| 摘要 |
A method for discriminating between different types of optical discs is intended to apply to an optical storage device with a pick-up head having three beams. A main beam push-pull signal and a sub-beam push-pull signal, both acquired by means of the photo-detector of the pick-up head, are superposed on each other to have an additive push-pull signal, whereas, on subtraction, the difference between the main beam push-pull signal and the sub-beam push-pull signal generates a differential push-pull signal. If the peak-to-peak voltage of the differential push-pull signal is greater than that of the additive push-pull signal, it is judged that the light spots derived from the sub-beams and the main beam of the three beams respectively fall on two contiguous lands and a groove therebetween on an optical disc inside the optical storage device. Also, if the peak-to-peak voltage of the differential push-pull signal is smaller than that of the additive push-pull signal, it is judged that the light spots derived from the sub-beams and the main beam separately fall on three contiguous grooves on the optical disc respectively.
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