Current Development in Theory and Applications of Wavelets
Volume 2, Issue 2, Pages 175 - 207
(August 2008)
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DEPTH ESTIMATION OF METALLIC OBJECTS USING MULTIWAVELETS SCALE-SPACE REPRESENTATION
A. Bhatti (Australia) and S. Nahavandi (Australia)
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Abstract:
The problem of dimensional defects in aluminum die-castings is widespread throughout the foundry industry and their detection is of paramount importance in maintaining product quality. Due to the unpredictable factory environment and metallic with highly reflective nature, it is extremely hard to estimate true dimensionality of these metallic parts, autonomously. Some existing vision systems are capable of estimating depth to high accuracy, however are very much hardware dependent, involving the use of light and laser pattern projectors, integrated into vision systems or laser scanners. However, due to the reflective nature of these metallic parts and variable factory environments, the aforementioned vision systems tend to exhibit unpromising performance. Moreover, hardware dependency makes these systems cumbersome and costly. In this work, we propose a novel robust 3D reconstruction algorithm capable of reconstructing dimensionally accurate 3D depth models of the aluminum die-castings. The developed system is very simple and cost effective as it consists of only a pair of stereo cameras and a defused fluorescent light. The proposed vision system is capable of estimating surface depths within the accuracy of 0.5mm. In addition, the system is invariant to illuminative variations as well as orientation and location of the objects on the input image space, making the developed system highly robust. Due to its hardware simplicity and robustness, it can be implemented in different factory environments without a significant change in the setup. The proposed system is a major part of quality inspection system for the automotive manufacturing industry. |
| Keywords and phrases: 3D depth estimation, aluminum die-casting, inspection system, multiwavelets transform modulus maxima, disparity estimation, stereo vision, scale-space representation, geometric refinement. |
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