| juice_e |
I have attached an image on this post of what i got so far. I have all the lenses and bulbs etc in place, i tooke a pic of a somewhat screen and i got alot of liens branching outwards from the middle which is comming from the fresnels, but isnt the actual fresnel grooves that you get from putting it too close to the LCD. Also in the picture, the LCD is NOT in because i cannot hook up to a source yet. If i put the LCD in place will that get rid of the lines or is this caused by something else. I hooked up the LCD before and focused an image of a box on the screen that says no input device detected and it focused very well but you can slightly see those lines on the white writting. Anyone know what is causeing it?
I added 2 pictures, both are the same but the one that looks more green is when the bulb wasnt warmed up that long and the other ones has some other colours comming in and that is when the bulb was on for about 5 minutes. |
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| Whatmo |
| What is the projection lens that you are using? Try to get the arc of your bulb in focus and see if it is still green. If it is it may be that your lens isn't corrected for abberration. |
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| juice_e |
How do i get the arc in focus, im not really sure what you mean?
Also, its not really that green, just a tiny bit. It s pretty much the camera that makes it look more green. Im more worried about those spiral looking lines comming out from the middle and that im not getting even light distribution, just a circle sort of . |
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| superdaveumo |
| I would guess those lines are the result of the arc reflecting off of your reflector? There is no LCD in there so that's not the culprit. I'd say just focus the arc. Do this by adjusting the fresnels until you get a nice picture of your arc (from the bulb) on your wall. Then slap that LCD in (at the right distance) and go to town! |
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| snortonnorton |
| wait, what do you mean focus till you can SEE the arc on the screen. isnt' the fresnel supposed to diffuse the light evenly on the screen withn no hot spots? seeing the arc is seeing a hot spot right? |
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| juice_e |
I dont have a reflector in yet either but nothing is painted blaack yet so could that be it?
Ya, i was thinking the same thing as snortonnorton, wont that mean that gives me a gross hotspot if i do that. |
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| snortonnorton |
yeah, but i'm thinking the lcd itself will also spread out some of the light.
what is your distance from the bulb to the fresnel?
and maybe you should try it with the lcd first before you change too much. |
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| juice_e |
Its 220mm from arc to first fresnel and im using the unplit design so both are together, lcd 20-30 mm aprox. after. the pj lens is about 14.86" i think i calculated it to be but its on a sliding piece so i can move it further or closer.
An d about the lcd, i cant put it in just yet because i need to hook it to my computer because i need a somewhat white screen because now all it is is black and it looks fine, until i take it out and see what is in the pictures..... |
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| dnsey |
| quote: | | o this by adjusting the fresnels until you get a nice picture of your arc (from the bulb) on your wall. |
The image of the arc should be focussed at the optical centre of the objective lens. The lens should in turn be focussed on the LCD. |
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| skullkeeper |
| whats the focal l of your lens |
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| juice_e |
| Focal length is 327mm .....Lumenlab lens....... |
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| juice_e |
I used all the conversion tools. And about moving the lens , i do, i have it on a slide so i can move it from 5mm to 17mm ish.. And when i move it, it still doesnt make a difference with the problems with the light.
Thanks for that url though, thats what i needed a month ago :) |
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| skullkeeper |
| the site is a big help i found it on google sence i dont know mm its a big help. maybe try shining a flashlight through your lens see if it puts out a green then if so your lens may have a greenish tint maybe. |
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| my1423 |
Stupid question.
Did you remove the green tinted film from your lexan?
Also try moving your lens away from the fresnel just a bit. May be close to being focused in infinity and that is where your getting the spiral lines. Very slight bend in fresnel causing slight diferance in outer pattern. Or you accedently got your fresnels swapped.
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| Cal Weldon |
| Moderation is a necessary nuisance. Thanks for your patience. |
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| my1423 |
| No Problem. You got to it almost immeadiadtly and it is a nessearry evil I guess. Just an inconveniance. Thanks |
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| juice_e |
| quote: | Originally posted by my1423
Stupid question.
Did you remove the green tinted film from your lexan?
Also try moving your lens away from the fresnel just a bit. May be close to being focused in infinity and that is where your getting the spiral lines. Very slight bend in fresnel causing slight diferance in outer pattern. Or you accedently got your fresnels swapped.
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Actually i just tested this once for 10 minutes and i didnt put the lexan in yet so thats not it but at first i thought i did that. I only tested it for 10 min kuz without the lexan, i didnt want to damage the fresnels. The fresnels are not swapped, i triple checked that too after.... What a pickle! |
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| Guy Grotke |
This is caused by have a slight misalignment of the two fresnel centers. You see a pattern of cancelled and reinforced light made where the rings in one fresnel interfere with the action of the rings in the other. I have seen a pattern that looks like a Japanese flag too. Shuffle one of those fresnels around a bit, relative to the other fresnel, until the pattern goes away. Or you can just space them 10 mm apart, and avoid the problem entirely.
You do need to run a new MH lamp for a while before it stabilizes. Some of the colors may fade out once it really gets going. Try running it for 20 minutes. |
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| juice_e |
Ok, thats the kind of answer i needed :) .. ya, the fresnels were offset a bit from eachother so im hoping thats it..... And i hope the colours even out a bit too .
But there is also the problem with the light . Shouldnt it be a rectangle pretty much, not a circle on that screen. But the lcd wasnt in its frame and the screen was only 3 feet away, about, instead of 8feet like its supposed to be. Will those have to do with it? |
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| Guy Grotke |
Use the real throw distance you plan to use. If it is focussed at 8' and the screen is only 3' away, then you will see a big round blob.
Using the real throw distance is important so you can get the right LCD-to-lens distance. With that, you can adjust your lamp and fresnel positions until you are getting nice even light mostly into the lens. If you set it all up with one throw distance, and then change that radically, it will need more adjustment. |
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| juice_e |
Ok, i did all that, set it up at 8feet. Its alot better, but the sides are still dim and a little orange looking but its not green no more but a tiny bit bit on the edges. But i ran it for 40 minutes or so while testing it so that slowly helped, hope it gets better.
I tried the whole setting it all up and then removing the lcd and pj lens and then focusing the arc image on a piece of papr where the pj lens should go. I moved the lamp closer and it gets WAY more focussed and the light distribution was sooo much better. I got it from this site: http://www.diyaudio.com/forums/showthread/t-68683.html
I Put the lens and lcd back in and the edges were fine so i guess thats what my problem was. But the wierd thing is is that the lamp is almost 1 inch closer to the first fresnel which made it about 190mm instead of 220mm. Should it be that far off or is that normal. |
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| Guy Grotke |
If moving the lamp to that position gave you a nice sharp arc image right where the center of the lens goes, then that is what you want. Your lamp arc distance is compensating for the imperfect match between the field fresnel focal length and the distance from the field fresnel to the center of the projection lens. If it was way far off, then I would suggest you look for a field fresnel that is a better match, but in your case I think its fine.
That is exactly what you needed to do to tune the condensor system. Congrats! |
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| juice_e |
| Sweet... Alright, than i am normal... Thanks to all who helped... I think im good till the end.. |
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