• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.614-618
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• 2015

This paper described an off-axis head-mounted display system. It is composed of a 7-piece coaxial relay lens group and a freeform surface combiner. This configuration has a simple structure and a wide field of view (FOV). In this design, a freeform surface is chosen as the combiner, to simplify the structure and attain good image quality. We generated this freeform surface by considering both coordinates and normals of discrete data points. Moreover, we realize a coaxial structure in the relay lens group, which is compact and benefits from a loose tolerance requirement. The HMD system we finally realized has a 40° × 30° FOV and 15-mm exit pupil diameter.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1364-1366
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• 1997

To operate electric power systems economically and stably, and to supply the electric power of good quality, it is necessary that the measured information (current, voltage, and so on) be detected and transmutted with high reliability and high effieincy. For the reason, the optical magnetic field sensor is possible to rapidly detect to over current and recover when electric power line have fault. In addition, the optical sensor have no electro magnetic distortion and no electric insulation. In this study, we designed OCR(Over Current Relay) using optical sensor. The designed OCR using optical sensor was measured characteristic and compared contentional OCR. This system have highest optical advantages and reliability.

• Journal of Satellite, Information and Communications
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• v.7 no.3
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• pp.63-68
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• 2012

The VLC (visible light communication) system is communication technology using visible rays (RGB) that come out in LED device. It is energy curtailment effect and possible in ubiquitous network service applications. Also, VLC system has the above advantage about that the communication throughout the whole room is enabled by high power lighting and lighting equipment with white colored LED which are easy to install and have good outward appearance. However, the signal detection performance for the receiver near the network of transmitter boundary is severely degraded and the transmission efficiency decreased due to the influence of the interference signal from the adjacent networks. In this paper, we propose an interference mitigation method with optical relay and optical beamforming scheme in VLC systems, and evaluate the reception performance. For the system BER, the proposed system demonstrates the performance enhancement compared to the not using the optical relay and optical beamforming scheme, and SNR performance gain and higher channel capacity is achieved.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.4
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• pp.441-447
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• 2012

Purpose: This paper is about development and design of the 1x optical path relay adapter for the beam splitting prism by us the day & night scope. Methods: To product the day & night scope by using the beam splitting prism and the commercial zoom optical system with the C-mount lens barrel structure, the optical path relay adapter, which doesn't change the image size of the zoom optical system and can stretch the position of the image-forming surface, is needed. We could design the 1x optical path relay adapter by using the CodeV program in which the Lens Module mode is offered. Results: We could design the optical path relay adapter used in the day&night scope with the beam splitting prism, of which characteristics have the EFL of -56.0 mm, the magnification of +1.0x, the distance from the 1st lens surface to the last lens surface of about 20.4 mm. The resolution of this system is characterized by 30 lp/mm at 40% MTF. This is enough to accommodate the designed optical path relay adapter can overcome the resolution of the 3rd generation of image intesifier tubes. Conclusions: By designing and applying the optical path relay adapter of which optical characteristics have the EFL of -56.0 mm, the magnification of +1.0x, the distance from the 1st lens surface to the last lens surface of about 20.4 mm, and the resolution of 30 lp/mm at 40% MTF, we could develop the new type day&night scope consisting of the beam splitting, the commercial zoom optical system with the C-mount lens barrel structure, and the 3rd generation of image intesifier tubes.

• Journal of Astronomy and Space Sciences
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• v.37 no.1
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• pp.11-18
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• 2020

Satellite optical communication has gained significant attention owing to its many quality features (e.g., a larger bandwidth, license free spectrum, higher data rate, and better security) compared to satellite microwave communication. Various experiments have been performed during many space missions to demonstrate and characterize inter-satellite links, downlinks, and uplinks. Korea has also planned to establish an experimental communication system using a geostationary earth orbit (GEO) satellite and the Geochang station as an optical ground station for low Earth orbit (LEO)-to-ground optical relay links. In this study, the performance of inter-satellite communication links and downlinks was investigated for the new Korean experimental communication system in terms of link margin, bit error rate (BER), and channel capacity. In particular, the performance of the inter-satellite links was analyzed based on the receiving apertures and the transmitting power, while that of the downlink was analyzed in terms of atmospheric turbulence conditions and transmitting power. Finally, we discussed two system parameters of receiving aperture and transmitting power to meet the three criteria of link margin, BER, and channel capacity.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1846-1849
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• 1998

An optical magnetic filed sensor, YIG (Yittrium Iron Garnet), response rapidly, to the power-line currents to be measured. In response to Faraday effect, it shows wide-and-linear measurable range. This paper reports the development and implementation of an OOCR (Optoelectric OverCurrent Relay) using this sensor. This relay is free from environmental electro-magnetic noises and has excellent insulation characteristics inherently. By using this OOCR, we can reduce insulation cost of protective relaying systems and its maintenance cost, and can achieve high reliability of the system.

• Current Optics and Photonics
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• v.2 no.3
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• pp.280-285
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• 2018

A new method to design a see-through off-axis head-mounted-display (OA-HMD) optical system with an ellipsoidal surface is proposed, in which a tilted ellipsoidal surface is used as the combiner, which yields the benefits of easier fabrication and testing compared to a freeform surface. Moreover, we realize a coaxial structure in the relay lens group, which is simple and has looser tolerance requirements, thus making assembly easier. The OA-HMD optical system we realize has a simple structure and consists of a combiner and 7 pieces of coaxial relay lenses. It has a $48^{\circ}{\times}36^{\circ}$ field of view (FOV) and 12-mm exit pupil diameter.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.140-146
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• 2018

Recently, VLC(Visible Light Communication) fusing with LED(Light Emitting Diode) used in indoor lighting and wireless communication technology has attracted attention. However, the VLC can communicate only within the coverage to measure the optical signal and the communication disconnection phenomenon is occur in the NLoS(Non-Line-of-Sight) area. In this paper, we propose VLC relay module to extend the coverage of VLC and improve the communication disconnection phenomenon in NLoS area. The proposed VLC relay module transmits the packet received from the transmitter to the VLC relay module and receiver. The experiment was carried out by installing one VLC transmitter and three VLC relay modules, communication coverage expansion and the improvement of communication disconnection phenomenon in the NLoS were confirmed by the increase of the VLC relay module. Also, we confirmed that the optical signal measurement performance is improved 2.4 times by using the dual sampling method.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.3
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• pp.284-290
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• 2000

The measurement of electric current using optical techniques provides a number of important practical advantages including effective isolation from high line potentials and freedom from the saturation effects observed in conventional current transformers. In this work the optical current sensor which uses thin YIG(Yittrium Ion Garnet) film as a Faraday element has been developed. We have characterized this optical current sensor and implemented it to the OOCR(Opto-electronic OverCurrent Realy) Performance of the OOCR shows the possibility of replacing the present overcurrent relays with OOCR.

• Journal of the Optical Society of Korea
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• v.12 no.4
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• pp.262-268
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• 2008

A compact imaging spectrometer (COMIS) for use in the STSAT3 microsatellite is currently under development. It is scheduled to be launched into a low Sun-synchronous Earth orbit (${\sim}700km$) by the end of 2010. COMIS was inspired by the success of CHRIS, which is a small hyperspectral imager developed for the ESA microsatellite PROBA. COMIS is designed to achieve nearly equivalent imaging capabilities of CHRIS in a smaller (65 mm diameter and 4.3 kg mass) and mechanically superior (in terms of alignment and robustness) package. Its main operational goal will be the imaging of Earth's surface and atmosphere with ground sampling distances of ${\sim}30m$ at the $18{\sim}62$ spectral bands ($4.0{\sim}1.05{\mu}m$). This imaging will be used for environmental monitoring, such as the in-land water quality monitoring of Paldang Lake, which is located next to Seoul, South Korea. The optics of COMIS consists of two parts: imaging telescope and dispersing relay optics. The imaging telescope, which operates at an f-ratio of 4.6, forms an image (of Earth's surface or atmosphere) onto an intermediate image plane. The dispersion relay optics disperses the image and relay it onto a CCD plane. All COMIS lenses and mirrors are spherical and are made from used silica exclusively. In addition, the optics is designed such that the optical axis of the dispersed image is parallel to the optical axis of the telescope. Previous efforts focused on manufacturing ease, alignment, assembly, testing, and improved robustness in space environments.