Research On Three-dimensional Measurement Of Color Time-coded Structured Light

In recent years,non-contact 3D measurement technology has been widely used in the manufacture of products,safety testing,cultural relic protection and medical diagnostics,etc.In this technique,the color time-coded structured light has become a research hotspot in the field of structured light because it does not need to scan the object,projects fewer images,carries more information and has higher measurement efficiency.However,the problems of system nonlinearity and color channel crosstalk caused by the inherent properties of the system device affect the practical application of the method.In this regard,this paper studies the nonlinear correction algorithm of the device and the color channel crosstalk compensation method in order to improve the measurement accuracy of the measured target object.The main research contents are as follows:(1)The main measurement errors in the 3D measurement system are caused by the nonlinearity of the system devices.Aiming at the problem that the red,green and blue channels of color image share one correction value in the current gamma precoding nonlinear correction algorithm,which cannot reflect the sensitivity difference of different color channels,this paper proposes a gamma precoding algorithm based on color gray image projection.According to the different response degree of the color channel to the system,the maximum response interval of each channel and the value of the color gray image suitable for projection are obtained,and the precoding correction value suitable for each channel is finally solved.Experimental comparison is made between the proposed method and the common correction gamma precoding algorithm and the nonlinear correction algorithm based on Hilbert transform.(2)There is a color channel crosstalk problem in the captured image.Based on the color crosstalk model,the color crosstalk matrix is calculated and used to compensate the color fringe.Comparing the fringe color before and after crosstalk compensation,it is found that the color imbalance is adjusted well,which verifies the feasibility of the method.By comparing the phase curves before and after the compensation of a row in the three channels,it is found that the curves are lengthwise stretched and the intensity of the color stripes is increased after the compensation,which verifies the effectiveness of the method.In addition,color stripe image is used to replace gray stripe image for projection,which reduces the number of projection by eight,and improves the amount of image information and object measurement efficiency.(3)The 3D measuring platform was built,and the camera and the projector were calibrated by the checkerboard calibration method of Zhang Zhengyou,and the measuring system parameters were obtained.The method in this paper is compared with the method in this paper based on the best fringe selection algorithm and the method in this paper without the color channel crosstalk compensation.Then the method in this paper is used to measure the surface of different materials in three dimensions,and the surface information of the object under test is better obtained,which verifies the effectiveness and applicability of the method in this paper.