System calibration

Automated applications of Quatm in routine system calibration and maintenance.

Overview

Besides physics experiments, Quatm also codes routine calibration tasks as standard experiment scripts, giving one-click execution and automatic recording. This covers common calibration needs such as camera dark noise, shutter response, frequency synthesiser verification and trigger-delay calibration.

Code structure

All calibration experiments follow the same structural pattern:

  • subclass the Experiment class
  • declare the device under test and the calibration parameters in build()
  • execute the calibration procedure in run() and record the results automatically

Typical calibration tasks

Camera dark-noise characterisation

Function: acquire image frames continuously under dark conditions and characterise the dark-current noise distribution.

Main steps:

  1. Switch off all light sources and set the camera exposure time
  2. Acquire N dark frames in a loop
  3. Compute the mean and the standard deviation of each pixel
  4. Save the noise map to HDF5

Devices involved: camera

Shutter response time measurement

Function: measure the delay of a mechanical shutter from the TTL trigger to fully open/closed.

Main steps:

  1. Align a photodetector with the beam behind the shutter
  2. Trigger the shutter open with a TTL signal and start high-speed acquisition synchronously
  3. Record the rise/fall edge times of the detector signal
  4. Repeat the measurement and average

Devices involved: shutter (TTL), photodetector

Frequency synthesiser verification

Function: verify the actual output frequency and power of a Valon 5009 or DDS frequency synthesiser.

Main steps:

  1. Set the frequency synthesiser to the target frequency
  2. Measure the actual output with a spectrum analyser
  3. Scan the frequency range and record the deviation
  4. Generate a calibration curve

Devices involved: Valon 5009/DDS (serial port), spectrum analyser

Camera trigger delay calibration

Function: measure the delay between the TTL trigger and the actual exposure window of the camera.

Main steps:

  1. Share the same TTL signal between the pulsed light source and the camera trigger
  2. Scan the trigger-delay parameter
  3. Detect the position at which the light pulse appears in each frame
  4. Calibrate the optimal delay value

Devices involved: camera, pulsed light source (TTL)