纸张平整度视觉精密测量系统

Visual Precision Measurement System for Paper Flatness

针对纸张平整度测量,研究和提出了基于四步相移法的面结构光三维测量方法.首先,DLP投射正弦条纹图像到待测纸张表面,光栅条纹以1/4周期为步长平移扫描.然后由相机采集经待测纸张表面形貌调制后的结构光分布信息,并利用四步相移法获取结构光图像的相位主值.最后采用多频外差原理实现解调,获得绝对图像相位的解调信息,经相位与高度之间的映射关系得到纸张高度信息并重建出纸张表面形貌.采用纸张表面点云高度坐标的极差和标准偏差对其平整度进行定量评价.实验结果表明,测量精度达到0.1mm,测量时间小于2秒,其稳定性和测量精度能够满足纸张平整度的测量要求.

Aiming at the paper flatness measurement, a method based on four-step phase-shifting algorithm has been studied and proposed for the structured light measurement. The sine light that projected to the paper surface by DLP is scanned in steps of 1/4 period. After modulated by the surface topography of the paper to be measured, the structured light distribution information is acquired by the camera along with the phase main value of the structured light obtained through four-step phase-shifting algorithm. Finally, the absolute phase demodulation can be achieved through the multi-frequency heterodyne principle and the paper surface topography can be reconstructed through the height information after mapping the relationship between the phase and height. Using paper surface coordinate point cloud height range and standard deviation for quantitative evaluation of its flatness, the experimental results show that the measurement accuracy and stability meet the requirement of paper flatness measurement with the accuracy of 0.1mm and the measurement time of less than two seconds.