Dynamic information storage or retrieval – With particular cabinet structure
Reexamination Certificate
1999-07-14
2002-11-26
Tran, Thang V. (Department: 2653)
Dynamic information storage or retrieval
With particular cabinet structure
Reexamination Certificate
active
06487158
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to optical disc drives and, more particularly, to a mechanism and method for securing and covering the optical pickup unit of an optical disc drive when the optical disc drive is not in use.
BACKGROUND OF THE INVENTION
Optical disc drives are devices that use light to translate information stored on an optical disc to a machine-readable format, e.g., binary data. Examples of optical disc drives are known in the art as compact disc drives (often referred to simply as CDS) and digital versatile disc drives (often referred to simply as DVDs). Some optical disc drives have the additional capability of being able to write data onto an optical disc by the use of a light source, e.g., a laser. Optical disc drives are being used in various applications including music and video playing and recording devices and computer data storage devices. As these applications become more portable, the optical disc drives also need to become more portable. For example, they must be compact and able to withstand the shock and vibration to which portable applications are commonly subject.
The optical disc is a round, flat device similar to a record. Digital data is stored in spiral tracks on the optical disc in much the same way analog audio information is stored in a spiral groove on a record. The data stored on an optical disc, however, is much more compact than the audio information stored on a record. For example, the radial distance between tracks on an optical disc is typically approximately 1.6 microns for a compact disc and less for a digital versatile disc. The data on the optical disc consists of a plurality of optical transitions that are detected or “read” by the optical disc drive as the optical disc spins. The optical disc may spin at varying speeds of up to 4000 rpm as data is being read from or written to the optical disc.
A schematic diagram of a side view of a conventional optical disc drive
400
is illustrated in FIG.
1
. The optical disc drive
400
is illustrated with an optical disc
190
attached thereto wherein data is stored on an optical surface
192
of the optical disc
190
. The optical disc drive
400
has three basic components, a drive motor
420
, an optical pickup unit
414
, and an optical mechanical assembly
408
. The drive motor
420
serves to spin the optical disc
190
at predetermined rates that typically vary from several hundred to several thousand rpm. The optical pickup unit
414
serves to read and write data from and to the optical surface
192
of the optical disc
190
. The optical mechanical assembly
408
serves to move the optical pickup unit
414
in a radial direction
440
relative to the optical disc
190
to predetermined locations relative to the optical disc
190
.
The optical pickup unit
414
typically has a laser, not shown, to illuminate the optical surface
192
, an objective lens
416
to focus the laser, and a photodetector, not shown, to translate light to machine-readable data. Other optical components may be located within the optical pickup unit
414
to direct light between the photodetector and the objective lens
416
. Mechanical components may be located in the optical pickup unit
414
and may serve to support the objective lens
416
and to move the objective lens
416
relative to the optical pickup unit
414
.
The optical pickup unit
414
emits incident light that is directed through the objective lens
416
and to the optical surface
192
of the optical disc
190
. The optical pickup unit
414
may, as an example, output approximately 20 milliwatts of coherent light having a wavelength of approximately 790 nanometers. Light is reflected from the optical surface
192
of the optical disc
190
through the objective lens
416
and back to the optical pickup unit
414
. The light reflected from the optical surface
192
of the optical disc
190
varies in intensity wherein the variations are caused by light reflecting from the optical transitions on the optical surface
192
as the optical disc
190
spins. These variations in intensity are representative of the data stored on the optical surface
192
.
As the optical disc
190
spins, the mechanical components in the optical pickup unit
414
move the objective lens
416
in a radial direction
440
and a normal direction
430
. Specifically, the optical pickup unit
414
moves the objective lens
416
normal to the optical surface
192
of the optical disc
190
to focus light between the optical surface
192
and the optical pickup unit
414
. This focusing allows a sharp image of the optical transitions on the optical surface
192
to be focused onto the photodetector, which improves the operation of the optical disc drive
400
. The optical pickup unit
414
moves the objective lens
416
radially relative to the optical surface
192
of the optical disc
190
to follow the tracks on the optical disc
190
as the optical disc
190
spins. This movement of the objective lens
416
is very fine because the objective lens
416
has to follow the tracks with a tolerance of approximately one micron in the radial direction
440
as the optical disc
190
spins. The objective lens
416
is generally mounted to the optical pickup unit
414
by the use of very delicate components. This delicate mounting is required in order for the objective lens
416
to move as precisely as is required to follow the tracks on the spinning optical disc
190
and to focus the optical transitions from the spinning optical disc
190
onto the photodetector.
As described above, the objective lens
416
has to move very precise distances in very short periods in order to follow the tracks on the optical surface
192
. This makes the optical pickup unit
414
a relatively delicate device. The fragile nature of the optical pickup unit
414
makes it susceptible to failure due to relatively mild shock or vibration. One cause of failure is due to the objective lens
416
becoming dislodged from the structural components in the optical pickup unit
414
that secure the objective lens
416
to the optical pickup unit. Another cause of failure is due to the components that move the objective lens
416
becoming damaged. These problems are more prevalent in optical disc drives used in portable devices because these optical disc drives are typically subjected to greater and more frequent shock and vibration.
Additional problems occur in optical disc drives that have the objective lens
416
exposed to a user when an optical disc
190
is being exchanged from the motor
420
. For example, a user may inadvertently touch the objective lens
416
, which may damage the optical pickup unit
414
or contaminate the surface of the objective lens
416
with oils from the user's skin. The user may also cause the optical disc
190
to contact the optical pickup unit
414
, which could damage the optical pickup unit
414
or the objective lens
416
. In addition, during the exchange of the optical disc
190
, the optical pickup unit
414
becomes exposed to the environment and may become damaged if contaminants from the environment enter it. An exposed optical pickup unit
414
may also be dangerous to the user if the optical pickup unit
414
becomes active in the presence of a user. Laser light is typically emitted by the optical pickup unit, which is a relatively bright and narrow beam of coherent light. This light may pose health risks to the user, such as causing irreversible and permanent damage to the user's retinas.
Therefore, a need exists for a mechanism incorporated into an optical disc drive that will secure the optical pickup unit in a fixed position and out of sight and reach of a user when the optical disc drive is not in use.
SUMMARY OF THE INVENTION
An optical disc drive having a cover member movably attached thereto that secures and protects an optical pickup unit is disclosed herein. The optical disc drive is a device that spins an optical disc and “reads” data from the spinning optical disc in a similar manner as a magnetic
Hewlett--Packard Company
Tran Thang V.
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