Qubic Light's LED Projector Looks Good - AVS Forum
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post #1 of 254 Old 12-18-2003, 02:59 AM - Thread Starter
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Qubic Light's LED Projector Looks Good

More microdisplay industry news here

PS Lumileds has announced the Luxeon III, a white-light LED capable of outputting 80 lumens with a 20K-hour lifetime.
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post #2 of 254 Old 12-18-2003, 08:16 AM
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I have several flashlights that have Luxeon III bulbs in them. Basically the L3 is just a version of the 1W Luxeon that is able to be over driven. There is a significant blue tint to the Led when you over drive it.

All in all, I am a LED fanatic, so I really hope to see a decent LED based projector in the next couple of years.

With that current projector, sounds like all they need is one of Vutec's 9 gain screens

Phil
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post #3 of 254 Old 12-18-2003, 08:31 AM
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I would also like to see an LED projector, hopefully earlier than the next couple of years.

I don't understand why they are using white LEDs and LCOS. It seems that red, green and blue LEDs with DLP would be a perfect combination.

Dave
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post #4 of 254 Old 12-18-2003, 09:04 AM
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Yeah, RGB LED with DLP would be several times more efficient, at least. Using white LEDs and then RGB filtering cuts light by two-thirds, and polarizing cuts it further in half. RGB LEDs are ideal for sequential color displays. The duty cycling would triple the lifespan (to 150,000 hours) and allow them to run at a much lower junction temperature, which raises efficiency.
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post #5 of 254 Old 12-18-2003, 09:41 AM
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Agreed. You could have the perfect 3-chip DLP/LCOS *or* single-chip DLP using red/green/blue LEDS...you'd need no color wheel since the LEDs have such fast on/off capability...they could literally sequence RGBRGB and probably do so faster than a colorwheel. You'd also be free of the "spoke time" because the whole surface of the chip would be instantly refreshed with the new color vs the "sweep" of color you get with a mechanical colorwheel (and that sweep or spoke time is not used for normal picture content...the DMD is either turned to "off" or used for some other process to boost brightess etc.).

-dave

1080p and lossless audio. EVERY BD should have them both.
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post #6 of 254 Old 12-18-2003, 09:57 AM
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It has been suggested that the fast on/off time of LEDs could lead to an effective colorwheel equivalent speed of >15X. Consider the possibilities of no rainbows and perfect convergence.

Dave
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post #7 of 254 Old 12-18-2003, 12:19 PM
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Exactly. It would actually be a strong case for single-chip projectors producing *clearly* (pun intended) superior pictures to those of mutli-chip designs without interjecting any of today's single-chip artifacts into the mix.

-dave

1080p and lossless audio. EVERY BD should have them both.
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post #8 of 254 Old 12-18-2003, 01:29 PM
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What kind of spectral output does r g b LEDs have? It is light emitting diode? Would you rather have laser emitting diode, do they exist?

I am sure you could flash the colors on and off faster, but the time to render color will only be improved by less spoke time. How much time is spoke time 10-15 percent? You might eliminate rainbows , but surely you would have the same problem with rendering color gradations in a fast moving picture.

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post #9 of 254 Old 12-18-2003, 02:28 PM
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LEDs tend to be narrowband emitters. They have a peak wavelength, and then output falls off fairly rapidly in both directions. You would probably aim your production for a given wavelength and then select the parts that come closest. My guess is that spoke time eats up 1-2 possible cycles per second, so LED/DLP would likely be good for 6-7x equivalent. Given that 5x gets pretty close to eliminating rainbows, that might just be good enough. The other problems associated with one chip DLP are still around, though probably slightly lessened because of more mirror time per second. Probably the best aspect of a LED projector is that the LEDs will likely last the entire life of the projector. Laser diodes do exist. Laser has a lot of potential with LCOS, because it is an inherently polarized source.
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post #10 of 254 Old 12-18-2003, 03:27 PM
 
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Curious, why can't one just use a white LED and color-corrected filters?
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post #11 of 254 Old 12-18-2003, 03:28 PM
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Are LEDs more energy efficient than laser diodes?

Can LEDs or laser diodes be designed for a specific peak wavelength, or is this limited by materials?
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post #12 of 254 Old 12-18-2003, 05:06 PM
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There are a number of reasons that white LEDs are not good projector sources. They are expensive relative to narrowband LEDs. The phosphor wears out and so they have a shorter lifespan. They have a poor spectrum, with spikes and dips. But most of all, white LEDs blow because RGB color filtering will lose 2/3 of the light. Why generate light and then throw it away? LEDs are already a lot less efficient than discharge lamps. However, when you use narrowband sources, you get an automatic tripling of efficiency versus filtered white light. This allows LEDs to be competitive with other sources. For a given output of light, a projector using RGB LEDs will use a third the power and generate less than a third of the heat than one with white LEDs, and the source will last at least three times as long. There's just no point.
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post #13 of 254 Old 12-18-2003, 05:43 PM
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Quote:


Originally posted by Andrikos

RGB LEDs with single chip DLP would be a perfect solution maybe 2-3 years out.

What improvements will take 2-3 years? Light output? Efficiency? Cost?

Would an LED-based DLP projector be equivalent in initial cost to one powered by a standard lamp?
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post #14 of 254 Old 12-18-2003, 07:56 PM
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2-3 more years for improved light output levels which are probably going to be provided by increased efficiency. Some colors are less efficient than others - red is very efficient, deep blue isn't, so the system will probably be limited by the least efficient colors.

Assuming prices remain constant or decline, the LED based DLP ought to be somewhat cheaper - the retail on the luxeons is in the $10-$30 range depending on specific characteristics.

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post #15 of 254 Old 12-18-2003, 08:44 PM
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Quote:


Originally posted by Ohlson
What kind of spectral output does r g b LEDs have? It is light emitting diode? Would you rather have laser emitting diode, do they exist?
...

I think that one of the problems with LEDs is that their primary emission is far away from the color of CRT phospers (and therefore also from the NTSC/ATSC standards). I don't know the frequencies offhand, but some googling could probably find the values.

Personally I would prefer LEDs to laser diodes because the LEDs theoretically should be more efficient, run cooler, have longer lifetimes and most importantly won't suffer from the scintillation problems that have to be solved in laser systems.

I'm not hard over on this though. A good laser system could change my mind.
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post #16 of 254 Old 12-18-2003, 11:29 PM
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Luxeons are less than $2 in quantity.
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post #17 of 254 Old 12-19-2003, 12:21 AM
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Andrikos
Why are the best crts color corrected?
I guess they are to output a narrow band spectrum of the optimum wavelength.

Why have a band when you can have a peak. If you add precise amounts of precise wavelengths you have many and good colors. I am sure this is better than adding reddish , kind of blue and a sort of green.

It was commented in the article that the manufacturer said the colors were more correct. The viewer found the colors different.

Dmds have a certain speed. If you have 60 frames per second they have a fixed amount of time to render that frame. With no spoke time the dmds get more time to render the frame. Can someone give a good estimate of this added time? If it is 20 percent more time we could go to 6x color wheel for NTSC. If you want to go higher then 6x then you would have to sacrifice color rendering or increase the speed of the dmd.

Mattias Ohlson
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post #18 of 254 Old 12-19-2003, 03:33 AM
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DMDs cannot load data faster than LEDs can currently be switched on/off. If you were to use LEDs as a source, you would be DMD load time limited, today.

HOWEVER, this would yield amazing results right now. When the HD2+ systems added a forrest green segment, they obtained 2 more real bits of green color depth. If *I* were using an array of LEDs as a light source, I would make sure I could control the number of each color that could be turned on at any one time. I would have forrest green (<100% of the green LEDs turned on) along with dark red and dark blue time portions. This would give me the opportunity to have 10 REAL bits per color with no spoke time penalty and no dithering.

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post #19 of 254 Old 12-19-2003, 06:37 AM
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One other positive about not needing a "mechanical" color-wheel.

With instant on/off LED light sources and single-chip DMDs, one could instantly change "refresh" rate. This means that the DMD could sync to 50Hz, 60Hz, 24Hz, 72Hz, whatever and instantly switch duty cycles without any video glitch or frame-rate conversion. You could play back a montage of film/video sequences with no visible scan-rate conversion artifacting.

*finally* would could get some movie playback from DLP without that darned 3-2 judder that no manufacturer has properly addressed.

1080p and lossless audio. EVERY BD should have them both.
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post #20 of 254 Old 12-19-2003, 08:49 AM
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I think by the time you got ~1000 lumens to the screen, the LEDs would end up costing more than a bulb, but it's a one-time cost and not a consumable. The real problem is gathering the light from the LEDs, collimating it, and getting it to the DLP. Several companies say they've got a solution to the problem, but I'm still curious about the details.
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post #21 of 254 Old 12-19-2003, 10:34 AM
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How long before 500 lumens output? In the dark cave this and possibly less lumens should be fine. It would feel better not to have to worry about the lamp. Buying lamg reminds me of the ink jet printer market. It is better to pay and to forget.

Mattias Ohlson
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post #22 of 254 Old 12-19-2003, 10:41 AM
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Quote:


Originally posted by scoby
The real problem is gathering the light from the LEDs, collimating it, and getting it to the DLP. Several companies say they've got a solution to the problem, but I'm still curious about the details.

Could you elaborate a little about the problems that you identified?

Dave
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post #23 of 254 Old 12-19-2003, 01:01 PM
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Search on entendue and poster Guy Kuo.

There is no difference in HDMI cables. If you can see the picture without visible dropouts or sparklies, the cable is working at 100%. No other cable will display a better version of that picture. You're simply wrong if you think there is a better digital cable than one that is already working.
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post #24 of 254 Old 12-19-2003, 06:55 PM
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To be honest, Ohlson, I don't know when we'll see 500 lumens. It all comes down to how much light these guys can gather. Obviously, since we don't know how they're overcoming the problem of etendue, we can't even guess at what light efficiency they're seeing. So we really don't know how many LEDs are needed as a source. The basic answer is that when we know how many lumens they're seeing now and at what efficiency, then we can probably estimate when we may see decent output, using Lumiled's roadmap as a guide. Until then, though, who knows?
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post #25 of 254 Old 12-20-2003, 05:58 AM - Thread Starter
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Ultra-Compact LED based Image Projector for Portable Applications

In my opinion this not very good idea: usage the transmissive LCD instead of LCOS or DMD.
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post #26 of 254 Old 12-20-2003, 07:32 AM
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Quote:


Originally posted by Andrikos
dcottle,
ANYTHING is more efficient than laser diodes. LASER needs a LOT of power and cooling.


Why does everyone here think LED's are more efficient than laser diodes? According to the graduate electrical engineering class I just took, laser diodes are always more efficient than the equivalent LED.

A laser diode is just an LED with special properties: frequency is tuned to the size of the resonant cavity in the silicon, cavity has mirror surfaces, etc.

The reason an LED is more inefficient than its equivalent laser diode: most of the light never leaves the silicon, it is reabsorped and turns into heat, where as in a laser diode, almost all of the light travels in a single path out of the mirror faces.

Also, the way coherent light emission is stimulated by other photons is more efficient than the way non-coherent light just randomly "occurs" in an LED.

I'm not saying all lasers are efficient, just that an LED tuned to be a laser is more efficient than the LED.
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post #27 of 254 Old 12-21-2003, 09:44 PM
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My neighbor is a business man/ engineer with a Taiwan facility which just produced a 20 watt LED (Supposedly one of the brightest LEDs) and he says the needs of the projector just to great for the near term LED's in the pipeline. They will focus on industrial lighting where there is need in hard to get to light (i.e. high ceilings). The volume is there not in projectors. When the LEDs reach a bright enough output as driven by other market opportunities then a version can be developed for projectors.
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post #28 of 254 Old 12-22-2003, 08:48 AM
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How about LED headlights for the application?



Quote:


Revolutionary: The LED headlights

LED headlights allow the designer more freedom, since they need less installation space than conventional ones. The cooled high-end lights, 18 on each side, are located much nearer the surface of the cover, which has also been reduced in size, so that the entire front end or the car is more harmonious in its styling.

LED - these three letters not only signify progress for the designers but also offer solid advantages such as longer life and energy consumption ten times lower than that of conventional bulbs.

As if this were not enough, LED technology offers further future potential. In a future development stage, LED headlights will make dynamic cornering beams possible without the need for movable parts in the system. The width and direction of the beam can be specifically adjusted by activating more light elements electronically.

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post #29 of 254 Old 03-05-2004, 04:39 AM - Thread Starter
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post #30 of 254 Old 03-05-2004, 06:49 AM
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Less than $1,000 retail. I wonder what panel technology they will use.
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Reply Digital Hi-End Projectors - $3,000+ USD MSRP

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