Far infra-red, mm and sub-mm astronomy requires very large arrays of detectors for future wide field cameras and spectrometers. We present an array of lens-antenna coupled Microwave Kinetic Inductance Detectors (MKID) for a wide field camera at 350 GHz. We discuss the optimization to maximize the usable detector yield and matching the array to the readout to enable array performance close to the background limit. We overview the optical characterization techniques required to have confidence in the instrument performance prior to on telescope integration, finally giving measured optical performance for an optimized array.@en