Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!bu-cs!purdue!decwrl!hplabs!hp-pcd!hplsla!hpvcla!johne
From: johne@hpvcla.HP.COM (John Eaton)
Newsgroups: comp.periphs
Subject: Re: Laser printer and photocopier in one?
Message-ID: <3960001@hpvcla.HP.COM>
Date: 20 May 88 15:56:46 GMT
References: <17036@cornell.UUCP>
Organization: Hewlett Packard, Vancouver, WA
Lines: 19

<
> It would seem that since laser printers and photocopiers are basically
> the same on the inside, someone would market a device that fulfills
> the functions of both.  Indeed, I have seen such a creature from Xerox...
----------

 I heard that they work on opposite principles. Lasers use a beam of light to
make a dot on the paper while copiers use the absense of light to make the 
dot. One theory is that since copiers are a optical scanned device they have 
to use a positive development system. Lasers can use either a positive or 
negative system depending on whether or not you invert the signal to the 
laser. Since your typical page has more whitespace on it than dots it it 
more efficient to use a negative system and only turn on the laser for the 
minimun time.



John Eaton
!hpvcla!johne