Abstract
A disk designed for compact disk (CD) 2X is employed to test its performance at CD 4X. The erasability at CD 4X is poorer than that at CD 2X. A sharp increase in jitter after overwriting for CD 4X was observed as a result of the existence of two different amorphous mark shapes. One of them is of normal shape and the other is extended with a tail in the trailing part. For overwriting more than 50 times, only one type of amorphous mark with tiny sharp tail was observed. This singular amorphous mark shape gives rise to a decrease in jitter. For much higher overwriting cycles, the jitter will increase with the amount of pinholes present.