Optical recording and reproducing method and apparatus using light beams of two different wavelenghts

摘要

In an optical recording and reproducing method and an apparatus employed for effecting the method, in a light beam of a wavelength lambda 1 is converted by a laser unit into a light beam having a wavelength lambda 2 which shorter than the wavelength lambda 1 through employment of a wavelength converting element, and the light beams with wavelengths lambda 1 and lambda 2 are converged at approximately the same spots on a recording medium. For recording a signal, a light intensity of the light beam of the wavelength lambda 1 projected onto the recording medium is arranged to be a light intensity for not effecting recording of the signal independently, and recording of the signal is effected through modulation of at least the light beam of the wavelength lambda 2 to be high or low intensity according to the signal to be recorded. For recording or reproducing signals, focus control and tracking control are effected by detecting only the light beam of the wavelength lambda 2 reflected from the recording medium.