Safe Scratches on CD

Overview

Objectives/Goals The objective of this project is to examine how CDs are protected against scratches and markings. The error correction mechanism is pre-studied before this project. Methods/Materials Use 30 CDs which are fully recorded with the same data. Then, continue to make scratches on the surface of a CD and test the readability until the data is no more readable. The tests are performed for several types of scratches such as radial scratch, circular scratch, and optical markings. The materials needed are: PC with CD-ROM drive 30 Blank CDs Exacto knife (making scratches) Permanent black marker (marking) Acetone (erasing markings) Results Experimental results show that a CD's protection against scratches depends on the pattern of scratches. When the scratches are thin and lie in the radial directions, the CD is well protected and the files opened in regular speed. However, with many scratches, reading operation finally stalled. When the scratches are thick or they lie in the circular direction, the files opened slowly, and tended to stall occasionally. Experimental results also show that a CD is very sensitive to markings. However, it returns to its normal condition once the marking is removed. Conclusions/Discussion A CD has different levels of protection against different patterns of scratches. It is very sensitive to circular scratches but radial scratches are relatively safe. This agrees with the error correction mechanism of a CD called the interleaving.

Competition history

• CSEF 2005 Applied Mechanics/ Structures & Mechanisms/ Manufacturing · Entry J0212

Resources

• CSEF project summary ↗

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