• Proceedings of the KIEE Conference
• /
• 2003.07c
• /
• pp.1920-1922
• /
• 2003

We have fabricated the pyrex glass microlens using thermal reflow process. Fabricated microlens is the plano convex refractive type and was fabricated with pyrex glass-Si anodic bonding wafer. The etched circle or cylindrical pyrex glass pattern was melted in a furnace $800^{\circ}C$ to $900^{\circ}C$ for about 15min. The surface roughness of the microlenses was measured by the AFM and average surface roughness of the microlenses was below 15min. The radius of curvature of the microlens was measured with phase shift interferometer.

• Journal of Sensor Science and Technology
• /
• v.17 no.5
• /
• pp.375-379
• /
• 2008

This paper reports a new fabrication method of polydimethylsiloxane (PDMS) microlenses with various curvatures by using a water-based mold. The hydrophobic surface of Polypropylene (PP) substrate was modified by corona discharge using tesla coil to have hydrophilic surface. Then hydrophilic surface of PP substrate takes hydrophobic recovery to have various contact angles from less than $25^{\circ}$ to about $84^{\circ}$. By using the water droplets with various contact angles as replica molds for PDMS process, we could obtain PDMS microlenses with various curvatures.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.09a
• /
• pp.23-28
• /
• 2005

Microlens arrays were fabricated using a modified LIGA process based on the exposure of a PMMA (Polymethylmethacrylate) sheet to deep x-rays and subsequent thermal treatment. A successful modeling and analyses for microlens formation were presented according to the experimental procedure. A nickel mold insert was fabricated by the nickel electroforming process on the PMMA microlens arrays fabricated by the modified LIGA process. For the replication of microlens arrays having various diameters with different foci on the same substrate, the hot embossing and the microinjection molding processes have been successfully utilized with the fabricated mold insert. Fabricated microlenses showed good surface roughness than the mold insert. The focal lengths of the injection molded microlenses were successfully measured experimentally and also estimated theoretically.

• Proceedings of the Optical Society of Korea Conference
• /
• 2008.07a
• /
• pp.451-452
• /
• 2008

• Journal of The Korean Astronomical Society
• /
• v.25 no.2
• /
• pp.79-90
• /
• 1992

The physical properties of the flux factor K and its application are discussed in connection to the high amplification events. The effects due to random motions of stars in a foreground galaxy are examined in the frame work of moving caustics of gravitational microlenses.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.1087-1090
• /
• 2008

Present research is devoted to the development of optical sheet intended to be used inside LCD Backlight unit in order to improve output axial Luminance. It deals with refractive by nature optical sheet having relief embossed top surface (microlenses array). Patterned reflecting layer can be coated on flat bottom surface.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07a
• /
• pp.528-530
• /
• 2005

In this paper, we present a new and practical method for achieving real-time wavefront measurement, dramatically increasing the resolution, dynamic range of Shack-Hartmann wavefront sensor and improving the wavefront reconstruction quality. In proposal method, a liquid crystal display panel (LCD) for the generation of an array of Fresnel microlenses is use instead of the static microlens array of the conventional Shack-Hartmann type sensor. An off-axis holographic microlens array is designed instead of the normal microlens array to increase the effective array and then the dynamic range. The focus properties of the off-axis lens are studied.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.05a
• /
• pp.465-469
• /
• 2003

Microlens arrays were fabricated using a novel fabrication technology based on the exposure of a PMMA (Polymethylmethacrylate) sheet to deep X-rays and subsequent thermal treatment. X-ray irradiation causes the decrease of molecular weight of PMMA, which in turn decreases the glass transition temperature and consequently causes a net volume increase during the thermal cycle resulting in a swollen microlens. A new physical modeling and analyses for microlens formation were presented according to experimental procedure. A simple analysis based on the new model is found to be capable of predicting the shapes of microlens which depend on the thermal treatment. For the replication of microlens arrays having various diameters with different foci on the same surface, the hot embossing and the microinjection molding processes has been successfully utilized with a mold insert that is fabricated by Ni-electroplating based on a PMMA microstructure of microlenses. Fabricated microlenses showed good surface roughness with the order of 1 nm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.37 no.5
• /
• pp.554-561
• /
• 2024

Micro light-emitting diodes (µLEDs) have been utilized in various fields such as displays, and smart devices, due to their superior stabilities. Since the applications of the µLEDs have been extended to medical devices and wearable sensors, excellent optical properties and uniformity of the µLEDs are important. Hence, several researchers have investigated to enhance the optical efficiency of the µLEDs through micro/nano lens. However, the reported methods for realizing the micro/nano lens have some drawbacks such as complex and high-cost manufacturing processes. Herein, we developed µLEDs with 3D-printed hydrogel microlenses. The printed hydrogel had high transparency and excellent adhesive strength, allowing it to attach onto top surface of the µLEDs without any additional adhesives. Microscale printing technology using a 3D printer achieved quick and fine printing in desired shapes and arrangements, showing the possibility of mass production. The 3D-printed microlens can be applied to improve not only the optical properties of µLEDs but also other optical devices.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2001.10a
• /
• pp.200-203
• /
• 2001

Micromolding methods such as micro-injection molding and micro-compression molding are most suitable for mass production of plastic micro-optics with low cost. In this study, plastic micro-optical components, such as refractive microlenses and diffractive optical elements(DOEs) with various grating patterns, were fabricated using micro-compression molding process. The mold inserts were made by ultrapricision mechanical machining and silicon etching. A micro compression molding system was designed and developed. Polymer powders were used as molded materials. Various defects found during molding were analyzed and the process was optimized experimentally by controlling the governing process parameters such as histories of mold temperature and compression pressure. Mim lenses of hemispherical shape with $250{\mu}m$ diameter were fabricated. The blazed and 4 stepped DOEs with $24{\mu}m$ pitch and $5{\mu}m$ depth were also fabricated. Optical and geometrical properties of plastic molded parts were tested by interferometric technique.