3-D Eyewear: Close up

http://www.dlp.com/cinema/new.aspx

 

Active eyewear devices

Active eyewear devices are wireless battery-powered glasses with liquid crystal shutters that are run in synchrony with the video field rate. Synchronization information is communicated to the glasses by means of an infrared (IR) emitter. When the emitter recognizes the vertical blanking synchronization pulse through the computer’s video signal, it broadcasts coded IR pulses to signify when the left eye and right eye images are being displayed. The glasses incorporate an IR detection diode that detects the emitter’s signal and tells the shutters when to close and transmit. Although viewing a 3-D movie with active glasses virtually eliminates ghosting, the glasses are expensive and need to be cleaned after every use.

 

Passive eyewear devices

An alternative to active glasses is the passive approach or ZScreen, which is a special kind of liquid crystal polarization modulator and requires theatres to install a silver screen. The ZScreen is placed in front of the DLP Cinema® projector lens(es) like a sheet-polarizing filter. The device changes the characteristic of polarized light and switches between left- and right-handed circularly polarized light at field rate. The advantage of circular polarized light is that audience members may move their heads a lot more before the stereoscopic effect is lost. Passive glasses are made of either cardboard or plastic that cannot be sanitized and therefore are for one time use.