Measurement of irradiance of 2 beam interference

[ppoonamk]

Hi,

I have an experiment set up to get two beam interference fringes. I would like to know how I could measure the actual amplitude of the irradiance from the experiment. I have with me a power meter and a CMOS camera. How can I go about this? Thank you

 

[sophiecentaur]

Your Camera Sensor will provide you with RGB values for each pixel. The response of the camera may not be linear - there may be a 'gamma' involved in the processing. If your power meter measures incident optical power, you could calibrate the CMOS sensor against it, to linearise the light / pixel value law. You would adjust the light level (neutral filter or iris) to vary the irradiance in a linear fashion with the power meter and look at the RGB (Y) values from the sensor. Of course, you would need to use a manual setting for the camera exposure and find a suitable range of values so that you get the 1 -256 values. A bit fiddly but quite doable with care, imo. You can then make a lookup table to convert camera values to relative illuminance.

 

[ppoonamk]

Hi,

Thank you for your idea. I made a lookup table to convert it to power readings and found the average calibration factor for a specific exposure time. Thank you so much for the help

 

[sophiecentaur]

I'm pleased that it's helped you with a solution. Digital cameras can be a brilliant 'free' piece of lab equipment.
BTY, is your calibration curve near a straight line? Are you sure you are set to Manual - cameras can be too damned smart sometimes?

 

[sardar]

for your question.

To measure the irradiance of 2 beam interference, you will need to use both the power meter and the CMOS camera. The power meter will measure the total power of the two beams, while the CMOS camera will capture an image of the interference pattern.

To get an accurate measurement of the irradiance, you will need to first calibrate the power meter by measuring the power of a single beam. This will give you a baseline value to compare to when measuring the total power of the two beams.

Next, use the CMOS camera to capture an image of the interference pattern. This will allow you to visually see the fringes and determine the relative amplitude of the interference pattern. You can then use the calibrated power meter to measure the total power of the two beams. By dividing the total power by the number of fringes in the image, you can calculate the average irradiance of the interference pattern.

It is important to note that the accuracy of your measurement will depend on the quality of your setup and the sensitivity of your equipment. Make sure to carefully calibrate and double check your measurements to ensure accurate results.

I hope this helps and good luck with your experiment!