3 watt 445nm lens focus

[AndyRoo]

Hello all,
Im a newby to the laser world and recently built a 3 watt 445nm setup. I have a g2 lense and noticed that the beam goes from a pinpoint to a rectangular shape as distance increases. Is there a way to keep the beam at a pinpoint regardless of distance? I am willing to purchase additional lenses if necessary. My goal is to use up to 250 1x1 inch mirror tiles to reflect the beam and create a "laser beam door."

 

[RedCowboy]

Any laser beam is either expanding or contracting by some amount all of the time.

 

[Ricker]

Well, if that's true, PLEASE use safety glasses while constructing this door. Mirrors are so darn easy to accidentally hit yourself with 3w's of laser directly into your retina and burn a hole into it causing permanent damage within one second of exposure. Try these Eagle Pair glasses they are OD 4+ and cover between 190-540nm light spectrum. You can find them HERE. As for lense help, Alaskan is a great resource here and a very nice guy, I'm sure if you ask him nicely he can give you some advice. Have fun!

 

[AndyRoo]

Thank you for the safety advice Ricker, I will be sure to use my glasses at all times. I've noticed that these lasers can be very dangerous and eye protection is a must! As far as the laser door is concerned, I have no detailed plans. However, I noticed the beam can be routed different directions using mirrors..which seemed like a fun idea at the time. I always thought a beam would stay a pinpoint size if focused to infinity. I did not know that the beam spreads out as distance increases, limiting the ability to use mirrors to reflect and reroute the beam because the beam would eventually become wider than the mirror. I'm starting to think that if the beam spreads out over distance (and there is no way to control this using a single lens) I would need additional lenses to refocus the beam at certain distances in order to keep the beam size small enough to reflect off 1x1 inch mirrors several times over and not lose light. Am I on to something here? I feel like a high powered laser and 250 1x1inch mirrors would be a fun way to waste a boring Sunday..

 

[joeyss]

Well, if that's true, PLEASE use safety glasses while constructing this door. Mirrors are so darn easy to accidentally hit yourself with 3w's of laser directly into your retina and burn a hole into it causing permanent damage within one second of exposure. Try these Eagle Pair glasses they are OD 4+ and cover between 190-540nm light spectrum. You can find them HERE. As for lense help, Alaskan is a great resource here and a very nice guy, I'm sure if you ask him nicely he can give you some advice. Have fun!

I have 2 sets and I where them both when burning with a 3 watt laser. It blocks so much light I can see combustion and stuff. All it takes is one bright spectacular reflection or even shining threw a window you'll get a few 100mw back reflected so if you don't have googles your eyes are history.