New projector, size not an issue

[TYZ]

I'm building a projector, so far I have gathered the following parts.

1: a BenQ 557S
2: a 3M 9550 OHP
3: one very SWEET projection lens (details to follow)
4: one very LARGE condensor lens (details to follow)
5: a 250 watt or 400 watt or a 1000 watt magnetic ballasted MH (Mogul base)
6: reflector to be determined (in consideration is one from here http://scientificsonline.com/product.asp_Q_pn_E_3053875 )

I want this to be a VERY bright and clear projector. I would rather NOT use mirrors to redirect light within the projector (thus my comment about size not being an issue, I have room for a prety big machine).

I have researched and found that the BenQ 557S is appropriate to a DIY projector (no cabling issues), I know that I am "pushing the envelope" by using the fresnell from the 3m (loss at the edges due to LCD panel to fresnel size ratio) but this MAY be acceptable.

The projection lens's I have at my access are the triplett that comes with the 3m or a very large AmPro lens. The ampro lens is gorgeous! It's front lens (screen side) is 75mm it's rear lens (LCD side) is 75mm, this lens is marked as "4:1". The lens external description is as follows, black annodized alluminum, total length 180mm with a thread mounting at 75mm from the LCD end, overall outside diameter 105mm. From what I have been able to determine the focal length from the image source is approximately 630mm, I haven't been able to find any information on this lens, the serial number on the lens means nothing to the folks that now service AmPro equipment.

I have the condensor and lamp assembly from the OHP that I can use (it's a completely functional 3m 9550) or I have a LARGE condensor lens that is 225mm with a focal of 203mm (approximately).

I am considering ordering one of the following reflectors ( http://scientificsonline.com/product.asp_Q_pn_E_3053875 ) if I can use my large condensor and a mogul based lamp (that I allready have).

Any comments or advice would be greatly appreciated please

TYZ

[Guy Grotke]

Wow, those are some nice looking parabolic reflectors! I might just get one of the 18" ones to play with. The tricky part will be getting the center of the LCD illuminated evenly (where the top of the bulb lights it directly). Depending on the bulb design, it might be too bright or too dim. You might have to put a bit of metal screen on the top of the bulb, or defocus the bulb slightly to fill in the center spot.

I think you can use EITHER a large parabolic reflector and a converging fresnel to get the parallel light rays into your objective lens, OR use a small spherical reflector, condensor lens, and a pair of fresnels. I don't think you can use both a parabolic reflector and a condensor lens.

It would be nice to have both objective lenses, so you could switch between short-throw and long-throw positions. The only problem is that you will need an upper fresnel (that could actually be put below the LCD) that matches the focal length of each of those lenses. The OHP lens should be easy to match, but the 630 mm fl lens will need a longer FL fresnel to get the light into the lens. LumenLabs sells a big, longer focal length fresnel you might try.