JPS59229773A - Record information reader - Google Patents

Abstract

PURPOSE:To ensure the accurate following despite the eccentricity, the surface warp, etc. of a disk as well as the external vibration and to secure the stable servo operation in a normal actuation mode, by controlling freely the gain of a servo loop in accordance with the external vibrations. CONSTITUTION:For instance, the detection output of a piezoelectric element, etc. is supplied to a peak holding circuit 16 via a BPF14 and an amplifier 15, and this holding ouput is used as the control signal of variable ATT17 and 18 provided at the output stage of each error generating circuit. The output of the amplifier 15 is rectified by a diode D1 constituting the circuit 16 and then peak- held positively by a capacitor C1. A switching element Q1 is turned on while the holding level is higher than the threshold value VT. Therefore the quantity of attenuation is reduced with ATT17 and 18. This increases the open loop gain of each servo loop.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recorded information reading device, and more particularly to a recorded information reading device having a servo loop for controlling the position of a recorded information detection point.

Servo loops that control the position of the recorded information detection point in the pickup include a so-called focus servo loop that controls the direction perpendicular to the recording surface of the recording disk, and a so-called tracking turbo loop that controls the position of the recording information detection point in the direction perpendicular to the recording track. There is.

FIG. 1 is a schematic block diagram of such a servo loop,
Based on the detection information obtained by the pickup 1, a tracking 1 error signal and a force error signal are generated by error signal generators 2 and 3, respectively. These error signals drive a tracking actuator 6 and a force actuator 7 through amplifiers 4 and 5, respectively. A recording information detection point (not shown) is biased in a direction perpendicular to the track by a focus actuator 6,
The focus actuator 7 biases the detection point in a direction perpendicular to the recording surface, so that the recording information detection point always accurately tracks the recording track despite eccentricity of the recording track, warping of the recording surface, etc. With this, it always converges on the recording surface.

In order to control the time axis of the read information, a so-called spindle movolube is added, and a clock signal is separated from the read information by the pickup 1 in the clock extractor 8. This clock signal is phase-compared with a reference signal from a reference signal generator 9 in a phase comparator 10, and the phase difference signal controls the rotation of a spindle motor 12 via an amplifier 11. This spindle motor 12
This causes a recording disk (not shown) to rotate at a predetermined rotational speed, thereby controlling the time axis of reproduced information.

In such a configuration, if it is predicted in advance that external vibrations, disc eccentricity history, etc. will have a large disc surface warp,
It is necessary to set a large loop gain during each servo loop for tracking and focusing, and to improve the track tracking ability of the recording information detection point in advance. However, as a result, the servo band inevitably expands constantly, resulting in sensitivity to noise, making the servo unstable, and each actuator generates vibration noise.

Therefore, if the interloop gain is set low, the tracking ability will be weakened due to disturbances, etc., and the servo will become disabled, resulting in mistracking.

The purpose of the present invention was to eliminate the drawbacks of the conventional ones as described above, and it is possible to accurately follow external vibrations, disk eccentricity, surface warping, etc., and to be stable even during normal operation. It is an object of the present invention to provide a recorded information reading device having a →no-vo loop capable of performing one-vo.

The recorded information reading device according to the present invention is characterized in that it detects external vibrations and can freely control the loop gain of the servo loop in accordance with the external vibrations.

Another recorded information reading device according to the present invention is characterized in that it detects a servo error signal of a servo loop and can freely control the loop gain of the servo loop in accordance with this error signal.

The present invention will be explained below with reference to the drawings.

FIG. 2 is a block diagram of an embodiment of the present invention, and parts equivalent to those in FIG. 1 are designated by the same reference numerals.

In this example, a vibration detector 13 for detecting external vibrations is provided, and this may use, for example, a piezoelectric element, or may use an electrostatic or optical detection element. Also, a so-called voice coil type conductive type element (moving coil type) may be used.

This detection output is input to a peak hold circuit 16 via a BPF (band pass filter) 14 and an amplifier 15. This hold output is connected to a variable ATT provided in each servo loop (for example, at the output stage of each error generation circuit).
(Attenuator) It is used as a 17°18 control signal.

The reason why the BPF 14 is inserted is to selectively extract only the vibration band components where the servo is likely to come off. The other configurations are the same as those in the example shown in FIG. 1, and their explanation will be omitted.

Amplifier 15, peak hold circuit 16 and variable ΔTT 17 (18
) is a circuit diagram showing a specific example. The amplifier 15 consists of an operational amplifier OP+ and resistors R+ and R2, and its output is rectified by a diode D1 constituting a peak hold circuit 16 and sent to a positive peak voltage capacitor C1. This bold output is a control signal for the variable ATT17 (18), and this ATT is connected to a resistor R3 inserted in series with the servo error signal line and a resistor R4 inserted in parallel to this signal line. Consisting of

A switching element (
A field effect transistor (Q+) is provided to supply a peak bold signal to the gate of this element Q1.

FIG. 4 is an operating waveform diagram of the circuit of FIG. 3, in which (A) is the input signal, that is, the detection signal waveform by the vibration detection element 13 of FIG. 2, (8) is the peak hold output waveform, and ( C) is a diagram that does not show the change in attenuation amount of ATTl 7 (18). Of course, when the detected waveform by the vibration detection element 13 is as shown in Figure (A), the hold output by the positive peak hold circuit 16 is as shown in Figure (B), so the dark value ■T of the switching element Q1 is as shown in Figure (A). Assuming that the hold level is at the level indicated by the dashed-dotted line in B), the switching element Q+ is turned on during the period when the hold level exceeds the dark value Vd. Therefore, the attenuation m of A-rT17.18 decreases as shown in Figure (C), and as a result, the loop gain increases during each servo loop.

Figure 5 shows the change characteristics of the loop gain versus frequency. When there is no vibration or when it is small, the open loop gain is small as shown in characteristic 19, but when the vibration becomes too large, the open loop gain is small. For example, since the attenuation amount of ATT17 and 18 becomes small, the loop gain increases as shown in characteristic 20. As a result, the closed-loop gain of each servo system becomes as shown by the dotted line, and the band becomes wider when the imaging becomes large.

Therefore, when vibration increases and the servo becomes easily disconnected, the interloop gain automatically increases, the closed loop band expands, and even large vibrations can be tracked sufficiently. Furthermore, since the band is normally small, stable servo operation is maintained without being sensitive to noise.

In addition, in the variable ATT17.18, the change in the damping Φ is digitally switched between two values, but the loop gain can be controlled in response to the amount of external vibration so that it can be changed freely in a so-called analog way. You may also do so. Further, the BPF 14 may be deleted depending on the frequency component of external vibration. Furthermore, it is clear that instead of using a variable ATT, the amplifiers 4 and 5 may be VCAs (voltage controlled amplifiers), and the amplifier gain may be controlled in accordance with the peak bold output.

The external vibration detection element 13 is installed near the pickup 1 (
Although it is effective to have a single detection element for the tracking servo and for the focus servo, it is effective to set each detection element to the corresponding servo system, but it is not limited to this. 4 (
It's good to try to pull it.

8r! 6 and 7 are block diagrams of other embodiments of the present invention, and parts equivalent to those in FIGS. 1 and 2 are designated by the same reference numerals. Note that the spindle servo loop is omitted. This example is applied when the eccentricity or warping of the recording disk is large, and in such a case, the error signal increases accordingly, so this is detected by the level detectors 21 and 22. Detect each and variable ATT17.1
8.

In the example of FIG. 6, the output levels of the amplifiers 4 and 5 are detected, and in the example of FIG. 7, the output levels of the error signal generators 2 and 3 are detected. The level detectors 21 and 22 have a rectifying and smoothing circuit configuration, and a DC level control signal corresponding to the error signal level is derived from the variable ATT 17.
．． 18 attenuation amount control. This variable ATT
Each of the configuration examples 17 and 18 is equivalent to the example shown in FIG. 3, and is configured to perform digital control or analog control.

By doing so, the loop gain characteristics change as shown in FIG. 5, and the same effect as in the example shown in FIG. 2 is produced.

FIG. 8 shows another embodiment of the present invention, in which the amplifier 4.5 is connected to the VCA instead of the variable ATT 17.18 shown in FIG. 6.7.
How can the amplifier gain be controlled by the level detectors 21 and 22 t11-! It was designed so that it would look like this. Figure 9 shows VCA
A specific example of 4.5 is shown in which Cd3 is composed of an operational amplifier OP2 and feedback resistors Rs and R6, and the amplifier gain is switched by controlling the short-circuiting and opening of the resistor R5 by a switching element Q2. A level detection output is applied to the gate of this element Q2. Note that the resistor R6 is the element Q
This is for gate bias of No.2. However, it is of course better to operate the element Q2 as a variable impedance element and avoid changing the amplifier gain in an analog manner.

As described above, according to the present invention, the loop gain can be controlled during the servo loop according to the vibration, disk shape, etc., and the optimum value of C can be achieved. It is possible to operate the servo system with a small amount of vibration, resulting in stable servo control, and in environments with large surface run-out or eccentricity, or in environments with large vibrations, the loop gain automatically increases, increasing the tracking ability of the servo system. Good servo operation is possible.Good results can be obtained even if not only the loop gain but also the frequency characteristics (transfer function) are varied.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of each servo system of a conventional recorded information reading device, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a circuit diagram of a specific example of a part of the blocks in FIG. Fig. 4 is an operating waveform diagram of the circuit in Fig. 3, Fig. 5 is a loop gain characteristic diagram of the board system shown in Fig. 2, and Figs. 6 to 8 show other embodiments of the present invention. Block diagram, Figure 9 is the VC of Figure 8
It is a circuit diagram of A. Explanation of symbols of main parts 1...Pickup 2...Tracking error signal generator 3...
... Focus error signal generator 6 ... Tracking actuator 7 ... Focus actuator 13 ... Vibration detection element 16 ... Peak hold circuit 17. 18...Variable AT T21.22...
...Level detector applicant Pioneer Co., Ltd. agent Patent attorney Motohiko Fujimura (1 other person)

Claims (2)

[Claims] (1) A recorded information reading device having a servo means for controlling the position of a recorded information detection point, characterized in that it detects external vibration and can freely control the loop gain of the servo means in accordance with the external vibration. Recorded information reading device. (2) A recorded information reading device having a servo means for controlling the position of a recorded information detection point, wherein an error signal in the servo means is detected and a loop gain of the servo means can be freely controlled according to the error signal. A recorded information reading device characterized by: