• 한국CDE학회논문집
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• 제16권1호
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• pp.11-20
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• 2011

A structured beam laser is often used to scan object and make 3D model. Multiple cameras are inevitable to see occluded areas, which is the main reason of the high price of the scanner. In this paper, a low cost 3D foot scanner is developed using one camera and two mirrors. The camera and two mirrors are located below and above the foot, respectively. Occluded area, which is the top of the foot, is reflected by the mirrors. Then the camera measures 3D point data of the bottom and top of the foot at the same time. Then, the whole foot model is reconstructed after symmetrical transformation of the data reflected by mirrors. The reliability of the scan data depends on the accuracy of the parameters between the camera and the laser. A calibration method is also proposed and verified by experiments. The results of the experiments show that the worst errors of the system are 2 mm along x, y, and z directions.

• International Journal of Precision Engineering and Manufacturing
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• 제9권4호
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• pp.16-21
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• 2008

The demand for three-dimensional (3D) shape measurements is increasing in a variety of fields, including the manufacture of molds and dies. The most popular technology for 3D shape measurement is the coordinate measuring machine (CMM) with a contact trigger probe. Although a CMM provides a high degree of accuracy, it is inefficient due to its long measuring time. It also has difficulty measuring soft objects that can be deformed by the touch of the contact probe. In addition, a CMM cannot digitize areas that are difficult to reach, and cannot capture very minute details on the surface of complex parts. For these reasons, optical non-contact measurement techniques are receiving more attention since they eliminate most of the problems associated with contact methods. Laser scanning is emerging as one of the more promising non-contact measurement techniques. This paper describes various acquisition considerations for laser scanning, including the accuracy of the 3D scan data, which depends on the charge-coupled device (CCD) gain and noise. The CCD gain and noise of a 3D laser scanner are varied while keeping the other conditions constant, and the measurement results are compared to the dimensions of a standard model. The experimental results show that a considerable time savings and an optimum degree of accuracy are possible by selecting the proper CCD gain and noise.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.101-105
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• 2002

In this paper we describe techniques for the automated creation of geometric correct 3-D models of the building using two 2-D laser scanners. One of the laser scanners is used for position estimation using a scan matching algorithm, while the other is used to build 3-D models of the facade of the buildings. Those models can be used for virtual reality, tele-presence, digital cinematography and urban planning applications. Results are shown for building models in our campus using real data acquired from two sensors.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2170-2174
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• 2005

Selective Laser Sintering (SLS) is a useful rapid prototyping technique for the manufacture of three dimensional (3D) solid objects directly from a scanning data. A new approach called a Selective Multi-Laser Sintering (SMLS) system has been developed at Korea Institute Machinery & Materials (KIMM) as an industrial type SFFS. This SMLS machine is built with a frame, heaters, nitrogen supply part, laser system. This system uses the dual laser and 3D scanner made in $Solutionix^{TM}$ to improve the precision and speed for large objects. The three-dimensional solid objects are made of polyamide powder. The investigation on each part of SMLS system is performed to determine the proper theirs design and the effect of experimental parameters on making the 3D objects. The temperature of the system has a great influence on sintering the polymer. Because the stability of the powder temperature prevents the deformation of each layer, the controls of the temperature in both the system and the powders are very important during the process. Therefore, we simulated the temperature distribution of build room using the temperature analysis with ANSYS program. Selected radiant heater is used to raise temperature of powder to melting point temperature. The laser parameters such as scan spacing, scan speed, laser power and laser delay time affect the production the 3D objects too. The combination of the slow scan speed and the high laser power shows the good results without the layer curling. The work is under way to evaluate the effect of experimental parameters on process and to produce the various objects. We are going to experiment continuously to improve the size accuracy and surface roughness.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1634-1637
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• 2003

Any given object on the motor-driven turntable is pictured from 8 to 72 different views with a digital camera. 3D shape reconstruction is performed with the integrated software called by Scanware from these multiple digital photographs. There are several steps such as configuration, calibration, capturing, segmentation, shape creation, texturing and merging process during the shape reconstruction process. 3D geometry data can be exported to cad data such as Autocad input file. Also 3D image model is generated from 3D geometry and texture data, and is used to advertise the model in the internet environment. Consumers can see the object realistically from wanted views by rotating or zooming in the internet browsers with Scanbull spx plug-in. The spx format allows a compact saving of 3D objects to handle or download. There are many types of scan equipments such as laser scanners and photogrammetric scanners. Line or point scan methods by laser can generate precise 3D geometry but cannot obtain color textures in general. Reversely, 3D image modeling with photogrammetry can generate not only geometries but also textures from associated polygons. We got various 3D image models and introduced the process of getting 3D image model of an internet-connected watchdog robot.

• International Journal of Precision Engineering and Manufacturing
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• 제8권4호
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• pp.50-55
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• 2007

Stereolithography (SLA) is a technique using a laser beam to cure a photopolymer liquid resin with three-dimensional computer-aided design (CAD) data, The accuracy of the prototype, the build time, and the cured properties of the resins are controlled by the SLA process parameters such as the size of the laser beam, scan velocity, hatch spacing, and layer thickness, In particular, the size of the laser beam is the most important parameter in SLA, This study investigated the curing properties of photopolymers as a function of the laser beam size, The cure width and depth were measured either on a single cure line or at a single cure layer for various hatch spacings and laser beam sizes, The cure depth ranged from 0.23 to 0.34 mm and was directly proportional to the beam radius, whereas the cure width ranged from 0.42 to 1.07 mm and was inversely proportional to the beam radius, The resulting surface roughness ranged from 1.12 to $2.23{\mu}m$ for a ratio of hatch spacing to beam radius in the range 0.5-2.0 at a beam radius of 0.17 mm and a scan velocity of 125 mm/sec.

• 한국정밀공학회지
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• 제20권9호
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• pp.197-204
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• 2003

This study proposes a method to reduce errors in scanning object and registration using a laser scanner. The method consists of 3 stages. First, there is an error induced by the difference of the distance between the probe and the object. It is possible to reduce the error by planning a scanning strategy: object setting, scan path. Second, the scan data of the tooling ball affects calculating the tooling ball center. A z-direction compensation is given to calculate more accurate registration points. Third, three points are used to determine a coordinate transformation on each frame. The maximum error usually lies on the third tooling ball in the conventional merging method. LSM (Least Square Method) is applied to a coordinate transformation to reduce the registration error.

• 지질공학
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• 제14권2호
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• pp.147-168
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• 2004

이 연구는 지하수유동에 영향을 주는 조ㆍ중ㆍ세립질 화강암 불연속면 거칠기의 특성을 비교한 것이다. 공초점 레이저 현미경으로 관찰된 거칠기 데이터는 스펙트럼 분석과 고속푸리에 변환에 의해 해석되었다. 또한 노이지가 제거된 거칠기 데이터에 대하여 거칠기 특성을 정량화하기 위하여 프랙탈 해석에 적용해 보았다. 이를 위해 조ㆍ중ㆍ세립질 화강암 코어를 대상으로 브라질리안 시험으로 인공 단열을 발생시켰다. 측정은 전체 12개의 공시체에서 36개의 조사선에서 실시되었다. 공초점 레이저 현미경을 사용하여 연속적인 거칠기를 이산 데이터로 표현할 수 있으며, 이렇게 하여 얻어진 이산데이터를 바탕으로 고속 푸리에 변환을 실시한 결과 제2 고조파 성분이 가장 큰 값을 보이고 있다. 또한 스펙트럼 에너지 분포는 조립질 공시체에서 0.9853, 중립질 공시체에서 1.0792, 세립질 공시체에서 0.6794의 평균값을 보이고 있으며, 이는 프랙탈 해석에서와 마찬가지로 거칠기가 클수록 저주파수 영역대에서 고조파의 에너지 분포가 높게 나타남을 알 수 있다.

• ETRI Journal
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• 제29권5호
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• pp.641-648
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• 2007

In this study, we suggest a new segmentation algorithm for processing airborne laser point cloud data which is more memory efficient and faster than previous approaches. The main principle is the reading of data points along a scan line and their direct classification into homogeneous groups as a single process. The results of our experiments demonstrate that the algorithm runs faster and is more memory efficient than previous approaches. Moreover, the segmentation accuracy is generally acceptable.

• 한국정밀공학회지
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• 제13권9호
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• pp.70-76
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• 1996

In the Stereolithography process, three-dimensional objects are built by sequentially curing, generated by horizontal slicing of a three-dimensional CAD model. The dimensional accuracy of a menufactured part depends on the accuracy of curing performed by laser beam radius and the half of curing width. When offsetting, some slices have collinear segments, coincident vertices, line jerks and open loops. After remove above issues we have correct offsets data. And in last step, these data are used to scan paths.