Patent ID: 7230903
Filing Date: 2007-06-12
Classification: G11B

Abstract:
1. A recording and playback apparatus comprising: a rotary drive which supports and rotates an optical recording medium, an optical head which directs a light beam to the optical recording medium rotated by the rotary driver through light condenser means and detects light reflected from the optical recording medium through the light condenser means using light detector means, and actuator means for moving the optical head, wherein the optical head comprises: a light source which emits the light beam, the light condenser means which feeds the light beam emitted from the light source to the optical recording medium, light splitter means which splits light into the light beam emitted from the light source and the light beam reflected from the optical recording medium, the light detector means which detects the light beam reflected from the optical recording medium and split by the light splitter means, variable optical coupling efficiency means which is disposed between the light source and the light splitter means and varies the optical coupling efficiency thereof, which is a ratio of the amount of light condensed on the optical recording medium to the total amount of light of the light beam emitted from the light source, and control means which controls the switching of optical coupling efficiency of the variable optical coupling efficiency means in response to switching between a write mode and a read mode to the optical recording medium, wherein the control means controls the switching of the optical coupling efficiency so that the relationship of CEW>CER holds where CEW represents the optical coupling efficiency during the write mode and CER represents the optical coupling efficiency during the read mode, and wherein the control means is configured to vary the optical coupling efficiency of the variable optical coupling efficiency means prior to the change of mode if the read mode is switched to the write mode, and the control means is configured to vary the optical efficiency of the variable optical coupling efficiency means subsequent to the change of mode if the write mode is switched to the read mode.