通过对常用离焦检测技术的分析, 提出了一种基于空间光学调制的离焦探测新方法。该方法利用压电陶瓷驱动变形镜对会聚光束进行调制, 在准焦位置放置针孔(或狭缝), 通过针孔(或狭缝)的调制光束被光电探测器接收, 经相关检波后获得离焦信息。测得的离焦信息包含离焦量和离焦方向, 且离焦信号电压与离焦量呈线性关系。搭建了实验装置, 利用100 Hz的正弦信号对光束进行调制, 检波后得到了焦前4 mm到焦后2 mm范围内的电压信号, 结果与理论推导相符。该技术适用于圆对称光束及非圆对称光束的离焦检测, 尤其适于具有柱面镜光路结构、需要快速、准确测量x和y方向离焦量的强激光领域。

A new method of defocus length detection based on optical modulator is presented after analyzing traditional detection methods. Using this method, the convergent beam is modulated with the piezoelectric ceramic driving deformable mirrors, and received by photoelectric detectors through a pinhole or slit. Then the defocus length can be obtained after correlation detection. The method can obtain defocus length and direction by one detector at the same time, and the defocus voltage varies linearly with defocus length. Experiments were conducted, in which the beam was modulated by a 100 Hz sine signal. Detected voltages within 4 mm before and 2 mm behind the focal plane were obtained, which are consistent with theoretical derivation. The technique can be applied to circular symmetric and non-circular symmetric beams, and is especially suitable for high power laser systems with cylindrical lens, which need simultaneous, accurate, and fast detection of defocus lengths in x and y directions.