光电系统离焦量对其猫眼效应回波功率的影响规律及原因分析

Original analysis and influence of the focal shift on the retroreflected power of cat′s eye effect

离焦量是决定光电系统猫眼效应回波功率强弱的关键因素。为了分析不同离焦情况对猫眼效应回波功率的影响规律及原因,通过对光电系统猫眼效应几何光学传输模型的分析,推导了包含离焦量的猫眼效应回波功率和等效回波波束球心的表达式,分析了不同离焦情况对回波功率的影响机理,并进行了实验验证。研究结果表明:在离焦情况下,猫眼效应回波波束可以等效为从目标处发出的一束锥状球面波,随着离焦量的增大,该球面波的球心距接收点的距离逐渐增大,因此回波功率逐渐衰减;正离焦时,该等效球面波的球心与接收点位于目标的同侧,负离焦时,球面波的球心与接收点位于目标的异侧,因此,在相同离焦量条件下,负离焦所导致的回波功率衰减程度比正离焦时更大;实验结果验证了这个结论。

Focal shift is a critical factor that determines the retro-reflected power of the cat＇s eye effect. In order to study the rule how the focal shift affected the retro-reflected power of the cat＇s eye effect, a propagation model on the basis of geometrical optics was built. Then the expressions of the retro-reflected power and the equivalent center of the retro-reflected beam including focal shift were deduced. After that, the influence mechanism under different focal shift was analyzed, some experiments were also done. The results show that the retro-reflected beam can be equivalent to a pyramidal spherical wave when there is a focal shift. With the increase of the focal shift, the distance between the acceptance point and the center of spherical wave becomes larger, so the retro-reflected power decays. The center of spherical wave and the acceptance point are at the same side when the focal shift is positive, otherwise at theopposite sides. Therefore, under the same focal shift, the attenuation caused by the negative focal shift is much larger than the positive one. The experimental result is inline with the theoretical results.