JPS6151623A - Information recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain stable tracking control by extracting a signal based only on a shift between a moving range center of an optical beam displacing means and its operating center to correct the shift thereby attaining the coincidence between the moving range center and its operating center without being affected by the eccentricity of an optical disc. CONSTITUTION:A tracking control signal of a drive coil 36 is fed to an AC component eliminating circuit 38, the tracking control signal having removed AC components is compared by comparators 39, 40 with a comparison voltage + or -V. The comparators 39, 40 output a signal when the signal is larger or smaller than the voltage + or -V, the output signal is fed to a one-shot circuit 42 to open a switch means 32 thereby interrupting the supply of the tracking control signal to a coil 36 and positioning an objective lens 37 to the center of the moving range. When the means 32 is closed, the tracking control is attained while the center of the moving range and the operating center are coincident.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an information recording/reproducing apparatus equipped with a tracking control circuit.

(B) Prior Art In order to record information in a spikele or concentric pattern by irradiating a disc with a light beam, or to reproduce this information, it is necessary to irradiate the disc with a light beam accurately. Therefore, the information recording and reproducing apparatus includes a tracking control circuit that detects the relative positional misalignment between the light beam and the information track and displaces the light beam in the width direction of the information track based on this tracking error signal.

FIG. 6 is a perspective view showing an optical head of this type of information recording and reproducing apparatus, which is found in, for example, Japanese Patent Publication No. 58-55566'll. The light beam emitted from the semiconductor radar (1) is collimated by a collimator lens (11), and is then collimated by a beam splitter (q) and 1/4 and irradiated onto a disk (not shown).

Next, the light beam reflected from the disk passes through an objective lens mark and a quarter-wave plate, and then passes through a beam splinter @
The optical path is bent at a right angle by the lens (161), and is incident on the half mirror u'71, where it is split into two.One of the split light beams passes through the cylindrical lens 0 to the photodetector (u'71). The information on the optical disc is reproduced by the output signal of this photodetector 09).The other split light beam is sent to a photodetector consisting of a pair of light receiving elements (20a) and (20b). (2) The output of each light receiving element (20&) (20b) is
It is input to differential amplifier +211.

Here, if the light beam is accurately irradiated onto the information track, the light intensity detected by the pair of light receiving elements (20a) (20b) will still be -, and the output of the differential amplifier 121J will be O. If the light beam deviates from the information track in its width direction, a pair of light receiving elements (20a) (20b
) detects different light intensities, and the output of the difference #@@ device (2) is positive or negative depending on the direction of deviation of the light beam.

Therefore, the output of the differential amplifier Qυ is a tracking error signal, and based on this signal, the tracking control circuit energizes the drive wheel provided in the actuator I to move the objective lens 0.5+ to the information track. The information track can be accurately tracked by moving in the middle direction.

In addition, the actuator (14) and the objective lens (151
In this structure, for example, as seen in Japanese Patent Application Laid-Open No. 58-199445, a ring-shaped magnetic band is fitted around the outer periphery of an objective lens, and this is supported by a pair of leaf springs. A fixed yoke with a pair of drive coils wound around the objective lens is arranged, and by adjusting the current applied to the drive coil, the objective lens can be moved to any desired size in the direction of the disk. You can move it with Also, I
When no signal is applied to the aAtll coil, the objective lens is located at the center of its range of motion.

As described above, tracking control in the information recording/reproducing apparatus is performed by displacing the objective lens toward the middle of the information track.

By the way, when performing random access to the information track of the disk using this kind of optical head, the equity is 1'11.
As seen in Public Bank No. 359-16347, the optical head is fed at high speed to the vicinity of the target information track with the tracking control operation cut off, and then the tracking control operation is started and the optical head is fed at low speed to reach the target. A method of searching information tracks is performed. Here, when the optical head is shifted from high-speed feed to low-speed feed, vibration occurs in the optical head and the objective lens also vibrates. Therefore, when tracking control operation is started in this situation, the objective lens is displaced. Tracking starts from this state, and the center of operation of the objective lens shifts from the center of the movable range of this lens.

(c) Intermediate point to be solved by the invention As mentioned above, when the operating center of the objective lens moves away from the center of the movable range of this lens, the movable range of the objective lens is relatively reduced. Therefore, accurate tracking control cannot be performed.

Thus, it is a diagram of means for controlling the position of the light beam relative to the information tracks of the disc, for example an objective lens. When the center of the movable range of the objective lens coincides with the center of operation of the objective lens, the tracking control signal T is in the form of a sine wave with a constant frequency centered at the zero level O, as shown in the same figure (Ill). 7. This sine wave shape is due to a misalignment between the center of the disk and the center of the information track (so-called eccentricity).On the other hand, if the center of the movable range of the objective lens and the center of operation of the objective lens are misaligned, As shown in FIG. 4B, the tracking control (id') T deviates from the zero level O and becomes a sine wave of a constant frequency with the positive or negative level at the core.

Therefore, a certain level range ±V centered around zero level O
It is conceivable to make the center of the movable range of the objective lens coincide with the operating center of the objective lens by setting the tracking control ID number d and controlling the tracking control number d so that it falls within this level range 1tC. Here, the control to bring the objective lens within the folding level range means temporarily cutting off the supply of tracking control No. A T to the drive coil of the objective lens to position the objective lens at the center of the movable range, and from this position. The next step is to start tracking.

However, if the eccentricity of the optical disc is large, as shown in Figure 2 (
As shown in C), the tracking control (T) becomes a sine wave with a very large amplitude, and even though the center of the objective lens's movable range almost coincides with the operating center of the objective lens. First, the value of the tracking control signal T deviates from the above-mentioned level range tester (2).Therefore, the above-mentioned level range ±V must be set to a large value, but in this state it is not effective for optical discs with small eccentricity. I can't raise it.

An object of the present invention is to reliably correct the deviation between the center of the movable range of the objective lens and the operating center of the objective lens, and to perform stable tracking control.

B) Means for Solving the Problems The present invention detects the amount of positional deviation of the light beam with respect to the information track of the disk, and adjusts the displacement means to an appropriate size based on the amount of positional deviation to control the position of the light beam. An information recording and reproducing apparatus equipped with a tracking control circuit that outputs a control signal of the same type, further comprising: a switch means for supplying and cutting off the control signal to the displacement means; and an ACIi component removal circuit for removing an AC component from the control signal. , and a control section that temporarily opens the switch means when the value of the control signal becomes larger than a predetermined value as a result of comparison between the AC component and the comparator.

(E) Functionally, the amplitude of the tracking control signal is proportional to the eccentricity of the optical disc, but the circumference i& is determined by the rotation of the optical disc and is constant regardless of the amount of eccentricity.

Therefore, by removing the AC component of the desired frequency from the tracking control signal, only the signal based on the deviation between the center of the movable range of the objective lens and the operating center of the objective lens can be obtained. By theoretically reducing this signal to zero, the objective lens's iJJ! The center of the VJ range concave and the movable center of the objective lens can be made to coincide.

(f) Embodiment FIG. 1 is a block circuit diagram showing an embodiment of the present invention. The optical head has exactly the same structure as shown in FIG. 3, and FIG. 1 shows the objective lens (37) and the drive circuit in the actuator. When the tracking error signal output from the differential amplifier (see FIG. 6) of the optical head ■ is applied to the tracking control circuit 6υ, the tracking control section FI! rC31) applies a tracking control signal to the optical hand ω via the switch means θ2. Specifically, the tracking control signal is applied to the bias circuit.

When used as a bias circuit, the first and second transistors 34)
The base of the can is connected. The emitters of the first and second transistors 04) are connected, and a drive coil is connected between this connection point and ground. Further, a positive voltage V and a negative voltage -V are applied to each collector of the first and second transistors 134) (c).

Thus, when performing the tracking control operation, the switch means θ is closed. When a tracking deviation occurs and the tracking control circuit (3η) outputs a tracking control signal with a positive value, the first transistor I→ is biased, and a current based on the magnitude of the tracking control signal flows through the drive coil ■ to the right in the figure. On the other hand, when the tracking control circuit (31) outputs a tracking control signal with a negative value, the second transistor (351) is biased and the current flows through the drive coil (351) to the left in the figure. By controlling the magnitude and direction of the current flowing through the drive coil (g) based on the tracking control signal in this way, the objective lens (3'7) is moved toward the middle of the track and tracking is performed.

By the way, the drive voltage of the drive coil (to), that is, the tracking control signal, is applied to an AC component removal circuit (2) consisting of four resistors R, a capacitor C, and an operational amplifier OP.

Specifically, the tracking control signal No. 3 is applied to the negative and positive input terminals of the operational amplifier OP through a resistor R and a capacitor C to the negative and positive input terminals of the operational amplifier OP. ...Added. Furthermore, a feedback resistor R is connected between the negative input terminal and the output terminal of the operational amplifier OP.
Also, a grounding resistor R is connected to the positive input terminal, and a resistor R
and the value of capacitor C determines the frequency of the AC component to be removed. For example, if the resistance R = 10Ω and the capacitor C = 4.7μF, then the AC frequency of 11Hz is
The components will be reduced to 1/6 to 1/7, and will be the same as those removed.

The tracking control signal 8 from which the AC component has been substantially removed is applied to the first and second comparator fields 14G and compared with positive and negative comparison voltages ±V.

Each comparator 31 f40 is a tracking! A signal is output when the IJ control signal is larger or smaller than the voltage.

When this signal is applied to the one-shot circuit 1424 via the OR gate '411, the one-shot circuit (42) applies a pulse of a certain width to the control circuit (424).
43 keeps the switch means C3 in an open state while the prayer pulse is being applied.

Note that the optical head (2) is moved in the radial direction of the disk by a motor (not shown).

When performing the above-mentioned random access, first the switch means 2 is opened and the optical head is moved at high speed. Thereafter, a tracking control signal is applied to the switching means (three of them are closed channels), and the optical head (° C.) is moved at a low speed.

Here, when the eccentricity of the optical disc is large, the tracking control signal has a very large amplitude as shown in FIG. 2(C). The desired tracking $ control signal is input to the AC component removal circuit, and as shown in FIG. 2(D), A
The C component is removed, resulting in a nearly direct current voltage. This voltage is a signal based on the deviation between the center of the movable range of the objective lens 137) and the center of operation of the force of the sealing lens G.

Thus, the substantially direct current '4 voltage from which the AC component has been removed is compared with a predetermined voltmeter V by the first and second comparators C' and 1t4G. Here, when a signal is output from the second comparator (3'J14(I), the first module indicates that the above-mentioned DC voltage is outside the range of the expected voltage ±V, and in this case, one shot The circuit (4) applies a pulse signal to the control circuit. The control circuit (43) temporarily opens the switch means (while the pulse signal is being applied). Therefore, the tracking control signal is driven. The supply to the coil (A) is cut off, and the objective lens (3η) is positioned at the center of its movable range.

Thereafter, when the switch means is in the open state, the tracking control signal is already in the form of a sine wave centered on the zero level, and when the AC component is removed from this signal, it naturally becomes approximately zero voltage. Therefore, the first and second comparators G9
(40 does not output a signal, the closed state of the switch means C33 is maintained, and thereafter, tracking control is performed in such a state that the center of the movable range of the objective lens C37 coincides with the center of operation.

It should be noted that it takes a certain amount of time to move from the displacement position of the objective lens G force to the center of the movable range, and the above movement may not be completed within the switching time of one sudden opening/closing operation. However, in this case, as the switching means C32 is not closed properly, the first or second comparator field outputs a signal again, so the opening/closing operation of the switching means 02 is performed again, and therefore, the above-mentioned movement is Complete for sure.

In this embodiment, an information recording/reproducing device in which an objective lens is used as a means for displacing a light beam has been described, but the present invention can also be applied to an apparatus using a reflecting mirror as a means for displacing a light beam. can.

(G) Effects of the Invention According to the present invention, the center portion of the movable range of the displacement means for displacing the light beam in the width direction of the information track;
Since the above-mentioned deviation is corrected by collecting signals based only on the deviation from the operating center of the displacement means and recognizing the magnitude of the signal, the movable range of the displacement means can be adjusted without being affected by the eccentricity of the optical disk. It is possible to align the center of the movement with the center of operation, and therefore stable tracking control can be performed.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing one embodiment of the present invention, and FIG.
The figure is a signal waveform diagram showing the tracking control signal according to its condition.
FIG. 6 is a schematic perspective view showing the optical head. mark)...Optical head, Cυ...Tracking control circuit, (32...Switch means, (Miscellaneous...AC night removal circuit, (39 (40 par° first and second comparators,
(43...control circuit.

Claims (1)

[Claims] (1) A tracking control circuit that detects the amount of positional deviation of the light beam with respect to the information track of the disk, and outputs a control signal of an appropriate magnitude to the displacement means that controls the position of the light beam based on the amount of positional deviation. In the information recording and reproducing apparatus, the information recording and reproducing apparatus includes: a switch means for supplying and cutting off the control signal to the displacement means;
an AC component removal circuit that removes the C component; a comparator that compares the magnitude of the control signal from which the AC component has been removed by the AC component removal circuit with a scheduled value; 1. An information recording/reproducing apparatus comprising: a control section that temporarily opens the switch means when the value becomes larger than the above value.