Three-Track Readout Method Using Two Offset Beams

A high-data-transfer-rate, high-track-density optical recording method using two offset beams to read the data on three tracks was investigated. One beam is offset towards the center track from the center of a side track. Therefore, the readout signal amplitude read from the side track is twice as large as that from the center track. The other beam is offset in the same way. An algorithm was developed to obtain the data from three tracks by using the readout signals from two offset beams. Using this algorithm, data can be retrieved simultaneously from three tracks with a one-to-one dependence between the amplitude levels and the data. This method also offers narrow-track-pitch recording without the need for additional crosstalk cancellation. Computer simulations and experimental results show that this method can achieve three-times-higher data transfer rates and 28%-larger recording density than conventional one-beam systems.