Optical recording medium, recording system and reproducing system

An optical reproducing method, comprising:

• providing a light beam having a prescribed wavelength and a prescribed intensity;
• providing an optical recording medium comprising in sequence a transparent substrate, a light-reflecting layer, a transparent intermediate layer and a light-absorbing layer, an information pit having been formed as an optically detectable change at mutually corresponding portions in the light-absorbing layer and the light reflecting layer, the light-reflecting layer and light-absorbing layer having mutually different maximum absorption wavelengths and the light-reflecting layer, transparent intermediate layer and light-absorbing layer having respectively prescribed thicknesses, so as to constitute a multi-layer optical element showing a high reflectance with respect to the light beam incident through the substrate, whereby the optical recording medium is free from causing a substantial optically detectable change when irradiated with the light beam through the substrate, whereas at least one of the light-reflecting layer and light-absorbing layer causes an optically detectable change when irradiated with the light beam when the light-reflecting layer, transparent intermediate layer and light-absorbing layer are disposed in different thicknesses;
• and
• irradiating the optical recording medium with a light beam through the substrate to reproduce a signal corresponding to the information pit.

An optical recording medium, comprising in sequence:

• a transparent substrate;
• a light-reflecting layer;
• a transparent intermediate layer comprising polyvinyl alcohol;
• and
• a light-absorbing layer,
• wherein the light-reflecting layer, the transparent intermediate layer and the light-absorbing layer in combination constitute a multi-layer optical element showing a high reflectance with respect to a reproducing light beam having a wavelength .lambda.r and the light-absorbing layer shows a maximum absorption wavelength .lambda..sup.abs max which is substantially equal to a wavelength .lambda.w of a recording light beam, and the light-reflecting layer shows a maximum absorption wavelength .lambda..sup.ref max shorter than .lambda.w.

An optical recording and reproducing method, comprising:

• providing a first light beam and a second light beam, each having a prescribed wavelength being different from each other and a prescribed intensity;
• providing an optical recording medium comprising in sequence a transparent substrate, a light-reflecting layer, a transparent intermediate layer, a light-absorbing layer and a protective substrate, the light-reflecting layer, transparent intermediate layer and light-absorbing layer having respectively prescribed thicknesses so as to constitute a multi-layer optical element showing a high reflectance with respect to the first light beam irradiated through the substrate, whereby the optical recording medium is free from causing a substantial optically detectable change when irradiated with the first light beam through the substrate, whereas at least one of the light reflecting layer and light-absorbing layer causes an optically detectable change when irradiated with the light beam when the light-reflecting layer, transparent intermediate layer and light-absorbing layer are disposed in different thicknesses;
• irradiating the optical recording medium with the second light beam through the protective substrate to cause an optically detectable change in the light absorbing layer and a corresponding portion in the light-reflecting layer, thereby recording information;
• and
• irradiating the optical recording medium with the first light beam through the substrate to reproduce the information.