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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 20, Issue 4 - Aug 2016
Volume 20, Issue 3 - Jun 2016
Volume 20, Issue 2 - Apr 2016
Volume 20, Issue 1 - Feb 2016
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Impact of Receiver on In-Band Crosstalk-Induced Penalties in Differentially Phase-Modulated Signals
Hu, Qikai ; Kim, Hoon ; Kim, Chul Han ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 223~227
DOI : 10.3807/JOSK.2016.20.2.223
The impact of optical receiver configuration on in-band crosstalk-induced penalty has been investigated in both theoretical and experimental analyses, for differential phase-shift keying (DPSK) and differential quadrature phase-shift keying (DQPSK) signals. Previously it has been shown that DPSK signals are ~6 dB more tolerant to in-band crosstalk than on-off keying (OOK) signals. However, we find that the tolerance difference between the two signals is reduced to ~3 dB when the decision threshold of the receiver is optimized to minimize the bit-error rate for each signal. Then we derive simple equations for the in-band crosstalk-induced penalty in DPSK and DQPSK signals with two different optical receiver configurations: balanced and single-ended direct-detection receivers. We confirm that the penalties obtained from our simple equations agree well with the measured results.
Information Authentication of Three-Dimensional Photon Counting Double Random Phase Encryption Using Nonlinear Maximum Average Correlation Height Filter
Jang, Jae-Young ; Inoue, Kotaro ; Lee, Min-Chul ; Cho, Myungjin ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 228~233
DOI : 10.3807/JOSK.2016.20.2.228
In this paper, we propose a nonlinear maximum average correlation height (MACH) filter for information authentication of photon counting double random phase encryption (DRPE). To enhance the security of DRPE, photon counting imaging can be applied because of its sparseness. However, under severely photon-starved conditions, information authentication of DRPE may not be implemented successfully. To visualize the photon counting DRPE, a three-dimensional imaging technique such as integral imaging can be used. In addition, a nonlinear MACH filter can be utilized for helping the information authentication. Therefore, in this paper, we use integral imaging and nonlinear MACH filter to implement the information authentication of photon counting DRPE. To verify our method, we implement optical experiments and computer simulation.
Design of a Low Distortion Head-Mounted Display with Freeform Reflective Mirror Based on Two Ellipsoids Structure
Wang, Junhua ; Liang, Yuechao ; Xu, Min ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 234~238
DOI : 10.3807/JOSK.2016.20.2.234
A new method to design a low distortion, even relative illumination, optical see-through head-mounted display (HMD) with a freeform reflective mirror (FFRM) based on the two similar ellipsoids structure is proposed. The HMD we have realized has a simple structure which consists of two similar ellipsoid surfaces, an FFRM, a 7-piece co-axis relay lens, and an OLED. This structure can be applied to offset distortion, reach even relative illumination, and correct the off-axis aberrations. The HMD we finally have realized has a near 3% low distortion, a higher than 80% relative illumination, and a 40°×30° field of view (FOV).
A Novel Approach to Mugshot Based Arbitrary View Face Recognition
Zeng, Dan ; Long, Shuqin ; Li, Jing ; Zhao, Qijun ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 239~244
DOI : 10.3807/JOSK.2016.20.2.239
Mugshot face images, routinely collected by police, usually contain both frontal and profile views. Existing automated face recognition methods exploited mugshot databases by enlarging the gallery with synthetic multi-view face images generated from the mugshot face images. This paper, instead, proposes to match the query arbitrary view face image directly to the enrolled frontal and profile face images. During matching, the 3D face shape model reconstructed from the mugshot face images is used to establish corresponding semantic parts between query and gallery face images, based on which comparison is done. The final recognition result is obtained by fusing the matching results with frontal and profile face images. Compared with previous methods, the proposed method better utilizes mugshot databases without using synthetic face images that may have artifacts. Its effectiveness has been demonstrated on the Color FERET and CMU PIE databases.
Single Exposure Imaging of Talbot Carpets and Resolution Characterization of Detectors for Micro- and Nano- Patterns
Kim, Hyun-su ; Danylyuk, Serhiy ; Brocklesby, William S. ; Juschkin, Larissa ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 245~250
DOI : 10.3807/JOSK.2016.20.2.245
In this paper, we demonstrate a self-imaging technique that can visualize longitudinal interference patterns behind periodically-structured objects, which is often referred to as Talbot carpet. Talbot carpet is of great interest due to ever-decreasing scale of interference features. We demonstrate experimentally that Talbot carpets can be imaged in a single exposure configuration revealing a broad spectrum of multi-scale features. We have performed rigorous diffraction simulations for showing that Talbot carpet print can produce ever-decreasing structures down to limits set by mask feature sizes. This demonstrates that large-scale pattern masks may be used for direct printing of features with substantially smaller scales. This approach is also useful for characterization of image sensors and recording media.
Simulation Research on the Thermal Effects in Dipolar Illuminated Lithography
Yao, Changcheng ; Gong, Yan ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 251~256
DOI : 10.3807/JOSK.2016.20.2.251
The prediction of thermal effects in lithography projection objective plays a significant role in the real-time dynamic compensation of thermal aberrations. For the illuminated lithography projection objective, this paper applies finite element analysis to get the temperature distribution, surface deformation and stress data. To improve the efficiency, a temperature distribution function model is proposed to use for the simulation of thermal aberrations with the help of optical analysis software CODE V. SigFit is approved integrated optomechanical analysis software with the feature of calculating OPD effects due to temperature change, and it is utilized to prove the validation of the temperature distribution function. Results show that the impact of surface deformation and stress is negligible compared with the refractive index change; astigmatisms and 4-foil aberrations dominate in the thermal aberration, about 1.7 λ and 0.45 λ. The system takes about one hour to reach thermal equilibrium and the contrast of the imaging of dense lines get worse as time goes on.
Design and Simulation of Two-Dimensional OCDMA En/Decoder Composed of Double Ring Add/Drop Filters and Delay Waveguides
Chung, Youngchul ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 257~262
DOI : 10.3807/JOSK.2016.20.2.257
A two-dimensional optical code division multiple access (OCDMA) en/decoder composed of four double-ring resonator add/drop filters and three delay waveguides is designed, and a transfer matrix method combined with fast Fourier transform is implemented to provide numerical simulations for the en/decoder. The auto-correlation peak level over the maximum cross-correlation level is larger than 3 at the center of the correctly decoded pulse for most of wavelength hopping and spectral phase code combinations, which assures the BER lower than 10
which corresponds to the forward error correction limit.
Broadband and Polarization Independent Terahertz Metamaterial Filters Using Metal-Dielectric-Metal Complementary Ring Structure
Qi, Limei ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 263~268
DOI : 10.3807/JOSK.2016.20.2.263
Broadband metal-dielectric-metal terahertz filters composed of complementary rings are designed and demonstrated. Four samples with different parameters were fabricated. Results measured using THz time-domain spectroscopy system show excellent agreement with simulations. Compared with the broadband filters reported before, the complementary ring structure in our design is insensitive to any polarization at normal incidence due to symmetry of the ring. Furthermore, the influence of structure parameters (such as period, radius, slot width, thickness and incidence angles) on the transmission characteristics has been investigated theoretically. The encouraging results afforded by designing of the filters could find applications in broadband sensors, terahertz communication systems, and other emerging terahertz technologies.
Near-Infrared Laser Stimulation of the Auditory Nerve in Guinea Pigs
Guan, Tian ; Wang, Jian ; Yang, Muqun ; Zhu, Kai ; Wang, Yong ; Nie, Guohui ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 269~275
DOI : 10.3807/JOSK.2016.20.2.269
This study has investigated the feasibility of 980-nm low-energy pulsed near-infrared laser stimulation to evoke auditory responses, as well as the effects of radiant exposure and pulse duration on auditory responses. In the experiments, a hole was drilled in the basal turn of the cochlea in guinea pigs. An optical fiber with a 980-nm pulsed infrared laser was inserted into the hole, orientating the spiral ganglion cells in the cochlea. To model deafness, the tympanic membrane was mechanically damaged. Acoustically evoked compound action potentials (ACAPs) were recorded before and after deafness, and optically evoked compound action potentials (OCAPs) were recorded after deafness. Similar spatial selectivity between optical and acoustical stimulation was found. In addition, OCAP amplitudes increased with radiant exposure, indicating a photothermal mechanism induced by optical stimulation. Furthermore, at a fixed radiant exposure, OCAP amplitudes decreased as pulse duration increased, suggesting that optical stimulation might be governed by the time duration over which the energy is delivered. Thus, the current experiments have demonstrated that a 980-nm pulsed near-infrared laser with low energy can evoke auditory neural responses similar to those evoked by acoustical stimulation. This approach could be used to develop optical cochlear implants.
2 Gbit/s VLC Scheme Using Time-Frequency Color-Clustered MIMO Based on BCYR LEDs
Han, Phyu Phyu ; Sewaiwar, Atul ; Chung, Yeon-Ho ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 276~282
DOI : 10.3807/JOSK.2016.20.2.276
A 2 Gbit/s visible-light communication (VLC) scheme using time-frequency color-clustered (TFCC) multiple-input multiple-output (MIMO) based on blue, cyan, yellow, and red (BCYR) light-emitting diodes (LEDs) is presented. In the proposed scheme, BCYR LEDs are employed to form four different color clusters. Data transmission using the four color clusters is performed in MIMO, so that the scheme achieves a very high speed of data transmission. Moreover, the scheme employs the TFCC strategy to yield high performance in terms of bit error rate (BER). TFCC operates in such a way that the original data and the two delayed versions of the data are multiplied by orthogonal frequencies and then transmitted using a specific color of the BCYR LED. In the receiver, color filters are employed to detect the data transmitted from the desired cluster. Selection combining (SC) is also performed to yield a diversity effect within each color cluster, to further improve the performance. Performance evaluation demonstrates that the proposed TFCC MIMO VLC offers a data rate of 2 Gbit/s and a bit error rate of 4×10
, at an E
value of merely 3 dB.
Design of an 8x Four-group Inner-focus Zoom System Using a Focus Tunable Lens
Lee, Daye ; Park, Sung-Chan ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 283~290
DOI : 10.3807/JOSK.2016.20.2.283
This study presents an 8x four-group inner-focus zoom lens with one-moving group for a compact camera by use of a focus tunable lens (FTL). In the initial design stage, we obtained the powers of lens groups by paraxial design based on thin lens theory, and then set up the zoom system composed of four lens modules. Instead of numerically analytic analysis for the zoom locus, we suggest simple analysis for that using lens modules optimized. After replacing four groups with equivalent thick lens modules, the power of the fourth group, which includes a focus tunable lens, is designed to be changed to fix the image plane at all positions. From this design process, we can realize an 8x four-group zoom system having one moving group by employing a focus tunable lens. The final designed zoom lens has focal lengths of 4 mm to 32 mm and apertures of F/3.5 to F/4.5 at wide and tele positions, respectively.
Comparative Study of Uniform and Nonuniform Grating Couplers for Optimized Fiber Coupling to Silicon Waveguides
Lee, Moon Hyeok ; Jo, Jae Young ; Kim, Dong Wook ; Kim, Yudeuk ; Kim, Kyong Hon ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 291~299
DOI : 10.3807/JOSK.2016.20.2.291
We have investigated the ultimate limits of nonuniform grating couplers (NGCs) for optimized fiber coupling to silicon waveguides, compared to uniform grating couplers (UGCs). Simple grating coupler schemes, which can be fabricated in etching steps of the conventional complementary metal-oxide semiconductor (CMOS) process on silicon-on-insulator (SOI) wafers without forming any additional overlay structure, have been simulated numerically and demonstrated experimentally. Optimum values of the grating period, fill factor, and groove number for ultimate coupling efficiency of the NGCs are determined from finite-difference time-domain (FDTD) simulation, and confirmed with experimentally demonstrated devices by comparison to those for the UGCs. Our simulated results indicate that maximum coupling efficiency of NGCs is possible when the minimum pattern size is below 50 nm, but the experimental value for the maximum coupling efficiency is limited by the attainable fabrication tolerance in a practical device process.
Dual Loop Optoelectronic Oscillator with Acousto-Optic Delay Line
Kim, Tae Hyun ; Lee, Sangkyung ; Lee, Chang Hwa ; Yim, Sin Hyuk ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 300~304
DOI : 10.3807/JOSK.2016.20.2.300
A dual loop optoelectronic oscillator (OEO) based on an acousto-optic modulator (AOM) for single mode operation with an acousto-optic delay line is demonstrated in this paper. When the OEO operates, the free spectral range is a function of the total loop length of the OEO, which is mainly dependent on the propagation time of the acoustic wave in the AOM. Due to the huge difference in the magnitude between the speed of light and the acoustic velocity in the AOM, the effective loop length converted to light-propagation length of the OEO increases to 3.8 km. With 150 MHz oscillation frequency, phase noise of -118 dBc/Hz at 10 kHz frequency offset, and -140 dBc/Hz at 200 kHz frequency offset, is achieved.
Review of Neurosurgical Fluorescence Imaging Systems for Clinical Application
Kim, Hong Rae ; Lee, Hyun Min ; Yoo, Heon ; Lee, Seung Hoon ; Kim, Kwang Gi ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 305~313
DOI : 10.3807/JOSK.2016.20.2.305
A number of fluorescence imaging techniques for use in the surgical removal of glioma have been developed over the course of the long history of neurosurgery. Various biomarkers, biochemical agents, and detection systems for glioma have also been developed. This review focuses on 5-aminolevulinic acid (5-ALA), which is used to detect glioma. Numerous forms of fluorescence-guided surgery use 5-ALA, which is helpful to the surgeon. The surgical microscope system is the observational method generally used with 5-ALA, while the loupe, endoscope, and exoscope are simpler alternatives. A system is needed for minimal resection and other issues that arise during neurosurgery. Such an enhanced system should be able to detect low-grade tumors and provide information on microinvasive diseases, resulting in an improved survival rate and better surgical skills. Development of systems that fulfill certain needs would help protect the brain function of the patient and broaden the use of such systems in neurosurgery.
Numerical and Experimental Investigation of the Heating Process of Glass Thermal Slumping
Zhao, Dachun ; Liu, Peng ; He, Lingping ; Chen, Bo ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 314~320
DOI : 10.3807/JOSK.2016.20.2.314
The glass thermal forming process provides a high volume, low cost approach to producing aspherical reflectors for x-ray optics. Thin glass sheets are shaped into mirror segments by replicating the mold shape at high temperature. Heating parameters in the glass thermal slumping process are crucial to improve surface quality of the formed glass. In this research, the heating process of a thermal slumping glass sheet on a concave parabolic mold was simulated with the finite-element method (FEM) to investigate the effects of heating rate and soaking temperature. Based on the optimized heating conditions, glass samples 0.5 mm thick were formed in a furnace with a steel concave parabolic mold. The figure errors of the formed glass were measured and discussed in detail. It was found that the formed glass was not fully slumped at the edges, and should be trimmed to achieve better surface deviation. The root-mean-square (RMS) deviation and peak-valley (PV) deviation between formed glass and mold along the axial direction were 2.3 μm and 4.7 μm respectively.
Transformation Optics Methodology for Changing the Appearance of an Object
Li, Yanxiu ; Kong, Fanmin ; Li, Kang ;
Journal of the Optical Society of Korea, volume 20, issue 2, 2016, Pages 321~324
DOI : 10.3807/JOSK.2016.20.2.321
Transformation optics methodology provides a new pathway for designing novel devices. It is based on changing a material’s permittivity and permeability. A design for changing the appearance of an object by transformation optics methodology is proposed here. Through a certain transformation, the relations of the metric spaces and the calculation of the material parameters are derived, and the aim of changing the apparent size of an object can be realized. Full wave simulations are performed to validate the proposed device’s performance. It is possible to think that the methodology will improve the flexibility of designing interesting applications in microwave and optical regimes.