This is an observation I've made and wondered the cause (though i have an educated guess) when I get my laser at what appeares to be perfect focus, the red dot turns white. Am I right that this is exact focal-length, and what causes the change in the laser color?
Perfect focus...
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TorchBoy
Flashlight Enthusiast
This sounds like it could be entertaining any way it goes.
It's not a change in color it's apparent brightness is oversaturating your eye. that means you probably shouldn't be looking at it.
I test most of my lasers by setting them up in my lab, putting on my glasses for the laser and firing them against a white pice of posterboard on a rolling tripod or cart or whatever and start out @ 2 feet. I keep checking the dot size and slowly work my way out further and further until I'm satisfied.
If I want a specific focal point, I'll measure out the distance set the posterboard up there and focus the lense until it get the tiniest dot I can.
I usually need help with both.
I test most of my lasers by setting them up in my lab, putting on my glasses for the laser and firing them against a white pice of posterboard on a rolling tripod or cart or whatever and start out @ 2 feet. I keep checking the dot size and slowly work my way out further and further until I'm satisfied.
If I want a specific focal point, I'll measure out the distance set the posterboard up there and focus the lense until it get the tiniest dot I can.
I usually need help with both.
Corona
Enlightened
See the "don't look into laser with remaining eye" thread 
Seriously, Aseras is likely spot-on (err, sry), your retina has those rods & cones that determine what you see, rods are far more sensitive than cones (hence first to saturate) but do not have color response (as do cones).
You should find it difficult to look upon the "white" spot, as your aversion reflex should be causing you to instinctively avert your gaze. And as mentioned, there's a reason your brain wants you to NOT stare at it. And we should almost always listen to our brains.
If you look at the spot through a suitable optical attenuator or filter, it will look red again. Another way is to shine the spot onto a neutral translucent surface (that will diffuse the beam, something like a white plastic kitchen cutting board), focus the spot to where it looks white (careful with that good eye) and then look at the reverse side of the surface. The diffused spot will be lower in peak intensity and again appear red.
Seriously, Aseras is likely spot-on (err, sry), your retina has those rods & cones that determine what you see, rods are far more sensitive than cones (hence first to saturate) but do not have color response (as do cones).
You should find it difficult to look upon the "white" spot, as your aversion reflex should be causing you to instinctively avert your gaze. And as mentioned, there's a reason your brain wants you to NOT stare at it. And we should almost always listen to our brains.
If you look at the spot through a suitable optical attenuator or filter, it will look red again. Another way is to shine the spot onto a neutral translucent surface (that will diffuse the beam, something like a white plastic kitchen cutting board), focus the spot to where it looks white (careful with that good eye) and then look at the reverse side of the surface. The diffused spot will be lower in peak intensity and again appear red.
nope, with laser goggles it still turns white.
My guess is I'm not seeing the endpoitn of the beam as much as a near-microscopic spark from where it's burning the paper/etc. though that's just my guess... though I dont knwo wnough about the eye to rule out if it is over-saturation...
My guess is I'm not seeing the endpoitn of the beam as much as a near-microscopic spark from where it's burning the paper/etc. though that's just my guess... though I dont knwo wnough about the eye to rule out if it is over-saturation...
TorchBoy
Flashlight Enthusiast
You'd have to have very expensive optics and very rigid mounting to get a microscopic focussed point. How much of an afterimage do you get in your vision?
2xTrinity
Flashlight Enthusiast
If the "white" is from sparking/burning, it should be detectable without looking directly at it, perhaps by looking with a spectroscope or diffraction grating and seeing if there are any other components emitter other than just red.
Corona
Enlightened
Could actually be ionizing the nitrogen in the air, if the power level is high enough at the focal point to do so. If it's a surface the surface itself could be exited into fluorescing, also.
would be interesting to fill a glass jar with argon (or argon-CO2 welding gas) and shoot through the glass, focusing inside the argon atmosphere. The spot should be a bluish color then.
Since you have and are using goggles, I assume this is a high power laser...so...what is the power level??
would be interesting to fill a glass jar with argon (or argon-CO2 welding gas) and shoot through the glass, focusing inside the argon atmosphere. The spot should be a bluish color then.
Since you have and are using goggles, I assume this is a high power laser...so...what is the power level??
no pointer is going to ionize anything no matter how much you focus it. I can barely do it with with multiwatt lasers.
Any dot through laser glasses are going to appear white or another color tinted by the color of the optic, usually you see the florescence of the material you are hitting ( which is why you can see the laser light that isn't blocked ) and not actual laser light. Try moving your dot along a wall, hit your light switch, the door frame, the door, celing fan whatever. every single one of them will look diffrent for no other reason.
Any dot through laser glasses are going to appear white or another color tinted by the color of the optic, usually you see the florescence of the material you are hitting ( which is why you can see the laser light that isn't blocked ) and not actual laser light. Try moving your dot along a wall, hit your light switch, the door frame, the door, celing fan whatever. every single one of them will look diffrent for no other reason.
The white is visible form all angles, that's why I believed it to be the spark, and it flickers asif it were a spark. (will try sometime to get it on film, but I dont think my digicam is good enough) It's white with OR without the goggles (yes, I know I shouldn't be using it without goggles...)
It's a ~135mw (WL Pulsar 125 rated at <150mw, and most tests show them to be ~135) however I also get the same result from my 200mw atek (rated @ >200mw) though I cant replicate that ATM because the atek's batteries are dead...
@ torchboy: How does one measuer afterimage? yes, I get one that lasts a bit, though with my goggles on I dont...
It's a ~135mw (WL Pulsar 125 rated at <150mw, and most tests show them to be ~135) however I also get the same result from my 200mw atek (rated @ >200mw) though I cant replicate that ATM because the atek's batteries are dead...
@ torchboy: How does one measuer afterimage? yes, I get one that lasts a bit, though with my goggles on I dont...
TorchBoy
Flashlight Enthusiast
You could time yourself looking at a blank wall or ceiling.
Corona
Enlightened
Up until after your post there was no mention whether this was a "pointer", industrial laser, or what. Which is why I asked:Aseras said:
Corona said:
Umm, yeah.Aseras said:
Corona said:
