In order to ensure the large focal length (telescopic regime survey), the optical system, built according to the principle of the multipleinternalreflection (see figure) is used.
为了确保大焦距(伸缩制度的调查)，光学系统，内置根据对等原则的多重反射(见图)是使用。
2
The multiplereflection within the circular disc provides a design feature to reduce the influence of non-total internal reflection and significantly improves the measurement linearity.