An exact reference wavefront for a single paraxial surface that provides two perpendicular remote image lines instead of a single focal point has not been provided in the recent literature. A naïve estimate would state that it may have a toric form. We provide a proof for the nonexistence of an exact toric reference wavefront for intermediate spaces in cross-cylindic symmetrical optical systems where the two principal images do not coincide. As it will be shown, such a shape exists only at the second order in the coordinates $x$ and $y$ in departure from a plane.

中文翻译：

---

缺少用于变形系统的完美中间参考波前。

在最近的文献中尚未提供用于提供两个垂直的远程像线而不是单个焦点的单个近轴表面的精确参考波前。天真的估计会表明它可能具有复曲面形式。我们提供了两个主像不一致的跨圆柱对称光学系统中中间空间不存在精确复曲面参考波前的证明。如图所示，这种形状仅在坐标$ x $和$ y $离开飞机时处于第二阶。