I am not using a rear fresnel with my led setup and at the minute am not using a projection/objective lens either..

But if i did want to use one how would I know what lens to get with no fresnel to match it to? What fl and how big a lens?

My tft is a 7" widescreen..

Been searching for a while but cant find anything concrete

Hi

If your LCD had been smaller say 5" I would have suggested trying a Lens from an old CRT projector... a 7" CRT lens would be pricey.

It appears that you are emulating what some people use for DIY TV projection where the TV is the light source and for the lens they use either a fresnel or a triplet.

A common lens for DIY TV Projection is a Beseler 18 EF Triplet.

Also a Polivision 4/Beta II lens triplet, (huge!, but more suited for a curved light source (TV)..unless you can figure out a way to compensate.)

A b*cket load of info on this type of projection/lens etc..... can be found at:

http://tv.groups.yahoo.com/group/DIYProjectionTV/

Cheers

Thanks for info..much appreciated Ill have a good look at that later.

HI
I am tring to get parts for my projector but i only managed to get a triplet lens.............the only thing is that it big (its from an old projector......verrry old........it only used this triplet lens, a mirror and a light bulb. it was used for reading books..........the light bulb lightened the book, and the mirror projected it forward to the tripplet lens)..........can u tell me please if i can use this lens for the projector?????or if u know how does it works comparing to the other triplet lens???............ it has 130 mm diameter and its 160mm long.............its bigger than what u usualy use.........i dont know what focus it has but i think its pretty big since the projector was used for classrooms presentations...........maybe i can adapt it to this project.________i tried to use it in front of my 21 inch tv and i managed to get a pretty good picture.................ofcourse it needed more light and the corners war bluring..............i got a small picture of a lens wich 90 % looks like mine.............an one more thing............fresnel lens from an overhead projector.......how are those working???ar they good for buildning a projector?????? ..............someone please point me in the right direction.............thanks

There's a good chance you can use that lens. Are there any markings or labels on it?
Fresnels from a OHP are usually too small to cover a LCD panel.

yes there are markings.................( EPICLAR f= 430/3,5 )...........an a serial number i think........... ( Sr.0703 )..................about the fresnel lens from OHP........i know they are smaller but do they function as better as yours???? because they've got diferent composition an i think the OHP has 2 fresnel lens stuck togheter...........in that case how do i separate them??????..............if they stay the same way doesnt that change the way they should work in a DIY projector..................excuse my bad english........I'm from Romania.............one reason i asked u about fresnel lens from an OHP............the only tipe of fresnel lens i found in my country are from OHP and even those are hard to fiind ..............thanks again

430mm is the focal length of the lens you have. If you can only obtain fresnels from OHPs,
then look for one that has or had a projection lens with a similar focal length - that would
work well. You don't need to seperate the two fresnels unless you need keystone correction.