High-density channel model and detection method for signal readout from super-resolution near-field structure discs

Abstract

Although a readout method using the super-resolution near-field structure (super-RENS) effect can overcome diffraction limits, readout characteristics for greatly surpassed high-density conditions do not become clear, because a high-density channel function having a differential response property is superimposed on a normal readout function. We propose a high-density channel model to indicate the properties of the super-RENS effect directly. This model can be expressed as a differential response function using the finite impulse response (FIR) filter model. It expresses the super-RENS readout process, which is divided on the basis of recording densities such as high and normal Blu-ray Disc™ densities. We estimated the properties of super-RENS readout signals by comparison between theoretical expressions and experiments. Results show that good signal quality require readout signals having sharp peaks and smaller offsets. We also evaluated the channel model by adding an adaptive FIR filter and a Viterbi decoder by simulations. Results show that the super-RENS disc can achieve a fourfold higher recording density if the signal-to-noise ratio (S/N) is improved to 6 dB in the case of partial response (PR) (1 + D + D 2).