• Korean Journal of Optics and Photonics
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• v.10 no.3
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• pp.201-207
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• 1999

The fiber-optical confocal scanning interference microscope with a simple configuration was constructed with a 4-port fiber-optic coupler, and the new method based on the phase shifting method was proposed for surface profiling by the system. In the method, the height of a specimen was determined from the phase of confocal beam. It was verified experimentally that the method was applicable to even the confocal interference microscope with a long-wavelength source and a low NA objective, and that the scanning time could be drastically reduced compared with the conventional method. Finally, it was found that our method is less sensitive to the variation of surface reflectivity than the conventional method.

• Journal of the Optical Society of Korea
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• v.17 no.1
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• pp.73-80
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• 2013

In the process of lithography using ultra violet light sources for semiconductor devices, most of defects are made by sub-micrometer pollutants generated at photochemical reactions. We proposed and developed a novel vibration-insensitive on-axis interferometer with a sub-micrometer lateral resolution by using the interference between two beams: one scattered from defects and the other reflected from a reference area without defects. The proposed system was successfully demonstrated to detect a small Al defect of 0.5 ${\mu}m$ diameter within the inspection time of less than 30 minutes over the area of the photo-mask which is 6 inch by 6 inch square.

• ETRI Journal
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• v.44 no.6
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• pp.966-976
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• 2022

Optical wireless communication, or free space optics, is a promising solution for backhauls in sixth-generation mobile systems. However, the susceptibility of optical links to weather conditions has led to FSO links being furnished with radio frequency (RF) backups. These Hybrid FSO/RF systems provide enhanced link availability but lead to RF resource wastage. Cognitive radio technology, in contrast, is well known for its optimal use of RF resources and may be combined with an FSO link to create a Cognitive Hybrid FSO/RF system. This work uses such a system to analyze a configuration for a mobile backhaul in sixth-generation mobile systems. This configuration can seamlessly coexist with established large scale RF cellular networks. The performance of this configuration is analyzed with respect to outage probability and average bit error by considering the impact of optical channel turbulence, misalignment loss, RF interference, and noise. Mathematical closed-form expressions are verified by simulations.

• Current Optics and Photonics
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• v.8 no.1
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• pp.1-15
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• 2024

This paper presents a brief introduction to self-interference incoherent digital holography (SIDH). Holography conducted under incoherent light conditions has various advantages over digital holography performed with a conventional coherent light source. We categorize the methods for SIDH, which divides the incident light into two waves and modulates them differently. We also explore various optical concepts and techniques for the implementation and advancement of SIDH. This review presents the system design, performance analysis, and improvement of SIDH, as well as recent applications of SIDH, including optical sectioning and deep-learning-based SIDH.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.34-35
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• 2001

The wavelength demultiplexer is an essential component in optical transmission systems using wavelength-division multiplexing(WDM), which can increase the number of channels and information capacity of optical fibers. For optical telecommunication, much attention has been given to demultiplexing two wavelengths in the 1.3${\mu}{\textrm}{m}$ of low dispersion band and 1.55${\mu}{\textrm}{m}$ of low loss window. Various integrated-optical devices have been proposed to perform this function, including conventional directional couplers, asymmetric Y-branching devices, asymmetric Mach-Zehnder interferometers and two-mode interference devices. (omitted)

• Transactions on Electrical and Electronic Materials
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• v.9 no.2
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• pp.84-88
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• 2008

In this paper, we analyze the errors associated with electric field interference for fiber-optic voltage sensors working in a three-phase electric system. For many practical conductor arrangements, the electric filed interference may cause errors unacceptable for the accuracy requirements of the sensors. We devised a real time compensation method for the interference by introducing geometric and weight factors. We realized the method using simple electronic circuits and obtained the real time compensated outputs with errors of 1 %.

• Proceedings of the Optical Society of Korea Conference
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• 2008.07a
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• pp.189-190
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• 2008

• Korean Journal of Optics and Photonics
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• v.16 no.3
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• pp.177-181
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• 2005

Although there are many ways to measure the diameter of a cylindrical object, in this study, the diameter of a cylindrical objects were measured by the geometric optical method and interference-diffraction method which are two kinds of tipical non-contact methods. In geometric optical method, the curved laser beam is formed on the cylindrical surface by spreading the inclined laser beam using the cylindrical lens. The curve is captured by CCD camera and the diameter is calculated by geometry. And the interference and diffraction patterns of investigated cylindrical objects are analyzed in interference-diffraction method. In this study, the cylindrical objects, whose diameters are $0.05\;mm\;\~\;100.50\;mm$ were measured by the geometric optical method and interference-diffraction method. The results show that in each method, the relative errors of the measurement are within $2\%$ and $1\%$, respectively and these non-contact methods can be applied in the quick measurement of many objects.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.480-483
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• 2018

In this paper, we study the interference canceling and image sensing processing technology of multiple light sources for high speed transmission in CMOS sensor based visible light communication system. To improve transmission capacity in optical camera communications via image sensors, different data must be transmitted simultaneously from each LED. However, multiple LED light source environments for high-speed transmission can cause interference between adjacent LEDs. In this case, since the visible light communication system generally uses intensity modulation, when a plurality of LEDs transmit data at the same time, it is difficult to accurately detect the respective LEDs due to the light scattering interference of the adjacent LEDs. In order to solve this problem, the ON / OFF state of many LEDs of the light source is accurately recognized by using a dual CMOS sensor, and the spectral estimation technique and the pixel image signal processing technique of each LED are proposed. This technique can accurately recognize multiple LED pixels and improve the total average bit error rate and throughput of a MISO-VLC system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.9
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• pp.746-751
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• 1998

There are several methods capable of determining he magnitude of optical anisotropy, such as spectrometric ellipsometry and polarized light reflectometry. The interference method is estimated to be no influence of surface scattering. The magnitude of anisotropy is a-As/sub 40/Ge/sub 10/S/sub 35/Se/sub 15/ thin film is analyzed by the reflection interference analysis method based on the difference depending on a phase of s- and p-polarized light. The theoretically analyzed value is compared with the result obtained by the measured technique.