| 摘要 |
A light flux reflected by the video disc is made incident upon a detection prism surface set at a critical angle with respect to a central light ray in the reflected flux. Two fluxes are situated on respective sides of a boundary plane, including central light ray and a prependicular ray to a plane of incidence. The fluxes are reflected by the reflection surface and are separately received by two light receiving regions divided along a boundary plane including the central light ray reflected by the reflection surface and perpendicular to the plan of incidence.
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