Long GAO^*, Chunhui WANG, Yiqin JI¹, Yanchao LI, Haifang CONG, and Yang QU

National Key laboratory of Tunable Laser Technology, Harbin Institute of Technology, Harbin 150001, China
¹Tianjin Key Laboratory of Optical Thin Film, Tianjin 300192, China

(Received August 19, 2010; Accepted October 6, 2010)

All-fiber digital heterodyne interferometry is a laser metrology technique employing pseudo-random codes phase modulated onto an optical carrier signal. In this heterodyne interferometer system, the optical signal includes signal reflected and transmitted from the sample, respectively. Compared with the conventional heterodyne interferometry, this enhanced optical system has much higher measurement sensitivity, and can distinguish the signal which reflected from the front and the rear surface of the sample. Analysis and simulation for the digital heterodyne interferometry are presented. It takes approximately 4 s to scan the whole surface with the diameter of 300 mm. The thickness profile of the sample is obtained in the experiment. The discussion about the experiment is given finally.

Key words: heterodyne interferometry, balanced detection, heterodyne detection, pseudorandom noise code

^*E-mail address: gaolong526@yahoo.cn