To study the structure of telecentric beam path for zoom lens system, the axial displacement equation for the stop was deduced, which keep the systemtelecentric in all zoom position.
Furthermore, the selection of the double telecentric optical system ensures the correction of the trapezoidal distortion introduced by the tilt object surface.
选择双远心光学结构，便于对倾斜物面所产生的梯形畸变进行矫正。
3
The optical system only consists of three germanium lenses with a "negative-positive-positive" reversed telephoto telecentric structure in the image space.