JP2689522B2 - Optical disk drive - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device, and more particularly to an optical disk device for counting the number of track crossings during a high speed track access operation with high accuracy.

[Conventional technology]

In the optical disc device, a track access operation is generally performed at the time of recording and reproducing information. During the access operation, the difference between the current track address and the target track address is obtained, and the track is advanced by the difference to perform positioning on the target track.

FIG. 3 shows a conventional example. In the conventional example shown in FIG. 3, the laser beam from the laser light source 51 passes through the collimator lens 52, the beam splitter 53, and the objective lens 54 and is applied to the optical disc 55. Further, the reflected beam from the optical disc 55 is changed in direction by the beam splitter 53 and becomes an input to the tracking error signal generating means 56. The tracking error signal generating means 56 outputs the tracking error signal S ₅₉ to the zero slice means 57. A track crossing pulse S ₅₇ is output from the zero slice means 57 to the track counter 58.

Next, the operation of this conventional example will be described. The laser beam emitted from the laser light source 51 is a collimating lens.
It is condensed by 52 and becomes a parallel beam, and the beam splitter 53
Through the objective lens 54 and focused on the surface of the optical disc 55. Next, the light reflected on the surface of the optical disk 55 contains a signal for discriminating between the groove on the track and the groove, and is condensed by the objective lens 54 to be a parallel bee, and the course is bent by the beam splitter 53 to perform tracking. It becomes an input of the error signal generating means 56.

The tracking error signal generating means 56 outputs a tracking error signal 59 corresponding to the track groove and the track groove as shown in FIG. 6 (b). Then, the tracking error signal S ₅₆ is zero-sliced by the zero-slicing means 57, and as shown in FIG. 6C, the track crossing pulse S _57.
And is counted by the track counter 58. Since this count number corresponds to the number of traversed tracks, if the vehicle stops at the target count number, it becomes the target track address position.

[Problems to be solved by the invention]

In the above-mentioned conventional example, the target positioning is performed by the head moving mechanism during the high-speed track access operation. At this time, the moving speed of the head moving mechanism is set by the speed reference signal to be a constant acceleration or a constant deceleration according to the remaining distance during the movement. When the acceleration and deceleration operations are performed, an external force is applied to the lens, so that a positional deviation occurs in the lens according to the acceleration or deceleration, and due to this positional deviation, the tracking error signal includes the tracking error signal shown in FIGS. An offset occurs as shown in.

If the band of the lens positioning servo system is set to ω _C , a position shift of “α / ω _c ² ” is generated with respect to the acceleration α when the head is moved. Therefore, the higher the acceleration, the faster the access. The offset amount of the tracking error signal S ₅₆ increases.

Since the tracking error signal S ₅₆ is amplitude-modulated in the data recording section and the preformat section,
When an offset occurs in the tracking error signal as shown in the figure, a gap occurs in the track crossing pulse S ₅₇ .
Therefore, it is difficult to accurately measure the number of track crossings, and the target track address position is displaced.

[Object of the invention]

It is an object of the present invention to provide an optical disk device which improves the disadvantages of the conventional example and can count the number of track crossings with high accuracy and track positioning with high accuracy even during a high-speed track access operation. is there.

[Means for solving the problem]

Therefore, in the present invention, when the information from the recording medium is recorded or reproduced by irradiating the recording medium with the light from the light source through the lens system, the reflected light from the recording medium is counted in order to count the number of track crossings of the head. Therefore, the tracking error signal generating means for generating a tracking error signal corresponding to the deviation of the beam spot on the recording medium from the track center is provided. Further, a lens position shift signal generating means for generating a lens position shift signal at the time of track following operation and track access operation, and a subtracting means for subtracting the output signal of the lens position shift signal generating means from the output signal of the tracking error signal generating means. , Waveform shaping means for generating a cross-track pulse from the output signal of the subtraction means. The output signal of the waveform shaping means is used as a stop control signal for moving the head. This aims to achieve the above-mentioned object.

[Action]

During track following operation and track access operation,
The amount of lens displacement, which is the cause of the offset, is detected by the lens displacement signal generating means, the lens displacement signal is subtracted from the tracking error signal to perform offset correction, and waveform shaping is performed to obtain a track crossing pulse.

(Example of the invention)

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. Here, the same reference numerals are used for the same components as those in the conventional example described above.

The embodiment shown in FIG. 1 includes a light source 51 and a lens system mounted on the head for recording or reproducing information on a recording medium 55. Further, the positional deviation of the beam spot from the tracking center position is detected based on the reflected light of the beam spot output from the light source 55 and the lens system from the recording medium 55, and the tracking error corresponding to the positional deviation amount is detected. A tracking error signal generating means 56 for outputting a signal is provided. The output of the tracking error signal generating means 56 is sent to a head moving control means (not shown), and a track counter 58 to be described later is provided.
Is used to control the movement or stop of the head together with the output signal.

The lens system is provided with a lens position shift signal generating means 10 for detecting a lens position shift and outputting a predetermined signal at the time of track following operation and track access operation. Further, the lens position deviation signal generating means 10 and the output signals of the tracking error signal generating means 56 described above are input, and a subtracting means 30 for subtracting the lens position deviation signal S ₁₄ from the tracking error signal S ₅₆ is provided. There is. Furthermore, a waveform shaping means 20 for generating a track crossing pulse S ₂₀ based on the output signal S ₃₀ of the subtraction means 30,
The track crossing pulse S which is the output of the waveform shaping means 20
A track counter 58 for counting ₂₀ is provided. Then, the stop control when the head is moved is performed by the signal output from the track counter 58.

The lens system specifically collects the light from the light source 51 and collimates the light into parallel rays.
52, a beam splitter 53 that allows the light from the collimator lens 52 to go straight as it is, and the light reflected from the recording medium 55 changes direction, and the focus of the light that has passed through the beam splitter 53 is on the surface of the recording medium 55. It is composed of an objective lens 54 for binding.

The lens position shift signal generating means 10 includes a reflecting mirror 11 attached to a tracking actuator (not shown), a light emitting diode 13 for applying light to the reflecting mirror 11, and light emitted from the light emitting diode 13 reflected by the reflecting mirror 11. It is provided with a lens position detector 12 that can know the position of the lens by sensing, and an operational amplifier 14 that generates a lens position shift signal 15 from the output of the lens position detector 12.

The tracking error signal generating means 56 is a photodetector 61 for converting the light from the beam splitter 53 into an electric signal,
And an operational amplifier 62 for amplifying the output signal of the photodetector 61. Here, as the subtraction means 30, a comparator is used.

Further, the waveform shaping means 20 uses the track crossing pulse S ₂₀
F / V converter 23 for F-V conversion, a band variable filter 22 for extracting the output signal of the subtraction means 30 with a frequency component corresponding to the speed signal output from the F / V converter 23, and a band variable A waveform shaping circuit 24 for shaping the output signal S ₂₂ of the filter 22.

 Next, the operation of the present embodiment will be described.

The light from the light source 51 is condensed by the collimator lens 52,
It becomes a parallel beam, passes through the beam splitter 53, is focused by the objective lens 54, and is applied to the surface of the recording medium 55. The light striking the surface of the recording medium 55 shows different reflection states between the grooves of the track and on the grooves. And a recording medium
The light reflected on the surface of 55 is condensed by the objective lens 54, becomes a parallel beam, the direction of which is changed by the beam splitter 53, and is converted by the photodetector 61 into an electric signal corresponding to the intensity of the light. Tracking error signal amplified by 62
It becomes S ₅₆ .

Further, in the lens position shift signal generating means 10, when the lens position shifts, the light (reflecting mirror) entering the lens position detector 12 is moved.
The amount of light of the light emitting diode 13 reflected at 11) changes.
Therefore, the lens position detector 12 outputs an electric signal corresponding to the position change of the lens. Then, the output signal of the lens position detector 12 is subtracted by the differential amplifier 14 to become a lens position shift signal 15.

Then, the influence of the offset is canceled by subtracting the lens position shift signal S ₁₄ from the tracking error signal S ₅₆ by the comparator that is the subtraction means 30.

Further, since it is necessary to detect the track crossing pulse in a very wide velocity range of 1 [mm / S] to 0.5 [m / S], the tracking error signal S ₅₆ is also several hundred [k] from a position close to the DC component. Hz] is required, and if the output signal of the subtraction means 30 is shaped by the waveform shaping circuit 24 as it is, even a noise component of the signal appears in the track crossing pulse S ₂₀ , so the band variable filter 22 crosses the track. The signal component corresponding to the speed is selectively taken out and the waveform is shaped.

Thus, by performing the waveform shaping, it is possible to obtain the track crossing pulse S _{20 in} which the influence of the offset is canceled as shown in FIG. Then, the track crossing pulse S ₂₀ is input to the track counter 58, the number of track crossings is counted, and is used for measuring the movement amount of the head moving mechanism and for the stop control.

〔The invention's effect〕

As described above, according to the present invention, a lens position shift signal generating means for converting the lens position shift into a predetermined signal and outputting the same during the track following operation and the track access operation,
Subtraction means for subtracting the output signal of the lens displacement signal generation means from the output signal of the tracking error signal generation means,
Since the waveform shaping means for generating the cross-track pulse from the output signal of the arithmetic circuit is provided, by using this, even during the high-speed track access operation, there is no influence due to the displacement of the lens or the eccentricity of the recording medium. The number of track crossings can be counted with high accuracy, and the band of the lens positioning servo system can be suppressed to a low level. Therefore, an excellent optical disk device that has never been used is not adversely affected by the resonance characteristics of the mechanical system. can do.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a waveform diagram showing an example of a tracking error signal and a track crossing pulse in the figure, FIG. 3 is a configuration diagram showing a conventional example, FIG. 4 is a relationship diagram of a head moving speed, a lens position and a tracking error signal, and FIG. FIG. 6 is a waveform diagram showing an example of a tracking error signal and a track crossing pulse when there is no offset, and FIG. 7 is a tracking error signal and a track crossing when there is an offset. It is a wave form diagram which shows an example of a pulse. 10 ... Lens position deviation signal generating means, 20 ... Waveform shaping means, 30 ... Subtracting means, 51 ... Light source, 56 ... Tracking error signal generating means.

Claims (1)

(57) [Claims] 1. A light source and a lens system mounted on a head for recording or reproducing information on a recording medium, and a tracking center based on a light beam reflected from the recording medium of a beam spot output from the light source and the lens system. A tracking error signal generating means for detecting a positional deviation of the beam spot from the position and outputting a tracking error signal corresponding to the positional deviation amount, and based on a signal output from the tracking error signal generating means. In an optical disk device having a function of generating a control signal for guiding the head to a target track address and controlling the drive of the head, the lens system detects a positional deviation of the lens during a track following operation and a track access operation, and determines a predetermined value. Equipped with lens position deviation signal generation means that outputs the signal of At the same time, it comprises a subtracting means for subtracting the output signal of the lens position deviation signal generating means from the output signal of the tracking error signal generating means, and a waveform shaping means for generating a track crossing pulse based on the output signal of the subtracting means. An optical disk device characterized in that the output signal of the waveform shaping means is used as a stop control signal for head movement.