axis-beyond object point是什么意思

用法例句

Lens equation of axis-beyond object point is derived by Fermat s principle, the process of derivation indicates clearly that near axial conditions are necessary and sufficient conditions of ideal image formation.

用费马原理推导透镜对轴外物点的物像公式,推导过程清楚表明近轴条件是理想成像的充分必要条件。