I wonder if the high end models for gaming and design purposes will make =
a difference.=20
They utilize a lazer and some has a resolution of 9000dpi.

Just wondering
Audun=20

-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@............... =
On Behalf Of Randall Peters
Sent: l=F8rdag 19 januar 2008 15:41=20
To: psn-l@..............
Subject: optical mouse sensor

My colleague, John Lee, and I have developed a package that may be =
interesting to amateur seismologists.  A paper has been posted at =
http://physics.mercer.edu/hpage/mouse-sensor.pdf
   As noted in this article, John will make available free to anybody =
who sends him an email request for a password--the LabView executable to =
operate the mouse.
    The resolution, at about 50 microns, is too small for direct =
application to seismology; however the method might be useful for =
calibrating instruments.  Also, anybody wanting to monitor the earth =
(stable pendulum as a plumb-bob) should be able to use this technique to =
watch for changes greater than 50 microradians.  The typical diurnal =
thermoelastic variation is about one-third that value, but over the =
course of weeks to months I predict there will be observable changes =
that are not being routinely measured in nearly the 'global' sense they =
ought to be.
     To allow easier use of the sensor I removed some materal from the =
bottom of my mouse using sandpaper.  By this means the gap-space over =
which the unit can operate is approximately doubled.  Without doing so, =
one has to be more careful with alignment and stability of the pendulum. =
 With my present capability (as wide as 3 mm) it is very easy to work =
with this instrument.
      Additionally, I have an idea that some of you may want to =
consider.
    Any truly outstanding vertical seismograph requires force-feedback.
The traditional approach is one that uses force balance.  The same =
'strong' force that keeps the instrument from even moving substantially =
(much less 'goiing to the rails' because of temperature/pressure
changes) is also used to provide the required near-critical damping.
For more than a year I have demonstrated with my modified Sprengnether, =
that a 'soft' force feedback has advantages over the traditional =
approach.  The feedback I have used with my Sprengnether derives from a =
long time constant integrated output from the capacitive sensor (large =
dynamic range area-varying, fully-differential unit).  Based on my =
experience with this instrument, I propose the following:
       Since the sensor used for force feedback can have terrible =
sensitivity compared to the sensor used for detecting earthquakes--build =
a `centering' (feedback) package that uses the mouse sensor.  The =
requirement for DAC output for the coil of the actuator can be managed =
(it appears) with a 'dirt cheap' homebuilt piece of electronics (an =
example at http://www.allaboutcircuits.com/vol_4/chpt_13/3.html  )
    Without a parallel port, your USB computer would need a printer =
cable (< $20) to operate this R/2R DAC.

Randall
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