JPS6344327A - Tracking device for optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To correctly write recording information in a target recording position by holding a track error signal, calculating and processing a holding signal, detecting an off-setting quantity and removing this from the track error signal. CONSTITUTION:A reflecting light beam from an optical information recording medium 2 is detected by a light detecting device 5 of an optical head 3 and the track error signal is sent through a differential amplifier 7 to a first and a second sample/hold S/H circuits 12 and 13. From the sum output of the detecting device 5 obtained from an adding amplifier 18, holding pulses S1 and S2 to set the holding timing before and after the border of an adjoining format with a border estimating means 17 are generated and the track error signal is stored into the circuits 12 and 13. From the output of the circuits 12 and 13, an off-setting quantity is calculated by an arithmetic circuit 14 and this is accumulated in a memory 15. By the control from a controller 19, switches 8 and 16 are turned on, the off-setting quantity of the memory 15 is removed from the track error signal with a differential amplifier 9 and the information is correctly recorded through a servo amplifier 10 to a target position.

Description

Detailed Description of the Invention (Industrial Field of Application) This invention relates to an optical information recording/reproducing device that records, reproduces, or erases information using a light beam. The present invention relates to a tracking device for controlling.

[Prior Art] Optical information recording and reproducing devices such as optical information files, CD players, and magneto-optical disk devices that record, reproduce, or erase information by optical means are known. Since the width of the track on the recording medium is narrow and the distance between adjacent tracks is also narrow, 1-racking control that allows the light beam to accurately follow the track is particularly important. Closed-loop servo control, which is performed based on a tracking error signal generated from an incident pattern on a detector of a light beam reflected or transmitted by a recording medium, is a generally practiced tracking II/III method. In this method, it is important to obtain an accurate tracking error signal.

However, although there is no problem during playback, when recording is attempted, an offset signal as an error is superimposed on the tracking error signal, and the track may be tracked at a position deviated from the target track. FIG. 4 shows an example of a recording disk. In this figure, a concentric or spiral recording track is divided into sectors and a plurality of areas Fa 80 along the circumferential direction. Each sector is divided into an indicator area section 81, a preformat section 82, and a pregroove section 83. In this indicator area section 81, a signal of a constant frequency representing the boundary between each sector has already been recorded. In addition, the preformat section 82
Address information such as sector numbers and track numbers is recorded in the . On the other hand, the pregroove section 83 corresponds to an area where the user of the device records new information, and no information has been recorded yet. However, a long groove of a constant depth is provided so that the [-ranking error signal is 11] during recording.

Suppose now that information is to be recorded on this format disc. A light beam is irradiated onto the disk while controlling tracking and focusing. The light beam passes through the indicator area section 81, the preformat section 82,
When the pre-groove portion 83 is irradiated, the light beam power changes from the previous READ power (low output power) to W.
Switch to RITE power (high output power) and record (1
be exposed. At this time, the light beam is modulated according to the recorded information. Here, at the same time as the recording operation starts, an offset signal is superimposed on the tracking error signal.
Tracking misalignment phenomenon occurs.

[Problems to be Solved by the Invention] When recording information in the pregroove portion, accurate tracking control is not performed, so that the recorded information is written at a point deviated from the intended recording position. Therefore, during playback, from the preformat section to the data section (
The pre-groove section after information recording is called this. ), tracking control may be disrupted and information may not be reproduced properly.

An object of the present invention is to enable recording information to be written accurately at a target recording position by removing an offset during recording.

[Means for Solving the Problems] In this device, the track error signal is held by the holding means, and the holding timing is set before and after the boundary of the format of the recording medium. The obtained hold signal is processed to detect the offset amount, and the detected offset amount is removed from the track error signal.

[Embodiment] FIGS. 1 to 3 show an embodiment of the present invention. A disk-shaped optical information recording medium (hereinafter referred to as a disk) 2 is removably fixed to the rotating shaft of the spindle motor 1. As the disk 2, for example, one having the format shown in FIG. 4 is used. An optical head 3 is provided facing the medium surface of the disk 2. The details of the optical system of the optical head 3 are omitted, and only the objective lens 4 that condenses the light beam and the photodetector 5 that detects the light beam reflected from the disk 2 are shown. Since the present invention is not limited by the configuration of the optical system of the optical head 3, any known configuration can be used for the optical system. A carriage moving means 6 is provided to move the optical head 3 in the radial direction of the disk 2 to enable searching for any desired track. As the moving means 6, well-known means such as a voice coil motor and an α belt are known.

The photodetector 5 has the function of reading a recording signal and detecting a track error signal. This example is
Since the track error signal is detected by the DuSh-Dull method, the output of the divided photodetector 5 is divided into two, and the differential amplifier 7 calculates the difference between the outputs. The output of the differential amplifier 7 is applied to a tracking coil of a tracking actuator 11 via a servo-operated SWB differential amplifier 9 and a servo amplifier 10. The tracking actuator 11 is
It is connected to an objective lens 4, and by moving the objective lens 4, the irradiation position of the light beam on the disk 2 is adjusted in the disk radial direction.

The output of the differential amplifier 7 is sent to the first sample and hold circuit 12.
, is also sent to the second sample and hold circuit 13, and the sample value is held at the timing at which the hold pulse St,82 is generated. Here, the held value is processed by the offset amount calculation circuit 14 to calculate the offset amount. The calculated offset amount is stored in the memory 15 and added to the inverted output of the differential amplifier 9 via the switch 16 which is turned on by the offset removal operation execution pulse 83 from the controller 19. hold pulse 8
1.82 is generated by the boundary prediction means 17. This boundary prediction means 17 detects the boundary between the preformat section 82 and the pregroove section 83 of the track from the sum output of the two-split photodetector 5 obtained from the addition amplifier 18. In addition,
Servo operation SW8 that opens and closes the tracking servo loop
is switched by the output of the controller 19. Next, the principle of the tracking offset amount removal method according to the present invention will be explained.

FIG. 2(a) shows a tracking error signal (output of the differential amplifier 7) obtained when the tracking servo loop is used as an oven.

The location where a large step difference occurs in the error signal is where the light beam transitions from the preformat section 82 to the pregroove section 83. This step is the preformat part 8
2 and the pregroove portion 83 with respect to the same human-emitted light signal. That is, even without changing the power of the light source, the amount of reflected light in the pregroove portion is, for example, half that in the preformat portion due to the difference in format structure.

Therefore, if there is no offset, the tracking error signal in the pregroove section should be exactly 1/2 that in the preformat section (this case is represented by the broken line 2).
(denoted by Q).

Therefore, the levels of the tracking error signal before and after the boundary between the preformat part and the pregroove part are Yl and Y2.
Then, Y, -2Y2...■ is satisfied.

On the other hand, if a track error signal is detected with the servo loop open for a track recorded with offsets superimposed, it will correspond to the offset amount ε, as shown by the solid line 21 in Fig. 2<a). A shifted signal is obtained.

In this case, if the level of the tracking error signal immediately after the boundary between the preformat section and the pregroove section is Y3, then Y3-Y2+ε .

From formulas (■) and (2), ε-Y+/2Y3...■ is obtained.

Therefore, before and after the pre-format section and the pre-groove section, the tracking error signal is controlled by the hold pulses Sl and S2.
By holding Yl and Y3, the offset amount ε can be calculated from the equation (2).

After that, the offset amount ε may be subtracted from the tracking error signal at the time of recording.

FIG. 3 shows an example of the boundary prediction means 17. Addition amplifier 1
By passing the output of 8 through a band pass filter (BPF) 171, an indicator area portion 81 (FIG. 4) is detected. Since the indicator area section 81 is set to have a significantly different frequency band from the other preformat section 82 and data section 83, it can be separated by the BPFI 71. The BPF 171 output is pulsed by a comparator 172 and then applied to mono multivibrators 173, 174, and 175 connected in series. The Q outputs of the mono multivibrators 174 and 175, which are delayed pulses of the detection pulse of the indicator area section 81, become sampling pulses S' and S2, respectively.

Next, the operation of the embodiment will be explained. First, while applying tracking servo to disk 2 without removing the offset (SW8 is ON).

5W16 is OFF) Information is written. The information written here is shifted from the target writing position by the amount of offset.

Next, this written information is reproduced by turning off the track servo, and the track error signal at that time is detected by the hold pulses S1 and S2 obtained from the boundary prediction means 17, and the first sample and hold circuit 12, It is stored in the second sampling and hold circuit 13. This sampling information is calculated by the offset amount calculation circuit 14 as v
4. The information that has been processed is stored in the memory 15. During this offset amount detection operation, SW8 is OFF and SWl is OFF.
Controller 1 is controlled so that 6 is also turned off. During normal recording operation, SW8.5W16 are both turned on.
state. By applying the contents of the memory 15, that is, the detected offset amount, to the inverting terminal of the differential amplifier 9, the offset amount is removed from the track error signal.
Accurate tracking control can be performed.

[Effects of the Invention] According to the present invention, since the offset in the tracking error signal is removed when recording information, it is possible to accurately write at the writing position corresponding to the color type.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
Figure 3 is a principle diagram of offset amount detection according to the present invention.
The figure is a specific circuit diagram of the boundary prediction means 17, and FIG. 4 is a diagram showing the structure of a conventional recording medium and an embodiment of the present invention. 5... Photodetector 7... Differential amplifier 9... Differential amplifier 10... Servo amplifier 11... Tracking actuator 12... First sample hold circuit 13... Second sample hold Circuit 14...
・Offset amount calculation circuit 15...Memory 17...
・Boundary prediction means Figure 1 Figure 2 Figure 3 Factors Figure 4

Claims (1)

[Claims] An optical information recording/reproducing device in which there is a difference in the amount of reflected light or transmitted light between adjacent formats of an information recording medium, comprising: an optical means for making a light beam incident on the recording medium; and a track of the recording medium. track error signal generation means for detecting a track error signal representing a deviation in the incident position of the light beam; a hold means for holding the track error signal; Hold timing setting means for setting forward and backward times, means for calculating an offset amount in the track error signal from the hold output of the hold means, and means for removing the calculated offset amount from the track error signal are provided. Features. A tracking device for an optical information recording/reproducing device.