JP2599365B2 - Tracking control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focusing means for focusing a light beam generated from a light source and a first detecting means for detecting a signal corresponding to a focusing state of the light beam on a record carrier. Second detection means for detecting a signal corresponding to the positional relationship between the light beam and the track on the record carrier; and moving the light beam focused by the focusing means in a direction perpendicular to the surface of the record carrier. A first moving means, a second moving means for moving the light beam in a direction substantially perpendicular to the track direction, and a first moving means driven in response to a signal from the first detecting means for recording Focus control means for controlling the light beam on the carrier to be always in a predetermined convergence state, and driving the second moving means in response to a signal from the second detection means, so that the light beam always scans the track correctly. Control tracking It relates to an optical information reproduction apparatus and a control means.

2. Description of the Related Art Generally, a focus or tracking control device includes:
A detection circuit for detecting a control signal, that is, a focus shift signal or a track shift signal, a signal processing circuit for amplifying the control signal to an appropriate magnitude and compensating for a phase of a control system, and controlling according to an output signal of the signal processing circuit Conventionally, these circuits are configured to use a bipolar power supply and to set a reference level of a signal to zero potential.

An example of such a tracking control device is disclosed in Japanese Patent Application Laid-Open No. 56-153562.

FIG. 4 is a block diagram showing a configuration of a conventional tracking control device, which will be described below.

The light beam generated from the light source 1 such as a semiconductor laser
After being converted into parallel light by the coupling lens 2, the light is reflected by the polarization beam splitter 3, passes through the λ / 4 plate 4 (where λ is the wavelength of the light beam), and is rotated by the motor 6 by the focusing lens 5. 7 is focused and irradiated.

The reflected light from the disk 7 passes through the converging lens 5, the λ / 4 plate 4, and the polarizing beam splitter 3, and irradiates a photodetector 8 having a two-part structure.

The direction of the dividing line of the photodetector 8 having a two-part structure is set so as to coincide with the connecting direction of concentric (or spiral) tracks on the disk 7 irradiated with the light beam in a predetermined focusing state.

Outputs A and B of the photodetector 8 are preamplifiers 9a and 9b, respectively.
After the amplification, the differential amplifier 10 obtains a difference output between the two preamplifiers 9a and 9b, that is, a track shift signal, and this signal is a phase compensation circuit 11 for compensating the phase of the tracking control system.
The signal is input to a tracking control element 13 via a drive circuit 12 for power amplification. Therefore, the tracking control element 13 is controlled so that the light beam on the disk 7 scans the track correctly.

The preamplifiers 9a and 9b, the differential amplifier 10, the phase compensation circuit 11 (collectively referred to as a signal processing circuit), and the drive circuit 12 are operated by large-capacity power supplies 14a and 14b having electrode characteristics (power supply voltage ± Vcc). All the control signals transmitted in the tracking control device have a reference level of zero potential.

Problems to be Solved by the Invention A conventional control device including a drive circuit requires two large-capacity power supplies to drive and drive a large current to a control element.

If the control circuit is configured to operate with one single power supply in order to use one large-capacity power supply, the reference potential does not become zero potential. Have been easily fluctuated, control accuracy has deteriorated, and accurate control cannot be performed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a low-cost and highly-reliable device that can integrate a large-capacity power supply and perform accurate control.

Means for Solving the Problems The present invention relates to a focusing means for focusing a light beam on a record carrier, a track displacement detecting means for detecting a displacement between a track on the record carrier and the light beam, and a light beam on the record carrier. Moving means for moving the beam in a direction substantially perpendicular to the track direction, and driving the moving means in response to a signal from the track shift detecting means so that the light beam on the record carrier always scans over the track. Tracking control means for controlling
A signal processing circuit having a power supply of a single polarity, operating at a bipolar voltage generated by the voltage of the power supply and the reverse voltage, operating at the power supply voltage of the single polarity, and moving in series with the moving means; And a drive circuit for driving both of the current detection resistors connected to the first circuit, the tracking control means being constituted, and the drive circuit being connected to an output terminal of the first means.
And a second operational amplifier having an output terminal connected to the current detecting resistor, and an inverting terminal of the first operational amplifier is connected to a signal at a connection point between the moving means and the current detecting resistor. Feeding back the corresponding signal, feeding back the output signal to the inverting terminal of the second operational amplifier to the corresponding signal,
A first signal from the signal processing circuit is input to a non-inverting terminal of the first and second operational amplifiers, and the first and second operational amplifiers are
And a second signal having a polarity opposite to that of the first signal is input to an inverting terminal of the operational amplifier.

Operation According to the present invention, the drive circuit is configured to operate by the first signal from the signal processing circuit and the second signal having the opposite polarity to the first signal from the signal processing circuit. Thus, tracking control can be performed with high accuracy with little offset fluctuation. Also, since the signal processing circuit with low power consumption is operated with a bipolar power supply voltage and the driving circuit with high power consumption is operated with a single polarity power supply voltage, a single power supply with a large capacity is required. The size and cost of the device can be reduced. Further, since a potential difference is generated in the current detection resistor by a difference in the amount of voltage feedback, no phase lag occurs due to the inductance of the moving means.
When the driving means is driven by the output voltage difference of the operational amplifier, almost the same dynamic range can be obtained as when the driving means is driven by the bipolar power supply voltage.

Embodiment An embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a tracking control device according to an embodiment of the present invention. The same parts as those of the conventional tracking control device are denoted by the same reference numerals, and description thereof will be omitted.

Voltage V _cc taken from a power supply 15 capable of outputting a large current (power supply voltage V _cc) is converted to a voltage of -V _cc by DC-DC converter 16. Voltage V _cc and the power supply 15, converted voltage -V _cc, the two bipolar voltages of the preamplifier 9a, 9b, are supplied to the differential amplifier 10 and phase compensation circuit 11,. Therefore, the signal detected by the photodetector 8 and
Since the reference level of the track shift signal, that is, the control signal, which is the output of the differential amplifier 10 to which the signal is input, can be set to zero potential, the influence of the fluctuation of the power supply voltage can be extremely reduced. Further, since the power consumption of the preamplifiers 9a and 9b, the differential amplifier 10 and the phase compensation circuit 11 is very small, the capacity of the DC-DC converter 16 may be small.

The control signal, which is the output of the differential amplifier 10,
11 via the control element 13 is input as a driving circuit 12 for driving the driving circuit 12 is configured to operate with only a single voltage V _cc power supply 15.

FIG. 2 is a block diagram showing the configuration of a current feedback type driving circuit 12 according to an embodiment.

Control element 13 with the load Z _L is connected in series with a current sensing resistor 27, it is connected to the output terminal of the operational increase contact 25 and 26.
The non-inverting input terminals of the operational amplifiers 25 and 26 are commonly connected, and an input terminal voltage v ⁺ is input from an input terminal 20a. From the input terminal 20b, the input voltage v ^- is through input resistor 21, an operational amplifier is input to the inverting input terminal 25 is also input to the inverting input terminal of the operational amplifier 26 through the same input resistor 23.

The feedback resistor 22 of the operational amplifier 25 is connected to the control element 13
The feedback resistor 24 of the operational amplifier 26 is connected from the output terminal of the operational amplifier 26 to the inverting input terminal of the operational amplifier 26.

The drive circuit 12 is configured to operate by the difference voltage between the input voltages of the input terminals 20a and 20b,
20a to the input voltage v ^+, the input voltage v to the terminals 20b ^- when is applied, the relationship between the input voltage and the load current I _L is as follows.

(However, the resistance values of resistors 21, 22, 23, 24, 27 are R ₁ , R
₂ , R ₃ , R ₄ , and R _S. In the drive circuit 12, the condition for performing the BTL operation, that is, a large load current flows to the control element 13, and the condition for stably driving this, is as follows. At this time, when (v ⁺ −v ⁻ ) is positive, a negative load current flows, and when (v ⁺ −v ⁻ ) is negative, a positive load current flows, and the output voltage V _O25 , The output voltages V _O26 of the operational amplifier 26 have opposite polarities.

As described above, according to the drive circuit 12, the control element 13
Load current I _L flowing through, regardless of its load Z _L, the input voltage v ^+, v ^- determined by the magnitude of the load current, it is possible to drive the control element 13 according to the polarity of a single A control element having an arbitrary load can be driven by the power supply voltage having the polarity.

As described above, according to the present embodiment, even if the power supply of the device is one single power supply, the power supply voltage is converted by the DC-DC converter 16 to create a bipolar power supply. Operate the signal processing part. Therefore, it is possible to eliminate a decrease in control accuracy due to a change in the reference level of the signal due to a change in the power supply voltage that may occur when the power supply is operated with a single power supply.

Also, compared to a conventional device that operates using two bipolar power supplies, only one large-capacity power supply can be used, so that the present invention can reduce the cost of the device.

Effect of the Invention As described above, according to the present invention, the signal processing circuit that is susceptible to power supply voltage fluctuations or temperature changes has a bipolar power supply configuration with reference to zero potential. Can be controlled very accurately, accurate control can be performed, and the drive circuit that is not easily affected by power supply voltage fluctuations or temperature changes has a single power supply configuration. The device can be made small, lightweight and highly reliable.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of a tracking control device according to an embodiment of the present invention, FIG. 2 is a detailed diagram of a drive circuit in FIG. 1, and FIG. FIG. 2 is a diagram showing the relationship between the input voltage, load current and output voltage of the drive circuit shown in FIG. 2, and FIG. 4 is a block diagram showing the configuration of a conventional tracking control device. 1 ... Semiconductor laser (light source), 2 ... Coupling lens, 3 ... Polarization beam splitter, 4 ... λ / 4 plate, 5
... Focusing lens, 6 ... Motor, 7 ... Disk, 8 ...
... photodetectors, 9a, 9b ... preamplifiers, 10 ... differential amplifiers, 11 ... phase compensation circuits, 12 ... drive circuits, 13 ... control elements, 14a, 14b ... large capacity power supplies, 15 ... Large capacity power supply, 16
…… DC-DC converter, 20… Drive circuit input terminal, 21…
... input resistor R _1, 22 ...... feedback resistor R _2, 23 ...... input resistor R _3, 24 ...... feedback resistor R _4, 25 ...... operational amplifier, 26 ...... operational amplifier, 27 ...... current detection resistor R _S .

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kazuharu Shirakami 1006 Kadoma, Kadoma City Matsushita Electric Industrial Co., Ltd. Document JP-A-60-261036 (JP, A)

Claims (1)

(57) [Claims] A focusing means for focusing a light beam on a record carrier having a track; a track displacement detecting means for detecting a positional displacement between the track on the record carrier and the light beam; A moving means for moving in a direction substantially perpendicular to the direction, and a tracking means for driving the moving means in response to a signal from the track deviation detecting means and controlling the light beam on the record carrier to always scan on the track. A signal processing circuit having control means and a power supply having a single polarity, operating with a bipolar voltage generated by a voltage of the power supply and a reverse voltage thereof; A tracking circuit comprising a driving circuit for driving both of the driving means and a current detection resistor connected in series with the driving circuit, wherein the driving circuit has an output terminal connected to the moving means; Output terminal to the current detecting resistor and the operational amplifier is constituted by a second operational amplifier being connected,
A signal corresponding to the signal at the connection point between the moving means and the current detection resistor is fed back to the inverting terminal of the first operational amplifier, and a signal corresponding to the output signal is fed back to the inverting terminal of the second operational amplifier. Inputting a first signal from the signal processing circuit to a non-inverting terminal of the first and second operational amplifiers;
A tracking control device, wherein a second signal having a polarity opposite to that of the first signal is input to inverting terminals of the first and second operational amplifiers.