Method and system for optical data storage

A method of optically reading data stored in a recording medium which comprises an optically active material in which a change in properties of the medium corresponding with recorded data has been induced in one or more regions, wherein the change in properties is detectable via a response of the medium to optical radiation having a first characteristic, and wherein the response of the medium can be inhibited by optical radiation having a second characteristic, the method comprising:

• irradiating a region of the recording medium with a first beam of optical radiation having the first characteristic, the first beam having sufficient intensity within a central portion of the irradiated region and being of sufficient duration to cause the response, but of insufficient intensity and duration to cause an optically induced change in properties of the recording medium;
• simultaneously irradiating the region of the recording medium with a second beam of optical radiation having the second characteristic, the second beam having a local intensity minimum within the central portion of the irradiated region, and a local intensity maximum in at least one portion of the irradiated region adjacent to the central portion which is sufficient to inhibit the response of the medium to the first beam of optical radiation;
• and detecting whether the medium exhibits the response to the first beam of optical radiation within the central portion of the irradiated region.

An optical data recording and reproduction apparatus comprising:

• a mounting configured to hold a recording medium which comprises an optically active material able to induce a change in properties of the medium, and to generate a material response indicative of the changed properties, in the presence of optical radiation having a first characteristic, and wherein the change in properties, and the response indicative of changed properties, can be inhibited by optical radiation having a second characteristic;
• a first optical source configured to control the emit radiation having the first characteristic;
• a first imaging system configured to controllably focus a first beam of optical radiation emitted from the first optical source onto a region of the recording medium, wherein the optical radiation has a maximum intensity within a central portion of the first beam;
• a second optical source configured to controllably emit radiation having the second characteristic;
• a second imaging system configured to controllably focus a second beam of optical radiation emitted from the second optical source onto the region of the recording medium, wherein the optical radiation has a local intensity minimum within a central portion of the second beam, and a local intensity maximum in at least one portion of the second beam adjacent to its central portion;
• and a controller configured to control at least the first optical source, the first imaging system, the second optical source, and the second imaging system, so as to simultaneously irradiate a selected region of a recording medium held in the mounting with optical radiation of a first selected intensity emitted from the first optical source, and with optical radiation of a second selected intensity emitted from the second optical source, to selectively record or read data to or from the recording medium.

A method of optically reading data stored in a recording medium which comprises a recording layer that comprises an optically active material in which a change in properties of the medium corresponding with recorded data has been induced in one or more regions and that stores data by the change in the properties of the medium, wherein the change in properties is detectable via a response of the medium to optical radiation having a first characteristic, and wherein the response of the medium can be inhibited by optical radiation having a second characteristic, the method comprising:

• irradiating a region of the recording layer with a first beam of optical radiation having the first characteristic, the first beam having sufficient intensity within a central portion of the irradiated region and being of sufficient duration to cause the response, but of insufficient intensity and duration to cause an optically induced change in properties of the recording medium;
• simultaneously irradiating the region of the recording layer with a second beam of optical radiation having the second characteristic, the second beam having a local intensity minimum within the central portion of the irradiated region, and a local intensity maximum in at least one portion of the irradiated region adjacent to the central portion which is sufficient to inhibit the response of the medium to the first beam of optical radiation;
• and
• detecting whether the recording layer exhibits the response to the first beam of optical radiation within the central portion of the irradiated region.

An optical data recording and reproduction apparatus comprising:

• a mounting configured to hold a recording medium which comprises a recording layer that comprises an optically active material able to induce a change in properties of the medium, and to generate a material response indicative of the changed properties, in the presence of optical radiation having a first characteristic, and wherein the change in properties, and the response indicative of changed properties, can be inhibited by optical radiation having a second characteristic;
• a first optical source configured to control the emit radiation having the first characteristic;
• a first imaging system configured to controllably focus a first beam of optical radiation emitted from the first optical source onto a region of the recording layer, wherein the optical radiation has a maximum intensity within a central portion of the first beam;
• a second optical source configured to controllably emit radiation having the second characteristic;
• a second imaging system configured to controllably focus a second beam of optical radiation emitted from the second optical source onto the region of the recording layer, wherein the optical radiation has a local intensity minimum within a central portion of the second beam, and a local intensity maximum in at least one portion of the second beam adjacent to its central portion;
• and
• a controller configured to control at least the first optical source, the first imaging system, the second optical source, and the second imaging system, so as to simultaneously irradiate a selected region of a recording layer held in the mounting with optical radiation of a first selected intensity emitted from the first optical source, and with optical radiation of a second selected intensity emitted from the second optical source, to selectively record or read data to or from the recording layer.