RGB DPSS Lasers - Which are the manufacturers with better qualities and costs?

[Peter]

Hi,

Nice pics, but what is the best R-G-B ratio if you want to build a set yourself? What I heard is that it is depending on the RED.

Examples:
600mW laser with 635nm should have a R:G:B ratio of 3:2:1.
300mW Red 635nm
200mW Green 532nm
100mW Blue 475nm

500mW laser with 650nm should a ratio of 3:1:1.
300mW Red 650nm
100mW Green 532nm
100mW Blue 475nm

IS THIS TRUE ???????????????



Greetings,
Peter

[buffo]

This is beating a dead horse, I know... (Sorry guys) But in this case the numbers are so far removed from reality that I just had to reply.

Peter - first thing to remember is that color balance is subjective. That is, what looks good to you might not look good to me. Always keep that in mind.

Also, realize that there is a wide range of color balance numbers that will all look good. So just because your numbers aren't "perfect" doesn't mean that it won't look good. Lots of projectors out there have LOUSY color balance when you look at the numbers, but in real life they look just fine.

Still, there is some science behind the numbers, and there is a range of acceptable values. (The numbers you posted are not in that range.) So let's look at the physics involved, and I'll try to explain where the numbers come from.

The human eye has a peak sensitivity at around 555 nm, which is yellow-green. This is for daylight-adapted viewing. (Bright light) As the amount of light entering the eye drops, the peak in vision sensitivity moves towards the blue end of the spectrum (closer to 500 nm). Also, scotopic vision (night vision) increases the apparent brightness of all wavelengths in the blue spectrum (up to around 460 nm or so). How this affects the overall color response for the eye depends on how dark it is.

While most laser shows are viewed in dark conditions, suffice it to say that even in a nightclub with the house lights off, there will still be enough light from the other lighting effects so that the patron's eyes will *NOT* be fully dark adapted. But there will be some shift, and this shift is difficult to quantify. So let's start with the easiest case - daylight viewing...

For daylight adapted eyes, the numbers for perfect color balance are:

4.6 x red at 647 nm
2.4 x blue at 488 nm
1 x green at 514 nm

However, we normally use either 635 nm red or 660 nm red, so how do you compensate for that? Likewise, we use 473 nm blue instead of 488. And finally, we use 532 nm green. ARGH!!! Already we've got too many conversions!

Take heart. Remember that it's not that crucial to be 100% accurate. But it is important to take into consideration the wavelengths you're using. The longer wavelength red you use, the more you'll need. Likewise, if you go with a shorter wavelength red (say, 635 nm), then you need less of it.

With your blue, it's just the opposite. The longer wavelength blue you choose, the brighter it will appear. So 473 nm will appear brighter than 456 nm. But both of these wavelengths will appear dimmer than 488nm blue at the same power level.

With the 532 nm green, most people choose to ignore that it's different than the 514 nm green that the original numbers are based on. That's not really accurate, but it's an assumption everyone makes. (Because of the peak shift due to low light conditions, this assumption is actually pretty good.)

But that brings up another point... We don't watch laser shows in daylight. So how do you compensate for partially-adapted night vision? Well, to be truthful, you GUESS!

A good rule of thumb is to have LOTS of red, because it's always going to be the hardest for your audience to see. (Doubly so when it's already dark, due to the color shift caused by scotopic vision.) Beyond that, you'd like to have around twice the blue available as green. More blue is always better, but blue is expensive... And since you don't know what the final light level will be in your nightclub, you can't really calculate a perfect number, so you just get something close...

Ideally, you'd like to have something like:

7 X red @ 660 nm
2.6 X blue @ 473 nm
1 X green @ 532 nm

or

2.5 X red @ 635 nm
2.6 X blue @ 473 nm
1 X green @ 532 nm

Ok - fine. That's the ideal case. But not everyone is running the ideal case. (In fact, very few people are!) For example, there are *lots* of people here on PhotonLexicon that are running projectors with 660 nm red and 473 blue with numbers like this:

4 X red @ 660 nm
2 X blue @ 473 nm
1 X green @ 532 nm

or

2 X red @ 635 nm
2 X blue @ 473 nm
1 X green @ 532 nm

And they all look *JUST FINE* that way. (See the pictures in the gallery section.) Also note that lots of people choose to add a more powerful green laser to the mix so that when they're doing beams, they get more "punch". That's perfectly fine. Just so long as you have analog modulation so you can dial the green back when you want a perfect white.

Also note that at higher power levels (above a watt or two) the eye will saturate. This means that you can't tell the difference between 1.2 watts of blue and 1.6 watts of blue. So once you get up into those higher power levels, it's OK to drop down to a 1 to 1 ratio between blue and green.

Now back to the numbers you posted: If you build a projector that is 3 X red @ 660 nm to 1 X blue @ 473 nm to 1 X green @ 532 nm, you will have an excess of green and you will be lacking red and blue. (Unless we're talking about a 3 watt + projector, that is.) Even if you use these same ratios with a 635 nm red, you're STILL going to be green heavy and coming up short on blue.

For a projector that has a total power output under 1 watt, you can get away with 4 X red @ 660 to 1.5 X blue @ 473 to 1 X green @ 532, but I wouldn't suggest that you go any lower than that.

And finally, do a search for color balance here on PhotonLexicon. There are literally dozens of posts on the subject. And like I said - color perception is subjective, so there are LOTS of opinions on the subject. But no matter what, the numbers you posted don't make any sense at all.

Adam

[Lasershow]

Ideally, you'd like to have something like:
7 X red @ 660 nm
2.6 X blue @ 473 nm
1 X green @ 532 nm
or
2.5 X red @ 635 nm
2.6 X blue @ 473 nm
1 X green @ 532 nm

Adam

Adam, very good your explanation and suggestion, but which is the type (Analog or TTL) and speed of the modulation (? KHz) that you suggest for RGB Laser to stay with very good selection of colors and control of the blanking?


José Carlos

[buffo]

Analog blanking is always preferred. For one, you get lots more colors. (millions of colors instead of just 7 colors with TTL) Second, with analog blanking you can adjust the power levels of each laser to get a *perfect* white, even if the power levels of your lasers are not perfectly balanced to start with.

If you use TTL lasers, then it becomes much more important to balance your power levels right from the start, because the lasers are either off or on at full power, so you can't make any more adjustments.

As for blanking speed - ideally you want a laser that will support 30Khz blanking. However, there is no accepted standard for rating the blanking speed of a laser, and many manufacturers don't even publish the information! This makes it hard to decide which laser to buy.

As a practical guide, you will probably be OK with a laser that supports at least 20Khz blanking, but faster is better. However, it is also very important to make sure that all three lasers are rated for the same blanking speed. If you have one laser that is much faster than the others, it will make streaks at the begining of your lines, and that looks terrible.

Adam

[Lasershow]

Analog blanking is always preferred. For one, you get lots more colors. (millions of colors instead of just 7 colors with TTL) Second, with analog blanking you can adjust the power levels of each laser to get a *perfect* white, even if the power levels of your lasers are not perfectly balanced to start with.

If you use TTL lasers, then it becomes much more important to balance your power levels right from the start, because the lasers are either off or on at full power, so you can't make any more adjustments.

As for blanking speed - ideally you want a laser that will support 30Khz blanking. However, there is no accepted standard for rating the blanking speed of a laser, and many manufacturers don't even publish the information! This makes it hard to decide which laser to buy.

As a practical guide, you will probably be OK with a laser that supports at least 20Khz blanking, but faster is better. However, it is also very important to make sure that all three lasers are rated for the same blanking speed. If you have one laser that is much faster than the others, it will make streaks at the begining of your lines, and that looks terrible.

Adam

Very good explanation, but I have Zion Controller of the Laser Electronics (link of the Zion Demo http://www.laserelectronicsltd.com/Zion%20setup.exe ) and therefore would I get to adjust with Zion the power levels and my color balance with modulation analog of the RGB Lasers?

Jose Carlos

[buffo]

That looks like some nice software there, José, but it only supports TTL blanking, so you're only going to get 7 colors out of it. It doesn't matter if you buy analog lasers or not, the software will not allow for anything other than off or on at full power.

Still, it looks like the software has a lot of other features, and you *can* do a lot of cool things even with only 7 colors. It's up to you if you want to spend the extra money to buy new software (and a new controller) to get analog color control.

What you may want to do is buy your lasers with analog blanking, but run them in TTL mode with your current software. Then, if you decide to upgrade the software in the future, your lasers will already support analog blanking.

On the other hand, if you don't think it's likely that you'll want to upgrade your software anytime in the near future, then you can save a lot of money on your lasers by purchasing them with TTL blanking instead of analog blanking. But you'll be stuck with only 7 colors.

Adam

[Lasershow]

What you may want to do is buy your lasers with analog blanking, but run them in TTL mode with your current software. Then, if you decide to upgrade the software in the future, your lasers will already support analog blanking.

Adam

If I decide to upgrade the software with adjustment of power levels and colors balance, will it be necessary to change the DAC board?

Jose Carlos

[buffo]

Yes. The software can only support what the DAC supports. So if the DAC is TTL, the software is too. Likewise, if the DAC supports analog blanking, the software will also support it.

Upgrading your software will mean buying a new DAC as well.

Adam

[MechEng3]

I have one projector that was using the following.........
220mw X red @ 635 nm
465mw X blue @ 473 nm
230mw X green @ 532 nm

It looks good as far as the white balance.......just wish the divergence was better on the 635's......leaves that red glow effect around a static image. It is not that noticed in a scanned image though.

[Dr Laser]

yea like 1hr into infected mushroom the melles just dies no out put although on the pc read out it was pulling 16amps

lucky the 3 chinese lasers i had work fine

2 x 500 532 and one 500mw rgb

Classic 3 setup.