Possible to make speckles without a Laser?

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Discussion Overview

The discussion revolves around the possibility of creating speckles on a surface using light sources other than lasers, specifically exploring the use of LEDs. Participants examine the nature of speckles and the conditions required for their formation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Hans inquires whether speckles can be created on a surface using an LED, referencing the use of a Michelson Interferometer to achieve interference patterns.
  • One participant seeks clarification on the definition of "speckles," asking if it refers to colors or physical pits on a surface.
  • Hans clarifies that he is referring to pits in the surface.
  • Another participant notes that speckles occur when coherent light interacts with a diffuse reflecting surface and questions the feasibility of obtaining coherent light from an LED.
  • Hans expresses uncertainty about how to achieve coherence with an LED.
  • A later reply suggests that speckles can be generated from any light source, including sunlight, and mentions the need for spectral filtering to enhance contrast.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the methods for generating speckles with LEDs, and multiple viewpoints regarding the feasibility and requirements for coherence remain present.

Contextual Notes

There are unresolved questions about the specific conditions necessary for generating speckles with non-coherent light sources and the implications of using different types of light.

Who May Find This Useful

This discussion may be of interest to individuals exploring optical phenomena, experimental physics, or those involved in optics and photonics research.

darthw
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Hello,
it is possibile to make speckles on a surface with a LED or something else? With a Michelson Interferometer you can get interferences with an LED -> are this already speckles?

regards,
Hans
 
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what do you mean by "speckles" ? Do you mean just colors on the surface or do you mean pits in the surface ?
 
Hello,
I mean the second one, this pits in the surface
 
You get speckle when coherent light hits a diffuse reflecting surface. Can you think of a way to get coherent light from an LED?
 
right now, no...I don´t know how to realize this :frown:
 
darthw said:
Hello,
it is possibile to make speckles on a surface with a LED or something else? With a Michelson Interferometer you can get interferences with an LED -> are this already speckles?

regards,
Hans

Sure- since speckle is a measure of spatial coherence, you can create speckles with any source. You can image speckle generated by sunlight: the speckles are about 0.06 mm in diameter and you need to spectrally filter the light to get good contrast.

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-37-17-3516
 
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Hello,

that sounds great. I´m trying to build up this experiment.
thx
 

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