| 摘要 |
PROBLEM TO BE SOLVED: To control a deflection amount of a laser beam and perform a correct fine moving tracking by providing a beam separating means separating a laser beam in between a relay lens group and an imaging lens group, forming the imaging lens group and the beam separating means integrally and detecting beams which are separat ed by transmitting the laser beam to an objective optical system to make the quantity of the laser beam controllable. SOLUTION: The angle of incidence of the laser luminous flux with respect to the objective optical system provided at the top end of an arm for coarse motion moving in a direction crossing with tracks of a magneto-optical disk is finely adjusted by the deflection means of a deflection mirror 26. The neighborhood of the deflection mirror 26 and the principal plane being the front side of the objective lens 10 is made so as to be roughly a conjugate relation. A condensing prism 61 forms a palno-convex lens in all and has the function of an imaging lens and, also, it is provided with a semitransparent film which is inclined by 45 degrees with respect to the optical axis of this head and has the function of a separation prizm. Moreover, it is provided with photodetectors 50A, 50B and controls the deflection quantity of a beam by detecting the turning amount of the deflection mirror 26 while receiving the peripheral part of the laser beam. |
