电子束快速成型设备偏扫系统工作频率高，磁偏扫装置的铁损、涡流等损耗导致偏扫轨迹产生偏差。通过获取偏扫区域内特征点基准偏扫参数并由插补算法计算区域内任意一点偏扫参数，能够较好地抑制动态偏差; 但由光学观察系统判断电子束斑点位置所获得的基准偏扫参数精确性较低。为提高偏扫轨迹精度，在现有电子束快速成型机上加装一种特征点参数采集装置，收集产生的二次反射电子，通过二次反射电子信号判断特征点通孔中心与电子束斑点中心的对中性。实验表明: 当电子束斑点位于特征点中心且聚焦于上表面时，二次反射电子信号最小，此时获得的基准偏扫参数精确性高，能够提高电子束偏扫加工的精度。

Electron beam rapid prototyping machine has high working frequency, trajectory deviation can be caused by many factors, such as iron losses and eddy. We conducted interpolation algorithm to restrain dynamic deviation by getting deflection scanning parameters. However, the way to acquire parameters through optical observation system has relatively low precision. In order to improve the trajectory precision, a parameter acquisition device is installed on the existing electron beam rapid prototyping machine, it can collect secondary reflection electrons and convert them into voltage signal and make it displayed. We can judge the relative position of hole center and electron beam center by the displayed signal. Experiments show that: when the electron beam focuses on the upper surface and its spot locates in the center of the feature point, secondary reflection electron signal is the minimum; meanwhile, the recorded deflection and scanning parameter has high accuracy, therefore the deflection scanning trajectory can be greatly improved.