Kazunori Takatsu

Data Detection using Pattern Recognition for Multi-level Optical Recording

An optical disc system using multi-level (ML) amplitude-modulation can achieve higher data capacity and transfer rates than previous systems without changing the drive or pick-up head except to add a new chip set to the ML. The ML system can provide a bit error rate (BER) that is fully correctable around the order of 10-5 with sigma to dynamic range (SDR) < 2%. We improved the margin of SDR using a new data detection method that uses pattern recognition and evaluated its performance.

Genetic algorithms applied to Bayesian image restoration

This paper describes genetic algorithms (GAs) applied to Bayesian image restoration. Crossover operation is discussed as a method used to find new search points in GAs. A suitable genotype and an efficient crossover method for a Bayesian image restoration will be proposed. Due to the independency of GAs from objective function forms, it is easy to introduce ideas into the objective functions. The idea of line process proposed by S. Geman and D. Geman [12] is introduced into the objective function, which provides better restored images. As a comparison, a stochastic relaxation (SR) method is applied to the image restoration problem, and the convergence properties of SR and GAs are also discussed.

Multi-level optical recording using a blue laser

Combining Data Detection using Pattern Recognition (DDPR) with LSB (Least Significant Bit) Limited Modulation (LLM) effectively reduces data errors in a blue laser optical disc system. We confirmed that a recording capacity of 25 GB is feasible for a system by using a laser diode of 405-nm wavelength and a 0.65 numerical aperture objective lens was effective to reduce data errors in a blue laser optical disc system.

A New Data Modulation Method for Multi-Level Optical Recording

Previously, we developed a data detection method named data detection using pattern recognition (DDPR) for multi-level data recording on optical discs. We have added a new data modulation process, least significant bit (LSB) limited modulation (LLM), to DDPR in order to reduce data errors. The LLM modulates 11-bit input data into four eight-level data symbols (3 bits×4 data=12 bits). The experimental results showed that coupling LLM with DDPR was effective to reduce data errors.