Multi-layer optical recording and reproducing method

Abstract

Abstract PURPOSE:To focus on an optional layer and to perform independent record/reproduction with a multi-layer optical recording medium which contains >=2 recording layers which vary their optical constants with irradiation of light, by applying the offset voltage to a focus servo circuit in response to the space between layers. CONSTITUTION:The reflected light of the record or reproduction light is received by two photodiodes from a multi-layer optical recording medium. Then the lens driving coil current is controlled with a servo mechanism so as to keep balance between the difference of both photodiodes and a focus error signal. Thus a focal point is set on the medium. For a multi-layer recording focus servo circuit, a focal point can be set to an optional layer (n) by defining the offset voltage corresponding to the space (d) between layers as Vd and applying the voltage Vn=nVd+Vo as a layer selecting signal.

Inventors

• 👤 Shigeru Oikawa
• 👤 及川　茂
• 👤 Akira Morinaka
• 👤 森中　彰

Bibliographic Details