1. An infrared seeker adapted for gimballed or non-gimballed mounting in a missile and the like, the seeker comprising: a vidicon adapted for mounting on the missile and directed toward a target area, the vidicon having a vidicon controller connected thereto; a threshold detector connected to the vidicon for receiving vidicon output therefrom, the threshold detector having a threshold control for providing a threshold setting to the detector, the vidicon output when in a non-imaging mode compared with the threshold setting and when the output exceeds the setting that area on the vidicon is considered a possible target; an analog to digital converter connected to the detector for receiving the possible target data; a video preprocessor connected to the converter for conditioning the target data; a computer central processing unit having a microprocessor connected to the preprocessor, the unit having a target detector and acquisition algorithm for determining whether or not the potential target data meets a predetermined criteria, the microprocessor having an image processor; and a scan control connected to the microprocessor and the vidicon controller, the scan control expanding the scan around the area of the potential target and if the potential target data meets the predetermined criteria the vidicon output from the expanded area is sent to the image processor for determination of the validity of the target.