5mW laser pointers

Thread Starter

Solderman

Joined Mar 3, 2012
8
I ordered 5 5 mW laser module's on DealExtreme.com, I am wondering if any body has made a pen into a laser pointer and when you click it the laser comes on? Well since I ordered 5 I am going to try it. I plan to use very small button cell batteries that will fit in the pen and have to cut away the tip of the pen so the laser pokes through. Then for the button I will either buy a small button at radio shack or put a thin piece of wire on the bottom notches on the pen and then put one on the top notches across from each other and do that with every other one. Please tell me if you think it will work, and I did't get them yet so I cant show u any pictures but once I am done I will post pics.
 

Wendy

Joined Mar 24, 2008
23,415
5mw are toys. Higher wattages are not.

Laser diode strongly resemble LEDs, but aren't. You will probably need a current regulator of some sort, even a minor surge will blow these parts.

Why are you trying to DIY when the finished products are so cheap?

Instead of a RS switch, when all tend to be as large as they get, think something like a tactile switch, which is momentary contact.

Here is an example of one.



http://www.bgmicro.com/14incherwith18incherredpusher100900.aspx

The part is ¼" X ¼"
 

bertus

Joined Apr 5, 2008
22,270
Hello,

Laserpointers of 5 mW can do great harm to the eyes.

Even a 1 mW laser pointer is already dangerous, see this quote:

Intensity of a 1 mW Laser versus the Sun

Here is a comparison between the maximum intensity on the retina of the Sun and the beam from a 1 mW HeNe laser. (Adapted from one of Simon Waldman's optics lectures.)
Standard Sun:

Maximum intensity of sunlight at ground level (directly overhead, no smog, etc.) = 1 kW/m2 or 1 mW/mm2.
Assuming pupil diameter is 2 mm (i.e., radius of 1 mm), the area is approximately 3 mm2. So, the power of the sunlight through the pupil = 3 mW.
Focal length of eye's lens = approximately 22 mm. Angular size of Sun from Earth = 0.5 degree = 9 mR. Thus, diameter of image formed = 22 mm x 9 mR = 0.2 mm and the area of image = 0.03 mm2.
The intensity of the Sun on the retina (Power/Area) = 3 mW/0.03 mm2 = 100 mW/mm2.
Typical 1 mW HeNe laser (or laser pointer):

Power (P) = 1 mW, wavelength (l) = 633 nm, radius of beam (w) = 1 mm, focal length of eye (f) = 22 mm. So, the diameter of spot = (2 x f x l)/(w x pi) = 9 x 10-3 mm and the area of spot = 6 x 10-5 mm2.
The power density of the HeNe laser on the retina is 1 mW/(6 x 10-5 mm2) = 16,667 mW/mm2 = 16.667 watts/mm2.
So the 1 mW laser has the potential to produce an intensity on the retina 167 times that of direct sunlight! But there are many more factors to consider in determining the real risk of damage. In addition to those noted below, the actual focal point when looking at a laser at close range will not be at the retina so the spot size will most likely be much larger than the diffraction limit of the calculation. Even if the spot from the laser beam is smaller, natural eye movements or movement of the source (e.g., some moron waving a laser pointer) will result in it hitting any given point for a shorter time than the larger spot from the Sun (which usually doesn't move very quickly).

But, at least, perhaps you'll now have a bit more respect for that little HeNe laser or laser pointer!

(From: Jim Webb )

The real problem behind this is that it is assumed that the power density is the significant factor in the thermal damage mechanism. The ability of the retina to dissipate heat is not dependent on the area covered, but the periphery (circumference) of the exposed area! The blood vessels are in the retina and not the sclera (the surface under the retina) - it is the blood flow that dissipates the heat and so can only act on the *edge* not the middle of the exposed area. In circumference terms, the ratio drops to 7 times. Furthermore because the larger spot is less efficient at dissipating heat, the effective power delivered by the laser beam is only about 2 times greater than that of the spot formed by the sun.
This quote is from the laser sfaty page of sams FAQ:
http://www.repairfaq.org/sam/lasersaf.htm

I would say stop playing dangerous.

Bertus
 
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