Kang Park

Development of a Real-time 3D Intraoral Scanner Based on Fringe-Projection Technique

Received 14 February 2012; received in revised form March 27 2012; accepted March 28 2012ABSTRACTReal-time three-dimensional shape measurement is becoming increasingly important in variousfields, including medical sciences, high-technology industry, and microscale measurements.However, there are not so many 3D profile tools specially designed for specifically narrowspace, for example, to scan the tooth shape of a human jaw. In this paper, a real-time 3Dintraoral scanner is proposed for the measurement of tooth profile in the mouth cavity. The pro-posed system comprises a laser diode beam, a micro charge-coupled device, a graticule, a piezo-electric transducer, a set of optical lenses, and a polhemus device sensor. The phase-shiftingtechnique is used along with an accurate calibration method for the measurement of the toothprofile. Experimental and theoretical inspection of the phase-to-coordinate relation is presented.In addition, a nonlinear system model is developed for collimating illumination that gives themore accurate mathematical representation of the system, thus improves the shape measurementaccuracy. Experiment results are presented to verify the feasibility and performance of the devel-oped system. The experimental results indicate that overall measurement error accuracy can becontrolled within 0.4 mm with a variability of ±0.01. Key Words: Calibration, Camera-laser scanner, Virtual fringe-projection setup

Visual, Haptic, and Auditory Realities Based Dental Training Simulator

This research paper presents a surface-based virtual dental sculpting simulator based on mixed auditory, visual, and tactile realities. The simulator can be used to perform different dental procedures (i.e., grinding, drilling, or surface scrubbing), and gain experience of using various virtual dental tools of different shapes. The surface-based dental model, which is extracted from a commercial 3D dental laser scanner, is used for simulating sculpting processes at less memory cost. Large amount of triangular mesh data is contained in scanned models; therefore, a model reduction algorithm is proposed for large triangular mesh data. For the computation of repulsive force feedback, a spring-damper force model with a force filter is used. Vertex deformation method is implemented along with an enhanced bi-tri subdivision method of triangles to perform precision sculpting simulation. In order to make the mesh regular, a number of mesh refinement algorithms are performed. Finally, considering the fidelity, stability, computer efficiency, and update rate of the haptic display, it can be concluded that these mixed realities based virtual system can generate stable simulation of material removal from a human tooth model with realistic auditory, visual, and force sensations.

Piezoelectric Transducer Based 3D Intraoral Scanner

There are not so many 3D profile tools specially designed for specifically narrow space, for example, to scan the tooth shape of a human jaw. In this paper, a real-time 3D intraoral scanner based on piezoelectric transducer is presented for the measurement of tooth profile in the mouth cavity. The proposed system comprises a laser diode beam, a micro charge-coupled device, a graticule, a piezoelectric transducer, a set of optical lenses, and a Polhemus device sensor. The phase-shifting technique is used along with an accurate calibration method for the measurement of the tooth profile. Experimental and theoretical inspection of the phase-to-height relation is described. Simulation and optical measurement results are presented to verify the feasibility and performance of the developed system.

Analysis and Performance Comparison of 3D Measurement Systems Based on Fringe Projection Profilometry

In this paper, four models of 3D measurement systems are evaluated based on collimating and perspective projections using a real-time 3D virtual scanning system. Fringe projection technique is utilized due to its popularity for real-time and high resolution applications. Analysis and performance comparison of the phase-to-coordinate relation for all four models is presented. Nonlinear system models are proposed to obtain the accurate 3D shape for collimating projection models. Finally, the coordinates acquisition, reconstruction, and display processes are performed, and results are presented to verify the proposed approaches.

The Target Modeling and The Shot Line Analysis System to Assess Vulnerability of the Ground Combat Vehicle

Received 17 September 2014; received in revised form 20 July 2015; accepted 28 July 2015ABSTRACTVulnerability assessment is a process to calculate the damage degree of a combat vehicle whenthe combat vehicle is attacked by an enemy. When the vehicle is hit, it is necessary to analyzethe shot line to calculate which components are damaged and judge whether the armor of thevehicle is penetrated by enemy’s warhead. To analyze the shot line efficiently, this paper pres-ents the target modeling and the shot line analysis system to assess vulnerability of the groundcombat vehicle. This system is easily able to do several functions: 1) the program reads STLfiles converted from CAD model which is designed by commercial CAD software. 2) It calcu-lates the intersection between triangle of STL mesh and the shot line, and check if the compo-nents of the model are penetrated. 3) This program can visualize the results using OpenGL. Thevulnerability assessment using the shot line analysis can be used to model the armor of thecombat vehicle and arrange the inner components effectively in the early stage of developmentof the combat vehicle.Key Words: Ground combat vehicles, Shot line analysis, Target geometry modeling, Vulnerabilityassessment

Development of Rafter Processing Machine and Simulation Verification

Han-ok (the Korean traditional house) is famous for its beauty and healthful aspects. However, its construction cost is too high because of the manual process of parts such as rafter, timber, etc. These days, many people want to build a modernized Korean traditional house at a low cost. In order to do so, the rafter machining process is required to be automatized using a CNC machine. It is also observed that, generally the timber does not have a uniform shape. Therefore, it is also needed to examine the timber shape before starting its processing. This paper presents the concept design of the rafter processing CNC machine, and a 3D laser scanning system. The laser scanner is developed to acquire 3D details of the timber shape. Furthermore, the results of simulated experiments are presented to investigate surface roughness during the machining process of the timber. Since cutting parameters largely influence on surface roughness and cusps formation, it is needed to achieve optimal machining parameters. Several experiments were carried out changing cutting parameters such as cutting tool diameter, feed-rate, and spindle speed.

Development of rafter processing machine for Korean traditional houses

The Korean traditional house is famous for its beauty and healthful aspects. However, its construction cost is too high because of the manual process of parts such as rafter, timber, etc. These days, many people want to build a modernized Korean traditional house at a low cost. In order to do so, the rafter machining process is required to be automatized using a CNC machine. It is also observed that, generally the timber does not have a uniform shape. Therefore, it is also needed to examine the timber shape before starting its processing. This paper presents the concept design of the rafter processing CNC machine, and a 3D laser scanning system. The laser scanner is developed for obtaining 3D details of the timber shape. Furthermore, the results of simulated experiments are presented to investigate surface roughness during the machining process of the timber. Because cutting parameters largely influence on surface roughness and cusps formation; therefore, to achieve optimal machining parameters, several experiments were carried out with small and larger cutting tool diameter, different of feed rate and spindle speed.