• Journal of the Korean Society of Visualization
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• v.8 no.3
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• pp.22-28
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• 2010

In the present study, we performed the velocity field measurement in a microchannel using a focal length variable micro liquid lens. The liquid lens is used as a beam expander in a micro-PIV system to acquire the scatter image of the seeded particle. A thin film-type micro liquid lens was made of PDMS material and it was attached on top of the 700-micron-wide working fluid supply channel trench. As a result, the focal length and contact angle of the liquid lens changed with variations in applied pressure.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1045-1046
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• 2010

• Korea-Australia Rheology Journal
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• v.19 no.3
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• pp.165-169
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• 2007

The light guide plate (LGP) of LCD-BLU (Liquid Crystal Display-Back Light Unit) is usually manufactured by forming numerous dots by etching process. However, the surface of those etched dots of LGP is very rough due to the characteristics of etching process, so that its light loss is relatively high due to the dispersion of light. Accordingly, there is a limit in raising the luminance of LCD-BLU. In order to overcome the limit of current etched-dot patterned LGP, micro-lens pattern was tested to investigate the possibility of replacing etched pattern in the present study. The micro-lens pattern fabricated by the modified LiGA with thermal reflow process was applied to the optical design of LGP. The attention was paid to the effects of different optical pattern type (i.e. etched dot, micro-lens). Finally, the micro-lens patterned LGP showed better optical qualities than the one made by the etched-dot patterned LGP in luminance.

• Transactions of Materials Processing
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• v.20 no.1
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• pp.60-63
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• 2011

BLU(back light unit) is one of kernel parts of LCD(liquid crystal display) unit. New 3-D micro-lens pattern for LGP(light guide plate), one of the most important parts of LCD-BLU, had been researched. Instead of dot pattern made by chemical etching or laser ablation, SCS(slanted curved surface) micro-lens pattern was designed with optical CAE simulation. This study introduce the method of design using optical CAE simulation for SCS micro-lens, the new fabrication method of micro-mold with SCS micro-lens pattern.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.280-283
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• 2004

Micro-lens patterned micro-mold fabrication method for Light Guiding Plate(LGP), kernel part of LCD-BLU(Back Light Unit), was presented. Instead of erosion dot pattern for LGP optical design, micro-lens pattern, fabricated by LIGA-reflow process, was applied. Optical pattern design method was also developed not only for negative pattern LGP, but also positive pattern LGP. During injection molding process, experimental study was conducted to improve replication quality and brightness of ${\sim}50um$ micro-lens pattern mold. The effect of mold temperature for the replication quality of micro-lens array was studied.

• Journal of the Optical Society of Korea
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• v.17 no.5
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• pp.447-453
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• 2013

A micro zoom system without moving elements by use of two liquid lenses is designed and optimized in this paper. The zoom equations of the system composed of two liquid lenses are deduced. The structure parameters including radius and thickness of a conical double-liquid electrowetting based lens are analyzed and calculated. Because the liquid thickness varies non-linearly with the radius of the interface, it's very difficult to optimize a real liquid lens using commercial optical design software directly. Through the Application Programming Interface (API) of the optical design software CODE V, a zoom system with two real electrowetting based liquid lenses is modeled and optimized. A two-liquid-lens zoom system without moving elements, with a zoom factor of 1.8 and a compact structure of 10 mm is designed for illustration. This can be useful for the camera design of mobile phones, tablets and so on. And this paper presents a convenient way of designing and optimizing a zoom system including liquid lenses by commercial optical design software.

• Korea-Australia Rheology Journal
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• v.19 no.3
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• pp.171-176
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• 2007

LCD-BLU (Liquid Crystal Display-Back Light Unit) of medium size is usually manufactured by forming numerous dots with $50{\sim}300\;{\mu}m$ in diameter by etching process and V-grove shape with $50\;{\mu}m$ in height by mechanical cutting process. However, the surface of the etched dots is very rough due to the characteristics of the etching process and V-cutting needs rather high cost. Instead of existing optical pattern made by etching and mechanical cutting, 3-dimensional continuous micro-lens of $200\;{\mu}m$ in diameter was applied in the present study. The continuous micro-lens pattern fabricated by modified LIGA with thermal reflow process was tested to this new optical design of LGP. The manufacturing process using LIGA-reflow is made up of three stages as follows: (i) the stage of lithography, (ii) the stage of thermal reflow process and (iii) the stage of electroplating. The continuous micro-lens patterned LGP was fabricated with injection molding and its test results showed the possibility of commercial use in the future.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.241-244
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• 2004

Microlens patterned micro-mold fabrication method for Light Guiding Plate(LGP), kernel part of LCD-BLU(Back Light Unit), was presented. Instead of erosion dot pattern for LCP optical design, microlens pattern, fabricated by LIGA-reflow process, was applied. Optical pattern design method was also developed not only for negative pattern LGP, but also positive pattern LGP. In order to achieve flow balance during the micro-injection molding process and dimensional accuracy, two LGP pattern was made in one micro-mold.

• Bulletin of the Korean Chemical Society
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• v.29 no.4
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• pp.731-735
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• 2008

The fluid ensemble in the liquid lens, which is composed of electrolyte and silicone oil, is the key material system to vary the focal length processing of the electrochemical desorption. In order to characterize the capability of the liquid lens according to response time and optical range, we prepared a fluid ensemble comprising the electrolyte and oil. To elucidate the physical mechanism of the effective response time, we examined the viscosity dependency while satisfying the requirements for the density and refractive index of the electrolyte and oil, respectively. The characterization results indicated that the response time (up and down) is influenced by the viscosity of the electrolyte and oil. On this basis, we prepared a fluid ensemble capable of reversibly adjusting for the focal length of the liquid lens, as well as the response time. The ensemble is applicable to various systems such as micro-lens and optical sensors.

• Journal of Information Display
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• v.11 no.2
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• pp.84-90
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• 2010

This paper presents the effects of a dielectric layer and an electrolyte on the driving performance of an electrowetting on dielectric (EWOD)-based liquid lens. The range of tunable focal length of the EWOD-based liquid lens was highly dependent on the conditions of the dielectric layer, which included an inorganic oxide layer and an organic hydrophobic layer. Moreover, experiments on the physical and optical durability of electrolyte by varying temperature conditions, were conducted and their results were discussed. Finally, the lens with a truncated-pyramid silicon cavity having a sidewall dielectrics and electrode was fabricated by anisotropic etching and other micro-electromechanical systems (MEMS) technologies in order to demonstrate its performance. The lens with $0.6-{\mu}m$-thick $SiO_2$ layer and 10 wt% LiCl-electrolyte exhibited brilliant focal-length tunability from infinity to 3.19 mm.