Hello, I try to optimize in term of brightness my pj based on a 7' lilliput.
here is the setting:
spheric reflector (64mm diameter)
1mm
double ended 250w metal halide bulb
4mm
precondensor (focal 75mm diameter 54mm)
126mm
Fresnel 1 consist in fact in 2 added fresnels (focal 220+focal 330) in order to decrease the resulting focal.
5mm
lcd 7' lilliput
5mm
Fresnel 2 (focal 380mm)
388mm
objectif lens (leitz wetzlar 400mm focal diameter 100mm)
my projection distance is 4,6m and give me a 1,6m base image
may be I'm wrong on certain point?
but 2 condensor fresnels allow to increase the brigtness by 3-4 compare to a 220mm focal setting but for sure it increase also the arc image 1,5 time and thus the need for a big projection lens.
the precondensor here add around 25% of brigtness (luxmeter measurements).
If I use the differents excellent information from this site to calculate
the image arc (info from guy grotke and rox and others) if find some estimation.
first calculation is the position of the precondensor and the virtual size arc increase induced by the precondensor.
second calculation from the virtual arc size and the fresnels focal to calculate the final image arc size.
in my setup image arc size is then 76mm.
with a 100mm projection lens it should be ok.
BUT when i put a bigger projection lens 125mm diameter focal 112mm I improve the brightness
from 80lumens with the 100mm lens I go to 110lumens with the 125mm lens.
Why not put the 125mm lens you 'll tell me. Because it's difficult to integrate in my actual vp and i need to do a different box to ingerate it.
So my first question is:
1) does the spheric reflector will increase the final arc image size. Or does a wromg placement (bulb not at the focal of the reflector) might do it.
2) does my 63mm diameter is sufficient for my 250w bulb or do I need a bigger reflector like the ikea napkin stuff.
3) Is there a better combination of fresnels which will allow me to get 110lumens with my 100mm projection lens. in fact something to decrease the arc image size.
Thanks for your help and sorry for the long writing.
here is the setting:
spheric reflector (64mm diameter)
1mm
double ended 250w metal halide bulb
4mm
precondensor (focal 75mm diameter 54mm)
126mm
Fresnel 1 consist in fact in 2 added fresnels (focal 220+focal 330) in order to decrease the resulting focal.
5mm
lcd 7' lilliput
5mm
Fresnel 2 (focal 380mm)
388mm
objectif lens (leitz wetzlar 400mm focal diameter 100mm)
my projection distance is 4,6m and give me a 1,6m base image
may be I'm wrong on certain point?
but 2 condensor fresnels allow to increase the brigtness by 3-4 compare to a 220mm focal setting but for sure it increase also the arc image 1,5 time and thus the need for a big projection lens.
the precondensor here add around 25% of brigtness (luxmeter measurements).
If I use the differents excellent information from this site to calculate
the image arc (info from guy grotke and rox and others) if find some estimation.
first calculation is the position of the precondensor and the virtual size arc increase induced by the precondensor.
second calculation from the virtual arc size and the fresnels focal to calculate the final image arc size.
in my setup image arc size is then 76mm.
with a 100mm projection lens it should be ok.
BUT when i put a bigger projection lens 125mm diameter focal 112mm I improve the brightness
from 80lumens with the 100mm lens I go to 110lumens with the 125mm lens.
Why not put the 125mm lens you 'll tell me. Because it's difficult to integrate in my actual vp and i need to do a different box to ingerate it.
So my first question is:
1) does the spheric reflector will increase the final arc image size. Or does a wromg placement (bulb not at the focal of the reflector) might do it.
2) does my 63mm diameter is sufficient for my 250w bulb or do I need a bigger reflector like the ikea napkin stuff.
3) Is there a better combination of fresnels which will allow me to get 110lumens with my 100mm projection lens. in fact something to decrease the arc image size.
Thanks for your help and sorry for the long writing.
i forgot to mention that the projection lens focal 400 and diameter 100mm is 100mm high
and that the 125mm diameter lens is 125mm high too.
I think this is important to choose the good focal fresnel no?
and that the 125mm diameter lens is 125mm high too.
I think this is important to choose the good focal fresnel no?
some answers
1) does the spheric reflector will increase the final arc image size. Or does a wromg placement (bulb not at the focal of the reflector) might do it.
It should not increase the size of the arc image, it you put the center of the lamp arc at the exact center of curvature of the sphere. It should just give you about 20-30% more light. If the lamp arc is not at that exact point, then it can give you a much wider bright area.
2) does my 63mm diameter is sufficient for my 250w bulb or do I need a bigger reflector like the ikea napkin stuff.
You need to make a precise drawing that shows the rays reflecting off the edges of your reflector, back through the center of the lamp arc, and then into your pre-condensor lens. If they spread as wide as the whole lens, then your reflector is big enough.
3) Is there a better combination of fresnels which will allow me to get 110lumens with my 100mm projection lens. in fact something to decrease the arc image size.
Sorry, I think the only way to get a small arc image is to start with a small arc! There is a concept in optics called something like "conservation of entendue" that says you can't take rays from a wide source and make them behave as if they came from a point source.
I am not surprised you get a brighter image with a larger diameter lens: Some light gets scattered by the LCD, and you need a lens that is about twice the width of your arc image to capture all the light.
1) does the spheric reflector will increase the final arc image size. Or does a wromg placement (bulb not at the focal of the reflector) might do it.
It should not increase the size of the arc image, it you put the center of the lamp arc at the exact center of curvature of the sphere. It should just give you about 20-30% more light. If the lamp arc is not at that exact point, then it can give you a much wider bright area.
2) does my 63mm diameter is sufficient for my 250w bulb or do I need a bigger reflector like the ikea napkin stuff.
You need to make a precise drawing that shows the rays reflecting off the edges of your reflector, back through the center of the lamp arc, and then into your pre-condensor lens. If they spread as wide as the whole lens, then your reflector is big enough.
3) Is there a better combination of fresnels which will allow me to get 110lumens with my 100mm projection lens. in fact something to decrease the arc image size.
Sorry, I think the only way to get a small arc image is to start with a small arc! There is a concept in optics called something like "conservation of entendue" that says you can't take rays from a wide source and make them behave as if they came from a point source.
I am not surprised you get a brighter image with a larger diameter lens: Some light gets scattered by the LCD, and you need a lens that is about twice the width of your arc image to capture all the light.
Well Thanks for your answer.
I realize that i did a lot of thinking to set everything in the box exept for the reflector.
I'm pretty sure that I didn't set the reflector at the right distance. My recent measurements show that my reflector give me only 16% more light than without reflector.
So yes from your answer it seems that I can decrease the size of the arc by putting the reflector to the right place. And no more🙂
As my precondensor lens is very small (54mm*54mm), i think that my reflector is big enough. I'll do a drawing as you propose to be sure.
Well with this sentence , you didn't let me too much chance to get 110lumen with my 100mm lens. I'll just consider that all the light is bigger than 110lumens and that my reflector tweaking will allow me to go to 110 lumens with my 100mm lens.🙂
I realize that i did a lot of thinking to set everything in the box exept for the reflector.
I'm pretty sure that I didn't set the reflector at the right distance. My recent measurements show that my reflector give me only 16% more light than without reflector.
So yes from your answer it seems that I can decrease the size of the arc by putting the reflector to the right place. And no more🙂
As my precondensor lens is very small (54mm*54mm), i think that my reflector is big enough. I'll do a drawing as you propose to be sure.
Well with this sentence , you didn't let me too much chance to get 110lumen with my 100mm lens. I'll just consider that all the light is bigger than 110lumens and that my reflector tweaking will allow me to go to 110 lumens with my 100mm lens.🙂
Well,
I realize that my reflector have a 16.3mm EFL
then even with the bulb directly stuck on the reflector, the distance between the center of the arc and the bottom of the reflector will be of 32mm minimum (reflector distance between side and center is 20mm) .
So I cannot set this reflector to the good distance
I realize that my reflector have a 16.3mm EFL
then even with the bulb directly stuck on the reflector, the distance between the center of the arc and the bottom of the reflector will be of 32mm minimum (reflector distance between side and center is 20mm) .
So I cannot set this reflector to the good distance
lamp is too big
This is why people like the small double-ended lamps. They can use a small reflector, and still get the arc in the right place. Maybe you can find a bigger reflector. Some people use a metal reflector with some material cut from one or two sides, so they can get the lamp arc in the right place.
BTW: The point where the lamp arc goes is called the "center of curvature". When you buy a spherical reflector from an optics supplier, they will tell you the EFL is the sphere radius * 2. If you put the lamp arc there, then the reflector works like a (bad) parabolic reflector to give you a parallel beam. That is not what you want!
This is why people like the small double-ended lamps. They can use a small reflector, and still get the arc in the right place. Maybe you can find a bigger reflector. Some people use a metal reflector with some material cut from one or two sides, so they can get the lamp arc in the right place.
BTW: The point where the lamp arc goes is called the "center of curvature". When you buy a spherical reflector from an optics supplier, they will tell you the EFL is the sphere radius * 2. If you put the lamp arc there, then the reflector works like a (bad) parabolic reflector to give you a parallel beam. That is not what you want!
Well good info for me. I was not cllear on that point.
so for a spherical reflector the efl is 2times the radius of the circle. and the lamp should be at the center of curvature (thus the radius distance from the bottom of the reflector).
Well this is even worse with my actual reflector. efl is 16.3mm thus the radius is 8.15mm and i'm at a distance which is 4 time the radius.
Ok I should receive an ikea napkin holder soon. I hope i can get at least a gain of 40% compared without reflector. Which is better then my actual 15%.
Thanks for the info.
GG did a small mistake there;
the EFL on a spherical reflector is R/2 (not twice).
your 16.3mm EFL, should have 32.6mm radius, exactly where your lamp should go from the back of the reflector...
renan, did you have any succes on the lilli antiglare improvement?
the EFL on a spherical reflector is R/2 (not twice).
your 16.3mm EFL, should have 32.6mm radius, exactly where your lamp should go from the back of the reflector...
renan, did you have any succes on the lilli antiglare improvement?
ok thanks for that precision.
then as the back of the reflector is 20mm from the front and the 250w mh bulb is 24mm large . So the arc is at 20+12+1= 33mm instead of 32.6mm . So i cannot to better with that one.
About the antiglare and lilli, i tried to remove the polariser. Well let me tell you that I don't think I'll do this on a nice 15' lcd or other.
The polariser stick very well to the lcd. As mine was broken, it just broke a little bit more.🙂
removing the polariser and put together the polariser show clearly why the lilly lcd is so dark . Polarisers works as they should work and limit the light to go through.
I've seen recnetly some screen with antiglare like an asus notebook with a 14' screen called wide color shine. These screen certainly have antiglare but I don't think by comparison that the lilli as one.
Conclusion: removing the polarising filters is too dangerous for a goofy like me. I'll Never do it on a working screen
then as the back of the reflector is 20mm from the front and the 250w mh bulb is 24mm large . So the arc is at 20+12+1= 33mm instead of 32.6mm . So i cannot to better with that one.
About the antiglare and lilli, i tried to remove the polariser. Well let me tell you that I don't think I'll do this on a nice 15' lcd or other.
The polariser stick very well to the lcd. As mine was broken, it just broke a little bit more.🙂
removing the polariser and put together the polariser show clearly why the lilly lcd is so dark . Polarisers works as they should work and limit the light to go through.
I've seen recnetly some screen with antiglare like an asus notebook with a 14' screen called wide color shine. These screen certainly have antiglare but I don't think by comparison that the lilli as one.
Conclusion: removing the polarising filters is too dangerous for a goofy like me. I'll Never do it on a working screen
well, the goal was not to remove the polarizer but the ANTIGLARE after the polarizer 😀.
I told you i was not sure about the lilli having the antiglare... It could be there is no antiglare so no improvement posible.
the 20+12+"1" what is it? the security gap bettween lamp and reflector? well, 33 to 32,6 no problem i belive 😀.
so 16% increase with reflector to no reflector... interesting...
I told you i was not sure about the lilli having the antiglare... It could be there is no antiglare so no improvement posible.
the 20+12+"1" what is it? the security gap bettween lamp and reflector? well, 33 to 32,6 no problem i belive 😀.
so 16% increase with reflector to no reflector... interesting...
oops: R/2 is correct
Right you are Rox. Well, that will certainly not be the last mistake I ever make! 😀
Right you are Rox. Well, that will certainly not be the last mistake I ever make! 😀
this is like when the student tell's his teacher about a mistake... the teacher sometimes gets very offended... It is not your case thanks god 😀
question authority!
Any time you stop thinking critically, and just accept what some authority says as TRUTH, then you are doomed to keep repeating the same mistakes over and over again.
Scientific progress requires doubt: Without it, there would never be any refinement of our understanding about how things work.
Any time you stop thinking critically, and just accept what some authority says as TRUTH, then you are doomed to keep repeating the same mistakes over and over again.
Scientific progress requires doubt: Without it, there would never be any refinement of our understanding about how things work.
20 is the distance from the bottom of the reflector to the side, 12 is half the 250w metal halide diameter and 1mm for security yes.
well i assume that 15% is not good. it should be more.
About the antiglare i understand the point but i cannot differentiate the polariser from one side to the other one ... so to remove the antiglare??? only solution remove the polariser and put a new one.
but this is too difficult to remove safely the polariser unless you can get lcd for 10$🙂
the removed polarizer would show you if it is antiglare included or not. If you see trhow the polarizer, do you see difused or not?
Ill try to post some pictures to show you how would you see, ut i can´t right now...
Ill try to post some pictures to show you how would you see, ut i can´t right now...
An externally hosted image should be here but it was not working when we last tested it.
look at the difuser sheet (like the antiglare) the square has been threated not to be difuse. Do you think the piece you removed is difusing like this sheet? or you can see throw it "clearly" ?
ok , in a first row i do not see any difference between the front and the back polariser.
i'll do some more test later
i'll do some more test later
there is an antiglare on the lilli
well after the soaking overnight in water of the lilli lcd , I removed the antiglare very easily.
I just remind you that i did this on a dead lilli so i cannot check the efficiency on the projection but the lcd is clearly clearer.
I'll try to do some luxmeter mesurement to see how much is the gain
well after the soaking overnight in water of the lilli lcd , I removed the antiglare very easily.
I just remind you that i did this on a dead lilli so i cannot check the efficiency on the projection but the lcd is clearly clearer.
I'll try to do some luxmeter mesurement to see how much is the gain
ok luxmeter measurements
antiglare absortion 5%
tranmissivity of lilli with antiglare 5%
tranmissivity without antiglare 10%
well seems a good way to double our lumen output
antiglare absortion 5%
tranmissivity of lilli with antiglare 5%
tranmissivity without antiglare 10%
well seems a good way to double our lumen output
yes indeed it increase the brightness.
So i removed the antiglare from my functionnal lilli and got a huge increase in lumen output.
with antiglare 80 lumens
without 147 lumens
So I have almost 100lux on a 1.6m base image. The color are very nice now and the contrast look better (i'll do some measurements soon).
So ROx thanks to attract my attention to this antiglare problem. It's easy to peel off from the lilli with some water.
Now I did some measurements with and without pre-condensor lens and it seems to me that with a precondensor lens , the arc image is closer than without???
Does the precondensor affects in some way the place were the ligh ray cross after the second fresnel???
So i removed the antiglare from my functionnal lilli and got a huge increase in lumen output.
with antiglare 80 lumens
without 147 lumens
So I have almost 100lux on a 1.6m base image. The color are very nice now and the contrast look better (i'll do some measurements soon).
So ROx thanks to attract my attention to this antiglare problem. It's easy to peel off from the lilli with some water.
Now I did some measurements with and without pre-condensor lens and it seems to me that with a precondensor lens , the arc image is closer than without???
Does the precondensor affects in some way the place were the ligh ray cross after the second fresnel???
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