U.S. Philips Corporation

Gerardus J Vos

Josephus J Braat

Gerardus L Jansen

Louis J Van Mal

A record carrier having standard and high-density information layers. The standard density layer, e.g. in a standard CD format, is positioned at the bottom of a substrate, and is read out through the substrate with a laser beam. The thickness of the substrate is within the CD specification, e.g. 1.2 mm. At least one high-density layer is formed by a material which is (nearly) transparent for the laser wavelength of standard CD players (.lambda.=780 nm), but is (at least partially) reflective for shorter wavelengths used for high-density discs (.lambda.=635 nm). To achieve a high density, a smaller track pitch and smaller pits are used in the high-density layer(s). To achieve better reading signals from both layers, the high-density layer is positioned closer to the side of entrance of the laser beam in the substrate. A higher numeric aperture of the focusing lens and, therefore, a smaller spot for the shorter wavelength results. The high-density layer is preferably positioned midway in the substrate, e.g. at 0.6 mm. Such high-density layer configuration is compatible with two-sided high-density discs which have a total thickness of 1.2 mm. The information content of the standard layer may be duplicated on the high-density layer, or it may be represented by a different coding scheme.

Optical information carrier including standard and high density layers

A television signal memory (21) for use, for example, in a circuit for increasing the number of fields with interleaved writing and reading, is controlled by a data signal to be written into (at 19) with the aid of a write clock signal (at 77), this data signal being obtained by sampling (at 5) of the television signal by means of a data clock signal (at 25) coupled to the line frequency of the television signal (37, 41). A phase detection circuit (33) detects each time a given phase relation, between the data clock signal (at 31) and a memory clock signal (at 51) obtained form a free running memory clock signal generator (55) having a higher frequency than the highest data clock signal frequency, is exceeded, and then suppresses a memory clock signal pulse in a pulse suppression circuit (71), and shifts the data in a data shift circuit (15) so that the memory receives a single write clock signal pulse during the occurrence of each data period.

Television siganl memory write circuit

In a data communication system comprising a plurality of data stations which are interconnected by a common communication medium, simultaneously occurring prospective users of the communication medium undergo an arbitration to determine which one will gain access to it at any time. The system according to the invention provides the arbitration without negatively affecting the capacity of the communication medium. In the system, arbitration takes place during the data communication to decide who will be the next user, arbitration and communication being effected in frequency bands which differ from each other.

Growing community of inventors

Eindhoven, Netherlands

Gerardus J Vos