Patent ID: 6956802

Claim:
An aperture ratio measuring apparatus for an optical recording medium having a recording surface provided with pre-pits which are repeatedly formed between tracks and carries information related to said tracks, comprising: an optical detector having a light receiving surface divided into a first and second light receiving faces in the tangential direction of said track, for receiving the reflected light of a light beam radiated onto said recording surface on said first and second light receiving faces to output first and second light detection signals corresponding to respective amounts of the received light on said first and second light receiving faces; a subtractor for calculating the difference between said first and second light detection signals output from said optical detector to generate a push-pull signal; a collection device for collecting sample data by sampling said push-pull signal for a predetermined period of time and for repeating the sampling operation for the predetermined period of time by a plurality of times; a frequency determination device for determining whether each data value corresponding to a pre-pit position of the sample data by the plurality of times collected by said collection device is obtained by a predetermined number of times or greater; and an aperture ratio calculator, when data values obtained by the predetermined number of times or greater are determined by said frequency determination device, for calculating as an aperture ratio, a ratio between the minimum value and the maximum value of values corresponding to a pre-pit component of the data values obtained by the predetermined number of times or greater.