how to focus a beam?

[lightforce]

or should I say what to expect out of a laser?

Just a disclaimer, this is my 2nd laser. So I am new.

I just got a cyan laser from a member here. It doesn't have an adjustable focus, and I think the dot is a bit big than what I was used to compared to my dx 200mw adjustable focus. Not sure if that's just how it is, it has a "g7" lense that I can't seem to get it super clean. (Judging by looking at the reflection under light.)

1. any tips on focusing this further
2. any tips on cleaning the diode and lens? I tried water and alcohol already.

here's a photo of the dot, shot with iphone 7 and brightness turned all the way down.https://imgur.com/a/arZLv3i

 

[10fenny]

Who'd you buy it from? Did you contact them about the focus?

 

[paul1598419]

Most lasers built by members here have an adjustable focus. If this is a Sanwu laser, I don't know if that is adjustable, but from your photo, it doesn't look like it is diverging too much. If there is garbage on your lens, it could only get there by careless handling of the laser. It is a good idea to keep them out of the air when not in use by wrapping it up or bagging it in a ziplock bag. If you can access the "G7" (?) lens, you should be able to adjust it, or change it out for a better one.

 

[lightforce]

I contacted him, but so far so response. it is definitely fixed, i just read a bit about expander. and also read that G7 is suppose to avoid the need for that. I guess that was the seller's intent. I am used to a pin or nearly a pin for focus, this shows about a ~5mm circle (estimate) I haven't try to burn anything yet, but aiming it on my arm briefly does seem to have that potential with the g7.

here's a pic of the housing https://imgur.com/a/hzh573Z

 

[Gazen]

I contacted him, but so far so response. it is definitely fixed, i just read a bit about expander. and also read that G7 is suppose to avoid the need for that. I guess that was the seller's intent. I am used to a pin or nearly a pin for focus, this shows about a ~5mm circle (estimate) I haven't try to burn anything yet, but aiming it on my arm briefly does seem to have that potential with the g7.

here's a pic of the housing https://imgur.com/a/hzh573Z

A 5mm circle from how far away? The purpose of a beam expander is to increase the diameter of the beam, reducing the divergence. The 490nm diode is single mode, so the divergence should be pretty good.

 

[paul1598419]

I have worked with many of these 495nm diodes that originally came from Sharp. They are a single mode diode with very good divergence specs as long as the lens is set to collimate the beam as well as possible. You won't want to use a beam expander with this as it is also not very powerful. Deal with getting the focus corrected and all your problems should be solved.

 

[lightforce]

About 10feet the beam shows a wide line instead about 1 Inch wide

Also the pattern is really like a Star and in the center is the wide line. It’s kinda cool, but not very clean looking.

 

[Gazen]

About 10feet the beam shows a wide line instead about 1 Inch wide

Also the pattern is really like a Star and in the center is the wide line. It’s kinda cool, but not very clean looking.

I haven’t tested the diode you’re using with a g7 lens, but I don’t think that there should be a line with a single mode diode, there isn’t one with mine which uses a 3 element.

1 inch at 10 feet is too large, the lens is probably at an improper distance from the diode, so it’s not focused to infinity.

 

[paul1598419]

I wonder if you are complaining about the rectangular artifact that reflects off many glass lenses and appear as a box just to the side of the focused dot. Otherwise, you have a bad diode or lens if it just won't focus down to about 4mm at ten feet. It is best to focus it against an matte black back stop. Otherwise you see too much of the excess light that spreads out from the focused dot.

 

[lightforce]

The diode has a piece of metal to make what ever light come out of it technically a half circle. All diodes are like that, that’s how the line is formed the half circle at a distance has the middle area with most light.

Is it possible to get an infinite aim with just one lens?

 

[GSS]

Can you post a pic of the front of the host without the laser on?

 

[lightforce]

https://i.imgur.com/Osot1im.jpg

https://imgur.com/gallery/Gf4Tdpf

Seller says it’s fixed only adjustable by screwing tight or less tight. The problem is I can focus it few inches in front anything further is not achievable. Similar problem with my dx laser except I can adjust the head and when it is very loose I can burn things 5+ feet away if I hold steady

I would like the aim/focus to be either constant (pin infinite) or a pin at ~5 ft or adjustable.

I was able to burn things with this if they are close and focused. U can see I added cpu cooler compund to help cooling. It makes a huge difference since the housing top area does get hotter with less use than before.

https://imgur.com/gallery/nOj2E5g

Glare at 8 feet underexposed photo in reality the glare is very pronounced

 

[lightforce]

The more I play with it the worse focus it seem to have, I must had the lens at an angle before to get “good” aim at 10feet because I think I finally have it now the burn focus is about 4 inches from the pointer. At 10 feet I get a huge circle showing all the dust on lens and glare ring . I need a new tip assembly, lens or both to get this focus the way I want.

 

[paul1598419]

What you are seeing as the "line" inside the diode's window is where the laser's die is located and allows heat to flow from it to the body of the case. It does not cut the light in half. On a single mode laser diode, the emitter, which is located on the die, is much narrower than a multi mode diode which produces more of a line than these single mode diodes do.

 

[steve001]

The more I play with it the worse focus it seem to have, I must had the lens at an angle before to get “good” aim at 10feet because I think I finally have it now the burn focus is about 4 inches from the pointer. At 10 feet I get a huge circle showing all the dust on lens and glare ring . I need a new tip assembly, lens or both to get this focus the way I want.

If I recall correctly the G7 lens has a focal length of 4mm or so. That means to collimate the diode's beam the lens needs to be one focal length distance from the diode.

 

[GSS]

The seller has you all confused. If you can turn it "tight or less tight" it is focusable, and he probably set it himself to what he thought was best.
Most likely you have smudged the G7 beyond being able to clean it now from all the handling and could of been by using the compound for extra heat sinking, water, and alcohol which needs to be 99% pure or again to much handling when trying to focus and either need a new G7 in a 9mm barrel to focus or any new lens for that matter. Its not going to be much of a burner at i'm guessing no more than 100mw? These cyan are mostly just a very pretty color.
Paul has had success with plastic lenses to tame up the spot. Don't try cleaning the diode window if you haven't already and should consider another focus knob if that one is custom made and its threading depth take up way to much of the lens barrel's threads..