Re: [CAD_CAM_EDM_DRO] Re: Laser specs ? optics ?

Guys,

Running a laser at even a 1/1000 duty cycle can cause eye damage if the
power levels are high enough. Even a 10 mW red laser for 100
milliseconds can cause retinal burns if it is well focused.

Ordinary digital still cameras or cheap TV security cameras can usually
"see" an IR laser spot -- they show it as a white light. (BTW, that's
an easy way to tell if your IR remote controls are actually working or
not.)

There are also chemically treated plastic strips which can be charged
with room light, and which then will fluoresce orange in the presence of
an IR beam of the correct wavelength. Only problem is that after they
are discharged, they have to be recharged before they work again, so
they are not a safe indicator of the absence of the laser.

Don't know what sort of power levels you are working at, but it is easy
to buy fiber coupled IR laser packages with 1 or 2 watts of invisible
output power which are more than adequate to produce eye, or even skin
burns. By the time you figure out that you are getting a burn, the
damage can be permanent. (I know -- I do laser eye surgery for a
living.) I've seen eBay offers for these lasers where the seller is
burning paper with the unfocused end of the fiber. Only problem is
that even a 1% reflection at this kind of power level, say from a shiny
pool of melted plastic, can cause permanent retinal damage.

You can buy IR absorbing safety glasses which will give some measure of
protection, but they have to be matched to the wavelength of the laser
you are using, and you have to be aware of their attenuation
efficiency. Even if the glasses block 99% of the IR, a 2 watt laser
diode could still push 20 mW through the safety lens, plenty to make a
retinal burn.

HTH,

(Another) Dave

turbulatordude wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@...> wrote:
>
>> turbulatordude wrote:
>>
>>
>>> Hi all,
>>>
>>> Anyone know where one can get optics for lasers ?
>>>
>>> Only some small lenses really. I am looking at the optics in laser
>>> pointers and it seems they do not create a very focused beam. more of
>>> a tightly aligned group of dots.
>> is is laser "speckle". It is a characteristic of ALL lasers,
>>
> unless you
>
>> run the beam through a device called a spatial filter.
>>
>
> I tried looking at a laser pointer dot and it appears that the speckle
> I am looking at has more to do with the surface, than the beam. it
> looks more like a print, as if you took a sponge on some paint and
> just touched it to a paper. all kinds of lattice, (if lattice is the
> proper term)
>
> I am assuming it has more to do with the material surface, and
> reflections, than the optics.
>
> Seems there is a lot to learn about this technology.
>
>
>> I run the laser with a
>> pulse generator at a 1:1000 ratio,
>> so it doesn't harm my eyes.
>>
>> I don't understand what the pulse does, nor how that would have any
>> effect on your eyes.
>>
>> I guess that before too much more, I should look into some sort of
>> safety glasses. The laser beam is an IR diode. Any suggestions ?
>>
>> Also, since IR is not visable to the naked eye, any suggestions on how
>> to 'see' it so as to help with lenses and alignment and all that ?
>>
>> Dave