Read in another thread that circular rings are present when you use a OHP because of the fresnel.
true or no?
true or no?
Probably depends on how good you lens are, with out my lcd screen on I can see rings, but with the lcd don't see then at all! mine are even pretty scratched up but it looks great I'd worry more about you panel quality.
I was the one who wrote that. I don't think it's a problem either. I have yet to see them through the LCD. I was just pointing that out as a very minute con to making a projector.
Ok, the rings are starting to bother me (I need something to complain about). Anyone else have any ideas on this? I imagine that this is a minor annoyance that everyone here w/ an OHP projector has to deal with. Is there a way to get some kind of filter to place between the fresnel and the LCD in order to diffuse the light so that it blurs the ring lines?
What kind of overhead projctor fo you have, I have a dukane 400 and haven't noticed any circles at all.
Rekr
Rekr
Damn thats a good projector, I was thinking of getting one, but I think rings would bug the hell out of me.
Rekr
Rekr
Thanks. The thing is beautifully bright. I got it on ebay for $400, and it would have probably been more except the seller had it in an odd category (business supplies instead of overhead projectors).
I don't think it's my projector's fault. Here's the deal. My fresnal has been warped because I had it running on the floor and the carpet was blocking the exhaust vent (luckily, this awesome projector automitically shut itself off and the LCD was not damaged). I'm getting a new and larger fresnel from an elmo 305.
Now I know your gonna think "well that's you problem right there", but the rings existed before this happend. I do not have any top glass, I've modded my OHP cover to hold the LCD (just like cruser did, see the NEC thread). I've got a few theories:
1. This is just something that most people don't notice, and having it slightly out of focus does the job just fine for them.
2. My panel is too close to the fresnel, or not far enough away.
Neither of these are convincing though. I'm totally lost. Anyways, does anyone else notice these rings? When I get the new fresnel, hopefully the rings won't be there, but I doubt that will be the case.
I don't think it's my projector's fault. Here's the deal. My fresnal has been warped because I had it running on the floor and the carpet was blocking the exhaust vent (luckily, this awesome projector automitically shut itself off and the LCD was not damaged). I'm getting a new and larger fresnel from an elmo 305.
Now I know your gonna think "well that's you problem right there", but the rings existed before this happend. I do not have any top glass, I've modded my OHP cover to hold the LCD (just like cruser did, see the NEC thread). I've got a few theories:
1. This is just something that most people don't notice, and having it slightly out of focus does the job just fine for them.
2. My panel is too close to the fresnel, or not far enough away.
Neither of these are convincing though. I'm totally lost. Anyways, does anyone else notice these rings? When I get the new fresnel, hopefully the rings won't be there, but I doubt that will be the case.
Similar Problem
I have a similar problem, but my single ring is multicolored (like a prism) and as far as I can tell it is actually a magnified image of the top of my bulb. Anyone have any ideas on how to fix this.
I have a similar problem, but my single ring is multicolored (like a prism) and as far as I can tell it is actually a magnified image of the top of my bulb. Anyone have any ideas on how to fix this.
Yes, but is someone says rings, we would most likely correctly assume that said rings are of a circular nature...
hey lifter, are the rings more prevailent when the projector is set closer to the screen or farther away
Lifter is there anyway to get a pic of the with and without rings image. I am not looking for quality pictures. Just what we can expect when building these things.
I'm really not the person to be asking because my fresnel is warped. I'll have the new one in a week. After that I can give more details on the situation- how bad it is, and what can be done to help.
Hey, lifter....
Have you received you new fresnel yet? I just discovered that mine is wraped as well. Not by much, but it could be the cause of my problems. I just wanted to know if your new fresnel fixed the problem.
Have you received you new fresnel yet? I just discovered that mine is wraped as well. Not by much, but it could be the cause of my problems. I just wanted to know if your new fresnel fixed the problem.
I have seen a few rings on my setup too, and I know what they are; interference patterns.
These are caused by interaction of 2 or more meshes through which a wave is send. In our case its eiter the 2 fresnels or 1 or 2 fresnels interacting with the pattern of the dots of the lcd.
Ppl with win98 can see that effect for themselves in the shutdown screen of win98 on a normal crt.
Correction of it is not as easy; maybe shifting the lcd or 1 fresnel solves it, but more likely you will just end up with interference patterns on another part of the screen.
Where there are multiple waves (eg. different light beams from different/adjecent rings of the fresnel) there are interference patterns. (fact)
All you can do is try to move the interference outside the visible part/projection area of the screen. (Or take a fresnel with less/more rings in it)
These are caused by interaction of 2 or more meshes through which a wave is send. In our case its eiter the 2 fresnels or 1 or 2 fresnels interacting with the pattern of the dots of the lcd.
Ppl with win98 can see that effect for themselves in the shutdown screen of win98 on a normal crt.
Correction of it is not as easy; maybe shifting the lcd or 1 fresnel solves it, but more likely you will just end up with interference patterns on another part of the screen.
Where there are multiple waves (eg. different light beams from different/adjecent rings of the fresnel) there are interference patterns. (fact)
All you can do is try to move the interference outside the visible part/projection area of the screen. (Or take a fresnel with less/more rings in it)
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