JPH06139590A - Device for drawing tracking servo - Google Patents

Abstract

PURPOSE:To obtain a tracking servo drawing device preventing influence due to a noise and eliminating the delay of timing of tracking drawing. CONSTITUTION:In an optical information recording and reproducing device recording and reproducing on an optical disk having a groove shape guide track, a comparator 5 having a hysterisis characteristic where a UTP(Upper Trip Point) value and a LTP(Lower Trip Point) value are different each other and the comparator 6 where an output signal is turned on/off by the zero point crossing of an input signal are provided. A tracking error signal is inputted to the comparator 5 and the comparator 6 through a low-pass filter 4. Respective output signals are inputted to a D flip-flop 8. The output signal of the flip-flop is used as an on track timing signal, on the other hand, the output signal of the comparator 5 is used as a traverse number of tracks signal through a pulse generator 7, and tracking servo control is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking servo retraction device for an optical recording / reproducing apparatus having an optical disk having grooved guide tracks.

[0002]

2. Description of the Related Art A conventional technique of this kind is disclosed in Japanese Patent Publication No. 62-
There is one disclosed in Japanese Patent No. 33648 (Japanese Patent Laid-Open No. 58-57640). In an optical recording / reproducing device,
The sum signal of the tracking signals generated when the light spot crosses the groove-shaped guide track and the reproduced RF signal are subjected to the envelope detection and then the waveform-shaped signal is ORed, and the level of the difference signal of the tracking signals is zero. The logical product of the signal at which the crossing timing is detected and the logical sum output signal is taken, the moment when the light spot passes directly above the groove-shaped guide track is detected, and the tracking servo is started at this timing. It was done.

Further, as a method of avoiding the influence of chattering due to noise, there is a tracking pull-in device having a structure shown in FIG. The tracking error signal generated when the light spot crosses the groove-shaped track 3-14 at the time of seeking the address is provided with a hysteresis characteristic at the reference level when binarized by the comparator 3-5. . L
When changing from level to H level, UTP (Upper Tr
When changing from H level to L level based on ip point), a hysteresis width is set based on LTP (Lower Trip Point) to avoid the influence of chattering, and the speed at which the light spot crosses tracks 3-14 is calculated. The hysteresis width is made variable by the signal.

[0004]

However, in the conventional device, at the moment when the light spot passes over the target track,
If there is a noise component such as address information or scratches on the track, the waveform-shaped signal causes chattering, and it is impossible to accurately count the number of crossing tracks and control ON / OFF of tracking pull-in.

Further, as shown in FIG. 3, it is considered to use a comparator having a hysteresis characteristic at the time of waveform shaping in order to avoid the influence of chattering. As shown, the timing of tracking pull-in is delayed. Approximately 10 flexible disks in an optical disk device
Since the disc is rotated at twice the high speed, the entry speed of the light spot into the target track cannot be sufficiently slowed down due to the influence of the eccentricity of the disc. For this reason, there is a problem that the amount of overshoot at the time of track pull-in is large and the time until settling of the light spot becomes very long, or in the worst case, pull-in fails, causing a runaway state. .

The present invention has been made in view of the above points, and provides a tracking servo retraction device which eliminates the above problems, avoids the influence of noise, and eliminates the delay in the tracking retraction timing. With the goal.

[0007]

In order to solve the above problems, the present invention provides a UTP (optical information recording / reproducing apparatus for recording / reproducing on an optical disc having a groove-shaped guide track as shown in FIG. Upper Trip Point) value and LTP
(Lower Trip Point) A comparator 5 having different hysteresis characteristics and a comparator 6 for turning on / off the output signal at the zero crossing of the input signal are provided, and the tracking error signal is set to the low pass filter 4. It is input to the comparator 5 and the comparator 6 via the output signals, and the respective output signals are input to the D flip-flop 8, which output signals are used as on-track timing signals, while the output signals of the comparator 5 are input. The greatest feature is that it is used as a transverse track number signal via the pulse generator 7 to perform tracking servo pull-in control.

[0008]

In the track pull-in device of the present invention, an accurate number of track crossings of the light spot which is not affected by noise or the like can be obtained from the output signal of the comparator 5 having the above-mentioned hysteresis characteristic, and the zero point of the input signal can be obtained. The output signal of the D-type flip-flop 8 obtained by these two input signals is turned on because the time when the light spot passes directly above the target track is detected from the output signal of the comparator 6 in which the output signal is turned on and off by crossing. By using it as a track timing signal, accurate tracking servo pull-in control can be performed without runaway.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing a configuration example of a tracking servo retraction device of the present invention. As shown in the figure, the tracking servo retractor according to the present invention has a photodetector 1 for detecting a reflected beam from a groove-shaped track, a differential amplifier 2 for taking a difference between two output signals p and q, and a sum. A sum amplifier 3, a low pass filter 4, a comparator 5 having a hysteresis characteristic, a comparator 6 for detecting a zero crossing, a pulse generator 7 for generating a signal of the number of moving tracks, and an on-track timing signal. D flip-flop 8 that occurs, CPU (central processing unit) that processes these signals
9, a servo circuit 10 for controlling the mechanism, a VCM and a tracking actuator 11, and a lens 12 of an optical system. The reflected light beam 15 from the disk 13 is detected by the photodetector 1 through the lens 12, and the VCM and the tracking actuator 11 are operated to control the head at a predetermined position.

An access operation for searching a target track will be described. The reflected light beam 15 reflected from the recording surface of the disk 13 is condensed by the lens 12 and detected by the photodetector 1. The photodetector 1 is composed of two light receiving parts, and the dividing boundary line of the central part is arranged parallel to the tangential direction of the groove-shaped track 14 of the disk 13. Therefore, when the light spot crosses the groove-shaped track 14, a phase difference occurs between the output signal p and the output signal q of the photodetector 1, and the signal is processed to determine the number, speed and direction of the light spot crossing the track. Find Find the position of the light spot.

The position is detected by counting the number of light spots crossing the track, and the speed is detected and controlled by obtaining the crossing frequency. Each time the access operation is performed once, the track follow-up control of the light spot is temporarily canceled, the light spot is moved to the target track position, and the light spot is again drawn into a predetermined track. Since the pulling-in operation of the tracking control is performed every time a track is searched, a particularly stable operation is required.

The comparator 5 in FIG. 1 has a proper UTP (Upper Trip Point) and LTP (Lower Trip P).
oint) is a comparator having a set hysteresis characteristic, and is for removing noise components such as address information and scratches on a track when counting the number of tracks crossing, and counting accurately. The comparator 6 outputs an output signal at the zero crossing of the track error signal and does not have a hysteresis characteristic. Therefore, the detection right above the track is accurately output.

FIG. 2 is a diagram showing signal waveforms of respective parts of the tracking pull-in device of the present invention. Track error signal a
When the light spot passes directly above the groove-shaped track, it passes through the zero point, and the address signal e is generated as noise in the address signal section. The track error signal a is binarized by the comparator 5 having a hysteresis characteristic and the output b is output. Although the output signal 6 is not affected by chattering, the head passes just above the track and falls with a delay of f. The output c of the comparator 6 is affected by noise, but falls when the head passes directly above.

Using the outputs of the above two comparators,
The output b of the comparator 5 is fed to the data of the D flip-flop 8.
An on-track timing signal d indicating directly above the target track is created by using the output c of the comparator 6 as a clock input, and the track is pulled in by the on-track timing signal d to perform an accurate target track search operation. To do.

[0015]

As described above in detail, according to the present invention, the following effects are expected. Even when the track error signal is disturbed by noise components such as address signals and scratches on the track, the moment when the light spot passes right above the target track is accurately detected, and tracking control is started at this timing. I did it. As a result, an accurate and stable access operation is performed with a simple circuit configuration, and an error in search is significantly reduced, so that the entire access time can be shortened. Also, because the track pull-in is stable, it can support high-speed rotation of the device,
It also reduces the power consumption of the device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a tracking pull-in device of the present invention.

FIG. 2 is a diagram showing a signal waveform of each part of the tracking pull-in device of the present invention.

FIG. 3 is a block diagram showing a configuration example of a conventional tracking pull-in device.

FIG. 4 is a diagram showing signal waveforms of respective parts of a conventional tracking pull-in device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photodetector 2 Differential amplifier 3 Sum amplifier 4 Low-pass filter 5,6 Comparator 7 Pulse generator 8 D flip-flop 9 CPU (central processing unit) 10 Servo circuit 11 VCM and tracking actuator 12 Lens 12 13 Disc 14 Groove-shaped track 15 Reflected light beam

Claims (1)

[Claims] 1. A tracking servo pull-in device of an optical recording / reproducing apparatus having a groove-shaped guide track for recording / reproducing information on / from an optical disc by laser light, wherein a spot of the laser light is provided. Is a first comparator having a hysteresis characteristic as a reference value for binarizing a tracking error signal generated when the track crosses the track of the optical disc, and an output signal is turned on by a zero crossing of the input signal. A second comparator for turning on / off, means for inputting the tracking error signal to the first comparator and the second comparator, and generating a tracking pull-in signal from the output signal thereof, Counting means for determining the number of tracks crossed by the laser spot from the output signal of the comparator is provided, and the tracking pull-in signal and the number of tracks are used for tracking pull-down. Tracking servo pull-in device characterized by performing pull-in control.