Saturation avoidance by adaptive fringe projection in phase-shifting 3D surface-shape measurement
Saturation avoidance by adaptive fringe projection in phase-shifting 3D surface-shape measurement
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DOI：
10.1109/isot.2010.5687390
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发表时间：
2010-10
期刊：
影响因子：
--
通讯作者：
C. Waddington;J. Kofman
中科院分区：
文献类型：
--
作者：
C. Waddington;J. Kofman
条纹投影系统能够实现高精度的非接触式三维曲面全场测量。然而，当测量表面反射率范围较大的物体时，该系统容易出现强度饱和和低信噪比（SNR）。当指向相机的光强度超过最大强度量化水平时，就会发生强度饱和。低信噪比发生时，有一个低强度调制相比，在图像中的噪声量。饱和和低信噪比会导致显著的测量误差。本文提出了一种通过最大输入灰度（MIGL）自适应调整投影条纹图案强度，在物体表面测量中避免饱和的方法。通过将在不同MIGL下捕获的相移图像的强度组合成一组复合相移图像，可以在保持高信噪比的同时避免饱和。在测量不同深度的黑白棋盘时，与使用均匀MIGL的最高精度测量相比，新开发的方法平均减少了0.25 mm的误差。
Fringe-pattern projection systems are capable of non-contacting 3D surface full-field measurement with high accuracy. However, the systems are prone to intensity saturation and low signal-to-noise ratio (SNR) when measuring objects with a large range of reflectivity across the surface. Intensity saturation occurs when the light intensity directed to the camera exceeds the maximum intensity quantization level. A low SNR occurs when there is a low intensity modulation compared to the amount of noise in the image. Saturation and low SNR can result in significant measurement error. This paper presents a method for saturation avoidance during object-surface measurement, by adaptively adjusting the projected fringe-pattern intensities, through the maximum input gray level (MIGL). A high SNR can be maintained while avoiding saturation by combining the intensities from phase-shifted images captured at different MIGL, into a set of composite phase-shifted images. In measurement of a black and white checkerboard at different depths, the newly developed method reduced errors by an average 0.25 mm compared to the highest accuracy measurement using a uniform MIGL.