University Corporation for Atmospheric Research

Montana State University

Nasa Langley Research Center

Wisconsin Alumni Research Foundation

Scott M Spuler

Matthew Hayman

Kevin S Repasky

Shane Mayor

Amin R Nehrir

Dirk Richter

Edwin W Eloranta

Bruce Morley

Farzad Cyrus Foroughi Abari

Robert Stillwell

William A Cooper

Mike Spowart

A beam transmitter, a receiver, and a LIDAR, along with methods to operate each are provided. The beam transmitter comprises a first and a second transmission channel (), each transmission channel including a first online laser, a first offline laser, and a first laser transmission selection switch operable to toggle between including the first online laser signal and the first offline laser signal in a first transmission beam. The beam transmitter further includes at least one light redirection device operable to coalign the first transmission beam with the second transmission beam. The receiver comprises a first splitter (), a first filter (), a first detector channel (), a second splitter (), a second filter (), and a second detector channel (). The LIDAR includes the beam transmitter, the receiver, and a shared telescope.

Differential absorption LIDAR for profiling temperature

A filter for a micropulse differential absorption LIDAR is provided. The filter comprises an etalon including a free spectral range substantially the same as a difference between a first laser wavelength and a second laser wavelength, the etalon further including a finesse providing substantial background noise suppression and substantially constant transmission of the first laser wavelength and the second laser wavelength over a predetermined range of wavelengths, and a first filter having a first filter bandpass selected to include the first laser wavelength and the second laser wavelength.

Optical filter

A shared optics and telescope for transmitting a transmission beam and receiving a return signal is provided. The shared optics and telescope includes a pair of axicon lenses operable to shape the transmission beam into an annular beam having an outer diameter and an inner diameter, a secondary mirror operable to deflect the annular beam into a deflected annular transmission beam, and a primary mirror that includes an inner mirror portion and an outer mirror portion, the inner mirror portion operable to expand the deflected annular transmission beam, and the outer mirror portion operable to collect the return signal.

Telescope

Lidar is an acronym for Light Detection And Ranging. The technology may be used to measure distance by illuminating a target with a laser beam and performing analysis on the reflected laser beam light. In the atmospheric sciences, Lidar may be used to study the optical depth of clouds, the impact of aerosols on clouds, and the interactions between aerosols and clouds on the climate. The present application proposes a lidar-based technology using a diode laser () beam sent through a tapered semiconductor optical amplifier () and an axicon pair expander () wherein the laser light may be transmitted through a telescope () at an object to be studied. Upon striking the object to be studied, the laser () is reflected and recovered by the telescope (). The reflected laser is then sent through a heated rubidium vapor cell () and a total detection channel () for analysis.

Diode laser based high spectral resolution lidar

A shared optics and telescope, a filter, and a micropulse differential absorption LIDAR are provided, with methods to use the same. The shared optics and telescope includes a pair of axicon lenses, a secondary mirror, a primary mirror including an inner mirror portion and an outer mirror portion, the inner mirror portion operable to expand the deflected annular transmission beam, and the outer mirror portion operable to collect the return signal. The filter includes an etalon and a first filter. The micropulse differential absorption LIDAR includes first and second laser signals, a laser transmission beam selection switch, a first laser return signal switch, and a toggle timer.

Micropulse differential absorption LIDAR

A photon counting system is provided. The photon counting system comprises an analog domain and a digital domain in communication with the analog domain. A detector is configured to detect photons. An analog digital converter is provided in the digital domain, while an amplifier circuit is provided in the analog domain that is configured to receive the detector's output, wherein the amplifier circuit's output is in communication with the analog digital converter. The output of the analog digital converter is in communication with a signal processing system that may perform accumulation of signals and store them in memory.

Analog photon counting

A method for correcting an ambient pressure measurement, a method for calculating a temperature, and an apparatus for affecting the same for an aircraft measuring system are provided. The methods include the steps of receiving an airspeed measurement from a laser sensor, receiving a total pressure measurement, and calculating an ambient pressure correction. A corrected ambient pressure or a calculated temperature may be calculated. The apparatus includes a laser sensor configured to provide an airspeed measurement, an aircraft instrument configured to provide a total pressure measurement, and a processing system.

Calibration of aircraft instruments using a laser sensor

A lidar system and method to enable simultaneous accurate and high spatial and temporal resolution measurements of atmospheric temperature, wind, and water vapor. The technology employs a laser (), a telescope (), an acousto-optic modulator () or an electro-optic modulator (), a Thulium-doped fiber amplifier (), and an optical circulator () which projects a laser signal into the atmosphere toward a phenomenon to be studied. The laser is reflected or backscattered by the atmospheric phenomena and retrieved by the telescope (), where the laser is processed by a signal sampler and processor () for analysis.

System and method to measure an atmospheric thermodynamic profile with a compact, all-fiber and eye-safe Lidar

A Raman shifter is provided with improved optical efficiency and robustness, particularly for high power applications. In one embodiment, a source system () includes a source pump laser () and a seed laser (). Beams from the pump laser () and seed laser () combine for transmission into a Raman cell (). Folding optics define a multi-pass pathway through the Raman cell (). Such folding optics may include an internal reflectance element. An entry window into the Raman cell, an exit window from the Raman cell, and the internal reflectance elements include surfaces disposed at a Brewster angle relative to the incident beam. The Raman cell medium is circulated in a direction transverse to the beam pathways through the cell. In this manner, improved optical efficiency and robustness is achieved as well as improved performance over a significant wavelength band.

Raman cell for high power applications

A lidar system capable of remotely identifying calibrated absolute aerosol backscatter coefficients of atmospheric aerosol particles by transmitting a beam of light and spectrally separating the intensity of Rayleigh and Mie backscattering is disclosed. The transmitter features high pulse energy to generate sufficient Rayleigh backscattering, enabling atmospheric scanning in a timely manner. The transmitter employs a seeded Nd:YAG laser and a seeded stimulated Raman scattering wavelength shifter to achieve narrow bandwidth, eye-safe laser pulses. The receiver employs a telescope, collimating lens, beam splitter, molecular absorption filter, focusing lenses, and avalanche photodiodes. Mie backscattering is blocked by the molecular absorption filter to provide a Rayleigh signal, which is used with knowledge of atmospheric density to calibrate the Mie signal. The system is intended for atmospheric research and aerosol monitoring applications where calibrated Mie scattering intensity is necessary to measure the optical depths of aerosol structures such as plumes, clouds, and layers.

Lidar system for remote determination of calibrated, absolute aerosol backscatter coefficients

An eye-safe atmospheric aerosol lidar featuring high transmit pulse energy to generate strong backscatter from long ranges in a single pulse together with an optically efficient receiver is disclosed. The transmitter employs a gas cell and non-focused laser beam geometry to convert short wavelength laser light to substantially safer and longer wavelength light by stimulated Raman scattering. The longer wavelength light is substantially safer than the shorter wavelength light thereby allowing the safe transmission of high energy pulses. The transmitter also features a diode injection seed and a beam expander which are effective to reduce the divergence of the long wavelength light below the field-of-view of the receiver. The receiver employs a telescope, collimating lens, interference filter, focusing lens, avalanche photodiode detector, amplifier and analog to digital converter. The transmit beam and receiver field of view are coaxial. Initial results demonstrate the ability of such technology to elucidate the structure of the atmosphere with high temporal and spatial resolution.

High pulse-energy, eye-safe lidar system

A polarization lidar system capable of remotely identifying characteristics of atmospheric aerosol particles by transmitting a polarized beam of light and analyzing polarization characteristics of received backscatter is disclosed. The transmitter features high pulse energy to remotely identify aerosol particles with substantially one pulse. The transmitter employs a thin film plate polarizer and a Raman wavelength shifter to achieve eye-safe, single-plane linearly polarized energy. The transmit beam and receiver field of view are coaxial. The receiver employs a telescope, a collimating lens, and a beam splitter. The beam splitter splits the received backscatter into a single-plane polarized beam whose polarization plane is parallel to the plane of transmission and a single-plane polarized beam whose polarization plane is perpendicular to the plane of transmission. Each split beam is directed through separate focusing lenses onto separate detectors. The detector signals are amplified and processed to remotely determine atmospheric aerosol particle characteristics.

Growing community of inventors

Westminster, CO, United States of America

Scott M Spuler