DO big screen tv's use a Fresnel lens for the screen?

I'm pretty sure they all don't, but looking at this ad I swear it looks like its out of a TV:


Ebay link

I used to own an old school plastic one for slide projectors and what he has there doesn't appear the same as I remember it. Maybe he's using a big tv screen as a Fresnel? Look at the upper left corner for an idea of what a REAL fresnel lens should look like.

I've seen the insides of several big screens, and have seen them with black trim tape around the edges like that. But I've never taken one out into the sun to see how it behaves. I know the screen of my big screen (i've been all inside it) doesn't behave like my old fresnel did.

Of course these can be used for all sorts of solar projects:


[edit on 7-12-2008 by IgnoranceIsntBlisss]

Yes they do. They make great burning tools to burn through aluminum cans and are excellent devices to use for solar water heaters.



Cheers!!!!

All older style big screen tvs come with fresnel lenses You have to peel off a layer of plastic though. I got my fresnel lens from a goodwill Bigscreen TV.

Cool. I'm gonna hunt a few down and post my results...

THEY DO!!!

I'm happy to report that ALL rear projection tv's contain these, although different grades exist if anyone is interested.

I've literally collected over 75 of these and have half a warehouse full of them in various stages of repair or scrap. Many other useful things in some of these as well.

Also if you take apart the projector heads inside the tv, there will be at least 3 and sometimes up to 9 high-quality, handheld sized, glass magnifying lenses.

These make excellent burning lenses for starting fires, as well as good all around magnifiers.

I even keep one in my first aid kit for use as not only a magnifier, but also as an instant cautery tool. (as long as the sun is out.)




[edit on 4/27/2009 by nasdack24k]

[edit on 4/27/2009 by nasdack24k]

Lovely things these seem to be. I'll have to hunt some down to play with

reply to post by titorite


So, even if the TV is a rear projection but NOT a plasma it would still contain a big fresnel lens? I know plasmas do but didn't know if other types of rear projection do like DLP, etc...

can you clarify...

I have a particular phillips 51" available for scrap that i'd like to pick up but only if it has a fresnel - model # 51PP9303H/17

thanks for any help

Argh. I had meant to take pictures of my warehouse full of big screens to (mostly) scrap out, before it finally cooled down enough to get the damn things out of here. I got about 80 off of craigslist in less than 3 months. The best route is to find a tv repair shop that is overloaded with specimens that customers left for dead. So my take is about 75 lenses and about 10 well working big screens all the way up to 70". Some I had to repair, some I didnt. Have alifetimes supply of spare parts. for the ones I'm keeping (I rent them out!). Have several still left to repair. Still have 5 outside I have to rip the screens from and scrap out. In one free CL deal I got a huge oldschool videowall of 15 aluminum housing panasonic projectors. So I ended up with a stack of matching high quality lenses, 1500 pounds of aluminum, and maybe 100 pounds of curcuit boards to scrap. Havent even gotten around to scraping anything yet. GOtta have a good 500 pounds of PCB's to unload.

Anyways, I'd guess that DLP's and LCD projectors have shoddy little thin fresnels inside them. Not worth your time. In fact most RP's built after 2000 have crappy thin floppy non-clear LINE lenses made out of vinyl, where the good ones are built from acrylic and are thick, stiff and clear SPOT lenses. Not all built after 200 are vinyl but the trend degrades the further you move from '00. It's odd that the better picture resolution got they managed to use crappier quality lenses. I guess you can still do some things with them, I have about 20 in my stack, but dont plan on impressing people with them like you can with the crisp acrylic spot lenses.

Mitsubishi's are the best. Best lenses, and they come with a nice hard black aluminum frame. I have a 60", four 52", and a couple 16x9 frames+lenses. These things are worth paying money for. Maybe I'll post some photos later in anyone is interested.

[edit on 15-12-2009 by IgnoranceIsntBlisss]

IgnoranceIsntBlisss,

Thank you for this thread! I've been doing some research on where to find an inexpensive yet high quality lens, and your thread has helped greatly. However, I must have bad luck, because all I have been able to find so far are the thin flimsy vinyl lenses. Do you have more information about the tv's from which you pulled the acrylic lenses (such as brands and model numbers)? Also, if it's not to much to ask, could you post some pictures of the nicer lenses you've found and if you still have them, the tv's from which you got them?

Thanks,
Clint

You say you have a variety of fresnal lenses. Can you tell me how I can determine if one is a spot focus fresnal lense or not?

It seemed to me that screens from after around 2004 became by standard the sloppy vinyl material. They can still burn stuff actually, but the blur... The real mind bender is that around the same time picture quality was on the up and up after being mostly stale before that TV industry wide for a good few years.

In any case, once you have a proper fresnel lens of any sort before you a simple sun+focal-point test will make it clear what form of beam it is designed for.

Just don't blind yourself. You need your vision to survive!