Concentric photodetector arrangement for focusing and tracking
AssigneeOptotech, Inc.
InventorIvan Prikryl
Life of this patent
Estimating the term…
Abstract
An optical data storage system includes a laser which is focused on an optical disk by an objective lens. A tracking actuator and a focus actuator move the objective lens about a tracking axis and focus axis respectively. The tracking and focus actuators respond to signals provided by a focus and tracking detector. The focus and tracking detector is formed by four photodetectors which are electrically isolated from one another. The third and fourth photodetectors are disposed about the outer peripheries of the first and second photodetectors, respectively, about an axis. Each photodetector emits an electrical signal representative of the radiation detected thereon.
Claims30
For use in conjunction with an optical data storage system of the type having an optical disk with information bearing tracks, laser means for providing a beam of radiation, and an objective lens for focusing the beam of radiation onto the information bearing tracks, a tracking and focusing detector for providing signals as a function of tracking and focus errors of the objective lens with respect to the information tracks on the optical disk, including:
- a first detector section positioned on a first side of an axis and having a radiation sensitive surface for detecting radiation modulated by the information carrying surface, and for providing a first signal representative thereof;
- a second detector section having a radiation sensitive surface positioned on a second side of the axis adjacent and electrically isolated from the first detector section, for detecting radiation modulated by the information carrying surface and for providing a second signal representative thereof, the radiation sensitive surfaces of the first and second detector sections capturing central portions of the radiation beam;
- a third detector section having a radiation sensitive surface positioned on the first side of the axis about a periphery of and electrically isolated from the first detector section, for detecting radiation modulated by the information carrying surface and for providing a third signal representative thereof;
- a fourth detector section having a radiation sensitive surface positioned on the second side of the axis about a periphery of and electrically isolated from the second detector section, for detecting radiation modulated by the information carrying surface and for providing a fourth signal representation thereof, the radiation sensitive surfaces of the third and fourth detector sections capturing peripheral portions of the radiation beam.
An optical head for use in an optical data storage system of the type having an optical disk with servo tracks for storing information, including:
- laser means for producing a beam of radiation to be focused on the optical disk;
- objective lens means for focusing the beam of radiation on the optical disk and for collecting modulated radiation from the optical disk;
- tracking drive means for driving the objective lens about a tracking axis in response to tracking drive signals;
- focus drive means for driving the objective lens about a focus axis in response to focus drive signals;
- and
- focus and tracking detector means for providing signals representative of focus and tracking errors of the objective lens with respect to the optical disk, including:
- a first photodetector defined by an inner edge and an outer periphery;
- a second photodetector defined by an inner edge, which faces the inner edge of the first photodetector, and by an outer periphery, the second photodetector being electrically isolated from the first photodetector;
- a third photodetector disposed about the outer periphery of the first photodetector and electrically isolated from the first and second photodetectors;
- and
- a fourth photodetector disposed about the outer periphery of the second photodetector and electrically isolated from the first, second and third photodetectors.
An optical data storage system, including:
- an optical disk;
- laser means for producing a beam of radiation to be focused on the optical disk;
- objective lens means for focusing a beam of radiation on the optical disk and for collecting modulated radiation from the optical disk;
- tracking drive means for driving the objective lens about a tracking axis in response to tracking error signals;
- focus drive means for driving the objective lens about a focus axis in response to focus error signals;
- focus and tracking detector means for providing signals representative of focus and tracking errors with respect to the optical disk, including:
- a first photodetector defined by an inner edge and an outer periphery and for producing a first detector signal as a function of received radiation;
- a second photodetector defined by an inner edge which faces the inner edge of the first photodetector and by an outer periphery, the second photodetector being electrically isolated from the first photodetector and for producing a second detector signal as a function of received radiation;
- a third photodetector disposed about the outer periphery of the first photodetector and electrically isolated from the first and second photodetectors and for producing a third detector signal as a function of received radiation;
- a fourth photodetector disposed about the outer periphery of the second photodetector and electrically isolated from the first, second and third photodetectors and for producing a fourth detector signal as a function of received radiation;
- and
- processing means connected to receive first, second, third, and fourth detector signals and to provide the focus and tracking error signals as a function of focus and tracking errors which are derived from various combinations of the first, second, third and fourth detector signals.
Dependencies are inferred from the claim text.