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[DPRG] Ambient light subtraction

Subject: [DPRG] Ambient light subtraction
From: Keith Next at Pitstock.com
Date: Wed Jul 23 19:17:41 CDT 2008

Hi Ray

There is a simple digital subtraction you can do. I do this with the linear
image sensors here at work. I also did this on one of my robots.

Take one ADC sample with the laser off. This will be your ambient light.
Take a second sample with the laser on. This is you illuminated sample.
Simply subtract the ambient from the illuminated sample and presto you have
a much better signal to work with.

If you want to go one step further you can integrate the subtracted samples
for a multi sample average. 

Cheers
Kiwi Keith

-----Original Message-----
From: dprglist-bounces at dprg.org [mailto:dprglist-bounces at dprg.org] On Behalf
Of ray xu
Sent: Thursday, 24 July 2008 8:48 a.m.
To: dprglist at dprg.org
Subject: RE: [DPRG]Wall-E -> 1GHZ computers laser rangefinding

My receiver is picking up ambient light.  Are there any ways to filter that
out?  Should I modulate my laser and put a bandpass filter on the receiver
end?

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