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The math behind fresnel lenses and focusing for the projector lens?
The math behind fresnel lenses and focusing for the projector lens?
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Old 16th August 2018, 10:10 AM   #1
cwinhall is offline cwinhall
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Default The math behind fresnel lenses and focusing for the projector lens?

Trying to get my head around how to make my diy projector as optimal as possible.

How can I work out what distances to have the fresnel lenses from the LCD in order to make the light hit both the LCD optimally and the projection lens?
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Old 16th August 2018, 11:51 AM   #2
Pano is offline Pano  United States
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The math behind fresnel lenses and focusing for the projector lens?
Sorry to say this a pretty much a dead section of the forums. You'll have better luck getting an answer on a dedicated video forum. Good luck with your project!
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Old 16th August 2018, 12:08 PM   #3
cwinhall is offline cwinhall
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Oh

Any suggestions?
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Old 16th August 2018, 12:10 PM   #4
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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The basic idea behind a Fresnel lens is simple. Imagine taking a plastic magnifying glass lens and slicing it into a hundred concentric rings (like the rings of a tree). Each ring is slightly thinner than the next and focuses the light toward the centre. ... Large Fresnel lenses are often used as solar concentrators and light houses. They parallel the light source, not focus it.
B&O many years ago perfected a light shift lens. That turned the rotary wave of the light source into one plane doubling the light usage through the LCD imagers. One per colour; Red, Green and Blue. The light box after that point does the focusing.
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Last edited by JonSnell Electronic; 16th August 2018 at 12:13 PM. Reason: Added information.
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Old 16th August 2018, 12:54 PM   #5
Pano is offline Pano  United States
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The math behind fresnel lenses and focusing for the projector lens?
Wish I could be of some help, but I'm not. Even tho I've been a video projectionist for over 30 years, none of the projectors I use contain Fresnel lenses. Overheard projectors do, stage lights do.

Hope you find your answer.
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Old 16th August 2018, 02:31 PM   #6
cwinhall is offline cwinhall
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Nearly every post I come across regarding DIY projectors using an LCD panel also incorporate fresnel lenses. One before the display and then 1 after. Depending if it is split or unsplit.

I thought this was a required step. Is that not the case?

Example post:

DIY Video Projector
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