| 摘要 |
PURPOSE:To suppress the reduction of signal output due to wavelength deviation by comprising a device so that a prescribed angle can be made between the axis of a wavelength plate whose phase leads and the axis of a polarization component whose phase leads more when the wavelength of a light source is increased. CONSTITUTION:A condition is studied by which the wavelength dependency of the phase difference (eta) of an optical system passing until reflected light from a disk plane is made incident on the wavelength plate 22 and the wavelength dependency of the phase difference (delta) of the wavelength plate 22 can be compensated. The wavelength plate 22 is manufactured by intersecting orthogonally and sticking the crystal axis of substance having double refraction, for example, two sheets of crystal plates. And the device is comprised so that the axis of the wavelength plate 22 whose phase leads out of two axes with polarization components in the optical system passing until the reflected light from a disk, is made incident on the 1/2-wave plate 22 and the axis with polarization components whose phase leads more when the wavelength input of the light source is increased, can make an angle pi/delta. Thereby, it is possible to suppress the reduction of the signal output due to the wavelength deviation. |
