Spatial light modulator based three-dimensional multiplanar display

A three-dimensional multiplanar display system is described and demonstrated that utilises a silicon backplane, ferroelectric liquid crystal spatial light modulator (FLCSLM) as an active optical element. The FLCSLM is used to generate a sequence of binary, phase-only Fresnel zone plates of various focal lengths which image a synchronised object screen into a series of depth planes forming a volume display. Binary zone plates used as lenses have some serious disadvantages, notably unwanted foci. These problems are examined and solutions are put forward. A similar FLCSLM acting as an amplitude modulator is used for the object transparency. Grey levels can be achieved through temporal dithering and colour by time multiplexing sources of different wavelengths. The high refresh rate of silicon backplane FLCSLMs allows a high number of depth planes to be addressed at video frame rates. The performance of the system makes it particularly suitable for use in a head mounted display. Head mounted displays commonly used in virtual reality produce depth cue conflicts for the user. These conflicts, particularly the lack of the correct accommodation (focusing) cues, have given rise to serious health concern. The lack of focus cues can be addressed through the use of the display system demonstrated here. The independent control that this system gives over the various depth cues gives it the potential to be a new and useful tool in examining the user's response to different virtual environments.