Compact dynamic head up display

Head up displays are provided. A head up display may have a base adapted for mounting to a firearm; a window positioned by the base so that a user of the firearm can observe a field of view through the window; an illuminator operable to generate a divergent illumination light; a light valve configured to modulate the divergent illumination light in accordance with an image provided by an image generator; and a collimating optic in an optical path between the light valve and the window that substantially collimates the image modulated illumination light. The window reflects at least a portion of the image modulated collimated light so that the observer observes the image substantially in focus with objects in field of view. Images presented may include data and images, including but not limited to thermal images.