• 대한전자공학회논문지SD
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• 제40권3호
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• pp.10-18
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• 2003

본 논문에서는 마흐-젠더 간섭계에서 진행파의 위상정보와 직교 편광을 이용하여 광학적 암호화 시스템을 제안하였다. 두 개의 서로 직교편광의 가간섭성에 의해 간섭현상이 제거되기 때문에 복호 영상이 안정하다. 암호화 과정에서는 원 영상이 수직편광과 수평편광간의 상대적인 위상차에 의해 랜덤한 편광상태를 가지는 영상으로 암호화 된다. 따라서 랜덤한 편광분포로부터 원 영상의 정보를 알 수 없다. 영상을 복호화하기 위해서는 암호화된 영상의 랜덤한 편광분포를 서로 직교하는 두 성분으로 나누고 키영상을 간섭계에 수직 경로에 위치시킨다. 복호 영상은 검광기를 사용하여 세기형태로 재생하였다.

• 한국광학회지
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• 제20권2호
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• pp.81-86
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• 2009

디지털 홀로그램과 굴절률 차이를 이용하여 사용된 광원의 파장보다 큰 단차를 측정하는 연구를 하였다. 위상차를 측정하여 단차를 측정하는 방식에서는 위상차가 $2{\pi}$보다 큰 경우에는 원리상 단차를 구하기 어렵다. 이를 보완하기 위하여 굴절률 차이를 이용하여 인위적으로 광경로차를 줄여 파장보다 큰 단차를 측정할 수 있는 디지털 홀로그래피 시스템을 구성하였고, 실험적으로 파장의 약 3배 이상의 단차를 측정하였다.

• Design & Manufacturing
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• 제14권1호
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• pp.63-68
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• 2020

Ultra-high brightness and thin displays need to optical micro-patterns which can uniformly diffuse the lights and low loss. The micro random patterns have characteristics to rise the optical efficiency such as light extraction, uniform diffusion. For this reason, various fabrication processes are studied for random patterns. In this study, the micro random patterns were machined by diamond turning which used a controlled cutting tool path with random cutting depth. The machined patterns had random shape and directionality along the circumferential direction. The average width and length of machined random pattern according to rotation radius were 40.13㎛~55.51㎛ and 37.25㎛~59.49㎛, and these results were compared with the designed result. Also, the machining error according to rotation radius in diamond turning using randomly controlled cutting depth was discussed.

• 전기학회논문지
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• 제62권12호
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• pp.1730-1736
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• 2013

Slanted and chirp interdigital transducer(IDT) configurations were studied for generating the surface acoustic wave(SAW) with wide bandwidths on a piezoelectric substrate. These devices can be applied to manipulate optical path of light along the waveguide, ultimately used for optical switches and holographic image implementation. Prior to fabrication, the coupling of modes(COM) modeling and simulation were performed to extract optimal design parameters. The optimally designed wideband device showed wide bandwidth of 30MHz, low insertion loss of -25dB, and abrupt side suppression ratio (SSR). Several design conditions were determined during device implementation, such as slanted angle, aperture length, number of fingers, and central frequencies of IDTs. These factors were experimentally analyzed and described in details in this paper.

• 대한기계학회논문집A
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• 제33권8호
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• pp.720-725
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• 2009

Among many kinds of parts for Liquid Crystal Display (LCD), a Back Light Unit (BLU) that changes the path of the light from light source to screen is the most important part to improve optical performances such as uniformity and average value of brightness. Up to recently, design process of BLU has been carried out by depending on the experience of design engineer. Using this approach, however, is proven that it is hard to effectively deal with difficulties in a process of the LCD development such as frequent design modifications, various design requirements, and short-term development. To cope with this situation, we applied a Process Integration and Design Optimization (PIDO) based design environment. PIDO is a software package to integrate multiple simulation processes and find a better solution using various design techniques. In this research, we found a design solution satisfying all design requirements by using the PIDO.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.191-194
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• 2003

Through using aspheric lens can result in advantages such as an improved optical transfer function, a reduced distortion path or the realization of special image field curvatures. Using the diamond turning method for generating aspherics, the company claim to be able to generate surfaces with a form error of less than $0.33\;{\mu}\;m$ and a surface roughness of less than $0.025\;{\mu}\;m$. In this paper, we are manufacturing thermal image aspheric lens. Thermal image system is electro-optical imaging device which can make visible the difference of infrared energy naturally emitted by objected. In the result of aspherical surface, the form accuracy of about $0.24\;{\mu}\;m$ P-V was obtained and the surface roughness Ra $0.004\;{\mu}\;m$. Also, a brief review of Ultra-precision system Korea photonics technology institute(KOPTI) is present in this paper.

• 한국전기전자재료학회논문지
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• 제29권8호
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• pp.494-498
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• 2016

In this paper, we proposed the 3-dimenstional (3D) analysis for calculating the optical characteristics of an autostereoscopic display with electric field driven liquid crystal (ELC) lens. From 3D analysis considering the slanting of lens, we calculate the cross-talk of each images and the distortion of viewing zone. Using geometric opics and extended Jones matrix method (EJMM), phase retardation of ELC lens according to position is calcuated and then optical path difference in 3D space considering tilt and azimuth angle of incident light is gotten. Then, intensity distribution is presented in the space. Through camparing the intensity distribution using ideal lens with the ELC lens, we identify the noise and image distortion of ELC lens. As a result, this analysis is expected to provide optimum design conditions for realistic and rigorous 3D display with ELC lens.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.605-610
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• 2014

Clouds play an important role in climate change, in the prediction of local weather, and also in aviation safety when instrument assisted flying is unavailable. Presently, various ground-based instruments used for the measurements of the cloud base height or velocity. Lidar techniques are powerful and have many applications in climate studies, including the clouds' temperature measurement, the aerosol particle properties, etc. Otherwise, it is very circumscribed in cloud velocity measurements because there is no Doppler effect if the clouds move in the perpendicular direction to the laser beam path of Doppler lidar. In this paper, we present a method for the measurement of cloud velocity using lidar's range detection and DIC (Digital Image Correlation) system to overcome the disadvantage of Doppler lidar. The lidar system acquires the distance to the cloud, and the cloud images are tracked using the developed fast correlation algorithm of DIC. We acquired the velocities of clouds using the calculated distance and DIC algorithm. The measurement values had a linear distribution.

• 전기학회논문지
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• 제57권8호
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• pp.1422-1428
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• 2008

In the current PDP technology, one of the most important issues in AC PDP is improvement of luminance and luminous efficacy. To improve luminance and luminous efficacy, new cell structure of PDP containing long discharge path is necessary. However, it causes an increment of firing voltage. In order to decrease firing voltage of AC PDP having long discharge gap, the protrusion electrode is proposed. To drop the firing voltage, the protrusion electrode is inserted into the forward area of the main discharge gap. This paper presents measurements of detailed optical and electrical characteristics of AC PDP with protrusion electrodes. The experimental results show that the proposed structure with gap 80um has lower firing voltage to 27V than that of the conventional long gap structure. Moreover, the ICCD(Intensified Charge Coupled Device) images of the proposed structure show quick discharge generation by 0.07usec and longer continuation by 0.05usec than that of the conventional long gap structure. Therefore, the proposed protrusion electrodes have higher luminance by 12.5% than that of the conventional structure, as having no decrement of Luminous efficacy.

• Current Optics and Photonics
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• 제3권2호
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• pp.164-171
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• 2019

Photoluminescence (PL) properties of GaN-based light-emitting diodes (LEDs) were analyzed to study the effects of carrier leakage on the luminescence properties at room temperature. The electrical leakage and PL properties were compared for LEDs showing leakages at forward bias and an LED with an intentional leakage path formed by connecting a parallel resistance of various values. The leakages at the forward bias, which could be observed from the current-voltage characteristics, resulted in an increase in the excitation laser power density for the maximum PL efficiency (ratio of PL intensity to excitation power) as well as a reduction in the PL intensity. The effect of carrier leakages on PL properties was similar to the change in PL properties owing to a reduction of the photovoltage by a reverse current since the direction of the carrier movement under photoexcitation is identical to that of the reverse current. Valid relations between PL properties and electrical properties were observed as the PL properties deteriorated with an increase in the carrier leakage. The results imply that the PL properties of LED chips can be an indicator of the electrical properties of LEDs.