• Current Optics and Photonics
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• v.7 no.1
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• pp.1-14
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• 2023

Wavefront-coding imaging can achieve high-quality imaging along with a wide range of defocus. In this paper, the anti-laser detection and damage performance of wavefront-coding imaging systems using different asymmetric phase masks are studied, through modeling and simulation. Based on FresnelKirchhoff diffraction theory, the laser-propagation model of the wavefront-coding imaging system is established. The model uses defocus distance rather than wave aberration to characterize the degree of defocus of an imaging system. Then, based on a given defocus range, an optimization method based on Fisher information is used to determine the optimal phase-mask parameters. Finally, the anti-laser detection and damage performance of asymmetric phase masks at different defocus distances and propagation distances are simulated and analyzed. When studying the influence of defocus distance, compared to conventional imaging, the maximum single-pixel receiving power and echo-detection receiving power of asymmetric phase masks are reduced by about one and two orders of magnitude respectively. When exploring the influence of propagation distance, the maximum single-pixel receiving power of asymmetric phase masks decreases by about one order of magnitude and remains stable, and the echodetection receiving power gradually decreases with increasing propagation distance, until it approaches zero.

• 한국연소학회:학술대회논문집
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• 1997.06a
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• pp.13-21
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• 1997

Excitations of eight pumping transitions for nitric oxide fluorescence imaging are analyzed under equivalent experimental conditions to determine the detection. Frequency mixed dye laser pumping, 1st anti-Stokes $H_2$ Raman of KrF excimer laser pumping and ArF excimer laser pumping show good sensitivities.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.9
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• pp.830-837
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• 2015

Space debris has been a major issue recently for the space-active nations because its growing population is expected to increase the collision risk with operational satellites. Radar and electro-optical system has been used for space debris surveillance, which may cause unnecessary anti-collision manoeuvers due to their low tracking accuracy. So an additional tracking system is required to improve the predicted orbit accuracy and then to jude the anti-collision maneouvers more efficiently. The laser tracking system has been considered as an alternative to decrease these unnecessary manoeuvers. Korea Astronomy and Space Science Institute has been developing a space object laser tracking system which is capable of laser tracking for satellites with retro-reflectors and for space debris using high power laser, and satellite imaging using adaptive optics. In this study, the tracking capability is analyzed for space debris using high power laser based on link budget, false alarm probability and signal detection probability.

• Applied Science and Convergence Technology
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• v.25 no.3
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• pp.61-65
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• 2016

Here, the rapid detection of Salmonella typhimurium by a portable surface plasmon resonance (SPR) biosensor in which the beam from a diode laser is modulated by a rotating mirror is reported. Using this system, immunoassay based on lipopolysaccharides (LPS)-specific monoclonal anti-Salmonella antibody was performed. For the purpose of orientation-controlled immobilization of antibodies on the SPR chip surface, the cysteine-mediated immobilization method, which is based on interaction between a gold surface and a thiol group (-SH) of cysteine, was adopted. As a result, using the portable SPR-based immunoassay, we detected S. typhimurium in the range from 10^7 CFU/mL to 10^9 CFU/mL within 1 hour. The results indicate that the portable SPR system could be potentially applied for general laboratory detection as well as on-site monitoring of foodborne, clinical, and environmental agents of interest.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1746-1749
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• 1997

A distributed optical fiber temperature sensor can continually monitor the measurand at every point along of its fiber length. It is based on OTDR technics which used extreamlly weak backward scattered light called Raman scattering. When the Pulsed high intensity laser light injected into the optical fiber there are several kind of backscattered light such as Rayleigh, Stokes, and anti-Stokes, etc. caused by impurities molecular vibrations. The temperature distribution is derived form the intensity ratio Raman scatted light-Stokes versus anti-Stokes-and the time function between light injection and signal detection. It is shown that the priniciple of distributed sensing, the system desing, and the result of experiments.

• Korean Journal of Optics and Photonics
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• v.16 no.6
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• pp.553-559
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• 2005

Pulsed terahertz (THz) radiation was generated by optical rectification and detected by a fee space electro-optic sampling (FS-EOS) method. We used ZnTe (110) crystals for both generation and detection. By coating dielectric anti-reflection film on the ZnTe crystal surface, we can reduce the reflectance of a pump laser beam from $30\%$ to $2\%$, and the terahertz pulse amplitude increased $27\%$ compared with an uncoated crystal. A wider bandwidth of THz radiation was obtained by using a thinner crystal but the signal intensity was decreased in this case. And variations of THz radiation by changing orientation of the ZnTe crystal with respect to the pump (or probe) laser polarization, and by changing the power of the pump laser have also been investigated and discussed.

• Structural Monitoring and Maintenance
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• v.2 no.3
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• pp.213-236
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• 2015

The paper presents an investigation into the mode conversion and scattering characteristics of guided waves at delaminations in laminated composite beams. A three-dimensional (3D) finite element (FE) model, which is experimentally verified using data measured by 3D scanning laser vibrometer, is used in the investigation. The study consists of two parts. The first part investigates the excitability of the fundamental anti-symmetric mode ($A_0$) of guided wave in laminated composite beams. It is found that there are some unique phenomena, which do not exist for guided waves in plate structures, make the analysis become more complicated. The phenomena are observed in numerical study using 3D FE simulations. In the second part, several delaminated composite beams are studied numerically to investigate the mode conversion and scattering characteristics of the $A_0$ guided wave at delaminations. Different sizes, locations and through-thickness locations of the delaminations are investigated in detail. The mode conversion and scattering phenomena of guided waves at the delaminations are studied by calculating reflection and transmission coefficients. The results show that the sizes, locations and through-thickness locations of the delaminations have significant effects on the scattering characteristics of guided waves at the delaminations. The results of this research would provide better understanding of guided waves propagation and scattering at the delaminations in the laminated composite beams, and improve the performance of guided wave damage detection methods.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1100-1109
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• 2006

In this study, two different technologies which can measure temperature simultaneously at many points are introduced. One is to use a thermal sensor cable that is comprised of addressable thermal sensors connected in parallel within a single cable. The other is to use an optic fiber with Distributed Temperature Sensing (DTS) system. The difference between two technologies can be summarized as follows. A thermal sensor cable has a concept of 'point sensing' that can measure temperature at accurate position of a thermal sensor. So the accuracy and resolution of temperature measurement are up to the ability of the thermal sensor. Whereas optic fiber sensor has a concept of 'distributed sensing' because temperature is measured by ratio of Stokes and anti-Stokes component intensities of Raman backscatter that is generated when laser pulse travels along an optic fiber. It's resolution is determined by measuring distance, measuring time and spatial resolution. The purpose of this study is that application targets of two temperature measurement techniques are checked in technical and economical phases by examining the strength and weakness of them. Considering the functions and characteristics of two techniques, the thermal sensor cable will be suitable to apply to the assessment of groundwater flow, geothermal distribution and grouting efficiency within 300m distance. It is expected that the optic fiber sensor can be widely utilized at various fields (for example: pipe line inspection, tunnel fire detection, power line monitoring etc.) which need an information of temperature distribution over relatively long distance.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.1
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• pp.51-60
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• 2014

In this study, ICT medical service provider's level of knowledge fire fighting safety and methods on coping with fires in the regions of Gwangju and Jeonam Province of Korea were investigated to determine the elements affecting such levels and provide basic information on the manuals for educating how to cope with the fire fighting safety in medical facilities. The data were analyzed using SPSS Win 14.0. The scores of level of knowledge fire fighting safety of ICT medical service provider's were 7.06(10 point scale), and the scores of level of recognizing how to cope with fire fighting safety were 6.61(11 point scale). level of recognizing how to cope with fire fighting safety were significantly different according to gender(t=4.12, p<.001), age(${\chi}^2$=17.24, p<.001), length of career(${\chi}^2$=22.76, p<.001), experience with fire fighting safety education(t=6.10, p<.001), level of subjective knowledge on fire fighting safety(${\chi}^2$=53.83, p<.001). In order to enhance the level of understanding of fire fighting safety and methods of coping by the ICT medical service providers it is found that: self-directed learning through avoiding the education just conveying knowledge by lecture tailored learning for individuals fire fighting education focused on experiencing actual work by developing various contents emphasizing cooperative learning deploying patients by classification systems using simulations and a study on the implementation of digital anti-fire monitoring system with multipoint communication protocol, a design and development of the smoke detection system using infra-red laser for fire detection in the wide space, video based fire detection algorithm using gaussian mixture mode developing an education manual for coping with fire fighting safety through multi learning approach at the medical facilities are required.