Shigemi Maeda

New Adaptive Equalization Method for Partial Response Maximum Likelihood System Optimizing Error Rate Performance

Adaptive equalization is essential in achieving wider system margins, such as tilt margin and defocus margin, in optical disk systems using partial response maximum likelihood (PRML) detection method. The most conventional method is the combination of the use of the least-mean-squares (LMS) algorithm and partial response (PR) equalization, but it does not optimize the characteristics of equalizers in terms of bit error rate (BER) performance. Integrating the concept of sequenced amplitude margin (SAM) with LMS, we developed a new adaptive equalization method, called least-mean-squared SAM error (LMSAM), which can minimize BER. After explaining the basic idea of LMSAM, we theoretically derived its implementable algorithm. We also reported favorable experimental results on the remarkable improvement of the tangential tilt margin and defocus margin with LMSAM. Furthermore, we analyzed the result from the viewpoint of frequency response and clarified why LMSAM can improve tilt margin.

Method for Evaluating Partial Response Maximum Likelihood System Performance Using Sequenced Amplitude Margin

We improve a media evaluation method for partial response maximum likelihood (PRML) systems using a sequenced amplitude margin (SAM). The improved method has many advantages over direct bit error rate (BER) measurement; it needs fewer samples and less time, it does not require a known test pattern, and it enables easy measurement of media characteristics without the influence of media defects. Some experimental results indicated that the calculated BERs correspond to the directly measured BERs in any type of optical disk system.

New Method for Adjusting Write Strategy Using Sequenced Amplitude Margin

We proposed a new method for adjusting write strategy in partial response maximum likelihood systems. It utilizes novel indices calculated from the sequenced amplitude margin and produces both a low bit error rate (BER) and a wide recording power margin.

New Equalizer Optimization Method for Partial Response Maximum Likelihood Systems Using Normal Equation with Sequenced Amplitude Margin

A new equalizer optimization method was proposed for partial response maximum likelihood systems. It provides a wider tangential tilt margin and defocus margin in an optical disk system that uses a blue laser (406 nm) and has a numerical aperture of 0.85.

Bit-Error-Rate-Based Evaluation of Energy-Gap-Induced Super-Resolution Read-Only-Memory Disc in Blu-ray Disc Optics

Bit error rate (bER) of an energy-gap-induced super-resolution (EG-SR) read-only-memory (ROM) disc with a zinc oxide (ZnO) film was measured in Blu-ray Disc (BD) optics by the partial response maximum likelihood (PRML) detection method. The experimental capacity was 40 GB in a single-layered 120 mm disc, which was about 1.6 times as high as the commercially available BD with 25 GB capacity. BER near 1 ×10-5 was obtained in an EG-SR ROM disc with a tantalum (Ta) reflective film. Practically available characteristics, including readout power margin, readout cyclability, environmental resistance, tilt margins, and focus offset margin, were also confirmed in the EG-SR ROM disc with 40 GB capacity.

Bit-Error-Rate Evaluation of Energy-Gap-Induced Super-Resolution Read-Only-Memory Disc with Dual-Layer Structure

Practically available readout characteristics were obtained in a dual-layer energy-gap-induced super-resolution (EG-SR) read-only-memory (ROM) disc with an 80 gigabytes (GB) capacity. One of the dual layers consisted of zinc oxide and titanium films and the other layer consisted of zinc oxide and tantalum films. Bit error rates better than 3.0×10-4 were obtained with a minimum readout power of approximately 1.6 mW in both layers using a Blu-ray Disc tester by a partial response maximum likelihood (PRML) detection method. The dual-layer disc showed good tolerances in disc tilts and focus offset and also showed good readout cyclability in both layers.

Cross-recording reduction by trial recording on a magneto-optical disk

A technique for reducing cross-recording on data storage media with high track density is described. In order to detect cross-recording sensitively, an inverted mark pattern was first recorded on adjacent tracks and then synchronized with a normal recorded mark pattern on the central track. These patterns were repeatedly recorded as the recording power was increased. Readout signals of the recorded mark pattern were evaluated on the central track in each condition, and an optimum recording power was precisely determined from the maximum amplitude of the signals. When this new technique was applied to a magneto-optical disk, the bit error rate was reduced to less than 10/sup -4/. This is the first technique to reduce cross-recording by laser power only.