> Isnt Light and radio (or RF) both electromagnetic 
> radiation, one
> visible, one not.?

As Herbert notes, both EM but "Radio" relates to one part of 
em spectrum.

BUT RADAR and LIDAR and xxDAR tend to implicitly mean a 
"time of flight" measurement system whose measurements 
depend on the speed of light (or em radiation) in (usually) 
air.

The article that started this does not use time of flight - 
the sensors are calibrated on magnitude of transmitted light 
reflected back from a highly reflective surface, and their 
use in the proposed system would lead to highly variable and 
unpredictable results unless all targets were highly 
reflective.

I was disappointed to see that the PIC was no more than a 
voltmeter and display controller - all the ranging work is 
carried out by the commercial module.

A system that did work, after a fashion, with reflection, 
could be achieved by arranging two detectors at different 
distances, or two sources, or 2 of each. Comparison of the 
results of varying source and/or detector distance would 
tell you (to some extent) how much of the amplitude loss was 
due to distance and how much was due to transmission loss 
during reflection. This involves solving a simple quadratic 
equation.


        Russell McMahon



> On Feb 9, 2008 7:03 AM, Spehro Pefhany 
> <speff@interlog.com> wrote:
>> Quoting Jinx <joecolquitt@clear.net.nz>:
>>
>> >> > http://www.pyroelectro.com/projects/ir_radar/index.html

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