Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Reexamination Certificate
2000-06-29
2001-12-04
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
C318S459000
Reexamination Certificate
active
06326756
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to method and apparatus for finding the digital value requiring to drive a motor of an optical disk device and applying a driving voltage according to the digital value to the motor.
2. Description of the Related Art
FIG. 1
depicts a block diagram of an optical disk device equipped in a personal computer (PC), which comprises an optical pickup
11
for reading recorded digital signals through detecting a laser beam reflected across pits formed in the surface of an optical disk
10
and converting them into electric signals; a spindle motor
12
a
for rotating the inserted optical disk
10
; a sled motor
12
b
for moving the optical pickup
11
radially on the disk
10
; an R/F unit
20
for equalizing and shaping analog RF signals detected by the optical pickup
11
into binary signals; a servo unit
30
for controlling the optical pickup
11
and the rotation of the optical disk
10
based upon a focussing error signal and a tracking error signal yielded from the R/F unit
20
; a motor driver
31
for driving the spindle motor
12
a
and the sled motor
12
b
separately; a voltage regulator
40
regulating the operating voltage supplied from an external source such as a PC slot to provide a constant voltage for signal processing; a digital signal processor (DSP)
50
for processing the binary signals shaped from the R/F unit
20
to restore them into original digital data; a microcomputer
60
for outputting a digital control voltage for driving the motors
12
a
and
12
b
and controlling the above elements while reproducing the optical disk
11
; and a D/A converter
70
for converting the digital control voltage from the microcomputer
60
into an analog voltage.
The above conventional optical disk device equipped in a PC performs reproduction process with the power supplied from the PC slot. When an optical disk
10
is inserted in a tray (not figured) equipped in the optical disk device and clamped by a clamper (not figured), the microcomputer
60
outputs control voltages to drive the spindle motor
12
a
and the sled motor
12
b
respectively through the motor driver
31
, thereby the spindle motor
12
a
rotates the optical disk
10
at a constant speed of 2,500 rpm owing to the driving voltage supplied from the motor driver
31
. At the same time, the sled motor
12
b,
which is a stepping motor, moves the optical pickup
11
to an initial reproduction position of the optical disk
10
. This operations done, the reproduction process starts.
During the reproduction, the optical pickup
11
should be moved radially on a request for search or movement. In this case, the microcomputer
60
controls the sled motor
12
b.
The detailed control process of the microcomputer
60
is as follows.
If the microcomputer
60
intends to apply a certain driving voltage, for example 1.5V, to the sled motor
12
b,
the microcomputer
60
applies the value of 01001100
(2)
which is a digital value of 76(=1.5÷5×255) to the D/A converter
70
because the microcomputer
60
divides the external operating voltage of 5V into 255 steps (in case of 8 bit D/A converter), and the D/A converter
70
converts the digital value of 01001100
(2)
into an analog voltage of 1.5 (=76÷255×5). Accordingly, the motor driver
31
generates micro step pulses corresponding to 1.5V, thereby the sled motor
12
b
is rotated so that the pickup
11
moves to target location.
However, the operating voltage supplied from an external source may be changed from 5.5V to 4.5V since the external power supplied from a PC slot has variance range of ±10%, and the microcomputer
60
cannot be aware of the changes of the supplied power. Accordingly, the microcomputer
60
still outputs the digital value for
76
to the D/A converter
70
if it is intends to apply 1.5V to the sled motor
12
b
even in the condition that the operating voltage has been changed as much as maximum 10%.
However, the analog voltage converted for the digital value of
76
by the D/A converter
70
, which converts the input digital value into an analog voltage in the basis of the supplied operating voltage, becomes not 1.5V but 1.3V (=76÷255×4.5) if the supplied operating voltage has been reduced to 4.5V. Accordingly, the sled motor
12
b
can not move the pickup
11
as much as desirable, which causes time delay in finding a target track since an additional movement is required.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide method and apparatus for computing a driving voltage for a desirable movement without being effected by an operating voltage even though the operating voltage supplied from an external source is changed, and applying the computed voltage to a motor, thereby achieves more accurate movement of an optical pickup at all times.
The apparatus according to the present invention comprises a converting means, which an operating voltage varying within a predetermined range is supplied to, for converting an applied constant reference voltage into digital data; a controlling means for calculating a digital control voltage for a given driving voltage to be applied to a motor so that the calculated voltage may have different value according to the digital data converted by said converting means; and a driving means, which the operating voltage is supplied to, for converting the calculated digital control voltage into an analog driving voltage to apply to the motor for moving an optical pickup.
The method according to the present invention comprises the steps of digitizing an analog constant reference voltage using a supplied operating voltage varying within a predetermined range; determining the present value of the supplied operating voltage based upon the digitized value; calculating a digital control voltage for a given driving voltage so that the calculated voltage may have different value according to the determined present value; and applying a driving voltage corresponding to the calculated digital control voltage to a motor for moving an optical pickup.
REFERENCES:
patent: 4825137 (1989-04-01), Nakajima et al.
patent: 4942563 (1990-07-01), Yamamuro
patent: 5570330 (1996-10-01), Okawa
patent: 5706264 (1998-01-01), Ando
patent: 5757747 (1998-05-01), Shimada
patent: 6054825 (2000-04-01), Hayner
patent: 6153997 (2000-11-01), Kobayashi et al.
patent: 10326450 (1998-12-01), None
JP-A-09-035273, Feb. 7, 1997, abstract only.
JP-A-05-282809, Oct. 29, 1993, abstract only.
Duda Rina I.
LG Electronics Inc.
Nappi Robert E.
LandOfFree
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