Hello everyone, I have a ST2000XM CCD camera from SBIG and i am trying to measure the number of photons coming from a pulsating laser. The steps i follow for the measurement are -Place the laser diode pcb card so the spot light is on the center of the image sensor. -I turn off the laser and take a grab measurement from the CCDOps toolbar, the Hist icon has the average number of counts.From that Average*1.92M (pixel number)=Total energy in ADC counts. That's my Dark measurement. -Similar to that i take a grab measurement with pulsating laser on and calculate the laser counts subtracting the new total counts from the Dark counts. -Now i want to turn the ADC counts to photons.At the CCDOps toolbar on Display->image info it displays the Electrons per A/D counts conversion 0.62. I turn the ADC counts to electrons. -From the CCD sensor KAI2000M datasheet page 18, the Monochrome Quantum Efficiency at 520 nm is about 0.52, now i can convert the electrons to photons. Do you think my method for measuring the amount of photons is correct?? I await for your answers, Thank you in advance
You have the right idea, but I think it will only get you a ballpark number. I would recommend you calibrate the camera system first. Do a photon transfer curve for the system. That will at least make sure you have an accurate gain for the CCD camera system - they do vary a little from unit to unit. Janesick's book is the bible on this subject, but a quick Google turned up this presentation: http://www.narrowbandimaging.com/images/ptc_talk_wsp_2009_crisp_final_comments_web.pdf The one thing I can't tell you how to calibrate is the QE at the wavelength you are using. Please be aware that the QE curves provided by the sensor manufacturers may be somewhat "smoothed"; they sometimes have very narrow hills and valleys. A laser is a very specific frequency, so there will likely be some error caused by that. Measuring QE accurately is a very difficult task; you would have to follow up with the sensor manufacturer to see if they have better data available.
