Lissajous figure-based single-frame collimation technique

An accurate collimation technique based on a double grating system is proposed. Transversal displacement of the grating is not required and then, automatic single-frame processing can be performed. Talbot self-images are projected onto a mask composed by several shifted diffraction gratings. A Lissajous figure is obtained with the signals acquired by a CMOS camera where the mask is simulated by software. The collimation degree is determined by measuring the ellipticity of the Lissajous figure. Visual or automatic procedures for simple and accurate collimation of a light source are proposed. Experimental results are obtained which show a resolution of δϕ ≈ 4.16 μrad in the divergence of the beam when a lens with focal length f = 25 mm and diameter D = 20 mm is used for collimation.