1. A method comprising: providing IR light from a source to an illumination unit, the illumination unit comprising a partially reflective layer with extraction features; providing uniform output extraction versus position across the partially reflective layer; and directing the IR light in a direction selected from a list consisting of the following: a normal direction to a display, a convergent direction from the display, a divergent direction from the display, a direction having a constant angular bias versus position across the display, and an interstitially-spaced multiple angular bias across the display by controlling an angle versus position of the partially reflective layer.