A battery-powered, pen-sized, portable instrument for measuring molecular fluorescence spectra of chemical and biological samples in the field has been proposed. Molecular fluorescence spectroscopy is among the techniques used most frequently in laboratories to analyze compositions of chemical and biological samples. Heretofore, it has been possible to measure fluorescence spectra of molecular species at relative concentrations as low as parts per billion (ppb), with a few nm spectral resolution. The proposed instrument would include a planar array (mosaic) of detectors, onto which a fluorescence spectrum would be spatially mapped. Unlike in the larger laboratory-type molecular fluorescence spectrometers, mapping of wavelengths to spatial positions would be accomplished without use of relatively bulky optical parts. The proposed instrument is expected to be sensitive enough to enable measurement of spectra of chemical species at relative concentrations

The proposed instrument (see figure) would include a button-cell battery and a laser diode, which would generate the monochromatic ultraviolet light needed to excite fluorescence in a sample. The sample would be held in a cell bounded by far-ultraviolet-transparent quartz or optical glass.

This Pen-Sized Instrument would measure the fluorescence spectrum of a sample with high resolution and sensitivity.

The detector array would be, more specifically, a complementary metal oxide/ semiconductor or charge-coupled-device imaging photodetector array, the photodetectors of which would be tailored to respond to light in the wavelength range of the fluorescence spectrum to be measured. The light-input face of the photodetector array would be covered with a matching checkerboard array of multi-layer thin-film interference filters, such that each pixel in the array would be sensitive only to light in a spectral band narrow enough so as not to overlap significantly with the band of an adjacent pixel. The wavelength interval between adjacent pixels (and, thus, the spectral resolution) would typically be chosen by design to be approximately equal to the width of the total fluorescence wavelength range of interest divided by the number of pixels. The unitary structure comprising the photodetector array overlaid with the matching filter array would be denoted a hyper-spectral mosaic detector (HMD) array.

To maximize the spatial resolution achievable by use of interference filters, it is necessary to ensure perpendicular incidence of light on the filters. In the proposed instrument, perpendicular incidence would be ensured by incorporation of a spatial filter between the sample cell and the HMD array. To minimize potential contributions of scattering of laser light, the HMD array would be oriented at a right angle to the ultraviolet laser beam.

To enable identification and characterization of molecules by use of the proposed instrument, it would be necessary to create a data library representing the HMD image outputs corresponding to fluorescence spectra of molecular species. A fully developed version of the instrument would include, as integral parts, an electronic memory containing the library and a processor for analyzing measurement data with reference to the data in the library.

This work was done by Kyung-Ah Son and Jeong Moon of Caltech for NASA’s Jet Propulsion Laboratory.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:

Innovative Technology Assets Management
JPL
Mail Stop 202-233
4800 Oak Grove Drive
Pasadena, CA 91109-8099
(818) 354-2240
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Refer to NPO-43539.

Topics:
Biological sciences Cartography Chemicals Imaging Imaging and visualization Lasers Metals Optics Parts Photonics Semiconductors
This Brief includes a Technical Support Package (TSP).
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Mosaic-Detector-Based Fluorescence Spectral Imager

(reference NPO-43539) is currently available for download from the TSP library.

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    Overview

    The document outlines NASA's development of a Mosaic-Detector-Based Fluorescence Spectral Imager, detailed in Technical Support Package NPO-43539. This innovative technology aims to enhance molecular fluorescence spectroscopy, which is widely used for analyzing chemical and biological molecules due to its high sensitivity (parts per billion) and high spectral resolution (sub-nanometer).

    The primary challenge addressed by this project is the miniaturization of fluorescence spectroscopy systems for in situ, real-time detection and monitoring in the field. Traditional fluorescence spectrometers often rely on moving filters, which can be bulky and inefficient. The document highlights several limitations of current technologies, including the size of linear variable filters, the restricted spectral ranges of wedge filters, and the need for optical paths in gratings.

    To overcome these challenges, the proposed solution employs a novel fluorescence detection scheme utilizing a mosaic-structured hyperspectral detector array (HMD). This array consists of multiple detectors, each equipped with a thin film filter and a silicon CCD/CMOS sensor tailored to specific wavelength ranges. This design allows for high-resolution hyperspectral analysis without any moving parts, making the device compact and portable.

    The fluorescence imager is designed to be pen-sized and battery-powered, offering high sensitivity and specificity with a rapid response time of less than three seconds. This capability is particularly beneficial for applications in chemical and biological warfare (CBW) detection, where quick and accurate analysis is crucial.

    Additionally, the document mentions the need for a data library of molecular fluorescence spectra, which will be integrated into the imager for field deployment. This electronic data library will enhance the imager's functionality by providing a reference for identifying and characterizing various chemical and biological molecules.

    In summary, the Mosaic-Detector-Based Fluorescence Spectral Imager represents a significant advancement in fluorescence spectroscopy technology, promising to deliver high-performance, portable solutions for real-time molecular analysis in various applications, including environmental monitoring and security. The project is part of NASA's broader efforts to leverage aerospace-related developments for wider technological and commercial applications.