Computer vision-based method of pre-alignment of a channel optical waveguide and a lensed fiber

The work is devoted to a technique of pre-alignment of a lensed fiber and a channel waveguide of a photonic integrated circuit using computer vision methods. The design and main units of a machine vision system with illumination of the adjusted objects in reflected light are described. The technique includes detection of the spatial position of the end face of the photonic integrated circuit, fixed at an angle of $90\pm 1^\circ$ to the horizontal axis of the frame, detection of the coordinates of the end face of the lensed fiber, and the subsequent correction of the position of the lensed fiber using a manipulator system. We propose a method of searching and selecting a single line corresponding to the end face of a photonic integrated circuit using a Hough transform; methods for grouping discontinuous contours of the lensed fiber and true contour determination. These methods are based on a priori knowledge of the lens geometry. Also, we describe options for suppressing noise and overcoming various defects in images. It has been shown experimentally that the error of angle determination of a lensed fiber depends on the distance between the lens and the end face of the photonic integrated circuit. The presented technique makes it possible to determine the longitudinal and angular displacements between the fiber lens and the end face of the photonic integrated circuit with errors less than $4$ $\mu$m and $0.05^\circ$, respectively.