在直接驱动激光聚变中，变焦辐照可使得激光焦斑随聚变靶丸缩小，可增大激光与靶的能量耦合效率。基于像传递技术并利用电光削波开关中的检偏棱镜同时实现光脉冲的分束与波形分割，这种方式可充分利用脉冲激光能量，可有多种光束分割形式，并具备脉冲整形的能力。在实验室实现了XeCl准分子激光3台阶变焦辐照，以条纹相机记录了焦斑变化过程。实验结果表明，电光削波开关中电光晶体驱动电压的前沿陡度直接影响到变焦台阶之间的边界陡度。

In direct-drive laser fusion, the laser-target coupling efficiency can be enhanced and therefore the necessary driving laser energy can be reduced if the laser spot is zoomed with the target during implosion. A focal zooming is realized by image relay, in which the laser pulse is separated and split by the prism in an optical swithch. By this scheme, the laser energy would not be wasted and that some multiple splitting ways and pulse shaping become possible. A three- stage focus zooming system of XeCl laser is established and the zooming process is recorded by a streak camera. The experimental results suggest that the edge gradient between the stages is determined by that of the driving pulse for the Pockels cell in the switch.