Patent ID: 7283447

Claim:
An optical disk which is constructed in such a manner that an information recording layer formed on a substrate is covered with a light transmission layer and in which the range of the thickness and the refractive index of the light transmission layer is set so that aberration due to a deviation of the thickness and the refractive index of the light transmission layer from each standard value falls within the range of certain acceptable values, wherein the thickness t of the light transmission layer is set within the range of f(n)−t 1 ≦t≦f(n)+t 2 , employing function f(n) of the refractive index n of the light transmission layer and constants t 1 , t 2 determined based on an acceptable value of aberration in the light transmission layer, the refractive index of the light transmission layer is set within the range of 1.5 to 1.7, the numerical aperture of a lens emitting laser light which is incident onto the light transmission layer is set to 0.65, and the function f (n) is shown by f ⁡ ( n ) = A 1 × n 3 n 2 - 1 × n 2 + A 2 n 2 + A 3 ⁢ ( mm ) employing constant A 1 , A 2 , A 3 , wherein the constant Al is 0.26200, constant A2 is -0.32400 and constant A3 is 0.00595; the acceptable value of aberration in the transmission layer is 0.03 λrms, the constants t 1 , t 2 are substantially set to 13 μm, predetermined position on curved lines that f(n)−t 1 and f(n)+t 2 show are sampled, and an area encircled by connecting each sample point by means of straight lines is set as the range of the thickness t of the light transmission layer, and the thickness of the light transmission layer is 0.6 mm.