| 摘要 |
PURPOSE:To perform the separation of a recording beam from a reproducing beam and the detection of a tracking error and a focusing error by the reproducing beam without necessitating an optical system which requires accuracy in assembling by combining a wedge prism, a ternary split optical detector, and a quaternary split optical detector. CONSTITUTION:Since a ridge line 33c sandwiched between two refracting planes 33a and 33b of the wedge prism 33 is arranged in parallel with the guide groove 10 of an information recording medium 9 observing from an optical standpoint, by receiving the reproducing beams 35a and 35b by the photoreceiving planes 36a and 36b of the ternary optical detector 36, respectively, and computing each output by a differential amplifier 26, an output signal TE for detecting the tracking error can be obtained. Also, by converging two reproducing beams 40a and 40b bi-sected at the wedge prism 38 on the parting line of the photoreceiving planes 41a and 41b and the photoreceiving planes 41c and 41d of the quaternary optical detector 41, the direction and the size of out-of-focus for detecting the focusing error can be obtained as the output signal FE of a differential amplifier 27. |
