1. A 3D image acquisition apparatus comprising: a pattern projection section which projects a predetermined pattern on an object; an imaging section which is disposed at a predetermined distance from said pattern projection section and images the object on which the predetermined pattern has been projected; and a depth calculation section which detects the projection pattern projected on the object on the basis of an image acquired by said imaging section, collates the detected projection pattern and the predetermined pattern projected by the pattern projection section, and calculates a depth of respective parts of the object on the basis of the correspondency of the collation, wherein the predetermined pattern projected by said pattern projection section is formed by alternately arranging areas with local maximum luminance values and areas with local minimum luminance values.