• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.12a
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• pp.145-148
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• 2000

Position-determining capacity is a very important condition in equipments for manufacturing semi-conductor or various instruments to measure physical displacement quantities of a moving object in submicron such as a distance of movement, direction, etc. and the accuracy of total system is influenced by detecting accuracy of these equipments. Therefore in this paper we have optically made up laser linear encoder based on optical diffraction principle to measure these displacement quantities and have processed optical signal using hardware-setup. In consequence we had acquired displacement for movement of scale using a diffraction grating by the accuracy of 0.5${\mu}{\textrm}{m}$ and had digitalized moving quantities of scale.

• Journal of Mechanical Science and Technology
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• v.18 no.7
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• pp.1177-1186
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• 2004

In this paper, the spray atomization characteristics of a gasoline direct-injection injector were investigated experimentally and numerically. To visualize the developing spray process, a laser sheet method with a Nd :YAG laser was utilized. The microscopic atomization characteristics such as the droplet size and velocity distribution were also obtained by using a phase Doppler particle analyzer system at the 5 ㎫ of injection pressure. With the experiments, the calculations of spray atomization were conducted by using the KIVA code with the LISA-DDB breakup model. Based on the agreement with the experimental results, the prediction accuracy of LISA-DDB breakup model was investigated in terms of the spray shapes, spray tip penetration, SMD distribution, and axial mean velocity. The results of this study provides the macroscopic and microscopic characteristics of the spray atomization, and prediction accuracy of the LISA-DDB model.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.1
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• pp.62-69
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• 1993

The accuracy of machine tools is the major factor concerned with the acuracy of the processed work. The feed errors of feed system in machine tool, therfore, make the machining errors of work directly on processing. In this point, this study focused on the generative elements of feed errors in CNC cylindrical grinding machine, such as supporting method of ball screw, the effect of pitch and yaw error and the position detecting method in servo system when operating its shaft of grinding wheel head. Furthermore, in order to improve the driving accuracy of this machine tool, feed errors are measured by a laser interferometer. Results obtained in this study provide some useful informations to attain high accuracy of CNC machine tool.

• Journal of the Korean Society for Precision Engineering
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• v.4 no.2
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• pp.36-46
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• 1987

An optical technique using laser for non-contact measurement of surface roughness and form accuracy of ground surfaces is presented. It is found that, when a ground surface is illuminated by a beam of laser light, the roughness height and slope distribution has significant influence on the pattern of reflection and it maintains an unique Gaussian distribution relationship with the surface roughness. The principle idea of the optical measurement system is therefore monitor the radiation, and then calibrate it in process against surface roughness by means of necessary digital data processing. On the other hand, measuring the form accuracy of a ground surface is accomplished by using a triangular method, which is based on observing the movement of an image of a spot of light projected onto the surface. The image is focused, through a series of lenses for magnification, on a photodetector array lf line configur- ation. Then the relative movement of image and consequently the form accuracy of the surface can be obtained through appropriate calibration procedures. Experimental test showed that the optical roughness measurement technique suggested in this work is very efficient for most industrial applications being capable of monitoring the roughness heights ranging 0.1 to 0.6 .$\mu$m CLA values. And form accuracy can be measured in process with a resolution of 10 .$\mu$m.

• Imaging Science in Dentistry
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• v.51 no.4
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• pp.429-438
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• 2021

Purpose: This study investigated the accuracy of laser-scanned models and 3-dimensional(3D) rendered cone-beam computed tomography (CBCT) compared to the gold standard (plaster casts) for linear measurements on dental arches. Materials and Methods: CBCT scans and plaster models from 30 patients were retrieved. Plaster models were scanned by an Emerald laser scanner (Planmeca, Helsinki, Finland). Sixteen different measurements, encompassing the mesiodistal width of teeth and both arches' length and width, were calculated using various landmarks. Linear measurements were made on laser-scanned models using Autodesk Meshmixer software v. 3.0 (Autodesk, Mill Valley, CA, USA), on 3D-rendered CBCT models using OnDemand 3D v. 1.0 (Cybermed, Seoul, Korea) and on plaster casts by a digital caliper. Descriptive statistics, the paired t-test, and intra- and inter-class correlation coefficients were used to analyze the data. Results: There were statistically significant differences between some measurements on plaster casts and laser-scanned or 3D-rendered CBCT models (P<0.05). Molar mesiodistal width and mandibular anterior arch width deviated significantly different from the gold standard in both methods. The largest mean differences of laser-scanned and 3D-rendered CBCT models compared to the gold standard were 0.12±0.23 mm and 0.42±0.53 mm, respectively. Most of the mean differences were not clinically significant. The intra- and inter-class correlation results were acceptable for all measurements(>0.830) and between observers(>0.801). Conclusion: The 3D-rendered CBCT images and laser-scanned models were useful and accurate alternatives to conventional plaster models. They could be used for clinical purposes in orthodontics and prostheses.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.5
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• pp.466-474
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• 2020

Semi-active laser missile systems with high accuracy are necessary to asymmetric threats, such as UAV(Unmanned Aerial Vehicle). They are usually used to attack stationary or slow moving targets, therefore we should study on the laser designator which can detect and track fast moving targets in order to deal with UAV. In this study, design specifications are came up through performance analysis of existing laser designators, and laser designation method for fast moving target is developed. The detection and tracking performance of developed laser designator are verified through inside/outside tests on ground/aerial stationary/moving targets. Through this study, we obtain laser designator techniques that could be applied to actual semi-active laser missile systems.

• Spatial Information Research
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• v.15 no.1
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• pp.53-65
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• 2007

Terrestrial laser scanner provides highly accurate, 3D images and by sweeping a laser beam over a scene or object, the laser scanner is able to record millions of 3D points' coordinates in a short period, so becoming distinguished in various application fields as one of the representative surveying instruments. This study deals with 3D building boundary extraction using Terrestrial Laser Scanner. The results shows that high accuracy 3D coordinates for building boundaries are possibly acquired fast, but terrestrial laser scanner is a ground-based system, so "no roofs", and "no lower part of building" due to trees and electric-poles, etc. It is expected that the combination of total station, terrestrial laser scanner, airborne laser scanner with aerial photogrammetry will contribute to the acquisition of an effective 3D spatial information.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1162-1166
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• 1990

We present a system to measure 3-dimensional coordinates of huge structures like ships, buildings and oil tanks. Two important units are a laser spot projector and a laser spot tracker. Employing a tactful image processing, our system has some features :e.g. compactness, cost, accuracy and robustness to hazardous emvironments.

• Proceedings of the Optical Society of Korea Conference
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• 1998.08a
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• pp.170-171
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• 1998

Here are proposed the tunable laser for optical memory which uses the acousto-optic deflector. This laser includes the acousto-optic deflector in the Littrow mount configuration so that we may control the beam deflection by means of the induced RF. Consequently, we can achieve the higher speed and accuracy to compare with the Littrow monut configuration only.

• The korean journal of orthodontics
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• v.46 no.1
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• pp.13-19
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• 2016

Objective: The aim of this study was to compare the accuracy of Bolton analysis obtained from digital models scanned with the Ortho Insight three-dimensional (3D) laser scanner system to those obtained from cone-beam computed tomography (CBCT) images and traditional plaster models. Methods: CBCT scans and plaster models were obtained from 50 patients. Plaster models were scanned using the Ortho Insight 3D laser scanner; Bolton ratios were calculated with its software. CBCT scans were imported and analyzed using AVIZO software. Plaster models were measured with a digital caliper. Data were analyzed with descriptive statistics and the intraclass correlation coefficient (ICC). Results: Anterior and overall Bolton ratios obtained by the three different modalities exhibited excellent agreement (> 0.970). The mean differences between the scanned digital models and physical models and between the CBCT images and scanned digital models for overall Bolton ratios were $0.41{\pm}0.305%$ and $0.45{\pm}0.456%$, respectively; for anterior Bolton ratios, $0.59{\pm}0.520%$ and $1.01{\pm}0.780%$, respectively. ICC results showed that intraexaminer error reliability was generally excellent (> 0.858 for all three diagnostic modalities), with < 1.45% discrepancy in the Bolton analysis. Conclusions: Laser scanned digital models are highly accurate compared to physical models and CBCT scans for assessing the spatial relationships of dental arches for orthodontic diagnosis.