Manufacturing method for optical recording medium, optical recording medium, optical information device, and information reproducing method

A manufacturing method for an optical recording medium, the method comprising:

• forming an optical recording medium having a cover layer, N information recording surfaces, and N−1 intermediate layers respectively disposed between the information recording surfaces, wherein N is a positive integer of 3 or more, wherein
• the information recording surfaces include a first information recording surface disposed closest to a surface of the optical recording medium where light is incident, and the first information recording surface is disposed on an opposite side of the cover layer from the surface,
• assuming that actual thicknesses of the cover layer and first through (N−1)-th intermediate layers of the optical recording medium having refractive indexes nr1, nr2, . . . , and nrN are respectively tr1, tr2, . . . , and trN in the order from the surface of the optical recording medium where light is incident, the thicknesses tr1, tr2, . . . , and trN are converted into thicknesses t1, t2, . . . , and tN of layers having a predetermined standard refractive index “no” which makes a defocus value equal to a defocus value of the actual thicknesses tr1, tr2, . . . , and trN,
• a difference DFF between the sum of a thickness “ti” through a thickness “tj”, and the sum of a thickness “tk” through a thickness “tm” is set to 1 μm or more, wherein i, j, k, and m are positive integers satisfying i≦j<k≦m≦N, and
• the thicknesses t1, t2, . . . , and tN are calculated by products of a function f(n) expressed by the following formula (1), and the thicknesses tr1, tr2, . . . , and trN:
• f(n)−1.088n3+6.1027n2−12.042n+9.1007 (1)
• in the formula (1), n=nr1, nr2, . . . , and nrN.