1. An apparatus for obtaining depth information using an optical pattern, the apparatus comprising: a pattern projector to generate the optical pattern using a light source and an optical pattern projection element (OPPE), and to project the optical pattern towards an object area, the OPPE comprising a pattern that includes a plurality of pattern descriptors; an image obtaining unit to obtain an input image by photographing the object area; and a depth information obtaining unit to measure a change in a position of at least one of the plurality of pattern descriptors in the input image, and to obtain depth information of the input image based on the change in the position.