Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2000-09-05
2004-08-10
Tran, Thang V. (Department: 2653)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044250, C369S053280, C369S094000
Reexamination Certificate
active
06775208
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for controlling the focus speed of a pick-up head, and more particularly, to the method for controlling the focus speed of the pick-up head while performing a layer jump operation over a multi-layer optical disk in an optical information reproducing device.
2. Description of the Related Art
An optical information reproducing device, such as CD-ROM\DVD-ROM\CD-RW\DVD-RAM, has been widely applied in multimedia computer systems and becomes one basic element of the computer systems. Some U.S. Pat. Nos., i.e. 4,783,774, 5,289,097, 5,246,479 and 5,345,347 may be referred in order to have an in-depth understanding of the optical information reproducing device.
Please refer to FIG.
1
.
FIG. 1
shows a function block diagram of a conventional optical information reproducing device
10
. Typically, an optical information reproducing device
10
includes a pick-up head
12
, a pre-amplifier
14
, a digital signal processor
16
, a microprocessor
18
, a servo controller
20
, a driver circuit
22
and an actuator
24
. The pick-up head
12
is for reading data stored on an optical disk
26
. The pre-amplifier
14
is electronically connected to the pick-up head
12
for amplifying the signal of data read from the optical disk
26
and generating an analog signal of reading data. The digital signal processor
16
is electronically connected to the pre-amplifier
14
for receiving the analog signal of reading data and generating a digital signal of reading data. The microprocessor
18
is electronically connected to the digital signal processor
16
for processing the digital signal of reading data according to a predetermined procedure. The servo controller
20
is electronically connected to the microprocessor
18
, digital signal processor
16
and pre-amplifier
14
for detecting and processing the signal of servo data read from the optical disc
26
, wherein the servo data includes servo burst, synchronous pulse and track number etc. The driver circuit
22
is electronically connected to the servo controller
15
for providing an actuating driving signal. The actuator
24
is electronically connected to the driver circuit
22
and pick-up head
12
for driving the pick-up head
12
to different radial positions in response to the actuating driving signal, or kicking an objective lens (not shown) of the pick-up head
12
to a focus on the optical disk
26
in response to another actuating driving signal.
Please refer to FIG.
2
.
FIG. 2
shows a schematic diagram of traditionally focusing a dual-layer optical disk
26
. While the optical information reproducing device
10
is applied to a dual-layer optical disk
26
for performing a layer jump operation, the objective lens of the pick-up head
12
will move from a first focus
27
to a second focus
28
over the optical disk
26
. First of all, the digital signal processor
16
sends a kick pulse signal
29
in response to a layer jump command of the microprocessor
18
. The kick pulse signal
29
is then sent to the actuator
24
through the servo controller
20
and driver circuit
22
. The actuator
24
, in response to the kick pulse signal
29
, kicks the objective lens of pick-up head
12
out of the first focus
27
of the optical disc
26
. When the objective lens moves closely to the second focus
28
of the optical disk
26
, the digital signal processor
16
sends a brake pulse signal
25
in response to a brake command of the microprocessor
18
. The brake pulse command
25
is then sent to the actuator
24
through the servo controller
20
and driver circuit
22
. The actuator
24
locks the objective lens of the pick-up head
12
over the second focus
28
of the optical disk
26
.
Please refer to FIG.
3
and FIG.
4
.
FIG. 3
shows a relative control signal diagram of the objective lens while unlocking the second focus
28
.
FIG. 4
shows another relative control signal diagram of the objective lens while unlocking the second focus
28
. Focus error signal S
e
shown in FIG.
3
and
FIG. 4
represents an error signal of the relative position between the objective lens and focus
27
and
28
, which is generated by the pick-up head
12
. Control pulse signal S
c
shown in FIG.
3
and
FIG. 4
represents a force signal for driving the objective lens, which is generated by the digital signal processor
16
. RF Level signal S
r
shown in FIG.
3
and
FIG. 4
represents a reading intensity signal of the pick-up head
12
, which is generated by the pick-up head
12
. However, due to the deviation of the optical disk
26
and the difference of the actuator
24
, while the optical information reproducing device
10
performing the layer jump operation on dual-layer disk
26
, it is not able to predict precisely the speed with which the objective lens moving closely to the second focus
28
of the optical disk
26
. If the relative speed between the objective lens and the second focus
28
is too high and the braking force applied to the objective lens is constant, the objective lens often overshoots and unlocks the second focus
28
, wherein the focus error signal S
e
has a diversifying trend with time as shown in FIG.
3
. On the other hand, if the objective lens can't reach the second focus
28
in time, it also won't be able to react immediately and speed up the objective lens to lock the second focus
28
as shown in FIG.
4
. Therefore while performing the layer jump operation over the dual-layer disk
26
, the conventional control method of the focus speed is unstable with respect to the objective lens of the optical information reproducing device
10
.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide a method for controlling a focus speed of a pick-up head to solve the above mentioned problem.
In a preferred embodiment, the present invention provides a method for controlling a focus speed of a pick-up head while performing a layer jump operation over a multi-layer optical disk in an optical information reproducing device. The optical information reproducing device includes the pick-up head, an actuator and a counter. The pick-up head has an objective lens positioned over a first focus of the multi-layer optical disk, in response to a signal reflected from the multi-layer optical disk, will generate a RF level signal. The actuator is electronically coupled to the pick-up head for driving the objective lens to perform the layer jump operation in response to a kick pulse signal. The counter generates a counter value in response to the kick pulse signal. The method comprises the steps of sending the kick pulse signal to the actuator for kicking the objective lens out of the first focus; processing the RF level signal and the counter value for generating a speed control data according to a predetermined procedure; and driving the objective lens to a second focus through the actuator in response to the speed control data. When the closing speed between the objective lens and the second focus is too high, the actuator will apply a greater braking force on the objective lens. When the closing speed between the objective lens and the second focus is too low, the actuator will apply a weaker braking force on the objective lens. If the objective lens can't reach the second focus in time, the actuator will apply a speeding force on the objective lens. Therefore, the optical information reproducing device applied with the method of the present invention will have a stable layer jump operation.
This and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various drawings and figures.
REFERENCES:
patent: 4783774 (1988-11-01), Enomoto
patent: 5246476 (1993-09-01), Yoshimura et al.
patent: 5289097 (1994-02-01), Erickson et al.
patent: 5345347 (1994-09-01), Hopkins et al.
patent: 5793721 (1998-08-01)
Hsu Wei-Hsin
Liu Ching-Hwa
Tsai Chun-Hsiang
Asustek Computer Inc.
Rabin & Berdo P.C.
Tran Thang V.
Vuong Bach
LandOfFree
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