Newsgroups: comp.robotics
Path: cantaloupe.srv.cs.cmu.edu!fs7.ece.cmu.edu!uss.switch.com!news
From: Tom Maier <tam@rnd.switch.com>
Subject: Re: Distance With IR?
Message-ID: <DAKq5I.6qp@switch.com>
Sender: news@switch.com (USENET News System)
Organization: Union Switch and Signal Inc.
References:  <3s5j8h$6nf@canyon.sr.hp.com>
Date: Thu, 22 Jun 1995 12:17:41 GMT
Lines: 22

paulgc@sr.hp.com (Paul Christensen) wrote:
>
> Hello Folx -
> 
> I heard of a guy that uses that sharp IR module to measure distance. He Sends
> out a IR stream at one freq then switches to another, and is somehow able to
> derive distance to an object by the delay. Can anyone out there give some
> help on how this is done?
> 
> paulgc@sr.hp.com
> 
I'm sure that this is possible, but it would be tough to switch fast
enough.  Light travels at 300 meters/microsecond.  Out and back 
you would have switch within 1 microsecond to *see* something at 150
meters (492 ft).  To see something at 4.92 feet, for example, you would 
have to switch the entire *system* at 10 nsec.  Not impossible, but not
easy either.

If the IR module could be continuous "swept" thru the frequency range, 
this would be *a lot* easier.

Tom
