• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1589_1590
• /
• 2009

본 논문에서는 구면 렌즈 검사를 위해 제작된 Fizeau형 위상 천이 간섭계(Fizeau-type Phase Shifting Interferometer : FPSI)에 비구면 해석 알고리즘을 적용한 소형 비구면 렌즈 해석 방법을 제안한다. 또한 본 논문에서 제안한 방법의 측정 결과와 기존 비구면 검사 시스템의 측정 결과를 비교하여 그 성능을 평가한다.

• Journal of Korean Ophthalmic Optics Society
• /
• v.17 no.4
• /
• pp.469-476
• /
• 2012

Purpose: The purpose of this study is to investigate the changes of asphericity according to diameter and direction of the cornea. Methods: The changes of asphericity according to diameter and direction of cornea is measured by using Pentacam(Oculus Co., Germany), as targeting 57 adults (average $27.0{\pm}4.8$, 20 men, 37 women) without any ophthalmic diseases, which may be effective in eyesight, and refractive surgery. Results: As diameter increases in every direction based on the corneal vertex, asphericity has attentively increased (p<0.05), and the size of asphericity in each direction from every measured diameter showed as superior > nasal > inferior > temporal. In group comparison by nearsightness and astigmatism level, asphericity measured high when nearsightness and astigmatism levels were higher, and this appears to be statistically attentive.(p<0.05). Conclusions: Asphericity of cornea significantly increased according to increase of diameter of cornea, and as measured figure or increased quantity appeared differently in all directions based on corneal vertex, so it helps to understand shape of cornea, and considered that is the part to be considered during manufacturing and fitting of RGP lenses.

• Korean Journal of Optics and Photonics
• /
• v.19 no.1
• /
• pp.31-35
• /
• 2008

A rod-type aspheric lens collimator for the optical telecommunication system which shows high coupling efficiency and experiences small coupling loss for misalignment errors is designed. The working distance, thickness, and diameter of the rod-type aspheric lens are determined to be close to those of the GRIN lens collimator in order to replace the GRIN lens with the rod-type aspheric lens. Since the coupling loss mainly originated from the spherical aberration of the lens, the spherical aberration in the rod-type aspheric lens is reduced drastically, and it turns out that the coupling efficiency of the rod-type aspheric lens collimator is higher than that of the available collimators, such as ball lens, GRIN lens, and C-type lens collimators.

• Korean Journal of Optics and Photonics
• /
• v.31 no.6
• /
• pp.328-333
• /
• 2020

In this paper, we study the analysis method for the aspherical tolerance of a Korsch telescope using a Q polynomial. It is important to analyze the tolerances for evaluating quality in high-precision fabrication of aspherical reflectors for high-resolution satellites. Thus we express the aspheric surface in terms of a Q polynomial in which each coefficient term is composed independently, and analyze the tolerance of a Korsch telescope. We also analyze the tolerance using Zernike fringe sag, which expresses the shape error of an aspherical mirror. By comparing the two results, we confirm that the Q-polynomial method can be used to analyze an aspherical mirror.

• Journal of Korean Ophthalmic Optics Society
• /
• v.14 no.1
• /
• pp.31-38
• /
• 2009

Purpose: This study was to evaluate corneal topography, contrast sensitivity and ocular response of a RGP, back surface aspherical contact lens compared with a spherical contact lens. Methods: A total 37 subjects were fitted with a spherical lens in right eye and an aspherical in the left eye and were evaluated for changes in corneal topography and contrast sensitivity over a 2-month period. Results: Thirty-four of 37 subjects completed the 2-month study. The corneal topography did not show differences between spherical and aspherical RGP lenses. The eyes fitted with the aspherical lenses demonstrated a greater reduction in contrast sensitivity compared with their spherical counterparts under photopic condition. Subjects preferred comfort and ocular responses provided by the spherical lens. Conclusions: Corneal topography when comparing spherical and back surface aspherical RGP lenses did not show any significant difference in the subjects. Spherical RGP lens yields better contrast sensitivity and preference than aspherical RGP lens at photopic condition. Further investigation of aberrations induced by contact lens design is warranted to explain the observed differences in visual performance.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1993.04b
• /
• pp.281-286
• /
• 1993

Projection TV에는 시각 품질을 최종적으로 표시하는 디스플레이 소자인 비구면플라스틱 렌즈를 적용하고 있으나 전량 일본에서 완제품으로 공급 받고 있다. 플라스틱 비구면 렌즈를 성형하기 위해서는 사출 공정에 대한 철저한 이해 와 폴리머의 광탄성 거동에 대한 개념이 핵심이라고 말할 수 있다. 복굴절성 실험은 폴리머의 유변학적 거동을 파악 하는데있어 가장 유용한 실험중의 하나이다. 본 글에서는 이와 관련된 사항인 복굴절성, 잔류 응력 형성 메카니즘, 밀도이완 작용의 상관관계와 비구면 렌즈의 성형 조건 및 공정에대해 기술 하였고, 또한 측정된 수지데이타를 이용 상용 S/W를 사용하여 유동, 냉각, 보압 ( 압축) 및 수축 해석을 실시 하여 각 stage에서 경험한 온도 와 압력의 이력에따라 변화하는 열 응력에 기인한 잔류 응력 계산 Pg을 개발 상용 S/W 와 비교 검증 하였다.

• Journal of Korean Ophthalmic Optics Society
• /
• v.12 no.4
• /
• pp.83-86
• /
• 2007

In this study, a program has been developed to enable a simulation of spherical aberration - originated from a spherical surface and an aspheric surface - via ray tracing and calculation of the degree of spherical aberration. This process has been verified for the variation of spherical aberration generated from ray tracing for aspheric surfaces such as an oval, a parabola, and a hyperbola. By comparing it with the spherical surface, the principle and necessity of the aspheric surface lens design have been understood. In addition, it allows confirming the accuracy of the simulation by developing a ray tracing program in relation to the mirror plane of a parabola.

• Applied Microscopy
• /
• v.36 no.3
• /
• pp.227-234
• /
• 2006

To investigate the comparative effect of spherical and aspherical RGP lens were worn during 3 weeks on rabbit's cornea. Four white rabbits were worn right eyes with spherical lens and 4 white rabbits were worn right eyes with aspherical RGP lens. Left eyes were served as control. The rabbits were sacrificed at 3 weeks after fitting and observed morphological changes by scanning electron microscopy and also investigate proliferation rate of the corneal epithelium with RGP wearing. After spherical RGP lens wearing, the epithet layer damaged compared to aspherical lens. The superficial cell layer strip off seriously, cell size significantly changed abnormal. Both spherical and aspherical RGP lens fitting group showed so many bacteria and back surface of lens was found like a fern shape. The aspherical RGP lens original material type was some formal than spherical lens. We thought that these pattern was significantly altered with spherical lens by prohibited transmitter oxygen from atmosphere therefore the epithelium shape was changed. This suggested wearing the aspherical lens might be less physiologic than shperical lens fitting.

• Journal of Korean Ophthalmic Optics Society
• /
• v.17 no.4
• /
• pp.373-380
• /
• 2012

Purpose: The present study was performed to investigate a relationship between the stable centrations of spherical RGP lens and aspherical RGP lens on cornea and corneal eccentricity. Methods: Two RGP lenses with different designs were fitted in alignment, steep or flat on total 84 eyes having corneal eccentricity of 0.28~0.78. The stable centration of lenses on cornea was analyzed by taking photographs with a high-speed digital camera. Results: The stable centrations of spherical and aspherical RGP lenses in horizontal direction were decentrated to temporal side. More centration to median side was shown when corneal eccentricity was larger. The difference between the stable centrations of spherical and aspheric RGP lenses according to corneal eccentricity was bigger when the fitting state was flatter. The difference in the stable centrations of aspherical RGP lens was smaller than that of spherical RGP lens regardless of fitting status. The stable centrations of spherical and aspherical RGP lenses in vertical direction were located below corneal apex regardless of fitting status however, there was no significant difference analyzed by the variation of corneal eccentricity. However, there were many cases that RGP lenses were in upper eyelid with increasing corneal eccentricity. Conclusions: The consideration of corneal eccentricity is required for RGP lens fitting and manufacturing aspherical RGP lens since the stable centration of spherical RGP lens as well as aspherical RPG lens' centration was changed depending on corneal eccentricity.

• Journal of Korean Ophthalmic Optics Society
• /
• v.12 no.4
• /
• pp.87-90
• /
• 2007

To manufacture the lens mold used in producing polycarbonate (PC) lenses, the core manufacturing is needed and this core manufacturing is generally performed by diamond turning machine (DTM) or computer numerical control (CNC) lathe. The numerical data about the lens core feature is necessarily needed for operating of these devices. Therefore, we developed the program which calculate the numerical data about the lens core feature. The program was composed to be able to input aspherical coefficients of lens feature, display the graph of lens feature, and save the numerical data file.