which filter to use?

[Notay]

HI - I have a continous wave laser system which directs its laser output into a photomultiplier tube (used to measure the number of photons in the laser light and provide a voltage signal).

This voltage signal is wired into DAQ  system and a simple program has been created to acquire the voltage signals from the photomultiplier tube. However we have now added a light chopper ahead of the laser beam before entering the PM tube to provide a pulsed signal. The chopper is currently set to 500hz chopping frequency and hence we now get a sinuosidal wave  in our DAQ program.

is there any way to eliminate the sinusodal wavelength from the program through some sort of a filter which would retain the change in laser intensity as if the chopper wheel was not there? We need to keep the chopper wheel in place so i cannot just remove it.

many thanks for your help.

Notay

[johnsold]

It might be better to capture the peak values (or average of several samples near the peak if the signal is noisy) rather than trying to use a filter.

Is your chopper a typical "bow tie" mirror or a crossed polarizer which changes amplitude continuously?  The reason I ask is that the typical chopper would produce a square wave signal, not a sinusoidal one.  With square waves it is much easier to track the amplitude variations of the laser.

Lynn