the system for deformation measurements by synchronizing it with the camera signal. The FCA is comprised of a Ȝ/2 wave plate for maintaining the polarization direction, a focusing lens, and a fiber-optic aligner. After FCA, the light is directed through a single mode polarized maintaining fiber from the FCA to the optical switch (OS). Fig. 1 Diagram of the set up for dual-wavelength DOEHS: LDD is the laser diode driver, LD is laser diode, M is the mirror, AOM is the accousto-optical modulator, FCA is the fiber coupler assembly, PM is the polarized maintaining fiber, OS is the optical switch, C is the collimator, Ȝ/2 is the Ȝ/2 wave plate, SFA is the spatial filter assembly, PBS is the polarizing beamsplitter cube, Ȝ/4 is the Ȝ/4 wave plate, PZT is the piezoelectric transducer, P is the polarizer, CCD is the CCD camera, SPS is the sound pressure system, OB is the object, and IP is the image and video processing computer. The optical head (OH) system arrangement is shown in Figure 2. This system is a Michelson configuration setup. The light coming from the OS is directed into a collimator (C), a Ȝ/2 wave plate and the spatial filter assembly (SFA). The function of the SFA is to filter high spatial frequencies of the beam and get a clean Gaussian beam profile. After the SFA, the light is directed through a polarized beamsplitter cube (PBS) which splits light into reference beam and object beam. The reference beam passes through a Ȝ/4 wave plate and is directed to a mirror (M) connected with a piezoelectric transducer (PZT) that is controlled by the IP and used for application of phase-shifting algorithms. The object beam is directed through the Ȝ/4 wave plate onto the object. The reflected object and reference beams are directed through the PBS again and combined at the surface of the CCD camera (CCD). Then the spatial intensity distributions recorded by the CCD are processed by the computer. 201
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