Tony
Indeed these things have been around for a good few years!
I have still an article in a lasers/optics trade magazine from December 1997
when the technique was first announced by the Fraunhofer Institute in
Dresden. Only one laser is involved, a short pulse Nd:YLF Neodinium :
Yttrium something Fluoride. The focal spot is so small that the damage
spot is made ony where you want it.
Several years ago laser oranments started appearing in shops and in Chester
too there's a shop doing an almost while you wait service zapping the block
in a little cubicle within the shop. I;ve never been in to ask if they;ll
take a TurboCAD dxf instead of scanning you head!
For making "Spectra" like sundials these would be so-so, so long as you've
calculated out the refraction to the depth of construction, ie the zapped
glass is the receiving surface, not as good as sandblasting though. And
(after 2 minutes experimentation with the ornament off my windowsill) i
don't think that enough glass would ever be destroyed to make a dense/opaque
enough gnomon also in the glass.
regards
Ian
Chester UK
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <sundial@rrz.uni-koeln.de>
Sent: Sunday, May 14, 2006 9:48 PM
Subject: Re: AW: Clever stuff!
I too have seen this technique used over the past four or five years. The
son
of a friend was busy developing the technique with his company then. Such
pieces have been commonly sold as paperweights and ornamental pieces for
quite a
while.
In fact last year there was a company in a local shopping Mall (Milton
Keynes in
the UK) who were producing 3d portraits while you waited. They took a
couple of
photographs which were scanned and then about 15 minutes later, hey presto
, a
3d portrait inside a glass paperweight. They were doing great business.
But as
for a sundial, I don't think so, call me a sceptic.
Terry
Quoting Hannes Kühtreiber <[EMAIL PROTECTED]>:
this laser engraving technique is not new at all, I remember seeing
some pieces more then five years ago, and they were nothing new then.
however, due to legal disputes about the patent the method is not -or
has not been- widely used.
I am not sure it would be very useful for sundials. You'd have to
produce a very tight layer of dots to show the shadow well. While the
newer machines can produce much finer dots (I think the piece in your
picture was made by an older model), they are still far from it.
why not sandblast the backside of a plate of glass?
hannes
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