| 摘要 |
PROBLEM TO BE SOLVED: To visually discriminate the presence or absence of eccentricity between two substrates or the amount of eccentricity and also to simply read out them even mechanically by moire fringes without using any special device by forming patterns respectively generating moire fringes on the two substrates to be stuck. SOLUTION: An eccentricity decision area 3 is provided at least in the area of one side of the inner side or the outer side of a recording area 2 on respective transparent substrates of an optical disk 1 to be constituted by sticking two sheets of transparent substrates. On the optical disk 1 shown in the figure, an absolute amount of eccentricity decision area 5 and a relative amount of eccentricity decision area 4 are respectively provided in the inner side and in the outer side of the recording area 2. In the eccentricity decision area 3, plural lines of trains of eccentricity decision track which is of a concentric circular shape or plural rounds of eccentricity decision track which is of a helical shape are formed as patterns generating moire fringes. Thus, the amount of eccentricity is calculated by the number of pairs of moire fringes and also the relative direction of eccentricity is judged by an angular direction along which pairs of moire fringes are generated. |
