초록 ▼

An ultrasound detection system that is relatively insensitive to rough workpiece surfaces, suppresses low frequency noise, and provides high sensitivity without the need for active stabilization. An optical probe beam is reflected and phase modulated by a workpiece surface that is being vibrated by

An ultrasound detection system that is relatively insensitive to rough workpiece surfaces, suppresses low frequency noise, and provides high sensitivity without the need for active stabilization. An optical probe beam is reflected and phase modulated by a workpiece surface that is being vibrated by ultrasound. A time-delay interferometer optically interferes the phase modulated probe beam with a time-delayed replica of itself. The optical interference generates optical interference fringes that move in accordance with the workpiece surface velocity. The interference fringes are detected by a non-steady-state photo-electromotive-force (NSS-photo-EMF) detector that generates an output signal when the frequency of fringe motion exceeds a predetermined threshold.

대표청구항 ▼

A detection system for detecting displacement of a workpiece surface, comprising: an optical beam generator which generates an optical probe beam and which is arranged so that said probe beam is reflected from said surface and phase modulated by said displacement, a velocity-sensing interferometer p

A detection system for detecting displacement of a workpiece surface, comprising: an optical beam generator which generates an optical probe beam and which is arranged so that said probe beam is reflected from said surface and phase modulated by said displacement, a velocity-sensing interferometer positioned to receive said reflected and phase-modulated probe beam and configured to generate, in response, interferometer beam that converge at a non-zero angle to form optical interference fringes which have a fringe motion in accordance with the velocity of said surface, and a fringe processing unit positioned to receive said interference fringes and configured to generate, in response, and output signal which corresponds to said fringe motion when the frequency of said fringe motion exceeds a predetermined threshold, wherein said fringe processing unit comprises a non-steady-state photo-electromotive-force (NSS-photo-EMF) detector.