...I was thinking also about multiline behaviour of 589 nm Spartans, but the temperature was not that low, also about Fresnell's diffraction, but the shape of the pattern is not corresponding to it, or there might be some internal reflections in optics (beam expander), but the intensity and shape of this pattern does not seem to be corresponding to it. Any other ideas?
If the Spartan 589 was moving, it is probably from the pulses, they pulse the output to produce a higher peak power which appears brighter. But if I read your post correctly, this wasn't a moving beam, so not sure.
I doubt you will either. I tested mine again and no pulsing was visible.Maybe I try it but I doubt I get something else than just single line.
Real laserpainting photo, absolutely no computer graphics. You can click on the artwork for higher resolution.
Behind the scenes
This artwork is exactly how I imagined it to be,
I took 2 test shots with some techique I was not completely decided to use and one without it - the final shot as I originally imagined it and as you see it here. This one was also the best of all three taken that night and I'm quite proud of it.
There is more behind and I had to follow carefully prepared work flow steps to do this artwork - on one hand to get it exactly as I had it in my mind and on the other to be sure I remained safe. I still improve my techniques and even processes how I compose and use lasers and optics. A lot of little hacks is helping me a to manage more complicated laserpaintings.
When I returned at half past eleven I was really exhausted. But happy as I saw the final shot processed and I was just amazed by that. It was a surprise for me as I spent processing time of this last photo by packaging my stuff and let the camera do its job while I was leaving and let the first view of the result when I was home.
I hope you enjoyed this laserpainting artwork as well as I did while creating it.
As usually in my mind has been born another idea for something where abstract and realism just meet and the artwork cannot decide what to be - depending on obseration, as usual for my artworks.