Optical Disc Track Pitch Variation for BCA Anti-Tampering
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Solution Overview
Problem
Existing optical discs face challenges in preventing tampering of barcode-shaped marks in the burst cutting area (BCA), as they can be easily erased or altered by read/write drives, making it difficult to distinguish between legal and pirated copies, and the optical head's tracking precision is compromised without prepits or pregrooves in the BCA.
Innovation Solution
The optical recording medium features prepits or pregrooves in the BCA region with a track pitch significantly greater than in the read-only or read/write areas, and a guard region with a changing track pitch between the BCA and other areas, making it difficult to alter BCA marks, while enabling accurate tracking and reproduction of barcode-shaped marks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the BCA uses the same track pitch as the read-only or read/write areas, then the optical head can track properly with the help of prepits or pregrooves, but the BCA marks can be easily erased or altered by read/write drives
Solution Approach 1:
The patent applies different track pitches to different regions of the optical disc. The BCA region uses a first track pitch that is significantly larger than the second track pitch used in read-only and read/write areas. This local differentiation allows the BCA marks to be protected from tampering while maintaining proper tracking capability in respective regions through their designated track pitches and prepits/pregrooves structures.
2Reliability
If the track pitch in the BCA region is made larger to prevent tampering, then BCA marks become difficult to alter, but the optical head tracking precision may be compromised
Solution Approach 1:
The patent implements local quality by assigning different track pitch characteristics to different functional regions. The BCA region employs a larger first track pitch to prevent tampering, while read-only and read/write areas use a smaller second track pitch for precise data access. Each region maintains its optimal tracking precision through region-specific prepits or pregrooves structures that are adapted to their respective track pitches.
Solution Approach 2:
The optical disc is segmented into distinct regions with different track pitch parameters. The BCA region is separated from read-only and read/write areas both physically and functionally, with each segment optimized for its specific purpose. This segmentation allows the BCA to achieve anti-tampering properties through larger track pitch while other regions maintain high precision through smaller track pitch.
3Ease of manufacture
If a single track pitch is used across the entire disc, then manufacturing is simplified, but it becomes difficult to distinguish between legal and pirated copies
Solution Approach 1:
The patent applies local quality by implementing different track pitch values in different regions of the optical disc. The BCA region uses a first track pitch that is larger than the second track pitch used in read-only and read/write areas. This regional differentiation provides authentication capability to distinguish legal copies from pirated copies while maintaining manufacturability through standardized production processes for each region type.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively prevents tampering with BCA marks by making it difficult to uniformly modify the marks and ensures accurate tracking and reproduction, even with varying drive mechanisms, thereby maintaining the integrity of the identification information.
Implementation Method 1
The marks are formed by a pattern using both a crystalline phase and amorphous phase of the phase-change recording stack
Data Source
AI summary
An optical disc or other optical recording medium enables reading barcode-shaped-BCA marks in a burst cutting area (BCA) with tracking on while making tampering with the BCA marks difficult. The optical disc 100 has a first area 102 containing tracks at a first track pitch d2, and a second area 101 containing tracks at a second track pitch d1. The barcode-shaped marks 104 are recorded in the second area, and the second track pitch is wider than the first track pitch.