Sun Visible With 3D Laser Scanning?

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AnthonyM
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Sun Visible With 3D Laser Scanning?

Post by AnthonyM »

Hi,
This isn't about any specific problem, more of an observation that I cant really explain about 3D laser scans in general - anyone have any idea why the sun seems to be captured in some form with 3D laser scanning? I tried to have a quick look online for any information but had no luck.

I have below some of the preview images from a scan recently completed with my FARO Focus scanner, but basically any outdoor scan when the sun is out looks very similar (i.e. centre where the sun is completely black as expected with rings in grey scale however surrounding it). My wild guess: sunlight is also entering the scanner and registering as an intensity value? Any ideas appreciated!
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Re: Sun Visible With 3D Laser Scanning?

Post by stevenramsey »

The sun is a massive laser
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Re: Sun Visible With 3D Laser Scanning?

Post by Scott »

https://www.zeiss.com/microscopy/us/sol ... light.html
Coherence of Light
"In general, non-laser light is distinguished from laser light by its much lower degree of coherence. Incoherent light, such as sunlight from a cloudy sky, and coherent light from a laser, are each limiting theoretical constructs. Even though using these conditional limits simplifies the process of writing equations that describe the image formation process in the microscope, neither coherence extreme can actually be realized in practice."
...
"Even though the sun is considered to be an incoherent source, sunlight has enough coherence to impart speckle to the image formed in a microscope."
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Re: Sun Visible With 3D Laser Scanning?

Post by smacl »

AnthonyM wrote: Mon Jun 14, 2021 10:02 am Hi,
This isn't about any specific problem, more of an observation that I cant really explain about 3D laser scans in general - anyone have any idea why the sun seems to be captured in some form with 3D laser scanning? I tried to have a quick look online for any information but had no luck.

I have below some of the preview images from a scan recently completed with my FARO Focus scanner, but basically any outdoor scan when the sun is out looks very similar (i.e. centre where the sun is completely black as expected with rings in grey scale however surrounding it). My wild guess: sunlight is also entering the scanner and registering as an intensity value? Any ideas appreciated!
While I can't answer your questions I'd be fascinated to know how distant the points surrounding the corona of the sun are from your setup as logged by your instrument :)
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AnthonyM
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Re: Sun Visible With 3D Laser Scanning?

Post by AnthonyM »

"The sun is a massive laser" - Its still odd to me that the sun itself is not recorded at all yet some artifacts in terms of the rings etc are still there in the 3D scan. So the scanner is picking up some solar wavelengths but not the sun itself.

Also strange that the scanner is recording anything at all in terms of solar radiation since even if the solar wavelengths recorded match those of the laser, the 3D laser scanner is meant to record the time of flight of the laser light generated internally and bouncing back to give an exact distance to surfaces and hence their geometry - there is no time of flight/distance data associated with the sun yet there it is :)
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