Special rear projektor

Hi Guys,

I am a newby on this site. I have read a lotsa threads about the projector building but i am stucked a bit.

I would need your help. Currently i am building a special projektor with an lcd panel. It is required a special objective focal lenght. I use in my system:
15" display
400W metal halid light source
2 fresnels in 310 *310 mm size with 220 or 330 focus which is the best (sandwich mode)

. I would like to create for this special projector which gives me a 110*160 cm size picture. My calculated objective focus results were between 80-135 mm in variofocus triplet lens.

The distance from the wall is maximum 1 meter cannot be more even shorter and the picture diagonale is about 194 cm.

I would like to use a triplet lens. Dou you know a place where can i find such kind of focal range between 80-140 triplet lenses ?

What do you all think how correct are my calculations?

Many thanks,



2004-07-25 10:06 pm
if you have 1 meter throw (trhow= distance from wall to proyector lens) then your desired image of 160" wide needs to be done with 160mm focal length proyection lens.

You can find lot of 160mm lens (photograpers lens for instance) but any of them won´t work in your setup. First of all the field angle (the angle where tje lens was designed for) is too narrow (photograpers work for 35 mm diagonal sizes only so your 15" screen is too far from there. You can try to proyect with a slide proyector lens in front of your lcd, it is not posible to capture more than 3" diagonal area in the best of the cases.

I believ it is posible to manufacture a lens that would have 80-160mm focal range and wide viewing angle (like a fisheye) but it will cost thousands of dolars to you. Forget that way.