| 摘要 |
PROBLEM TO BE SOLVED: To provide a high density recording and reproducing device in which an optical recording medium is irradiated with a light beam of a short wavelength band in order to give a large recording capacity to the optical recording medium. SOLUTION: The smaller the diameter of an optical beam condensed on the recording layer is, the larger the recording capacity of the optical recording medium becomes, and the shorter the wavelength of the light beam condensed on the optical recording medium is, the smaller the diameter of the light beam becomes. Thus, in the high density recording and reproducing device, a higher harmonic wave having a shorter wavelength with respect to an emitting light is obtained by passing the emitting light from a laser light source 1 through a higher harmonic wave output band 4 composed of a nonlinear optical material. A filter 6 through which the light beam passing through the higher harmonic output band 4 is made incident is used as a band filter which preliminarily passes only the wavelength band of a second higher harmonic wave (approximately 1/2 times a basic wavelength), thus the wavelength of the light condensed on the recording layer of an optical disk 2 becomes a short wavelength and the recording capacity of the optical disk 2 becomes large. |
