Optical three-dimensional measuring method based on phase coding technology

Abstract

The invention relates to an optical three-dimensional measuring method based on a phase coding technology, belonging to the technical field of three-dimensional measurement. The method comprises the following steps of: (1) producing a grating coding stripe image by a computer; (2) projecting the grating coding stripe image by using digital projection equipment; and (3) acquiring the grating coding stripe image and performing coding solution and three-dimensional measurement by adopting a phase-shift algorithm. The method is characterized in that: the number of pixels in each grating period of the grating coding stripe image generated in step (1) is equal to the step number of the adopted phase-shift algorithm; and the gray scale of the pixels in each grating period of the grating coding stripe image is needed to meet sine or cosine curve distribution, and the gray-scale value of the pixels are extreme points of the corresponding sine or cosine function. Compared with the traditional sine phase-shift coding method, the method has strong interference resistance to the nonlinear influence of gamma rays of the digital projection equipment, the coding has higher stability, reliability and correctness, and the method is important in the aspect of accurate measurement of an optical three-dimensional outline on the external surface of an object.

Description

Technical field [0001] An optical three-dimensional measurement method based on phase encoding technology relates to the field of computer vision measurement, belongs to the technical field of three-dimensional measurement methods and instruments, and in particular relates to the structured light encoding technology of an optical three-dimensional measurement system. Background technique [0002] Optical-based non-contact three-dimensional object shape measurement technology has been greatly developed, and this technology has been widely used in product design and manufacturing, quality inspection and control, robot vision and other fields. In addition, with the advancement of digital projection technology, the three-dimensional measurement technology of structured light based on digital projection equipment has been rapidly expanded, occupying an increasingly important position in the entire field of optical three-dimensional measurement technology. In the method, firstly, ...

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Problems solved by technology

[0010] One is the active method (Gai Shaoyan, Da Feipeng. A grating phase self-correction method based on a digital projector, Acta Automatica Sinica, 34(11):1363-1368(2008).), in the calculated phase Select the local error area, calculate the stripe gray level that needs to be projected by reverse compensation, and change the projected stripe gray level so that the collected stripe gray level has an ideal sinusoidal distribution, but this method is theoretically feasible , in practical applications, since each pixel has different gamma nonlinear reflection, it is difficult to obtain good results by this method

[0011] The second type of method is the method of passive compensation (H.Guo, H.He, and M.Chen.Gamma correction for digital fringe projection profilometry, Appl.Opt.43, 2906-14(2004).), this type of method considers that the phase The encoding errors have the same periodicity. First, extract the phase error within one cycle or several cycles, establish the corresponding phase error compensation phase comparison table, realize the phase error calibration, and then reversely compensate the solved phase encoding according to the error comparison table. To realize the correct encoding of the phase, the precondition of this type of method is that the phase encoding error has the same cycle. By making statistics on the phase error in one or more cycles, an error comparison table is established for corresponding compensation. However, to realize this application in the application The same periodic phenomenon basically does not exist, so the error cannot be completely eliminated by this method, and the residual phase error after compensation is still not negligible for high-precision three-dimensional measurement

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