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 scattered 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 method of using a LIDAR apparatus, the method comprising:
generating a polarized signal;
applying at least some portion of the polarized signal onto a semi-transparent media;
receiving two or more scattered signals from the semi-transparent media, wherein there is an ambiguous interpulse overlap between the two or more received scattered signals;
separating the two or more received scattered signals into a first component and into a second component to remove the ambiguous interpulse overlap between the received two or more scattered signals;
determining one or more characteristics of the separated first component and the separated second component; and
determining, with computational equipment based on the one or more of the characteristics of the separated first component and the separated second component, one or more of: i) optical depth of a portion of the semi-transparent media, ii) physical depth of the semi-transparent media, iii) optical purity of the semi-transparent, and iv) topography characterization of the semi-transparent media.
2. The method of claim 1 , wherein the polarized signal is generated from a laser or a light emitting diode (L.E.D.).
3. The method of claim 2 , wherein the laser comprises at least one of a polarized laser, a pulsed laser, and a continuous wave (C.W.) laser.
4. The method of claim 1 , wherein the polarized signal comprises electromagnetic radiation.
5. The method of claim 1 , wherein the polarized signal comprises a polarized light signal.
6. The method of claim 1 , wherein the one or more characteristics of the first component and the separated second component comprises information indicative of one or more of: (i) a frequency of the first component, (ii) a frequency of the second component, (iii) an amplitude of the first, (iv) an amplitude of the second component, (v) a phase of the first component, (vi) a phase of the second component, (vii) a polarization of the first component, and (viii) a polarization of the second component.
7. The method of claim 1 , wherein the one or more characteristics of the first component and the separated second component comprises information indicative of one or more of: (i) an orientation of the first component and the second component, (ii) an angular spread of the first component and the second component, (iii) a degree of polarization of the first component and the second component, (iv) an azimuthal polarization pattern of the first component and the second component, (v) a high order scattering profile of the first component and the second component, and (vi) a range of a respective property being one of the properties (i) to (vi).
8. The method of claim 1 , wherein the semi-transparent media comprises a first surface and a second surface.
9. The method of claim 8 , wherein the topography characterization of the semi-transparent media comprises a topography of the first surface and topography of the second surface.
10. The method of claim 9 , wherein the first surface comprises a water surface and the second surface comprises a submerged surface.
11. The method of claim 10 , wherein the physical depth of the semi-transparent media comprises a relative distance between the water surface and the submerged surface.
12. The method of claim 1 , wherein the optical purity of the semi-transparent comprises a water quality measurement.
13. The method of claim 1 , wherein the semi-transparent media is one or more of a soft target or a hard surface.
14. The method of claim 1 , wherein the first component and the second component comprise one or more of a cross-planar polarization component and a co-planar polarization component.
15. The method of claim 1 , wherein the topography characterization of the semi-transparent media is a bathymetry characterization.