| 摘要 |
PROBLEM TO BE SOLVED: To prevent such a problem that light beams from the light source for optical transmission and reception or light beams except for external signal light enter the sensor for optical transmission and reception as noise light, by disposing a 1/4 wavelength plate in the region between a collimator lens and a sub mirror where a non-collimated light beam passes, thus achieving a bidirectional optical communication with high accuracy. SOLUTION: A telescope optical system 2 is equipped with, in the order according to the propagation of light when the system is used for receiving light, a main mirror 4, a sub mirror 5, a 1/4 wavelength plate 7, and a collimator lens 6, and the 1/4 wavelength plate 7 is disposed in the region between the collimator lens 6 and the sub mirror 5 where a non-collimated beam passes. In this system, part of the transmission light from an inner optical system 3 is reflected by the surface of the collimator lens 6 of the telescope optical system 2. However, the reflected transmission light never passes the 1/4 wavelength plate 7 so that it is not reflected by a polarized light beam splitter 10 but all of the light is transmitted and does not reach a receiving sensor 12. Therefore, the light may not have any adverse effect on the receiving characteristics. |
