LED Light - Beam Charactoristic?

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Discussion Overview

The discussion revolves around the beam characteristics of high-powered LED lights, particularly the presence of bright and dimmer sections along the beam when projected through air. Participants explore potential explanations for this phenomenon, comparing it to HID beams which do not exhibit the same behavior.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that the observed variations in brightness could be due to the lenses or reflectors in the flashlight creating a convergent beam rather than a divergent one.
  • Others question how a convergent beam could produce multiple bright spots at regular intervals, indicating a need for further explanation.
  • Variations in fog density are proposed as a possible factor affecting the beam's appearance, although some participants note that the air does not appear visually foggy.
  • One participant speculates that the phenomenon could be a common occurrence related to environmental conditions, as similar observations have been reported in different locations.
  • Another viewpoint suggests that imperfections in the LED reflector, such as varying curvature, could lead to different focal lengths, resulting in uneven brightness across the beam.
  • Participants express curiosity about why this effect is more pronounced in LEDs compared to HID beams, prompting further inquiry into the differences between the two types of lighting.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the cause of the observed beam characteristics, with multiple competing explanations and uncertainties remaining in the discussion.

Contextual Notes

There are limitations in the discussion regarding the lack of specific measurements or experimental setups to validate the proposed explanations. The assumptions about environmental conditions and the characteristics of the light sources are not fully resolved.

Tea Jay
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For some of the high powered LED lights, the beam seems to have bright and dimmer sections along its length when projected through air.

They seem to be regularly spaced rather than random. Some people have described it as looking as though the beam would get thinner and wider along its length.

It was not observed (noticed) for HID beams for example...just for high powered LED.


What would be an explanation for that?

Off hand, I wondered if it were some sort of resonance/harmonic between the emitter frequencies and the media or wavelength of the light?
 
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It's probably just the lenses or reflectors in the flashlight making a beam that is convergent rather than divergent.
 
How would that make the beam cross over more than once though?

IE: If it had one bright spot in the middle somewhere...I could se that...but what would be happening for the beam to have a spot like that every so many meters, etc?
 
Variations in fog density?
 
Delta Kilo said:
Variations in fog density?
Yeah, that would be a media issue...but its not visually foggy at least...albeit I'm sure there is plenty of vapor in the air nonetheless.

It would need to be a regularly spaced interval of vapor to explain people in Australia and NJ and TX describing the same thing...but no one measured it specifically...so it could be a common, habitat phenomenon.

Why would this affect an LED, but not an HID beam though?
 
If the reflector of the LED is not well finished (varying curvature across its diameter) then you can expect a number of focal lengths to be involved. It looks that different bits of your beam are focussed at different points. I think you probably get what you pay for.
 
Tea Jay said:
Yeah, that would be a media issue...but its not visually foggy at least...albeit I'm sure there is plenty of vapor in the air nonetheless.

It would need to be a regularly spaced interval of vapor to explain people in Australia and NJ and TX describing the same thing...but no one measured it specifically...so it could be a common, habitat phenomenon.


well it may not be fog, but there is something there else you wouldn't be seeing the beam being reflected back to you as it is. so its water vapor, dust ... something ??
and variations in that media is going to cause variations in the brightness of the beam along its length as its reflected back to you


Why would this affect an LED, but not an HID beam though?

dont know, set up your experiment again so we can see both beams going out side by side


Dave
 

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