Southwest Sciences Inc

Method and apparatus for imaging internal structures of transparent and translucent materials

U. S. Patent 7,079,294, issued July 18, 2006

Optical coherence tomography (OCT) and spectral interferometry (SI) are imaging techniques that precisely measure depth into the sample using a broadband light source and optical interference techniques. These techniques can be applied to biomedical samples or to in nondestructive evaluation of coatings, for instance. The drawbacks of these approaches: OCT requires a very broad bandwidth detector, and SI is subject to background signals that limit the depth from which signals can be detected.

This invention describes a simple and robust modification of the SI technique. A mirror in one arm of the interferometer is dithered, and the return signal is detected with reference to the dither frequency. Thus spectra with a mirror phase of 180° are subtracted from spectra with a phase of 0°. A dynamic range of 105 dB has been demonstrated, permitting imaging into samples as deep as 3 mm. Background signals present in SI are eliminated. Depth resolution of 11 um has been achieved in such samples.

Contact Information

Southwest Sciences, Inc.
1570 Pacheco St., Suite E-11, Santa Fe, NM 87505
tel. (505) 984-1322/ fax (505) 988-9230



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