Quantitative nondestructive evaluation of multilayer thin films based on two dimensional optical coherence tomography
CHEN Dan yang, TONG Jun hai, ZHONG Shun cong, ZHANG Qiu kun, LIN Jie wen, FU Xi bin
(1.Electronic Engineering Department, Zhangzhou Institute of Technology, Zhangzhou 363000, China;2.Laboratory
 of Optics, Terahertz and Non destructive Testing & Evaluation, School of Mechanical Engineering and 
Automation, Fuzhou University, Fuzhou 350108, China;3.Fujian Key Laboratory of Medical 
Instrument and Pharmaceutical Technology, Fuzhou 350000, China;4.Xiamen 
Special Equipment Inspection Institute, Xiamen 361000, China)

Abstract: In order to achieve fast accurate thickness measurement and nondestructive evaluation of multilayer thin films, a two dimensional optical coherence tomography (OCT) was developed. The developed system did not need to point by point scan the sample and therefore, the problem of low imaging efficiency was avoided by point by point scanning. In addition, the theory of removing OCT conjugate mirror image was presented; also, five step phase shifting interferometry method was employed the system to remove the effect of OCT conjugate mirror image and finally to avoid image aliasing. A PZT actuator was used to drive the reference mirror to achieve the five phase. By using the system, the internal structure of mobile toughened glass film was accurately measured, including toughened glass, the first electrostatic glue, explosion proof film and the second electrostatic glue. Experimental results demonstrated that the home made system had high accuracy and high speed imaging performance for the measurement of multilayer thin films. It could be recommended for non destructive evaluation of multilayer thin films.

Key words: interference fringes; optical coherence tomography; multilayer thin film; thickness measurement