Wang Zhangying, Li Kui, Gao Nan, Meng Zhaozong, Zhang Zonghua
Opt Express. 2023 Nov 6;31(23):38318-38333. doi: 10.1364/OE.504447.
Fringe projection profilometry (FPP) has been widely used in many fields due to its fast speed, high accuracy and full-field characteristics. However, it is still a challenging problem to deal with high dynamic range (HDR) objects for traditional FPP, which utilizes a single exposure time or a single projection intensity. Overexposure will occur in areas with large reflectivity, which exceeds the maximum capturing capacity of camera sensors, resulting in the failure to obtain the accurate intensity, absolute phase and three-dimensional (3D) data. In this paper, a uniform blue image is projected to divide object surface into three areas with different reflectivity by using different intensity responses of RGB channels of color images. Crosstalk coefficient function is applied to obtain intensity of overexposed areas, and then the optimal exposure time of areas is calculated by the linear photometric response of the camera. Finally, three sets of blue fringe patterns with optimal exposure time are synthesized into the fused HDR images to calculate the absolute phase. Experimental results confirm that the proposed method can accurately measure HDR objects with large variation range of reflectivity.
条纹投影轮廓术（FPP）因其速度快、精度高和全场特性而在许多领域得到广泛应用。然而，对于传统的FPP来说，处理高动态范围（HDR）物体仍然是一个具有挑战性的问题，传统FPP采用单一曝光时间或单一投影强度。在反射率大的区域会出现过曝光，这超过了相机传感器的最大捕捉能力，导致无法获得准确的强度、绝对相位和三维（3D）数据。本文通过利用彩色图像RGB通道的不同强度响应，投影一幅均匀的蓝色图像将物体表面划分为三个具有不同反射率的区域。应用串扰系数函数获取过曝光区域的强度，然后通过相机的线性光度响应计算这些区域的最佳曝光时间。最后，将具有最佳曝光时间的三组蓝色条纹图案合成到融合的HDR图像中以计算绝对相位。实验结果证实，所提出的方法能够准确测量反射率变化范围大的HDR物体。
