Optical storage apparatus with track seeking control system

• US 5,768,229 A
• Filed: 12/20/1996
• Issued: 06/16/1998
• Est. Priority Date: 05/20/1996
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Fujitsu Limited
• Inventors: Ikeda, Toru
• Primary Examiner(s): Tran, Thang V.
• Application Number:
  US08/781,958
• Time in Patent Office: 543 Days
• Field of Search: 369/44.28, 369/44.29, 369/44.35, 369/44.34, 369/32, 369/44.32, 369/44.36, 360/78.05, 360/78.06
• US Class Current: 369/44.28
• CPC Class Codes: G11B 7/08529 Methods and circuits to control the velocity of the head as it traverses the tracks
• CPC Class Codes: G11B 7/08541 involving track counting to determine position

Abstract

A low speed lens lock control unit detects an amount of an optical axial deviation of an objective lens from an offset of a tracking error signal which is obtained in a low speed seeking mode and drives a carriage actuator so as to set the optical axial deviation of the objective lens to zero. A high speed lens lock control unit detects an amount of an optical axial deviation of the objective lens from an offset of a tracking error signal which is obtained in a high speed seeking mode and drives a lens actuator so as to set the optical axial deviation of the objective lens to zero.

Claims

1. An optical storage apparatus comprising:

a lens actuator for moving an objective lens to irradiate a light beam to a medium in a direction transverse to tracks on the medium;

a carriage actuator for moving a carriage on which said lens actuator is mounted in the direction which transverses the tracks on the medium;

a tracking error signal forming circuit for forming a tracking error signal according to a position of said light beam in the direction which transverses the tracks on the basis of a photosensitive output of a return light from the medium;

a low speed seek control unit for moving the light beam to a target position at a low speed by a driving of said lens actuator;

a high speed seek control unit for moving the light beam to a target position at a high speed by a driving of said carriage actuator;

a low speed lens lock control unit for detecting an amount of an optical axial deviation of said objective lens from an offset of the tracking error signal which is obtained in said low speed seeking mode and driving said carriage actuator so as to set the optical axial deviation of said objective lens to zero; and

a high speed lens lock control unit for detecting an amount of an optical axial deviation of said objective lens from an offset of the tracking error signal which is obtained in said high speed seeking mode and driving said lens actuator so as to set the optical axial deviation of said objective lens to zero.

2. An apparatus according to claim 1, wherein said low speed lens lock control unit has:

a peak value detecting unit for detecting a positive peak value and a negative peak value of each cycle of the tracking error signal; and

an offset calculating unit for calculating a value of 1/2 of a difference between said positive and negative peak values as an offset amount and detecting a pseudo lens position detection signal.

3. An apparatus according to claim 1, wherein said high speed lens lock control unit has a low pass filter for removing high frequency components by a cut-off frequency corresponding to a frequency of the tracking error signal in the high speed seeking mode and detecting an offset amount corresponding to a change in envelope of said tracking error signal as a lens position signal.

4. An apparatus according to claim 1, wherein said low speed and high speed lens lock control units have:

a low pass filter for removing high frequency components of the tracking error signal and detecting an offset amount which traces a change in envelope as a lens position signal; and

a filter characteristics switching unit for switching a cut-off frequency of said low pass filter to a low band side in the low speed seeking mode and to a high band side in the high speed seeking mode.

5. An apparatus according to claim 1, wherein said low speed and high speed lens lock control units have:

a low pass filter for a high speed for removing high frequency components by a cut-off frequency on a high band side corresponding to a frequency of the tracking error signal in the high speed seeking mode and generating as a lens position signal; and

a low pass filter for a low speed, serially connected to said low pass filter for a high speed, for removing high frequency components by a cut-off frequency on a low band side corresponding to a frequency of the tracking error signal in the low speed seeking mode and generating as a lens position signal.

6. An apparatus according to claim 1, wherein when the number of tracks to a target track is less than a predetermined value, the light beam is moved at a low speed by said low speed seek control unit.

7. An apparatus according to claim 1, wherein when the number of tracks to a target track exceeds a predetermined value, the light beam is moved at a high speed by said high speed seek control unit, and when the number of tracks to the target track reaches another predetermined value during said high speed movement, a control mode is switched to a low speed movement of the light beam by said low speed seek control unit.

8. An apparatus according to claim 1, wherein said low speed seek control unit controls a speed of said lens actuator so as to trace a target speed which was set in accordance with the number of tracks to a target track and applies an acceleration or a deceleration for an inertia compensation corresponding to the acceleration or deceleration of said lens actuator to said carriage actuator with respect to each of an acceleration period of time and a deceleration period of time of said speed control.

9. An apparatus according to claim 8, wherein said low speed seek control unit supplies an inertia compensation current Iv obtained by multiplying an inertia compensation coefficient α

1 to an acceleration or deceleration current Ia of said lens actuator to said carriage actuator.

10. An apparatus according to claim 9, wherein said inertia compensation coefficient α

1 is defined by the following equation;

space="preserve" listing-type="equation">α

1=(Kv/Ka)·

{Ma/(Ma+Mv)}

where,

Ka;

acceleration gain of said lens actuator

Kv;

acceleration gain of said carriage actuator

Ma;

mass of said lens actuator

Mv;

mass of said carriage actuator.

11. An apparatus according to claim 1, wherein said high speed seek control unit controls a speed of said carriage actuator so as to trace a target speed which was set in accordance with the number of tracks to a target track and applies an acceleration or a deceleration for an inertia compensation corresponding to the acceleration or deceleration of said carriage actuator to said lens actuator with respect to each of an acceleration period of time and a deceleration period of time of said speed control.

12. An apparatus according to claim 11, wherein said high speed seek control unit supplies an inertia compensation current Ia obtained by multiplying an inertia compensation coefficient α

2 to an acceleration or deceleration current Iv of said carriage actuator to said lens actuator.

13. An apparatus according to claim 12, wherein said inertia compensation coefficient α

2 is defined by the following equation;

space="preserve" listing-type="equation">α

2=(Ka/Kv)·

{Mv/(Ma+Mv)}

where,

Ka;

acceleration gain of said lens actuator

Kv;

acceleration gain of said carriage actuator

Ma;

mass of said lens actuator

Mv;

mass of said carriage actuator.

14. An apparatus according to claim 1, wherein said low speed seek control unit and said high speed seek control unit smoothly change an acceleration current and a deceleration current of the seek control, thereby smoothly accelerating and decelerating said lens actuator and said carriage actuator.