Claims
- 1. An optical disk unit that emits a light beam to an optical disk, which includes an information recording layer and a light transmission layer for protecting the information recording layer, and that causes the light beam to fall the optical disk from the light transmission layer, thereby recording information or reproducing information, comprising:
a light emitting unit that emits a light beam with a predetermined wavelength; a focusing unit configured to focus the light beam from the light emitting unit at a predetermined position of the information recording layer of the optical disk; a wavefront transforming optical element provided along an optical axis defined between the light emitting unit and the focusing unit, to transform a wavefront of the light beam guided to the focusing unit to the light emitting unit; a thickness difference detection unit to detect a thickness difference of the light transmission layer of the optical disk positioned between the focusing unit and the information recording layer of the optical disk; a wavefront transforming optical element control unit to control the wavefront transforming optical element, the wavefront transforming optical element is reducing a spherical aberration based on a thickness error of the light transmission layer of the optical disk; a beam splitter provided between the wavefront transforming optical element and the focusing unit, the beam splitter reflecting in a predetermine direction a part of the light beam oriented from the wavefront transforming optical element to the focusing unit; a light detector that receives a light beam split from the light beam oriented from the wavefront transforming optical element to the focusing unit by the beam splitter, and outputs an electrical signal corresponding to the light amount of the received light beam; and an output control unit that controls the light amount of the light beam radiated by the light emitting unit based on the magnitude of the electrical signal outputted from the light detector.
- 2. An optical disk unit according to claim 1, wherein either one of the said wavefront transforming optical element includes a first lens and a second lens either one is a convex lens and the other is a concave lens.
- 3. An optical disk unit according to claim 2, wherein a lens moved along the optical axis is the convex lens.
- 4. An optical disk unit according to claim 2, wherein an opening restriction mechanism free of an effect of change in beam diameter on the focusing unit caused when either of the first and second lenses of the wavefront transforming optical element is moved is provided at the light incidence side of the light detector.
- 5. An optical disk unit according to claim 2, wherein the light detector has a light receiving region whose diameter is smaller than that when the light beam split by the beam splitter is incident.
- 6. An optical disk unit according to claim 4, wherein the light detector is integrally provided at least one of a predetermined position in the vicinity of a light emitting side of the beam splitter and a light emitting face thereon.
- 7. An optical disk unit according to claim 2, the light emitting unit further comprising:
a second beam splitter provided between the light emitting unit and the focusing unit, the second beam splitter splits a light beam oriented from the light emitting unit to the optical disk and a reflection light beam reflected by the optical disk from each other; and a second light detector that outputs an electrical signal corresponding to light amount of the reflection light beam split by the second beam splitter; wherein the wavefront transforming optical element control unit to control the one of the first lens and the second lens of the wavefront transforming optical element based on an output signal outputted by the second light detector indicating a thickness difference of the light transmission layer of the optical disk and to suppress a spherical aberration with respect to the light transmission layer of the optical disk.
- 8. An optical disk unit according to claim 1, the wavefront transforming optical element is changeable relevant to a passing light beam applied to a predetermined voltage.
- 9. An optical disk unit according to claim 8,
a wavefront transforming optical element control unit setting a voltage to be applied to the wavefront transforming optical element based on the electrical signal outputted from the second light detector, and controlling the wavefront transforming optical element so as to reduce the spherical aberration with respect to the thickness difference of the recording layer of the optical disk.
- 10. An optical disk unit according to claim 2, the light emitting unit include a back monitor element capable of monitoring light intensity of a light beam radiated by itself, wherein the light intensity of the light beam focused on the information recording layer of the optical disk via the focusing unit can be set under the control of the output control unit based on a back monitor signal outputted by the back monitor element and the output signal outputted by the second light detector indicating the light amount of the light split by the second beam splitter.
- 11. An optical disk unit according to claim 2, the light emitting unit includes a back monitor element capable of monitoring light amount of a light beam radiated by itself, wherein an approximate position of the first lens or the second lens of the wavefront transforming optical element can be set by controlling the wavefront transforming optical element control unit based on a back monitor signal outputted by the back monitor element and the output signal outputted by the second light detector indicating the light amount of the light split by the second beam splitter.
- 12. An optical disk unit according to claim 8, the light emitting unit includes a back monitor element capable of monitoring light amount of a light beam radiated by itself, wherein a predetermined voltage to be applied to the wavefront transforming optical element can be set by controlling the wavefront transforming optical element control unit based on a back monitor signal outputted by the back monitor element and the output signal outputted by the second light detector and indicating the light amount of light split by the second beam splitter.
- 13. An information recording/reproducing apparatus for recording information into a recording medium using a light beam or reproducing information recorded in the recording medium by a light beam, comprising:
an optical head unit including:
a light emitting unit that radiates a light beam with a predetermined wavelength; a focusing unit that focuses the light beam from the light emitting unit at a predetermined position of a recording layer; a first beam splitter provided between the light emitting unit and the focusing unit, the first beam splitter splits the light beam oriented from the light emitting unit and a reflection light beam reflected on the recording layer from each other; a first light detector that outputs an electrical signal corresponding to light amount of the reflection light beam split by the first beam splitter; a wavefront transforming optical element provided along the optical axis defined between the light emitting unit and the focusing unit, the wavefront transforming optical element changing the wavefront of the light beam guided from the light emitting unit to the focusing unit; a wavefront transforming optical element control unit that controls the wavefront transforming optical element based on the electrical signal outputted from the light detector so as not to transform the wavefront of the light beam focused on the recording layer by the focusing unit due to the thickness error of a light transmission layer positioned between the recording layer and the focusing unit; a second beam splitter provided between the wavefront transforming optical element and the focusing unit, the second beam splitter reflecting in a predetermined direction a part of the light beam oriented from the wavefront transforming optical element to the focusing unit; a second light detector that receives a light beam split from the light beam oriented from the wavefront transforming optical element to the focusing unit by the second beam splitter, and outputs an electrical signal corresponding to the light amount of the received light beam; and an output control unit that controls the light amount of the light beam radiated by the light emitting unit based on the magnitude of the electrical signal outputted from the light detector; a motor that rotates an optical disk at a predetermined speed; a control unit that outputs an electrical signal received and converted in a photoelectric manner by the first detector of the optical head unit as information recorded in the optical disk; and a memory that supplies information to be recorded, to the output control unit of the optical head unit.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2001-294849 |
Sep 2001 |
JP |
|
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-294849, filed Sep. 26, 2001, the entire contents of which are incorporated herein by reference.