Hi!
I've been doing some heavy pondering again and I'd like share some of my thoughts.
For past few days I've been calculating lots of procentages of loss of lumens on our setups, mainly getting results of about 85-99,5% loss of light.
I've been also investigating about the true amount of lumes produced by leds, and I found old documents (like this http://ledproductstore.com/white_light.htm) dating back to the days when the first bright white leds arrived on the marked and they state that the leds of THOSE days produced 20 lumens/w and I remember seen some estimates that the lumen/w ratio would be getting better very fast. The first bright white leds were about those 5000-6000mcd ones if I remember right. These days we have even these about 10000mcd leds, so I think the lumen/w ratio might be something like 35-40 lumens/w.
Ok.
If we want to produce somewhat visible and also somewhat viewable image on a screen at NIGHTTIME with well darkened room we need no more then about 200-300 lumens output on our projector. Damn, some of us would probably be happy with 150 lumens at night if the light source needs no cooling and lasts over 10000 hours.
Ok. Lets set the goal to 150 lumens output.
We loose lots of light on our diy setups usually already in the optics of the lightsource. At least my optics ripped from a diaprojector lose at least 36% of the light right in the beginning and I would not be suprised if most of the OHP's would have the same situation.
With leds the beam should be quite ok from the beginning, quite optimized good paraller light, 15-20 degrees beam and so on, probably very little loss of lumens at that point.
I think there are panels meant for projecting and at least LCD-projectors with so well optimized optics and films and all that we might be able to find something that lets 20% of the light trough it (I might be a bit too optimistic but well... lets go on just for the sake of trying to be inventive). That means we need 750 lumens to get to the very humble goal of 150 lumens for nighttime viewing (maybe this kind of setup would be perfect for bedroom? projection to the ceiling? everybody likes to watch tv in bed I guess, why not like this?). To achieve 750 lumens with leds we need 18,75 watts (750 lumens/40 lumens/w) of leds, that is 46 leds with a 120mA/3,4v, 40 lumens/watt.
Wha-wha-what? Yes, you read right. 46 leds.
Ok... all the numbers are a bit optimistic and the goal of 150 lumens is very very humble but check this out:
Let's try out how insane will the result be with goal of 250 lumens (enough brightness for ok image at evening with curtains on windows, and quite ok for night time viewing or for darkened rooms, remember again, this is over 10000 hour life lightsource with very small need for cooling) and take some of the optimism out of the numbers:
15% light let trough by optics and lcd --> 1666 lumens needed
1666 lumens / 35 lumens/w = 47,6 watts
85 watts = 117 leds
By driving the leds on the edge of their rated maximum voltages and currents (these calculations were done with normal voltages and currents) would able to boost the amount of light about 20-30%, and that would end up also to the final output of lumens, in the last example of mine it would mean possibly over 300 lumens 🙂
Is the damn thing worth the trouble and the cost ($1,2 per led = $140 lightsource with damn lots of soldering) I dunno... Not yet, maybe with just a bit more brighter leds and a lower light loss on lcd-panels, lets hope something comes a long in the future. Seems that we might be closer then we thought we were.
At this moment you can get a 100w halogen that lasts for 2000 hours with cooling that is about non-existent and still it outputs over 2000 lumens so if I would really be doing a projector for just nighttime viewing in bedroom I probably would use something like that myself....
I am just thinking and calculating this stuff for the fun of it. Maybe some of you get kicks out of these calculations and get the courage to try some of this stuff out or something. I wouldn't, not yet at least. My projector seems to be able to let 7% out of the light that the light source provides, so I'd be needing something like 250 leds to get that 250 lumens trough the thing, and the absolute maximum that I could easily fit there is about 90 5 mm leds.
Ok. That's it. Now I am going to sleep. Let's see what you think about this stuff.
Regards
HB
I've been doing some heavy pondering again and I'd like share some of my thoughts.
For past few days I've been calculating lots of procentages of loss of lumens on our setups, mainly getting results of about 85-99,5% loss of light.
I've been also investigating about the true amount of lumes produced by leds, and I found old documents (like this http://ledproductstore.com/white_light.htm) dating back to the days when the first bright white leds arrived on the marked and they state that the leds of THOSE days produced 20 lumens/w and I remember seen some estimates that the lumen/w ratio would be getting better very fast. The first bright white leds were about those 5000-6000mcd ones if I remember right. These days we have even these about 10000mcd leds, so I think the lumen/w ratio might be something like 35-40 lumens/w.
Ok.
If we want to produce somewhat visible and also somewhat viewable image on a screen at NIGHTTIME with well darkened room we need no more then about 200-300 lumens output on our projector. Damn, some of us would probably be happy with 150 lumens at night if the light source needs no cooling and lasts over 10000 hours.
Ok. Lets set the goal to 150 lumens output.
We loose lots of light on our diy setups usually already in the optics of the lightsource. At least my optics ripped from a diaprojector lose at least 36% of the light right in the beginning and I would not be suprised if most of the OHP's would have the same situation.
With leds the beam should be quite ok from the beginning, quite optimized good paraller light, 15-20 degrees beam and so on, probably very little loss of lumens at that point.
I think there are panels meant for projecting and at least LCD-projectors with so well optimized optics and films and all that we might be able to find something that lets 20% of the light trough it (I might be a bit too optimistic but well... lets go on just for the sake of trying to be inventive). That means we need 750 lumens to get to the very humble goal of 150 lumens for nighttime viewing (maybe this kind of setup would be perfect for bedroom? projection to the ceiling? everybody likes to watch tv in bed I guess, why not like this?). To achieve 750 lumens with leds we need 18,75 watts (750 lumens/40 lumens/w) of leds, that is 46 leds with a 120mA/3,4v, 40 lumens/watt.
Wha-wha-what? Yes, you read right. 46 leds.
Ok... all the numbers are a bit optimistic and the goal of 150 lumens is very very humble but check this out:
Let's try out how insane will the result be with goal of 250 lumens (enough brightness for ok image at evening with curtains on windows, and quite ok for night time viewing or for darkened rooms, remember again, this is over 10000 hour life lightsource with very small need for cooling) and take some of the optimism out of the numbers:
15% light let trough by optics and lcd --> 1666 lumens needed
1666 lumens / 35 lumens/w = 47,6 watts
85 watts = 117 leds
By driving the leds on the edge of their rated maximum voltages and currents (these calculations were done with normal voltages and currents) would able to boost the amount of light about 20-30%, and that would end up also to the final output of lumens, in the last example of mine it would mean possibly over 300 lumens 🙂
Is the damn thing worth the trouble and the cost ($1,2 per led = $140 lightsource with damn lots of soldering) I dunno... Not yet, maybe with just a bit more brighter leds and a lower light loss on lcd-panels, lets hope something comes a long in the future. Seems that we might be closer then we thought we were.
At this moment you can get a 100w halogen that lasts for 2000 hours with cooling that is about non-existent and still it outputs over 2000 lumens so if I would really be doing a projector for just nighttime viewing in bedroom I probably would use something like that myself....
I am just thinking and calculating this stuff for the fun of it. Maybe some of you get kicks out of these calculations and get the courage to try some of this stuff out or something. I wouldn't, not yet at least. My projector seems to be able to let 7% out of the light that the light source provides, so I'd be needing something like 250 leds to get that 250 lumens trough the thing, and the absolute maximum that I could easily fit there is about 90 5 mm leds.
Ok. That's it. Now I am going to sleep. Let's see what you think about this stuff.
Regards
HB
another great post HB, good job😉
heres a thought...100 watt halogen bulbs outputs 2k lumens lasts 2k hours its bright, yes i agree, BUT i dont think it would be bright enough.Heres why i think this, I read alot of posts and visit many websites and alot of people have 400 watt metal halides which usually are 33k+ lumens and usually lasts 10k hours and they are thinking of upgrading to 1000 watt MH system...how will a 100 watt halogen be NEAR these Metal halides? i do have an open mind i think it is possible maybe by using a special optic system or projector design..but otherwise i dont see this as reasonable solution. and as i ALWAYS say...i CAN be wrong.
-IMHO-
jimmy
heres a thought...100 watt halogen bulbs outputs 2k lumens lasts 2k hours its bright, yes i agree, BUT i dont think it would be bright enough.Heres why i think this, I read alot of posts and visit many websites and alot of people have 400 watt metal halides which usually are 33k+ lumens and usually lasts 10k hours and they are thinking of upgrading to 1000 watt MH system...how will a 100 watt halogen be NEAR these Metal halides? i do have an open mind i think it is possible maybe by using a special optic system or projector design..but otherwise i dont see this as reasonable solution. and as i ALWAYS say...i CAN be wrong.
-IMHO-
jimmy
Great post! I am probably not the first, but i like saying i pioneerd what i have named modified backlight projection (basically modifing the backlight of a lcd panel so it is superbirght and can be used to project with. lol i feel like such an expert). One day i was constructing my projector and desided just for yux, i would place my delta Iv lens on the lcd panel before I took it apart. I was able to project a 6 foot screen using only the original backlight to the lcd screen and it was a little brighter than the ebay 100" bigscreen tv thing. While leds may not yet be cost effective for lager lcd screens, they will work great with smaller 4-5 inch screens! As soon as i get some money in from ebay, i am going to attempt this task. I do not know if anyone else is up to the feat, if not, i guess i'll be the test subject. Thanks alot for this post, as it does have alot of informitive information.
So you haven't noticed that these people who have 33k+ lumen lamps usually use monitor LCDs and they dont seem to let even 99% out of the light? I am speculating that if we use lcd-panels that are well optimized for projecting then leds or other low wattage solutions might be used.Negative Design said:
Regards
HB
Henry, I have gone over the numbers a few time in other threads. In terms of optics and efficiency, I think you are bang on. In my experience, 20% transmissivity is at the top end of the panel (33% is the theoretical maximum), and 50% optical efficiency is typical.
The state of the art in White Leds is actually about 25 lumens\watt. However, if you backlight, you can use single color LEDS (better optical efficiency as well as you lose less in the LCD filters). You are then working towards 30 lumens/watt on average as state of the art.
In terms of cost, all the brightness claims aside, in high volumns, you can probably achieve a cost on the order of $0.15 U.S. per Lumen. Possibly you can get as low as $0.10-$0.12 per Lumen in really high volumns. However, for the average DIYER, I would say you are on the order of $0.30 - $0.50 per lumen best case. A copy of one of my previous post is below.
Verbose, at one of the companies I worked at, we used to put our superbright "near" daylight viewable [600 NIT] LCDs on the overhead and watch movies when we were working late. The scaler was not great, but it still looked pretty good. That was in 1994.
Alvaius
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For me personally, something on the order of 500 lumens is suitable for a good size image in a dim room. I would like brighter, but I can live with this. Dependent on the LCD, you may be able to get 15% transmissivity. If I had to hazard a guess, taking the backlight efficiency into account, the optics efficiency, etc. I would expect that at best, you would get 50% of the light out that you put in. So, the overall efficiency will be on the order of 0.15*0.5 or 0.075. Light input will need to be at least 500/0.075 or almost 7,000 lumens. For arguments sake, let's say the 1 watt Luxeon's are on the order of 30 lumens (color dependant, but an okay average). You would need on the order of 200 of them. You could use the 5 watt (actually they are exactly 4 times as bright as the 1 watt) and get that number down for at least the green and blue portion.
In my mind, the minimum brightness that would be acceptable, and this is way on the low end would be 200 lumens, so you could get by with say 80 or so 1 watt units. Those 1 watt LEDS are at least 5 times as bright as any 5mm superbright LED that I am aware of. You can use pulsed operation to get higher perceived brightness, but it is my experience that the superbright LEDS can not actually be run with a high maximum pulse current. You can do it, and it will work, but it will actually very quickly degrade the LED in an application like this where it is run continually. So of those 5mm superbrights, to get good brightness you would require on the order of at least 400 and possibly more like a thousand of them. That sounds like a lot, but I think my math is accurate and I have seen backlights (pre Lumileds) that used on the order of that many LEDS to achieve a solid state, daylight readable backlight for a standard 15" or so panel.
200 of a $10 LED may seem like a lot of dollars, but on a per hour basis, you are looking at 4 cents an hour versus 15 cents for a typical bulb. Of course if you were buying those LEDS in volume, the cost would come down.
I would also be very careful using the white 5mm LEDS. The interaction of the heat from the die, the phospor, and the epoxy tends to degrade the output quite quickly compared to non-white LEDS. I have seen on the order of down 30% at only 10,000 hours and accompanied by a significant change in the color of the output. You are much better off mixing Red, Green, and Blue LEDS for both life time, and then you can control the color temperature of the back light.
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The state of the art in White Leds is actually about 25 lumens\watt. However, if you backlight, you can use single color LEDS (better optical efficiency as well as you lose less in the LCD filters). You are then working towards 30 lumens/watt on average as state of the art.
In terms of cost, all the brightness claims aside, in high volumns, you can probably achieve a cost on the order of $0.15 U.S. per Lumen. Possibly you can get as low as $0.10-$0.12 per Lumen in really high volumns. However, for the average DIYER, I would say you are on the order of $0.30 - $0.50 per lumen best case. A copy of one of my previous post is below.
Verbose, at one of the companies I worked at, we used to put our superbright "near" daylight viewable [600 NIT] LCDs on the overhead and watch movies when we were working late. The scaler was not great, but it still looked pretty good. That was in 1994.
Alvaius
***********************************************
For me personally, something on the order of 500 lumens is suitable for a good size image in a dim room. I would like brighter, but I can live with this. Dependent on the LCD, you may be able to get 15% transmissivity. If I had to hazard a guess, taking the backlight efficiency into account, the optics efficiency, etc. I would expect that at best, you would get 50% of the light out that you put in. So, the overall efficiency will be on the order of 0.15*0.5 or 0.075. Light input will need to be at least 500/0.075 or almost 7,000 lumens. For arguments sake, let's say the 1 watt Luxeon's are on the order of 30 lumens (color dependant, but an okay average). You would need on the order of 200 of them. You could use the 5 watt (actually they are exactly 4 times as bright as the 1 watt) and get that number down for at least the green and blue portion.
In my mind, the minimum brightness that would be acceptable, and this is way on the low end would be 200 lumens, so you could get by with say 80 or so 1 watt units. Those 1 watt LEDS are at least 5 times as bright as any 5mm superbright LED that I am aware of. You can use pulsed operation to get higher perceived brightness, but it is my experience that the superbright LEDS can not actually be run with a high maximum pulse current. You can do it, and it will work, but it will actually very quickly degrade the LED in an application like this where it is run continually. So of those 5mm superbrights, to get good brightness you would require on the order of at least 400 and possibly more like a thousand of them. That sounds like a lot, but I think my math is accurate and I have seen backlights (pre Lumileds) that used on the order of that many LEDS to achieve a solid state, daylight readable backlight for a standard 15" or so panel.
200 of a $10 LED may seem like a lot of dollars, but on a per hour basis, you are looking at 4 cents an hour versus 15 cents for a typical bulb. Of course if you were buying those LEDS in volume, the cost would come down.
I would also be very careful using the white 5mm LEDS. The interaction of the heat from the die, the phospor, and the epoxy tends to degrade the output quite quickly compared to non-white LEDS. I have seen on the order of down 30% at only 10,000 hours and accompanied by a significant change in the color of the output. You are much better off mixing Red, Green, and Blue LEDS for both life time, and then you can control the color temperature of the back light.
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Exactly how big are these LED's? How many could you fit in say a 17" LCD that has two backlights?
the LED thing has been done by serveral people early on in this project and they all failed, some even used reflectors to concentrate the light produced by the LEDs but in the end it was just a lot of wasted time and money. In the Original Thread you will find image links / posts about it (don't know if the images will still work, but pictures were taken of the setup and stuff)
There have been in recent times newer led's developed.
Lumileds (I think) are leds that can goto a full watt rating and rather hurt if looked at, also 650 000mcd LED was used in case modding (computer stuff) with great success. I'm not sure if this is any use to you at all.
Lumileds (I think) are leds that can goto a full watt rating and rather hurt if looked at, also 650 000mcd LED was used in case modding (computer stuff) with great success. I'm not sure if this is any use to you at all.
They failed because they were trying to use leds with larger panels. They had to have space between the lcd and the projection lens, therefore light was lost. By using leds with a 5" lcd and a delta iv, there will be little light loss becuse there will not be many places for light to escape and be wasted. I am also implimenting the use of 3m dual brightness and reflective films. From what i read, they made a lightsource out the the leds kind of like a light bulb. I plan to mod the leds directly into the backlight. If you still do not belive this will work, the next time you have an extra 5" lcd and delta Iv laying around, place the delta on top of the lcd screen and fire it up so you can see a nice 5 foot image.
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