• 한국광학회지
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• 제23권1호
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• pp.1-5
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• 2012

근축회절 이론에서는 횡배율이 달라도 파장과 수치구경이 같으면 항상 동일하게 회절한다. 하지만 수치구경이 큰 광학계에서는 비근축 회절효과에 의하여 횡배율에 따라 회절 특성이 변화하게 된다. 이 연구에서는 높은 수치구경을 가지는 무수차 광학계에서 나타나는 비근축 회절효과를 주요면의 만곡이라는 관점에서 해석하고, 배율이 다른 무수차 원추곡면경의 결상에서 비근축회절효과에 의한 MTF의 변화를 살펴보았다.

• Journal of the Optical Society of Korea
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• 제20권4호
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• pp.470-475
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• 2016

In this paper, the effects of filter parameters on a supercontinuum-based all-optical thresholder are experimentally investigated. By tuning the filter parameters, the power transfer function and power transmission function are tailored. The experimental results show that a thresholder with short center wavelength has a better power function, and the slope in the middle level of the thresholder increases with increasing bandwidth. Through tuning the filter parameters, the thresholder can achieve a steplike power transfer function for optical thresholding, and a steplike power transmission function for optical self-switching. This makes the supercontinuum-based thresholder more flexible, and allows customization of performance to meet different demands in various applications.

• 한국광학회지
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• 제15권5호
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• pp.461-468
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• 2004

본 논문에서 연구된 정밀모형안은 정시안에서 1.2 시력의 적정한 수차를 가진 모형안임을 확인하였다. 망막의 특성을 생략한 안광학계에 광전달함수를 사용하여 망막에서의 광세기 분포를 조사하여 자각식으로 측정한 임상자료와 비교하였다. 망막의 광학적 특성을 나타내는 안구의 수차, 회절, 망막 대비감도, Stiles-Crawford 효과, 동공크기를 포함한 대비감도함수를 계산하였다. 모형안에 동공직경 1 mm와 8 mm의 범위에서 정시안과 비정시안에 대해 대비감도함수와 변조전달함수를 비교하여 시력을 예측하였다.

• 광학세계
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• 제12권6호통권70호
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• pp.39-48
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• 2000

광학설계 시리즈 마지막회로 3. 광학설계의 평가를 게재한다. (7월호-1. 광학계의 형상설계, 9월호-2. 광학설계의 최적화 기법) 광학계의 수차 평가(Spot Diagram Analysis, 파면수차) 및 광학계의 결상특성 평가(Point Spread Function, Optical Transfer Function)에 사용되는 일반적인 방법에 대하여 정리하였다. 지금까지 소개했던 시리즈가 광학실무 종사자들에게 조금이라도 도움이 되기를 바란다.

• 전자공학회논문지B
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• 제33B권12호
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• pp.31-44
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• 1996

Since optical delay line signal processing which utilizes optical fiber as delay line elements can provide high speed and broadband signal processing, the optical delay line signal processing has numerous applications. Recently, many research papers which optical delay line signal processing techniques are being applied to OCDMA are published. The author has published paper on the design method for optical fiber filters of lattice structure. However, the previous design method does not realize the transfer function all the time. It can be realized with constraints. In this paper, we propose the design method that can realize the transfer function all the time without any constraints for the optical fiber filter of lattice structure.

• 한국통신학회논문지
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• 제25권1B호
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• pp.105-111
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• 2000

광트랜스버셜 필터를 이용하여 희망하는 특성을 실현하기 위해서는 주어진 전달함수의 차수 만큼의 광섬유 증폭기를 사용하여야 한다. 본 논문에서는 단지 한 개의 광섬유 증폭기를 이용하여 주어진 전달함수의 정수 배를 실현할 수 있는 광트랜스버셜 필터에 대하여 논한다. 이때 광신호 에너지를 유효하게 사용하기 위하여 광신호 에너지를 최소로 하는 설계법을 적용하였다. 그리고 제안한 광트랜스버셜 필터를 이용한 몇 가지의 응용에 대하여 논하였다.

• Journal of the Optical Society of Korea
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• 제20권3호
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• pp.381-388
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• 2016

The performance of a staring infrared imaging system can be characterized based on estimating the modulation transfer function (MTF). The slant edge method is a widely used MTF estimation method, which can effectively solve the aliasing problem caused by the discrete undersampling of the infrared focal plane array. However, the traditional slant edge method has some limitations such as the low precision of the edge angle extraction and using the approximate function to fit the edge spread function (ESF), which affects the accuracy of the MTF estimation. In this paper, we propose a modified slant edge method, including an edge angle extraction method that can improve the precision of the edge angle extraction and an ESF fitting algorithm which is based on the transfer function model of the imaging system, to enhance the accuracy of the MTF estimation. This modified slant edge method presents higher estimation accuracy and better immunity to noise and edge angle than other traditional methods, which is demonstrated by the simulation and application experiments operated in our study.

• Journal of the Optical Society of Korea
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• 제20권6호
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• pp.762-769
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• 2016

The dynamic modulation transfer function (MTF) for image degradation caused by sinusoidal vibration is formulated based on a Bessel function of the first kind. The presented method makes it possible to obtain an analytical MTF expression derived for arbitrary frequency sinusoidal vibration. The error obtained by the use of finite order sum approximations instead of infinite sums is investigated in detail. Dynamic MTF exhibits a stronger random behavior for low frequency vibration than high frequency vibration. The calculated MTFs agree well with the measured MTFs with the slant edge method in imaging experiments. With the proposed formula, allowable amplitudes of any frequency vibration are easily calculated. This is practical for the analysis and design of the line-of-sight stabilization system in the remote sensing camera.

• IEIE Transactions on Smart Processing and Computing
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• 제6권3호
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• pp.141-150
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• 2017

Images obtained from underwater are usually degraded due to the environmental conditions. Some of the typical degradation factors include turbidity and color degradation. These degradations can be attributed to the absorptive and scattering properties of underwater degradation in terms of optical parameters, such as modulation transfer function (MTF), optical transfer function (OTF),point spread function (PSF), and color constancy. In this paper, we use the CODE V optical simulation software to mimic underwater conditions and model the imaging platform, thereby studying various parameters, such as PSF and MTF, and we use the PSF to remove the underwater turbidity. Experimental results show increased performance with the algorithm, compared to other existing methods.

• 대한기계학회논문집B
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• 제20권8호
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• pp.2681-2692
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• 1996

The finite-volume method for radiation in a three-dimensional non-orthogonal gas turbine combustion chamber with absorbing, emitting and anisotropically scattering medium is presented. The governing radiative transfer equation and its discretization equation using the step scheme are examined, while geometric relations which transform the Cartesian coordinate to a general body-fitted coordinate are provided to close the finite-volume formulation. The scattering phase function is modeled by a Legendre polynomial series. After a benchmark solution for three-dimensional rectangular combustor is obtained to validate the present formulation, a problem in three-dimensional non-orthogonal gas turbine combustor is investigated by changing such parameters as scattering albedo, scattering phase function and optical thickness. Heat flux in case of isotropic scattering is the same as that of non-scattering with specified heat generation in the medium. Forward scattering is found to produce higher radiative heat flux at hot and cold wall than backward scattering and optical thickness is also shown to play an important role in the problem. Results show that finite-volume method for radiation works well in orthogonal and non-orthogonal systems.