Invention Grant
- Patent Title: Method and apparatus for simultaneous observation of three-degrees of vibrational freedom using single heterodyne beam
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Application No.: US15088201Application Date: 2016-04-01
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Publication No.: US09651477B1Publication Date: 2017-05-16
- Inventor: Bradley W. Libbey , James D. Perea
- Applicant: The United States of America, as represented by the Secretary of the Army
- Applicant Address: US DC Washington
- Assignee: THE UNITED STATES OF AMERICA, AS REPRESENTED BY THE SECRETARY OF THE ARMY
- Current Assignee: THE UNITED STATES OF AMERICA, AS REPRESENTED BY THE SECRETARY OF THE ARMY
- Current Assignee Address: US DC Washington
- Agent Richard J. Kim
- Main IPC: G01N21/17
- IPC: G01N21/17 ; G01H9/00

Abstract:
A laboratory system has demonstrated the measurement of three degrees of vibrational freedom simultaneously using a single beam through heterodyne speckle imaging. The random interference pattern generated by the illumination of a rough surface with coherent light can be exploited to extract information about the surface motion. The optical speckle pattern is heterodyne mixed with a coherent reference. The recorded optical data is then processed to extract three dimensions of surface motion. Axial velocity is measured by demodulating the received time-varying intensity of high amplitude pixels. Tilt, a gradient of surface velocity, is calculated by measuring speckle translation following reconstruction of the speckle pattern from the mixed signal.
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