What should the dot look like???

[photongeek]

After having (finally :) built Kenom's DIY using Senkat's GB LD, I'm wondering what the shape of the focused dot should look like. Instead of being circular, it resembles a "crescent moon" shape. Is this normal for this laser? Thanks.

 

[Rhith]

Well it could be that the lens is just dirty. My guess is that the diode wasn't pressed in perfectly strait resulting in the light to hit it a slight angle. It should still be working fine though since light energy is light energy!
Maybe some pictures to show the severity?

 

[Kenom]

The "dot" will have many shapes to it but the most common being a bar of some sort. If your getting a "crecent" it's most likely because one side of the diode is in a smaller bit than the other and it's not lining up with your lens perfectly. It's been my experience that it is going to shine to one side just a small amount and no amount of tightening or tweaking is going to make it right. So I wouldn't be concerned about it.

 

[Rhith]

Seems me and Kenom were writing at the same time!
But I guess it's a good thing that our theories line up!

 

[Skram0]

My Senkat diode makes a really nice dot. Even unfocused @ 3' on the wall it's a nice circle. The LDs that comes with the AixiZ modules are not a dot, more of a bar. Unfocused and large it turns out to be a large bar. The BR LDs (ones I've seen) are a bar also with some light around the other edges too. So I think if yer GB red LD is not a perfect circle, then somethin ain't right..

Here's my GB unfocused to where the lens is almost falling out, and it's at a 3 foot distance from a white wall in a dark room. Even this one is almost bar-like.

 

[pseudonomen137]

Any chance of a pic of said crescent?

 

[photongeek]

These are the best shots I could do. It looks like there's a lot of dirt on or in the lens. This first picture, is with the lens removed and shot from about four feet. It does look like a bar.

 

[photongeek]

This next pic is with the lens barely on and again taken from four feet. You can see it looks off center. If it's focused very small, with my goggles on, it takes the shape of a crescent. Is the aperture hole supposed to be slightly enlarged?

 

[rubberband]

did you press in the diode so that it is flush with the module. if not the output may be crooked and explain the elyptical looking dot.

 

[a_pyro_is]

That's what it looks like to me as well RB.
Photon, have a look at the back of the diode, it should be flush with the module it's mounted in.

 

[photongeek]

Thanks Guys. I'll try to press it into the module a little more.

 

[rubberband]

yea just make sure one side isn't protruding more than then other.

Mitch

 

[trist-10]

This may seem like a silly response, but are you sure your batteries arn't just dying? My dot is starting to look more and more mis-shaped, but i'm hoping that's because of my batteries losing juice, not my diode dying :-/

 

[Benm]

I've constructed a few of these, and the 'dot' usually has a brighter, bar-shaped area within it. However, for me it's always been in the middle of the dot, not off to one side. So i guess the alignment of the diode is a bit off in this case.