Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



My Tiny Green Giant (505nm) Copper Build with Beam Shot

RB astro

Super Moderator
Staff member
Joined
Apr 6, 2014
Messages
2,505
Points
113
Looks good, nice work.
A set screw to get the negative lead on the host.... That's a pretty good idea. Like the build
Thanks guys. :D

I wonder if the reason I don't have it when using an acrylic lens is because they aren't AR coated at all.
Might have to try one out for myself.

Here's what the splash looks like, quite severe up close but the spot's nice and tight.

 



ZRaffleticket

Well-known member
Joined
Feb 4, 2010
Messages
2,994
Points
113
Yeah, that's how my 480, 490 (rip), and 505 looked with every lens I had. Really wish these didn't have the ugly box reflection.
 

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
15,870
Points
113
Yeah, I get that with any glass lenses I've tried so far. Where is the fabric look coming from?
 

RB astro

Super Moderator
Staff member
Joined
Apr 6, 2014
Messages
2,505
Points
113
Yeah, that's how my 480, 490 (rip), and 505 looked with every lens I had. Really wish these didn't have the ugly box reflection.
Yeah, I get that with any glass lenses I've tried so far. Where is the fabric look coming from?
Not sure, maybe the lens needs cleaning as this was projecting on a flat wall.

:thinking:
 
Last edited:

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
15,870
Points
113
Maybe it's from different lines interfering with each other. It does sort of look like an interference pattern. I never noticed that with mine. I wonder if it is a clue. Very strange indeed.
 

Alaskan

Well-known member
LPF Site Supporter
Joined
Jan 29, 2014
Messages
11,649
Points
113
it's the fabric of space-time, weird, it sure looks like fabric. Awful splash, I'd make some kind of mask to get rid of it, if no other solution.
 

steve001

Well-known member
Joined
Jun 3, 2007
Messages
2,342
Points
83
I wonder if the reason I don't have it when using an acrylic lens is because they aren't AR coated at all. I think Zack (Zraffleticket) said he got it a little with his acrylic lens, but I don't see any at all with mine.
Perhaps it the quality of the lens, meaning there could be defects within the lens, imperfectly curved surfaces, microscopic scratches and plain old shumtz on the lens surfaces. AR on a high quality lens should not cause the effect.
 

steve001

Well-known member
Joined
Jun 3, 2007
Messages
2,342
Points
83
A bit out of my depth Steve.
Could you link to something you'd recommend, still a noob I'm afraid mate.

:beer:
Edmund Optics offers a great deal of free information about lenses. As does Thor Labs. Single lenses are known as "singlets"
The square projection could be cause by internal reflection after the lens. That could be determined by the beams profile of the bare diode. See if the diode window is clean.
You could also see what the beam profile looks like by placing the bare lens in front of the diode.

Minus the square splash the spot looks round or very nearly round. It that correct?

Keep in mind optics and well made optics are the most important part of a laser system. Without them
a laser is just s fancy led flashlight
 
Last edited:

RB astro

Super Moderator
Staff member
Joined
Apr 6, 2014
Messages
2,505
Points
113
Minus the square splash the spot looks round or very nearly round. It that correct?
Correct.

Tomorrow I'll try a different lens.
Also, thanks for the info Re: Edmund Optics.

:beer:
 

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
15,870
Points
113
Perhaps it the quality of the lens, meaning there could be defects within the lens, imperfectly curved surfaces, microscopic scratches and plain old shumtz on the lens surfaces. AR on a high quality lens should not cause the effect.
I have many quality lenses that have been kept out of the air and away from dust and "shumtz". It shows up ONLY with glass lenses, but not at all with uncoated acrylic lenses. I have looked at there windows of most of these diodes and there is no apparent scratches of defects that I could see. It doesn't seem to help to use glass lenses AR coated for this WL either.
 

steve001

Well-known member
Joined
Jun 3, 2007
Messages
2,342
Points
83
I have many quality lenses that have been kept out of the air and away from dust and "shumtz". It shows up ONLY with glass lenses, but not at all with uncoated acrylic lenses. I have looked at there windows of most of these diodes and there is no apparent scratches of defects that I could see. It doesn't seem to help to use glass lenses AR coated for this WL either.
That isn't sensible since lab modules would use glass lenses in many cases and are AR coated.
I have a laser that produces a squarish artifact on one side of the spot. Without optics in place there is a thin ring which morphs into that squarish shape when the beam is collimated . That ring is caused by the rim of the diode can where it meets the window.

Try this. Let's see where the problem starts. Set up a working laser with no optics. Place a lens in the beam path that you think caused the artifact. See if it produces that result. Try lenses with wide diameters.
 
Last edited:

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
15,870
Points
113
I'll see what I can do later. I know this doesn't seem sensible, but it is what it is. The interference pattern in the one RB Astro has is another anomaly in this rectangular artifact that makes no sense. So, you believe it is a defect in the way the window was made that allows a ring of light to escape and become this rectangular artifact? And the best way to compensate for it is using a larger diameter lens or a longer FL one? I will see what I can try and go from there.
 
Last edited:

steve001

Well-known member
Joined
Jun 3, 2007
Messages
2,342
Points
83
I'll see what I can do later. I know this doesn't seem sensible, but it is what it is. The interference pattern in the one RB Astro has is another anomaly in this rectangular artifact that makes no sense. So, you believe it is a defect in the way the window was made that allows a ring of light to escape and become this rectangular artifact? And the best way to compensate for it is using a larger diameter lens or a longer FL one? I will see what I can try and go from there.
It's not the window. It's a reflection off of that tiny portion of the diode can that meets the window. The rectangular effect is caused by the collimation squeezing the ring down. I
Now that I think I've found the cause I'm not sure a wider diameter lens would work. Try it.

P.S. Edmund Optics offers edge blacken lens to eliminate internal lens reflections for their singlets
 

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
15,870
Points
113
I knew what you meant by the window. It was quicker to say the way the window was made than to go into a whole description. I've seen this ring that you talk about and it makes perfect sense that the space between the window and the can is allowing light to escape. I'm just not convinced that this is the cause of that rectangular artifact. The ring can be seen if you use a single element glass lens without a focus ring as coming out around the lens. I've seen it and I just can't make the geometry work for the rectangle.
 

RA_pierce

Well-known member
Joined
Sep 16, 2007
Messages
3,414
Points
83
Regarding the beam artifacts:

The diodes with the cleanest beam profiles I've seen are low power red (660-635nm) diodes.
Everything else seems to have some kind of artifact. The high power 200-300mW LPC 655nm diodes have a line that crosses through the beam and the ~400nm Blu-Ray drive diodes (PHR, BDR, etc) and all the ~455nm diodes I've used have a rectangular artifact similar to these green diodes.
This is an artifact caused by the emitter, I think. Removing the can from the diode does not remove the artifact and lenses only obscure the artifact to varying degrees.
High transmission optics like the G-2 lenses produce more severe artifacts because they are positioned close to the emitter to capture most of the diode's output. The single element design minimally deforms the beam profile so the artifacts are usually more pronounced with these optics.
The 3-element lenses are positioned farther from the emitter so more light is lost (hence the lower output power), essentially clipping off the fringes of the beam profile. The result from these 3 element lenses is a rounder beam up close but it's not efficiently reshaping the beam, just clipping it with a narrow entry aperture, so you get a terrible diffraction pattern at a distance.

The short version: this artifact is an inherent quality of the diode. Changing the lens or removing the can will not remove it.

You can use a narrow aperture after the lens to cut off the ugliness but unless the aperture is positioned at least a few centimeters from the lens, you won't notice a big difference.

DPSS and gas lasers produce much cleaner beams with beautiful gaussian profiles for some reason that has to do with the lasing medium. Don't ask me why that is - I'm a biologist, not a physicist.
 
Last edited:




Top