RESUMO
A multiaxis heterodyne interferometer concept is under development for observations of 5 deg of dynamic freedom using a single illumination source. This Letter presents a laboratory system that combines elements of heterodyne Doppler vibrometry, holography, and digital image correlation to simultaneously quantify in-plane translation, out-of-plane rotation, and out-of-plane displacement. The sensor concept observes a dynamic object by mixing a single optical field with heterodyne reference beams and collecting these combined fields at the image and Fourier planes, simultaneously. Polarization and frequency multiplexing are applied to separate two segments of a receive Mach-Zehnder interferometer. Different optical configurations are utilized; one segment produces a focused image of the optical field scattered off the object while the other segment produces an optical Fourier transform of the optical field scattered off the object. Utilizing the amplitude and phase from each plane allows quantification of multiple components of transient motion using a single, orthogonal beam.
RESUMO
A phase-resolved heterodyne shearing interferometer concept is under development for high-rate, whole field observations of transient surface motion. The sensor utilizes frequency and polarization multiplexing with two temporal carrier frequencies to separate each segment of a shearing Mach-Zehnder interferometer. Post-processing routines have been developed to recombine the segments by extracting the scattered object phase from Doppler shifted intermediate carrier frequencies. The processing routines provide quantitative relative phase changes and information required to generate phase resolved shearographic fringe patterns without temporal or spatial phase shifting. Separation of each segment allows for adjustment of shearing distance and direction as well as simultaneous whole field Doppler velocity (LDV) measurements. This paper presents background theory and numerical model results leading to a sensor concept.
RESUMO
A laboratory system has demonstrated the measurement of three degrees of vibrational freedom simultaneously 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 displacement, is calculated by measuring speckle translation following extraction of the speckle pattern from the mixed signal. This paper discusses the laboratory sensor concept, signal processing, and experimental results compared with numeric simulations.
