Thanks for the info on pulsing, I'm guessing if you used a 555 that you had a 50% duty cycle and therefore the perceived brightness was about 1.5x brighter?
I have seen research in the past that suggests that LED's can take up to a couple of amps so long as the duty cycle is small enough giving an even bigger increase in perceived brightness. I wouldn't suggest anybody takes it this far unless they really know what they're doing (or are prepared to kill a lot of LED's).
The problem here is that nobody has yet posted how white LEDs respond to being pulsed, sure the efficiency will drop, but my main concern is the colour - if they go more towards blue then it's no use to us.
Steve
I have seen research in the past that suggests that LED's can take up to a couple of amps so long as the duty cycle is small enough giving an even bigger increase in perceived brightness. I wouldn't suggest anybody takes it this far unless they really know what they're doing (or are prepared to kill a lot of LED's).
The problem here is that nobody has yet posted how white LEDs respond to being pulsed, sure the efficiency will drop, but my main concern is the colour - if they go more towards blue then it's no use to us.
Steve
Yes there absolutely will be a color shift with changes in the current through the LED. While the output of the blue will be somewhat linear over large currents, the phosphor output has a faster roll-off as the blue output increases. You can see this in good white LED data sheets.
There is another issue to be wary of. While there is the general conception that as long as you keep the average current at the rated current of the LED, you will not impact the life. This is not really true. The life of an LED is greatly impacted by the temperature of the die. The hotter the die gets, the quicker it degrades. The current rating for an LED is a factor of current density in the LED, but also a factor of the ability to get the heat out of the LED. 5mm LEDS are really bad at this. Keeping to the current rating will in general ensure the steady state temperature of the die will stay below some value where the manufacturer can guarentee the life of the LED. However, when you pulse that LED at currents significantly above the rated current of the device, you will instantaneously heat the die well above its designed operating temperature and could severely reduce the life of the LED. In most pulsed applications, i.e. a TV remote control, this is not a factor as the total on time is small. However, for a lighting application, you need to consider this.
Alvaius
There is another issue to be wary of. While there is the general conception that as long as you keep the average current at the rated current of the LED, you will not impact the life. This is not really true. The life of an LED is greatly impacted by the temperature of the die. The hotter the die gets, the quicker it degrades. The current rating for an LED is a factor of current density in the LED, but also a factor of the ability to get the heat out of the LED. 5mm LEDS are really bad at this. Keeping to the current rating will in general ensure the steady state temperature of the die will stay below some value where the manufacturer can guarentee the life of the LED. However, when you pulse that LED at currents significantly above the rated current of the device, you will instantaneously heat the die well above its designed operating temperature and could severely reduce the life of the LED. In most pulsed applications, i.e. a TV remote control, this is not a factor as the total on time is small. However, for a lighting application, you need to consider this.
Alvaius
I didn't experience any color shift although I was using a red/orange LED. If there puched too hard they generally turn an yellow/orange color.
The duty cycle I used was less than 1%. Even if pulsing wasn't used to get a greater brightness, it could be used to reduce the heat ouput of a cluster. Even at 50% duty cycle at thier rated current, you wouldn't be able to tell the difference. That, I'm sure, would increase the life of the LED's.
I'm keen to get a 5W luxeon and try this except there $50 AUD each...
A little expensive if I manage to kill it. I might start with a luxeon 1W first. Since the die is coupled to the package with thermal conductivity in mind I think I should be able to push it quite far without discolouring.
Well guys i tried my light guide idea the otherday and ive got news. LED's will work!! and dont think you need a billion lumens because you dont, not atleast with "my" light guide idea.
You also dont need a bunch of leds to see if you have enough light to project, you only need one led and one guide. Each led and guide will light up a square area on the lcd, and all you have to do to see if you have anough light is to run this behind the lcd and project it. One thing i noticed was the fact that for some reason more light from leds with this idea passes through the lcd then a metal halide light, why? not sure but i think ive got it figured.
With a simple test of my guide, i used a single super bright 8000mcd blue led, and this projuced enough light to project an image of its given area quite brightly at a screen size of 100inches, (with the light going through all optics and the lcd). I predict with a 3w lexan led we could quite easily make an image brighter then what we could do with a 150w mh! quite easily.
How the guide is made and what we need to do im keeping a mystery, until atleast i have enough money and time to make a fully working prototype projector, but then again, it might be worth me paitenting it 😀 .
Trev🙂
You also dont need a bunch of leds to see if you have enough light to project, you only need one led and one guide. Each led and guide will light up a square area on the lcd, and all you have to do to see if you have anough light is to run this behind the lcd and project it. One thing i noticed was the fact that for some reason more light from leds with this idea passes through the lcd then a metal halide light, why? not sure but i think ive got it figured.
With a simple test of my guide, i used a single super bright 8000mcd blue led, and this projuced enough light to project an image of its given area quite brightly at a screen size of 100inches, (with the light going through all optics and the lcd). I predict with a 3w lexan led we could quite easily make an image brighter then what we could do with a 150w mh! quite easily.
How the guide is made and what we need to do im keeping a mystery, until atleast i have enough money and time to make a fully working prototype projector, but then again, it might be worth me paitenting it 😀 .
Trev🙂
Keep in mind that to make up what is perceived as white light, you need a lot more red and especially green than blue.
I can tell you for a fact that you will need a lot more than a single 3W LED. I have seen what 60W of Luxeon white into a display with about 50% optical efficiency before the panel looks like. Yes it is bright, but not commercial projector bright. You could get better transfer by pumping the same amount of energy out of RGB though.
It is really simple physics. A LED panel, by the very nature of its construction, can only allow so much light to pass through, and it is not very much. The best LEDS put out on the order of 30 lumens/watt (averaged across all colors). If you have start of the art panels and are transmitting 12% of the light, and you want 500 lumens out of your projector, you need about 4200 lumens going into the panel or about 140watts of LED going in. With properly tuned filters (i.e. custom), you could probably get that transfer up, but even if you hit 20%, you are still talking about 85watts of LED.
There is no way around this. I am not trying to rain on anyones parade, but you can't avoid the basic math of the problem.
Alvaius
I can tell you for a fact that you will need a lot more than a single 3W LED. I have seen what 60W of Luxeon white into a display with about 50% optical efficiency before the panel looks like. Yes it is bright, but not commercial projector bright. You could get better transfer by pumping the same amount of energy out of RGB though.
It is really simple physics. A LED panel, by the very nature of its construction, can only allow so much light to pass through, and it is not very much. The best LEDS put out on the order of 30 lumens/watt (averaged across all colors). If you have start of the art panels and are transmitting 12% of the light, and you want 500 lumens out of your projector, you need about 4200 lumens going into the panel or about 140watts of LED going in. With properly tuned filters (i.e. custom), you could probably get that transfer up, but even if you hit 20%, you are still talking about 85watts of LED.
There is no way around this. I am not trying to rain on anyones parade, but you can't avoid the basic math of the problem.
Alvaius
alvaius said:
Who said anything about 1 3w led? lol ill have 12.
As for the brightness, you are missing the conception on how it works, you are also missing the point on how eficient the light engine is when using guides, its an eficientcy we will never get with mh lighting due to heat and its this eficientcy gain that allows us to use leds. By using the guides ive designed and with their eficientcy properties along with their condenseing properties its has allowed me to be able to project quite easily with a minimum of leds. It adds up, the closer the light source is to the medium the brighter the light is, the more condensed the light is to its medium the more light reaches its target, the less surfaces the light has to go through the less reflections occur. Now see how ineficient the old mh system is with the light being at its focal point with all of the inaficientcys noted above, and you can soon see that the lack of light projuced from a led becomes enough.
The guide i made is that eficient, when i place a peice of paper over the guide there is next to no light loss, sure it wont light up the room with the paper being there as the paper is difusing it but its still blinding bright, without the paper the whole room lights up, this is only with a 8000mcd led, wait until i get a 80lm led. And as i stated earlier i tried this one led in my projector, and i was able to project the led on the wall at a screen size of 100inches with minimal loss of light compared to the led being out of the system. With those comparisons the led in the projector was about half of what it was out of the projector projected at the same size and distance with a projection lens, dont be fooled, it was bright, try to get that amount of eficientcy with a mh setup, you wont, cos you cant, the light engine eficientcy just isnt there.
Trev🙂
There is a big difference between perceived brightness and measured brightness. If you say it looked half as bright, given your eye is logarithmic in response, that could have been 1/4 as bright. Add in your eyes changing sensitivity as the light level changes.
I will also assume that you were in a darkened room? The scotoptic (dark) response of the eye is much different from the photoptic(bright) response. You are much more sensitive to blue in a dark room, making it seem perceptably even brighter.
Distance from the source to the LCD makes little difference, as long as the light is collected and projected on the surface without leakage outside the LCD. I.e. if you have 500 lumens and you project it from 5 " or 50", it does not matter as long as that 500 lumens falls completely on the LCD (assuming it covers the same area as the LCD). inverse square law does not apply in this case.
No matter what you did for a guide, you still have the polarizers on the LCD, the color filters, coatings, the glass itself, the crystal, etc. that are all going to block light. No matter how you build your guide, you can only get percentage X through the display, and that percentage is <20%.
I know you probably don't believe me, so I suggest you go get a light meter. However, don't do the test with a red, blue, or white LED. Most of the cheap meters are not accurate with these. Stick to a green LED.
Alvaius
I will also assume that you were in a darkened room? The scotoptic (dark) response of the eye is much different from the photoptic(bright) response. You are much more sensitive to blue in a dark room, making it seem perceptably even brighter.
Distance from the source to the LCD makes little difference, as long as the light is collected and projected on the surface without leakage outside the LCD. I.e. if you have 500 lumens and you project it from 5 " or 50", it does not matter as long as that 500 lumens falls completely on the LCD (assuming it covers the same area as the LCD). inverse square law does not apply in this case.
No matter what you did for a guide, you still have the polarizers on the LCD, the color filters, coatings, the glass itself, the crystal, etc. that are all going to block light. No matter how you build your guide, you can only get percentage X through the display, and that percentage is <20%.
I know you probably don't believe me, so I suggest you go get a light meter. However, don't do the test with a red, blue, or white LED. Most of the cheap meters are not accurate with these. Stick to a green LED.
Alvaius
Well at the end of the day i dont care about any light meter as all i realy care about is the fact that the image when im done will be fine for me. What your eyes see is what matters, not what the light metter sees. I simply stated leds will work, just that, try it out yourself with hands on experience in a real world environment and you will clearly see for yourself that they do work. If this concept could be done with mh lamps, sure id use it, but it cant due to heat issues and cost.
Thats right, but reflection does and thats one of our biggest losses and thats where the light guide wins over any system without one. Particles in the air also play a role, ill give u an idea on losses. Just 2 days ago i did a test on 3 projection lenses, all had the same ar coating and all had a differnt focal length matched to the top frensel, all also had the same f number. The first projected an image of 100inches at a distance of 4.2m, the image was very bright, the second lens projected the image of 100inches at 5m, the image was dimmer, the last lens projected a 100inch image at 5.6m, guess wich one was the brightest? the first. Inverse law didnt apply here either but in a real world environment even though these lenses had the same ar coatings and f numbers and the only difference was the focal point the first wins. I also did that test having the projector in the same spot so the throw was at the same distance in all the 3 tests, what happend then was the longer the focal on the lenses the smaller the image became, now i bet your saying ok the smaller image was brighter, wrong it wasnt, they wer all the same, and i have good eyes fyi. Distance does make a difference in a real world environment, sometimes science cant explain. I agree one what your trying to say, but ive seen for myself the difference isnt so small as science says it is.
I used to be like you in thinking that leds will never work with their lack of light output and acociated problems, but since ive cracked the nut shell and worked out a way to make them work, ive soon seen for myself they will work, and far better then expected.
Trev🙂
Thats right, but reflection does and thats one of our biggest losses and thats where the light guide wins over any system without one. Particles in the air also play a role, ill give u an idea on losses. Just 2 days ago i did a test on 3 projection lenses, all had the same ar coating and all had a differnt focal length matched to the top frensel, all also had the same f number. The first projected an image of 100inches at a distance of 4.2m, the image was very bright, the second lens projected the image of 100inches at 5m, the image was dimmer, the last lens projected a 100inch image at 5.6m, guess wich one was the brightest? the first. Inverse law didnt apply here either but in a real world environment even though these lenses had the same ar coatings and f numbers and the only difference was the focal point the first wins. I also did that test having the projector in the same spot so the throw was at the same distance in all the 3 tests, what happend then was the longer the focal on the lenses the smaller the image became, now i bet your saying ok the smaller image was brighter, wrong it wasnt, they wer all the same, and i have good eyes fyi. Distance does make a difference in a real world environment, sometimes science cant explain. I agree one what your trying to say, but ive seen for myself the difference isnt so small as science says it is.
I used to be like you in thinking that leds will never work with their lack of light output and acociated problems, but since ive cracked the nut shell and worked out a way to make them work, ive soon seen for myself they will work, and far better then expected.
Trev🙂
eyes versus meters
Human eyes are like a camera with auto-iris: You can't tell if one image is brighter than another, unless you can look at both at once, side-by-side.
On the other hand, we can all make our own "relative brightness" meters for very little money. All you need is a small silicon PV cell connected to a multimeter that can measure currents less than 1 Amp. Put the PV cell at the end of a short paper tube (hint: look in the bathroom). Point the tube at a white image on your screen and read the current off the meter. (Make sure you have the tube perpendicular to the screen.) This gives you a reference value to write down. Then you can take your time to make a change in projector position, lenses, reflectors, etc. When you have it all together, measure it again.
Just for fun, decide if it is brighter or dimmer than the reference reading BEFORE you actually measure it the second time. Don't be surprised if your eyes deceive you!
Human eyes are like a camera with auto-iris: You can't tell if one image is brighter than another, unless you can look at both at once, side-by-side.
On the other hand, we can all make our own "relative brightness" meters for very little money. All you need is a small silicon PV cell connected to a multimeter that can measure currents less than 1 Amp. Put the PV cell at the end of a short paper tube (hint: look in the bathroom). Point the tube at a white image on your screen and read the current off the meter. (Make sure you have the tube perpendicular to the screen.) This gives you a reference value to write down. Then you can take your time to make a change in projector position, lenses, reflectors, etc. When you have it all together, measure it again.
Just for fun, decide if it is brighter or dimmer than the reference reading BEFORE you actually measure it the second time. Don't be surprised if your eyes deceive you!
LEDs
Nice things about LEDs:
1. They have narrow illumination cones, so the light is mostly going in a useful direction.
2. They are narrow band, so they don't make a lot of bad UV or near IR.
3. The very long wavelength IR radiated by the heatsink can be kept away from the LCD with a single pane of low-E glass.
Bad things:
1: One quarter the efficiency of MH bulbs. The makers of one of the superbright arrays says it takes >800 Watts of their LEDs to get the same amount of light as a 150-200 Watt MH bulb.
2: Still hundreds of times more expensive per lumen than MH.
3: They die if they get too hot, and low efficiency means a lot of heat. So you will need a lot of air flow over a big heatsink, or maybe water cooling.
Nice things about LEDs:
1. They have narrow illumination cones, so the light is mostly going in a useful direction.
2. They are narrow band, so they don't make a lot of bad UV or near IR.
3. The very long wavelength IR radiated by the heatsink can be kept away from the LCD with a single pane of low-E glass.
Bad things:
1: One quarter the efficiency of MH bulbs. The makers of one of the superbright arrays says it takes >800 Watts of their LEDs to get the same amount of light as a 150-200 Watt MH bulb.
2: Still hundreds of times more expensive per lumen than MH.
3: They die if they get too hot, and low efficiency means a lot of heat. So you will need a lot of air flow over a big heatsink, or maybe water cooling.
Thank you Guy for re-inforcing what I was trying to say.
Some thought for Ace:
- transmission losses through air for the distances we are talking about is insignificant
- I wonder if when you did your tests with the various focal length, you were truly collecting all the light from your source. I expect that you were not. On the F/number, unlike imaging optics, this is not as much of a factor in terms of light output. However, that assumes you are collecting all the light in the optic system.
- Whether you believe what science can measure or not, the reality is, there is a high correlation between the theory and the reality of the implementation.
- I am not "one of those people who says LED's won't work". I am one of those people with the knowledge of optics, LEDS, projection systems, and the corresponding experience to know their real limitations. I would love to see LED based projectors as I have a little bit of a vested personal interest in seeing them work. I will never discourage experimentation and DIY, but like other DIYers [I am one], I would like it if someone pointed out when I was likely going in the wrong direction so that I could evaluate what I am trying to accomplish, learn more about the subject, and change my direction to increase my chances of success.
- In terms of reflection losses, you are correct, you can lose a lot through an LCD. Transmissive losses through the polarizers are somewhat dominant, however they all add up. This is the real killer.
.... I do have hands on experience in real world environments
Some thought for Ace:
- transmission losses through air for the distances we are talking about is insignificant
- I wonder if when you did your tests with the various focal length, you were truly collecting all the light from your source. I expect that you were not. On the F/number, unlike imaging optics, this is not as much of a factor in terms of light output. However, that assumes you are collecting all the light in the optic system.
- Whether you believe what science can measure or not, the reality is, there is a high correlation between the theory and the reality of the implementation.
- I am not "one of those people who says LED's won't work". I am one of those people with the knowledge of optics, LEDS, projection systems, and the corresponding experience to know their real limitations. I would love to see LED based projectors as I have a little bit of a vested personal interest in seeing them work. I will never discourage experimentation and DIY, but like other DIYers [I am one], I would like it if someone pointed out when I was likely going in the wrong direction so that I could evaluate what I am trying to accomplish, learn more about the subject, and change my direction to increase my chances of success.
- In terms of reflection losses, you are correct, you can lose a lot through an LCD. Transmissive losses through the polarizers are somewhat dominant, however they all add up. This is the real killer.
.... I do have hands on experience in real world environments
Well you know, i tried my idea, it worked, it works so well im amazed myself, i shared my thoughts and findings on the matter and all i get is nothing but picky little negative vibes basically saying that what i do is wrong and what i find in my findings is a lie. ( btw, when i did the 3 lens tests i changed the frensels to acomodate the 3 lenses focals, im not stupid nor 12).
To be honest im quite sick of this crap going on, i was here to help you guys out and to atleast give a few some inspirations on making the dream of leds as a projector light source come true. It works, i know how to get them going and right now its not my problem if you cant.
Trev🙂
To be honest im quite sick of this crap going on, i was here to help you guys out and to atleast give a few some inspirations on making the dream of leds as a projector light source come true. It works, i know how to get them going and right now its not my problem if you cant.
Trev🙂
How science works
People perform experiments using objective measurements. When they find something interesting, they publish their findings in a complete description so that it can be repeated by other investigators. Then those other investigators replicate the originator's findings, and publish that fact.
People who refuse to perform objective measurements, keep parts of their experiment secret, and then express irritation when others question them, don't have much credibility.
Science works by peer review. (On the other hand, industry is all about trade secrets.) This type of forum is perfect for the amateur scientist to publish, and get peer review and verification. Or it can be used to troll, tease, bully, and generally entertain...
So Trev, if you are going to tell us how wonderful dichroic spherical reflectors are, please also tell us where we can get one so we can replicate your results. If you are going to tell us how great your LED illumination experiment works, please explain what your setup does and why it works. And most of all: Don't take it personally when you get peer review that doesn't agree with your ideas. The back and force exchange of ideas is the most valuable part of this forum.
People perform experiments using objective measurements. When they find something interesting, they publish their findings in a complete description so that it can be repeated by other investigators. Then those other investigators replicate the originator's findings, and publish that fact.
People who refuse to perform objective measurements, keep parts of their experiment secret, and then express irritation when others question them, don't have much credibility.
Science works by peer review. (On the other hand, industry is all about trade secrets.) This type of forum is perfect for the amateur scientist to publish, and get peer review and verification. Or it can be used to troll, tease, bully, and generally entertain...
So Trev, if you are going to tell us how wonderful dichroic spherical reflectors are, please also tell us where we can get one so we can replicate your results. If you are going to tell us how great your LED illumination experiment works, please explain what your setup does and why it works. And most of all: Don't take it personally when you get peer review that doesn't agree with your ideas. The back and force exchange of ideas is the most valuable part of this forum.
Ace,
There is a big difference between calling you a lier and questioning your results. I am not telling you what you are doing is wrong, I am simply questioning whether your results are truly what you think they are (I have no doubt that you feel your results are good).
Your claim is that you have achieved a significant increase in the efficiency of passing light through an LCD panel. I question whether this is possible, given the structure of the LCD and the inherent limitations in how it is built. I think my questioning your results is valid, as you have presented no measured results for review and you have provided no details on your implementation which is not in the DIY spirit.
I have put posts on here and other DIY sites and had holes shot all into it (thank you Jocko!). I am glad that it occured, because I had made assumptions based on my knowledge and obviously there was holes in that knowledge that I was unaware of (again, thank you Jocko).
Alvaius
There is a big difference between calling you a lier and questioning your results. I am not telling you what you are doing is wrong, I am simply questioning whether your results are truly what you think they are (I have no doubt that you feel your results are good).
Your claim is that you have achieved a significant increase in the efficiency of passing light through an LCD panel. I question whether this is possible, given the structure of the LCD and the inherent limitations in how it is built. I think my questioning your results is valid, as you have presented no measured results for review and you have provided no details on your implementation which is not in the DIY spirit.
I have put posts on here and other DIY sites and had holes shot all into it (thank you Jocko!). I am glad that it occured, because I had made assumptions based on my knowledge and obviously there was holes in that knowledge that I was unaware of (again, thank you Jocko).
Alvaius
Thought I should add my views as I've been watching quitely while the debate has been heating up.
1) I have every belief that LED's can work, and MORE efficiently than MH, a) there cone ouput is much easier to guide and so the light loss from a MH in the form of wasted light / badly reflected light shouldn't happen with so much with LED's, b) I know I keep going on about pulsing but I think it is another way forward - especially as the human eye percieves this to be much more than the average output.
2) ace3000_1, please don't get discouraged, there are plenty of people here patient enough to wait for you to publish your findings. As has already been said though, you have to expect some scepticism in the mean time!
Steve
1) I have every belief that LED's can work, and MORE efficiently than MH, a) there cone ouput is much easier to guide and so the light loss from a MH in the form of wasted light / badly reflected light shouldn't happen with so much with LED's, b) I know I keep going on about pulsing but I think it is another way forward - especially as the human eye percieves this to be much more than the average output.
2) ace3000_1, please don't get discouraged, there are plenty of people here patient enough to wait for you to publish your findings. As has already been said though, you have to expect some scepticism in the mean time!
Steve
contrast 40 000:1
Hello!!!
For those of you who don't think that LED's as a backlight for an LCD will work, I just have to say "sorry" because it will......and actually it has allready bin made by a company called Sunnybrook. It is an LCD display that uses a cluster of ultra bright LED's as a backlight and produces a contrast ratio of 40 000:1.. Believ it or not!!!
Here is som links:
www.sunnybrooktech.com
http://gizmag.com/go/3414/
Acording to the bright LED's and high contrast ratio wouldn't it be perfect to just use it for a projector by simply adding the Fressnel and the tripplet lenses......What do you think??? I think it sounds great......
Hello!!!
For those of you who don't think that LED's as a backlight for an LCD will work, I just have to say "sorry" because it will......and actually it has allready bin made by a company called Sunnybrook. It is an LCD display that uses a cluster of ultra bright LED's as a backlight and produces a contrast ratio of 40 000:1.. Believ it or not!!!
Here is som links:
www.sunnybrooktech.com
http://gizmag.com/go/3414/
Acording to the bright LED's and high contrast ratio wouldn't it be perfect to just use it for a projector by simply adding the Fressnel and the tripplet lenses......What do you think??? I think it sounds great......
40000:1 LCD
Still, there's a huge difference between the brightness of an LCD monitor you view directly, and what a projector uses to make an image that is several times as large. Users look directly at that so-called high contrast LCD display. Try looking into your projector from 2 feet away!
Nobody says that LEDs can't be used to make a projector. The problems are that you would need so many LEDs that it would use 4 times as much power, generate 4 times as much heat, and cost about 100 times as much as a MH bulb projector. But it would work just fine, if you used red, green, & blue LEDs (instead of blue + yellow phosphor LEDs).
Still, there's a huge difference between the brightness of an LCD monitor you view directly, and what a projector uses to make an image that is several times as large. Users look directly at that so-called high contrast LCD display. Try looking into your projector from 2 feet away!
Nobody says that LEDs can't be used to make a projector. The problems are that you would need so many LEDs that it would use 4 times as much power, generate 4 times as much heat, and cost about 100 times as much as a MH bulb projector. But it would work just fine, if you used red, green, & blue LEDs (instead of blue + yellow phosphor LEDs).
... and if you look at the technical details of their display, it has close to 800 1 watt LEDS. Though they quote 40,000:1 contrast ratio on the front web page, in the details, they actually quote it as 40,000:1 dynamic range and explain the difference. I hate to think of how nasty matching those 800 LEDS for color temperature was.
No one has questioned whether LED for an LCD backlight will work. It is currently available from Sony in an LCD TV, and from specialty display manufacturers primarily in high-rel applications. In fact, there is application notes available on what to do:
http://www.lumileds.com/pdfs/AS14.PDF
I can even justify the cost of LED when you take into account the long life.
No one has questioned whether LED for an LCD backlight will work. It is currently available from Sony in an LCD TV, and from specialty display manufacturers primarily in high-rel applications. In fact, there is application notes available on what to do:
http://www.lumileds.com/pdfs/AS14.PDF
I can even justify the cost of LED when you take into account the long life.
800 1 watt LEDS
So they are using 800 Watts to light a direct-view LCD screen.
What if you wanted to project that to a 100" screen? You would need about 35 times that much light to get an image with the same brightness. (And that assumes a perfect screen.) So you would have to pay for 28 KWatts of electricity, not to mention buying the 28,000 LEDs, not to mention having your house burn down! (That's like running 18 space heaters, so you would also need to have 240 Amp service with 120 volt, or 120 Amp service with 240 volt power.)
But I think there is a practical way to use LEDs for projection: If some manufacturer will just make RGB arrays of LEDs in a rectangular shape with pixels from edge to edge and a suitable heatsink and I/O connector on the back. Then we would be able to assemble a bunch of these into whatever size panel we want. There would be no 80% loss through an LCD, since there would be no reason to use an LCD. The tiny LEDs would be both light source and image display. We could build a projector panel, or just build a big-screen panel, in any resolution and aspect ratio we wanted.
So they are using 800 Watts to light a direct-view LCD screen.
What if you wanted to project that to a 100" screen? You would need about 35 times that much light to get an image with the same brightness. (And that assumes a perfect screen.) So you would have to pay for 28 KWatts of electricity, not to mention buying the 28,000 LEDs, not to mention having your house burn down! (That's like running 18 space heaters, so you would also need to have 240 Amp service with 120 volt, or 120 Amp service with 240 volt power.)
But I think there is a practical way to use LEDs for projection: If some manufacturer will just make RGB arrays of LEDs in a rectangular shape with pixels from edge to edge and a suitable heatsink and I/O connector on the back. Then we would be able to assemble a bunch of these into whatever size panel we want. There would be no 80% loss through an LCD, since there would be no reason to use an LCD. The tiny LEDs would be both light source and image display. We could build a projector panel, or just build a big-screen panel, in any resolution and aspect ratio we wanted.
I didn't mean that any of you guy(s) didn't believe in the LED's as a backlight or light. I ment those others....the ones who read and just think it will not work....and I don't know hwo but I know I have read some negative posts about LED's, maby not in this thread or on this site but somewhere.....
I don't know much about the lighting thing but i am still curios about that display in a projector.
since they clame the display is 30 times brighter than a "normal" display. Wouldn't it be possible to project a screen with an area 30 times bigger and get 1/30 of the brightness witch is the same as a "normal" display?????
"GUY" isn't there a differens between looking straight into a projector and comparing it to looking straight on that LCD, since the projector allreddy have all the light "compressed" by the lenses. And if you have a display that's 30 times brighter than a normal display and put a fresnel and a triplet infront of it....atleast I wouln't want to stare into it from 2 feets away...
these are just some thoughts i have....they are probably wrong but I am just curios about them.....and what you think😕
I don't know much about the lighting thing but i am still curios about that display in a projector.
since they clame the display is 30 times brighter than a "normal" display. Wouldn't it be possible to project a screen with an area 30 times bigger and get 1/30 of the brightness witch is the same as a "normal" display?????
"GUY" isn't there a differens between looking straight into a projector and comparing it to looking straight on that LCD, since the projector allreddy have all the light "compressed" by the lenses. And if you have a display that's 30 times brighter than a normal display and put a fresnel and a triplet infront of it....atleast I wouln't want to stare into it from 2 feets away...
these are just some thoughts i have....they are probably wrong but I am just curios about them.....and what you think😕
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