JPH01155577A - 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 mean frequency of plural track cross pulses 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 for accessing an objective track by the optical spot 8, the track cross pulse 13 is interpolated by the pulse 14 of the mean frequency of plural track cross pulses 13 immediately before the spot 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.

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. . Additionally, the tracking position of a tiny laser beam spot on an information track during information recording or reproduction is usually controlled by providing a guide groove on the surface of the recording medium with the optimal depth and width for the tiny spot. This is done so that a minute light spot follows the guide groove.

In this tracking position control, tracking error signals are generally used to generate various control signals. For example, a track cross pulse generated when a light spot crosses a track is used as a tracking error signal. Detection is being carried out from 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, No. 173
It is described in No. 76. In this method, the light spot is moved at high speed by the desired number of tracks (strokes), the control mode is switched a predetermined distance from the center of the target track, and the light spot is moved to the target track using normal position control. Positioning is disclosed.

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 light spot to the target track, if the light spot crosses an area where there is no group during movement, an error occurs in counting the number of tracks moved. 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 calculates the difference between the optical disc and the optical disc, moves the optical spot until the difference becomes 0 or a value close to O, and accesses the target track with the optical spot, the apparatus comprising: a track guide on the optical disk; When a light spot crosses a region where no groove exists, the track cross pulse is interpolated using a pulse signal having an average frequency of a plurality of track cross pulses immediately before the spot enters the region.

(Function) In the present invention, when a light spot crosses an area without a group during track access, a track cross pulse is generated only in the area without a group using a pulse signal with a constant frequency equal to the average frequency of the previous plural track cross pulses. interpolation is performed 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 inside, a lens actuator that drives the condensing lens in two axes, a focusing direction and a tracking direction, and a lens position detector that detects the position of the condensing lens with respect to the optical herad housing. 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 8 to move at high speed to the target track. At this time, the position of the optical head is determined by the head control circuit 20 and the head actuator 3 based on the lens position signal detected inside the optical head.
The position is controlled via. 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. In this interpolation pulse generator 7, a zero frequency division circuit 40, which is composed of counters 3G, 32, a register 31, a frequency division circuit 40, and a gate 33, converts the track cross pulse 13 to a predetermined value, such as 1/4 or 1.
Divide by a value of /8. The counter 30 counts the pulse period of the frequency-divided track cross pulse 16 using the reference clock 24. The register 31 registers the value of the counter 30 each time the frequency-divided track cross pulse 16 is generated, that is, the period of the immediately previous frequency-divided track cross pulse 16, and more specifically, the frequency division ratio in the frequency divider circuit 40. The time intervals of a plurality of corresponding track cross pulses are stored. At this time, the output of the counter 30 is 0, which is stored in the register 31 by shifting bits upward by the frequency division weight of the frequency dividing circuit 40.For example, if the frequency division ratio of the frequency dividing circuit 40 is 1/8, Shift 3 bits and transfer the value of counter 30 to register 31
Store in. By doing so, the average pulse interval corresponding to the number of track cross pulses divided by the frequency dividing circuit 40 is stored in the register 31. Therefore, even if noise is introduced into the track error signal due to a disk defect or the like and an error occurs in the time interval of the track cross pulse 13, the influence can be reduced by averaging.

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 interpolation pulse generator 7 time-averages the track cross pulses 13 by the frequency division ratio of the frequency dividing circuit 40, and generates an interpolation pulse signal 14 having the average time interval.
Output. In this way, when the light spot enters the preformat area, the preformat area signal 21 indicating that it is a preformat area is input, and the gate circuit 33 is closed. By doing so, the frequency-divided track cross pulse 16 is no longer input to the counter 30, and the values of the counter 30 and register 31 change easily. Therefore, the counter 32 outputs the time-averaged interpolation pulse immediately before the preformat area, and inputs it to the track movement control circuit 1 via the switch 6.

In this way, in the embodiment of FIG. 1, when the optical spot 8 moves across the preformat area to the target track, even if the track error signal 11 cannot be detected.
Accurate track movement can be achieved. moreover,
Track error signal 11 due to disk 4 defect, etc.
Even if an error occurs in the time interval of the track cross pulse 13 due to noise, the influence can be reduced by averaging.

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, accurate track access can be performed by interpolating the track cross pulse, and short-term The light spot can be moved to the target track in between. Furthermore, in the present invention, even if noise is introduced into the track error signal due to a disk defect or the like and an error occurs in the time interval of the track cross pulse, the influence can be reduced by taking an average.

[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. 2 is a waveform diagram showing a signal. 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, 40
...Frequency dividing 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 plurality of track cross pulses immediately before the spot enters the area A track access device characterized in that the track cross pulse is interpolated by a pulse signal having an average frequency.