Analysis of Focal Point Displacement
Jiang Peizheng,Zeng Zhuoxiong,Quan Xiaobo
(Xi'an Jiaotong University, Xi'an 710049, China)

Abstract: Encountered in measurement of PDPA is the problem of focal point displacement. Mirror image method is proposed, and with the use of geometric optics is involved focal point displacement of plane and curved surface in three layer medium is derived. Taking the cylinder, for example, the model thickness and medium effect are studied. The displacement of ideal and actual focus increases with the increment of thickness and relative refractive. Using the refractive-match method, the refractive discrepancy of air and model medium are analyzed. They should not be Large in order to improve focusing.
Keywords: laser Doppler measurement;image;geometry optic;flow-field