Slide Scanner Repair Manual Diagnostics and Troubleshooting
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of the CCD as well. Very small tilt adjustments can sometimes be made by loosening the
mounting screws and rotating the fixed rail of the ball-slide, but the operator should be
warned that doing so will add an equal tilt to the carriage, and may exacerbate dynamic
affects.
Note: A tilt of the carriage on the ball slide does not affect static horizontal color
registration.
Dynamic (Motion Effects)
Dynamic errors of the color registration are referred to as motion artifacts. The single most
important measurement of the dynamic misregistration is the Peak swing misalignment .
Peak swing is the maximum misregistration minus the minimum in pixels along the entire
height of the chevron test pattern on either side of the V. If the Peak swing approaches or
exceeds twice the allowed Peak R-B Misalignment, then adjustments to correct static color
misregistration will not, by themselves, fix the problem. They are primarily caused by
deviations in the speed or direction of the carriage as it moves the target from top to bottom.
They can also be broken down into horizontal and vertical, but in practice, they are primarily
vertical, due to the constraints placed on the drive system by the ball-slide.
The primary dynamic errors can be broken down into point defects or cyclical patterns.
Cyclical errors typically occur once or twice per motor revolution, which is equivalent to 200
lines. 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.
In general, cyclical artifacts generate higher RMS vertical motion errors than do point
problems. 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 location of point artifacts, and identify the entire
profile of the problem.
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.
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