• Korean Journal of Optics and Photonics
• /
• v.14 no.4
• /
• pp.359-364
• /
• 2003

We propose a novel vertical directional coupler with polarization independent very short coupling lengths using the double-sided deep-ridge waveguide structure which could be implemented using double-sided process to polarization insensitive deep-ridge waveguide structures and investigate the effect of various structure parameters on the coupling length. Variation of coupling length for the variation of the waveguide width is smaller than that for the variation of the core thickness. Coupling length decreases as the inner cladding layer thickness and the core thickness decrease. The waveguide width with the polarization independent coupling length decreases as the inner cladding layer thickness decreases for the same core thickness and the core thickness decreases for the same inner cladding layer thickness.

• Korean Journal of Optics and Photonics
• /
• v.20 no.4
• /
• pp.241-248
• /
• 2009

We suggest a new method to determine the off-alignment error of the composite film, together with in-plane($R_{in}$) and out-of-plane retardation($R_{th}$) of the compensation film, simultaneously. The composite film consists of a polarizing film and a compensation film for improvement of viewing angle of a liquid crystal display. We regarded the compensation film as o-plate with its optic axis along an arbitrary direction. By using an extended Jones matrix method, the polarization characteristics of the composite film are examined. The calculated Fourier constants, ($\alpha$, $\beta$) curves of the composite film as the azimuth angle is varied at the incident angles of $0^{\circ}$ and $50^{\circ}$, respectively, are used to determine the axis misalignment, the tilt angle and the azimuth angle of the compensation film by adopting the linear regressional analysis technique. Since this method can be applied for the inspection of the composite film even after laminating the polarizing film and the compensation film, it will be useful for simplifying the manufacturing process and reducing the production cost of liquid crystal display panels.

• Journal of Sensor Science and Technology
• /
• v.5 no.5
• /
• pp.55-62
• /
• 1996

This paper describes development of Polarized Stereo Monitoring System (KAERI-PSM) and compares the remote handling performance of KAERI-PSM with that of other monitoring systems, electric shutter type stereo monitoring system and general TV monitoring system. Remote handling performance is evaluated by total time and error number on remote operating experiments. Four kinds of remote handling experiments are carried out through 1) directly 2) general TV 3) electric shutter type monitor, and 4) KAERI-PSM. In these experiments six employees are participated and PUMA robot with force-torque reflectional joystic is used. The result of experiments show that camera angle against object is significant factor in monitoring and stereo monitoring system give more performance benifits in terms of accuracy and speed of remote handling operation than general TV monitoring system. In comparision of the polarized and electric shutter type stereo monitoring system, both have similar accuracy and speed for remote handling operation, but the former is superior in image quality and stability of the performance.

• Economic and Environmental Geology
• /
• v.52 no.4
• /
• pp.313-322
• /
• 2019

SAR (Synthetic Aperture Radar) remote sensing data is a very useful tool for near-real-time identification of landslide affected areas that can occur over a large area due to heavy rains or typhoons. This study aims to develop an effective algorithm for automatically delineating landslide areas from the polarimetric SAR data acquired after the landslide event. To detect landslides from SAR observations, reduction of the speckle effects in the estimation of polarimetric SAR parameters and the orthorectification of geometric distortions on sloping terrain are essential processing steps. Based on the experimental analysis, it was found that the IDAN filter can provide a better estimation of the polarimetric parameters. In addition, it was appropriate to apply orthorectification process after estimating polarimetric parameters in the slant range domain. Furthermore, it was found that the polarimetric entropy is the most appropriate parameters among various polarimetric parameters. Based on those analyses, we proposed an automatic landslide detection algorithm using the histogram thresholding of the polarimetric parameters with the aid of terrain slope information. The landslide detection algorithm was applied to the ALOS-2 PALSAR-2 data which observed landslide areas in Japan triggered by Typhoon in September 2011. Experimental results showed that the landslide areas were successfully identified by using the proposed algorithm with a detection rate of about 82% and a false alarm rate of about 3%.

• Proceedings of the Korea Crystallographic Association Conference
• /
• 2002.11a
• /
• pp.38-39
• /
• 2002

Spectroscopic ellipsometer(SE)는 박막의 두께, 굴절률, 흡수율, 에너지 갭, 결정상태, 밀도, 표면 및 계면의 거칠기 등에 관한 유용한 정보들을 제공한다. (1-3) SE는 빛을 탐침으로 사용하기 때문에 비파괴적이고 비접촉식 박막물성 측정방법이며 편광변화에 대한 상대적 물리량을 측정함으로써 정밀도와 재연성이 매우 높은 장점들을 갖고 있다. 따라서 SE는 반도체 메모리 소자, 평판 디스플레이, DVD와 CD와 같은 데이터 저장장치 등을 제작하는 공정에서 박막에 관련된 공정계측장비로 사용되고 있다. 특히, 최근의 차세대 반도체 소자 개발에 관한 연구 등(4-6)에서는 수 nm 두께의 다양한 초박막들에 관한 물성연구가 주관심사이기 때문에 최고의 성능을 갖는 계측장비와 기술이 요구되고 있다. 따라서 본 연구에서는 그림과 같은 편광자(polarizer)-시료(sample)-검광자(analyzer)로 구성된 PSA구조의 표준기용 rotating-analyzer SE를 제작하게 되었다. 현재까지 개발된 ellipsometer의 수많은 종류들 중에서 null 형, rotating element 형, 그리고 phase modulation 형이 가장 많이 사용되고 있다. 여기서 element란 polarizer, analyzer, 또는 compensator와 같은 광 부품들을 지칭하는데 이 중 하나 또는 둘을 회전시키기 때문에 그 종류 또한 매우 많다. 이들 중에서 회전검광자형 ellipsometer는 입사각 정렬이 우수하고, 파장에 무관한 편광기만 사용하므로 비교적 넓은 광량자 에너지영역에서 정확도 높은 데이터를 얻을 수 있기 때문에 박막 상수의 정밀측정에 가장 적합하다. 특히, 본 연구에서 제작된 ellipsometer에는 간섭계 장치, polarizer tracking,(2) zone average,(1) 그리고 low-pass filter 등을 사용함으로써 측정오차를 최대한 줄이는 노력을 하였다.

• Journal of the Korea Society of Computer and Information
• /
• v.12 no.3
• /
• pp.131-136
• /
• 2007

This paper proposes a new approach to eliminate the reflectance component for the detection of text in color images. Color images, printed by color printing technology, normally have an illumination component as well as a reflectance component. It is well known that a reflectance component usually obstructs the task of detecting and recognizing objects like texts in the scene, since it blurs out an overall image. We have developed an approach that efficiently removes reflectance components while preserving illumination components. We decided whether an input image hits Normal or Polarized for determining the light environment, using the histogram which consisted of a red component. We were able to go ahead through the ability to extract by reducing the blur phenomenon of text by light because reflection component by an illumination change and removed it and extracted text. The experimental results have shown a superior performance even when an image has a complex background. Text detection and recognition performance is influenced by changing the illumination condition. Our method is robust to the images with different illumination conditions.

• Korean Journal of Optics and Photonics
• /
• v.7 no.4
• /
• pp.419-427
• /
• 1996

Thermally-stabilized fiber-optic current sensors are proposed and demonstrated. The sensor head is made of two coil formers combined perpendicularly. In this sensor head, bending-induced birefringences can be reduced to the level much smaller than those of the single former type because the eigen-axes of the two perpendicular coil formers are made orthogonal to each other. Moreover, thermal variation of the birefringence is also expected to be minimized by the orthogonality of the two polarization eigen-axes. We changed the temperature slowly in the range of 20~45$^{\circ}C$ during 100 minutes. The overall linearity of the sensor is better than 1.2% in the range of 0~1000A. The long-term fluctuation of the sensor is less than 1% when measured for 3 hours at 500A and room temperature. Two orthogonally-polarized laser diodes are combined together to make the incident beam unpolarized. In the signal processing, the signals are separated by two parts and normalized respectively, which minimize the efects of optical fluctuations coming from sources, connectors, etc.

• Korean Journal of Optics and Photonics
• /
• v.18 no.5
• /
• pp.295-302
• /
• 2007

This paper presents a rigorous comparison of the design characteristics of polarization-insensitive directional coupler (DC) and multimode interference (MMI) coupler based on rib type waveguides, by using longitudinal modal transmission-line theory (L-MTLT). It shows that the multimode mixing and interference property of MMI can be structurally designed through the continuous evolution of the two-mode coupling property of DC. It also compares and analyzes the coupling efficiency along with the coupling length and the wavelength between polarization-insensitive DC and MMI. From the design properties obtained, it demonstrates for the first time the integration of polarization-insensitive DC or MMI with a Bragg grating and evaluates precisely the filtering characteristics. The numerical results reveal that the DC, as long as it is designed to have the same coupling length for TE and TM modes, has better performance than the MMI in polarization-insensitive filtering behaviour. However, it shows that the MMI with much less coupling length than DC is preferred in the miniaturization of integrated devices.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1997.10a
• /
• pp.381-386
• /
• 1997

본 논문에서는 개발된 편광방식 스테레오 모니터링(KAERI-PSM) 시스템의 성능을 평가하기 위해 6 D.O.F.의 퓨마 로보트를 이용한 원격조작 실험을 수행하였다. 카메라의 관측각도를 달리하는 3가지 원격조작실험은 6명의 실험자가 힘반향 조이스틱을 사용하여 로보트 암을 (1)직접 (2)일반 평면모니터 및 (3)개발된 편광방식 스테레오 영상 모니터를 통하여 보면서 6가지의 조합된 방법으로 총 36번 수행하여 걸린 평균시간과 평균 에러 발생 수를 비교하는 것이다. 실험 결과 스테레오 영상 모니터를 사용한 경우 일반 평면모니터를 이용했을 때 보다 훨씬 짧은 시간에 정확히 원격작업을 수행할 수 있었으며, 물체 이동에 대한 카메라의 각도가 실험의 주요한 변수가 됨을 알 수 있었다.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.9
• /
• pp.56-63
• /
• 1999

Conventional method to improve the response time of the Cat-SPPCM was to increase fanning beam using cylindrical lens. But, in this case the temporal instability of this SPPCM is increased, and fanning beam plays a role as noise, so that it decreases the reflectivity. Thus, fanning beam must be controlled to improve the properties of SPPCM. In this paper, we propose the method to increase the reflectivity of SPPCM and decrease the response time by focusing line-shaped input beam into photorefractive crystal using cylindrical lens and decrease the temporal instability of output beam by using mixed-polarized beam instead of simple extraordinary polarized beam. Optical experiments show that the reflectivity of proposed SPPCM is increased twice and the response time is reduced by 15 times. Also, we observed that the temporal instability of SPPCM is reduced when the polarization angle of the mixed-polarized beam is between $10^{\circ}$ and $30^{\circ}$ . We used a $45^{\circ}-cut\;BaTiO_3$ crystal which has high electro-optical coefficients in optical experiments.