• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.3 s.303
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• pp.51-64
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• 2005

The proposed algorithm is to achieve the robust optical flow detection which is applicable for the case that the outlier rate is over $80\%$. If the outlier rate of optical flows is over $30\%$, the discrimination between the inliers and outlier with the conventional algorithm is very difficult. The proposed algorithm is to overcome such difficulty withthree steps of grouping algorithm; 1) constructing the 2 D histogram with two axies of the lengths and the directions of optical flows. 2) sorting the number of optical flows in each bin of the two-dimensional histogram in the descendingorder and removing some bins with lower number of optical flows than threshold 3) increasing the resolution of the two-dimensional histogram if the number of optical flows in a specific bin is over $20\%$ and decreasing theresolution if the number of optical flows is less than $10\%$. Such processing is repeated until the the number of optical flows falls into the range of $10\%-20\%$ in all the bins. The proposed algorithm works well on the different kinds of images with many of wrong optical flows. Experimental results are included.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.763-764
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• 2013

A three-dimensional image capturing device and its signal processing algorithm and apparatus are presented. Three dimensional information is one of emerging differentiators that provides consumers with more realistic and immersive experiences in user interface, game, 3D-virtual reality, and 3D display. It has the depth information of a scene together with conventional color image so that full-information of real life that human eyes experience can be captured, recorded and reproduced. 20 Mega-Hertz-switching high speed image shutter device for 3D image capturing and its application to system prototype are presented[1,2]. For 3D image capturing, the system utilizes Time-of-Flight (TOF) principle by means of 20MHz high-speed micro-optical image modulator, so called 'optical resonator'. The high speed image modulation is obtained using the electro-optic operation of the multi-layer stacked structure having diffractive mirrors and optical resonance cavity which maximizes the magnitude of optical modulation[3,4]. The optical resonator is specially designed and fabricated realizing low resistance-capacitance cell structures having small RC-time constant. The optical shutter is positioned in front of a standard high resolution CMOS image sensor and modulates the IR image reflected from the object to capture a depth image (Figure 1). Suggested novel optical resonator enables capturing of a full HD depth image with depth accuracy of mm-scale, which is the largest depth image resolution among the-state-of-the-arts, which have been limited up to VGA. The 3D camera prototype realizes color/depth concurrent sensing optical architecture to capture 14Mp color and full HD depth images, simultaneously (Figure 2,3). The resulting high definition color/depth image and its capturing device have crucial impact on 3D business eco-system in IT industry especially as 3D image sensing means in the fields of 3D camera, gesture recognition, user interface, and 3D display. This paper presents MEMS-based optical resonator design, fabrication, 3D camera system prototype and signal processing algorithms.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1219-1222
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• 2005

As the optical communication is introduced to the backbone network at first and becomes a general communication method of network, the demand of kernel parts of optical communication such as PLC(Planar Light Circuit), Coupler, and WDM(Wavelength Division Multiplexing) element increases. The alignment and the attachment technology are very important in the fabrication of optical elements. In this paper, the driving mechanism of ultra precision stage is studied with the aim of optimal design of stage. The travel and the resolution of stage are investigated. The hysteresis of the stage is generated because of PZT actuator. The hysteresis and the inverse hysteresis are modeled in X, Y, and Z-axis motion. The input data of desired displacement to the stage according to input voltage is obtained from the inverse hysteresis equation. In the result of experiments with the input data, the errors due to hysteresis are well compensated.

• Smart Structures and Systems
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• v.1 no.1
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• pp.63-82
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• 2005

This paper introduces a technology for robust and low maintenance cost sensor network capable to detect accelerations below a micro-g in a wide frequency bandwidth (above 1,000 Hz). Sensor networks with such performance are critical for navigation, seismology, acoustic sensing, and for the health monitoring of civil structures. The approach is based on the fabrication of an array of high sensitivity accelerometers, each utilizing Fabry-Perot cavity with wavelength-dependent reflectivity to allow embedded optical detection and serialization. The unique feature of the approach is that no local power source is required for each individual sensor. Instead one global light source is used, providing an input optical signal which propagates through an optical fiber network from sensor-to-sensor. The information from each sensor is embedded onto the transmitted light as an intrinsic wavelength division multiplexed signal. This optical "rainbow" of data is then assessed providing real-time sensing information from each sensor node in the network. This paper introduces the Fabry-Perot based accelerometer and examines its critical features, including the effects of imperfections and resolution estimates. It then presents serialization techniques for the creation of systems of arrayed sensors and examines the effects of serialization on sensor response. Finally, a fabrication process is proposed to create test structures for the critical components of the device, which are dynamically characterized.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.100.2-100.2
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• 2014

The DOTIFS is a new multi-object Integral Field Spectrograph (IFS) planned to be designed and built by the Inter-University Center for Astronomy and Astrophysics, Pune, India, (IUCAA) for cassegrain side port of the 3.6m Devasthal Optical Telescope (DOT) being constructed by the Aryabhatta Research Institute of Observational Sciences, Nainital. (ARIES) It is a multi-integral field unit (IFU) spectrograph which has 370-740nm wavelength coverage with spectral resolution R~1200-2400. Sixteen IFUs with microlens arrays and fibers can be deployed on 8 arcmin field. Each IFU has $8.7^{{\prime}{\prime}}{\times}7.4^{{\prime}{\prime}}$ field of view with 144 spaxel elements. 2304 fibers coming from IFUs are dispersed by eight identical spectrographs with all refractive and all spherical optics. In this work, we show optical design of the DOTIFS spectrograph. Expected performance and result of tolerance and thermal analysis are also shown. The optics is comprised of f=520mm collimator, broadband filter, dispersion element and f=195mm camera. Pupil size is determined as 130mm from spectral resolution and budget requirements. To maintain good transmission down to 370nm, calcium fluoride elements and high transmission optical glasses have been used. Volume Phase Holographic grating is selected as a dispersion element to maximize the grating efficiency and to minimize the size of the optics. Detailed optics design report had been documented. The design was finalized through optical design review and now ready for order optics.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.3
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• pp.185-195
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• 2000

Detection of cracks in concrete beams using optical fiber sensors is useful for monitoring of concrete structures. In this study, optical time domain reflectometry (OTDR) is used to detect cracks. Resolution of OTDR is the main contributor to detect cracks in concrete structures. The OTDR used in this study can detect cracks with high precision of 0.5 m. Two mortar beams, reinforced with a 19 mm diameter steel bar, are made with the dimensions of 140 mm (width) ${\times}$ 200 mm (depth) ${\times}$ 2.000 mm (length). Two fibers are embedded inside each beam and two fibers are attached under the beams. The application of measurement system which consists of fiber and FC/PC connecter is studied. For this, theory of optics, resolution, crack moment, and size of specimens are investigated. From the measured data, it is verified that fibers which are attached under the beam can detect the crack in beams effectively. However, fibers embedded inside the beam are unable to detect cracks in beams using the OTDR in this study.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.81-86
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• 2005

As the optical communication is introduced to the backbone network at first and becomes a general communication method of network, the demand of kernel parts of optical communication such as PLC(Planar Light Circuit), Coupler, and WDM(Wavelength Division Multiplexing) element increases. The alignment and the attachment technology are very important in the fabrication of optical elements. In this paper, the driving mechanism of ultra precision stage is studied with the aim of optimal design of stage. The travel and the resolution of stage are investigated. The hysteresis of the stage is generated because of PZT actuator. The hysteresis and the inverse hysteresis are modeled in X, Y, and Z-axis motion. The input data of desired displacement to the stage according to input voltage is obtained from the inverse hysteresis equation. In the result of experiments with the input data, the errors due to hysteresis are well compensated.

• Korean Journal of Optics and Photonics
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• v.7 no.2
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• pp.101-111
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• 1996

Optical microscopes integrated with CCD cameras are widely used for automatic inspection of precision circuit patterns fabricated on glass masks and silicon wafers. For this application it is important to position the object always is focus so that the image appears in good quality while the microscope scans the object. However, as the magnification of the microscope is taken large for fine resolution the depth of focus becomes small, often in submicron ranges, requiring special care in focusing. This study proposes a new auto-focusing method, which can be readily incorporated in existing optical configuration of microscope. This method is based on optical triangulation using a separate beam of laser and two photodiodes, eliminating focus errors caused by surface roughness and waviness. Experimental results prove that the method can produce focus error signals which are very sensitive with a resolution of 5 nm within 0.5 ${\mu}{\textrm}{m}$ accuracy.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.1
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• pp.129-137
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• 2000

In this paper, a new method of noncontact measurement has been developed for a 3 dimensional topography in semiconductor wafer, implementing a new optical probe based on the precision defocus measurement. The developed technique consists of the new optical probe, precision stages, and the measurement/control system. The basic principle of the technique is to use the reflected slit beam from the specimen surface, and to measure the deviation of the specimen surface. The defocusing distance can be measured by the reflected slit beam, where the defocused image is measured by the proposed optical probe, giving very high resolution. The distance measuring formula has been proposed for the developed probe, using the laws of geometric optics. The precision calibration technique has been applied, giving about 10 nanometer resolution and 72 nanometer of four sigma uncertainty. In order to quantitize the micro pattern in the specimen surface, some efficient analysis algorithms have been developed to analyse the 3D topography pattern and some parameters of the surface. The developed system has been successfully applied to measure the wafer surface, demonstrating the line scanning feature and excellent 3 dimensional measurement capability.

• Bulletin of the Korean Chemical Society
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• v.11 no.5
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• pp.411-415
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• 1990

The dabsylation of amino acids has been applied to resolve their optical isomers with the use of chiral mobile phase in high performance liquid chromatography. The dabsyl amino acids were successfully separated on reversed phase column($C_{18}$) by adding a chiral L-benzylproline-Cu(II) chelate to the mobile phase. The separation selectivity of the dabsyl amino acid enantiomers was not less than that of dansyl amino acids. The retention order of the dabsyl amino acid enantiomers was as those of the dansyl amino acid enantiomers except dabsyl threonine. The optical selectivity of the dabsyl amino acids increase with pH of the mobile phase and concentration of the chelate, but slightly decreases with concentration of buffer and organic solvent composition. However serine, methionine, valine, and leucine showed a slight decrease in the optical selectivity with increase in pH. The retention times of the dabsyl amino acids decreases with increasing pH and acetonitrile concentration but increases with the concentration of the chiral chelate added. The mechanism of the optical resolution is based on a stereospecific interaction including a intramolecular hydrophobic effect and SN-2 reactivity of the ligand exchange chromatography.It is advantageous to detect absorption at 436 nm, which is less interferent them the other detection systems. The derivatized dabsyl amino acids are stable for a month.