Auto-focus printing below 1,1 {33 {0 magnification

Claim 1

In photographic printing apparatus including a housing and a print plane, a negative holder and a magnifying lens of fixed focal length positioned in a lens carriage in said housing between said print plane and said negative holder, an automatic focusing drive mechanism operative to maintain said apparatus in focus for a continuous range of magnification varying from less than unity to substantially more than unity, said mechanism comprising: first linear positioning means coupled to said lens carriage and operative to position said lens the required distance from said print planE to effect a given magnification; second positioning means coupled to said negative holder; support means extending from said lens carriage; a bell crank having first and second arms, said bell crank being pivotally supported by said support means; bearing means supported on said first arm of said bell crank and connected to said second positioning means to control the position thereof; cam groove means supported by said housing and cam follower means supported by said second arm of said bell crank and positioned to ride in said cam groove means whereby movement of said cam follower means in said cam groove means upon movement of said lens by said first positioning means will cause rotation of said bell crank and corresponding movement of said bearing means to control the relative position between said lens carriage and said negative holder for the required distance to maintain focus or any selected magnification.