It is important to regularly assess the quality and performance of microscopes.
This blog post will gather and describe a practical guide to microscopes quality control
What need to be assessed?
Resolution
Fiel Illumination Uniformity
Channel alignement (Co-registration)
Illumination stability
Stage drift
Stage repositioning accuracy
Detector Noise
Illumination power warmup kinetic
After startup, an instrument takes time to reach a stable steady state. This duration defines the warmup period. it is critical to have at least once recorded a warmup kinetic to define the warm up period
Acquisition protocol
- Place a power meter sensor (Thorlabs S170C) on the stage
- Center the sensor on the objective
- Select the wavelength of the light source you would like to monitor on your power meter controller or software
- Zero the sensor
- Turn on the light source
- Record power over time
- Repeat steps 3 to 6 for each light source
Results
For each light source plot the measured power output (mW) over time.
For this instrument the warmup time is virtually null.
Calculate the relative power: Relative Power = Power/MaxPower and plot the relative power (%) over time
The 385nm, 475nm and 630nm light sources show some variability but this should not affect the measurement.
Conclusion
Warmup time for this specific instrument should be about 10 minutes
Illumination max power
This measure evaluates the maximum power produced by each light source. It accounts for the quality of the light source and the elements present on the light path. We expect a slow decrease over time (years) accounting for the aging of the hardware (light source itself and other optical components).
Warm up the system prior proceeding to the measurements
Place the S170C sensor onto the stage.
Center the sensor on the objective
Select the wavelength on your power meter
Zero the sensor
Measurements are made at the sample position with no objective. Input set to 100%. The maximum power output is measured using the Thorlabs power meter P100 and the S170C sensor.
It is important to warmup the system prior proceeding to the measurement of maximal power output.
Illumination power stability
The light sources used on a microscope should be constant or at least stable over the time scale of an experiment. For this reason
The protocol below is inspired by https://www.protocols.io/view/illumination-power-stability-and-linearity-measure-5jyl853ndl2w/v2
Record a kinetic of light intensity over time to define the optimal warmup time for your light source. Typical values are 10 min for LED and Arc lamps, 1h for lasers.
Place the S170C sensor onto the stage.
Center the sensor on the objective
Select the wavelength on your power meter
Zero the sensor
Measure the power