Design Of Confocal Microscope For Thickness Measurement Of Ultra-thin Transparent Materials

In recent years,with the rapid development of science and technology,the manufacturing level and technical means of transparent materials have been continuously improved,and a large number of new products have emerged,among which ultra-thin transparent materials are typical representatives.Generally speaking,transparent materials with the thickness less than 1.5mm are referred to as ultra-thin transparent materials.Compared with ordinary transparent materials,ultra-thin transparent materials are more flexible and have better optical performance.Accordingly,as one of the most important parameters affecting the quality of ultra-thin transparent materials,the measurement of its thickness is becoming more and more demanding,which also poses a new and higher challenge to the thickness measurement of ultra-thin transparent materials,so it is imperative to study new methods and techniques of thickness measurement.Based on the investigation and analysis of various thickness measurement methods of transparent materials at home and abroad,a method of measuring the thickness of ultra-thin transparent materials by using confocal microscope is proposed in this paper.The method is based on the principle of confocal microscopy,using its axial tomography characteristics and combining with the high precision displacement platform to make the upper and lower surfaces of the measured samples coincide with the focal plane of the microscopic objective,respectively.Within the time interval between the two optical signals received by the detector,the measured sample thickness can be calculated according to the displacement of the displacement platform.The characteristics of this method are: strong generality,high resolution,measurement range matching the thickness range of ultra-thin transparent materials,which realizes the non-contact,high-precision measurement of the thickness of ultra-thin transparent materials.Based on Fourier optics theory,this paper analyzes the principle of confocal microscopy,deduces the diffusion function of confocal optical imaging points,and studies the effects of numerical aperture,illumination wavelength and pinhole on the resolution of the system and establishes the physical model of the thickness measurement of transparent material,which provides the theoretical basis and calculation basis for the design of the system and the construction of the prototype.This paper also describes the principle and overall structure design of thickness measurement of ultra-thin transparent materials,determines the structural parameters of confocal microscopy system and the optical path scheme of the system and mainly designs the installation and adjustment device of optical system,mechanical structure and pinhole,the tolerance of optical system is analyzed.Finally,the principle prototype is built to verify the feasibility of the measurement method,and analyze.