We propose a high-speed optical disk system using thin flexible optical disks (HS-FOD) recording up to 15,000 rpm. The thin optical disk system is composed of three technical elements: media employing a thin and flexible substrate 0.1 mm thick, a mechanical stabilizer, and a high-speed tracking servo employing a feed-forward control with zero phase error tracking (ZPET-FF control). The HS-FOD system has an optical head with numerical aperture (NA) of 0.85 and is compatible with the optical system of a Blu-ray disc or a broadcast-use optical disk. We have successfully performed disk rotation stably and have performed precisely a focus servo and a tracking servo at 15,000 rpm. We also achieved writing and reading data at 15,000 rpm and recording 252 Mbps of random pattern data and could get small values of jitter below the tolerance. These results are enough to record professional high-definition television (HDTV) video signals in formats such as HD-D5 for broadcast-use.

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A low-power wordline voltage generating system is developed for low-voltage flash memories. The limit for the stand-by current including the operation current for the band-gap reference and the stand-by wordline voltage generator is discussed. The system was implemented on a 1.8-V 32-Mb flash memory fabricated with a 0.25-m flash memory process and achieved with very low stand-by current of 2 A typically, and high operating frequency of 25 MHz in read operation at 1.8 V. A low-voltage level shifter with high-speed switching is also proposed.

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Originally developed for application with laser beams, trap detectors are widely used as transfer standards in modern monochromator radiometry. However, a non-optimized beam focus applied to trap detectors can result in significant spectral errors. This paper shows that a defocused and improperly aligned beam entering a Si reflection trap detector can cause an apparent modification of the measured relative spectral responsivity. This is true especially in the ultraviolet (UV) region of the spectrum, where the measured relative differences are of the order of several percent due to the significant influence of the direct band-band transitions of Si on the reflectance of the Si photodiode. The spectral range from 248 nm to 600 nm was investigated in detail. Calculated curves, simulated by a computerized geometrical model, were fitted to the measured data. The geometrical model uses experimental spectral reflectance data.