I thought I would open an old subject because I would like some comments.

Recently, I have been talking to giorgaki about reflectors and have read tons of material about the subject gone all the way back to 2005 through 3 forums and I feel like I'm .....
I've not really gotten what I've been looking for so maybe I just haven't found it yet. And that is a reflector that will do the job for a 15.4 LCD panel using a 220mm Fresnel, or even take the rear Fresnel out.
My picture is relatively okay for me, but like most I want more.
So, I've found some reflectors and maybe a solution but I need some advice.

I mentioned a custom reflector on the completed projectors post I have and I spoke to my friend more about it. He is only interested in the aluminizing process. So I found some reflectors that he could do but I'm not sure which one would be the best to try. I'm not even sure that the shape would be right for us but they look pretty good.
Here is what I found @ http://www.bhphotovideo.com/c/shop/1673/Reflectors.html

7" diameter



or

12"diameter






There's even a 16" diameter reflector like the 12" above too.
I think that our 46mm diameter t15 bulb would go through the end of these allowing adjustment of the focal point. Even if it isn't I could re-size the opening.
These reflectors have too dull a finish for us, but he could aluminize them to make a really good telescope quality finish. I'm just not sure which one to try.... There not that expensive and he could probably do about 10 of these in his vacuum chamber. I thought maybe the 12" would be enough for a 15.4 LCD panel. The smaller one may need a aspheric lens.

Which one would you try?

MAYBE the 12" diameter, but...

Those reflectors aren't made to increase a point-source light. They're meant to increase the overall illumination from the lamp. There's a big difference.

Those reflectors will throw more light onto a floor or something, but when used in out projectors the idea is to get light from the LCD to the projection lens. In order to do that, the light has to come from as small an area as possible. Light that comes from more than a certain distanc away from the center point doesn't get to the projection lens, and therefore doesn't help us out at all.

For that, you want a spherical reflector, and you want the lamp source as close to the center of the sphere as possible.

With the 12" reflector, it appears as though you're meant to have the lamp sticking out perpendicular to the center. This works fine for floor illumination, but for a projector, it sucks. The end casing of the lamp is in the way, and also other components of the lamp, like the wire. These will cast shadows on the LCD. In a non-focused application this doesn't matter, but because we ARE focusing on it...

Well, you can try, but I don't think that this is the right path.

Basically, my angle is that from having had a look at Emil's work from the German DIY community, where a very short arc single ended 250w MH lamp is used in an MR16 reflector and as sNOOp demonstrated a few months back, the results proved to be incredible. The only shortcoming was that the reflector (Decostar Osram 60 degree reflector) is just not suited to cover such a large panel (which required the use of concave lenses to help spread the light out, but vignetting did not look too good)

I did some experiments of my own with similar lamp and MR16 reflector and what I achieved was a very bright and even circle of light, except that the circle did not cover the screen and the heat was ridiculous since all the light was now being directed towards the screen. From what I saw, there was very little spillage around the triplet (standard size, not Pro or anything like that).

So in a sense, it works, and pretty well too. Just need a correct sized reflector or one that will accommodate a large panel like a 15.4" panel from a distance of 220mm. I unfortunately do not have the knowledge to determine what exact shape or size reflector should be used

http://www.diy-community.de/showthread.php...29&page=122