Instrument Troubleshooting - Polarization-Lab/ULTRASIP-FIREXAQ GitHub Wiki

The camera is making a high pitched sound

Turn the camera off immediately and let it sit for a bit, this sound means it is overheating. When the ImagEM camera is turned on, the fan will initially be running but will turn off as soon as a measurement is taken unless the fan is manually enabled in the code. To enable the camera fan, use the following:

src.SensorCoolingFan = ‘on’

It is also recommended to use if statements to check if the camera fan is on before every image acquisition:

if src.SensorCoolingFan ~= 'on’

src.SensorCoolingFan = ‘on’

end

If the fan was on the entire time given by the fan indicator on the camera, then an addition cooling method is needed.

Inconsistent light source in lab setting

Run Record.m. This script plots the average camera counts versus the elapsed time. A temporally consistent source will have a relatively flat plot. It may fluctuate between +/- 2000 counts due to the inherent noise of the camera.

Try changing the batteries or the bulb, if neither work, try a different source.

ELL14 is not aligned properly

Place a polarizer in front of the source, level with what you want to be considered zero and run either Calibrate.m or AlignUV.m. Both scripts output the correct offset for the ELL14 motor. When the script finishes running, change the "home" variable to the position given by the script and run ELL14Connect(comPort, home). Use copy and paste to avoid errors.

Example of misaligned (left) versus aligned (right) using Calibrate.m:

Image capture takes a significant amount of time

The camera object must be started before it can take a measurement. When capturing an image with UV_Data.m, the camera, if it is not already started, will start itself, take an image, and then stop itself. The start function takes a significant amount of time to complete, more than the actual image capture in most cases.

For applications where the camera settings do not change, it is wisest to manually start the camera at the beginning of the script using start(vid) so that the image capture function can skip the start and stop phase of taking data. To stop the camera, use the command stop(vid) when done taking data.

DoLP is not (or not close enough to) 100% when it should be

There are many problems to consider when the DoLP is lower than expected. However these are the most common:

  • One possibility is that the diattenuation of the polarizer used in the instrument isn’t high enough. This issue can be mitigated by stacking polarizers or replacing said polarizer with a better one.

  • Another possibility (only for laboratory setting) is that stray light with unknown polarization might be getting into the system. Covering the setup of the camera with a blackout curtain usually eliminates this problem.

Retake the measurement and see if the same DoLP appears. If not, then:

  • The light source could be temporally non uniform. If this is a problem, run Record.m to investigate further.

  • The ELL14 motor could have gotten stuck on something and didn’t get to the position it needed to get to. When this is the problem, an unusual sound will come from the motor.

  • Try adding a one to two second pause between moving the motor and capturing an image. Although the reason why this works is not yet understood, doing so greatly improves data quality.