| 摘要 |
PURPOSE:To suppress the evil effect of double refraction of a disk base to a reproduced signal, by setting a proper incident polarized direction of the incident laser light. CONSTITUTION:The variation of the S/N with a 30kHz band width to the difference DELTAn between refractive index nt of the circumference direction and refractive index nr of the radius direction of a disk base having 1.2mm. thickness is set on the basis of the S/N value obtained when no double refraction exists at the disk base (DELTAn=0). Then the direction theta of incident linear polarization is shown in the form of a parameter. In such a characteristic diagram, it is understood that the S/N has an extremely stabilized and good characteristic is obtained when the direction theta of the incident laser light is tilted by 7 degrees. (The direction theta is based on the circumference direction of a magneto-optical storage element; and the plus and minus of the DELTAn value make the phase advanced axis correspond to the radius and circumferential direction with correspondence to a phase plate respectively.) That is, the evil effect of double refraction of the disk base can be prevented by setting properly the direction theta of the incident laser light. |
