Images sensed through object lenses 100R and 100L, having zoom lenses, with image sensors 102R and 102L are processed by image signal processors 104R and 104L, and an image of an object in each of the sensed images is separated from a background image on the basis of the processed image signals. The separated image signals representing the image of the object enter the image processor 220, where a three-dimensional shape of the object is extracted on the basis of parameters used upon sensing the images. The parameters are automatically adjusted so that images of the object fall within the both image sensing areas of the image sensors 102R and 102L and that they fall within the both focal depths of the image sensors 102R and 102L.