Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!lll-winken!arisia!fischer
From: fischer@arisia.Xerox.COM (Ronald A. Fischer)
Newsgroups: comp.sys.mac
Subject: Re: New mouse design... WHY?!
Summary: xerox mouse technology
Message-ID: <736@arisia.Xerox.COM>
Date: 9 May 89 22:01:29 GMT
References: <7891@batcomputer.tn.cornell.edu> <431a1e09.a590@mag.engin.umich.edu> <12893@ut-emx.UUCP>
Organization: Xerox PARC
Lines: 47

The Xerox optical mouse design was invented at PARC in the 70s.  It
uses a pad printed with a fine grid of hexagonal interlocked black and
white dots and a special image recognizer chip in the mouse.  The
pattern on the pad is so fine that it looks like a solid gray unless
you scrutinze it.  The chip is mounted above an array of infrared leds
that illuminate the pad.  A lens and image conduit are molded into the
bottom of the transparent chip case.  The actual IC is mounted upside
down in the case so that the lens can focus the pad image on a small
CCD-like array built onto the chip's surface.  The array is scanned by
some recognition circuits that "watch" the white and black spots on
the pad image shift left right up or down or on the diagonals.  The
chip outputs quadrature.

Xerox optical mice are very small and lightweight.  They slide easily
on the plastic coated sheets that have adhesive to fasten them to your
(real) desktop.  I like them better than any other mouse I've ever
used.

These are also probably the cheapest mice in the world to manufacture.
The case contains a tiny PC board that holds the single image
recognizer chip, illumination leds and the three buttons.  That's
about all.

The design is versatile too.  A disabled person needed a less jumpy
mouse and (being that this was Xerox) someone just photocopied the
mouse pad on an enlarging copier, making the pattern bigger and
response slower.  There is probably a practical upper limit to this
when the image chip no longer sees the pattern but only blobs covering
the whole field.

Personally, I think this mouse design is another example of the
amazing work done at Xerox to bring their interface technology to the
public.  Perhaps Apple could license this technology and *really*
decrease the cost of their mice while making them almost immune to
dirt (you occasionally have to wipe off the pads that they slide on,
but this is trivial compared to cleaning the little rollers in Apple
mice).

Another interesting packaging option would be to make a trackball with
the hex pattern embedded in its surface and track it with the image
recognizer chip.

(ron)

PS- To head off the complaints, there was a time when an odd problem
caused the mice to "creep" when aligned in certain ways with the pad.
This has been fixed for about two years.  No one likes creepy mice ;-)