1. A system for measuring viewing zone characteristics of an autostereoscopic three-dimensional (3D) image display device, comprising: at least one image sensor that is provided on a front side of the image display device, and measures characteristics of luminance distribution of viewpoint images in a depth direction (Z-direction) formed from at least two local areas which are designated in advance in a horizontal direction (X-direction) of the image display device; and a determination unit that determines, as an optimum viewing distance (OVD), a position of the image sensor corresponding to a depth direction (Z-direction) having a horizontal direction (X-direction) minimum deviation of a center position of luminance distribution of light generated from the same viewpoint image of each of the at least two local areas by analyzing the characteristics of luminance distribution on an X-Z plane measured from the image sensor, wherein the autostereoscopic 3D image display has pixels which provides view point images and each of the at least two local areas comprises at least 10 pixels for each view image.