Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1992-05-20
1994-12-27
Warden, Robert J.
Optics: measuring and testing
By particle light scattering
With photocell detection
356351, 356357, 356360, G01B 902, G01B 1106
Patent
active
053770064
ABSTRACT:
A photoacoustic signal detection method for detecting information about a surface of a sample and a subsurface of the sample, including the steps of producing an optical frequency difference between an intensity-modulated excitation/probe light beam and a reference light beam, focusing the intensity-modulated excitation/probe light beam on the surface of the sample to generate a photoacoustic effect or a photothermal effect at the surface of the sample, thereby producing thermal distortions in the sample, causing heterodyne interference to occur between a reflected intensity-modulated excitation/probe light beam from the surface of the sample and the reference light beam to produce heterodyne interference light including a frequency component having a frequency equal to twice the intensity modulation frequency, converting the heterodyne interference light to an electric signal including a frequency component having a frequency equal to twice the intensity modulation frequency, extracting from the electric signal at least one of an amplitude and a phase of the frequency component having the frequency equal to twice the intensity modulation frequency, and detecting information about the surface of the sample and the subsurface of the sample based on the extracted at least one of the amplitude and the phase.
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Carpenter Robert
Hitachi , Ltd.
Warden Robert J.
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