High-precision Positioning Algorithm Research Based On The Four-quadrant Detector

With the gradual development of modern technology, the requirements of target tracking and positioning accuracy are getting higher and higher in target measure, the end of the guided weapons, laser communication and collimation and many other areas. The main subject is taking analysis of four-quadrant detector’s characteristics (QD) which commonly used in the positioning system. Because of the low noise, high sensitivity and high bandwidth characteristics, QD is widely used in target tracking, positioning and collimation system.This topic comes from the actual project," the invented of displace measurement system based on QD ", the project mainly consists of three parts, displace measurement system’s error correction method, high-precision positioning algorithm based on QD, the develop of measurement system devices. This topic assumed in this subject is the second part, the high-precision positioning algorithm based on QD.This topic first does a research of the theory how QD worked as well as positioning theory of QD. We theoretically analyzed the effect factors of QD positioning accuracy. At present, when we use the generic positioning algorithm to locate the spot center, the spot energy distribution model we used is uniform, and the relationship between the error signal and the spot position to take the linear approximation approach. Using Matlab to simulation and analysis this algorithm, we get the error generated by the algorithm itself dominate the impact of the positioning accuracy. For the shortcomings of universal positioning algorithm, this paper studies generic algorithm based on a high-precision positioning algorithm based on the Gaussian spot model for accurate, rapid detection of the spot position information.This paper elaborates the theory of high-precision positioning algorithm and implementation process, and using Matlab to do a simulation of the algorithm. Obtained by the simulation results of the two algorithms, the use of QD for target tracking and positioning, high-precision positioning accuracy of the algorithm is less than0.2μm, compared to the170μm error of the general algorithm has been greatly improved.QD system, the spot center location positioning device performance and detection accuracy than by the positioning algorithm, the width of the dark areas as well as the spot size will have an impact on the four-quadrant detector performance. Obtained through simulation: the dynamic range of the detector sensitivity and detection of the spot size will have an impact; the wider the width of the dark zone, the greater the impact on the QD positioning accuracy.