Physical Sciences

There would be no repositioning for different observations of the same specimen.

A proposed optoelectronic instrument would perform several different spectroscopic and imaging functions that, heretofore, have been performed by separate instruments. The functions would be reflectance, fluorescence, and Raman spectroscopies; variable-color confocal imaging at two different resolutions; and wide-field color imaging.

The instrument was conceived for use in examination of minerals on remote planets. It could also be used on Earth to characterize material specimens. The conceptual design of the instrument emphasizes compactness and economy, to be achieved largely through sharing of components among subsystems that perform different imaging and spectrometric functions. The input optics for the various functions would be mounted in a single optical head. With the exception of a targeting lens, the input optics would all be aimed at the same spot on a specimen, thereby both (1) eliminating the need to reposition the specimen to perform different imaging and/or spectroscopic observations and (2) ensuring MICRO-EPSILON eddy 3700 NCDT 0.08 nanometer eddy-current displacement sensors NEW Xtreme Resolution! that data from such observations can be correlated with respect to known positions on the specimen.

ImageThe figure schematically depicts the principal components and subsystems of the instrument. The targeting lens would collect light into a multimode optical fiber, which would guide the light through a fiber-selection switch to a reflection/fluorescence spectrometer. The switch would have four positions, enabling selection of spectrometer input from the targeting lens, from either of one or two multimode optical fibers coming from a reflectance/fluorescence microspectrometer optical head, or from a dark calibration position (no fiber). The switch would be the only moving part within the instrument. For reflection spectroscopy, light from an incandescent lamp would be focused onto another multimode optical fiber, would pass through a mode scrambler, and would illuminate the specimen through a microscope head. Light reflected from the specimen would be collected through the same optical fiber and would be directed into the reflection/fluorescence spectrometer via beam splitter 1. To illuminate the specimen for fluorescence spectroscopy, light from an ultraviolet laser would be directed, via beam splitter 2, into the same optical fiber used to illuminate the specimen for reflectance spectroscopy. The fluorescent light from the specimen would be collected and sent to the reflection/fluorescence spectrometer in the same manner as that of the reflected light.

For Raman spectroscopy, light from a laser diode would be focused onto a single-mode optical fiber and would pass through fiber Bragg grating 1, which would lock the wavelength. This light would be guided through two directional couplers to the microscope head. Raman-shifted light captured by the lens would be collected through the same single-mode optical fiber, and would be guided to the Raman spectrometer through one of the directional couplers and fiber Bragg grating 2, which would reject the reflected (unshifted) light. The Raman spectrometer and its associated optical components were described in “Confocal Single-Mode-Fiber-Optic Raman Microspectrometer ”(NPO- 20932),NASA Tech Briefs , Vol.25, No.4 (April 2001), page 10a.

The imaging portion of the instrument would include a charge-coupled- device (CCD)color camera, which would be used to provide contextual information for the point-imaging (confocal) subsystems. The lens for this camera and the lens for confocal imaging would be different but integrated into a single unit in the microscope head, as depicted in the detail at the bottom of the figure. The aforementioned multimode optical fiber used for reflection and fluorescence spectroscopy and the aforementioned single-mode optical fiber used for Raman spectroscopy would also be used for confocal imaging at a lower and a higher resolution, respectively.

This work was done by Pantazis Mouroulis of Caltech for NASA ’s Jet Propulsion Laboratory . For further information, access the Technical Support Package (TSP) free on-line at under the Physical Sciences category. NPO-30650

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