• Journal of the Optical Society of Korea
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• 제10권1호
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• pp.23-27
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• 2006

We are studying the application of an adaptive optics system to upgrade the beam quality of a laser. The adaptive optics (AO) system consists of a bimorph deformable mirror, a Shack-Hartmann sensor and a control system. In most AO applications, the beam aperture is considered to be circular. However, in some cases such as laser beams from unstable resonators, the beam apertures are annulus or a holed-rectangle. In this paper, we investigate how well a bimorph deformable mirror of ${\Phi}120\;mm$ clear aperture can compensate phase distortions for three different beam configurations; 1) ${\Phi}120\;mm$ circular aperture, 2) ${\Phi}100\;mm$ annulus aperture with a ${\Phi}20\;mm$ hole and 3) $70\;mm{\times}70\;mm$ square aperture with a hole of $30\;mm{\times}30\;mm$. This study concludes that the bimorph mirror, which might be considered as a modal controller, can compensate tilt, defocus, coma and astigmatism, and spherical aberration for all three beams.

• Molecules and Cells
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• 제24권2호
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• pp.177-184
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• 2007

Approximately 200 individual skeletal elements, which differ in shape and size, are the building blocks of the vertebrate skeleton. Various features of the individual skeletal elements, such as their location, shape, growth and differentiation rate, are being determined during embryonic development. A few skeletal elements, such as the lateral halves of the clavicle and parts of the skull are formed by a process called intramembranous ossification, whereby mesenchymal cells differentiate directly into osteoblasts, while the majority of skeletal elements are formed via endochondral ossification. The latter process starts with the formation of a cartilaginous template, which eventually is being replaced by bone. This requires co-regulation of differentiation of the cell-types specific for cartilage and bone, chondrocytes and osteoblasts, respectively. In recent years it has been demonstrated that Wnt family members and their respective intracellular pathways, such as non-canonical and the canonical $Wnt/{\beta}$-catenin pathway, play important and diverse roles during different steps of vertebrate skeletal development. Based on the recent discoveries modulation of the canonical Wnt-signaling pathway could be an interesting approach to direct stem cells into certain skeletal lineages.

• 천문학회보
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• 제41권1호
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• pp.73.3-74
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• 2016

본 연구에서는 비구면 반사경의 형상오차를 3가지 방법으로 측정, 비교하였다. 실험에 사용한 포물면 반사경의 구경은 108 mm, 유효초점거리는 444.5 mm 이다. 첫 번째로 접촉식 형상측정방식인 FTS(Form TalySurf)를 이용하여 표면 거칠기와 반사경의 최적 곡률 반경(BestFitt Radius) 값을 측정하였다. 두 번째로는 비접촉식 형상측정방식인 UA3P(Ultrahigh Accurate 3-D Profilometer)를 이용하여 반사경의 형상 정밀도를 측정하였다. UA3P를 이용할 경우 반사경의 전체 형상을 측정할 수 있다. 세번째로 Shark-Hartmann 센서를 이용한 광학측정방법으로 반사경의 형상 정밀도를 측정하였다. 측정에 필요한 레이저 광학계는 레이저, 콜리메이터, 핀홀, 카메라 렌즈 및 비구면 광학계를 이용하여 설계하였다. 본 연구에서 도출한 각 측정 방법의 신뢰도를 바탕으로 간섭계 사용에 제약이 있는 자유형상곡면의 반사경 표면의 형상오차 측정에 적용할 계획이다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.336-339
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• 2007

The enhanced control of OLED deposition processes by Organic Vapor Phase Deposition $(OVPD^{(R)})$ is discussed. $OVPD^{(R)}$ opens a wide space of process control parameters. It allows the accurate and individual control of deposition layer properties like morphology and precise mixing of multi component layers (co-deposition) in comparison to conventional deposition manufacturing processes like e. g. VTE (vacuum thermal evaporation).

• Current Optics and Photonics
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• 제6권1호
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• pp.1-9
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• 2022

This paper proposes a robust, simple zonal wavefront-estimation method in a grid sampling model. More slopes are added to the integral equation of the algorithm to improve the accuracy and convergence rate of this approach, especially for higher-order optical aberrations. The Taylor theorem is applied to clarify the mathematical description of the remaining error in the proposed method. Several numerical simulations are conducted to ensure the performance and improvement in comparison to the Southwell and previous algorithm. An experiment is also conducted according to deflectometry output and the results are verified using a reference measured with a stylus system.

• Journal of applied mathematics & informatics
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• 제41권2호
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• pp.401-411
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• 2023

The effects of longitudinal velocity dusty fluid flow in a weak magnetic field are investigated in this paper. An external uniform magnetic field parallel to the flow of dusty fluid influences the flow of dusty fluid. Besides that, the problem under investigation is completely defined in terms of identifying parameters such as longitudinal velocity (u), Hartmann number (M), dust particle interactions β, stock resistance γ, Reynolds number (Re) and magnetic Reynolds number (Rm). While using suitable transformations of resemblance, The governing partial differential equations are transformed into a system of ordinary differential equations. The Hankel Transformation is used to solve these equations numerically. The effects of representing parameters on the fluid phase and particle phase velocity flow are investigated in this analysis. The magnitude of the fluid particle is reduced significantly. The result indicates the magnitude of the particle reduced significantly. Although some of our numerical solutions agree with some of the available results in the literature review, other results differs because of the effect of the introduced magnetic field.

• 천문학회보
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• 제45권1호
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• pp.67.1-67.1
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• 2020

Adaptive Optics (AO) is the technology for ground-based telescopes to overcome the interference caused by atmospheric turbulence. We are developing an AO system for the 1-m telescope at Seoul National University Observatory (SNUO). The seeing size of the SNUO is 2 arcseconds on average, and 0.85 arcseconds at best condition. Our system is based on MEMS deformable mirror and Shack-Hartmann wavefront sensor. We developed the wavefront sensor using a cheap CMOS camera, and measured phase disturbance at SNUO. To verify the performance of the AO system, we designed an artificial phase disturber that produces similar scale phase error, measured at SNUO. We carried out laboratory tests in which the AO system measures and corrects the wavefront using the phase disturber and an F/6 light source, the same as that of SNUO telescope. The control system was developed in C++. The system performs closed-loop PI correction up to 100 Hz at a consumer-grade PC.

• 천문학회보
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• 제46권2호
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• pp.53.3-53.3
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• 2021

Adaptive Optics (AO) was first studied in the field of astronomy, and its applications have been extended to the field of laser, microscopy, bio, medical, and free space laser communication. AO modelling and simulation are required throughout the system development process. It is necessary not only for proper design but also for performance verification after the final system is built. In KASI, we are trying to develop the AO Python Package for AO modelling and simulation. It includes modelling classes of atmosphere, telescope, Shack-Hartmann wavefront sensor, deformable mirror, which are the components for an AO system. It also includes the ability to simulate the entire AO system over time. It is being developed in the Super Eye Bridge project to develop a segmented mirror, an adaptive optics, and an emersion grating spectrograph, which are future telescope technologies. And it is planned to be used as a performance analysis system for several telescope projects in Korea.

• International Journal of Internet, Broadcasting and Communication
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• 제16권3호
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• pp.77-84
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• 2024

Aberration is still a problem for making augmented reality displays. The existing methods to solve this problem are either slow and inefficient, consume too much battery, or are too complex for straightforward implementation. There are still some problems with image quality, and users may suffer from eye strain and headaches because the images provided to each eye lack accuracy, causing the brain to receive mismatched cues between the vergence and accommodation of the eyes. In this paper, we implemented a computer simulation of an optical aberration using Zernike polynomials which are defocus, trefoil, coma, and spherical. The research showed that these optical aberrations impact the Point Spread Function (PSF) and Modulation Transfer Function (MTF). We employed the phase conjugate technique to mitigate aberrations. The findings revealed that the most significant impact on the PSF and MTF comes from the influence of spherical aberration and coma aberration.

• 한국안광학회지
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• 제19권2호
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• pp.199-206
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• 2014

목적: 특정 범위의 근시도 및 난시도에서 근시도 변화에 따른 고위수차의 증감 분석을 통해 근시도와 고위수차의 상관관계 알아보고자 하였다. 방법: Hartmann-Shack방식의 LADARWave 장비를 이용하여 총 992 안의 고위수차를 분석하였고, 현성굴절검사로 측정된 근시도값의 증가와 고위수차의 상관관계를 알아보았다. 결과: 전체 실험대상안에서 근시도가 증가함에 따라 총코마수차와 구면수차가 통계적으로 유의하게 증가하였으며, 트레포일 수차, 난시수차, 테트라포일 수차는 감소하였다. 근시도가 작은 군일수록 근시도에 따른 총코마수차의 변화가 더 급격하였으며 근시도가 작은 군에서는 통계적으로도 유의한 변화가 나타났다. 근시도가 -3.00 D 미만인 군은 근시도에 따른 구면수차값의 변화가 크지 않은 반면에 -3.00 D 이상인 군과 -6.00 D 이상인 군에서는 근시도에 따른 변화의 폭이 컸다. 특정 난시도 범위에서 근시도와 고위수차의 상관관계를 알아보았을 때 총코마수차는 난시도가 -1.00 D 이하인 군에서만 통계적으로 유의한 감소가 나타났다. 구면수차의 경우는 난시도가 작은 군일수록 근시도 증가에 따른 구면수차의 증가 폭이 더 커졌으며 모든 난시군에서 통계적으로 유의한 변화가 나타났다. 수평 및 수직코마수차는 특정 근시도 및 특정 난시도군별 일관성있는 증감관계가 성립하지 않았으며 통계적으로도 유의하지 않았다. 결론: 본 논문에서 밝힌 저위수차와 고위수차와의 상관관계를 통하여 시력의 질과 관련된 이해와 시력의 질 향상에 도움을 줄 수 있을 것으로 보여진다.