Lens focussing systems and means for moving lens means of an optical projection system

Claim 1

A LENS FOCUSSING SYSTEM COMPRISING A FIRST MOVABLE MEANS CONSTRAINED TO MOVE PARALLEL WITH THE OPTICAL AXIS OF THE FOCUSSING SYSTEM, A MOUNTING FOR RECEIVING A LENS MEANS OF THE SYSTEM AND ARRANGED TO BE MOVABLE PARALLEL TO THE OPTICAL AXIS WITH THE FIRST MOVABLE MEANS, SECOND MOVABLE MEANS CONSTRAINED TO MOVE PARALLEL WITH THE OPTICAL AXIS IN A DIRECTION OPPOSITE TO THE DIRECTION OF MOVEMENT OF THE FIRST MOVABLE MEANS, THE SECOND MOVABLE MEANS INCLUDING PULLEY MEANS SPACED FROM THE DIRECTION OF MOVEMENT OF THE FIRST MOVABLE MEANS AND HAVING AN AXIS WHICH EXTENDS PARALLEL WITH A DIRECTION NORMAL TO THE OPTICAL AXIS, CONTROL MEANS ADAPTED TO EFFECT MOVEMENT OF THE SECOND MOVABLE MEANS SO THAT THE SECOND MOVABLE MEANS UPON A CHANGE IN LENGTH OF THE OPTICAL PATH MOVES BY A PROPORTIONAL AMOUNT, AND COUPLING MEANS INCLUDING A BAND OR THE LIKE OF FIXED LENGTH ANCHORED AT ITS ENDS RESPECTIVELY TO AN ABUTMENT AND TO THE FIRST MOVABLE MEANS AND CO-OPERATING AT AN INTERMEDIATE LOCATION THEREON WITH THE PULLEY MEANS OF THE SECOND MOVABLE MEANS, WHEREBY MOVEMENT OF THE SECOND MOVABLE MEANS UPON ACTUATION OF THE CONTROL MEANS IMPARTS MOVEMENT TO THE FIRST MOVABLE MEANS SUFFICIENT TO BRING THE LENS MEANS INTO FOCUSSING POSITION IN THE OPTICAL PATH.