Active christiansen effect LIDAR system and method
Inventors
Murray, James • Lundquist, Paul • Seely, Jason • Rako, Steve • Boyd, Micah
Assignees
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Publication Number
US-10436907-B1
Publication Date
2019-10-08
Expiration Date
Abstract
Provided herein are systems and methods for an active sensing instrument actively utilizing the Christiansen effect to sense and adapt to suspended scatterers such as dust. The instrument enhances detection of remote surfaces that are partially or fully obscured at visual wavelengths due to those suspended scatterers. The system also may be used to measure properties and spatial distributions of the suspended scatterers themselves. Though the system is broadly applicable to remote detection through scattering media, it is particularly drawn to remote sensing through dust particles in the atmosphere as may be produced from helicopter fly-overs, dust storms, or other events that draw up substantial concentrations of mineral-based dust particles into the air.
Core Innovation
The invention provides an Active Christiansen-effect LIDAR optical system for imaging through atmospheres containing suspended scatterers, including particles or surfaces. One or more tunable lasers are operable to provide radiation beams having selectable wavelengths within a wavelength range, and a beam scanning mechanism directs the radiation beams through sequences of angles with an exit aperture for emission, including a multi-polygon, multi-beam scanner.
The system includes a wavelength-sensitive imaging system adapted to generate digitized images of scattering from particles or surfaces impinged by the radiation beams, with an entrance aperture different from the exit aperture. An image processor uses the digitized images to generate calculated volumetric coordinates of points where the radiation beams impinge surfaces, using orientation and position information of the entrance aperture and exit aperture along with the sequences of angles.
A wavelength controller selects wavelengths of the tunable lasers to optimize the digitized images of scattering and is configured to select wavelengths iteratively to maximize intensity of images of scattering from particles or surfaces. The described optimization uses a calculated intensity at a range threshold based on estimates of volumetric laser scatter and absorption, with a pre-selected volume to exclude near-range contributions, and further includes optional polarization-based suppression and an asymmetric vignetting aperture for attenuation of portions of the digitized images.
Claims Coverage
The partial content includes six independent claims. Across these independent claims, the coverage centers on an optical system with selectable-wavelength tunable lasers, a scanning mechanism with an exit aperture, a wavelength-sensitive imaging system with separate entrance and exit apertures, a wavelength controller that optimizes selected wavelengths for scattering images, and an image processor that generates calculated volumetric coordinates. Additional independent claim variations further specify geometric calibration, volumetric-range threshold optimization, polarization-based suppression, and asymmetric vignetting attenuation.
Selectable-wavelength tunable lasers with multi-polygon, multi-beam scanning and bistatic entrance/exit apertures
An optical system having one or more tunable lasers providing selectable wavelengths within a wavelength range; a beam scanning mechanism directing radiation beams through sequences of angles with an exit aperture, wherein the beam scanning mechanism is a multi-polygon, multi-beam scanner; an imaging system sensitive to the wavelength range generating digitized images of scattering with an entrance aperture different from the exit aperture; a wavelength controller selecting wavelengths to optimize the digitized images; and an image processor generating calculated volumetric coordinates of points where the radiation beams impinge surfaces.
Volumetric coordinate calculation using entrance/exit aperture relative geometry and scan angles
An optical system having one or more tunable lasers with selectable wavelengths; a beam scanning mechanism with an exit aperture directing radiation beams through sequences of angles; an imaging system generating digitized scattering images with an entrance aperture different from the exit aperture; a wavelength controller selecting wavelengths to optimize the digitized images; and an image processor generating calculated volumetric coordinates, wherein the image processor uses information about a relative orientation and a relative position of the entrance aperture and the exit aperture along with the sequences of angles to calculate volumetric coordinates associated with digital images of scattering.
Iterative wavelength selection maximizing scattering intensity outside a pre-selected volume
An optical system having one or more tunable lasers with selectable wavelengths; a beam scanning mechanism with an exit aperture; an imaging system generating digitized scattering images with an entrance aperture different from the exit aperture; a wavelength controller selecting wavelengths to optimize the digitized images; and an image processor generating calculated volumetric coordinates, wherein the wavelength controller iteratively selects wavelengths to maximize intensity of images of scattering from particles or surfaces, and the particles or surfaces have calculated volumetric coordinates outside of a pre-selected volume.
Iterative wavelength selection maximizing calculated intensity at a range threshold based on volumetric scatter and absorption estimates
An optical system having one or more tunable lasers with selectable wavelengths; a beam scanning mechanism with an exit aperture; an imaging system generating digitized scattering images with an entrance aperture different from the exit aperture; a wavelength controller selecting wavelengths to optimize the digitized images; and an image processor generating calculated volumetric coordinates, wherein the wavelength controller iteratively selects wavelengths to maximize a calculated intensity at a range threshold based on estimates of volumetric laser scatter and absorption.
Polarization-state alteration at pre-specified distances with polarization filtering
An optical system having one or more tunable lasers providing radiation beams with selectable wavelengths; a beam scanning mechanism with an exit aperture; an imaging system generating digitized scattering images with an entrance aperture different from the exit aperture; a wavelength controller selecting wavelengths to optimize the digitized images; and an image processor generating calculated volumetric coordinates, wherein the tunable lasers provide radiation beams with exit polarization states such that scattered polarization states resulting from scatter from particles at pre-specified distances entering the imaging system are altered from the exit polarization states, and wherein the imaging system further includes a polarization filter that suppresses transmission of light with polarizations different from the exit polarization states.
Asymmetric vignetting aperture to attenuate portions of digitized scattering images
An optical system having one or more tunable lasers with selectable wavelengths; a beam scanning mechanism with an exit aperture; an imaging system generating digitized scattering images with an entrance aperture different from the exit aperture; a wavelength controller selecting wavelengths to optimize the digitized images; and an image processor generating calculated volumetric coordinates, wherein the imaging system further includes an asymmetric vignetting aperture configured to attenuate portions of the digitized images.
Overall, the independent-claim coverage combines selectable-wavelength tunable lasers, a scanning mechanism with an exit aperture, a wavelength-sensitive imaging system with a separate entrance aperture, and a wavelength controller that optimizes selected wavelengths for digitized scattering images. The image processor generates calculated volumetric coordinates, with at least one independent claim further specifying use of relative entrance/exit aperture geometry and scan angle sequences. The independent claims additionally cover iterative wavelength selection that maximizes intensity at a range threshold using estimates of volumetric scatter and absorption, the exclusion of points within a pre-selected volume, polarization-state alteration with a polarization filter, and attenuation of digitized images using an asymmetric vignetting aperture.
Stated Advantages
Not explicitly described in patent.
Documented Applications
Pilotage in degraded visual environments.
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