Hybrid Young interferometer for high resolution measurement of dynamic speckle using high birefringence liquid crystal

It is well known that the Young interference experiment is the fundamental setup to combine two beams and to construct the phase modulated light. Moreover, homodyne phase demodulator is based on signal decoding in back Fourier focal plane using bicell photodetector (B-PD). On the above base, we propose a novel experimental approach to the signals demodulation by using the optical interferometer which operates in homodyne mode, combined with liquid crystal spatial light modulators operating both phase as speckle modulator. Dynamic phase changes between the two beams can be controlled by monopixel liquid crystals cell placed in one branch of the interferometer. A phase modulation effect in a signal arm of interferometer is observed as a dynamic shift of the speckle pattern. Simple arithmetic combination of signals from B-PD placed in speckle pattern plane is only one necessary numerical manipulation to obtain exactly phase difference. Concept of signals demodulation in the Fourier focal plane can be only used for exactly defined geometrical (B-PD as well as Young interferometer) and physical parameters (polarization, wavelength). We optimize the setup geometry to obtain extremely high measurement resolution. In this paper we focus on the principles of operation of each part of the system as well as discussion their requirement in order to increase the signal to noise ratio.