1. A stereoscopic image display apparatus comprising: a first three-dimensional display device includes, a first display unit configured to display a 2D image, the 2D image including elemental images, and a first light control unit configured to control directions of light rays emitted from the first display unit, wherein the first display unit displays each of the elemental images in a first specific area determined with the directions of the controlled light rays, so as to display a three dimensional image; a multi camera configured to capture multi-viewpoint images of a real object from specific view points placed at certain intervals, wherein the multi-camera has a projection plane serving as an imaging reference plane; an image processing unit configured to process images taken by the multi camera, the image processing unit including; a parallax image generation unit configured to generate parallax image data including clip parallax images having specified ranges which are clipped from the multi-viewpoint images based on information about clipping ranges of the multi-viewpoint images, a sort processing unit configured to sort pixels from the clip parallax images and rearrange the sorted pixels to generate the elemental images, and a display condition adjustment unit configured to adjust parameters required to display the three-dimensional image, wherein the parameters are so adjusted as to capture the real object as the multi-viewpoint images having a desired size at the vicinity of the projection plane with reference to the displayed three-dimensional image, wherein the image processing unit is configured to correct the imaging reference distance and the intervals of the view points based on the adjusted parameters and the imaging condition to derive a corrected imaging reference distance and a corrected interval, which are required to display the three-dimensional image without any distortion.