| 摘要 |
<p>PROBLEM TO BE SOLVED: To reproduce the information of a disk without performing a special switching operation so as to provide convenience for the user by automatically discriminating whether the disk inserted in a player is a DVD(digital video disk) or a CD(compact disk). SOLUTION: Information recorded on the CD or the DVD is image-formed on upper surfaces of four photodiodes (PDs) positioned in 1st, 2nd, 3rd and 4th phase limits of a quadripartite photodetector 18. Outputs of the four PDs a and d and then b and c are outputted to adders 40 and 38 in a push-pull signal generator 34 and added up respectively. Then, outputs of the adders 38 and 40 are outputted via a differential amplifier 42 to a comparator 36, and a comparison is made with a reference voltage by the comparator 36 to discriminate whether this signal is of the DVD or the CD, and hence a discriminated signal is outputted. On the other hand, outputs of the PDs positioned in diagonal symmetry are outputted in detecting a focus error FE or tracking error TE signal.</p> |
