Re: Laser links ?

--- In CAD_CAM_EDM_DRO@y..., "rainnea" <rainnea@b...> wrote:

> Now, what would be really useful
> would be a means of turning a cheap
> laser pointer into a short-range
> distance finder and using it to
> digitise / scan parts on a mill
> or router as it could be a lot faster
> than a touch probe,
>
> Rab
>

Interesting how following a completely different topic's thread can
lead to answers.

What came to mind for me when reading your post was one of those
cheep (less than $50) USB webcams, combined with some heavy pixel &
number crunching.

The angle of the laser pointer is a known constant. So is the angle
of the webcam. By scanning a picture captured from the webcam you
should be able to find the red dot from the laser. It's vertical
placement in the picture would allow you to calculate the angle.

Thinking about it, I was unsure if horizontal location of the laser
dot would come into play.

Then I started reading the "automotive alternator as a stepper motor"
tread. It led to Don Lancaster's site, which is full of all sorts of
weird and wonderful things.

One article there caught my eye. It discussed "Position Sensitive
Detectors" and "Optical Rangefinding Secrets". Even discusses a
special purpose chip specifically for this kind of application. The
link to it is: http://www.tinaja.com/glib/muse131.pdf

Looks like the part he mentioned is discontinued, but there are
replacements. It's a framed site, but this like is right to the
product table, bypassing a long convoluted route to get there. Note
if you are manually typing the link, there are Underscores (_) before
and after "measuring".
http://www.sharpsma.com/sma/products/opto/OSD/distance_measuring_senso
rs.htm

If somebody follows this up and actually implements it, please make
sure you report back to the list, and post info in the files section.

Ian