dichroic lamp
I know that OSRAM has a couple of small MH lamps that come inside dichroic elliptical reflectors as a unit. (They will run several hundred dollars US each, I believe.) They were designed for driving optical cable. I'm sure they are not the only maker of this type of lamp, but I don't think you will find anything in the price range of a typical DIY projector lamp.
I have seen one website where a fellow cut off the socket-end of a tungsten-halogen lamp with a built-in parabolic dichroic reflector, using a Dremel abrasive wheel. Then he stuck a naked MH arc chamber inside at the focal point. This was one of those "DON'T TRY THIS AT HOME, KIDS!" experiments, where everybody had to go into another room before he turned it on.
I think you can get pretty much the same effect by using an aluminum elliptical reflector with a hot or cold mirror placed at the second focal point. This type of reflector does not send the reflected rays through the arc, (like a spherical does), so the lamp runs cooler.
I know that OSRAM has a couple of small MH lamps that come inside dichroic elliptical reflectors as a unit. (They will run several hundred dollars US each, I believe.) They were designed for driving optical cable. I'm sure they are not the only maker of this type of lamp, but I don't think you will find anything in the price range of a typical DIY projector lamp.
I have seen one website where a fellow cut off the socket-end of a tungsten-halogen lamp with a built-in parabolic dichroic reflector, using a Dremel abrasive wheel. Then he stuck a naked MH arc chamber inside at the focal point. This was one of those "DON'T TRY THIS AT HOME, KIDS!" experiments, where everybody had to go into another room before he turned it on.
I think you can get pretty much the same effect by using an aluminum elliptical reflector with a hot or cold mirror placed at the second focal point. This type of reflector does not send the reflected rays through the arc, (like a spherical does), so the lamp runs cooler.
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