Spherical Micro-lens Array of PMMA Produced by Micro-molding

Micro-lens （ML） and Micro-lens array （MLA） are important optical components widely used in many fields; Soft-lithography, a vital little process technology, has its unique performance to produce ML and MLA; The cylinder and spherical MLA of polymethyl methacrylate （PMMA） were successfully obtained by micromolding inSoft-lithography. Some suitable experimental parameters in the process were discussed, and the imaging property of the MLA was also studied simply.

Compressional Deformation in Indentation Process for Microlens Array Mold

The structure of a microlens array（ MLA） can be formed on copper by an indentation process which is a new manufacture approach we applied here instead of a traditional method to test the material property,thereby work time can be saved. Single-indentation and multi-indentation are both conducted to generate a single dimple and dimples array,namely micro lens and MLA. Based on finite element simulation method,factors affecting the form accuracy,such as springback at the compressed area of one single dimple and compressional deformation at the adjacent area of dimples arrays,are determined,and the results are verified by experiments under the same conditions. Meanwhile,indenter compensation method is proposed to improve form accuracy of single dimple,and the relationship between pitch and compressional deformation is investigated by modelling seven sets of multi-indentations at different pitches to identify the critical pitch for the MLA＇s indentation processing. Loads and cross-sectional profiles are measured and analyzed to reveal the compressional deformation mechanism. Finally,it is found that MLA at pitches higher than 1. 47 times of its diameter can be manufactured precisely by indentation using a compensated indenter.

Crosstalk-free integral imaging display based on double plano-convex micro-lens array

A crosstalk-free integral imaging display consisting of a display panel and double piano-convex micro-lens array is proposed. The double piano-convex micro-lens array includes two micro-lens arrays, A and B. Micro-lens array A is used to eliminate crosstalk by completely reflecting crosstalk lights. Micro-lens array B, located near microqens array A, is used to display three-dimensional images. Computer simulations based on ray-tracing are conducted. Crosstalk-free reconstruction images may be clearly observed from the simulation results.

High-speed, large-area and high-precision fabrication of aspheric micro-lens array based on 12-bit direct laser writing lithography

Aspheric micro-lens array(AMLA),featured with low dispersion and diffraction-limited imaging quality,plays an important role in advanced optical imaging.Ideally,the fabrication of commercially applicable AMLAs should feature low cost,high precision,large area and high speed.However,these criteria have been achieved only partially with conventional fabrication process.Herein,we demonstrate the fabrication and characterization of AMLAs based on 12-bit direct laser writing lithography,which exhibits a high fabrication speed,large area,perfect lens shape control via a three-dimensional optical proximity correction and average surface roughness lower than 6 nm.In particular,the AMLAs can be flexibly designed with customized filling factor and arbitrary off-axis operation for each single micro-lens,and the proposed pattern transfer approach with polydimethylsiloxane(PDMS)suggests a low-cost way for mass manufacturing.An auto-stereoscopic-display flexible thin film with excellent display effect has been prepared by using above technology,which exhibits a new way to provide flexible auto-stereoscopic-display at low cost.In brief,the demonstrated fabrication of AMLAs based on direct laser writing lithography reduce the complexity of AMLA fabrication while significantly increasing their performance,suggesting a new route for high-quality three-dimentional optical manufacturing towards simplified fabrication process,high precision and large scale.

Direct generation of a stable multi-beam pulsed 355 nm UV laser based on a micro-lens array

Multi-beam laser processing is a very popular method to improve processing efficiency. For this purpose, a compact and stable multi-beam pulsed 355 nm ultraviolet(UV) laser based on a micro-lens array(MLA) is presented in this Letter. It is worth noting that the MLA is employed to act as the spatial splitter as well as the coupling lens. With assistance of the MLA,the 1064 nm laser and 532 nm laser are divided into four sub-beams and focused at different areas of the third-harmonic generation(THG) crystal. As a result, the multi-beam pulsed 355 nm UV laser is successfully generated inside the THG crystal. The measured pulse widths of four sub-beams are shorter than 9 ns. Especially, the generated four sub-beams have good long-term power stability benefitting from the employed MLA. We believe that the generated stable multi-beam355 nm UV laser can meet the requirement of high-efficiency laser processing, and the presented method can also pave the way to generate stable and long-lived multi-beam UV lasers.

A Novel Artificial Superposition Compound Eye

A new artificial superposition compound eye model is presented based on micro-lens array. In all compound eyes,it has the advantages of small volume,light weight,wide FOV,high sensitivity and much higher energy utilization ratio. Nevertheless,its structure is relatively complicated,especially the GRIN medium in the crystalline cone. Therefore,the modeling,analysis and fabrication for it are burdensome. In the established model,the GRIN is replaced by a curved micro-lens array. Thus,the modeling,analysis and optimization process are simple,and the components of artificial superposition compound eye are easy to be fabricated. The system is modeled by ZEMAX software. With the help of raytracing,its principle is analyzed,and the sensitivity comparison between the superposition compound eye and the apposition compound eye is done. The model's validity is proven.

Mechanism of brittle fracture in diamond turning of microlens array on polymethyl methacrylate

Diamond cutting is a popular method to fabricate microlens array (MLA) on polymethyl methacrylate (PMMA);however, it is limited by brittle fracture, which is formed easily on the surface of MLA during the cutting process. In this paper, the formation mechanism of the brittle fracture is studied via a series of experiments including the slow tool servo (STS) cutting experiment of MLA, surface scratching experiment and suddenstop cutting experiment. The effects of undeformed chip thickness, feed rate, and machining track on brittle fracture formation are investigated in detail. In addition, based on the fracture formation mechanism, a bi-directional cutting approach is proposed to eliminate the regional brittle fracture of the microlens during diamond cutting. An experiment was then conducted to verify the method;the results demonstrated that bi-directional cutting could eliminate brittle fracture entirely. Finally, a spherical MLA with the form error (vPV) of 60 nm and the surface roughness (Ra) of 8 nm was successfully fabricated.