DIY Video Projector Part II

[xblocker]

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

[amblix1]

Originally posted by cowanrg
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.

sweet, do you have photos of a completed one, or screenshots?

[amblix1]

do you all think this CRT lens
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=1370138301

would work for this projector setup using a 5" LCD?

http://www.geocities.com/zark5150/

I really do not want to use a fresnel lens

[multiplexor]

Originally posted by xblocker
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

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.

[cowanrg]

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.

Originally posted by amblix1


sweet, do you have photos of a completed one, or screenshots?

[eebasist]

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?

[cowanrg]

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....

[amblix1]

Originally posted by cowanrg
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....

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 :/

[Mario007]

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.

[eebasist]

i wasnt aware that it was tried.....i was commenting that there are two focus rings for the outside and inside edges thats why i thought it could work....i do know how physics works, but i dont have the specs of crt lenses