Abstract: A new approach is proposed to detect the collimated phase of a beam. The common lateral shearing interferometer composed of a parall el plate was improved in structure, and frequency synthesis theory in Fourier optics was applied to the inspection of collimated light beam by means of lateral shearing interferometer. For the common lateral shearing interferometer, a beam can be judged by the density of interference stripes, while the judgment results from the tilt angle of the stripes in this article. After images have been obtained Radon transform is applied to judge the tilt of the interference stripes. Therefore, the range of beam’s caliber and its accuracy are enhanced in a wide-range.

Key words: inspection of collimated light beam, shearing interferometer, frequency synthesize of interference patterns