Research On Phase-shifting Bond Technology For Short And Medium Coherent Light Sources In Zero-position Optical Interference

Phase-shifting interference is the most commonly used technology in digital wavefront interferometry.It has the advantages of simple algorithm,high accuracy,and good repeatability.It is widely used in high-precision measurement of optical element surface shape.The phase shift problem in the large-aperture optical element interferometry is the main reason restricting the development.The use of piezoelectric ceramics to directly drive large mirrors has problems with structural stability and multi-point driving consistency.Wavelength tuning is highly dependent on a precision-tuned laser light source,which is difficult to develop due to poor beam quality and low power and low life.In this dissertation,a low-coherent spectroscopic delay phase shift method suitable for large-aperture phase-shifting interferometry is studied in this paper.The problem of optical path matching and phase-shifting of large-aperture interference cavities is transferred to small-aperture low-coherence light source modules.This method solves the current problems by performing spectral delay,optical path matching and phase shifting on the light source.It has the advantages of high accuracy,stability,and separation from a large-diameter interference cavity.It can realize the measurement under the condition of different cavity lengths and can meet the requirements of parallel flat plate measurement.The full text of the research is as follows:The basic principles of phase-shifting interferometry and phase-shifting algorithms are described,and the basic principles of wavelength-shifting and PZT phase-shifting are analyzed.The theory of low coherent interference is expounded,and the phase shift method of low coherent light source is further discussed.Based on the requirements of phase shift,this paper analyzes the low coherent light source that meets the measurement needs.At the same time,an experimental system was designed and constructed,and the coherent length of the light source was measured using a delayed coherent matching method.In addition,the key components of the low coherent light source spectral delay phase shift system are analyzed and studied.This paper analyzes the delay matching,phase shift control and fringe contrast control in the low-coherent light source spectral delay phase shift.The pyramidal prism group and the optical path matching algorithm scheme are introduced into the spectral delay technology,which solves the problems of large variation of the interference cavity length and difficult optical path matching.At the same time,the phase shift error of the light source PZT phase shift was analyzed and corrected.A 600 mm aperture interference system was used for testing and verification.The comparison between the measurement results of the spectral delay and the wavelength phase shift method was used to verify the feasibility of the light source PZT phase shifting scheme in a large aperture interferometer.In addition,the system was used to measure other bricks and compared with the Zygo interferometer,which proved the reliability of the low coherent light source system for measuring parallel plates.