hi,
could anyone tell me the distance they have put there fresnel lenses from the psone lcd with the split option as i cant seem to get any picture and i think it is to do with the distance of the fresnels to the lcd as i have tryed every other option.
thanks🙂
could anyone tell me the distance they have put there fresnel lenses from the psone lcd with the split option as i cant seem to get any picture and i think it is to do with the distance of the fresnels to the lcd as i have tryed every other option.
thanks🙂
fresnel lenses
hi monqals im not sure.
i got them from ebay because i couldn't find them anywhere close to me. they are 4" by 6" and i cut them down to fit the size of the psone screen and they are 0.5mm thick plastic.
hi monqals im not sure.
i got them from ebay because i couldn't find them anywhere close to me. they are 4" by 6" and i cut them down to fit the size of the psone screen and they are 0.5mm thick plastic.easiest way i've found to figure out what the focal length is quite obvious:
get a VERY VERY small thing, like a pin, spec of dirt or something. Get a metric ruler. put the speck of dirt on a clean, plain surface. hold the fresnel parallel to the ground above the speck, approx 12 inches away. look down through the fresnel and find the speck. now move the fresnel slowly away from the speck, until the speck becomes HUGE on the fresnel. you should have the speck fill the size of the fresnel. hold it there, with your other hand, grab the ruler and measure the distance from the front of the fresnel to the ground. this distance is the focal length.
get a VERY VERY small thing, like a pin, spec of dirt or something. Get a metric ruler. put the speck of dirt on a clean, plain surface. hold the fresnel parallel to the ground above the speck, approx 12 inches away. look down through the fresnel and find the speck. now move the fresnel slowly away from the speck, until the speck becomes HUGE on the fresnel. you should have the speck fill the size of the fresnel. hold it there, with your other hand, grab the ruler and measure the distance from the front of the fresnel to the ground. this distance is the focal length.
if you bought it on ebay it's probably a page magnifier and not a real fresnel lens like the ones that everybody use.. "our" fresnel lens are about 3mm thickness... and don't bend so easily like your probably do.
Theres a few good sites to buy fresnels if you want. like lumenlab (in USA) or exclusive-online and izzotek (if you live in europe).
Theres a few good sites to buy fresnels if you want. like lumenlab (in USA) or exclusive-online and izzotek (if you live in europe).
hi guys,
im still having problems with my projector so i tryed replacing the lcd with a sheet of acetate with a picture about the size of the lcd and it worked but when i took the acetate out and replaced it with the lcd it dident work anymore.
does anybody know why???
i thought it was the light output from my 75w dicloric lamp so i changed it for a 150w flood lamp but still doesn't work. can anyone help.😕
would i be better with a 250w class A projector lamp with dicloric reflector. or not?
thanks🙂
im still having problems with my projector so i tryed replacing the lcd with a sheet of acetate with a picture about the size of the lcd and it worked but when i took the acetate out and replaced it with the lcd it dident work anymore.
does anybody know why???
i thought it was the light output from my 75w dicloric lamp so i changed it for a 150w flood lamp but still doesn't work. can anyone help.😕
would i be better with a 250w class A projector lamp with dicloric reflector. or not?
thanks🙂
considering you loose about 90% of your light through the LCD you most likely need another light source. Those lights probabally aren't bright enough, have way to large of an arc gap, and are yellow due to thier low color temperature. You might want to look into one of the lower wattage metal halide light setups if you are looking for good results.
or flip your lcd around so that the light is shining through the back of the LCD. i've read that lcd's are designed to have light through the back.
you'll have to add a mirror to flip the image back around of course (or use image flipping settings on your computer if using that for a source)
you'll have to add a mirror to flip the image back around of course (or use image flipping settings on your computer if using that for a source)
Let us know what the focal length of your fresnels are. Best way to find out is take it outside in the sun and focus to the smallets dot. (like we burn paper or ants). Make sure the grooved side facing the sun and the flat side facing the floor. Measure the distance to the floor and the fresnel and it should give you the focal length.
Lets say the focal length is 300mm and you have 2 fresnels both identical.
The first fresnel from the lamp (collimator/condensor) should be facing flat side to the lamp, grooved side to the projection lens and should be exactly 300mm away from the center of the element of the bulb.
Then the LCD (backside to the light, and rotated 180 degree) another 15mm from the condensor fresnel.
Then the second fresnel (Collimator/field), groove side facing the bulb and flat side facing the projection lens, another 20mm away from the LCD. Any closer to the LCD will project the grooves onto the wall.
If the Fresnel lens were 300mm, then Idealy the projection lens focal length you need should be about 10mm less than the focal length of the fresnel. The projection lens then is mounted focal length of projection lens away from the LCD and NOT the second Fresnel.
So lets say the focal length of projection lens is 290mm. The lens should be placed 290mm away from the LCD. You might want to use a mirror at 45 degree angle somewhere in between to flip the image over as it will be opposite without it.
You will notice the projection lens will be about 30mm less than the focal point of the second fresnel. That is ok because it gives the opportunity of full use of diameter of projection lens rather than focusing a dot on there. You may even after all this need to make slight adjustments.
Hope this helps. Let us know and post us some pics.
Lets say the focal length is 300mm and you have 2 fresnels both identical.
The first fresnel from the lamp (collimator/condensor) should be facing flat side to the lamp, grooved side to the projection lens and should be exactly 300mm away from the center of the element of the bulb.
Then the LCD (backside to the light, and rotated 180 degree) another 15mm from the condensor fresnel.
Then the second fresnel (Collimator/field), groove side facing the bulb and flat side facing the projection lens, another 20mm away from the LCD. Any closer to the LCD will project the grooves onto the wall.
If the Fresnel lens were 300mm, then Idealy the projection lens focal length you need should be about 10mm less than the focal length of the fresnel. The projection lens then is mounted focal length of projection lens away from the LCD and NOT the second Fresnel.
So lets say the focal length of projection lens is 290mm. The lens should be placed 290mm away from the LCD. You might want to use a mirror at 45 degree angle somewhere in between to flip the image over as it will be opposite without it.
You will notice the projection lens will be about 30mm less than the focal point of the second fresnel. That is ok because it gives the opportunity of full use of diameter of projection lens rather than focusing a dot on there. You may even after all this need to make slight adjustments.
Hope this helps. Let us know and post us some pics.
hi gizmotech
the focal length of my fresnels 270mm. and i have managed to get it working. 😀 finelly as i have recentlly changed it from a 75w dicloric bulb to a A class projection lamp. i was thinking of getting a MH bulb set up but as i came across the projection lamp i thought i would give it a try and its working well now. i will try and post some pics tomorrow because the camra isant working at the moment.
the focal length of my fresnels 270mm. and i have managed to get it working. 😀 finelly as i have recentlly changed it from a 75w dicloric bulb to a A class projection lamp. i was thinking of getting a MH bulb set up but as i came across the projection lamp i thought i would give it a try and its working well now. i will try and post some pics tomorrow because the camra isant working at the moment.
Truth be told I had the same question about focal lengths because I am building a little dinky pj for the fun of it using the page magnifiers from staples. To test the focal length I took a bright light and sent it through the fresnel, and holding the focus lenses I moved it back and forth until it focused the image of the pen that I had taped on the fresnel. I decided to post this in case someone comes by with the same question.
And I am excited to see some pics of your results( I will be using the psone screen also.)
And I am excited to see some pics of your results( I will be using the psone screen also.)
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