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ArcticMyst Security by Avery

Hole in center of beam?

bhank

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May 7, 2009
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I've recently noticed a "hole" down the center of the beam of my 445nm build using an A140 diode in a JayRob host. When I first noticed the "hole" I also heard a slight jiggle and narrowed it down to the lens assembly. Turns out the retaining ring on the back of the assembly had come a bit loose so I tightened that up but still the hole remains. I concluded that the obstacle is in the lens assembly because the diode itself produced a nice smooth pattern with no disruptions, just like it's supposed to. So my question then is, could it be a misalignment of the optics in the lens assembly? I would think that's the problem because I can see nothing in there at all, it seems clean. I apologize, I would provide pictures but my cameras are not working at the moment :yabbem:. It's a nearly perfect circle just off center in the oval produced by the diode, but again it is not being generated in the diode, it is the lens.

P.S. I got a picture uploaded to my "outside" album but had trouble uploading it to the post. Maybe that will help a bit.

Thanks in advance for any suggestions or input,
Blaine
 





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Sep 16, 2007
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I had a lens that did exactly this.
It was because the lens elements were too close together.
Adding a spacer fixed the "hole" in the beam.

The new full threaded Aixiz lenses contain a few batches of crappy lenses.
I use the old half-threaded ones. They don't come loose and I have never gotten a defective one.
 

bhank

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Thanks for such a quick response and the info. What type of spacer did you use?
 
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Oddly enough I had built a 445 that also exhibited the same effect. When viewed under smoke the effect was much more prominent. It kind of looked like two beams coming out of the lens. I have a laser with an older half-threaded Aixiz 405 that is doing something similar except the 'hole' is on the edge of the beam rather than down the middle.
 
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This could indeed be due to a misalignment of the optics. When I took apart the 3 element Aixiz lenses, I put them together the wrong way, resulting in a strange laser output.

I hope this image might show what I meant:

output.jpg


Note that the strange hole is the beam with a hourglass shaped output, at one time there was even a big hole in the thin part.
 

Benm

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I've had a similar issue, but the beam shape was normal, just with a tiny dark area in the middle of the stripe. This was when i was testing with a stock plastic lens, and the laser seemed to have degraded it causing a dark spot in the middle of the beam.

Replacing the plastic lens with a 405-450 coated glass one resolved the issue.
 
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I had this problem too, the spacer is too short so two of the lenses are touching. I fixed it by simply bending the spacer with pilers so that it acted like a spring. (the shape sort of resembles a pringles chip now.)
 

bhank

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Thank you all for your input. I'm glad that it's most likely something easily fixed haha. I have been real busy and haven't had a chance to fix it yet but will soon.

Again thanks for your help :yh:
 




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