| 摘要 |
PURPOSE:To improve a CN ratio and recording density by making the wavelength of a reproducing laser light shorter than the wavelength of a recording laser light, and reproducing a signal. CONSTITUTION:For a means to make the wavelength of the reproducing laser light shorter than the wavelength of the recording laser light and to reproduce the signal, as a small output semiconductor laser to output an irradiation energy in the degree of 1mW through an optical system, the semiconductor laser of the short wavelength small output of a wavelength 600nm order is in the course of a practical use, and when a second higher harmonics generating element 21 to utilize a non-linear effect is combined to a long wavelength laser 11, even a reproducing laser light 93 of a wavelength 400nm order can be obtained. In such a way, by shortening the wavelength of the reproducing laser light 93, the convergency limit can be contracted to <=1.2mu, at most to the degree of 0.76mum. Thus, without lowering the CN ratio, the interval mutually between recording spots and the interval mutually between information tracks can be contracted, and the recording density of an optical disk 1 and a signal transfer speed can be improved. |
