Limited use DVD-video disc

#1. Field of the Invention

#The present invention relates to a limited-use digital versatile disc (DVD), such as a DVD-video disc that permits only a predetermined number of uses of a video movie. The preferred exemplary embodiment utilizes a dye disposed on the DVD that changes optical properties after being exposed to a DVD reader laser to insure that only a predetermined limited number (e.g., two) use(s) of the DVD are permitted.

#2. Description of Related Art

#These and other objects and advantages of this invention will become apparent from the following more detailed description of the exemplary embodiments taken in conjunction with the accompanying drawings in which:

#FIG. 1A is a bottom view, with a part broken away, of a conventional DVD;

#FIG. 1B is a detailed view of the part broken away from FIG. 1A;

#FIGS. 1A-1B and 2 illustrate a conventional DVD including two distinct circular pieces of molded plastic 100, 150 that are bonded or glued together by an adhesive layer 170. Starting from the center of the disc, the disc includes a center hole 110 for mounting the disc into a DVD reader, an unused center area 108, a data area 105 for storing user data and error correction data, and an unused outside area 106. The data area 105 comprises one or more storage layers, each storage layer having a single track 102 that spirals around the disc. The spirals of each track contain microscopic bumps (or pits) for encoding recorded data. Each storage layer also includes a reflective layer 120 arranged over the track, including the bumps contained in the track, to reflect a laser light from the DVD reader so that the data recorded in the track can be read.

#The total diameter of a typical currently used disc is either 12 cm (as shown in FIG. 1A) or 8 cm and the total thickness of the disc is typically 1.2 mm. The inner and outer radii of the data area 105 for a typical 12 cm disc is 24 cm and 58 cm, respectively, and thus the size of the data area 105 for a 12 cm disc is approximately 8759 mm2. The area of the unused center area and the center hole of a 12 cm disc is 1809 mm2 and the area of the unused outside area is 741mm2. The width (labeled “a” in FIG. 1B) of the track that spirals around the disc is typically 740 nm and the minimum length (labeled “b” in FIG. 1B) of a bump in the track is typically 400 nm. These and other physical parameters of conventional currently available DVDs are summarized in Table I.

#TABLE I DVD Parameters 1 Storage Layer 2 Storage Layers User Data Capacity 12 cm Disc 4.7 billion bytes 8.54 billion bytes 8 cm Disc 1.46 billion bytes 2.66 billion bytes Numerical Aperture 0.60 0.60 Data Bit Length 0.267 μm 0.293 μm Channel Bit Length 0.133 μm 0.147 μm Minimum Bit Length 0.400 μm 0.440 μm Maximum Bit Length 1.86 μm 2.054 μm Disc Diameter 12 cm Disc 120 mm 120 mm 8 cm Disc 80 mm 80 mm Disc Thickness 0.60 × 2 0.60 × 2 mm Disc Center Hole 15.0 mm 15.0 mm Data Area Inner Radius 24.0 mm 24.0 mm Data Area Outer Radius 12 cm 58.0 mm 58.0 mm 8 cm 38.0 mm 38.0 mm User Data per Sector 2048 Bytes 2048 Bytes Number of Sectors in 12 cm Disc 2,294,912 2,084,960 Average Number of Sectors per 49.9 49.9 Spiral Average Data Amount per Track 102,400 bytes 102,400 bytes Rotation Speed 9–10 rev/sec 9–10 rev/sec Laser Wavelength from DVD 600/635 nm 600/635 nm Reader