Methods and apparatus for recording and retrieval of optically readable data employ a recording medium (100) which comprises an optically active material (108) able to induce a change in properties of the medium in the presence of optical radiation having a first characteristic, such as a first optical frequency, and wherein the change in properties can be inhibited by optical radiation having a second characteristic, such as a second optical frequency. During recording, a region of the recording medium (100) is irradiated with a first beam (506) of optical radiation having the first characteristic, the beam having a sufficient intensity within a central portion of the irradiated region and being of sufficient duration to cause an optically induced change in properties of the recording medium. Simultaneously, the region of the recording medium (100) is irradiated with a second beam (508) 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 optically induced change in properties of the recording medium. A similar method is employed for retrieval, however the intensity of the first beam (506) is reduced to prevent changes in material properties within the recording medium (100).

A slider configured for heat-assisted magnetic recording comprises an optical sensor coupled to first and second bond pads. The optical sensor comprises a bolometer and a reference sensor. The bolometer is situated at a location of the slider that receives at least some of the light and exposed to an ambient temperature at the slider. The bolometer produces a signal in response to a change in the ambient temperature and the change in output optical power. The reference sensor is situated at a location of the slider unexposed to the light and exposed to the ambient temperature. The reference sensor is coupled to the bolometer and configured to produce a signal in response to the change in the ambient temperature. The optical sensor is configured to generate a sensor signal indicative of changes in output optical power of a laser source without contribution due to ambient temperature changes.

A slider configured for heat-assisted magnetic recording comprises an optical sensor coupled to first and second bond pads. The optical sensor comprises a bolometer and a reference sensor. The bolometer is situated at a location of the slider that receives at least some of the light and exposed to an ambient temperature at the slider. The bolometer produces a signal in response to a change in the ambient temperature and the change in output optical power. The reference sensor is situated at a location of the slider unexposed to the light and exposed to the ambient temperature. The reference sensor is coupled to the bolometer and configured to produce a signal in response to the change in the ambient temperature. The optical sensor is configured to generate a sensor signal indicative of changes in output optical power of a laser source without contribution due to ambient temperature changes.

In a multilayer optical disc having information layers conforming to a plurality of different optical disc standards, because the type of each information layer is not recorded in the other information layers, in read and write operations by a compatible optical disc device conforming to a plurality of optical disc standards, every time the information layer being accessed changes, it has been necessary to read the type of the information layer and select a method of generating a tracking error signal adapted to the type of information layer, so access has taken time. In order to solve the above problem, in the optical multilayer disc according to the present invention, having information layers conforming to a plurality of different optical disc standards, in an area in one of the information layers, information about the other information layers is recorded. The time required to access the other information layers can be reduced by using this information to select a tracking error signal generating method.

In a multilayer optical disc having information layers conforming to a plurality of different optical disc standards, because the type of each information layer is not recorded in the other information layers, in read and write operations by a compatible optical disc device conforming to a plurality of optical disc standards, every time the information layer being accessed changes, it has been necessary to read the type of the information layer and select a method of generating a tracking error signal adapted to the type of information layer, so access has taken time. In order to solve the above problem, in the optical multilayer disc according to the present invention, having information layers conforming to a plurality of different optical disc standards, in an area in one of the information layers, information about the other information layers is recorded. The time required to access the other information layers can be reduced by using this information to select a tracking error signal generating method.

A reproducing device (100) includes (i) an optical pickup (6) for irradiating, with reproduction light, an optical disk (1) which is a super-resolution medium, (ii) an RF signal processing circuit (9) for converting, into a reproduction signal, light which reflected off optical disk (1), (iii) an i-MLSE detecting section (141) for evaluating quality of the reproduction signal, and (iv) a spherical aberration correcting section (142) for correcting a spherical aberration by using a result of evaluation of the quality of the reproduction signal.

A reproducing device (100) includes (i) an optical pickup (6) for irradiating, with reproduction light, an optical disk (1) which is a super-resolution medium, (ii) an RF signal processing circuit (9) for converting, into a reproduction signal, light which reflected off optical disk (1), (iii) an i-MLSE detecting section (141) for evaluating quality of the reproduction signal, and (iv) a spherical aberration correcting section (142) for correcting a spherical aberration by using a result of evaluation of the quality of the reproduction signal.

A circuit includes a light source, a sensor, and a switch. The sensor measures output of the light source and provides an electrical signal to a feedback loop that is indicative of the measured output of the light source. The switch is positioned in the feedback loop and is movable between a first position and a second position depending upon whether the feedback loop is operating in a first mode of operation or a second mode of operation. During the first mode of operation the output of the feedback loop adjusts at least one operating parameter of the light source responsive to the electrical signal. During the second mode of operation the output of the feedback loop does not adjust the at least one operating parameter of the light source responsive to the electrical signal.

A lens holder includes a holder body and a winding wire wound around the holder body. The holder body includes a winding body, a first projection and a second projection each projecting from a surface of the holder body, and a winding terminal positioned between the first projection and the second projection, and provided on the surface of the holder body. A part of the winding wire is wound around the winding body to form a coil. An end of the winding wire is wound around the second projection and connected to the winding terminal.

A lens holder includes a holder body and a winding wire wound around the holder body. The holder body includes a winding body, a first projection and a second projection each projecting from a surface of the holder body, and a winding terminal positioned between the first projection and the second projection, and provided on the surface of the holder body. A part of the winding wire is wound around the winding body to form a coil. An end of the winding wire is wound around the second projection and connected to the winding terminal.