Research Of DMD-based Maskless Lithography Technique And Methods Of Microlens Rapid Prototyping

Microlens is an important optical element with the advantages of light weight,small size and high integration,etc.,which has a wide range application in the optics,optoelectronic systems,micro-electromechanical systems,sensors and other fields.In recent years,a variety of microlens fabrication methods are also emerging,how to quickly and effectively produce the required microlens and microlens array structures have been aroused the attention by more and more researchers and industry.In this paper,as a means of research based on digital micromirror device(DMD)maskless lithography technology,some rapid and effective microlens fabrication methods were proposed.Based on the DMD exposure projection theory,a DMD maskless lithography platform was designed and constructed.Based on the exposure platform,the research of three dimensional(3D)light modulations was performed.Then,on the basis of this,the research on the microlens molding method by multi-parameter modulation is carried out,and finally the research of flexible production of biomimetic compound eye lens was also carried out.Thus,the application of maskless lithography technology can be extended.The main research work is as follows:In this paper,firstly the structure,working principle,working characteristics and applications DMD-based are introduced in detail for the purpose of research.Followed by a study was carried out based on DMD exposure projection imaging theory.Based on the theoretical basis,a set of maskless lithography system was designed and constructed independently.The system mainly includes uniform lighting system,DMD control system,CCD focus control system and projection imaging system.And according to the basic performance tests of the system,the minimum resolution size can reach about 2.44?m,and the quality of the lithography can also meet the design requirements.On this basis,the research of 3D light modulation technology was performed.The technique is a single scan technology based on DMD maskless lithography.Firstly through the design of the required 3D graphics of the theoretical contour,and then the calculation of 3D microstructure spatial exposure dose distribution,and lastly through the study and optimization of 3D slice algorithms,a high quality resulting 3D microstructure contour was obtained quickly and effectively.In addition,considering the limitation of DMD resolution and the steps between adjacent slices,the method of improving the quality of aspheric microlens has been studied.The method combined the 3D modulation technology and the proposed noncontact upside-down reflow technology.The results showed that the method can effectively improve the quality of the resulting lens and compensate for the lack of DMD 3D light modulation technology.The microlens forming method by multi-parameter modulation was studied based on the lithography platform.The method mainly used the centrifugal force generated by the spin coating process to make the photoresist in the micro-hole to form the meniscus shape,and then adjusted the spin-coating speed,size of micro-hole,photoresist concentration and soft baking temperature and other parameters to control the meniscus radius of curvature,and finally different shapes and sizes of microlens patterns can be easily obtained through the PDMS rapid transfer process.Finally,the fabrication of a complex biomimetic compound eye lens on the curved substrate is carried out.Based on the actual size of the insect compound eyes in nature,the fabrication process and method,and the measurement of the optical properties of the biomimetic compound eye lens were carried out,respectively.In this study,a single scan lithography technology based on DMD can complete the pre-modeled biomimetic compound eye lens structure by a one-time rapid processing.And then according to the difference of glass softening point(Tg)about the AZ P4620 and S 1813 two positive photoresists,the required biomimetic compound lens microstructure after two times reflow.In addition,in order to avoid the defects of the microlens structure during the reflow process,the edge bulge phenomenon is also studied.For the measurement of the optical characteristics of the biomimetic lens,the size of the focal length,the point spread function and the imaging ability were both measured by the self-built optical measuring system.The results showed that the biomimetic compound lens structure produced by this method can meet the design requirements,and exhibited a larger numerical aperture than the insect compound eyes in nature.