Nichia to Ship Green Diode Laser

Coherence just means all the photons are in phase with each other. All the diffusion grating will do is make it blurry, not change the phase of the photons. Beam shape has little to do with coherence. The raw unfocused output of the diode is still coherent light.

The phosphor wheels I have on my desk glow brightly just from the light from my monitor or TV.

Sure Casio could have used a green and blue LED, but lasers are typically a lot stronger than LED's and more efficient as well. I believe lasers will continue in portable presentation (the Casio projector is not meant to watch movies people!) projectors, only because they can get more lumens from lasers than they can from LED's.

The diodes in a 140 are driven to 1600mW at a 66.666%/sec duty cycle. Thats 38 watts for blue and green light both. There are no LED's that I know of that put out that much power as efficiently as a similar laser diode array will.

@pontiac, that's what I mean. Nothing is as good as putting out bright monochromatic light as LDs.

qumefox said:

Coherence just means all the photons are in phase with each other. All the diffusion grating will do is make it blurry, not change the phase of the photons. Beam shape has little to do with coherence. The raw unfocused output of the diode is still coherent light.

Click to expand...

Once you use a diffusion grating, the light goes in all different directions and the photons no longer have matching phases.

ossumguywill said:

Once you use a diffusion grating, the light goes in all different directions and the photons no longer have matching phases.

Click to expand...

Thats not necessarily true, the photons will still be coherent, they'll just be coherent all over the place instead of in a nice beam.

If you have two photons in phase traveling from a single a point (the diode) and then they both hit a diffusion grating, and one goes straight but the other gets sent off on a diagonal, they will no longer be in phase to each other when they intersect a chosen plane in space due to the extra time it takes to travel in a diagonal direction. If you got them to re-intersect I suppose they would be in phase again, but they probably will never see each other again.

ossumguywill said:

If you have two photons in phase traveling from a single a point (the diode) and then they both hit a diffusion grating, and one goes straight but the other gets sent off on a diagonal, they will no longer be in phase to each other when they intersect a chosen plane in space due to the extra time it takes to travel in a diagonal direction. If you got them to re-intersect I suppose they would be in phase again, but they probably will never see each other again.

Click to expand...

Your logic is wrong in this application. If you use this logic, then all light would lose coherence when passing through any lens. Since that's what lenses do. They bend light by varying degrees depending on where it passes through the lens.

The photons can still be in phase even if they're on different sides of the universe.... Their position in space or direction of travel has nothing to do with coherence.

None of this changes what I stated earlier though. The 445's are only in the casio's so they wouldn't need a green source. The LD/phosphor wheel is an extremely complicated setup.. RGB LED's are simple, and and are actually the normal light sources for DLP's now days for TV's and most high lumen (>3000) projectors still use mercury vapor lamps.

The only reason casio would have to go with a more complicated arrangement would be a cost issue, since LED's are certainly capable of getting up to the 2500 lumen mark in projectors.

ossumguywill said:

If you have two photons in phase traveling from a single a point (the diode) and then they both hit a diffusion grating, and one goes straight but the other gets sent off on a diagonal, they will no longer be in phase to each other when they intersect a chosen plane in space due to the extra time it takes to travel in a diagonal direction. If you got them to re-intersect I suppose they would be in phase again, but they probably will never see each other again.

Click to expand...

Where exactly did you get this info, because it is misguided. Photons do not need to be intersecting with each other to be coherent, nor do they need to be traveling in the same direction.

Two waves can be in sync even though they are going in different directions

I guess what I'm saying is that even if they're coherent, to the phosphor wheel it's no different than an LED. When those photons hit the phosphor wheel after a diffuser they're all different phases, which is why

qumefox said:

The phosphor fluoresces much more brightly with coherent light I believe. But that's relatively easy to test too if someone has a phosphor wheel, a 445, and a blue phatlight.

Click to expand...

is irrelevant.

This whole argument is irrelevant. Casio's goal is to make a profit. If they have two ways to achieve the same outcome, they're going to choose the cheaper route. We just got lucky that the cheaper route in this case happened to include 24 1W 445nm laser diodes.

I am just wanting to point out that if you have hopes of there ever being a DLP PROJECTOR (not other devices.. only things using DLP technology) that have loads of red, green and blue laser diodes in them, your going to be sadly disappointed. LED power rates increase a lot faster than do LD's.. So DLP's using lasers won't always be the most cost effective solution.

Well, I disagree (as it's clear LDs have developed a LOT faster) but I guess we'll see who's right in the future.

They have? Name me a visible spectrum LD (not DPSS) that's on the market that will do more than a couple of watts? LED's are up to well over 20+ watts now. LD's have a long way to catch up.

And yes, as they say. Time will tell, and I hope i'm wrong, since i'd love to see high power green and red for dirt cheap as well. However as long as i've been dealing with DLP.. which has pretty much been since it's consumer introduction.. I just fail to see how lasers will make DLP smaller, quieter, cooler, and most importantly, cheaper, unless someone happens to come out with a red phosphor or something that they can drive with the blue as well.

It's pretty clear that for casio, LDs were cooler, cheaper, smaller, whatever than an equivalent LED. There's a reason the red on a A13/140 projectors is washed out. Not to mention the fact that within a few years, we've gone from a max of ~200mW visible to ~2W visible. With a several-micrometer sized die. Let's see LEDs develop that fast.

I'm getting tired of arguing this particular point though. A projector full of R,G, and B diodes won't meet ANY of those criteria though. 445 LD's were only cheaper because it replaced TWO light sources. Not just one. Hell even if they did start using LD's for the red.. you still won't have green. They aren't going to replace a cheap phosphor wheel with a large, hot expensive green diode array.

As for reds. even if they got 1W reds, it would still take at least as many, if not more, depending on the wavelength.. for proper color balance. You do know how much of the projector size real estate the blue diode block takes up already right? And how hot it gets? People already complain about these projectors being loud. I can only imagine how much worse it'd be with cooling for another 24 diodes in them.

The problem here is your looking at this from a standpoint of 'what you want to happen', not from a standpoint of marketing trends, technology limitations, and cost effectiveness.

From the 'what you want to happen' standpoint. I'm no different than you. I want cheap red and green as well..

I'm just saying if you actually look at the situation objectively.. Don't get your hopes up for anything remotely similar to what occurred with the 445's, to happen to red or green. And also don't be surprised when the 445's in casio's get usurped by LED's and the price for blue goes back up.

Dude, IT DIDN'T REPLACE ANY LIGHT SOURCES. If blue LEDs were cheaper, they could have used THOSE to phosphoresce the wheel. You don't need lasers to phosphoresce anything. On top of that, as these diodes get more powerful they will take up less space, which means you can fit R,G, and B diodes in the same space. Maybe we won't get 72 diodes in a projector, but we will still get plenty. LDs are moving along a lot faster than LEDs, so I'm not concerned about superbright diodes going away.

Whatever. I think since we keep saying the same thing over and over again, continuing this is fairly pointless. Believe what you will. Time will tell, but I wouldn't advise holding your breath waiting for a DLP to be released with more than 445's in them. By the time strong enough red and greens get on the market anyway, DLP will have been replaced by raster scanning beams like the pico projectors anyway.

Alright, just wait a while. No one called this happening at all, I know you'll be caught off guard by the intrusion of laser projection tech.