| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical head capable of easily, precisely and optically positioning it so that uniformity of an intensity distribution of a light beam doesn't occur on a pupil of an objective lens and easily miniaturizing and thinning it. SOLUTION: This optical head is provided with a semiconductor laser 21, a diffraction grating 22 diffracting divergent luminous flux outgoing from the semiconductor laser 21 and generating at least three pieces of light beams, the objective lens 27 converging at least three pieces of light beams generated by the diffraction grating 22 on an optical recording medium 28 and light receiving means 30, 32 light receiving return light reflected by the optical recording medium 28. In such a case, the optical head is provided with a numerical aperture control means provided with a liquid crystal shutter 23 held by a hold member common to at least the diffraction grating 22, selectively limiting an aperture of divergent luminous flux from the semiconductor laser 21 and controlling the numerical aperture of the objective lens 27. |
