High-Accuracy Angle Detection for the Ultrawide FOV Acquisition Scheme in Free-Space Optical Links

To achieve rapid establishment of free-space optical (FSO) links, we previously proposed an ultrawide field-of-view (FOV) acquisition scheme, which combines the fisheye lens and Voigt anomalous dispersion optical filter. In this paper, we focus on the angle detection accuracy of this ultrawide FOV acquisition scheme, which is one of primary factors for rapid establishment of FSO links. The positioning process is composed of two parts. One is the spot location, which acquires the position of the imaging spot of the incident beam. The other is the mapping from spot location to incident angle, with which the position of imaging spot can be turned into the angles of the incident beam. For the first part, an improved centroid locating algorithm is present to realize the subpixel accuracy of spot location, and theory and simulation are carried out to demonstrate the improved accuracy of this algorithm. For the second part, we propose the fisheye lens calibration algorithm, which integrates the fisheye lens projection model and natural neighbor interpolation algorithm. In addition, by combining with the measured data, the angle detection accuracy of this method can be improved gradually with the increased number of the measured data. The simulation results indicate that this new method can provide high-precision positioning of the laser beams, and the maximum angle detection error of this ultrawide FOV acquisition scheme can be less than 0.054° (0.94 mrad).