Hi,
I have searched this forum for any recent comments on this subject, but I couldn't find much. Sorry if I overlooked some.
Here is my idea:
Using 8mm WIDE ANGLE 40° 70kmcd White LEDs(sold on ebay)
and
from http://www.3dlens.com/shop/fresnellens.php
to make the lights source of a lcd projector.
I thought getting 3 such fresnel-lenses, cutting the larger fresnel of, keeping the small ones. Then combining them to a plate of 7x10 little fresnels, about 35x35mm each. That would match my 17" screen pretty well.
Behind each little fresnel, I would place a group of 4 of the mentioned leds(for higher luminance, reducing danger of failure and widening the angle a little: as the focal point of the fresnels is 40mm). Each little fresnel should collimate(condense) the produced light from the group of leds.
If " ( 1 - cos(beam_width/2)) * 2pi * cd = lumens " is the correct formula for converting cd to lumens(which I found on this forum). Then each led would produce ~103 lumen.
Now using 7*10*4 leds, that would make ~29k lumen. Which is extremely high. So if my calculations are incorrect, and it only produces 1 tenth of this, it still is a very nice luminance.(If the calculations are correct, a group of 3 leds could be used, or using the leds on a lower voltage, for even less power consumption)
Advantages:
-Low costs: these leds aren't very expensive($7 for 100), 1fresnel plate = $2
-Low power consumption: each led uses 0.1W, even with 300leds, that would still only use 30W
-Less spacy: the leds are placed 4cm from the fresnels
-Less heat production: no more trouble cooling the light bulb, saving even more money
I'm fairly new to building projectors, so my view may be very idealistic . Please correct my starter errors, and give me some advice on the feasibility of this idea.
PS: the rest of the projector would use traditional optics(large fresnel to collect the light to a triplet lens...)
I have searched this forum for any recent comments on this subject, but I couldn't find much. Sorry if I overlooked some.
Here is my idea:
Using 8mm WIDE ANGLE 40° 70kmcd White LEDs(sold on ebay)
and
An externally hosted image should be here but it was not working when we last tested it.
from http://www.3dlens.com/shop/fresnellens.php
to make the lights source of a lcd projector.
I thought getting 3 such fresnel-lenses, cutting the larger fresnel of, keeping the small ones. Then combining them to a plate of 7x10 little fresnels, about 35x35mm each. That would match my 17" screen pretty well.
Behind each little fresnel, I would place a group of 4 of the mentioned leds(for higher luminance, reducing danger of failure and widening the angle a little: as the focal point of the fresnels is 40mm). Each little fresnel should collimate(condense) the produced light from the group of leds.
If " ( 1 - cos(beam_width/2)) * 2pi * cd = lumens " is the correct formula for converting cd to lumens(which I found on this forum). Then each led would produce ~103 lumen.
Now using 7*10*4 leds, that would make ~29k lumen. Which is extremely high. So if my calculations are incorrect, and it only produces 1 tenth of this, it still is a very nice luminance.(If the calculations are correct, a group of 3 leds could be used, or using the leds on a lower voltage, for even less power consumption)
Advantages:
-Low costs: these leds aren't very expensive($7 for 100), 1fresnel plate = $2
-Low power consumption: each led uses 0.1W, even with 300leds, that would still only use 30W
-Less spacy: the leds are placed 4cm from the fresnels
-Less heat production: no more trouble cooling the light bulb, saving even more money
I'm fairly new to building projectors, so my view may be very idealistic . Please correct my starter errors, and give me some advice on the feasibility of this idea.
PS: the rest of the projector would use traditional optics(large fresnel to collect the light to a triplet lens...)
sounds like you are planning to have multiple light sources spread out over the surface of the 17" panel. will the light be spread even across the panel? will you need to use a diffuser sheet of some sort? I may be old school but I build mine with a 400w MH bulb and a good cooling system. I have a nice bright 120" diag image at 12 feet with a 17" panel in it. what triplet and field fresnel combo are you using? what size screen do you plan to have when you are up and running?
candela -> lumen
My calculations were indeed wrong, shouldn't have been 103 lumen, but 26.5 lumen instead. Which makes ~7500 lumen, still very nice for a projector.
I found this little conversion tool:
http://led.linear1.org/lumen.wiz
which uses the formula I quoted above.
As a reply to TESCORP, I've got a 17" packard bell panel
panel-specs
-nice resolution of 1280x1024
-only 30ms response time 🙁
But it will have to do for now.
As fresnel and triplet lens, I haven't decided yet. Was planning to do some research including on this forum to figure that out. If anyone could suggest something, that would certainly be welcome 🙂.
My calculations were indeed wrong, shouldn't have been 103 lumen, but 26.5 lumen instead. Which makes ~7500 lumen, still very nice for a projector.
I found this little conversion tool:
http://led.linear1.org/lumen.wiz
which uses the formula I quoted above.
As a reply to TESCORP, I've got a 17" packard bell panel
panel-specs
-nice resolution of 1280x1024
-only 30ms response time 🙁
But it will have to do for now.
As fresnel and triplet lens, I haven't decided yet. Was planning to do some research including on this forum to figure that out. If anyone could suggest something, that would certainly be welcome 🙂.
you could use a 330mm FL triplet and a 330mm FL field fresnel but you may have dim corners, theres the bessler opaque lens, with a 550mm fresnel, and theres a 500mm FL triplet lens and 550mm field fresnel.
The 330 triplet is going to give you a 133" diag image at 12 feet,
The 500 triplet will give you a 120" diag image at the same distance.
the 330 will use a smaller enclosure compared to the 500 which would need a longer enclosure to work with the longer focal length of the optics.
I am using a vertical folded design I call the Pro-V. it has a 500mm triplet, F.S. mirror, 550mm field fresnel, 17" samsung panel and main board, 220mm collimator fresnel, lexan for the heat shield, 400W MH bulb and ballast.
hope this info helps!!
The 330 triplet is going to give you a 133" diag image at 12 feet,
The 500 triplet will give you a 120" diag image at the same distance.
the 330 will use a smaller enclosure compared to the 500 which would need a longer enclosure to work with the longer focal length of the optics.
I am using a vertical folded design I call the Pro-V. it has a 500mm triplet, F.S. mirror, 550mm field fresnel, 17" samsung panel and main board, 220mm collimator fresnel, lexan for the heat shield, 400W MH bulb and ballast.
hope this info helps!!
FRESNEL LENS 13" FL, 12.5" X 9.8"
This looks like a good fresnel, it covers my 17" panel almost completely.And the 330mm focal length is very common.
Next... the lens... would I be able to find a decent one for under $30??
I'm quite low on budget...
This looks like a good fresnel, it covers my 17" panel almost completely.And the 330mm focal length is very common.
Next... the lens... would I be able to find a decent one for under $30??
I'm quite low on budget...
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