Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1998-09-04
2001-09-11
Edun, Muhammad (Department: 2651)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044140, C369S112040
Reexamination Certificate
active
06288985
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to storage devices for computer systems. In particular, the present invention relates to optical and magneto-optical storage devices.
In optical and magneto-optical storage devices for computer systems, a beam of light is projected on to a disc surface that reflects the light in to a sensor. The surface of the dine is patterned to represent data that is typically stored in concentric tracks around the disc. The data is read from the disc by positioning the beam of light over a particular track on the disc and sensing the intensity and polarity of the reflected light from the disc.
To position the beam of light over a particular track, the art currently uses a course actuator in combination with a galvo-mirror assembly. The course actuator moves a lens assembly and a turning mirror over the disc. The light beam is projected toward the turning mirror, which reflects the light beam down into the lens assembly causing the light to focus on a track on the disc. The galvo-mirror assembly is used to direct the light toward the turning mirror. By applying an electrical current to the galvo-mirror assembly, the angle at which the light beam strikes the turning mirror and the lens assembly can be changed. By changing the angle at which the light beam is incident on the lens assembly, it is possible to move the light beam across one or more tracks while keeping the lens assembly fixed over a particular track. Thus, the galvo-mirror assembly provides fine control of the light beam.
Although the position of the light beam can be changed quickly using the galvo-mirror assembly, the light beam provided by the galvo-mirror system is less than ideal. In particular, at some angles of incidence of the light beam on the lens, the light beam can suffer from coma and astigmatism. Coma causes the spot of light on the disc to have a flare distribution and astigmatism causes different polarities of the light to focus at different distances relative to the surface of the disc. Thus, a fine control actuator is needed that can move the spot of light on the disc without causing as many imperfections in the spot of light.
SUMMARY OF THE INVENTION
A storage device for retrieving data stored on a medium includes a lens having a focal axis. The storage device also includes a light source capable of generating light having a direction of propagation that is substantially parallel to the focal axis of the lens as the light passes through the lens. A support assembly supports the lens over the medium and a lens actuator coupled to the support assembly is capable of moving the lens relative to the light while maintaining the focal axis of the lens substantially parallel to the direction of propagation of the light through the lens.
Under the present invention, a disc drive for a computer system includes a lens capable of directing light and a light beam production assembly capable of creating a light beam and directing the light beam toward the lens. A lens support structure supports the lens and a coarse actuator coupled to the light beam production assembly and the lens support structure moves the lens support structure and the light beam production assembly so that the lens moves to different positions over the disc while substantially maintaining a position of the light beam within the lens. A fine actuator coupled to the lens support structure is capable of moving the lens while substantially maintaining a position of the light beam relative to the disc.
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Gage Edward
Jordache Nicholas
Edun Muhammad
Seagate Technology LLC
Westman Champlin & Kelly PA
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