Remote measurement of shallow depths in semi-transparent media

Patent metadata

Field	Value
Publication number	US-10684362-B2
Application number	US-201615092015-A
Country	US
Kind code	B2
Filing date	Apr 6, 2016
Priority date	Jun 30, 2011
Publication date	Jun 16, 2020
Grant date	Jun 16, 2020

Abstract

Through discrimination of the scattered signal polarization state, a lidar system measures a distance through semi-transparent media by the reception of single or multiple scattered signals from a scattering medium. Combined and overlapped single or multiple scattered light signals from the medium can be separated by exploiting varying 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 two surface timing measurements and achieving sub-pulse width resolution.

First claim

What is claimed is:

1. A lidar system, comprising:
a transmitter configured to output a pulse of polarized light to a medium;
a receiver configured to collect scattered light from the medium, wherein the scattered light comprising a received pulse;
a detector
configured to receive at least a respective component of the scattered light; and
timing electronics coupled to each of the detector, wherein an output of the timing electronics comprises a value indicative of a relative distance based on an amount of time elapsed between inner portions of the received pulse of the scattered light, thereby achieving a sub-pulse width resolution, optionally wherein the value is based on an optical separation of respective component portions of the scattered light.

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 prism in optical communication with the laser.

4. The lidar system of claim 2 , wherein the laser comprises at least one of a polarized laser, pulsed laser, and a continuous wave (CW) laser.

5. The lidar system of claim 2 , wherein the laser and a polarizer in optical communication with the laser is configured to produce a polarized light comprises a known polarization.

6. The lidar system of claim 5 , wherein the polarized light comprises circular polarization.

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

8. The lidar system of claim 7 , wherein the receiver further comprises a spectral filter.

9. The lidar system of claim 7 , further comprising a polarizing splitter, wherein the detector is in optical communication with the polarizing splitter.

10. The lidar system of claim 7 , wherein the respective component of the received pulse of the scattered light comprises a cross-planar polarization component and a co-planar polarization component.

11. The lidar system of claim 10 , wherein the detector is calibrated to receive substantially the cross-planar polarization component and the co-planar polarization component.

12. The lidar system of claim 7 , wherein the detector is calibrated to the respective portion of the single or multiple scattered lights.

13. A lidar system, comprising:
a source of polarized light configured to output a pulse of polarized light;
a light receiver configured to receive single or multiple scattered lights comprising received pulses having varying angular spread or depolarization, the light receiver comprising a polarizing beam splitter, wherein the polarizing beam splitter is configured to split the received pulses into cross-planar polarization components and a co-planar polarization components;
a sensor system configured for sensing information indicative of one or more properties of two portions of received light in the collection, wherein the properties of each of the portions of the received light comprise one or more of:
(a) an orientation of the portion,
(b) an angular spread of the portion,
(c) a degree of polarization of the portion,
(d) an azimuthal polarization pattern of the portion,
(e) a high order scattering profile of the portion, and
(f) a range of a respective property being one of the properties (a) to (e); and
computational equipment configured for determining an elapsed time between the two portions of the received light, based on a difference between the properties of the portions, and a relative distance based on the elapsed time, wherein the elapsed time is less than a duration of the pulse.

14. The lidar system of claim 13 , wherein the source of polarized light comprises:
a laser;
a half-wave plate; and
a polarizer.

15. The lidar system of claim 14 , wherein the laser is selected from the group consisting of a polarized laser, pulsed laser, and continuous wave (CW) laser.

16. The lidar system of claim 13 , 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.

17. A method of measuring a relative distance between a first surface and a second surface with differing polarization characteristics, comprising the steps of:
generating polarized light;
scattering at least some portion of the polarized light from the first surface and at least some portion of the polarized light from the second surface;
receiving the scattered light from the first surface as a received first surface pulse and receiving the scattered light from the second surface as a received second surface pulse, wherein the received first surface pulse and the received second surface pulse have a portion that overlaps in an ambiguous intrapulse overlap portion;
separating the received first surface pulse and the received second surface pulse into a first component and a second component, the first component and the second component having a relative difference in polarization between each other, wherein the separation removes the ambiguous intrapulse overlap;
determining an amount of time elapsed between the first component and the second component; and
calculating a relative distance between the first surface and the second surface based on the amount of time elapsed, thereby achieving a sub-pulse width resolution.

18. The method of claim 17 , wherein the first surface comprises a relatively polarization preserving surface and the second surface comprises a relatively polarization-altering surface.

19. The method of claim 17 , wherein the first surface is a water surface and the second surface is a surface beneath the water, the first surface and the second surface are different surfaces.

20. The method of claim 17 , wherein the generating a pulse of polarized light step comprises the steps of generating light pulse with a laser; and passing the light pulse through a polarizer.

Assignees

• Univ Colorado Regents
• Astra Lite Inc

Inventors

• Thayer Jeffrey P
• Gisler Andrew W
• Mitchell Steven
• Hayman Matthew

Classifications

• Y02A90/30

  Assessment of water resources · CPC title

• G01C13/008

  measuring depth of open water · CPC title

• G01S17/89

  for mapping or imaging · CPC title

• G01S17/10

  using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) · CPC title

• G01S7/499 Primary

  using polarisation effects · CPC title