• Current Optics and Photonics
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• v.4 no.4
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• pp.336-344
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• 2020

Exact optical characterization of virtual and augmented reality devices using conventional luminance measuring methods is a time-consuming process. A new measurement method is proposed to estimate in a relatively short time the boundary of ray trajectories emitting from a specific position on a virtual images. It is assumed that the virtual image can be modeled to be formed in front of one's eyes and seen through some optical aperture (field stop) that limits the field of view. Circular and rectangular shaped virtual images were investigated. From the estimated ray boundary, optical characteristics, such as the viewing direction and three dimensional range inside which a eye can observe the specified positions of the virtual image, were derived. The proposed method can provide useful data for avoiding the unnecessary measurements required for the previously reported method. Therefore, this method can be complementary to the previously reported method for reducing the whole measurement time of optical characteristics.

• Current Optics and Photonics
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• v.8 no.3
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• pp.307-312
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• 2024

Measuring the three-dimensional (3D) spatial light intensity distribution of an autostereoscopic multiview 3D display at the user position is time-consuming, as luminance has to be measured at different positions around the user position. This study investigates a method to quickly estimate the 3D distribution at the user position. For this purpose, a measurement setup using a white semitransparent diffusing screen or a two-dimensional (2D) spatial sensor was devised to measure the 2D light intensity distribution at the user position. Furthermore, the 3D spatial light intensity distribution at the user position was estimated from these 2D distributions at different viewing distances. From the estimated 3D distribution, the characteristics of autostereoscopic 3D display performance can be derived and the candidate positions for further accurate measurement can be quickly determined.

• Journal of the Korean Chemical Society
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• v.60 no.3
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• pp.181-186
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• 2016

The hydrophilic ophthalmic lens with addition of 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate (HPMA) and Ag nanoparticles were manufactured. And also, the cross-linker ethylene glycol dimethacrylate (EGDMA) and the initiator azobisisobutyronitrile (AIBN) were used for polymerization. The polymerization of the hydrogel lens material was conducted through thermal polymerization in 100 ℃ for 1h. The optical and physical characteristics of hydrogel lens were evaluated by measuring water content, refractive index and optical transmittance. The water content of sample containing HEA, HEMA and HPMA was in the average of 82.12%, 37.06% and 21.57%, respectively. And also, refractive index of the sample containing HEA, HEMA and HPMA was in the average of 1.3540, 1.4330 and 1.4649, respectively. In case of the optical properties of the sample, the results showed that the near-UV transmittance was 82.67%, 80.32% and 79.83%, and the visible transmittance was 89.72%, 88.24% and 86.89%, respectively. And also, optical transmittance of the sample containing Ag nanoparticles showed that the near-UV transmittance of 10.59% and visible transmittance of 43.74% were obtained. From the results, the molecular length influenced on the water content and refractive index of the polymerized material.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3233-3238
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• 2011

The fluorescence of norfloxacin was quenched by various nucleotides. The ratio of the fluorescence intensities in the absence and presence of nucleotide was linearly dependent on nucleotide concentration, suggesting that quenching occurred through the formation of nonfluorescent norfloxacin-nucleotide complexes. The gradient of the linear relationship represented the equilibrium constant of complex formation; it decreased with increasing temperature. The slopes of van't Hoff plots constructed from the temperature-dependent equilibrium constants were positive in all cases, indicating that complex formation was energetically favorable - i.e., exothermic, with negative Gibb's free energy. The equilibrium constant increased when triphosphate was used instead of monophosphate. It also increased when the oxygen at the $C'_2$ position of the nucleotide was removed. Both enhancements were due to entropic effects: entropy decreased when complexes with AMP or GMP formed, while it increased when norfloxacin complexed with ATP, GTP, dAMP and dGMP.

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.3
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• pp.65-70
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• 2007

This research aims at knowing educational objectives and understanding the whole departmental processes of two-year education programs of junior colleges in the field of ophthalmic optics. Our analyses can be categorized by on liberal art courses, compulsory subjects and optional subjects. The educational purpose of all the seven colleges was training the professional worker, meets well the educational requirements of two year college. All seven colleges' curriculum is open to the national licence examination subjects, but more academic credits are demended in eye examination of refraction, test of ocular function, professional sense of cultural subjects field, leadership in organization and course of marketing related subjects, and stronger relation with clinical examination are also required.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.2
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• pp.107-115
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• 2011

Purpose: To design and fabricate the distributed auto edging machine for the development. Methods: We got the necessary data needed in design by using CAD. Based on the these data, we fabricated the trial product for the development of the distributed auto edging machine. Results: The patternless mode could be operated by receiving the eyesize data from the auto lay-outer with the RS232C transmission system and the pattern mode could be operated by setting the pattern on the left side of the machine. The distributed auto edging machine were composed with combinations of many elements; head, auto arm, pattern clamp and grinding wheels. The head part controlled the grinding of ophthalmic lens by operating the vertical and horizontal motors. The wheels part was comprised of glass mode, plastic mode, V-bevel mode and polish mode. The slide in the auto arm was equipped on the below of the patten and the slide could hold up the pattern which was rotated by fixed shaft. The pattern clamp could move the head part to the up and down or right or left way by the manual operation of optometrists. Conclusions: We could succeed in making the trial product by applying it to the development of the distributed auto edging machine which could be used as the patternless mode and pattern mode, selectively. Therefore, it was confidently expected that this product was very helpful for the optometrists to dispense the ophthalmic lens because of its cost-efficiency and convenience.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.4
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• pp.433-438
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• 2011

Purpose: To investigate the proper distance from patient to target when measuring refractive error using open view target type auto-refractor(OVTAR), it was compared refractive errors between by OVTAR using N-vision-K5001 auto-refractor and internal fixation target type auto-refractor(IFTAR) using Canon auto-refractor. Methods: 21 subjects(42 eyes) aged 22.2(${\pm}$3.4) years old who had over 1.0 of corrected visual acuity and no ocular disease were participated for this study. Noncycloplegic measurements of refractive error were performed using a IFTAR(RK-F1, Canon, Japan) and an OVTAR(N-vision-K5001, Shin-nippon, Japan). The distances from subjects to targets in using the open the view target type auto-refractor were 1 m, 3 m, 4 m and 6 m. The refractive errors were compared between by IFTAR and by 1 m, 3 m, 4 m and 6 m target distances respectively using OVTAR. Results: At 1 m fixation distance the mean of refractive errors for total subjects was not significantly different between by OVTAR(-2.75${\pm}$1.84 D) and by IFTAR(-2.95${\pm}$2.04 D)(p=0.06). However at 3, 4 and 6 m fixation distance refractive errors by OVTAR were significantly lower myopic refractive errors than by IFTAR(p<0.05). Conclusions: The distance from subject to fixation target is needed over 3 m for the measurement of refractive error using OVTAR even not to 5~6 m distance.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.1
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• pp.115-119
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• 2009

Purpose: This study has been conducted to know the relation among accommodative amplitude, response, and facility. Methods: 61 subjects were students without any ocular diseases and presbyopia in a university, Korea. After far distance visual acuity was fully corrected, the amplitude was measured through Push-Up test, the response was measured through Jackson crossed cylinder ${\pm}$0.25D and the facility was measured through +2.00/ -2.00D flipper. Results: The relation among accommodative facility, response and amplitude had not indicate significant level in monocular and binocular. In binocular, 12 eyes (19.6%) had a difference in amplitude, 9 eyes (14.7%) had a difference in response, 2 eyes (3.2%) had a difference in facility from norm which would be expected from their age. 4 eyes (6.5%) had difference in both amplitude and response. 2 eye (3.2%) had difference in both amplitude and facility. In all three of the amplitude, response, facility had not difference. Conclusions: The evaluation of accommodative functions and a patients accommodative dysfunction is examined all facets of amplitude, response, and facility.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.1
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• pp.47-52
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• 2012

Purpose: This study was to evaluate visual fatigue with passing of watching 3D TV in short term and with experience of watching 3DTV in long term. Methods: 98 adult subjects aged $33.5{\pm}5.5$ years (22 to 51 years; 12 females and 86 males) agreed to participate in this study. Subjects were asked to watch 52 inch LED 2D and 3D television (Shutter glasses method) at 2.7 meters for 65minutes with wearing their habitual glasses or contact lenses. For evaluating visual fatigue, subjects were verbally responded to 11 questions : eye straining, eye paining, dry eye, sore eye, watery eye, photophobia, blur vision, diplopia, eye fatigue, headache, and dizziness with scale 0 to 3 at each measurement while watching 3D and 2D TV. Results: The mean scores of visual fatigue were $2.08{\pm}2.14$, $3.19{\pm}3.02$, $3.40{\pm}3.37$, $3.53{\pm}3.07 $for after 5 minutes, 25 minutes, 45 minutes, and 65 minutes respectively for 3D TV, and $0.40{\pm}1.03$, $0.22{\pm}0.70$, $0.22{\pm}0.58$, and $0.17{\pm}0.52$ after 25, 45, and 65 minutes respectively for 2D TV. Visual fatigue for watching 3D TV was significantly higher than for watching 2D TV at all measurements sessions (paired t-test, p < 0.001). The visual fatigue significantly increased during watching 3D TV for 65 minutes (p < 0.001, RM-ANOVA). The visual fatigue during watching 3D TV was significantly increased until 25 minutes (paired t-test, p < 0.001), stable after that. For correlation between visual fatigue and 3D watching experience, the more 3D watching experiences were significantly the less visual fatigues in photophobia, blur vision, diplopic and dizzy symptoms (ANOVA, all F(1, 96) = 4.500, all p < 0.05), but there was not significantly different in the other symptoms (ANOVA, F (1, 96) = 2.123, p = 0.148). Conclusions: Visual fatigue for watching 3D TV was higher than for watching 2D TV, increase by 25 minutes. It was different by symptoms for correlation between visual fatigue and 3D watching experience.

• Journal of the Korean Ceramic Society
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• v.52 no.3
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• pp.180-185
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• 2015

Low-cost ceramic membrane supports with pore sizes in the range of $0.52-0.62{\mu}m$ were successfully prepared by uniaxial dry compaction method using inexpensive raw materials including kaolin, bentonite, talc, sodium borate, and alkaline-earth oxides in carbonate forms (e.g., $MgCO_3$, $CaCO_3$, and $SrCO_3$). The prepared green supports were sintered at $1000^{\circ}C$ for 8 hr in air. The effect of alkaline-earth oxide additives on the flexural strength of clay-based membrane supports was investigated. The porosity of the clay-based membrane supports was found to be in the range of 33-34%. The flexural strength of the clay-based membrane supports with 1% alkaline-earth carbonates was found to be in the range of 42.8-52.7 MPa. The addition of alkaline-earth carbonates to clay-based membrane supports resulted in large increases (47-80%) in the flexural strength of the membrane supports, compared to that of membrane supports without alkaline-earth carbonates. The typical flexural strength of the clay-based membrane support with 1% $SrCO_3$ was 52.7 MPa at 33.8% porosity.