Multi-lens focussing arrangement for laser graphics imaging apparatus

摘要

An arrangement for focussing a laser beam onto the imaging surface of a laser graphics imaging apparatus includes a viewing stage having a focussing lens and an associated eye lens that are mutually displaceable along a first optical axis through which the imaging surface is monitored in the course of the formation of a laser graphics pattern. Coupled with the viewing stage is a laser-beam imaging stage having a beam diameter adjustment lens and a beam splitter disposed along a second optical axis which intersects the first optical axis. The location of the beam splitter is such that a laser beam incident along the optical axis of the laser beam-imaging stage is directed through and focussed by the focussing lens onto the imaging surface. Displacement of the beam diameter adjustment lens causes the diameter of the pattern-forming laser beam to be varied. The beam splitter is disposed along the optical axis of the first stage at a location between the focussing lens and associated eye lens that is fixed relative to the imaging surface irrespective of displacement of the focussing lens and the eye lens with respect to the imaging surface. The laser beam is focussed onto the imaging surface by adjusting the displacement of the focussing lens relative to the imaging surface.