JP3113328B2 - Optical recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for recording and / or reproducing information by irradiating a convergent beam onto a recording medium having a groove formed at a predetermined pitch.

[0002]

2. Description of the Related Art Optical disks have been awarded as recording media capable of recording information at high density. Such optical disks include those in which a groove (groove) for beam guide is formed in advance in a concentric or spiral shape. In such an optical disk, in order to prevent crosstalk during reproduction, information is recorded only on one of a group and a land portion between the groups. Recording of information is performed by scanning the groove or land with a convergent beam modulated by the information, thereby changing the optical characteristics of the groove or land.

Recently, however, an information reading apparatus capable of recording information on both the groove and the land has been introduced (1990 ODS Digest P.18 and 19).
Proceedings of the 1990 Spring Society of Applied Physics (29P-G-9)
926). Such a reader is shown in FIG. In the figure, 1 is a semiconductor laser emitting three independent beams,
Reference numeral 2 denotes a collimating lens, 3 denotes a beam splitter, 4 denotes an objective lens, 5 denotes a disk, 6 denotes a converging lens, 7 denotes a photodetector, and 8 denotes a crosstalk canceller.

[0004] The three beams emitted from the semiconductor laser 1 are applied on a disk 5 to a groove or a land portion from which information is to be read and a land portion or a groove adjacent to both sides of the groove or the land portion. Converges. Here, the spot of each beam on the disk 5 is a track whose center spot is to be reproduced.
The spots at both ends are arranged so as to scan the tracks on both sides thereof, respectively. Each beam is reflected by the disk after being modulated by information on the groove or land. Each reflected beam is applied to the objective lens 4, beam
The light is converged on the photodetector 7 via the splitter 3 and the converging lens 6. On the photodetector 7, three sensors for receiving the respective beams are arranged. Each sensor cross-talk cancels an electrical signal corresponding to the light intensity of each beam.
And outputs it to the La 8. The crosstalk canceller 8 is superimposed on the main signal by appropriately adding and subtracting the electric signal (sub signal) corresponding to the other two beams from the electric signal (main signal) corresponding to the information reading beam. Remove crosstalk components. Therefore, a good reproduced signal without crosstalk can be obtained.

[0005] Incidentally, in recording and reproduction of an optical disk, it is usually necessary to control the displacement of the beam spot so that the beam track scans a recording track when the disk is rotated. For this reason, the optical disk recording / reproducing apparatus is always provided with a tracking means for adjusting the position of the beam spot. The position adjustment of the beam spot is performed by applying a control signal corresponding to the magnitude and direction of the deviation of the beam spot with respect to the track, a so-called tracking error signal, to the tracking means.

[0006]

An optical recording / reproducing apparatus for a disk on which a groove and a land are formed also includes such a tracking control device.
However, such a tracking control device positions a beam spot on a desired groove, for example, and performs position control of the beam spot such that the beam spot is not positioned in a portion between the grooves. Even if such a tracking control device is employed in such an optical recording / reproducing device, tracking control can be performed only so that the beam spot follows either the groove or the land. Therefore, when information is recorded in both the groove and the land as in the above-described conventional example, such a tracking control device cannot be employed as it is. Therefore, when a conventional tracking control device is employed for such a disk, it is necessary to independently arrange two optical head systems shown in FIG. 4 for the groove and the land.

Therefore, the present invention solves such inconvenience,
It is an object of the present invention to provide an optical recording / reproducing apparatus capable of performing beam tracking control with a single optical head system even for a disk having information recorded on both the groove and the land. I do.

[0008]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a recording medium having grooves formed at a predetermined pitch and lands formed between the grooves, by irradiating a convergent beam onto the recording medium. In an optical recording / reproducing apparatus for recording and / or reproducing information, a tracking means for displacing a beam spot in a tracking direction by a tracking error signal corresponding to a deviation of the beam spot from a track; Zero-crossing point detecting means for detecting a timing located at a boundary with the section by a differential signal of the tracking error signal, and polarity control means for inverting the polarity of the tracking error signal in accordance with the timing detected by the zero-crossing point detecting means And the scanning position of the beam spot as a groove. A track jump pulse generating means for applying a jump pulse for switching to a tracking section to the tracking means; and a switch means for switching between an open / close state between the polarity control means and the tracking means. becomes Te, the jump pulse is composed of a kick pulse for starting a track jump, the said kick pulse with opposite polarity of the brake pulse, the
The track jump pulse creating means switches between the kick pulse and the brake pulse in accordance with the timing detected by the zero cross point detecting means, and the switch means is turned off in response to the rise of the kick pulse, Is turned on in response to the falling edge of.

[0009]

When the beam spot is shifted in the radial direction of the disk on which the groove and the land are formed, the tracking error signal is transmitted from the groove to the groove (from the land to the land). The signal becomes a sine-wave signal having a period during which the spot moves as one cycle. FIG. 5 shows an example of the relationship between the beam spot shift and the tracking error signal. In the figure , 101 is a group,
102 is a land part, 103 is a beam spot. Here, when the beam spot 103 is positioned on the land portion 102, the beam spot 103 is moved rightward when the tracking error signal is positive, and the beam spot 103 is moved leftward when the tracking error signal is negative. Need to be done. On the other hand, grayed the beam spot 103
When the tracking error signal is positive, it is necessary to move the beam spot 103 to the left when the tracking error signal is positive, and to move the beam spot 103 to the right when the tracking error signal is negative.

In the present invention, the polarity of the tracking error signal applied to the tracking means is inverted depending on whether the beam spot scans the groove or the land. Thus, the direction of movement of the beam spot according to the sign of the tracking error signal is the same during scanning of both the groove and the land. Further, a kick pulse for starting a track jump, the tracking jump by the jump pulse consisting of a polarity opposite of the brake pulse is performed with the kick pulse.

[0011]

Embodiments of the present invention will be described below. In this embodiment, when the scanning of the beam is switched from the groove to the land, a track jump pulse is applied to the tracking means to change the beam spot to the groove.
A jump is made between lands, and in response to the track jump, the polarity of the tracking error signal applied to the tracking means is inverted. As a method of generating the tracking error signal, various methods such as a conventionally known push-pull method and a heterodyne method can be used. In the present embodiment, description will be made using the push-pull method. The displacement of the beam spot in the tracking direction uses an existing objective lens driving actuator used in a compact disk player or the like. That is, this is performed by displacing the objective lens for beam convergence in the tracking direction. still,
Such push-pull method and objective lens driving actuator
The description of the details of the data is omitted.

FIG. 1 shows a circuit block diagram of the present embodiment. In the figure, reference numeral 10 denotes a two-segment photodetector which receives a beam reflected from a groove or a land to be scanned. When the beam spot is positioned exactly on the groove or land to be scanned,
The magnitude of the signal output from each detector is equal,
When the beam spot deviates from the groove or land to be scanned in the tracking direction, the signal output from one of the detectors becomes larger than the other depending on the deviating direction.

Reference numeral 11 denotes a differential signal generator which receives each signal output from the photodetector 10 and outputs a signal (tracking error signal) indicating the difference between the signals. After the phase of the difference signal is compensated by the phase compensator 12, the polarity of the difference signal is adjusted by the polarity controller 13. The polarity control unit 13 inverts the positive and negative polarities of the tracking error signal according to the signal from the zero cross point detection unit 20. The tracking error signal whose polarity has been adjusted in this manner is transmitted to the switch 14. Here, the switch 14 is turned off during the normal tracking control.
It is in the N state. Accordingly, the tracking error signal is normally applied to the tracking actuator driving unit 15 via the switch 14. The tracking actuator driving section 15 responds to the tracking error signal by an objective lens driving actuator.
Then, the beam spot 16 is driven, whereby the tracking adjustment of the beam spot is performed.

Numeral 17 is a timing pulse generating unit which is a jump pulse generating unit 1 for switching the beam scanning from the groove to the land or from the land to the groove.
8. A pulse signal is output to the switch 14 and the zero-cross point detection unit 20. In response to the rise of the pulse signal, the switch 14 is turned off and a kick pulse for starting a track jump is applied to the tracking actuator drive circuit 15 from the jump pulse generator 18. Such a kick pulse is a positive level signal. The objective lens is driven by the application of the kick pulse, and the beam spot is moved in the radial direction of the disk (for example, in the direction from the inner circumference to the outer circumference of the disk).

On the other hand, the rising edge of the pulse signal activates the zero-cross point detector 20. When the beam spot jumps as described above, the tracking error signal output from the difference signal generator 11 fluctuates accordingly. The differentiating circuit section 19 supplies a signal obtained by differentiating the tracking error signal to the zero cross point detecting section 20. The zero-cross point detection unit 20 applies a control signal to the polarity control unit 13 at the timing when the differential signal crosses zero. Here, the timing at which the differential signal crosses zero is the timing at which the beam spot is located at the boundary between the groove and the land. The polarity control unit 13
In accordance with the control signal, the polarity of the tracking error signal transmitted to the switch 14 is inverted.

The control signal output from the zero-cross point detector 20 is also supplied to the jump pulse generator 18 at the same time. The jump pulse generator 18 stops the output of the kick pulse in response to the control signal, and supplies a brake pulse for stopping the inertial movement of the objective lens to the tracking actuator instead. The brake pulse is a negative level signal having a polarity opposite to that of the jump pulse, and has a predetermined time width based on the inertial movement of the objective lens. Then, in response to the rise of the brake pulse, the timing pulse generator 17 switches the switch 1
4. Jump pulse generator 18 and zero-cross detector 2
The pulse signal applied to 0 falls. The switch 14 is turned on in response to the fall of the pulse signal, and the operations of the jump pulse generator 18 and the zero-cross point detector are stopped.

FIG. 2 is a timing chart showing the relationship between the beam spot jump and the signals at points a to d in the above embodiment. The timing chart is for the case where the beam spot jumps from the groove to the land. As shown in the figure, the jump pulse switches from the kick pulse to the brake pulse at the boundary between the groove and the land. In addition, the beam spot is grayed
The switch 14 is kept in the OFF state until shifting from the loop to the land. Further, the polarity of the tracking error signal is inverted at the timing when the differential signal at point b crosses zero, that is, when the beam spot reaches the boundary between the groove and the land. Therefore, when the switch 14 is turned on again, the polarity of the tracking error signal applied to the tracking actuator drive circuit 15 is inverted as compared with the tracking error signal before the track jump. .

In this embodiment, when a disk is formed concentrically or spirally on a disk,
For example, a series of information may be recorded on the groove and the land portion alternately one turn at a time from the inner peripheral portion to the outer peripheral portion of the disk. The information may be recorded on the land, and thereafter, the information may be recorded on the land by returning to the inner peripheral portion. Here, when information is recorded on the disk as in the former case, a pulse is generated from the timing pulse generator 17 every time the disk makes one rotation so that the track jump and the polarity inversion operation can be performed. In the case where information is recorded as in the latter case, scanning of all the groups from the inner periphery to the outer periphery is completed, and the scanning position returns to the inner periphery again. In the timing, a pulse may be generated from the timing pulse generator 17 to perform the track jump and the polarity inversion operation.

Although the embodiments of the present invention have been described above, the present invention is not limited to the recording / reproducing apparatus using the crosstalk canceller described as the above-mentioned prior art. Information can be recorded in both of them, and any recording and reproducing apparatus can be adopted as long as the apparatus needs to scan both the groove and the land with a beam spot. For example, as described in Japanese Patent Application No. 2-207453 previously filed by the applicant, information is recorded on the group and the land with different optical characteristics (different optical anisotropy directions). The present invention is also applicable to a recording / reproducing apparatus of an optical recording medium for recording.

FIG. 3 shows an embodiment in which the present invention is applied to such a recording / reproducing apparatus. This embodiment shows an information recording system, in which information is recorded by irradiating a beam whose polarization plane is orthogonal to the groove and the land. In the present embodiment, the tracking control system shown in FIG. 1 is employed as it is. The components of the tracking control system are denoted by the same reference numerals as those in FIG. 1, and the description thereof is omitted.

In FIG. 1, reference numeral 21 denotes a light source which emits a linearly polarized laser beam. 22 is an AO modulator that modulates the intensity of the laser beam according to an information signal to be recorded;
23 is a Faraday rotator for rotating the polarization plane of the beam by 90 ° in response to a signal from the Faraday rotation drive circuit 31, 24 is a beam expander, 25 is a disk, 26
Is a half mirror, 27 is an objective lens actuator, 2
Reference numeral 8 denotes a half mirror, 29 denotes a photodetector for reproduction and focus servo, and 30 denotes a converging lens that converges a beam on the photodetector 10 for tracking.
A recording layer made of a photochromic material is prepared on the disk 25. Of course this disk 25
A groove and a land are formed on the top.

In this embodiment, similar to the above embodiment,
The polarity of the tracking error signal applied to the tracking actuator drive circuit is inverted according to the track jump between the groove and land portions. The operation of the polarity inversion is achieved in exactly the same manner as in the above embodiment. However, in the present embodiment, as described above, the group
Since the polarization plane of the recording beam needs to be orthogonal to the land and the land, a control signal is applied to the Faraday rotator driving circuit 31 in response to the track jump, and the Faraday rotator 23 responds to the control signal. The plane of polarization is inverted by 90 °.

Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments.
Various other changes are possible. For example, in the above embodiment,
Although a disk is used as a recording medium, the present invention is not limited to this. A tape may be used as a medium, and groups and lands may be alternately formed on a straight line.

[0024]

As described above, according to the present invention, it is possible to perform tracking control according to groove scanning and land scanning without preparing two separate optical head systems, and to perform a track jump accurately. I can do it. Further, according to the present invention, a track jump can be smoothly performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment.

FIG. 2 is a timing chart of the embodiment.

FIG. 3 is a block diagram of another embodiment.

FIG. 4 is a block diagram of a conventional example.

FIG. 5 is a diagram illustrating a relationship between a position of a beam spot and a tracking error signal.

[Explanation of symbols]

13 Polarity controller (tracking switching means) 15 Actuator driving circuit for tracking (tracking means) 16 Objective lens actuator (tracking means)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 7/085 G11B 7/09 G11B 7/095

Claims (1)

(57) [Claims] An optical recording / reproducing apparatus for recording and / or reproducing information by irradiating a convergent beam onto a recording medium having grooves formed at a predetermined pitch and lands formed between the grooves. A tracking means for displacing the beam spot in a tracking direction by a tracking error signal corresponding to a deviation of the beam spot from a track; and a timing at which the beam spot is located at a boundary between the groove and the land portion. Zero-crossing point detecting means for detecting the differential signal of the signal, polarity control means for inverting the polarity of the tracking error signal in accordance with the timing detected by the zero-crossing point detecting means, Jaws for switching between A track jump pulse generating means for applying a pump pulse to the tracking means; and a switch means for switching between an open / close state between the polarity control means and the tracking means. The jump pulse starts a track jump. The track jump pulse creating means switches between the kick pulse and the brake pulse in accordance with the timing detected by the zero cross point detecting means. An optical recording / reproducing apparatus, wherein the switch means is turned off in response to a rise of the kick pulse and turned on in response to a fall of the brake pulse.