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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Optical Society of Korea
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Journal DOI :
Optical Society of Korea
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Volume & Issues
Volume 17, Issue 6 - Dec 2013
Volume 17, Issue 5 - Oct 2013
Volume 17, Issue 4 - Aug 2013
Volume 17, Issue 3 - Jun 2013
Volume 17, Issue 2 - Apr 2013
Volume 17, Issue 1 - Feb 2013
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A Feedforward Partial Phase Noise Mitigation in the Time-Domain using Cyclic Prefix for CO-OFDM Systems
Ha, Youngsun ; Chung, Wonzoo ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 467~470
DOI : 10.3807/JOSK.2013.17.6.467
We propose a blind feedforward phase noise mitigation method in the time-domain for a coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. By exploiting the redundancy of the cyclic prefix (CP), the proposed scheme acquires the overall phase noise difference information during an OFDM block and attempts to mitigate the phase noise in the time domain using a linear approximation. The proposed algorithm mitigates common phase error (CPE) and inter-carrier-interference (ICI) due to phase noise simultaneously, improving the system performance, especially when decision-directed equalizers are used. The simulation results demonstrate the effectiveness of the proposed feedforward phase noise mitigation approach in time domain.
Enhancing the Performance of Coherent Sources SAC OCDMA Networks via Spatial Multiplexing
Alhassan, Ahmed M. ; Badruddin, Nasreen ; Saad, Naufal M. ; Aljunid, Syed A. ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 471~480
DOI : 10.3807/JOSK.2013.17.6.471
The beating of two or more lasers that have the same or a finite difference in the central frequencies, is the main source of noise in spectral amplitude coding optical code division multiple access (SAC OCDMA) systems. In this paper we adopt a spatial multiplexing (SM) scheme for SAC OCDMA systems to mitigate this beat noise. The results show that for different code weights and different data rates SM SAC can support a larger number of users than the conventional SAC for all different laser source configurations. However, SM SAC requires a more complex system than the conventional SAC, and almost twice as much optical component.
A Method for the Measurement of Methane Gas Based on Multi-beam Interferometry
Ye, Jiansen ; Li, Zhuo ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 481~485
DOI : 10.3807/JOSK.2013.17.6.481
A method for the measurement of the concentration of methane is experimentally demonstrated. The wavelength filter and gas cell are combined by using one Fabry-Perot etalon, which is filmed with the reflectivity of 96%. The optical broadband source is not only filtered to match the absorption wavelength of methane, but also absorbed by the methane in the same Fabry-Perot etalon. The concentration of the methane can be detected directly by measuring the transmission intensity. Compared with the conventional method, the proposed method possesses low costand high stability.
Portable Infrared Laser Transmitter Based on a Beam Shaper Enabling a Highly Uniform Detectable Beam Width
Yue, Wenjing ; Kim, Haeng-Jung ; Lee, Sang-Shin ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 486~490
DOI : 10.3807/JOSK.2013.17.6.486
A portable infrared laser transmitter delivering a highly uniform detectable beam was demonstrated. It incorporates a flexible beam shaper, comprising a perforated diffuser sheet in conjunction with a pinhole. The beam shaper plays the prominent role of flexibly tailoring the incoming light via both scattering and diffraction, in order to equalize the effective beam width over a long distance. The intensity profile of a generated beam was practically observed, demonstrating that a substantially uniform beam of 70-cm width was achieved for a given threshold detection level, with an average deviation of 6% over a range of 600 m.
A Frequency-Doubling Optoelectronic Oscillator using a Three-Arm Dual-Output Mach-Zehnder Modulator
Chong, Yuhua ; Yang, Chun ; Li, Xianghua ; Ye, Quanyi ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 491~493
DOI : 10.3807/JOSK.2013.17.6.491
This paper proposes a frequency-doubling optoelectronic oscillator employing a novel three-arm dual-output Mach-Zehnder modulator (MZM). One output of the MZM generates the fundamental-frequency signal which is recycled by the microwave optical fiber link for oscillation, and the other output can generate the frequency-doubled signal. Experiment was conducted using a commercial two-arm MZM, a phase modulator, and an optical fiber link of 89 meters in length. A 19-GHz frequency-doubled signal was successively obtained with fundamental signal suppression more than 36 dB.
Optical Encryption and Information Authentication of 3D Objects Considering Wireless Channel Characteristics
Lee, In-Ho ; Cho, Myungjin ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 494~499
DOI : 10.3807/JOSK.2013.17.6.494
In this paper, we present an optical encryption and information authentication of 3D objects considering wireless channel characteristics. Using the optical encryption such as double random phase encryption (DRPE) and 3D integral imaging, a 3D scene with encryption can be transmitted. However, the wireless channel causes the noise and fading effects of the 3D transmitted encryption data. When the 3D encrypted data is transmitted via wireless channel, the information may be lost or distorted because there are a lot of factors such as channel noise, propagation fading, and so on. Thus, using digital modulation and maximum likelihood (ML) detection, the noise and fading effects are mitigated, and the encrypted data is estimated well at the receiver. In addition, using computational volumetric reconstruction of integral imaging and advanced correlation filters, the noise effects may be remedied and 3D information may be authenticated. To prove our method, we carry out an optical experiment for sensing 3D information and simulation for optical encryption with DRPE and authentication with a nonlinear correlation filter. To the best of our knowledge, this is the first report on optical encryption and information authentication of 3D objects considering the wireless channel characteristics.
Depth Resolution Analysis of Axially Distributed Stereo Camera Systems under Fixed Constrained Resources
Cho, Myungjin ; Shin, Donghak ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 500~505
DOI : 10.3807/JOSK.2013.17.6.500
In this paper, we propose a novel framework to evaluate the depth resolution of axially distributed stereo sensing (ADSS) under fixed resource constraints. The proposed framework can evaluate the performance of ADSS systems based on various sensing parameters such as the number of cameras, the number of total pixels, pixel size and so on. The Monte Carlo simulations for the proposed framework are performed and the evaluation results are presented.
Analysis of Color Uniformity of White LED Lens Packages for Direct-lit LCD Backlight Applications
Joo, Byung-Yun ; Ko, Jae-Hyeon ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 506~512
DOI : 10.3807/JOSK.2013.17.6.506
Recently, the color separation issue of wide-spreading white LEDs has attracted attention due to their wide applicability as light sources in direct-lit LCD backlights. These wide-spreading LED packages usually consist of LED chips, a color-conversion phosphor layer, and a light-shaping lens. The technical aspect of this color issue was related to a method for balancing the yellow spectral component emitting from phosphors with respect to the blue one from the LED chip as a function of viewing angle. In this study, we suggested an approach for carrying out quantitative analysis for the color separation problem occurring in wide-spreading LED packages by optical simulation. In addition, the effect of an internal scattering layer on the color uniformity was investigated, which may be considered as a potential solution for this problem.
Detecting Digital Micromirror Device Malfunctions in High-throughput Maskless Lithography
Kang, Minwook ; Kang, Dong Won ; Hahn, Jae W. ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 513~517
DOI : 10.3807/JOSK.2013.17.6.513
Recently, maskless lithography (ML) systems have become popular in digital manufacturing technologies. To achieve high-throughput manufacturing processes, digital micromirror devices (DMD) in ML systems must be driven to their operational limits, often in harsh conditions. We propose an instrument and algorithm to detect DMD malfunctions to ensure perfect mask image transfer to the photoresist in ML systems. DMD malfunctions are caused by either bad DMD pixels or data transfer errors. We detect bad DMD pixels with
pixel by white and black image tests. To analyze data transfer errors at high frame rates, we monitor changes in the frame rate of a target DMD pixel driven by the input data with a set frame rate of up to 28000 frames per second (fps). For our data transfer error detection method, we verified that there are no data transfer errors in the test by confirming the agreement between the input frame rate and the output frame rate within the measurement accuracy of 1 fps.
Zoom Lens Design for a 10x Slim Camera using Successive Procedures
Park, Sung-Chan ; Lee, Sang-Hun ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 518~524
DOI : 10.3807/JOSK.2013.17.6.518
This study presents a new design method for a zoom lens, in which real lens groups are designed successively to combine to form a lens modules zoom system. The lens modules and aberrations are applied to the initial design for a four-group inner-focus zoom system. An initial design with a focal length range of 4.2 to 39.9 mm is derived by assigning the first-order quantities and third-order aberrations to each module along with the constraints required for optimum solutions. After obtaining the lens module zoom system, the real lens groups are successively, not separately, designed to get a zoom lens system. Compared to the separately designed real lens groups, this approach can give a better starting zoom lens and save time. The successively designed groups result in a zoom system that satisfies the basic properties of the zoom system consisting of the original lens modules. In order to have a slim system, we directly inserted the right-angle prism in front of the first group. This configuration resulted in a compact zoom system with a depth of 12 mm. The finally designed zoom lens has an f-number of 3.5 to 4.5 and is expected to fulfill the requirements for a mobile zoom camera having high zoom ratio of 10x.
Modeling Alignment Experiment Errors for Improved Computer-Aided Alignment
Kim, Yunjong ; Yang, Ho-Soon ; Song, Jae-Bong ; Kim, Sug-Whan ; Lee, Yun-Woo ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 525~532
DOI : 10.3807/JOSK.2013.17.6.525
Contrary to the academic interests of other existing studies elsewhere, this study deals with how the alignment algorithms such as sensitivity or Differential Wavefront Sampling (DWS) can be better used under effects from field, compensator positioning and environmental errors unavoidable from the shop-floor alignment work. First, the influences of aforementioned errors to the alignment state estimation was investigated with the algorithms. The environmental error was then found to be the dominant factor influencing the alignment state prediction accuracy. Having understood such relationship between the distorted system wavefront caused by the error sources and the alignment state prediction, we used it for simulated and experimental alignment runs for Infrared Optical System (IROS). The difference between trial alignment runs and experiment was quite close, independent of alignment methods; 6 nm rms for sensitivity method and 13 nm rms for DWS. This demonstrates the practical usefulness and importance of the prior error analysis using the alignment algorithms before the actual alignment runs begin. The error analysis methodology, its application to the actual alignment of IROS and their results are described together with their implications.
Optical Design of a Reflecting Telescope for CubeSat
Jin, Ho ; Lim, Juhee ; Kim, Youngju ; Kim, Sanghyuk ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 533~537
DOI : 10.3807/JOSK.2013.17.6.533
Space telescope optics is one of the major parts of any space mission used to observe astronomical targets or the Earth. This kind of space mission typically involves bulky and complex opto-mechanics with a long optical tube, but attempts have been made to observe a target with a small satellite. In this paper, we describe the optical design of a reflecting telescope for use in a CubeSat mission. For this design we adopt the off-axis segmented method for astronomical observation techniques based on a Ritchey-Chr
tien type telescope. The primary mirror shape is a rectangle with dimensions of
, and the secondary mirror has dimensions of
. The focal ratio is 3 which can yield a 0.383 degree diagonal angle in a
CMOS color image sensor with a pixel size of
. This optical design can capture a
area of the earth's surface at 700 km altitude operation.
Similarity Analysis for the Dispersion of Spiraling Modes on Metallic Nanowire to a Planar Thin Metal Layer
Lee, Dong-Jin ; Park, Se-Geun ; Lee, Seung-Gol ; O, Beom-Hoan ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 538~542
DOI : 10.3807/JOSK.2013.17.6.538
We propose a simple model to elucidate the dispersion behavior of spiraling modes on silver nanowire by finding correspondence parameters and building a simple equivalent relationship with the planar insulator-metal-insulator geometry. The characteristics approximated for the proposed structure are compared with the results from an exact solution obtained by solving Maxwell's equation in cylindrical coordinates. The effective refractive index for our proposed equivalent model is in good agreement with that for the exact solution in the 400-2000 nm wavelength range. In particular, when the radius of the silver nanowire is 100 nm, the calculated index shows typical improvements; the average percentage error for the real part of the effective refractive index is reduced to only 5% for the
order mode (11.9% in previous results) and 1.5% for the
order mode (24.8% in previous results) in the 400-800 nm wavelength range. This equivalent model approach is expected to provide further insight into understanding the important behavior of nanowire waveguides.
Photoluminescence Study on O-plasma Treated ZnO Thin Films
Cho, Jaewon ; Choi, Jinsung ; Yu, SeGi ; Rhee, Seuk Joo ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 543~547
DOI : 10.3807/JOSK.2013.17.6.543
A temperature dependent (10K-290K) photoluminescence (PL) study for two differently prepared ZnO thin films (as-grown and O-plasma treated) is presented. Four characteristic peaks were identified for both samples: (i) neutral donor-bound excitons (
), (ii) two electron satellites (TES), (iii) phonon replica of
-1LO), and (iv) donor-acceptor pair transition (DAP). As the sample temperature increased,
-1LO and DAP transitions became indistinct. This was accompanied by newly-rising emission of free electron-acceptor transitions (e,
). The spectral evolution with temperature for as-grown samples also showed the optical emission from free excitons, which became dominant at higher temperatures. Some features related to O-plasma were identified in PL spectra: (i) different positions of TES transitions (28meV lower than
for as-grown samples and 35meV for O-plasma treated samples), (ii) the decrease of spectral intensity in both emissions of
and DAP after O-plasma treatment, and (iii) no noticeable transition from free excitons after the O-plasma treatment.
Qualitative Analysis and Plasma Characteristics of Soil from a Desert Area using LIBS Technique
Farooq, W. Aslam ; Tawfik, Walid ; Al-Mutairi, Fahad N. ; Alahmed, Zeyad A. ;
Journal of the Optical Society of Korea, volume 17, issue 6, 2013, Pages 548~558
DOI : 10.3807/JOSK.2013.17.6.548
In this work, laser induced breakdown spectroscopy (LIBS) is used to investigate soil samples collected from different desert areas of Riyadh city in Saudi Arabia. Both qualitative analysis and plasma parameters are studied via the observed LIBS spectra. These experiments have been done using a Spectrolaser-7000 system with 50 mJ fundamental wavelength of Nd:YAG laser and detection delay time of 1 microsecond. Many spectral lines are highly resolved for many elements like Al, Fe, Mg, Si, Mn, Na, Ca and K. The electron temperatures Te and electron densities Ne, for the constituent of generated LIBS plasma, are determined for all the collected samples. It is found that both Te and Ne vary from one desert area to other. This variation is due to the change of the elemental concentration in different desert areas that affects the sample's matrices. Time dependent measurements have also been performed on the soil samples. While the signal-to-base ratio (SBR) reached its optimal value at 1 microsecond, the plasma parameters Ne and Te reach values of
and 9235 K, respectively, at 2.5 microsecond. The later indicate that the plasma cooling processes are slow in comparison to the previously observed results for metallic samples. The observed results show also that in the future it is possible to enhance the exploitation of LIBS in the remote on-line environmental monitoring application, by following up only the values of Ne and Te for one element of the soil desert sample using an optical fiber probe.