Using Drop-on-Demand Technology For Fabricating Polymer Refractive Microlens Array

Electronics has shrunk this world and communication system is using optical fiber to convey more and more data and to convey message faster and faster so that it makes the world become smaller and smaller. In fact, these applications require shorter and shorter dimensions of optical elements to form concept of micro-optical element, which can be classified into two kinds: refractive element and diffractive element, sharing different manufacture techniques. In the 1980's, communicational industry for long distance was one in the field, where micro-optical elements were used. But now integrated optical components that consist of laser diode, micro-optical element and optical fiber are used as the basis of high effective optical network. Besides, micro-optical elements can be made of glass, plastics, silicon or semiconductor materials.Microlens array is one of the important micro-optical elements. Comparatively speaking, microlenses arrays made of glass have been studied for a relatively long time and developed well, compared with those made by other materials. However, the cost of them is high and manufacture technique is complicated. Therefore, applications of them are limited to some extent. Recently manufacture techniques of micro-optical elements made of lightweight optical materials have become interest research. In particular optical gradient polymers have attracted special attention because of the controllability of their mechanical and thermal properties and the fact that they can simplify the manufacturing process, leading to less expensive and superior components. There is several manufacture techniques as followings: resist-melting method, gray-scale mask, hot bossing method, sol-gel method and photo-induced cross-linking polymerization etc. In these methods, resist-melting method is widely applied in the scientific research due to the advantages of simple techniques and controllable parameter. Nevertheless, owing to conventional resist intrinsic characteristics, it isn't suitable to be resulting material for microlens or other structure and only to be pattern material or mask. So that it is the reason why it's unsuitable for practical applications.Apart from it, due to complicated fabrication in the mask pattern, gray-scale mask method isn't fit for mass-production. As for the hot embossing method, the plastic microlens can be separated from the mold when the polymer is cooled to glass transfer temperature during the process of manufacturing microlens array, which results in increase of surface roughness degree and decrease in its optical quality.Apart from these methods above, there is another method, named micro-jet printing, which derives from ink-jet printing and is usually used in ink-jet printer. Micro-optical elements manufactured by this technique have come into being commercial products. In other countries there are also reports about manufactured products by this technique. In contrast, similar reports about this technique have not been seen yet in our country. Based on micro-jet printing method, this paper systematically studies the theory and preparation technique of microlens to fill in the vacancy in the fields of science and technology in china. On the basis of equipments, we transform a microcomputer digital printing mucus machine into a device for micro-jet printing. The computer controls the total fabrication process. They comprise a drop-on-demand micro-jet printing system. In the study, PMMA is selected as material, achieving the preparation of microlens array and exploring the technique for mass production. And the fabricated microlens quality is also measured and evaluated, which provide parameter evidence for future mass production.This paper mainly includes four parts:Chapter one briefly describes about the development situation of microlens array and its applications in the industry and military domain. Because of its wide applications studies on fabrication technology become worldwide focus content. Therefore, in this chapter several fabrication techniques are simply introduced and their advantages and disadvantages are also shown. The second chapter contains two parts: the first part is about liquid surface tension theory and the relationship between solution's surface tension and solution concentration, which is the basis of formation of microlens; the second part expounds theory of lens wave aberrations, which is important evidence of evaluation for microlens quality. The third chapter chiefly depicts properties and fabrication techniques of plano-convex refractive microlens arrays. In addition, it is elaborate to discuss the method for improving microlens shape and mechanism of microlens formation. In the fourth chapter, we have measured...