• Title/Summary/Keyword: SM.030.

Search Result 9, Processing Time 0.018 seconds

Modified digital serrodyne processor for FOG (FOG용 개량형 디지털 serrodyne 신호처리)

  • 예윤해;문영백
    • Korean Journal of Optics and Photonics
    • /
    • v.12 no.1
    • /
    • pp.10-16
    • /
    • 2001
  • A new digital serrodyne (DS) signal processor for the close-loop fiber optic gyroscope was designed and implemented. It is based on a new algorithm that can solve the remaining problems of the existing digital serrodyne processing by utilizing a new modulation wavefonn. The algorithm was implemented in an FPGA and tested. Theoretical limit and experimental value of the random walk were measured to be 2.6 and 3.3 deg/hr/$\sqrt{Hz}$, respectively. And drift of the processor is smaller than that by Shupe's effect.effect.

  • PDF

Index of refraction measurement using the reflection characteristics of terahertz electromagnetic pulses (테라헤르츠 전자기 펄스의 반사특성을 이용한 굴절률 측정)

  • 전태인
    • Korean Journal of Optics and Photonics
    • /
    • v.12 no.1
    • /
    • pp.1-4
    • /
    • 2001
  • Via terahertz (THz) reflection radar, the characterizations of reflected THz electromagnetic pulses are reported. Quasi-optical techniques are used to efficiently reflect pulses of THz electromagnetic radiation from an aluminum mirror and several conducting and nonconducting materials. An incident THz pulse is reflected up to 9 times to know the magnitude change of a reflected pulse from the aluminum mirror. Using this method, aluminum board, undoped silicon, quartz, and LDPE samples' reflection coefficient and index of refraction can be measured. These results suggest a possible application of transient THz reflection spectroscopy without surface contact.ontact.

  • PDF

Measurements of optical wavelength using an optical fiber retarder (광섬유 위상지연기를 이용한 광파장 측정)

  • 이현우;김용평
    • Korean Journal of Optics and Photonics
    • /
    • v.12 no.1
    • /
    • pp.5-9
    • /
    • 2001
  • A wavemeter was realized using the phenomena that the phase lag between principal polarization states in an optical retarder is a function of wavelength. The change in the polarization state of the optical beam as it passes through the optical retarder is dependent on wavelength. The wavelength of the optical beam is determined by comparing the power difference between principal polarization states. A prototype wavemeter was successfully implemented using a polarization maintaining fiber with birefringence $3\times10^{-4}$ and length 100 mm as the optical retarder. The measurement resolution was 0.08 nm over a wavelength region of 1554.38 nm-1557.l9 nm, which agreed well with theoretically calculated results. In addition, the dependence of operating characteristics on temperature was analyzed theoretically and experimentally.mentally.

  • PDF

Measurements of optical wavelength using WDM coupler (WDM 결합기를 이용한 광파장 측정)

  • 이현우;김용평
    • Korean Journal of Optics and Photonics
    • /
    • v.12 no.5
    • /
    • pp.389-393
    • /
    • 2001
  • A wavemeter is realized using the fact that the coupling coefficient of a WDM coupler is a function of wavelength. Prototype devices with 1500 nm/1600 nm and 1510 nm/1550 nm WDM couplers are successfully fabricated and tested in the laboratory. The measurement resolutions are $\pm$0.27 nm over a wavelength range of 1515 nm~1576 nm for the device with 1500 nm/1600 nm WDM coupler and $\pm$0.103 nm over a wavelength range of 1520 nm~1543 nm for th4e device with 1510 nm/1550 nm WDM coupler. The dependence of operating characteristics on the input signal power is insignificant. However the temperature dependence is ~0.06 nm/$^{\circ}C$.

  • PDF

Characteristics of Photodetectors for spectral radiance measurements (분광복사휘도 측정용 광검출기의 특성 평가)

  • 서정철;박승남;김봉학
    • Korean Journal of Optics and Photonics
    • /
    • v.12 no.5
    • /
    • pp.376-381
    • /
    • 2001
  • We have fabricated a spectroadiometric system to measure spectral radiance of optical sources and evaluated its characteristics such as spectral responsivity, nonlinearity, and so on. The measurement system with PMT, Si, InGaAs, and IR-enhanced InGaAs detectors has shown a good linearity and a wide spectral responsivity of 250∼2500 nm. This spectroradiometric system will be used as the primary national standard system of spectral radiance measurements.

  • PDF

Moir'e fringes generated by the superposition of elongated circular grating and Talbot image and their applications (Elongated Circular Grating의 Talbot 결상을 이용한 무아레 무늬 발생과 응용)

  • Lee, Sang-Il;Jo, jae-Heung;Chang, Soo;Rim, Cheon-Seog
    • Korean Journal of Optics and Photonics
    • /
    • v.12 no.1
    • /
    • pp.25-31
    • /
    • 2001
  • The Talbot effect of an elongated circular (EC) grating composed of a line grating and two semicircular gratings with well matched pitches is experimentally presented. As the relative positions between the fixed EC grating and the moving Talbot image of another EC grating or a self Talbot image are one-dimensionally deformed, we can visually observe moire fringes generated by their superposition. Two examples of their applications, that is, the measurement of the wedged angle of a wedged prism and of the fine rotational angle of a mirror are described.cribed.

  • PDF

Construction of laser induced grating spectrometer and measurement of thermal grating in $C_3H_8$ flame (레이저 유도 격자 분광장치 제작 및 $C_3H_8$화염에서 열 격자 측정)

  • 박철웅;한재원;이중재;이영우;고동섭
    • Korean Journal of Optics and Photonics
    • /
    • v.12 no.6
    • /
    • pp.446-451
    • /
    • 2001
  • We made a laser induced grating spectrometer(LIGS) and measured the thermal grating signal generated in a $C_3$ $H_{8}$ flame. The thermal grating was formed in the C7Ha flame with two second-harmonic Nd:YAG pulse laser beams, and an LIGS signal was generated by Bragg scattering of a probe laser beam A $r^+.laser(488 nm). We found the modulation period of the signal depends linearly on the spacing of the grating set in the flame. We determined flame temperature by fitting the modulated signal and soot concentration with signal strength. Using this technique, we also obtained temperature profile and soot-particle distribution in a $C_3$ $H_{8}$ flame .e .

  • PDF

The characteristics of terahertz electromagnetic pulses by electrical and optical parameters. (전기적 광학적 변화가 테라헤르츠 전자기 펄스의 모양에 미치는 영향)

  • 전태인
    • Korean Journal of Optics and Photonics
    • /
    • v.12 no.6
    • /
    • pp.503-506
    • /
    • 2001
  • When DC voltages from 5 V up to 90 V are applied to a transmitter chip excited by an ultrafast lacer beam, the terahertz electromagnetic pulses and their spectra are changed. The spectrum shifts to the high frequency range when the high DC voltage is applied to the chip. At that time, the signal-to-noise ratio is increased from 250: 1 to 10,000: 1. The spectrum can expand up to 4 THz by optimal realignment of the THz system. Also, two terahertz electromagnetic pulses are generated from a receiver chip when the laser detection beam is reflected to the back side of the chip.

  • PDF

A Nomogram for Predicting Extraperigastric Lymph Node Metastasis in Patients With Early Gastric Cancer

  • Hyun Joo Yoo;Hayemin Lee;Han Hong Lee;Jun Hyun Lee;Kyong-Hwa Jun;Jin-jo Kim;Kyo-young Song;Dong Jin Kim
    • Journal of Gastric Cancer
    • /
    • v.23 no.2
    • /
    • pp.355-364
    • /
    • 2023
  • Background: There are no clear guidelines to determine whether to perform D1 or D1+ lymph node dissection in early gastric cancer (EGC). This study aimed to develop a nomogram for estimating the risk of extraperigastric lymph node metastasis (LNM). Materials and Methods: Between 2009 and 2019, a total of 4,482 patients with pathologically confirmed T1 disease at 6 affiliated hospitals were included in this study. The basic clinicopathological characteristics of the positive and negative extraperigastric LNM groups were compared. The possible risk factors were evaluated using univariate and multivariate analyses. Based on these results, a risk prediction model was developed. A nomogram predicting extraperigastric LNM was used for internal validation. Results: Multivariate analyses showed that tumor size (cut-off value 3.0 cm, odds ratio [OR]=1.886, P=0.030), tumor depth (OR=1.853 for tumors with sm2 and sm3 invasion, P=0.010), cross-sectional location (OR=0.490 for tumors located on the greater curvature, P=0.0303), differentiation (OR=0.584 for differentiated tumors, P=0.0070), and lymphovascular invasion (OR=11.125, P<0.001) are possible risk factors for extraperigastric LNM. An equation for estimating the risk of extraperigastric LNM was derived from these risk factors. The equation was internally validated by comparing the actual metastatic rate with the predicted rate, which showed good agreement. Conclusions: A nomogram for estimating the risk of extraperigastric LNM in EGC was successfully developed. Although there are some limitations to applying this model because it was developed based on pathological data, it can be optimally adapted for patients who require curative gastrectomy after endoscopic submucosal dissection.