Optical phase-shifting methods based on low coherence laser for large aperture Fizeau interferometer

Abstract PZT is commonly used as the phase shifter in interferometric systems with small apertures for decades. However, it becomes more difficult to be applied to the system with large aperture. In this paper, the phase shifting procedure is moved to the source module with a low coherence laser, which makes phase shifting independent of the large interference cavity. The path matching procedure based on intensity variation is introduced to compensate the path difference between the two arms. The experiments based on PZT and wavelength tuning methods are both carried out on a 600mm Fizeau interferometer for verification of the proposed method. The difference between the two results is 0.0015λ(PV). Besides, repeated experiments are performed, showing excellent repeatability and stability and the standard deviation of RMS is 0.0011λ via PZT method. The analysis of error sources is also performed, including the poor contrast and the nonlinearity of PZT. Both the experimental results and the error analysis verify the feasibility of the proposed method in large aperture interferometer.