• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.305-313
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• 1996

Lens design method by using equivalent lenses was already introduced, but the method has a limitaion that all lenses should be in the air. Therefore, we often get improper solution in designing cemented lenses. In this study, the lens conversion from thick lens to equivalent lens and its reversal was generalized without any preconditions, and the third order aberration fomulrae were derived for the generalized equivalent lens system. The generalized equivalent lens conversion were applied to typical cemented doublet and triplet, and they show that the third order aberrations of the generalized equivalent lenses have better agreements with their corresponding thick lenses than the previous conversion method.

• Korean Journal of Optics and Photonics
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• v.9 no.4
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• pp.251-257
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• 1998

The equivalent lens conversion is extended to lens group conversion, and the more generalized conversion method is developed. The new conversion method can be used for hte direct thick-to-thick lens conversion. By using the equivalent lens conversion, a thin lens system can be converted into various thick lens system which have different axial thicknesses, but those converted lens systems have identical paraxial property and similar aberration characteristic. For an example, the equivalent lens conversion technique is applied to modification of a thelephoto lens design. The axial thicknesses of the front group elements of the system are reduced to 75% of their original values. The modified design by using the equivalent lens conversion has same focal length with original, and it has smaller aberration changes than the other design of which axial thicknesses are changed only.

• Korean Journal of Optics and Photonics
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• v.25 no.1
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• pp.14-20
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• 2014

The equivalent of a thick lens is a lens which has the same power of refraction and paraxial imaging characteristics for a reference ray, but with a different axial thickness. In this study, thick lenses of an optical system were converted to their equivalent lenses referenced to pupil imaging. Aberration changes due to the lens conversion were compared to the general equivalent lens conversion referenced to object imaging.

• Korean Journal of Optics and Photonics
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• v.23 no.1
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• pp.17-22
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• 2012

An equivalent lens is a lens which has the same total power of refraction and the same paraxial imaging characteristics for the marginal rays as another lens, but has a different axial thickness. In this study, an analytic lens conversion from a thick lens to its equivalent lens is investigated, then it is shown that the equivalent lens is a solution of a quadratic equation. Every thick lens corresponds to one of two real roots of this quadratic equation. Therefore, except in the case of a unique solution, the equation has a conjugate solution, the other of the two roots. The conjugate solution has the same axial thickness, power, and paraxial imaging characteristics, but it has different shape and aberration characteristics. The characteristics of an equivalent lens and its conjugate solution are examined by using a sample lens.

• Korean Journal of Optics and Photonics
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• v.9 no.5
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• pp.282-290
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• 1998

The equivalent lens conversion technique is applied to design achromatic doublet and aplanatic doublet. A thin doublet which has zero axial thicknesses, are corrected for the third order aberrations at first, and the thin doublet is converted into thick lens system by using the equivalent lens conversion. Two types of cemented doublets, the Fraunhofer type and the Steinheil type, are designed by using a crown glass BaK-2 and a flint glass SF-2. In the thin doublet design, there are two achromatic solutions and a aplanatic solution for the both types.

• Korean Journal of Optics and Photonics
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• v.33 no.6
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• pp.275-286
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• 2022

As a first step in the optical design process, we derive a recursive numerical calculation method that can give a solution to the Gaussian equation that the paraxial rays satisfy. Given the refractive power, the angle of incidence to the first principal plane of the lens, the angle of exit to the second principal plane of the lens, and the distance between the principal planes, the radii of curvature of the front and back surfaces of a lens can be obtained by applying the recursive numerical calculation method proposed in this paper according to the thickness of the lens. If a module consists of two or more lenses, the thickness and radius of curvature of each lens can be similarly determined after selecting the distance between the principal planes of the lens under the condition of the design specification while increasing the number of lenses one by one.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.1
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• pp.39-45
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• 2009

Purpose: The purpose of this study is to compare the visual performance by contrast sensitivity (CS) and disability glare (DG) in low astigmatic eyes corrected with toric soft lenses and other optical corrections. Methods: Twenty university students with myopia (-1.00 to -6.50D Sph. with astigmatism up to 1.50 cyl) were enrolled and corrected by five different methods: 1) soft toric lenses; 2) spherical soft contact lenses; 3) RGP lenses; 4) best spectacle corrected visual acuity; 5) spherical equivalent spectacles. All subjects had corrected vision acuity of 20/20 or better. Contrast sensitivity and disability glare were measured using the OPTEC 6500 contrast sensitivity view-in tester included the EyeView Functional Vision Analysis software at photopic or mesopic conditions with glare. Results: At photopic condition, best corrected spectacle wearers had the highest monocular contrast sensitivity at all spatial frequency followed by soft toric lenses, RGP lenses, spherical equivalent spectacles, and spherical soft contact lenses. However, all of them were in normal contrast sensitivity value at photopic condition. At mesopic condition with glare, toric soft lenses were the highest and followed by RGP lenses, spherical equivalent spectacles, best spectacle corrected visual acuity and spherical soft contact lenses. It was observed that spherical soft contact lens wearers demonstrated lower range than normal contrast sensitivity value at mesopic condition with glare. Conclusion: Toric soft lenses gave better visual performance than spherical soft lenses in low astigmatic eyes. Subjects requiring the use of contact lenses under mesophic conditions could benefit from toric soft lenses.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.4
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• pp.501-509
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• 2015

Purpose: To evaluate the reliability of refractive power by comparing the marked refractive power in an automatic phoropter and actually measured spherical/cylindrical refractive power. Methods: Actual refractive power of minus spherical lens and cylindrical lens in an automatic phoropter was measured by a manual lensmeter and compared with the accuracy of marked refractive power. Furthermore, combined refractive power and spherical equivalent refractive power of two overlapped lenses were compared and evaluated with the refractive power of trial lens. Results: An error of 0.125 D and more against the marked degree was observed in 70.6% of spherical refractive power of spherical lens which is built in phoropter, and the higher error was shown with increasing refractive power. Single cylindrical refractive power of cylindrical lens is almost equivalent to the marked degree. Combined spherical refractive power was equivalent to spherical refractive power of single lens when spherical lens and cylindrical lens were overlapped in a phoropter. Thus, there was no change in spherical refractive power by lens overlapping. However, there was a great difference, which suggest the effect induced by overlapping between cylindrical refractive power and the marked degree when spherical lens and cylindrical lens were overlapped. Spherical equivalent refractive power measured by using a phoropter was lower than that estimated by trial glasses frame and marked degree. The difference was bigger with higher refractive power. Conclusions: When assessment of visual acuity is made by using an automatic phoropter for high myopes or myopic astigmatism, some difference against the marked degree may be produced and they may be overcorrected which suggests that improvement is required.

• Journal of Korean Ophthalmic Optics Society
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• v.2 no.1
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• pp.55-60
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• 1997

Numerically compares a calculation about a variable process of visual acuity for a artificial myopia with previously the tested result. The calculation is used to the value of Gullstrand's theoretical eyes and a method of geometrical optics. The theoretical eye simplified a entrance pupil and retina. Optical lens and eye changed a equivalent lens. Refractive power of a equivalent lens is converted to focal length within theoretical eyes, and this was calculated about relation of a blur circle on the retina and visual acuity.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.3
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• pp.255-264
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• 2011

Purpose: To study the effect of hyaluronic acid(HA), which was widely used in artificial tears, multi-purpose solution(MPS), cosmetics, and drug acting on the musculo-skeletal system, in wettability and comfort of contact lens, we compared HA including lens(+HA) with HA excluding lens(-HA) by clinical evaluation. Methods: During four weeks, the selected 28 university student volunteers who did not have any eye disease wore +HA contact lens on their right eyes, and -HA contact lens on their left eyes, and then compared right eyes to left eyes as control. After prescribing by spherical equivalent calculation, over-refraction by auto-refractometer, and contact lens wearing for two weeks and four weeks, tear evaluation, the anterior of eyes examination, fitting convenience evaluation, surface wetting test, surveys were checked up. Results: Compared with the control group (-HA contact lens), +HA contact lens provided better wetting properties. The amount of released tear in -HA contact lens group became less in four weeks than before, but that in +HA contact lens group showed no significant difference from the initial one. In terms of the redness in eye, there was no significant difference between +HA and -HA contact lens groups. Fitting of +HA contact lens on eye was much easier than the control, -HA contact lens. From the results of survey, comfort, wettability, ease of cleaning, and dryness of eye in +HA contact lens group were generally better than those of -HA group, but redness and contact lens handling showed little difference. Conclusions: The addition of HA in soft contact lens(+HA) may enhance the wettability of lens during lens wearing, resulted in the better comfortable wearing of lens eventually.