ST "First Contact":
(they enter a nineteen-thirties night club pursued by two Borg)
MAITRE D': I'm sorry, gentlemen but we're closing, and you do understand we have a strict dress code? So if you boys don't leave right now I'll...
(the Borg discover the Maitre d' is a hologram)
To clarify the two Borg scan the character and figure out he's a hologram.
ST TNG "I Borg":
CRUSHER: That's right. He's gotten every one. Eight out of eight. That blows the top right off the spatial-acuity percentiles.
LAFORGE: It's the prosthetic eye. It seems to be giving him very complex visual information.
CRUSHER: Like some kind of holographic imaging system.
LAFORGE: That could be helpful. Hugh, I'd like to take a closer look at your eyepiece. Is that okay?
BORG: Here. (he takes the eyepiece off and hands it to Geordi)
ST Voyager "Relativity":
SEVEN: My ocular implant can detect irregularities in space-time.
TORRES: Torres to bridge. We've found the problem.
So my question is, since the borg were able to figure out these were holo images inseconds simply by scanning them, and their occular implants were so advanced as to see temporal fluctuations at a level above starfleets abilities hundreds of years later, how were they not able to pick out Picard and Lily out of the crowd immediately?