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Science Forum Index » Energy Forum » Math/formula/design specs for making lowcost plastic or glas
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Message |
| Peter_purple |
 Posted: Fri Oct 31, 2003 7:19 am |
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Guest
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Hi everyone,
Curious if there are any equations/maths anyone knows on web etc for
designing
a fresnel lens,
ie. Say I have a area of 2sq metres (circle) and want to make it into a
fresnel lens,
what ring sizes do I need to get a certain (short) focal length, what is
the
recomended spacing between rings, if not what is the dia of the cross
section
of each ring etc ?
Looking to generate a small heater for cooking food and thought that
since I have
room to place a circular sheet of plastic or glass, all I need is to
position it
and arrange some stickon hemispherical rings on it to make a fresnel
type lens ?
peter purple in perth going country soon, |
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| Don Libby |
| Posted: Fri Oct 31, 2003 7:19 am |
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Guest
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"Peter_purple" <purple@203.0.178.192> wrote in message
news:3FA25365.118C483E@203.0.178.192...
Quote: Hi everyone,
Curious if there are any equations/maths anyone knows on web etc for
designing
a fresnel lens,
Now then. First we must acknowledge Australia as the most bizarre
experiment in human evolution ever attempted. (For example, aaave yu evaaa
eeerd a boistrous crowd ov oztralianz vocalizing thair opin-y-uns aaafta
kwaffin tooo many cans o' Fostaaaz in CA-NA-DA? Eh?)
Secondly, and without predjudice perpetrated by the first part
notwithstanding, we must review the literature of Eighteenth Century Optiks,
when Men were Men, and Lighthouses (and their manufacturers) were the
repositories of All Knowledge of Fresnel Lenses!
Consider, for example, re-reading the Principia Optika by Sir Isaac Newton
Fresnell (the III), who, upon visiting an house of Ill Repute in London (AD
1793) was therewith and without predjudice, sentenced to serve out 'is
mortal days as an 'umble servant of God in New South Wales, until Death do
'e paaat. Fer eva 'n eva, emen!
-dl |
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| Roland Paterson-Jones |
| Posted: Sat Nov 01, 2003 5:57 pm |
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Guest
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It's simple angle-wise calculation.
Take your focus point, and work out the wavelength you are interested in
(probably infra-red, or even visible light, if you have a black pot).
Decide how high your lens will be.
Then scribble concentric circles on your lens so that the gap between each
circle is the target wavelength from the perspective of the pot (i.e. times
cos theta, where theta is the angle from vertical above your pot)
Does that help?
Roland
--
Roland and Lisa Paterson-Jones
Forest Lodge, Stirrup Lane, Hout Bay
http://www.rolandpj.com/forest-lodge
mobile: +27 72 386 8045
e-mail: forest-lodge@rolandpj.com
"Peter_purple" <purple@203.0.178.192> wrote in message
news:3FA25365.118C483E@203.0.178.192...
Quote: Hi everyone,
Curious if there are any equations/maths anyone knows on web etc for
designing
a fresnel lens,
ie. Say I have a area of 2sq metres (circle) and want to make it into a
fresnel lens,
what ring sizes do I need to get a certain (short) focal length, what is
the
recomended spacing between rings, if not what is the dia of the cross
section
of each ring etc ?
Looking to generate a small heater for cooking food and thought that
since I have
room to place a circular sheet of plastic or glass, all I need is to
position it
and arrange some stickon hemispherical rings on it to make a fresnel
type lens ?
peter purple in perth going country soon,
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