Research On Micro-optical Device Based On Laser Direct Writing Technology

Micro-optical devices have been widely used in optical design, optical communication, three-dimensional display, and its application domain is continued to expand. The design, fabrication and application of micro-optical devices have been the hot topics of this domain for many years. Laser direct writing is an important micro-fabrication technology. It has the advantages of high precision, powerful 3D fabrication ability, maskless, high efficiency and so on. Based on laser direct writing technology, this thesis makes a study on the design, fabrication and application of micro-optical devices including microlens array, tunable microlens, corner cube array. The research work of this thesis consists of two main aspects, including the design and fabrication of micro-optical devices and their application in three-dimensional display.In the design and fabrication processes of micro-optical devices, to solve the existing problems in fabrication of microlens array, we first propose a method combining grayscale lithography and photoresist reflow technology. Using the new method, large F/# refractive micro-lens arrays have been fabricated. In addition, combining the defoucs laser direct writing and grayscale lithography technology, the range of F/# was further expanded and hence the F/12 refractive microlens arrays were achieved. After that a double-layer harmonic diffractive microlens arrays with large diameter and large numerical aperture were designed and fabricated. By these methods, we broadened the range of parameters of microlens array successfully. At last, the production of large format (18cm×12.6cm) microlens array was achieved by the precise electroforming and UV replication. To solve the existing problems in design and fabrication of diffractive tunable microlens, we proposed a tunable Fresnel lens based on harmonic diffractive structure, whose focus can be switched among the three discrete positions. High diffraction efficiency and image quality has been realized. Meanwhile, based on the nano-imprinting technique, a rapid fabrication method has been designed to produce high diffraction efficiency tunable Fresnel lens.To solve the existing problems in fabrication of corner cube array, we have designed and fabricated a new type of corner cube arrays with high retroreflection efficiency and shallow structures. Based on the laser direct writing, precise electroforming and UV replication techniques, we have successfully produced a 12cm×12cm corner cube array with a good retroreflection effect.In the application study of micro-optical devices , we focused on the autostereoscopic display technology based on micro-optical devices. In view that there is a lack of general and complete theory in the field of autostereoscopic display technology, we first analyzed the common law of a variety of autostereoscopic display technologies from geometrical optics point of view. Then from the physical optics point of view, a common model based on the focus error was established. At last, we applied the light field theory to the autostereoscopic display, and established the unified description of a variety of autostereoscopic display technologies in a light field theory. Besides, on the basis of previous research,we described a light field-based autostereoscopic display theory primarily, which clearly explained the record and the output process of three-dimensional information in the autostereoscopic display. In addition, we analyzed the aliasing artifacts problem and described the sampling theorem in autostereoscopic display quantitatively. The model of extracting the light field information has successfully explained the problems of information structure that the observer is received deviated from the best observer position.Based on the work above, the microlens array based autostereoscopic display technology was experimentally studied. At first, digital record of autostereoscopic display information was realized using the digital imaging principle. Then we proposed a pseudoscopic image conversion algorithm based on light field extracting model. Using the proposed algorithm and the conjugate camera algorithm pseudoscopic image problem in autostereoscopic display was solved digitally. Based on the light field theory we designed a simulation display program of autostereoscopic display. The program can be used to scan and analysis the three-dimensional information layer by layer in depth, and even verify the correction of the autostereoscopic display information. At last a flow to design the autostereoscopic display devices was presented. Based on the flow we successfully designed two types of display devices and achieved the full parallax color 3D display and circular-viewing 3D display of large-format three-dimensional scene, and obtained a relatively remarkable 3D effect.