The reason for this is, that the measurement result is depending very much
on the part's surface condition and reflectivity.
Case 1: Surface is extremely shiny od extremely dark. Result : Detector
reaches its upper or lower sensitivity limit. Problem can be reduced by
spraying the part with a removable white paint (i.e. white chalc spray used
as developing agent in destruction-free material testing for fraction search
by ink).
Case 2: The laser spot has a certain diameter. If you reach the edge of a
part, portions of the spot are cut away unsymmetrically. Therefore, awrong
part height is calculated (triangulation priciple)
Though the resolution and the inherent accuracy of laser scanners is usually
very high, you can easily have noise and deviations adding up to one
millimeter.
Regards
Juergen
Juergen Bauer, Siemens AG, EC CS A PD
E-Mail: Juergen.Bauer@spy.siemens.de
Adress: Siemensstr. 13, 67346 Speyer, Germany
Phone: +49-6232-30-2501; Fax -2110
http://www.siemens.de/ec/eccs/auto/index.htm
----Original Message-----
From: MIN CHANG-SHIK [SMTP:mcs9413@lge.co.kr]
Sent: Tuesday, January 05, 1999 10:26 AM
To: bert@hymarc.com; rp-ml@ltk.hut.fi
Subject: Re: 3D Laser Digitizer(Scanner) for mold inspection
Thank you for your good opinion in advance Mr.Vandenberg.
I found something strange in chart you had presented.
I wonder how I can understand the accuracy of 3D scanner
is 10 - 1000 micron.
1000 micron shoud be 1 mm.
It's a terrible acccuracy viewing from my experience.
I would say '10 - 1000 micron' should be '10-100 micron'.
What do you think about this?
Any reply you can give me would be greatly appreciated..
Best regards.
PS: Would you please give me some informations about Hymarc
3D digitizing devices?
>
> MIN CHANG-SHIK wrote:
> >
> > Can 3D laser scanner be used as an inspection tool like CMM ?
>
> companies such as Process Design Technologies (PDT) offer an inspection
> service based on laser scanning. Surfacer's verdict program is designed
> to provide inspection results based on (laser)scan data.
>
> Yes 3D laser scanners can be used for inspection.
>
> However, there are differences between touch probing and laser scanning
> technology. For the purposes of stimulating discussion, I offer the
> following (rough) chart.
>
> topic touch probing laser scan
> -----------------------------------------------------------------------
> planning online, offline, CAD based usually on-line
> measurement speed slow fast
> absolute accuracy (est) 2->25 um 10-1000 um
> data analysis Least squares, feature based global comparison
> rate of technology change slower faster
> ------------------------------------------------------------------------
>
> Note these opinions do not neccessarily reflect that of Hymarc Ltd.
>
> --
> Bert van den Berg E-mail: bert@hymarc.com
> Hymarc Ltd. http://www.hymarc.com
> 35 Antares Drive Tel: (613) 727-1584
> Ottawa, Ontario K2E 8B1 Fax: (613) 727-0441
>
Chang-Shik,Min
Precision Technology Center,LG-PRC / LG Electronics Inc.
19-1,Cheongho-Ri,Jinwuy-Myon,Pyungtaek(451-713), R.O.Korea
(Voice)+82-333-660-7090
(Fax)+82-333-660-7384
For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
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