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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/04/2008 at 02:08
riverdelta View Drop Down
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Members,
If you glue with transparent glassglue two prisms together, what happens with the lightbeams?
Is it working as a new prism or the edges which glued together still works as a brim
for the lightbeams?

Please reply
Thank you in Advance
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/04/2008 at 14:39
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If the glue has to be in the optical path; then they pick the glue with the index of refraction matching the glass.  Nowadays, with the anti-reflective coatings being as good as they are, you see a lot less glue used for this.  In the past, oftentimes you could use properly index-matched glue to alleviate some of the air-to-glass surface reflections.

With scopes, the most common use would cemented objective lens doublets (as opposed to air-spaced lens combinations).

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/04/2008 at 18:47
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That's news to me.  I honestly never thought that two lenses inside one of my scopes may in fact be glued together, surface- to- surface.  It simply never occured to me.  Interesting.


Edited by RONK - June/04/2008 at 18:48
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/04/2008 at 19:00
koshkin View Drop Down
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Originally posted by RONK RONK wrote:

 
That's news to me.  I honestly never thought that two lenses inside one of my scopes may in fact be glued together, surface- to- surface.  It simply never occured to me.  Interesting.


http://en.wikipedia.org/wiki/Doublet_(lens)
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/05/2008 at 04:15
riverdelta View Drop Down
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Members,
Thanks for your answers. I have another one.
Anti-reflection coatings gives more entering beams, if I am correct.
Has ARcoating influence on departing beams f.i. from glass to air
or is it normal corner story.?

Thanks in advance
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/05/2008 at 09:35
koshkin View Drop Down
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Can you rephrase this?  I am not sure what the question is.

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/06/2008 at 03:34
riverdelta View Drop Down
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Koshkin,
May be it not a relevant question, but in general coatings only works
for incoming light from air to glass and do nothing with outgoing beams glass to air?

Thanks in Adcance
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/06/2008 at 09:38
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They work for both.  A properly made coating wil help minimize reflections from both air-to-glass and glass-to-air interfaces.

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/09/2008 at 21:45
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An uncoated lens to airsurface is generally said to loose 4% light.
The best coatings takes this down to 0,25-50%.
 
In the past it was not only lenses that was glued but also the prisms, so here is some examples.
 
An M16 binocular has like all porro binoculars two prisms in the prism housing, one in the upper part and one in the lower part and that is the reason for this look of the binocular.
 
So by cementing together the two prisms to air to glass surfaces was removed, wish is quite an improvement. This also makes the prisms housings much shorter and makes the looks of the binocular very different.
The models with cemented prisms in porro version is called porro ll.
 
A way of furthing improving the transmission was to cement together the field lens with the prisms, and thus making the H construction.
It was invented by London company Ross and was soon copied by Zeiss.
This actual binocular is made in february 1936 and in the first batch of coated binoculars by Zeiss
 
In 1935 Herr Smakula of Zeiss invented the first coating and that made the cemented prisms not as usefull as before as they was so much more expensive to build.
But for a few years Zeiss contiuned to build Porro ll constrution with cemented field lens H.
This binocular is marked for coating by the T for Transparantzbelag.
 
Today the porro ll constrution is still used but only for the very expensive equipment and of high magnification like this Nikon 20x120
 
 
Regards Technika
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/11/2008 at 07:31
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Members,
Thank you for the extensive explanation.

Riverdelta
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