COLLIMATOR VIEWFINDER Russian patent published in 1996 - IPC

FIELD: optical instrument engineering. SUBSTANCE: collimator viewfinder has beam splitter slanted to viewfinder axis, which beam splitter is shifted relatively the axis of the reflector and mark, disposed inside its case at the other side of viewfinder axis. Mark and slanted beam splitter are disposed between the beam splitter and eye, as a result light transmission is increased in collector's channel. When viewing image of the mark without illumination, the mark is placed above the reflector. Reflectivity coefficient of the beam splitter excesses over its light transmission coefficient. To improve reliability of the device, the viewfinder may be made of two wedges, which form flat-parallel plate. In this case, reflector and mark are made onto the wedge, being closer to observer's eye. To improve contrast of mark image at the surrounding background, light-attenuating coating may be applied onto entrance surface of the wedge being farest from the eye of observer. For any variant of making viewfinder, to control contrast of mark image, two polarizers may be installed in front of the beam splitter. One of beam splitters may rotate about viewfinder axis. EFFECT: reduced dissipated light; improved light transmission. 2 dwg