Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!nrl-cmf!mailrus!cwjcc!tut.cis.ohio-state.edu!rutgers!att!ihuxv!asmith
From: asmith@ihuxv.ATT.COM (00704a-Smith)
Newsgroups: sci.electronics
Subject: Re: visible infrared? (Mouse Systems Mouse)
Keywords: LED,IR,visible,mouse,Mouse Systems
Message-ID: <3099@ihuxv.ATT.COM>
Date: 4 Jan 89 15:31:01 GMT
References: <743@optilink.UUCP> <501@igor.Rational.COM> <1574@kodak.UUCP>
Reply-To: asmith@ihuxv.UUCP (00704a-Smith,A.)
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 22

In article <1574@kodak.UUCP> ornitz@kodak.UUCP (barry ornitz) writes:
>I thought this sounded funny, but I just opened up my PC Mouse to be sure.
>There are two LED's, visible red and IR.  Next to the LED's are two spherical
>lenses mounted in holes in the printed circuit board.  These lenses focus the
>reflected light via a reflector on the top cover of the mouse to two associated
>photodetectors mounted on the circuit board.  A second giveaway is the fact 
>that the mouse pad is printed in two colors giving a different contrast to
>the red and IR beams.
>
                                                    Barry

Yes. Optical mice work with two pairs of LEDs and photodetectors. One
pair is used to detect horizontal motion while the other is used for
vertical motion. The stripes are different colors because the LED's 
operate at different frequencies so as not to interfere. One color stripe
runs horizontally while the other runs vertically.
               
                                                  Art

Bug? What bug? That's a feature!!
The ideas presented here have nothing to do with reality or my
employer.