Yes you could get an image 30 times bigger at 1/30th the brightness minus some optical losses. However, I think there are some practical issues, namely the matching of 800 LEDS such that the color of the backlight for each area is the same. You are likely better off with either a light pipe for mixing, or for the pusposes of what we are talking about here..you just need to put the LEDS a ways behind the display so that several of them mix.
Alvaius
Alvaius
30 times brighter?
I assumed that their "30 times brighter" claim was just some more marketing hype. If it really puts out 30 times as much light as a standard LCD monitor, wouldn't it be painful to look at? I think they meant that the added contrast makes it look subjectively "brighter". Otherwise, why would they start with an 800 Watt backlight? Why not just make it standard brightness with a 27 Watt backlight. They have to control each of those LEDs individually: 800 1 Amp MOSFETs would be pretty expensive, just to make it arbitrarily 30 times brighter. I think they needed all of that light, just to get a nice looking direct-view display. All the LED backlit LCDs I have seen are very small or very dim. That's why all commercial LCD monitors use CCFL lamps.
On the other hand, if it really does put out 30 times as many lumens as a standard LCD monitor, then you are right: You should be able to project their monitor up to a a size about 5 times as large. (Don't forget, the light gets spread over an area, so it goes down by the square.) I can't tell how large their LCD is. If it is 15", then that gets you a 75" image.
As for my comment about looking into a projector, I meant from the screen. I think it will still be much brighter than looking at a normal LCD. And by the way, my real name is just Guy, pronounced in the English manner, not the French. 😀
I assumed that their "30 times brighter" claim was just some more marketing hype. If it really puts out 30 times as much light as a standard LCD monitor, wouldn't it be painful to look at? I think they meant that the added contrast makes it look subjectively "brighter". Otherwise, why would they start with an 800 Watt backlight? Why not just make it standard brightness with a 27 Watt backlight. They have to control each of those LEDs individually: 800 1 Amp MOSFETs would be pretty expensive, just to make it arbitrarily 30 times brighter. I think they needed all of that light, just to get a nice looking direct-view display. All the LED backlit LCDs I have seen are very small or very dim. That's why all commercial LCD monitors use CCFL lamps.
On the other hand, if it really does put out 30 times as many lumens as a standard LCD monitor, then you are right: You should be able to project their monitor up to a a size about 5 times as large. (Don't forget, the light gets spread over an area, so it goes down by the square.) I can't tell how large their LCD is. If it is 15", then that gets you a 75" image.
As for my comment about looking into a projector, I meant from the screen. I think it will still be much brighter than looking at a normal LCD. And by the way, my real name is just Guy, pronounced in the English manner, not the French. 😀
Guy, you have probably never looked at a Luxeon backlight display. You are able to achieve high brightness with a reasonably amount of power. Efficiency is on the order of CCFL backlights. Sony has a TV and Mitsubishi has some monitor products using CCFL.
Reading the tech background on this display, they strobe the LEDs in order to improve the overall dynamic range. Essentially a sub-image on the LEDS at lower resolution. They probably need really bright LEDS to make this work. However, they could no doubt turn them all on and make it really bright, however, you would need one heck of a system to take out the heat. You are looking at dissipating 675W of heat if they were all on.
Alvaius
Reading the tech background on this display, they strobe the LEDs in order to improve the overall dynamic range. Essentially a sub-image on the LEDS at lower resolution. They probably need really bright LEDS to make this work. However, they could no doubt turn them all on and make it really bright, however, you would need one heck of a system to take out the heat. You are looking at dissipating 675W of heat if they were all on.
Alvaius
strobing the LEDs
I'd bet you money they "strobe" the LEDs using a PWM scheme, so they can use just one MOSFET switch running in saturation mode per LED. If they wanted to run them with variable current, it would take a latching DAC or a sample-and-hold circuit, plus a much heftier transistor per LED.
I think many small LCD modules have LED backlights. I have some that do. Bigger LCDs are backlit with CCFLs. (For example, 100% of the LCD computer monitors and TVs larger than 6".) Why is that? Why do manufacturers use LEDs for small displays and CCFLs for larger ones?
MONEY: A few LEDs can back-light a small display well enough to read it in a dark room, and the cost is minimal. But for a larger display, the expense of a CCFL and inverter circuitry is still less than the cost of all the LEDs required.
I have read technical info on some of the very high intensity LED arrays. I also looked at the price!!!!! Thousands of dollars for the light output of a 250 Watt MH bulb. The difference is that the LED array has seperately controlled red, green, and blue emitters so it can be used as a universal spotlight for stage lighting. They also must be cooled so they don't exceed 140 degrees C. Above that they only emit IR (as they melt).
I am sure you can build a projector with an LED light source. It will just cost much more than one with a MH lamp, it won't be as bright, it will use more power, and you will need more fan cooling.
But there are more competitive alternatives: What about an array of CCFLs or even standard fluorescent tubes right against the back of the LCD?
I'd bet you money they "strobe" the LEDs using a PWM scheme, so they can use just one MOSFET switch running in saturation mode per LED. If they wanted to run them with variable current, it would take a latching DAC or a sample-and-hold circuit, plus a much heftier transistor per LED.
I think many small LCD modules have LED backlights. I have some that do. Bigger LCDs are backlit with CCFLs. (For example, 100% of the LCD computer monitors and TVs larger than 6".) Why is that? Why do manufacturers use LEDs for small displays and CCFLs for larger ones?
MONEY: A few LEDs can back-light a small display well enough to read it in a dark room, and the cost is minimal. But for a larger display, the expense of a CCFL and inverter circuitry is still less than the cost of all the LEDs required.
I have read technical info on some of the very high intensity LED arrays. I also looked at the price!!!!! Thousands of dollars for the light output of a 250 Watt MH bulb. The difference is that the LED array has seperately controlled red, green, and blue emitters so it can be used as a universal spotlight for stage lighting. They also must be cooled so they don't exceed 140 degrees C. Above that they only emit IR (as they melt).
I am sure you can build a projector with an LED light source. It will just cost much more than one with a MH lamp, it won't be as bright, it will use more power, and you will need more fan cooling.
But there are more competitive alternatives: What about an array of CCFLs or even standard fluorescent tubes right against the back of the LCD?
Actually 100% of the large LCD are not backlit with CCFL. Maybe 99.9%, but we are starting to see large TVs (Sony), and large monitors (Mitsubishi). The efficiency is not terrible compared to CCFL. You are getting about 30 lumen/watt out of LCD and maybe 40-50 or less (realized) in CCFL. The problem with putting a bunch of CCFL behind the display is that you get hot spots on the display, and the tubes do not age evenly. You can concentrate a lot more light from LED, so you can edge light and get very even distribution across the display.
One advantage of the LED is 2 times the life of the best CCFL if not more, and more rugged (military guys and high rel love this). The compactness of the light source also make LED easier for high bright.
The other disadvantage of CCFL in high bright is keeping that heat away from the LCD. LCD like to be warm, but not hot. It is not good for the materials. With LED you get lots of heat, but it is easily controlled in terms of where it goes.
However, the reason that LED are used by Sony and Mitsubishi has to do with quality of the light. You can get much better saturated colors, especially blue and red using LED light sources. If you look at a CIE color chart, essentially you can get out a lot closer to the corners. I have seen side by side displays illuminated with CCFL and with Luxeons. The difference is astounding. The Luxeon backlight has much purer and realistic colors. You don't get that washed out look with other CCFL backlights.
Alvaius
One advantage of the LED is 2 times the life of the best CCFL if not more, and more rugged (military guys and high rel love this). The compactness of the light source also make LED easier for high bright.
The other disadvantage of CCFL in high bright is keeping that heat away from the LCD. LCD like to be warm, but not hot. It is not good for the materials. With LED you get lots of heat, but it is easily controlled in terms of where it goes.
However, the reason that LED are used by Sony and Mitsubishi has to do with quality of the light. You can get much better saturated colors, especially blue and red using LED light sources. If you look at a CIE color chart, essentially you can get out a lot closer to the corners. I have seen side by side displays illuminated with CCFL and with Luxeons. The difference is astounding. The Luxeon backlight has much purer and realistic colors. You don't get that washed out look with other CCFL backlights.
Alvaius
idea for an experiment
It would be very interesting to see how much more light we need to project an image versus normal backlighting. I think you could take a working DIY projector and insert neutral density filters between the MH lamp and the LCD, until the directly viewed LCD screen was equivalent to one with a standard backlight. Given that ratio, you would then adjust for the difference in LCD to projected image size. This would give us a multiplier like 30: Meaning you need 30 times brighter than the backlight to project a 100" image.
Another way to do it would be to substitute lower power (but known lumen-rated) halogen bulbs in place of the MH bulb, until you reached backlight level.
That multiplier value would be very useful to know in order to calculate how many LEDs, CCFLs, etc. would be required to turn a standard directly-viewed LCD into a projector with equivalent image brightness.
It would be very interesting to see how much more light we need to project an image versus normal backlighting. I think you could take a working DIY projector and insert neutral density filters between the MH lamp and the LCD, until the directly viewed LCD screen was equivalent to one with a standard backlight. Given that ratio, you would then adjust for the difference in LCD to projected image size. This would give us a multiplier like 30: Meaning you need 30 times brighter than the backlight to project a 100" image.
Another way to do it would be to substitute lower power (but known lumen-rated) halogen bulbs in place of the MH bulb, until you reached backlight level.
That multiplier value would be very useful to know in order to calculate how many LEDs, CCFLs, etc. would be required to turn a standard directly-viewed LCD into a projector with equivalent image brightness.
I think this point is key to a design, with MH bulbs it is recommended not to blow air directly onto them so a design needs the fans to be away from the bulb, with LEDs we don't have this concern, we can force as much air as we like over them and as such the heat can be contained in a very small area.
It is pretty easy to convert from NITS (how a screen brightness is measured) to Lumens (how projectors are measured). Hence it is pretty easy to estimate how bright an image on an LCD will be if projected.
Alvaius
Alvaius
Ace_1000 IM'd me for weeks asking about this idea and that idea, but when he finished he never gave credit where credit was due. Not even a thanks for a tip here and there.
Vince
(the guy who started this whole thing in the first place.)
Vince, I am pretty new to this community, but it seems obvious that you not only know what you are talking about, but have results to back it up. I personally don't need to hear Trev give you credit to trust every word you say.
Anyway, I just bought 100 20,000mcd Ultra white leds on ebay for $35 shipped. I know its not enough to do a whole project, but it should be enough for me to run some experiments. At least it appears that price should no longer be an issue with LED's.
If anyone has any suggestions for experiments than let me know. I am by no means a optics/lighting genious.
Anyway, I just bought 100 20,000mcd Ultra white leds on ebay for $35 shipped. I know its not enough to do a whole project, but it should be enough for me to run some experiments. At least it appears that price should no longer be an issue with LED's.
If anyone has any suggestions for experiments than let me know. I am by no means a optics/lighting genious.
I'm sure everyone will agree that there is still a lot of respect for vince around this place and it saddens me to see his above post. If it wasn't for him I wouldn't have my own DIY projector right now and I wouldn't be considering LED's as an alternative light source still!
redsand189: Do you have a DIY projector with MH bulb or anything like that? If so you probably want to compare the brightness as a starting point and move on from there. Last time I put any time into thinking about it I was planning to use 16 banks of 8x3 LED's joined together in a 4:3 ratio (4 banks high, 2 wide) and was then going to experiment with strobing them one at a time to give them a low duty cycle whilst maintaining a steady input current. I digressed onto other projects and so never even got around to ordering the LED's. Basically I think you'll find plenty of experiments yourself once you get started.
redsand189: Do you have a DIY projector with MH bulb or anything like that? If so you probably want to compare the brightness as a starting point and move on from there. Last time I put any time into thinking about it I was planning to use 16 banks of 8x3 LED's joined together in a 4:3 ratio (4 banks high, 2 wide) and was then going to experiment with strobing them one at a time to give them a low duty cycle whilst maintaining a steady input current. I digressed onto other projects and so never even got around to ordering the LED's. Basically I think you'll find plenty of experiments yourself once you get started.
I am ordering a projector for parts. My goal is to build a projector into my media center pc, so I have an all-in-one home theater device.
In the beginning I was LED's or bust, and went out and purchased 100 LED's. After reading tons of posts on LED's in projectors I am not so sure. However, I have 100 LEDs so I still want to have some fun!
In the beginning I was LED's or bust, and went out and purchased 100 LED's. After reading tons of posts on LED's in projectors I am not so sure. However, I have 100 LEDs so I still want to have some fun!
That's cool, you may have a few heat issues building it into a PC but I guess that just makes it more of a challenge 🙂
I was the same to start with, I wanted LED's and nothing else would do. Even a year ago when I started LED's were just too expensive still so I compromised with a MH setup with a 15" LCD. I'd still like to go with LED's and a smaller screen so that it's more compact, I consider that a Mk.2 projector now though, something for the future when I next have spare time.
I was the same to start with, I wanted LED's and nothing else would do. Even a year ago when I started LED's were just too expensive still so I compromised with a MH setup with a 15" LCD. I'd still like to go with LED's and a smaller screen so that it's more compact, I consider that a Mk.2 projector now though, something for the future when I next have spare time.
led retrofit
The projector I have is the infocus lp-130 the replacement lamp for this projector runs about 300 bones way into the range of i want an alternative light source thats much cheaper. how would you convert mcd's to lumens?
http://www.extremeflashlights.com/
"HOW BRIGHT IS AN EXTREME FLASHLIGHT
Very bright! Our flashlights range from 15 lumens to a whopping 500 lumens."
so if my lp-130 is rated at 1100 lumen then a five hundred lumen led would deliver half the brightness which im sure would whack into the quaility of the picture. next question has anyone retrofitted a lp-130 with a less expensive light source with satisfactory results?
The projector I have is the infocus lp-130 the replacement lamp for this projector runs about 300 bones way into the range of i want an alternative light source thats much cheaper. how would you convert mcd's to lumens?
http://www.extremeflashlights.com/
"HOW BRIGHT IS AN EXTREME FLASHLIGHT
Very bright! Our flashlights range from 15 lumens to a whopping 500 lumens."
so if my lp-130 is rated at 1100 lumen then a five hundred lumen led would deliver half the brightness which im sure would whack into the quaility of the picture. next question has anyone retrofitted a lp-130 with a less expensive light source with satisfactory results?
Re: led retrofit
Your PROJECTOR is rated 1100 lumen. That bulb is very likely to produce something like 10000-15000 lumens, that's how much those 100-130w UHP bulbs usually produce. The projector optics usually eat something like 90% of the light. So... you need something like at least 5000 lumen lightsource to be able to get any decent results, and that's with a precisely optically optimal lightsource.
We diyers usually have non-optimal setups, that's why the brute force of 150-250w MH bulbs suite well to us usually with their 10000-25000 lumen outputs.
-HB-
ßornagainpagan said:
Your PROJECTOR is rated 1100 lumen. That bulb is very likely to produce something like 10000-15000 lumens, that's how much those 100-130w UHP bulbs usually produce. The projector optics usually eat something like 90% of the light. So... you need something like at least 5000 lumen lightsource to be able to get any decent results, and that's with a precisely optically optimal lightsource.
We diyers usually have non-optimal setups, that's why the brute force of 150-250w MH bulbs suite well to us usually with their 10000-25000 lumen outputs.
-HB-
bringing this topic up again, I'm now seeing 40,000mcd 5mm LED's and 100,000mcd 10mm LED's available on ebay. Compared to the previous generations of LED's whose max was 20,000 in 5mm and 12,000 in 5mm before that, it seems they're getting more viable. Only problem I see is possible blurriness due to the more stray light and of course, the color temperatures. The 10mm led's would be easier to work with and draw the same amount of current as the 5mm, giving us a little more efficiency with a narrower beam. At 40 cents each, they're getting tempting to play with
I've already been playing with 40,000mcd 5mm, I bought 50 and managed to blow about half up unfortunately. I'm still looking in the region of 500 5mms, basically I'm thinking pack as many as possible behind whatever screen.
I also got some 10mms (think they were 60,000) along with the brightest red green and blue that I could find, the 10mm white had a much nicer colour temperature but have less lumen output per area, The RGB setup would have been nice but I couldn't find LEDs equal to each other which made it difficult to set up.
I'm going to ask the supplier if he can lower the colour temperature of the 5mms eventually but I want to ask for an accurate quote based on how many I need so I need to have picked an LCD first.
I also got some 10mms (think they were 60,000) along with the brightest red green and blue that I could find, the 10mm white had a much nicer colour temperature but have less lumen output per area, The RGB setup would have been nice but I couldn't find LEDs equal to each other which made it difficult to set up.
I'm going to ask the supplier if he can lower the colour temperature of the 5mms eventually but I want to ask for an accurate quote based on how many I need so I need to have picked an LCD first.
So what is the latest on the LEDs?
I've done numerous automobile retrofits, and will be trying to create a LED light for projecting a 15" Samsung Syncmaster 150mp.
Which is better:
- Small cluster of 100 5mm 25,000mcd 20* viewing angle leds targeted at the general center of a fresnel lense or
- Spread out cluster with 100 5mm 25,000mcd 20* viewing angle spread over a fresnel lense with more leds concentrated on the corners of the fresnel
I plan on bypassing the first condenser lense, and using a ohp condenser for the last lense, with fresnels on both sides of the 15" lcd.
I've done numerous automobile retrofits, and will be trying to create a LED light for projecting a 15" Samsung Syncmaster 150mp.
Which is better:
- Small cluster of 100 5mm 25,000mcd 20* viewing angle leds targeted at the general center of a fresnel lense or
- Spread out cluster with 100 5mm 25,000mcd 20* viewing angle spread over a fresnel lense with more leds concentrated on the corners of the fresnel
I plan on bypassing the first condenser lense, and using a ohp condenser for the last lense, with fresnels on both sides of the 15" lcd.
If you want to consider another way, look up LumiLEDs' website. Their lamps are much brighter and somewhat more expensive, but I Can't imagine it taking a hundred 5W white LEDs!
If you can wait a long time ( yeah right ) then there is a project underway to make a 100W LED putting out 7000=ish Lumen.
Have fun, and be sure to take pictures.
As to the question you asked, I have no idea. Sorry, just wanted to make sure you had all the options...
If you can wait a long time ( yeah right ) then there is a project underway to make a 100W LED putting out 7000=ish Lumen.
Have fun, and be sure to take pictures.
As to the question you asked, I have no idea. Sorry, just wanted to make sure you had all the options...
Unless you're planning on projecting a very small screen I can't imagine 100* 25,000mcd LEDs are going to be enough, If I could find a small LCD panel to use I'd be planning 300+ * 40,000mcd.
I'm not sure about using a front fresnel, I'd always considered treating LEDs as a direct source with roughly parallel rays (most of the light comes out the front), so I'm sorry I can't answer the question on directionality.
I'd also never considered putting more around the edges although it is a very good idea.
Let us know how you get on,
Steve
I'm not sure about using a front fresnel, I'd always considered treating LEDs as a direct source with roughly parallel rays (most of the light comes out the front), so I'm sorry I can't answer the question on directionality.
I'd also never considered putting more around the edges although it is a very good idea.
Let us know how you get on,
Steve
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