how to filter surounding light
I want to measure reflected light from an object with an photo diode
but i don't want surrounding light to effect measurement .
I thought of lighting the object with infrared light pulsed at a certain
frequentie and detect the signal back and read the detected level.
My fear is this way is sensitive for noise and i wand a high level
Are there good filters that pass light at an certain wave length?
an other way i thought of is to first measure surrounding light then light the
object with an additional light source measure again and subtract the
surrounding light from measurement with additional light
this method has also risks like is the surrounding light changes
Any body with suggestions or idea to this matter?
Electonic Wokshop Scoop
See also: www.piclist.com/techref/logic/dsps.htm?key=filter
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