User-friendly Raman sensor for numerous applications
Traditional micro-Raman systems are capable of fine-scale mineralogy; but these are used for on-site analysis. Most micro-Raman systems are designed and implemented to operate in dark rooms. Such Raman systems: (1) require sample collection and (2) require protection from background radiation from daylight. With the use of continuous wave (CW) lasers and a time-unsynchronized detection approach, it is also difficult to distinguish biofluorescence from mineral luminescence. These limitations will significantly reduce the capability of these micro-Raman systems in terms of the variety of samples that can be analyzed.
- Ultra-compact Raman measurements of separation over a range of several centimeters (without sample collection)
- Day or night operation Detection of all minerals: light and dark
- Detection of water, biological and organic compounds.
- Raman signal detection in the presence of fluorescence
Researchers at NASA’s Langley Research Center have developed an ultra-compact Standoff micro-Raman sensor that will provide a superior instrument for many commercial applications, as well as future NASA missions. This sensor will be able to collect Raman spectra and quickly generate mineralogical images of daytime targets from a distance of several centimeters without the need to collect the sample. This sensor is capable of inspecting and identifying minerals, organics, and biogenic materials within several centimeters and with a high resolution of 10 micrometers.
This instrument will overcome some of the limitations (requiring sample collection and daylight background radiation shielding) of traditional micro-Raman systems to provide a superior instrument. The instrument will perform Raman spectroscopy from a miniature device (handheld or mounted on a small moving head). The instrument will allow investigation of mineralogy, biology, fluorescent trace elements, biological materials, polar ices and gas hydrates. You will perform a very high resolution (micrometer) objective demonstrated at an objective distance of 20 centimeters.
The technology has several potential applications:
- Analysis of precious metals and jewels.
- Narcotic identification
- explosives detection
- Inspection of incoming raw materials, quality control of the final product and other applications in the pharmaceutical industry
- Detection and identification of contaminants in silicon wafers
- geological investigation
Patent number: 11,175,232
Ultra-compact separation micro-raman sensor
December 19, 2018 – UNITED STATES OF AMERICA REPRESENTED BY THE ADMINISTRATOR OF NASA
Ultra-compact separation micro-Raman sensors configured to receive Raman scattering from a substance are described. A laser device can be configured to transmit a laser at a first wavelength. The laser can expand to a predetermined size, focus through a lens, and strike an unknown substance. A filter can reflect the laser and Rayleigh scattering from the substance, but can allow Raman scattering and laser-induced fluorescence from the substance. One or more lenses and/or filters may receive and pass Raman scattering and/or laser-induced fluorescence to a light sensor. Received Raman scattering and/or laser-induced fluorescence can be compared to known substance fingerprints to determine substance identity. The wavelength of the laser, the width of the laser and other parameters can vary depending on the distance between the ultra-compact micro-Raman separation sensor and the substance.
CROSS-REFERENCE TO RELATED PATENT APPLICATION(S)
This patent application claims benefit and priority from 62/617,684, filed January 16, 2018, the contents of which are incorporated herein by reference in their entirety.
STATEMENT ON FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
The invention described herein was made in the performance of work under contract to NASA and by an employee of the United States Government and is subject to the provisions of Public Law 96-517 (35 USC § 202) and may be manufactured and used by or for the Government for government purposes without the payment of any royalty thereon or otherwise. Pursuant to 35 USC § 202, the contractor elected not to retain title.
Determining the identity of a substance, such as a mineral, can be difficult, especially when the substance cannot be easily recovered and analyzed. For example, during space explorations, a crew may wish to identify a substance on a planetary surface, but the substance may be too difficult to retrieve and test, much less bring back to Earth for more rigorous testing. Additionally, some tests that can be used to identify a substance (eg, tests that require combustion) may be difficult to perform outside of a laboratory and/or Earth environment.
One way to identify substances is Raman spectroscopy. Raman spectroscopy involves shining light (eg, from a laser) at a particular wavelength into a substance. While the vast majority of substance scattering as a result of light is at the same wavelength as light (a phenomenon called Rayleigh scattering), a fraction of light (called Raman scattering) is scattered at a longer wavelength. or shorter wavelength than light. This higher or lower wavelength results from the transfer of energy between the light and the substance. Wavelength analysis of Raman scattering provides information about molecular vibrations, photons, excitation, and/or other energetic information about the substance, which can be analyzed to determine the identity of the substance.
Raman spectroscopy generally requires that a substance be manually collected and shielded from ambient radiation. Take, for example, a lunar rover with a Raman spectroscopy device on the surface of the Moon. A rover operator may wish to determine the identity of an unknown substance found on the Moon. The Raman spectroscopy device can be configured to shine a laser at the substance at 500nm and measure the Raman scattering of the substance. Even if the Raman spectroscopy device measurement device was configured to filter light at wavelengths corresponding to the laser (eg, 500nm), ambient radiation (eg, sunlight) can understand a multitude of wavelengths that make identification and measurement difficult. extremely difficult Rayleigh scattering. To avoid such ambient radiation, the lunar rover may be required to shield the substance from other forms of radiation, for example, by using a cover. In some cases, for example when the Raman scattering of a substance is particularly similar to ambient radiation, the substance may require collection (eg within a container) and/or transport to a darkroom for further analysis. Such collection and/or transport can be particularly difficult where, for example, the substance is too hard, heavy or brittle to be easily collected and/or transported, too large or unwieldy to cover adequately, and/or where frequent measurements they can be made in such a way that harvesting and storage can put undue mechanical stresses on the harvesting devices.
Raman spectroscopy is conventionally performed using light in a continuous waveform, which can impede the accuracy of measurements. For example, a particular form of biofluorescence may be short-lived, while a particular form of mineral luminescence may be long-lived. The use of a continuous wave laser, for example, prevents the easy distinction between biofluorescence and luminescence, particularly in the presence of already distracting ambient radiation.
Aspects of the present disclosure include a stand-alone ultra-compact Raman sensor and methods related thereto. In accordance with one or more embodiments, a laser device may transmit a laser at a particular wavelength, which may be reflected and filtered to strike a surface of an unknown substance. Rayleigh scattering, Raman scattering, and laser-induced fluorescence of the substance may occur. Rayleigh scattering may be filtered and/or Raman scattering and laser-induced fluorescence may be filtered, diffused and/or reflected at one or more sensors. A light sensor can analyze the spectrum of received light and determine if the received light matches a fingerprint of known substances.
In one aspect, the stand-alone ultra-compact Raman sensor is configured to operate without requiring the substance to be shielded from ambient radiation and/or without requiring direct physical contact or movement of the substance. Using a beam expander, one or more lenses, one or more filters, and/or by varying the properties of the laser, the stand-alone ultra-compact Raman sensor can isolate Raman scattering from the substance. In one or more embodiments, the separate ultra-compact Raman sensor may be reconfigured based on, for example, the distance between the separate ultra-compact Raman sensor and the substance. For example, the size of the laser can be controlled by a beam expander such that one or more parts of the substance are exposed to the laser and one or more second parts of the substance are not exposed to the laser. Similarly, the standalone ultra-compact Raman sensor can also vary, for example, the laser wavelength based on a prediction of substance identity. One or more of the changes or alterations to the system or device may be made automatically based on a processor that processes computer-executable instructions on a computer-executable medium. As such, 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 better understood and appreciated by those skilled in the art by reference to the following specification, claims, and accompanying drawings.
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