• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.9
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• pp.751-756
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• 2012

In this paper, we propose a foreground extraction and depth map generation method using a time-of-flight (TOF) depth camera. Although, the TOF depth camera captures the scene's depth information in real-time, it has a built-in noise and distortion. Therefore, we perform several preprocessing steps such as image enhancement, segmentation, and 3D warping, and then use the TOF depth data to generate the depth-discontinuity regions. Then, we extract the foreground object and generate the depth map as of the color image. The experimental results show that the proposed method efficiently generates the depth map even for the object boundary and textureless regions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.3
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• pp.643-650
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• 2014

A hardware implementation of phase calculator for extracting 3D depth image from TOF(Time-Of-Flight) sensor is described. The designed phase calculator adopts redundant binary number systems and a pipelined architecture to improve throughput and speed. It performs arctangent operation using vectoring mode of DCORDIC(Differential COordinate Rotation DIgital Computer) algorithm. Fixed-point MATLAB simulations are carried out to determine the optimal bit-widths and number of iteration. The phase calculator has ben verified by FPGA-in-the-loop verification using MATLAB/Simulink. A test chip has been fabricated using a TSMC $0.18-{\mu}m$ CMOS process, and test results show that the chip functions correctly. It has 82,000 gates and the estimated throughput is 400 MS/s at 400Mhz@1.8V.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.219-224
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• 2011

In this study, a piezoelectric smart sensor that can be embedded inside of concrete structures is developed to investigate the early stage of concrete curing. A waterproof coating is used to protect the piezoelectric sensor from moistures of concrete mixture. Also, a mortar case is utilized to encapsulate the sensor to protect it from impact loads. To estimate the strength of concrete, a self-sense guided-wave actuated sensing technique is applied. In the guided wave, its velocity is varied according to the mechanical properties of concrete such as modulus of elasticity. Because modulus of elasticity directly affects the strength of concrete, the guidedwave's velocity also affects the concrete strength development. To verify the feasibility of using the proposed approach, the smart sensor was embedded into a 100MPa concrete cylinder and the self-sense guided wave is continuously measured throughout the curing process. The measurements showed that the propagation time (TOF) of the measured guided waves gradually decreased as the curing age increased. Especially, at the early age of the curing process, the variation of the TOF was very significant. Furthermore, the results showed that there is a linear relationship between the TOF of the self-sense guided waves and the strength of concrete existed. It is safe to conclude that the proposed approach can be used very effectively in monitoring of the strength development of high strength concrete structures.

• Journal of the Korean Society of Radiology
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• v.13 no.6
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• pp.841-846
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• 2019

Effect of misalignment on the performance was evaluated for the development of time-of-flight(TOF)-PET detector. A pair of TOF-PET detector consists of Lutetium-yttrium oxyorthosilicate(LYSO) scintillation crystal with a volume of 3 mm × 3 mm × 20 mm and Geiger-mode avalanche photodiodes(GAPD) photo-sensor with a active area of 3.07 mm × 3.07 mm. Analog output signals from TOF-PET detector were sent to the pre-amplifier and then fed into the gain adjust circuit for achievement of gain homogeneity for each detector. The amplified signals were recorded and digitized by data acquisition system based on oscilloscope. The effect of the detector misalignment between LYSO and GAPD was examined for four different alignment offsets of 0.0 mm, 0.5 mm, 1.0 mm and 1.5 mm for a pair of TOF-PET detector. The photopeak position decreased from ~400 mV to ~250 mV with increasing detector misalignment. the energy resolution and time resolution were degraded from 11.6% to 16.2%, and from 477 ps to 632 ps, respectively. This study demonstrated that PET detector performance was degraded considerably depending on the detector misalignment, which would be a critical issue for the development of TOF-PET detector.

• The KIPS Transactions:PartC
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• v.15C no.1
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• pp.31-36
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• 2008

The clock frequency difference of sensor nodes is one of main parameters in TOF estimation and affect to degrade ranging algorithms to estimate positions of mobile nodes in wireless sensor networks. The specification of IEEE802.15.4a describes asynchronous TWR and SDS-TWR insensitive to frequency difference without any additional network synchronization. But the TWR and SDS-TWR can not eliminate sufficiently the effect of frequency difference of node pair, packet processing delay and its difference. Especially use of low cost oscillator with wide range offset, sensor node with different hardware and software can make the positioning errors worse. We propose an estimation method of frequency differences, and apply the measured frequency differences to TWR and SDS-TWR. We evaluate the performance of the proposed algorithm with simulation, and make certain that the proposed method enhances the performance of existing algorithms with positioning errors less than 25 cm.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.595-597
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• 2004

In this paper range measurement systems using ultrasonic and visual sensors are designed. By varying the focus of a camera, the range to a target pattern is computed. Pour different methods are tested for the focusing-based range measurement. The best result is obtained when counting edge pixels found by Laplacian operator. Higher accuracy can be obtained by fusing the measurement of camera focusing with that of ultrasonic sensor. The system designed is experimented within the range of 300-450mm.

• Journal of Sensor Science and Technology
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• v.23 no.1
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• pp.46-50
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• 2014

In this paper, we report a novel algorithm based on phase displacement, which supplements conventional TOF methods for distance measurement using an ultrasonic wave. The proposed algorithm roughly measures the distance between the transmission part and the receiving part by using the initial TOF. Thereafter, the precise distance is determined by measuring the phase displacement value between the synchronizing transmission signal and the signal obtained at the receiving end. A distance measurement experiment using a micrometer was performed to verify the accuracy of the ultrasonic wave sensor system. We found that the mean errors from the one adopting the distance measurement algorithm based on phase displacement varied from a minimum of 0.03 mm to a maximum of 0.09 mm. In addition, the standard deviation varied from a minimum of 0.04 mm to a maximum of 0.07 mm, thus giving a precision of ${\pm}0.1$ mm.

• Journal of Sensor Science and Technology
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• v.21 no.1
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• pp.13-20
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• 2012

Due to its high conductivity, pyrylium has been frequently used in electron transfer reactions or in the synthesis of various organic materials. It has also been used as a sensor material. Traditionally, the compounds have been synthesized using various methods; mostly in a multiple steps. In this study, two pyrylium salts, 2, 6-di-(4'-methylphenyl) pyrylium fluoroborate and perchlorate were synthesized. The synthesis of these products was confirmed by 1H-NMR, LC/TOF-MS and FT-IR analyses while their photo-properties were analyzed using UV/VIS spectrophotometry. In addition, the electron transfer capacities of the salts were analyzed with a conductivity meter, it was found that their electron conductivities were high. When the synthesized compounds were dissolved in acetone, a green fluorescent material was observed to form. The fluorescent material can be used as a sensitizer in the electrical industry.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.198-201
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• 2012

This is a study about a platform realization measuring the extent of reaction in nerve, as giving a electrical impulse on a nerve pulp regulating a function of muscle, about a measurement of nerve reaction in the amount of current, the lasting time of current, and the position of electrode from a electrical impuls. The position of an electrode in a electrical nerve impuls have nothing to do with all nerves from exercise to all things. There is the Single Twitch Stimulation, Train-of-four, and Double Burst Stimulation in the form of nerve stimulation. This report is needed for selecting MCU of low electric power for a base in embedded system and measuring the extent of reaction after making a sensor interface to know sensitivity of measuring sensor in basic reaction of nerve impuls. The platform is realized to select a high efficiency AD Convertor for raising accuracy in measured data. As the platform in this report was developed for a medical appliances, it was designed to consider user safety in electric power Isolation when making electric power circuit.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.6
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• pp.733-742
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• 2017

LADARs are used for important sensors in various applications, for example, terrain information sensors in self driving cars, safety sensors for factory automation, and 3D map constructions. This study develop important component technologies to improve the performance of a LADAR system under development in Korea. The component technologies include diode temperature regulation, reducing distance error in outdoor environment, and signal processing technique for better detection of distant objects. This paper explains the suggested component technologies and experimental results of the developed LADAR system. Also, the developed system is operated and tested an a single axis driving platform to acquire 3D information from 2D LADAR.