Study On Linnik White Light Interferometry Through Transparent Medium

With the development of ultra-precision machining technology,the requirements of ultra-precision detection technology are getting higher and higher.And as a new non-destructive,fast and high-precision measurement method both in geometric testing and other related fields,white light microscopy interference technology is applied more and more extensively.The emerging growth and working environment of the micro/nano device-the liquid or vacuum,requires the measurement to through the transparent medium to detect the static and dynamic behavior of the device,and the introduction of the transparent medium hinders the measurement.In view of the above problems,we build up a Linnik white light microscopy interference system,which is compensated at the reference beam to measure the surface topography and film thickness through transparent medium.The main work of this paper is as follows:1.Aiming at the present situation of transparent medium measurement,a white light microscopy interference system based on Linnik-type is constructed.2.By studying the principle of white light microscopy interference,the influence of the system on the optical path after adding the transparent medium is found.After the transparent medium is added to the system,it not only changes the focus of the objective lens,resulting in blurred images,but also increases the optical path difference,resulting in interference signal disappearing.A method of compensating for this problem at the reference beam is proposed.3.The accuracy of the phase extraction method,the influence of the effective thickness,the wavelength shift and the nonlinear phase of the objective lens on the measurement of the film are simulated.We propose a wavelength correction method to reduce the impact on the measurement according to the simulation results and the actual results.4.The measurement of the absolute distance,surface topography and film thickness whether the system added to transparent medium or not by using the white light spectrum interference measurement method is achieved,which proves that the system can measure through the transparent medium and has the nano-level precision.Using the testing system,the measurement of the thickness of the transparent medium itself is achieved.5.The measurement of the surface topography whether the system added to transparent medium or not by using the white light scanning interference measurement method is achieved.