2D automatic alignment of optical spatial filtering system by PID control

Abstract

In this work, an interface that allows the automation of the alignment process in spatial filter systems is proposed. Optical spatial filtering is a method used in interferometry for the generation of regular laser illumination beams, where a pinhole aperture is focused on a convergence point of a lens. For the experimental setup, an emerging laser beam is focused to a point, where the correct position of the aperture can be found by adjusting the linear displacement with motorized devices. To obtain the position of the pinhole in an (X, Y) plane, a displacement arrangement implemented with micrometric servomotors and a CCD camera; controlled by a PID control algorithm, is used. The automatic adjustment of the position of the resulting beam intensity pattern registered in the camera is carried out by the servo motors until the optimal position coordinates are found. Process control related to positioning and subsequent estimation is executed with Python and synchronized in Lab View.