Shape and colour measurement of colourful objects by fringe projection
Shape and colour measurement of colourful objects by fringe projection
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DOI：
10.1117/12.794561
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发表时间：
2008-08
期刊：
影响因子：
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通讯作者：
Zonghua Zhang;C. Towers;D. Towers
中科院分区：
文献类型：
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作者：
Zonghua Zhang;C. Towers;D. Towers
在本文中，我们提出了一种通过将单独的红、绿、蓝彩色条纹图案投射到彩色物体表面来测量其形状和颜色信息的新方法。就物体表面的颜色而言，三个颜色通道中每个像素位置的调制值是不同的。例如，当将蓝色条纹图案投射到一个红色点上时，相应像素的条纹调制过低，无法准确计算相位（形状）信息；但使用红色条纹图案时会获得较高的条纹调制。因此，可以通过投射红色条纹图案来计算红色点的相位信息。对于每个物体点，通过比较三个颜色通道的调制值，可以选择调制最大的通道，从而通过相移算法可靠地获得相位信息。条纹级数信息是通过使用最佳三频选择方法获得的，因此在确定表面有台阶或大斜率的物体的条纹级数和三维形状时具有最大的可靠性。由于使用了三个颜色通道，可以从相同的条纹图案中以高动态范围提取物体表面的颜色信息。颜色通道之间的色差是不可避免的，但可以通过基于软件的方法消除。使用最近开发的彩色条纹投影系统，将单独的彩色条纹图案投射到具有不同颜色图案的杯子、彩色盒子和盘子以及彩色棋盘格卡片上，以测试所提出的方法。结果显示了可测量的颜色范围，并且可以可靠地获得彩色物体的形状和颜色信息。
In this paper, we present a novel method to measure shape and colour information of a colourful object by projecting separate red, green and blue colour fringe patterns onto the object surface. With regard to the object surface's colour, the modulation at each pixel position in the three colour channels has different values. For example, when projecting blue fringe patterns onto a red point, the corresponding pixel has too low a fringe modulation to accurately calculate the phase (shape) information; but with red fringe patterns a high fringe modulation is obtained. Therefore, phase information of the red point can be calculated by projecting red fringe patterns. For each object point, by comparing the modulation values from the three colour channels, it is possible to choose the channel having maximum modulation, and hence phase information can be reliably obtained by the phase-shifting algorithm. The fringe order information is obtained by using the optimum three-frequency selection method, so there is a maximum reliability in determining the fringe order and the 3-D shape of an object with step or large slopes on the surface. Since three colour channels are used, colour information of the object surface can be extracted with high dynamic range from the same fringe patterns. Chromatic aberration between colour channels is unavoidable and can be eliminated by a software-based method. Using the recently developed colour fringe projection system, separate colour fringe patterns are projected onto a mug having different colour patterns, a colourful box and plate, and a colour checker card to test the proposed method. The results show the range of colours that can be measured and that shape and colour information of colourful objects can be reliably obtained.