My ProView 15.4" 1280x800 HD project...

[Guy Grotke]

You will be putting your pre-condensor lens within a few millimeters of the MH lamp, so it MUST be heat resistant glass. B270 glass is not! They will break. You need Pyrex or borosilicate.

Rolyn Optical has some in their paper catalog for $66 to $85. (Which I suspect Squeeky already found.) They don't appear on their website as a category, but you can type their part numbers into the search box to see specs & prices.

25.0100 114.3 mm D 165 mm fl $66.20
25.0105 114.3 mm D 190 mm fl $67.25
25.0110 114.3 mm D 229 mm fl $68.41
25.0120 114.3 mm D 305 mm fl $68.47

25.0140 152.4 mm D 305 mm fl $84.20
25.0150 152.4 mm D 406 mm fl $84.97

[Inkog]

Hi Guy,

I was aware I would need Pyrex, but had no idea how to tell if it was from the information they provided. Thanks for the heads up thou, I greatly appreciate all the help thus far. Do you think a 220mm fl condenser fresnel will work well with this LCD (392mm diag)? I noticed you have recommended a larger than 330mm field fresnel FL when using a 450mm projection triplet. What would you recommend?

Squeek,

I'd be happy to work together on our PJs, as I'll need all the help I can get . I've also been thinking of using the s400dd, I just can't find an electronic ballast for it anywhere. If you (or anyone else) has found a source please let me know.

I think that spherical reflector from Surplus Shed is damn near perfect for the s400dd bulb using a 220mm fresnel with no pre-condenser. See below. I will get a couple of those to play with Good Find bro

(By the way all, of my sketches are 1px==1mm)

[18wheeler]

here is the formulas you can use when calculate the light lost rate:

V = (4 Pi/3) r^3

V = (2 Pi/3) r^2 * h

[ace3000_1]

Guy, B270 can handle upto 300c no probs, aslong as you cool the condenser there isnt a breakage issue.

Standard float glass will.

Trev

[Guy Grotke]

I don't think a MH lamp in close proximity will melt a standard glass condensor, but I think it could heat it unevenly enough to crack it. I have seen pictures of condensor lenses that cracked during normal use. None of those were Pyrex or borosilicate glass. I guess a design with the right amount of cooling air on both sides of the lens could prevent this. I just don't know how to determine that "right amount".

Those Ushio retrofit SS400DD lamps are only designed to run on an S51 HPS ballast. (That's High Pressure Sodium) They are designed to retrofit an HPS fixture with a nicer lamp. Running them on an electronic ballast has not always worked well, according to other posters on this and other forums. You can find one locally (shipping is expensive) or get one form places like www.goodmart.com.

[ace3000_1]

I don't think a MH lamp in close proximity will melt a standard glass condensor,

It wont melt it, it will crack it, its from the expansion rate being too great on the center of the lens. They dont heat evenly either, the hottest part is right in the center (about the size of the arc).

What happends is the center gets so hot it has to expand more then the outer. The outer is cooler and therfore boom, it gives.

I used to think that they heated evenly aswell, it wasnt until i got a temp probe out (that melted btw) and tested it. I also saw the heat difference on a particular lens on the plano side as the coating in the center changed colour to the outer. The coating in the center was burnt.

Trev

[Guy Grotke]

Inkoq:

I think a 220 mm fl condensor fresnel would work fine without a pre-condensor lens. If you do want to use a pre-condensor lens, then you might have to go to a 330 mm condensor fresnel. The question is if you can get the lamp arc close enough to the pre-condensor lens to light the corners of your fresnels. Difficult with a T15 lamp (15/8" diameter). A 330 mm fl fresnel gives you more room for the cone of light to expand.

Lumenlab has some longer fresnels that are suitable for a 450 mm fl projector lens. I use one of their 790 mm fresnels by adding some space between the fresnels and the LCD. Their new 650 mm fl fresnel would probably be better.

[Squeeky]

Well, I can't speak for Inkog, but the pro lens at LL are a little too much for me. I love Brain and LL but I can't afford fresnels that expensive, I was going to go with Alans 15.5" at diylabs. I want to thank everyone for helping on this, hopefully we will get a nice HDTV 15" projo.

[Inkog]

I agree, they are pricey

I just put a call into Fresnel Technologies, Inc. to get prices and availability. I was told a engineer would contact me sometime today. They have UVF Acrylic that blocks almost all UV and all middle and far IR. I'm guessing these won't be cheap, but hopefully they have some stock items we could source on the cheap. I'll let you know how this goes.

Like most, I do not have an unlimited supply of resources for this project. I researched and figured I was going to spend at least 700USD to make this HD pj come to reality with acceptable results. I figure if I'm going to invest that much $$ on this thing, if I find slightly more expensive parts that will provide greatly enhanced performance, I'll probably bite the bullet.

[Squeeky]

Did some thinking on reflectors and pre-condensers

Ok there is condenser that list 114mm dia and 165mm fl

If I understand optics correctly finding a matching spherical mirror would be ideal, just sandwhich the bulb between the two at equal distances.

It's not exact but close, surplusshed has a spherical mirror 76mm in dia w 152mm FL.
I have also found several other mirrors with close optics directly from optics stores.

Would these two items work together in harmony? Inkog SS also has hot mirrors but they are very small, 50mmx55mm.

I think it might be time to do some trial and error. Any chance you wanna come to Ohio Inkog