@KenCitron I think the problem is deeper than that. Diode lasers just do not naturally emit a round beam. We tame it into a more elliptical shape and then trim off the remaining cruft with another elliptical hole “spatial filter”. The other fainter lines are I suspect from one or more of the lenses being at a faint angle relative to the beam. That causes other reflections.
Think there is a chance it is just a little reflection off of the brass where the diodes light is elliptical? Maybe it is an easier fix than we think. Might be worth a try.
@KenCitron I don’t want to sound dismissive but I would not want to be the one to risk my printer’s warranty trying to tweak the inside of the laser module. Just because it was screwed together in a kind of right alignment does not mean if you dissect it that you will be able to even get back to that less than ideal configuration. Odds are high that the inner brass ring is epoxied, among other challenges.
Your probably right.
What is the warranty on this anyways?
I’ve been thinking about it more - and there has to be more than 1 lens in there, - the rectangular one we can see must be blocking visibility of one or more lenses behind it.
Two reasons I can think of that there has to be at least one other lens in there - firstly the one we can see is obviously a cylindrical lens which isn’t enough to focus a diode on it’s own. Cylindrical lenses focus in one dimension instead of two - so what it’ll be there for is to squash the elliptical beam - which as @EvanFoss notes is what you get from diode lasers. Secondly the visible curvature on the lens is very pronounced which presumably means a very short focal length - so it must be combined with another lens(es) to produce the effective focal length of around 30cm the laser appears to have.
@KenCitron I don’t think the flare is due to internal reflections - my guess is that it’s the result of not using more expensive apsheric lenses - without which you get “spherical abberation” and fractional differences in lens placement during assembly means that some flares are worse than others.
Not sure about the laser module in Form1+, but the laser modules i’ve seen usually have a spring under the lens and the threaded retaining ring is not glued. The idea being that you can adjust the focus of the lens by turning the ring (the spring pushes the lens onto the ring).
Regarding the lens being rectangular… Are you sure it really is rectangular and you’re not seeing the rectangular die of the laser diode?
@Ante_Vukorepa have you looked at the photo’s above? there’s nothing mounted in the laser barrel thread, and the rectangular lens is clearly visible - as I note above its a cylindrical lens - which must be to squash the elliptical beam - and that there has to be one or more other lenses behind that.
I doubt lens not being aspherical is the source of the flare.
The laser module i’m using has a very cheap lens (the whole module is cheap) and there is no flare at all. The defocused beam projected onto a wall or a ceiling produces a very regular disc. I’m using an iris precisely to filter out various internal reflections from the barrel, ring, lens etc.
The only thing not using an aspherical lens will do is make the focused dot irregular (elliptical or smeared). Since the laser diode die is rectangular anyways (and longer on one axis), you wouldn’t gain much with an aspherical lense.
I did and what i’m seeing (the rectangular part in the top left) looks very much like the surface of the laser diode. Give me a few minutes and i’ll take a photo of a dismantled laser module to show you what i meant.
@Ante_Vukorepa here it is again annotated - trust me when I say that the object I circled is not a diode - that would be impossible since it’s the last thing in the path of the beam out of the laser barrel - if that was the diode, then there’s no lenses at all - which is not possible. Plus the photos might not be great, but it’s a completely clear transparent object.
If you’re referring to the blue thing above and to the left of the lens - then I suppose that could be a diode - I doubt it though - it’s a lot larger that what’s visible in that shot - and it’s a flat surface that’s pretty much perpendicular to the lens - mounted slightly behind it.
Here we go.
Anatomy of a typical laser diode module.
This is what the inside looks like when you remove the lens.
And this is what a typical diode looks like:
@Ante_vukorepa yup - all completely different from the F1+ laser - nothing mounted in the laser barrel thread which is about 6mm across - and the object I’ve circled is nearly that entire width. It’s also highly curved as can be seen from the specular reflections of the lamps, and the brass semicircle it’s sitting on stretches beyond the width of the barrel threads.
I am familiar with what a laser diode can looks like - in this case the diode is mounted much further back and is not visible. The F1+ laser is much longer than the original laser - it’s 6cm long.
Ah. From the photo, it looked like what i was seeing is a distorted image of the diode (seen through one or possibly multiple lens).
@Ante_Vukorepa yeah - unfortunate limitations of 2D photos - video might have worked better I suppose, but then not many would have bothered to click through…
@Ante_Vukorepa - actually what I was wondering is if the spiky flare is the result of passing the spherical abberation halo from the first lens(es) through the final cylindrical lens, which only focuses in one dimension.
That’s entirely possible, but from everything i’ve seen so far, the flare is not symmetrical, right? Usually when a flare has a head and a tail that’s a reflection of some kind.
Then again, maybe that part is due to misalignment between the lenses, or maybe there’s an internal reflection from one side of the cylindrical lens?
@Ante_Vukorepa It is those internal reflections that are on my mind.
@Ante_Vukorepa - well the flare is vaguely symmetrical in that it’s flattish and typically has two sides - also the axis that passes through the middle of the flare on both sides is parallel to the line of the two scores on the lip of the laser barrel and hence matches perpendicularly with the axis of the cylindrical lens. So it matches up with light being squeezed out the sides by that lens.
edit: I suppose the above does not preclude the flare being the result of internal lens reflections - but what I still really don’t think is that anything is reflecting from non-lens surfaces.
Wow I learned quite a bit on this.
So what is the easiest fix? A pinhole in a cover do the trick?
@KenCitron Take a little bit and reread the posts in the thread referenced in the original post. You are kind of joining this almost 400 posts late. This is why a pinhole aka “Spatial Filter” won’t do the job.