Dynamic information storage or retrieval – Information location or remote operator actuated control – Selective addressing of storage medium
Reexamination Certificate
2000-02-25
2004-10-12
Psitos, Aristotelis M (Department: 2653)
Dynamic information storage or retrieval
Information location or remote operator actuated control
Selective addressing of storage medium
C369S030130, C369S030150
Reexamination Certificate
active
06804176
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to an information recording/reproducing method and apparatus and to a transmission medium for use therein and, more particularly, relates to an information recording/reproducing method and apparatus and to a transmission medium that is able to search a desired track reliably despite employing a simplified structure.
2. Description of the Background
FIG.7
shows the principal elements of a conventional optical disc device, in which an optical disc
2
is rotated at a pre-set speed by a spindle motor
1
. A pickup
3
associated with the head mechanism illuminates laser light radiated from an enclosed laser diode via an objective lens
4
to the optical disc
2
for recording/reproducing the information. A sled motor
6
, is configured for transporting the pickup
3
via a gear
7
along a sled guide rod
5
in the radial direction of the optical disc
2
.
A servo amplifier
8
generates focussing error signals, tracking error signals, and traverse signals from an output signal of the pickup
3
to output the thus generated signals to a servo processor
9
. The traverse signal is a signal generated by comparing the tracking error signal with a zero level as a reference level.
The servo processor
9
processes the focussing error signals in a pre-set fashion to route the processed focussing error signals via a focussing drive amplifier
10
to the pickup
3
to drive the objective lens
4
in the correct focussing direction. The servo processor
9
also processes the tracking error signals in a pre-set fashion to send the processed signals to the pickup
3
via a tracking drive amplifier
11
to drive the objective lens
4
by a tracking actuator to make small adjustments in the tracking direction. The servo processor
9
also is responsive to the output signals from the servo amplifier
8
to generate a sled drive signal from the voltage signals of the low range component and sends this sled drive signal via a sled drive amplifier
12
to the sled motor
6
to transfer the pickup
3
via a gear
7
along a sled guide rod
5
in the radial direction of the optical disc
2
. The servo amplifier
8
also controls the spindle motor
1
to control the rotation of the optical disc
2
.
FIG. 8
represents a circuit structure mainly for the tracking servo and the sled servo. The tracking error signals are fed to a first low boost filter (LBF)
23
and outputted via a high-range, phase-lead, high boost filter (HBF)
36
, an adder
32
, and an amplifier
33
. A speed verifying unit
34
detects a rising edge and a falling edge of an input traverse signal and verifies the transfer speed of the pickup
3
using the edge interval and outputs a result of the decision to a tracking drive controller
35
. During ordinary reproduction, neither the speed verifying unit
34
nor the tracking drive controller
35
is used. During fine search, however, the tracking drive controller
35
is responsive to a signal from the speed verifying unit
34
to generate pulses for driving the pickup
3
in the direction toward the outer rim of the disc or to generate pulses for driving the pickup
3
in the direction toward the inner rim of the disc and outputs the so-generated pulses to the adder
32
.
The tracking drive output is again fed as a sled error signal to a second low boost filter
37
and subsequently fed to a sled drive controller
39
. This signal is amplified by an amplifier
40
to drive the sled motor as a sled motor drive output signal, which drives the pickup
3
in the direction toward the outer rim or toward the inner rim of the disc along the sled guide rod
5
.
Referring to the timing chart of
FIGS. 9A-9E
, the operation for performing a fine search will be explained. Fine search means the operation of jumping the pickup
3
track-by-track in the direction toward the outer rim or toward the inner rim of the disc to transfer the pickup
3
a pre-set number of tracks, such as from 10 to 1000 tracks, in order to search for the desired track. In the fine search, the pickup moves first and then the sled follows.
As an example of operation, if a controller in the form of a micro-computer, not shown, issues a command for doing a fine search toward outer rim side tracks for a pre-set number of tracks, the tracking drive controller
35
outputs a tracking drive kick pulse, shown in
FIG. 9D
, to effect a jump of the objective lens
4
by one track in the direction toward the outer rim of the disc. It is assumed that a signal of positive polarity is a signal for transferring the objective lens
4
in the direction toward the outer rim of the optical disc
2
, and that a signal of negative polarity is a signal for transferring the objective lens
4
in the direction toward the inner rim of the optical disc
2
. Therefore, in this example, a kick pulse of positive polarity is output from the tracking drive controller
35
and is routed via the adder
32
and the amplifier
33
to the tracking drive amplifier
11
and thence to the pickup
3
. This causes the objective lens
4
of the pickup
3
to jump by one track in the direction toward the outer rim of the optical disc
2
. Similar operations are carried out in succession until a jump of the pre-set number of tracks is achieved.
In such case, the tracking error signal output by the servo amplifier
8
is varied sinusoidally each time the pickup performs a track jump, as shown in FIG.
9
A. The traverse signal, generated by comparing the tracking error signal to the zero level reference, is a rectangular signal having a rising edge or a falling edge at the zero-crossing point of the tracking error signals. The speed verifying unit
34
detects the rising and falling edges of the traverse signal and generates edge detection signals, as shown in FIG.
9
C. The speed verifying unit
34
also measures an interval T of the edge detection signals to check whether this interval T is larger than a pre-set reference value, that is, to check the period or speed, of the fine search. If the interval T is larger than a reference value, that is, if the fine search speed is slower than the reference speed, the speed verifying unit
34
outputs a signal of, for example, positive polarity and if the interval T is smaller than the reference value, that is, if the fine search speed is faster than the reference speed, the speed verifying unit
34
outputs a signal of negative polarity.
The tracking drive controller
35
generates tracking drive kick pulses, based on results of the decision from the speed verifying unit
34
, in meeting with the fine search direction. Since the fine search direction in this case is toward the outer rim of the disc, the tracking drive controller
35
generates a tracking drive kick pulse of positive polarity if the signal from the speed verifying unit
34
is of positive polarity. On the other hand, if the signal from the speed verifying unit
34
is of negative polarity, it generates a tracking drive kick pulse of negative polarity.
Thus, if the fine search speed is slower than the reference speed, the objective lens
4
is kicked or jumped by the tracking pulse in the direction toward the outer rim of the optical disc
2
, that is, in the fine search direction. Conversely, if the fine search speed is faster than the reference speed, the objective lens
4
is fed with a tracking drive kick pulse to move it in the direction toward the inner rim of the optical disc
2
. It should be noted that, because the objective lens
4
is continuously jumping in the direction toward the outer rim of the optical disc
2
as the disc is being played back, by this tracking drive kick pulse in the direction toward the inner rim of the disc the objective lens
4
is braked against driving in such direction, with the result that servo is applied so that the fine search speed will be a pre-set reference speed, without actually being jumped in the direction toward the inner rim.
Meanwhile, with the pickup
3
being halted on the sled guide rod
5
, if the objective le
Maioli Jay H.
Psitos Aristotelis M
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