| 摘要 |
PURPOSE:To improve a C/N ratio without revising a wavelength and a numerical aperture of a light source and to attain recording/reading with high density. CONSTITUTION:An optical disk provided with a substrate 2 and a recording layer 3 consisting of a thermooptical material changing an optical characteristic according to a temperature is rotated, and a laser beam is converged and irradiates the optical disk, and by detecting the reflected beam or the transmission beam, recorded information is read out. In the optical disk, projecting and recessing parts 4 with a period of order of a diffraction limit or below of the laser beam are arranged on the substrate 2 sellectively, and the recording information is formed according to the presence or the length of a part provided with the projecting and recessing parts 4. The projecting and recessing parts may be provided on the recording layer 3. Further, a thermal reflection layer or a thermal insulation layer may be provided on at least one side surface of the recording layer 3. |
