headtracker / mag lens / macro lens (linaccess at yokoy.de)

[Luke Hutchison]

Is the processing time for 640x480 the reason you're only using 90x30?

You can actually dramatically increase the precision to which you can read
back the bright point's location by fitting a paraboloid to the intensity
values in the neighborhood of the brightest pixel, then reading off the
location of the extremum of the paraboloid.  You will get at least one order
of magnitude more accuracy that way than looking at the integer coords of
the brightest pixel (perhaps as much as two orders of magnitude).

Luke


On 9/4/07, linaccess at yokoy.de <linaccess at yokoy.de> wrote:
>
> Hello Mary Lou,
>
> On Tue, 04 Sep 2007 12:13:34 -0400
> Mary Lou Jepsen <mljatolpc at gmail.com> wrote:
>
> > lenses are cheap.  it depends on what exactly you are doing with the
> > software.
>
> tracking a little shiny point at the head and transform it into
> mousepointer movements. Here is the description:
> http://www.olpcaustria.org/mediawiki/index.php/Headtracker
>
> With the XO camera we typicaly use only 90x30 pixel from the 640x480
> pixel. So I want to magnify the operative area with a lens.
> Here is a picture of the area:
>
> http://www.olpcaustria.org/mediawiki/index.php/Headtracker#magnification_lens
>
>
>
> > American Science and Surplus is a good way to experiment:
> > http://sciplus.com/category.cfm?subsection=21
> >
>
> thank you for that link. A plastic lens is what I am searching for.
>
>
> > then to china for mass production at very low price point.
> >
> >
> > - Mary Lou
> >
> >
>
> regards,
>
> yokoy
> --
>
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