finally got my lens for £10 and I am very pleased with it BUT there is terrible light distribution I have tried various glasses in front of the light but it does not seem to help. Had it up and running tonight and I must say with the focus slightly out of perfect the image is great (perfect focus shows the pixels too much) and I think I should be able to get a good image up to about 80" ish maybe a little more.
the further back I am able to go the better ideally I want to throw the image about 10 foot but somehow I dont think its going to happen.
the further back I am able to go the better ideally I want to throw the image about 10 foot but somehow I dont think its going to happen.
Halogen
a 75w halogon is much too dim and also has a very 'warm' colour temperature.
You would get better results using a Metal Halide bulb.
a 75w halogon is much too dim and also has a very 'warm' colour temperature.
You would get better results using a Metal Halide bulb.
I'm kinda thinking that myself I got the inspiration for the 75 watt from http://www.diyaudio.com/forums/showthread.php?s=&threadid=41154&highlight= but looking again at Markoh's lamp he seems to have a shallower reflector than the one on mine which may be why I cannot get rid of the hot spot. I am going to mess around with a 150 watt halogen (simply because I already have those) and if thats acceptable then I may invest in metal halide.
I am having some trouble here I cant seem to get this light distribution sorted out here is a quick drawing of what I have.
I have missed the reflector off this but I have tried with and without at various distances.
I have tried various condensor lenses with no success. Everything I do results in me having a bright center with a dark but still visible outer edge.
I would like to hear some suggestions but unfortunatly will not be able to try anything out because my attempts to correct this resulted in a broken uv glass from getting the light too close. The lcd wont survive very long without it 🙁
An externally hosted image should be here but it was not working when we last tested it.
I have missed the reflector off this but I have tried with and without at various distances.
I have tried various condensor lenses with no success. Everything I do results in me having a bright center with a dark but still visible outer edge.
I would like to hear some suggestions but unfortunatly will not be able to try anything out because my attempts to correct this resulted in a broken uv glass from getting the light too close. The lcd wont survive very long without it 🙁
It is a start
Hey looks like you are off to a good start....Try to keep the wife happy 😀 I'm doing the same thing http://www.diyaudio.com/forums/showthread.php?s=&threadid=44837...I picked up a slide projector and am using a 5" PS One screen. What is different is that my slide projector came with a 300W bulb, unlike the 150 that you guys are talking about....The thing is bright....I pluged it in and almost blinded myself!!!
Good luck!
Hey looks like you are off to a good start....Try to keep the wife happy 😀 I'm doing the same thing http://www.diyaudio.com/forums/showthread.php?s=&threadid=44837...I picked up a slide projector and am using a 5" PS One screen. What is different is that my slide projector came with a 300W bulb, unlike the 150 that you guys are talking about....The thing is bright....I pluged it in and almost blinded myself!!!
Good luck!
I will be glad to get this little problem sorted out but am really looking forward to darkening the room pumping the surround and watching LOTR all the way through.
Have you tried this
Being a newbe I don't know much either, but have you tried a condesor lens between the light and the first fresnel...?
shipto said:
Being a newbe I don't know much either, but have you tried a condesor lens between the light and the first fresnel...?
yes I have tried various lenses I have lying around but Have just thought of something I have the lenses out of the origional slide projector but i cut up the holders for my first try which dropped. I will try over the weekend to get them arranged the as they where in the beginning maybe that will solve it? Just need to find another bit of uv glass now which should be easy enough to get hold of.
light distribution
Maybe you should try removing the LCD panel and the upper fresnel. Then put a sheet of white paper where the LCD panel would go. Look at the light on the paper: Is it uniform? Does it have the same width and height as your lower fresnel? This setup lets you adjust the lamp, condensor, etc. until you get it right.
Then remove the paper and put the LCD and the upper fresnel back in. Move the paper between the upper fresnel and the projector lens. Does the light converge into the lens? If not, maybe you can adjust the upper fresnel until it does. Once that is done, you will have to adjust the projector lens to focus the image. You might have to adjust one, then the other, a few times to get it focussed with all the light hitting the lens.
If the light engine is adjusted correctly but it still looks bad, maybe your projector lens just does not have a wide enough angle... You could try a big magnifying glass projecting a 15" image to see if it looks more uniform.
You could almost double your light output, by adding a spherical reflector. A dichroic one would be the best, since it would not reflect the IR, but I don't know where you can get one. Once you do get the lamp adjusted, you could try an experiment with a soup ladle, a mixing bowl, or anything reflective with a true spherical shape. Avoid a parabolic or flat reflector: Those don't help for this application.
Maybe you should try removing the LCD panel and the upper fresnel. Then put a sheet of white paper where the LCD panel would go. Look at the light on the paper: Is it uniform? Does it have the same width and height as your lower fresnel? This setup lets you adjust the lamp, condensor, etc. until you get it right.
Then remove the paper and put the LCD and the upper fresnel back in. Move the paper between the upper fresnel and the projector lens. Does the light converge into the lens? If not, maybe you can adjust the upper fresnel until it does. Once that is done, you will have to adjust the projector lens to focus the image. You might have to adjust one, then the other, a few times to get it focussed with all the light hitting the lens.
If the light engine is adjusted correctly but it still looks bad, maybe your projector lens just does not have a wide enough angle... You could try a big magnifying glass projecting a 15" image to see if it looks more uniform.
You could almost double your light output, by adding a spherical reflector. A dichroic one would be the best, since it would not reflect the IR, but I don't know where you can get one. Once you do get the lamp adjusted, you could try an experiment with a soup ladle, a mixing bowl, or anything reflective with a true spherical shape. Avoid a parabolic or flat reflector: Those don't help for this application.
ok played around with it tonight and I think I have solved it I had the light too close which is a bit of a shame because it is I was hoping to cut it down but hey its going to work.
I think the main thing to help me get it set up right will be to make the object lens a permanent housing which I can do tomorrow if I have the right size tank cutter in my kit.
After that I really need to get the uv glass I only tested it for 10 minutes tonight before the screen started to blacken where it was running for hours before.
I think the main thing to help me get it set up right will be to make the object lens a permanent housing which I can do tomorrow if I have the right size tank cutter in my kit.
After that I really need to get the uv glass I only tested it for 10 minutes tonight before the screen started to blacken where it was running for hours before.
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