• Applied Microscopy
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• v.32 no.2
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• pp.81-90
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• 2002

In this review, the author discussed how the Fresnel and Fraunhoffer Diffraction can be deduced from the Huygens-Fresnel principle and Kirchhoff Diffraction Theory. Fresnel diffraction became the basic theory of the CTEM image theory, and Fraunhoffer diffraction became the base for electron diffraction and HRTEM image theory by Fourier transformation. The author also discussed the diffraction based on Born series.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.296-297
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• 2000

프라운호퍼 회절에 의하여 주어진 세기 무늬를 발생시키는 회절광학소자(Diffractive Optical Element, DOE)는 회절무늬소자, 키노폼(kinoform), 컴퓨터 푸리에 홀로그램 (computer-generated Fourier hologram) 등으로 불리우며, 광정보처리, 광연결, 레이저가공에서 중요한 역할을 한다. 이 소자를 설계하는 매우 다양한 방법들이 제안되었는데, iterative Fourier transform 알고리즘(IFTA)과 이를 변형한 알고리즘들이 가장 널리 사용된다. IFTA는 fast Fourier transform(FFT)를 활용하므로 계산시간이 절감되지만 국소 최소점에 고착되는 stagnation문제가 있어 이를 해결하기 위한 많은 변형된 알고리즘들이 제안되었다. 본 연구에서는 최근에 제안한 new Pnoise algorithm with hybrid input-output algorithm(NPA-HIOA)$^{(1)}$ 의 설계 성능을 IFTA, hybrid input-output 알고리즘(HIOA), new Pnoise 알고리즘(NPA)$^{(2)}$ , Nonlinear Least-Square (NLS)$^{(3)}$ 등의 기존의 알고리즘들과 비교하고자 한다. (중략)

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.1
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• pp.89-91
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• 1999

Fresnel-Kirchhoff's Integration enables us to achieve the diffraction pattern for the triangle stop. We have arranged the integral variables on the generalized coordinates and unlike the rectangularity or circle, the center of mass of the triangle does not have the symmetric position on the origin of the coordinates. Hence the solution for the system shows a difficulty for the expression in the simple formula which we see in the case of the rectangularity or circle.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.4
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• pp.193-197
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• 2018

The ratio of the period of a diffractive element to the input beam size is a critical parameter in a diffractive beam shaper. We measured and calculated the Fraunhofer diffraction patterns of a periodic hologram with an input beam size similar to the period of the hologram. The measured intensities show very complicated patterns and are strongly dependent upon the center position of the laser beam relative to the hologram. Using a diffraction formula for a periodic hologram, we calculated the diffracted light intensities and fit them to the measured ones. The measured and calculated intensities are in good agreement even when the beam diameter of the incident laser is similar to the period of the hologram. We can therefore use this formula to estimate the output of a periodic beam shaper even under such an extreme condition.

• Korean Journal of Optics and Photonics
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• v.28 no.1
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• pp.1-8
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• 2017

A method for inspecting defects in display substrates utilizing Fourier optics is proposed in this paper. A cost-effective inspection system can be realized with the proposed method, because it does not require a high-magnification microscope. Also, the proposed method can avoid tight tolerance for variations in displacement between substrate and camera, which is stems from shallow depth of field of the high-magnification microscope. In addition, possible damage caused by collisions between substrate and the inspection equipment can be avoided. The decision algorithm can be simpler than for a conventional inspection system, because spatial shift of periodic substrate patterns does not affect the intensity distribution of the diffracted light, by the Fourier transform property. The proposed method is explained with numerical studies, and experiments are carried out to check its feasibility for color-filter substrates of a liquid-crystal display.