Common-path and compact wavefront diagnosis system based on cross grating lateral shearing interferometer

Abstract

A common-path and compact wavefront diagnosis system for both continuous and transient wavefronts measurement is proposed based on cross grating lateral shearing interferometer (CGLSI). Derived from the basic CGLSI configuration, this system employs an aplanatic lens to convert the wavefront under test into a convergent beam, which makes it possible for CGLSI to test the wavefront of collimated beams. A geometrical optics model for grating pitch determination and a Fresnel diffraction model for order selection mask design are presented. Then a detailed analysis about the influence of the grating pitch, the distance from the cross grating to the order selection mask and the numerical aperture of the aplanatic lens on the system error is made, and a calibration method is proposed to eliminate the system error. In addition, the differential Zernike polynomials fitting method is introduced for wavefront retrieval. Before our experiment, we have designed several grating pitches and their corresponding order selection mask parameters. In the final comparative experiment with ZYGO interferometer, the wavefront diagnosis system exhibits both high precision and repeatability.

Generation and evolution of vortex array with variable-ratio lateral-shearing interferometry

“…The shear ratio β is equal to S/T, where S denotes the shear amount and T represents the beam diameter of the test wavefront in the image plane [32,33]. The bigger shear ratio means the smaller interference region and lower spatial resolution [32].…”

Variable-ratio lateral-shearing interferometry with a vortex-splitting grating

“…Different shear ratios respond to the different measurement accuracy. For example, the common-path cross grating lateral shearing interferometer (CGLSI) was presented in 2014, which is able to suppress the environment vibration and retrieve the wavefront under test [10]. In 2015, Tong Li et al continued their research and demonstrated a QWLSI based on randomly encoded hybrid grating (REHG) [11].…”

Simultaneous two-step phase-shifting lateral shearing interferometry for aspherical surface based on an orthogonal shear displacer

“…For example, YONG BUM SEO, et al [13] presented a new method for measuring free-form surfaces based on spatial phase-shifting lateral shearing interferometry, using a birefringence crystal to realize lateral shearing interference, but the optical path construction is more complex, the eight interference fringes were taken in a single exposure process, and the phase is reconstructed by four-step phase-shifting algorithms. For example, Tong Ling, et al [16] proposed a wavefront diagnosis system based on a cross grating lateral shearing interferometer, it has a common path and compact configuration structure and can be used to measure continuous and instantaneous wavefront. The cross grating is the beam displacer component in this system, and the mask lets only ±1 order diffracted light passe through it, to realize the lateral shearing in x-and y-directions.…”