传统的格雷码加相移法已经广泛应用于三维测量，但是相位解包裹一般需要投影多幅格雷码条纹，如何实现快速、准确的三维测量仍具有一定挑战性。提出了一种基于几何约束的改进格雷码条纹投影三维测量方法，可以有效减少格雷码条纹的数量。为了实现高速条纹投影，使用二值抖动技术将8位正弦相移条纹转换为1位二值图像。总共使用六幅条纹图像，其中三幅相移条纹用于计算截断相位，三幅格雷码条纹用于对截断相位进行初步展开获得伪展开相位，最后利用几何约束对伪展开相位进行解包裹获得绝对相位。实验结果表明，所提方法可以有效地重建被测物体的三维形貌。

Conventional Gray-code (GC) plus phase-shifting methods have been extensively utilized for three-dimensional (3D) shape measurements. Nevertheless, how to achieve fast and accurate measurement remains challenging because multiple GC patterns are necessary for absolute phase recovery. An enhanced GC method based on geometric constraint was proposed, which would decrease the number of fringe patterns. The 8-bit phase-shifting patterns could be transferred into 1-bit binary ones by using the binary dithering approach to realize high-speed projection. Specifically, a total of six binary patterns including three phase-shifting patterns and three GC patterns were employed in the proposed method. The phase-shifting patterns were adopted to compute the wrapped phase, and then the GC patterns could be utilized to unwrap the wrapped phase to obtain a pseudo unwrapped phase. In the end, the absolute phase would be reconstructed after using the geometric constraint to unwrap the pseudo unwrapped one. The experiments demonstrate that the enhanced GC method is an effective way to reconstruct the 3D shapes of measured objects.