| 摘要 |
An external ring flange (23) on the inner tube (11) is tensioned between a pair of elastic O-rings (24) which encompass the inner tube on either side of the flange. These O-rings are accommodated in a seat (20) formed by the outer tube (10), and consisting of a widened tube end part. The ring flange (23) is fitted on a ring (21) screwed on to the inner tube (11). The widened end part (20) of the outer tube is closed by a lock ring (25) screwed into it, and serving to tension the ring flange (23) between the O-rings (24). The inner tube locates against the lock ring (25) with a sealing ring (26) interposed between them. An eyepiece tube is fixed to the outer tube by a screw union, and inside the tube is a flat-ground glass disc with an anti-reflection layer and encompassed by an elastic sealing ring. In a slot in the inner tube is a light diode for projection of a red light beam against the centre of the sight lens (14). |
