Red beam visibility.. how much power?

[steve-o]

i feel an angioplasty coming on..
You could always take up smoking..makes it easy to align and see beams

[buffo]

You could always take up smoking..makes it easy to align and see beams

Yeah, but it's hell on the optics... (You think it's hard to get tar stains out of clothing? Just think what it does to your mirrors!)

Adam

[PNjunction]

Potatoes, pig fat, and lasers. Now, if this ain't my kind of thread...

Pixpop... a 5mm beam sounds like you have the glass MI lens, which I was thinking of getting. Good as it may be at what it's designed for, your experience has me doubting the intended choice for my purposes. MI also offers the same housing, but with an acrylic lens, which states a 3.4mm beam (and $10 US cheaper).

If I can ask the opinions of the resident peanut gallery once again...

If I understand correctly, there's a trade off between wanting to see a nice, visible, red beam from my vantage point (being the one who will be building and operating said laser), and also giving some visibility to those standing slightly off to the side?

Second question regarding the MI stuff (because I really like the housing, and heat sink... and therefore want to buy it ).

The glass lens with a 5mm beam dia., has a NA of .53, where the plastic lens gives a 3.4mm dia., but with only a .28 NA. The NA of the glass is almost double! My very limited knowledge of optics only knows that a higher NA is more "efficient", but which one will I, and others, be able to see better?

Apologies if I did not completely understand the explanations given to my questions starting from this post. Not enough cash flow ATM to learn by trial and error, so trying to make the best choice, first shot.

[pixpop]

Pixpop... a 5mm beam sounds like you have the glass MI lens, which I was thinking of getting.

Yes, it's the glass one. But don't forget.. when I made the beam smaller (with a shorter lens), it didn't really become more visible.

[pixpop]

Second question regarding the MI stuff (because I really like the housing, and heat sink... and therefore want to buy it ).

Forgot to mention.. the brass collimator is barely adequate for a 100 mW laser (in terms of heat, I mean). If you use their adapter (for 5.6mm) I advise gluing the laser to the adapter with some arctic silver epoxy. Haven't tried their heatsink though.

[PNjunction]

Definitely interesting info, pixpop. At this point, I'm wondering if the MI stuff will visibly perform any better than my spare Aixiz case/plastic lens, for which I have no specs.

The one I'm already using with a Rohm diode doesn't seem to have a very thin beam either. Without measuring, it looks to be at least 3mm wide, possibly more.

Which leads me to wonder why you're getting no visibility out of yours. My reddie is a 658nm diode, only running enough current to give an estimated 55mW, maybe 60mW, and it pumps out a fairly fat beam. Yet I can clearly see the beam at night, indoors or out. This may be a really dumb question, but are you sure you're using the correct diode from the burner? In other words, is it possible you might be using the CD reading diode, and not the DVD burning one?

Edit: Do you live in an area with extremely clean air?

[carmangary]

Weird. I have the 658nm diode from the Dr. Lava group buy using the cheap Aixiz diode holder that you have. I am running at a measured 115mw and cannot see the beam without a little fog.

I am also interested to know if the MI mount gives a better beam quality since I also have the fat beam.

[PNjunction]

Yeah, it's interesting how people are reporting seemingly conflicting experiences with their stuff, even when using the same diodes from the same batch.

In fact, I responded this morning to your CPF post with a couple questions/ideas, as it was surprising to see the current vs. output. Of course, I'm only going by Dr. Lava's power plot for the Rohm, some of the anecdotal stories written about these diodes, and my own very limited experience. In my case, I'm just running the "kit" from the GB, and two E2 lithium primaries. I can easily see the beam on a clear night (when using it as a star pointer), and it looks even nicer on a hazy evening (and it's not even summer yet!). I can even see the beam a little bit while looking straight ahead, holding the laser about 2 ft. in front of me, and pointing it at the ceiling... which also lights up most of a small to medium size room in bright red.

I can only hypothesize that there must be many variables to account for all this. People living in very different locations, climates, and elevations, potentially wide differences in Vf from diode to diode, possibly even differences in perception from person to person, and likely a half dozen other things.

I really need to get a meter on mine. The switch needs to be rewired, so will measure actual current when taking care of that.

[pixpop]

Which leads me to wonder why you're getting no visibility out of yours. My reddie is a 658nm diode, only running enough current to give an estimated 55mW, maybe 60mW, and it pumps out a fairly fat beam. Yet I can clearly see the beam at night, indoors or out. This may be a really dumb question, but are you sure you're using the correct diode from the burner? In other words, is it possible you might be using the CD reading diode, and not the DVD burning one?

Edit: Do you live in an area with extremely clean air?

Not extremely clean.. I'm in LA. But it is very dry. I haven't tried to see the laser outside, maybe will try that this weekend. It's not an issue with power, because I measured the power coming out of the collimator with my lasercheck set to 650 nm. I set the laser current so that I got 100 mW out of the collimator. Also note, the CD reading & writing diodes are 780 nm.

[carmangary]

On a humid night I can see my 7mw 635nm laser beam outside. In clean dry air I don't see a thing. I think it all just depends on the particulate in the air.