KEYWORDS: Speckle, 3D modeling, 3D image reconstruction, 3D metrology, 3D image processing, Digital image correlation, Semiconductor lasers, Reconstruction algorithms
Three-dimensional reconstruction based on speckle projection method can acquire 3D data by only one speckle image of object, which is suitable for measuring moving or deforming object, and has been widely used in many field. However, conventional speckle 3D reconstruction systems often require speckle projection devices with complex structures, which are relatively large in volume and high in cost. In addition, the digital image correlation algorithms used to search corresponding points, which is time-consuming and not conducive to rapid acquisition of 3D data. In this paper, a low-cost laser speckle 3D reconstruction system is built by using semiconductor lasers. At the same time, by optimizing the image correction and sub-pixel matching optimization algorithms, the corresponding points searching can be done more quickly, which improves the efficiency and accuracy of speckle 3D reconstruction. The experiments proves that the low-cost laser speckle 3D reconstruction system presented can effectively realize fast 3D digital imaging and measurement, largely promote the time efficiency of 3D data calculation, and the measurement error can reach ±0.3mm, which can meet the requirements of miniaturization and low-cost applications with low accuracy requirements.
Test sieves with dense grid structure are widely used in many fields, accurate gird size calibration is rather critical for success of grading analysis and test sieving. But traditional calibration methods suffer from the disadvantages of low measurement efficiency and shortage of sampling number of grids which could lead to quality judgment risk. Here, a fast and precise test sieve inspection method is presented. Firstly, a coaxial imaging system with low and high optical magnification probe is designed to capture the grid images of the test sieve. Then, a scaling ratio between low and high magnification probes can be obtained by the corresponding grids in captured images. With this, all grid dimensions in low magnification image can be obtained by measuring few corresponding grids in high magnification image with high accuracy. Finally, by scanning the stage of the tri-axis platform of the measuring apparatus, whole surface of the test sieve can be quickly inspected. Experiment results show that the proposed method can measure the test sieves with higher efficiency compare to traditional methods, which can measure 0.15 million grids (gird size 0.1mm) within only 60 seconds, and it can measure grid size range from 20μm to 5mm precisely. In a word, the presented method can calibrate the grid size of test sieve automatically with high efficiency and accuracy. By which, surface evaluation based on statistical method can be effectively implemented, and the quality judgment will be more reasonable.
KEYWORDS: Stereoscopy, 3D image processing, Data acquisition, Fringe analysis, Phase shifting, Demodulation, Fourier transforms, 3D acquisition, Real time imaging, Structured light
A method for real-time three-dimensional (3D) imaging based on Hilbert transform is proposed. Based on the properties
of Hilbert transform and De Bruijn sequence, we design an encoding technique based on color fringe patterns to realize
3-D reconstruction of the phase distribution and range images. The calculation of phase map is implemented by using
two sinusoidal fringe patterns with phase shifting 0 and π / 2 each other. Two phase-shifted fringe patterns are assigned
to the red and blue channel of a color pattern, respectively. The phase unwrapping is accomplished with aid of the De
Bruijn sequence pattern stored in the green channel. The experiment results show that the proposed method can not only
acquire 3D data in real-time and one-shot fashion, but also obtain high-resolution and high-density range image data
without any error propagation.
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