• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.2
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• pp.31-36
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• 2003

Electronic or measuring instruments equipped with aspherical lens have recently been used since aspherical lens is more effective than spherical one. for the mass production of aspherical lenses, specific molds with precisely machined cores should be prepared. Some researches on the aspherical lens machining have been carried out to date. However, ultra-precise finding of aspherical or mold core has not been fully studied. In this study, the ultra-precise grinding and evaluating system were established to investigate the finding characteristics of aspherical lenses. Unlike conventional grinding process, since a highly-precise lathe were operated in a clean room without vibration the experimental results can be very useful for further studies on ultra-precise grinding process.

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.2
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• pp.39-43
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• 1999

In this study, It obtained results that the exact spherical diopter to practice test by using Cross cyliner lens and Red Green Card method. In the test used to the 1750 eyes of middle and high school students. The results was as follows ; 1. Using Cross cylinder lens method, I tested a exact spherical diopter after accommodation. At -0.25 Dptr the ratio of spherical Dptr error limits were measured as 58% and at -0.75 Dptr they were oppeared as 1%, at -1.00 Dptr they are not measured. In this method, the error limits of exact spherical Dptr was 91% from 0 Dptr to -0.25 Dptr. 2. Using Red Green Card method, they were measured as 45% at -0.25 Dptr. and measured as 20% at -0.50 Dptr. From the result of these test, Cross cylinder lens method was a better detailed method than Red Green Card method.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.417-421
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• 2004

We can see that two images of reflection are observed on the surface of a ophthalmic lens. These are the image reflected from front surface and back surface of lens, respectively. The reflective image shows to be affect by surface refractive power of front and back surface of lens. Total refractive power of lens is calculated by refractive power of front and back surface of lens. Accordingly, the ratio of image on the lens surface is able to measure refractive power of ophthalmic lens without helping of the lensmeter. The ratio of two reflective image measured on the lens surface is compared with the calculated ratio by the power measurement.

• Transactions of the Society of Information Storage Systems
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• v.1 no.1
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• pp.78-83
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• 2005

The Blu-ray disc as a next generation high density optical medium uses an objective lens of high numerical aperture(NA 0.85) and blue laser in order to increase the recording density. The double layer is also useful for doubling the density. The spherical aberration of Blu-ray disc is very sensitive to the thickness of the disk because of high numerical aperture. This paper suggests a method to compensate the spherical aberration caused by the change of disk thickness, by using the Liquid Crystal lens instead of the Liquid Crystal panel. It was possible to develop both the LC panel generating the optical phase difference and LC lens changing the optical power. In this paper, we analyzed the aberration performance and a position sensitivity of the two type LC elements when the samples deviate from the optical axis of the objective lens. The results of applying this analysis show that the LC lenses rather than the LC panels have a significant assembling tolerance. The theoretical characteristics of the two elements are calculated and compared with the measurement data.

• Korean Journal of Optics and Photonics
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• v.26 no.6
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• pp.299-305
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• 2015

Using Snell's Law without approximation, we analyzed focal points for parallel rays incident upon the cornea of a human eye. To calculate a ray's incident angle versus incident height for focusing on the same point, we used the ray reverse tracing method. We derived the theoretical conditions for an aspherical lens to remove the spherical aberration caused by a human eye. In this research, we held the rear surface of the lens to be spherical, for simple calculation, and calculated the lens curvature of the front surface to design an aspherical surface.

• Korean Journal of Optics and Photonics
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• v.19 no.2
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• pp.108-115
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• 2008

We designed optical systems for a mobile phone camera using a spherical SELFOC lens and an aspherical plastic lens. Since the radial index distribution gives an additional design parameter for optical design, an aspheric lens could be replaced by a spherical lens. The imaging performances of the design were compared with conventional 2P design composed of two aspherical plastic lenses. In the first stage of study, we designed 1GRIN 1P lenses by using commercially available SELFOC materials. But, the conventional 2P lenses had better performance than the 1GRIN 1P lenses. In the 1GRIN 1P designs, the performance depends on index variation of GRIN material, the larger variation gives the better performance. Hence, we tried to design by using fictitious GRIN materials which have large index variation. We found if the index variation could be increased to about 3 times that of currently available SELFOC materials, the 1GRIN 1P lens will have equivalent or better performance than the conventional 2P design.

• Journal of the Optical Society of Korea
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• v.17 no.2
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• pp.219-223
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• 2013

The purpose of this study was to determine the relationship between the spherical equivalent visual acuity (VA) and uncorrected astigmatism. On 108 emmetropic eyes, the spherical equivalent VA was measured for cross cylindrical lens (CC lens)-induced astigmatic eyes and the VA-astigmatism relation determined. On 158 astigmatic eyes, the spherical equivalent VA and corrected astigmatism were measured and the measured values were compared with the calculated values from the VA-astigmatism relation by correlation coefficient analysis. Subsequent to that, the relationship between spherical equivalent VA and uncorrected astigmatism was made. The relationship was fitted for an exponential equation. Correlation coefficient between calculated values by equation and measured values for astigmatic eyes was 0.991 (p<0.01). The relationship between the spherical equivalent VA and the uncorrected astigmatism was decided as follows (spherical equivalent VA / uncorrected astigmatism): 1.0 / 0.25 D, 0.9 / 0.50 D, 0.8 / 0.75 D, 0.7 / 1.00 D, 0.6 / 1.25 D, 0.5 / 1.50 D, 0.4 / 2.00 D, 0.3 / 2.50 D, 0.2 / 3.00 D, 0.1 / 4.00 D, and 0.05 / 4.75 D. In conclusion, the relationship table devised from this study is a useful reference for predicting uncorrected astigmatism by measurement of decimal VA in spherical equivalent.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.1
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• pp.37-45
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• 2012

Purpose: The change of alignment between RGP lens and cornea according to the lens design was investigated by comparing the areas of fluorescein pattern in central and peripheral regions analyzed by astigmatic degree and corneal type when spherical and aspherical RGP lenses fitted in alignment. Methods: The fluorescein patterns of 90 eyes (19-30 years, $25.12{\pm}3.52$) having with-the-rule astigmatism were analyzed after spherical and aspherical RGP lenses fitted in alignment. Then, their fluorescent areas in central and peripheral regions were calculated and compared for the quantitative evaluation. Results: The case showing concordant base curve between spherical and aspherical RGP lenses in alignment fitting was 72% however, the possibility to have same base curves between spherical and aspherical RGP lenses in alignment fitting was to be less in the case of symmetric bowtietyped cornea and high astigmatism. The fluorescent area in peripheral region of aspherical RGP lens in alignment fitting was smaller than it of spherical RGP lens. Peripheral fluorescent areas in both RGP lenses decreased according to the increase of astigmatic degree and peripheral area in symmetric bowtie-typed corea was smaller than round-typed cornea's peripheral area. In the case of same astigmatic degree, peripheral fluorescent area of aspherical RGP lens was smaller in both corneal types. Conclusions: The results above suggest the changing degree in the alignment between RGP lens and cornea can be varied according to lens design, corneal astigmatism and corneal type. Thus, the results obtained from the quantitative analysis of the alignment between lens design and cornea may be used as the basic information about the establishment of guidelines for RGP lens fitting, the development of proper lens design, and different tear volume in partial regions.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.956-961
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• 2004

This paper proposes a study on the spherical lens manufacturing by simultaneous 3 axis for NC lathe. We use friction drive system for moving system in experimental diamond turing machine. The diamond turning machine use manufacturing for high quality lens, mirror and many optics products. Especially, the high tech industry require a lot of lens. For example, optical engineering. medical science, space engineering and material engineering etc. The friction drive system is very simple and quiet, compared to ball screw system. We find a problem at the simultaneous 3 axis and suggest a solution. Also, when we manufactured a micro lens. find a problem and solution.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.12
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• pp.1033-1038
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• 2009

Recently, Light Emitting Diode (LED) has many advantages in comparison with conventional light sources; low power consumption, long lifetime, and less environmental pollution. Therefore, the use of LED is increasing rapidly. In general, however, spherical lens is used in LED-lighting which cause many problems induces by optical aberration of spherical lens; low illumination, yellow belt, unpleasant feeling in human eye. As a solution of these problem, aspherical lens can be employed. This study reported the improvement of LED-lighting performance by adopting aspherical lens. From the commercial program, $LightTools^{TM}$, the optical problem were ensured. And then, to improve these problem, optimum aspheric form was designed using Code $V^{TM}$.