Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!shadooby!samsung!uunet!opel!johnk
From: johnk@opel.uu.net (John Kennedy)
Newsgroups: comp.terminals
Subject: Re: Touch Screens  ( Request for Information )
Message-ID: <310@opel.uu.net>
Date: 14 Nov 89 12:26:35 GMT
References: <715@tokugowa.UUCP>
Reply-To: johnk@opel.UUCP (John Kennedy)
Distribution: na
Organization: Second Source, Inc., Annapolis, MD
Lines: 59

In article <715@tokugowa.UUCP> trl@tokugowa.UUCP (the GOOD Doctor) writes:
>
>          Therefore I need to find a new touch screen which will work.
>
>Any and all suggestion, pointers and/or helpfull comments greatly appreciated!
>                   

You didn't say whether your terminals could be PC's.  If so, read on - 

About a year ago, I was working on a project which needed a touch-entry
screen for air traffic control applications.  We looked at several technologies
of touch entry: resistive, capacitive, infrared beams, etc.  Each had advantages
and disadvantages, and users were very opinionated about the cons
of each:  abrasion, parallax errors, whether or not you could use a pencil
rather than a finger, etc.  The approach we ended up with seemed to make
every one happy. 

That was the use of IR beam technology over a flat panel CRT.  

Normally, the IR approach utilizes an array of infrared LEDs and photocells
along all four edges of the CRT screen.  Its disadvantage in the past was
that the LEDS and sensors had to be placed at a sufficient height above
the plane of the screen in order to see over the "horizon", as presented
by the curved glass of the CRT.  This caused a massive parallax problem
if the user was not directly in front of the screen.

Zenith now makes a CRT, EGA and VGA compatible, whose front glass is completely
flat.  The IR device is an overlay, which is just a frame that sticks onto the
bezel surrounding the glass.  This overlay can now rest much closer to the
face of the CRT than before, thus greatly reducing the parallax problem.
The overlay is like a picture frame, containing no glass, plastic, etc. in
its center.  It just surrounds the glass of the CRT.

The overlay is made by Carroll-Touch, I think in the Dallas area.
It seems that they are a division of a larger company, like AMP, or somebody.
Its interface to its host is via a configurable RS-232 interface.  It resolves
multiple beam breaks by reporting the center of the beams being brokes, and
rejects simultaneous entries in non-contiguous areas.  What it reports is
programmable, such as whether to report makes and breaks, fingers sliding
around, etc.

I guess the major disadvantage of this system was that the Zenith monitor
comes with a blue anti-glare coating on the glass, as you would find on
a camera lens.  It grows fingerprints at the slightest touch.  Combine
that with a system that you're supposed to touch, and you find yourself
cleaning glass often.

Nonetheless, the system was demonstrated a year ago at the Air Traffic
Controllers Association conference, to rave reviews.

(ok, i don't work for either of the companies whose products got plugged )

John


-- 
John Kennedy                     johnk@opel.uu.uunet
Second Source, Inc.
Annapolis, MD