Review of 1W 447nm laser pointer AliExpress wang yaochen's store $33.60

[zyxwv99]

No photos (no camera). No laser power meter. No spectrometer. No multi-tester.

This is what I really wanted but couldn't afford:

(a real 1W 447nm blue laser pointer with massive copper heat sink) http://laserpointerforums.com/f39/s...-501b-lasers-copper-heatsink-110-a-78452.html

This is what I actually bought:

AliExpress, from the land of Alibaba, where magic and stupendous bargains are yours for the asking! 445nm/447nm/450nm 1000mw/1 Watt Waterproof focusable blue purple laser pointer burning star pointer torch-in Laser Pointers from Office & School Supplies on Aliexpress.com

This same seller, "wang yaochen's store," is also offering a 20W (20,000mW) blue laser pointer for $266.

Ordered August 2, 2013
Arrived August 17, 3013
Total: 15 days (free shipping)

The packaging was very solid and sturdy. It came in an attractive gift box (7"x4"x1.5"), paperboard but very sturdy.

Laser dimensions: 5 1/2" long, 1" diameter at thickest part, 7/8" at thinnest part.

Unscrews into three parts:

1) Tailcap with button on it. 1.25" long. Aluminum. Button is orange silicone and glows in the dark.

2) Midsection. 4" long. Aluminum. Inside the front end, the laser module is visible, brass, about 3/8" diameter with very small aperture (less than 1/16") with something shiny like glass and a bit of yellow metal on one side inside the glass. Looking into other side (space for battery) I see little circuit board (driver) sticking out of black foam with spring on end.

3) Front part with lens. Lens looks like about 1/8" diameter, front aperture nearly 1/4" diameter. Aluminum.

Includes:

UltraFire BRC 18650 3500mAh 3.7V lithium-ion rechargeable battery with re/discharging protection circuit

Battery charger with light than turns green when you put in a battery that's already charged, red when you try to plug it in with a battery that's already charged.

This is a focusing laser. At five feet the dot can be focused down to on oval 1/8" by 1/4". A 5 feet one inch equals approximately 1 degree, so at this distance the dot is 7.5 x 15 minutes of arc.

It can light a match in two seconds without having to paint it black with a marking pen. It can burn holes in white paper, but the tiny flame is confined within the beam. It can make smoke come up from the side of telephone pole no matter what color the wood is. It can produce a painful sting when applied to the skin, but people pull away before any 1st-degree burns occur. I repeated the experiment on two cashiers at McDonalds. They both shouted "Ouch!" before jumping back and looking very surprised.

Throw: it can't shine as far as my 50mW 532nm green. It can hit a palm tree five backyards away. It can do reflective street signs a block away, but that doesn't really count.

Wavelength: the light looks blue most of the time, but deep violet at other times. Considering how many things in modern life are enhanced with Fluorescent Whitening Agents (FWAs) including paper, fabrics, manufactured doors, etc., a powerful 405nm laser would blue on most things too. Shined on anything dark, it doesn't just look indigo, but far violet. Just like 405nm. I pointed my 5mW 405nm unit alongside this one and asked a friend: "Do these look like the same color to you?"

The answer was, "Yup."

Now my big question is: how much power would a 405nm laser need to have in order to look as bright as what I have? According to "CIE 1931" a 405nm laser would need to be 6.7 watts to equal the visibility of a 5mW 532nm green. According to "Judd-Vos 1978 2-degree" it would need to be 926mW.

I'm going to compare it to a 5mW 650nm red. At five feet, focused on something non-fluorescent, they both look about the same. According to Judd-Vos 1978 2-degree a 405nm laser would need to be 22.980112538121200 times as powerful to look the same, and thus about 115mW.

So that's what I think I got for $33.60: 115mW 405nm focusing laser that can light matches and make people go "Ouch!"

 

[micaiah]

That's a great price for a fun gadget, but I would be curious to know what the actual output is with a LPM. I can't imaging that some of the other items this guys is selling would live up to their listings. A 20,000 mW laser pointer??!!!! I don't think so. I think all his listings have an extra zero in the power rating. Either way if your goal was to buy a cool little gadget for a cheap price I think you succeeded.

 

[MessiTom]

You should measure amperage at the tail cap

also,
you dont even have a cam phone??

 

[Leodahsan]

You could open the laser... and identify the diode. Its more cheap than a bare diode! If its a M140..... :eg:

 

[Kookapeli]

so it's a 115mW 405, not a 1W 445 ???

 

[Livinloud]

You could always send it to a member with a LPM, myself included, and have them meter it for you. Some members have a spectrometer as well, iirc ARG does but he is "international". Id be interested in buying one based on the results of yours so PM me if you want to work out a meter arangement

 

[zyxwv99]

I can't figure out how to open it up to identify the diode. I suppose there's another section the front of the main section that unscrews only that part is threaded (and probably glued in too). If I put a wrench or pliers on it, it will strip the threads.

Since it's a focusing laser, the beam can be expanded to about 15 degrees. Expanding the beam makes it easier to see the color, and I'm pretty sure it's 405nm. (If it were 447nm, I'd be jumping up and down for joy.)

As for sending it off to be metered, that just sounds like way too much work (although I'll look to see if there's anyone in my area). One of these days I'll have an LPM. Until then we just have clues. For example, I can see the Rayleigh scattering not only in complete darkness but even in near-darkness. However, I can't make out the color, just vaguely greenish, suggesting that I'm seeing it with scotopic rather than photopic vision.

 

[Encap]

Sounds like a 405nm and price is about right for a 100mw 405nm.

No way to tell without testing.

 

[Blaster]

From what you say its a lot more than 105 mW ..and violet you can bearly see violet so must be 445 nm sting straight away on skin Again more power than 105 mW ...to sting really fast think 300 mW at least from violet or blue i believe its probably around 500 mW range to ignite white paper even if only in small area it takes a lot to get white paper a lite at all

 

[zyxwv99]

If you focus it just right, the sting can be felt in about 1/3 second, not exactly instant but pretty quick, and powerful enough to be described as painful.

By the way, I think this would be a great assignment for a physics or engineering class: give them a handful of laser pointers of various wavelengths and power, then ask them to characterize each laser using only tools that would be available to the average person in an average household. Figure out the wavelength without a spectrometer (although you can cheat by finding out what wavelengths are commonly available). Estimate the power without a laser power meter by things like comparing visibility of an unknown with a known of another wavelength, throw, beam visibility, burning, sting on skin, etc.

 

[cantthinkofone]

Personally I don't think a school board would enjoy a class of immature kids with overpowered lasers. I don't. Maybe I'm wrong though

 

[zyxwv99]

Personally I don't think a school board would enjoy a class of immature kids with overpowered lasers. I don't. Maybe I'm wrong though

I don't know what kind of high school or university you attended, but you have a disturbingly vivid imagination. I can almost visualize graduate students at the Stanford Linear Accelerator Center (SLAC) jumping around and saying, "Betcha can't stand in front of the proton beam and count to ten!"

"Oh yeah? Watch this!"

ZAP!

Several decades ago, students in a physics class at San Francisco's Lowell High School built their own linear accelerator with $20,000 worth of donated parts. Schools like that win awards and have alumni who actually amount to something.

 

[cantthinkofone]

I don't participate but I know that the highschool in my city has a physics class. I wasn't saying that all are like that I'm just saying I don't trust kids with laser often.

 

[zyxwv99]

I think I know what you mean. Sometimes I answer questions about lasers on Yahoo! Answers. People there seem to be constantly getting hit in the eye with lasers and wondering why everything looks pink. Then they say things like, "Me and my friend were messing around, and I got hit in the eye for about 10 seconds." In other words, they're playing games to see who can stare into the laser the longest.

You wouldn't believe how many times I've told them to hurry to the emergency room of the hospital. If you're seeing pink, your retina is probably bleeding.