The number of infrared focal plane detector units used in the third-generation infrared imaging technology has reached 320x240 yuan or more, and its performance has been improved by nearly 3 orders of magnitude. At present, the unit sensitivity of the 3~5um focal plane detector is 2~3 times higher than that of the 8~14um detector. Therefore, the overall performance indicators of medium-wave and long-wave thermal imagers based on 320x240 elements are not much different, so 3~5um focal plane detectors are particularly important in the third-generation focal plane imaging technology. In the long run, HgCdTe focal plane detectors with high quantum efficiency, high sensitivity, and coverage of medium and long wavelengths are still the first choice for the development of focal plane devices.