Proceedings Article | 31 December 2008
KEYWORDS: Fourier transforms, 3D metrology, Image processing, Electronic filtering, 3D image processing, Cameras, Optical filters, Charge-coupled devices, 3D image reconstruction, Modulation
In the industrial detection, the three dimensional of the products are needed measuring usually, so the products can be known eligible or not. The measurement is needed both the high precision and fast speed. In the article, the smooth part of the mouse is taken as the measure object. Grating projected method is used to reconstruct the three dimensional of it. In the experiment, the intersect principle of fourier transform profilometry is used. The electronical grating is projected on the mouse, the deformed grating is collected in the Charge Coupled Device (CCD). And the deformed grating without the mouse is also collected. The fourier transform is used to process the image. In the traditional fourier transform profilometry, the phase is worked out as follows: After fourier transform, the zero frequency spectra is shifted to the origin of frequency, then filter the needed signal. Then the needed signal is shifted to the center of frequency, and then the zero frequency is shifted to both sides. After inverse fourier transform, the imaginary part is getting, so the phase is getting. But it has a difficult in the traditional method, because of three times frequency shift, and the center frequency is difficult to confirm, the frequency shift can't be correct and the filter can't be designed correctly. The error can be transferred, so the result of filter is not well, it has bad effect to the later measurement. The result of measurement is not well certainly. In order to conquer the difficult, after the fourier transform, filtering the needed signal without frequency shifting, then inverse fourier transform. So the phase of mouse relational with the frequency and coordinate is getting. The phase of the reference surface is getting by the same method. Then the difference phase is getting. At last, according to the relation of difference phase and the height in the grating projected method, the three dimensional profilometry of the mouse is reconstructed. The method is more simply and higher precision without three times frequency shift. The three dimensional profilometry reconstruct is realized by two images. It takes 0.3 second to reconstruct the three dimensional profilometry. The precision is 0.5mm. The result indicates that the method suits the smooth object with fast speed and high precision. It is fit for the needed in the practical measurement.
