A response to Sam_Jacoby

That’s 7 years of bad luck right there.

@CraigBroady Thank you for trying to respond.

@KevinHolmes I think what that was meant to imply is that the photo is consistent with how the optics assembly would appear if photographed as you have it. I imagine the following two scenarios could be at play here.

There is every possibility that the definition of collimator to us as a two lens system is only one to them. After all they only need a beam to be more or less coherent until it hits the resin. To us that would be focused for that limited context though it would fit some definition of collimated.

It could also be that there are two lenses in there and that one or both of them is at the wrong distance to properly collimate. Manufacturing tolerances are as much a function of price as they are design.

Yes ether one of these means that the spot size will drift as the beam moves off the center of the resin tray.

Ether way @CraigBroady has said the following which means we know they are taking our issues seriously. I guess all we can push for now is for formlabs to change how they QA the laser’s collimator & spatial filter. In the meanwhile I think they deserve a chance to show some progress on the issue.

@CraigBroady seems to think this issue affects a minority of users. I am curious to see how small a fraction is. I know of a fraction that is. My gut says that this is the kind of bug most users do not understand that they even have. I mean if you are coming from the world of poorly built FDM machines even a bad day with a Form1+ would look pretty damn perfect.

@KevinHolmes and others I wonder if we could find more users and convince them to print your giant plus signs. I think more data would help narrow down just how wide the tolerance on these parts is.

@EvanFoss I don’t know about how common it is but @SachaGloor had flare and printed well, and now @Annino who also had flare has done a beautiful set of test prints here, even @Steve_Johnstone’s latest prints in a warmer environment are looking good see the later ones in this post. So there are definitely printers with flare that work well. None of this is to say that these problems are or are not rare, just that we have multiple good examples of printers with them and printers without them.

  1. it’s not binary (flare = bad prints; no flare = no bad prints)
  2. “flare” does not say much without knowing the intensity of it comparative to the central hotspot

I wish there was some way we could actually measure the optical power in the flare. I wonder if I took a piece of the photopaper I was using if there was some way I could calibrate it.

Well I can’t give you a method for exact measurements however I can give you a method for relative comparisons. See my laser spot dissection thread here. Read the description for details on how the relative light levels correlate. Also with some trickery and measurement of incident lighting off the surface of the paper you could probably do some rough calculations to get decent approximations of intensity.

@RocusHalbasch all due respect - as I’ve said before you are the one who tracked down the original F1 galvos and I worship you for that.

But… I really don’t think dslr spot-shots are going to be any help at all. Firstly - not even that many hard core geeks have a dslr (@Ante_Vukorepa hoping you’ll back me here) - secondly I don’t think that even dslr spot-shots are necessarily going to tells us that much - even when the guy taking them knows exactly - and I mean exactly - what to do …

Changing the shutter speed on the DSLR shouldn’t be some random thing. You cant do this without knowing approximately how long the laser scans the surface (which is much faster than a cameraphone can capture) when printing. If that measurement is known. Then you need to set the shutter speed of the camera to match that time. The resulting photo of the laser spot will then be what you’re looking for.

I just got caught up on this thread again. It is another meat grinder. At the risk of getting my finger stuck in it, I didn’t have a problem with @CraigBroady 's post. If the goal is more FormLabs presence on these type of posts, running Craig or Sam through the grinder isn’t going to bring them back.


Eh, actually, i’ve got a few of them and quite a few people i know have one, so probably can’t offer a good perspective :slight_smile:

Actually, no, that wouldn’t be enough, because there’s a chance the laser power is modulated during a print (either by PWM or - highly unlikely - by current). But either way, it’s irrelevant, because the objective was to find commonality between individual cases. You don’t need to know what the beam profile looks like during a print for that, you just need to keep the procedure consistent from case to case.

In other words, nobody cares what the intensity is (in absolute terms).
The interest is - finding out how the beam profile and the central hotspot change in shape from one case to the other, ceteris paribus (i.e. relative differences).

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@JoshK Agreed. They said what they can and we should respect that.

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@KevinHolmes wow. That was harsh, and not meaning any insult, possibly a bit narrow minded. I decided to write up those directions only after noticing a fair number of users on the forums have them, and seem to know how to use one. As for needing to know exactly how to use them the steps are fairly simple if you have one, or can borrow one. The results and value behind them would likely be being able to actually see and identify the part of the flare responsible for problem artifacts. This could make identifying flare problems easier and more reliable than using test prints alone, and give users a way to more clearly show they do indeed have a laser problem. Also you don’t have to own a DSLR you can borrow one.

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interesting - so I’m a lonely geek in seeing a dslr as spurious - totally pointless tech if you really get to it imo, but ok, accepted - there’s a lot of dslrs out there.

Nonetheless @RocusHalbasch I don’t think I was being harsh - I just dont see how zoomed in dslr spot-shots are going to tell us anything, simply because I think it would require someone with prints such as @SachaGloor and others with “good” lasers to post comparative pics from dslrs.

Moreover - going by what I’ve seen of spot-shots so far - it looks like every laser has it - and that it’s really hard to tell from even the most intensely detailed spot-shots whether a particular part of the flare is truly “evil”.

The whole dslr approach to me just seems impractical.

You clearly missed the whole point of what I did with the DSLR. When you look at a flare or take a picture of one the shape you see is not the part responsible for flare problems. There is a smaller part in the middle of it that is actually responsible, but you can’t see that because the area around it is all so bright all you register is that it’s bright. So while everyone has flare only some of us have it bad enough to cause problems, but our eyes are not good enough to look at a spot and see the difference even though there obviously is one. So I wanted to see all of the detail in the middle of the spot, in the part that our eyes only register as a really bright blob. DSLRs are a perfect tool for this purpose. The pictures are NOT a zoom of the flare. They are all taken at the same exact zoom level. They are light sensitivity levels. I started with the DSLR configired to be very insensitive to light so the only part of the laser spot visible was the 300um brightest spot in the middle of the normally 10mm-15mm blob that comes out all white in most laser spot pictures. This tiny dot is the part that does most of the curing of the resin. Then I doubled the sensitivity to light and took another. I continued doubling the sensitivity and taking shots till the whole spot we are used to was visible. Since each shot is progressively done with a clear step in light sensitivity you can actually know the relative difference in brightness, and if you measured the incident light coming off the paper you could probably tie the whole scale to a measured amount of light and approximate the actual intensity of the light at different locations in the spot. However I think all of the approximations are unnecessary and the pics alone will do.

You also mentioned we would need good shots to. That is why I wrote up the recipe for how to replicate what I did, and what do you know @Steve_Johnstone is going to have his wife take some with her DSLR and his latest prints have been coming out pretty good since he increased the temp of the room he prints in, so those may do the trick. We can also ask @SachaGloor and @Annino if they have acces to a DSLR and might be willing to replicate it.

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I should be able to take a shot for you, just need to charge my DSLR battery :smile:

So you know it’s more like 14 shots. The following thread entails the process:

Thanks again for all the help. Also check out the new laser spot templates.

Can we move the DSLR talk to a different thread. I know I started us down that path but it is kind of dragging this thread off topic.

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@EvanFoss actually I agree completely and it has it’s own thread already so any further responses should probably go there.

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So if the lens is secured by a brass plate, looks like a typical threaded holder then maybe the light is refracting off the inside edge of the brass.
Possible to use an oxidizer on the brass? Something like Blacken It should do the trick without adding anything to dimensions.