As advanced infrared systems are designed and developed, the requirement for greater sensitivity and resolution is continually encountered. System performance parameters relating to these requirements always depend on the signal-to-noise ratio of the total focal plane. Under optimum operating conditions for the best materials, the response is directly proportional to the total area of sensitive material on the focalplane Ap, whereas the noise varies as Ap1/2 thus system sensitivity varies as Ap1/2. However, resolution depends inversely on the dimensions of the sensitive elements. Thus, higher performance systems will require multielement focal planes of small, closely packed detectors.