Is it maybe putting out a lot of IR before the galvos?
That could explain why you can measure 810mw a few centimetres away but only 150mw from a larger distance.
Don't know what you have but some cheap lasers are notorious for being underpowered and having a large amount of IR in their output.
EDIT: Ignore my incoherent ramblings. Must have had too much shandy last night at the pub. 650nm is a diode laser so not IR pumped!


				
				
				
					
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