Slide Scanner Repair Manual Diagnostics and Troubleshooting
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Mean Vertical Misalignment
- The derived vertical component of misalignment caused by
misadjustment of aspect ratio.
In our example this is -0.04 pixels which is within the spec of 0.64 pixels. The test result is the
vertical offset caused by the fixed lead screw pitch. The operator can adjust out aspect ratio
offset by changing the horizontal magnification to match the fixed vertical magnification.
Best Mag Time Change (
m
sec) -
The derived number that reports to the operator how much
to adjust the Mag time to fix a problem.
In our example the reported number is 0.3 microseconds, indicating that no adjustment is
needed. When adjustment is required, it’s done by moving the lens block. The amount and
direction of lens block movement is suggested by the Best Mag Time Change number in units
of microseconds. See Mag and Focus adjustment procedure for more details.
Mean Horizontal Misalignment-
The derived horizontal component of misalignment typically
contributed by CCD tilt.
In our example the misalignment is derived as 0.01 pixels. If this number is high, the CCD tilt
is also typically a high number.
Estimated CCD Tilt (degrees) -
The derived number that reports to the operator how much
and what direction to adjust the tilt.
Tilt numbers such as the one in our example (0.01) are so close to zero that they may be
ignored. In cases where the motion test fails because of excessive tilt, the Estimated CCD tilt
number is used as guide to change the CCD tilt. With respect to the right side of the CCD
board, (as viewed from the front of the scanner) if the number is positive adjust the CCD
board down, if the number is negative adjust the CCD board up.
Peak swing misalignment - The derived number.
In our example the misalignment is 1.11 pixels.
Note: If the peak swing number approaches, or exceeds, twice the allowed “Peak (R-B)
Misalignment”, then adjustments to tilt or mag will not, by themselves, fix a
misregistration problem. An error of this magnitude indicates carriage problems
such as a defective leadscrew, guide rail, etc.
In our “good scanner” example, the Peak swing misalignment is 1.11. Twice the peak
(misregistration) of 0.63 would be 1.26 (2 times 0.63). Twice the allowed peak would be 2.22
(2 times 1.10) and our test result easily passes this test.
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