Lens Problems

I recently bought a 1.3W 445nm laser from Blord. Being a noobie in the laser hobby, I really had no idea what to expect. The laser is a very nice build. I was going to do a review of it today, but I came across some issues that I think have to do with the lens.

First up: an obvious scratch on the lens. I've always been very good about keeping care of my laser (I've only had it for a few weeks and was sure to use the lens cap when not using it), so I'm not really sure how this happened. I took rubbing alcohol and a Q-Tip as Blord suggested, and it's still there, which leads me to believe that it is, in face, a scratch and not just debris.

Close up of the lens




As you can see, the scratch is right in the middle. When I project it on a wall:

WITHOUT the lens on - straight from the diode window


WITH the lens on and slightly focused, you can see how the scratch makes a visible difference in the dot/rectangle




When focused all the way, two noticeable dots result from the scratch instead of just one proper one.

This also prompts me to ask another question. Is the static surrounding the dot perfectly normal in a laser? I'm not sure just how perfectly round the dot should be and I expect some glow from it, but I see little "cracks" around the dot. I cannot explain it well, but I took a picture of what I'm talking about.



A little bit further back



and rotated the lens to show that the "static" isn't just from the camera



Can anyone clear this stuff up for me?

Thanks,
-Scott

Resize those photos.

Buy a new lens, they are like 5$.

Sorry, I'm not quite sure how to resize images with BB code. I'll do it manually later.

What kind of lens should I look to buy? (Are there different sizes or does one fit all)?

As long as the barrel is threaded for M9X0.5 you'll be fine. Any G lens, or two element/three element coated lenses will work.

Resize the images using an image editor/viewer (like Irfanview), not BB code.

On another note, that's a pretty cool lens-scratch that results in a treble clef:

Looks like something has burned into the lens. I always double check them before the lasers when out. Such an anomaly would be immediately noticed.

And there is always some debris or light reflection around the dot. You can't do much about it.

The raw output looks good so changing the lens would remedied the problem.
I can asked DTR to sent you a new glass lens. That would be faster than sending it from Belgium. Time to invest in a G2 lens ?

Blord said:

Looks like something has burned into the lens. I always double check them before the lasers when out. Such an anomaly would be immediately noticed.

And there is always some debris or light reflection around the dot. You can't do much about it.

The raw output looks good so changing the lens would remedied the problem.
I can asked DTR to sent you a new glass lens. That would be faster than sending it from Belgium. Time to invest in a G2 lens ?

Click to expand...

Sure, what's a G2 lens though?

Whats that junk on that stool looks like Kizdawg parrots were sitting on it.

jander6442 said:

Whats that junk on that stool looks like Kizdawg parrots were sitting on it.

Click to expand...

Ha, they're dead leaves from a plant that was sitting there a second ago.

By "static" Im guessing you mean the interference pattern? Have a quick look on google or search here, it has been discussed often and is completely normal.

G2 is a high power single element lens (DTR) it will increase your output by around 25 - 30% and it is very similar to the G1, which Jayrob sells. Both of these are a lot more expensive than a standard 3 ele glass lens and cost around $45 each. :beer:

grainde said:

By "static" Im guessing you mean the interference pattern? Have a quick look on google or search here, it has been discussed often and is completely normal.

G2 is a high power single element lens (DTR) it will increase your output by around 25 - 30% and it is very similar to the G1, which Jayrob sells. Both of these are a lot more expensive than a standard 3 ele glass lens and cost around $45 each. :beer:

Click to expand...

I'm not sure what it's called. The best I can describe it are little cracks and lines surrounding the dot. They twist and turn with the lens or when I rotate the laser.

Will the G2 lens eliminate some of this?

SSinischo said:

I'm not sure what it's called. The best I can describe it are little cracks and lines surrounding the dot. They twist and turn with the lens or when I rotate the laser.

Will the G2 lens eliminate some of this?

Click to expand...

Hmm not sure what you mean by that? If artifacts in the output rotate with the lens, then they are almost certainly due to the lens. If you cant clean it, then changing or upgrading the lens to a G2 should help. :beer:

Edit: Just so you know a G2 will give a higher power output, but your beam profile and dot and will suffer. I use a G2 for LPM measurements and engraving wood etc, but to enjoy the beam and have reasonably sized dot I switch back to the 3 ele lens.

For all the hobby-related purposes, G2 doesn't really make the dot and profile "suffer".

The difference in divergence is measurable, but not really noticable unless you were to grab two lasers side by side and do distance tests.

For all intents and purposes, getting a G2 lens is a one-way upgrade, No downsides.

Really, thats odd? With mine the beam seems much wider and the dot wont to focus to such a fine point, as I get with any of my 3 elements, over a large distance. Close up I can focus it very well, but far away not at all and yes my lens screws in past the focal point...maybe I should get a second one to compare...?:beer:

Edit: On my single modes, it makes no difference however.

Well I only had the chance to try out one type of single-element lens, not too different from G2, and while the beam profile at aperture was noticably different (more zoomed out, no clipped endings), and increase in burning power was apparent, divergence didn't really get pushed into what I'd call "worse" zone.

But then again I'm OK with Mitsubishi's red profile anyway, so yeah. I don't really give much crap about beam profiles.

Just get a lens, glass, coated for your wavelength, and in the right size threaded barrel. The size used by aixiz is most common. Chances are, if it looks right, it probably is. If you find something you are going to buy but still aren't 100% sure about it, just post it up!

Seeing the scratch in the middle of the lens on the front side looks like at some point maybe something hard fell in there and rattled around for a bit. Looks kinda like a cartoon T-Rex skull. The scratch not only blocks out that weird pattern in the middle of your dot, but also scatters a lot of that light outside the dot, resulting in a haze of interference (the staticy speckly halo).

I too was gonna make a smart ass comment on how it's supposed to project a treble cleff, that's what diffraction pattern tips do