JP2001195761A - Tracking error controller for optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tracking error controller causing no dead zone even when a position at which an optical disk medium is irradiated with convergent laser approaches on-track. SOLUTION: This tracking error controller is provided with a path for binarizing an error signal obtained from a quadripartite photo-detector 11 detecting a reflection beam from the optical disk by comparators 13a-13d and delaying one side between the signals obtained from a pair of photo-detectors A, B existing in a vertical relation for the tangential direction of a track, and existing in the position in front in the advance direction of the track through a first delay device 14a, and a path for delaying one side between the signals obtained from a pair of photo-detectors C, D existing in the vertical relation for the tangential direction of the track, and existing in the position backward in the advance direction of the track through a second delay device 14b on the same tangential side as the path delaying through the first delay device 14a, and this controller generates an output of a phase comparator in optional width even in the case of approaching the on-track, and detects the stable tracking error signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tracking error control device for an optical disk.

[0002]

2. Description of the Related Art A conventional optical disk tracking error control apparatus is configured as shown in FIG. In FIG. 4, reference numeral 11 denotes a four-divided light-receiving element in which a light-receiving part is divided into four parts;
2a, 12b, 12c, 12d are current-to-voltage converters, 13
a, 13b, 13c, 13d are comparators, 15a,
15b is a phase comparator, 16 is an adder, and 17 is a low-pass filter.

A conventional tracking error control device for an optical disk irradiates a convergent laser beam onto an optical disk medium, collects the reflected light, detects the reflected light, and outputs the error signal as a current. The four outputs are converted into voltage signals by the current-to-voltage converters 12a to 12d, respectively. Each output is output from comparators 13a to 13
The output of the comparator 13a and the comparator 13b are compared by the first phase comparator 15a, and the outputs of the comparator 13c and the comparator 13d are compared by the second phase comparator 15b.

[0004] Each of the phase comparators 15a and 15b outputs a ternary signal as a tracking error signal. The outputs of the phase comparators 15a and 15b are added by an adder 16, and the output is integrated by a low-pass filter 17 and converted into an analog voltage. The operation of the tracking error control device thus configured will be described with reference to FIG.

FIG. 5 shows a state where the position at which the convergent laser is irradiated on the optical disk medium moves from the inner circumference to the outer circumference in the track direction. When the reflected light from the optical disk medium deviates from the on-track, a phase difference occurs in the light returning to the diagonal of the four-division light receiving element 11. The reflected light is converted into a current by the four-divided light receiving element 11 and the current-voltage converter 12
It is converted to a voltage at a to 12d. The output is obtained from the signals A and B of the four-segment light receiving element 11 which is placed in front of the track direction among a pair of light receiving elements having a vertical relation to the track tangential direction among the signals binarized by the comparator. The obtained signals are as indicated by A1 and B1 in FIG. 5, and the phase difference increases as the irradiation position of the laser beam departs from the on-track position. During on-track, the signal waveforms have the same phase relationship. The ternary pulse width of the signals A1 and B1 passed through the phase comparator 15a becomes narrower as the track approaches on-track, and its output waveform becomes like E1.

Similarly, signals obtained from C and D of the four-division light receiving element 11 placed rearward in the track direction are as shown by C1 and D1 in FIG. The phase difference increases as the irradiation position deviates. The signals of C1 and D1 are also applied to the phase comparator 15b.
Also, the ternary pulse width of the signal passing through becomes narrower as it approaches on-track, and its output waveform becomes like F1.

The signals E1 and F1 are added by the adder 16 to form G1. The G1 signal is integrated via the low-pass filter 17, and the positional relationship between the middle point of the tracking error signal and the on-track such as H1 is detected as a tracking error signal as a voltage value.

[0008]

However, in the above-described conventional configuration, the pulse width of the output signal of the phase comparator becomes narrower as approaching on-track, so that the operation speed of the phase comparator is limited and the vicinity of the on-track is limited. , And a dead zone K occurs in which the tracking error signal does not respond to the track position.

Therefore, the on-track information is stable,
In addition, there is a problem that accurate detection cannot be performed. The present invention solves the above-mentioned conventional problems. Even when the position at which the converging laser is irradiated on the optical disk medium approaches on-track, a stable tracking error signal is generated in high-speed double-speed reproduction without generating a dead zone. It is an object of the present invention to provide a tracking error control device that can detect the tracking error.

[0010]

According to a first aspect of the present invention, there is provided a tracking error control apparatus for an optical disk, comprising: a divided light receiving element for irradiating an optical disk medium with a convergent laser and condensing and detecting reflected light; An optical disc apparatus for binarizing outputs of the divided light receiving elements and comparing a phase of outputs of a pair of light receiving elements perpendicular to a track tangential direction among the binarized signals to detect a tracking error signal, A delay unit for delaying one signal is provided at a stage preceding the phase comparison.

According to a second aspect of the present invention, in the optical disk tracking error control apparatus, a controller for changing a delay amount of the delay unit according to a linear velocity of the reproduction signal is provided. . According to a third aspect of the present invention, there is provided a tracking error control apparatus for an optical disk, wherein the optical disk medium is irradiated with a convergent laser to collect and detect reflected light, and the output current of the four-division light receiving element is converted into a voltage. Four current-to-voltage converters, four comparators for binarizing the outputs of the four current-to-voltage converters,
A first delay for delaying one of the outputs of the pair of light receiving elements in a vertical relationship to the track tangential direction among the output signals of the two comparators on the side of the light receiving element placed forward with respect to the track direction; One of the output signals of the four comparators and one of the output signals of the pair of light receiving elements which are perpendicular to the track tangential direction among the output signals of the four comparators. A second delay unit for delaying the signal on the tangential side with the path delayed through the delay unit, and an output of the first delay unit and a light receiving element disposed forward with respect to the track direction. A first phase comparator for comparing the phase of the signal with the other signal on the side, and a phase comparison between the output of the second delay unit and the other signal on the side of the light-receiving element placed rearward in the track direction. A second phase comparator An adder that adds an output of the first phase comparator and an output of the second phase comparator, and a low-pass filter that integrates an output of the adder and outputs a tracking error signal. Features.

According to a fourth aspect of the present invention, there is provided an optical disk tracking error control apparatus according to the third aspect.
A controller for changing the delay amount of the second delay unit according to the linear velocity of the reproduction signal is provided. With this configuration, the pulse width of the output signal of the phase comparator increases as it approaches on-track, so that the output pulse width of the phase comparator near on-track is kept at a certain value or more, and the operation speed of the phase comparator is limited. It is possible to generate an accurate tracking error signal during on-track without being performed.

Further, by controlling the delay amount of the delay unit to an amount proportional to the linear velocity of the track of the optical disk medium, it is possible to widen the output pulse width of the phase comparator near the on-track in accordance with the reproduction speed. Thus, stable tracking error control can be performed at the time of high-speed reproduction such as 8 × speed or more in a DVD-ROM.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. (Embodiment 1) FIGS. 1 and 2 show (Embodiment 1) of the present invention. FIG. 1 shows a tracking error control device according to the present invention, and components having the same functions as those in FIG.

In FIG. 1, a first delay 14a is provided between the output of the comparator 13a and the input of the phase comparator 15a.
And the output of the comparator 13b and the phase comparator 1
It differs from FIG. 4 only in that a second delay 14b is interposed between the inputs of 5b. The operation of the tracking error control device for the optical disk of the present embodiment configured as described above will be described below.

FIG. 2 shows a state where the position at which the convergent laser is irradiated on the optical disk medium moves from the inner circumference to the outer circumference in the track direction. When the reflected light from the optical disk medium deviates from the on-track, a phase difference occurs in the light returning to the diagonal of the four-division light receiving element 11. The reflected light is converted into a current by the four-divided light receiving element 11 and converted into current by the voltage converters 12a to 12a.
It is converted to a voltage in 2d. Its output is the comparator 13
Of the signals binarized by a to 13d, a pair of light receiving elements which are perpendicular to the tangential direction of the track are obtained from A and B of the four-divided light receiving element 11 placed forward with respect to the track direction. The signals thus obtained are as indicated by A1 and B1 in FIG. 2, and the phase difference increases as the irradiation position of the laser beam departs from the on-track position. At the time of on-track, the signal waveform has the same phase relationship.

Similarly, the signals C1 and D1 obtained from the C and D of the four-divided light receiving element 11 placed rearward in the track direction also have a phase difference as the irradiation position of the laser beam deviates from the on-track position. Becomes larger. here,
The output of A1 is delayed by time t by the first delay unit 14a, and becomes I1 in FIG. Similarly, the output of D1 is delayed by the time t by the second delay unit 14b, and the output of J1 in FIG.
become that way.

The I1 and B1 signals pass through the first phase comparator 15a, and the ternary pulse width of the output signal becomes wider as approaching on-track, and the output waveform becomes as shown by E1 in FIG. If the phase difference generated as a tracking error at this time is T, the pulse width of E1 can be expressed as Tt. Similarly, the signals of C1 and J1 are also supplied to the second phase comparator 1
Via 5b, the ternary pulse width of the signal also becomes wider as it approaches on-track, and its output waveform becomes as shown by F1 in FIG. Similarly, the pulse width of F1 can be expressed as T + t.

Since the signals E1 and F1 are added by the adder 16, the pulse width of the output is G1 = (T + t).
+ (T-t), and the first and second delay units 14a, 14a,
The phase difference delayed at 14b is canceled and can be extracted as a true error signal, as shown by G1 in FIG. The G1 signal is integrated via the low-pass filter 17, and the positional relationship between the midpoint of the tracking error signal and the on-track like H1 in FIG. 2 is detected as a tracking error signal as a voltage value.

As described above, the first and second delay units 14a, 1
By using 4b, the output pulse widths of the phase comparators 15a and 15b can be increased as they approach on-track. Therefore, it is possible to easily reduce the dead zone near the on-track of the tracking error signal in high-speed reproduction without improving the operation speed of the phase comparator in which the circuit delay occurs most.

(Embodiment 2) FIG. 3 shows (Embodiment 2) of the present invention, and differs from (Embodiment 1) in the following points. The first and second delay units 1 of this (second embodiment)
Reference numerals 4a and 14b denote delay devices which can vary the delay amount.
Is a controller for controlling the amount of delay of the delay units 14a and 14b in proportion to the linear velocity of tracking of the optical disk.

The operation of the tracking error control device thus configured will be described below. In the first embodiment, the first and second delay units 14a and 14d
Can be set only to the value of the shortest pit length of the RF signal component. This is because, if the setting is made more than that, the output of the delay device will not be generated. Therefore, it can be set only to a value corresponding to the maximum reproduction speed of the optical disk device.

However, it is possible to arbitrarily change the delay amounts of the first and second delay units 14a and 14d as in (Embodiment 2), and make the variable amount proportional to the linear velocity of tracking. By automatically controlling the delay amount by the controller 18, the delay amount can be set to an optimum value of the reproduction speed in the optical disk device.

[0024]

As described above, the present invention increases the output pulse width of the phase comparator near the on-track by providing the delay unit after the output of the comparator. An excellent optical disk tracking error control device capable of accurate and stable tracking control can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a tracking error control device according to a first embodiment of the present invention;

FIG. 2 is a waveform chart of the embodiment.

FIG. 3 is a configuration diagram of a tracking error control device according to a second embodiment of the present invention;

FIG. 4 is a configuration diagram of a conventional tracking error control device.

FIG. 5 is a waveform chart of the conventional example.

[Explanation of symbols]

 11 Four-division light receiving element 12a-12d Current-voltage converter 13a-13d Comparator 14a, 14b First and second delay unit 15a, 15b First and second phase comparator 16 Adder 17 Low-pass filter 18 Controller

Claims (4)

[Claims] An optical disk medium is provided with a divided light receiving element for irradiating a converged laser beam and condensing and detecting a reflected light, and binarizes the output of each of the divided light receiving elements. In an optical disc apparatus for detecting a tracking error signal by comparing phases of outputs of a pair of light receiving elements which are perpendicular to a tangential direction of a track, tracking of an optical disc provided with a delay unit for delaying one signal at a stage preceding the phase comparison. Error control device. 2. The optical disk tracking error control device according to claim 1, further comprising a controller for changing a delay amount of the delay unit according to a linear velocity of the reproduction signal. 3. A four-divided light receiving element for irradiating a converging laser beam on an optical disk medium to collect and detect reflected light, four current-voltage converters for converting the output current of the four-divided light receiving element into voltages, Four comparators for binarizing the outputs of the four current-to-voltage converters; and among the output signals of the four comparators, the output of a pair of light receiving elements having a vertical relationship to the tangential direction of the track is located forward with respect to the track direction. A first delay unit for delaying one of the signals on the side of the light receiving element placed at the first position, and a track among the outputs of a pair of light receiving elements that are perpendicular to the track tangential direction among the output signals of the four comparators A second delayer for delaying a signal on the same tangential side as a path delayed via the first delayer on one side of the light receiving element placed rearward in the direction; delay A first phase comparator for comparing the phase of the output of the second delay unit with the output of the second delay device and the other signal on the side of the light receiving element placed forward with respect to the track direction. A second phase comparator for comparing the phase of the other signal on the side of the light receiving element placed behind, and an addition for adding an output of the first phase comparator and an output of the second phase comparator A tracking error control device for an optical disc, comprising: a device; and a low-pass filter that integrates an output of the adder and outputs a tracking error signal. 4. The optical disk tracking error control device according to claim 3, further comprising a controller for changing a delay amount of the first and second delay units in accordance with a linear velocity of the reproduction signal.