Dynamic beam-steering by a pair of rotating diffractive elements

Abstract

We experimentally demonstrate a compact, on-axis device for two-dimensional steering of the direction of a transmitted beam. It consists of two adjacent diffractive optical elements (DOEs) corresponding to two decentered Fresnel lenses with opposite optical powers. The DOEs can be rotated independently. By controlling the rotation angles of the two elements it is possible to direct an incident beam into a continuous two-dimensional range of deflection angles. Compared to a classical grating scanner based on two adjacent gratings, our approach has the advantage that undesired diffraction orders are defocused. Therefore, if such a system is used in an optical scan head for laser material processing, the undesired diffraction orders do not focus in the plane of the work piece, thus avoiding damage due to hot spots. Another application of the device is to extend the field of view in imaging systems. There, the device may be placed in front of the entrance lens of a camera, which allows one to control the viewing direction without the need of turning the whole camera system.