Based On Variable-wavelength Laser To Measure The Parallelism Of The Parallel Plate

Phase-shifting technique is a significant method in measuring the wavefront. It can be divided into two techniques according to the phase-shifting modes: software phase-shifting interferometry and hardware phase-shifting interferometry, in which the phase-shifting technique by PZT and corresponding interferometers are widely applied in actual manufacturing. And the phase-shifting technique by wavelength tuning is developed in recent years. Compared with the traditional hardware phase-shifting interferometry , it has its particular characteristics. Firstly, the laser source is also the phase-shifter. Secondly, the value of phase-shifting is relative to the measuring surface.The metrology of parallel plates in the optical fabrication and test is very important. While using the traditional Phase Shifting Interferometry, it causes large errors because of the superposition of three interferograms generated from three isolated surfaces in the measurement process. Thus the subject of this article is with great importance to the measurement of optical element like parallel plate. The main research work of this article is as following: the paper expatiates the developing status of phase-shifting technique, summarizes the characteristics of traditional hardware phase-shifting technique and the advantages and disadvantages of phase-shifting technique via wavelength tuning, and expatiates the necessity and signification of the research of wavelength phase-shifting interferometry. This article studies the principle of weighted multi-step phase-shifting algorithm, and this paper expatiates the idea of algorithms, designing theory, detailed designing process. Wavelength tuning interferometry system of the parallel plates has been established, and several interferograms have been collected using the phase shift of wavelength tuning, several parameters of parallel plate have been figured out. The result is also compared with the normal test method which has to suppress the reflection of parallel plate's back surface. The comparison result shows that the designed are effective.