Editing Infrared homing (section)

===Linear scan===
Some of the earliest German seekers used a linear-scan solution, where vertical and horizontal slits were moved back and forth in front of the detector, or in the case of ''Madrid'', two metal vanes were tilted to block off more or less of the signal. By comparing the time the flash was received to the location of the scanner at that time, the vertical and horizontal angle-off can be determined.{{sfn|Kutzscher|1957|p=216}} However, these seekers also have the major disadvantage that their FOV is determined by the physical size of the slit (or opaque bar). If this is set too small the image from the target is too small to create a useful signal, while setting it too large makes it inaccurate. For this reason, linear scanners have inherent accuracy limitations. Additionally, the dual reciprocating motion is complex and mechanically unreliable, and generally two separate detectors have to be used.