• Title/Summary/Keyword: Spectral resolution

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Spectral Resolution Enhancement of Acousto-Optic Tunable Filter(AOTF) using Incident Angle Variation (음향광학변조필터의 입사각 변화를 이용한 분해능 향상 방법)

  • You, Jang-Woo;Ahn, Jeong-Ho;Kim, Dae-suk;Kwak, Yoon-Keun;Kim, Soo-Hyun;Lee, Yun-Woo;Whang, In-Duk
    • Proceedings of the KSME Conference
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    • pp.607-612
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    • 2004
  • Spectral resolution enhancement method of Acousto-Optic Tunable Filter (AOTF) using incident light angle variation is described. AOTF is a small, mechanically rigid, high speed and spectral resolution light tunable filter. The basic theory of AOTF and its experimental verification is described. AOTF can generate two opposite polarized light simultaneously which wavelength can be changed by incident angle variation. We focused on the common region of two filtered light at the specific incident angle. This region can be used to enhance the spectral resolution of AOTF.

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Sensitivity of Input Parameters in the Spectral Wave Model

  • Park, Hyo-Bong
    • Journal of Ocean Engineering and Technology
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    • v.23 no.2
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    • pp.28-36
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    • 2009
  • Many researches have been done to define the physical parameters for the wave generation and transformation over a coastal region. However, most of these have been limited to the application of particular conditions, as they are generally too empirical. To yield more reasonable wave estimation using a spectral wave model, it is important to understand how they work for the wave estimation. This study involved a comprehensive sensitivity test against the spectral resolution and the physical source/sink terms of the spectral wave model using SWAN and TOMAWAC, which have the same physical background with several different empirical/theoretical formulations. The tests were conducted for the East Anglian coast, UK, which is characterized by a complex bathymetry due to several shoals and offshore sandbanks. For the quantitative and qualitative evaluation of the models' performance with different input conditions, the wave elements and spectrums predicted at representative sites the East Anglia coast were compared/analyzed. The spectral resolution had no significant effect on the model results, but the lowest resolution on the frequency and direction induced underestimations of the wave height and period. The bottom friction and depth-induced breaking terms produced relatively high variations in the wave prediction, depending on which formulation was applied. The terms for the quadruplet and whitecapping had little effect on the wave estimation, whereas the triads tended to predict shorter and higher waves by energy transferring to higher frequencies.

HYPERSPECTRAL IMAGING SPECTROMETER WITH A NOVEL ZOOMING FUNCTION

  • Choi Jin;Kim Tae Hyung;Kong Hong Jin;Lee Jong-Ung
    • Proceedings of the KSRS Conference
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    • pp.213-216
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    • 2005
  • A novel hyperspectral imaging spectrometer controlling spatial and spectral resolution individually has been proposed. This imaging spectrometer uses a zoom lens as a telescope and a focusing element. It can change the spatial resolution fixing the spectral resolution or the spectral resolution fixing the spatial resolution. Here, we report the concept of the hyperspectral imaging spectrometer with the novel zooming function and the optical design of a zoom lens as the focusing element. By using lens module and third-order aberration theory, we have presented the initial design of four-group zoom lens with external entrance pupil. And the optimized zoom lens with a focal length of 50 to 150 mm is obtained from the initial design by the optical design software. As a result, the designed zoom lens shows satisfactory performances in wavelength range of 450 to 900 nm as a focusing element in an imaging spectrometer. Furthermore, the collimator lens of the imaging spectrometer is designed through the third-order aberration correction by using an iterative process.

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Design and Calibration of Acousto-Optic Tunable Filter(AOTF) for Near Infrared Spectral Analysis (근적외선 분광 분석을 위한 음향광학변조필터의 설계 및 교정)

  • You, Jang-Woo;Kim, Dae-Suk;Kwak, Yoon-Keun;Kim, Soo-Hyun;Lee, Yun-Woo;Hwang, In-Duk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.11
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    • pp.1697-1702
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    • 2004
  • In this paper, we proposed the design and calibration method for the near infrared Acousto-Optic Tunable Filter (AOTF). The theory and design principles of AOTF for the visible light are well known since I.C.Chang has developed the parallel tangent condition for the non-collinear AOTF. Deflection angle, frequency-wavelength relation, spectral resolution, etc. were calculated based on the theory of AOTF. From this result, important parameters - incident and acoustic angle - to fabricate AOTF were decided. We measured the spectral resolution and the relation between electrical driving frequency and the Optical wavelength of diffracted light to calibrate the near infrared AOTF. About 40 ∼ 80 MHz electrical frequency was required to get 1200 ∼ 2200 nm near infrared light. Spectral resolution was less than 10 nm in the near infrared region.

Symmetry Exploitation of Diffraction Gratings to Enhance the Spectral Resolution

  • Lee, Eun-Seong;Lee, Jae-Yong
    • Journal of the Optical Society of Korea
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    • v.15 no.3
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    • pp.216-221
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    • 2011
  • A diffraction grating is a highly symmetric optical element with a physical structure that is invariant under translational spatial movements. The translational symmetry is reflected in the fields that are diffracted from the grating. Here, we introduce a plane-parallel mirror pair onto the grating, which translates the fields through double reflections, and we describe a method of exploiting the symmetry to enhance the spectral resolution of a diffraction grating beyond the limit that is set by the number of grooves. The mirror pair creates another virtual grating beside the original one, effectively doubling the number of grooves. Addition of more mirror pairs can further increase the effective number of grooves despite the increased complexity and difficulty of experimental implementation. We experimentally demonstrate the spectral linewidth reduction by a factor of four in a neon fluorescence spectrum. Even though the geometrical restriction on the mirror deployment limits our method to a certain range of the whole spectrum, as a practical application example, a bulky spectrometer that is nearly empty inside can be made compact without sacrificing the resolution.

On the Design Considerations of Auditory Preprocessors Based on Human Auditory System (인간의 청각시스팀에 기반한 음성전처리기의 설계점에 대하여)

  • Rhee, M.Kil;Lee, Young-jik
    • Electronics and Telecommunications Trends
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    • v.8 no.2
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    • pp.69-91
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    • 1993
  • In the conventional speech processing, the technique of FFT(Fast Fourier Transform) is usually applied to the finite number of samples within the window of specified length using the fixed sampling rate. In this case, the temporal resolution is dependent upon the length of window while the spectral resolution is dependent upon the number of samples within the window. Thus, once the temporal resolution is determined the spectral resolution is also determined or vice versa. To resolve this type of dilemma, a new type of bank-filter similar to the characteristics of cochlear model needs to be considered. Furthermore, wide dynamic range of cochlea certainly helps the stable extraction of speech features. In the paper, the human auditory system will be briefly introduced and previous works on auditory preprocessors based on cochlear model will be reviewed. As a conclusion, the design considerations of auditory preprocessors based on cochlear model will be addressed.

Spectral resolution evaluation by MCNP simulation for airborne alpha detection system with a collimator

  • Kim, Min Ji;Sung, Si Hyeong;Kim, Hee Reyoung
    • Nuclear Engineering and Technology
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    • v.53 no.4
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    • pp.1311-1317
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    • 2021
  • In this study, an airborne alpha detection system, which consists of a passivated implanted planar silicon (PIPS) detector and an air filter, was developed. A collimator applied to the alpha detection system showed an enhancement in resolution and a degradation in detection efficiency. The resolution and detection efficiency were compared and analyzed to evaluate the performance of the collimator. Thus, the resolution was found to be more important than the efficiency as a determining factor of the detection system performance, from the viewpoint of radionuclide identification. The performance was evaluated on three properties of the collimator: hole shape, hole length, and the ratio between the hole and frame pitches. From the hole shape performance evaluation, a hexagonal collimator showed the highest resolution. Further, the collimator with a hole pitch of 14 mm was found to have the highest resolution while that with a frame pitch of 4-6 mm (i.e., 1.2-1.4 times longer than the hole pitch) showed the highest resolution.

Algorithm to Improve Mass Spectral Resolution of Gas Chromatography Mass Spectrometer (가스크로마토그래피 질량분석기의 질량 스펙트럼 해상도 개선 알고리즘)

  • Choi, Hun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.67 no.9
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    • pp.1232-1238
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    • 2018
  • This paper proposes methods for improving mass spectral resolution for a gas chromatograph mass spectrometer. The slope signs of the 1st and 2nd fitting functions for the ion signal block of each mass index are obtained, and the unnecessary element signals in the ion signal block are removed. The spectrum can be obtained by obtaining the second-order fitting function of the reconstructed ion signal block using only the effective ion signals. In addition, the resolution of the mass spectrum can be improved by correcting the error caused by the shift of the spectral peak position. To verify the performance of the proposed methods, computer simulations were performed using the actual ion signals obtained from the GC-MS system under development. Simulation results show that the proposed method is valid.

Simultaneous Spectral Resolution and Sensitivity Enhancement in MR spectrum: Maximum Likelihood Deconvolution Reconstruction

  • Jeong, Gwang-Woo;Jeong, Jenny Eunice;Kang, Heoung-Keun
    • Journal of the Korean Magnetic Resonance Society
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    • v.15 no.2
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    • pp.157-174
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    • 2011
  • Although the use of apodization functions in connection with postprocessing of a 2D NMR spectrum proves improved spectral quality, there is usually a trade-off between resolution enhancement and noise suppression due to a classical "uncertainty principle." In this study, therefore, a mathematical deconvolution technique called "Maximum Likelihood Deconvolution (MLD)" was adopted to achieve the spectral resolution and sensitivity enhancement simultaneously. The MLD technique greatly facilitates visualization and restoration of the genuine spectral information from complex 2D NMR spectra that would be problematic with the conventional apodization/FT processing. In particular, application of the MLD to the 2D-NOE spectrum would be very useful to derive the important proton connectivities, which are essential to achieve elucidating the 3D molecular structure.

Nanoscale-NMR with Nitrogen Vacancy center spins in diamond

  • Lee, Junghyun
    • Journal of the Korean Magnetic Resonance Society
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    • v.24 no.2
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    • pp.59-65
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    • 2020
  • Nitrogen-Vacancy (NV) center in diamond has been an emerging versatile tool for quantum sensing applications. Amongst various applications, nano-scale nuclear magnetic resonance (NMR) using a single or ensemble NV centers has demonstrated promising results, opening possibility of a single molecule NMR for its chemical structural studies or multi-nuclear spin spectroscopy for quantum information science. However, there is a key challenge, which limited the spectral resolution of NMR detection using NV centers; the interrogation duration for NV-NMR detection technique has been limited by the NV sensor spin lifetime (T1 ~ 3ms), which is orders of magnitude shorter than the coherence times of nuclear spins in bulk liquid samples (T2 ~ 1s) or intrinsic 13C nuclear spins in diamond. Recent studies have shown that quantum memory technique or synchronized readout detection technique can further narrow down the spectral linewidth of NMR signal. In this short review paper, we overview basic concepts of nanoscale NMR using NV centers, and introduce further developments in high spectral resolution NV NMR studies.