In 1990, newer, faster computational algorithms (invented by
allowed for the first-ever interactive holography.
shows the interactive holovideo display system as it
appeared in 1991.
Photo of Interactive Holovideo Display System The holographic fringe pattern use to create the interactive image in the above photo contained 2 MB of information, and was computed on a massively parallel supercomputer (a Connection Machine Model 2 with 16 Kprocessors). A time-multiplexed scanned acousto-optic modulator (engineered by Pierre St.-Hilaire) transfers the fringe pattern onto a beam of light at a rate of over 100 MB/s.
In the most recent work, a 36-MB system produces an image that is approximately 140 mm wide, 80 mm tall, and 150 mm deep. The following picture shows schematically the layout of the current 36-MB holovideo display system.
This is what the display setup looks like:
A new approach to fringe computation - called Diffraction-Specific fringe computation - has yielded two types of holographic bandwidth compression. Diffraction-Specific fringe computation is based on the spatial and spectral discretization of the hologram. The hologram is treated as a regular array of holographic elements called "hogels." Each hogel is a small piece of the hologram and possesses a homogeneous spectrum (distribution of spatial frequencies). The first method of holographic bandwidth compression, called Hogel-Vector Encoding, is a two-step process. First, an array of hogel vectors (each one representing the discretized spectrum of one hogel) is computed from the 3-D object scene description. In the second step, each hogel vector is decoded into a hogel (the usable fringe) through the linear superposition of a set of precomputed basis fringes. Hogel-Vector decoding has been implemented using the Cheops Image Processing system and the Splotch Engine - a superposition stream-processing daughter card, as well as on many diverse computational platforms. The second technique of holographic bandwidth compression is called Fringelet Encoding. A fringelet is computed for each hogel, and each fringelet is rapidly decoded to produce fringes. This method is designed to reduce the total number of calculations required per fringe sample, increasing computation speeds by over 100 times. Fringelet Encoding promises to greatly simplify the design and contruction of holovideo displays. Besides providing speed increases and reduction of bandwidth, the strength of these holographic encoding techniques is their simplicity, which enables implementation in simple specialized hardware, leading to further efficiencies. Hogel-vector encoding also allows for holographic imaging to be compbined with other forms of (2-D) digital multimedia.
MIT holovideo researchers have included many members of the Spatial Imaging Group at the MIT Media Lab led by Stephen Benton.
MIT Holovideo Sponsors
Work at the MIT Media Lab Spatial Imaging Group was supported by our numerous sponsors, past and present: