An etendue squeezing optic includes light guiding elements that are extruded sideways to guide light to a wide outlet surface for efficient injection into an edge face of a flat light guide such as a backlight panel for a visual display, in combination with a light source optically coupled to the light inlet through an air-gap, so that light entering the optic through the air-gap is confined to a cone of directions determined by a critical angle of refraction into the optic from air at the air-gap.