Question on laser reflection (pic included)

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    Laser Reflection
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Discussion Overview

The discussion revolves around the observation of different output widths from three lasers of varying wavelengths (656 nm, 532 nm, and 405 nm) projected onto a wall. Participants explore potential optical properties and human perception factors that might explain the observed phenomenon, particularly the wider output of the green laser compared to the others.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes the significant difference in output width of the green laser compared to the red and blue lasers and questions the optical properties that could explain this.
  • Another participant inquires whether the extra brightness was visible to the naked eye or only in the camera image, suggesting that there are significant reasons behind the observation.
  • A later reply confirms that the extra brightness was indeed visible to the naked eye, indicating that the camera image did not capture the full detail.
  • One suggestion is to check if the lens on each laser is clean, as smudges could affect the output.
  • Another participant points out that human eyes have a sensitivity peak around green light, which may explain the perceived brightness differences, while sensitivity for 405 nm is at the edge of the visible range and 656 nm is less sensitive.
  • It is mentioned that cameras also have increased sensitivity to green light, which could influence the observed differences in brightness.

Areas of Agreement / Disagreement

Participants express various viewpoints regarding the reasons for the observed differences in laser output, with some focusing on optical properties and others on human perception. There is no consensus on a singular explanation, and multiple competing views remain.

Contextual Notes

Participants reference the need for further research into eye and camera sensitivities, indicating that the discussion may depend on specific definitions and assumptions about light perception and optical behavior.

TRB8985
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Good morning all,

I'm currently working in some undergraduate research involving lasers and recently had the opportunity to play around with a few that my research professor has at our disposal. I've included a picture below of a strange phenomenon that has me a little puzzled, but then again I haven't taken any optics courses.

https://scontent-ord1-1.xx.fbcdn.net/hphotos-xat1/v/t1.0-9/12509680_10156372942255580_8733921899061724202_n.jpg?oh=6d59dee08a311015be6e8811bd211c64&oe=573793A9

While the quality of the image isn't the best, what I've done is place the outputs of three 90 mW lasers of 656 nm, 532 nm, and 405 nm up on a wall located in a room with very little to no textural disturbances on the surface of the wall. I can't seem to understand why the green laser would have such an enormously wide output compared to the two others.

Is there a property in optics that might explain this? I thought maybe diffuse reflection would be greater for longer wavelengths or something along those lines, but the red laser would have to display that property too, so I'm a little stumped.

Any ideas?
 
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TRB8985 said:
what I've done is place the outputs of three 90 mW lasers of 656 nm, 532 nm, and 405 nm up on a wall located in a room with very little to no textural disturbances on the surface of the wall. I can't seem to understand why the green laser would have such an enormously wide output compared to the two others.

Question to you
was this extra brightness just visible in the camera image ? or visible directly by eye as well ?

There are some significant reasons ...
... ohhh and to help you in your quest ... google search eye and digital camera sensor sensitivitiesDave
 
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Hey Dave,

This extra brightness was also visible via the naked eye as well, and is especially more pronounced. Unfortunately, none of the crazy reflective detail translated to the photo.

Thanks for your recommendations!
 
First thing I would do is make sure the lens on each laser is clean and free of smudges, dirt, etc. It could be something as simple as a smudge on the green laser that's causing it.
 
Or batteries?
 
Humans eyes have their sensitivity peak around green, while 405 nm is at the edge of the visible range and the sensitivity for 656 nm is worse as well. That explains a large part of the observed difference. Cameras are more sensitive to green light as well to improve image quality, but image processing takes care of this.
 
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mfb said:
Humans eyes have their sensitivity peak around green, while 405 nm is at the edge of the visible range and the sensitivity for 656 nm is worse as well. That explains a large part of the observed difference. Cameras are more sensitive to green light as well to improve image quality, but image processing takes care of this.
yes and this is what I was wanting the OP to google research on and he would have discovered that :smile:Dave
 

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