To output a guide signal in the direction of a target without being affected by a false target by a system wherein a plurality of image pickup units shoot the image in the direction of an identical target to generate a three- dimensional image and a target is detected by processing the three-dimensional image.

A three-dimensional image processor 19 compares a three- dimensional image generated from a three-dimensional image generator 15 with with an overall profile data indicative of the overall profile of an aircraft stored in a target profile data base 18 in the form of points of a mesh on an x, y, z coordinate having origin at the forward end of the aircraft thus determining the angle of attack of a target. An apparent target width is then determined from the width and the angle of attack of the target. Subsequently, the distance from a guide unit 1 to the apparent target is calculated using two points corresponding to two points on the target 2 of an image formed by a video signal 7 and the focal length of a first image pickup unit. Three-dimensional image of the target and the background in the field of view is calculated through the operation. A peak is detected from the target thus obtained as the target position in the field of view.