Advice on what green laser to buy (50mW - 100mW)

[hiphiphooray]

Hello all,

I'm looking to purchase a new laser pointer to use when camping. I'd like something with high beam visibility during the day, that doesn't require safety goggles to look at the beam (or dot from at least 100m away) and the capability to start a campfire in under a minute (with a lens if needed).

I'm leaning towards a green laser (for visibility) with 50-100 mW. But I'd like some additional advice on what a 150 mW green laser would offer me over a 50 or 100 mW laser. Is 50 mW too little for what I want? Is 150 mW too much?

Thanks in advance

Edit: Also, any particular advice on what company to buy from? Money is not too much of a concern.

 

[Razako]

Hi, I'll do my best here to answer your questions.

-Nothing will give you good beam visibility during the day.
-You won't be able to start a camp fire unless you got into the 2-3W range. No green lasers fall into that range.
-The part about not needing goggles to look at the beam or dot from 100mw is easy to achieve. With most lasers you'll be fine looking at the dot from 100mw away, and the beam is harmless to see even on higher powered lasers.
-You probably want a 100mw green laser if you want to use it for general pointing and such at night. I'd recommend the Sanwu lasers 304 as a good starting point. You can also check out the pointers on jetlasers or optotronics if you have a higher budget.

 

[Encap]

What Razako said + rep to R

 

[hiphiphooray]

Hi, I'll do my best here to answer your questions.

-Nothing will give you good beam visibility during the day.
-You won't be able to start a camp fire unless you got into the 2-3W range. No green lasers fall into that range.
-The part about not needing goggles to look at the beam or dot from 100mw is easy to achieve. With most lasers you'll be fine looking at the dot from 100mw away, and the beam is harmless to see even on higher powered lasers.
-You probably want a 100mw green laser if you want to use it for general pointing and such at night. I'd recommend the Sanwu lasers 304 as a good starting point. You can also check out the pointers on jetlasers or optotronics if you have a higher budget.

Thanks for the quick response.

Two follow up questions:
1. What are the upper limits before safety starts becoming a serious concern (like when does looking at the dot from about a foot away become dangerous)?
2. Even with a focusing lens I couldn't burn some kindling below 1-2W?

 

[Radim]

1. Power up to 5 mW is eye safe (if not mislabeled, IR filtered in case of 532 nm and if you do not intentionaly stare into the beam without blinking, observe it via optics etc.) above is not. Further it depends on various conditions. It is not wise to look at dot from one foot if you use higher powers.
2. I'm affraid it is not, but it depends on material you are trying to ignite. Even with 100 mW I can ignite match tip without focus lens.

 

[Encap]

Thanks for the quick response.

Two follow up questions:
1. What are the upper limits before safety starts becoming a serious concern (like when does looking at the dot from about a foot away become dangerous)?
2. Even with a focusing lens I couldn't burn some kindling below 1-2W?

All laser safety is a serious concern--in the hands of people who don't know what they are doing--the wrong hands.

Hand held laser sales are limited by FDA to lasers < 5mW in USA. See US FDA web site here: https://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/ucm478707.htm
"FDA regulations limit the visible light power of hand-held laser pointers to 5 milliwatts (mW). Even at the 5mW legal limit, a laser aimed directly into the eye can cause temporary flash blindness. This will not likely cause permanent injury, because most people have a protective reflexes such as looking away, blinking, or making other movements to protect the eyes. However, reflections of the laser beam from mirrors or metallic surfaces may not induce the protective reflex quickly enough to avoid injury. In addition, intentionally keeping your eyes open and staring into a 5 mW beam will cause eye injury. Lasers that emit more than 5mW visible light power can cause irreversible eye injury of increasing severity as the power increases"

You are much better off with a box of kitchen matches if you want to start a fire or a magnesium emergency fire starter like this one than a laser if you want to start a fire see: https://www.amazon.com/Genuine-Issue-Magnesium-Survival-Firestarter/dp/B0002X1IOM

See laser hazard chart here: http://www.lasersafetyfacts.com/resources/Laser-hazard-distance-chart.pdf

More information here: Laser classification table - Laser Safety Facts

 

[hiphiphooray]

Hey thanks for the responses. To clarify, I'm aware of the FDA regulations on 5 mW laser pointers. However this based on direct expsure to the eye. I'm strictly referring to the ambient, reflected light due to the laser speckle.

 

[Radim]

Hey thanks for the responses. To clarify, I'm aware of the FDA regulations on 5 mW laser pointers. However this based on direct expsure to the eye. I'm strictly referring to the ambient, reflected light due to the laser speckle.

Depends. Observing dot is dangerous at close distances. If we do not speak about invisible, blue and violet lasers, than let's say up to about 50 mW is quite comfortable IMO. 100 mW is a bit bright dot to be with you in one room. But it depends on many factors. But really this cannot be considered as advice not to use eye protection. You can have reflected beam hit, which might exceed 5 mW and blink reflex is not sufficient to protect you.

If you wish to use laser for illumination, consider some diverging lens.

 

[Encap]

Hey thanks for the responses. To clarify, I'm aware of the FDA regulations on 5 mW laser pointers. However this based on direct expsure to the eye. I'm strictly referring to the ambient, reflected light due to the laser speckle.

Is an imposible question--no way to answer it in any real world meaningful or responsible way.
What can anyone say other than if whatever you do and do it with doesn't damage you eyes it doesn't---if that is what you mean by "safe".

It is safe to say at the output powers you are considering i.e to ignite kindling, you need laser goggles.

If you want to play with dangerous games with dangerous lasers of whatever output power use appropriate laser goggles for eye safety reasons if you value your eyes, eyesight, and don't forget goggles for other people who may be with you.

 

[hiphiphooray]

Depends. Observing dot is dangerous at close distances. If we do not speak about invisible, blue and violet lasers, than let's say up to about 50 mW is quite comfortable IMO. 100 mW is a bit bright dot to be with you in one room. But it depends on many factors. But really this cannot be considered as advice not to use eye protection. You can have reflected beam hit, which might exceed 5 mW and blink reflex is not sufficient to protect you.

If you wish to use laser for illumination, consider some diverging lens.

Thanks. I will likely go for a 50-70 mW green laser. The main purpose will be for star gazing and observing the beam or dot from a distance.

A few more questions:
1. Is there any noticeable difference between 532nm and 520nm?
2. What company is recommend for a 50-70mW green laser? Preferrably one that is <250$ and has a long duty cycle.
3. Is there any battery life difference between rechargeable batteries and standard batteries?

 

[Radim]

You are welcome.
You can have also variable power. Look for Wicked lasers Evo, but they have quite a bad reputation as a company from problems in the past. But my experience with them was good. And I like Evo so much.

1. Yes, 520 nm is diode laser and 532 nm is diode pumped solid state frequency doubled laser. You can see there is much more complexity beyond the second from its type. More things might failure compred to diode, it is more temperature sensitive, less efficient, but with better beam specs - especially divergence, at low powers even 520 might reach to TEM00 IMO but for 532 nm TEM00 is typical - look up for TEM00 and other modes here to see what I mean. In terms of color 520 nm is considered to be more green (as by human perception), but I say it is more into blue compared to 532 nm. You can notice difference by eye easily.
2. I think you have some tips in posts above and search forum for that.
3. Depends on laser you select. For some only rechargable are available. But if you compare AA for example better are alkaline (lithiums are best) due to higher voltage.

 

[NightExplorer96]

To me 520nm and 532nm looks basically the same until you have them one by one next to each other and still, they look pretty darn similar. Interestingly enough, the camera captures the beams of both & dots as very different colors op:

Just visually however, 515nm and below is where you'd start to see an easily visible difference between the two!

-Alex

 

[Radim]

It depends how that particular camera handles it with RGB conversion IMO, for mine camera they look the same (or nearly the same). Both wavelengths are out of RGB colorspace.

Edit: See the correction of this post in discussion below. It is likely because of particular adjustment I made for a reason mentioned below again.

 

[NightExplorer96]

It depends how that particular camera handles it with RGB conversion IMO, for mine camera they look the same (or nearly the same). Both wavelengths are out of RGB colorspace.

Hmmmmm maybe the balance or something was off. :wtf:

-Alex

 

[Radim]

Not sure. I played a lot with RAW and I could not get significant difference of these two. Maybe I'll do some more experiments only with 520 nm and 532 nm to see what I can get. The fact is I did not tried only these two, so some adjustment combinations might have been omitted as I wanted overall laser wavelenghts used in my artworks to fit into RGB to capture human eye view as close as possible.

 

[Vision]

Long enough exposure and a dark room, you'll be able to see the difference.