1. A projector comprising: a projection device having a projection lens; a focus adjuster for adjusting the focus of said projection lens; a zoom adjuster for adjusting the zooming of said projection lens; an imager having a plurality of cameras for capturing respective images of a projection object; a projection area calculator for calculating a projection area of an image depending on a distance from the projection lens based on a zoomed position from said zoom adjuster; a three-dimensional position detector for detecting a three-dimensional position of a predetermined object point corresponding to identical object points in the respective images captured by said cameras from the images captured by said cameras and the projection area of the image calculated by said projection area calculator; and a distance detector for detecting the distance up to the object point from the three-dimensional position of said predetermined object point.