Interlayer crosstalk reduction of a multilayer Blu-ray Disc using a grating in a three beam optical system

Abstract

In multilayer optical discs, light reflected by out-of-focus layers, which we call interlayer crosstalk, causes the tracking error signal to fluctuate, making the readout signal unstable. We previously proposed a novel method to use a grating along the optical axis in the return path of a pickup to suppress the fluctuation of a differential push-pull (DPP) signal. We develop a pickup and evaluate its performance to stabilize the DPP signal experimentally. DPP signal fluctuation is suppressed to one-third (6% to 2%), and also satisfactory readout jitters (about 8%) are obtained for a triple-layer Blu-ray Disc (BD), which demonstrate the validity of this method to reduce interlayer crosstalk of multilayer optical discs.