DESIGN AND MICROFABRICATION OF EDGE-LIT OPTICAL LIGHT CURTAINS

Plastic optical light guides can be used for a variety of interior and exterior vehicle light curtains such as cabin illuminators and automotive tail lights. The edge-lit wave guide is an optically transparent substrate coupled with one or more energy efficient light emitting diodes (LEDs). The light rays from the source travel through the substrate based on the principle of total internal reflection. If a surface of the optical wave guide is patterned with optical microstructures then the light rays will scatter and refract throughout the medium, primarily exiting opposite to the patterned surface. Uniform illumination over this active surface region is a function of the individual optical microstructure\u27s shape and the spatial distribution of the microstructures. The goal of this research is to investigate the light dispersion characteristics in both smooth and micro-patterned optically transparent substrates, and utilize optical simulation software to develop viable design approaches for fabricating small and medium sized light curtains. The study first identifies an appropriate optical microstructure (i.e. cylindrical indentations) that can be reliably imprinted on the surface of an optically transparent polymethyl-methacrylate (PMMA) substrate using a multi-axis micromilling machine. The optical simulation software Light Tools is then used to determine the most appropriate microstructure radius and spatial positioning of elements for uniform light distribution. The key design and fabrication parameters for near optimal performance are summarized and used to establish the process plan for the high-speed precision micromilling operations. Experiments are performed on several 100 mm x 100 mm x 6 mm polymer light guide panels (LGPs) including a customized design with a hexagonal arrangement of microstructures. Both interior and boundary regions of the sample LGPs are investigated for intensity distribution, optical transmission efficiency, and light loss. Although the experiments involve relatively small flat PMMA LGPs, the optical design and microfabrication methods can be readily extended to larger surface areas or curved optically transparent polymer substrates for contoured light curtains

An effective system for parameter optimization in photolithography process of a LGP stamper

In the current thin-film transistor liquid crystal display industry, the light guide plate (LGP) of the backlight module has become thinner and smaller, and the backlight module needs to be illuminated uniformly and effectively. The parameter setting for the photolithography process of a LGP stamper often relies on the engineers' experiences by means of trial-and-error or design of experiment to obtain a suitable and more reliable process parameter setting, which requires a large amount of time, manpower, and cost. This research proposes a novel two-stage optimization system for photolithography process integrating the Taguchi method, back-propagation neural networks, genetic algorithms, particle swarm optimization, and related technologies to effectively generate optimal process parameter settings. The first stage is to reduce the process variance. The second stage is to find the final optimal process parameter settings for the best quality specification. Experimental results show that the proposed system can create the best process parameters which not only meet the quality specification for the micro-dots on the photoresist, but also effectively enhance the overall process stability. ? 2013 Springer-Verlag London