The authors have developed a novel laser beam mastering apparatus using a deep-UV (DUV) laser for a high-density optical disc. A direct focusing mechanism, where the recording beam itself is also used for focusing, is applied in the laser beam recorder (LBR). The mechanism solves the focus depth issue and provides stable focusing. The evaluation results for the 23.3-Gbytes-capacity read-only-memory (ROM) disc revealed that uniform recording can be realized. Jitter variations in the tangential and radial directions were suppressed to less than 0.2% and 0.07%, respectively. A low residual tracking error signal was also attained. The measurement results for the 25-Gbyte-capacity disc show reasonable jitter not only for a resist/glass disc, but also for an injection-molded disc. The tilt margin of the disc confirmed that the disc was practical for application in the market. Furthermore, the evaluation of the 27 GByte disc indicated the possibility of higher density ROM disc mastering.

For an optical disk system using an objective lens of numerical aperture (NA) 0.7 and a GaN laser, the performances of the groove-recording scheme were investigated. A disk having 17 GB capacity showed the initial jitter of 11.9% with an equalizer for digital versatile disks (DVD). With an adaptive equalizer and a Viterbi decoder, sufficiently low bit error rates and wide tilt margins were obtained.

The paper describes a novel laser beam mastering system with technologies of direct focus servo, high contrast photoresist material, recording signal compensation. Although the optics consists of conventional 266 nm laser with numerical aperture (NA) 0.9 objective lens, it successfully realizes an over 20 Gbytes capacity Read-Only-Memory (ROM) disc.

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