• Current Optics and Photonics
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• v.6 no.5
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• pp.473-478
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• 2022

To overcome the capture-range problem in phase-diversity phase retrieval (PDPR), a geometrical-optics initial-estimate method is proposed to avoid a local minimum and to improve the accuracy of laser-wavefront measurement. We calculate the low-order aberrations through the geometrical-optics model, which is based on the two spot images in the propagation path of the laser, and provide it as a starting guess for the PDPR algorithm. Simulations show that this improves the accuracy of wavefront recovery by 62.17% compared to other initial values, and the iteration time with our method is reduced by 28.96%. That is, this approach can solve the capture-range problem.

• Journal of The Korean Association For Science Education
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• v.27 no.6
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• pp.488-496
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• 2007

The aims of this study are to investigate how Kepler found a scientific problem for the retinal image theory and to investigate how Korean middle-school students respond when the same situation is applied to them. Kepler found the scientific problem in the eye vision through the critical analysis of contemporary theories of vision, based on his relevant knowledge of optics. When the same situation was applied to the Korean middle-school students, only a few students found the same scientific problem as Kepler. From the results, it is suggested that in developing creativity teaching materials, situations like Kepler's problem finding need to be included in programs.

• Journal of the Korean Operations Research and Management Science Society
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• v.25 no.2
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• pp.87-100
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• 2000

As a result of rapid advances in communication technology, fiber optics have begun to be adopted in most telecommunication systems 3s an economic choice Due to the trend of evolution toward broadband communication network with fiber optics and electronic devices. the network design problem for broadband communication has been received a great deal of research attention recently. In this paper, we address a topological design problem for broadband local access network with uncertain demands, which has received surprisingly little attention so far. in our problem, we select a set of hubs and links for constructing network expected penalty cost for the amount of undersupplied In addition to the usual cost terms of the fixed demand problem Our problem can be approximated as a mixed 0-1 integer programming problem by using Szwarc’s linear approximation technique. Then the problem is transformed successfully into a version of classical network design model. Some computational experiments for the model and concluding remarks are described.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1749-1752
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• 2007

The Near to Eye Display (NED) solves the problem of having a display larger than a small portable device. The virtual image of the NED is created using a microdisplay and imaging optics. It is important that the optics does not interfere with the human visual system and that the device is light, compact and easy to wear. In this paper the principles of a biocular NED, which is based on a novel diffractive Exit Pupil Expander (EPE), are presented. The optical system is compact and intrinsically free from distortions and misalignments.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.2
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• pp.81-86
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• 2013

In this paper, the parameter identification for localization scheme for the optics-based micro sensor node is conducted. We analyzed short measurement range problem which can be occurred in optical based micro sensor node localization method using a time of flight. And we set up the theory for distance and maximum reflected laser power to overcome the problem by identifying hardware parameters like laser power, effective area of MEMS CCR, sensitivity of photodetector, and so on. Experimental results of measurement of maximum reflected laser power were compared with results of the theory. By using the theory, we can identify hardware parameters of localization scheme to measure particular position of the optics-based micro sensor node.

• Journal of the Optical Society of Korea
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• v.19 no.1
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• pp.84-87
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• 2015

For large optical elements which are tested by many sub-apertures, it takes too much time for a sub-aperture stitching algorithm to get the stitching result. To solve this problem, we propose a fast sub-aperture stitching algorithm to quickly compensate for piston, tilt, and defocus errors. Moreover, the new algorithm is easy to understand and program. We use partial derivatives of measurement data to separately solve piston, tilt, and defocus errors. First, we show that the new algorithm has a lower time complexity than the currently used algorithm. Although simulation results indicate that the accuracy of the new algorithm is lower than the current algorithm in all 20 simulations, our experimental results validate the algorithm and show it is sufficiently accurate for general use.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.2
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• pp.161-164
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• 2001

The purpose of our study was stability of tear film for Korean. In the 1970s, the major problem for the contact lens practitioner was the management of contact lens parameters. In the 1980s, oxygen permeability was the main problem in contact lens practice: now it is dry eyes. To appropriately fit the patient with contact lenses it is imperative to know in advance if the patient has a marginal dry eye. Based on the initial diagnosis appropriate care can be taken to minimize problems with the result that the patient can successfully wear contact lenses. A well known test for dry eyes is Schirmer test which has shown to be useful for diagnosing Sjogren syndrome. Biomicroscopy can often unmask numerous problems. The classical test for marginal dry eye is measuring the tear break up time(TBUT). A dry eye problem with contact lenses is often caused by the lid. If an incomplete blink is responsible for the dry eye it is possible to change the situation by blinking exercises. The result of these test, mean value of age was 22.8, mean value of blink rate was 19 times/min, mean value of Schirmer test was 25 mm/5 min, mean value of TBUT was 7.1 sec.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.2
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• pp.41-55
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• 1989

Successive iteration of geometrical optics(GO)is suggested to calculate wedge diffraction fields. For a wedge and given source, the GO field may be obtained when the fields by the half spaces are found and the shadow regions are determined. Furthermore, one may caluculate the sources which are equivalent to the discontinuities of the GO field along the shadow boundaries and form a new wedge problem with the equivalent sources instead of the original one. It is shown that the field by the wedge and the equivalent sources equals to the diffraction field which GO requires for the complete solution. Also, it is shown that the field generated by the equivalent sources in the unbounded space, or the incident field in the new wedge problem, equls to the diffraction field approximated by the physical optics. The new wedge problem is solved here by another application of the GO to approximate the diffraction field and the result is compared with that by the physical optics. For a validity of the successive iteration of GO , infinite iteration of GO is performed analytically and the convergence is examined ofr conducting wedges, of which the exact solution is available.

• ETRI Journal
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• v.41 no.3
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• pp.316-325
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• 2019

Accurate suppressive jamming is a prominent problem faced by radar equipment. It is difficult to solve signal detection problems for extremely low signal to noise ratios using traditional signal processing methods. In this study, a joint sensing dictionary based compressed sensing and adaptive iterative optimization algorithm is proposed to counter suppressive jamming in information domain. Prior information of the linear frequency modulation (LFM) and suppressive jamming signals are fully used by constructing a joint sensing dictionary. The jamming sensing dictionary is further adaptively optimized to perfectly match actual jamming signals. Finally, through the precise reconstruction of the jamming signal, high detection precision of the original LFM signal is realized. The construction of sensing dictionary adopts the Pei type fast fractional Fourier decomposition method, which serves as an efficient basis for the LFM signal. The proposed adaptive iterative optimization algorithm can solve grid mismatch problems brought on by undetermined signals and quickly achieve higher detection precision. The simulation results clearly show the effectiveness of the method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.8
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• pp.624-628
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• 2013

With the recent development of less-costly uncooled detector technology, expensive optics are among the remaining significant cost drivers in the thermography camera. As a potential solution to this problem, the fabrication of IR lenses using chalcogenide glass has been studied in recent years. We report on the molding and evaluation of a ultra-precision chalcogenide-glass lens for the thermography camera for body-temperature monitoring. In addition, we fabricated prototype thermography camera using the chalcogenide-glass lens and obtained the thermal image from the camera. In this work, it was found out that thermography camera discerned body-temperature between 20 and $50^{\circ}C$ through the analysis of thermal image. It is confirmed that thermography camera using the chalcogenide-glass lens is applicable to the body-temperature monitoring system.