Front projector with focal distance adjustment - has lever transmission of accelerating axial motion of transfocator

摘要

The front projector has a transfocator. The uniform rotation of the focal distance adjustment from shorter to longer focal distance on transfocators is effected by lever transmission of an accelerating axial motion of the transfocator, to equalize the axial beam shift of the centre of perspective during focal distance adjustment and sharpness adjustment. Preferably the vertically pivoting part of the stand head is mounted in one or more small and one or more large curved segments, with coincident axes of curvature passing through the point of intersection of the stand head with the optical axis of the camera objective.