I just can't get anythng better than 2.2mrad

any suggestions, beam diameter at aperture is 3.5mm. With the lens i have, i just can't get anything better than 2.2mrad. With such a large beam, it should be fairly easy to get something better, but i just can't.

Any suggestions? A better lens maybe?

Which lens does rayfoss use, because my laser uses the same host as their "higher powered" ones.

Well what's the wavelength, and power?

kevinmassey said:

Well what's the wavelength, and power?

Click to expand...

and what lens

kevinmassey said:

Well what's the wavelength, and power?

Click to expand...

532nm, 350-250mw depending on battery's charge.

Got a picture of your current lens and host?

Sure. You really can't tell much from the lens picture, But it looks like a rayfoss host. A problem i had with the original lens is it was centered in it's aluminum disk. However, the laser module is off center, so i had to pop out the stock lens and glue a new lens off-center to straighten the beam. However, i can't seem to find a lens that gets good divergence. The best one, on there now, came from a digital camera. It has excellent transmission, but the best beam divergence i can get is 2.2mrad...

I'm sorry that the glue job looks crappy, but it works. I like using jb-weld to glue lenses. It doesn't damage the AR coatings and it comes off easily if you want it to. The "crud" is red grease. It works quite well on aluminum threads. I always grease my threads, no matter the application. The last thing i want to do is use a tap and die on a laser.



I need to re-polish this. Also, anyone know a good way to get those nicks out of the fins? I (stupidly) glued the threads of the two piece host, and to unscrew the front for a repair, i had to use a 2' pipe wrench .
I was thinking of just using a lathe to take off 1mm of aluminum, unless someone has part of a rayfoss host to donate...

Uranium said:

any suggestions, beam diameter at aperture is 3.5mm. With the lens i have, i just can't get anything better than 2.2mrad. With such a large beam, it should be fairly easy to get something better, but i just can't.

Any suggestions? A better lens maybe?

Which lens does rayfoss use, because my laser uses the same host as their "higher powered" ones.

Click to expand...

The problem is son you need a longer focal length lens.

steve001 said:

The problem is son you need a longer focal length lens.

Click to expand...

I know, but i'm not quite sure where to get one. And wouldn't a longer focal length = wider beam? It's already 3.5mm diameter.

Uranium said:

I know, but i'm not quite sure where to get one. And wouldn't a longer focal length = wider beam? It's already 3.5mm diameter.

Click to expand...

So tell me what is it you want. 1. lower divergence ? or 2. A beam of less than 3.5 mm dia. ?
When I buy a lens I use Optics, Imaging, and Photonics Technology - Edmund Optics. They have a very wide selection of lenses [ singlets ] that are AR coated or uncoated.

One thing clean off the glue from that lens and try this glue instead Bond 527 or Beacon 527 for your next lens. It's easily peeled from the lens yet will hold the lens firmly in place without damaging the AR coating. Only glue at the circumference of the lens to the host. I use a tooth pick to apply this glue.

Lower divergence and smaller beam diameter are essentially the same goals, since they can be interchanged with beam expanders or contractors.

I suppose the first thing to do here is to assert that your dpss unit is functioning properly - run them beam through a lens and make sure that what comes out is a single spot, not some odd multimode pattern.

At 3.5 mm diameter, you should be aiming for a divergence in the order of 1 mrad or so, perhaps a littlle bit more. If that cannot be achieved using any optics, i'd suspect the laser to be faulty.

It seems to be mutimode, TEM33. However it's not well defined. It's as if it's a TEM00 beam had been laid atop the TEM33 beam. (Square beam)

(this laser has been through so much abuse, it's a wonder it still lases at it's rated power)

Uranium said:

It seems to be mutimode, TEM33. However it's not well defined. It's as if it's a TEM00 beam had been laid atop the TEM33 beam. (Square beam)

(this laser has been through so much abuse, it's a wonder it still lases at it's rated power)

Click to expand...

Benm said:

Lower divergence and smaller beam diameter are essentially the same goals, since they can be interchanged with beam expanders or contractors.

Click to expand...

I always read expand the beam lowers divergence confirmed through practical application on my part. The resulting 3.5 beam diameter could be the result of the negative focal lens.

Benm said:

I suppose the first thing to do here is to assert that your dpss unit is functioning properly - run them beam through a lens and make sure that what comes out is a single spot, not some odd multimode pattern.

Click to expand...

Uranium could also remove the collimation lens and project the resulting spot onto a distant flat surface.

Benm said:

At 3.5 mm diameter, you should be aiming for a divergence in the order of 1 mrad or so, perhaps a littlle bit more. If that cannot be achieved using any optics, i'd suspect the laser to be faulty.

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Uranium the only way you'll get results will be to experiment with optics. A cheap source for optics is this place Anchoroptics.com

Now those prices are reasonable. I'm not sure what the people at edmund is smoking but i want some.

Uranium said:

Now those prices are reasonable. I'm not sure what the people at edmund is smoking but i want some.

Click to expand...

Why would you buy from Edmund Optics ? Because you are getting a high quality precision product and you know exactly what you are buying. Edmund makes their own lenses. Plus they have a large selection of focal lengths, sizes, materials, design wavelengths coupled with tech info and they come AR coated or not. Very few companies worldwide have such a large off the shelf selection with comprehensive information.
Anchor Optic-Many of those lenses are not AR coated and are best used for non critical performance. Good manufacturing processes make all the difference in how much light gets through the lenses.


Edmund offers a thick free catalog, Anchor too. Anchor Optics is a sub-division of Edmund Optics.

That sounds like an advertisement.

Bump.

So i took apart my laser and centered the module in the host. (It was off by .5mm). I originally accompanied for that by moving the lens off-center. Now that that is fixed, i used a new lens of the small power. It's uncoated, but it has excellent transmission anyway. However i still can't get anything better than a 3.25" spot at 120ft.

Also, i was shocked to find out my laser had a thermistor and thus thermal protection.