AVS Addicted Member
Join Date: Dec 2000
Location: brookeville, maryland, usa
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 554 Post(s)
Let's examine the spinning phosphor wheel. What is it? Why does it spin. What kind of light, wavelength spectrum band width, etc etc comes off of a burning phosphor. I am no expert but will now start some research. There have been courses and presentations at Infocom on this technology which is held I think under various competing patents. There are patents out there which can be researched.
It is clear that other than the blue which goes from the laser through the chip (twice) and could be called non extracted or primary light, red and green is extracted (by a form of diachromatic filtration) from the light generated by the burning phosphor on the wheel. The blue can pass through the wheel through a slit or around it using a beam splitter. Each spot of phosphor will be ignited by the laser and will quickly start to tail off (extinguish) until it is reignited on the next revolution. None of this is like a plasma or CRT in the sense there are not 3 separate phosphors (one each for R,G, and B), called 3P light, and the light emitted from each spot of phosphor does not directly hit your peepers. The light is heavily filtered to produce R and G. Because its R and G, the wheel doesn't need to produce white and production of a yellow light would produce the most efficient production of R and G. OK Its off to do some research or maybe but highly unlikely, an expert who actually knows (took the courses, attended the presentations, works in the art, can chime in. They are out there. Maybe Scott can come up with an expert and do a pod cast. Sooner or later this technology will be commonplace in all but the cheapest projectors. It is the wave of the future. But at present it is impracticable for 1000 Lumens class projectors. Heat is not a real issue and ventilation is really not required via air exhaust. However, noise is an issue from the fans and it would seem a hush box or booth will be required. There are other problems that needed solving for this technology and some of which are related to the high for HT use light output. early attempts at using this technology resulted in machines with low contrast and inability to reach good calibrations.
NEC has a machine coming out that solves most of these problems. The one weakness is more light than even a big boy needs and contrast levels which aren't impressive given the performance levels of cheap HT machines. Fine for commercial theaters. So the NEC base provides a base machine for the projection industry to modify through carefully designed apertures to lower the light and raise the contrast. This is a DCI machines and comes with a DCI server. You need to obtain content and you will need to pay for it and your access will be limited to short periods of time (days etc). But it will be obtainable and legally I might add.
The NEC machine is rated as being able to light a 33 ft wide 1.8 gain screen at 14 ft lamberts.
Few big boys have screen this large. The projector is rated a a low 1750 to one on off contrast. The machine is three chip DLP (.69) with a true 2K resolution of 2048 x 1080. anyhow the contrast level for commercial theaters is adequate, for HT it won't fly. The perfect storm arises and projector companies can modify the NEC machine by the addition of an aperture place (nothing simple in design here) to cut down the light and raise the contrast. Ideally, one can raise the contrast substantially so it approaches say 5000 to one (I am just guessing) and light up a 20 ft wude screen with a gain of 1.0 or even less to allowe for acoustical transparency.Plus a low gain screen reduces throw requirements.
In a commercial theater, multiple lamps are used and this presents all sorts of problems. The spinning wheel is the future of affordable commercial theater usage. Is it the best possible? Probably not until we get direct three beam laser. Called 3P light. That is three lasers, one for each chip. Coming, but big big bucks especially at 4K and not problem free.
Feel free to correct my limited knowledge. I am gearing up.
call me at: 240 876 2536
Last edited by mark haflich; 07-15-2014 at 03:55 PM.