• Imaging Science in Dentistry
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• v.38 no.4
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• pp.203-208
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• 2008

Purpose : The purpose of this study was to develop a system for the measurement and simulation of the TMJ movement and to analyze the mandibular movement quantitatively. Materials and Methods : We devised patient-specific splints and a registration body for the TMJ movement tracking. The mandibular movements of the 12 subjects with facial deformity and 3 controls were obtained by using an optical tracking system and the patient-specific splints. The mandibular part was manually segmented from the CT volume data of a patient. Three-dimensional surface models of the maxilla and the mandible were constructed using the segmented data. The continuous movement of the mandible with respect to the maxilla could be simulated by applying the recorded positions sequentially. Trajectories of the selected reference points were calculated during simulation and analyzed. Results : The selected points were the most superior point of bilateral condyle, lower incisor point, and pogonion. There were significant differences (P<0.05) between control group and pre-surgical group in the maximum displacement of left superior condyle, lower incisor, and pogonion in vertical direction. Differences in the maximum lengths of the right and the left condyle were 0.59${\pm}$0.30 mm in pre-surgical group and 2.69${\pm}$2.63 mm in control group, which showed a significant difference (P<0.005). The maximum of differences between lengths of the right and the left calculated during one cycle also showed a significant difference between two groups (P<0.05). Conclusion : Significant differences in mandibular movements between the groups implies that facial deformity have an effect on the movement asymmetry of the mandible. (Korean J Oral Maxillofac Radiol 2008; 38 : 203-8)

• Korean Journal of Remote Sensing
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• v.34 no.6_2
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• pp.1215-1227
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• 2018

Sea ice motion is an important factor for assessing change of sea ice because the motion affects to not only regional distribution of sea ice but also new ice growth and thickness of ice. This study presents an application of multi-temporal high-resolution optical satellites images obtained from Korea Multi-Purpose Satellite-2 (KOMPSAT-2) and Korea Multi-Purpose Satellite-3 (KOMPSAT-3) to measure sea ice motion using SIFT (Scale-Invariant Feature Transform), SURF (Speeded Up Robust Features) and ORB (Oriented FAST and Rotated BRIEF) feature tracking techniques. In order to use satellite images from two different sensors, spatial and radiometric resolution were adjusted during pre-processing steps, and then the feature tracking techniques were applied to the pre-processed images. The matched features extracted from the SIFT showed even distribution across whole image, however the matched features extracted from the SURF showed condensed distribution of features around boundary between ice and ocean, and this regionally biased distribution became more prominent in the matched features extracted from the ORB. The processing time of the feature tracking was decreased in order of SIFT, SURF and ORB techniques. Although number of the matched features from the ORB was decreased as 59.8% compared with the result from the SIFT, the processing time was decreased as 8.7% compared with the result from the SIFT, therefore the ORB technique is more suitable for fast measurement of sea ice motion.

• Journal of Astronomy and Space Sciences
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• v.28 no.4
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• pp.333-344
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• 2011

An optical tracking system has advantages for observing geostationary earth orbit (GEO) satellites relatively over other types of observation system. Regular surveying for unidentified space objects with the optical tracking system can be an early warning tool for the safety of five Korean active GEO satellites. Two strategies of positioning on the observed image of Communication, Ocean and Meteorological Satellite 1 are tested and compared. Photometric method has a half root mean square error against streak method. Also eccentricity method for initial orbit determination (IOD) is tested with simulation data and real observation data. Under 10 minutes observation time interval, eccentricity method shows relatively better IOD results than the other time interval. For follow-up observation of unidentified space objects, at least two consecutive observations are needed in 5 minutes to determine orbit for geosynchronous orbit space objects.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.1
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• pp.128-135
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• 2009

Techniques for tracking the same region of physical space with the temporal sequences of images by matching the contours of constant phase show robust and stable performance in relative to the tracking techniques using or assuming the constant intensity. Using this property, we describe an algorithm for obtaining the robust motion parameters caused by the global camera motion. First, we obtain the optical flow based on the phase of spacially filtered sequential images on the region in a direction orthogonal to orientation of each component of gabor filter bank. And then, we apply the least squares method to the optical flow to determine the affine motion parameters. We demonstrate hat proposed method can be applied to the vision based pointing device which estimate its motion using the image including the display device which cause lighting condition varieties and noise.

• Journal of Environmental Science International
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• v.28 no.5
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• pp.521-526
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• 2019

In this study, a solar light collector that collects and transmits solar light required for crop production in a closed plant production system was developed. The solar light collector consisted of a Fresnel lens for collecting solar light, and a tracking actuator for tracking solar light from sunrise to sunset to increase the light collection efficiency. The optical fiber that transmitted solar light was made of Glass Optical Fiber (GOF), and it had an excellent optical transmission rate. After collecting the solar light, the amount of light was measured at 5, 10, 15, 20, 25, and 30 cm distances from the GOF through the darkroom by using a light sensor logger connected to a quantum and pyranometer sensor. Compared with solar light, the light intensity of pyranometer sensor measured at 5 cm was 114% higher than solar light, and 61% at 10 cm. In addition, it was observed that it is possible to transmit the necessary amount of light for growing crops up to about 15 cm (as over 22%) through GOF. Therefore, adding diffusers to the solar light collector should be expected to replace artificial light in plant factories or plug seedlings nurseries for leafy vegetables. More studies on the solar light collection devices and the light transmission devices that have high light collection efficiency should be conducted.

• Journal of the Optical Society of Korea
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• v.20 no.4
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• pp.488-499
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• 2016

We present a design and optical simulation of a cost-effective hybrid daylighting/LED system composed of mixing sunlight and light-emitting diode (LED) illumination powered by renewable solar energy for indoor lighting. In this approach, the sunlight collected by the concentrator is split into visible and non-visible rays by a beam splitter. The proposed sunlight collector consists of a Fresnel lens array. The non-visible rays are absorbed by the solar photovoltaic devices to provide electrical power for the LEDs. The visible rays passing through the beam splitters are coupled to a stepped thickness waveguide (STW) by tilted mirrors and confined by total internal reflection (TIR). LEDs are integrated at the end of the STW to improve the lighting quality. LEDs’ light and sunlight are mixed in the waveguide and they are coupled into an optical fiber bundle for indoor illumination. An optical sensor and lighting control system are used to control the LED light flow to ensure that the total output flux for indoor lighting is a fixed value when the sunlight is inadequate. The daylighting capacity was modeled and simulated with a commercial ray tracing software (Lighttools^TM). Results show that the system can achieve 63.8% optical efficiency at geometrical concentration ratio of 630. A required accuracy of sun tracking system achieved more than ±0.5^o . Therefore, our results provide an important breakthrough for the commercialization of large scale optical fiber daylighting systems that are faced with challenges related to high costs.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.37 no.6
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• pp.10-21
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• 2000

The Cellular Noninear Networks structure for Distance Transform(DT) and the robust optical flow detection algorithm based on the DT are proposed. For some applications of optical flows such as target tracking and camera ego-motion computation, correct optical flows at a few feature points are more useful than unreliable one at every pixel point. The proposed algorithm is for detecting the optical flows on the trajectories only of the feature points. The translation lengths and the directions of feature movements are detected on the trajectories of feature points on which Distance Transform Field is developed. The robustness caused from the use of the Distance Transform and the easiness of hardware implementation with local analog circuits are the properties of the proposed structure. To verify the performance of the proposed structure and the algorithm, simulation has been done about various images under different noisy environment.

• Journal of Astronomy and Space Sciences
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• v.32 no.3
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• pp.229-235
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• 2015

We estimated the orbit of the Communication, Ocean and Meteorological Satellite (COMS), a Geostationary Earth Orbit (GEO) satellite, through data from actual optical observations using telescopes at the Sobaeksan Optical Astronomy Observatory (SOAO) of the Korea Astronomy and Space Science Institute (KASI), Optical Wide field Patrol (OWL) at KASI, and the Chungbuk National University Observatory (CNUO) from August 1, 2014, to January 13, 2015. The astrometric data of the satellite were extracted from the World Coordinate System (WCS) in the obtained images, and geometrically distorted errors were corrected. To handle the optically observed data, corrections were made for the observation time, light-travel time delay, shutter speed delay, and aberration. For final product, the sequential filter within the Orbit Determination Tool Kit (ODTK) was used for orbit estimation based on the results of optical observation. In addition, a comparative analysis was conducted between the precise orbit from the ephemeris of the COMS maintained by the satellite operator and the results of orbit estimation using optical observation. The orbits estimated in simulation agree with those estimated with actual optical observation data. The error in the results using optical observation data decreased with increasing number of observatories. Our results are useful for optimizing observation data for orbit estimation.

• Journal of Astronomy and Space Sciences
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• v.30 no.1
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• pp.49-58
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• 2013

ARGO-M is a satellite laser ranging (SLR) system developed by the Korea Astronomy and Space Science Institute with the consideration of mobility and daytime and nighttime satellite observation. The ARGO-M optical system consists of 40 cm receiving telescope, 10 cm transmitting telescope, and detecting optics. For the development of ARGO-M optical system, the structural analysis was performed with regard to the optics and optomechanics design and the optical components. To ensure the optical performance, the quality was tested at the level of parts using the laser interferometer and ultra-high-precision measuring instruments. The assembly and alignment of ARGO-M optical system were conducted at an auto-collimation facility. As the transmission and reception are separated in the ARGO-M optical system, the pointing alignment between the transmitting telescope and receiving telescope is critical for precise target pointing. Thus, the alignment using the ground target and the radiant point observation of transmitting laser beam was carried out, and the lines of sight for the two telescopes were aligned within the required pointing precision. This paper describes the design, structural analysis, manufacture and assembly of parts, and entire process related with the alignment for the ARGO-M optical system.

• Transactions of the Society of Information Storage Systems
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• v.1 no.2
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• pp.115-120
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• 2005

As a popularity of a portable digital device such as a cellular phone, a digital camera and a MP3 player is spreading, the demand of the mobile storage device increases rapidly. A bluray technology using 405nm laser diode and objective lens having high NA(Numerical Aperture), 0.85, satisfies a miniaturization and a high capacity which are the requirements of the portable device. To develop SFFOP(small form factor optical pickup), it is prerequisite to minimize the number of optical components and establish evaluation and assembly method of micro optical pickup system as well as mass production method of micro optical component. To minimize optical elements of optical pickup, there have been many researches to use P-HOE(Polarized Holographic Optical Element) due to its extremely small size and versatile function. However, P-HOE is handled and assembled very accurately in SFFOP. In this paper, static error signal detection method is developed for an alignment of P-HOE in SFFOP. Using developed static error signal detection method, P-HOE can be aligned very accurately with real time result of static error signals of pickup such as FES(focusing error signal) and TES(Tracking Error Signal). The developed static error signal detection method is verified by the evaluation of commercialized DVD Pickup. And finally. developed static error signal detection method is applied for the assembly of P-HOE in SFFOP system satisfies specification of BD(Blu-ray Disk).