• Korean Journal of Optics and Photonics
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• v.13 no.5
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• pp.384-389
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• 2002

A new idea of the wavelength locking module for DWDM application was investigated in the present research. Only one etalon photo-diode is generally used in the internal/external wavelength locking system. For the internal wavelength locking module with 50 GHz applications, an algle tuning method of the etalon commonly applied. However, the alignment process of the etalon with the angle tuning method is limited because the lock performance is extremely sensitive accoriding to the change of the tilting angle. In an optical viewpoint, the alignment tolerance of the locker module with the etalon PD array block was good, and the precise tuning of the wavelength was possible. The characteristics of free spectral range (FSR) and peak shift of wavelength according to the tilting angle with the locker module was investigated. For the present module, the optimized initial tilting angle was experimentally obtained.

• Korean Journal of Optics and Photonics
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• v.19 no.4
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• pp.276-286
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• 2008

The representative alignments for taking a stereo image by using a stereoscopic camera are the toed-in and the parallel alignment. In this paper, we tried to find important factors in the process that captures the stereo image by modifying parallel type 3D camera alignment to take the same object information as, for instance, when toed-in type was used. The modified parallel type 3D camera has merits in both types. As a result, three important factors are found by simulation to be inter-camera distance, field of view and convergence angle for both types. And the change of the convergence angle is known to be the most important factor at the stereo fusible area in processing. The effective ranges of these factors to simulate perfectly toed-in type by modified parallel type are strongly dependent on a user's circumstances such as mobile, official, theater and so on. Additionally, the error of the simulation is reduced when the focal length of the stereo camera is short and the convergence angle becomes smaller.

• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.392-398
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• 2003

We present a novel concept of a phase-shifting diffraction-grating interferometer, which is intended for the optical testing of concave mirrors with high precision. The interferometer is configured with a single reflective diffraction grating, which performs multiple functions of beam splitting, beam recombination, and phase shifting. The reference and test wave fronts are generated by means of reflective diffraction at the focal plane of a microscope objective with large numerical aperture, which allows testing fast mirrors with low f-numbers. The fiber-optic confocal design is adopted for the microscope objective to focus a converging beam on the diffractive grating, which greatly reduces the alignment error between the focusing optics and the diffraction grating. Translating the grating provides phase shifting, which allows measurement of the figure errors of the test mirror to nanometer accuracy.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.189-196
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• 2002

The components and alignment parameters of a flat-field soft x-ray spectrometer used in the wavelength range below 50 $\AA$ are determined, and the characteristics of the spectrometer are analyzed. It consists of a toroidal mirror, a slit, a varied line-spacing concave grating, and a soft x-ray detector. The space-resolved spectral image of a source is formed on a single plane using the tordidal mirror and the 2400-grooves/mm varied line-spacing concave grating. The former is used to compensate for the astigmatism caused by the grazing incidence of soft x-ray light on the concave grating. The spectral and spatial resolutions of the spectrometer are calculated by applying the wave front aberration theory, and the diffraction efficiency is calculated by applying the scalar diffraction theory.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.2
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• pp.143-151
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• 2012

Purpose: The present study was conducted to investigate whether there is any difference in the centration of spherical RGP lens on cornea according to corneal types, corneal astigmatism and lens fitting states. Methods: Spherical RGP lens was fitted on 29 eyes of round-typed cornea and 45 eyes of symmetric bowtie-typed cornea with 0.00~2.75 D of corneal astigmatism in alignment, steep or flat. Their lens centrations on cornea were analyzed by taking photographs. Results: The centration of spherical RGP lens in the vertical direction was decentrated to downward direction in all cases, and the degree of decentration was not consistent. The lens centration in horizontal direction was significantly more-decentrated to the temporal meridian as base curve of lens was increased, and the degree of decentration was different according to the corneal type, corneal astigmatism and fitting states. With the same degree of astigmatism, the lens decentration to the temporal meridian was bigger in round-typed cornea than that in symmetirc bowtie-typed cornea. Conclusions: The centration of spherical RGP lens varies depending on lens fitting states, corneal astigmatism, and corneal types. Thus, the consideration of these factors may improve the success rate in RGP lens prescription.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.429-434
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• 2010

A novel T-type polyester 7 containing 1-(2,5-dioxyphenyl)-2-{5-(1,2,2-tricyanovinyl)-2-thienyl}ethenes as nonlinear optical (NLO) chromophores, which are part of the polymer backbone, was prepared and characterized. Polyester 7 is soluble in common organic solvents such as dimethylsulfoxide and N,N-dimethylformamide. It showed a thermal stability up to $300^{\circ}C$ in thermogravimetric analysis thermogram and the glass-transition temperature ($T_g$) obtained from differential scanning calorimetry thermogram was around $113^{\circ}C$. The second harmonic generation (SHG) coefficient ($d_{33}$) of poled polymer films at 1,560 nm fundamental wavelength was around 1.85 pm/V. The dipole alignment exhibits a greater thermal stability even at $10^{\circ}C$ higher than $T_g$, and there is no SHG decay below $125^{\circ}C$ due to the partial mainchain character of the polymer structure, which is acceptable for nonlinear optical device applications.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.7.1-7.1
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• 2011

Nanoporous templates have been widely used for the development of new functional nanostructured materials suitable for electronics, optics, magnetism, and energy storage materials. We have prepared nanoporous templates by using thin films of mixtures of polystyrene-block-poly (methyl methacrylate) (PS-b-PMMA) and PMMA homopolymers. These templates have cylindrical nanoholes spanning the entire thickness of the film. Some applications of nanoporous templates are introduced: a) anti-reflective coating, b) the preparation of conducting polymer nanowires of poly (pyrrole), poly (3,4-ethylenedioxy-thiopene) onto a glass coated with indium-tin-oxide, and c) the separation membranes for biomaterials. We found that when the pore fraction of nanoholes in the film was ~0.68, almost zero reflectance at a specific wavelength, which can be changed with film thickness, was achieved at visible wavelengths Furthermore, ultra high density array of conducting nanowires was successfully prepared onto various substrates including flexible polymer. Due to highly alignment of polymer chain along the nanowire direction, the conductivity was much increased. Furthermore, these nanoporous films were found to be very effective for the separation of human Rhinovirus type 14 (HRV 14), major pathogen of a common cold in humans, from the buffer solution. We also found that when the pore size was effectively controlled down to 6 nm, a single file diffusion was observed.

• Korean Journal of Optics and Photonics
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• v.15 no.1
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• pp.56-62
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• 2004

We present a diffraction grating interferometer of large equivalent wavelength specially designed for flatness testing of rough surfaces. Two transmission diffraction gratings are illuminated on the object under test by use of two measurement beams with different angles of incidence, which yields a large equivalent wavelength. This interferometer design minimizes unnecessary diffraction rays and the systematic error caused by the diffraction gratings, and provides a large working distance and easy alignment. To improve the measurement accuracy, phase shifting technique is applied and the equivalent wavelength error caused by defocus is calibrated. Test results obtained from mirror surfaces and machined rough surfaces are discussed.

• Journal of the Semiconductor & Display Technology
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• v.9 no.1
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• pp.17-21
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• 2010

Currently miniaturized electron-optical columns find their way into electron beam lithography systems. For better lithography process, it is required to make smaller spot size and longer working distance. But, the micro-columns of the multi-beam lithography system suffer from chromatic and spherical aberration, even when the electron beam is exactly on the symmetric axis of the micro-column. The off-axis error of the electron emitting source is expected to become worse with increasing off-axis distance of the focusing spot. Especially the electron beams far from the system optical axis have a non-negligible asymmetric intensity distribution in the micro-column. In this paper, the effect of the off-axis e-beam source is analyzed. To analyze this effect is to introduce a micro-column model of which the e-beam emitting source is aligned with the center of the electron beam by shifting them perpendicular to the system optical axis. The presented solution can be used to analysis the performance of the multi-electron-beam system. The performance parameters, such as the working distances and the focusing position are obtained by the computational simulations as a function of the off-axis distance of the emitting source.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.51-59
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• 1994

We constructed travelling type Nd:YAG laser with a negative branch confocal unstable ring (NBCUR) resonator like a Newtonian telescope type using four flat mirror and two positive lenses. Annular output beam was obtained by using scraper mirror. This laser oscillator has 22 optical faces and optical alignment was done by equal inclination interferance method. We inserted a Faraday rotator of permanent magnet type designed in the laboratory for unidirectional operation. We obtained laser output energy of 80m.I with electrical input energy of 70 J. and we obtained that peak power of 0.5MW through Q-switching with BDN dye.