Compact wavefront diagnosis system based on the randomly encoded hybrid grating

Abstract

A compact wavefront diagnosis system with nice repeatability based on the randomly encoded hybrid grating (REHG) is proposed. The REHG comes from the ideally calculated grating for quadriwave lateral shearing interference, and it consists of a binary amplitude grating and a phase chessboard. The phase chessboard simulates the phase modulation of the ideally calculated grating, while the binary amplitude grating is designed and fabricated based on the randomly encoding method. In this method, the amplitude distribution on the ideally calculated grating is firstly divided into discrete grids. And the radiant flux in each grid is quantized into several quantization levels. The binary amplitude grating is then generated by encoding the pixels in the grids with 1 and 0, which stands for whether the light can pass through or not, so that the total radiant flux in each grid on this grating approximate to the flux in the corresponding grid on the ideally calculated quadriwave grating. In addition, random pattern is employed in the encoding process to avoid introducing extra diffraction orders. The far-field diffractions of the REHG only contain the ±1 orders in two orthogonal directions, and no order selection mask is needed for quadriwave lateral shearing interference. Due to the common-path configuration, the wavefront testing results obtained by the REHG lateral shearing interferometer exhibits nice repeatability and good suppression over environmental noise and vibration.