Polaroid SprintScan SS35, Repair Manual

Page: 132 / 187

Slide Scanner Repair Manual Diagnostics and Troubleshooting
132
ball-slide, but the operator should be warned that doing so will add an equal tilt to the
carriage, and may make the problem worse.
Notes: • A tilt of the carriage on the ball slide does not affect static horizontal color
registration.
• Any reduction in Mean Vertical or Horizontal Offset will typically reduce Peak
Misalignment by the same amount. A Mean Vertical Offset of 0.2 pixels is often
worth repairing.
Motion Test
The single most important vertical motion measurement is the Peak swing misalignment .
The Peak swing is the maximum misregistration minus the minimum in pixels along the
entire height of the chevron test pattern (GMT Target) on either side of the V. If the Peak
swing approaches or exceeds twice the allowed Peak R-B Misalignment (1.1 pixels), then
mechanical adjustments to correct static color misregistration will not, by themselves, fix
the problem. This type of error is primarily caused by deviations in the speed or direction
of the carriage as it moves the target from top to bottom. They are caused by wobble in
the lead screw or in its interaction with the follower nut and the guide rail. Point defects
are isolated disruptions in the carriage travel which are typically associated with burrs (or
dirt) on the lead screw, guide rail, or within the ball-slide assembly.
The best way to identify the source of dynamic misregistration is to run the stand-alone
version of the motion test, Motion&CR&Res. The stand-alone motion test provides the
same detailed data as the integrated IPT version, but also provides a visual map of the
R-B misregistration line per line along the ascending and descending legs of the V’s. This
information can help to pinpoint the exact location of the problem along the carriage travel
distance.
Note: There are other secondary aberrations which might cause the same types of
artifacts, but to a much lesser degree.
These include: other axis rotational misalignment of the CCD, certain chromatic or
geometric aberrations in the lens, or lack of co-planarity between the slide and
CCD due to holder problems. Each and every problem might have its own
signature, and combinations of effects may make characterization or isolation of
the source difficult. If addressing the major causes above does not solve the
problem, try replacing the lens, carriage & transport, CCD & mounting block, or
cast optical housings, in that order to isolate the cause.