• 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.

• 한국가시화정보학회:학술대회논문집
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• 2001.12a
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• pp.123-137
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• 2001

PIV (particle image velocimetry) systems use a camera to take snapshots of particles carried by a fluid at some precise instants. Signal processing methods are then used to compute the flow velocity field. In this paper, the design of the camera objective (optics) is addressed. The optimization is done in order to maximize the signal-to-noise ratio of in-focus particles. Four different kinds of noise are considered: photon shot noise, thermal and read noise, background glow shot noise, and noise made by the other particles. A semi-empirical model for the lens aberrations of a two-doublet objective is first addressed, since further, it is shown that lens aberrations (low f-value $f_{\#}$) should be used instead of the Fraunhofer diffraction (high f-value) for the fitting of the particle image size with the pixel size. Other important conclusions of the paper include the expression of optimum values for the magnification M, for the exposure period $\tau$ and for the pixel size $\xi$.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.15-18
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• 2005

We have designed and fabricated a thermal scanning electron microscopy. It includes an electron source, two condenser lenses, one objective lens, a scanning coil and a stigmator coil for focusing in column and also have a secondary electron detector for constructing the image in chamber with a high vacuum condition and control part for operating the SEM. Especially, in order for us to find out the optical characteristics, our attention and studies have been concentrated on the effects of two condenser lenses and one objective lens for high resolution with SEM. Finally, we developed a high resolution thermal scanning electron microscopy.

• Transactions of the Society of Information Storage Systems
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• v.1 no.2
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• pp.121-126
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• 2005

Recently, an optical disc system has been proposed using blue laser diode, high NA objective lens and groove only disc structure. A new method is needed to readout CD and DVD in this Blu-Ray Disc Recorder. In order to readout CD and DVD in Blu-Ray Disc Recorder, we adopted dual-lenses actuator in consideration of optical utilization efficiency, optical performance and insurance of sufficient W.D(working distance). This dual-lenses actuator has two objectives in radial direction, one is for CD/DVD and the other is for BD. We had to solve the induced problems of collision between disc and lens, DC tilt increase, AC tilt increase, 2nd resonance deterioration and AC sensitivity drop caused by disposing two lenses in an actuator. Also we developed high response twin- objective actuator with radial tilt function to apply high-speed BD Recorder or BD Player. Consequently we presented that two kinds of dual-lenses actuators for BD Recorder have been possessed good performance in 3 axis directions. And we measured eye patterns of CD, DVD and BD by using one BD optical pick-up with dual-lenses actuator.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.7 no.2
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• pp.45-51
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• 1989

Lens distortion would produce image displacement, therefore correction of lens distortion is required urgently to improve accuracy of results in photogrammetry. The objective of this study is to find out lens distortion coefficients versus focussing distance on non-metric and metric camera and to investigate propriety of application of lens distortion coefficients to three dimensional analysis. Analytical plumb line method which needs not perform control survey and space resection and requires only one photograph was used in order to get lens distortion coefficients. As the result of this study, the coefficients of radial and tangential distortion change as focussing distance changes, and consequently it is reasonable to apply the eigenvalues of lens distortion coefficients according to focussing distance. When these coefficients were applied to actual measurement, standard errors decreased about 30% or 76% remarkably.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.2
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• pp.56-68
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• 1994

The objective of camera calibration is to determine the internal optical characteristics of camera and the three-dimensional position and orientation of camera with respect to the real world. Calibration procedure for computer vision should be automatical, accurate and applicable to general purpose cameras and lenses. In this paper, we present camera calibration method which meets the above requirements. The algorithm is based on the two-stage method which takes into account lens distortion in the second stage. In this paper, the overdetermined nonlinear system is established in terms of the constraints to all directions and our calibration algorithm is proposed which is constructed by using Marquardt iterations and our calibration algorithm is proposed which is constructed by using Marquardt iteration method in solving nonlinear equations. Experimental results indicate that lens distortion should be taken into consideration for the calibration of the general-purpose lens. With 24 calibration points acquired out of 512$\times$512 image, the proposed algorithm came up with average error of less than 1 pixel and showed a higher accuracy over the conventional two-stage method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.555-556
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• 2014

In this paper, topology optimization of two-dimensional acoustic lenses is presented by using the phase field method. The objective of the optimization is to maximize the acoustic pressure at a specified domain inside the acoustic domain for a given frequency, and the constraint is imposed on the amount of the material of the acoustic lens. Topology optimization of two-dimensional acoustic lenses are obtained as the steady state of the phase transition described by the Allen-Cahn equation. The Helmholtz equation modeling the wave propagation is solved by using a finite element method. The effectiveness of the proposed method is verified by applying it for several two-dimensional acoustic lens system design problems.

• Korean Journal of Optics and Photonics
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• v.12 no.6
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• pp.460-462
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• 2001

We have analyzed the characteristics of IR lens mounting with elastomer and applied the results to the mounting of a silicon lens with diameter 117 mm which is the objective of a thermal imaging system. The elastomer, the 577 primerless silicone adhesive (Dow Corning Co.) which is heat cure type, and the mount material, A16061 are used for our analysis. Theoretical analysis gives the result that the space between lens and mount is required to be more than 250 ${\mu}{\textrm}{m}$ under the operational temperature conditions of -40~+6$0^{\circ}C$.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.7
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• pp.98-103
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• 1998

Recently, DVD/CD compatible driver is needed for DVD and CD is widely used as a new optical data restoring device. The optical systems of DVD and CD driver are different because they have different optical feature. If only one objective lens is used, the change of an aperture or a dual focal length of the lens is required. This method, however, increases the number of parts and results in loss of the power of laser light. Hence, we propose a dual lens actuator design that can read DVD and CD respectively. Albeit magnetic spring is important mechanism in the dual lens actuator design, there has not been the systematic approach to design the mechanism in the preceding researches. In this article. the guideway to design magnetic spring is presented by using the qualitative theoretical approach and the finite element analysis.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.1
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• pp.187-192
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• 2000

The objective of this study was to investigate the problems of soft contact lens wear on the women college students. The results were as follows 1. Almost the purchase of soft contact lens was the optical shop. 2. Almost the motive of soft contact lens use was the discomfort of glasses wear. 3. Almost the good feeling of glasses wear was moderate degree. 4. On the main reason of exchange of contact lens, teens was contact lens damage and tweenths was lifespan of contact lens. 5. On the contact lens wearing time at one day, teens was over 10 hours and tweenths was from 7 hours to 10 hours. 6. On the contact care and treatment, teens was a lens washing and storage and tweenths was a lens washing and disinfectant. 7. On the main difficult of contact lens handling, teens was a lens separation in eye and disinfection of lens case and tweenths was a solution treatment and insertion of contact lens in the eye. 8. On the contact lens insertion in the eye, the most difficult item was hanging of the eyelid and fear thinking in teens and fear thinking in tweenths. 9. On the difficult in separate of contact lens wear, a most subjects were eye opening. 10. On the most inconvenient state in contact lens wearing, the subjects were eye redness, foreign body and eye pain. 11. On the advantage of contact lens wearing, teens was decrease in glasses side effects and twenties was a beauty.