改进的阶梯相位去包裹算法研究

为减少投影条纹数量,提高测量速度,提出了一种 改进的阶梯相位去包裹算法。算法 采用彩色条纹投影测量物体三维形貌,将正弦和阶梯相位条纹分别输入彩色图像的红 色和蓝色通道构成彩色条纹,由DLP投影仪将四步相移彩色条纹投影到待测物体上,由彩色 CCD相机采集。利用颜色分离技术得到2组四步相移条纹图,其中一组为4幅正弦条纹,由四 步相移法求得正弦条纹包裹相位,另一组4幅阶梯相位编码条纹图,由与正弦条纹周期一致 的阶梯相位构成,经阶梯相位解码确定条纹级次,利用自校正算法去除条纹级次噪点后,实 现相位去包裹。进行了实际测量,结果表明,本方法 测量精度与采用四步相移法相当,但只需4幅条纹图,有效减少了投影和采集的条纹数量, 提高了测量速度。

An improved phase unwrapping method based on stair phase encoding

An improved phase unwrapping method is proposed in order to reduce the projection fringes and improve the measurement speed in three dimensional(3D) surface measurement.Color fringe patterns are generated by computer encoding with sinusoidal fringe and stair phase fringe patterns in red and blue channels .These color fringe patterns are projected onto the tested objects by digital-light-processing (DLP) projector.The deformed fringe patterns are capt ured by a color CCD camera.Then,the recorded fringe patterns are separated into their RGB components,and 2groups of four step phase shifting fringe patterns are obta ined. One group of the stripe is four sinusoidal pattern,and the wrapped phase is dete rmined by four-step phase shifting method.The other group of stripe is four ste p phase shifting stair phase fringe,whose stair changes are perfectly aligned with the d iscontinuities of sinusoidal fringe phase,which is used to determine the fringe order for the phase unwrapping.The self-correction method is applied to eliminate the noise of fringe order.Finally,the experimental evaluation is conducted to prove the validity of the proposed method.The results are analyzed a nd compared with those of the method by reference(14).The results are s imilar to those of the four-step phase method.But it needs only 4f ringe patterns,can effectively reduce the number of fringe projections and impro ve the measurement speed.