Information reading and recording device for optical disk

An optical information reading and recording device comprising;

• an optical source;
• a lens arranged between the optical source and an optical recording medium for condensing a light emitted from the optical source on the optical recording medium;
• a diffraction optical element arranged between the optical source and the optical recording medium, in the diffraction optical element, the time when diffraction efficiency is maximum and transmission efficiency is minimum and the time when diffraction efficiency is minimum and transmission efficiency is maximum being determined by the direction of polarization of light;
• a polarization light changeover element for changing a polarization direction of the light emitted from the optical source, wherein the polarization direction of the light emitted from the optical source is changed between in the case of reading information recorded in the optical recording medium and in the case of recording information to the optical recording medium, wherein said polarization light changeover element is arranged between said optical source and said diffraction optical element in an optical axis.

An optical head comprising:

• an optical source;
• a diffraction optical element;
• a polarization light changeover element for changing a polarization direction of the light emitted for the optical source, wherein the polarization direction of the light emitted from the optical source is changed between in the case of reading information recorded in an optical recording medium and in the case of recording information to the optical recording medium, wherein said polarization light changeover element is arranged between said optical source and said diffraction optical element in an optical axis;
• and
• a signal detector for detecting an optical signal from the optical recording medium,
• wherein the polarization light changeover element is a liquid crystal element for changing over a polarization direction of light arranged on an optical path between the optical source and the diffraction optical element, and a voltage on the liquid crystal element is controlled so as to set a polarization direction of light so that a transmission efficiency of the diffraction optical element can be maximum in the case of recording and also a voltage of the liquid crystal element is controlled so as to set a polarization direction of light so that a diffraction efficiency of the diffraction optical element can be maximum in the case of reading.

An optical head comprising:

• an optical source;
• a diffraction optical element;
• a polarization light changeover element for changing a polarization direction of the light emitted for the optical source, wherein the polarization direction of the light emitted from the optical source is changed between in the case of reading information recorded in an optical recording medium and in the case of recording information to the optical recording medium, wherein said polarization light changeover element is arranged between said optical source and said diffraction optical element in an optical axis;
• and
• a signal detector for detecting an optical signal from the optical recording medium,
• wherein the polarization light changeover element is a half wave plate, for rotating a polarization direction of light, which is arranged between the optical source and the diffraction optical element, a direction of the optical axis of the wave plate is set at a polarization direction of light in which a transmission efficiency of the diffraction optical element becomes maximum in the case of recording, the polarization direction of light is set so that the transmission efficiency of the diffraction optical element can be maximum in the case recording when the half wave plate is not provided, the polarization direction of light is set so that the transmission efficiency of the diffraction optical element can be maximum in the case of reading when the half wave plate is provided, and the half wave plate is moved so that it can be taken in and out with respect to the optical axis in the cases of recording and reading.

An optical head comprising:

• an optical source;
• a diffraction optical element;
• a polarization light changeover element for changing a polarization direction of the light emitted for the optical source, wherein the polarization direction of the light emitted from the optical source is changed between in the case of reading information recorded in an optical recording medium and in the case of recording information to the optical recording medium, wherein said polarization light changeover element is arranged between said optical source and said diffraction optical element in an optical axis;
• and
• a signal detector for detecting an optical signal from the optical recording medium,
• wherein the polarization light changeover element is a half wave plate, for rotating a polarization direction of light, which is arranged between the optical source and the diffraction optical element, the half wave plate is moved so that it can be taken in and out with respect to the optical axis in the cases of recording and reading, wherein the polarization direction of light is set so that the transmission efficiency of the diffraction optical element can be maximum in the case recording, and the polarization direction of light is set so that the diffraction efficiency of the diffraction optical element can be maximum in the case of reading.