双频条纹投影是一种重要的三维测量方法。在实际测量过程中,如何兼顾测量速度和测量精度具有重要意义。介绍了一种混合双频算法,该算法共需要投射4幅条纹图像,包括3幅高频条纹图像和1幅低频条纹图像。采用三步相移计算高频条纹的背景强度和高频条纹截断相位;将低频条纹减去背景强度,并采用希尔伯特变换提取低频截断相位;采用几何约束方法展开低频截断相位,并将低频展开相位用于展开高频截断相位。为了验证所提方法的有效性,分别开展了仿真和实验研究。实验结果验证了所提方法可以有效地恢复出被测物体的三维形状。

The dual-frequency fringe projection is an important method for three-dimensional (3D) shape measurement. In the actual measurement process, how to balance the speed and accuracy has a remarkable impact on practical applications. This paper introduces a hybrid dual frequency algorithm, which needs to project four fringe images, including three high frequency fringe images and one low frequency fringe image. First, the background intensity and truncation phase of high frequency fringes are calculated based on three-step phase shift. Second, the background intensity is subtracted from the low-frequency fringes, and the low-frequency truncated phase is extracted by Hilbert transform. The low frequency truncation phase is unwrapped by the geometric constraint method, and the low frequency truncated phase is used to unwrap the high-frequency truncated phase. In order to verify the effectiveness of the proposed method, simulation and experimental studies are carried out respectively. Experimental results show that the proposed method can effectively restore the three-dimensional shape of the measured object.