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Looking for advice on separating layers from a rear projector TV screen (slrpnk.net)

submitted 1 week ago by JacobCoffinWrites@slrpnk.net to c/diy@slrpnk.net

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Hi, I've been looking for a chance to get a huge fresnel lens from a rear projector TV for awhile and I finally found one junked (and rained on) on garbage day and managed to get the screen off before the truck took it.

The problem is that the screen seems to be different in composition from others I've seen online. There was one dark tinted, but otherwise clear plastic sheet, and an opaque one that might be a fresnel lens with a diffuser layer glued on. The TV was a Mitsubishi which are supposed to be a good source for fresnel lenses but the overall design and wide aspect ratio of the screen suggest it was a newer model. It definitely did have a projector inside (a single one with a sort of bubble dome on it).

I'm wondering if anyone knows more about these tvs, or has any suggestions for getting the two layers apart - the thin sheet seems to be both adhered very well and brittle - it only pries off in tiny chunks. I'm thinking about using a heat gun, I don't know if there's some other truck to this I should know.

Thanks very much for any advice!

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[–] alzymologist@sopuli.xyz 2 points 1 week ago (1 children)

They might have switched to diffractive optics to combine lens and diffuser in one structure. I was anticipating to see it in newer small embedded screens, but haven't encountered anything like this yet. You might peel some of whatever peels off on the side and see if there is periodic pattern underneath or just more of same.

[–] JacobCoffinWrites@slrpnk.net 2 points 1 week ago

I was wondering if it was something like this, thanks! I'll see if I can get enough of it off to see if the main sheet is a fresnel lens

[–] lettruthout@lemmy.world 2 points 1 week ago (1 children)

The one I salvaged from the trash came apart very easily from another layer but the more I think back it might still have been adhered to an opaque layer. I can double check later this week. It still worked dangerously well. I did some testing but it produces a scarily powerful beam.

What are you planning to do with yours?

[–] JacobCoffinWrites@slrpnk.net 4 points 1 week ago (2 children)

Thanks! I'm hoping to build a solar forge - I used to do some blacksmithing using coal, but some videos of these things show them burning through steel - if they can get that hot, I could even forge weld again. I've still got most of my tools, minus the forge.

[–] lettruthout@lemmy.world 3 points 1 week ago (1 children)

Awesome! Please post your progress! I was thinking of building a solar thermal system but the engineering to pull that off in my location was not feasible. Now I’m moving and will be getting rid of it. Do you want it? (I’m in the Los Angeles area.)

[–] JacobCoffinWrites@slrpnk.net 2 points 1 week ago* (last edited 1 week ago)

I'm clear on the other side of the continent but I really appreciate it, thank you! I hope you can find someone who'll use it! And I'll definitely post my progress!

[–] alzymologist@sopuli.xyz 3 points 1 week ago (1 children)

Awesome! I once (more than 10 years ago, wow) had an idea to attach solar heater to vacuum/gas CVD system to make graphene, but my PI at the time said it's dumb idea, sure it will work, no novelty there. Now I have no idea why I would want to make graphene, and pass all the free lenses in second hand shops. Now if making the forge is feasible (I had doubts), I'm totally doing it too, in Finland!

[–] JacobCoffinWrites@slrpnk.net 2 points 1 week ago

If it works, I'll share any designs and lessons learned here!