First off: I've been working on this projector for over 2 years (I odn't have alot of time) and finally got it ready for testing this weekend. It's a smaller design, using a 7" Lilliput screen with a 330/220 mm fresnal lengths, together in front of the LCD.

Here is a link which will shed more light on my design:

http://ehrof.blogspot.com/2006/12/few-more...r-pictures.html

Also, I'm using a mirror before the LCD.

Now my problem:

My light isn't evenly displayed over the LCD. I can't figure out if it's the mirror, the reflector underneath the light, or the first frensal lense. Here are pictures that show my problem (note: I'm not a very good photographer, and it's actually brighter in real life. As well, the colours are off, because this is on a blue wall. I just want to get the brightness down! The central brightness is what it should be everywhere):

Ok, can't get the photo to attach. It's located here:
http://ehrof.blogspot.com/2006/12/crappy-image-so-far.html

well the first thing that jumps to mind is where you mentioned you have both fresnels in front of the LCD.. i believe you want them behind.. or atleast the collimator fresnel.. you want the light from the bulb to pass through the LCD collimated, off angle light is not allowed to pass through.

Try fresnels behind.. and make sure they are arranged correctly.

I didn't make that very clear I guess. They are behind the LCD, and in the correct order.

Is it possible that it's a reflector problem? Or is it definately an frensal dealio? I think I may need to pick up a new frensal lens.

Make sure the fresnels have the grooves facing each other. Make sure they are spaced a little apart. And spacing is critical. You need to have everything adjustable. Just sliding the lamp forwards or backwards 10mm can make a HUGE difference.

From your photo, the mirror may be ok. If it was even a little bit out of alignment, you would probably get different brightness from top to bottom or left to right (or both).

As Jonjandran suggests, the light position may be a little out (literally). You may be able to minimise the 'hotspot' in the centre of the image by moving the light in a tiny amount and then testing. You may have to move it in small increments over and over again to get it right, as a small movement can make a big difference.

Im having a similar problem with my 15 LL design. The centre of the image is bright and very clear. The corners are very dark and a little blurry. When i move the triplet around, the image is lit up evenly but is very blurry

If your spacings between freznels and to the lcd is good, and everything is perpendicular, you might need to move your lamp. First of all, is your lamp properly centred in x and y?

Are you using the 220mm rear fresnel? What is the distance form the centre of the lamp arc to the centre of the rear fresnel? If it is 220mm or so you may need to move it forward a bit to reduce the hot-spotting. Unless you have an easily adjustable setup, this may be a bit tedeous, but mark where it is now, and crank it forward a few mm and test again. You might find the ideal position at 210 + 5mm. Also place a mark here for reference.

If you haven't read Durachko's masterful tweaking guide, it covers everything you will need to know!

Thanks mate i will check out that guide. I dont really have an adjustable setup it was all done with eye.

When i tested it out with an old flood light, the picture was pretty nice. The lamp i am using now is one of those old 400W MH football ones and its a little hard to move around.

Yeah, the best projectors are usually the ones that have a bit of adjustability built in for all components. A little adjustment here and a little adjustment there can make a HUGE difference in final results. Best of luck!