JPH0944881A - Skew detecting device and optical recording medium reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a skew detecting device capable of highly precisely detecting tilt of a recording medium by adopting a high-order spectroscopic means of a luminous flux. SOLUTION: The luminous flux emitted from a light source(LD) 15 in a prescribed direction is high-order-divided into a main luminous flux and plural sub-luminous fluxes by a beam splitter(BS) 16 and an object lens 2 to be converged on an optical disk 6. Respective return light beams of emitted main luminous flux and plural sub-luminous fluxes are led to a photodetector(PD) through the object lens 2, the BS 16 and a multi-lens 17. Information received by the PD 18 is outputted to a reproducing signal processing part 12 for reproducing the optical disk and the skew detector 13 detecting skew in the tangential direction. An optical pickup 11 is driven by a skew servo 14 according to the detection result of the skew detector 13.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. TECHNICAL FIELD OF THE INVENTION Conventional Technology (FIG. 7) Problem to be Solved by the Invention (FIG. 7) Means for Solving the Problem Embodiments of the Invention (FIGS. 1 to 6)

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a skew detecting device and an optical recording medium reproducing device, and is particularly suitable for application in detecting a tangential inclination (tangential skew) of a recording medium.

[0003]

2. Description of the Related Art Conventionally, in skew detection of an optical recording medium reproducing apparatus, a skew detecting apparatus 1 as shown in FIG.
Is used. The skew detecting device 1 includes an objective lens 2, an optical pickup 3, a skew sensor 4 including a light emitting diode and a sensor, and a guide shaft 5. The skew sensor 4 detects the skew of the optical disk by irradiating the surface of the optical disk 6 with the light flux from the light emitting diode and making the returning light incident on the sensor.

[0004]

The skew sensor 4 detects the tilt of the optical disk 6 in order to correct the skew, and the tilt of the optical disk 6 in the radial direction due to the weight of the disk itself ( Radial squeeze)
And there is a tangential slope (Tanjienshiarusukiyu). Of the two types of inclination, the skew for the radial skew can be detected with a high degree of accuracy, and thus is conventionally arranged as skew detection in the radial direction of the optical disk 6.

However, if an attempt is made to detect a skew in the tangential direction of the optical disk 6 with the skew sensor 4 composed of a light emitting diode and a sensor, there is a problem that an accurate skew cannot be obtained. Moreover, considering the dead zone and temperature characteristics of the skew sensor, the required resolution was not obtained.

Further, the tolerance of the high-density optical disk in recent years is smaller than that of the conventional optical disk because the recording density is increased. In particular, there is a problem that the tolerance of the optical disk against skiing becomes severe.

The present invention has been made in consideration of the above points, and detects the tangential inclination (tangential skew) of a recording medium with high accuracy without being affected by the dead zone and temperature characteristics of the skew sensor. It is intended to propose a skew detection device and an optical recording medium reproducing device to be obtained.

[0008]

In order to solve such a problem, according to the present invention, in a skew detecting device for detecting a tilt of a recording medium, a light beam emitted from a light source in a predetermined direction is divided into a main light beam and a plurality of sub-light beams. High-order spectroscopic means for high-order splitting into a recording medium, and light quantity detection means for respectively injecting respective return lights of the main light flux and a plurality of sub-light fluxes and detecting the light quantity of the light flux, and a sub-light flux. A signal generating means for generating a skew signal based on the skew signal and a control means for driving a movable body including the high-order spectroscopic means, the light amount detecting means and the objective lens based on the skew signal are provided.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 in which parts corresponding to those in FIG.
In, the configuration of the optical disk device 10 of the present invention is shown.
The optical disk device 10 includes an optical pickup 11, a reproduction signal processing unit 12 for reproducing a recording medium, a skew detecting unit 13 for detecting skew in the tangential direction, and a skew servo 14 for driving the optical pickup 11 according to the detection result. I'm running.

The optical pickup 11 collects the irradiation light emitted from the LD (laser diode) 15 onto the surface of the optical disk 6 via the BS (beam splitter) 16 and the objective lens 2 and the like. The reflected light reflected by is guided to a photo detector (hereinafter, referred to as PD) 18 through the objective lens 2, the BS 16 and the multi-lens 17.

In the optical disk device 10, the three-spot method is used for tracking and the astigmatism method is used for focus. The state of spot irradiation on the disk surface at this time is shown in FIG. In the three-spot method, the main beam is applied to the center of the track, and two side beams S1 and S2 are provided at positions vertically offset from each other on both sides of the main spot M1 with respect to the pit row direction. It is designed to irradiate.
The beam intervals are equal intervals X as shown in FIG. A cross-sectional view of spot irradiation on the disk surface at this time is shown in FIG.
Shown in

The reflected light of the spot irradiation on the surface of the optical disk 6 shown in FIGS. 2 and 3 is condensed on the PD 18 through the optical system. As shown in FIG. 4, the PD 18 is composed of three PDs 18a, 18b and 18c corresponding to the main spot M1 and the three side spots S1 and S2, respectively. H,
I to L. Each light receiving unit A to D, E to H, I
The skew is detected from the light reception outputs of .about.L.

The skew detection at this time is calculated for each of the side beams and the main beam by the same calculation method as for the focus error signal by the astigmatism method. Is obtained, and the tangential skew signal is obtained by subtracting the calculation result of the main beam from the difference. The skew servo drives the optical system in response to the tangential skew signal.

That is, from the light receiving outputs of the light receiving portions E to H of the PD 18b, which is irradiated with one of the side spots S1, (E
+ G)-(F + H) is calculated, and the other side spot S
(I + K)-(J + L) is calculated from the light-receiving outputs of the light-receiving units I to L of the PD 18c irradiated with 2. The difference between the values calculated from the light reception outputs of both side beams is obtained. In addition, (A + C)-(B + D) is calculated from the light receiving outputs of the light receiving parts A to D of the PD 18a to which the main spot M1 is irradiated, and the calculated value is subtracted from the difference value of both side beams to obtain the Tanjienshiarski. You signal is required.

In the above structure, the focus spot error signal having an S-shaped curve as shown in FIG. 5 is obtained at the main spot M1 of the three spots M1, S1 and S2 irradiated on the surface of the optical disc 6. Suppose The side spots S1 and S2 also obtain the same focus error signal as that of the main spot M1. Equivalently, in the side spot, if the beam interval is X and the inclination of the disk is θ, then

[Equation 1] Defocus is represented only by. The amount of differential orcus is
The skew detecting unit 13 of the optical disc device 10 detects the skew, and the skew servo 14 servos the optical pickup 11 based on the detection result. Since this defocus amount is calculated by calculation from the light receiving output of the PD 18 similarly to the focus error signal, there is no dead zone,
It has almost no temperature characteristics.

For example, when the beam interval X is 25 [μm], the disk inclination θ is 0.1 [°] (= 1.7 [mrad]), and the focus pull-in range is 10 [μm], the defocus amount is

[Equation 2] Becomes Since the signals obtained from both side spots S1 and S2 have opposite polarities, the defocus amount obtained by the equation (2) is doubled to obtain the following equation.

(Equation 3) Becomes This is 0.8 with respect to the focus range of the focus.
It is [%]. Since the control band can be low frequency, 1
It is possible to apply servo with an accuracy of about [%].
Therefore, the skew can be dramatically reduced.

According to the above construction, both side spots S
1 and S2 are respectively calculated by the same method as the method of calculating the focus error signal by the astigmatism method,
By calculating the difference between the two calculation results and further subtracting the light amount of the main spot M1 from the difference, the tangential skew of the optical disk 6 can be detected with high accuracy.

In the above embodiment, three PDs are used.
Although the detection of skew by using 18a, 18b, and 18c has been described, the present invention is not limited to this and three or more PDs may be used to detect skew by high-order light. For example, as shown in FIG. 6, five beams and five PDs 18a to 18e corresponding thereto are used to detect skew. At this time, the PDs 18a to 18e are arranged one by one between each of the three PDs 18a to 18c used in the above-mentioned embodiment, and the total number of PDs 18d and 18e is increased.
At this time, the skew detector 13 has PDs 18a to 18e.
The amount of light applied to the light receiving parts A to D, E to H, I
˜L, M, N are detected according to the received light output. By the way, it is the PD 18a that is irradiated with the main spot M1.

In the above-mentioned embodiment, when the beam is divided into three beams by grating or the like, primary light is generated,
Beam interval X is 25 [μm], disk inclination θ is 0.1
[°] (= 1.7 [mrad]), the defocus amount in the case where the pull-in range of the focus is 10 [μm] has been described, but the present invention is not limited to this, and when the beam is divided into three beams by grating or the like. It is also possible to generate not only the primary light but also a higher order light and generate an error signal with this higher order light.

Here, the case of using the nth order light will be described. Beam interval X is 25 × n [μm], disk tilt θ
Is 0.1 [°] (= 1.7 [mrad]) and the pull-in range of the focus is 10 [μm], the defocus amount is

(Equation 4) It is represented by Since both side spots output signals with opposite polarities,

(Equation 5) It is represented by

When n = 2, that is, the secondary light is used, 1.6 [%] is obtained from the formula (5) with respect to the pull-in range of 10 [μm] at the inclination of the disc of 0.1 [°]. When used, the range of pull-in is at a disk inclination of 0.1 °
For 10 [μm], it becomes 2.4 [%] from the equation (5). By thus generating the high-order light, the sensitivity of the error signal can be further improved as compared with the primary light.

Further, in the above-mentioned embodiment, the optical disc is subtracted by subtracting the difference between the error signal calculated from the light receiving output by the side spots S1 and S2 and the error signal calculated from the light receiving output by the main spot M1. Although the method of detecting the tangential inclination of 6 has been described, the present invention is not limited to this, and when a high-precision focus servo is used, subtraction is performed from the error signal calculated from the light reception output of the main spot. Instead, it is possible to detect the tangential skew of the optical disk with high accuracy only by the difference between the error signals calculated from the light receiving outputs of both side spots.

Further, in the above-mentioned embodiment, the optical disk device 10 having the tangential squeeze detecting section 12 is provided.
However, the present invention is not limited to this, and a radial skew detecting unit for detecting a tilt in the radial direction may be added together with the tangential skew detecting unit of the present invention. In this case, the inclinations of the optical disk in the tangential direction and the radial direction can be detected.

[0025]

As described above, according to the present invention, in the skew detecting device for detecting the inclination of the recording medium, the luminous flux emitted from the light source in the predetermined direction is divided into a main luminous flux and a plurality of sub luminous fluxes. Then, the high-order spectroscopic means for guiding to the recording medium and the respective returning lights of the main light flux and the plurality of sub-light fluxes are respectively incident,
A movable body including a light quantity detecting means for detecting the light quantity of the light flux, a signal generating means for generating a skew signal based on the sub-light flux, and a high-order spectroscopic means, a light quantity detecting means and an objective lens based on the skew signal. By including the driving control means, it is possible to realize a skew detecting device and an optical recording medium reproducing device capable of detecting the inclination of the recording medium in the tangential direction with high accuracy without being affected by the dead zone of the skew sensor and the temperature characteristics.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of an optical disk device for detecting tangential squeeze of the present invention.

FIG. 2 is a schematic diagram showing a state of spot irradiation on a disk surface.

FIG. 3 is a schematic cross-sectional view showing a state of spot irradiation on the disk surface shown in FIG.

FIG. 4 is a schematic diagram showing a photodetector corresponding to 3 spots.

FIG. 5 is a characteristic curve diagram showing an S-shaped curve of a focus error signal.

FIG. 6 is a schematic diagram showing the arrangement of photo detectors when five beams are used.

FIG. 7 is a schematic cross-sectional view showing a skew detecting device of a conventional optical disk device.

[Explanation of reference numerals] 1 ... skew detector, 2 ... objective lens, 3, 11
...... Optical pickup, 4 ... Skew sensor, 5 ... Guide axis, 6 ... Optical disc, 10 ... Optical disc device,
12 ... Reproduction signal processing unit, 13 ... Skew detecting unit, 1
4 ... Skewer Servo.

Claims (6)

[Claims] 1. A skew detecting device for detecting the inclination of a recording medium, wherein a light source for emitting a light beam in a predetermined direction, the light beam emitted from the light source is divided into a main light beam and a plurality of sub-light beams in high order, High-order spectroscopic means for guiding to the recording medium, and respective return lights of the main light flux and the plurality of sub-light fluxes guided to the recording medium by the high-order spectroscopic means are respectively incident, and the light amount of the light flux is changed. A light amount detecting means for detecting the light amount, a signal generating means for generating a skew signal on the basis of the sub-light flux applied to the light amount detecting means, and the high-order spectroscopic means, the light amount detecting means, and the light amount detecting means on the basis of the skew signal. A skew detection device, comprising: a control unit that drives a movable body including an objective lens. 2. The skew detecting device according to claim 1, wherein the high-order spectroscopic means is composed of a grating and / or a hologram. 3. The signal generating means comprises a detecting means for detecting an astigmatism signal from the sub-beam and an arithmetic means for calculating a skew signal based on the astigmatism signal. The skew detection device according to claim 1. 4. An optical recording medium reproducing apparatus provided with a skew detecting section for detecting a tilt of a recording medium, wherein the skew detecting section emits a light beam in a predetermined direction and the light beam emitted from the light source. Higher-order spectroscopic means for high-order splitting into a main light flux and a plurality of sub-light fluxes and leading to the recording medium, and the main light flux and the plurality of sub-light rays guided to the recording medium by the high-order spectroscopic means. Each of the return lights of (1) and (2) is input, and a light amount detecting means for detecting the light amount of the light flux, a signal generating means for generating a skew signal based on the sub-light flux with which the light amount detecting means is irradiated, and the skew signal An optical recording medium reproducing device comprising: a high-order spectroscopic means, a light quantity detecting means, and a control means for driving a movable body including an objective lens based on the above. 5. The optical recording medium reproducing apparatus according to claim 4, wherein the high-order spectroscopic means is composed of a grating and / or a hologram. 6. The signal generating means comprises a detecting means for detecting an astigmatism signal of the sub-beam and an arithmetic means for calculating a skew signal based on the astigmatism signal. The optical recording medium reproducing device according to claim 4.