| 摘要 |
PURPOSE:To realize the miniaturization and the saving of space while securing light transmission efficiency, incident light quantity to a photodetector and an S/N by making incident linear polarization from a light source e.g. P polarization on a first hologram element, converging the 0-order light of the P polarization passing through the element with a converging means and making it incident on an information recording medium. CONSTITUTION:If only a 1st-order defracted light is concerned similarly to the first hologram element 8, the 0-order light, that is, the P polarization L6 among luminous fluxes transmitting through second hologram elements 9a, 9b and separated are made incident on photodetectors 10b, 10e, and an S polarization L5 being the 1st-order defracted light is made incident on photodetectors 10a, 10c, 10d, 10f. Thereafter, by detecting a difference signal between an addition signal from the elements 10b, 10e and the addition signal from the elements 10a, 10c, 10d, 10f with a differential amplifier 7, the detection of an information signal on a magneto-optical disk 4 with a high S/N ratio is attained. In such a manner, the light transmission efficiency by an objective lens 3 being the converging means and the incident light quantity to the elements 10a-10f are secured, and the S/N of the signal is secured. |
