Digital Phase-Shifting Point Diffraction Interferometer and Optical System Wave Aberration Measurement Method

Abstract

A digital phase shift point diffraction interferometer. The interferometer consists of a light source (1), a small-hole mask (2), a first spatial light modulator (3), a second spatial light modulator (6), a two-dimension photoelectric detector (8) and a computer (9). The first spatial light modulator (3) is configured as a raster by means of the computer (9), and serves as a splitter. The second spatial light modulator (6) is configured as a pin hole window mask, and serves as a filter for filtering diffraction orders except 0 order and +1 (or -1) order, so as to enable 0-order light to achieve diffraction by means of a pin hole (61) to generate a quasi-ideal spherical wave serving as a reference light wave, and +1 (or -1) order light serves as an object light wave by means of a window (62). The two light waves interfere, an interferogram is acquired, and an optical system wave aberration to be measured is extracted from the interferogram. Also provided is a method for measuring a wave aberration of an optical system using a digital phase shift point diffraction interferometer. A distance between an object light wave and a reference light wave at image plane convergent points is adjustable, and therefore great interference fringe density is achieved without reduction of an interference fringe contrast.

Description

technical field [0001] The invention belongs to the field of optical detection, and in particular relates to a digital phase shift point diffraction interferometer and a method for measuring wave aberration of an optical system. Background technique [0002] The wave aberration measurement of optical imaging system is very important for imaging quality control. Interferometry is an important method for measuring wave aberration in optical imaging systems. Traditional interferometry uses a spherical reference mirror as a reference surface to generate spherical waves as reference light waves, which interfere with the object light waves to be measured to form interference fringes. The measurement accuracy of this type of method is limited by the surface shape accuracy of the reference surface. Due to the limitation of the manufacturing technology and cost of the high-precision reference surface shape, this type of method cannot meet the high-precision wave aberration measuremen...

AI Technical Summary

Problems solved by technology

[0003] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art, and to provide a digital phase-shift point diffraction interferometer and a method for measuring wave aberration of an optical system. Modulator, the spatial light modulator in front of the optical system is set as a grating through the computer, digital phase shift can be achieved by digitally moving the grating in the direction perpendicular to the grating lines, and the spatial light modulator of the image plane is set as a pinhole window mask , through the combined use of two spatial light modulators, the distance between the pinhole and the window of the image plane mask can be adjusted, the grating period is small, the distance between the pinhole window is large, and the grating period is large, the pinhole The distance between the windows is small, so as to avoid the problem of poor contrast of interference fringes, and also make the density of interference fringes adjustable

Images