| 摘要 |
An optical information storage unit for irradiating a light on a recording medium which has a recording surface with a land and a groove, and detecting a reproduced signal from a reflected light received from the recording medium, is constructed to include a first optical element separating the reflected light received from the recording medium into at least three bundles of rays, a second optical element compensating phases of the bundles of rays separated by the first optical element, and a third optical element detecting polarization states of the bundles of rays separated by the first optical element. An amount of phase compensation made by the second optical element is such that an absolute value of a difference between an amount of phase compensation required to reproduce a signal from the land and an amount of phase compensation required to reproduce a signal from the groove is greater than or equal to 60 DEG but less than or equal to 180 DEG .
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