Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
2001-02-22
2002-09-17
Edun, Muhammad (Department: 2653)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S053100, C369S044320
Reexamination Certificate
active
06452883
ABSTRACT:
This application incorporates by reference Taiwanese application Ser. No. 089103293, Filed Feb. 24, 2000.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a method and apparatus for estimating a radial speed of an optical disk. More particularly, the present invention relates to a method and apparatus applied in an optical storage device for estimating a radial speed without being affected by eccentric phenomenon.
2. Description of Related Art
As demand for high capacity storage medium increases, optical discs become more important. Research into methods of rapidly and reliably reading data stored in the optical disc has become a major effort for all manufacturers.
FIG. 1
is a structure diagram for illustrating conventional servo controllers of an optical storage device. A disc
102
is put upon a spindle motor
104
and rotated by the spindle motor
104
. Digital data stored in a plurality of tracks on the disc
102
is read by an optical pick-up
106
. The optical pick-up
106
is assembled on a sled
108
and moved to a suitable position by moving the sled
108
via a sled motor
110
for reading data stored in the disc
102
.
FIG. 2
is a function block diagram of the servo controller of the optical storage device shown in FIG.
1
. Referring to
FIGS. 1 and 2
, the spindle motor
104
begins to rotate when the optical storage device is activated. Laser diode within the optical pick-up
106
emits a laser and a focusing mechanism is activated by the servo controller of the optical storage device. The focusing mechanism focuses the laser beam reflected off the optical disc
102
onto an optical sensor
204
of the optical pick-up
106
. Then, the servo controller activates a tracking mechanism such that the optical pick-up
106
locks the tracks to be read. The optical sensor
204
of the optical pick-up
106
is used for receiving optical signals of the laser beams reflected by the disc
102
and then transforms these optical signals into electric signals that are further processed by a pre-amplifier
206
. The pre-amplifier
206
then outputs analog signals to a control chip
208
. The analog signals can be radio frequency (RF) signals related to the data, focusing error (FE) signals, tracking error (TE) signals, radio frequency ripple (RFRP) signals etc., of which the focusing error signals are used to control the focusing operation of the optical pick-up
106
.
The control chip
208
outputs control signals to power amplifiers
210
and
212
. Output signals of the power amplifier
210
are then transmitted to a lens actuator
214
for controlling fine adjustments of the focusing, tracking and seeking operations of the lens, while output signals of the power amplifier
212
are transmitted to a sled motor
216
for controlling rough adjustments of the tracking and seeking operations of the optical pick-up. The resulting data of the lens actuator
214
and the sled motor
216
are fed back to the optical sensor
204
and, in this way, the optical pick-up
106
can successfully read data stored in the disc.
The lens mounted on the optical pick-up
106
moves up and down vertically until the reflected laser beam focuses on the optical sensor
204
. The tracking operation means that the lens mounted on the optical pick-up
106
is fine adjusted in short horizontal distances such that spots, generated by the laser beams and then focused through the lens, can lock the demanded tracks on the disc
102
. As for the seeking operation, the lens mounted on the optical pick-up
106
and the sled
108
move horizontally to find the target tracks on the disc
102
. In addition, a complete sinusoidal signal is generated in track crossing signal, such as the TE signal or the RFRP signal, while the optical pick-up jumps one track.
Referring to
FIG. 3
, which shows a timing diagram of a tracking error signal TE, a tracking error zero cross signal TEZC, a radio frequency ripple signal RFRP, and a radio frequency ripple zero cross signal RFZC respectively. The TE signal is used to indicate tracking errors; namely, when the spots focused on the disc have an offset relative to target track, the TE signal also varies according to the offset. At time t0, t2, is and t4, the spots are correctly focused on the target tracks of the disc
102
, and therefore the voltage of the tracking error signal TE is Vref and the slopes of the tracking error signal TE corresponding to time t0, t2 and t4 are positive. At time t1 and t3, spots are focused between two adjacent tracks. At these times, the potential of the tracking error signal TE is also Vref, but the slopes of the tracking error signal TE corresponding to time t1 and t3 are negative. When the track is locked, the tracking error signal TE maintains as Vref. The tracking error zero cross signal TEZC can be obtained by comparing the tracking error signal TE with the reference potential Vref. When the tracking error signal TE is larger than Vref, TEZC signal is high; otherwise it is low.
In addition, the radio frequency ripple signal RFRP is defined as the difference between the upper envelope and the lower envelope of the radio frequency signal RF. When the spot is focused on the track of the disc
102
, the RFRP signal reaches a peak value; when the spot is focused between tracks of the disc
102
, the RFRP signal reaches a bottom value. The phase of the RFRP signal leads the phase of the TE signal by 90 degree when the optical pick-up
106
shifts outwards with respect to the disc
102
, and the phase of the RFRP signal lags behind the phase of the TE signal by 90 degree when the optical pick-up
106
shifts inwards with respect to the disc
102
. Therefore, by detecting the phase difference between the RFRP signal and the TE signal, the direction of the optical pick-up
106
shifting with respect to the disc
102
is obtained. Furthermore, when the amplitude of the RFRP signal is larger than the average value of the RFRP signal, the RFZC signal is high, otherwise low.
The number of track jumped by the optical pick-up
106
is obtained by calculating the number of the rising edges of the TEZC signal or the RFZC signal. The period T between two adjacent rising edges is defined as taken in jumping one track. The inverse of T is defined as a relative radial speed V
ld
of the optical pick-up
106
with respect to the disc
102
. For example, as shown in
FIG. 3
, in the period to t
0
t
4
, the optical pick-up
106
crosses two tracks and the radial speed V
ld
is 2/(t
4
-t
0
) Hz.
FIG. 4
shows an eccentric phenomenon for the disc, which generally exists in all discs. The eccentric phenomenon results from manufacturing errors during the manufacturing of the discs, or clamping errors while the disc is put on the spindle motor
104
. The tracks on the disc have a common center, which is called an ideal disc center O
1
; while the disc is put on the spindle motor, the disc is rotated against the eccentric disc center O
2
, or called the center of the spindle motor
104
. As shown in
FIG. 4
, the distance between the centers O
1
and O
2
is defined as an eccentricity of the disc
102
.
Referring both to
FIGS. 4 and 1
, when the optical storage device system activates the focusing operation but does not activate the tracking servo control, the horizontal position of the optical pick-up
106
is fixed at location P. If no eccentricity exists, the center O
2
of the spindle motor
104
is the same as the ideal disc center O
1
. Consequently, when the spindle motor
106
rotates at frequency FRQ, no radial speed exists and the optical pick-up is locked along the track. In contrast, if the eccentricity exists, the center O
2
of the spindle motor
104
is not coincided with the ideal disc center O
1
. Consequently, a radial speed component periodically exists between the disc
102
and the optical pick-up
106
when the spindle motor
106
rotates at a frequency FRQ. Then, the TE and RFRP signals are asserted as sinusoidal waveform.
In addition, when the optical pick-up is fixed at the location P, when the tracking and
Edun Muhammad
Rabin & Berdo P.C.
Via Technologies Inc.
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