Optical information recording and reproducing system and optical disk

Abstract

A read only optical disk is provided which includes (1) information sectors having recorded therein first encoded data obtained by encoding data by a first error detection/correction code to perform error detection and correction of the data and (2) check sectors each having recorded therein second encoded data obtained by encoding data among the first encoded data recorded in a plurality of selected information sectors by a second error detection/correction code. The second encoding by the second error detection/correction code is performed with respect to the data of the plurality of selected information sectors which are selected from respective tracks and are arranged sequentially at predetermined intervals in the circumferential direction on the tracks. As a result, in this read only optical disk, even when a two-dimensional defect (i.e., one extending circumferentially and radially) is present on the disk, there is no case in which two or more information sectors associated with the check sector cannot be subjected to error correction. Also, as a result of having one track including (2.sup.m -1) information sectors and one check sector which has overall parities of the information sectors recorded therein, it becomes possible to record in the check sector and in each of the information sectors, respectively, an address, which is peculiar to each sector, to thereby, realize the reproduction of data with high reliability.