Hey experts
I'd like to build a circuit which can detect people within 10-15 metres in a small angle of about 15 degrees (or narrower if possible). It should be fast enough to detect even if people run through the "beam".
The circuit should be relatively compact and will run on battery power (no particular voltage decided yet)
Is such a circuit realistic?
If you have any thoughts to share or links to someplace where someone already invented this little circuit, please feel free to post.
All help will be appreciated.
Thanks