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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of the Optical Society of Korea
Journal Basic Information
Journal DOI :
Optical Society of Korea
Editor in Chief :
Shin, Jung Hoon
Volume & Issues
Volume 15, Issue 4 - Dec 2011
Volume 15, Issue 3 - Sep 2011
Volume 15, Issue 2 - Jun 2011
Volume 15, Issue 1 - Mar 2011
Selecting the target year
An Iterative Algorithm to Estimate LIDAR Ratio for Thin Cirrus Cloud over Aerosol Layer
Wang, Zhenzhu ; Liu, Dong ; Xie, Chenbo ; Zhou, Jun ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 209~215
DOI : 10.3807/JOSK.2011.15.3.209
A new iterative algorithm is developed to estimate LIDAR ratio for a thin cirrus cloud over an aerosol layer. First, the thin cirrus cloud is screened out and replaced by a modeled LIDAR signal and the extinction coefficients of the aerosol layer are derived using the Fernald backward method. These aerosol coefficients are referred as the "actual values". Second, the original LIDAR signal which includes the thin cirrus cloud is also inverted by the Fernald backward method down to the aerosol layer but using different LIDAR ratio for the thin cirrus cloud. Depending on the different assumptions about the LIDAR ratio of the thin cirrus cloud, different sets of aerosol extinction can be derived. The "actual values" which are found in the first step can be used to constrain this iterative progress and the correct LIDAR ratio of the thin cirrus cloud can be found. The detailed description of this method and retrieval examples are given in the paper. The cases compared with other methods are presented and the statistical result is also shown and agrees well with other studies.
Symmetry Exploitation of Diffraction Gratings to Enhance the Spectral Resolution
Lee, Eun-Seong ; Lee, Jae-Yong ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 216~221
DOI : 10.3807/JOSK.2011.15.3.216
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.
An Amplified WDM-PON Using Broadband Light Source Seeded Optical Sources and a Novel Bidirectional Reach Extender
Kang, Byoung-Wook ; Kim, Chul-Han ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 222~226
DOI : 10.3807/JOSK.2011.15.3.222
We demonstrated the feasibility of an amplified wavelength-division multiplexed passive optical network (WDM-PON) architecture based on broadband light source (BLS) seeded optical sources and a novel bidirectional reach extender. Our bidirectional reach extender could provide an amplification of both downstream and upstream signals as well as a BLS output for the upstream WDM signal generation. An error-free 1.25 Gb/s signal transmission over a 100-km long single-mode fiber was achieved in a bidirectional WDM-PON using BLS seeded reflective semiconductor optical amplifier (RSOA) sources.
External Optical Modulator Using a Low-cost Fabry-Perot LD for Multicasting in a WDM-PON
Lee, Hyuek-Jae ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 227~231
DOI : 10.3807/JOSK.2011.15.3.227
An external optical modulation using absorption s in a Fabry-Perot laser diode (FP-LD), has been proposed and experimentally demonstrated for multicasting in a WDM-PON. The center wavelengths of absorption s in an FP-LD move to short-wavelength rapidly by only a small current (~1 mA) injection. If the current injection is stopped, the s move back to the original position. Such a movement of the s can make the FP-LD act as an external optical modulator, which is found to modulate at a maximum modulation speed of 800 Mbps or more. For a multicasting transmitter in a WDM-PON, the proposed modulator can be cost-effectively applied to a multi-wavelength laser source with the same periodicity of the longitudinal mode. Instead of the multi-wavelength laser source, tunable-LDs are used for experiments. The 32 channel multicasting system with the proposed modulator has been demonstrated, showing power penalties of 1.53~4.15 dB at a bit error rate of
with extinction ratios better than 14.5 dB at 622 Mbps.
Performance Analysis of Electrical MMSE Linear Equalizers in Optically Amplified OOK Systems
Park, Jang-Woo ; Chung, Won-Zoo ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 232~236
DOI : 10.3807/JOSK.2011.15.3.232
We analyze the linear equalizers used in optically amplified on-off-keyed (OOK) systems to combat chromatic dispersion (CD) and polarization mode dispersion (PMD), and we derive the mathematical minimum mean squared error (MMSE) performance of these equalizers. Currently, the MMSE linear equalizer for optical OOK systems is obtained by simulations using adaptive approaches such as least mean squared (LMS) or constant modulus algorithm (CMA), but no theoretical studies on the optimal solutions for these equalizers have been performed. We model the optical OOK systems as square-law nonlinear channels and compute the MMSE equalizer coefficients directly from the estimated optical channel, signal power, and optical noise variance. The accuracy of the calculated MMSE equalizer coefficients and MMSE performance has been verified by simulations using adaptive algorithms.
Analysis of Temperature Dependence of Thermally Induced Transient Effect in Interferometric Fiber-optic Gyroscopes
Choi, Woo-Seok ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 237~243
DOI : 10.3807/JOSK.2011.15.3.237
Thermal characteristics, such as diffusivity and temperature induced change in the fiber mode index of rotation sensing fiber coil are critical factors which determine the time varying, thermo-optically induced bias drift of interferometric fiber-optic gyroscopes (IFOGs). In this study, temperature dependence of the transient effect is analyzed in terms of the thermal characteristics of the fiber coil at three different temperatures. By applying an analytic model to the measured bias in the experiments, comprehensive thermal factors of the fiber coil could be extracted effectively. The validity of the model was confirmed by the fact that the extracted values are reasonable results in comparison with well known properties of the materials of the fiber coil. Temperature induced changes in the critical factors were confirmed to be essential in compensating the transient effect over a wide temperature range.
2-step Phase-shifting Digital Holographic Optical Encryption and Error Analysis
Jeon, Seok-Hee ; Gil, Sang-Keun ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 244~251
DOI : 10.3807/JOSK.2011.15.3.244
We propose a new 2-step phase-shifting digital holographic optical encryption technique and analyze tolerance error for this cipher system. 2-step phase-shifting digital holograms are acquired by moving the PZT mirror with phase step of 0 or
/2 in the reference beam path of the Mach-Zehnder type interferometer. Digital hologram with the encrypted information is Fourier transform hologram and is recorded on CCD camera with 256 gray-level quantized intensities. The decryption performance of binary bit data and image data is analyzed by considering error factors. One of the most important errors is quantization error in detecting the digital hologram intensity on CCD. The more the number of quantization error pixels and the variation of gray-level increase, the more the number of error bits increases for decryption. Computer experiments show the results to be carried out encryption and decryption with the proposed method and the graph to analyze the tolerance of the quantization error in the system.
A Quantitative Study of the Quality of Deconvolved Wide-field Microscopy Images as Function of Empirical Three-dimensional Point Spread Functions
Adur, Javier ; Vicente, Nathalie ; Diaz-Zamboni, Javier ; Izaguirre, Maria Fernanda ; Casco, Victor Hugo ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 252~263
DOI : 10.3807/JOSK.2011.15.3.252
In this work, for the first time, the quality of restoration in wide-field microscopy images after deconvolution was analyzed as a function of different Point Spread Functions using one deconvolution method, on a specimen of known size and on a biological specimen. The empirical Point Spread Function determination can significantly depend on the numerical aperture, refractive index of the embedding medium, refractive index of the immersion oil and cover slip thickness. The influence of all of these factors is shown in the same article and using the same microscope. We have found that the best deconvolution results are obtained when the empirical PSF utilized is obtained under the same conditions as the specimen. We also demonstrated that it is very important to quantitatively check the process` outcome using several quality indicators: Full-Width at Half-Maximum, Contrast-to-Noise Ratio, Signal-to-Noise Ratio and a Tenengrad-based function. We detected a significant improvement when using an indicator to measure the focus of the whole stack. Therefore, to qualitatively determinate the best deconvolved image between different conditions, one approach that we are pursuing is to use Tenengrad-based function indicators in images obtained using a wide-field microscope.
3D Holographic Image Recognition by Using Graphic Processing Unit
Lee, Jeong-A ; Moon, In-Kyu ; Liu, Hailing ; Yi, Faliu ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 264~271
DOI : 10.3807/JOSK.2011.15.3.264
In this paper we examine and compare the computational speeds of three-dimensional (3D) object recognition by use of digital holography based on central unit processing (CPU) and graphic processing unit (GPU) computing. The holographic fringe pattern of a 3D object is obtained using an in-line interferometry setup. The Fourier matched filters are applied to the complex image reconstructed from the holographic fringe pattern using a GPU chip for real-time 3D object recognition. It is shown that the computational speed of the 3D object recognition using GPU computing is significantly faster than that of the CPU computing. To the best of our knowledge, this is the first report on comparisons of the calculation time of the 3D object recognition based on the digital holography with CPU vs GPU computing.
Improvement of Color and Luminance Uniformity of the Edge-Lit Backlight Using the RGB LEDs
Son, Chang-Gyun ; Yi, Jong-Hoon ; Gwag, Jin-Seog ; Kwon, Jin-Hyuk ; Park, Gyeung-Ju ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 272~277
DOI : 10.3807/JOSK.2011.15.3.272
The effect of the M-window color mixing bar on the characteristics of color mixing and hot spots in the edge-lit backlight employing red (R), green (G), blue (G) light emitting diodes (LED) were studied in terms of the structure of the M-window color mixing bar. The rays from RGB LEDs entering the M-window bar were mixed by internal reflection and scattering inside the M-window bar so that the hot spots and color separation were minimized. The M-window bar was designed and fabricated and the simulation results are matched quite well to experimental data.
Optical Noise Removal in the Focal Plane of the Spaceborne Camera
Park, Jun-Oh ; Jang, Won-Kweon ; Kim, Seong-Hui ; Jang, Hong-Sul ; Lee, Seung-Hoon ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 278~282
DOI : 10.3807/JOSK.2011.15.3.278
We discuss two possible optical noise sources in an electro-optic camera loaded on a low earth orbit satellite. The first noise source was a reflection at the window for signal rays incident upon the window which is placed before the FPA plane. The second noise source came from a reflection at the surface of the FPA cell when the signal flux is not entirely absorbed. We investigate the noise generation processes for two optical noise sources, and a parametric solution is used to estimate the optical noise effects.
Bandwidth Improvement for a Photonic Crystal Optical Y-splitter
Danaie, Mohammad ; Kaatuzian, Hassan ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 283~288
DOI : 10.3807/JOSK.2011.15.3.283
In this study, a wide-band photonic crystal Y-splitter for TE modes is proposed. A triangular lattice of air holes etched in a GaAs slab is used as the platform. In order to numerically analyze the structures, plane wave expansion (PWE) and finite difference time domain (FDTD) methods are used. In comparison with the structures reported in the literature, the proposed topology has a less complexity while it provides more than 100nm bandwidth. The simplicity of the design, its high transmission ratio and its wide bandwidth makes it a suitable choice for the implementation of photonic crystal integrated circuits.
Polarization Converting Waveguide Devices Incorporating UV-curable Reactive Mesogen
Chu, Woo-Sung ; Kim, Sung-Moon ; Kim, Jun-Whee ; Kim, Kyung-Jo ; Oh, Min-Cheol ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 289~292
DOI : 10.3807/JOSK.2011.15.3.289
Reactive mesogen (RM) is an organic liquid crystal molecule that can be self-aligned to have an optic axis of birefringence when coated over a polyimide alignment film. A free-standing optical wave-plate film consisting of RM and low-loss optical polymers was fabricated in this work, and the film was inserted across the polymer waveguide to form an integrated optical polarization converter. For convenient evaluation of the polarization converters, a waveguide polarizer and analyzer were fabricated in series. The polarization conversion efficiency was measured to be 25 dB for the wavelength range from 1520 to 1580 nm. The wave plate exhibited a temperature-dependent retardation of
for a temperature change from 25 to
Fourier Domain Optical Coherence Tomography for Retinal Imaging with 800-nm Swept Source: Real-time Resampling in k-domain
Lee, Sang-Won ; Song, Hyun-Woo ; Kim, Bong-Kyu ; Jung, Moon-Youn ; Kim, Seung-Hwan ; Cho, Jae-Du ; Kim, Chang-Seok ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 293~299
DOI : 10.3807/JOSK.2011.15.3.293
In this study, we demonstrated Fourier-domain/swept-source optical coherence tomography (FD/SS-OCT) at a center wavelength of 800 nm for in vivo human retinal imaging. A wavelength-swept source was constructed with a semiconductor optical amplifier, a fiber Fabry-Perot tunable filter, isolators, and a fiber coupler in a ring cavity. Our swept source produced a laser output with a tuning range of 42 nm (779 to 821 nm) and an average power of 3.9 mW. The wavelength-swept speed in this configuration with bidirectionality is 2,000 axial scans per second. In addition, we suggested a modified zero-crossing method to achieve equal sample spacing in the wavenumber (k) domain and to increase the image depth range. FD/SS-OCT has a sensitivity of ~89.7 dB and an axial resolution of 10.4
in air. When a retinal image with 2,000 A-lines/frame is obtained, an acquisition speed of 2.0 fps is achieved.
Design and Fabrication of a Multi-modal Confocal Endo-Microscope for Biomedical Imaging
Kim, Young-Duk ; Ahn, Myoung-Ki ; Gweon, Dae-Gab ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 300~304
DOI : 10.3807/JOSK.2011.15.3.300
Optical microscopes are widely used for medical imaging these days, but biopsy is a lengthy process that causes many problems during the ex-vivo imaging procedure. The endo-microscope has been studied to increase accessibility to the human body and to get in-vivo images to use for medical diagnosis. This research proposes a multi-modal confocal endo-microscope for bio-medical imaging. We introduce the design process for a small endoscopic probe and a coupling mechanism for the probe to make the multi-modal confocal endo-microscope. The endoscopic probe was designed to decrease chromatic and spherical aberrations, which deteriorate the images obtained with the conventional GRIN lens. Fluorescence and reflectance images of various samples were obtained with the proposed endo-microscope. We evaluated the performance of the proposed endo-microscope by analyzing the acquired images, and demonstrate the possibilities of in-vivo medical imaging for early diagnosis.
Design of Plasmonic Slot Waveguide with High Localization and Long Propagation Length
Lee, Ki-Sik ; Jung, Jae-Hoon ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 305~309
DOI : 10.3807/JOSK.2011.15.3.305
We present an efficient design approach for a plasmonic slot waveguide using a genetic algorithm. The analyzed structure consists of a nanometric slot in a thin metallic film embedded within a dielectric. To achieve high confinement without long propagation length, the thickness and width of the slot are optimally designed in order to optimize the figures of merit including mode confinement and propagation length. The optimized design is based on the finite element method and enhances the guiding and focusing of light power propagation.
Measuring of the Perceptibility and Acceptability in Various Color Quality Measures
Kim, A-Ri ; Kim, Hong-Suk ; Park, Seung-Ok ;
Journal of the Optical Society of Korea, volume 15, issue 3, 2011, Pages 310~317
DOI : 10.3807/JOSK.2011.15.3.310
Perceptibility and acceptability are the most often used threshold units in the field of color science. The former refers to a just perceptible difference and the latter evokes a tolerable color difference. Such thresholds can be very significant to color quality control processes in the printing industry and should be defined in quality measure units. Optical density (OD) and color difference models are usually utilized as color quality measures and have been provided in a considerable number of commercial measuring devices such as spectrophotometers. However, their merits and traits are far less understood in the literature. The present study intends to evaluate performance of those color quality measures including the OD and widely known color difference models, e.g.
. A set of psychophysical assessments were carried out in order to accumulate the perceptibility and acceptability thresholds data, and their central trend was compared with the color quality measure estimates.