A LED printer uses the xerographic(see xerography) process similar to a
laser printer. But instead of using a laser to create
an image on the photosensitive drum, it uses an array of
LEDs. This array is much smaller than a laser imaging unit,
so the printers can be made more compact and cheaper.
The printout quality from a LED printer is similar to a laser
printout(). The LED printer technology is, as far as i know, only
used by OKI (I think they have the patent). OKI uses this technology
in their printers and faxes thus helping to keep down the price.
To bad they try to save money on all other parts of the devices
and build them in a way that makes them a pain in the ass to
repair.