In some implementations, an optical device includes a one-way mirror formed by a polarization selective mirror and an absorptive polarizer. The absorptive polarizer has a transmission axis aligned with the transmission axis of the reflective polarizer. The one-way mirror may be provided on the world side of a head-mounted display system. Advantageously, the one-way mirror may reflect light from the world, which provides privacy and may improve the cosmetics of the display. In some implementations, the one-way mirror may include one or more of a depolarizer and a pair of opposing waveplates to improve alignment tolerances and reduce reflections to a viewer. In some implementations, the one-way mirror may form a compact integrated structure with a dimmer for reducing light transmitted to the viewer from the world.