• Journal of Korean Ophthalmic Optics Society
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• v.16 no.1
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• pp.97-106
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• 2011

Purpose: This review article was written to theoretically compare the depressing force (pressure, adhesion) to the cornea between when the spherical lenses were being tightly and flat fitted. Methods: Mathematical equations and their numerical solution programs (model) were formulated to calculate the depressing (adhesion) force to the cornea by both the tightly and flat fitted contact lenses. Based on this proposed model the effects of parameters characterizing a contact lens such as BCs, diameters, edge shape and corneal shape (ratio of long and short corneal axis, p) on the depressing force to the cornea were predicted/analyzed in both tightly and flat fitting regimes. Results: Corneal adhesion increased as the corneal p-value increased. Adhesion increase caused by the increased p-value was much larger in flat fitted case than in tight fitted one. Corneal adhesion reduced abruptly as the BC increased in flat fitting regimes while the adhesion rise was insignificant in tight fitting ones. Reduction in corneal adhesion due to lens-size increase was predicted to be insignificant in both tight and flat fitting regimes. Both the lens edge shape (edge angle) and thickness were relevant only in tight fitting regime. Corneal adhesion increased as the increased with tight-fitted lenses. As the thickness of tight fitted lenses increased, corneal adhesion inversely decreased. Conclusions: The two most significantly affecting the depressing force to cornea were found to be the degree of corneal bending toward the periphery and the BCs of lenses.

• Journal of Korean Clinical Health Science
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• v.3 no.4
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• pp.435-443
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• 2015

Purpose. This study was to investigate comparison of the near eye position according to the spectacle and contact lens wearing. Methods. We measured the AC/A ratio and near horizontal phoria using modified Thorington method in each case spectacle and contact lens wearing of equivalent spherical power after measuring the full corrected diopter for 20 subjects (men 5, woman 15, $21.15{\pm}1.35$ years) without specific ocular diseases, ocular surgery experience and vision anomalies. Results. It was shown high correlation between spectacle and contact lens wearing as AC/A ratio is a correlation coefficient 0.99 (p=0.00), near horizontal phoria is a correlation coefficient 0.95 (p=0.00). And contact lens wearing increased as AC/A ratio by $0.32{\pm}1.35$ ${\Delta}/D$ (p=0.31) and near horizontal phoria by $-0.17{\pm}2.18$ ${\Delta}$ (p=0.73) than spectacle wearing but there was no statistically significant difference. As the higher myopic grade AC/A ratio increased and then was shown decreased tendency in -6.00 D < $SED{\leq}-4.00$ D group (p>0.05) and as the higher myopic grade near exophoria increased but there was no statistically significant difference (p>0.05). Conclusions. We should consider that the subjects who had the lower AC/A ratio or higher near exophoria in -6.00 D < $SED{\leq}-4.00$ D group were necessary to measure AC/A ratio and near horizontal phoria when they were wearing contact lens because contact lens wearing tended to increase the near exophoria than spectacle wearing.

• Transactions of Materials Processing
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• v.15 no.1 s.82
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• pp.3-8
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• 2006

The demand fer small and high-capacity optical data storage devices has rapidly increased. The areal density of optical disk is increased by using higher numerical aperture objective lens and shorter wavelength source. A wafer-scale stacked micro objective lens with a numerical aperture of 0.85 and a focal length of 0.467mm for the 405nm blue- violet laser was designed and fabricated. A diffractive optical element (DOE) was used to compensate the spherical aberration of the objective lens. Among the various fabrication methods for micro DOE, the UV-replication process is more suitable fur mass-production. In this study, an 8-stepped DOE pattern as a master was fabricated by photolithography and reactive ion etching process. A flexible mold was fabricated for improving the releasing properties and shape accuracy in UV-replication process. In the replication process, the effects of exposing time and applied pressure on the replication quality were analyzed. Finally, the surface profiles of master, mold and molded pattern were measured by optical scanning profiler. The geometrical deviation between the master and the molded DOE was less than $0.1{\mu}m$. The diffraction efficiency of the molded DOE was measured by DOE efficiency measurement system which consists of laser source, sample holder, aperture and optical power meter, and the measured value was $84.5\%$.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.1-5
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• 2010

This paper deals with a method to measure the thickness of scale-layer, iron oxide formed on the surface of the rolling steel, using a dielectric lens antenna. The dielectric lens antenna has an independent characteristic with the frequency in the X-band and changes the spherical wave radiated from a horn antenna into a plane wave at the focusing point. Using this concept, we regard a scale-layer on the rolling steel as a dielectric-PEC(Perfect Electric Conductor) layer and apply a theoretical analysis of the normal-incident plane wave. To reduce the phase error arising from the use of the dielectric lens antenna, this paper utilizes a regression process algorithm. In comparison with the conventional iteration algorithm, the present algorithm led to a unique solution for the thickness of the scale-layer.

• Journal of the Optical Society of Korea
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• v.19 no.2
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• pp.136-143
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• 2015

Image deblurring by a deconvolution method requires accurate knowledge of the blur kernel. Existing point spread function (PSF) models in the literature corresponding to lens aberrations and defocus are either parameterized and spatially invariant or spatially varying but discretely defined. In this paper, a parameterized model is developed and presented for a PSF which is spatially varying due to lens aberrations and defocus in an imaging system. The model is established from the Seidel third-order aberration coefficient and the Hu moment. A skew normal Gauss model is selected for parameterized PSF geometry structure. The accuracy of the model is demonstrated with simulations and measurements for a defocused infrared camera and a single spherical lens digital camera. Compared with optical software Code V, the visual results of two optical systems validate our analysis and proposed method in size, shape and direction. Quantitative evaluation results reveal the excellent accuracy of the blur kernel model.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.09a
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• pp.35-40
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• 2005

The demand for small and high-capacity optical data storage devices has rapidly increased. The areal density of optical disk is increased using higher numerical aperture objective lens and shorter wavelength source. A wafer-scale stacked micro objective lens with a numerical aperture of 0.85 and a focal length of 0.467mm for the 405nm blue- violet laser was designed and fabricated. A diffractive optical element (DOE) was used to compensate the spherical aberration of the objective lens. Among the various fabrication methods for micro DOE, the UV-replication process is more suitable for mass-production. In this study, an 8-stepped DOE pattern as a master was fabricated by photolithography and reactive ion etching process. A flexible mold was fabricated for improving the releasing properties and shape accuracy in UV-molding process. In the replication process, the effects of exposing time and applied pressure on the replication quality were analyzed. Finally, the shapes of master, mold and molded pattern were measured by optical scanning profiler. The deviation between the master and the molded DOE was less than 0.1um. The efficiency of the molded DOE was measured by DOE efficiency measurement system which consists of laser source, sample holder, aperture and optical power meter, and the measured value was $84.5\%$.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.455-462
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• 2004

In this paper, we measured and analysised the power change of tear lens for 85 patients - 170 myopia eyes - who are fitted using RGP lens, considering the BGR of RGP lens, the corneal astigmatism power, and corneal curvature. We got the following results from these experiments; 1. When the BCR of RGP lens changes, the diopters of tear lens of "on-k", 0.05Pt, 01.0Ft, 0.05St, and 0.10St are -0.25D, -0.46D, -0.63D, +0.07D, and +0.26D, respectively. 2. When the corneal astigmatism power changes, the diopters of tear lens of group below 0.75D, group of 1.00D~1.25D, group of 1.50D~1.75D, and group over 2.00D in "on-k" state, are -0.25D, -0.18D, -0.09D, and -0.39D, respectively. 3. When the corneal astigmatism power changes and the BCR of test lens is changed by 0.05mm step, the change values of tear lens diopter for 0.05St and 0.05Ft approximate to ${\pm}0.25D$, while these for 0.10St and 0.10Ft don't approximate to the value below ${\pm}0.25D$.[are irregular value below ${\pm}0.25D$.] 4. When the corneal curvature and the HCR of RGP lens change, the diopters of tear lens of group below 7.50mm, group of 7.55~7.80mm, group of 7.85~8.20mm, and group over 8.25mm in "on-k" state, are -0.40D, -0.11D, -0.20D, and -0.19D, respectively. 5. When the BCR of test lens is changed by 0.05mm step and the corneal curvature increases, the change values of tear lens diopter decrease, while these over 8.25mm are mean value ${\pm}0.17D$ and the value below ${\pm}0.25D$.

• Journal of The Korean Ophthalmological Society
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• v.59 no.11
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• pp.1009-1016
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• 2018

Purpose: To assess the effect on axial elongation and associated factors between spectacles and of orthokeratology lens (OK) wearing in children with mild to moderate myopia. Methods: A total of one hundred subjects, ranging in age from 6 to 13 years, and with mild to moderate myopia no more than -4.50 diopters in spherical equivalent, visited our clinic from 2013 to 2015. The OK group (75 eyes) and the spectacles group (64 eyes) were compared and analyzed on the axial elongation and associated factors. Results: In the OK group, axial length was elongated in 1 year period with a mean increase of $0.24{\pm}0.29mm$. In spectacles group, axial length was elongated in 1 year period with a mean increase of $0.42{\pm}0.20mm$. The statistically significant suppression of axial elongation was observed in OK group compared to the spectacles group (Mann-Whitney U test, p < 0.05). For OK group, the age of starting OK (Pearson's correlation, r = -0.481, p < 0.05) was the only influencing factor on axial elongation, which had negative correlation with axial elongation. In spectacles group, the age of starting spectacles had negative correlation with axial elongation (Pearson's correlation, r = -0.462, p < 0.05) and baseline spherical equivalent, spherical diopter, cylindrical diopter from manifest refraction had positive correlation with axial elongation. Comparison of axial elongation in orthokeratology lens group and spectacles group by age groups (6 to 9 years [28 eyes], 9 to 13 years [47 eyes]), 9 to 13 years of orthokeratology lens group had the stronger suppression of axial elongation (Mann-Whitney U test, p < 0.05). Conclusions: The OK effectively suppresses axial elongation compared to the spectacles. Although the patients are in age from 9 to 13 years, the axial elongation was effectively suppressed.

• Korean Journal of Optics and Photonics
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• v.16 no.5
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• pp.440-445
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• 2005

The limitation of measurement accuracy and reliability of autostigmatic null lens system are studied for the cases of using inter-distance of null lenses as the adjustment factor of alignment and fixing the distance by mounting. If we investigate the first case, the wavefront aberration of null lens system is compensated by the adjustment process even though the shape of aspherical surface is not properly fabricated. As the result, it brings about the problem of measurement reliability. However, for the fixing process by mounting null lenses, it doesn't cause the reliability problem because the wavefront aberration of null lens system is not compensated. Further, the fixing process shows nearly same result in measurement accuracy to the adjustment process, that is, $0.0316{\lambda}$ vs. $0.0326{\lambda}$. So, we can conclude the setup for autostigmatic null lens system must be constituted by means of the fixing process. Meanwhile, we introduce and define the alignment aperture on aspheircal mirror, which can be approximated as spherical zone for alignment of null lens system, and besides, we calculate the required fabrication accuracy of the zone for the necessary measurement accuracy.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1422-1425
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• 2003

In the design of optical system, important variables of optical system (including indices, shapes, spaces, stops. etc.) must manipulate in order to balance out offensive aberration. In this paper, it carried out a basic study on the design of micro optical system usable for the acquaintance of visual information in the particular conditions such as capsule type endoscopes. In this study, specification for design of optical system selected voluntarily and the basic design of optical system carried out by using the ray tracing method on the assumption that ideal lenses without aberrations. In the designed optical system, the optimization including aberration correction and the performance evaluation of optical system carried out by using the CODE-V. The final designed optical system consists of seven sheets of lenses. Also the results of performance evaluation. the micro optical system combined with aspherical lenses was confirmed to have improved optical performance as compared with the micro optical system consisted of spherical lenses.