JPS6098534A - Tracking lead-in device - Google Patents

Abstract

PURPOSE:To attain always stable tracking lead-in by detecting a relative speed between a beam spot and an information track and executing the tracking lead- in under the condition of a sufficiently low relative speed. CONSTITUTION:When the relative speed between the beam spot 11 and a guide groove for tracking is reduced down to a certain value, the output of a monostable multivibrator is turned to the ''0'' level. At the starting of the device or under the OFF state of a tracking servo at the end of accessing to the track, a tracking lead-in instruction is inputted from an external controller to a lead-in control circuit 9 through a signal line 10. The output of the monostable multivibrator 8 is monitored, and when the output is turned to the ''0'' level, a switch 4 is closed and the state is continuously kept. Thus, the tracking lead-in can be executed at the time of the low relative speed, so that the tracking lead-in can be attained always stably.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an optical information reproducing apparatus that uses optical means to record information on a recording medium or to reproduce information that has already been recorded. Regarding 1t3, @ζ relates to the tracking position control device ζ of the device.

An optical type that uses a laser beam as a light source and modulates this laser beam with a pulsed signal from an external information source to record binary information on a recording medium on a disk, or to read information that has already been recorded. In an information recording/reproducing device, in order to accurately record or reproduce information, focus control is used to adjust the focal position of the condenser lens in the optical axis direction so that the recording medium surface is always at the focal position of the condenser lens. is controlled, and
To control the track position of the laser beam on the information track during recording or reproduction of 4W information, usually the optical spot on the recording medium has an optimal width and an optimal depth for the wavelength of the laser beam used. Provide a guide groove,
Track position control is performed so that the beam spot follows the guide groove. When the device is started up and after the beam spot is accessed between tracks, the track position control is off, so the tracking pull-in for the beam spot's information track 0 is performed, that is,
Tiger.

It is necessary to position the beam spot relative to the currently located information track from a state where position control is off.

At this time, the information track is vibrating greatly due to the eccentricity of the disk, so there is a good chance that tracking pull-in will occur when the relative velocity between the beam spot and the information track is large. In this case, the beam spot However, it is not possible to follow the information track and the vehicle goes out of control, so it is necessary to temporarily turn off the tracking position control and perform tracking pull-in again after a certain period of time has elapsed. In this way, if tracking pull-in fails, it takes several tens of m5ec to pull in again, and as a result,
This will lead to an increase in track access time, and the performance of the device will deteriorate.

An object of the present invention is to detect the relative speed between the beam spot and the information track in order to eliminate the above-mentioned drawbacks, and perform tracking pull-in while the relative speed is sufficiently low.Thus, stable tracking pull-in is possible at all times. It is an object of the present invention to provide a tracking retraction device.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a tracking pull-in device according to the invention. The laser source emitted from the optical helad 1 is controlled by a focus control circuit (not shown).
The beam is focused on a beam spot 11 such that the focal point is always on the recording medium surface of the disk 6. At this time, although not shown in FIG. ζ, a tracking position error of the beam spot 11 with respect to a tracking guide groove provided on the surface of the disk 6 is detected. Normally, since the disk 6 is eccentric, the tracking guide groove vibrates greatly, so a tracking position error signal is detected even if the beam spot 11 is stationary. The detected tracking position error signal is amplified by the position error amplifier 21 and then input to the filter amplifier 3, where phase compensation of the tracking servo thread is performed. filter amplifier 3
The output of the filter amplifier 3 is input to the switch 4, but since the switch 4 is normally open when starting up the device and accessing the track of the beam spot 11, the output of the filter amplifier 3 is not input to the power amplifier 5. , Therefore, the internal ζ of the optical head 1 connected to the power amplifier 5
This tracking actuator is not driven, and the positioning and follow-up operation of the beam spot 11 with respect to the tracking guide groove is performed slowly. -10,000, position error amplifier 2
The output is input to a comparator 7, where it is compared with the OV signal level and a zero-cross pulse of the tracking position fffi difference signal is generated. The zero-cross pulse is input to the monostable multi-vibrator 81. Every time a zero-cross pulse occurs, the monostable multi-vibrator 8
Start. Since the monostable multivibrator 8 is retriggerable, when a zero-cross pulse occurs at a time interval within the output pulse width of the monostable multivibrator 8, the output of the monostable multivibrator 8 continues to maintain the "1" level. Then, only when the time interval of the zero-cross pulse becomes equal to or greater than the output pulse width, the output drops to the "η" level.

That is, when the relative velocity between the beam spot 11 and the tracking guide groove becomes small to some extent, the output of the monostable multivibrator 8 becomes "U" level.

In this way, when the tracking servo is off at the start of the device or at the end of track access, when a tracking pull-in command is input from the external controller to the pull-in control circuit 9 via the signal line 10, the monostable multi-by-break 80 ) The output is monitored, and when the output reaches the "U" level, the switch 4 is closed and maintained in that state.

By doing so, as described above, tracking pull-in can be performed before the relative speed between the beam sbot 11 and the tracking guide groove is small, and tracking pull-in can be performed stably at all times.

FIG. 2 is a diagram showing operating waveforms of the tracking pull-in device of FIG. 1. When the switch is open and the track position control is off, due to the eccentricity of the disk 6, the track and king position error signals 20 are detected even when the beam spot 1 is stationary, and the comparator 7 generates a zero cross pulse. Ru. This zero-cross pulse l thus activates the monostable multi-by break 8, and when the relative velocity between the tracking guide groove and the beam spot 11 is large, the output 2] of the mono-stable multi-by break 8 is "
1" level. Previously, when the tracking pull-in command 23 is input from the external controller to the pull-in control circuit 9 through the signal line 10, the output 21 of the monostable multivibrator 8 is kept at the "1" level. Then, the open signal continues to be output to the switch 4, and the track position control remains off.
The relative speed to the tracking guide groove beam spot 11 is small. 1. When the time interval between the zero-cross pulses from the comparator 7 becomes longer, the output 21 of the monostable multi-bi break 8 momentarily drops to the "0" level 221. At this time, the pull-in control circuit 9 detects this "0" level 22 and sends a signal 2 to close the switch 41.
4, and switch 4 is used as a leap. In this way, the track position control is turned on, and the beam spot 11 is positioned at the currently located tracking guide groove.As described above, the relative speed between the beam spot and the tracking guide groove is detected, By performing the tracking pull-in with the phase (rj speed is f minutes), the tracking pull-in can be performed stably.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the tracking pull-in device according to the present invention, and a diagram showing operational waveforms of the tracking pull-in device shown in FIG. In the figure, 1... optical head, 2... position error amplifier, 3... filter amplifier, 4... switch,
5... Power amplifier, 6... Disc, 7... Comparator, 8... Monostable multi-vibration break, 9...
・・Retraction control circuit, 11・・Heam spot wowazoi 1 indicates 0

Claims (1)

[Claims] Recording information on a recording medium using optical means, or
An optical information recording/reading device that reads previously recorded information and controls the tracking position of a light spot with respect to a concentric circular or spiral data track provided on the recording medium. , a tracking control circuit that positions and follows the original spot on the data track; a comparator that compares the magnitude of a tracking error signal indicating a position error of the optical spot with respect to the data track with a reference signal; and the comparison circuit. A retriggerable monostable multivibrator whose trigger input is the track cross pulse output from the device, and the output of the monostable multivibrator and an external tracking pull-in command are used as inputs to turn on/off the tracking control circuit. A tracking pull-in device comprising a pull-in control circuit that controls turning off, and performs pull-in of track and kink position control when the time interval of the track cross pulse exceeds a preset value. .