Optical system for optical disc drive

An optical system for an optical disc drive, comprising:

• a laser source that emits a laser beam;
• an objective optical system that receives said laser beam and converges the laser beam on an optical disc;
• a deflection mirror provided between said laser source and said objective optical system, said deflection mirror being rotatable about a rotation axis, the laser beam emitted by said laser source being reflected by said deflection mirror and directed toward said objective optical system, the laser beam proceeding from said deflection mirror toward said objective optical system proceeding in a direction parallel to an optical axis of said objective optical system when said deflection mirror is located at a neutral position;
• a first driver which rotates said deflection mirror;
• a rotation amount detecting system that detects a rotation angle of said deflection mirror with respect to said neutral position;
• and
• a second driver which moves said deflection mirror in a direction along which the laser beam is incident, from said laser source, onto said deflection mirror, said second driver moving said deflection mirror so that the laser beam deflected by said deflection mirror is incident on said objective optical system substantially at the same position regardless of rotation amount of said deflection mirror, wherein said second driver moves said deflection mirror in accordance with the rotation angle of said deflection mirror, and wherein an amount (h) of movement of said deflection mirror is determined based on an equation:
• h=L tan(2θ),
• where L represents a distance between said deflection mirror and said objective optical system, and θ represents the rotation angle of said deflection mirror.