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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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Wavelength-Tunable, Passively Mode-Locked Erbium-Doped Fiber Master-Oscillator Incorporating a Semiconductor Saturable Absorber Mirror
Vazquez-Zuniga, Luis A. ; Jeong, Yoonchan ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 117~129
DOI : 10.3807/JOSK.2013.17.2.117
We briefly review the recent progress in passively mode-locked fiber lasers (PMLFLs) based on semiconductor saturable absorber mirrors (SESAMs) and discuss the detailed characterization of a SESAM-based, passively mode-locked erbium-doped fiber (EDF) laser operating in the 1.5-
spectral range for various configurations. A simple and compact design of the laser cavity enables the PMLFL to generate either femtosecond or wavelength-tunable picosecond pulses with high stability as the intra-cavity filtering method is altered. All the cavities investigated in our experiments present self-starting, continuous-wave mode-locking with no Q-switching instabilities. The excellent stability of the source eventually enables the wavelength-tunable PMLFL to be used as a master oscillator for a power-amplifier source based on a large-core EDF, generating picosecond pulses of >10-kW peak power and >100-nJ pulse energy.
Polarization Properties of Quasi-Homogeneous Beams Propagating in Oceanic Turbulence
Chen, Feinan ; Zhao, Qi ; Chen, Yanru ; Chen, Jingjing ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 130~135
DOI : 10.3807/JOSK.2013.17.2.130
Based on the extended Huygens-Fresnel principle and generalized Stokes theory, the evolution of polarization properties of beams generated by quasi-homogenous (QH) sources propagating in clear oceanic water was studied by the use of the oceanic turbulence spatial spectrum function. The results show that the beams have similar polarization self-reconstructed behavior under different turbulence conditions in the far field, but if the propagation distance is not long enough, the degree of polarization (DOP) fluctuates with much more complexity than state of polarization (SOP) of QH beams. The self-reconstructed ability of DOP at the special distance in turbulence would get to the best value if the values of coherence of width were chosen suitably, but for SOP, it has no best value.
Determination of Transverse Magnifications by Distortion Analysis
Lee, Sukmock ; Kim, Byungoh ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 136~141
DOI : 10.3807/JOSK.2013.17.2.136
A method to determine the transverse magnification (TM) of an imaging system is discussed. This method is different in that TM can be determined accurately by using distortion analysis. We demonstrate the validity of the method via numerical simulation with accompanying experimental data for a thick bi-convex lens.
A Design of Mid-wave Infrared Integral Catadioptric Optical System with Wide FOV
Yu, Lin Yao ; Jia, Hong Guang ; Wei, Qun ; Jiang, Hu Hai ; Zhang, Tian Yi ; Wang, Chao ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 142~147
DOI : 10.3807/JOSK.2013.17.2.142
In order to deduce the difficulty of fixing the Ritchey-Chretien (R-C) dual reflective optical system and enhance the stability of the secondary mirror, a compact integral structure is presented here composed of two transmitting and two reflective aspheric surfaces. The four surfaces were manufactured from a single germanium lens and integrated together. The two reflective surfaces formed by coating the inner reflecting films were assembled in one lens. It makes the installation of the two mirrors easier and the structure of the secondary mirror more stable. A design of mid-wave infrared (MWIR) compact imaging system is presented with a spectral range chosen as
. The effective focal length is f=90 mm. The field of view (FOV) for the lens is
. It has good imaging capability with Modulation Transfer Function (MTF) of all field of view more than 0.55 close to the diffraction limitation. Outdoor experiments were carried out and it is shown that the integral catadioptric optical system performs well on imaging.
Reference Functions for Synthesis and Analysis of Multiview and Integral Images
Saveljev, Vladimir ; Kim, Sung-Kyu ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 148~161
DOI : 10.3807/JOSK.2013.17.2.148
We propose one- and two-dimensional reference functions for processing of integral/multiview imaging. The functions provide the synthesis/analysis of the integral image by distance, as an alternative to the composition/decomposition by view images (directions). The synthesized image was observed experimentally. In analysis confirmed by simulation in a qualitative sense, the distance was obtained by convolution of the integral image with the reference functions.
2D/3D Convertible Integral Imaging Display Using Point Light Source Array Instrumented by Polarization Selective Scattering Film
Song, Byoungsub ; Min, Sung-Wook ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 162~167
DOI : 10.3807/JOSK.2013.17.2.162
A two-dimensional (2D) / three-dimensional (3D) convertible display system based on integral imaging is proposed to adopt a novel switchable point light source array, which is implemented using the polarization modulator and the polarization selective scattering film that transmits or scatters the incident light due to its polarization direction. The 2D and the 3D display modes of the proposed system can be modulated by controlling the polarization direction of back light using the polarization modulator. We explain the basic principles of the proposed system and verify the feasibility of the system through preliminary experiments.
Reflective Thermochromic Display on Polyethylene Naphthalate Film
Heo, Kyong Chan ; Son, Phil Kook ; Sohn, Youngku ; Yi, Jonghoon ; Kwon, Jin Hyuk ; Gwag, Jin Seog ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 168~171
DOI : 10.3807/JOSK.2013.17.2.168
A reflective flexible display was fabricated by placing a thermochromic pigment on a polyethylene naphthalate (PEN) substrate coated with an indium tin oxide (ITO) film, and its thermo-optical characteristics were investigated. The reflective thermochromic display showed good image quality with a reflectance of approximately 65%. As a flexible display, the display showed reliability without damage to the image even after the display was bent strongly. The reflective display cell exhibits continuously the gray level according to the temperature controlled by applied voltage. This low cost display is expected be used in outdoor poster applications where information needs to be presented clearly.
Strain-imposed External Cavity Tunable Lasers Operating for NIR Wavelength
Kim, Jun-Whee ; Kim, Kyung-Jo ; Son, Nam-Seon ; Oh, Min-Cheol ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 172~176
DOI : 10.3807/JOSK.2013.17.2.172
For demonstrating widely tunable external cavity lasers operating for near-infrared (NIR) wavelength, a flexible polymer waveguide with an imbedded Bragg grating is incorporated. Due to the superior flexibility of the polymer material, the reflection wavelength of the Bragg grating is widely tunable by imposing tensile and compressive strains on the flexible Bragg grating. A third-order Bragg grating is formed on the device for facilitating the fabrication method. With a superluminescent laser diode as a gain medium of ECL, the tunable laser exhibited output power of -3 dBm and a tuning range of 32 nm.
Power-Scalable, Sub-Nanosecond Mode-Locked Erbium-Doped Fiber Laser Based on a Frequency-Shifted-Feedback Ring Cavity Incorporating a Narrow Bandpass Filter
Vazquez-Zuniga, Luis Alonso ; Jeong, Yoonchan ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 177~181
DOI : 10.3807/JOSK.2013.17.2.177
We present an all-fiberized power-scalable, sub-nanosecond mode-locked laser based on a frequency-shifted-feedback ring cavity comprised of an erbium-doped fiber, a downshifting acousto-optic modulator (AOM), and a bandpass filter (BPF). With the aid of the frequency-shifted feedback mechanism provided by the AOM and the narrow filter bandwidth of 0.45 nm, we generate self-starting, mode-locked optical pulses with a spectral bandwidth of ~0.098 nm and a pulsewidth of 432 to 536 ps. In particular, the output power is readily scalable with pump power while keeping the temporal shape and spectral bandwidth. This is obtained via the consolidation of bound pulse modes circulating at the fundamental repetition rate of the cavity. In fact, the consolidated pulses form a single-entity envelope of asymmetric Gaussian shape where no discrete internal pulses are perceived. This result highlights that the inclusion of the narrow BPF into the cavity is crucial to achieving the consolidated pulses.
Comparative Experimental Analysis of Thermal Characteristics of Ytterbium-Doped Phosphosilicate and Aluminosilicate Fibers
Lee, Seungjong ; Vazquez-Zuniga, Luis A. ; Lee, Dongyoung ; Kim, Hyuntai ; Sahu, Jayanta K. ; Jeong, Yoonchan ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 182~187
DOI : 10.3807/JOSK.2013.17.2.182
We present a comparative experimental analysis of the thermal spectroscopic characteristics of a phosphosilicate (P)-based ytterbium-doped fiber (YDF) against an aluminosilicate (Al)-based YDF in the temperature range of 25 to
. We also characterize the fibers as gain media in a cladding-pumped amplifier configuration. While both fibers exhibit comparable trends in their thermal characteristics, there are noticeable distinctions in the fluorescence lifetime reduction rate and the spectral dependence of the transition cross-sections. The P- and Al-based YDFs present thermal lifetime reduction rates of
, respectively. In particular, in the spectral region at ~940 nm, the absorption cross-section of the P-based YDF undergoes significantly less thermal change compared to that of the Al-YDF. In the cladding-pumped amplifier configuration operating at a total gain of 10 dB, the Al-based YDF generally performs betters than the P-based YDF in the temperature range of 25 to
. However, it is highlighted that in the high temperature range of over
, the latter shows a less gain reduction rate than the former, thereby yielding higher relative output power by 3.3% for a 1060-nm signal, for example.
Lane Detection Algorithm for Night-time Digital Image Based on Distribution Feature of Boundary Pixels
You, Feng ; Zhang, Ronghui ; Zhong, Lingshu ; Wang, Haiwei ; Xu, Jianmin ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 188~199
DOI : 10.3807/JOSK.2013.17.2.188
This paper presents a novel algorithm for nighttime detection of the lane markers painted on a road at night. First of all, the proposed algorithm uses neighborhood average filtering, 8-directional Sobel operator and thresholding segmentation based on OTSU's to handle raw lane images taken from a digital CCD camera. Secondly, combining intensity map and gradient map, we analyze the distribution features of pixels on boundaries of lanes in the nighttime and construct 4 feature sets for these points, which are helpful to supply with sufficient data related to lane boundaries to detect lane markers much more robustly. Then, the searching method in multiple directions- horizontal, vertical and diagonal directions, is conducted to eliminate the noise points on lane boundaries. Adapted Hough transformation is utilized to obtain the feature parameters related to the lane edge. The proposed algorithm can not only significantly improve detection performance for the lane marker, but it requires less computational power. Finally, the algorithm is proved to be reliable and robust in lane detection in a nighttime scenario.
Fast Fringe-field-switching Liquid Crystal Cell with a Protrusion Structure
Park, Sung Il ; Choi, Sun-Wook ; Kim, Ki-Han ; Song, Dong Han ; Shim, Yu Ri ; Lee, Sun Yong ; Kang, Sung Gu ; Yoon, Jeong Hwan ; Kim, Byeong Koo ; Yoon, Tae-Hoon ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 200~204
DOI : 10.3807/JOSK.2013.17.2.200
We propose a cell structure for the fast switching of liquid crystals by the fringe field. By forming protrusion between patterned electrodes, we can obtain enhancement of response time. The protrusion reduces the effective cell gap, with which a fast response time can be realized. There is little decrease in the transmittance because the protrusion is located between patterned electrodes. We confirmed that the total response time can be decreased by 33% with little loss of the transmittance by optimizing the shape of the protrusion structure.
Evaluation of Diffuse Reflectance in Multi-layered Tissue for High Intensity Laser Therapy
Lee, Sangkwan ; Youn, Jong-In ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 205~212
DOI : 10.3807/JOSK.2013.17.2.205
Pain is one of the quite common symptoms in clinics and many treatment methods have been applied to relieve pain. Among the treatments, high-intensity light therapy for pain has been introduced, but this therapy has not been fully supported by confirmed efficacy due to the absence of quantitative assessments and treatment feedback data in real time. In this study, the evaluation of light distribution in tissue was performed with current high-intensity light sources quantitatively using light-tissue interaction simulations. The diffuse reflectance in tissue was generated using Monte Carlo simulation that traces photons as they undergo multiple scattering and absorption within each tissue layer (skin, fat, and muscle) and within multi-layered tissue. The results showed that the highest diffuse reflectance and the deepest penetration of tissue were achieved at
=830 nm when compared with other wavelengths like
=650 nm, 980 nm and 1064 nm.
New Non-uniformity Correction Approach for Infrared Focal Plane Arrays Imaging
Qu, Hui-Ming ; Gong, Jing-Tan ; Huang, Yuan ; Chen, Qian ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 213~218
DOI : 10.3807/JOSK.2013.17.2.213
Although infrared focal plane array (IRFPA) detectors have been commonly used, non-uniformity correction (NUC) remains an important problem in the infrared imaging realm. Non-uniformity severely degrades image quality and affects radiometric accuracy in infrared imaging applications. Residual non-uniformity (RNU) significantly affects the detection range of infrared surveillance and reconnaissance systems. More effort should be exerted to improve IRFPA uniformity. A novel NUC method that considers the surrounding temperature variation compensation is proposed based on the binary nonlinear non-uniformity theory model. The implementing procedure is described in detail. This approach simultaneously corrects response nonlinearity and compensates for the influence of surrounding temperature shift. Both qualitative evaluation and quantitative test comparison are performed among several correction technologies. The experimental result shows that the residual non-uniformity, which is corrected by the proposed method, is steady at approximately 0.02 percentage points within the target temperature range of 283 K to 373 K. Real-time imaging shows that the proposed method improves image quality better than traditional techniques.
Predicting of Uncorrected Astigmatism from Decimal Visual Acuity in Spherical Equivalent
Moon, Byeong-Yeon ; Kim, Sang-Yoeb ; Cho, Hyun Gug ;
Journal of the Optical Society of Korea, volume 17, issue 2, 2013, Pages 219~223
DOI : 10.3807/JOSK.2013.17.2.219
The purpose of this study was to determine the relationship between the spherical equivalent visual acuity (VA) and uncorrected astigmatism. On 108 emmetropic eyes, the spherical equivalent VA was measured for cross cylindrical lens (CC lens)-induced astigmatic eyes and the VA-astigmatism relation determined. On 158 astigmatic eyes, the spherical equivalent VA and corrected astigmatism were measured and the measured values were compared with the calculated values from the VA-astigmatism relation by correlation coefficient analysis. Subsequent to that, the relationship between spherical equivalent VA and uncorrected astigmatism was made. The relationship was fitted for an exponential equation. Correlation coefficient between calculated values by equation and measured values for astigmatic eyes was 0.991 (p<0.01). The relationship between the spherical equivalent VA and the uncorrected astigmatism was decided as follows (spherical equivalent VA / uncorrected astigmatism): 1.0 / 0.25 D, 0.9 / 0.50 D, 0.8 / 0.75 D, 0.7 / 1.00 D, 0.6 / 1.25 D, 0.5 / 1.50 D, 0.4 / 2.00 D, 0.3 / 2.50 D, 0.2 / 3.00 D, 0.1 / 4.00 D, and 0.05 / 4.75 D. In conclusion, the relationship table devised from this study is a useful reference for predicting uncorrected astigmatism by measurement of decimal VA in spherical equivalent.