Phase Shifting Interferometry And Two Dimensional Phase Grating Transverse Shear Technology Research And Application

Based on the principle of phase shift interferometry and experimental conditions, we designed a photoinduced anisotropic phase shifter on the base of bacteriorhodopsin. It was used to measure the phase shifting. Because that linear polarization induced light was absorbed selectively by randomly distributed polar bacteriorhodopsin molecular, the molecular then showed a nonuniform orientation distribution, so it leaded to a macroscopic anisotropy. This macroscopic anisotropy was closely related to polarization properties of the induced light. When the circularly polarized light got through the anisotropic bacteriorhodopsin film, the characteristics of emergent light were completely determined by the polarized induced light. A new phase shifter was designed on the base of the principle above. The principle of phase shifting interferometry for phase shifter was derived by Jones matrix method. As for this type of phase shifter, we do not need to move any internal device of Michelson interferometer in the work process. What we do is that changing polarization orientation of the induced light in the external light path, and then the phase shift is generated correspondingly in interference pattern. The experimental device is beneficial to improve the ability of anti vibration.The obtained reconstruction results by the least square method are consistent with the actual phase, that is to say, the feasibility of this phase shifter is verified. In application process of photoinduced anisotropic phase shifter based on bacteriorhodopsin films, we collect four interference patterns with CCD by four step phase shifting method, and then use the least squares phase unwrapping algorithm. Under the experimental conditions of 4 times and 10 times imaging magnification, as the micro lens array is used as experimental sample, good reconstruction results are obtained. The feasibility and stability of the phase shifting device are further proved. Because that the phase shift interference experiment is based on the principle of double light path interference, the object lights and reference lights propagate along the different optical path. It is not suitable for the measurement in practical applications, because the optical path is easily influenced by the environment conditions(vibration, noise etc.). The transverse shear technology is a shear light path interference technique. It does not need the strict experimental conditions. Besides, its anti vibration ability is strong, the operation is simple, and the experimental effect is relatively stable. Thus, it is often used at nondestructive testing and engineering measurement field in practical application.In this paper, via using the two-dimensional transverse shear principle and phase grating lateral shearing interferometer, the polyvinyl alcohol(PVA) films were measured. According to the Fourier transform results of the interference pattern, the spectrum distribution of the interference pattern was obtained. The phase derivatives in the X direction and Y direction were further obtained by spectrum distribution, and then good results were got through least squares reconstruction algorithm. Compared the phase shift interference reconstruction result with shearing interferometry for micro lens array, both methods can obtain the profile information. However, the shearing interference shows low requirements on the environment and the quality of laser light source. Besides, it is not sensitive to vibration. So, it is suitable for the application outside the laboratory.The phase gradient interference pattern obtained by four step phase shift interference is used to solve the phase gradient in two-dimensional plane of tested phase object, and then the phase distribution of the object is obtained by linear integral of the phase gradient, which is called phase gradient integral method. Because it can avoid the complicated phase unwrapping process during phase reconstruction, this method is a simple and effective phase reconstruction algorithm. However, when the flat convex cylindrical lens was used as measured phase object in the previous phase shift experiments, the reconstruction results are not consistent with the actual phase object by the phase gradient integral method when the objects have linear phase distribution. That is because the phase gradient of linear phase is zero. In order to correctly reconstruct the phase of the object, we should make corrections for phase gradient reconstruction for linear phase distribution. By using the least square method and the phase gradient integral algorithm, the phase reconstruction by experimental results of the micro lens array is similar with the actual phase object. It is an important guiding for phase distribution reconstruction by using phase gradient integral method.