• 정보저장시스템학회:학술대회논문집
• /
• 2005.10a
• /
• pp.17-21
• /
• 2005

High-density image sensors have microlens array to improve photosensitivity. It is conventionally fabricated by reflow process. The reflow process has some weak points. UV imprinting process can be proposed as an alternative process to integrate microlens array on photodiodes. In this study, the UV imprionting process to integrate microlens array on image sensor was developed using W transparent flexible mold and simulated image sensor substrate. The UV transparent flexible mold was fabricated by replicating master pattern using siliconacrylate photopolymer. The releasing property and shape accuacy of siliconacrylate mold was analysed. After UV imprinting process, replication quality and align accuracy was analysed.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.8
• /
• pp.1242-1245
• /
• 2001

Plastic microlenses play an important role in reducing the size, weight, and the cost of the systems in the fields of optical data storage and optical communication. In the present study, plastic microlens arrays were fabricated using micro-compression molding process. The design and fabrication procedures for mold insert were simplified by using silicon instead of metal. A simple but effective micro compression molding process, which uses polymer powder, were developed for microlens fabrication. The governing process parameters were temperature and pressure histories and the micromolding process was controlled such that the various defects developing during molding process were minimized. The radius and magnification ratio of the fabricated microlens were 125$\mu\textrm{m}$ and over 3.0, respectively.

• Proceedings of the KIEE Conference
• /
• 1999.07g
• /
• pp.3316-3318
• /
• 1999

PMMA(poly-methyl methacrylate) microlens array is fabricated using transparent acrylic resin. PMMA is commonly used material for plastic lens due to its excellent visibility larger than 90% and other optical characteristics so much close to those of glass. Orthodontic resin (DENTSPLY International Inc.), commonly used in dentistry, is an transparent acrylic resin kit including MMA liquid and polymerization powder. Their mixture results in PMMA through polymerization. Using the resin PMMA layer is formed on the substrate through spin-coating. Designed pattern of lens structure is transferred to PMMA layer by RIE (Reactive Ion Etching) with oxygen plasma. Final lens shape is formed by thermal treatment that causes PMMA to reflow, The thickness of PMMA spun on the substrate is $17{\mu}m$ that is also final sag of microlens, Designed diameters of the microlenses are $200{\mu}m$, $300{\mu}m$,and $500{\mu}m$, respectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.09a
• /
• pp.29-34
• /
• 2005

A optical head unit for nano optical probe away was developed. The optical probe array is generated by Talbot effect. The shape and thickness of microlens array(MLA) were designed to minimize the spot size at the foci of MLA. To increase the optical efficiency of the system and obtain the large tolerance for fabrication, aperture size was theoretically optimized. Then microlens illuminated aperture array(MLIAA) as an optical head unit was fabricated using a ultra violet(UV) molding process on aluminum aperture array. In this process, Al aperture array was fabricated separately using the photolithography and reactive ion etching(RIE) process. Optical properties of the generated optical probes were measured and compared at Talbot distance from the aperture array having a diameter of $1{\mu}m$ and MLIAA.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2012.10a
• /
• pp.323-324
• /
• 2012

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08b
• /
• pp.1159-1162
• /
• 2007

We have developed $16{\mu}m{\times}16{\mu}m$ digital micromirror array suitable for seamless-picture projection display system. This structure can improve the picture quality by making seamlesspicture image when combined with high-fill-factor microlens array to focus lights onto the mirror center. The fabricated micromirror shows excellent dynamic performances including the resonant frequency of 400 kHz.

• 발명특허
• /
• v.27 no.4 s.310
• /
• pp.66-73
• /
• 2002

• Journal of the Korean Society for Precision Engineering
• /
• v.30 no.6
• /
• pp.644-649
• /
• 2013

Today, there are lots of progresses in the field of lens researches, especially in the microlens fabrication. Unlike normal lenses, microlens has been widely used as a role of improving the performance of photonic devices which increase the optical precision, and also used in the fields of the display. In this paper, polymer microlenses with $300{\mu}m$ diameter were replicated through hot-embossing from nickel mold which was fabricated by micro-EDM. After hot-embossing process, the polymer microlenses have a rough surface due to the crater formed by micro-EDM process, which is projected onto the surface of the lenses. The surface of polymer microlenses was polished using solvent vapor to improve the surface roughness of the microlenses without changing their shape. In the experiment, the surface roughness was improved with the processing time and vapor temperature. Also, the roughness improvement was greatly affected by the solubility difference between polymer and solvent.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.04a
• /
• pp.7-13
• /
• 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 micro lens 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 micro lens which depend on the thermal treatment. For the replication of micro lens 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 micro lenses. Fabricated microlenses showed good surface roughness with the order of 1nm.

• Clean Technology
• /
• v.11 no.4
• /
• pp.205-211
• /
• 2005

There have been many technologies and materials proposed for realizing microlens array, and plastic injection is recognized as the most promising one because of several merits such as optical properties, impact resistance, formability, lightening and environmental adaptability. Since PR reflow for injection template fabrication enables the lens shape control easier, and the sample technology more effective for mass production, it lowers the cost, enhances integration, and reduces process steps, which leads to be environmentally benign. However injection of polymers may face the difficulty of formability depending on their properties. In order to overcome the difficulty, fast heating/cooling technology was introduced in this study, and microlenses were fabricated and evaluated. template obtained by PR reflow method was heated and cooled fast during injection to fabricate microlens array. PC and PMMA polymer materials were compared, and it was realized that PMMA showed much better formability due to its lower melting temperature. Injection parameters of pressures and velocities were driven out for injection optimization.