The two ruler rods form an Angle which is overlapped on a measured Angle. The read number of the Angle reticle reflected onto the graduation ruler is a measured Angle.
两尺杆形成一个角重叠于被测角上，反映在刻度尺上的角度刻线读数就是被测角度。
2
When the display zone is overlapped with the image zone, the handling unit can compute the overlapping parts and read the corresponding number image and displays it on the screen.