John Says: January 10th, 2006 at 10:09 am This is interesting news, but I fear that the rainbow effect will not be eliminated even though the color wheel is gone. This display artefact is due to the fact that color is presented to the eye in a time sequential fashion (e.g. red, then green, then blue, then red, then green, then blue, etc.). This rapid flashing of colors is what creates the rainbow effect. The same will be done with LED illumination. The difference is that a color wheel is not required to produce this color time sequence because the red, green, and blue LEDs can bve pulsed individually (when needed). The only way to get “rid” of the rainbow effect in a single chip system (like DLP) will be to flash the colors so fast that the eye can’t see it (and the systems have been getting better in this regard over the last couple of years). The main benefit from the use of LEDs should be (1) much better lifetime since LED life is far longer than the lamps usually used, (2) “deeper” colors since the LEDs will be designed to have a wider color gamut when compared to the lamp plus color wheel system, and (3) possibly quieter operation since the color wheel will be absent and (I believe that) high powered LEDs will be easier to cool compared to the less efficient high intensity discharge lamp. Whew! I feel so much better getting that off my shoulders!

Henning Says: January 10th, 2006 at 10:43 am Yes, that makes sense. I stand corrected. Thinking about it though, I thought that the LED’s can flash much faster than the colour wheel can change from colour to colour. For exapmle, as the wheel makes a single rotation, there are seven possible colours that can be displayed. But in the same amount of time, a much larger number of on/off LED switches could be done. Therefore rainbows would still be a possibility, but a much smaller one.

Bari Says: January 18th, 2006 at 3:12 pm I read an entry on another blog by someone who works for TI, that the speed of the LED switching is equivalent to a 48X colour wheel. I believe that the fastest color wheel now is a 6X or 7X speed, and that those eliminate the rainbow effect for almost everyone. This surely will do the same for those that still see them. Also, the quote above “Now I can finally put a DLP projector on my list of serious HDTVs” is premature. This technology is just in TVs. For LEDs to be used in projectors they’d have to be a lot brighter. Not impossible, but I think that will be a few years (and I’m sure more expensive). Something to look for though.

Henning Says: January 18th, 2006 at 3:13 pm Great point. Thanks for the info.

Scott Jangro Says: July 27th, 2006 at 3:58 am I don’t like color wheels either, especially when they scream in pain. Unfortunately I’ve got one. Just changed mine: http://www.jangro.com/a/2006/07/24/samsung-dlp-replace-color-wheel/ Quiet again! I’ve learned a lot about DLP in the process. I have to say, I don’t think I’ve ever seen the rainbow effect.

Daniel Says: August 28th, 2006 at 7:47 pm Just get an LCD display! The latest Projection LCD displays are upto 1920 x 1080 in resolution and have rise and fall time of ~ 2.5 ms, which is very fast. At 720p or 1080p, the images are crystal clear and beatiful. Systems priced $1500-2500 (online) offer all these features. Their only disadvantage is lamp life, but lamps are easily changable.

Brian Says: January 11th, 2007 at 6:12 pm Bari Says: January 18th, 2006 at 3:12 pm I read an entry on another blog by someone who works for TI, that the speed of the LED switching is equivalent to a 48X colour wheel. —————————– This is inaccurate information. Theoretically possible, yes. But not real life. The spin rate is not limited by the color wheel. It is limited by the TI formatter that sends the data to move the mirrors. At 48x each red, green or blue field would be just over 100uSecs long. That is impossible for the movement of the mirrors and more importantly, the transmission of the data to keep up. You also have to take into account the “turn on” and “turn off” times of the LEDs. These times are short but they are real. The shorter the pulse the dimmer the output because the beginning and end of each pulse is lost to the intensity ramping up and ramping down. LED illuminated systems have zero benefit over lamp/CW systems other than the fact that they eliminate 2 short lifespan components. Everything else, “increased color gamut” as an example, is just marketing hype.

Bill Warner Says: March 5th, 2007 at 5:02 pm Increased color gamut is *NOT* marketing hype. The color spectrum output of a single high pressure lamp is inferior to that of three dedicated color-pure LED’s. (there are several published white papers backing this statement up) There are in fact, several REAL advantages to LED over lamps. #1. Less heat #2. Less energy wasted producing heat/infra-red and off-color energy #3. Darker black, due to truly being “OFF” (unlike a slow lamp) #4. More accurate colors #5. Longer lifespan (~20,000 hrs) #6. Slower drop-off of light output toward end-of-life #7. LED replacement may not need recalibration, as lamp does. #8. Quieter, due to no color wheel and less fan requirement. #9. Quicker turn-on times to watch TV (~7 seconds) #10. Color-shift does not occur over time, as in lamp-based engine. There are scientific reasons for all of these advantages. Granted, some of these are more obvious than others. But, they are real.

Fair enough Says: June 28th, 2007 at 9:08 am That is correct Bill and nice but: - LED can only be used for low brightness projection screens that is the same as asking someone to chop their arms off (dont touch brightness) or projectors can put tens of them to make it significantly brighter and still not bright enough

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