Web steering for an image recorder

In an imaging apparatus for imaging successive regions of an energy-sensitive medium with an energy beam, a mechanism for positionally guiding the medium into positional registration to the energy beam so that each of a plurality of successive regions of the repositioned medium may be imaged by the energy beam, the imaging apparatus positional registration mechanism comprising:

• marking means for recording registration marks upon the energy-sensitive medium at a region thereof;
• transport means for moving successive regions of the medium into position relative to the energy beam so that each of a plurality of successive regions of the repositioned medium may be imaged by the energy beam, the transport means being controllable in its movement of the medium so as to more precisely establish the positioning thereof;
• and
• regional image registration control means responsive to the registration marks of a one imaged region of the energy-sensitive medium at a time after the medium has been moved relative to the energy beam for controlling the transport means so that positional errors in the repositioning of the medium may be reduced, and so that each successively-imaged region of the image is in better registration, one region to the next, the regional image registration control means including
• a split four quadrant photodetector, affixed to the frame, for sensing the optically-recorded registration marks, and
• a servomechanism, affixed to the frame, responsive to the sensed registration marks for physically moving at least one of the plurality of nip rollers so as to alter the path of the energy-sensitive medium during its repositioning.

In an imaging apparatus for imaging successive regions of an energy-sensitive medium with an energy beam, a mechanism for positionally guiding the medium into positional registration to the energy beam so that each of a plurality of successive regions of the repositioned medium may be imaged by the energy beam, the imaging apparatus positional registration mechanism comprising:

• marking means for recording registration marks upon the energy-sensitive medium at a region thereof;
• transport means for moving successive regions of the medium into position relative to the energy beam so that each of a plurality of successive regions of the repositioned medium may be imaged by the energy beam, the transport means being controllable in its movement of the medium so as to more precisely establish the positioning thereof;
• regional image registration control means responsive to the registration marks of a one imaged region of the energy-sensitive medium at a time after the medium has been moved relative to the energy beam for controlling the transport means so that positional errors in the repositioning of the medium may be reduced, and so that each successively-imaged region of the image is in better registration, one region to the next;
• and
• a clamping means for holding the energy-sensitive medium stationary relative to the energy beam during the imaging of each successive region, the clamping means comprising
• a pressure pad that is moved into contact with, and away from, the energy-sensitive medium in order to respectively allow the medium to be held stationary, or repositioned by the transport means, relative to the energy beam.

A registration method, performed in an imager having a frame that moves an energy-sensitive medium stepwise in position and that exposes the energy-sensitive medium at each successive position with an energy beam, directed to positionally registering successive images successively exposed in successive regions of the medium, one image to the next, the registration method comprising:

• stepwise mechanically repositioning the energy-sensitive medium relative to the frame and transversely relative to an energy beam in order that successive regions of the medium may be successively imaged with the energy beam, one region to the next;
• and, before each stepwise repositioning,
• recording optically detectable registration marks upon the energy-sensitive medium at each imaged region thereof;
• and then, at a time after the medium has been repositioned relative to the frame and transversely relative to the energy beam,
• optically sensing the recorded registration marks associated with a region already imaged;
• and, responsively to the sensed registration marks of this already-imaged region,
• controlling a next stepwise mechanical repositioning of the medium responsive to the sensed registration marks in order that, by this controlling, positional errors in this next stepwise mechanical repositioning of the medium may be reduced, this positional error reduction being to the effect that each successively imaged region of the image will be in better positional registration, one region to the next.

A registration mechanism for an imaging apparatus that records an image on a photosensitive medium that displays an immediate change in at least one property upon imaging, the mechanism comprising:

• a frame;
• an optical stage means, affixed to the frame, for generating a signal beam producing upon the photosensitive medium (i) an image, and (ii) optically detectable registration marks;
• a drive means, affixed to the frame, for stepwise positioning successive regions of the photosensitive medium relative to the frame and transversely relative to the optical stage means so that, as stepwise repositioned, the photosensitive medium may be imaged and marked in a region thereof, the drive means being controllable in its spatial repositioning of the medium;
• means for optically sensing the registration marks of a previously imaged and marked region of the photosensitive medium as each new region is successively stepwise transversely positioned by the drive means relative to the optical stage means;
• and
• control means responsive to the optically sensed registration marks for controlling the drive means in its spatial repositioning of the photosensitive medium transversely relative to the signal beam in order that, by this controlling of the drive means, positional errors in the stepwise repositioning of the medium may be reduced.