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Optical Mouse Used As Cheap Motion Sensor
drphil writes " Dr. Tuck Wah Ng, a member of the Faculty of Engineering at the National University of Singapore uses an optical mouse as a cheap non-contact motion sensor in his research. If a resolution of a little less than 60 microns is sufficient, you really can't beat the price. Dr. Ng has studied the viscoelastic deformation of plastics using a hacked optical mouse - published in J. Chem. Ed. vol 81, p 1628, 2004. You'd need to be a subscriber of the journal to see anything but the abstract, but any university science/chemistry library would have a copy of this issue of the Journal of Chemical Education. (Viscoelastic deformation, in plain English, is the degree to which a plastic stretches when you pull on it)"
That's a nice link there, I'm sure the first 1 or 2 people who saw it may have been interested.
The article clearly says to go to your nearest Chem Dept Library and read the article.. Sheesh.
Not really new-I'm sure many Slashdotters who are IEEE members enjoyed the September 2004 issue of IEEE Computer magazine which covered the theme of biologically inspired robotics. There is a paper in that issue by S. Thakoor et al. which uses an optical mouse chip for terrain feature tracking for a flying aerial robot. You can't read the paper if you don't have IEEE digital library access, but here is the link:
3 8abs.htm
http://csdl.computer.org/comp/mags/co/2004/09/r90
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Researchers looking into the hearing of flies attach the fly to a fixed support above it, and allow it's feet to touch a ping pong ball dotted with sharpie-marker dots. The ball rests on an optical mouse with some foam to hold it in place. By playing sounds from different directions and measuring where the fly moved in reaction they where able to determine how directionally-accurate the hearing of the fly was.
This is all per some TV show, maybe Discovery's This Week
If a resolution of a little less than 60 microns is sufficient, you really can't beat the price
Hmmm. This inspired me to try to see if I could move my optical mouse without moving the cursor. It's possible, but very difficult. It obviously depends on the sensitivity setting.
Footprints project overview
"God fights on the side with the best artillery." - Napoleon, Marshal of France - speaking truth to power
but "motion" cannot be described in "microns." I think you mean "cheap displacement sensor".
And viscoelasticity is not necessarily a plastic-related thing. Some metals and composites may strain in a viscoelastic manner. Biological tissue is also generally deemed viscoelastic. Basically, it means: the amount of stress in the material is proportional to the rate at which it is displaced (or strained, in more correct terms).
IWARS.
People, in general, disappoint me. Politicians even more so.
60 microns is too low a resolution for that purpose.
Isn't this what mice do already?
Well, an optical mouse is actually a rather complex piece of work that goes a bit beyond a sensor (which in the case of a mouse is actually a minicam), just pull the circuit board from one and have a look. Then add in the cost of the plug, wire, etc.
Mice are cheap, and you can use the time you would have spent designing and building a data acquisition unit doing your real work.
Where I can't get what I want, or where what I want cost thousands of dollars when I can build it myself, better, for ten, I build, and I'm glad to do it.
When I can buy what I need off the shelf for twenty five dollars, or spend a week designing and building it myself for twenty dollars, well, I usually just go buy the sucker (unless I'm simply smitten by the intellectual challange of the thing for some reason).
But here is what I suppose is the biggest reason for using the mouse:
The software is already written, so you can just plug it in and it works.
KFG
I've seen quite a few papers recently that talk about using multiple cheap (<£30) webcams to do gesture recognition. Ok the images aren't great but the improvements you get from using £1000+ video set-ups with fancy lenses etc aren't that great.
I used to have a better sig but it broke.
The results are public, just not the copyrighted article. Since tax dollars do not go to the journals, they charge for subscriptions -- print or electronic.
That said, most scientists I know are frustrated by this as well, and do what they can to allow freer access to their work. So, if you want access to almost any scientific article, try the following (in order):
1) Go to the author's web page. Most journals allow authors to put copies of their papers online, and many scientists take advantage of this.
2) Go to a nearby university library. If they don't subscribe to the journal in question, ask a librarian, it may be possible to get it from another university.
3) Go to arxiv.org (formerly xxx.lanl.gov). Many articles are published there as preprints, but may or may not be the final published version.
4) Finally, email one of the authors. In all liklihood, they will be happy to send you a PDF of their article if it is not available via another mechanism.
The restrictions on the dissemination of scientific literature do not stop anyone with even a tiny bit of motivation. Also, a few journals require subscriptions, but allow google to index the full text, which means the whole article may be in google's cache.
Searching Google Scolar for "optical mouse motion sensor Ng" provides some useful information. The PDFs are slashdotted like others have mentioned, but the "View as Html" pages are the google cache. The graphs are worthless, but the text is all there.
This got me thinking... me and my geek engineer brain...
Seems to me by mounting a small mass between springs right above the sensor, you could probably measure acceleration fairly accurately. The spring deflection would be precisely related to the acceleration, the mass, and the spring constant, two of which are known (or can be measured independently) and are fixed values.
F=ma, where force = mass times acceleration
F=kx, where force = spring constant times displacement
so
a = kx/m
(Figuring out the units is left as an exercise for the reader.)
So as the combined mouse/spring/mass assembly was accelerated, the cursor would deflect accordingly. Calibration would be straightforward: since k is fairly linear for most springs (within small ranges), and m is fixed, simply turning the sensor on its side (e.g., subjecting it to exactly 1.0g) gives a very nice data point.
Might be a cheap and fun way to build a sensor, say for measuring cornering force on your car, etc. Also might be a neat high school physics class experiment.
That is, unless Microsoft already patented that use... *grin*
--Brandon / Split Infinity Music