Help to choose a laser pointer for daylight use

[Mikk0]

Hello.:yh: I hope this thread goes in to right category.

My friend who is going to be ab architecture teacher (building restauration) and asked me to suggest him a laser pointer. He is going to need it to show students the details of buildings (outside and inside) in daylight.
I've read that at least 35mW is needed for daylight use but could not suggest him anything because I have not lot experience with lasers. So I'm asking you to suggest an affordable green/blue laser pointer.

Few requirements: laser spot must be visible in daylight at least 20m and should (preferably) run on primary batteries (AA,AAA). Also, pencil shape body is preferred.

Thanks in advance, Mikko

 

[RA_pierce]

I'd suggest 50-100mW at least.
After all, the Sun is the brightest object in our solar system so you are competing with a lot of light.

If your friend is on a budget, he can try this:
Silver chrome green laser 100mW/good finish [OLSGL100] - $69.66 : Welcome to O-Like.com, Your source for laser products
It should at least be ~80-90mW of green.

O-like is a pretty honest company but the power ratings typically do not exclude the light that is excess infrared. That is, even though it says "100mW" only 80-90% of it is actually useful green light.

If your buddy can afford something a little better, I would recommend:
X75 Compact Portable >75mW Laser - X-Series - Novalasers Inc. (which seems to be out of stock at the moment)
or the 75mW or 95mW variant from here:
Green Laser Pointer ----- 532nm Laser ----- Viper Series Lasers :: Handheld Lasers :: Dragon Lasers

Personally, I prefer to spend a little extra and get the higher quality lasers.
The reason is: NovaLasers and Dragonlasers both sell CNI products (one of the best Chinese laser pointer manufacturers) which are IR filtered and typically have better divergence and more reliable power.
This means that you get the power that you pay for (usually a little bit more) with no excess infrared light and the beam will travel farther without diverging (expanding) as much.

 

[Mikk0]

Thanks for the reply. The lasers you suggested lasers are very nice but what about those cheaper chinese lasers like: "DX True 100mW Green Laser Pointer Pen" or "200mW 532nm UltraFire WF-502B Flashlight-shaped Green Laser " ? I know that the quality is lower, but they seem be at least half power what they advertise.

 

[RA_pierce]

Thanks for the reply. The lasers you suggested lasers are very nice but what about those cheaper chinese lasers like: "DX True 100mW Green Laser Pointer Pen" or "200mW 532nm UltraFire WF-502B Flashlight-shaped Green Laser " ? I know that the quality is lower, but they seem be at least half power what they advertise.

They may be close to the advertised power but the problem is not only power but stability as well.

Since 532nm green lasers are DPSS, they are sensitive to minute changes in wavelength and therefore, temperature.
As the laser warms up, the diode that pumps the crystals (in a DPSS laser) may shift wavelength.
for 532nm DPSS, the crystals lase at maximum efficiency when pumped with 808nm light. If the pump diode's wavelength strays too far from 808nm, the efficiency will drop significantly. This is common with cheap lasers that are not built with very good quality components. Aside from that, they sometimes die an early death or the beams shoot out at an angle and scatter off the aperture making a useless smear of light...
There are plenty of other things that can affect performance and I've been surprised in the past by how awful some of these lasers really can be.

For this reason, it is a gamble when you buy the cheapies.
I've tried many different cheap lasers and sometimes they turn out alright but typically they are garbage and virtually useless without some significant adjustments.

With diode lasers like 405nm violet and 660nm red, the construction is much simpler so there are fewer things that can go wrong. 532nm DPSS green lasers are more complex and require careful assembly if it is to work reliably.

The rule is, "you get what you pay for."
I would recommend staying far away from sites like DX if you want anything more than 50mW.
O-like.com is probably going to be the best quality for the price and they are decent.

I also suggest looking around the buy, sell, trade section to see if anyone is offering something that could work.