[Ronja] Make Magazine: hacking DVD-burner lasers - works for RONJA?

[Gyurkó Martin]

Hi All!

I got a lot of bad DVD burners because mostly the LD is not broken and I 
wanted to extract these and use for the 100Mbit/s network.
I then faced the big problem of finding out, how the leads have to be 
connected. So if anybody wants to use the LD of a DVD burner, first test 
it  out _without_ dissassembling the pickup head! Also the currents 
would be interresting.
It is not true, that evey burner diode has the same pinout.

The fact is, if you don't collimate laser diode light, it is almost like 
a very bright LED.
So you have a point-like very high power light source.
If you only collimate it with the 130mm diameter lens, then you will 
have a beam power density of:
p= 200mW / (65^2 * pi ) = 0.015 mW/mm^2
Let's take an eye, with a maximum open lens iris of 10mm diameter, (A = 
78,5mm^2).
That is a total power of
P= A*p = 1.183 mW

Here we see, that with a perfectly collimated beam, the power is 
slightly above the 1 mW Class-I limit at the exit of the tube at a 130mm 
assembly. So if you are looking into it, then normally there would not 
be any damage, because the iris is never open at 10mm.
Also the laser doesn't need to be operated at the highest power. Only 
use as many power as you really need to establish connection.

The real problems begin, if your setting gets wrong, and the beam gets 
focussed!
Also dont use it with smaller lenses! The power density would increase!

This guy, using the flashlight lens, which has a diameter of 20mm, is an 
idiot. That thing is really irresponsible.

bye,
Martin



Karel Kulhavy írta:
> On Thu, Aug 09, 2007 at 01:18:58AM -0600, Colin Stanners wrote:
>   
>> I saw in Make magazine 10 an article about modifying dvd-burner lasers
>> to use as "laser pointers". These devices work at ~200mw and must have
>> very impressive specs speed-wise to be able to burn DVDs... since
>> a big problem for 10mbit RONJA is getting fast and inexpensive RX/TX
>> hardware, would these work?
>>     
>
> Well yes a 200mW laser diode would be technically fine. But you need quite
> careful optical and mechanical setup to ensure eye safety even in case of
> failure. Remember Ronja is operating in an open space.
>
> But do you need to buy a DVD burner and smash it with a hammer?  Why not just
> go to an electronic part store and buy just the 200mW diode?
>
>   
>> Also a story just appeared on Slashdot about this, which reminded me to
>> send you this message... they may have more details.
>>     
>
> I didn't even watch the video. The guy is an idiot. If he hits someone's eye,
> either directly or with an accidental reflection, the target gets a permanent
> dead spot burned out in his retina. Then the damaged one sues his ass off and
> Mr.  Laser goes to jail for permanent health damage. Someone should call the
> police now because this is endangering the public health even if performed at
> home - you can burn out an eye of a by-passer in the street through the window.
> It's in the public health interest to have this guy arrested before someone
> gets handicapped from this.
>
> Next time slashdot could feature a mad gunman or a guy throwing grenades in the
> street.
>
> CL<
>
>   
>> -C
>>     
>
>