• Journal of Korean Ophthalmic Optics Society
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• v.19 no.1
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• pp.93-98
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• 2014

Purpose: We were aim to investigate individual difference of visual acuity (VA) decrease and the change of contrast threshold (CT) according to the level of optically induced retinal defocus. Methods: A total of 69 eyes were examined using consist of ten-graded decimal vision chart (Landolt's ring). After conducted full correction of subject's refractive error, a monocular VA and CT were measured according to sequential increase by 0.25 D each time. Results: VA gradually decreased according to the increase of retinal defocus level. Individual difference of VA decrease was range from 1.2 to 0.6 in retinal defocus induced by +0.25 D. When retinal defocus was induced as much as +0.50 D and +0.75 D, it was in the range of 1.0 to 0.3 and 0.9 to 0.1 respectively. With +1.00 D, some participants didn't even recognize the 0.1 in the chart. With +1.75 D, whole participant did not recognize the 0.1. Also, CT was gradually decreased with increase of the retinal defocus level. Conclusions: Examiners should consider individual difference in the decrease of VA according to the level of residual refractive error when determining final prescription of a patient.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.174-180
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• 2019

In this study, we evaluated and analyzed the properties of polymeric transparent films used in military vehicle covers according to weathering test. Two types of polymer films (Film A and Film B) that are mostly used for military vehicle covers were selected. The weathering treatment condition and tester are described in KS K 0706, and the following weathering times were tested: 0hour, 40hours, 160hours and 320 hours. The tensile strength, elongation and thermal decomposition behavior and optical characteristics were analyzed. The tensile strength tended to decrease - increase - decrease with increasing weathering treatment time in both transparent films. The thermal decomposition temperature gradually decreased. Regarding the optical property, the light transmittance decreased and the haze tended to increase. However, film A showed almost similar optical characteristics after 160-hour weathering treatment.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.2
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• pp.261-270
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• 2014

Purpose: To study the effect of an artificially induced dioptric blur on acuity and contrast sensitivity using the $Optec^{(R)}$ 6500. Methods: Healthy 31 subjects aged $22.90{\pm}1.92$ (male 16, female 15) who were recruited from university students with 6/6 (20/20) or better corrected visual acuity and normal binocularity. They were measured objective and subjective refraction for full correction and dioptric blur using 0.00 ~ +3.00 D (+0.50 D steps) trial lenses and trial frame. They were measured binocularly visual acuity and contrast sensitivity with the $Optec^{(R)}$ 6500 (Stereo Optical Co., Inc., Chicago, Illinois, USA) under day conditions (photopic condition, $85cd/m^2$). Results: The higher dioptric blur, the less distance visual acuity and decrease rate of visual acuity. The higher dioptric blur, the less contrast sensitivity at all frequencies, and the peak of contrast sensitivity was shifted from middle frequency (6 cpd) to low frequency (1.5 cpd). When the visual acuity was best visual acuity to 0.77, there was the peak point at 6 cpd which was normal contrast sensitivity peak point. Conclusions: If the low refractive error is uncorrected or the refractive error is inappropriate, the contrast sensitivity is decreased and the peak point of contrast sensitivity frequency is shifted abnormally though small uncorrected refractive error. So it will be considered that regular eye test and decision of refractive error correction is important.

• Journal of Broadcast Engineering
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• v.27 no.1
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• pp.3-12
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• 2022

Image deblurring aims to remove image blur, which can be generated while shooting the pictures by the movement of objects, camera shake, blurring of focus, and so forth. With the rise in popularity of smartphones, it is common to carry portable digital cameras daily, so image deblurring techniques have become more significant recently. Originally, image deblurring techniques have been studied using traditional optimization techniques. Then with the recent attention on deep learning, deblurring methods based on convolutional neural networks have been actively proposed. However, most of them have been developed while focusing on better performance. Therefore, it is not easy to use in real situations due to the speed of their algorithms. To tackle this problem, we propose a novel deep learning-based deblurring algorithm that can be operated in real-time on HD resolution. In addition, we improved the training and inference process and could increase the performance of our model without any significant effect on the speed and the speed without any significant effect on the performance. As a result, our algorithm achieves real-time performance by processing 33.74 frames per second at 1280×720 resolution. Furthermore, it shows excellent performance compared to its speed with a PSNR of 29.78 and SSIM of 0.9287 with the GoPro dataset.

• Polymer(Korea)
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• v.25 no.5
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• pp.649-656
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• 2001

Miscibility of poly(4-vinylpyridine) (P4VP) blends with poly(vinyl acetate-co-vinyl alcohol) (VAc-VAL copolymers) was investigated as a function of comonomer composition of VAc-VAL copolymers. Differential scanning calorimetry (DSC) and thermo-optical microscopic (TOM) analysis confirmed that P4VP is miscible with VAc-VAL copolymers containing more than 30 mole% VAL. Fourier transform inflated (FT-IR) spectroscopic analysis revealed that the strong intermolecular hydrongen bonding interaction between the vinylpyridine and VAL hydroxyl group was formed. Theoretical phase diagram was constructed by the calculation using the Association model, a thermodynamic model for hydrogen-bonded polymer blend systems developed by Coleman et al. The calculated theoretical binodal phase diagrams were in good agreement with the experimentally determined cloud point curves.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.2 s.308
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• pp.19-29
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• 2006

As the security of personal information is becoming more important in mobile phones, we are starting to apply iris recognition technology to these devices. In conventional iris recognition, magnified iris images are required. For that, it has been necessary to use large magnified zoom & focus lens camera to capture images, but due to the requirement about low size and cost of mobile phones, the zoom & focus lens are difficult to be used. However, with rapid developments and multimedia convergence trends in mobile phones, more and more companies have built mega-pixel cameras into their mobile phones. These devices make it possible to capture a magnified iris image without zoom & focus lens. Although facial images are captured far away from the user using a mega-pixel camera, the captured iris region possesses sufficient pixel information for iris recognition. However, in this case, the eye region should be detected for accurate iris recognition in facial images. So, we propose a new fast iris detection method, which is appropriate for mobile phones based on corneal specular reflection. To detect specular reflection robustly, we propose the theoretical background of estimating the size and brightness of specular reflection based on eye, camera and illuminator models. In addition, we use the successive On/Off scheme of the illuminator to detect the optical/motion blurring and sunlight effect on input image. Experimental results show that total processing time(detecting iris region) is on average 65ms on a Samsung SCH-S2300 (with 150MHz ARM 9 CPU) mobile phone. The rate of correct iris detection is 99% (about indoor images) and 98.5% (about outdoor images).