Small Business/SBIR

Applications Vary for Mars Technology

LIQUID CRYSTAL TUNABLE FILTERS (LCTF) being developed for use in a future Mars mission rover are being used in a variety of research and low-cost commercial applications. This is being accomplished with Small Business Innovation Research (SBIR) program support from NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

Made by Cambridge Research and Instruments (CRI), the LCTF technology is used as optical filters that can be quickly tuned, electronically in a matter of milliseconds, to determine the best frequency and to select the best wavelength for imaging. The LCTF allows only specific colors of visible or infrared light to pass through to a camera lens.

A detailed and clear image is made by combining the available images using multispectral imaging techniques. With its optical properties, the liquid crystal is sandwiched between two sheets of material, usually a glass plate or other transparent material. The tunable filter is able to tune to the proper pass or reject frequency, thus allowing the selection of the best wavelength for imaging.

The medical imaging field has the most important commercial applications thus far. The LCTF is used in front of a microscope lens to quickly generate green, blue and red images, which are captured digitally using a monochromatic Charge Coupled Device (CCD) camera. These images, brought together, provide a clear color picture. Using a black and white (monochromatic) CCD camera for color pictures is important because it provides three times the spatial resolution of its color counterpart and is lower in cost.

Because there are no moving parts or changing of lens filters, the registration of the images is exact, with no blurring of the image. The picture requires no further processing and is readily saved or transmitted to another location.

Things not visible to the human eye can often be imaged using the LCTF and multispectral techniques. Separate images are prepared at different parts of the visible or infrared spectrum, and the images of their differences and contrasts are combined to prepare a new image. For example, a fingerprint may be difficult to see because of underlying printed material. Dyes highlight the fingerprint. Images are captured at parts of the spectrum where the dye is, and is not, visible. An image developed on the basis of the difference in images suppresses the writing and reveals the fingerprint. The Internal Revenue Service uses similar LCTF-based techniques to detect forgeries and altered documents.

JPL illustrated the power of multispectral imaging techniques using an LCTF when legible images of the Dead Sea Scrolls were obtained. Little contrast existed between the ancient papyrus and the ink, making it unreadable to the unaided eye. However, in the spectrum's near-infrared band, the parchment becomes more reflective while the carbon-based ink remains dark. An LCTF made it possible to quickly scan the spectrum for the best imaging frequency.

JPL is using the LCTF on the Field Integrated Design and Operations (FIDO) rover, a demonstration platform for next-generation technology for Mars exploration. The filter is placed in front of a panoramic camera on the rover, allowing it to prepare images in three distinct wavelengths. The images enable scientists to determine the type of minerals surrounding the rover. This information is used for target selection and navigation purposes.

For more information, contact Patricia McGuire at the Jet Propulsion Laboratory.
Call 818/354-1258, Fax: 818/354-2385, E-mail: Patricia.A.McGuire@jpl.nasa.gov Please mention you read about it inInnovation.