Papers by Author: Won Kyu Jeung

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Authors: Won Kyu Jeung, Yong Jun Kim, Seog Moon Choi
Abstract: A new thermal bimorph actuator for large out-of-plane displacement is designed, fabricated and tested. The deflecting beam is composed of polyimide, heater, and polyvinyl difluorides with tetrafluoroethylene (PVDF-TrFE). The large difference of coefficient of thermal expansion (CTE) of two polymer layers (polyimide and PVDF-TrFE) can generate a large deflection with relatively small temperature rising. Compared to the most conventional micro actuators based on MEMS (micro-electro mechanical system) technology, a large displacement, over 1 mm at 20 mW, could be achieved. The proposed actuator can find applications where a large vertical displacement is needed while keeping compact overall device size, such as a micro zooming lens, micro mirror, micro valve and optical application.
Authors: Won Kyu Jeung, Chang Hyun Lim, Tae Hoon Kim, Seog Moon Choi
Abstract: A novel rectangular shape microlens array having high sag for solid-state lighting is presented. The rectangular shape of proposed microlens can maximize the fill factor of silicon based light-emitting-diode (LED) packaging and minimize the optical loss through the reduction of unnecessary reflection at the same time. Microlens, which has high sag, over 3 75 μm and large diameter, over 3 mm can enormously enhance output optical extraction eff iciency. Moreover wafer level packaging technology is adopted to improve the aligning accu racy and mass production of LED packaging. This wafer level microlens array can be direc tly fabricated on LED packaging using replication method. It has many advantages in optica l properties, low cost, high aligning accuracy, and mass production.
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