• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.93-99
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• 2011

This paper presents a new type of optical silicon accelerometer using deep reactive ion etching (DRIE) and micro-stereolithography technology. Optical silicon accelerometer is based on a mass suspended by four vertical beams. A vertical shutter at the end of the mass can only moves along the sensing axis in the optical path between two single-mode optical fibers. The shutter modulates intensity of light from a laser diode reaching a photo detector. With the DRIE technique for (100) silicon, it is possible to etch a vertical shutter and beam. This ensures low sensitivity to accelerations that are not along the sensing axis. The microstructure for sensor packaging and optical fiber fixing was fabricated using micro stereolithography technology. Designed sensors are two types and each resonant frequency is about 15 kHz and 5 kHz.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5B
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• pp.397-404
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• 2006

As an increase in recent optical network-based IP services, GMPLS management framework becomes more important than ever before. In this paper, we propose the dynamic GMPLS path management algorithm, which can satisfy the users with their traffic engineering recovery requirements and find out the best backup service path under multiple link failures. To be more specific, we are deriving the soluble conditions of a backup path which is satisfied in a GMPLS network. In addition, through proposing the fast backup path selection algorithm, we can sufficiently satisfy a user's recovery requirement and minimally protect the suspension of the service against a link failure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3B
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• pp.72-84
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• 2005

Optical burst switching networks usually employ one-way reservation by sending a burst control packet with a specific offset time, before transmitting each data burst Same. Due to such a Property, burst-contentions occur when multiple bursts contend for the same wavelength in the same output link simultaneously in a node, leading to burst losses, eventually degrading the quality of service. Therefore, in this paper, we propose a dynamic routing algorithm using minimum local state information in order to decrease burst-contentions. In this proposed scheme, if burst loss rate exceeds a threshold value at a certain node, a new alternative routing path is chosen according to burst priority and location of burst generation, which enables the contending bursts to detour around the congested link. Moreover, for reducing the effect of sending bursts on the primary path due to the alternative path, we also apply a minimum path-cost based routing on link-cost concept. Our simulation results show that proposed scheme improves the network performance in terms of burst loss probability and throughput by comparing with conventional one.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.2
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• pp.186-194
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• 2004

Micro-stereolithography is a newly proposed technology as a means that can fabricate a 3D micro-structure of free form. It makes a 3D micro-structure by dividing the shape into many slices of relevant thickness along horizontal surfaces, hardening each layer of slice with a focused laser beam, and stacking them up to a desired shape. In this technology, differently from the conventional stereolithography, scale effect is dominant. To realize micro-stereolithography technology, we developed the micro-stereolithography apparatus which is composed of an Ar+ laser, x-y-z stages. controllers. optical devices and scan path generation software. Related processes were developed, too. Using the system, a number of micro-structures were successfully fabricated. Some of these samples are shown for prove this system. Laser scan path generation algorithm and software considering photopolymer solidification phenomena as well as given 3D model were developed. Sample fabrication of developed software shows relatively high dimensional accuracy compared to the uncompensated result.

• The Journal of Korea Robotics Society
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• v.15 no.1
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• pp.55-61
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• 2020

Getting on and off an elevator is one of the most important parts for multi-floor navigation of a mobile robot. In this study, we proposed the method for the pose recognition of elevator doors, safe path planning, and motion estimation of a robot using RGB-D sensors in order to safely get on and off the elevator. The accurate pose of the elevator doors is recognized using a particle filter algorithm. After the elevator door is open, the robot builds an occupancy grid map including the internal environments of the elevator to generate a safe path. The safe path prevents collision with obstacles in the elevator. While the robot gets on and off the elevator, the robot uses the optical flow algorithm of the floor image to detect the state that the robot cannot move due to an elevator door sill. The experimental results in various experiments show that the proposed method enables the robot to get on and off the elevator safely.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11C
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• pp.85-93
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• 2001

In this paper, a path restoration method independent of failure location in all-optical networks is proposed and its wavelength requirements are calculated. In the proposed method, since a single backup wavelength is used for any link failure, a node can consist of only fixed wavelength transmitters, resulting in the levels node cost. Hence, restoration process can be triggered just after the failure detection, if combined with edge-disjoint path restoration method. This feature and the parallel cross-connection message transfer technique proposed in this paper make the restoration process faster. Also, it is shown the wavelength requirements in the proposed method are similar to the ones in the method using tunable backup wavelength, resulting in little increment for transmission cost.

• Journal of IKEEE
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• v.1 no.1 s.1
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• pp.138-155
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• 1997

Wireless optical communication is able to obtain high antenna gain as well as utilize to transmit the high-speed information with large capacity than the RF communication. However, the propagation path (atmosphere) is considered as an attenuator occured turbulence, absorption and scattering. These undesired phenomena diminish the amount of light that is collected at the receiver. To evaluate the effect of the atmospheric turbulance and scattering, this paper perform the ground-to-ground wireless optical LAN experiment by using the (2,1,6) convolutional coder and Viterbi decoder, and analyze numerically the earth-station antenna diameter due to the propagation path condition and upstream/downstream link.

• Current Optics and Photonics
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• v.7 no.1
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• pp.38-46
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• 2023

Optical Fourier-domain reflectometry (OFDR) sensors have been widely used to measure distances with high resolution and speed in a noncontact state. In the electroplating process of a printed circuit board, it is critically important to monitor the copper-plating thickness, as small deviations can lead to defects, such as an open or short circuit. In this paper we employ a phase-based OFDR sensor for in situ relative distance sensing of a sample with nanometer-scale resolution, during electroplating. We also develop an optical-path difference (OPD)-regulated sensing probe that can maintain a preset distance from the sample. This function can markedly facilitate practical measurements in two aspects: Optimal distance setting for high signal-to-noise ratio OFDR sensing, and protection of a fragile probe tip via vertical evasion movement. In a sample with a centimeter-scale structure, a conventional OFDR sensor will probably either bump into the sample or practically out of the detection range of the sensing probe. To address this limitation, a novel OPD-regulated OFDR system is designed by combining the OFDR sensing probe and linear piezo motors with feedback-loop control. By using multiple OFDR sensors, it is possible to effectively monitor copper-plating thickness in situ and uniformize it at various positions.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.9
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• pp.723-732
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• 2001

In this paper, the neurofuzzy controller of optically guided AGV is proposed to improve the path-tracking performance A differential steered AGV has front-side and rear-side optical sensors, which can identify the guiding path. Due to the discontinuity of measured data in optical sensors, optically guided AGVs break away easily from the guiding path and path-tracking performance is being degraded. Whenever the On/Off signals in the optical sensors are generated discontinuously, the motion errors can be measured and updated. After sensing, the variation of motion errors can be estimated continuously by the dead reckoning method according to left/right wheel angular velocity. We define the estimated contour error as the sum of the measured contour in the sensing error and the estimated variation of contour error after sensing. The neurofuzzy system consists of incorporating fuzzy controller and neural network. The center and width of fuzzy membership functions are adaptively adjusted by back-propagation learning to minimize th estimated contour error. The proposed control system can be compared with the traditional fuzzy control and decision system in their network structure and learning ability. The proposed control strategy is experience through simulated model to check the performance.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.263-269
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• 2012

In this paper, we propose a new dual optical encryption method for binary data and secret key based on 2-step phase-shifting digital holography for a cryptographic system. Schematically, the proposed optical setup contains two Mach-Zehnder type interferometers. The inner interferometer is used for encrypting the secret key with the common key, while the outer interferometer is used for encrypting the binary data with the same secret key. 2-step phase-shifting digital holograms, which result in the encrypted data, are acquired by moving the PZT mirror with phase step of 0 or ${\pi}/2$ in the reference beam path of the Mach-Zehnder type interferometer. The digital hologram with the encrypted information is a Fourier transform hologram and is recorded on CCD with 256 gray level quantized intensities. Computer experiments show the results to be encryption and decryption carried out with the proposed method. The decryption of binary secret key image and data image is performed successfully.