I redid the bead testing with UV fluorescent beads, 1um.
Using the green LED for illumination, I tested the Fast, Medium and Fine focus, looking again at resolution. Both the Fast and Medium focus gave the same results as previous tests. 1.9um. The theoretical resolution is (0.69 - 0.84um) for the 18x / 0.40 objective.
The fine focus however did give a 1.6um resolution so slightly better in focus.
Next I tried to improve the focus, by just changing the z steps. I tries +100, +200 & -100, -200. At +200 the focus was slightly better, the resolution was 1.37um, so better.
A nice change would be to be able to look at the image zoomed in while you focus. That way you could get a much better focus. That would improve the resolution. Is there a way to do a focal stack now?
On the razor blade method, I tried looking at the distance between the 80%-20% change. Looking at the numbers, the best I could get was 5.71um. Not sure how to improve this method, but the procedure is much more straight forward and probably easier to automate.
