2022/04/12 - Microscope development meeting

Attendees

Attending:

Ian has polished the microscope picam code adding some camera specific functionality.
Ian has added some documentation in cockpit for device specific config. Not complete yet but much better than the complete lack of documentation that existed before
Ian has started implementing a Ludl controller. So far only supporting the stage and has substantial speed issues but is a work in progress. The controller can also support filter wheels, shutters and some basic digital and analog IO with the relevant modules. Ian's controller is very old but apparently the control set is still compatible. He has a newer Ludl controller as well in use that could be tested against.

Tom has several fixes in cockpit that need to be merged. Ian will look at them, although the most complex is about the python 3.8 windll loading issue. Tom has a suggested fix that we should check on other system before pulling.
Julio has been devoting significant effort to SLM calibration, including moving the magic modulation parameter out of the code into a config option.
The calibration process of he SLM and polarisation rotator was discussed.

How far out to push the diffraction beams, via the diffraction angle SLM parameter. Ian says that CryoSIM uses about 80% maximum to increase contrast in the collected data due to the effect of the modulation transfer function of the objective dropping dramatically at the edges of the back pupil.
Julio also had issues with the SLM images at very short camera exposures. The SLM has True Frame parameter which flips the control voltages every N frames to prevent charging and consequent damage to the SLM. He solved this by using more ND filters and longer exposures on the camera directly observing the SLM diffraction spots.
Ian Showed a powerpoint from Chris optomising the SLM modulation on the Oxford CryoSIM setup. He sent a pdf of this to Julio and will upload the original somewhere but it is large (90MB).