Recording and playback apparatus and optical head

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, and
• 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.