JP2720581B2 - Error signal detecting device for optical information reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an error signal detecting device of a servo device of an optical information reproducing apparatus, which causes an information reading means to follow an information track of an information recording medium.

2. Description of the Related Art In recent years, an optical information reproducing apparatus that optically reads information from a recording medium such as a video disk and a digital audio disk has been widely used. In these, information is recorded on an information track having a fine width. In order to reproduce information from the information track, generally precise tracking control is required. In order to perform tracking control, it is necessary to detect a tracking error, and this is usually performed using optical means. In order to optically detect the tracking error, a method of detecting a tracking error from a phase difference between respective signals output from two portions of a photoelectric detector that receives a detection light and outputs an electric signal (hereinafter, a method of detecting the tracking error) This is called a “phase difference method”).

However, the signals detected from the two parts of the photoelectric detector are superimposed with the phase difference signal representing the tracking error and the phase difference due to the optical axis shift of the optical pickup and the lens aberration, so that the servo is stabilized. Adjustment of the phase balance between the above two signals is indispensable for improving the performance of the device.

Hereinafter, the above-mentioned conventional optical information reproducing apparatus will be described with reference to the drawings.

FIG. 5 is a block diagram showing a tracking error signal detecting device of a conventional optical information reproducing device using a phase difference method.

In FIG. 5, reference numeral 1 denotes a photoelectric detector for forming a far-field image of light converged on a recording medium, and has four light receiving cells A, B, C, and D. 2a is an adder for adding the signals extracted from the cells A and C, and 2b is an adder for adding the signals extracted from the cells B and D. 7a is a phase shift circuit provided after the adder 2a, and 7b is a phase shift circuit provided after the adder 2b. 5
Is a phase comparator for comparing the phases of the output signals of the phase shift circuits 7a and 7b, and this phase comparator 5 outputs a tracking error signal.

The operation of the tracking error signal detection device configured as described above will be described below.

It is assumed that the photoelectric detector 1 includes four light receiving cells A, B, C and D as shown in the figure. The signals of the cells C and D of the photoelectric detector located on one side of the dividing line substantially perpendicular to the direction in which the information track mapping extends are added to the adding means 2a and 2b, respectively.
Thus, the signals of the cells A and B of the photoelectric detectors arranged in the respective diagonal directions are added. When there is no tracking error, there is theoretically no phase difference between these sum signals, but it is already known that when a tracking error occurs, a phase difference occurs between them (for details, see Japanese Unexamined Patent Publication No. -93222). Therefore, the phase of the output signal from the adding means 2a and the phase of the output signal from the adding means 2b can be compared by the phase comparator 5 (for example, JP-A-57-181433).

However, as described above, the signals detected from the two parts of the photoelectric detector are superimposed with a phase difference signal indicating a tracking error and a pseudo phase difference due to an optical axis shift or lens aberration of the optical pickup. Adjustment of the phase balance of the two sum signals is indispensable for stabilizing the tracking servo and improving the performance of the device. For this purpose, a phase shift circuit 7a and a phase shift circuit 7b are provided to cancel the pseudo phase difference The amount of phase shift is adjusted as follows. Here, two phase shift circuits are provided to balance the two.

FIG. 6 is a block diagram showing a configuration of a first conventional example of the phase shift circuits 7a and 7b. 8 is an OP amplifier, 9 is a variable resistor. By changing the value of the variable resistor 9,
The operation gain of the OP amplifier 8 changes. The roll-off transfer characteristic of this time the OP amplifier 8, output from the input signal V _S
The frequency-phase transfer characteristic to V _OUT changes. This is used as a phase shift circuit.

FIG. 7 is a block diagram showing a configuration of a second conventional example of the phase shift circuits 7a and 7b. 8 is an OP amplifier, 9 is a variable resistor. By changing the value of the variable resistor 9, the frequency-phase transfer characteristic from the input signal V _S to the output V _OUT changes. This is used as a phase shift circuit.

However, in the above configuration, since the resistance value of the variable resistor 9 is a parameter of the amount of phase shift, manual adjustment of changing the resistance value of the variable resistor is required. Met. For this reason, the first problem was to eliminate the need for the variable resistor in order to achieve non-adjustment by automatic adjustment by the introduction of digital servos due to the development of digital technology in recent years.

Also, since two phase shift circuits (7a, 7b) are provided to balance the outputs from the two parts of the photoelectric detector 1, two control input terminals need to be provided when the circuit is integrated into an IC. was there. Conversely, if a fixed resistor is attached to one of the control input terminals and built into the IC, the number of required control input terminals will be one, but the adjustment range of the phase shift will be narrow and it will not be possible to secure a sufficient adjustment range There is a problem, and the second problem is that a single control input terminal is required after a sufficient adjustment range is secured for streamlining the system.

In view of the above two problems, the present invention can adjust a phase balance for canceling a pseudo phase difference superimposed on the above two signals due to an optical axis shift or a lens aberration of an optical pickup without using a variable resistor. It is another object of the present invention to provide an error signal detection device for an optical information reproducing device that can reduce the number of control input terminals while securing a sufficient adjustment range for streamlining the system.

Means for Solving the Problems In order to solve the first problem, an error signal detecting device of an optical information reproducing apparatus of the present invention forms a far-field image of converged light on a recording medium on which information is recorded. A first phase shift circuit and a second phase shift circuit that adjust respective phases of a first signal and a second signal that are detected and combined from a plurality of locations of the photoelectric detector to be used;
A phase comparator for detecting a phase difference between an output signal of the phase shift circuit and an output signal of the second phase shift circuit, and a first control device for outputting a control voltage or a control current to the first phase shift circuit And outputting a control voltage or control current to the second phase shift circuit.
Wherein the first phase shift circuit and the second phase shift circuit determine a phase adjustment amount based on the control voltage or the control current.

Further, in order to solve the second problem, the apparatus further comprises a third control device for sending a control output to each of the first phase shift circuit and the second phase shift circuit.
Is characterized in that one of the phase shift amounts of the first phase shift circuit and the second phase shift circuit is controlled to be large while the other is small. .

According to the present invention, the first phase shift circuit and the second phase shift circuit determine the phase adjustment amount based on the output voltage or output current of the first control device and the second control device. Parameter is voltage or current,
Automatic adjustment of phase amount. In addition, since there is provided a third control device for controlling one of the phase shift amounts of the first phase shift circuit and the second phase shift circuit to be large while the other phase shift amount is small, When a circuit relating to shift is systemized, a single control input terminal of the system can be used to secure a wide range of phase adjustment.

Hereinafter, an error signal detecting device for an optical information reproducing apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of an error signal detecting device of an optical information reproducing device according to a first embodiment of the present invention.

In FIG. 1, reference numeral 11 denotes a photoelectric detector which forms a far-field image of light converged on a recording medium, and has four light receiving cells A, B, C, and D. 12a is an adder for adding the signals extracted from the cells A and C, and 12b is an adder for adding the signals extracted from the cells B and D. 13a
Is a first phase shift circuit connected downstream of the adder 12a, and 14a is a first control device for sending a control voltage or control current to the first phase shift circuit 13a. 13b is a second phase shift circuit connected after the adder 12b, 1
Reference numeral 4b denotes a second control device which sends a control voltage or control current to the second phase shift circuit 13b. Reference numeral 15 denotes a phase comparator for comparing the phases of the output signals of the first phase shift circuit 13a and the second phase shift circuit 13b, and this phase comparator 15 outputs a tracking error signal.

FIG. 2 is a circuit diagram showing a configuration of the first phase shift circuit 13a and the second phase shift circuit 13b.

In Figure 2, differential, differential, coupled differential circuit in the order of the differential 3 is composed of two transistors and the transistor Q ₁ facing each other in the differential, emitter resistance of the transistor Q ₁ (Not shown) and a capacitor C connected in parallel with the emitter resistor form a low-pass filter. A constant current source is connected to the emitters of the two opposing transistors, and a differential current I flows. The differential current I is supplied to the first control device shown in FIG.
Changing the 14a or the second control device that is an output control voltage or control current 14b, the emitter current IQ ₁ of the transistor Q ₁ is (not shown) emitter resistance of the transistor Q ₁ changes has the aforementioned change The amount of phase shift by the low-pass filter changes. Assuming that the phase shift amount at this time is Φ, Φ = −tan _-1 (f / f ₀ ) f ₀ = I / (π × C × V _t ) f: Frequency of input signal V _s V _t : Thermal voltage Is done. Further, since the bias voltage of the output signal of the differential 1 circuit changes according to the differential current I, the differential 2 circuit generates the same voltage as the bias voltage of the differential 1 output signal in the differential 3 circuit. Is provided. Thus, the first phase shift circuit 13a and the second phase shift circuit 13b can be configured by controlling the differential current I of the differential 1 and differential 2 circuits.

As described above, according to the present embodiment, the phase shift amounts of the first phase shift circuit 13a and the second phase shift circuit 13b are determined by the control voltage output from the first control device 14a and the second control device 14b. Since it is changed by the control current, automatic adjustment of the phase shift amount can be realized.

FIG. 3 is a block diagram showing an error signal detecting device of the optical information reproducing device according to the second embodiment of the present invention. In the configuration in FIG. 3, the same portions as those in the configuration in FIG. 1 are denoted by the same reference numerals, and detailed description is omitted. In FIG. 3, a third control device (differential control device) 16 is provided,
The output is supplied to a first phase shift circuit 13a and a second phase shift circuit 13b. The third control device 16 controls the first phase shift circuit 13a and the second phase shift circuit 13b with a control voltage (or control current).
When the output to one of them is increased, a differential output is supplied so as to decrease the output to the other.

FIG. 4 is a circuit diagram showing a configuration of the third control device 16, in which a control signal is inputted, a transistor provided opposite to this transistor, and a constant connected to the emitters of the two transistors. It consists of a current source.

The error signal detecting device of the optical information reproducing apparatus according to the second embodiment of the present invention configured as described above has the third configuration.
The operation will be described below with reference to FIGS.

The basic operation is almost the same as that of the first embodiment shown in FIGS. 1 and 2, but the first phase shift circuit 13
a, the phase shift amount of the second phase shift circuit 13b is
It is controlled by a control voltage (current) generated differentially by the third controller 16.

The third control device 16 is configured as shown in FIG.
When the control current of the first phase shift circuit 13a increases, the control current of the second phase shift circuit 13b decreases.

As described above, according to the present embodiment, when the control current of each of the first phase shift circuit 13a and the second phase shift circuit 13b is increased, when one phase shift amount is increased, the other phase shift amount is decreased. By providing the third control device that generates differentially as described above, a sufficient control range can be ensured and the number of control input terminals can be reduced to one, so that the system can be rationalized.

Although the photoelectric detector 11 is divided into four parts in the first and second embodiments, it may be divided into more parts. Further, the adjustment of the phase shift of the present embodiment can be applied not only to the tracking error signal detecting device but also to the focusing error signal detecting device.

As described above, the error signal detecting device of the optical information reproducing apparatus according to the present invention has the first control device for controlling the first phase shift circuit and the second control device for controlling the second phase shift circuit.
The first control device and the second control device output a voltage or a current to the first phase shift circuit and the second phase shift circuit to control the first and second phase shift circuits. The phase shift amount of the phase shift circuit can be automatically adjusted. The error signal detecting device of the optical information reproducing apparatus according to the present invention includes a third control device, and the third control device controls the phase shift amounts of the first phase shift circuit and the second phase shift circuit to be small. Therefore, when a phase shift circuit is systemized, a wide range of phase adjustment can be ensured, and only one control input terminal of the system can be used, so that the system can be rationalized.

[Brief description of the drawings]

FIG. 1 is a block diagram of an error signal detecting device of an optical information reproducing device according to a first embodiment of the present invention, FIG. 2 is a circuit diagram showing a configuration of first and second phase shift circuits, and FIG.
FIG. 4 is a block diagram of an error signal detection device of an optical information reproducing device having a third control device according to a second embodiment of the present invention. FIG. 4 is a circuit diagram showing a configuration of the third control device. 5
FIG. 1 is a block diagram showing a configuration of an error signal detecting device of a conventional optical information reproducing apparatus, FIG. 6 is a circuit diagram showing a configuration of a first conventional phase shift circuit, and FIG. 7 is a second conventional phase shift circuit. FIG. 3 is a circuit diagram illustrating a configuration of a shift circuit. 11: photoelectric detector, 13a: first phase shift circuit, 13b: second phase shift circuit, 14a: first control device, 14b: second control device, 15: phase comparison , 16... Third control device.

Claims (2)

(57) [Claims] 1. A first signal and a second signal which are detected and synthesized from a plurality of locations of a photoelectric detector on which a far-field image of light converged on a recording medium on which information is recorded is formed. A first phase shift circuit for adjusting the phase of
A phase shift circuit for detecting a phase difference between an output signal of the first phase shift circuit, an output signal of the second phase shift circuit, and an output signal of the second phase shift circuit; A first control device that outputs a control voltage or control current to a first phase shift circuit; and a second control device that outputs a control voltage or control current to the second phase shift circuit. Wherein the phase shift amount of the phase shift circuit and the second phase shift circuit is determined based on the control voltage or the control current. 2. A first signal and a second signal which are detected and synthesized from a plurality of locations of a photoelectric detector on which a far-field image of light converged on a recording medium on which information is recorded is formed. A first phase shift circuit for adjusting the phase of
A phase shifter for detecting a phase difference between an output signal of the first phase shift circuit and an output signal of the second phase shift circuit; the first phase shift circuit and the second phase shift circuit. A third control device for sending a control output to each of the phase shift circuits.
Wherein the controller controls one of the phase shift amounts of the first phase shift circuit and the second phase shift circuit to be larger and the other phase shift amount to be smaller. An error signal detecting device for an information reproducing device.