Remote measurement of shallow depths in semi-transparent media
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.
1. A lidar system, comprising:
a transmitter configured to output a pulse of polarized light to a medium, the transmitter comprising a laser and a polarizer in optical communication with the laser;
a receiver configured to collect single or multiple scattered lights from the medium, the multiple scattered lights comprising received pulses having varying angular spread or depolarization;
a first detector, the first detector comprising a sensors array of light sensors;
a second detector, the second detector comprising a second sensors array of light sensors, wherein the first detector and the second detector are each configured to receive at least a respective component of the single or multiple scattered lights from the receiver, and wherein the light sensors of the first sensors array and the second sensors array are each configured to receive a respective portion of the received pulses; and
timing electronics coupled to each of the first detector and the second 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 pulses of the single or multiple scattered lights, thereby achieving a sub-pulse width resolution, optionally wherein the value is based on an optical separation of respective component portions of the single or multiple scattered lights.
2. The lidar system of claim 1 , wherein the transmitter further comprises a half-wave plate in optical communication with the laser.
3. The lidar system of claim 1 , wherein the transmitter further comprises a prism in optical communication with the laser.
4. The lidar system of claim 1 , 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 1 , wherein the polarized light comprises a known polarization.
6. The lidar system of claim 1 , 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 first detector and the second detector are in optical communication with the polarizing splitter.
10. The lidar system of claim 7 , wherein the respective component of the received pulses of the single or multiple scattered lights comprises a cross-planar polarization component and a co-planar polarization component.
11. The lidar system of claim 10 , wherein the first detector is calibrated to receive substantially the cross-planar component and the second detector is calibrated to receive substantially the co-planar component.
12. The lidar system of claim 7 , wherein the first detector and the second detector are each 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 first detector comprising a sensors array of light sensors, wherein the first detector is configured to receive the cross-planar polarization components, and wherein the light sensors of the sensors array are each configured to receive a respective component of the cross-planar polarization components;
a second detector comprising a second sensors array of light sensors, wherein the second detector is configured to receive the co-planar polarization component, and wherein the light sensors of the second sensors array are each configured to receive a respective component of the co-planar polarization component; and
timing electronics coupled in electrical communication with the first detector and the second detector configured to output a value indicative of a relative distance based on an amount of time elapsed between inner portions of the received pulses of the single or multiple scattered lights, thereby achieving a sub-pulse width resolution.
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.