Unfocused Laser Strikes Cat , reflection strikes me in th eye

[EpicHam]

Hello folks,
I was going for a walk by the seaside as usual.
Then I noticed there were movement on the beach, it was too small to be human... was kinda curious about what it was
I didn't have a flashlight with me , so i thought...
Well.. I guess an unfocused, uncollimated laser at distance is pretty much like a flashlight ,only with coherent wavelength right?

So.. I screwed the focussing lens off and shone it at the UMO (Unidentified Moving Object)

It turns out it was a cat at around 10m away, when I was about to turn it off, the cat turned towards my position and its the light strikes it in the eye and then reflected right back into mine.

Getting a bit of the faint flash blindness at the moment.
Should I be worried?

 

[csshih]

really? you're worried that a reflection from some other living being's eye has damaged your own?

 

[EpicHam]

really? you're worried that a reflection from some other living being's eye has damaged your own?

I mean.. if a puny human with horrible eyesight got a bit of flash blindness, what about the cat?
And of course, myself??

The cat didn't even look away when his head turned towards the uncollimated source...
I just assumed it didn't feel distressed?

 

[ryansoh3]

If it was unfocused, there is a very low chance of damaging the eye at 10m, don't worry about the cat or yourself.

 

[EpicHam]

If it was unfocused, there is a very low chance of damaging the eye at 10m, don't worry about the cat or yourself.

I'm really relieved ...
But MAN!!!
Its eyes lit up like a torch when his head turned towards me :O

 

[Things]

Yup, I've always got spiders in my house with reflective eyes too, they're creepy.

 

[EpicHam]

Yup, I've always got spiders in my house with reflective eyes too, they're creepy.

how do they like 1000mW of justice?

 

[Livinloud]

unfocused and without a lens are two different things depending on your laser. my 445nm without a lens is still a really tight beam while my 532nm without a lens is a HUGE cone shaped beam or really unfocused.

 

[EpicHam]

unfocused and without a lens are two different things depending on your laser. my 445nm without a lens is still a really tight beam while my 532nm without a lens is a HUGE cone shaped beam or really unfocused.

without a lens.
As in bare diode exposing in the air flinging around and the light coming out as a cone in an almost 60o fashion

 

[Sigurthr]

You should be fine, but the cat may have some damage depending on the irradiance at that distance.

 

[EpicHam]

You should be fine, but the cat may have some damage depending on the irradiance at that distance.

oh damn :twak:
But it wasn't even focused?

At 700mW and uncollimated.
It should be even less powerful than a regular flashlight right?

 

[Livinloud]

my 1.5W 445nm without a lens will still light a 2x4 on fire

 

[EpicHam]

my 1.5W 445nm without a lens will still light a 2x4 on fire

At 10m?

 

[ixfd64]

I once heard that cats' eyes have a higher threshold of optical damage (something like 50 mW compared to 15 mW for humans). But I could be wrong.

 

[Sigurthr]

Irradiance calculations are complex and I haven't done them in years.

You take the surface area of the eye and work out the energy deposition of the source at that distance over that surface area. Then you calculate the minimum spot size based on the action of the eye lens and determine if that level of irradiance is greater than established safe levels. You can make a more generalized effort by comparing the irradiance to that of the sun on a clear day at noon at sea level and using this as a maximum safe level.

Long story short it doesn't take much to cause some form of damage.

In your case the reflection from the cat's eye reduces the source energy deposition from that of the laser to that of the reflection of the laser (which includes the reduction in total light from initial source to that of reduced area based on the reflective surface).

The larger the target spot is in comparison to the the size of the reflective mirror the lower the total energy reflected is in relation to the energy of the source.

 

[Things]

I would have thought a cat's eye would be more susceptible to damage due to their larger pupil (at night anyway). Without a lens at 10m is nothing to worry about, and the fact the cat's eyes reflected a decent amount back means very little was probably adsorbed in the eye.