Mysterious Tiny Spots in a Laser Spot

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In summary, the tiny spots seen inside a laser spot on a wall are called speckles, which are interference fringes formed in the eye from different distances. This is due to the coherent nature of laser light, which allows for interference and cancellation. LEDs can also produce similar effects, as they have monochromatic light but are not as coherent as lasers. These speckles have led to advancements in technology, such as holograms.
  • #1
YellowTaxi
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Does anyone know what those tiny spots are you can see inside a laser spot on a wall. They seem arranged something like a honeycomb - hexagonally packed tightly against each other.

They seem to follow the motion of your head around when you see them too, so I guessed that maybe I'm seeing my own retina - the rods and cones inside the back of my own eye ? Is that what they are ?

cheers
 
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  • #2
They are called speckles - there are interference fringes formed in your eye from different bits of wall that are a whole or half multiple of the wavelength difference in distance
 
  • #3
The reason you seem them for a laser beam and not for an ordinary beam of light is that the laser light is coherent (the waves are all in step, so they can actually interfere with each other). In non coherent light, the waves are in random phases so you will not get addition and cancellation in any particular place.
We had to wait for someone to invent a good laser before we could make holograms of objects, which rely entirely on the coherence for the formation of a visible, photographable interference (diffraction) pattern.
 
  • #4
Right, that's a bit complicated though..

I noticed I saw much the same thing (speckles) last night , there was an LED glowing in the corner of the room just before I went to bed, and it gave the same or a very similar effect to a laser spot speckle. So can LEDs cause the same fringes when you look straight into them ?
 
  • #5
Yes, LEDs and lasers are pretty similar - the light is still monochromatic thought not as coherent.
 
  • #6
thanks
 

What are mysterious tiny spots in a laser spot?

Mysterious tiny spots in a laser spot refer to small, unexplained spots that can appear in the focused area of a laser beam. These spots may be seen as a deviation from the expected uniformity of the laser beam and can be a cause of concern for scientists and researchers using lasers in their experiments.

What causes mysterious tiny spots in a laser spot?

The exact cause of these spots is not fully understood, but they may be a result of imperfections or impurities in the optical components of the laser system. They can also be caused by dust or other particles in the air that interfere with the laser beam.

Are mysterious tiny spots in a laser spot harmful?

In most cases, these spots are harmless and do not affect the performance of the laser. However, if the spots are particularly large or numerous, they can decrease the precision and accuracy of the laser beam, which can be a concern for certain experiments or applications.

Can mysterious tiny spots in a laser spot be prevented?

While it is difficult to completely prevent these spots from appearing, they can be minimized by regularly cleaning and maintaining the optical components of the laser system. Using high-quality, clean optics and keeping the environment free of dust and other particles can also help prevent the appearance of these spots.

Is there a way to remove mysterious tiny spots in a laser spot?

There is no effective way to remove these spots once they have appeared. However, if they are causing significant issues, the laser system may need to be recalibrated or the optical components may need to be replaced. If the spots are caused by particles in the air, improving air filtration systems can help reduce their appearance.

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