High-precision laser centroid extraction algorithm for slight positional variations using four-quadrant detectors

This article presents a high-precision algorithm for extracting laser centroids using a four-quadrant detector (4QD), specifically designed for situations where laser position shifts happen on the nanoscale. The algorithm uses an iterative method to create a functional relationship between position changes and the differential output signals from the 4QD. We have validated the algorithm through simulations and experimental tests.