Z-focus on rectangular grids

[Falling Man]

I'm running PFE on a JEOL 8200 and setting up analyses on a rectangular grid.  The "Start" and "Stop" positions have different Z-axis positions.  However, when PFE calculates the Z position for the points on the grid it uses the value for the "Stop" point and assigns that to all of the points on the grid.  As such, most of the points, with the exception of "Stop" are out of focus.  Has anyone seen this problem?  Solutions?

[Probeman]

I'm running PFE on a JEOL 8200 and setting up analyses on a rectangular grid.  The "Start" and "Stop" positions have different Z-axis positions.  However, when PFE calculates the Z position for the points on the grid it uses the value for the "Stop" point and assigns that to all of the points on the grid.  As such, most of the points, with the exception of "Stop" are out of focus.  Has anyone seen this problem?  Solutions?

Hi Rick,
You are correct.  The two point rectangular grid assumes the current position for all z values. 

The Z position interpolation works for the traverse because two points define a line, though not a plane. But we probably could make an assumption about the slope of the plane and interpolate the Z positions when the Z positions of the two rectangular corners are different.

In the meantime just use the polygon grid dialog in the Digitize window. Define 4 points for a rectangle (at least three or more for any shape polygon) and the app fits either an average Z position or plane fit interpolated Z for all Z positions.
john

[Falling Man]

OK, I see the issue.  Z-interpolation for the rectangular grid would be useful, however.  Perhaps, you could use the X-Y positions of UL/LR to choose either UR/LL, drive the stage to one of those position, focus Z and then use the polygon feature to fit a plane and interpolate Z.

Thanks!

[John Donovan]

OK, I see the issue.  Z-interpolation for the rectangular grid would be useful, however.  Perhaps, you could use the X-Y positions of UL/LR to choose either UR/LL, drive the stage to one of those position, focus Z and then use the polygon feature to fit a plane and interpolate Z.

Thanks!

Hi Rick,
That's a good idea. 

I'll have it default to one of the other corners with the current Z, but also allow the user to update that third point to something different, just in case that corner is not good for stage focusing.
john

[John Donovan]

OK, I see the issue.  Z-interpolation for the rectangular grid would be useful, however.  Perhaps, you could use the X-Y positions of UL/LR to choose either UR/LL, drive the stage to one of those position, focus Z and then use the polygon feature to fit a plane and interpolate Z.

Thanks!

Hi Rick,
I think I implemented a Z focus in the digitize rectangular grid dialog along the lines you suggested.



With this new Z focus position one can select average Z or a 3D plane fit for the interpolated Z positions.

Please let me know if this works for you.
john

PS This method allows the user to perform a z focus at any stage position (other than the two corners), but I just realized that I should add code to update the x/y focus position, whenever the user updates one of the other corners.  Then one can simply use the Move To button to move to it and focus the stage.

Edit by John: OK, I added an automatic update of the 3rd corner position when either of the two diagonal corners are updated.  Download is available now.