Editing Infrared homing (section)

====Crossed array seekers====
The ''crossed array seeker'' simulates the action of a reticle in a con-scan system through the physical layout of the detectors themselves. Classical photocells are normally round, but improvements in construction techniques and especially solid-state fabrication allows them to be built in any shape. In the crossed-array system (typically) four rectangular detectors are arranged in a cross-like shape (+). Scanning is carried out identically to the con-scan, which causes the image of the target to scan across each of the detectors in turn.{{sfn|Deuerle|2003|p=2407}}

For a target centered in the FOV, the image circles around the detectors and crosses them at the same relative point. This causes the signal from each one to be identical pulses at a certain point in time. However, if the target is not centered, the image's path will be offset, as before. In this case the distance between the separated detectors causes the delay between the signal's reappearance to vary, longer for images further from the centerline, and shorter when closer. Circuits connected to the mirrors produce this estimated signal as a control, as in the case of the con-scan. Comparing the detector signal to the control signal produces the required corrections.{{sfn|Deuerle|2003|p=2407}}

The advantage to this design is that it allows for greatly improved flare rejection. Because the detectors are thin from side to side, they effectively have an extremely narrow field of view, independent of the telescope mirror arrangement. At launch, the location of the target is encoded into the seeker's memory, and the seeker determines when it expects to see that signal crossing the detectors. From then on any signals arriving outside the brief periods determined by the control signal can be rejected. Since flares tend to stop in the air almost immediately after release, they quickly disappear from the scanner's gates.{{sfn|Deuerle|2003|p=2407}} The only way to spoof such a system is to continually release flares so some are always close to the aircraft, or to use a towed flare.