Volumetric displays, in which an image that physically occupies space is built up from many 2D cross sections, has many attractive features including smooth parallax in all directions, coincident focus and fixation points, and wide viewing angles. However, existing volumetric displays require an image forming apparatus that occupies the same volume as the image itself. Large volumetric displays therefore tend to be very expensive and bulky, and may not be practical at all beyond a certain size. DTI has demonstrated optics that can project miniature (about 1 cubic inch) 3D volume filling images into a volume of arbitrary size limited only by the dimensions of a screen-like (i.e. of large area and relatively thin) optical assembly. This greatly reduces the size requirements for the image forming device and its mechanical or optical scanning mechanisms, while producing very large images that can occupy space ranging from the area in front of the display to infinity behind it. The viewing area can be of about the same lateral dimensions as the screen-like assembly, without violating etendue conservation. The optics also simplify the challenges associated with electronic holography, since a very small electronic hologram can be employed as the image source.