The only limitation is that it requires quite a bit of extra
circuitry, and only works well in dark environments.  The circuitry
problem could probably be dealt with (simplified).  The ambient light
is going to be a more difficult problem (sense while no LEDs are on,
sense while adjacent LEDs are on, detect difference, etc).

-Adam

On 4/12/06, Russell McMahon <apptech@paradise.net.nz> wrote:
> File this idea away for future reference.
> Use of a multi-LED display as a touch sensor simultaneously with its
> use as a display.
> Off LEDs are used as sensors of adjacent on LEDs with light paths
> being interrupted by fingers interrupting the light paths.
>
> Interestingly, cites a 1977 Forrest Mims comment.
>
>         http://mrl.nyu.edu/~jhan/ledtouch/index.html
>
> Presumably this could be done as part of multiplexing a display with
> no visual effect on displayed information.
> Cries out for interactive display.
> Analog sensing possible.
> Use of IR LEDS (perhaps mixed with visible ones) could allow visually
> dark sensor.
>
> ____________
>
>
> Upper level is a personal research page from Jeff Han at NYU.
> Some interesting material.
>
>         http://mrl.nyu.edu/~jhan/
>
>
>
>
>
> Ref: Matthew McMahon
>
>
>
>
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