NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/sci/electron/19190

Internet Message Format | 1992-11-19 | 2.0 KB

Path: sparky!uunet!olivea!spool.mu.edu!agate!dog.ee.lbl.gov!news!nosc!crash!cmkrnl!jeh
From: [e-mail]
Newsgroups: sci.electronics
Subject: Re: Tracking the position of a diode in 3space
Message-ID: <[e-mail]>
Date: 19 Nov 92 09:47:46 GMT
References: <[e-mail]> <[e-mail]>
Organization: Kernel Mode Consulting, San Diego, CA
Lines: 32

In article <[e-mail]>, [e-mail]
(The Devil Reincarnate) writes:
> In article <[e-mail]> [e-mail] (James Harrison) writes:
>>
>>We have an application for the tracking of the position of a person in
>>a larger room with little or no hardware carried by the person being
>>tracked.  What we would ideally like to do is know the position of the
>>person in a large room (x, y).
>>
>>Anyone done this?  Know it can/can't be done?
>
>   Try the IR movement detectors. A sharp enough definition would give an X-Y-Z
> position if the three detectors were placed on two adjacent walls and the ceiling.

I don't believe that this will work.  According to what I've read about these
devices, they contain just one IR pickup.  Therefore they can't tell where
anything is, even in a single dimension.  They can only tell that something is
moving, somewhere, across their field of "vision".

How it works:  The IR detector is placed behind a curved Fresnel lens.  The
lens divides the field into in-focus and out-of-focus areas. As an IR source
moves across the field, the IR detector "sees" alternating high and low levels
of IR.

A simple high-pass filter (with cutoff at a few Hz or so) and pulse detector
does the rest.  They aren't sensitive to stationary heat sources, or slow-
moving ones like the sun, because these do not generate pulses fast enough,
or at all.

    --- Jamie Hanrahan, Kernel Mode Consulting, San Diego CA
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