However, one can infer that the minor action Perception check can be used to spot a "normally" hidden creature.
The inference (read: Houserule, since afaik its not covered clearly in the RAW) I make is that a character can make a minor action Perception check to look at a specific location (is there someone hiding there ), versus a standard action perception check to look all around (is there someone hiding in this room ).
But at present I consider that to be a houserule on my part.
Carl