• Current Optics and Photonics
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• v.3 no.1
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• pp.72-77
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• 2019

This study was performed to analyze the optical aberrations of the cornea induced by myopic refractive surgery. Corneal total higher-order aberrations, spherical aberration and coma for 4-mm and 6-mm pupils were measured using a wave-front analyzer. The amount of aberrations of the oblate corneal optics by the achieved correction was found to be larger than for the prolate corneal shape with complete eye, in an emmetropia control group. The change in corneal shape acts as an optical factor that degrades the quality of the retinal image; it seems to be one of the important factors related to quality of vision.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.353-362
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• 2014

Purpose: The present study was aimed to investigate the change of higher-order aberrations induced by aging and the effect of myopic degree on the correlation between age and higher-order aberrations. Methods: The higher-order aberrations in 931 eyes aged from 20 to 60 were measured by using a LADARWave device employing Hartmann-Shack system to analyze the effect of myopic degree measured by manifest refraction test on higher-order aberrations. Results: Coma and vertical coma aberrations were significantly decreased by the increase of myopic degree while vertical astigmatic aberration was significantly increased. The correlations of age and coma, vertical coma, spherical, vertical trefoil, horizontal trefoil, vertical astigmatic, horizontal astigmatic and vertical tetrafoil aberrations depended on the myopic degree, except for horizontal coma and horizontal tetrafoil aberrations. Conclusions: It is suggested to consider the myopic degree for the refractive correction including the laser surgery based on the present result that higher-order aberrations are affected by the myopic degree.

• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.256-261
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• 2006

Wavefront aberrations of a laser beam that was reflected from an off-axis parabolic (OAP) mirror were measured to evaluate the optical performance of the OAP mirror. For a diamond turned OAP mirror, the root-mean-square (rms) value of higher-order aberrations was only $0.03{\mu}m$ for the laser beam size of about 34 mm. The other OAP mirror which was polished at a domestic company had the rms value of higher-order aberrations of $2.07{\mu}m$ for the same beam size. Although the diamond turned OAP mirror was well fabricated to have a small amount of aberrations, the aberrations were induced by the misalignment of the OAP mirror. Especially, 0 degree astigmatism increased with the sensitivity of $0.372{\mu}m/mrad$ when the OAP mirror was tilted in the tangential plane, which agreed well with the calculated results using a commercial ray tracing software.

• Journal of Korean Clinical Health Science
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• v.7 no.1
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• pp.1232-1237
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• 2019

Purpose. In this study, two types of soft contact lenses with different materials were selected to compare the time of tear film destruction and high order aberrations before and after wearing. Methods. Thirty patients (60 eyes) in their 20s were included in this study. Two lenses with different materials, Group 4 (Etafilcon A) and Group 5 (Narafilcon A) were selected. Using aberration analyzer and keratometry, high-order aberration and tear film test (NIF-BUT, NIAvg-BUT) were performed before and after wearing. Results. When comparing the higher aberrations of the Etafilcon A and Narafilcon A lenses, the higher aberrations of the Narafilcon A lens were higher overall. For the initial tear film break-up time (NIF-BUT) after wearing, the Etafilcon A lens was reduced by 4.0 seconds and the Narafilcon A lens increased by 0.6 seconds. For the mean tear film break-up time (NIAvg-BUT) after wearing, the Etafilcon A lens decreased by 2.4 seconds and the Narafilcon A lens increased by 1.7 seconds. Conclusions. NIF-BUT and NIAvg-BUT of Narafilcon A lens were increased. The lens with relatively low water content and higher oxygen permeability than the lens with high water content has relatively less tear evaporation, which means that the time of destruction of the tear film is increased.

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.373-380
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• 1993

A five mirror system with a reduction magnification(M=+1/5) is designed for DUV optical lithography. Initially, numerical solutions of all zero 3rd order aberrations and zero 5th order spherical aberration are obtained for the spherical mirror system. Next, by the optimization method, the aspherization is carried out to the two spherical mirrors to obtain a system that has as less residual aberrations, higher NA and improved MTF as possible. We have finally obtained the system of which NA is 0.45 and the resolution is about 500 cycles/mm at the 50% MTF value criterion and the depth of focus of $1.0{\mu}m$ for the nearly incoherent illumination$({\sigma}=1.0)$ and the wavelength of 0.248 m(KrF excimer laser line).

• Proceedings of the Optical Society of Korea Conference
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• 2005.07a
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• pp.58-59
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• 2005

• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.252-259
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• 1993

A holosymmetric four-mirror system with unit magnification is designed for use in the micro-lithography using a deep ultraviolet wavelength of $0.248 {\mu}m$(KrF excimer laser line). In the holosymmetric system all orders of coma and distortion are zero. By applying this principle to the 4-spherical mirror system, we have obtained only one exact solution for the unit magnification holosymmetric four-spherical mirror system with all zero third order aberrations. For correction of the residual higher order aberrations of the system, aspherization is introduced keeping the holosymmetric properties. We have obtained near diffraction-limited performance for the wavelength of 0.248 pm within N.A. of 0.33 and image field diameter of 7.6 mm.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.2
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• pp.179-186
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• 2013

Purpose: To compare corneal asphericity, visual acuity (VA), and ocular and corneal higher-order aberrations (HOAs) between myopic refractive surgery and emmetropia groups. Methods: Twenty three subjects ($23.0{\pm}2.5$ years) who underwent myopic refractive surgery and twenty emmetropia ($21.0{\pm}206$ years) were enrolled. The subjects'criteria were best unaided monocular VA of 20/20 or better in both two groups. High and low contrast log MAR visual acuities were measured under photopic and mesopic conditions. Corneal and ocular HOAs were measured using Wavefront Analyzer (KR-1W, Topcon) for 4 mm and 6 mm pupils. Corneal asphericity was taken by topography in KR-1W. Results: There was no significant difference in VA between two groups under either photopic or mesopic conditions. In ocular aberrations, there were significant differences in total HOAs, fourthorder and spherical aberration (SA) for a 6 mm between two groups (p=0.045, p<0.001, and p<0.001, respectively). In corneal aberrations, there was a significant difference in SA for 4 mm (p=0.001) and 6 mm (p<0.001) pupils between two groups and there were statistically significant differences in total HOAs (p<0.001) and fourth-order aberrations (p<0.001) between two groups for a 6 mm pupil. There was a significant correlation in emmetropia between Q-value and SA in ocular aberrations for 4 mm and 6 mm pupils (r=0.442, p=0.004, and r=0.519, p<0.001) and in corneal aberrations for 4 mm and 6 mm pupils (r=0.358, p=0.023, and r=0.646, p<0.001). No significant correlations were found between Q-value and SA in refractive surgery group. Conclusions: VA in myopic refractive surgery is better than or similar to emmetropia. Nevertheless, the more increasing pupil size is, the more increasing aberrations are. Thus, it could have an influence on the quality of vision at night.

• Proceedings of the Optical Society of Korea Conference
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• 1991.06a
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• pp.81-87
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• 1991

A design of a four-mirror optical system for submicron lithography using KrF excimer laser beam(λ=248nm) is presented. By using the third order aberration theory, analytic solutions for a telecentric, flat-field, and anastigmatic four-spherical-mirror system (reduction magnification 5$\times$) are found. Aspherization is carried out to the spherical mirror surfaces in order to reduce the residual higher order aberrations and vignetting effect. Finally we obtain a reflection system useful in submicron lithographic application.

• Korean Journal of Optics and Photonics
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• v.4 no.1
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• pp.1-8
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• 1993

A design of four-mirror optical system with reduction magnification 5X for deep UV ($\lambda$=248 nm of KrF excimer laser) submicron lithography is presented. Initially by using the paraxial quantities, the domain of solution for $t=d_1+d_2+d_3$<0 (d;: distance between the mirror $c_i$ and $c_{i+1}$ is found for the system which is free from the four off-axial Seidel first order aberrations that are coma, astigmatism, field curvature, and distortion. The solution with $d_5$=2.95 (normalized with respect to $c_i$= -1) is choosen and the aspherization is carried out to the spherical mirror surfaces ($c_3$ and $c_4$ in order to reduce the axial and residual off-axial higher order aberrations. The numerical aperture of the final system is as large as 0.4, which gives Rayleigh resolution of 0.38 $\mu\textrm{m}$.