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Hi folks, thought y'all might like this. I did something like this back when I first got my Leadlight green pointer, years ago and found it very interesting how clean the somewhat oval dot was when translated into a 3D height map. I've been doing A LOT with my scary high power 1.3W 445nm build, and of course it was inevitable that I'd want to view and document the profile of the "dot" at a distance.
For this experiment, I set up the laser in a semi darkened room, and focused the "dot" so that it was as perfect as I could achieve at 30ft away using the normal Aixiz 405nm for 12mm housings optics. I set this up to strike a sheet of common white printer paper taped to the side of a box, and set up a camera to take photographs as straight on to the beam as I could get. I quickly found what I already knew - that the "dot" isn't a dot at all, but more of a short line. Interestingly enough, wave interference (best guess) causes it to appear as a double line with a darker band in the center, and multiple encircling bands of weaker beam surrounding those. Each of the two centermost "dots" measured approximately 15mm long by 2 - 3mm wide, and were fairly clean rectangles given the distance involved.
To do the rendering, I clamped the power switch on the laser so that I could walk to the target and observe the "dot" close up, and then I took several photographs. I picked the best of the photographs of the "dot", and used it as a "displacement map" in Lightwave 3D v9.3. I then used the original photograph as a texture map to give it it's proper character as a blue laser dot. The result allows you to see better how the beam strength varies across the profile, as if it were a hill that you could walk around and study the shape of.
Needless to say, it's not a very dotlike structure. I'm used to diode lasers being distorted, but these blues are very non dotlike at any kind of a distance. From these basic observations, I was able to deduce beam dimensions for any given distance, assuming low air distortion and pure linearity with distance vs. scale, and found that at several hundred feet, the "dot" would approach 400mm long and 80mm wide, pretty interesting. Someday if I can ever find the proper environment to test this in, I'll have to actually try it. :beer:
BTW, I believe the source of this laser diode is an A130 projector, if anyone wants to know.
For this experiment, I set up the laser in a semi darkened room, and focused the "dot" so that it was as perfect as I could achieve at 30ft away using the normal Aixiz 405nm for 12mm housings optics. I set this up to strike a sheet of common white printer paper taped to the side of a box, and set up a camera to take photographs as straight on to the beam as I could get. I quickly found what I already knew - that the "dot" isn't a dot at all, but more of a short line. Interestingly enough, wave interference (best guess) causes it to appear as a double line with a darker band in the center, and multiple encircling bands of weaker beam surrounding those. Each of the two centermost "dots" measured approximately 15mm long by 2 - 3mm wide, and were fairly clean rectangles given the distance involved.
To do the rendering, I clamped the power switch on the laser so that I could walk to the target and observe the "dot" close up, and then I took several photographs. I picked the best of the photographs of the "dot", and used it as a "displacement map" in Lightwave 3D v9.3. I then used the original photograph as a texture map to give it it's proper character as a blue laser dot. The result allows you to see better how the beam strength varies across the profile, as if it were a hill that you could walk around and study the shape of.
Needless to say, it's not a very dotlike structure. I'm used to diode lasers being distorted, but these blues are very non dotlike at any kind of a distance. From these basic observations, I was able to deduce beam dimensions for any given distance, assuming low air distortion and pure linearity with distance vs. scale, and found that at several hundred feet, the "dot" would approach 400mm long and 80mm wide, pretty interesting. Someday if I can ever find the proper environment to test this in, I'll have to actually try it. :beer:
BTW, I believe the source of this laser diode is an A130 projector, if anyone wants to know.