▁a ▁C CD ▁reader ▁and ▁a ▁pen ▁or ▁las er ▁sc anner ▁is ▁that ▁the ▁C CD ▁reader ▁is ▁meas uring ▁em itted ▁ambient ▁light ▁from ▁the ▁bar code ▁whereas ▁pen ▁or ▁las er ▁sc ann ers ▁are ▁meas uring ▁reflected ▁light ▁of ▁a ▁specific ▁frequency ▁origin ating ▁from ▁the ▁sc anner ▁itself . ▁LED ▁sc ann ers ▁can ▁also ▁be ▁made ▁using ▁C M OS ▁sens ors , ▁and ▁are ▁replacing ▁earlier ▁Las er - based ▁readers . ▁ ▁Camera - based ▁readers ▁ ▁Two - dimensional ▁imag ing ▁sc ann ers ▁are ▁a ▁newer ▁type ▁of ▁bar code ▁reader . ▁They ▁use ▁a ▁camera ▁and ▁image ▁processing ▁techniques ▁to ▁decode ▁the ▁bar code . ▁ ▁Video ▁camera ▁readers ▁use ▁small ▁video ▁cam eras ▁with ▁the ▁same ▁C CD ▁technology ▁as ▁in ▁a ▁C CD ▁bar code ▁reader ▁except ▁that ▁instead ▁of ▁having ▁a ▁single ▁row ▁of ▁sens ors , ▁a ▁video ▁camera ▁has ▁hundreds ▁of ▁rows ▁of ▁sens ors ▁arranged ▁in ▁a ▁two ▁dimensional ▁array ▁so ▁that ▁they ▁can ▁generate ▁an ▁image . ▁ ▁Lar ge ▁field - of - view ▁readers ▁use ▁high ▁resolution ▁industrial ▁cam eras ▁to ▁capture ▁multiple ▁bar ▁codes ▁simultaneously . ▁All ▁the ▁bar ▁codes ▁appearing ▁in ▁the ▁photo ▁are ▁dec oded ▁instantly ▁( Image ID ▁pat ents ▁and ▁code ▁creation ▁tools ) ▁or ▁by ▁use ▁of ▁plugins ▁( e . g . ▁the ▁Bar code p edia ▁used ▁a ▁flash ▁application ▁and ▁some ▁web ▁cam ▁for ▁query ing ▁a ▁database ), ▁have ▁been ▁realized ▁options ▁for