• Korean Journal of Construction Engineering and Management
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• v.25 no.3
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• pp.68-82
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• 2024

The planning stage of laser scanning is crucial for acquiring high-quality 3D source data. It involves assessing the target space's environment and formulating an effective measurement strategy. However, existing practices often overlook on-site conditions, with decisions on scanner deployment and scanning locations relying heavily on the operators' experience. This approach has resulted in frequent modifications to scanning locations and diminished 3D data quality. Previous research has explored the selection of optimal scanner locations and conducted preliminary reviews through simulation, but these methods have significant drawbacks. They fail to consider scanner inaccuracies, do not support the use of multiple scanners, rely on less accurate 2D drawings, and require specialized knowledge in 3D modeling and programming. This study introduces an optimization technique for laser scanning planning using 3D simulation to address these issues. By evaluating the accuracy of scan data from various laser scanners and their positioning for scanning a retaining wall structure in a small-scale building, this method aids in refining the laser scanning plan. It enhances the decision-making process for end-users by ensuring data quality and reducing the need for plan adjustments during the planning phase.

• Proceedings of the Korean Vacuum Society Conference
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• 2008.08a
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• pp.225-225
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• 2008

• The Journal of Engineering Geology
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• v.29 no.3
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• pp.237-249
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• 2019

The roughness changes on a fracture surface were analyzed via a multi-stage compression test under high temperatures to assess how the cracks in a rock mass affect groundwater movement. The analyzed samples consist of coarse granitic rocks from approximately 40 and 270 m depth, and fine granitic rocks from 500 m depth. The compression test was conducted on $20{\times}40{\times}5mm$ samples using a loading system where the pressure increases in 10 MPa increments to 120 MPa. A high-resolution 3D confocal laser scanning microscope (CLSM) was used to observe the surface changes, including the roughness changes, at each pressure step. The roughness change was calculated based on the roughness factor. The experimental results indicate that the roughness of the fracture surface varies with rock type under the stepwise pressure conditions. These data provide a basis for predicting groundwater flow along rock fractures.

• Korean Journal of Optics and Photonics
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• v.19 no.2
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• pp.132-139
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• 2008

In scanning laser optical tweezers, high speed scanning stages are used to manipulate a laser beam spot. Due to the inertia of the stage, the output scanning signal decreases with increased frequency of the input signal. This discrepancy in the signals is difficult to observe since most of the energy from the laser beam is blocked out to avoid CCD damage. In this paper, we propose two methods to alleviate these problems. Firstly, frequency responses of piezo stages are measured to analyze the signal drops and the input signal is compensated accordingly. Secondly, an overlay of the scanning path is drawn on the live monitoring screen to enhance the visibility of the scanning path. The result is a drop-compensated scanning with clear path view.

• Journal of Computing Science and Engineering
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• v.8 no.4
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• pp.187-198
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• 2014

In this paper an efficient image encryption scheme based on cyclic rotations and multiple blockwise diffusions with two chaotic maps is proposed. A Sin map is used to generate round keys for the encryption/decryption process. A Pomeau-Manneville map is used to generate chaotic values for permutation, pixel value rotation and diffusion operations. The encryption scheme is composed of three stages: permutation, pixel value rotation and diffusion. The permutation stage performs four operations on the image: row shuffling, column shuffling, cyclic rotation of all the rows and cyclic rotation of all the columns. This stage reduces the correlation significantly among neighboring pixels. The second stage performs circular rotation of pixel values twice by scanning the image horizontally and vertically. The amount of rotation is based on $M{\times}N$ chaotic values. The last stage performs the diffusion four times by scanning the image in four different ways: block of $8{\times}8$ pixels, block of $16{\times}16$ pixels, principal diagonally, and secondary diagonally. Each of the above four diffusions performs the diffusion in two directions (forwards and backwards) with two previously diffused pixels and two chaotic values. This stage makes the scheme resistant to differential attacks. The security and performance of the proposed method is analyzed systematically by using the key space, entropy, statistical, differential and performance analysis. The experimental results confirm that the proposed method is computationally efficient with high security.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.39-40
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• 2006

Digital image-projection and several modifications are the classical applications of Digital Micromirror Devices (DMD), however further applications in the field of optical metrology are also available. Operated with certain patterns, a DMD can function, for instance, as an array of pinholes that may substitute the Galvanic mirror or the stage scanning system presently used for 2 dimensional scanning in confocal microscopes. The various process parameters that influence the result of measurement (e.g. pinhole size, lateral scanning pitch and the number of pinholes used simultaneously, etc.) should be configured precisely for individual measurements by appropriately operating the DMD. This paper presents suitable conditions for the diffraction limited analysis between DMD-optics-CCD to achieve the best performance. Also sampling theorem that is necessary for the image acquisition by scanning system is simulated with OPTISCAN which is the simulator based on the diffraction theory.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.173-181
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• 2005

We report on the design and fabrication of an electrostatic 2-axis MEMS stage possessing a platform with a size of $5{times}5mm^2$. The stage, as a key component, would be used in developing probe-based storage devices in the future. It was fabricated by forming numerous $5{\times}5{\mu}m^2$ etching holes in the central platform, as a result, reducing the total number of masks to 1, thereby simplifying the whole fabrication process. Experimental results show that the driving range of the stage was $32{\mu}m$ at the supplied voltage of 20V and the natural frequency was approximately 300Hz. The mechanical coupling between x- and y-motion was also measured and verified to be $25\%$.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.3
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• pp.27-32
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• 2008

This paper describes a contact atomic force microscope (AFM) that can be used for high-speed precision measurements of microstructured surfaces. The AFM is composed of an air-bearing X stage, an air-bearing spindle with the axis of rotation in the Z direction, and an AFM probe unit. The traversing distance and maximum speed of the X stage are 300 mm and 400 mm/s, respectively. The spindle has the ability to hold a sample in a vacuum chuck with a maximum diameter of 130 mm and has a maximum rotation speed of 300 rpm. The bandwidth of the AFM probe unit in an open loop control circuit is more than 40 kHz. To achieve precision measurements of microstructured surfaces with slopes, a scanning strategy combining constant height measurements with a slope compensation technique is proposed. In this scanning strategy, the Z direction PZT actuator of the AFM probe unit is employed to compensate for the slope of the sample surface while the microstructures are scanned by the AFM probe at a constant height. The precision of such a scanning strategy is demonstrated by obtaining profile measurements of a microstructure surface at a series of scanning speeds ranging from 0.1 to 20.0 mm/s.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.50-56
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• 2021

This study examines 3D scanning and how it is used in the construction field. 3D scanning technology was applied to a real space and compared with drawings in the planning and construction stages. 3D scanning technology has been widely applied in the field of construction, design, construction, and safety. The results of comparing 3D scanning data with drawings are as follows. First, the external shape and dimensions do not show much difference. Second, the internal shape and dimensions are different. Third, indoor lighting layouts are different in all buildings. 3D scanning should be an essential element in the construction stage before completion and should be used for supervision tasks such as material management, improving the efficiency of construction, and safety management through continuous 3D scanning using automation and robots. Follow-up studies in the field of architecture, such as BIM and process management, will be needed.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.201-204
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• 2001

A Confocal Laser Scanning Microscope (CLSM) is applied to determine three-dimensional fiber orientation states in injection-molded short fiber composites. Since the CLSM optically sections the composites, more than two planes either on or below the surface of composites can be obtained. Therefore, three dimensional fiber orientation states are determined without destruction. To predict the orientation states, velocity and temperature fields are calculated by using a hybrid FEM/FDM method. The change of orientation state during packing stage is also considered by employing a compressible Hele-Shaw model. The predicted orientation states show good agreement with measured ones. However, some differences are found at the end of cavity. They may result from other effects, which are not considered in the numerical analysis.