Position of MFT head

jpbrown

Dear All

Looking for some help with understanding the automatic focusing on a Fotonowy MFT unit. Does anyone know whether there is a way to see where the 3.¼.0 MFT software thinks that the optical head is located along the positioning pillar? (E.g., maybe a distance from a zero value either in um, “turns,” or “clicks”). I can measure the distance with a micrometer (although not as accurately as I would like), and it occurred to me that there might be way of looking at the value in the software.

Does the software track the position of the MFT head?
What happens if you drive the optical head down to the bottom (or up to the top) of the positioning pillar? Are there limit switches at either end? If so, do the limit switches have the effect of zeroing any internal tracking of the position of the optical head?
I’m guessing that the there is no absolute mechanical zero on the unit, and that any internal quantification of the movement of the head is relative to the initial defocused position. Is this right?
Does the Debug Tracing facility produce any output about the position of the head (or activity of the motor that drives the head) which either provides a number for position, or could be used as a proxy for the position of the optical head?

Thanks for any help

zbyszek

jpbrown

Yes, it does. The software tracks steps of the stepper motor of the MFT. One step is about 12.5 um.
At the top of the pillar there is a mechanical limit switch. It sets the steps to 0. The accuracy of the switch is from 200 to 500 um. There is also a mechanical limit switch at the end of the optical head. That one prevents the head from going through a measured object.
There is an absolute zero due to the point 2, but we do not rely on it when auto-focusing. During the autofocusing the head goes up and the electronics detects maximum of the reflected light. This maximum corresponds to the focal distance between the final lens and a measured object.
I don’t know. Most likely it is there. However we can output those steps in the status bar for you, if this is helpful.

jpbrown

We can output those steps on the status bar for you> Great! How do we do this?

zbyszek

jpbrown
You say you need it and after a couple of days there is a new version of MFT software with the requested feature.

jpbrown

OK. I need it. Would it be possible to get the new version for Friday (US time)?

zbyszek

We have started the software changes to meet your requirement but it turns out we need to modify the firmware as well. Otherwise, when you press arrow keys on the instrument, the meter readings will be incorrect.

No chance it could be ready for tomorrow.

jpbrown

Got it. No worries - it was a big ask. When do you think it will be ready?

zbyszek

jpbrown
We need about two weeks to make the firmware update ready.
What is the S/N of the instrument that you are using?

This measuring feature will work like this:
You will see the some distance in um in the status bar.
There will be a key combination Ctrl-M Z to zero the meter.
When you move the head, through the software or by arrow keys on the device, the counter will go negative when the motion is downwards from the zero mark and positive for upward motion.

Will this be sufficient for you?

zbyszek

It is ready.