Design of Color Fringe Projection Sequences for 3D Shape Measurements

This paper studies the effect of different color fringe projection sequences for 3D shape measurement of general objects. A novel color correction method is also presented for reducing the image color errors induced from color coupling effect and color imbalance effect. First, three sequences of projected fringe patterns, including basic projection sequence, disordered projection sequence and ordered projection sequence, are proposed for 3D shape measurement by the digital fringe projection method. Effects of these three projection sequences on the quality of measured 3D object shapes are compared. It is found that the ordered projection sequence can reduce the phase errors effectively and improve the quality of the shape reconstruction results. Then, the image color intensity ranges for the red, green and blue color channels are adjusted respectively such that the color coupling effect and color imbalance effect can be reduced. The adjusted color intensities will also result in a breakthrough for measuring non-white object surfaces. Finally, an integrated program is developed in Visual .NET C++ by combining phase-shifting, phase-wrapping, and phase-unwrapping algorithms. 3D shapes of test objects are measured by this integrated program. From the research results, it shows that the reconstruction quality of the 3D shapes is improved by using the proposed ordered projection sequence and the adjusted color intensities.