• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.10
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• pp.771-777
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• 2013

This paper dealt with the development of a LED floodlight for naval vessels to replace the conventional floodlight using an incandescent and a halogen lamp. We found a technical solution for current problems of conventional lights and also improved optical characteristics by developing a LED floodlight which has a typical long-lived light source with high efficiency. To satisfy the requirements specified in Korea Standard Vessels (KS V), the optical structure was designed with selected LED package and lens. A LED module was composed of 10 LEDs in series for stable luminous output, and an aluminium heat sink was adopted for effective heat-radiation design. The LED floodlight was fabricated as a module type so that it can easily replace the conventional light source. The power consumption of the prototype floodlight was only a tenth of a conventional one with the same optical performance. Also, a test showed the floodlight satisfied the electrical, optical and environmental requirements of the standards.

• Journal of Astronomy and Space Sciences
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• v.31 no.2
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• pp.177-186
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• 2014

The Immersion Grating Infrared Spectrometer (IGRINS) is a near-infrared wide-band high-resolution spectrograph jointly developed by the Korea Astronomy and Space Science Institute and the University of Texas at Austin. IGRINS employs three HAWAII-2RG Focal Plane Array (H2RG FPA) detectors. We present the design and fabrication of the detector mount for the H2RG detector. The detector mount consists of a detector housing, an ASIC housing, a Field Flattener Lens (FFL) mount, and a support base frame. The detector and the ASIC housing should be kept at 65 K and the support base frame at 130 K. Therefore they are thermally isolated by the support made of GFRP material. The detector mount is designed so that it has features of fine adjusting the position of the detector surface in the optical axis and of fine adjusting yaw and pitch angles in order to utilize as an optical system alignment compensator. We optimized the structural stability and thermal characteristics of the mount design using computer-aided 3D modeling and finite element analysis. Based on the structural and thermal analysis, the designed detector mount meets an optical stability tolerance and system thermal requirements. Actual detector mount fabricated based on the design has been installed into the IGRINS cryostat and successfully passed a vacuum test and a cold test.

• Korean Journal of Optics and Photonics
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• v.23 no.4
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• pp.154-158
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• 2012

In this paper, for low cost infrared optical equipment, we design and fabricate an infrared optical system for an uncooled detector using PGM(Precision Glass Molding) lenses. The designed infrared optical system has a good athermalization, and the material of all of its lenses is a chalcogenide glass suitable for the PGM method. In addition, we also fabricate the same infrared optical system using SPDT(Single Point Diamond Turning) lenses in order to measure the optical performance of PGM lenses. We measure the MTF(Modulation Transfer Function) of the two infrared optical systems which use the PGM lenses and the SPDT lenses. And then we compare and analyze the images of them both. As a result, we find that they have only a very small difference in optical performance. If the use of PGM lenses increases, we expect to reduce the cost of infrared optical equipment.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.103-103
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• 2014

Manufacturing of lens and mirror using Diamond Turning Machine (DTM) offers distinct advantages including short fabrication time and low cost as compared to grinding or polishing process. However, the DTM process can leave mid-frequency error in the optical surface which generates an undesirable diffraction effect and stray light. The mid-frequency error is expected to be eliminated by mechanical polishing after the DTM process, but polishing of soft surface of ductile aluminum is extremely difficult because the polishing process inevitably degrades the surface form accuracy. In order to increase its surface hardness, we performed electroless nickel plating on the surface of diamond-turned aluminum (Al-6061T6) off-axis mirrors, which was followed by the 6-hour-long baking process at $200^{\circ}C$ for improving its hardness. Then we polished the nickel plated off-axis mirrors to remove the mid-frequency error and measured polished mirror surfaces using the optical surface profilometer (NT 2000, Wyko Inc.). Finally, we ascertained that the mid-frequency error on the mirror surface was successfully removed. During the whole processes of nickel plating and polishing, we monitored the form accuracy using the ultra-high accurate 3-D profilometer (UA3P, Panasonic Corp.) to maintain it within the allowable tolerance range (< tens of nm). The polished off-axis mirror was optically tested using a visible laser source and a pinhole, and the airy pattern obtained from the polished mirror was compared with the unpolished case to check the influence of mid-frequency error on optical images.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.7
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• pp.13-20
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• 2004

In order to set up the design of micro optical bench, optical coupling efficiencies of two sets of test benches are calculated. Simple linear connections of incoming and outgoing optical fibers with and without ball lenses are designed. Positional errors that are possible in actual fabrication processes we considered in the calculations and their tolerances are determined from -3 ㏈ conditions. For a simple fiber-to-fiber connection, the lateral misalignment should be limited to 2.7 um and tilt error 5.8o. In case of the fiber-to-fiber with ball lens, the working distance between fibers can be extended over 60 um. The optical coupling efficiency depends strongly on the positional errors of ball lenses along the optical axis, and it is also found that the lateral and vertical positional errors should be considered simultaneously in order to keep the high coupling efficiency.

• Korean Journal of Optics and Photonics
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• v.28 no.6
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• pp.290-294
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• 2017

The Cassegrain telescope consists of a primary concave mirror and a secondary convex mirror. In the case of a secondary mirror, it is more difficult to test wavefront error than for a primary mirror, because it reflects the entire testing beam, as it is convex in shape. In this paper we tested the wavefront error of a complex aspheric convex secondary mirror by using the Simpson-Oland-Meckel Hindle test. To separate the systematic errors, such as fabrication error and alignment error of a meniscus lens, we adopted the QN absolute test (pixel-based absolute test using the quasi-Newton method) as well. Finally, we compared the measured result with that of an ASI (Aspheric Stitching Interferometer) made by the QED company, which resulted in an rms difference of only 2.5 nm, showing a similar shape of astigmatism aberration.

• Polymer(Korea)
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• v.29 no.4
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• pp.418-421
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• 2005

Three-dimensional (3D) microfabrication process using two-photon polymerization (TPP) is developed to fabricate the curved microstructures in a layer, which can be applied potentially to optical MEMS, nano/micro-devices, etc. A 3D curved structure can be expressed using the same height-contours that are defined by symbolic colors which consist of 14 colors. Then, the designed bitmap figure is transformed into a multi-exposure voxel matrix (MVM). In this work a multi-exposure voxel matrix scanning method is used to generate various heights of voxels according to each laser exposure time that is assigned to the symbolic colors. An objective lens with a numerical aperture of 1.25 is employed to enlarge the variation of a voxel height in the range of 1.2 to 6.4 um which can be controlled easily using the various exposure time. Though this work some 3D curved micro-shapes are fabricated directly to demonstrate the usefulness of the process without a laminating process that is generally required in a micro-stereolithography process.

• Laser Solutions
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• v.14 no.2
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• pp.8-12
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• 2011

As the aged population grows around the world, many medical instruments and devices have been developed recently. Among the devices, a drug delivery stent is a medical device which requires precision machining. Conventional drug delivery stent has problems of residual polymer and decoating because the drug is coated on the surface of stent with the polymer. If the drug is impregnated in micro hole array on the surface of the stent, the problem can be solved. Micro sized holes are generally fabricated by laser machining; however, the fabricated holes do not have an enough aspect ratio to contain the drug or a good surface finish to deliver it to blood vessel tissue. To overcome these problems, we propose a vibration-assisted machining mechanism with PZT (Piezoelectric Transducers) for the fabrication of micro sized holes. If the mechanism vibrates the eyepiece of the laser machining head, the laser spot on the workpiece will vibrate vertically because objective lens in the eyepiece shakes by the mechanism's vibration. According to the former researches, the vibrating frequency over 20kHz and amplitude over 500nm are preferable. The vibration mechanism has cylindrical guide, hollowed PZT and supports. In the cylinder, the eyepiece is mounted. The cylindrical guide has upper and low plates and side wall. The shape of plates and side wall are designed to have high resonating frequency and large amplitude of motion. The PZT also is selected to have high actuating force and high speed of motion. The support has symmetrical and rigid characteristics.

• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.107-113
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• 1999

Low-aberration holographic scanners that eliminate the need for lenses and mirrors promise to greatly reduce the cost of laser printers and image scanners. In this study, a holographic optical element that can simultaneously scan and focus a laser beam is designed with analytic ray tracing method. An analytic and experimental work is conducted in which we investigated the hologram structure and hologon configuration for linear aberration-free scanning. For a prototype scanner, a He-Ne laser is used to manufacture and reconstruct the hologram, and the measured bow is about $\pm$133$\mu\textrm{m}$ and spot size(half-intensity beamwidth) in under 100$\mu\textrm{m}$ for a 300 mm scan length without using a correcting lens or mirror. The diffraction efficiency is about 55$\pm$5%, which is acceptably flat. The experimentally measured results agrees with the computed values. From this fact, we can conclude that the computed results using ray tracing method are practical and useful values, and have a potential for use in high resolution laser printers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05c
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• pp.21-23
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• 2004

We report experimental results demonstrating a novel metal defined polymer optical waveguide with a low loss in electro-optic polymers for the first time. The polymer optical waveguides are created using a metal film on the top of upper cladding without any conventional etching process. The fabricated waveguides have an excellent lateral optical mode confinement at both 1.31 ${\square}m$ and 1.55 ${\square}m$ wavelength, resulting in a fiber-to lens optical insertion loss of ~ 7 dB at 1.55 ${\square}m$ and ~4.5 dB at 1.31 ${\square}m$ wavelength in a 3.5cm total length for TM polarizations, respectively. We also present the optical loss dependence of the waveguide as a function of optical wavelengths. These results may be used in the complex design of integrated polymer optical circuits that need simpler and cheaper fabrication process.