JPH0877569A - Disk device - Google Patents

Abstract

PURPOSE: To stably pull in a focus servo by accurately monitoring any change of the state of a focus error signal. CONSTITUTION: Information of an optical disk 1 is read out by a pickup 4, and the focus error signal is generated by an FE circuit 5 based on a read-out signal read out by the pickup 4. A level of the focus error signal is monitored by a CPU 9, and switches 11 and 12 are turned on, provided the level of the focus error signal is lowered below a 2nd set value after passing over a 1st set value, so that an objective lens actuator is commanded to be pull in the focus servo.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a disk device,
In particular, the present invention relates to a disc device suitable for performing control for pulling an optical disc, such as a compact disc or a mini disc, on which information such as music and data is recorded into a focus servo.

[0002]

2. Description of the Related Art Conventionally, in a disk device, focus servo control for adjusting the focal lengths of an optical disk and a pickup is performed. In this focus servo control, the objective lens is sequentially shifted from the near side of the optical disc to the far side, or the objective lens is gradually shifted from the far side of the optical disc to the near side to generate an S-shaped focus near the focal point. After monitoring the error signal status and confirming that the focus error signal level has once exceeded a certain threshold voltage, the focus servo is turned on again when the focus error signal level reaches the midpoint potential. It is turned on and pulled into the focus servo.

[0003]

However, the relative distance between the objective lens and the optical disk may not monotonically decrease due to the influence of surface wobbling of the optical disk. When such a decrease occurs near the S-shaped region where the level of the focus error signal changes in a sine wave shape to form an S shape,
The objective lens once entering the S-shaped region may return to deviate from the S-shape and the focus error signal may output a waveform other than the original S-shape. in this case,
Since the S-shaped middle point voltage of the focus error signal is substantially equal to the voltage at the S-shaped end, the conventional disk device cannot distinguish between the middle point and the end point, and the level of the focus error signal is the end point level. However, since the servo is applied assuming that it is the midpoint of the S-shape, the focus servo may be applied at an incorrect position and the servo pull-in may fail.

SUMMARY OF THE INVENTION The present invention solves the conventional problems, and an object of the present invention is to provide a disk device capable of accurately monitoring a change in the state of a focus error signal and performing stable focus servo pull-in. And

[0005]

In order to achieve the above object, the present invention provides a driving means for rotationally driving a disc and an objective lens for converging a light beam from a light source to focus on a track of the disc. An objective lens actuator that displaces the objective lens according to a command to perform focus servo, a reading unit that receives a light beam from the disk and outputs a reading signal, and a reading signal that is read by the reading unit. A focus error signal generating means for generating a focus error signal, and a focus error signal generated by the focus error signal generating means for monitoring the focus error signal after the focus error signal exceeds a first set value higher than a reference value of the focus error signal. The ratio that outputs the comparison signal on condition that it has fallen below the second set value which is lower than the reference value of the error signal. Means and is obtained by constituting the The disk device and a pull command means for commanding to pull the focus servo on the objective lens actuator in response to the comparison signal from the comparison means.

In constructing the above-mentioned disk device, as the pull-in commanding means, one for instructing the objective lens actuator to pull in the focus servo by deceleration in response to the comparison signal from the comparing means can be used.

[0007]

Therefore, according to the present invention, the condition is that the focus error signal exceeds the reference value of the focus error signal, that is, the first set value higher than the midpoint of the S-shaped waveform, and then drops below the second set value. Since the focus servo pull-in is instructed to, the middle point and the end point of the focus error signal having an S-shaped waveform can be reliably distinguished, and the servo is erroneously applied at the end point of the focus error signal. This can be prevented, and the focus servo can always be applied at the midpoint of the S-shaped waveform to stably pull in the focus servo. Further, since the pull-in of the focus servo is performed by decelerating, the pull-in of the focus servo is gradually performed, and the pull-in capability can be improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a disk device of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a disk device of the present invention. In FIG. 1, the disc device includes an optical disc 1, a spindle motor 2, an objective lens 3, a pickup 4, an FE circuit 5, a servo circuit 6, a search voltage generation circuit 7, a step pulse generation circuit 8, and a CPU.
9, the switches 10, 11, 12 and the adder 13 are provided.

Information such as music is recorded on the optical disc 1, and the optical disc 1 is rotationally driven by a spindle motor 2 as a driving means. An objective lens 3 is arranged below the optical disc 1, and a light beam emitted from a light source (not shown) is incident on the objective lens 3, and the light beam incident on the objective lens 3 is The optical disc 1 is converged by the objective lens 3
It's supposed to focus on the track. Further, this objective lens 3 displaces the objective lens 3 in the focal direction,
It is connected to an objective lens actuator (not shown) that executes focus servo. The objective lens 3 is supported by a pickup 4, and the pickup 4 has a built-in light source that generates a light beam and a photoelectric conversion element that receives the light beam from the optical disc 1 and outputs a read signal. That is, the pickup 4 constitutes a reading means. The read signal read by the pickup 4 is output to the FE circuit 5.

The FE circuit 5 is configured as a focus error signal generating means for amplifying the read signal read by the pickup 4 and for shaping the amplified signal into a waveform to generate a focus error signal. The focus error signal generated by the FE circuit 5 is output to the servo circuit 6 and the CPU 9. The servo circuit 6 receives the focus error signal from the FE circuit 5 and executes the position control by the focus servo. That is, a signal relating to position control is output to the objective lens actuator via the switch 12. The objective lens actuator includes an adder 13 and a switch 10.
The signal from the search voltage generating circuit 7 is input via the, and the step pulse from the step pulse generating circuit 8 is input via the adder 13 and the switch 11. The search voltage generating circuit 7 is configured to generate a lamp-shaped voltage to gradually displace the objective lens 3 during focus search. The step pulse generation circuit 8 is adapted to generate a brake pulse for decelerating the speed of the objective lens 3 when the focus servo is turned on.

On the other hand, the CPU 9 monitors the voltage level of the focus signal from the FE circuit 5, and the voltage level of the focus error signal is the reference value V of the focus error signal.
After exceeding the first set value V _COMP1 higher _ref, lower than the reference value V _ref of the focus error signal the second set value V
_The comparison means is configured to output a comparison signal on the condition that the voltage is lower than _COMP2, and the pull-in command means is configured to instruct the objective lens actuator to pull in the focus servo in response to the comparison signal. That is, the CPU 9 monitors the voltage level of the focus error signal, and switches the switches 10, 11, 12 according to the voltage level of the focus error signal during focus search.

Next, the focus servo pull-in operation of the disk device shown in FIG. 1 will be described with reference to FIG.

First, when the switch 10 is closed by a command from the CPU 9 and the objective lens actuator is driven according to the lamp voltage from the search voltage generation circuit 7, the FE circuit 5 is read from the read signal read by the pickup 4.
Produces a focus error signal. in this case,
When the objective lens actuator is gradually driven so that the distance between the objective lens 3 and the optical disc 1 crosses the in-focus position, the focus error signal crosses the letter S like the dotted line of the waveform A as shown in (a). The voltage of the waveform collapsed. However, when the relative distance between the objective lens 3 and the optical disc 1 cannot be monotonously changed due to the influence of the surface wobbling of the optical disc 1, once the S-shaped waveform is generated, the direction is changed to change the S-shaped region. It may come off and a voltage like the waveform B may be generated.

Here, when the focus servo is turned on at the timing when the level of the focus error signal once exceeds the first set value and crosses again, when the waveform of the focus error signal is A, the focus servo is turned on at the point A '. Be drawn in.

However, the waveform of the focus error signal is B
When the waveform becomes, the point B'is also regarded as the middle point of the S-shape, and the focus servo is turned on, so that the servo pull-in fails. Therefore, in this embodiment, as shown in FIGS. 2B and 2C, the focus servo signal is not pulled in only when the level of the focus error signal exceeds the first set value, and the level of the focus error signal is increased. Is to cross the first set value once and cross again, and then the focus servo pull-in is executed at the timing when the value falls below the second set value. further,
When the switch 12 is turned on to turn on the focus servo, as shown in (e), the switch 11 is turned on for a predetermined time (T ₁ ) to reduce the moving speed of the objective lens 3 to improve the pull-in characteristic. I have decided.

[0017]

As is apparent from the above-described embodiment, the present invention focuses on the condition that the focus error signal exceeds the first set value and then drops below the second set value when pulling in the focus servo. Since the servo pull-in is performed, the focus error signal can be accurately monitored for a change in state, and stable focus servo pull-in can be performed. Further, since the focus servo is gradually pulled in, the pull-in characteristic can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a disk device of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the disk device shown in FIG.

[Explanation of symbols]

 1 Optical Disc 2 Spindle Motor 3 Objective Lens 4 Pickup 5 FE Circuit 6 Servo Circuit 7 Search Voltage Generation Circuit 8 Step Pulse Generation Circuit 9 CPU 10, 11, 12 Switch 13 Adder

Claims (2)

[Claims] 1. A drive means for rotationally driving a disk, an objective lens for converging a light beam from a light source to focus on a track of the disk, and displacing the objective lens according to a command to execute a focus servo. Objective lens actuator, reading means for receiving a light beam from a disc and outputting a read signal, focus error signal generating means for generating a focus error signal based on the read signal read by the reading means, and focus error The focus error signal generated by the signal generating means is monitored to detect that the focus error signal exceeds a first set value higher than the reference value of the focus error signal and then drops below a second set value lower than the reference value of the focus error signal. Comparing means for outputting a comparing signal to the condition, and the objective lens in response to the comparing signal from the comparing means A disk device comprising a pull-in command means for instructing the actuator to pull in a focus servo. 2. A drive means for rotationally driving a disk, an objective lens for converging a light beam from a light source to focus on a track of the disk, and displacing the objective lens according to a command to execute a focus servo. Objective lens actuator, reading means for receiving a light beam from a disc and outputting a read signal, focus error signal generating means for generating a focus error signal based on the read signal read by the reading means, and focus error The focus error signal generated by the signal generating means is monitored to detect that the focus error signal exceeds a first set value higher than the reference value of the focus error signal and then drops below a second set value lower than the reference value of the focus error signal. Comparing means for outputting a comparing signal to the condition, and the objective lens in response to the comparing signal from the comparing means A disk device provided with a pull-in command means for instructing the actuator to pull in the focus servo by deceleration.