Research Of MOE Rapid Prototyping Method Based On DMD Digital Lithography

Miniaturization and intelligence are the main developing directions of modern industry and technology.After the development of circuit and machinery towards miniaturization,the micro-optical electromechanical system(MOEMS),which integrates light,machine and electricity,is the inevitable result of further responding to this trend.Therefore,the requirement of miniaturization,array,integration and intelligence for optical elements is also put forward,which promotes the miniaturization of micro-optics and miniaturized optical elements.Compared with traditional optical elements,micro-optical elements(MOEs),possessing the advantages of small size,flexible design and arraying,are widely used in biological medicine,digital communication,dexterous weapons and many other aspects.Besides,driven on by social objective needs and economic interests,a series of MOEs fabrication methods based on micro-electronics,micro-machinery,semiconductor processing technology was prepared.However,how to fabricate MOEs with high efficiency and low cost is still the focus of research.This paper takes digital micromirror device(DMD)digital lithography technology as the research object to study the rapid prototyping process of MOEs,including the principle of digital lithography system based on DMD,the modulation theory of three-dimensional(3D)light,the spatial distribution of exposure dose,the slicing algorithm of contour reconstruction and the surface thermoplastic molding technology.Based on the study,a hexagonal compound eye microlens array(HCE-MLA)was proposed and fabricated in the experiment,so as to demonstrate the rapid prototyping process in this paper.The main research work of this paper is as follows:1)Firstly,the digital lithography system based on DMD is introduced in detail,including the type and performance of the exposure light source,the principle and type of beam collimation and homogenizing unit in the lighting system,the structure and working principle of DMD chip,and the key parameters of the projection system.On this basis,the DMD-based lithography system with UV-LED exposure light source is selected,whose minimum resolution can reach 0.6 ?m,entirely complies with the design requirements,and the graphics obtained after lithography have good quality.2)Then,the theory of three-dimensional light modulation and the technology of MOEs rapid prototyping are described.Three-dimensional optical control is a method for rapid reconstruction of target contour.Its core content is to calculate exposure dose distribution based on target contour and obtain exposure region by slicing algorithm.The thinking of using this method to reconstruct for,first of all get the mathematical model of micro-optics element or contour function,according to the target contour and the relationship between exposure dose calculated exposure dose of spatial distribution,and the slicing algorithm to obtain the exposure area and combined with the spatial distribution of the exposure dose that corresponding exposure dose,multiple exposures in lithography system eventually a complete reconstruction of MOEs.In addition,the basic process of photolithography and thermal reflow strategies are introduced,and different thermal reflow strategies are used to shape the microlens array in experiments,so as to study the characteristics of different thermal reflow strategies micro-nanometer processing.3)Finally,the HCE-MLA with very high fill factor is studied.The experiment uses a positive thick photoresist AZ4620,and the profiles of the microlens is designed as a parabolic.Firstly,the spatial distribution of the exposure dose is theoretically calculated,and the equalarc-mean slicing strategy is analyzed.On this basis,the data of the multilayer slice is obtained and the digital mask pattern is designed.By using the modulation theory of the threedimensional light,multiple exposures are carried out on the hexagonal cylinder obtained after the first photolithography,and the HCE-MLA with smooth surface and good quality is obtained by thermal reflow strategy.On the basis of this experiment,different slice layers were set and corresponding microlens contours were measured to study the influence of slice layers on the accuracy of contour reconstruction.