Hi everyone,
This is a long shot, but I'm going to explain my problem and hope that someone has seen this issue before.
PROBLEM:
I am using a Newport PR50PP rotation stage that is controlled by a SMC100PP motorcontroller via LabVIEW. In my experiment, I rotate the stage 180 degree clockwise by 36 increments and then rotate back to "zero" counterclockwise. This "zero" point should be the same "zero" I started from before rotation. The issue is that it is off by almost an entire degree. I need it to always start at the same spot.
The big issue - The computer / rotation stage thinks it is back to the original "zero". I record the internal rotation unit of the stage after each movement and it tells me that it is at the same 0.00 it started at.
Q. Is this a communication issue between LabVIEW and the PR50PP or a mechanical problem?
OTHER NOTES:
- The rotation shift is repeatable and linear. I repeated it over 15 times and got roughly the same mismatch.
- How I discovered this problem -- I have a half-wave plate on the rotation stage and looked at it between cross polarizers. I recorded the Cos^2 intensity pattern from each sweep. Each pattern is rotated from the one before even though the computer records that they should be at the same position.
- I am running LabVIEW 2011 and using the SMC controls given by Newport. They communicate via USB to Serial.
- Attached is a technical description of the problem that my labmate wrote up.
Any insight is greatly appreciated.
~ Liz Cloos