JPS6076037A - Tracking servo mechanism of optical disk device - Google Patents

Abstract

PURPOSE:To obtain an optical disk device which secures the higher integrated eccentricity follow-up performance by sharing the high band control in the 1st tracking servo means, and the low band control in the 2nd tracking servo means, respectively. CONSTITUTION:The 1st detector (for track shift) 8 consists of the combination of a 2-split photodetector and a differential amplifier, for instance. Then a relative position shift amount DELTAX1 is detected between a light spot and a target track by the output of the circuit 8. In other words, the double feedback control is applied. Thus the two control systems operate stably just by separating control bands of two feedback groups with the distance of a prescribed amount (8 times for example), since the relation mH>>mL is usually obtained between the mobile mass mL of a lens VCM5 and the mobile mass mH of a head VCM4. Therefore, the low band component of eccentricity is followed by the head VCM4, and the lens VCM5 follows up the high band component to which the VCM4 can scarcely follow up.

Description

Detailed Description of the Invention +a) Technical Field of the Invention The present invention relates to a control circuit in an optical disk device such as an optical disk device or a magneto-optical disk device, and particularly relates to a control circuit in an optical disk device such as an optical disk device or a magneto-optical disk device. The present invention relates to a tracking servo mechanism that performs dual control of a tracking servo means and a tracking servo means that drives the entire optical head including its drive device.

(b) Conventional technology and problems A conventional example will be explained with reference to the drawings.

FIG. 1 shows a configuration diagram of a tracking servo mechanism of a conventional optical disc device. As shown in the figure, this servo mechanism houses a Nubindle motor 1, a recording medium 2 rotated by the Nubindle motor 1, an optical system for inputting and outputting information such as a light source (not shown) and a condensing lens 6, and is mounted on bearings, etc. It consists of a supported optical head 8 and a drive device 4 for moving the entire head in the radial direction of the recording medium 2.

On the other hand, in a normal optical disk device, the information tracks formed concentrically or spirally with the disk surface of the recording medium 2 have a pitch of 1.5 to 3 μnl, whereas the recording medium 2 has an eccentricity of about 100 μm. exists. Therefore, it is necessary to detect the relative positional deviation between the information track and the minute optical spot formed on the disk surface 1 of the recording medium 2 by the condensing lens 6, and to perform feedback control to eliminate this. . This amount of positional deviation can be detected inside the optical head 3. However, since this output is simply fed back to the drive device 4, sufficient band characteristics cannot be obtained at this stage.

Therefore, within the optical head 3, the condensing lens 6 is usually supported by an elastic body 7, as shown in FIG. It is possible to move the optical nubot to a high band (less than fun), and the output of the positional deviation amount detector that does not blur is this V C
IVi 51' is fed back. The first tracking servo means controls the condensing lens 6 and the elastic body 7 by the first driving device 5 described below.

Therefore, even if the drive device 4 is stationary, the eccentricity tracking is circular, but in this case, the control performance must be improved more than the current level, and the drive device 4 must be fixed by a separate means, and When the V CM 5 approaches the limit of its movable range, it is necessary to have a control circuit to control the drive device 4 and re-fix its position, which has the disadvantage that the control system becomes h.

(C) Object of the Invention To provide an optical disk device in which higher eccentricity tracking performance can be obtained overall by having a first tracking servo means share high band control and a second tracking servo means share low band control. The purpose is to provide a tracking servo mechanism.

According to the present invention, information is optically recorded and reproduced on a recording V & body of a disc ball, and minute microscopic information for recording and reproduction is formed on an information track formed on the recording medium. A first tracking servo means for tracking the light spot includes a first detector for detecting a relative positional deviation between the information track and the minute optical hub; and a first drive device that controls a light spot.
13] of the first driving device, and the entire optical head section including the first driving device is superimposed on the thread of the tracking servo means of the first driving device.
This is realized by providing a second tracking servo means ttS that controls the moving part so that it is always at its reference position.

The second tracking servo means includes a second detector that detects the amount of displacement from the base t of the movable part in the first drive device, and a second drive that controls the amount of displacement to zero. The configuration with the device is the first embodiment, and nIJ
an equivalent circuit having the same frequency eL number characteristic as the input signal of the first drive device that relatively detects the displacement;
There is a second embodiment that includes a second drive circuit that controls the output of the equivalent circuit to zero, and a third drive circuit that amplifies the output of the second detector in the first embodiment. There is an eighth embodiment that includes a detector, and feeds back a sum signal of the output of the third detector and the output of the first detector to the first drive device, and provides these means. This is achieved by

(e) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

At the south exit, parts corresponding to those in FIG. 1 will be designated by the same reference numerals and their repeated explanation will be omitted. In addition, the second driving VCM4
．． The first driving device 5 is abbreviated as lens VCM5.

FIG. 2 is a configuration diagram of a tracking servo mechanism of an optical disc device showing a first embodiment of the present invention.

In the figure, reference numeral 8 denotes a first detector (track deviation amount detection circuit), which is composed of, for example, a two-split photodetector and a differential amplifier. The output of the track deviation amount detection circuit 8 determines the relative positional deviation amount Δ between the optical Nubot and the target track.
Detect Xi. Various methods have already been devised as means for detecting the amount of positional deviation, such as the pre-group method and the beam method.

Reference numeral 10 denotes a second detector (lens position detector), which detects 83 the lens power deviation ΔX2 from the equilibrium position of the elastic support 7 supporting the lens. This detection means can be easily implemented by using the principle of an optical linear encoder or by pasting a nuttrain meter on the elastic support 7. Then, the output of the track deviation amount detection circuit 8 is fed back to the lens VCM 5 via the phase compensation circuit 9.

The output of the lens position detector 10 is also fed back to the head VCM 4 via the phase compensation circuit 11.

In other words, there is a reason to apply a double feedback system f, but the i [mass mL and head VCM
Since the movable mass ffn1g of No. 4 normally has a relationship of mH>>mL, the two control systems can operate stably by simply separating the control bands of the two feedback groups by a required amount (for example, about 8 times). In this way, the head VCM4 will follow the low-frequency component of the eccentricity, and the lens V CIvj 5 will follow only the open castle component that the head vcM4 cannot follow. Since the eccentricity of the high frequency component is usually of small amplitude, the IITIvJWL range of lens CM5 may be narrow. Also, the r+J movement range of the lens VC+45 is about the same)
Since this is the same as that expanded to the movable range of V CM 4, there is no need to consider the nJ movable range of lens vCIφ5, and it is extremely convenient for random access of the optical disc device.

The following explanation is about the second dragging servo means attached to the first tracking servo means and the stabilizing means for the two control systems. There are second and third embodiments to be discussed.

FIG. 3 is a mechanical diagram showing the second embodiment of the present invention. Instead, the equivalent circuit lO' having the same frequency characteristic sound as the displacement/input signal of the lens V CM 5 is shown in phase? It is branched from the output side of the ril compensation circuit 9 and inserted between it and the input side of the phase compensation circuit 11. In a spring-supported VCiM in which the condensing lens 6 is supported by an elastic member 7, its displacement/current characteristics are a secondary thread with a natural frequency determined by its spring constant and the movable part 'R), so calculations are required. The equivalent circuit 10' can be easily realized by a circuit using an amplifier. With this tracking servo mechanism, the accuracy is poor, but the configuration has the advantage that the adjustment speed is easy with the intermediate wheel.

FIG. 4 is a mechanical diagram showing a third embodiment of the present invention,
Compared to the first hlu example, the one-tub core followability is improved. Figure 5 shows an example of the frequency/gain characteristic curve, that is, the band characteristic. It is ideal if the overall one-round transfer gain is the product of the individual one-round transfer gains of the two servo loops in that one-degree region. However, A
iJ As mentioned above, if the mass mH>>Tnl, the influence of the force generated by the lens VCM5 on the movable part mass rnH of the head VCIφ4 can be ignored, but the head V
11 of lens V CM 5 due to the force generated by CM 4
The acceleration of the force that j moving part', ('f 11j nl H, The gain of the range is the servo on the lens VCM5 side.
It will be no different from the case of single slag. In the eighth embodiment shown in FIG. 4, the acceleration is added to the input of the lens vCM5 via an adder 18 in order to cancel out the acceleration that the movable part of the lens VCM5 receives.

In particular, it is sufficient to detect a support supported by a bearing or the like as illustrated.

As shown by the curve L+H, it is the product of the single loop gains of the two servos P-G, so a high gain can be obtained.

Its eccentricity tracking performance is improved. It would also be possible to combine the second embodiment and the eighth embodiment described above.

(f) Effect of @Ming As explained in detail above, according to the optical disk tracking servo mechanism of the present invention, the apparent lens VCM
This has the same effect as expanding the movable circumference of the optical head VCM to the stroke of the optical head VCM, which not only makes it easier to control the optical head, but also makes it easier to achieve higher tracking accuracy than in the past.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the structure of a tracking servo mechanism of a conventional optical dimec device, FIG. 2 is a first embodiment of the tracking servo mechanism of an optical dimec device according to the present invention, and FIG. FIG. 4 shows the third embodiment, and FIG. 5 shows the frequency/gain characteristic curve of FIG. 4. In the figure, 2 is a recording medium, 3 is an optical head unit including a first drive device, 4 is a second drive device 45 is a first drive device, 6 is a condenser lens, 7 is an elastic group, 8 is a first drive device Detector (track deviation amount detection circuit), 9 and 11 are phase compensation circuits, 1
0 is the second detector (lens position detection U), lO is the equivalent circuit, 12 is the eighth detector, 13 is the adder, ■ is the head V
CM band characteristic curve, L shows the band characteristic curve of lens VCM, and fI+L shows the total band characteristic curve. Figure 1 7 Figure 2 1 3rd Kl

Claims (1)

[Scope of Claims] (1) To optically record and reproduce information on a recording medium with a disc, and to cause the information track formed on the ITJ recording medium to follow a minute light sporatra for the recording and reproduction. a first tracking servo means for detecting the amount of relative positional deviation between the information track and the minute light spot; and a first driving device that controls the minute light spot so as to make the bottom of the positional deviation zero, the first driving device superimposed on the thread of the first tracking servo means. a second drive device that drives the entire optical head unit including a second drive device, and a second detector that detects a positional deviation amount of the movable portion of the first drive device from a reference position, the second detector a second tracking servo means fed back to the second driving device to zero the output of the first trunking servo, and the control band of the first trunking servo is at least eight times that of the second trunking servo. (2) As the second detector, a tracking servo machine (llj) for an optical disk device δ, characterized by taking the following steps; A tracking servo mechanism for an optical disk device according to claim 1, characterized in that a circuit having such characteristics is used. (8) The residual force VC of the front Jd second drive device is Claimed in a patent comprising: a third detector that generates an output; the sum of the output of the third detector and the output of the l-th detector is fed back to the first drive device. Trunking servo of the optical disc device according to item 1 above +M 4'+4°