Optical information reproducing method, optical head device, and optical information processor

An optical head device for reproducing information from an optical recording medium,

• the optical recording medium comprising:
• a recording layer containing the information;
• and
• a mask layer that is located close to the recording layer and includes a nonlinear optical material whose optical properties are changed in accordance with incident light intensity,
• the optical head device comprising:
• a radiation light source for radiating light that is polarized in a first direction;
• a focusing optical system for converging the light emitted from the radiation light source on the optical recording medium to form a tiny spot;
• a polarization separation optical system for dividing reflected light from the optical recording medium into a first polarized component that is polarized in the first direction and a second polarized component that is polarized in a second direction perpendicular to the first direction;
• and
• a photodetector for detecting a reproduction signal by receiving the second polarized component separated by the polarization separation optical system.

An optical information processing apparatus comprising:

• an optical recording medium;
• and
• an optical head device,
• the optical recording medium comprising:
• a recording layer containing information;
• and
• a mask layer that is located close to the recording layer and includes a nonlinear optical material whose optical properties are changed in accordance with incident light intensity,
• the optical head device comprising:
• a radiation light source for radiating linearly polarized light that is polarized in a first direction;
• a focusing optical system for converging the light emitted from the radiation light source on the optical recording medium to form a tiny spot;
• a polarization separation optical system for dividing reflected light from the optical recording medium into a first polarized component that is polarized in the first direction and a second polarized component that is polarized in a second direction perpendicular to the first direction;
• and
• a photodetector for detecting a reproduction signal by receiving the second polarized component separated by the polarization separation optical system.