Patent ID: 7852734

Claim:
A recording and playback apparatus comprising: a rotary drive configured to support and rotate an optical recording medium; an optical head configured to direct a light beam to the optical recording medium rotated by the rotary driver through a light condenser and to detect light reflected from the optical recording medium through the light condenser using with a light detector; and an actuator configured to move the optical head, wherein the optical head includes, a light source configured to emit the light beam, the light condenser configured to feed the light beam emitted from the light source to the optical recording medium, a light splitter configured to split light into the light beam emitted from the light source and the light beam reflected from the optical recording medium, the light detector configured to detect the light beam reflected from the optical recording medium and split by the light splitter, a variable optical coupling efficiency device which is disposed between the light source and the light splitter and is configured to vary 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, a control device configured to control the switching of optical coupling efficiency of the variable optical coupling efficiency device in response to switching between a write mode and a read mode to the optical recording medium, wherein the control device is configured to control 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, wherein the control device is configured to vary the optical coupling efficiency of the variable optical coupling efficiency device prior to the change of mode if the read mode is switched to the write mode, and the control device is configured to vary the optical efficiency of the variable optical coupling efficiency device subsequent to the change of mode if the write mode is switched to the read mode, wherein the control device is configured to control the variable optical coupling efficiency device so that the relationship of TWR≧TRW holds where TWR represents a first response time which the variable optical coupling efficiency device takes to transition from an optical coupling efficiency of CEW to an optical coupling efficiency of CER and TRW represents a second response time which the variable optical coupling efficiency device takes to transition from an optical coupling efficiency of CER to an optical coupling efficiency of CEW.