An optical disk system using a blue laser diode and a single objective lens that has a numerical aperture of 0.7, is proposed. A sufficiently low jitter value was obtained with a read-only disk having 17-Gbyte capacity. The paper also includes discussion on the influence of the laser noise and RF modulation method on the playback signal.

A method to observe sonoluminescing bubble motion has been studied. By a single flash of a stroboscope much shorter than the acoustic cycle, a charge coupled device (CCD) camera captures an instantaneous image of the bubble, which includes the dancing condition. Changing the flash timing of the stroboscope slowly made it possible to observe periodical expansion and contraction of the bubble. It is clarified that the bubble size and the phase at the time the bubble collapses changes according to the amplitude of sound pressure.

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.