• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.6_1
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• pp.529-536
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• 2007

Registration between image and object space is a fundamental step in photogrammetry and computer vision. Along with rapid development of sensors - multi/hyper spectral sensor, laser scanning sensor, radar sensor etc., the needs for registration between different sensors are ever increasing. There are two important considerations on different sensor registration. They are sensor invariant feature extraction and correspondence between them. Since point to point correspondence does not exist in image and laser scanning data, it is necessary to have higher entities for extraction and correspondence. This leads to modify first, existing mathematical and geometrical model which was suitable for point measurement to line measurements, second, matching scheme. In this research, linear feature is selected for sensor invariant features and matching entity. Linear features are incorporated into mathematical equation in the form of extended collinearity equation for registration problem known as photo resection which calculates exterior orientation parameters. The other emphasis is on the scheme of finding matched entities in the aide of RANSAC (RANdom SAmple Consensus) in the absence of correspondences. To relieve computational load which is a common problem in sampling theorem, deterministic sampling technique and selecting 4 line features from 4 sectors are applied.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.322-327
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• 2012

Parallel-plate-type scanning sensors have been commercially used for X-ray imaging sensors. In this study, we manufactured the scan typed 1D X-ray image sensor that can be used to obtain scanning images, by using the plasma display panel (PDP) fabrication process. We fabricated drift and pixel electrodes in the glass chamber and injected Xe gas at atmospheric pressure. We evaluated the intensity of a pixel signal depending on the bias voltage on the drift electrode and investigated the characteristics of shielding effect on the single pixel using lead (Pb). The adsorption rate of X-ray photon is low (4%) on the soda lime glass (1.1mm) and the electrical signal detected on the X-ray sensor was increased in the high bias voltage. We acquired digital X-ray scanning image with our DAS (data acquisition system) and sensor scanning system.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.6
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• pp.459-466
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• 2005

The scanning laser source (SLS) technique has been proposed recently as an effective way to investigate small surface-breaking defects, By monitoring the amplitude and frequency changes of the ultrasound generated as the SLS scans over a defect, the SLS technique has provided enhanced signal-to-noise performance compared to the traditional pitch-catch or pulse-echo ultrasonic methods, An extension of the SLS approach to map defects in microdevices is proposed by bringing both the generator and the receiver to the near-field scattering region of the defects, To facilitate near-field ultrasound measurement, silicon microcantilever probes are fabricated using microfabrication technique and their acoustical characteristics are investigated, Then, both the laser-generated ultrasonic source and the microcantilever probe are used to monitor near-field scattering by a surface-breaking defect.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.562-565
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• 2002

Recent technologic innovations have created possibilities for restorative dentistry, such as computer-aided design and computer-aided manufacturing. This article presents a CAD process that has been developed for the fabrication of dental restorations. This process uses a 4-axes driving mechanism and an improved optical displacement sensor, successfully applied in other industries. In optical displacement sensor, the light beam emitted from the LED is converged through the light source lenses and thrown on the object to be detected. When the light beam is reflected from the object, however, it is diffused. The diffused light beam is converged again by the receiver lenses and cast on the optical position detector element as a small spot.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.51 no.3
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• pp.155-160
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• 2002

This paper focuses on the problem of local obstacle avoidance of mobile robots. To solve this problem, the safety direction section search algorithm is suggested. This concept is mainly composed with non-collision section and collision section from the detecting area of laser scanning sensor. Then, we will search for the most suitable direction in these sections. The proposed local motion planning method is simple and requires less computation than others. An environment model is developed using the vector space concept to determine robot motion direction taking the target direction, obstacle configuration, and robot trajectory into account. Since the motion command is obtained considering motion dynamics, it results in smooth and fast as well as safe movement. Using the mobile base, the proposed obstacle avoidance method is tested, especially in the environment with pillar, wall and some doors. Also, the proposed autonomous motion planning and control algorithm are tested extensively. The experimental results show the proposed method yields safe and stable robot motion through the motion speed is not so fast.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.61-70
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• 2001

This paper introduces a new digitization method with sensor fusion for shape measurement in reverse engineering. Digitization can be classified into contact and non-contact type according to the measurement devices. Important thing in digitization is speed and accuracy. The former is excellent in speed and the latter is good for accuracy. Sensor fusion in digitization intends to incorporate the merits of both types so that the system can be automatized. Firstly, non-contact sensor with vision system acquires coarse 3D point data rapidly. This process is needed to identify and loco]ice the object located at unknown position on the table. Secondly, accurate 3D point data can be automatically obtained using scanning probe based on the previously measured coarse 3D point data. In the research, a great number of measuring points of equi-distance were instructed along the line acquired by the vision system. Finally, the digitized 3D point data are approximated to the rational B-spline surface equation, and the free-formed surface information can be transferred to a commercial CAD/CAM system via IGES translation in order to machine the modeled geometric shape.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.187-193
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• 2003

This paper presents an on-machine measurement method of flatness error fur surface machining processes. There are two kinds of on-machine measurement methods available to measure flatness errors in workpieces: i.e., surface scanning method and sensor scanning method. However, motion errors are often engaged in both methods. This paper proposes an idea to realize a measurement system of flatness errors and its rigorous application for estimation of motion errors of the positioning system. The measurement system is made by modifying the straightness measurement system, which consists of a laser, a CCD camera and processing system, a sensor head, and some optical units. The sensor head is composed of a retroreflector, a ball and ball socket, a linear motion guide unit and adjustable arms. The experimental .results show that the proposed method is useful to identify flatness errors of machined workpieces as well as motion errors of positioning systems.

• Journal of Sensor Science and Technology
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• v.33 no.2
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• pp.63-69
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• 2024

A novel method for measuring hydrogen concentration is introduced, along with its working principle and a novel detection algorithm. This configuration requires no additional reference compartment for potentiometric electrochemical measurements; therefore, it is the most suitable for measuring dissolved hydrogen in the liquid phase. The sensor's electromotive force saturates at a certain point, depending on the hydrogen concentration during the heating process of the sensor operation. This dynamic temperature scanning method provides higher sensitivity than the constant temperature measurement method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.10
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• pp.1416-1426
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• 2021

In the case of a scanning type multi-channel LiDAR sensor, the distance error called a walk error may occur due to a difference in received signal power. This work error causes different distance values to be output for the same object when scanning the surrounding environment based on multiple LiDAR sensors. For minimizing walk error in overlapping regions when scanning all directions using multiple sensors, to calibrate distance for each channels using convolution on external system. Four sensors were placed in the center of 6×6 m environment and scanned around. As a result of applying the proposed filtering method, the distance error could be improved by about 68% from average of 0.5125 m to 0.16 m, and the standard deviation could be improved by about 48% from average of 0.0591 to 0.030675.

• Proceedings of the Korean Vacuum Society Conference
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• 1996.02a
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• pp.122-122
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• 1996