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Optically corrected pen: MM 638 V1

steve001

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Raw LD output...pouring into the first cylindrical.....Holy Sh$t.....Well.....therein lies the problem of not fitting that Near Field geometry onto this very small Cylindrical lenses.

The beam slow axis is rapidly diverging....every mm down beam of the LD window !!!

I do not know what you have room for....but I would sure throw a 2mm EFL Collimation lens in front of that LD !!!!!!

I appreciate the drive to keep things small....but....elimination of the Collimation lens...is....well....unadvisable !!

Good Luck !!

CDBEAM
I hear ya.
The loss from that first optic is not huge. As I said, the divergence figures straight out of the diode, in reality, seem to be a bit worse than what is specified on the datasheet.
Theoretically, the small diameter lenses should have been sufficient but I didn't expect it to be perfect. I am pretty content with the beam profile despite the 25% loss to the optics (excusing the wings).

Seeing what I have here I wonder if the aspheric collimator will help a bit with the lobes/wings/whatever.

Do you report a number for losses in your Dragon's Head build?
I'll go check that thread again...
Edit: it appears you're getting just under 1W at around 1200mA.
Based on what to expect with a regular ol' lens in front of the diode, that doesn't seem too bad.



Thanks!
Though I've searched the interweb I've not found an answer.
When beam correcting to a circular profile do you first collimate then circularize?

Or do you circularize the beam then collimate.

Can the beam be circularize to round sufficiently to not need additional collimation for lowering the beam divergence?
 
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RA_pierce

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Though I've searched the intervenes I've not found an answer.
When beam correcting to a circular profile do you first collimate then circularize?

Or do you circularize the beam then collimate.

Can the beam be circularize to round sufficiently to not need additional collimation for lowering the beam divergence?
This is what I'm attempting to do here.
The idea is to collimate each axis individually with an appropriate cylindrical lens. This should simultaneously collimate and circularize the beam (or at least approximate an ellipse).
I opted to skip the collimation lens. Of course there are drawbacks as CDBEAM discussed but, looking at his and my results, the resulting beam is comparable perhaps with a little less loss if you collimate before correction.
 

Benm

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I get what you mean.
I tried what I proposed in my earlier response to you and ended up with a 30% drop in power after excluding the lobes. A worse result than I hoped for.

The only way to get all of the lobes on the power meter sensor is to get the laser very close. At this distance, masking may strip off the lobes but will also take some of the "main beam" with it.
I'm not sure how else I can clarify.
It's tricky to do instead, at a distance the 'dot' probably is too large to fit onto the sensor surface, something you get with these multimode things regardless of what corrective optics you use.

Getting rid of the sidelobes is also virtually impossible at the laser end - putting an aperture at the output doesn't help because these lobes just have more divergence, but equal or lower diameter very close to the laser.
 

RA_pierce

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Just wanted to show off the new laser.
I'll update the first post with details later.

I set the laser to 400mW output and crammed it into a chrome pen (of course). I think it looks pretty good despite a few imperfections.

I didn't bother with masking the beam much since the "natural" beam patterns are interesting.



 
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Just wanted to show off the new laser.
I'll update the first post with details later.

I set the laser to 400mW output and crammed it into a chrome pen (of course). I think it looks pretty good despite a few imperfections.

I didn't bother with masking the beam much since the "natural" beam patterns are interesting.



clean build-great laser pen:cảm ơn:
 

steve001

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Thanks!

Update: Phase 2 write-up is now posted in the first post. A drawing of the schematic will be posted after I get around to making one. Thanks for looking.
If you decide to refine this solution what I think you should do is setup an optical table and use some lens holders to workout the best lens positions before final assembly.
 

BowtieGuy

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Great looking pen, RA, love those reds; thanks for the updates. :yh:
BTW, I've still got the 1W 445nm chrome pen that I bought from you, it's still going strong almost 4yrs. later! :beer:
 




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