Use of diffracted Gaussian beams in position sensing

Authors present a novel method in position sensing based on the diffraction of Gaussian beams, their propagation properties and their spatial modulation . The idea is to focus two modulated and collimated Gaussian beams into a slit. The resulting diffracted beams at the slit illuminate a photodetector whose signal is demodulated by a lock-in amplifier. The response of the lock-in amplifier is a function of the slit position with respect to the two modulated Gaussian beams. Resolution of 25 pm can be achieved.