Method and Apparatus for Full Phase Interferometry
U. S. 7,394,546, issued July 1, 2008
This invention provides a way to create high resolution, subsurface images. Such images are needed in many fields including biology and medicine (tissue structure and pathology, cell morphology, tumor detection), materials science (composite, ceramic and microstructured materials characterization), and semiconductor device characterization. The scientific name for this invention is complex differential spectral interferometry, or CDSI. The term "complex" refers to its ability to determine both the real and imaginary parts of the interferogram. This is equivalent to distinguishing a sine wave from a cosine wave.
CDSI is closely related to differential spectral interferometry (DSI) but improves DSI to better recover complex interferograms and resolve the complex conjugate ambiguity. Key components include the dithered mirror (which modulates the path difference at frequency f) and the lock-in amplifiers operating at f and 2f. Compared to other methods of full phase interferometry, the present invention provides a better complex conjugate rejection ratio and allows simultaneous acquisition of the quadrature components of the complex spectral interferogram.
Other related optical techniques include confocal and two-photon fluorescence microscopy, confocal Raman spectroscopy, near-field optical microscopy, and optical coherence tomography (OCT), which is a term used for optical coherence reflectometry (OCR).
For more information, contact Kris Peterson.
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