I say approximately because distortion at the edge of the field in an eyepiece changes this relationship somewhat.
说近似，是因为边缘变形改变了这种线性关系。

An image of the object is projected by the objective lens on to the photocathode of an image convert tube. If the screen is so far away from the eyepiece that the camera can be placed between.
如果投影屏距目镜很远, 照相机可放在两者之间。