Extended the linear measurement range of four-quadrant detector by using modified polynomial fitting algorithm in micro-displacement measuring system.

Highlights • New method to improve the linear measurement range of Four-quadrant detector. • The new proposed method effectively enhances the accuracy of light spot position. • The light spot detection sensitivity of detector was analyzed and calculated. • The measuring range of detector from 20 μm up to 60 μm with the resolution is 20 nm. Abstract In this paper, we propose new method to improve the linear measurement range of four-quadrant detector (4QD) in micro-displacement measuring system. Based combines the central approximation method and polynomial fitting algorithm due to their opposite error characteristics of the spot position measurements, the voltage-displacement curves of four spot models, circular spot with flat energy distribution, circular spot with Gaussian energy, a novel method is designed to analyze the detecting the linear measurement range on a 4QD. The experimental results show that the proposed algorithm improves the detecting sensitivity and effective measure ranges of the 4QD, which the measuring range of 4QD is extend from 20 μm up to 60 μm, and the resolution is 20 nm. Finally, the proposed method was designed to ensure the most efficient use of the detecting sensitivity and effective measure ranges of the 4QD. [ABSTRACT FROM AUTHOR]