| 摘要 |
PROBLEM TO BE SOLVED: To provide a recording and reproducing method, by which no crosstalk is generated even in an optical disk for high density recording, and to provide the device and disk therefor. SOLUTION: A luminous flux is emitted from a condensing lens 5 to the recording area of an optical disk D in which a guiding groove G,... and a non- guiding groove L,... alternately arrayed successively in the radial direction are both recording areas. In reproducing an information signal using an optical detector 7 equipped with a light receiving face, which is in an image-forming relation with the recording area of the optical disk D and which is provided with the size about equal to a light spot on the light receiving face; assuming the wavelength of light for reproducing is λ, refraction factor of the substrate of the optical disk D is n, diameter of the condensing lens 5 is (a), and focal distance of the condensing lens 5 is f, a height H between the face of the guiding groove G,... and that of the non-guiding groove L,... of the optical disk D is H>(λ/n).(f/2a)<2> ... (2); recording and reproduction are performed using such optical disk D as meets the expression (2) or such condensing lens 5 are capable of satisfying the expression (2). |
