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首页> 外文会议>SPIE Conference on Automated Visual Inspection and Machine Vision >Robust phase unwrapping based on non-coprime fringe pattern periods for deflectometry measurements
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Robust phase unwrapping based on non-coprime fringe pattern periods for deflectometry measurements

机译：基于非协调条纹图案的鲁棒相展开，用于偏转测量

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Phase-measuring deflectometry is a technique for non-contact inspection of reflective surfaces. A camera setup captures the reflection of a sine-modulated fringe pattern shifted across a screen; the location-dependent measured phase effectively encodes the screen coordinates. As the used fringe patterns are much narrower than the screen dimension, the resulting phase maps are wrapped. The number-theoretical solution uses the Chinese remainder theorem to calculate an unwrapped phase map from repeated measurements with coprime fringe widths. The technique is highly susceptible to phase noise, i.e. small deviations of the measured phase values generally lead to unwrapped phase values with large errors. We propose a modification and show how non-coprime period widths make phase unwrapping robust against phase noise. Measurements with two non-coprime fringe period widths introduce the opportunity to discriminate between "legal" measured phase value pairs, that potentially originate from noise-free measurements, and "illegal" phase value pairs, that necessarily result from noise-affected measurements. Arranged as a matrix, the legal measurements lie on distinct diagonals. This insight not only allows to determine the legality of a measurement, but also to provide a correction by looking for the closest legal matrix entry. We present an experimental comparison of the resulting phase maps with reference phase maps. The presented results include descriptive statistics on the average rate of illegal phase measurements as well as on the deviation from the reference. The measured mean absolute deviation decreases from 1.99 pixels before correction to 0.21 pixels after correction, with a remaining maximum absolute deviation of 0.91 pixels.
机译：相位测量偏转测量是用于反射表面的非接触检查的技术。相机设置捕获正弦调制条纹图案的反射在屏幕上移动;位置相关的测量阶段有效地编码屏幕坐标。由于所使用的条纹图案比屏幕尺寸要窄得多，因此将得到的相位映射被包裹。数字理论解决方案使用中文剩余定理来计算从具有共同测量的未包装的相位图谱。该技术高易受相位噪声的影响，即测量相值的小偏差通常导致具有大误差的未包装相值。我们提出了一种修改，并展示非协调期宽度如何使相位展开稳健的反对相位噪声。具有两个非协调条纹周期宽度的测量介绍了区分“合法”测量的相位值对之间的机会，其可能来自无噪声测量和“非法”相位值对，这必须由噪声影响的测量结果产生。被排列为矩阵，法律测量位于不同的对角线上。这种洞察力不仅允许确定测量的合法性，还可以通过查找最接近的法律矩阵条目来提供校正。我们介绍了所得相位映射与参考相位映射的实验比较。所呈现的结果包括关于非法相位测量的平均速率以及与参考的偏差的描述性统计数据。测量的平均绝对偏差在校正后从1.99像素降低到校正后0.21像素，其剩余最大绝对偏差为0.91像素。

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