Software > PictureSnapApp

Check on image orthogonality

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This is an example of "spurious accuracy" in PictureSnap. That is to say, accuracy too good to be true, or at the very least, we got lucky!

A student had mounted their samples in the sample holder when we realized it would be a good idea to have a picture of them to make navigating her samples easier. So we decided to just use our document camera and take a picture of the entire holder.

I placed the sample holder under the camera and while watching the live image in the camera software, rotated the sample holder until it looked fairly orthogonal to my eye at least. We snapped the picture, cropped it and opened it into the PictureSnap feature in Probe for EPMA (we could instead have used PictureSnapApp but didn't this time). Here is the screen shot with the calibration points displayed:

One trick we did, is to utilize some scribed lines, I made on the sample holder a while back, to obtain the X/Y stage coordinates, and then use the optical camera on the EPMA to specify the Z height on the actual samples. This way, we are aligned to the sample holder in X/Y and calibrated to the samples in Z.   8)

So where is the "spurious accuracy"?  Well here is a screen shot of the calibration window, and remember, we just plopped the sample holder down on the counter and rotated it for approximate orthogonality by eye:

0.07% rotation?  Now that is lucky!


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