Projection optical device for microreaders capable of varying magnification

Claim 1

In a microreader of the type having: a. a projection screen fixed with respect to a support; b. information means containing an array of information to be read; and c. optical means for projecting an information image from said information means onto said projection screen; the improvement wherein said optical means is capable of varying its magnification and comprises: d. projection lens means mounted on said support for movement along said information means and including a first reflector for projecting the information image; e. reflector means mounted on said support for movement in the same direction as said projection lens means and including second and third reflectors for receiving the information image projected by said first reflector and displacing and reversing the direction of the information image projection onto the projection screen; and f. drive means for moving said projection lens means and said reflector means in synchronism with a displacement ratio of 2: 1, said drive means comprising: i. four pulleys fixed on said support; ii. a movable pulley connected to said reflector means for movement therewith; iii. wrapping connector means trained respectively about two of said fixed pulleys, said movable pulley and the remaining two fixed pulleys; iv. means for rotating one of said fixed pulleys; and v. means for fixing another one of said fixed pulleys against rotation and for adjusting its position about its rotational axis to permit movement of said reflector means independently of said projection lens means.