Old 01-15-2013, 01:39 AM #17
Class 4 Laser
 
Join Date: May 2007
Location: Queensland, AU
Posts: 7,549
Rep Power: 2560
Things has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond repute
Things Things is offline
Class 4 Laser
 
Join Date: May 2007
Location: Queensland, AU
Posts: 7,549
Rep Power: 2560
Things has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond reputeThings has a reputation beyond repute
Default Re: Why does laser light look like little particles moving about?

Quote:
Originally Posted by tommmtom View Post
Just curious, not sure if it's just me, why does laser light appear to be little particles on the surface you point it at?
Reading is the key



Last edited by Things; 01-15-2013 at 01:40 AM.
Things is offline   Reply With Quote


















Old 01-15-2013, 02:04 AM #18
TomD's Avatar
Class 1M Laser
 
Join Date: Apr 2012
Location: Metro Manila
Posts: 123
Rep Power: 68
TomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond repute
TomD TomD is offline
Class 1M Laser
TomD's Avatar
 
Join Date: Apr 2012
Location: Metro Manila
Posts: 123
Rep Power: 68
TomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond reputeTomD has a reputation beyond repute
Default Re: Why does laser light look like little particles moving about?

Quote:
Originally Posted by Things View Post
Reading is the key
Silly me. Overeager with my photo there.
TomD is offline   Reply With Quote
Old 01-18-2013, 08:12 PM #19
pschlosser's Avatar
Class 2M Laser
 
Join Date: Dec 2012
Location: Santa Rosa, CA
Posts: 909
Rep Power: 66
pschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond repute
pschlosser pschlosser is offline
Class 2M Laser
pschlosser's Avatar
 
Join Date: Dec 2012
Location: Santa Rosa, CA
Posts: 909
Rep Power: 66
pschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond reputepschlosser has a reputation beyond repute
Default Re: Why does laser light look like little particles moving about?

The speckle pattern is easier to see and photograph when viewing the secondary reflection.



If you take the output of a HeNe laser, bounce it off surface A, and onto surface B. What you see on surface B looks much like the photo. As long as the surfaces and the light source are stationary, the speckles will not move or change. However, you will see secondary speckles that do move. Speckles within the speckles.

The photo (above) was apparently taken by bouncing the beam off the back of a cellphone (plastic surface) and on to a wall.

It is funny this comes up, because I have memory of a phenomenon that I want to demonstrate to my kids, but have failed. When viewing the spot on a wall from a red HeNe laser, if I slowly rotate my head to the right while keeping my gaze focused on the spot, I see the speckles moving to the left. No surprise, you might say. Light enters my eye and gets inverted by the lens. Thus, on the back of my eye, things are inverted across my retina.

But here is the kicker. I recall looking at a different wavelength of light from a different laser, and noting the speckles move up and down, as I rotate my head to the left and right. But, for the life of me, I've been unable to recreate this phenomenon for my children. I originally saw this 20 years ago, so maybe my memory is failing.

I've only worked with a few kinds of gas lasers, in the past. If I am remembering correctly, this could only have occurred with a HeCd, Kr or an Ar laser. My money is on the Argon laser. I'm looking for one, btw.
pschlosser is offline   Reply With Quote
Old 01-18-2013, 10:32 PM #20
Teslanium's Avatar
Class 1M Laser
 
Join Date: Feb 2012
Location: California USA
Posts: 130
Rep Power: 15
Teslanium is a splendid one to beholdTeslanium is a splendid one to beholdTeslanium is a splendid one to beholdTeslanium is a splendid one to beholdTeslanium is a splendid one to beholdTeslanium is a splendid one to beholdTeslanium is a splendid one to beholdTeslanium is a splendid one to behold
Teslanium Teslanium is offline
Class 1M Laser
Teslanium's Avatar
 
Join Date: Feb 2012
Location: California USA
Posts: 130
Rep Power: 15
Teslanium is a splendid one to beholdTeslanium is a splendid one to beholdTeslanium is a splendid one to beholdTeslanium is a splendid one to beholdTeslanium is a splendid one to beholdTeslanium is a splendid one to beholdTeslanium is a splendid one to beholdTeslanium is a splendid one to behold
Default Re: Why does laser light look like little particles moving about?

The direction of movement of the speckle pattern depends on your movement (if any) and whether/ how far your eyes are focused in front of/behind the surface. I have found that the speckle pattern moves one way when my eyes are focused closer to me from the surface while I am moving, and moves in the opposite direction if my gaze is focused beyond it while I am moving (unless I reverse direction simultaneously). If I focus at the surface the granular appearance changes but not with a directional shift, a random kind of "boiling" motion.

Fun to play with this phenomenon!

T.
__________________
Current lasers:
594.1nm 1mW HeNe from Particle Measuring Systems
Various 532nm pointers
532nm 200mW Optotronics pointer
532nm 500mW "Optotronics Viasho GB"
650nm 150mW "Senkat"
460nm 100mW (84mW peak) Skylaser GB DPL
405nm 400mW (499mW peak) Skylaser GB DPL

Non-operating:
632nm 20mW multimode Melles Griot HeNe
Multiline 20-80mW aircooled Ar-Ion

"That's WAY too bright!" "Yep... and your point is...?'"
Teslanium is the poster formerly known here as Ragnarok.

Last edited by Teslanium; 01-18-2013 at 10:35 PM.
Teslanium is offline   Reply With Quote
Reply





Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

























Privacy Policy | Advertising Disclaimer | Terms of Use


 


All times are GMT. The time now is 10:08 AM.


Powered by: vBulletin
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO
Privacy Policy | Advertising Disclaimer | Terms of Use
Copyright (C) 2017 Laser Pointer Forums, LLC