When were bar code scanners invented?

The answer depends on how exactly you define "scanner". The pantelegraph,developed by Giovanni Caselli and used commercially in the 1860s, is generally considered first such device for practical use. It worked a bit like a FAX machine, using electromagnetic components to scan and reproduce images. However, it only transmitted what a person was writing or drawing.

The credit for the first image scanning and transmission device probably goes to the Belinograph in 1913; it eventually formed the basis for AT&T's "Wirephoto" service used in the 20's and 30's.