针对三维形貌测量中结构光照明系统投影速度慢、结构复杂、在线集成困难的问题,提出了一种基于声光栅的变频条纹投射系统。该系统利用拍频信号驱动声光偏转器,在声光晶体中形成两个重叠的光栅,光源发出的激光以布拉格角入射,形成两束一级衍射光,经透镜聚焦形成光强按正弦规律分布的结构光条纹。建立了数学模型,同时提出了一种新的相位凝固技术,使条纹空间频率和相位的变化规律得到了很好的解释。该系统结构紧凑、体积小,全电控可调,无任何机械移动部件,具有条纹投影速度快、精度高、动态可编程的特点。应用该系统对石膏像形貌进行测量,获得了用于三维成像的相位图。该投射系统对于解决复杂几何形状物体的三维测量问题具有较高的工程应用价值。

A new acoustic grating fringe projector (AGFP) was developed for solving the problems of the low speed, complex structure and hard on-line integration of the traditional structure light illuminator in three-dimensional (3-D) measurement. An acousto-optic deflector (AOD) driven by a beat frequency signal generated two overlap gratings inside the acousto-optic (AO) crystal and diffracted the incident laser beam into two first-order beams. The two first-order beams were brought together by a projection lens and the fringe pattern was generated by the interference of them. We established the math model of the fringe pattern and proposed a new method called ‘phase freezing’ to explain the changes of the spatial period and phase of fringes. The acousto-optic technique for producing fringe patterns provided a number of significant benefits, such as completely solid state, small scale, electronically control without any mechanical moving part, high precision and dynamic programmable ability. We obtained a precise phase map of a plaster statue with the device. The projection system is of great engineering value in high-accuracy three-dimensional non-contact complicated profile measurement.