CCD detection and Modulation: Can it be done?

[Scott Sutherland]

Posted to CCD-world:
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Hello All:

My company uses CCD detectors as integrating detectors for low light
level spectroscopy.  I have an application in which I need to discriminate
between my analytical signal and ambient light.  If I were using 
a photomultiplier tube, the solution would be simple.  I would chop
my excitation light source (which generates my analytical signal when
it interacts with my sample) at some set frequency (chosen not to
have interference from common frequencies (e.g. 60 Hz)) and then I
would look at the response from the PMT that was modulated at that
frequency.  The ambient light would be DC and would then be descriminated.

I cannot think of ANY way to achieve this type of simple modulation with
an INTEGRATING detector like a CCD.  Does anyone out there have any 
suggestions?

Thanks for any help.

Scott Sutherland
Senior Scientist
GAMMA-METRICS

BTW, the one of our major applications requires that the CCD signal be
read out every 10 msec, so the modulation solution would need to be
able to discriminate between CW and modulated light in a 10 msec window.
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