Optical disc apparatus

• US 20040136280A1
• Filed: 10/20/2003
• Published: 07/15/2004
• Est. Priority Date: 04/20/2001
• Status: Active Grant

• Current Assignee: Careers Fast Track Pty., Ltd., Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Careers Fast Track Pty., Ltd.
• Inventors: Kuze, Yuuichi, Watanabe, Katsuya, Yamada, Shin-ichi, Fujiune, Kenji
• Granted Patent: US 7,257,053 B2
• Time in Patent Office: Days
• US Class Current: 369/44.32
• CPC Class Codes: G11B 7/08511 with focus pull-in only
• CPC Class Codes: G11B 7/0946 specially adapted for operation during external perturbations not related to the carrier or servo beam, e.g. vibration
• CPC Class Codes: G11B 7/24082 Meandering

Abstract

An optical disk apparatus having a high reliability by evading collision between a condensing lens and an optical disk regardless whether the focus control is in the operative state or in the inoperative state, thereby preventing damage to the condensing lens and the optical disk. When the focus control is in the inoperative state, by using a reflection light amount from the optical disk (1), it is ascertained that the focus of the light beam is in the vicinity of the information surface and the condensing lens (15) is driven to be apart from the optical disk (1).

Claims

1. An optical disk apparatus, comprising:

a converging means for converging and irradiating a light beam from a light source toward a rotating information carrier;

a focus displacement signal detection means for generating a signal in accordance with a positional displacement of a focus of the light beam with respect to an information surface of the information carrier;

a focus shifting means for shifting the converging means in a direction normal to the information surface of the information carrier;

a focus control means for driving the focus shifting means in accordance with the signal from the focus displacement signal detection means, and performing a control such that the focus of the light beam follows the information surface of the information carrier;

an information surface detection means for detecting whether the focus of the light beam is near the information surface of the information carrier, if the focus control means is in an inoperative state; and

a collision evasion means for generating a driving signal for the focus shifting means such that the converging means is displaced in a direction away from the information carrier if a signal is generated by the information surface detection means.

3. The optical disk apparatus according to claim 1 or 2, wherein the driving signal generated by the collision evasion means is a two-value signal of a signal of a reference level and a signal of a constant level that is such that the converging means is displaced in the direction away from the information carrier.

4. The optical disk apparatus according to claim 1 or 2, wherein the driving signal generated by the collision evasion means is a pulse signal having a predetermined peak value such that the converging means is displaced in a direction away from the information carrier.

5. The optical disk apparatus according to claim 4, wherein the driving signal generated by the collision evasion means is saturated at an output of a preset predetermined value.

6. The optical disk apparatus according to claim 1 or 2, wherein the driving signal generated by the collision evasion means is a ramp signal having a constant slope.

7. The optical disk apparatus according to claim 6, wherein the driving signal generated by the collision evasion means is saturated at an output of a preset predetermined value.

8. The optical disk apparatus according to claim 1 or 2, wherein the driving signal generated by the collision evasion means if no signal is generated by the information surface detection means or the vibration detection means is a signal such that the converging means is displaced with a predetermined slope in a direction approaching the information carrier.

9. The optical disk apparatus according to claim 6, wherein the driving signal generated by the collision evasion means is saturated at an output of a preset predetermined value.

2. An optical disk apparatus, comprising:

a converging means for converging and irradiating a light beam from a light source toward a rotating information carrier;

a focus displacement signal detection means for generating a signal in accordance with a positional displacement of a focus of the light beam with respect to an information surface of the information carrier;

a focus shifting means for shifting the converging means in a direction normal to the information surface of the information carrier;

a focus control means for driving the focus shifting means in accordance with the signal from the focus displacement signal detection means, and performing a control such that the focus of the light beam follows the information surface of the information carrier;

a vibration detection means for detecting a vibration of the apparatus; and

a collision evasion means for generating a driving signal for the focus shifting means such that the converging means is displaced in a direction away from the information carrier if a signal of at least a predetermined value is generated by the vibration detection means.

10. An optical disk apparatus, comprising:

a converging means for converging and irradiating a light beam from a light source toward a rotating information carrier;

a focus displacement signal detection means for generating a signal in accordance with a positional displacement of a focus of the light beam with respect to an information surface of the information carrier;

a focus shifting means for shifting the converging means in a direction normal to the information surface of the information carrier;

a focus control means for driving the focus shifting means in accordance with the signal from the focus displacement signal detection means, and performing a control such that the focus of the light beam follows the information surface of the information carrier; and

a collision evasion means for constantly generating a driving signal for the focus shifting means such that the converging means is displaced in a direction away from the information carrier if the focus control means is in an inoperative state.

11. An optical disk apparatus, comprising:

a converging means for converging and irradiating a light beam from a light source toward an information carrier having a spiral-shaped track that has a tiny fluctuation in radial direction at a predetermined period;

a focus displacement signal detection means for generating a signal in accordance with a positional displacement of a focus of the light beam with respect to an information surface of the information carrier;

a focus shifting means for shifting the converging means in a direction normal to the information surface of the information carrier;

a focus control means for driving the focus shifting means in accordance with the signal from the focus displacement signal detection means, and performing a control such that the focus of the light beam follows the information surface of the information carrier;

a fluctuation amplitude detection means for detecting an amplitude of the fluctuation of the track; and

an anomaly detection means for judging, from an amplitude change over a predetermined time of a signal from the fluctuation amplitude detection means, whether the operation of the focus control means is anomalous, and generating a driving signal for the focus shifting means such that the converging means is displaced in a direction away from the information carrier.

12. The optical disk apparatus according to claim 11, wherein the fluctuation amplitude detection means is provided with a fluctuation detection sensitivity switching means for switching a detection sensitivity with which the amplitude of the fluctuation of the track is detected, depending on whether information is recorded or information is reproduced.

13. The optical disk apparatus according to claim 11, wherein the anomaly detection means is provided with an anomaly level switching means for switching a signal change level of the fluctuation amplitude detection means at which anomaly is judged, depending on whether information is being recorded or information is being reproduced.

14. The optical disk apparatus according to claim 11, further comprising a recorded region detection means for detecting whether a region onto which the light beam is irradiated is in a recorded or an unrecorded state, and a fluctuation detection sensitivity switching means for switching a detection sensitivity of the fluctuation amplitude detection means in accordance with a detection result of the recorded region detection means.

15. The optical disk apparatus according to claim 11, further comprising a recorded region detection means for detecting whether a region onto which the light beam is irradiated is in a recorded or an unrecorded state, and an anomalous level switching means for switching a signal change level of the fluctuation amplitude detection means at which anomaly is judged in accordance with a detection result of the recorded region detection means.

16. The optical disk apparatus according to claim 11, further comprising a track displacement signal detection means that generates a signal in accordance with a positional displacement of the focus of the light beam with respect to the track of the information carrier;

a track shifting means for shifting the converging means in a direction traverse to the track of the information carrier; and

a tracking control means for driving the track shifting means in accordance with the signal from the track displacement signal detection means and performing a control such that the focus of the light beam follows the track of the information carrier;

wherein the anomaly detection means operates only when the tracking control means is in an operative state.

17. The optical disk apparatus according to claim 11, further comprising:

a track displacement signal detection means that generates a signal in accordance with a positional displacement of a focus of the light beam with respect to the track of the information carrier;

a track shifting means for shifting the converging means in a direction traverse to the track of the information carrier; and

a tracking control means for driving the track shifting means in accordance with the signal from the track displacement signal detection means and performing a control such that the focus of the light beam follows the track of the information carrier;

wherein the anomaly detection means switches the detection time or the amplitude change level of the signal amplitude change of the fluctuation amplitude detection means at which it is judged that the operation of the focus control means is anomalous, depending on whether the tracking control means is in an operative state or an inoperative state.

18. An optical disk apparatus, comprising:

a converging means for converging and irradiating a light beam from a light source toward a rotating information carrier;

a focus displacement signal detection means for generating a signal in accordance with a positional displacement of a focus of the light beam with respect to an information surface of the information carrier;

a focus shifting means for shifting the converging means in a direction normal to the information surface of the information carrier;

a focus control means for driving the focus shifting means in accordance with the signal from the focus displacement signal detection means, and performing a control such that the focus of the light beam follows the information surface of the information carrier; and

an anomaly detection means for judging that the operation of the focus control means is anomalous when a change in the signal from the focus displacement signal detection means over a predetermined time is within a predetermined range, and generating a driving signal for the focus shifting means that is such that the converging means is displaced in a direction away from the information carrier.

19. The optical disk apparatus according to claim 18, further comprising a multiplication means for multiplying the signal from the focus displacement signal detection means with a predetermined value;

and a gain switching means for switching a multiplication factor of the multiplication means, depending on whether information is being recorded or information is being reproduced.

20. The optical disk apparatus according to claim 18, wherein the anomaly detection means further comprises a judgment level switching means for switching, depending on whether information is being recorded or information is being reproduced, a signal level at which the signal of the focus displacement signal detection means that is compared with that signal level is judged to be anomalous.

21. The optical disk apparatus according to claim 18, further comprising a multiplication means for multiplying the signal from the focus displacement signal detection means with a predetermined value;

a recorded region detection means for detecting whether a region onto which the light beam is irradiated is in a recorded or an unrecorded state; and

a gain switching means for switching a multiplication factor of the multiplication means, in accordance with a detection result of the recorded region detection means.

22. The optical disk apparatus according to claim 18, further comprising a recorded region detection means for detecting whether a region onto which the light beam is irradiated is in a recorded or an unrecorded state;

and a judgment level switching means for switching, in accordance with a detection result of the recorded region detection means, a signal level at which the signal of the focus displacement signal detection means that is compared with that signal level is judged to be anomalous.

23. The optical disk apparatus according to claim 18, further comprising a track displacement signal detection means that generates a signal in accordance with a positional displacement of a focus of the light beam with respect to the track of the information carrier;

a track shifting means for shifting the converging means in a direction traverse to the track of the information carrier; and

a tracking control means for driving the track shifting means in accordance with the signal from the track displacement signal detection means and performing a control such that the focus of the light beam follows the track of the information carrier;

wherein the anomaly detection means operates only when the tracking control means is in an operative state.

24. An optical disk apparatus, comprising:

a converging means for converging and irradiating a light beam from a light source toward a rotating information carrier;

a focus displacement signal detection means for generating a signal in accordance with a positional displacement of a focus of the light beam with respect to an information surface of the information carrier;

a focus shifting means for shifting the converging means in a direction normal to the information surface of the information carrier;

a focus control means for driving the focus shifting means in accordance with the signal from the focus displacement signal detection means, and performing a control such that the focus of the light beam follows the information surface of the information carrier;

a focus integration means for integrating the signal from the focus displacement signal detection means when a change of the signal from the focus displacement signal detection means is within a predetermined range;

a clearing means for clearing an integration value of the focus integration means when the change of the signal from the focus displacement signal detection means exceeds the predetermined range; and

an anomaly detection means for judging that the operation of the focus control means is anomalous when the absolute value of the integration value of the focus integration means is at least a predetermined value, and generating a driving signal for the focus shifting means that is such that the converging means is displaced in a direction away from the information carrier.

25. The optical disk apparatus according to claim 24, wherein the focus integration means comprises a multiplication means for multiplying the signal from the focus displacement signal detection means with at least two kinds of multiplication factors, corresponding to the case that information is being recorded and the case that information is being reproduced, and wherein the result of the multiplication with the multiplication means is integrated.

26. The optical disk apparatus according to claim 24, wherein the clearing means switches the range over which the change of the signal from the focus displacement signal detection means is detected and compared, depending on whether information is being recorded or information is being reproduced.

27. The optical disk apparatus according to claim 24, further comprising a multiplication means for multiplying the signal from the focus displacement signal detection means with a predetermined value;

a recorded region detection means for detecting whether a region onto which the light beam is irradiated is in a recorded or an unrecorded state; and

a gain switching means for switching a multiplication factor of the multiplication means, in accordance with a detection result of the recorded region detection means.

28. The optical disk apparatus according to claim 24, further comprising a recorded region detection means for detecting whether a region onto which the light beam is irradiated is in a recorded or an unrecorded state;

wherein the clearing means switches the range over which the change of the signal from the focus displacement signal detection means is detected and compared, depending on a detection result of the recorded region detection means.

29. An optical disk apparatus, comprising:

a converging means for converging and irradiating a light beam from a light source toward a rotating information carrier;

an optical detection means for partitioning and receiving the light beam reflected by the information carrier;

a focus displacement signal detection means for generating a signal in accordance with a positional displacement of a focus of the light beam with respect to an information surface of the information carrier, by calculating a differential of partitioned regions of the optical detection means;

a focus shifting means for shifting the converging means in a direction normal to the information surface of the information carrier;

an offset application means for applying an offset to the signal from the focus displacement signal detection means;

a focus control means for driving the focus shifting means in accordance with the signal from the focus displacement signal detection means and the offset application means, and performing a control such that the focus of the light beam follows the information surface of the information carrier; and

a vibration detection means for detecting a vibration of the apparatus;

wherein, based on the signals from the vibration detection means, the offset application means applies such an offset that the converging means is displaced in a direction away from the information carrier.

30. The optical disk apparatus according to claim 29, wherein the offset application means makes the applied offset amount larger, the larger the signal from the vibration detection means is.

31. The optical disk apparatus according to claim 29, wherein the focus displacement signal detection means is provided with a balance multiplication means that applies individual gains to the signals before the differential calculation, and wherein the balance multiplication means switches the gains such that an operating point of the focus control means does not change, in accordance with the offset applied by the offset application means.

32. The optical disk apparatus according to claim 29, wherein the offset applied by the offset application means is saturated at a predetermined level.

33. An optical disk apparatus, comprising:

a converging means for converging and irradiating a light beam from a light source toward a rotating information carrier;

a focus displacement signal detection means for generating a signal in accordance with a positional displacement of a focus of the light beam with respect to an information surface of the information carrier;

a focus shifting means for shifting the converging means in a direction normal to the information surface of the information carrier;

a focus control means for driving the focus shifting means in accordance with the signal from the focus displacement signal detection means, and performing a control such that the focus of the light beam follows the information surface of the information carrier; and

a search means for shifting the converging means such that the light beam is irradiated onto a desired track on the information carrier;

wherein the search means sets the focus control means to an inoperative state when the focus control means is operative.

34. The optical disk apparatus according to claim 33, wherein the search means sets the focus control means to an inoperative state if the number of tracks across which the focus of the light beam is shifted is a predetermined number or greater.

35. The optical disk apparatus according to claim 33, wherein the search means sets the focus control means to an inoperative state if the direction in which the focus of the light beam is shifted across the tracks is a direction toward the outer periphery of the information carrier.

36. The optical disk apparatus according to claim 33, wherein the search means sets the focus control means to an inoperative state if a target track to which the focus of the light beam is to be shifted transversely is within a range of a predetermined distance from the outermost periphery of the information carrier.