Pit Depth Modulation: Multiplying the Capacity and Speed of CDs and DVDs

Ever-Increasing Demands for More Storage Capacity Demand for DVDs continues to grow; DVD system sales are estimated to increase from 95 million units sold in 1998 to over 175 million units in 2001. This popularity is not surprising given that a DVD can hold enough data (up to 8.5 gigabytes on a dual layer disc) to play back an entire motion picture on a standard television with far greater clarity than a standard VHS videotape. A single-sided DVD, however, does not have sufficient capacity to store the same movie at the much greater level of resolution required for high-definition television (HDTV)—which requires 15-20 gigabytes (GB) per disc. The shortfall of storage capacity for HDTV applications represents a large challenge. The recent proliferation of digital technology for other uses, such as audio recordings and computer storage, has created a voracious worldwide appetite for ways to store huge amounts of data. The fast-moving computer and consumer electronics sectors are highly competitive, promoting widespread demand for digital media and driving the need for more storage capacity. Digital storage is vitally important for delivering telecommunication and entertainment services, as well as computer programs to households. Given the high stakes, competition among datastorage companies in the United States, Japan, Europe, Australia, and elsewhere is intense. Hundreds of millions of dollars have been spent researching a variety of methods to increase data storage speed and capacity.