Hi all. So a while ago I bought all the pieces for a projector from someone. I got the LCD, lamp/ballast, 2xfresnel, triplet for a split setup. I don't know exactly where he got them, but I believe that he got them all as a kit possibly from lumenlab when it was up and running. So I think all the pieces are good for the purpose (I know LCD and lamp will work because I can physically see that). So here's my problem, I can't get a rectangular image output. I posted something about this a long time ago and haven't been able to work on it again until now. I'm relearning what I knew then and I have some questions/ideas that maybe someone can help with. So here's the problem:
I attached a pic of the most focused picture I can get. It clearly isn't good. The more I mess around though, the more I think the triplet is fine, and the fresnel are the issue. After passing through the 2nd fresnel, I can't get the image to focus down to a "point". Like when I use the lenses separately I can measure the focal length and the light goes down to a point, but the image of LCD never gets as small as the triplet. So Obviously it'll never work, right? I attached photos of how small it gets. One is the smallest it gets, the other is at the calculated distance via focalcalc. Neither is adequate. So now I'm wondering if the fresnels the guy gave me aren't right for some reason. I know I have them oriented correctly (grooves towards LCD) and at the right distances (focalcalc and trial-and-error). But I'm thinking that he got larger fresnels and cut them down. Would this make it so they won't focus down correctly? If this, or any other issues, would make these fresnels bad, I'm happy to buy others, but I want to buy something that will work. They don't sell fresnels with dimensions I need (330mmx360mm). So should I use too small and cut off screen? Or use bigger and cut down (this seems like it wouldn't work to me). Any ideas on what might be causing my problems are appreciated. Thanks!
I attached a pic of the most focused picture I can get. It clearly isn't good. The more I mess around though, the more I think the triplet is fine, and the fresnel are the issue. After passing through the 2nd fresnel, I can't get the image to focus down to a "point". Like when I use the lenses separately I can measure the focal length and the light goes down to a point, but the image of LCD never gets as small as the triplet. So Obviously it'll never work, right? I attached photos of how small it gets. One is the smallest it gets, the other is at the calculated distance via focalcalc. Neither is adequate. So now I'm wondering if the fresnels the guy gave me aren't right for some reason. I know I have them oriented correctly (grooves towards LCD) and at the right distances (focalcalc and trial-and-error). But I'm thinking that he got larger fresnels and cut them down. Would this make it so they won't focus down correctly? If this, or any other issues, would make these fresnels bad, I'm happy to buy others, but I want to buy something that will work. They don't sell fresnels with dimensions I need (330mmx360mm). So should I use too small and cut off screen? Or use bigger and cut down (this seems like it wouldn't work to me). Any ideas on what might be causing my problems are appreciated. Thanks!
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From your images it looks like the distance between your lamp and collector fresnel is off. Try adjusting the lamp by bringing it closer or farther away from the lenses.
Also check this; hold a piece of paper about an inch or two away from one of the corners of your lenses as the light travels into the triplet. If you see a corner forming on the paper then it's most probably not your distance between the lamp and fresnels and might be a defect in the lenses, if you don't see a corner and see the edge of a circle or nothing at all then it's definitely your lamp distance.
Also check this; hold a piece of paper about an inch or two away from one of the corners of your lenses as the light travels into the triplet. If you see a corner forming on the paper then it's most probably not your distance between the lamp and fresnels and might be a defect in the lenses, if you don't see a corner and see the edge of a circle or nothing at all then it's definitely your lamp distance.
Alright, so I tried what you suggested. As you can hopefully see, although the LCD goes to the edge of the wood, the picture doesn't come anywhere close, and also has no clear shape. So would this suggest that the lamp is too close and not fully reaching the outside of my LCD? If so how can I figure out where the lamp should be? I moved it about 4 inches father back and it didn't change much. The current case though doesn't allow for much more room. I'd happily reconstruct of it'll get it to work, but I'm concerned that it won't...
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OK, In order for us to help you, we need more info, such as distances between the two fresnels, between lamp and first fresnel, between lens and second fresnel, focal lengths and more pictures showing the inside of your box.
Also as you're using a split design make sure you don't have too much distance between the two fresnels and that both fresnels are facing their rings towards the screen. Also judging from your last picture it seems to me like there's quite a gap between your screen and second fresnel.
I still think it's an issue with the distance between your lamp and fresnels as if you have the fresnels facing the right way this would be my only guess.
Also have you considered turning this into an unsplit design with both fresnes behind the screen? Why have you chosen to do a split design? Do you need keystone?
Please provide us with more info so that we can help you accordingly
Also as you're using a split design make sure you don't have too much distance between the two fresnels and that both fresnels are facing their rings towards the screen. Also judging from your last picture it seems to me like there's quite a gap between your screen and second fresnel.
I still think it's an issue with the distance between your lamp and fresnels as if you have the fresnels facing the right way this would be my only guess.
Also have you considered turning this into an unsplit design with both fresnes behind the screen? Why have you chosen to do a split design? Do you need keystone?
Please provide us with more info so that we can help you accordingly
Alright, I've attached some more photos that hopefully give a good sense of what I'm working with. To answer your question, the reason I'm doing a split design is because I acquired these parts from someone who bought everything (and I think paid to have a case designed) but never finished. So I got all the parts cheap and wanted to complete it. But while the case is well constructed, the design limits changes I can "easily" make.
To be clear, I'm happy to make changes that aren't easy. But if I can fix this without having to build a new case or construct additional pieces, that would be best. Not only for aesthetics, but for example, the LCD is already mounted. If I don't have to move and remount, then there is no chance I break it...
Fresnels are both placed with grooves facing in toward LCD. Center of lamp is variable between 5 and 9" behind first lens. Not measurable, but distance between first lens and LCD is 1.25". Distance between LCD and second lens is variable as grooves are cut to place in different positions. Ranges between 1" and 3".
I would consider doing unsplit if that'll make it easier to troubleshoot etc. What are the advantages for unsplit? And I'll be happy if I can just get this to work. At this point it's a me vs the machines type mentality. It doesn't need to be perfect image, just viewable. So I won't worry about keystoning for now.
I really appreciate your help. It's become a bit of a thorn in my side that the projector is beating me. Let me know if I can provide any more information that will help. Thanks!
To be clear, I'm happy to make changes that aren't easy. But if I can fix this without having to build a new case or construct additional pieces, that would be best. Not only for aesthetics, but for example, the LCD is already mounted. If I don't have to move and remount, then there is no chance I break it...
Fresnels are both placed with grooves facing in toward LCD. Center of lamp is variable between 5 and 9" behind first lens. Not measurable, but distance between first lens and LCD is 1.25". Distance between LCD and second lens is variable as grooves are cut to place in different positions. Ranges between 1" and 3".
I would consider doing unsplit if that'll make it easier to troubleshoot etc. What are the advantages for unsplit? And I'll be happy if I can just get this to work. At this point it's a me vs the machines type mentality. It doesn't need to be perfect image, just viewable. So I won't worry about keystoning for now.
I really appreciate your help. It's become a bit of a thorn in my side that the projector is beating me. Let me know if I can provide any more information that will help. Thanks!
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Sorry for the late reply, in your original post you included a screenshot of a focalcalc diagram, in there you have the collector fresnel as 220mm and most likely the field fresnel as 330mm as you have the 300mm triplet.
I would suggest taking the fresnels out and going outside on a sunny day and measuring their focal lengths as the guy that built the projector might have mixed the field with the collector fresnel. When you have them out it's also a good idea to look through them (not towards the Sun of course) and see if they more or less behave like a normal lens would and if they have any defects in the grooves or anything else unusual.
Once you determine which one is the field and which one is the collector place them the right way in the projector, if they weren't already, and now based on your distance between the projector and your projection screen, use Focalcalc to calculate roughly the distances between your lamp and collector and your field and triplet.
Now check to see how far off are the real distances to your Lumnelab distances.
Again I think this is something to do with either your distances or the fresnels being inverted and I don't think the lamp or the triplet are responsible.
Let us know how you get on
I would suggest taking the fresnels out and going outside on a sunny day and measuring their focal lengths as the guy that built the projector might have mixed the field with the collector fresnel. When you have them out it's also a good idea to look through them (not towards the Sun of course
) and see if they more or less behave like a normal lens would and if they have any defects in the grooves or anything else unusual.Once you determine which one is the field and which one is the collector place them the right way in the projector, if they weren't already, and now based on your distance between the projector and your projection screen, use Focalcalc to calculate roughly the distances between your lamp and collector and your field and triplet.
Now check to see how far off are the real distances to your Lumnelab distances.
Again I think this is something to do with either your distances or the fresnels being inverted and I don't think the lamp or the triplet are responsible.
Let us know how you get on
Maybe I'm missing something, but focalcalc doesn't seem to use the lamp in any distances. So what do you mean by that?
I'll double check that the fresnels aren't swapped. Hopefully that's the issue, because right now the other distances and orientations are correct.
Do you think I should try to do an unsplit design?
Also I want to clarify an assumption I've been making. When the light leaves the lamp, it is moving apart. Then the first fresnel collimates the light so that it travels straight through the LCD. Then the second fresnel concentrates the light into the triplet. So if that's true, then any distances between first fresnel and second don't matter, because no matter how far, light travels in straight line. Is that an accurate summary of what's happening?
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