| 摘要 |
PURPOSE:To stabilize reading by providing a first diffraction grating to send light outside a waveguide plane, a second diffraction grating to diffract the light again, a convergence means to converge and irradiate the light, and a light receiving means to receive reflected light. CONSTITUTION:The light emitted from a semiconductor laser 5 is made incident on a waveguide layer 2, and are formed nearly as parallel rays by a waveguide type lens 14, and are emitted outside the waveguide by the function of the first diffraction grating 11. Emitted light are reflected on a reflecting layer 7, and receive diffraction by the second diffraction grating 12, and are converged by a lens 3, and form a focal point on an optical information medium 20, then, optical information 21 is read out. The gratings 11 and 12 are provided with wavelength distribution characteristics in the angles of diffraction, respectively, and each diffraction grating is arranged so as to negate respective the wave length distribution characteristic. In other words, the grating 12 is arranged so as to receive and diffract diffracted light again. At this time, the wavelength distribution characteristic can be negated even when the fluctuation of wave length is generated in the laser 5, and the distribution of the wavelength charac teristic can be reduced. |
