JPH05325209A - Track servo pull-in device - Google Patents

Abstract

PURPOSE:To provide a track servo pull-in device which speedily, precisely and stably performs a track pull-in. CONSTITUTION:An MPV 14 receives various information including positional deviations in an information track and an optical pickup relating to a differential amplifier 10, track.cross pulses 102, which are required for counting the number of track crossings relating to a waveform shaping circuit 11, a total reflected light quantity generated during a track crossing relating to an adder 12 and land.groove pulses 104 which show whether the center of an optical spot is located at a land section or a groove section from a waveform shaping circuit 13. At the MPV 14, the track.cross pulses 102 are monitored and as the optical pickup moves, the monitored number of pulses 102 are subtracted from the preset number of track.cross pulses and when the subtracted number becomes zero, the land groove pulse 104 is confirmed to be a high level and then, a track pull-in signal is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track servo pull-in device provided in an optical disk device, and more particularly, for moving and positioning an optical pickup on an information track of an information recording medium.

[0002]

2. Description of the Related Art Generally, in this type of optical disk device, an information track formed concentrically or spirally on an information recording medium is irradiated with a semiconductor laser and a laser beam focused by a condenser lens is predetermined. The information is recorded / reproduced by focusing on the light diameter of. When information is recorded / reproduced in this manner, the optical pickup is moved to a specific information track from a large number of information tracks formed on the information recording medium, and the optical pickup is made to accurately follow the information track. There is a need. Conventionally, a speed signal obtained by F / V converting a track cross pulse has been used as a timing signal for causing an optical pickup to follow an information track. That is, the track servo pull-in device provided in the optical disk device outputs this speed signal to M
Monitor with PU (Micro Processing Unit),
Positioning is performed when the speed of the optical pickup has sufficiently decreased, and a track pull-in signal is output.

[0003]

In the above-mentioned track servo pull-in device, the track pull-in operation is performed when the speed of the optical pickup is sufficiently slowed down. Therefore, when the target track is reached, reliable pull-in is performed. However, it has not been decided whether the center of the light spot is on the land or the groove, and therefore it is difficult to pull in when pulling in with the opposite polarity (groove), for example. Often.

That is, since such disadvantages have not been sufficiently addressed, it is difficult for the conventional track servo pull-in device to perform the track pull-in operation stably at high speed and accurately.

The present invention has been made in view of the above circumstances, and a technical object thereof is to provide a track servo pull-in device capable of pulling a track accurately at high speed and accurately.

[0006]

According to the present invention, an optical pickup is moved and positioned with respect to an information track formed concentrically or spirally on an information recording medium to record and reproduce information. In a track servo pull-in device provided in an optical disk device, a track error detecting means for detecting a positional deviation between an information track and an optical pickup and outputting a positional deviation detection signal, and a track necessary for counting the number of track crossings from the positional deviation detection signal. -Track cross pulse detection means for detecting cross pulses, total reflected light amount detection means for detecting the total reflected light amount generated when passing through the track and outputting a reflected light amount detection signal, and the center of the light spot from the reflected light amount detection signal A run for detecting a land / groove pulse indicating whether it is in the land part or in the groove part. - and the groove pulse detection means,
The track / cross pulse is monitored, and the number of the track / clock pulse is subtracted from the predetermined number of track / cross pulses set in advance with the movement of the optical pickup. When the subtracted value becomes zero, the land / groove pulse is detected. A track servo pull-in device provided with track pull-in signal generating means for generating a track pull-in signal after confirming that the level is high.

[0007]

In the track servo pull-in device of the present invention, the position shift between the information track and the optical pickup, the track cross pulse necessary for counting the number of track crossings, the total reflected light amount generated when the track passes, and the center of the light spot are determined. Land that indicates whether it is in the land part or the groove part
The number of track clock pulses monitored is subtracted from the preset number of predetermined track cross pulses as the optical pickup moves while detecting the groove pulse and monitoring the track cross pulse. At that point, the track pull-in signal is generated after confirming that the land / groove pulse is at a high level.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The track servo pull-in device of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the basic structure of a track servo pull-in device according to an embodiment of the present invention. As shown in the figure, the track servo pull-in device includes a semiconductor laser 1 arranged in an optical pickup of an optical disc device, a collimator lens 2, a polarization beam splitter 3, 1 / which constitutes the optical pickup.
A four-wave plate 4, an objective lens 6, an actuator 5 for driving the objective lens 6, and a two-divided photodetector 9, and
A differential amplifier 10 and an adder 12 connected to the split photodetector 9; a shaping circuit 11 connected to the differential amplifier 10;
Shaping circuit 13 connected to adder 12 and shaping circuit 1
1 and 13, and the MPU 14 connected thereto.

Of these, the semiconductor laser 1 is supplied with an electric current by a laser driving circuit (not shown) and irradiates a laser beam for recording and reproducing information. The collimator lens 2 is for converting the divergent laser beam emitted from the semiconductor laser 1 into a parallel laser beam. The polarization beam splitter 3 separates the light flux reflected from the information recording medium 7, and thereby allows the light flux of the incident light flux to go straight without being bent. The quarter-wave plate 4 is for changing the polarization state of the laser light flux from linearly polarized light to circularly polarized light, and the condenser lens 8 condenses the parallel laser light flux to form a minute light spot on the information recording medium 7. It is for forming.

Guide grooves for information tracks are formed on the surface of the information recording medium 7 at a fine pitch, and information is recorded along the guide grooves. When the position of the focused light spot on the information recording medium 7 deviates from the center of the information track, the light intensity in the far field of the light reflected by the information recording medium 7 due to the diffraction and scattering of the light by the guide groove is in the track direction. On the other hand, a difference in intensity is generated on the left and right. The two-divided photodetector 9 catches this intensity difference as a positional deviation of the light spot with respect to the center of the information track, and the track error signal 101
And is provided with at least two photodetection elements that are separately arranged in the left-right direction.

Further, the reflected light reflected by the information recording medium 7 is returned to a parallel light flux by the condenser lens 8 and becomes 1 /
It is incident on the four-wave plate 4. Polarization beam splitter 3 is 1
Refracts the optical path of the reflected light emitted from the / 4 wavelength plate 4,
The light is guided to the two-divided photodetector 9. The two-division photodetector 9 separates and detects the left and right light intensities of the reflected light in the far field. A current indicating the left and right intensities of the reflected light output from the two-divided photodetector 9 is input to the differential amplifier 10. The differential amplifier 10 outputs a difference output corresponding to the difference in intensity of left and right light, that is, a track error signal 101. The track error signal 101 is input to the shaping circuit 11,
Compared at zero level. By this comparison, the shaping circuit 11
Outputs a track cross pulse 102.

On the other hand, the current indicating the left and right intensities of the reflected light output from the two-divided photodetector 9 is also input to the adder 12. The adder 12 has an output corresponding to the sum of the left and right light intensities,
That is, the track sum signal 103 indicating the total reflected light amount is output. This track-sum signal 103 is a shaping circuit 13
Is input to and compared at a predetermined level. By this comparison, the shaping circuit 13 outputs the land / groove pulse 104.

Next, how the MPU 14 detects a timing signal to pull in a track will be described. As a method of moving the optical pickup to the target information track, the target movement amount is calculated from the difference between the position of the target information track and the current information track position, and the movement amount of the optical pickup is subtracted from the target movement amount. Then
It suffices to move the optical pickup so that the subtraction result becomes zero.

The actual amount of movement of the optical pickup can be obtained by counting the track cross pulses 102. The track cross pulse 102 output from the shaping circuit 11 is counted by the counter in the MPU 14,
It is subtracted from a preset number of predetermined track cross pulses (that is, the amount of movement to the target track), and the subtraction value is monitored until it becomes zero.

On the other hand, the land / groove pulse 104 output from the shaping circuit 13 indicates whether the center of the light spot is at the land portion or the groove portion on the information recording medium 7, and at high level it is turned on. Land and low level represent on-groove. The MPU 14 has a track cross pulse 102 and a land groove pulse 1
04 is monitored, and the value obtained by subtracting the number of track cross pulses 102 from the movement amount to the target track is zero,
In addition, after confirming that the land / groove pulse 104 is at a high level (that is, on-land state), the track pull-in signal is output, and the tracking servo loop is closed.

FIG. 2 is a timing chart of each signal when recording / reproducing information on / from an information track by the track servo pull-in device.

Here, the rectangular track cross pulse 102 output from the shaping circuit 11 corresponds to the positive / negative of the waveform of the track error signal 101 output from the differential amplifier 10, and the adder 12 outputs it. The output track sum signal 103 is the track cross pulse 1
Correlating the positive peak to the rising edge of 02, the shaping circuit 13
It has been explained that the rectangular land / groove pulse 104 output from the above corresponds to the positive / negative of the waveform of the track sum signal 103.

The track servo pull-in device having such a structure has a collimator lens 2, a polarization beam splitter 3, a quarter-wave plate 4, an objective lens 6, an actuator 5 for driving the objective lens 6, and an actuator 5, which constitute an optical pickup. The two-divided photodetector 9 and the differential amplifier 10 connected to the two-divided photodetector 9 form a track error detecting means, and the shaping circuit 11 serves as a track / cross pulse detecting means. Pickup and adder 12
And form the total reflected light amount detecting means, and the shaping circuit 13 serves as the land / groove pulse detecting means.

In addition, the MPU 14 shifts the position between the information track and the optical pickup, the track cross pulse necessary for counting the number of track crossings, the total amount of reflected light generated when the track passes, and the center of the light spot on the land portion. Detecting a land / groove pulse that indicates whether it is present or not, and monitoring the track cross pulse, the track pickup clock pulse is monitored from the preset number of preset track cross pulses as the optical pickup moves. The track pull-in signal generating means for generating the track pull-in signal is used at high speed and at an appropriate level after confirming that the land / groove pulse is at a high level when the subtracted value becomes zero. Exactly, stable track pull-in can be always performed.

[0021]

As described above, according to the track servo pull-in device of the present invention, the target movement amount is calculated from the difference between the target track position and the current track position.
Subtract the amount of movement of the optical pickup from the target amount of movement, move the optical pickup so that the subtraction result becomes zero, and monitor the land / groove pulse to confirm that this is at a high level before pulling in the track. Since the signal is output, the optical pickup can be pulled in even when the speed of the optical pickup is relatively high, and there is no fear of pulling in the opposite polarity. Therefore, a fast and accurate stable track pull-in operation can be performed.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of a track servo pull-in device according to an embodiment of the present invention.

FIG. 2 is a timing chart of each signal when recording / reproducing information on / from an information track by the track servo pull-in device of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Collimating lens 3 Polarizing beam splitter 4 1/4 wavelength plate 5 Actuator 6 Objective lens 7 Information recording medium 8 Condensing lens 9 Two-division photodetector 10 Differential amplifier 11, 13 Shaping circuit 12 Adder 14 MPU 101 Track error signal 102 Track cross pulse 103 Track sum signal 104 Land groove pulse

Claims (1)

[Claims] 1. A track servo pull-in device provided in an optical disc device for recording and reproducing information by moving and positioning an optical pickup with respect to an information track formed concentrically or spirally on an information recording medium, Track error detecting means for detecting a positional deviation between the information track and the optical pickup and outputting a positional deviation detection signal, and a track for detecting a track cross pulse necessary for counting the number of track crossings from the positional deviation detection signal. -Cross pulse detection means, total reflected light amount detection means for detecting the total reflected light amount generated when passing through the track and outputting a reflected light amount detection signal, and whether the center of the light spot from the reflected light amount detection signal is in the land portion, Alternatively, a land / groove pulse that detects a land / groove pulse indicating whether it is in the groove part Monitor means and the track cross pulse, and when the number of the track clock pulses is subtracted from the preset number of track cross pulses preset with the movement of the optical pickup, the subtracted value becomes zero. And a track pull-in signal generating means for generating a track pull-in signal after confirming that the land / groove pulse is at a high level.