TMZ reports that Justin Bieber is saying he didn't know he hit anyone as he left the Laugh Factory, and police are clearing him of any wrongdoing ... this time.

We're told LAPD interviewed Bieber and his representatives as well as witnesses -- and cops now say this is not a hit and run case ... and fault lies with the photog for being a pedestrian in the roadway. 

Police say the photog wasn't seriously injured.