JPS63152029A - Generation device for tracking error signal - Google Patents

Abstract

PURPOSE:To obtain a tracking error signal where there is no offset by controlling the signal level of output components from four light receiving areas out of the outputs from two addition means with level detection signals according to the respective outputs from four division type light receiving element. CONSTITUTION:The level detection signals are generated according to the signal levels of the respective outputs from the four light receiving areas of the four division type light receiving element 1 and the signal level of the output components from four light receiving areas out of the outputs from two addition means 4 and 7, which respectively add the outputs from two pairs of the light receiving areas symmetrical concerning an intersecting point of two lines dividing the four division type light receiving element 1, is controlled with the level detection signals. The signal according to the phase difference of the outputs from two addition means 4 and 7 is generated as the tracking error signal. Therefore, the levels of the output components of the respective elements in two signals obtained by respectively adding the outputs from two pairs of symmetrical elements are equal each other even if the position of a light spot formed on the light receiving surface of the four division type light receiving element 1 is displaced. Thus, the phase difference between two signals does not alter and the occurrence of the offset of the tracking error signal can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking error signal generation device, and more particularly to a tracking error signal generation device in an apparatus for recording or reproducing information on an optical recording medium.

1. In a device that records or reproduces information on an optical recording disk, there is a so-called tracking error that indicates a separation state between the information detection optical spot of the pickup and the recording track in the direction perpendicular to the recording track (disk radius). A device for generating a signal is provided, an example of which is shown in FIG.

In FIG. 3, reference numeral 1 denotes a 4-split type light receiving element, and the light that has passed through the recording surface of the spot light for information detection of the pickup shines onto the light receiving surface of this 4-split type light receiving element 1.

shot. The 4-segment light receiving element 1 includes four elements 1a to 1 arranged adjacent to each other so as to form four light receiving areas divided by two straight lines α and β that are perpendicular to each other.
It consists of d. The outputs of elements 1a and 1C, which are arranged symmetrically with respect to the intersection of straight lines α and β, are supplied to an adder 4 via buffer amplifiers 2 and 3, respectively.

Further, each output of elements 1b and 1d is supplied to an adder 7 via buffer amplifiers 5 and 6, respectively.

The summed outputs of the adders 4 and 7 are waveform-shaped by waveform shaping circuits 8 and 9 including comparators and the like, and then supplied to a phase difference detection circuit 10. In the phase difference detection circuit 10, the output p of the waveform shaping circuit 8 is connected to the clock input terminal of the D-type flip-flop 12 and the D-type flip-flop 1.
4 reset input terminal. At the same time, the output p of the waveform shaping circuit 8 is supplied to the inverter 15. The inverter 15 outputs an inverted signal p- of the output p and is supplied to the clock input terminal of the D-type flip 70 tube 11 and the reset input terminal of the D-type flip-flop 13.

The output r of the waveform shaping circuit 9 is transferred to the D-type flip-flop 11.
and the clock input terminal of the D-type flip-flop 13.

At the same time, the output r of the waveform shaping circuit 9 is supplied to the inverter 16. An inverted signal r- of the output r is outputted from the inverter 16 and input to the reset input terminal of the D-type flip-flop 12 and the D-type flip-flop 14.
is supplied to the clock input terminal of

An electric WA voltage is applied to the D input terminals and set input terminals of the D-type flip-flops 11 to 14. Q output of D type flip 70 tubes 11 and 12 Q + and Q 2
G, t, OR (vijA 111) 'F"t"
The signal is supplied to the negative input terminal of the differential amplifier 18 via the terminal 17. Further, the Q outputs q3 and q↓ of the D-type flip-flops 13 and 14 are supplied to the positive input terminal of the differential amplifier 18 via the OR gate 19. The output of this differential amplifier 18 is output via an LPF (low pass filter) 20 as a tracking error signal e.

In the above configuration, the four-segment light receiving element 1 has the center of the light spot formed on the light receiving surface by the light from the recording surface coincident with the intersection of the straight lines α and β, and the straight line α is the light spot for information detection. It is assumed that the arrangement is such that the pattern of the intensity distribution of light from the recording surface is parallel to the direction of movement as it moves following the recording track. At this time,
When the information detection light spot is moving following the recording track, the pattern of the intensity distribution of light within the light spot formed on the light receiving surface of the light receiving element 1 is, for example, in the direction from element 1a to 1b ( (downward in the figure), but the pattern of the intensity distribution of this light is symmetrical with respect to the straight line α. Then, the phase difference between the waveform shaping outputs p and r becomes "0", the D-type flip-flops 11 to 14 remain in the reset state, and the Q outputs q1 to q4 remain at a low level. As a result, the negative phase input of the differential amplifier 18 ×
There is no level difference between the input signal y and the positive phase input y, the output of the differential amplifier 18 becomes the ground level, and the level of the tracking error signal e output from the LPF 20 becomes equal to the ground level.

Next, the information detection light spot is displaced in the inner circumferential direction, and 4
Refer to FIG. 4 for a case where the pattern of the light intensity distribution within the light spot formed on the light receiving surface of the split type light receiving element 1 is displaced, for example, in the direction from the element 1d to the element 1a (leftward in the figure). explain. FIG. 4(A) is a waveform diagram of the waveform-shaped output p, FIG. 4(B) is a waveform diagram of the inverted output p-, FIG. 4(C) is a waveform diagram of the waveform-shaped output r, and FIG. ) is a waveform diagram of the inverted output r-, (E) is a waveform diagram of the Q output q1, (F) is a waveform diagram of the Q output q2,
The figure (G) is a waveform diagram of the Q output q3, and the figure (H) is the waveform diagram of the Q output q3.
A waveform diagram of the output q4, (I) is a waveform diagram of the negative phase input X of the differential amplifier 18, and (J) is a waveform diagram of the positive phase input y of the differential amplifier 18.

When the pattern of the light intensity distribution is displaced in the direction from element 1d to element 1a, the phase of the waveform shaping output p and the inversion output p- is higher than the phase of the waveform shaping output r and the inversion output r- of the information detection light spot. It moves forward by an angle corresponding to the amount of displacement. Then, the D-type flip-flops 11 and 12 correspond to the angle.

Q outputs q1 and q2 are set in the set state for the corresponding time.
is at a high level only during the time corresponding to the angle in question. Also,
D-type flip-flops 13 and 14 remain in the reset state, and Q outputs q3 and q4 remain at low level. As a result, of the negative phase input X and the positive phase input y of the differential amplifier 18, only the negative phase input X remains at a high level for a period of time corresponding to the displacement amount of the information detection optical spot. For this reason,
The differential amplifier 18 outputs a negative pulse having a pulse width corresponding to the amount of displacement of the information detection optical spot, and outputs a pulse of negative polarity to the LP.
The level of the tracking error signal e outputted from F20 becomes negative, and its absolute value becomes a value corresponding to the amount of displacement of the information detection light spot.

Next, the information detection light spot is displaced in the outer circumferential direction, and 4
Refer to FIG. 5 for the case where the pattern of the intensity distribution of light within the light spot formed on the light-receiving surface of the split-type light-receiving element 1 is displaced, for example, in the direction from element 1a to 1d (to the right in the figure). explain. 5(A) to 5(J) show the waveforms of the same signals as those shown in FIG. 4(A) to 4(J), respectively.

When the light intensity distribution pattern is displaced in the direction from element 1a to element 1d, the phase of the waveform shaping output p and the inversion output p- is higher than the phase of the waveform shaping output r and the inversion output r- of the information detection light spot. It is delayed by an angle corresponding to the displacement ω. Then, the D type flip-flops 13 and 14
is in a set state for a time corresponding to the angle, and the Q outputs q3 and q4 are at a high level for a time corresponding to the angle. Moreover, the D-type flip-flops 11 and 12 are
It remains in the reset state and the Q outputs q1 and q2 remain at low level. As a result, only the positive phase input y of the negative phase input X and the positive phase input y of the differential amplifier 18 remains at a high level for a period of time corresponding to the displacement amount of the information detection optical spot. Therefore, the differential amplifier 18 outputs a positive pulse having a pulse width corresponding to the amount of displacement of the information detection optical spot, and the level of the tracking error signal e output from the LPF 20 becomes positive and its absolute value is a value corresponding to the amount of displacement of the information detection light spot.

In the conventional tracking error signal generation device as described above, when only the objective lens of the pickup device in which the 4-split type light receiving element 1 is housed is displaced in order to perform tracking control, the light receiving surface of the 4-split type light receiving element 1 is displaced. The position of the light spot formed in FIG. 6 moves from the position shown by the solid line U to the position shown by the broken line V or W in FIG. Then, due to the deviation of the position of the information detection light spot on the recording surface of the recording medium from the recording track, the pattern of the intensity distribution of light within the light spot formed on the light receiving surface of the 4-segment light receiving element 1 becomes a straight line α. Similarly to the case where the elements 1a to 1d are asymmetric, the amount of light incident on the elements 1a to 1d becomes unbalanced. For this reason, for example, when the position of the light spot formed on the light-receiving surface of the four-part light-receiving element 1 is at the position shown by the broken line V in FIG. 6, the outputs of the elements 1a to 1d are respectively The amplitudes of the respective outputs of the elements 1a to 1d become unbalanced as shown in each of A) to (D) of the same figure. As a result, the phase difference between the diagonal sum components output from the adder circuits 4 and 7 no longer corresponds accurately to the distance between the information detection light spot and the recording track, resulting in an offset in the tracking error signal. was there.

Due to the occurrence of this offset, a track skipping LI operation of the information detection point is performed, and elements 1a to 1d
When the sum of the outputs of changes as shown in Figure 8 (A>), 4
When the position of the light spot formed on the light-receiving surface of the split-type light-receiving element 1 is at the position indicated by the solid line ( ) in FIG. 6, a tracking error signal as indicated by the solid line U' in FIG. 8(B) is generated. When the position of the light spot formed on the light-receiving surface of the four-segment light-receiving element 1 moves to the position shown by the broken lines ■ and W in FIG. 6, the broken line in FIG. V
The level of the tracking error signal changes as shown by ' and W'.

λ Dish Two Emperors 1 An object of the present invention is to provide a tracking error signal generation device that can generate a tracking error signal without offset.

The tracking error signal generating device according to the present invention generates a level detection signal according to the signal level of each output of the four light-receiving areas of a 4-split photodetector, and detects the intersection of two straight lines that divide the 4-split photodetector. After controlling the signal levels of the output components of the four light-receiving regions among the outputs of the two adding means that add the outputs of two pairs of light-receiving regions that are symmetrical with respect to each other using a level detection signal, the phase difference between the outputs of the two adding means is determined. The configuration is such that a signal corresponding to the tracking error signal is generated as a tracking error signal.

Support-5-1 Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2.

In FIG. 1, a four-part light receiving element 1 and buffer amplifiers 2, 3, 5.6 are connected in the same way as in the device shown in FIG. However, in this example, the outputs of the buffer amplifiers 2.3 and 5.6 are respectively supplied to variable gain amplifier circuits 21.22.23.24 as level control means. The variable gain amplifier circuits 21 to 24 are configured to amplify the input signal with a gain depending on the level of the control signal. The outputs of the buffer amplifiers 2, 3, and 5°6 amplified by these variable gain amplifier circuits 21 to 24 are sent to level detection circuits 25, 26, 27, and 28, respectively.
is supplied to. These level detection circuits 25.26.
Reference numerals 27 and 28 are composed of, for example, a ΔM detection circuit, and a level detection signal corresponding to the signal level of each output of the buffer amplifiers 2, 3, 5, and 6 amplified by the variable gain amplifier circuit 21, 22, 23, and 24. is configured to occur. Each output of these level detection circuits 25 to 28 is
They serve as control inputs for variable gain amplifier circuits 21 to 24, respectively.

The respective outputs of the variable gain amplifier circuits 21 and 22 are supplied to the adder circuit 4, where they are added and combined. In addition, variable gain amplifier circuit 2
The respective outputs of 3.24 are supplied to the adder circuit 7 and are added and synthesized. The respective outputs of these adder circuits 4 and 7 are supplied to a phase difference detection circuit 10 via waveform shaping circuits 8 and 9, respectively.

In the above configuration, the phase difference between the waveform shaping outputs p and r becomes 0'' when the information detection optical spot moves following the recording track, as in the apparatus shown in FIG. 3. Then, The D-type flip-flops 11 to 14 in the phase difference detection circuit 10 remain in the reset state, and the Q outputs q1 to q4 remain at low level.As a result, the negative phase input X and the positive phase input of the differential amplifier 18 There is no level difference between y and the output of the differential amplifier 18 becomes the ground level, and the LPF
The level of the tracking error signal e output from 20 becomes equal to the ground level.

Next, the information detection light spot is displaced in the inner circumferential direction, and 4
If the pattern of the light intensity distribution within the light spot formed on the light receiving surface of the split type light receiving element 1 is displaced, for example, in the direction from the element 1d toward the element 1a (leftward in the figure), the device shown in FIG. Similarly, waveform shaping output p and inverted output p
The phase of - advances from the phases of the waveform shaping output r and the inverted output r- by an angle corresponding to the amount of displacement of the information detection optical spot.

Then, the D-type flip-flops 11 and 12 in the phase difference detection circuit 10 enter the reset state for a time corresponding to the angle, and the D-type flip-flops 13 and 1
4 remains in the reset state. As a result, of the negative phase input X and the positive phase input y of the differential amplifier 18, only the negative phase input A negative pulse having a pulse width corresponding to the displacement amount of the detection light spot is output, and the level of the tracking error signal e becomes negative, and its absolute value becomes a value corresponding to the displacement amount of the information detection light spot. Become.

Next, the information detection light spot is displaced in the outer circumferential direction, and 4
If the pattern of the light intensity distribution within the light spot formed on the light receiving surface of the split type light receiving element 1 is displaced, for example, in the direction from element 1a to 1d (to the right in the figure), the device shown in FIG. Similarly, waveform shaping output p and inverted output p
- lags behind the phases of the waveform shaping output r and the inverted output r- by an angle corresponding to the amount of displacement of the information detection light spot.

Then, the knobs 13 and 14 of the D-type flip-flop 70 in the phase difference detection circuit 10 are set for a time corresponding to the angle change, and the D-type flip-flops 11 and 1
2 remains in the reset state. As a result, only the positive phase input y of the negative phase input It depends on the amount of displacement of the detection light spot. A pulse of positive polarity having a pulse width is output, and the level of the tracking error signal e becomes positive, and its absolute value becomes a value corresponding to the displacement of the information detection light spot.

In the above operation, even if the position of the light spot formed on the light receiving surface of the 4-split type light receiving element 1 is displaced and the amplitude of each output of the elements 1a to 1d becomes unbalanced, the variable gain amplifier circuits 21 to 24 Since the gain of each of the outputs of the variable gain amplifier circuits 21 to 24 changes depending on the outputs of the level detection circuits 25 to 28, the outputs of the adder circuits 4 and 7 are adjusted so that the signal levels of the outputs of the variable gain amplifier circuits 21 to 24 are approximately equal to a predetermined value. The levels of the output components of the elements 1a to 1d can be made equal to each other. Furthermore, two elements 1a and 1b1 are arranged at symmetrical positions with respect to the straight line β.
The phase difference between the outputs of the two variable gain amplifier circuits 21 and 23, 22 and 24 corresponding to the outputs of 1C and 1d does not change depending on the position of the light spot formed on the light receiving surface. There is no phase difference between the outputs of 7,
Does an offset occur in the tracking error signal e?
− can be prevented.

FIG. 2 is a block diagram showing another embodiment of the present invention, in which a four-division light receiving element 1, buffer amplifiers 2.3, 5.6
．． Addition circuit 4.7. The waveform shaping circuit 8.99 and the phase difference detection circuit 10 are connected in the same manner as in the apparatus shown in FIG. However, in this example, the buffer amplifier 2.3.5
．． 6 are supplied to each of the level detection circuits 25 to 28 and each of the variable resistance circuits 29 to 32.

The two variable resistance circuits to 32 are configured so that their resistance values change depending on the level of each output from the level detection circuits 25 to 28. The outputs of the variable resistance circuits 29 and 30 are supplied to the adder circuit 4 and are added and combined. Further, the outputs of the variable resistance circuits 31 and 32 are supplied to an adder circuit 7 and are added and combined.

Note that these adder circuits 4 and 7 each include two input resistors R1 and R2, R3 and R4, and operational amplifiers 33 and 34.
and feedback resistors Rs and Rs.

In the above configuration, if the resistance values of the variable resistance circuits 29 and 30 are Ra and Rb, respectively, then in the adder circuit 4, each output of the buffer amplifiers 2 and 3 has a coefficient Rs / (R
+ +Ra) and R5/(R2+Rb), and then adding them together to generate a signal. Similarly,
The resistance values of variable resistance circuits 31 and 32 are RC and R, respectively.
d, in the adder circuit 7, the buffer 7 amplifier 5.
Coefficients 86/(R3+RC) and R6/(
A signal is generated by multiplying each of R3+Rd) and then adding them. Therefore, even if the position of the light spot formed on the light-receiving surface of the four-part light-receiving element 1 is displaced and the amplitudes of the outputs of the elements 1a to 1d become unbalanced, the elements output from the adder circuits 4 and 7 1a to 1d
The levels of each output component of can be made equal to each other,
Similar to the device shown in FIG. 1, it is possible to prevent an offset from occurring in the tracking error signal e.

As detailed above, the tracking error signal generating device according to the present invention generates a level detection signal according to the signal level of each output of the four light receiving areas of the four-split type light receiving element, and After controlling the signal levels of the output components of the four light-receiving regions among the outputs of the two adding means that add the outputs of two pairs of light-receiving regions that are symmetrical with respect to the intersection of two straight lines dividing the element, using a level detection signal, Since the configuration is such that a signal corresponding to the phase difference between the outputs of the two adding means is generated as a tracking error signal, even if the position of the light spot formed on the light receiving surface of the 4-split type light receiving element is displaced, 4 By adding the outputs of two pairs of elements that are symmetrical with respect to the intersection of two straight lines that divide the two elements, and making the levels of the output components of each element in the two signals equal to each other, the position between the two signals can be calculated. It is possible to prevent the phase difference from changing, and it is possible to prevent the offset of the tracking error signal from occurring.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a block diagram showing an embodiment of the present invention.
A block diagram showing a conventional tracking error signal generation device, FIG. 4 is a waveform diagram showing the operation of each part of the device in FIG. 3, FIG. 5 is a waveform diagram showing the operation of each part of the device in FIG. 3,
6 is a diagram showing the position of a light spot formed on the light receiving surface of the 4-segment type light-receiving element 1, and FIG. 7 is a diagram showing the position of the light spot formed on the light-receiving surface of the 4-segment type light-receiving element 1. FIG. 8 is a waveform diagram showing the outputs of the elements 1a to 1d when the elements 1a to 1d move. FIG. It is a diagram. Explanation of symbols of main parts 1... 4-split type light receiving element 4.7... Addition circuit

Claims (3)

[Claims] (1) Two beams that intersect with each other at a point near the center of the intensity distribution of reflected beams obtained from an optical system that irradiates a light beam onto the recording surface of a recording medium to form a light spot for reading or writing information. Adding the outputs of a light-receiving element having four light-receiving areas divided by a straight line and two pairs of light-receiving areas arranged at symmetrical positions with respect to the intersection of the two straight lines among the four light-receiving areas. A tracking error signal generation device that includes at least two adding means for generating a tracking error signal as a tracking error signal according to a phase difference between each output of the two adding means,
level detection means for generating a level detection signal according to the signal level of each output of the four light receiving areas, and a signal of each output component of the four light receiving areas being output from the two adding means based on the level detection signal; A tracking error signal generation device comprising: level control means for controlling a level. (2) The tracking according to claim 1, wherein the level control means is comprised of a variable gain amplification circuit that amplifies each output of the four light receiving areas with a gain according to the level detection signal. Error signal generator. (3) The level control means comprises a variable resistance circuit connected in series to the input resistance of the addition means and whose resistance value changes according to the level detection signal. tracking error signal generation device.