The concept of optical image quality is extended to include the total electro-optical system performance. A complex software package called the End-to-End simulation has been developed with the total system performance as its merit function. The example discussed has as its merit function, time delay errors. Subsystems modeled include the object, the "real" optical system, the detector and its associated circuitry, and the electronics used in signal processing. Validation of the modules comprising the total package is discussed.