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uScope Navigator (Scan)

White Fields Focus Slower Than Non-White Fields
uScope Navigator (Scan)

Article ID: NSC1077
Created: 1 Sep 2017
Reviewed: 26 Oct 2017

Information in this article applies to:

  • uScope Navigator V4.0 and Later

Symptom

When scanning using exhaustive focus, I've noticed that the uScope takes a long time to capture a field that completely or mostly white. What is going on and is there any way I can speed up these scans?

Cause

White (or blank) fields are a challenge for whole slide scanners. The reason has to do with the way focus algorithms determine whether or not a field is in focus. Focus algorithms (like exhaustive focus) compare the focus score created for each image in a stack of images captured for a field. The image with the best (highest) score is the best focused and is therefore the one used for the scan.

In an effort to always capture the best focused image, the exhaustive focus algorithm extends the Z stack depth if focus doesn't converge within the normal stack depth. This has the effect of increasing the scan time by valuing focus quality over scan speed.

Blank fields have no content and, as a consequence, do not have focus scores that converge on a best focused image. So, the focus algorithm continues extending the focus stack depth and, therefore, spends more time looking for a well-focused image that doesn't exist.

Resolution

Unfortunately, at this time, there is no work-around or resolution to this issue. A future release of uScope Navigator will incorporate some type of blank field detection or avoidance process.

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