JPH0433545Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to an optical recording disk reproducing device.

BACKGROUND ART In an optical recording disk reproducing device, the interval between the information tracks on the recording disk (hereinafter simply referred to as disk) is very narrow, several microns, so when disturbances such as vibrations are applied from the outside, the capture range of the servo may be affected. This caused the servo to become disconnected. Therefore, it has been necessary to detect the addition of a disturbance by some method, widen the servo band when the disturbance is added, and increase the disturbance rejection ability.

Conventionally, the following switching circuits have been used to automatically switch the servo band of a servo system for pickup control. FIG. 1 shows only those parts of the optical recording disk reproducing apparatus that are necessary for explaining the prior art. In this figure, reference numeral 1 denotes a pickup that irradiates light toward the disk 2 and forms an information reading point 3 on the recording surface to read the recorded information on the disk 2 and photoelectrically converts the read signal. Place reading point 3 in the direction perpendicular to the recording surface of disk 2 (focus direction) and disk 2.
It has a built-in actuator (not shown) for moving in the radial direction (tracking direction).

The output signal of the pick-up 1 is amplified by a preamplifier 4 and then supplied to a focus error generation circuit 5 that generates an error signal in the focus direction and a tracking error generation circuit 6 that generates an error signal in the tracking direction. A focus servo circuit 7 in which a focus error signal output from the focus error generation circuit 5 controls the position of an objective lens (not shown) in the pickup 1 in the focus direction with respect to the information recording surface of the disk 2.
is supplied to A tracking error signal output from the tracking error generation circuit 6 is supplied to a tracking servo circuit 8 that controls the information reading point 3 in the tracking direction. The tracking servo circuit 8 is configured so that the servo band can be switched between a predetermined first band and a second band wider than the first band in response to an external control signal.
This tracking servo circuit 8 is supplied with a control signal generated by a level detection circuit 9. The level detection circuit 9 inputs the focus error signal output from the focus error generation circuit 5,
It is detected that the absolute value level of this error signal exceeds a predetermined reference level, and the control signal is output.

FIG. 2 shows a specific circuit configuration of the level detection circuit 9. In this figure, 10a and 10b are constant voltage diodes that generate a predetermined reference voltage for level detection, and 11a and 11b are comparators that compare the tracking error signal with the reference voltage obtained by the constant voltage diodes 10a and 10b. , 12
A and 12b are transistors for wired ORing the outputs of the comparators 11a and 11b.

Next, the operation will be explained.

Recorded information on the disk 2 is read by a pickup 1, photoelectrically converted, and then amplified by a preamplifier 4. The amplified signal is input to a focus error generation circuit 5 and a tracking error generation circuit 6, and these generation circuits 5 and 6 generate a focus error signal and a tracking error signal. These error signals are respectively supplied to a focus servo circuit 7 and a tracking servo circuit 8, which drive actuators built into the pickup 1 to control the position of the information reading point 3 relative to the disk 2 in the focusing direction and the tracking direction. .

At this time, if no disturbance such as vibration is applied to the tracking servo, the amplitude of the tracking error signal is
It is smaller than the reference voltage obtained at 0b, and the outputs of the comparators 11a and 11b become -V. As a result, the transistors 12a and 12b become non-conductive, and the output of the level detection circuit 9 becomes +V.
This output is used as a control signal for servo band switching.
The signal is supplied to the tracking servo circuit 8, and sets the servo band of the circuit 8 to the first band.

On the other hand, if a disturbance is applied, a disturbance signal compressed by the servo gain of the tracking servo circuit 8 will appear in the tracking error signal, and if this becomes large, it will deviate from the servo's capture range and cause the servo to become disconnected. . Therefore, the reference voltage provided by the constant voltage diodes 10a and 10b is set within the capture range. When the tracking error signal exceeds this reference voltage, the outputs of the comparators 11a and 11b become +V, the transistors 12a and 12b become conductive, and the output of the level detection circuit 9 becomes O[V]. By this output, the servo band of the tracking servo circuit 8 is set to a second band wider than the first band. This increases the degree of compression of the disturbance signal, making it difficult for servo failure to occur.

FIG. 3 shows the tracking error signals of A when no disturbance is applied and B when a disturbance is applied. In Fig. 3, a is the residual error component due to the eccentricity of the disk and the waviness of the information track, and b is the residual error component caused by the constant voltage diode 1.
Reference voltages obtained at 0a and 10b, and c are the servo capture ranges.

In conventional devices configured in this way, the judgment as to whether or not a disturbance has been applied is made simply based on the signal level of the tracking error signal, so the disturbance component in the tracking error signal may exceed a predetermined reference voltage. When this occurs, the servo band is widened to increase the degree of compression of the disturbance component. However, if the voltage returns to within the predetermined reference voltage again, the servo band is immediately returned to its initial state (first band). Since the time it takes to converge to the target track is determined by the response of the initial servo band, there is a drawback that the response when converging to the target track is poor.

Summary of the invention The present invention was developed to eliminate the drawbacks of the conventional ones as described above. The purpose of the present invention is to provide a recording disk playback device.

The optical recording disk playback device according to the present invention is
The peak value of the signal level of the tracking error signal or focus error signal is held, and when the hold output level exceeds a predetermined reference level, the servo band of the tracking servo system is changed from the first band to the first band. It is also characterized by switching to a wider second band.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 4 is a circuit diagram showing an embodiment of the present invention, in which parts equivalent to those in FIG. 2 are designated by the same reference numerals. In this embodiment, peak hold circuits 20A and 20B are provided to hold the peak values of the signal levels on the positive and negative potential sides of the tracking error signal, and the outputs of the peak hold circuits 20A and 20B are is the comparison input of the comparators 11a and 11b.
The peak hold circuit 20A includes a detection diode 21a for detecting a tracking error signal.
, a hold capacitor 22a for holding the tracking error signal detected by this diode 21a, and this capacitor 22
It is composed of a discharge resistor 23a that determines the time for discharging the stored charge a and widening the servo band. Similarly, the peak hold circuit 20B includes a detection diode 21b, a hold capacitor 22b, and a discharge resistor 23b.

FIG. 5 shows the waveforms of each part in FIG. 4, and the waveforms a to f correspond to the waveforms of parts a to f with the same reference numerals in FIG. 4. In FIG. 5a, A is a tracking error signal when the conventional circuit is used, B is a tracking error signal when the circuit according to the present invention is used, and E1 and E2 are given by constant voltage diodes 10a and 10b. This is the reference voltage used.

Next, the circuit operation of the present invention will be explained with reference to the waveform diagram of FIG.

First, the tracking error signal a is divided into a positive potential side and a negative potential side by the detection diodes 21a and 21b, and the hold capacitor 22
It is held at a and 22b. At this time, if no disturbance is applied, the hold capacitor 22
The terminal voltages b, d of the terminals a, 22b do not exceed the reference voltages E1, E2 generated by the constant voltage diodes 10a, 10b, and the outputs c, e of the comparators 11a, 11b both become -V. This output c, e
makes the transistors 12a and 12b non-conductive, so that the output f becomes +V. This output f
is supplied to the band switching control input terminal of the tracking servo circuit 8 (see FIG. 1), and sets the servo band to a predetermined first band.

Next, when a disturbance is applied, a disturbance component appears in the tracking error signal, and the hold capacitors 22a and 22b hold its peak value. Here, for example, when the terminal voltage b of the hold capacitor 22a exceeds the reference voltage E1, the output C of the comparator 11a is inverted and becomes +V. The output c of this comparator 11a is the transistor 12
a is made conductive, which causes the output f to be 0 [V]
becomes. This output f causes the servo band of the tracking servo circuit 8 to be switched from the first band to a second band wider than the first band. At this time, the terminal voltage d of the hold capacitor 22b on the negative potential side
does not exceed the reference voltage E2, the output e of the comparator 11b is -V, and the transistor 1
2b is in a non-conductive state, but the output f is maintained at 0 [V] by the transistor 12a.

When the servo band of the tracking servo circuit 8 is widened, the tracking error signal a is compressed more than the error signal in the first band and at the same time starts to converge to the target track. After this, in the conventional circuit, the tracking error signal a changes to the reference voltage E.
As soon as the tracking error signal a falls below the reference voltage E1, the servo band returns to the first band, but in the circuit according to the present invention, the servo band remains wide even after the tracking error signal a falls below the reference voltage E1. As a result, the response upon convergence to the target track can be improved compared to the conventional circuit.

After the servo band is switched from the first band to the second band, the servo band is widened until the terminal voltage b of the hold capacitor 22a falls below the reference voltage E1, and at the same time the servo band changes to the second band. to the first band.

Note that in the above embodiment, a tracking error signal is used to detect the presence or absence of disturbance, but the same effects as in the above embodiment can be achieved even if a focus error signal is used.

Further, in the above embodiment, it is used to switch the servo band, but it can also be used to control opening and closing of the servo loop. In this case, during search operation or jump operation, the loop is automatically opened even if the operation is started without an external signal to open the servo loop, and when the loop is closed, the hold capacitor's hold time is By making the average time for the information reading point to pass between adjacent tracks due to the eccentricity of This makes it possible to omit control signals for opening and closing the loop.

Effects of the invention As explained above, according to the invention, the tracking error signal (or focus error signal)
The peak value of the signal level is held, and the servo band switching timing is judged based on the hold output, improving the response of the servo system after disturbance is applied and converging to the target track. Thus, an optical recording disk reproducing device can be obtained which can shorten the time required for reproducing an optical recording disk.

In addition, in this invention, due to the peak hold effect, the servo band is expanded for a while after that, not only when a disturbance is applied, but also when the tracking error signal exceeds the reference voltage due to jump or search operation. Since the servo system can be placed at a later time, the response of the servo system after the jump operation or search operation can be improved, and the effects of improving the stability of the jump operation and shortening the time of the search operation can also be obtained.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an example of an optical recording disk reproducing device configured to allow switching of servo bands, Fig. 2 is a circuit diagram showing a conventional example, and Fig. 3 is a change in tracking error signal in the conventional example. FIG. 4 is a circuit diagram showing an embodiment of the present invention, and FIG. 4 is a waveform diagram of each part for explaining the circuit operation of FIG. 4. FIG. Explanation of the symbols of the main parts, 1... Pick up,
2... Recording disk, 7... Focus servo circuit, 8... Tracking servo circuit, 9... Level detection circuit, 10a, 10b... Constant voltage diode, 11a, 11b... Comparator, 20A,
20B...Peak hold circuit.

Claims (1)

[Scope of utility model registration request] A tracking servo system is provided for controlling the position of an information reading point of a pickup for reading recorded information on a recording disk in the disk radial direction with respect to the recording disk, and the servo band of the tracking servo system is a predetermined first band and a predetermined first band. An optical recording disk reproducing device configured to be able to switch between a first band and a second band wider than the first band, which inputs a tracking error signal or a focus error signal and holds the peak value of the error signal level. a peak hold circuit; and a comparator that generates an output when the output level of the peak hold circuit exceeds a predetermined reference level; the servo band of the tracking servo system is set to a first band in accordance with the output of the comparator. What is claimed is: 1. An optical recording disk reproducing device characterized by switching from 1 to 2 bands to a second band.