DIY Video Projector Part II

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#502
cowanrg said:
hehe, yeah, it will come BACK up soon. you must be a newbie. when the site went down, it had over 35K hits 🙂

ill try and get it back up this weekend. i had a problem with my host. and lost interest in the projector thing.

ill try though, there is a lot of good info there for newbies.
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sweet, do you have photos of a completed one, or screenshots?
 
#504
xblocker said:
multiplexor,
OHPs don't use a single lens for projection, they mostly have doublets or triplets for correction of spherical and chromatic abberations. A single lens can't do that!

xblocker
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hmm I see. I always thought when i looked at one, i would see a round lens which looked like it was one piece.

does surplusshed have a lens i could use then, without buying an OHP?

i'm gonna read some other threads and the wicki thing to see if more info exists on it 🙂

thanks for pointing that out though.
 
#505
yeah, i have both. a few galleries of screenshots of various finished products. as well as pictures of projectors and such.

i just kinda left the project behind becuase at this point, there still isnt enough info to make a really great design. mine works FINE, but is nowhere NEAR consumer models, and i dont think we will be able to do one of those for under $500 for awhile.

btw - zark's design DOESNT WORK. plus, CRT lenses dont work for lcd panels. they were designed to work for the curvature of CRT tubes, so, either the middle or the edges will be in focus, and the other will be out of focus... they dont work for flat surfaces.

and, the LOA's (lights of america) that he uses are NOT good. i had one, just threw it away finally yesterday. they are bright, but the light goes everywhere, its FAR from focused.

amblix1 said:


sweet, do you have photos of a completed one, or screenshots?
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#506
for some reason i still believe that a crt lens will work.....i have 3 crt projectors at home. and i know the lens has two focus rings on it....one for the middle of the image, and one for the edges of the image.......would this allow it to focus to a flat panel?
 
#507
here is the deal, you are taking a FLAT source and putting it into a curved lens. therefore, the distance from various points on the panel is longer or shorter, so the panel will look in focus in places, and out of focus in others.

its just how physics works. try it first, but back in the OLD diy projector thread, it was found that this would NOT work.

a CRT lens works with a CRT tube, they are both curved....
 
#508
cowanrg said:
here is the deal, you are taking a FLAT source and putting it into a curved lens. therefore, the distance from various points on the panel is longer or shorter, so the panel will look in focus in places, and out of focus in others.

its just how physics works. try it first, but back in the OLD diy projector thread, it was found that this would NOT work.

a CRT lens works with a CRT tube, they are both curved....
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damnit get your site up now hahahahaha j/k 🙂


what about using a fresnel before the LCD to concentrate the light into one spot, such as lighthouses :/
 
#511
Mario007 said:
Umm most overhead projectors do use an fresnel light before the lcd to spread the light evenly to avoid hot spotting. Cowan I have a computer that is setup using apache webserver I would be willing to host or mirror your site if you want.
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Ok thats what I thought, I knew OHPs use them but I wont be using an OHP. Well I guess all I need then is a good lens. Im not picky on quality, just something to play my video games on at night
 
#512
possibly. i have the site done, and hosting done, it just got pulled because of some disputes with my hosting over traffic...

this site pulls a LOT of people when its up. i think i was doing like 4K page visits a day near the end. i forgot how much bandwidth was used, but its more than a cable/dsl can handle for sure. it was in the multiple GB/month range.

ill get it back up and see if i need a mirror. where you located?


Mario007 said:
Umm most overhead projectors do use an fresnel light before the lcd to spread the light evenly to avoid hot spotting. Cowan I have a computer that is setup using apache webserver I would be willing to host or mirror your site if you want.
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#513
I live in Portland, Oregon west coast. Wow that sure is a lot of bandwidth. You might look into compressing your images a lot. Possibly a non intrusive banner ad would help you pay for your hosting? I will host as much bandwidth as I can for free in the name of diy projection. 320k upload.
 
#516
Simply because the lights of america flourcesents aren't very high lumen which means you would have to have an awsome reflector for them. Plus his lens is a crt lens which means as was already pointed out would give an out of focus look on the outside edges. But maybe he figured some way around that. Bending his lcd panel 🙂 JK.
 
#517
zark

zark's idea was quite similar to my first idea, as i was browsing my partsexpress catalog and saw the cheap auto lcds. if you look at the screenshots on his site, you will see that they suck a$$. bright in the middle, dim in distorted on the edges. its like the video version of a bagel. the crt lens forces you to put the lcd within 1"--actually less--of the lens. i busted apart a fuji crt lens i got for 6 bucks and there are actually some potentially usable elements inside. read the original thread--it's all inthere
 
#519
delt iv

buy one and try it , if you like. they're pretty cheap. apparently, they made a lot of these at some point. edmund has beesn selling them for years. i beleive theyre from the old scool huge front projection tv's of years ago. nothing wrong with them, but not really what we're looking for
 
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