Design of beam scanners based on Talbot-encoded phase plates

Abstract

Abstract Beam scanners have wide applications in many fields. But conventional scanners have many shortcomings such as limited scanning frequency, high cost and low reliability. At the same time, phase gratings are efficient devices for deflecting light in prespecified direction. We propose a new kind of optical beam scanner by using a Talbot-encoded phase plate. Our architecture is practical and easily fabricated and has stable capability. It includes a monochromatic light source, a programmed controlled shifter, a detector and a phase plate. This phase plate consists of a pair of complementary phase plates with Talbot phase coding structure. Talbot phase coding structure is a new kind of binary phase coding structure. There are periodically repeated gratings on the surface of the phase plates. The complementary plates are placed paralleled to each other and they can be shifted along the direction perpendicular to their central axes. When the light passes through the pair of phase plates, it will be deflected. And the relative shift between the two plates will determine the deflected angle. By changing the shift between the plates with the shifter, we can get accurately deflected angles. When there is no shift between the plates, the light will go straight without any deflection. We have designed the required phase plates according to the number of scanning points N, maximum deflected angle θ and the diffraction efficiency η. And satisfactory experimental results have been obtained. The phase plates can be mass-produced by employing the binary-optical manufacture technology so that the costs of the scanners can be reduced.