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Tri-band heterodyne phase shift phase demodulation method

A phase shift and phase solution technology, applied in instruments, measuring devices, optical devices, etc., can solve problems such as poor anti-noise ability, complex algorithm, and large amount of calculation.

Inactive Publication Date: 2008-01-23
HUAZHONG UNIV OF SCI & TECH
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Problems solved by technology

However, these methods have disadvantages such as poor anti-noise ability, complex algorithm, and large amount of calculation.

Method used

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  • Tri-band heterodyne phase shift phase demodulation method
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  • Tri-band heterodyne phase shift phase demodulation method

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example

[0062] (1) Three grating stripes with frequencies of 70, 64, and 59 are selected according to the heterodyne principle.

[0063] (2) Use a projector to project 12 grating stripes to the measured object, and shoot them with two projection cameras on the left and right. During the whole process, 24 grating images are obtained. Figure 4 shows four images with a grating frequency of 70 captured by the left camera.

[0064] (3) Use the four-step phase shift method to dephase the grating images of the three frequencies to obtain the phase value φ 1 , φ 2 , φ 3 , and its corresponding relative grayscale image is shown in Figure 5.

[0065] (4) Using the heterodyne principle to calculate Φ 12 , Ф 23 , Ф 123 , and the corresponding grayscale image is shown in Figure 6.

[0066] (5) for φ 1 Perform phase unwrapping to obtain a phase grayscale image as shown in Figure 7.

[0067] According to the phase map after the phase unfolding of the pictures taken by the left and right came...

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Abstract

The invention discloses a three-frequency heterodyne phase-shifting de-phasing method, which comprises the following procedures: (1) three stripes of different frequencies are selected for projecting; (2) the three stripes of different frequencies are projected; two cameras are used for taking pictures, the included angle between the optic axes of the two cameras is 0-40 degree, each camera takes 12 images of grating; (3) the grating images are de-phased by 4-step phase-shifting way, and the main relative phase is obtained; (4) the main phase is worked out; (5) phase development is carried out on the main phase, and the grey scale diagram of the phase is obtained. The invention uses secondary heterodyne technology, can reduce error, greatly improve the de-phasing accuracy, hence improve the accuracy of the measuring system. By using a method in conjunction with the heterodyne principle, the invention not only gives play to the advantage of the phase-shifting way, but also can accurately get the phase of the measured object.

Description

technical field [0001] The invention belongs to the field of reverse engineering measurement, and in particular relates to a three-frequency heterodyne phase-shifting phase resolution method, which is suitable for a surface structured light reverse measurement system. Background technique [0002] Reverse engineering plays an important role in shortening the product design cycle and assimilating advanced technologies and products at home and abroad. The quality of reverse engineering measurement equipment directly affects the accuracy and completeness of the description of the measured entity, and then affects the quality of the reconstructed CAD surface and solid model, which is the basis of reverse engineering. [0003] The binocular grating projection structured light measurement method combines the structured light method and the stereo vision method. The measurement principle is: the projected light beam is projected on the surface of the object through the grating to f...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01B11/00G01B11/03G01B11/24G01B11/245G01B11/25
Inventor 王从军周钢李中伟李晓宁朱本璋秦大辉杨彪
Owner HUAZHONG UNIV OF SCI & TECH
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