Tunable Lau effect: Optical frequency sweeping

For controlling the visibility of the Lau patterns, we disclose the use of a zoom system that implements a zero-throw, tunable magnification of the source grating. The zoom system implements a nonmechanical technique, for controlling the in-register condition of the Lau patterns. We show that one can increase the sharpness the Lau fringes, by exploiting the noncyclic autocorrelation of the Fourier coefficients, associated to the grating acting as spatial filter. The described technique can be thought of as a frequency sweeping technique, which tunes the visibility and the shape of the Lau fringes. •Controlling Fringe Visibility in the Lau Effect.•Varifocal Lenses for Magnifying the Source Grating.•Noncyclic Autocorrelations of the Barker Sequences.•Autocorrelation Coefficients for sharp fringes.