DPRG mailing list archives: [DPRG]Wall-E -> 1GHZ computers laser rangefinding

Sun Jul 27 15:23:16 CDT 2008

Good observation.  In the IR range there is still plenty of spectral
content, although from a energy delivered as natural light source it is
beginning to fall off.  On the other hand, in the UV spectrum the earth's
atmosphere is quite good at blocking a large percentage of the energy coming
through.

http://squ1.org/files/wiki/solar/spectral-content.gif

-Kenneth

-----Original Message-----
From: dprglist-bounces at dprg.org [mailto:dprglist-bounces at dprg.org]On
Behalf Of John Swindle
Sent: Sunday, July 27, 2008 1:43 PM
To: dprglist at dprg.org
Subject: RE: [DPRG]Wall-E -> 1GHZ computers laser rangefinding

Folks:

I disagree with one of the comments about using IR instead of
visible light, supposedly because there is too much visible light
noise in the environment. A similar reasoning error is made when
thinking about using 40KHz for sonar, thinking that there's less
sound noise around that frequency. Just because we can't hear or
see something says nothing about how much noise there is at those
frequencies. Indeed, there's lots of IR noise. Everything is
somewhat hot. And for sonar, the harmonics of our machines and
our squeaky sneakers are well above our range of hearing. The key
to rejecting noise is the modulation.

Back to my passive sonar stuff now. (I'm using audible sound so
that I can debug it with my ears instead of always depending on
the microphones and calculations.)

John Swindle

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