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FrozenGate by Avery

Pulsar NO Wings "-o-"






The output of diodes is elliptical kinda like a football instead of being round. You can correct it and make it look round by using something called an anamorphic prism pair. I didnt really understand what you were talking about from the picture you posted but that is what I assume you are talking about. Whatever a pulsar is probably has an anamorphic prism pair in it to correct the football shape and make it round.

Also, here is a link to anamorphic prism pairs from thorlabs

http://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=149&pn=PS870&CFID=9770011&CFTOKEN=98779961
 
likewhat said:
The output of diodes is elliptical kinda like a football instead of being round. You can correct it and make it look round by using something called an anamorphic prism pair. I didnt really understand what you were talking about from the picture you posted but that is what I assume you are talking about. Whatever a pulsar is probably has an anamorphic prism pair in it to correct the football shape and make it round.

Also, here is a link to anamorphic prism pairs from thorlabs

http://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=149&pn=PS870&CFID=9770011&CFTOKEN=98779961
Click to expand...

Haha, pulsar with anamorphic prisms? Naah, they didnt even bother sticking a driverboard in that thing (its a pen-form red unit running direct off 2xAAAs).

I'm not sure what causes it, I've heard it may be from running the diode a little too hard, but its not the elliptical shape of the profile. Its like a dot with a line through it - perfectly through the center. At first it would seem like a scratch on a lens, but its not, and I have NO IDEA what the heck does cause it.
 
pseudonomen137 said:
[quote author=likewhat link=1199383942/0#1 date=1199385932]The output of diodes is elliptical kinda like a football instead of being round. You can correct it and make it look round by using something called an anamorphic prism pair. I didnt really understand what you were talking about from the picture you posted but that is what I assume you are talking about. Whatever a pulsar is probably has an anamorphic prism pair in it to correct the football shape and make it round.

Also, here is a link to anamorphic prism pairs from thorlabs

http://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=149&pn=PS870&CFID=9770011&CFTOKEN=98779961
Click to expand...

Haha, pulsar with anamorphic prisms? Naah, they didnt even bother sticking a driverboard in that thing (its a pen-form red unit running direct off 2xAAAs).

I'm not sure what causes it, I've heard it may be from running the diode a little too hard, but its not the elliptical shape of the profile. Its like a dot with a line through it - perfectly through the center. At first it would seem like a scratch on a lens, but its not, and I have NO IDEA what the heck does cause it.[/quote]

Do you think a very small aperture hole on the collimation lens was used to block out all the artifacts and make the beam nice and round?
 
He's referring to this:
DSCF0650sm.jpg


A while back, I started a thread on it here: http://www.laserpointerforums.com/forums/YaBB.pl?num=1195435478
 
Oh, that is weird. I have never seen a diode do that before, but since everyone who has that type of diode sees the same thing it is probably related to that model/make of diode.

On the mention of putting in a aperture to rounden it up, that would give you a round dot surrounded by a bunch of rings. You cant filter astigmatism out of a beam, you have to correct it.
 
Beam Shot from Pulsar 150.
 

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pseudonomen137 said:
I'm not sure what causes it, I've heard it may be from running the diode a little too hard, but its not the elliptical shape of the profile. Its like a dot with a line through it - perfectly through the center. At first it would seem like a scratch on a lens, but its not, and I have NO IDEA what the heck does cause it.
Click to expand...

I think the line is caused by light diffracting around the 'fast axis' of the LD. In a LD the lasing cavity is constrained by the nature of the PN junction (very thin, 'pancake' shaped). If you set the focus to infinity and project the spot onto a wall 20-30 feet away an uncorrected single mode diode (using a no beam correction optics) will project an elliptical spot. The long part of the ellipse projects from the narrow part of the emitter rectangle - the smaller aperture causes more diffraction. See the diagram. The faint line may also have to do with the bragg grating used to enforce a single mode in most of these diodes.

Basically the line is an artifact intrinsic to the construction of these diodes. Most manufacturers offer upscale laser diode modules that have optics that correct the spot to a nice round dot, but then they cost $$$. Anyway it's really a cosmetic thing as over 95% of the energy will be in the central ellipse even for a relatively 'dirty' beam.

Not certain why the pulsar doesn't show it.

LD_schematic.jpg
 
When observing this phenomena with the several diodes that I have, this artifact seems to come and go randomly. Sometimes it's very pronounced, sometimes faintly visible, and sometimes not there at all. At times, you can actually watch it fade in and out.
 
The picture posted has them you just cant see it since the laser dot was taken at such close range (notice the stat of one of -0- on the top left of the dot), my pulsar 75 had it and my new modded pulsar from pseudonomen137 has it.
 
I think that must have just been a coincidence. I've have ones with the hole englarged that don't do it, as well as ones with the small holes that do do it.
 
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