• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1823-1825
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• 2007

Based on Faraday effect, the variation of current flowing through the conductor can be encoded as that of azimuth angle of light polarization propagating through the fiber coil wound onto the conductor. The amount of current can be obtained by measuring the variation of the light intensity transformed from that of the azimuth angle through a polarization analyzer. In this paper we propose a fiber-optic current sensor system that employs a fiber polarization analyzer as a sensor interrogation device. The fiber polarization analyzer was prepared by inscribing a long-period fiber grating on a high birefringent fiber. At the fixed wavelength of 1522.5 nm, the fabricated fiber device has the polarization extinction ratio of more than 25 dB. The measurement of large current up to 600 Arms was accomplished based on a simple fiber interrogation device and the measurement output of the sensor system showed a good linearity.

• Journal of Korean Association for Spatial Structures
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• v.16 no.1
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• pp.85-94
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• 2016

In this study, an acceleration sensor that has optical fibers to measure the inclination and acceleration of a structure through contradictory changes in two-component FBG sensors was examined. The proposed method was to ensure precise measurement through the unification of the deformation rate sensor and the angular displacement sensor. A high sensitivity three-axis accelerometer was designed and prepared using this method. To verify the accuracy of the accelerometer, the change in wavelength according to temperature and tension was tested. Then, the change in wavelength of the prepared accelerometer according to the sensor angle, and that of the sensor according to the change in ambient temperature were measured. According to the test results on the FBG-based vibration sensor that was developed using a high-speed vibrator, the range in measurement was 0.7 g or more, wavelength sensitivity, 2150 pm/g or more, and the change in wavelength change, $9.5pm/^{\circ}C$.

• Proceedings of the KIEE Conference
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• 1997.07b
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• pp.593-596
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• 1997

The main purpose of this paper is to develop sensing device of joint angle using loss of opfical fiber. The source of light to optical fiber is infrared rays diode, and receiver is a photo transistor. The bent angle of optical fiber is measured with rotary encoder, and The change of voltage due to the loss of light is measured with micro computer PIC16C74. The sensing device may be used to Functional Electrical stimulation(FES) System for Rehabilitation patient.

• Journal of the Optical Society of Korea
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• v.12 no.2
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• pp.79-87
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• 2008

We have developed a miniature fisheye lens with $190^{\circ}$ field of view operating simultaneously in the visible and the near infrared wavelengths. The modulation transfer function characteristic for the visible wavelength is sufficient for a mega-pixel-grade image sensor. The lens also has a fair resolution in the infrared wavelength region. The calibrated $f-{\theta}$ distortion is less than 5%, and the relative illumination is over 90%. In consequence, a sharp wide-angle image can be obtained which is uniform in brightness over the entire range of field angles. The real image heights for the visible and the near infrared wavelengths have been fitted to polynomial functions of incidence angle with sub-pixel accuracies. Combined with the near equidistance projection scheme of the lens, this lens can be advantageously employed in various image-processing applications requiring a wide-angle lens.

• Journal of Sensor Science and Technology
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• v.13 no.2
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• pp.96-100
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• 2004

Optical fiber sensors have been used to detect small amounts of chemical species. In this work, a new thin polymer-clad fiber sensor is developed. Polyaniline is chemically synthesized and thin clad layers of the polymer are easily deposited on optical fiber by dip-coating technique. The optical property of polyaniline as a sensing material is analyzed by UV-Vis-NIR. The light source is stabilized He-Ne laser at 635 nm wavelength with 1 mW power. The light power transmitted through the optical fiber is measured with a spectrophotometer. By selecting a fixed incident angle, variation of transmitted light intensity through the optical fiber can be detected as gas molecules absorbed in the polyaniline clad layer. Among the various gases, the fabricated optical fiber sensor shows good sensitivity to $NH_{3}$ gas. The optical fiber sensors was shown more improved properties than polymer based sensors which measure conductivity changes.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.586-591
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• 2015

In recent years, along with the rapid development of LED technology, indoor positioning systems based on visible light communication (VLC) have been researched. In this paper, we propose an accurate indoor positioning method using white-light LEDs and a dual image sensor. Indoor LED lights are located at the ceiling in a room and broadcast information on their positions using VLC technology. A mobile device with a dual image sensor receives LED position information by VLC and estimates its position and azimuth angle. Simulation and experimental results are given to show the performance of the proposed indoor positioning system.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.4
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• pp.503-507
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• 2013

Purpose: This study was to design wide angle mobile camera corrected optical distortion for peripheral area, which were reduced optical distortion and TV distortion by using 4 aspherical lenses. Methods: The optical design was satisfied with ${\pm}1%$ optical distortion in viewing angle of $95^{\circ}$ and total length of optical system was less than 4.5 mm which was considering a thickness of mobile camera. 1/3.2 inch (5M) CCD sensor was used in the optical system and set design condition to satisfy MTF which was over than 20% in 140 lp/mm. Results: Optimized wide angle mobile camera showed ${\pm}1%$ optical distortion in full field of $95^{\circ}$ viewing angle and TV distortion was 0.46% so that distortion of peripheral area was reduce. MTF showed over than 20% in every field. Ray aberration and astigmatism were small amount so that it showed stable performance. Conclusions: Obtain wider and clearer view which is reduced image distortion of surrounding area via optical method in wide angle mobile camera which has wider view angle than current mobile camera. And it was able to fix a demerit when it occurred via software correction. It is able to apply to study of camera which is related to spectacles.

• Journal of Microbiology and Biotechnology
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• v.17 no.9
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• pp.1445-1451
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• 2007

A sensitive optical waveguide lightmode spectroscopy-based immunosensor was developed to detect vitellogenin in seawater flatfish (Paralichthys olivaceus). For this purpose, anion-exchange column chromatography with DE-52 resin was used to purify flatfish vitellogenin from flatfish serum containing vitellogenin that had been induced using an intraperitoneal $17{\beta}$-estradiol injection. The anti-flatfish vitellogenin antibody used as the biological component of the above immunosensor was prepared using the purified flatfish vitellogenin. The change in the incoupling angle according to the complexation between the flatfish vitellogenin and its antibody, immobilized over an optical grating coupler sensor chip, was measured to calculate the sensor response. The immunosensor was quite specific to flatfish vitellogenin binding, based on no sensor response in the case of bovine serum albumin immobilization. When plotted using double-logarithmic scales, the sensor responses increased linearly in flatfish vitellogenin concentrations of 0.00675-67.5 nM, with a detection limit of 0.0675 nM. The reusability during seven repetitive measurements was reasonably fair for the preliminary screening of flatfish vitellogenin.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.544-546
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• 2004

This paper designs and evaluates a complementary filter for fusion of inertial sensor signals. Specifically, the designed filter is applied to inverted pendulum control where the pendulum's angle information is obtained from low-cost tilt and gyroscope sensors instead of an optical encoder. The complementary filter under consideration is a conventional one which consists of low- and high-pass filters. However, to improve the performance of the filter on the gyroscope, we use an integrator in the filter's outer loop. Frequency responses are obtained with both tilt and gyroscope sensors. Based on the frequency response results, we determine appropriate parameter values for the filter. The performance of the designed complementary filter is evaluated by applying the filter to inverted pendulum control. Experiments show that the performance of the designed filter is comparable to that of an optical encoder and low-cost inertial sensors can be used for inverted pendulum control with the heir of sensor fusion.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.2
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• pp.20-25
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• 2007

This paper describes a second-generation dual sine-grid surface encoder for 2-D position measurements. The surface encoder consisted of a 2-D grid with a 2-D sinusoidal pattern on its surface, and a 2-D angle sensor that detected the 2-D profile of the surface grid The 2-D angle sensor design of previously developed first-generation surface encoders was based on geometric optics. To improve the resolution of the surface encoder, we fabricated a 2-D sine-grid with a pitch of $10{\mu}m$. We also established a new optical model for the second-generation surface encoder that utilizes diffraction and interference to generate its measured values. The 2-D sine-grid was fabricated on a workpiece by an ultra precision lathe with the assistance of a fast tool servo. We then performed a UV-casting process to imprint the sine-grid on a transparent plastic film and constructed an experimental setup to realize the second-generation surface encoder. We conducted tests that demonstrated the feasibility of the proposed surface encoder model.