• Korean Journal of Optics and Photonics
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• v.26 no.4
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• pp.217-225
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• 2015

This paper shows the best selection and combination of glass in lens design, to correct a chromatic aberration using achromatic and apochromatic conditions. Using this research result, we have designed a telecentric lens for machine vision in the full range of visible light. We obtain good optical quality in the form of a quite small RMS wavefront error of $0.057{\lambda}$ in the super-broadband wavelength range 380 nm -780 nm. This result is better than that for a common telecentric lens in the visible wavelength range 486.1-656.2 nm.

• Korean Journal of Optics and Photonics
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• v.5 no.2
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• pp.252-259
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• 1994

The method of calculating overlap dispersion caused by group velocity mismatch between uv and visible pulses in ultrafast pump-probe experiments is presented to discuss limitations of the time resolution and signal intensity. The calculations show arrangements using a single focusing lens shall result in undesirable time resolution and low signal intensity. Achromatic doublets result in unrealistic solutions. However, dramatic improvement in the time resolution and signal intensity is expected in the optical arrangements using separate lens for each pulse and in the arrangements using a cutoff secondary lens with a main lens. lens.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.3
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• pp.261-270
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• 2013

Purpose: Adsorption properties of lysozyme and albumin according to physiochemical properties of commercial contact lens classified with the FDA categories and a contact lens fabricated in the laboratory were investigated. Methods: The contact lens were prepared using HEMA(2-hydroxyethyl methacrylate) and TRIM(3-(trimethoxysilyl) propyl methacrylate) in a cast mold. Artificial tears containing lysozyme and albumin were prepared. We measured the amounts of protein adsorbed on the each lenses with varying adsorbed time (48 hour) and the pH range (6, 6.8, 7.4, 8.2, 9) of artificial tear. Amount of the proteins absorbed on the contact lenses were measured by using HPLC. Results: Time to reach the equilibrium of protein adsorption for silicone hydrogel lens was taken longer than hydrogel lens. The amount of adsorbed both lysozyme and albumin at equilibrium were greater for the hydrogel lens than the silicone hydrogel lens, and larger for the ionic lens than the non-ionic lens. Lysozyme was more adsorbed on the higher water content of contact lens, whereas albumin was more adsorbed on the lower water content of contact lens. Only lysozyme was adsorbed on the Group IV hydrogel lens of ionic higher water content. The adsorption of protein on contact lens increased with pH of artificial tears as close to the isoelectric point of each protein. Conclusions: The adsorption amount of lysozyme is more affected by the ionic strength of the contact lens surface than the water content of contact lens. Albumin adsorption is more affected by water content than the ionic strength of the contact lens surface. For the adsorption of proteins on the silicone hydrogel lens, the pore size, determined both by the number of Si atoms and the chemical structure of the silicone-containing monomers, as well as the polarity of contact lens should be also considered.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.3
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• pp.229-235
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• 2011

Purpose: The present study was performed to evaluate the safety of ophthalmic lenses in domestic market since eyeglasses wearers could be exposed to the negligent accident by damaged ophthalmic lenses. Method: Totally, 160 ophthalmic lenses (NK55, ${n_{d}}$ = 1.56) with the refractive powers of -3D, -6D, +3D, +6D manufactured by 4 companies in domestic market were evaluated using drop ball test. In accordance with FDA standard, steel ball (~16 g) was freely dropped on these ophthalmic lenses from 127 cm high and the surfaces of lenses were observed. Results: From the study, center thicknesses of NK55 ophthalmic lenses manufactured by 4 different companies showed somewhat different numbers even though the lenses had the same refractive index and powers. All convex lenses of +3D, +6D were evaluated as the safe lenses since there was no damage such as crack and broken found on the lens surfaces after drop ball testing. However, some noticeable broken was shown on the surfaces of concave lenses with relatively thinner center thickness. Especially, 59(73.8%) of total 80 concave lenses with the refractive power of -3D and -6D classified as unacceptable lenses to FDA standard. Conclusions: From the results, the negligent accident by damaged ophthalmic lenses should be considered as well as the correction of visual acuity, design and price when customers purchase eyeglasses. Thus, the enforcement regulation like drop ball testing of uncut ophthalmic lens could be suggested to guarantee the safety of ophthalmic lenses in domestic market.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.4
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• pp.381-388
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• 2012

Purpose: In this study, the changes in the shape of silicone hydrogel lenses, dryness of lens and objective/ subjective symptoms that could be induced by repeating dryness of lens and objective/subjective symptoms were investigated. Methods: After drying and rehydrating of silicone hydrogel lenses with different lens material and thickness for 4 times, their overall diameters and base curves were compared. Subjective symptoms, non-invasive tear break-up time (NIBUTs) and blinking rate were evaluated after wearing dehydrated silicone hydrogel lens. Results: Overall diameter and base curve increased in all tested silicone hydrogel lenses by repeating dryness and rehydration. The degree of change in over all diameter and base curve were variable on the material. There were irregular change of lens parameters in thicker lens. When the subjects wore silicone hydrogel lenses after drying and rehydrating, their NIBUTs were decreased and blink rates were increased regardless of lens material or thickness. In addition, repetitive drying of silicone hydrogel lenses affected the lens fitting. Therefore, subjective symptoms such as itching, pain, irritation, foreign body sensation, dryness tended to be increased. Conclusions: The results obtained from the study may suggest to develop durable silicone hydrogel contact lenses against dry environment since the changes in parameters of silicone hydrogel lens and the subjective discomfort were observed after repetitive drying and rehydration.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.3
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• pp.659-666
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• 2015

In this paper, we propose a novel reconstruction method of spatially filtered 3D images in integral imaging based on parallel lens array. The parallel lens array is composed of two lens arrays, which are positioned side by side through longitudinal direction. Conventional spatial filtering method by using convolution property between periodic functions has drawback that is the limitation of the position of target object. this caused the result that the target object should be located on the low depth resolution region. The available spatial filtering region of the spatial filtering method is depending on the focal length and the number of elemental lens in the integral imaging pickup system. In this regard, we propose the parallel lens array system to enhance the available spatial filtering region and depth resolution. The experiment result indicate that the proposed method outperforms the conventional method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1637-1642
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• 2010

In this paper, we present the fabrication of a high-quality diffractive-lens mold having submicron patterns, which is suitable for an ultra-slim optical system. In order to fabricate high-quality diffractive lens with a variety of submicron patterns, the multi-alignment method was used; high-resolution electron-beam lithography and FAB plasma etching were carried out to obtain the patterns. The most important key technology in the multi-alignment method is to reduce alignment error, lithography error, and etching error. In this paper, these major fabrication errors were minimized, and a high-quality diffractive lens with a diameter of $267\;{\mu}m$ (NA = 0.25), minimum pattern width of 226 nm, and thickness of 819 nm was successfully fabricated.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.197-198
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• 2006

본 연구에서 개발하는 성형렌즈는 그림1과 같이 한쪽 면이 비구면인 평볼록 형상이다. Glass렌즈의 고온압축성형을 위해서는 초정밀 가공기술로 제작된 성형Mold가 필요하며, Mold재질에 따른 성형기술의 확립이 필수적이다. 또한, 성형Mold의 표면과 융착반응이 없는 Glass소재가 요구된다. 본 실험을 위한 성형Mold는 코발트(Co) 함량 0.5 %의 초경합금(WC; 일본, Everloy社, 002K)을 초정밀 연삭가공하여 제작하였다. Glass소재는 전이점(Transformation Point; Tg) $572\;^{\circ}C$,항복점(Yielding Point; At) $630\;^{\circ}C$의 열적 특성을 갖는 K-BK7(일본, Sumita社)을 사용하였으며, d선에서 굴절률 및 아베수는 각각 1.51633, 64.1이다. 비구면 Glass렌즈 성형은 GMP(Glass Molding Press; 일본, Sumitomo社, Nano Press-S)장비를 사용하여 성형온도 $625\;^{\circ}C$, 서냉온도 $550\;^{\circ}C$로 고정하고 성형압력를 200-800 N 범위에서 변화시켰다. 표 1에 성형변수로 사용한 서냉속도와 서냉전환온도 조건을 나타낸다. 표1과 같이 각 서냉조건별로5장의 렌즈를 성형 후 특성값이 평균치에 가까운 3장을 선별하여 그 특성을 비교하였다. 각 조건에 따른 성형렌즈의 형상정도(일본, Panasonic社, UA3P, 자유곡면형상측정기), 두께(일본, Mitutoyo社, MDC-25M, 마이크로메터), 굴절률(일본, Shimatus社, KPR-200, 정밀굴절률측정기) 및 MTF[해상도](독일, Trioptics社, Image Master HR, MTF-Field)를 측정하여 각각의 광학적 특성을 비교 평가하였다. 비구면 Glass렌즈 성형장비와 형상측정기를 그림 2, 3에 각각 나타낸다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.557-560
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• 2020

최근, 광소자에서 공간 변조되는 wavefront profile 특성을 광소자의 표면 단차 변화 없이 단일 두께 박막 상에서 자유로이 구현할 수 있는 기하위상 홀로그램 (geometric phase hologram) 기반의 optical component에 대한 관심이 증대되고 있다. 특히 이를 이용해 제작된 기하위상 렌즈 (geometric phase lens)는 dynamic phase의 공간적 차이에 의해 구현되던 기존 bulk optics 기반의 lens 대비 초박형으로 제작이 가능한 파장 선택적 flat optics 기술로써, 다초점 및 경량화를 요구하는 차세대 디스플레이 기술 (augmented reality 또는 AR, mixed reality 또는 MR) 및 광파변조 및 제어를 요구하는 홀로그래픽 카메라 분야에 대한 응용처로 많은 주목을 받고 있다. 이에 본 논문에서는 해당 기하 위상렌즈에 대한 원리 및 이에 따른 개발이슈 및 해결법에 대해 연구 하였으며, 이에 대한 응용처로 기하위상 렌즈의 편광에 따른 이중초점특성을 이용해, 기존 단일 초점 형성이 가능한 AR기기 대비, 다초점 형성이 가능한 switchable dual-depth 3D AR device를 compact한 모듈과 함께 구현하였다. 또한, 기하위상렌즈의 광파 변조 및 분리특성을 이용한 기하위상 렌즈기반의 자가간섭 홀로그래픽 시스템(GP-self-interference incoherent digital holographic, GP-SIDH)에 편광 이미지센서 적용과 함께 맞춤형 설계/제작된 기하 위상렌즈를 적용함으로써, 기존 GP-SIDH 시스템대비 안정적으로 실시간 복소 홀로그램 획득이 가능한 실시간 공간영상정보 획득용 GP-SIDH을 동영상 프레임으로 구현하였다.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.2
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• pp.15-26
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• 2009

Purpose: To compare and analyze the ocular changes after wearing conventional and 2-weeks cosmetic tinted contact lens, which were made of different material and fabrication method. Methods: Thirty five university students, age of twenties, participated in this study. With daily wearing schedule, they had worn temporary cosmetic tinted lens for 2 weeks and conventional tinted lens for two month in their right and left eye, respectively. Subjective symptoms and objective signs were graded by using CCLRU scales and corneal thickness were measured after 1 day and 2 months wearing, and under or over 5 hours wearing in a day, respectively. Results: Major subjective symptoms found in the student wearing cosmetic tinted contact lens for a 1 day and 2 months were dryness, redness, foreign body sensation and itchiness. It was also found that those symptoms were more severe in left eye (conventional cosmetic tinted contact lens) than right eye (2-weeks cosmetic tinted contact lens). However, symptoms of redness in both eyes showed statistically significant difference in the case of 1 day and 2 months wearing and under or over 5 hours wearing in a day (p=0.000). After 2 months wearing, left eye with conventional cosmetic tinted contact lens showed limbal redness (p=0.000) and bulbar conjunctival redness (p=0.012) with statistically significance, whereas there was no significant difference in both eyes before lens wear. Left eye showed statistically significant changes in all objective signs, but right eye showed palpebral conjunctival redness, corneal staining and conjunctival staining. Therefore, it was concluded that conventional cosmetic tinted contact lens may be more effective on ocular changes after wearing of lens. A statistically significant changes in both eyes after wearing lens were found that corneal thickness increased about $5{\mu}m$ (p=0.001) in right eye whereas $7{\mu}m$ (p=0.004) in left eye. Conclusions: A statistically significant number of participants in this study preferred to wearing of high Dk/t temporary cosmetic tinted contact lens made by sandwich method which resulted in less ocular changes and may give more healthy and safe ocular conditions.