Key Engineering Materials Vols. 364-366

Abstract: Freeform optics fabrication has become one of the hottest topics in optics industry in recent years. Although it still remains a challenge, many have tried different ways of manufacturing it. Some have achieved degrees of success. By means of a Nanotech 350-FG five axis diamond turning machine, we too have successfully produced some prototype freeform optics and lens arrays with Slow Tool Servo and Milling method. The produced freeform optics are mainly for automobile LED headlamps and the lens arrays are for LED illumination. In order to produce the freeform optics, we developed our own DT Slow Tool Servo program which is capable of generating a DT program for diamond turning a universal/general 3D freeform surface. Slow Tool Servo technique and Diamond Milling technique were mainly employed to produce these freeform surfaces. The manufacturing process and machining parameter details will be given in the paper. The two main methods we used will be compared and discussed as well. In measuring the freeform surface, a 3D white light interferometer was used to scan and obtain the surface coordinates. The software made by ourselves enabled us to compare the measure results of the work piece with that of the design drawings. The deviation of our finished forms is within 5 um from that of the nominal. The surface quality Rq is about 10 nm. Measuring equipment and methodology will also be discussed in the paper.

Abstract: Following the development of the thin-LCD, many researchers have improved the traditional backlighting module to make it thinner, lighter, and brighter which has already become the trend. The light guide plate is a very important component in backlighting module. Generally, the traditional light guide plate (LGP) is made of PMMA material. Injection molding technique is applied to fabricate the traditional LGP. In this research, Polydimethylsiloxane (PDMS) material was used to make the LGP, which was fabricated by using MEMS technique. In order to modify the traditional LGP, the micro prisms were constructed on the bottom surface of the PDMS LGP. Silicon mold was used to define the geometry of the micro-prism. Anisotropic etching technique was applied to fabricate the prism silicon mold. A liquid PDMS mixture was cast onto the prism silicon mold and the PDMS LGP was completed. White LED was utilized to be the light source of the PDMS LGP. After going through the illuminative test, PDMS LGP was demonstrated successfully of guide light function and its 77% of illuminative uniformity was achieved requirement of a general v-grooved light guide. The thickness of the PDMS LGP is easy to control and the PDMS is a heat-resistant and cheap material; therefore, the space and fabrication cost are saved. The field of MEMS has experienced rapid growth in the recent decade. In the future, the PDMS LGP can make displays thinner and brighter for thin-LCD applications.

Abstract: The manufacturing of optics is an important field of technology and will serve keymarkets today and in the future. Nevertheless, the application of complex optical elements is much restricted today despite of their outstanding functional advantages. Furthermore, the replication of structured optical components requires high precision molds. Diamond machining processes like diamond milling and cutting as well as abrasive polishing are appropriate micro-structuring techniques for optical molds. The combination of these key machining technologies with replication techniques within closed process chains will open the possibility to produce high precision complex optical elements as mass-product articles for many optical applications. Important machining techniques for optical mold manufacture are presented and discussed.

Abstract: Miniaturization is a worldwide trend in manufacturing industry. Though lithography has been introduced to meet the basic needs, the technology is limited by its process complexity and the parts geometry to be produced. This research attempted to overcome the above obstacles by applying laser machining approaches on general 3D micro-parts. The machining model is based on a layer-by-layer concept. Experimental verification was made on a 1mm stainless steel sheet by applying a diode-pumped Nd:YVO4 laser with Q-switch option. Three main parameters: power, repetition rate and the speed of laser process were set to optimize the process quality. In the research round holes with the diameter ranging from 10 μm to 30 μm were drilled. The following step was the machining of a sloped groove with the area size of 100 μm × 100 μm for validation.

Abstract: When the Neural Network model is used to interpolate the non-circular curves, there are shortcomings of converging slowly and getting into the local optimum easily. A novel numerical control interpolation algorithm based on the GA (Genetic Algorithms) and NN (Neural Network) was introduced for the ultra-precision machining of aspheric surfaces. The algorithm integrated the global searching of GA with the parallel processing of NN, enhanceed the convergence speed and found the global optimum. At the end, the quintic non-circular curve was taken as an example to do the emulation and experiment. The results prove that this algorithm can fit the non-circular curve accurately, improve the precision of numerical control interpolation and reduce the number of calculating and interpolation cycles.

Abstract: MEM (Micro-Electro-Mechanical System) is the integration system of mechanical elements, sensors, actuators, and electronics on a silicon substrate using the micro fabrication technology, in general. A new MEMS formation technology is proposed in this paper. The improved drop-on-demand ink jet was used and the MEMS was formed on the plastics and silicon substrate. The plastics resins were injected from the drop-on-demand head on the substrate and the dropped resins were cured using ultraviolet rays. Thus micro lenses were formed.

Abstract: In this paper, a new generation method for diamond turning non-axisymmetry aspheric mirrors is introduced. A rotary arm that carried a diamond tool combined with fast tool servo was used to replace the straight guides employed by most diamond turning machines. The micro linear feed of the fast tool servo was real-time calculated with the use of high resolution angular feedback on the work spindle and the swing tool. Synchronized motion of the fast tool servo according to rotating angles of the workpiece and the diamond tool produced ultra-precision non-axisymmetry aspheric surfaces. The corresponding mathematical models of NC program are presented.

Abstract: Grazing incidence optics used in soft X-ray microscopes require supersmooth surface and highly accurate figure. We considered the fabrication of a Wolter type I mirror, one of grazing incidence optics, with axial-symmetric inner reflecting surfaces using single-point diamond turning. Electroless nickel was chosen as reflecting material Cutting conditions for machining the inner reflecting surface were restricted because of long arm of a single-crystal diamond tool. The machined Wolter type I mirror had approximately 270 nm P-V in figure error and 3 nm Ra in surface roughness. The direct-machined Wolter type I mirror could be successfully used in a soft Xray microscope based on laser-produced X-ray source.

Abstract: This paper discusses the research of optimal process for lightguiding plate of backlight module of liquid crystal display. The PMMA material was used on lightguiding plate. This paper indicates that the different processing parameters (mold temperature, injection temperature, first period injection speed, second period injection speed, third period injection speed, packing pressure and packing time) are important for optimal research for lightguiding plate of backlight module. This paper introduces the extension engineering, simulated annealing and genetic algorithm on soft computing for optimal process and compares the results with experiment. The results show that the optimal process group is A1 B1C2 D3 E2 F2 G3 for extension engineering, simulated annealing, genetic algorithm or experiment. The mold temperature is the most important processing parameter of the flatness of lightguiding plate for soft computing and experiment. The calculation times for extension engineering, simulated annealing and genetic algorithm are less than experiment’s time.

Abstract: This work used micro dispensing technology to fabricate the master of microlens array, then uses electroforming technology to replication the Ni mold insert of microlens array and finally used micro hot embossing to replicate the plastic microlens array. This work used the Si10 resin by AutoStrade Company for dispensing material. The resin material was exposed to 80W halogen light. The resin will be hardened and become convex by surface tension effect on exposition. It can be used as the master of microlens array. This work sputtered a silver layer of 150 nm thick on the master for conducting electricity layer. The electroforming technology replicateed on the Ni mold insert from the master of microlens array. Finally, the micro hot embossing technology was used to replicate the molded microlens array. The molding experiment used PMMA and PC optical film. The experiment studied the influence of processing parameters of hot embossing by processing temperature, embossing pressure, embossing time and de-molding temperature. This work used the Taguchi’s Method to search the best processing parameter for molded microlens array. This work used the microscope, surface profiler and SEM to measure the surface profile of master, mold insert and molded microlens array. This work also used AFM to measure the surface roughness of master, mold insert and molded microlens array. In addition, this work measured the optical strength and the focal length to discuss optical characteristics of molded microlens array.