• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.6
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• pp.785-791
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• 2021

In this paper, we propose a methodology for estimating the optimal traversable destination from the location-based information of the object recognized by the mobile robot to perform the object delivery service. The location estimation process is to apply the generalized Voronoi graph to the grid map to create an initial topology map composed of nodes and links, recognize objects and extract location data using RGB-D sensors, and collect the shape and distance information of obstacles. Then, by applying the hybrid approach that combines the center of gravity and thinning method, the optimal moving position for the service robot to perform the task of grabbing is estimated. And then, the optimal node information for the robot's work destination is updated by comparing the geometric distance between the estimated position and the existing node according to the node update rule.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.4
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• pp.305-312
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• 2005

In this thesis, Lohmann's algorithm and FFT (fast Fourier transform) are used to synthesize binary-phase holograms. FFT computing is carried out for the calculation of complex wavefronts of $128{\times}128$ sampling points of an object that is numerically specified. Then using the Lohmann's algorithm, the amplitude and the phase of complex wavefronts are encoded in binary holograms on each sampling points. PC (personal computer) and laser printer are used to plot binary-phase holograms and CGH (computer generated holograms) films are obtained from this plot by photographic reduction. Holographic images of numerically specified objects are reconstructed from the He-Ne laser and the inverse Fourier optics system. We estimate the quality of holographic images according to the sampling number, application of random phase, amplitude clipping and bleaching the CGH film. We derive optimized conditions to reconstruct better holographic images and to reduce the speckle noise. FFT and Lohmann's algorithm are implemented with MS Visual BASIC 6.0 for the programming of binary-phase hologram.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.6
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• pp.561-566
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• 2015

In this paper, the operating stiffness of a parallel robot used to handle heavy packages is optimized. Because the studied model, called a "pick and place robot," is applied for packaging logistics, it is important for the robot to be lightweight so that it may respond rapidly and have high stiffness to allow sufficient operating precision. However, these two requirements of low weight and high stiffness are mutually exclusive. Thus, the dynamic characteristics of the robot are analyzed through multibody dynamics analysis, and topology optimization is conducted to achieve this exclusive performance. Lastly, the reliability of the topology optimization is verified by applying the optimized design to the parallel robot.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.455-463
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• 2007

In this paper, it is proposed how to implement the object detection system which is able to apply to vehicular applications, unmanned facilities, automatic door and others with microwave. As the technology which detects an object with microwave is becoming more popular, it seems impossible to avoid mutual interference and jamming caused by limited frequency bandwidth. The system in this paper detects an object by correlating the code of TX and RX signals with the pseudo-random code having best quality in interference and jamming environment. In order to generate simulant doppler signal for detecting the distance of an fixed object where there is no doppler effect, the phase of TX signal is shifted continually. Also, the saturation of receiver was removed and the error of distance measurement was decreased by controlling the power of TX signal for getting constant RX signal. The proposed system detects a object which ranges from 0.5 m to 2.0 m and informs vocally whether there is the object within 1.0 m or not.

• Korean Journal of Optics and Photonics
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• v.27 no.3
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• pp.101-105
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• 2016

In this study we propose the novel optimization method of the phase-only computer-generated hologram (CGH), to improve calculation speed compared to the conventional method. While the conventional method is calculated using numerical analysis, the novel method is calculated using the phase-shift characteristic of Fourier transformation. In addition, the selectivity of noise filtering lets it decrease the calculation time. The validity of the reconstructed image using the novel method is verified by comparing simulation results to ideal and conventional data, and the improvement of texture and sharpness of the reconstructed image is confirmed by simulation.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.311-313
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• 2020

컴퓨터 생성 홀로그램(CGH)에서 시야각은 매우 중요한 특성이다. 시야각에 따라 홀로그램을 볼 수 있는 영역이 결정되며 시야각을 넘어가게 되면 재구성된 오브젝트가 잘려 보이게 된다. CGH의 최대 시야각은 회절 격자 방정식에 의해 결정이 되며, 해당 수식에 따르면 홀로그램 재생 장치인 공간 광 변조기(SLM)의 픽셀 피치에 반비례한다. SLM의 픽셀 피치를 줄이는 것은 어렵고 비용이 많이 들기 때문에 본 논문에서는 고해상도 랜덤 바이너리 위상 마스크를 SLM에 부착하여 CGH의 시야각을 확장하는 방법을 제안한다. CGH를 계산하는데 자주 사용되는 반복 푸리에 변환 알고리즘(IFTA)에 위상 평균화 단계를 도입하여 SLM과 위상 마스크간의 픽셀 크기 및 개수의 차이를 극복하였다. 또한 스칼라 회절 이론을 바탕으로 한 홀로그램 시뮬레이션에 제안한 방법을 적용 후 가상 눈 모델을 도입하여 두 개의 물체로 이루어진 홀로그램을 재구성하고 여러 각도에서 관찰하여 시야각이 향상되는것을 검증하였다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.149-154
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• 2004

In the semiconductor and the optical industry a new transport system which can replace the conventional sliding system is required. These systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problem. In this paper, the relationship of transporting speed according to the change of flexural beam shape and the effect of transporting speed according to the change of weight and amplification voltage are verified. The vibration behavior of flexural beam in the ultrasonic transport system is experimented using Laser Scanning Vibrometer.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.25-29
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• 2003

In the semiconductor and the optical industry a new transport system which can replace the conventional sliding system is required. These systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problem. In this paper, the object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal excitation frequency, finding phase-difference between two ultrasonic wave generators are performed. The relationship of transporting speed according to the change of flexural beam shape is verified and the system performance for practical use is evaluated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1170-1173
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• 2003

In the semiconductor and the optical industry a new transport system which can replace the common system is required. The common systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches, the optical lens. The ultrasonic wave driven system solve these problem. In this paper the object transport system using the excitation of ultrasonic wave is proposed. the experiments for finding the optimal excitation frequency, finding phase-difference between two ultrasonic wave generators are performed. The effect of transporting speed according to the change of amplification voltage is verified. In addition, the system performance for actual use is evaluated

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.151-158
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• 2005

In the semiconductor and the optical industry, a new transport system which can replace the conventional sliding systems is required. The sliding systems are driven by the magnetic field and conveyer belts. The magnetic field nay damage semiconductor and the contact force may scratch the optical lens. The ultrasonic wave driven system can solve these problems. In this paper, an object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal progressive frequency and the phase-differences between two ultrasonic wave generators are performed. The relationships between transportation speed and the excitation frequency, flexural beam shapes and amplification voltage are investigated.