colorado System)
• Inventors: Mitchell, Steven, Thayer, Jeffrey P., Hayman, Matthew
• Granted Patent: US 9,476,980 B2
• Time in Patent Office: Days
• US Class Current: 356/5.01
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating
• CPC Class Codes: G01S 7/499 using polarisation effects

Abstract

Through discrimination of the scattered signal polarization state, a lidar system measures a distance through semi-transparent media by the reception of scattered signals from a first surface and scattered signals from a second surface. Combined and overlapped light signals scattered from the two surface signals can be separated by exploiting their differing polarization characteristics. This removes the traditional laser and detector pulse width limitations that determine the system'"'"'s operational bandwidth, translating relative depth measurements into the conditions of single surface timing measurements and achieving sub-pulse width resolution.

Claims

1. A lidar system, comprising:

a transmitter configured to output polarized light to a target;

a receiver configured to collect scattered light from the target;

a first detector;

a second detector, wherein the first detector and second detector are each configured to receive at least a respective portion of the scattered light from the receiver; and

timing electronics coupled to each of the first detector and the second detector.

2. The lidar system of claim 1, wherein the transmitter comprises:

a laser; and

a polarizer in optical communication with the laser.

3. The lidar system of claim 2, wherein the transmitter further comprises a half-wave plate in optical communication with the laser.

4. The lidar system of claim 2, wherein the transmitter further comprises a prism in optical communication with the laser.

5. The lidar system of claim 1, wherein the laser comprises at least one of a polarized laser, pulsed laser, or continuous wave (CW) laser.

6. The lidar system of claim 1, wherein the polarized light comprises a known polarization.

7. The lidar system of claim 1, wherein the polarized light comprises circular polarization.

8. The lidar system of claim 1, wherein the receiver comprises a telescope.

9. The lidar system of claim 8, wherein the receiver further comprises a spectral filter.

10. The lidar system of claim 1, further comprising a polarizing splitter, wherein the first detector and the second detector are in optical communication with the polarizing splitter.

11. The lidar system of claim 1, wherein the respective portion of the scattered light comprises a cross-planar polarization component and a co-planar polarization component.

12. The lidar system of claim 11, wherein the first detector is calibrated to receive the cross-planar component and the second detector is calibrated to receive the co-planar component.

13. The lidar system of claim 1, wherein the first detector and the second detector are each calibrated to the respective portion of the scattered light.

14-25. -25. (canceled)

26. A lidar system, comprising:

a source of polarized light;

a light receiver configured to receive scattered light, the light receiver comprising a polarizing beam splitter, wherein the polarizing beam splitter is configured to split the scattered light into a cross-planar polarization component and a co-planar polarization component;

a first detector, wherein the first detector is configured to receive the cross-planar polarization component; and

a second detector, wherein the second detector is configured to receive the co-planar polarization component.

27. The lidar system of claim 26, wherein the source of polarized light comprises:

a laser;

a half-wave plate; and

a polarizer.

28. The lidar system of claim 27, wherein the laser is selected from the group consisting of a polarized laser, pulsed laser, and continuous wave (CW) laser.

31. The lidar system of claim 26, wherein the first detector and the second detector each comprises a photomultiplier tube, the photomultiplier tube counts photons in the cross-planar polarization component and the co-planar polarization component, respectively.

29-30. -30. (canceled)

32-45. -45. (canceled)

46. A lidar system, comprising:

a laser light source, wherein an output of the laser light source is laser light;

a polarizing beam splitter, wherein the laser light is aligned with the transmission axis of the polarizing beam splitter, and wherein an output of the polarizing beam splitter is linearly polarized light;

a quarter-wave plate, wherein the linearly polarized light transmitted by the polarizing beam splitter is received at the quarter-wave plate, and wherein,

in a first mode of operation, the fast or slow axes of the quarter-wave plate is oriented 45-degrees to the linear polarized light output of the polarizing beam splitter, wherein circularly polarized light is emitted by the quarter-wave plate;

in a second mode of operation, the quarter-wave plate is oriented such that fast and slow axes of the quarter-wave plate are aligned with the linearly polarized light output of the polarizing beam splitter, wherein linearly polarized light is emitted by the quarter-wave plate; and

a detector, wherein light reflected by the polarizing beam splitter is received at the detector.

47. The lidar system of claim 46, further comprising timing electronics coupled to the detector.

48-70. -70. (canceled)