Back to results
US 6,788,628 B2Granted
Optical head and optical data recording/reproducing apparatus using the same
AssigneeNEC Corporation
InventorRyuichi Katayama
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeNEC Corporation
InventorRyuichi Katayama
Estimating the term…
In an optical head for use in an optical data recording/reproducing apparatus of the present invention, light emitted from a semiconductor laser is split into a main beam that is zeroth order light and sub-beams that are plus and minus first-order diffracted light. A focus error signal is detected from each of the main beam and sub-beams. A diffractive optical lens causes the main beam and sub-beams to differ in light intensity distribution from each other when incident to an objective lens. As a result, when a disk or optical recording medium has a thickness error, the focus error signal derived from the main beam and focus error signals derived from the sub-beams differ in zero-crossing point from each other. The thickness error is detected on the basis of the difference between the zero-crossing points.
An optical head comprising:
In an optical data recording/reproducing apparatus comprising a light source, an objective lens for condensing light output from said light source on an optical recording medium, and a photodetector to which light reflected from said optical recording medium is incident, said light output from said light source is split into a main beam and a sub-beam different from each other in a light intensity distribution when input to said objective lens,
Dependencies are inferred from the claim text.