Ideal RGB Balance

[mliptack]

Blow me!

Seriously though - I've done my best to stay out of this one, despite the baiting from both you and Allthat!

HAHA - I knew you were trying to stay away - I could sense it. Sorry buddy - I had to go there. Of course between the posts from Allthat and myself, I think we covered the ground you have so neatly covered in the past. So I give you the credit here - after all it seems as though you are the master of color balance

As for 457 nm blue - when I can afford one I'll look into the numbers for color balance. But I don't see that happening for quite some time.

Adam

I think everyone can agree when I say - it would be great to see it happen sooner than later! I would love to see one of those new MediaLas 1200 445nm lasers in operation!

A 1 watt 457nm 10kHz analog modulated / 10% stability only costs $17,008.74

I'm sure a group buy could get it down a few dollars...literally - just a few dollars.


New fishing boat or a 1 watt laser? Yeah, I thought so.

I would go for the laser - fishing can be fun - but lasers IMO win hands down. Plus with a one watt you could lase the fish and they'll just float to the surface lol

[godfrey]

Plus with a one watt you could lase the fish and they'll just float to the surface lol

*&#king awesome!

[norty303]

Whilst not about colour balance, this is about RGB power so it might get an answer here.... if not, sorry for the hijack!

If you have an RGB projector with 100, 200 and 400mw respectively of grn, blue and red, most will describe that as being 700mw. However, do the lasers actually sum coherently to mean that the total output is 700mw, or is the beam simply as powerful as its most powerful component?

E.g. Would the aforementioned 700mw RGB be as dangerous as a 700mw green? Equally, is the brightness then limited to the brightness of the greatest component, or once it becomes white, is it perceived as much brighter? E.g. is a 700mw RGB white brighter than a 700mw green? I appreciate the answers to those questions may be different regarding power and output and brightness.

[godfrey]

Whilst not about colour balance, this is about RGB power so it might get an answer here.... if not, sorry for the hijack!

No problem - will try to answer.

If you have an RGB projector with 100, 200 and 400mw respectively of grn, blue and red, most will describe that as being 700mw. However, do the lasers actually sum coherently to mean that the total output is 700mw, or is the beam simply as powerful as its most powerful component?

It is 700mW as they are all combined - provided all the beams are fairly aligned.

E.g. Would the aforementioned 700mw RGB be as dangerous as a 700mw green? Equally, is the brightness then limited to the brightness of the greatest component, or once it becomes white, is it perceived as much brighter? E.g. is a 700mw RGB white brighter than a 700mw green?

Any laser, regardless of color is dangerous above 5mW - even the ones that are not in the visible light spectrum...Visible being (Violet, Blue, Green, Yellow, Red) non visible being UV and IR.

Is a 700mW white brighter than a 700mW green - that depends on the wavelength of the green I suppose - 555nm is the typical peak wavelength our eyes are sensitive to. While 532nm green isn't far from there, it is seen as being much brighter than other colors that our eyes don't respond well to such as dark reds and dark blues.


I hope that helped somewhat.


Phil

[norty303]

Any laser, regardless of color is dangerous above 5mW - even the ones that are not in the visible light spectrum...Visible being (Violet, Blue, Green, Yellow, Red) non visible being UV and IR.

Thanks godfrey, I knew i should've put a disclaimer stating that I know that all lasers are dangerous, etc, etc

What i was trying to get at was, does the 700mw RGB have as much energy in its beam with all colours on as a single colour 700mw laser? Or is it capped by the largest?

[buffo]

Norty;

First, an RGB beam consisting of 100 mw of green, 200 mw of blue, and 400 mw of red most certainly *does* have a total of 700 mw of energy. It is entirely appropriate to label this as a 700 mw projector. However, with regard to the second part of your question where you compare a 700 mw green-only beam to the 700 mw RGB beam above, there are really two answers:

If your question is about real-world power levels, or about labeling requirements, or just about how to act around an RGB projector that has a combined total output of 700 mw, then for these purposes you should assume that a 700 mw RGB beam is identical to a 700 mw green-only beam. They will both cause the same about of *total* energy to be deposited in a target.

However, in terms of "apparent brightness" (to the human eye), a 700 mw green-only beam will appear brighter than a 700 mw white (rgb) beam. This is due to the way our eye's percieve color. (We favor green wavelengths.) This doesn't change the actual power of the beam, only the way our eyes (or more importantly, our brains) percieve it. This is all you need to know for laser show applications.

Now, if you're really trying to dig into the physics involved, and are curious about the effects of that absolute power measurement - especially in terms of the limits of an RGB beam vs a monochromatic one - then that's a different discussion. One that gets deep pretty fast, I might add.

Technically, a monochromatic beam at 700 mw will be able to be focused to a smaller spot than an RGB beam. The difference is irrelevent for our applications, but if you want to be perfectly accurate, the diffraction limit is going to be different (and wider) for a multi-color beam. So while the total power is the same, it's possible to reach a higher power-per-unit area with a monochromatic laser and a lens than with an RGB laser and a lens. The difference is very slight, however, and is only relevent for highly specialized applications that have nothing do to with laser light shows.

So this is mostly irrelevent. You still label an RGB projector as a 700 mw projector, and the beam still has the power to damage things (like eyeballs!) that is roughly equal to the power of a 700 mw green-only beam. (Technically, there *are* some differences between the two beams, but unless you want to start an advanced discussion on optics and quantum mechanics, the differences are very small and are not important to our application.)

Also remember that, because of the different color response of the human eye, the green-only beam will *appear* brighter than the RGB one, even though they both contain the same about of energy.

Adam

[mliptack]

Similarly - A Red 700mw will look less bright than a 700mw Balanced RGB projector.

[godfrey]

I just want to toss in a quick question that I'm thinking about...

In an RGB design, since you have three wavelengths vibrating at different rates, is the power just slightly less or greater since they arrive at slightly different times?

Or, just like sound waves, would it just sound like three different sine waves being played versus a single sine wave with the same amplitude?

Red 384-482 THz
Green 520-610 THz
Blue 610-659 THz

Since light waves vibrate in the Terahertz region I realize we can't hear them.....think of how loud it would be if you could.

[buffo]

In an RGB design, since you have three wavelengths vibrating at different rates, is the power just slightly less or greater since they arrive at slightly different times?

The analogy with sound doesn't work. You're dealing with wavelengths on the order of a few hundred nanometers! At that scale the analogy really doesn't work, because *nothing* is that flat.

Depending on where your surface is (plus or minus a few nanometers) the waves might arrive at the same time and interfere constructively, or at opposite times and interfere destructively, or at some happy medium in-between. So unless you've got a surface that is perfectly flat (within a couple nanometers), there is always going to be part of the target that gets the full power of the beam at the same time. (And if you've got such a perfectly flat surface, I want to know where you got it from!)

Or, just like sound waves, would it just sound like three different sine waves being played versus a single sine wave with the same amplitude?

I don't really know how to answer this question. Light doesn't "sound" like anything. If you're referring to the impact the individual waves have on the sufrace, then a better question would be: if you had three pure audio tones at 400 Hz, 550 Hz, and 700 Hz, and they all were beamed at the rough face of a mountain top, what would it sound like TO THE MOUNTAIN? (Or, what is the effect of the sound waves acting on the rough face of the mountain.)

But this is really absurd. The problem with the sound analogy is the geometry of our ears is very precise (and small) compared to the wavelengths of the sound we hear, so it makes a difference if the waves arrive in sync or not. But with light, it's the other way around.

Our eyes, (and indeed, most surfaces in general) are several orders of magnitude more coarse than the wavelengths of visible light. So you're always going to have both contructive and destructive interference going on when the light strikes the surface. (This is the source of the "speckle" you see when you shine a laser at a wall and see dark spots in the dot of light.)

Adam

[godfrey]

Depending on where your surface is (plus or minus a few nanometers) the waves might arrive at the same time and interfere constructively, or at opposite times and interfere destructively, or at some happy medium in-between. So unless you've got a surface that is perfectly flat (within a couple nanometers), there is always going to be part of the target that gets the full power of the beam at the same time. (And if you've got such a perfectly flat surface, I want to know where you got it from!) Adam

Yes, my question was geared towards interference of multiple waves since their arrival time for each frequency will be different...and you have answered that question very well.


Thanks a bunch!


Phil