532 DPSS vs 520 DI

[carlos3621]

here is a side by side of 532nm (center lasers), and 520nm (outer lasers), outdoors.
the center lasers are 5 watts of 532, the outer lasers are 3 watts of 520nm.
judge for yourselves, to me they looked almost identical.

specs of inner lasers: 5 watts 637 , 5 watts 532, 7 watts 445.
specs of outer lasers: 3 watts 637, 3 watts 520, 2.5 watts 462.

if I had to do over, I would have gotten all 520 green, just based on modulation, longevity, and serviceability..

yes in person, the beams from the 532 are a little bit tighter, but i still should have opted for 520nm.

[-bart-]

I'm sorry but photos are pretty useless in this respect.
Ccd's have a particular sensitivity-curve for blue, red and green, and so does your monitor.
Taking photographs of two wavelengths a few nm apart is not an 'objective ' way to prove anything.
It says nothing about the common perception of color, let alone the individual perception.

Depending upon the type of vision you assume , scotopic, mesopic or photopic the theoretical perceived brightness difference is barely a few percent. Besides subjective factors, divergence and the specific scattering in smoke or haze may also affect the perceived brightness.

Personally I like DI diodes better because of their superior modulation. Since I avoid using pure monochromatic colors in my work, I use a broad range of mixed greens. Therefor I personally don't have this feeling, "my green looks different from yours".
If one only uses one standard monochromatic green, the differences may be more noticeable.

[White-Light]

I'm not sure if you can save colour configs for Beyond/FB3 (I know the QM has the colour trainer separately), that might be my fix...

You can save and load colour profiles in Beyond.

[White-Light]

Should have said Norty, it's located under the main File dialogue in the Advanced Colour Settings Window File > Save Profile or Load Profile.

[carlos3621]

Well, the pic was just a non scientific sample, but in real life, they did look the same ( yellows),
Ive yet to encounter a client or customer show up and measure wavelengths on-site, ��
You need to relax a bit, after all, were in the biz of lightshows, not a science lab.

[planters]

Despite all my laser experiments, I have yet to actually see a DI green laser. It still amazes me that a low cost DPSS laser works at all. Having built a lab vanidate, I now know how much has to be just right and how easy it is to screw something up because I have managed to screw up just about anything I could screw up (somethings more than once). These have just too much working against them.

My experience with the commercial DPSS lasers is that they suffer from very non-linear modulation and because this is both a non-linear output for a linear change in modulation voltage as well as a temporal delay in output, the green is hard to map. Now that the output of the direct greens is comparable to the DPSS per $, there seems little to recommend the older DPSS lasers.

[carlos3621]

Dpss non-linear modulation is a problem, once you start using them in pairs or more, that's when you really start having issues with the overall show look.

[swamidog]

Despite all my laser experiments, I have yet to actually see a DI green laser. It still amazes me that a low cost DPSS laser works at all. Having built a lab vanidate, I now know how much has to be just right and how easy it is to screw something up because I have managed to screw up just about anything I could screw up (somethings more than once). These have just too much working against them.

My experience with the commercial DPSS lasers is that they suffer from very non-linear modulation and because this is both a non-linear output for a linear change in modulation voltage as well as a temporal delay in output, the green is hard to map. Now that the output of the direct greens is comparable to the DPSS per $, there seems little to recommend the older DPSS lasers.

most of the laser show videos i post are with a low power single mode DI green laser.

[planters]

Now that the output of the direct greens is comparable to the DPSS per $, there seems little to recommend the older DPSS lasers.

There I go, quoting myself. What an ego!

But seriously, I just remembered that there may be an interesting application for these increasingly less attractive DPSS lasers. Years ago there was a impressive small dye laser that was pumped by as little as several mW of diode laser power focused on the waist in a hemispherical cavity. The rear window in the flowing dye cell was transmissive to the pump diode light but highly reflective to the dye lasing band. The output mirror had 1-2% transmission and I believe a 100mm ROC. This mirror was placed almost exactly 100mm from the reflective surface of the flat mirror which was in fact the rear cell window and hence formed a tiny spot in contact with the liquid. The pump diode was also focused, but from the other side of the cell to this same spot, at the same surface within the liquid of the cell.

The coupling efficiency was extremely good and rather unaffected by the geometry of the pump spot. So multiple diodes, multimode diodes and as I see it, multiple, low order poor beam quality DPSS lasers can be used to pump this kind of laser. I think a LS dye module could be modified to do this without too much re-engineering. Their conversion efficiency was around 35%.

[buffo]

Despite all my laser experiments, I have yet to actually see a DI green laser.

Come back to SELEM! Nearly half the projectors present will have 520 nm green. Lots of people have been jumping on the DI green bandwagon recently. (Including me... Of the 4 RGB units I have, two use 520 for green and the other two use 532)

My experience with the commercial DPSS lasers is that they suffer from very non-linear modulation and because this is both a non-linear output for a linear change in modulation voltage as well as a temporal delay in output, the green is hard to map.

Some DPSS designs are better than others. Also, there is a knee in the modulation curve (at least on most DPSS units I've tested) that really screws things up. If you stay below it, it's far easier to map the response. The problem is that the knee is low in the power band, so you can't access full power without throwing everything off. DZ had a nice post explaining all this in much greater detail back when he was selling his color correction boards, but I can't find his post at the moment.

Now that the output of the direct greens is comparable to the DPSS per $, there seems little to recommend the older DPSS lasers.

For graphics work, I agree.

However, As I posted above, beams and atmospheric effects still look better with 532 nm green, at least in my opinion. The difference is quite noticeable when you have the two side-by-side.

If anyone would like to see this demonstrated again at SELEM this year, it would be quite easy to do...

Adam