JPS60675A - Pickup servo device - Google Patents

Abstract

PURPOSE:To offer a servo device not so much affected by a scratch on the disc or the external vibration by extracting a relative signal between a moving part and a fixed part of a pickup and mixing the signal with a servo error signal to apply servo. CONSTITUTION:An error is mixed to a reference voltage VR by a mixer 12 and amplified and fed to a track servo coil 6. On the other hand, the movement of the pickup to the fixed part is extracted by a detection coil 9. A track error signal 11 is obtained from the pickup at the same time. Each signal is fed back negatively via amplifiers B1, B2. When no feedback loop of the amplifier B1 exists, the gain as shown in fig. B withstanding an external vibration is set. Then a differentiating element is given to the B1 loop to attain the curve in Fig. A for the servo loop including the signal 11. The gain is attained for a loop gain required for the component for warp or the like and the system is not susceptible to the lower side band component of carrier and a scratch. The external disturbance to this disc system is applied as shown in Y. The servo loop to the external vibration X is supplied in-phase by the feedback amplifiers B1, B2, so that the loop gain is increased as shown in B.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pickup servo device that generates an optical disk (t(f+)), and is particularly suitable for a pickup servo device that is resistant to scratches and dirt on the disk as well as external disturbances and vibrations.

In digital audio discs (1) AI) and video discs (VD), it is necessary to perform track servo and focus servo on minute tracks using an optical head or the like.

Variation factors that are generally applied to discs include eccentricity, anti-shaft,
There may be uneven presses, etc., and if the frequency is plotted on the horizontal axis and the total gain is plotted on the vertical axis in the rA < 1 diagram, as shown by curve N, the higher the frequency, the lower the gain, so there are also fluctuation factors. It's getting less.

In order to servo all of these correctly, it is only necessary to have a servo gain that exceeds the above song iJNk as shown in Figure A of m1.5. However, when considering the entire disk elevating device, there is a tendency to set the servo gain larger than the gain shown in Figure 1A to compensate for the loss of track71 due to vibrations added from the outside, which may cause the focus to shift. .

For example, if the fluctuation factor of the disk is 0. If the acceleration element of IG is used, and if it is a ZARPO system that follows acceleration up to 0.1G, even if this vibration is added, track deviation or track deviation will occur, and one row can withstand up to 1G of disturbance vibration. A gain of 10 times as shown in FIG. 1B is required for the following. As a result, the servo band expands by that amount, making it impossible to beat the four moves. Then, the lower energy S of the signal information
crowded the servo band, and the S/N of the servo number 1 decreased.
There was a drawback that it caused the actuator to consume unnecessary power. Furthermore, a big problem is that if there are scratches or dirt on the disk, it will be added to the error signal as noise, and since it is a large noise with a wide band, the wider the servo response, the more it will respond to this noise and cause track jumps. It was a huge error.

Therefore, in order to be strong against scratches, etc., it is necessary to reduce the servo gain, and to prevent vibrations, etc., it is necessary to increase the entire servo gain. There was no light.

Does the present invention address the above drawbacks? The overall purpose is to provide a pickup servo that achieves both of these without contradicting each other.

For this reason, in the present invention, errors caused by fluctuations and components of the disk itself such as disk eccentricity, and external loss j components added to the family are detected separately without using the same detection system for each. 40The above object of the present invention is to extract the servo error signal from the information YK recorded on the disk,
In a disk player that performs pickup servo,
This is achieved by providing a pickup servo device tt characterized in that the relative signal between the movable part and the fixed part of the pickup is taken out and mixed with the servo error signal to perform servoing of the pickup. The invention will now be described in detail with reference to FIGS. 2 and 3.

Figure 2 (a) is a perspective view of the main parts of the optical pickup.
An optical head section 1 is attached to the tip of a swing arm 2, and when a shaft 3 is rotated, a laser beam is fully emitted through an objective lens 4 to read information on a disk D. Of course, by making the lens system movable in the vertical direction and performing focus servo, the actuator portion 5 drives the entire swing arm 2 left and right, thereby performing full track servo. A cross-sectional view of a part of the actuator is shown in FIG.
The yoke 8 is inserted into the coil 6, the yoke is fixed, and the swing arm rotates! A gap is provided between the coil 6 and the coil 6 so that the coil 6 does not collide with each other even if the coil 6 is in contact with the coil 6. By connecting the coil 6, the current in the coil 6 cuts off the magnetic flux going to the magnet 7 and the joke 8, and drives the swing arm 2, thereby operating as a so-called linear motor. Track servo is performed by this coil 6, and all track signals on the disk D are amplified by the pickup 1, and the track error signal 11 is extracted by a known means such as a three-beam or push-pull method as in the past. On the other hand, below the fixed magnet 7, a detection coil 9 and a yoke 10 are mounted on the arm 2 in the same way as the drive unit 5, and a voltage proportional to the speed of movement of the system swing arm 2 is connected to the detection coil 9. I can get it out.

Next, a block diagram of the pickup servo of the present invention is shown in ';33; Put it in 6. The pickup is pivoted by this coil. - In this embodiment, a signal corresponding to the speed of the pickup is obtained, which is extracted from the motion detection coil 9 for all movements relative to the fixed part of the pickup. At the same time, the track error signal 11 is obtained from the signal boosted from the pickup as in the conventional case, and each of these signals is negatively fed back to the input via the feedback amplifier BλB1. The characteristics of a normal pickup correspond to the output from the amplifier A1, as shown in Figure 1A and B, and the culm with a high frequency, 12
dB/oct line and its response swing is 1J
is decreasing. This is due to the quality components of the pickup. On the other hand, the fluctuation component N required for track servo, such as disk eccentricity, also falls at 12 dB10 ct as shown in the figure, and these are the characteristics that keep the acceleration constant, and generally, as explained earlier, The servo gain characteristic of A is obtained by feeding back the track error signal 11 through a frequency linear amplifier. For this reason J
For the l and li fabrics, gain settings are made as shown in FIG. 1A or as shown in FIG. 1B.

Here, in the present invention, the feedback amplifier Bl returns J・,′t
A1 and B can withstand external photography without a loop.
Next, by inserting a differential element into the loop of B1, the multi-velocity information is made into a signal corresponding to acceleration, and this negative feedback amount is fed back to the input, for example, 20 d.
If set to B, the servo loop including all the track error signals 11 will become like the curve shown in FIG. 1A. This means that, for example, when the amplifier A1 and coil 6 are set to B, the gain is lowered to A in Figure 1 due to the negative feedback of i1h.This causes the gain of the track servo system. The variable element of this disk system is the third (second )Y, on the other hand, acceleration fluctuations due to vibrations from the outside affect both the fixed t1μ of the actuator 5 and the disk as shown in X, and for both, the servo loop is and B2 are added in the same phase to the return loop of B2, so the loop gain is B
It becomes large as shown in .

Here, even if the loop gain is large like '&B', the feedback amplifier Ih f loop has no scratches on the disc, so it is the first
There is even a 1 gA loop ridge, which is the purpose of the servo system that is scratch resistant and drive resistant. This is done every week, and the drawback of kneading is that it easily responds to scratches at the tip, but this can also be done using the loop of the amplifier B1, and these drawbacks can also be removed. Effective O This implementation series was applied to a tracking servo that supports all pickup g movements, but the carriage +41:'e that swings only the lens system and applies servo to the AC component and moves the entire pickup in the track direction The same thing can be done even if it is separated from the component servo.For focus servo other than track servo, for example, the focus servo is performed at the upper and lower lines NJJ of the lens, etc.For stone products, the lens system is moved, and the entire phototransistor etc. 9 detected by the optical system of
It is possible to create a similar servo system by
In addition, the same thing can be done even if the drive coil's back electromotive force 4 is completely taken out without adding the detection t. Ih
The negative feedback loop of is 1 for constant acceleration, that is,
2 dB/oat has been explained, but of course other antecedents can be used and Ia can be set depending on the nature of the noise and disturbance.

4.1 Figure 1 is a servo gain diagram showing the relationship between frequency and gain, Figure JJ2 (B) is +: Sft+ view of the bag portion of the pickup used in the invention, Figure 21 ( B) is a directional view of the actuator lid section of No. 20 (A), and FIG. 3 is a system diagram of the pickup servo device of the present invention.

1...Pickup 2.Yu swing arm, 3@
・・Shaft 4・Objective lens 6・tt Sen coil 7・Magnet 8・0 yoke

Claims (1)

[Claims] A servo error signal is extracted from the information recorded on the disk, and in a disk player that performs pickup servo, the relative signal between the movable part and the fixed part of the pickup is extracted and mixed with the servo error signal. A pickup servo device that performs the servo of the pickup and has a total of 1 characteristics