JPH01155576A - Track access device - Google Patents

Abstract

PURPOSE:To attain accurate track access by interpolating a track cross pulse only in an area where there is no group by means of the pulse signal of a prescribed frequency, which is equal to the frequency of the track cross pulse immediately before when an optical spot crosses the area where there is no group in the middle of track access. CONSTITUTION:When the optical spot 8 crosses the area where a track guide groove on an optical disk 4 does not exist in access to an objective track by the optical spot 8, the track cross pulse 13 is interpolated by the pulse 14 of the prescribed frequency having the frequency equal to that of the track cross pulse 13 immediately before it enters the area where the track guide groove does not exist. Thus, accurate track access is attained even if the optical spot crosses the area where there is no group in the middle of track access.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an optical information recording and reproducing device that uses optical means to record information on a recording medium or to reproduce information that has already been recorded. In particular, the present invention relates to a track access device used in a tracking control system of an optical information recording/reproducing device.

(Prior art) A laser beam is used as a light source, and the laser beam is modulated with a pulsed signal from an external information source to record binary information on a recording medium on a disk, or to record information that has already been recorded. In an optical information recording and reproducing device, in order to accurately record or reproduce information, the position of the condenser lens is controlled by focus control so that the surface of the recording medium is always at the focal point of the condenser lens. . In addition, to control the tracking position of a minute light spot of a laser beam relative to an information track during information recording or reproduction, a guide groove with an appropriate depth and width is usually provided on the surface of the recording medium for the minute light spot. This is done so that a minute light spot follows the guide groove.

In this track position control, it is common practice to generate various control signals using a tracking error signal generated from a guide groove. For example, a track cross pulse generated when a light spot crosses a track is detected from a tracking error signal.

In particular, in response to the demand for faster track access, a patent application filed in 1985 by the same applicant as the present application shows that a method of directly counting the number of moved tracks and moving the light spot to the target track is effective. No. 17375, same No. 17
It is described in No. 376. In this method, the light spot is moved at high speed by the desired number of tracks (strokes),
It is disclosed that the control mode is switched from a predetermined distance before the center of the target track, and the light spot is positioned on the target track by normal position control.

In the above-mentioned Japanese Patent Application No. 17375/1988 and No. 17376, the track cross pulse is generated by comparing the track error signal with a constant potential using a comparator or the like.

(Problem to be Solved by the Invention) However, in order to correct sector ID information or servo error signals, optical discs usually have areas in which no track guide grooves (groups) exist in each sector. . Furthermore, there is usually a plurality of sectors on one track, and when accessing a track, the light spot is forced to cross an area where there is no group. In an area without such a group, a track error signal cannot be obtained, so a track cross pulse based on the track error signal cannot be generated in that area.Therefore, a track cross pulse can be obtained only from the tracking error signal, In conventional track access devices that count the track cross pulses and move the optical spot to the target track, if the optical spot crosses an area without a group during movement, an error occurs in counting the number of moving tracks. Accurate track movement is not possible.

An object of the present invention is to eliminate the above-mentioned drawbacks, and to prevent the light spot from crossing an area without a group during track access.
An object of the present invention is to provide a track access device that can perform accurate track access.

(Means for Solving the Problems) Means provided by the present invention to solve the above-mentioned problems is a track access method for moving a light spot from a current track to a target track on an optical disc of an optical information recording/reproducing device. At times, a track cross pulse indicating that the light spot has crossed a track is generated from the track error signal, and the track cross pulse is counted to calculate the number of tracks from the current track to the target track and the track cross pulse. The apparatus accesses the target track with the optical spoiler by calculating the difference between the optical disc and the optical disc and moving the optical spot until the difference becomes 0 or a value close to 0. When the light spot crosses a region where no track guide groove exists, the track cross pulse is interpolated by a pulse signal of a constant frequency that has a frequency equal to the frequency of the track cross pulse immediately before entering the region. do.

(Function) In the present invention, when a light spot crosses an area without a group during track access, the track cross pulse is interpolated only in the area without a group using a pulse signal with a constant frequency equal to the frequency of the previous track cross pulse. to reduce the counting error of track cross pulses.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

The optical head 2 includes a condensing lens, a lens actuator that drives the condensing lens in two axes, a focal direction and a tracking direction, and a lens position detector that detects the position of the condensing lens with respect to the optical and y-direction housings. It is equipped with

The movement of the light spot 8 focused on the recording surface of the disk 4 from the current track to another target track is based on a stroke signal 9 input from the outside, a track error signal, and a track error signal. This is performed by the track movement control circuit 1 controlling the track actuator in response to the generated track cross pulse. The detailed operation at the time of track access is described in Japanese Patent Application Nos. 17375-1988 and 17376, cited above, filed by the same applicant as the present application.
It is stated in the specification of the No. That is, the track movement control circuit 1 receives a stroke signal 9 indicating the stroke to the target track from an external controller, and presets it in an internal stroke counter. The preset value of the stroke counter is subtracted by a track cross pulse generated from the track error signal 11 in the track cross pulse generator 5, which indicates that the light spot 8 on the disk 4 has crossed the track, and the output of this stroke counter is subtracted. The signal causes the optical spot 8L to move at high speed to the target track. At this time, the position of the optical head is controlled via the head control circuit 20 and head actuator 3 based on the lens position signal detected inside the optical head. The above specification describes that the light spot can be moved to the target track at high speed in this way.

There are guide tracks (groups) on the recording surface of disc 4.
Sector ID area when the track is divided into multiple sectors (contains signals indicating the start of the sector, track address, sector address, etc.) when processing and forming a disk.
Or, a mirror area where no group exists is provided for correcting focus/track error signals. These areas are referred to as preformat areas here. Since groups are not formed accurately in such preformat areas, the amplitude of the track error signal may decrease or the track error signal may not be generated. There is.

Therefore, the track cross pulse generator 5 generates the track cross pulse 13 from the track error signal 11, and at the same time, the interpolation pulse generating circuit 7 generates the interpolation pulse 14 of the track cross pulse. thus,
In a preformat area where an accurate track error signal cannot be generated, the switch 6 receives a preformat area signal 21 indicating the preformat area from the outside.
Accordingly, the interpolation pulse 14 is sent to the track movement control circuit 1 instead of the track cross pulse 13 only in the preformat area. Thus, as the light spot 8 moves across the preformatted area to the target track,
Track movement can be performed accurately even if the track error signal 11 is not generated.

FIG. 2 is a detailed block diagram of the interpolation pulse generator 7 shown in FIG. 1. This interpolation pulse generator 7 is connected to the counter 3
0.32, a register 31 and a gate 33. The counter 30 counts the pulse period of the track cross pulse 13 using the reference clock 24. register 3
1 stores the value of the counter 3o each time the track cross pulse 13 occurs, that is, the cycle of the immediately previous track cross pulse. The counter 32 uses the value stored in the register 31 as a preset value, operates as a rate counter counted down by the reference clock 24, and outputs the interpolation pulse 14. That is, the interpolated pulse 14 is
A pulse signal delayed by one pulse from the track cross pulse 13 is output. In this way, when the light spot enters the preformat area, the preformat area signal 21 indicating that the light spot is in the preformat area is input.
Gate circuit 33 is closed. By doing this, the track cross pulse is no longer input to the counter 30,
The values of the counter 30 and register 31 no longer change. Therefore, the interpolation pulse 14 is calculated by the counter 32 according to the period of the track cross pulse immediately before the preformat area.
is output and input to the track movement control circuit 1 via the switch 6. In this way, when the optical spot 8 moves across the preformat area to the target track, accurate track movement can be achieved even if the track error signal 11 cannot be detected.

FIG. 3 is a waveform diagram showing signals of various parts in the embodiment of FIG. 1. The signal amplitude of the track error signal 11 decreases in the preformat area 12, or becomes almost zero, and the track cross pulse generator 5 becomes unable to generate a track cross pulse. Therefore, in this embodiment, an interpolation pulse 14 is generated by the interpolation pulse generation circuit 7 in the preformat area to compensate for the missing part of the track cross pulse, thereby generating an accurate track cross pulse 15, and the light spot 8 Try to make accurate movements.

(Effects of the Invention) According to the present invention described above, even if a light spot crosses an area without a group during track access, more accurate track access can be performed by interpolating the track cross pulse. The light spot can be moved to the target track in a shorter period of time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing details of the interpolation pulse generation circuit of FIG. 1, and FIG. 3 is a block diagram showing the details of the interpolation pulse generation circuit of FIG. FIG. 3 is a waveform diagram showing signals. 1... Track movement control circuit, 2... Optical head, 3
...Head actuator, 4...Disk, 5.
...Track cross pulse generator, 6...Switch,
7... Interpolation pulse generator, 8... Light spot, 9...
... Stroke signal, 20... Head control circuit.

Claims (1)

[Claims] During track access to move a light spot from a current track to a target track on an optical disc of an optical information recording/reproducing device, a track cross pulse indicating that the light spot has crossed a track is generated from a track error signal, and the track cross pulse is generated from a track error signal. Counting the pulses, calculating the difference between the number of tracks from the current track to the target track and the counted value of the track crossing pulse, and moving the light spot until the difference becomes 0 or a value close to 0. In the apparatus for accessing the target track with the optical spot, when the optical spot crosses an area on the optical disk where no track guide groove exists, the optical spot has a frequency equal to the frequency of the track crossing pulse immediately before entering the area. A track access device characterized in that the track cross pulse is interpolated using a pulse signal having a constant frequency.