JPH04114322A - Optical disk device - Google Patents

Abstract

PURPOSE:To exactly detect track moving velocity even at any position on a disk by storing the track cross angle of a beam spot in advance even when this angle is different, and correcting it. CONSTITUTION:For a tracking error signal obtained from the photodetector of an optical head 1, a track cross signal detection part 2 detects a pulse corresponding to track crossing. This signal is inputted to a current track counter 3. On the other hand, the pulse signal from the detection part 2 is transmitted to a velocity detection part 8, and current moving velocity is detected. In this case, while receiving the value of the current track counter 3, a correction reference part 11 calculates the track crossing angle or track of the beam spot, and a detected velocity correction part 12 corrects the detected velocity. The corrected detection velocity is transmitted to a comparison part 9 together with the output signal of a command velocity detection part 7 and transmitted to a swing arm actuator driving circuit 13 as a drive signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disc device, and more particularly to an optical disc device that searches a designated track from among a large number of tracks at high speed during recording or reproduction.

Conventional technology Optical disks have a higher recording density than magnetic disks and are capable of large-capacity recording. However, the track pitch is ~2μ
m, which is very small, so during recording and reproduction, it is necessary to make the optical spot follow the target track of the rotating disk with high precision (hereinafter, this operation will be referred to as track following). Furthermore, in order to record or reproduce data on a predetermined track on a disk, an operation is required to move the optical spot to the target track (hereinafter, this operation will be referred to as access).

To achieve these, generally semiconductor laser light sources,
A light detection sensor, various optical components such as prisms, and an objective lens actuator for irradiating a minute light spot onto the target track of the disk are constructed on a carriage, and these are further moved in the radial direction of the disk by a linear motor. A method is used to That is,
This is achieved by using an objective lens actuator to minutely control the position of the objective lens in the radial direction relative to the disk surface during track following or short-distance access, and by moving the entire carriage significantly using a linear motor during access. .

When using an optical disk as an external storage device for a computer, it is necessary to access the optical disk at high speed in order to improve the throughput of the entire system. In order to increase access speed, the carriage must be moved at higher speeds, but with the method described above, it is necessary to mount a large number of optical components within the carriage, and there is a limit to weight reduction.

Therefore, various methods have been developed to reduce weight. One of these is to install only the objective lens and reflection mirror on the swing arm, which is a movable part, and fix the other optical systems separately from these. There is also a method to reduce the weight of the movable parts by installing it in the main body.

A conventional optical disc device will be explained below.

FIG. 5 is a block diagram of the main parts of a conventional optical head system of an optical disk device. The swing arm section 50, which is a movable section, includes a rotating member 53, an objective lens 51, and reflective mirrors 52a and 52b.
It consists of The permanent magnet 60 is connected to the focus coil 54a, the I-racking coil 54b1 and the yoke 5.
The hollow shaft 55 constitutes a magnetic circuit together with 5a, 55b, etc.
It is configured to be able to move up and down or rotate around axis c.

That is, the swing arm portion 50 is in the focus direction 56a.
The arm is moved up and down to adjust the focus of the light spot on the disk l, and the arm is rotated in the radial direction 56b to control the movement of the light spot. The fixed optical system 57 is configured separately from these, and the light from the semiconductor laser 59 is shaped by a prism or the like in the fixed optical system 57, and then guided to the hollow shaft 55C, and is guided to the objective lens 51 of the swing arm section 50. A spot is formed on the disk l. The reflected light from the disk 1 returns to the fixed optical system 57 via the swing arm section 50 again, and after the light path and polarization are separated, signals are detected by photodetectors 58a and 58b. That is, most of the optical system is provided in a fixed part, and by using a swing arm 50, which is a rotating member, directly below the disk l, the movable part is made smaller and lighter, and high-speed access is achieved.

Next, the access control method will be explained. When the light spot moves in the radial direction and crosses the track due to the rotation of the swing arm 50, a track crossing signal as shown in FIG. 6 can be obtained via the output of the photodetector in the optical head. Point a in the figure corresponds to the case where the light spot is on the land of the track, and point b corresponds to the case when the groove is irradiated. In other words, this corresponds to one period of the sine wave shown in the same figure, or crossing one track.By counting the number of waves, it is possible to know the number of times the light spot crosses the track, and it is possible to detect the movement of the light spot during access. It can be used for.

Therefore, as an access control method, a target speed is set according to the distance to the target track, that is, the number of tracks to the target track, this set value is given as a speed command value for moving the optical head, and a track crossing signal is sent to the optical head during movement. A method is used in which the actual speed is detected at , the moving speed of the optical head is controlled by successive approximation servo control, and high-speed access is performed by optimal speed control.

In addition, in order to perform more accurate speed control, the period of the track crossing signal is counted as shown in the block diagram of FIG.
A method of controlling speed based on this output value has also been proposed.

In this way, the count value of the period (frequency) of the groove break signal when the optical spot crosses the track becomes an important information value for speed control and position control when the optical head moves.

However, in the conventional configuration described above, as shown in the trajectory of the light spot (dotted line) in FIG. 8, the trajectory of the light spot on the disk is centered on the hollow part, and When the light spot crosses the track, the light spot crosses the track almost perpendicularly to the tangential direction of the track at the center (b) in the radial direction of the disk recording area, but at the outer periphery, as shown in FIG. The tracks in (a) and the inner circumference (C) draw sloping trajectories. Therefore, for example, even if the light spot crosses the track at the same speed, the period (frequency) of the track cross signal will differ depending on the position of the disk, making it impossible to accurately detect the moving speed. In particular, if the length of the arm section is shortened in order to speed up access, the variation in the crossing angle of each track within the disk surface tends to increase, and the error in the crossing signal period becomes even larger.

Means for Solving the Problems The present invention provides a method for moving an objective lens across at least some of a plurality of tracks on an optical disk in a direction obliquely shifted from perpendicular to the tangential direction of the tracks. track crossing detection means for detecting that the light spot crosses the track by this movement and generating a signal; counting means for detecting the signal period or frequency of the detection means; a movement control means for controlling at least one of the moving speed or the position of the means; a storage means for storing in advance the cross-track angle of the light spot or the track-to-track movement trajectory; and a count value of the counting means based on the storage means. A count correction means is provided for correcting.

Effect With the above configuration, even if the track crossing angle of the optical spot is different, by storing this in advance and applying correction, it is possible to correct the pulse period obtained from the track crossing signal. Therefore, it is possible to treat all tracks as if they were passing at the same angle, for example, in a direction perpendicular to the tangential direction of the track, making it possible to accurately detect the track moving speed at any position on the disk. .

Embodiment FIG. 1 is a control block diagram of an optical disc device in an embodiment of the present invention. 1 is an optical head, 2 is a track crossing signal detection section, 3 is a current track counter, 4 is a target track counter, 5 is a subtraction circuit, 6 is a speed table, 7 is a command speed output section, 8 is a speed detection section, and 9 is a Comparison unit, 10 is a control unit, it is a correction reference unit, 12 is a detected speed correction unit, 1
3 is a swing arm actuator drive circuit.

The control operation of the optical disc device of this embodiment configured as described above will be explained below.

From the tracking error signal obtained from the photodetector of the optical head l, a pulse corresponding to the track crossing is detected by the track crossing signal detection section 2. This signal is currently input to the track counter 3.

The current track counter 3 and the target track counter 4 are set with the current track and target (destination) track at the start of access by the control unit IO, and the current track counter 3 increments or subtracts one count at a time according to the input of the track crossing signal. It will be done. These two counter values are input to the subtraction circuit 5, and the number of remaining tracks up to the target track is set here. Speed control is performed by the distance to the target position, that is, by the number of remaining tracks. An optimal speed profile corresponding to the number of remaining tracks is set in advance in the speed table 6, and the command speed at that point is output to the command speed output section 7.

On the other hand, the pulse signal from the track crossing signal detection section 2 is F
/V converter etc. is sent to the speed detection section 8,
It is configured to detect the current moving speed.

At this point, the correction reference section 11 calculates the current track counter 3.
In response to the value, the track crossing angle or trajectory of the light spot is calculated, and the detected speed correction section 12 corrects the detected speed. That is, since the track crossing angle (trajectory) of the optical spot differs from track to track, the track crossing pulse obtained by the speed detection section does not accurately represent the approaching speed to the target track. Figure 2 (a), (b)l:
: Shows the movement of the optical spot at the outer periphery and the center of the disk and the track crossing signal. Even if the absolute moving speed of the optical spot is the same, the optical spot crosses the track diagonally at the outer periphery (a). ) and the center part that vertically crosses the track, the frequency of the obtained track crossing signal differs as shown in the figure, and this is because speed control based on the number of remaining tracks is performed incorrectly.

The detected speed corrected by the detected speed correction section 12 is sent to the comparison section 9 together with the output signal of the commanded speed detection section 7, and is sent to the swing arm actuator drive circuit 13 as a drive signal. That is, feedback control of the speed is performed so that the commanded speed and the current speed are equal, and optimal speed control of the swing arm actuator is performed.

As a configuration example of the correction reference section 11, as shown in FIG. 3, a memory may be used, and when the current track counter value is input and the tilt angle is θ, CO8θ may be set as the correction value output. In addition, the arc-shaped locus can be calculated mathematically, or the fourth
As shown in the figure, it may be divided into several blocks in advance and corrected using values obtained by calculation.

Effects of the Invention According to the present invention, since the speed of the optical head during access can be accurately detected, highly accurate speed control is possible, and a faster and more reliable access function can be realized.

[Brief explanation of the drawing]

FIG. 1 is a control block diagram of an optical disc device according to an embodiment of the present invention, and FIG. 2 is a diagram showing a light spot locus and a track crossing signal depending on the difference in track position. Fig. 3 is a configuration diagram of the correction section, Fig. 4 is a diagram showing a correction value detection method,
Fig. 5 is a diagram showing the main parts of the optical head system of a conventional optical disk device, Fig. 6 is a principle diagram of track crossing signal detection, and Fig. 7
The figure shows an example of a speed control method using a track cross signal, and Figure 8 shows the trajectory of a light spot (
(Dotted line) and FIG. 9 are explanatory diagrams of problems in movement detection in the conventional example. 54a... Focus coil 54b... Tracking coil 55a b... Yoke 55c... Hollow shaft 57...
Fixed optical system 58a, b... Photodetector 59... Semiconductor laser 60... Name of Mizuku Magnet agent Patent attorney
Akira Okaji and 2 others 1... Optical head 2... Track crossing signal detection unit 3... Current track detection counter 4... Target track counter 5... Subtraction circuit 6... Speed table 7.・
・Command speed output section 8...Speed detection section 9...Comparison section 10...Control section 11...Correction reference section
12... Detection speed correction section 13... Swing arm actuator drive circuit 50... Swing arm section 51... Objective lens 52a, b... Reflection mirror 53... Rotating member Fig. Fig. 6-F-17] - Fig. 9 (b)

Claims (1)

[Claims] In an optical disc device for reproducing or recording an optical disc having a groove-shaped guide track for recording signals or a track consisting of a recorded signal train, converting means for detecting a signal using transmitted light; and moving the converting means so that the converting means traverses at least some of the plurality of tracks on the optical disk in a direction obliquely shifted from perpendicular to the tangential direction of the tracks. means of transportation,
Track crossing detection means for detecting that the conversion means crosses the track by the movement of the conversion means and generating a signal; counting means for detecting the signal period or frequency of the detection means; based on the output value of the counting means. a movement control means for controlling at least one of the moving speed or the position of the moving means; a locus reference means for storing or calculating in advance a track-crossing angle or an inter-track movement locus of the converting means; An optical disc device comprising: count correction means for correcting the count value of the counting means.