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.
DIGITAL PHASE SHIFT POINT DIFFRACTION INTERFEROMETER AND OPTICAL SYSTEM WAVE ABERRATION MEASURING METHOD