BEAM SHAPING OPTICAL DEVICE, OPTICAL HEAD, AND OPTICAL INFORMATION MEDIUM DRIVE DEVICE

摘要

A beam shaping optical device enabling the suppression of the deterioration of collimation quality due to a variation in temperature. The lens face of collimation lenses (2) near a light source (20) abuts on a backward face (3a) at one end of a lens-barrel (3). Grooves (11) are formed in an outside projected face at one end of the lens-barrel (3) at a plurality of portions symmetrical with respect to an optical axis (O). An adhesive agent (15) filled in the grooves (11) is applied to the outer peripheral surface of the collimation lenses (2) to fix the collimate lens (2) to the lens-barrel (3). Since the grooves (11) are formed shallower than the backward face (3a), the adhesive agent (15) does not invade into the backward face (3a). The lens-barrel (3) is pressed by a plate spring (13) against a wall surface of V-shape in cross section formed on the inner peripheral surface of a lens-barrel holder body part (5) so that the lens-barrel can be held at the specified position of the lens-barrel holder body part (5). A variation amount DeltaL per unit temperature of a distance ranging from a reference plane to a holding position for the collimation lenses (2) is set to be equal to the sum of the movement variation amount Deltat per unit temperature of the light source (20) relative to the reference plane and the variation amount Deltaf per unit temperature of the back focus of the collimation lenses (2).