JPH01220229A - Gain controller for focusing servo - Google Patents

Abstract

PURPOSE:To stably adjust the gain of focusing servo by providing a means to detect the level of a focusing servo error signal, and a means to control the level of disturbance to be impressed by the level of the focusing servo error signal. CONSTITUTION:The title device is provided with the means 30 to detect the focus error signal in the open state of a focusing servo loop, and the means 20 to control the level of the disturbance to be impressed by the level of the focus error signal. And by setting the level of the disturbance to be impressed on the focusing servo loop at an appropriate level, correct gain control can be performed not depending on the optical dispersion of a disk or an optical pickup. In such a way, it is possible to obtain a gain controller for the focusing servo for an optical disk player in which gain control can be performed stably not depending on the optical dispersion of the disk or the optical pickup.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a focus servo gain adjustment device for an optical disc player that uses a light beam to reproduce information recorded on a disc.

2. Description of the Related Art In an optical disc player that reproduces information signals recorded on a spiral or concentric track of a disc using a light beam of an optical pickup,
Focus servo detects the shift of the focus of the light beam relative to the recording surface of the disk, so-called focus error, and uses the output of the focus error signal to move the focus lens of the optical pickup in a direction perpendicular to the recording surface of the disk to focus. This is to ensure that the error is zero.

Incidentally, the gain of the focus servo is adjusted by applying a disturbance of a specific frequency to the servo loop from the outside. FIG. 3 shows the configuration of a conventional focus servo gain adjustment method. In fig.

Reference numeral 10 denotes an optical disk on which information signals are recorded, and 11 denotes an optical pickup which makes a light beam 12 enter the optical disk. 13 is the output 11 of the optical pickup 11 mentioned above.
This is an error signal generation circuit that inputs 1 and generates a focus error signal. 19 is a frequency response analyzer with a disturbance oscillator 20 and a gain detector 21 inside.
Then, the disturbance oscillator 2o outputs a sinusoidal disturbance signal S corresponding to the desired gain intersection frequency to the adder 18. The adder 18 receives the output Y of the error signal generation circuit 13.
and the above-mentioned disturbance signal S, and the output x is outputted to the loop filter 14 of the focus servo. The loop filter 14 is for performing low frequency compensation and phase compensation of the servo loop. The output 141 of the loop filter 14 is
The output 211 of the gain detector 21 is input to the variable gain amplifier 15 whose gain is controlled, and the output 151 is input to the actuator drive circuit 16 where the power is amplified and the output 161 drives the actuator 17 for moving the focus lens. do.

Of the focus servo gain adjustment device configured as described above, the parts other than the adder 18 and the frequency response analyzer 19 are the same as those of a conventional optical disc player, so a description thereof will be omitted. Focus servo for optical disc players is described in many documents (for example, "Compact Disc Reader", pages 138-143, Ohmsha, 1982).
Year). Here, we will explain conventional focus servo gain adjustment using a frequency response analyzer.

Focusing on the output disturbance signal S of the disturbance oscillator 20 in FIG. 3, it is applied to the focus servo loop via the adder 18, goes around the loop, and returns to the input of the adder 18.

Therefore, if we calculate the ratio between the output X of the adder 18 and the input Y, it is clear that this ratio is the gain of the focus servo loop at the frequency of the disturbance signal S.

Here, the 7 requency response analyzer 19 will be explained using FIGS. 3 and 4.

In FIG. 4, 20 is the above-mentioned disturbance oscillator.

The input Y of the adder 18 goes to the Y input amplifier 22, and the output
Connected to input amplifier 23. Y input amplifier 22 and X
The output of the input amplifier 23 is Fourier transformed by the microcomputer 24 and outputted. If the ratio of these respective outputs is determined by the comparator 25, the gain of the focus servo loop at the frequency of the disturbance signal S can be determined (for example, MODIEL of NF Circuit Design Block Co., Ltd.).
S-5720゜15730 FRKQUI! :NCY
RXSPONSK ANALYZICI' instruction manual (pages 1-6). And the output 211 of the comparator 26
The variable gain amplifier 16 is controlled to adjust the gain of the focus servo loop.

Problems to be Solved by the Invention However, with the above configuration, the gain of the focus servo loop cannot be adjusted correctly unless the output level of the disturbance oscillator is appropriately set.

The reason for this is that optical discs such as compact discs (AN) have significant optical variations depending on the disc, and there are also optical variations in the optical player's pickup itself, so the level of the disturbance signal (i.e.
Even if the voltage value is kept constant, the amount of deflection of the focus lens (that is, the physical dimension in which the lens actually moves) varies depending on the disk or pickup. Therefore, if the level of the disturbance signal is too large, the servo will become unstable, and in the worst case, the servo will become disconnected. In addition, we have solved the problem of excessive quilting, which reduces the level of the disturbance signal, and the levels of the X and Y input signals to the frequency response analyzer become small, worsening the S/N of the measurement system and making it impossible to make correct adjustments. had.

In view of the above problems, the present invention provides a focus servo gain adjustment device for an optical disc player that can perform stable gain adjustment regardless of optical variations in the disc or pickup.

Means for Solving the Problems In order to solve the above problems, the focus servo gain adjustment device of the present invention includes means for detecting a focus error signal when the focus servo loop is open, and detecting a focus error signal based on the level of the focus error signal. and means for controlling the level of applied disturbance.

Effect of the Invention With the above-described configuration, the present invention can appropriately set the level of disturbance applied to the focus servo loop, and can perform correct gain adjustment regardless of optical variations in the disk or pickup.

Embodiment Hereinafter, a focus servo gain adjustment device according to an embodiment of the present invention will be described with reference to one drawing. FIG. 1 shows the configuration of a focus servo gain adjustment device in an embodiment of the present invention. In FIG. 1, 30 is an error signal level detector that detects the level of the output Y of the error signal generation circuit 13. This output 301 controls the level of the output disturbance signal S of the disturbance oscillator 2o.

31 is an oscillator, and its output 311 is input to the actuator drive circuit 16 via a switch 32. Other configurations are the same as before.

The operation of the focus servo gain adjustment device configured as described above will be described below with reference to FIGS. 1 and 2.

First, the switch 32 is connected to the (A) side and the actuator 17 is driven by the output 311 of the oscillator 31 to move the focus lens in the focus direction (perpendicular to the disk surface). At this time, the output Y of the error signal generation circuit 13 is the second before and after the light beam focuses on the recording surface of the disk.
Draw a figure 8 curve as shown in the figure (the peak value of this figure 8 curve reflects optical variations in the disc and pickup as the voltage value X(v), but the optical distance is constant. For example, 6 μm in Figure 2). The peak value of this figure 8 curve is detected by the error signal level detector 3o. As the error signal level detector 30, a so-called peak hold circuit is used. And this output 3o1(E('
v)), the disturbance oscillator 20 is controlled so that the output S has a peak value of K/5 (7). This allows the level of disturbance applied to the focus servo loop to be reduced to 1 μm regardless of optical variations in the disk or pickup.
It can be done.

Next, by connecting the switch 32 to the (B) side, the focus servo loop is closed and focus pull-in is performed.

There are various methods of focus pull-in operation, but since they are well known, their explanation will be omitted. Next, gain adjustment is performed in the same manner as in the conventional method while keeping the output level of the disturbance oscillator 2o at K/5. As described above, according to this embodiment, the level of the focus error signal when the switch 32 is connected to the (M) side and the focus servo loop is in the open state is detected by the error signal level detector 3o, and the output E is detected by the error signal level detector 3o. By setting the output of the disturbance oscillator 20 to 15.

The disturbance level can be reduced to 1 μm regardless of optical variations in the disk or pickup, and 1 μm is sufficiently small compared to 5 μm, which is the D range of the focus servo, so that the servo does not come off, and the S/N of the measurement system is sufficient. Therefore, correct gain adjustment can be made using a frequency response analyzer.

In this embodiment, the error signal level detector 3° is a peak hold circuit, but the output Y of the error signal generation circuit 13 is subjected to Mu/D (analog/digital/I/) conversion and its peak-to-peak (peak-to-peak) to peak)
A value may be determined and the output level of the disturbance oscillator 20 may be controlled using this value. Further, the output waveform of the first oscillator 31 is a sine wave if it is at a level that allows a figure-eight curve of the focus error signal to be obtained in the error signal generation circuit.

Triangular waves, sawtooth waves, etc. may be used.

Effects of the Invention As described above, the present invention provides means for detecting the level of a focus servo error signal when the focus servo loop is open, and means for controlling the level of disturbance applied based on the level of this focus error signal. By providing this, it is possible to stably adjust the focus servo gain without depending on optical variations in the optical disc or pickup.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a focus servo gain adjustment device in an embodiment of the present invention. Figure 2 is a characteristic diagram that explains the figure 8 curve of the focus error signal, Figure 3 is a block diagram of a conventional focus servo gain adjustment device, and Figure 4 is a block diagram that explains the frequency response analyzer. It is a diagram. 1o...Optical disc, 11...Optical pickup, 18...Adder, 17...
... Actuator, 19 ... Frequency response analyzer, 2o ... Disturbance oscillator, 21 ... Gain detector %3o ...
Error signal level detector, 31...oscillator. Name of agent: Patent attorney Toshio Nakao Haga 1 person No. 4
figure

Claims (1)

[Claims] In the focus servo loop of an optical disc player,
A gain adjustment device that adjusts the open loop gain by applying a disturbance of a specific frequency, the gain adjustment device comprising means for detecting the level of a focus error signal when the focus servo loop is in an open state, and applying according to the level of the focus error signal. A gain adjustment device for a focus servo, comprising means for controlling a level of disturbance.