1. A method of decoding hierarchically orthogonal structured light, the method for obtaining a 3-D image by encoding layers of the structured light to carry hierarchically orthogonal address information, radiating the encoded layers of light to a target object by a projector, and decoding an image of structured light layers captured by an imaging processor to obtain relevant address information using an operation processor, the method comprising: identifying, at the operation processor, boundary lines from different layers of the structured light that represent same boundaries as boundaries encoded at identical positions on the projector; and converting, at the operation processor, the identified boundary lines into identical boundary positions to correct detected boundary lines being determined as noise.