Versatile Multilayer Disc Versatile Multilayer Disc Versatile Multilayer Disc (VMD or HD VMD) is a high-capacity red laser optical disc technology designed by "New Medium Enterprises, Inc.". VMD was intended to compete with the blue laser Blu-ray Disc format and had an initial capacity of up to 30GB per side. At CeBIT in March 2006, NME demonstrated a prototype VMD player and announced that they were expecting to launch the format in the third quarter of 2006. At the Custom Electronic Design & Installation Association trade show in September 2007, NME exhibited two players set for release in October 2007. There were 20
Optical medium Optical medium An optical medium is material through which electromagnetic waves propagate. It is a form of transmission medium. The permittivity and permeability of the medium define how electromagnetic waves propagate in it. The medium has an "intrinsic impedance", given by where formula_2 and formula_3 are the electric field and magnetic field, respectively. In a region with no electrical conductivity, the expression simplifies to: For example, in free space the intrinsic impedance is called the characteristic impedance of vacuum, denoted "Z", and Waves propagate through a medium with velocity formula_6, where formula_7 is the frequency and formula_8 is the wavelength