The Research Of Lenses Axial Space Measurement Using Confocal Focusing Technology

In the optical systems, such as lithography objective lens, high precision microscopeobjective lens, satellite camera, and so on, high performance lens is widely used. The axialspace between lenses is an important parameter of the lens. It needs to be controlled strictly,while the each axial space deviation will result in aberrations, Reduce the lens imagingquality. Therefore, to research of lenses axial space measurement technology, which hashigh accuracy, large working distance and strong anti-interference ability, will haveimportant academic and practical value.Based on laser confocal chromatography focusing technique, a non-contact and highprecision lenses axial space measurement technology is researched in this thesis. And theprinciple is as follows. Firstly, the axis of lenses is adjusted accurately to make it strictlyconsistent with the axis of the confocal system;Secondly, the vertexes of the lenses’ surfaces are identified precisely using the axialchromatography property and the peak in the axial response curve of the confocalmicroscopy.At last, the lenses axial spaces are calculated using the ray tracing algorithm.The main research work in this thesis includes:(1) Based on laser confocal chromatography focusing technique, research themeasurement principle of lenses axial space and annular beam measurement principledeeply. The axial space calculation formulas were derived in detail using geometrical opticsray tracing theory.(2) A simulation model was created in ZEMAX, and the suppression of wave frontaberration was analyzed while the annular pupil was used. The simulation experimentsverified that the axial space calculation formulas were correct.(3) The measurement system mechanical structure and control system structure weredesigned. The mechanical structure consists of sub-confocal system, air-bearing slider,Five-dimensional adjustor, motorized Stages, distance measurement interferometers. Thecontrol system structure include the motion control of motorized Stages, imageacquisition and display, Synchronous trigger signal, environmental Compensation ofdistance measurement;(4) The experimental apparatus were built for lenses axial space measurement in laboratory, and the measurement principle and lenses axial space ray tracing algorithm wereboth verified. The error sources in the system were investigated at last.Preliminary experimental results indicate that the system has high accuracy, and themeasurement deviation of single lens thickness is less than0.5μm. The research in thisthesis provides an effective way to solve the axial space measurement problem for anassembled lens, which couldn’t be measured accurately at present.