Abstract: A stereoscopic display unit (10, 110) including at least two projection units (14, 16) for projecting optical signals corresponding to the left and right image fields respectively of a stereoscopic image, and an optical focusing system (18) for focusing the two image fields to at least two focus regions at a viewing position outside of the display unit (10, 110). The left and right image fields are each respectively focused into the respective eyes of at least one viewer (72) when located at said viewing position. The optical focusing system (18) includes at least one retroreflective mirror (64, 210) and a semi-reflective mirror (66) disposed at an angle to the at least one retroreflective mirror (64, 210), the semi-reflective mirror (66) being partially reflective and partially transmissive, the optical signal being reflected between the at least one retroreflective mirror (64, 210) and the semi-reflective mirror (66) and to said viewing position.