Easy-to-use Raman sensor for many applications

Conventional micro-Raman systems can perform fine mineralogy. However, they are used for in situ analysis. Most micro-Raman systems are designed and implemented for darkroom operation. Such Raman systems require (1) sample collection and (2) shielding of sunlight background radiation. Using continuous-wave (CW) lasers and non-time-gating detection approaches, it is also difficult to distinguish between biofluorescence and mineral luminescence. These limitations greatly reduce the capabilities of these micro-Raman systems in terms of the types of samples that can be analyzed.

advantage

• Standoff ultra-compact Raman measurements in the range of a few centimeters (no sample collection)
• Day or night operation Detection of all minerals: light and dark
• Detection of water, biological and organic compounds
• Detection of Raman signal in the presence of fluorescence

technology

Researchers at NASA Langley Research Center have developed a Standoff Ultra-Compact micro-Raman sensor that provides an excellent instrument for future NASA missions as well as many commercial applications. The sensor collects Raman spectra and can quickly produce mineral images of targets during the day from a distance of several centimeters without the need to collect samples. The sensor can inspect and identify minerals, organics and biological materials to within a few centimeters and with a high resolution of 10 micrometers.

This instrument overcomes several limitations of conventional micro-Raman systems (requiring sample collection and shielding of sunlight background radiation) to provide a superior instrument. This instrument performs Raman spectroscopy from a small device (handheld or mounted on a small rover head). The instrument enables mineralogy, biology, fluorescent trace element, biomaterials, polar ice, and gas hydrate investigations. It offers very high resolution objectives (micrometers) with object distances within 20 cm.

application

This technology has several potential applications.

• Analysis of Precious Metals and Jewelry
• drug identification
• explosives detection
• Inspection of incoming raw materials, QC of final products, and other uses in the pharmaceutical industry
• Detection and identification of contaminants on silicon wafers
• Geological survey

Publication

Patent number: 11,175,232

Standoff ultra-compact micro-Raman sensor

December 19, 2018 – United States of America Represented by NASA Administrator

A stand-off ultra-miniature micro-Raman sensor configured to receive Raman scattering from a material is disclosed. The laser device may be configured to transmit laser at the first wavelength. A laser can be magnified to a given size, focused through a lens, and incident on an unknown substance. Filters may reflect laser and Rayleigh scattering from the material, but may allow Raman scattering and laser-induced fluorescence from the material. One or more lenses and/or filters can receive the Raman scattered and/or laser-induced fluorescence and pass it to the optical sensor. The received Raman scattering and/or laser-induced fluorescence can be compared to known fingerprints of the substance to determine the identity of the substance. The laser wavelength, laser width, and other parameters can be changed based on the distance between the standoff ultra-compact micro-Raman sensor and the material.

explanation

Cross-reference to related patent applications

This patent application claims the benefit of and priority to 62/617,684 filed January 16, 2018, the contents of which are hereby incorporated by reference in their entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The inventions described herein were made by employees of the U.S. Government under contract to NASA, are subject to the provisions of Public Law 96-517 (35 USC § 202), and are licensed by: may be manufactured and used. For government purposes and for government purposes without royalty payments. Pursuant to 35 USC § 202, the contractor has elected not to retain title.

Overview

Identifying the identity of a substance such as a mineral can be difficult, especially if the substance cannot be easily obtained and analyzed. For example, during space exploration, a crew member might want to identify material on the surface of a planet, but that material would be very difficult to retrieve and test, let alone for more rigorous testing. cannot be brought back to Earth. Additionally, some tests that can be used to identify substances (eg, tests that require combustion) can be difficult to perform outside the laboratory and/or terrestrial environment.

One way to identify substances is Raman spectroscopy. Raman spectroscopy involves shining light (eg, from a laser) at a particular wavelength on a substance. Most of the resulting scattering of light from matter occurs at the same wavelength as the light (a phenomenon called Rayleigh scattering), but some of the light (called Raman scattering) is scattered at higher wavelengths. increase. Or wavelengths lower than light. This higher or lower wavelength results from the energy transfer between light and matter. Analysis of Raman scattering wavelengths provides information about molecular vibrations, photons, excitations, and/or other energy information about matter and can be analyzed to determine the identity of matter.

Raman spectroscopy typically requires the material to be manually collected and shielded from ambient radiation. For example, consider a lunar rover with a Raman spectrometer on the lunar surface. Rover operators may want to identify unknown materials found on the moon. A Raman spectrometer can be configured to irradiate a material with a laser at 500 nm and measure Raman scattering from the material. Even if the Raman spectrometer’s measurement device is configured to filter out light at wavelengths corresponding to lasers (e.g. 500 nm), ambient radiation (e.g. light from the sun) is a multitude of objects to identify and measure. May contain wavelengths. Computing Rayleigh scattering is very difficult. To avoid such ambient radiation, the lunar rover may need to shield materials from other forms of radiation, for example using covers. In some cases, e.g., if the Raman scattering of a material is particularly similar to environmental radiation, the material may need to be collected (e.g., in a container) and/or transported to a darkroom for later analysis. I have. Such collection and/or transport may be limited, for example, if the material is too hard, heavy or fragile to be easily collected and/or transported, if it is too large or cumbersome to adequately cover, and / or can be especially difficult when frequent measurements are required. Created so that collection and storage can put undue mechanical stress on the collection equipment.

Traditionally, Raman spectroscopy is performed using continuous waveforms of light, which can compromise measurement accuracy. For example, certain forms of biofluorescence may be short-lived, whereas certain forms of mineral luminescence may be long-lived. For example, the use of continuous wave lasers prevents easy differentiation between biofluorescence and luminescence, especially in the presence of already distracting ambient radiation.

summary

Aspects of the present disclosure include standoff micro-Raman sensors and associated methods. According to one or more embodiments, a laser device can transmit laser at a particular wavelength, which can be reflected and filtered to strike the surface of an unknown material. Rayleigh scattering, Raman scattering, and laser-induced fluorescence from matter can occur. Rayleigh scattering can be filtered out, and/or Raman scattering and laser-induced fluorescence can be filtered out, diffused, and/or reflected back to one or more sensors. A light sensor analyzes the spectrum of the light it receives and determines whether the light it receives matches the fingerprint of a known substance.

In one aspect, the standoff micro-Raman sensor is configured to operate without the need to shield the material from ambient radiation and/or without requiring direct physical contact or movement of the material. Through the use of beam expanders, one or more lenses, one or more filters, and/or various properties of the laser, stand-off ultra-compact Raman sensors can separate Raman scattering from matter. . In one or more embodiments, the standoff micro-Raman sensor can be reconfigured based on, for example, the distance between the standoff micro-Raman sensor and the material. For example, the size of the laser may be controlled by a beam expander such that one or more portions of the material are exposed to the laser and one or more second portions of the material are not exposed to the laser. Similarly, stand-off ultra-compact Raman sensors can, for example, change the laser wavelength based on material identity predictions. One or more of the changes or modifications to a system or device may be automatically performed based on a processor processing computer-executable instructions on a computer-executable medium. Accordingly, the system or device can operate more efficiently than known systems or methods.

These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and accompanying drawings.

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Original NASA Presentation

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