Film-Tech Forum ARCHIVE: Bulb layout in Digital units

This is topic Bulb layout in Digital units in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Monte L Fullmer (Member # 2797) on 03-30-2011, 01:56 PM:

Okey, a newbie question here:

In all we know that with 35mm projection in majority of the applications (Cinemecannica's did have side shooting lamphouses for the V8 setups), the path of light from reflector thru film, lens to screen has always been in a straight line.

Now, comes digital where the light path gets bent everywhere inside the unit via prism arrangement until it leaves the lens to screen.

You would think that light loss is great in this form of application.

Now, the newbie question: why is the bulb layout set at 90 degrees in the majority of the applications - from small LED/DLP table units to cinema applications intead of firing forward to the lens?

Granted, it's prob due to the light engines to where it looks like I just answered my own question here, but you'd think that there would be more light response if the path of light could be straighter with redesigning of the light engines to accept foward firing bulbs.

thx- Monte

Posted by Carsten Kurz (Member # 5396) on 03-30-2011, 06:19 PM:

Among other things, DLP is reflective technology. And there are three DLPs in cinema projectors. There's no way to have a straight forward lightpath with a reflective imager. Same with LCOS.
Some machines have an additional 90 degree mirror from lamphouse to light engine - I guess, mostly to shorten total machine length.

But that doesn't mean these machines loose that much light. As a matter of fact, due to new designs of mirrors, integrators, 'digital bulbs', prisms, coatings, etc. the light efficiency of series-2 1.2" DLPs is even better than that of traditional 35mm lamp houses. At least for 2D.

- Carsten

Posted by Monte L Fullmer (Member # 2797) on 03-30-2011, 09:07 PM:

Okey, that makes sense of the reflective format being that I forgot of DLP using those microtilt mirrors - one can tell that I needed to be educated in DLP cinema some more since I'm now more into floor operations than booth operations...

thx-Monte

Posted by Dave Macaulay (Member # 813) on 04-02-2011, 04:57 PM:

I think a 35mm projector using the light integrator system as in digital video projectors would be a great idea. The integrator evens out the light from the lamphouse and presents a nice flat illumination.