Information recording apparatus employing pit edge shifting wherein an error correcting circuit generates an error correction code which is added at part of bits of a predetermined plurality of bits constituting a unit of digital information

Claim 1

An information recording apparatus of the type for recording digital information by forming an information pit on an information recording medium, wherein the improvement comprises: the digital information consists of units each consisting of a predetermined plurality of bits and is recorded by assigning each unit consisting of said plurality of bits one information pit in such a manner that the shape of said information pit is discretely changed according to each said unit consisting of said plurality of bits; there is provided error correction code adding means for adding an error correction code for correcting an error in part of bits of said plurality of bits; the positions of both a rising edge and a falling edge of said information pit are changed in a discrete fashion according to said digital information consisting of plural units of data each consisting of the predetermined plurality of bits; each unit of said digital information consisting of said plurality of bits is assigned a coordinate point in a two-dimensional plane, and the positions of the rising edge and the falling edge of said information pit are changed corresponding to the x and y coordinates, respectively, of said coordinate point; said coordinate points in the two-dimensional plane defined in relation to respective values the digital information consisting of said plurality of bits can have are divided into two groups so that any of said coordinate points nearest to each other are separated into different groups; mapping is performed based on a predetermined bit in such a manner that digital information consisting of said plurality of bits having a value whose predetermined bit is 0 is assigned a coordinate point belonging to one group and digital information having a value whose predetermined bit is 1 is assigned a coordinate point belonging to the other group; and the coordinate points belonging to each group are divided into two subgroups so that any coordinate points nearest to each other are separated into different subgroups and mapping is performed with respect to another predetermined bit of the digital information in a similar manner so that digital information consisting of said plurality of bits is assigned a coordinate point in either subgroup, whereby said digital information consisting of said plurality of bits is assigned a coordinate point in the two-dimensional plane.