August 1972 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Lithium niobate is used today as the substrate for surface acoustic wave (SAW) filters, oscillators, optical waveguides, and many other applications. It, along with barium niobate, was used experimentally by Radio Corporation of America (RCA) for storing optical images that can be read out later using a laser. This 1972 issue of Popular Electronics included a brief news item referencing the work being done. I could not locate any information that indicates any significant commercialization of the process. Patent US3799642 was awarded in 1974 to RCA Corporation for "Holographic Recording on Photochromic Lithium Niobate."
New Hologram Crystals Permanently Store Images
Development of a crystal capable of storing hologram images as atomic patterns which can be read out, one by one, by slow rotation in a laser beam has been announced by RCA. The development may ultimately lead to a new document storage system in which files of statistics, engineering drawings, computer data, and other graphic material are permanently stored in crystals the size of sugar cubes.
The significance of the announcement is that crystals 500 times more sensitive than ever before and a system for permanently "fixing" images stored in them have been developed. Though holograms have been stored in crystals before, a very powerful laser was required and the holograms tended to erase during the readout process.
The RCA holograms can be retrieved relatively easily by the same low-power gas laser used during the storage process. Furthermore, a display from such a hologram can be 15 times brighter than that from a conventional photographic-film negative.
Metallic impurities in the lithium niobate and barium niobate crystals are responsible for the increased sensitivity. Storage capacity is theoretically a trillion bits per cubic centimeter of crystal.
Posted December 29, 2017