Problems Scanning Dark Metal

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_camuz
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Problems Scanning Dark Metal

Post by _camuz »

Hi!

My name is Carlos, and I'm new to this forum. I have a BLK360 and I've been tasked with a megascan of +850 scans... I've been scanning a large metal statue and although the scan has a range of about 60m (fabricant specs), I'm finding it difficult to scan a metal statue which is about 40m distance to the farthest point.

I'm wondering if any of you have had a similar problem, and how did you solve it. Not sure if it is a color issue or a thermal one. I've scanned the back from the statue which I have access to from a stair going all the way up there when the sun is shining at it. And I've tried scanning the front both when the surface has the sun shining on it and when the sun is hitting on the back. The scanner is simply not working as it should.

Any pointers or any suggestions you might have? Thanks in advance for your kind suggestions
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jcoco3
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Re: Problems Scanning Dark Metal

Post by jcoco3 »

Hi Carlos, and welcome to the forum :)

I am not experienced with a BLK360, but from what I have seen elsewhere on this forum the issue you are having is common. It is not only the BLK360, but most scanners operating on 905nm wavelength laser. It probably doesn't help that the BLK360's optical lens diameter for receiving the returned light is also on the small side. Basically it is a reflectivity problem, and unfortunately the sunlit conditions that are favorable to color imagery are not as favorable for 905nm laser scanning. You can try to scan the statue at night, but at the ranges you have available I would only expect an improvement and not a night and day difference. Sorry for the pun :roll:

There are many others here with more experience with the BLK360, so hopefully you will get some better help from them.
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Re: Problems Scanning Dark Metal

Post by landmeterbeuckx »

_camuz wrote: Thu Apr 01, 2021 4:08 pm Hi!

My name is Carlos, and I'm new to this forum. I have a BLK360 and I've been tasked with a megascan of +850 scans... I've been scanning a large metal statue and although the scan has a range of about 60m (fabricant specs), I'm finding it difficult to scan a metal statue which is about 40m distance to the farthest point.

I'm wondering if any of you have had a similar problem, and how did you solve it. Not sure if it is a color issue or a thermal one. I've scanned the back from the statue which I have access to from a stair going all the way up there when the sun is shining at it. And I've tried scanning the front both when the surface has the sun shining on it and when the sun is hitting on the back. The scanner is simply not working as it should.

Any pointers or any suggestions you might have? Thanks in advance for your kind suggestions
60 m specs is always less in reality. Take half for decent measurements. The angle of the beam in relation with the height of the statue causes also problems. You should look into a higher spec'd scanner for these sort of objects like a p series or a faro s350 or of course a riegl😉
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Re: Problems Scanning Dark Metal

Post by jcoco3 »

Yep, what Lieven said. Either of those scanners would slay that statue. I need to look up the beam divergence on the BLK360, then ponder the effect a larger spot size on surfaces downrange would have on the intensity of the returned light to the optics. I know the beam diameter plays a big role in range noise when a large spot lands on a non flat surface and creates ambiguity, but for just measuring the magnitude of returned intensity I have not given it enough thought. I mean the scanner is basically just "watching" for returned dispersed (no longer a coherent laser) light, and what difference does it make if its a tiny high intensity point or a larger spot...wait maybe I just answered my own question. Could it be that it needs the higher contrasting intensity against the wash of surrounding sunlight. Signal to noise issue I suppose?

I feel like I should know this already, but here's hoping somebody less ignorant enlightens me :D


Edit:
Beam Divergence
BLK360 .4mrad
Faro Focus s350 .3mrad
Reigl vz-4001 .35mrad

I probably should have listes the beam diameter at exit too, and perform some distance vs spot size comparisons, but I got to get back to other things.
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Re: Problems Scanning Dark Metal

Post by _camuz »

wow! thanks for the quick reply!... Well I'm just gonna try one last time when the sun is hitting right into it. If it's not working I'll just have to work with what I have then.

Thanks again!
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