• Korean Journal of Optics and Photonics
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• v.34 no.3
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• pp.117-123
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• 2023

The size of an optical surface can significantly affect the performance of an optical system, and high spatial frequency errors have a greater impact. Therefore, it is crucial to measure the surface figure error with high frequency. To address this, a new method called rotational prism stitching interferometer (RPSI) is proposed in this study. The RPSI is a type of stitching interferometer that enhances spatial resolution, but it differs from conventional stitching interferometers in that it does not require the movement of either the mirror tested or the interferometer itself to obtain sub-aperture interferograms. Instead, the RPSI uses a beam expander and a rotating Dove prism to select particular sub-apertures from the entire aperture. These sub-apertures are then stitched together to obtain a full-aperture result proportional to the square of the beam expander's magnification. The RPSI's effectiveness was demonstrated by measuring a 40 mm diameter spherical mirror using a three-magnification beam expander and comparing the results with those obtained from a commercial interferometer. The RPSI achieved surface testing results with nine times higher sampling density than the interferometer alone, with a small difference of approximately 1 nm RMS.

• Journal of The Korean Association For Science Education
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• v.26 no.7
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• pp.835-842
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• 2006

The aims of this study are to investigate how Kepler found a scientific problem for the retinal image theory and how abductive reasoning was used in his theory development, and to find implications for teaching creativity in science class from his thinking processes in the scientific discovery. Through the analysis of the related literatures, it was found that Kepler's problem finding in his retinal image theory came from the critical analysis of contemporary theories of vision, based on his relevant knowledge of optics, as he formulated his own hypothesis to build a new theory in eye vision employing optical phenomenon in spherical lens, which is a kind of abductive reasoning. From the results, three suggestions are proposed, that: (a) in the development of creativity teaching material, the situations like Kepler's problem finding need to be included in the programs; (b) it should be taught that relevant scientific knowledge is important for problem finding and hypothesis formulating; and (c) the experience of successful problem solving by themselves could help them find new scientific problem(s).

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.252-259
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• 2008

The deep-sea mining system is generally composed of surface vessel, lifting system, buffer, flexible pipe and miner. The mining system can be regarded as a large-scale system in which each subsystem is interconnected to other ones. In order to control a large-scale system, decentralized control approaches have been proposed recently. In this paper, as a basic study on application of decentralized control, firstly, the mining system was modeled in a simplified way. Lifting system and buffer were regarded as a spherical pendulum and the flexible pipe was taken as a two-dimensional linear spring connection. Based on the simplified model dynamics, the mining system can be decentralized two subsystems, the one consisting of surface vessel, lifting system and buffer, and the other, the miner. Next, this paper proposed the design of controller for each decentralized subsystem by regarding the interacting terms as disturbances. The controllers kept the constant distance between two subsystems during the miner was moving on the specified track. Finally, the efficiency of proposed controller was proven through the numerical simulation of the derived model.

• Investigative Magnetic Resonance Imaging
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• v.16 no.1
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• pp.67-75
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• 2012

Purpose : We studied enhanced method to view the vessels in the brain using Magnetic Resonance Angiography (MRA). Noticing that Maximum Intensity Projection (MIP) image is often used to evaluate the arteries of the neck and brain, we propose a new method for view brain vessels to stereo image in 3D space with more superior and more correct compared with conventional method. Materials and Methods: We use 3T Siemens Tim Trio MRI scanner with 4 channel head coil and get a 3D MRA brain data by fixing volunteers head and radiating Phase Contrast pulse sequence. MRA brain data is 3D rotated according to the view angle of each eyes. Optimal view angle (projection angle) is determined by the distance between eye and center of the data. Newly acquired MRA data are projected along with the projection line and display only the highest values. Each left and right view MIP image is integrated through anaglyph imaging method and optimal stereoscopic MIP image is acquired. Results: Result image shows that proposed method let enable to view MIP image at any direction of MRA data that is impossible to the conventional method. Moreover, considering disparity and distance from viewer to center of MRA data at spherical coordinates, we can get more realistic stereo image. In conclusion, we can get optimal stereoscopic images according to the position that viewers want to see and distance between viewer and MRA data. Conclusion: Proposed method overcome problems of conventional method that shows only specific projected image (z-axis projection) and give optimal depth information by converting mono MIP image to stereoscopic image considering viewers position. And can display any view of MRA data at spherical coordinates. If the optimization algorithm and parallel processing is applied, it may give useful medical information for diagnosis and treatment planning in real-time.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.4
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• pp.409-415
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• 2011

Purpose: To design applied anamorphic lens that focal length ratio is 3:1 optical system to improve detecting distance. Methods: We defined a boundary condition as $50^{\circ}{\sim}60^{\circ}$ for viewing angle, horizontal direction 36mm, vertical direction 12 mm for focal length, f-number 4, $15{\mu}m{\times}15{\mu}m$ for pixel size and limit resolution 25% in 33l p/mm. Si, ZnS and ZnSe as a materials were used and 4.8 ${\mu}m$, 4.2 ${\mu}m$, 3.7 ${\mu}m$ as a wavelength were set. optical performance with detection distance, narcissus and athermalization in designed camera were analyzed. Results: F-number 4, y direction 12 mm and x direction 36 mm for focal length of the thermal optical system were satisfied. Total length of the system was 76 mm so that an overall volume of the system was reduced. Astigmatism and spherical aberration was within ${\pm}$0.10 which was less than 2 pixel size. Distortion was within 10% so there was no matter to use as a thermal optical camera. MTF performance for the system was over 25% from 33l p/mm to full field so it was satisfied with the boundary condition. Designed optical system was able to detect up to 2.9 km and reduce a diffused image by decreasing a narcissus value from all surfaces except the 4th surface. From sensitivity analysis, MTF resolution was increased on changing temperature with the 5th lens which was assumed as compensation. Conclusions: Designed optical system which used anamorphic lens was satisfied with boundary condition. an increasing resolution with temperature, longer detecting distance and decreasing of narcissus were verified.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.3
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• pp.187-192
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• 2006

The purpose of this research was to measurement real accmmnodative response amount of emmetropia using both eyes open-view auto-refractometer. We classified 377(male 146, female 231)eyes showing good naked vision at least 1.0, with a spherical equivalent refraction of under ${\pm}0.50D$ and cylindercal refraction of under -0.75D, from 10 to 59(mean $25.8{\pm}12.4$) years into 5 groups with 10 year interval and analyzed change of the near astigmatism and accommodative response amount to distinction of age. Age comparison, total mean 1.47D, 10 years age group 1.63D, 20 years age group 1.57D, 30 years age group 1.71D, 40 years age group 0.97D, and 50 years age group 0.05D. It was no difference between 10 to 30 years age group, But it showed the decre8.se which is remarkable from above 40 years age group and it does not almost response from above 50 years age group. Sexual difference, the man appeared some highly in male(mean $26.4{\pm}12.3$ years) 1.56D m female(mean $26.4{\pm}12.3$) 1.43D. Near-astigmatism power change, mean +0.12D, 10 years age group +0.06D, 20 years age group +0.16D, 30 years age group +0.09D, 40 years age group +0.05D, and 50 years age group +0,06D. No significant difference of astigmatism powers among the an groups, but from all years age group the astigmatism power appeared more highly far-astigmatism than near-astigmatism. Near-astigmatism axis change in the far-astigmatism changes at under ${\pm}10^{\circ}$ 103 eyes, above ${\pm}10^{\circ}$ rotation clockwise direction 108 eyes, above ${\pm}10^{\circ}$ rotation counter-clockwise direction 101 eyes. It was analyzed near-astigmatism axis change.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.211-221
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• 2004

The purpose of this study is to evaluate the distribution and change of curvature of the anterior corneal surface with age in emmetropia. 504 subjects who have emmetroia with good naked vision of at least 0.6-1.0 (spherical equivalent: +0.75D- -0.75D) participated in this study. The 504 subjects into 8 groups with 10 year interval from 3-year to 83-year, and their corneal curvatures were analyzed using manual keratometry. The results are as follows. In individual analysis: First, regression analysis of corneal curvature radius with age has given an equation: Y = -0.003x + 7.796 (r = -0.26). The average corneal curvature radii was measured to be $7.68{\pm}0.25mm$ at 38.3-year and range was 6.98-8.54 mm. Second, frequency of corneal curvature radius were obtained in 36% between 7.61 and 7.80 mm, 78% between 7.41 and 8.00 mm, 96% between 7.21 and 8.20 mm, 100% between 6.98 and 8.54 mm. Third, as for the comparison of corneal curvature radius with respect to sex, The mean value of male (n = 304, mean: 37.6-year $7.72{\pm}0.24mm$, Range: 7.09-8.54 mm) is larger than that of female (n = 200, mean: 39.3-year $7.62{\pm}0.24mm$, Range: 6.98-8.42 mm) by 0.1mm (p<0.01). In groups analysis: First, regression analysis of corneal curvature radius with age has given an equation: $Y=-0.0066x^2+0.0227x+7.7282$ (r = -0.90). Second, vertical and horizontal curvature radius decreased with age (p < 0.01). Especially the decrease of horizontal curvature radius were more pronounced than the decrease of vertical (horizontal:10-70 age group: 0.38 mm decrease, vertical:10-70 age group: 0.20 mm decrease). Third, difference between steep and flat meridian (astigmatism) progressively decreased with age. (low age group:0.18 mm difference, high age group: 0.08 mm difference). Fourth, the corneal curvature radius of male was larger than female's in total groups(p < 0.01). Consequently, the change of corneal curvature radius with age progressively decreased in all conditions (mean, vertical, horizontal, male, and female) and this change was more outstanding in horizontal rather than in vertical.

• Journal of The Korean Society of Grassland and Forage Science
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• v.23 no.1
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• pp.49-58
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• 2003

This study was conducted to determine the effect of seeding times and mixture rates of oat and forage rape on the growth characteristics and forage yields during rest periods from March to June after the harvest of potatoes in potato cultivation fields located in the areas about 600m above the sea level in Jeju. The experiment was a split plot desist with seeding times(early, middle and late March) sown . at intervals of ten days from early March to late March as the nam plots and mixture rates as subplots, consisted of oat single(150kg/ha), forage rape single(15kg/ha), oat/rape mixtures 75 : 25% (112.5kg/ha of oat and 3.75kg/ha of rape), oat/rape mixtures 50 : 50％(75kg/ha of oat and 7.5kg/ha of rape) and oat/rape mixtures 25 : 75％(37.5kg/ha of oat and 11.3kg/ha of rape). The germination and establishment of eat and rape were not significantly different among seeding times and mixture rates. The plant heights were higher when seeded middle March compared to seeding times of early and late March. The growth stage of the oats seeded early March was dough stage, while that of oats seeded middle or late March was milk stage. The dry matter yields per ha were higher(p<0.05) when seeded middle March than those of seeding time of early and late March. The crude protein contents of rape single, mixtures and oat single treatments were 15.9, 12.4∼14.5 and 8.5％, respectively.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.2
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• pp.195-200
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• 2011

Purpose: We analyzed the influence of myopic's eye-glasses wearing on myopia progress after cycloplegic refraction. Methods: The 33 people (66 eyes) were school children from 8 years to 12 years having no experience eye-glasses wearing, they were taken cycloplegic refraction at the 100th, the 200th and 300th days in order to evaluate myopia progression. We investigated the eye-glasses wearing group (experimental group, 32 eyes) and the non-eye-glasses wearing group (control group, 34 eyes). The eye-glasses power of the experimental group were -0.50 D, -0.75 D, -1.00 D, -1.25 D and -1.50 D. We compared experimental group with control group for myopia progress according to period, age, and refraction error and investigated the myopia progress according to the eye-glasses power of experimental group. Results: At the 300th day from the first cycloplegic refaction, spherical equivalent for the experimental group increased as -1.03${\pm}$0.43 D (t=13.36, p<0.001) and for the control group increase as -0.61${\pm}$0.35 D (t=10.05, p<0.001) and two groups were statistical difference. Myopia power for experimental group increased 60.75%, for control group increased 56.66% at the 300 days. According to eye-glasses power increased 41.19${\pm}$15.25% at -1.50 D, 36.74${\pm}$19.29% at -1.25 D, 56.57${\pm}$20.21% at -1.00 D, 87.26${\pm}$49.38% at -0.75 D and 106.69${\pm}$59.60% at -0.50 D. Conclusions: The myopia power for the eye-glasses wearing group was 0.46 D faster than the non-eye-glasses wearing group at the 300th day from the first cycloplegic refraction. We will consider the effect of non-eye-glasses wearing to protect the progressing myopia and prescribe the under correction for school children having no experience eye-glasses wearing.

• Journal of Korean Ophthalmic Optics Society
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• v.2 no.1
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• pp.133-143
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• 1997

A population-based study of people aged above 20 years showed that 32% had emmetropia and 68% had ammetropia(myopia 56.6%. hyperopia 11.4%) city in Korea. The percentage of ammetropia in population based study is higher than that of clinic(O.P.D.) based. A 83.3% of the ammetropia had myopia. which is higher than 76.3% of 1968 and 76.9% of 1975 years. A 16.7% of the ammetropia had hyperopia. which is lower than 19.4% of 1968 and 17.3% of 1975 years. In the kind of refractive error. 32.1% of 985 eyes examined had compound myopic astigmatism. 18.2% had simple myopic astigmatism. 14.2% had simple myopia. 6.8% had simple hyperopic astigmatism, 5.0% had mixed astigmatism, 4.7% had compound hyperopic astigmatism and 3.6% had simple hyperopia. In the difference of binocular refractive error, 29% had 0.50~2.00 Dptr difference and 3.6% had difference above 2.00 Dptr. In age related myopic refractive error, 76.7% of people aged 20~29 years and 74.0% of 30~39 years had myopia. It is due to overstudy for entrance into a university that the percentage of myopia is higher than that of abroad. In age related hyperopic refractive error, 2.9% of people aged 20~29 years, 0.6% of 30~39 years. 6.3% of 40~49 years, 16.0% of 50~59 years and 63.9% of 60~69 years had hyperopia. It shows that the age related hyperopic refractive error was significantly increased at aged 40~49 years. The right eye had more myopic refractive error than left eye.