Help out a newb :)

Bigg'un

Member
2005-02-17 11:38 pm
NS
Ok, well I am building my projector, but I can't get the darn image focused....

I can get he middle and right hand side to focus alright, but not the left hand side or bottom left. I am about to mod my lens holder, as I noticed the "circle" of light from the second fresnel seemed to be placed a bit high and to the right, above the lens's actual location, could it be that I just have the main projection lense off by a little bit or what the heck is happening? I have the fresnels and LCD aligned as best I can (I have used a square and all the "proper tools", my eyes aren't that straight now!).

FYI, I am using the long throw projection kit from the diyprojecitoncomapny.com site, any tips would be awesome, becaus eI'd like to do something other than watch movies on this too (IT looks fine for movies becuase you don't notice the slight blur with the movement, that and the middle part of the screen is just about right).


Thanks in advance for the help!

Mostly I am interested in the "aura" that is going around the lense and not through it, nothing I do seems to move the ring of light into the 135 triplet...hase about 2 inches of wasted light around the top portion and left and right "sides".
 
mis-alignment

Yeah, it sounds like something is off-axis. It is a lot easier to troubleshoot this if you remove everything but the condensor fresnel from the light path. Then you can use a piece of white paper to look at the light coming out of the condensor fresnel (Should be a nice even rectangle of light that does not change size much as you move the paper away from it.)

Then put the field fresnel back in, and use the paper to check the light coming out of it. (Should be a converging "cone" of light that can be focussed to give an image of the lamp arc, about at the middle of the place where the projection lens will go.)

If either is off, then you have an alignment problem. Did you cut your fresnels evenly on opposite sides, so the centers are still on the central axis?
 

Bigg'un

Member
2005-02-17 11:38 pm
NS
Thanks for the help, I actually seem to have slight warped fresnels from shipping/heating, so I'll be looking for some low E glass to sandwitch them in the next week or so as cash allows. I have a new light comming as well so that will be something else to factor in...400watt mogul "grow-op" light more or less, not the best colour (4100K), but 36,000 lumens and lots brighter, cooler and closer to the right colour temp than my 500 watt halogen work lamp I've been testing with :)

I'll let you know what happens in the next little while. If by some chance I can't use low-e what is the next best substitute IYHO?

Thanks a bunch!
 
better IR glass?

I have not tried it, but I think this might be better:

http://www.diyprojectorcompany.com/...id=80&osCsid=fcb4f474a18dfb50f407eaf433403430

Low-E reflects really long wavelength IR, like the heat that gets emitted by your furniture when it is in sunlight. So a lot of the more energetic short wavelength IR (like from the sun or your lamp) will get through it. I think the glass above reflects more of the IR band.