mRad?

[polo]

Hello, I was wondering about mRad? Basically I read that a DL viper 95mw has something like 1.5 mRad which means that the beam will get bigger by 1.5mm for every metre it travels, Is that correct? If so that means over the distance of 50 metres the dot will be over 5cm in diameter which to me sounds terrible and closely compares with my cheapy green laser from Dealextreme?
Thanks,
Polo.

 

[532 with Envy]

Beam divergence measures how much a laser beam expands per meter. For example, a laser with a beam divergence of 1.0mRad will have its beam expanded by 1.0mm per meter.(this was pulled randomly from the web at the wicked lasers site)

http://en.wikipedia.org/wiki/Beam_divergence

http://www.photonlexicon.com/forums/showthread.php/5722-how-do-you-work-out-mrad-of-a-laser

 

[Misanthrop]

Beam divergence measures how much a laser beam expands per meter. For example, a laser with a beam divergence of 1.0mRad will have its beam expanded by 1.0mm per meter.(this was pulled randomly from the web at the wicked lasers site)

http://en.wikipedia.org/wiki/Beam_divergence

http://www.photonlexicon.com/forums/showthread.php/5722-how-do-you-work-out-mrad-of-a-laser

 

[DrSid]

Not sure if I understand the question. Yes, you understand mRad well.
If you are surprised that it is about the same as cheap laser .. that's fine. Divergence is mostly defined by output aperture .. and that would be about the same. Higher power lasers usually have larger crystals, so they usually have larger aperture .. and thus usually better divergence. But at the same power the divergence is to be expected about the same. It's simply not questions of price.
Of course the laser can be badly focused .. but that could be fixed.
To decrease divergence you need beam expander .. something what makes beam thick at the aperture. It's additional (or different) lens for the laser. Some laser manufacturers makes them as accessory for their laser. You can also build one, if you are familiar with optics.

 

[Synchros]

Holy crap... is there a measure of how much Janice Dickinson's mouth expands per year? She's so damned hideous. She needs to go, she's so vile.

I just puked looking at her.

 

[sopark4000]

1.5 mRad is pretty much standard for most laser pointers available for purchase these days. As drsid mentioned you can use a beam expander to decrease divergence at the expense of having a wider beam at the aperture. DL sells a beam expander for the viper. As I said though most lasers available are advertised at 1.5mRad. I own a DL hulk and I can tell you that in my experience DL makes high quality lasers. A bit expensive but definitely high quality.