Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1999-07-28
2001-10-16
Tran, Thang V. (Department: 2651)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044320, C369S053140
Reexamination Certificate
active
06304528
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk reproducing apparatus having a vibration detecting device capable of measuring an amplitude of vibrations caused by mass eccentricity of an optical disk.
2. Description of the Related Art
In recent years, the recording and reproducing speed of an optical disk reproducing apparatus has been remarkably enhanced. In the optical disk reproducing apparatus, the reproducing speed has been enhanced by increasing the rotational speed of the optical disk.
However, when the rotational speed of an optical disk is increased, vibrations caused by mass eccentricity of the optical disk have adverse effects on the control of a servo and the like, which gives disagreeable feelings to a user of an optical disk reproducing apparatus. In order to prevent or reduce adverse effects of the vibrations caused by an optical disk having large mass eccentricity, when such an optical disk is mounted, an optical disk reproducing apparatus limits the rotational speed thereof. The measurement of the amplitude of vibrations is an important technique for assisting in preventing adverse effects of the vibrations caused by an optical disk having mass eccentricity in an optical disk reproducing apparatus.
FIG. 6
is a block diagram of a conventional optical disk reproducing apparatus
600
. Reference numeral
1
denotes a base,
2
denotes a disk motor attached to the base,
1
,
3
denotes an insulator supporting the base
1
,
4
denotes an optical disk attached to the disk motor
2
,
21
denotes an acceleration sensor attached to the base
1
, and
22
denotes a measurement portion for determining an amount of mass eccentricity, based on an output from the acceleration sensor
21
.
When the disk motor
2
is rotated at a predetermined velocity, centrifugal force which is proportional to an amount of mass eccentricity of the optical disk
4
is generated. The base
1
supported by the insulator
3
vibrates at an amplitude determined by the amount of mass eccentricity of the optical disk
4
, the entire mass of the base
1
and components mounted thereon, and the spring constant of the insulator
3
.
The vibrations of the base
1
are converted into an electrical signal by the acceleration sensor
21
. The measurement portion
22
measures the amplitude of the vibrations of the base
1
based on the electrical signal converted by the acceleration sensor
21
.
However, in the above-mentioned optical disk reproducing apparatus
600
, the acceleration sensor
21
and a signal amplifier (not shown) for amplifying a signal from the acceleration sensor
21
are provided, which increases cost.
Furthermore, space is required for mounting the acceleration sensor
21
and the signal amplifier.
SUMMARY OF THE INVENTION
An optical disk reproducing apparatus of the present invention includes a body, a disk motor which rotates a disk in which information recording tracks are formed concentrically or spirally on an information recording surface, a base fixed onto the disk motor and elastically suspended with respect to the body, and an optical head which is suspended with an elastic member from the base and is displaceable in a radial direction of the disk. The apparatus further includes: a track cross detecting portion for generating a track cross pulse, based on a reproduction signal when a light beam emitted from the optical head crosses the information recording tracks; a track cross direction detecting portion for detecting a track cross direction representing a direction in which the light beam emitted from the optical head crosses the information recording tracks; a motor control portion for controlling a velocity of the disk motor and outputting rotational angle information of the disk motor; a counting portion for counting the track cross pulse generated by the track cross detecting portion, based on the track cross direction detected by the track cross direction detecting portion and the rotational angle information output from the motor control portion; and a measurement portion for measuring an amplitude of vibrations of the base, based on a count result of the counting portion.
In one embodiment of the present invention, the motor control portion rotates the disk motor at a first velocity and a second velocity which is higher than the first velocity, the track cross pulse includes a first track cross pulse generated at the first velocity and a second track cross pulse generated at the second velocity, the count result includes a first count result at the first velocity and a second count result at the second velocity, the counting portion counts the first track cross pulse at the first velocity and the second track cross pulse at the second velocity, and the measurement portion computes a difference between the first count result at the first velocity and the second count result at the second velocity.
In another embodiment of the present invention, the rotational angle information includes an absolute position of a rotational angle of the disk, the absolute position includes a rotational angle &thgr;[i] (i is a natural number, 0°≦&thgr;[i]≦360°) obtained by dividing the disk by a plurality of angular segments, and the counting portion counts the track cross pulse from a rotational angle &thgr;[i−1] to a rotational angle &thgr;[i] (i is a natural number, 0°≦&thgr;[i−1]<&thgr;[i]≦360°) to obtain a count result N(&thgr;[1]).
In another embodiment of the present invention, the counting portion discards the count result N(&thgr;[i]) in a case where a difference in an absolute value between the count result N(&thgr;[i]) and a count result N(&thgr;[i]+180) between which a rotational angle of the disk is apart by 180°.
In another embodiment of the present invention, the motor control portion rotates the disk motor at a first velocity and a second velocity which is higher than the first velocity, the track cross pulse includes a first track cross pulse generated at the first velocity and a second track cross pulse generated at the second velocity, the count result N(&thgr;[i]) includes a first count result N
1
(&thgr;[i]) at the first velocity and a second count result N
2
(&thgr;[i]) at the second velocity, the counting portion counts the first track cross pulse at the first velocity and the second track cross pulse at the second velocity, and the measurement portion computes a difference M(
0
[i]) between the first count result N
1
(&thgr;[i]) of the counting portion at the first velocity and the second count result N
2
(&thgr;[i]) of the counting portion at the second velocity, and obtains a maximum value of the difference M(&thgr;[i]) to measure an amplitude of vibrations of the base.
In another embodiment of the present invention, the rotational angle information includes an absolute position of a rotational angle of the disk, the absolute position includes a rotational angle &thgr;[i] (i is a natural number, 0°≦&thgr;[i]≦360°) obtained by dividing the disk by angular segments at 60°, and the counting portion counts the track cross pulse for each rotational angle 60° to obtain a count result N(&thgr;[i]).
In another embodiment of the present invention, the motor control portion rotates the disk motor at a first velocity and a second velocity which is higher than the first velocity, the count result includes a first count result at the first velocity and a second count result at the second velocity, the measurement portion represents a subtraction result between the first count result at the first velocity and the second count result at the second velocity as a vector having a corresponding disk rotational angle as a phase angle and the subtraction result with a sign as an absolute value, and the measurement portion computes six differential vectors between the vectors adjacent to
Fujiune Kenji
Kanda Yoshihiro
Kuze Yuuichi
Matsushita Electric - Industrial Co., Ltd.
Renner , Otto, Boisselle & Sklar, LLP
Tran Thang V.
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