Combining 405 and 638?

[Jmillerdoc]

Anyone here tried this? What is the expected color? 520 ish? I've got a couple PBS cubes and violet / red diodes I need to use. Was thinking of giving this a try. If anyone here has done this and has pics I would love to see them.
Thanks,
Jmillerdoc

 

[swamidog]

you end up with a kind of weird magenta/fuchsia color.

Anyone here tried this? What is the expected color? 520 ish? I've got a couple PBS cubes and violet / red diodes I need to use. Was thinking of giving this a try. If anyone here has done this and has pics I would love to see them.
Thanks,
Jmillerdoc

 

[Tmack]

Think of it as combining the colors not averaging the wavelength.

 

[Bionic-Badger]

Yeah, the color you perceive is based on your eye's chromatic response. You can predict what colors you'll get if you look at something like the CIE diagrams.

 

[Jmillerdoc]

I tried to actually read the CIE article you referenced above....in the end I decided I would just stick to looking at the pretty colors. Heavy reading. So it's not an averaging of the wavelengths but rather a "mixing" or the colors. I was making the assumption it was some sort of averaging based on the red/green mix gave a yellowish color. Actually I am more impressed with the idea that I can create a pinkish color rather than a green. I've got plenty of green lasers but no pink ones.

Ok then, second question is what type of power ratio would be best when mixing a 405 and a red? Does varying the power rstio of each color make a dramatic difference in the ultimate color acheived? I've got the 500mw 405nm diodes and several different variants of red (Mitsu 638/300 and 638/500 as well as the 826 650nm diode). I'm not as interested in total power output as I am end results of a nice looking color and beam. Maybe it would be best to use the single mode lower power red diode in conjunction with my 405nm? Pushing both to the max with low loss lenses could get me around 1w total power I suspect. Any good suggestions here?

 

[CheeseHasLeafs]

The brightness calculator says that 650nm red is about 167% brighter than 405nm. I'm not sure how reliable it is, but it doesn't sound too far wrong. If I were you I'd use that 500mw 405 and the lower power single mode red one. When you're mixing the colours, getting approximate equivalent brightness and keeping the beam divergence similar is much more important.

 

[Bionic-Badger]

You should probably look into combining 445nm and red if you want to make magenta. 405nm is hard to see, more expensive per mW, the diodes can only go up to about 500-600mW, and the diodes are a lot more sensitive to shocks, etc.

The CIE diagram you see is also normalized for brightness. So if you were combining beams of equal brightness, you'd get those colors, but not equal power. The reality is that your eyes are more sensitive to some wavelengths of light than others and you need more power for some wavelengths to make them seem as bright as others. You can look at your eye's general sensitivity to certain wavelengths here. For example, 1W of 638nm red is roughly as bright as 200mW of 532nm green and 6W of 445nm blue. Those ratios aren't exact, as those are daylight conditions, but people use R:G:B ratios such as 2:1:4 depending on lighting conditions.

 

[Jmillerdoc]

You should probably look into combining 445nm and red if you want to make magenta. 405nm is hard to see, more expensive per mW, the diodes can only go up to about 500-600mW, and the diodes are a lot more sensitive to shocks, etc.

The CIE diagram you see is also normalized for brightness. So if you were combining beams of equal brightness, you'd get those colors, but not equal power. The reality is that your eyes are more sensitive to some wavelengths of light than others and you need more power for some wavelengths to make them seem as bright as others. You can look at your eye's general sensitivity to certain wavelengths here. For example, 1W of 638nm red is roughly as bright as 200mW of 532nm green and 6W of 445nm blue. Those ratios aren't exact, as those are daylight conditions, but people use R:G:B ratios such as 2:1:4 depending on lighting conditions.

Are you certain abut the relative brightness of 1w or 638 compared to 6w of 445 being equal? I know there is variability between people but I can't imagine my eyes are so much different than the average. I have a 1w 638nm (granted its probably more like 643-645 as hard as its being pushed) and a 2w 445 and I would say the beam is two to three times as bright on the 2w blue compared to the red at 1w. Is this the beam your referring to or the illumination on an object? I would have to go back and look but I can see where the red illumated surface might appear brighter, but the beam is definitely much much dimmer. You are correct it would be easier to mix blue and red, to be honest I don't know why we settled on the violet and red. Probably just thought it looked cool in a picture and hadn't really considered how similar a 445+638 might look. I'm gonna have to mix a 3w 445 with a 1w 638 and see what it looks like and show it to Chris in person. I bet he will be very impressed with it. It will definitely be much brighter.

So glad you brought this up, I really am standing here scratching my head wondering why in the hell I didn't think of that to begin with.

It should make a really nice purple color correct? Wonder what it would look like if I used a PBS to combine 700mw of 405 with 3w of 445 and then mix that with the red....think it would make any perceivable difference? Probably too much hassle to do that, just curious though. It's already a bit of a challenge to mix two beams together.

Thanks to the advice!

 

[DJNY]

Here is the 640/445 ratio you need for producing a violet-looking-beam
http://laserpointerforums.com/f52/upcoming-review-cni-rb-447nm-640nm-63342.html#post904098

 

[Deleted member 16589]

Jmillerdoc I did this a few years back http://laserpointerforums.com/f57/additive-color-mixing-67424.html#post971935
It may answer a few of your questions.

 

[Bionic-Badger]

Are you certain abut the relative brightness of 1w or 638 compared to 6w of 445 being equal? I know there is variability between people but I can't imagine my eyes are so much different than the average. I have a 1w 638nm (granted its probably more like 643-645 as hard as its being pushed) and a 2w 445 and I would say the beam is two to three times as bright on the 2w blue compared to the red at 1w.

Color perception and brightness is kind of hard to nail down for laser beam brightness. For one, the data for color brightness perception is based on photopic (daytime-adjusted) color vision, whereas we typically look at laser beams in dark condition, but not necessarily night (scotopic) conditions. Also the perceived brightness is generally assumed to follow the cone's response at the center of the eye's fovea (2 degree arc or 10 degree arc), whereas you might not have that exact condition looking at the beam with your peripheral vision as well.

Also, almost all the color matching data is still dependent on the original CIE measurements made in 1931. Subsequent models are still based on that data, with different ways of scaling that data to perform mixing. It's not to say it's bad data, but it relied a lot on the light sources they could use at the time. In order to calculate the eye's response to a wavelength like 615nm, which they had no chromatically pure light source for, the observer was supposed to match the color to another and the eye's response was back-calculated out.

There are other shortcomings too. The model didn't account for blue response of younger observers (older peoples' eyes naturally filter blue wavelengths better better than young), and there is very little data (or methodologies) for determining mesopic color vision -- i.e. between day and night, or even briefly bright colors, like you'd see in a laser show.

Finally, your eyes adapt according to viewing conditions. If you have both blue and red in the same area, you might perceive then differently than having other colors in the area too. Some theorize that color vision is very opponent-process dependent -- that you your perception of one color may be in response to the stimulation by another, or even masked by that other color (i.e. you can't see red + green, only one or the other).

 

[Jmillerdoc]

Thanks Mr. Badger, very good explanation. Now that you mention it I do recall learning somewhere in either medical school or in my Psychology undergrad about this opponent dependent process you mention. What I think is pretty interesting is we have literally thousands of people from all over the globe viewing this forum who work with, play with, experiment with....lasers of all types and colors, and each of these have different experiences with what they see independently of others on the forum. Since we are usually separated from each other we only have the ability to view what we see and then compare it to what others say on this forum or elsewhere. It would be pretty cool to get hundreds of us together in a meet of sorts and record our experience with some of these things we are discussing. I've often read something here and scratched my head thinking "I wonder what I'm doing wrong, or why I'm not seeing this or that the way others say it is supposed to be". This is an example above. I've got the laser colors discussed and when it was brought to my attention this 638 was supposed to be much brighter than the 445 I was in disbelief. To a degree, for me, I still am. Red to me is always the hardest color to see as bright. Even my 700mw 405 appears almost as bright as the 638 of a similar power.

I haven't looked for one but I was wondering if people on the forum ever do any sort of laser meets anywhere? My former hobby of DIY audio does this all the time. It would be fun for sure!