Moiré alignment and positioning using a synthetic Fresnel zone plate

A new method for optical alignment and positioning is proposed. The actual position and shape of a spherical wavefront emerging from an optical system to be aligned are interferometrically encoded as “live” fringes similar to a Fresnel zone plate (FZP). Any in-plane misalignment and inaccurate positioning are detected in real-time as a unique moiré pattern by overlapping the “live” fringes and a synthetic interferometric FZP which is regarded as a reference grating. Experimental data are presented and future applications are suggested.