Systematic error analysis and correction in quadriwave lateral shearing interferometer

To obtain high-precision and high-resolution measurement of dynamic wavefront, the systematic error of the quadriwave lateral shearing interferometer (QWLSI) is analyzed and corrected. The interferometer combines a chessboard grating with an order selection mask to select four replicas of the wavefront under test. A collimating lens is introduced to collimate the replicas, which not only eliminates the coma induced by the shear between each two replicas, but also avoids the astigmatism and defocus caused by CCD tilt. Besides, this configuration permits the shear amount to vary from zero, which benefits calibrating the systematic errors. A practical transmitted wavefront was measured by the QWLSI with different shear amounts. The systematic errors of reconstructed wavefronts are well suppressed. The standard deviation of root mean square is 0.8  nm, which verifies the stability and reliability of QWLSI for dynamic wavefront measurement.