1. A system for combining multi-spectral images of a scene, the system comprising: a channel for transmitting a scene image in a first spectral band; a separate second detector for sensing the scene in a second spectral band, the second detector having an image output representative of the scene; a display for receiving the image output of the second detector, and displaying an image from the second spectral band; and a beam mixer for combining the image output in the first spectral band with the displayed image, and conveying the combined multi-spectral images to an output.