JP2601119B2 - Disc playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk reproducing apparatus for reading information from an optical disk using an optical head, and more particularly to a disk reproducing apparatus capable of surely jumping to a target track several hundred tracks away.

[0002]

2. Description of the Related Art CD (Compact Disc) and MD
2. Description of the Related Art In a disk reproducing apparatus that reproduces information from an optical disk such as a (mini disk), in order to stably trace a target track with a laser beam emitted from an optical head,
It has a servo system to correct minute tracking errors. In order to change the irradiation position of the laser beam, a disc reproducing apparatus that uses both a feed system that translates the entire optical head in parallel and a rotation system that rotates only an actuator equipped with an objective lens provided in the optical head at high speed, Generally, large beam movement is performed by a feed system, and minute beam movement is performed by a rotation system. Therefore,
The feed system is used for normal operations such as reproduction, and the rotation system is used for tracking control and track jump.

In the case of a three-beam type optical head, FIG.
(The light receiving system is omitted). That is,
The laser beam generated by the laser diode 31 is divided into three beams (one main beam and two sub-beams) by the diffraction grating 32, and this is incident on the objective lens 34 through the beam splitter 33. The three beams that have passed through the objective lens 34 are irradiated on the lower surface of the disk 1. The position in the surface direction can be finely adjusted by the tracking coil 35, and the focus in the depth direction is the focus coil 3.
6 allows fine adjustment.

FIG. 5 is an explanatory diagram of a rotation system including the objective lens 34. As shown in FIG. The objective lens 34 whose laser beam irradiation surface faces upward is supported on the upper surface of a cylindrical actuator 37. This actuator 3
A system for rotating the objective lens 34 supported by the actuator 37 in a plane parallel to the disk is configured by arranging the tracking coil 35 as a stator inside the rotor 7. 38 is the actuator 3
7 is the rotation axis. The actuator 37 is a return spring 39
When the voltage applied to the tracking coil 35 is removed to eliminate the rotational driving force (indicated by a solid arrow), the objective lens 34 becomes elastic with the spring 39. Automatic return to the midpoint position by force (indicated by the dashed arrow). Although there are various types of the return spring 39, a leaf spring type, a wire type, a rubber damper type, and a hinge type are generally used.

In order to perform a track jump for changing a target track at a high speed in a search mode or the like, when the above-described rotating system is used, for example, the first half of the track jump is moved in an acceleration mode by beam movement (actuator rotation).
There is an acceleration / brake type track jump method in which the beam is moved in the braking mode in the latter half. FIG. 7 is an explanatory diagram of this. In this method, an acceleration pulse having a pulse width corresponding to the first half of the track jump and a deceleration pulse (reverse polarity) having a pulse width corresponding to the second half of the track jump are sequentially applied to the tracking coil 35, and the beam is moved by the acceleration pulse. Accelerate and brake beam movement with deceleration pulses. At the time of this track jump, the tracking is forcibly turned off, so that the TE signal has a signal waveform of a variable frequency corresponding to the track passing speed (the track position is at the time of TE = 0 and increasing).

[0006] The deceleration pulse is generated immediately before the target track.
Turns off at the falling edge of the TE signal . Then, the point at which the TE signal monotonically increases and crosses zero is the target track. If tracking is turned on here, the jump to the target track is completed (the case indicated by the broken line). However, the actuator 37 returns to the target position by the force of the spring 39 for returning the actuator 37 to the middle point.
If it is reversed before (the case shown by the solid line), TE
The signal does not monotonously increase because it contains one waveform (reverse signal) that does not cross zero. For this reason, there arises a problem that tracking-on cannot be performed on the target track. That is, tracking is turned on at the trailing upper rising of the TE signal indicated by a broken line, the reverse rotation signal, such as a solid line because does not turn on.

[0007] In order to improve the problem of such an acceleration / brake type track jump system and to make it possible to surely converge on a target track several tracks ahead, for example, Japanese Patent Publication No.
In the method disclosed in Japanese Patent No. 39154, when it is detected that the beam moving speed has become equal to or less than a predetermined value, the control is shifted from the track jump control to the tracking control. Further, in the method disclosed in Japanese Patent Publication No. 4-39155, when it is detected that the moving direction of the beam is reversed in the direction opposite to the track jump direction, the control is shifted from track jump control to tracking control.

[0008]

[Problems to be solved by the invention]
In the braking track jump method, basically, it is necessary to optimally set the acceleration pulse and the deceleration pulse in accordance with the position of the objective lens and the jumping distance (the number of tracks). However, this control is difficult in practice. For this reason, even when the jump of several hundred tracks is performed by the method of the related art described above,
Reliable and rapid convergence to the target track cannot be expected.
In order to avoid this point, when the jump is repeated every several tracks, it takes time to jump to the target track several hundred tracks ahead. In addition, there is a disadvantage that unnecessary signals are generated because signals are picked up during the jump.
In addition, there is also a problem that it is affected by individual differences of the optical head such as a return spring of the actuator, a moment of inertia, and a frictional force of the rotating part.

SUMMARY OF THE INVENTION An object of the present invention is to provide a disk reproducing apparatus which can solve such a problem and can surely and quickly converge to a target track several hundred tracks ahead.

[0010]

According to the present invention, there is provided a disk reproducing apparatus for irradiating an optical disk with a light beam and receiving the reflected light, and a tracking control means for causing the beam to follow a target track on the disk. In the first half of the track jump that changes the target track,
And fast jump control means for moving the beam at a high speed, in the second half of the track jump, the beam the
A first feature is that a constant speed jump control means for moving at a constant speed lower than the first half of the track jump is provided.

[0011] A disk reproducing apparatus according to the present invention provides an optical head for irradiating a light beam to a disk surface of an optical disk and receiving reflected light thereof, and rotating the optical head in a plane parallel to the disk surface to form the beam. Rotating means for moving the optical head and returning the rotational position of the optical head to a predetermined position
Elastic return means for causing the beam to follow a target track on the disk, tracking control means, and in the first half of a track jump for changing the target track,
And fast jump control means for moving the beam at high speed by the rotary drive means, the second half of the track jump, the tiger the beam by the rotary drive means
Constant speed jump control means for moving at a constant speed lower than the first half of the track jump, and a compensation voltage for canceling the return force by the elastic return means in the second half of the track jump.
By comprising a means for providing prior Symbol rotation driving means is a second feature.

[0012]

According to the present invention, since the jump is performed at a high speed in the first half of the track jump, it is possible to quickly approach the target track. Further, in the latter half of the track jump, the jump is performed at a lower constant speed, so that the return of the beam immediately before the target track (reversal of the actuator) hardly occurs. Therefore, reliable convergence to the target track can be expected. In addition, the return force generated by the return spring of the actuator is canceled by the compensation voltage applied to the tracking coil, so that the convergence to the target track can be further ensured.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a main part configuration diagram showing one embodiment of the present invention. In this figure, 1 is an optical disk such as a CD or MD, 2 is a spindle motor for rotating the disk 1 at a constant linear velocity, 3 is an optical head (optical pickup) for reading information optically from the disk 1, and 4 is an optical head Amplify the output (photocurrent) of 3 and EFM (8-14 modulation)
RF (high-frequency) amplifier having a function of outputting a signal, a TE (tracking error) signal, an FE (focus error) signal, and the like. A digital signal 7 for obtaining disc reproduction position (time) information from the EFM output of the RF amplifier 4 The processing unit 5 obtains the TE signal and the FE signal from the RF amplifier 4 and the disc reproduction position information from the digital signal processing unit 7, and performs tracking control, feed control, focus control,
A servo processor 6 outputs a signal for controlling the spindle motor and the like. A drive amplifier 6 amplifies the TE signal and converts it into a trace position correction signal of the optical head 3, and these constitute a normal tracking servo system. . The servo processor 5 performs tracking control and track jump control using the tracking coil 35 in FIG. 3 and performs focus control using the focus coil 36.

In this embodiment, R
The DC component generated according to the rotation angle of the objective lens 34 is detected from the TE signal output of the F amplifier 4
A position detection circuit 8 for detecting the position information (the rotation angle of the actuator 37 with reference to the midpoint), and a DC component DC required to cancel the return force of the spring 39 based on the output of the position detection circuit 8 And an adder 10 for adding the DC to the tracking control voltage.

[0015] As shown in FIG.
Hz LPF (Low Pass Filter) 81 and ADC
(A / D converter) 82 and DAC (D / A converter) 83
LPF 81 takes in the TE signal,
The DC 82 converts this into a digital signal. The digital signal is temporarily stored in the store register 11 of the microcomputer, and when the microcomputer calculates the position information of the objective lens 34 from the digital signal, the digital signal is stored in the store register 11. The DAC 83 converts the position information read from the store register 11 into an analog signal and inputs the analog signal to the drive circuit 9. This analog signal is a source of a DC component that cancels the return force of the spring 39.

The rotation angle of the actuator 37 and the spring 3
9 is approximately proportional to the restoring force, the DC component (compensation voltage) necessary to cancel this is also
As shown in FIG. 6, it is substantially proportional to the actuator angle. FIG. 6 shows that when the actuator angle is θ1,
In order to cancel the return force of the spring 39 at that time and hold the actuator 37 at the rotational position, the DC voltage V1 obtained from the control characteristics is required as the DC component of the tracking control signal. In practice, the actuator angle at the start of the track jump may not be 0, so the value of the compensation DC is calculated based on the actual jump start actuator angle.

Servo processor 5 for track jump
As shown in FIG. 4, the high-speed jump mode and the constant-speed jump mode are used together, and in the first high-speed jump mode, most (70 to 80%) of the beam from the current position to the target track is moved at a high speed. In the high-speed mode, a brake pulse having a polarity opposite to that of the start pulse is applied to the tracking coil 35 in order. When a start pulse is applied,
The actuator 37 starts rotating in the target track direction,
At the same time, the TE signal starts to change as the beam moves.
Therefore, the moving speed of the beam is determined by detecting the period of the TE signal, and when the moving speed exceeds a predetermined value, the rotation of the actuator 37 is braked by a brake pulse. Then, when the beam moving speed falls below a certain value due to the rotational braking, the mode shifts from the high speed jump mode to the constant speed jump mode.

In the constant speed jump mode, the beam movement speed is maintained at a predetermined target speed while appropriately outputting acceleration and deceleration pulses. This target speed is set to a value lower than the moving speed in the high-speed jump mode. By counting the TE signal, the number of tracks that have already jumped can be determined, so that it is possible to detect that the track has reached the target track. When the target track is reached, neither the acceleration pulse nor the deceleration pulse is applied, and the tracking servo function waits for the target track to converge. The convergence to the target track in the constant speed jump mode is easier to converge than in the conventional braking mode because the beam moving speed is controlled to a constant speed.

In this embodiment, in order to ensure convergence to the target track, in this embodiment, the compensation DC
Is generated and applied to the tracking coil 35 through the adder 10. Since this compensation DC is in accordance with the rotation angle of the actuator 37 at each point in time, it is sufficient to offset the return force of the return spring 39 at that time. Therefore, when this compensation DC is applied, the actuator 37 maintains its rotational position as if there is no return spring 39. Therefore, convergence to the target track at the end of the constant speed jump mode is reliably performed in a state where there is no disturbance such as the reverse rotation of the actuator 37. What
After tracking on, compensation DC is no longer needed
Then, as shown in FIG.

In a disk reproducing apparatus having a feed system,
After rotating the actuator 37 to jump to the target track, the entire optical head 3 is slid so as to return the actuator 37 to the midpoint position.
The above-mentioned compensation DC becomes unnecessary. Therefore, after the jump is completed, the compensation DC is controlled so as to return to 0 immediately or gently in accordance with the feed.

[0021]

As described above, according to the present invention, it is possible to jump to a target track several hundred tracks ahead reliably and quickly. In addition, there is no need to pick up a signal in the middle of a jump, so that no unnecessary output is generated. In addition, since the position of the objective lens is taken into consideration, there is an advantage that the optical head is less affected by individual differences.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram showing an embodiment of the present invention.

FIG. 2 is a detailed configuration diagram of the position detection circuit of FIG.

FIG. 3 is a schematic configuration diagram of a three-beam optical head.

FIG. 4 is an operation explanatory diagram of the present invention.

FIG. 5 is a configuration diagram of a rotation system of the optical head.

FIG. 6 is a characteristic diagram showing a relationship between an actuator angle and a compensation voltage.

FIG. 7 is an explanatory diagram of a conventional acceleration / braking type track jump method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Spindle motor, 3 ... Optical head, 4 ... RF (high frequency) amplifier, 5 ... Servo processor, 6 ... Drive amplifier, 7 ... Digital signal processing part, 8
... Position detection circuit, 9 ... Drive circuit, 10 ... Addition unit, 1
1 ... store register, 31 ... laser diode, 34 ...
Objective lens, 35 tracking coil, 37 actuator, 38 rotation axis, 39 return spring.

Claims (2)

(57) [Claims] An optical head for irradiating an optical disk with a light beam and receiving a reflected light thereof; a tracking control unit for causing the beam to follow a target track on the disk; and a first half of a track jump for changing the target track. in a fast jump control means for moving the beam at a high speed, in the second half of the track jump, the tiger said beam
And a constant speed jump control means for moving at a constant speed lower than the first half of the jump. 2. An optical head for irradiating a disk surface of an optical disk with a light beam and receiving reflected light thereof, and a rotation driving means for rotating the optical head in a plane parallel to the disk surface to move the beam. Elastic return means for returning the rotational position of the optical head to a predetermined position; tracking control means for causing the beam to follow a target track on the disk; and rotating the first half of a track jump for changing the target track. High-speed jump control means for moving the beam at a high speed by driving means; and moving the beam at a constant speed lower than the first half of the track jump by the rotary driving means in the latter half of the track jump. Fast jump control means, and in the latter half of the track jump, cancel the return force by the elastic return means Disk reproducing apparatus characterized by comprising a means for providing a compensation voltage before Symbol rotation driving means.