• Journal of the Optical Society of Korea
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• v.16 no.4
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• pp.343-348
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• 2012

This paper described an off-axis five-mirror-anastigmatic telescope. It is composed of three aspheric surfaces and one spherical surface while the third mirror and fifth mirror have the same parameters at the same place. This configuration is useful for having wide field of view. The strip full field of view for the near infrared telescope is $20^{\circ}{\times}0.2^{\circ}$. The entrance pupil is located in front of the first mirror. There is an intermediate image between the second mirror and the third mirror. The entrance pupil diameter is 100 mm and the effective focal length is 250 mm. The spectral range is $0.85-1.75{\mu}m$. The pixel pitch is $15{\mu}m$. The image quality is near the diffraction limit. Some methods were used to restrain the stray light such as a field stop near the intermediate image, the baffle, the narrow-band pass filter and a stop in front of the focal plane.

• Journal of ILASS-Korea
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• v.26 no.4
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• pp.212-218
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• 2021

The present study aims to develop the Surface Plasmon Resonance (SPR) imaging system facilitating the real-time measurement of the concentration of evaporating binary mixture droplet (BMD). We introduce the theoretical background of the SPR imaging technique and its methodology for concentration measurement. The SPR imaging system established in the present study consists of a LED light source, a polarizer, a lens, and a band pass filter for the collimated light of a 589 nm wavelength, and a CCD camera. Based on the Fresnel multiple-layer reflection theory, SPR imaging can capture the change of refractive index of evaporating BMD. For example, the present study exhibits the visualization process of ethylene glycol (EG)-water (W) BMD and measures real-time concentration change. Since the water component is more volatile than the ethylene glycol component, the refractive index of EG-W BMD varies with its mixture composition during BMD evaporation. We successfully measured the ethylene glycol concentration within the evaporating BMD by using SPR imaging.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.803-806
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• 2010

본 논문에서는 스크린을 터치를 하지 않고 또한 스크린의 영역의 크기에 상관없이 제스처를 이용하여 인터랙션이 가능한 제스쳐 인식 모듈을 이용한 대규모 멀티 인터랙티브 디스플레이 시스템을 제안한다. IR laser를 이용하여 인터랙션 영역을 생성하고 band pass filter를 장착한 적외선 카메라를 이용하여 인터랙션 영역 안의 영상을 획득한다. 획득되어진 영상은 제안하는 영상처리모듈을 이용하여 이진화->블랍-라벨링 과정을 거쳐 잡음을 제거한 후 인터랙션 영역 안에서 이루어지는 인터랙션 좌표를 획득한 후 Packet으로 저장한다. 저장 된 Packet은 네트워크 통신 시스템을 이용하여 Server로 보내어지고 Server에서는 메타포분석모듈을 이용하여 분석하여 결과를 메타포이벤트로 저장한 후 콘텐츠에 보낸다. 콘텐츠에서는 받은 메타포이벤트에 따라서 콘텐츠 결과를 보여 줌으로써 스크린을 터치 하지 않아도 터치 인터랙션이 가능하며 스크린 영역에 제한 없이 많은 사용자가 동시에 사용이 가능한 시스템 사용이 가능하도록 한다. 본 시스템은 향후 보다 다양한 인터랙션과 시스템 크기의 확장으로 보다 많은 사용자가 동시에 사용가능하며 다양한 인터랙션을 사용할 수 있는 인식 디바이스로써 활용이 가능하다.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11c
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• pp.551-559
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• 2000

An integrated on-line inspection system was constructed with seven cameras, half mirrors to split images, 720 nm and 970 nm band pass filters, illumination chamber having several tungsten-halogen lamps, one main computer, one color frame grabber, two 4-channel multiplexors, and flat plate conveyer, etc., so that a total of seven images, that is, one color image from the top side of an apple and two B/W images from each side (top, right and left) could be captured and displayed on a computer monitor through the multiplexor. One of the two B/W images captured from each side is 720nm filter image and the other is 970nm. With this system an on-line grading software was developed to evaluate appearance quality. On-line test results to the Fuji apples that were manually fed on the conveyer showed that grading accuracies of the color, defective and shape were 95.3%, 86% and 91%, respectively. Grading time was 0.35 sec per apple on an average. Therefore, this on-line grading system could be used for inspection of the final products produced from an apple sorting system.

• International Journal of Korean Welding Society
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• v.1 no.2
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• pp.23-29
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• 2001

In this study, a preview-sensing visual sensor system is constructed far weld seam tracking in GMA welding. The visual sensor system consists of a CCD camera, a diode laser system with a cylindrical lens, and a band-pass-filter to overcome the degrading of image due to spatters and/or arc light. Among the image processing methods, Hough transform method is compared with the central difference method from a viewpoint of the capability for extracting the accurate feature position. As a result, it was revealed that Hough transform method can more accurately extract the feature positions and it can be applied to real time weld seam tracking. Image processing which includes Hough transform method is carried out to extract straight lines that express laser stripe. After extracting the lines, weld joint position and edge points are determined by intersecting the lines. Even though the image includes a spatter trace on it, it is possible to recognize the position of weld joint. Weld seam tracking was precisely implemented with adopting Hough transform method, and it is possible to track the weld seam in the case of offset angle is in the region of $\pm$ $15^{\circ}$.

• ETRI Journal
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• v.45 no.2
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• pp.193-202
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• 2023

We demonstrate the transmission of uncompressed 4K videos over the photonics-based terahertz (THz) wireless link using a directly modulated distributed feedback laser diode (DFB-LD). For optical heterodyne mixing and data modulation, a DFB-LD was employed and directly modulated with a 5.94-Gb/s non-return-to-zero signal, which is related to a 6G-serial digital interface standard to support ultra-high-definition video resolution. We derived the optimal frequency of the THz carrier by varying the wavelength difference between DFB-LD output and Tunable LD output in the THz signal transmitter to obtain the best transmission performances of the uncompressed 4K video signals. Furthermore, we exploited the negative laser-to-filter detuning for the adiabatic chirp management of the DFB-LD by the intentional discrepancy between the center wavelength of the optical band-pass filter and the output wavelength of the DFB-LD. With the help of the abovementioned methods, we successfully transmitted uncompressed 4K video signals over the 2.3-m wireless transmission distance without black frames induced by time synchronization error.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.375-382
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• 2010

This paper presents the extraction of natural frequencies and mode shapes of a cable-stayed bridge using data acquired from GNSS. The response signals of 6 GNSS measuring points installed at the Seohae cable-stayed bridge are used for analysis of dynamic characteristics. Using normalization process and a third order Butterworth filter for the measured signals, the related pass band's signals have been isolated. Then, the acceleration data by double differentiation for these signals are obtained. Total five natural frequencies have been extracted by the fast Fourier transform and compared to the results of different studies. For the acceleration obtained from GNSS signals, the mode shapes of the bridge have been successfully extracted by TDD technique.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.4
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• pp.7-11
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• 2006

In this paper, it is reported that film-bulk-acoustic resonator with high c-axis oriented AIN film on $Mo/SiO_2/Si(100)$ using metal-organic-chemical-vapor deposition was fabricated. The resonant frequency and anti-resonant frequency of the fabricated resonator were observed with 3.189[GHz] and 3.224[GHz], respectively. The quality factor and the effective electromechanical coupling coefficient(${k_{eff}}^2$) were measured with 24.7 and 2.65[%], respectively. The conditions of AIN deposition were substrate temperature of $950[^{\circ}C]$, pressure of 20Torr, and V-III ratio of 25000. A high c-axis oriented AIN film with $4{\times}10^{-5}[\Omega{cm}]$ resistivity of Mo bottom electrode and $4[^{\circ}]$ of AIN(0002) full-width at half-maximum(FWHM) on $Mo/SiO_2/Si(100)$ was grown successfully. The FWHM value of deposited AIN film is useful for the RF band pass filter specification for GHz-band wireless local area network.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.4
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• pp.201-215
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• 1999

Field measurements were made for long- and short-period waves and current velocities at the harbor mouth using pressure-type wave gauges and a current meter, respectively, at the Gamcheon Harbor which has a rectangular shape with a narrow entrance. The measured pressure data were subjected to spectral analyses after removing tidal effects by applying trend removal and high-pass filtering. For the band averaging of the raw spectra, in order to obtain good resolution over the entire frequency, instead of a constant band width, variable band widths were used, which gradually increase as marching from the lowest frequency towards higher frequencies. The Helmholtz resonance mode at the Gamcheon Harbor shows the relative amplification ratio of 9.2 at the wave period of 31.7 minutes, which is quite large compared with those at the harbors located on the east coast of Korea. The second and the third resonance period was 10.3 and 5.4 minute, respectively. On the other hand, the analysis of every 24 hours data shows that during storms the spectral densities are very large compared to those during calm seas and also the second and third resonances are predominant.

• The Journal of the Acoustical Society of Korea
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• v.18 no.5
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• pp.12-20
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• 1999

In this paper, we compared speaker verification performance of the speech data collected in clean environment and in channel environment. For the improvement of the performance of speaker verification gathered in channel, we have studied on the efficient feature parameters in channel environment and on the preprocessing. Speech DB for experiment is consisted of Korean doublet of numbers, considering the text-prompted system. Speech features including LPCC(Linear Predictive Cepstral Coefficient), MFCC(Mel Frequency Cepstral Coefficient), PLP(Perceptually Linear Prediction), LSP(Line Spectrum Pair) are analyzed. Also, the preprocessing of filtering to remove channel noise is studied. To remove or compensate for the channel effect from the extracted features, cepstral weighting, CMS(Cepstral Mean Subtraction), RASTA(RelAtive SpecTrAl) are applied. Also by presenting the speech recognition performance on each features and the processing, we compared speech recognition performance and speaker verification performance. For the evaluation of the applied speech features and processing methods, HTK(HMM Tool Kit) 2.0 is used. Giving different threshold according to male or female speaker, we compare EER(Equal Error Rate) on the clean speech data and channel data. Our simulation results show that, removing low band and high band channel noise by applying band pass filter(150～3800Hz) in preprocessing procedure, and extracting MFCC from the filtered speech, the best speaker verification performance was achieved from the view point of EER measurement.