| 摘要 |
PURPOSE:To improve the recording density and to expand the band by radiating lights of plural wavelengths to plural kinds of pits having an optical depth corresponding to a prescribed wavelength and reproducing the information recorded on each pit. CONSTITUTION:Plural kinds of pits having optical depth corresponding to a prescribed wavelength exist on an optical information recording medium 10. For example, two kinds of pits 30, 31 of different depth are recorded on the medium 10 and a transparent protective layer 32 having a refractive index (n) is covered uniformly. Then two beams having two kinds of wavelengths such as a fundamental wave B1 of wavelength lambda1 and a 2nd harmonic wave B of wavelength lambda2 are radiated to the pits 30, 31 to reproduce two systems of signals from one and same medium. Thus, the band of the recording signal is spread and the recording density is improved. |
