JPH0719383B2 - Information reader - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information reading device, and more particularly to a control device for an actuator that moves a pickup information reading point.

[0002]

BACKGROUND ART For example, there is a tracking servo control device in an optical information reading device having a structure as shown in FIG. That is, the luminous flux emitted from the laser light source 1 enters the recording surface of the recording disk 6 through the lens 2, the beam splitter 3, the quarter-wave plate 4 and the objective lens 5. The laser light is converged by the objective lens 5 and becomes a pickup light spot as a minute information detection point on the recording surface. Reflected light (or transmitted light) from the disk 6
Are separated by the beam splitter 3 and applied to the light receiving surfaces of the pair of photoelectric conversion elements 9a and 9b. The outputs of both photoelectric conversion elements 9a and 9b are amplifiers 10a, 10b and L.
It is applied to the differential amplifier 12 via PFs (low-pass filters) 11a and 11b, respectively. This difference output is equalizer 1
The signal is input to the drive amplifier 14 via 3 and serves as a drive signal for the drive coil 8 that operates as a so-called actuator for moving the objective lens 5 in the direction orthogonal to the recording track. In this case, a signal is supplied from the amplifier 14 to the coil 8 via the loop switch S 1.

As shown in FIG. 2, a pair of photoelectric conversion elements 9a and 9b are mounted so that the light receiving surface thereof is divided by a single dividing line 9c, and the dividing line 9c is attached in the recording track tangential direction ( (Shown in the direction of the arrow Y), and these elements 9a and 9b are provided symmetrically with respect to the optical axis 7'of the reflected light of the light spot. still,
Reference numeral 7 denotes an incident light optical axis, and 15 denotes a disk rotating spindle motor. With this configuration, when the center of the pickup light spot deviates from the center of the recording track in the direction orthogonal to the track, the photodetector 9 responds to this deviation.
The intensity distribution of the light incident on a and 9b becomes asymmetrical, and a difference occurs between the outputs of both detectors. Therefore, a so-called tracking error signal is obtained by obtaining the difference between the low frequency components of these two detectors by the differential amplifier 12, so that the objective lens 5 is moved in the track orthogonal direction (disk radial direction) using this error signal. If it is moved, the pickup spot is biased accordingly, and accurate tracking operation is always possible.

The output of the differential amplifier 12 also has a direct current component extracted through an equalizer 22 and a drive amplifier 23, and drives a carriage motor 24 via a switch S 2. The rotation of the carriage motor 24 moves the pickup carriage 100 in the direction perpendicular to the recording track on the disk 6. The purpose of controlling the movement of the pickup carriage is as follows. When tracking control is performed by performing bias control of the light spot for information detection using only the lens 5, this lens 5
Since the so-called tracking actuator for the bias of does not have a stroke enough to read the entire area of the disc, the tracking actuator and the carriage 100
Is required to be moved in the disk radial direction, that is, in the track orthogonal direction.

Reference numeral 21 is a fast-forward drive circuit for performing fast-forward control of the pickup 100 and the recording disk 6 in the direction perpendicular to the track.
By selecting the output of 1, the carriage motor 2
4 is driven and the fast-forward control is performed. At this time, the switch S 1 is opened and the tracking servo loop is cut off, thereby preventing noise due to random movement of the tracking actuator and application of unnecessary impact force to the tracking actuator.

Since the objective lens 5 is supported at the neutral position by the spring 25, the force for supporting the lens 5 when the tracking servo loop is broken is only the acting force by the spring 25. . Therefore,
The objective lens 5 is vibrated by abrupt acceleration and deceleration of the pickup 100 during fast-forwarding or by external vibration, so that it cannot be supported at a fixed position.

Therefore, when a so-called search operation for searching for a target track is performed by disconnecting the tracking servo loop, the accuracy of counting the number of tracks, the accuracy of setting the position of the information detection point on the target track, and turning on the servo loop again Has a drawback that the transient response characteristic is extremely deteriorated, which is a serious obstacle to the high speed search operation.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an information reading apparatus capable of performing stable and high-speed search by preventing unnecessary vibration of the tracking actuator when the tracking servo loop is broken during fast-forward search. .

[0009]

An information reading apparatus according to the present invention comprises a carriage for positioning a pickup with respect to a recording medium, an actuator for performing a fine position control of an information reading point of the pickup with respect to a recording track, and the actuator for controlling the actuator. An information reading device having a tracking servo loop which operates so as to follow an information reading point and to follow the recording track, wherein the deviation amount of the information reading point by the actuator with respect to the recording track has a pair of detection outputs. Correspondingly, detection means configured to cause a difference between the pair of detection outputs,
A means for obtaining a difference between the high-frequency components of the pair of detection outputs, a means for obtaining a difference between the low-frequency components of the pair of detection outputs, and a combination of the difference between the envelope components and the difference between the low-frequency components. Means for controlling the drive of the actuator based on the added and synthesized output while the tracking servo loop is disconnected.

[0010]

The information reading device according to the present invention controls the drive of the actuator based on the addition combined output of the deviation amount component of the information reading point with respect to the recording track and the tracking error component while the tracking servo loop is broken. , Set the bias of the actuator.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a block diagram showing an embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. In this example, in addition to the configuration of FIG. 1, a circuit for detecting the difference between the envelope components of the high frequency components of the outputs of the photodetectors 9a and 9b is provided. That is, the high frequency component D of each output A 1, A 2 of the amplifiers 10a, 10b
1 and D 2 are HPF (high pass filter) 17a,
17b, these components D 1 and D 2 are rectified by full-wave rectifiers 18a and 18b, and rectified output E 1
, E 2 has been obtained. These outputs E 1 and E 2 are input to LPFs 19a and 19b to extract low frequency components to obtain envelope components F 1 and F 2, and a differential amplifier 20 obtains a difference component G between these envelope components F 1 and F 2. I am trying.

Then, the difference component C of the low-frequency components B 1 and B 2 of the detection output by the detectors 9a and 9b is amplified by the amplifier 26, and this is added to the adder 27.
In (1), the difference G of the envelope of the high frequency component is added and combined. This addition output H is equalizer 33 and amplifier 3
It becomes one input of the level comparator 32 via 4 and is compared with the reference level 31. This comparison output becomes an actuator drive signal when the tracking servo loop is broken.

4 and 5 show respective operation waveforms of the circuit block of FIG. In each of these waveforms, the center of the reflected light beam from the disk generated by the lens 5 following the track in the disk radial direction is the photodetector 9a,
This is the case where the actuator is displaced from the dividing line 9c of 9b, that is, the state shown by the dotted line in FIG. 2, and the displacement of the actuator is displaced from the neutral point. In this state, the time course of each waveform is shown when the tracking servo loop is open and the light spot moves diagonally across the recording track on the disk surface.
In both figures, t 0 indicates the time when the light spot coincides with the center of one track, and t −1 and t +1 indicate the time when the center coincides with the center of both tracks adjacent to the inner and outer circumferences. The vertical axis represents the signal level. However, t 0, t -1, and t +1 indicate the same time common to FIGS. 4 and 5.

FIGS. 4A and 4B show a set of photoelectric conversion elements 9a,
9b shows the amplified signals A 1 and A 2 of the respective detection outputs, and the output A 1 of the detector 9a having a large irradiation area is shown.
Is smaller, the RF component, the envelope component, and the DC component are all large with respect to the output A 2 of the detector 9b, which are in a substantially proportional relationship. The phase relationship between the envelope components of both signals A 1 and A 2 has a phase difference from the track center line as shown in FIGS. 4 (a) and 4 (b). The phase difference is due to the intensity distribution of the reflected light from the disc becoming asymmetrical with respect to the optical axis as the light spot and the track center line are displaced. FIG. 4 (c) shows both signals A 1 and A 2
The low frequency components B 1 and B 2 of the above are shown, and the difference between the two signals B 1 and B 2 is shown in FIG. 6D, which is the tracking error signal itself in the so-called push-pull system. As shown in the figure, there is a DC offset, and this DC offset indicates the displacement of the lens 5 in the disk radial direction. Figure 4 (e),
(f) is the waveform of the high frequency (RF) components of the outputs of the detectors 9a and 9b, that is, the recording information signal components D1 and D2. It becomes an envelope. Figure 5 (g),
(h) shows the waveforms of the signals E1 and E2 obtained by full-wave rectifying the RF waveforms D1 and D2, and (i) shows the waveforms E1 and E2.
2 is an envelope detected by integrating 2 with LPFs 19a and 19b. FIG. 5 (j) shows signals F1 and F2.
Comparing the waveforms of Fig. 4 (d) and Fig. 5 (j), the DC offsets at time t 0 are both in phase, but the AC component is in the opposite phase relationship. It is in. Therefore, by adding and synthesizing both signals C and G at an appropriate ratio, only the DC offset from which the AC component has been removed is obtained at the output H of the adder 27 as shown in FIG. 5 (k). The level of this signal H represents the displacement of the objective lens 5 in the radial direction of the disk, that is, the amount of deviation of the tracking actuator. The displacement amount of the actuator is controlled to a constant value determined by the reference level 31. Here, the reference level 31 is not limited to a fixed value, for example,
The output level of the amplifier 34 immediately before the tracking servo loop is broken may be stored in a memory and this stored output may be used.

Although the tracking servo loop and the position servo loop added separately are switched by the switch in the above embodiment, the position servo loop may be always operated. In this case, an effect equivalent to adding a stiffness component to the actuator can be obtained equivalently, and an arbitrary stiffness amount can be given to an actuator having a small stiffness component or zero.

Further, the present invention is not limited to the optical information reader, but can be applied to other information readers such as a capacitance type.

[0017]

As described above, according to the present invention, when the tracking servo loop is broken, another servo loop is added, and the tracking actuator is controlled by the added servo loop so that the amount of deviation thereof becomes approximately a constant value. Since it is settled, stable and highly accurate search can be realized especially at high speed search.

[Brief description of drawings]

FIG. 1 is a block diagram of an information reading device having a conventional tracking servo loop.

FIG. 2 is a diagram showing a relationship between a photoelectric conversion element and a light spot.

FIG. 3 is a block diagram of an embodiment of the present invention.

4 is an operation waveform diagram of each part of the apparatus of FIG.

5 is an operation waveform diagram of each part of the apparatus of FIG.

[Explanation of symbols for main parts]

5 ... Objective lens 6 ... Recording disk 8 ... Drive coil (actuator) 9 ... Photodetector 17a, 17b ... HPF 18a, 18b ... Full-wave rectifier 19a, 19b ... LPF 20 ... Differential amplifier 27 …… Adder 31 …… Reference level 32 …… Level comparator S1 …… Tracking servo loop switch 100 …… Pickup

Claims (1)

[Claims] 1. A carriage for positioning a pickup with respect to a recording medium, an actuator for controlling a minute position of an information reading point of the pickup with respect to a recording track, and an actuator for controlling the information reading point. And an information reading device having a tracking servo that operates so as to follow the recording track, the deviation amount of the information reading point by the actuator with respect to the recording track having a pair of detection outputs. And a means for obtaining a difference between an envelope component of a high frequency component of the pair of detection outputs, and a pair of the detection outputs. Means for obtaining the difference in the low frequency component of the above, and means for adding and synthesizing the difference in the envelope component and the difference in the low frequency component, An information reading device characterized in that the actuator is driven and controlled based on the addition and synthesis output while the servo is off.