Collimated wavefront reconstruction based on wavelength phase-shifting shear interferometry

The lateral shearing interferometry based on wavelength phase-shifting is proposed to achieve the collimated wavefront reconstruction of an interferometer. The emergent wavefront of an interferometer is reflected by front and rear surfaces of a wedge respectively, and returns through a corner cube, forming shearing interferogram on the CCD of the interferometer. The wavelength phase-shifting method is used to extract the phase information of the shearing interference fringes to achieve the collimated wavefront reconstruction. The impact of the relative shear ratio on the accuracy of the wavefront reconstruction is analyzed and the relationship between the relative shear ratio and its influencing f actors is derived. The estimation method of the constant component of the OPD in wavelength phase-shifting is given. Three wavefronts have been measured and their PV (peak to valley) values are 3.22λ, 2.10λ and 0.83λ. This method simplifies traditional lateral shearing measurement of collimated wavefront and improves the measurement accuracy. It is particularly suitable for measuring emergent wavefront of wavelength phase-shifting interferometers.