There are a wide range of 3D display technologies available and they all have to solve the same fundamental problem: how to direct a different image to the left and right eyes. The optical technologies available to direct light in this way have resulted in many 3D display designs, commerically available designs fall into two broad catagories stereoscopic and autostereoscopic.
The taxonomy above is arranged so that the number of simultaneous views each display type has increases from left to right. From two view stereoscopic displays, to horizontal parallax multi-view displays, to full horizontal and vertical parallax volumetric displays. The number of views needed to drive a display, or its parallax resolution, is a critical factor for display designers, content producers and users since it directly affects the whole imaging process from capture through to display.
This type of display requires the viewer to wear a form of glasses at the eyes. The glasses filter the light arriving at the eye to ensure each eye sees the correct image.
The benefit of autostereoscopic 3D display is that it removes the need for viewers to wear glasses. Instead an optical system directs light so that the correct view is seen in each eye automatically.
Headmounted Displays One way to ensure the two images are sent to the correct eye is to head mount a display in-front of each eye. These stereoscopic displays are often used in VR simulation systems. We don't consider them in detail here, though the programming application of them is very similar to other stereoscopic displays.
Holographic Displays What about holograms? Some electronic holographic displays have been conceived and built, however true holographic displays are not yet a practical technology. What is adopted in some designs is a holographic optical element (HOE) replacing a more complex optical component; the result is usually an auto-stereoscopic display.