you'll need a cam thats sensitive to the Infrared range, which is invisible to the human eye..
just take any remote, point it at your lens, press a button, take a pic/look at LCD and see whether you can see some light coming from your remote..
all you need to do next is to get an IR filter, a tripod and a bright sunny day..
anyway, do take a look the IR forum also.. there's more to just that..