Name of phenomenon that causes laser spot to have a "texture"

[kecked]

Great set of posts. Enjoyed this.

[Photonbeam]

I disagree since you can change the size of the speckles with a pinhole... See my post below. The speckles are an interference pattern on your retina.

Ron

I was referring to subjective laser speckle.

[kecked]

Can you film the effect? If yes it isn't your eyes. Never tried. Here's another good one. Thinking the alignment of your projector is off because blue and red don't line up....Happens as you get older. Your glasses have just enough of a prism effect to mess with you.

[ronhip]

I was referring to subjective laser speckle.

I apologize, but I don't know what "subjective laser speckle" is. Can you enlighten me?

Ron

[hitekvoop]

you can use the pinhole effect to apply some correction to your vision as well. If you're a glasses wearer, take them off and find something far enough away that it's fuzzy. Now make a small pinhole with your fingers and move it around close to your eye. You'll notice edges become sharper and, in a pinch, you could even read something you wouldn't otherwise be able to.

[ronhip]

Can you film the effect? If yes it isn't your eyes. Never tried. Here's another good one. Thinking the alignment of your projector is off because blue and red don't line up....Happens as you get older. Your glasses have just enough of a prism effect to mess with you.

If you mean that the different color laser spots are different sizes, that's another optical effect in your eye - chromatic aberration. Different colors come to a focus at different distances from your retina. You can only focus on one color. For me, that's red. Blue is a larger smudge. When I've asked the ophthalmologist about this, he knew nothing about the effect. Hadn't ever heard of chromatic aberration! What are they teaching these guys? Apparently not optics, which is surprising given what they do...

Not lining up might be due to a prism effect in your glasses. I've never observed that one. I'll look for it!

Isn't it cool that you can see all these optical effects with lasers?

Ron

[kecked]

http://physics.stackexchange.com/que...tern-is-formed

It's very cool. and why I love lasers. Yes blue is a blob for me too.

BUT why is it not a blog from an ion laser.

[ronhip]

Can you film the effect? If yes it isn't your eyes. Never tried. Here's another good one. Thinking the alignment of your projector is off because blue and red don't line up....Happens as you get older. Your glasses have just enough of a prism effect to mess with you.

Sorry, just because you can film it doesn't necessarily mean that the effect is not in your eye. In the case of filming these effects, the phenomenon can also be ON THE FILM (or the CCD...)! Just like on your retina.

Ron

[ronhip]

http://physics.stackexchange.com/que...tern-is-formed

It's very cool. and why I love lasers. Yes blue is a blob for me too.

BUT why is it not a blog from an ion laser.

Ion lasers work fine. I first observed the chromatic aberration from the colors of an ion laser (krypton or mixed-gas argon-krypton) when I was doing Laserium. I was a fanatic about aligning the 4 colors from the 4 scanner sets to a single point on the dome (Morrison Planetarium in San Francisco, if you were wondering...) and noticed the blobiness of the result. Making a pinhole in front of my eye shrunk all the dots to the same size!

Ron

[Eidetic]

"Objective" speckle is the granularity one can see in a spot illuminated by an expanded laser beam. The specks don't move with changes in viewer perspective. "Subjective" speckle is the granularity that is seen in such a spot that does move with changes in viewer perspective. The viewer can be either a human eye or a camera. The size of the specks depends on the numerical aperture of both the illumination system and the viewing system. That's why subjective speckles look bigger if you look at the spot through a pinhole. Smaller apertures make bigger speckles. They're called "subjective" because their size depends on the viewer. The specks are not images of the rods and cones. They are areas of destructive interference on the surface of the retina.