Research On 3d Measurement Technology Based On Color Gray Structured Light With Stripe Dividing

Non-contact 3D measurement technology is widely used in industry and real life for its advantages of high efficiency, high automatization and low cost. Structured light as a kind of non-contact 3D measurement technology has high practicality and developing potential. The coding structured light method which has the advantages of high efficiency, high speed and no scanning is considered as the developing direction of structured light 3D measurement technology. Color coding has much more reliability than grey coding. Compared with the space coding method and direct coding method, time coding method for its advantages of higher accuracy and high sampling density becomes the research direction of color coding structured light. Improving accuracy is the eternal pursuit of the measurement field, and improving sampling density is a highly challenging task in the 3D vision measurement. Therefore, this paper studies time color coding structured light 3D non-contact measurement technology and experimental device to improving accuracy and sampling density.To improve the accuracy of coding structured light, from the error analysis of traditional Gray code center decoding principle, the method of color edge Gray code decoding is proposed, which takes color stripe edge as sampling point and eliminates the 0.5 least significant bit inherent quantization error from stripe center decoding. Edge decoding is corresponding with the inside of red/blue stripe in high-order image, not with the edge of red/blue stripe in high-order image, which reduces misjudge probability of the Gray code value greatly, and enhances decoding reliability. In addition, contrast to grey stripe, color stripe can reduce the edge detection error from stripe diffusion.To improve sampling density of the code structured light, insert different color stripe of specific breadth between adjacent colorful stripes based on color edge Gray code, sample on the edge and center of specific breadth stripe, which can improve sampling density withnot adding project patterns. Adopting the coding method of stripe dividing color Gray code to 3D measurement, the key factor of ensuring measurement precision is detecting the edge and center of color stripe taken as sampling dot accurately. For the character of code stripe and line scan technology, sub-pixel stripe edge detecting algorithm based on color component intersecting point and sub-pixel stripe center detecting algorithm based on color component gravity model method are supposed. And relative simulation experiments have been made to validate the feasibility and veracity of the method.Considering the factors of system hardware, ambient light illumination, shooting angle and space object geometry shape, color distortion of color stripe image from these factors can impact stripe detection precision. So it is necessary to revise color. In this paper, color calibration to projection apparatus and camera under natural light is adopted to remove the influences from different color components. Normalized color model l1l2l3 space realizes the normalization of color stripe image, which can remove the influences from the factors of ambient light illumination, shooting angle and space object geometry shape, and ensure detecting the edge and center of color stripe on sub-pixel order accurately. Simulate projection apparatus, camera, measurement object and environment, and the simulation code images have been used to reconstruct object surface under specific math model with 3dmax and Matlab. Contrast experiments between color Gray code center coding, decoding and stripe dividing color Gray code coding, decoding.It constructs the experiment devices based on stripe dividing color Gray code coding method, and designs the system parameters, calibrates parameters of experiment devices using linear calibration. Uncertainty of the measurement has been analyzed and 3D measurement experiments for typical and complex surfaces have been made. From the results of the experiments, in the measurement range, the maximum measurement error is less than 2mm, measurement accuracy is 0.2%, and reconstructed complex surface can match the measurement surface and reflect the surface pattern smoothly and particularly.This research provides new principle and technology for structured light, realizes 3D measurement under high accuracy and dense sampling, which is important to improve the structured light 3D measurement technology level and enlarge application domain.