Based Virtual Grating And Moire Fringe Measuring The Interference Cavity Air Turbulence

The virtual grating phase shifting moire fringe is a method to manipulate the static interferogram with carrier fringes. The carrier frequency can be estimated by an the computer program, and four phase shifting reference interferogram can be generated. Each reference interferogram is superimposed to the actual interferograms to be tested. Then four moire fringe patterns are created. According the phase shifting algorithm, the four phase shifting interferograms are manipulated to get the wavefront information.The paper introduces several frequently-used methods to measure air disturbance.The principle of the method to measure air disturbance based on interferometry and the method of virtual grating phase shifting moire fringe is studied. According the principle, computer program for manipulating the interferogram is written, including virtual grating creating, moire fringe generation, phase unwrapping, and so on. Through some experiments with ZYGO interferometer, the infection to measurement result for air disturbance in interferometer cavity is quantitatively analysed, including different length of the cavity, heating the different area of optical cavity. Through some experiments with infrared interferometer, the infection to measurement result for air disturbance in interferometer cavity is also analysed, including different length of the cavity, heating in the cavity and blowing smog into the cavity.