JP2003045058A - Optical disk inclination detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate inclination detection signals for which the influence of objective lens shift is small with high sensitivity in any optical disk. SOLUTION: In an optical disk inclination detector converging a luminous flux on the optical disk 5 by an objective lens 4, leading the reflected light to a light receiving means 7 and detecting the inclination of the optical axis of the objective lens and the optical disk on the basis of output from the light receiving means by an inclination detection means 8, the optical disk is provided with a prepit and the light receiving means 7 is provided with a first area receiving the center part of the luminous flux in the track direction of the optical disk 5 and a second area receiving peripheral parts holding it there between and is provided with a division sensor receiving the luminous flux so as to bisect the respective areas in the radial direction of the optical disk 5. The inclination detection means 8 forms a first difference signal in the first area and a second difference signal in the second area, multiplies the first difference signal by a prescribed value k at the position of the prepit and then obtains a difference between the first difference signal and the second difference signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting an inclination between an optical disk and an optical axis of an objective lens of an optical head in an optical disk drive, and an apparatus using the method.

[0002]

2. Description of the Related Art In recent years, the density of optical disk devices has been increasing, and the higher the density, the stronger the demand for improvement in the accuracy of the optical head system. Above all, the perpendicularity between the optical disk and the optical axis of the objective lens of the optical head is strictly required. When the optical disc is tilted with respect to the optical axis of the objective lens of the optical head, the image forming performance of the light spot is significantly deteriorated. Therefore, it is necessary to detect this tilt with high accuracy and correct some performance during recording and reproduction. Is required.

The tilt of the optical disk has been conventionally detected by providing a dedicated tilt detector (so-called tilt sensor) on the optical head, but with the miniaturization of the optical disk device and the optical head, such a dedicated detector is used. Has become difficult to establish.

Therefore, there has been proposed an optical disc tilt detection method using a light receiving element in the optical system of the optical head, which does not require a dedicated tilt detector.

As such an inclination detecting method, for example, there is a method described in Japanese Patent Laid-Open No. 07-141673, and its outline will be described below.

When the optical disc is irradiated with light, when the optical disc is not tilted, the light beams diffracted by the tracks on the optical disc are 0-order light, + 1st-order light and -1st-order light.
In the far field region, they interfere uniformly with a constant phase difference, and form an intensity distribution depending on the track structure.

On the other hand, when the optical disc is tilted, so-called coma aberration occurs, and a non-uniform phase distribution occurs in the diffracted light,
As a result, a non-uniform interference intensity distribution occurs in the interference region.

That is, for example, when the optical disc is tilted by a certain amount + θ in the radial direction of the optical disc, the intensity near the center in the interference region of the 0th-order light and the + 1st-order light becomes relatively strong, while the 0th-order light and the diffracted- The intensity near the center in the interference region of the primary light becomes relatively weak. On the other hand, when a certain amount of −θ is tilted, the intensity near the center in the interference region of the 0th-order light and the diffraction + 1st-order light becomes relatively weak, while the 0th-order light and the diffraction−1st
The intensity near the center in the interference region of the next light becomes relatively strong.

Therefore, in order to detect such non-uniformity, the difference between the small area in the interference area and another portion is taken, and the difference is used as the optical disk tilt detection signal.

In this way, optical disc tilt detection that does not require a dedicated detector is realized.

[0011]

However, in the optical disc tilt detection method as in the above-mentioned conventional example, since the push-pull signal is detected to detect the tilt of the optical disc, the push-pull signal is not properly detected. The optical disk has a problem that it is difficult to detect a good tilt.

Further, the small area is 0 diffracted by the optical disk.
Since the area is smaller than the area where the light flux of the next-order light and the ± 1st-order light flux overlap, the position of the detected light flux also moves when the objective lens moves in the direction perpendicular to the track. There is also a problem that the tilt detection signal is affected by the vertical movement of the.

In consideration of the above-mentioned conventional problems, the present invention is capable of highly accurate tilt detection even on an optical disc in which a push-pull signal is not well detected, and is affected by the movement of the objective lens. An object of the present invention is to provide a difficult optical disc tilt detection device.

[0014]

In order to solve the above problems, an optical disk tilt detecting device of the present invention condenses a light beam from a light source onto an optical disk by an objective lens,
In an optical disc tilt detecting device that guides light from the optical disc to a light receiving unit, and the tilt detecting unit detects the tilt between the optical axis of the objective lens and the optical disc based on the output from the light receiving unit, the optical disc has a prepit. The light receiving means has at least a first region for receiving a central portion of a light beam in the track direction of the optical disc and a second region for receiving a peripheral portion sandwiching the central region of the light beam, and each region is provided in the optical disc. The tilt detecting means includes a split sensor that receives a light beam so as to divide the light beam into two equal parts in a radial direction, and the tilt detecting means includes a first difference signal and a second difference signal in the first region.
The second difference signal is generated in the area of, and one of the first and second difference signals is multiplied by a predetermined value at the position of the pre-pit, and then one of the difference signals is multiplied by the predetermined value. And a difference signal of the other difference signal.

Further, the optical disk tilt detecting device of the present invention is
The light flux from the light source is condensed on the optical disk by the objective lens, the light from the optical disk is guided to the light receiving means, and the tilt detecting means tilts the optical axis of the objective lens and the optical disk based on the output from the light receiving means. In the optical disc tilt detection device for detecting the optical disc, the optical disc has a pair of prepits for sample servo, and the light receiving means includes a first region for receiving at least a central portion of a light beam in a track direction of the optical disc and a peripheral portion sandwiching the first region. And a second sensor for receiving a light flux so as to divide each area into two equal parts in the radial direction of the optical disc, and the tilt detecting means includes a second sensor for detecting the light flux in the first area. 1 difference signal, second difference signal in the second region,
At the position of the pre-pit pair, after multiplying either one of the first and second difference signals by a predetermined value, between one difference signal and the other difference signal multiplied by the predetermined value. A means for obtaining a difference, the output from the inclination detecting means at the first prepit of the prepit pair and the second output of the prepit pair.
Of the pre-pit, the means for taking the sum with the output from the inclination detecting means is provided.

Further, the optical disk tilt detecting device of the present invention is
The light flux from the light source is condensed on the optical disk by the objective lens, the light from the optical disk is guided to the light receiving means, and the tilt detecting means tilts the optical axis of the objective lens and the optical disk based on the output from the light receiving means. In the optical disc tilt detecting device for detecting the optical disc, the optical disc has a groove for a tracking guide, and the light receiving means has at least a first region for receiving a central portion of a light beam in a track direction of the optical disc and a peripheral portion sandwiching the first region. A tilt sensor having a second area for receiving light, and a split sensor for receiving a light flux so as to divide each area into two equal parts in the radial direction of the optical disc, wherein the tilt detecting means has a first area in the first area. Difference signal, the second difference signal is generated in the second region, and the first and second difference signals are generated in the region where the tracking guide groove is provided.
Is a means for taking a difference between one of the difference signals multiplied by the predetermined value and the other difference signal.

With the above arrangement, the radial tilt of the optical disc can be detected.

Further, since one of the first and second difference signals is multiplied by a predetermined value and the difference between the first and second difference signals is taken, the radial direction of the objective lens is increased. It is possible to obtain the tilt detection signal in the radial direction of the optical disk, which can eliminate the influence of the movement of the objective lens and is not affected by the movement of the objective lens in the radial direction.

As the optical disc, for example, a CD,
Examples thereof include CDR, DVD, and magneto-optical disk.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a structural block diagram of an optical head according to the present invention. In the figure, 1 is a light source, 2 is an optical axis of an outward optical system, 3 is a beam splitter, 4
Is an objective lens, 5 is an optical disk, 6 is a sensor optical system,
Reference numeral 7 is a light receiving means, 8 is a tilt detecting means of the optical disc, 9 is a difference signal generating means in the tilt detecting means 8, 10 is an amplifying means for multiplying the input signal in the tilt detecting means 8 by k, and 11 is in the tilt detecting means 8. Differential signal generating means, and TILT is inclination detecting means 8
Represents the tilt detection signal generated by.

FIG. 2 is a diagram showing the light receiving area of the light receiving means 7 and the appearance of spots on the light receiving means. In the figure, the ball pattern is a light-receiving light beam spot where the 0th-order and ± 1st-order lights of the diffracted light due to pits, grooves, etc. overlap. Further, 7a, 7b, 7c, 7d, 7e, 7f (7e, 7f
Indicates a first area, and 7a, 7b, 7c, 7d become a second area), each is an independent light receiving area, and the arrow indicates the direction parallel to the track on the optical disk 5. The width in the track direction of the light receiving regions 7e and 7f (first region) is
Approximately 1 / about the spot diameter of the light beam incident on the light receiving means 7.
It has a size of 4.

The light beam from the light source 1 is emitted from the beam splitter 3
And is focused on the track of the optical disc 5 by the objective lens 4. The light flux reflected by the optical disk 5 again passes through the objective lens 4, is reflected by the beam splitter 3, and is guided to the light receiving means 7 by the sensor optical system 6. The sensor optical system 6 has an astigmatism generation means corresponding to the astigmatism method of the focus error detection method.

As shown in FIG. 2, the light beam incident on the light receiving means 7 is divided into six light receiving regions 7a to 7f and received, and the inclination of the optical disc 5 in the disc radial direction with respect to the optical axis of the optical system of the forward path of the optical head ( A signal (tilt detection signal) indicating the deviation from the vertical is generated.

Next, a method of generating the tilt detection signal will be described.

3 (a) and 3 (b) show the pre-pit portion of the optical disc and the state when the spot traces the pre-pit portion and the state of the sum signal obtained from the light receiving means 7 at that time and corresponding to the total amount of received light. FIG. In the figure, A is a traced track, 31 and 32 are spots, 21 is a clock pit, 22 is a first wobble pit, 23 is a second wobble pit, 24 is an address pit, and T1 is a trace. Spot is spot 3
At the instant of 1, T2 represents the instant at which the spot being traced is at spot 32.

In this embodiment, the clock pit 2
1. While tracing at least one of the address pits 24, the inclination detection signal is generated from the output from the light receiving means 7.

A case where the tilt detection signal is obtained at the instant T1 will be described.

FIG. 4 is a block diagram showing a circuit configuration of the inclination detecting means 7. In the figure, 20 corresponds to the amplification means 10 of FIG. 1, and TILT corresponds to TILT of FIG. The output from each light receiving area is output to the light receiving areas 7a to 7f.
Let Sa be Sb.

First, using the light receiving means 7 shown in FIG. 2, a push-pull signal PP1 in the vicinity of the center of the light-receiving spot and a push-pull signal PP2 in other areas are produced.

Each push-pull signal is PP1 = (Sa + Sb)-(Sc + Sd) PP2 = (Se-Sf) according to the circuit shown in FIG.

When the optical disk 5 is tilted, as described above, the push-pull signal mainly including the central portion of the superposition is caused by the non-uniform behavior in the superposed portion of the 0th-order diffracted light and the 1st-order diffracted light. The push-pull signal PP1 which does not include the central portion of the overlap with PP2 exhibits different behavior.

FIG. 5 is a graph plotting push-pull signals PP1 and PP2 when the optical disc is tilted. The conditions are as follows: the light source wavelength is 660 nm, the numerical aperture (NA) of the objective lens is 0.6, the track pitch is 0.54 μm,
The pit size is 0.4 μm in full width at half maximum and the pit depth is about 50 nm. In the graph, black plots (●, ■) are designed when the objective lens 4 is at the design center in the optical disc radial direction, and white plots (◯, □) are designed when the objective lens 4 is designed in the optical disc radial direction. The figure shows a case where the center is shifted by 200 μm in the outer peripheral direction. Square mark (■, □) is PP1, circle mark (●, ○) is P
P2 is shown. In the legend, Se-Sf + 200 and (Sa + Sb)-(Sc + Sd) +200. Here, the value of 200 μm is about 1 of the diameter of the objective lens 4.
It is an amount corresponding to a percentage.

Looking at the graph, each signal increases and decreases almost monotonically according to the tilt of the optical disk. At the same time, each signal has an offset due to the shift of the objective lens.

A characteristic is that the push-pull signal PP1
And the push-pull signal PP2 is different in the offset amount due to the objective lens shift. This is due to the displacement of the center of gravity of the component of the intensity distribution of the 0th-order diffracted light, which is a component that does not contribute to the intensity of interference between the 0th-order diffracted light and the ± 1st-order light in the received light beam, mainly due to the shift of the objective lens It is a thing.

Another characteristic is that the change with respect to the inclination of the disk has opposite polarities between the push-pull signal PP1 and the push-pull signal PP2. Therefore, it is expected that the inclination detection sensitivity will be improved by taking the difference between the push-pull signal PP1 and the push-pull signal PP2. This alone is a method similar to the conventional example.

Therefore, in this embodiment, a difference is set between the push-pull signal PP1 and the push-pull signal PP2 so as to cancel the offset amount due to the objective lens shift.

In FIG. 5, when there is no disc tilt,
That is, looking at each signal value at 0 mradian, Se-Sf + 200 = -0.107 (Sa + Sb)-(Sc + Sd) + 200 = -0.21
1 Se−Sf = 0 (Sa + Sb) − (Sc + Sd) = 0 Therefore, the offset amount at PP1 = −0.107 The offset amount at PP2 = −0.211 From the above, the offset amount at PP1 and the offset at PP2 The quantity ratio (= k) is about 2.0.

As described above, the value of k is determined by measuring each signal value when there is no objective lens shift and when there is a predetermined amount of shift.

Therefore, a signal is created by subtracting 2.0 times PP2 from PP1. This is the tilt detection signal according to this embodiment.

According to the circuit of FIG. 4, TILT = (Sa + Sb)-(Sc + Sd) -k (Se
-Sf).

FIG. 6 is a graph in which a value obtained by normalizing the tilt detection signal thus created by the sum Io in the mirror section is plotted against the tilt of the optical disk. In the graph, the black plot indicates that the objective lens 4 is at the design center in the radial direction of the optical disc, and the white plot indicates that the objective lens 4 is shifted by 200 μm from the design center in the radial direction of the optical disc toward the disc outer peripheral direction. It shows the time. Here, the sum Io in the mirror section is Sa + Sb + Sc + Sd + k (Se + Sf) 2 in the mirror section.

From the graph of FIG. 6, when the objective lens 4 is at the design center in the radial direction of the optical disk and the objective lens 4
It can be seen that is a signal which changes monotonically with respect to the tilt change of the optical disc which is almost the same as when the optical disc radial direction is shifted from the design center by 200 μm toward the disc outer peripheral direction.

As described above, according to this embodiment,
Since a signal that is not affected by the objective lens shift is generated from the signal that changes with respect to the tilt of the optical disc, it is possible to detect the tilt with high accuracy even in the pre-pit portion, and
It is possible to realize an optical disc tilt detection device that is not easily affected by the movement of the objective lens.

(Second Embodiment) In the present embodiment,
The structure of the optical head and the structure of the light receiving means are the same as those in the first embodiment. First, a method of generating the tilt detection signal will be described.

7 (a) and 7 (b) show a prepit portion of an optical disc, a state when a spot traces the prepit portion, and a state of a sum signal obtained from the light receiving means 7 at that time and corresponding to the total received light amount. FIG. In the figure, B is a traced track, 33 and 34 are spots, 22 is a first wobble pit, 23 is a second wobble pit, 24 is an address pit, and 25 and 26 are:
A groove for recording / reproducing an information signal, W-T1, is a traced spot at the spot 33, that is, a moment when the first wobble pit 22 is detected, and W-T2 is a traced spot at a spot 34. At a moment in
That is, it represents the moment when the second wobble pit 23 is detected. The first wobble pit 22 and the second wobble pit 23 form a pair to form a pre-pit pair for sample servo.

In the present embodiment, an inclination detection signal is generated from the output from the light receiving means 7 when the first wobble pit 22 and the second wobble pit 23 are detected.

That is, the push-pull signal PP1 in the vicinity of the center of the light-receiving spot in FIG. 2 and the push-pull signal PP2 in the other areas are created in accordance with W-T1 and W-T2. Each push-pull signal is PP1 = (Sa + Sb)-(Sc + Sd) PP2 = (Se-Sf) according to the circuit shown in FIG. PP1 WT1 and WT
The value added with 2 is (SA + SB)-(SC + SD), PP
The added value of W-T1 and W-T2 of 2 is expressed as SE-SF.

Here, the reason for performing the addition will be described.

As shown in FIG. 7A, the prepit pair for sample servo is located at a position shifted by the same value in the opposite direction relative to the track center. Therefore, when a push-pull signal is created by W-T1 and W-T2 at the time of track tracing, a tracking error of reverse polarity occurs, and the push-pull signal of either W-T1 or W-T2 is used. In that case, that is, when the tilt detection signal of the first embodiment is created, the influence of tracking error occurs. Therefore, in order to suppress the influence of the tracking error, the tracking error having the opposite polarity is canceled by the addition. In this way, it is possible to obtain a tilt detection signal that is not affected by tracking errors.

FIG. 8 shows the case of tilting the optical disc (SA
It is the graph which plotted + SB)-(SC + SD) and SE-SF. The conditions are that the light source wavelength is 660 nm, the numerical aperture (NA) of the objective lens is 0.6, and the track pitch is 0.
The pit size is 54 μm, the full width at half maximum is φ0.4 μm, and the pit depth is about 50 nm. In the graph, black plots (●, ■) are white plots (○, ■) when the objective lens 4 is at the design center in the radial direction of the optical disc.
□) indicates the time when the objective lens 4 is shifted by 200 μm from the design center toward the disc outer peripheral direction in the radial direction of the optical disc. Square marks (■, □) are (SA + SB)-
(SC + SD) and circles (●, ○) indicate SE-SF.

When the optical disc 5 is tilted, due to the non-uniform behavior in the overlapping portion of the diffracted 0th order light and the diffracted 1st order light as described above, the added value mainly includes the central portion of the overlap. The addition value of the push-pull signal and the addition value of the push-pull signal that does not include the central portion of the superposition show different behavior.

As can be seen from the graph, each signal increases and decreases almost monotonically according to the tilt of the optical disc. At the same time, each signal has an offset due to the shift of the objective lens.

As in the first embodiment, also in this embodiment, (SA + SB)-(SC + SD), SE-
A difference is taken between SFs so as to cancel the offset amount due to the objective lens shift.

In FIG. 8, when there is no disc tilt,
That is, looking at each signal value at 0 mradian, SE-SF + 200 = -0.208 (SA + SB)-(SC + SD) + 200 = -0.42
8 SE-SF = 0 (SA + SB)-(SC + SD) = 0 Therefore, the offset amount at PP1 = -0.208 The offset amount at PP2 = -0.428 From the above, the offset amount at PP1 and the offset at PP2 The quantity ratio (= k) is about 2.0.

In this way, the value of k is determined by measuring each signal value when there is no objective lens shift and when there is a predetermined amount of shift.

Therefore, (SA + SB)-(SC + SD)
The signal is obtained by subtracting SE-SF of 2.0 times.
This is the tilt detection signal according to this embodiment.

FIG. 9 is a graph in which a value obtained by normalizing the tilt detection signal thus created by the sum Io in the mirror section is plotted against the tilt of the optical disk. In the graph, the black plot indicates that the objective lens 4 is at the design center in the radial direction of the optical disc, and the white plot indicates that the objective lens 4 is shifted by 200 μm from the design center in the radial direction of the optical disc to the outer circumferential direction of the disc. It shows the time. Here, the total sum Io in the mirror section is twice the value of Sa + Sb + Sc + Sd + k (Se + Sf) in the mirror section.

FIG. 10 is a block diagram showing a circuit configuration in this embodiment in which the process for obtaining FIGS. 8 and 9 is circuitized. According to the circuit of FIG. 4 described above, the tilt detection signal is detected at the moment when the first wobble pit is detected (W-T1).
Sample-hold at, and sample-hold at the moment when the second wobble pit is detected (WT2), and add them as inclination detection signals ST1 and ST2, respectively,
The tilt detection signal TILT of this embodiment is used.

As described above, according to this embodiment,
It is possible to realize an optical disc tilt detection device that can detect the tilt with high accuracy even in the sample servo prepits of the sample servo optical disk in which the prepits are not arranged on the track and that is not easily affected by the movement of the objective lens. .

(Third Embodiment) In the present embodiment,
The structure of the optical head and the structure of the light receiving means are the same as those in the first and second embodiments. First, a method of generating the tilt detection signal will be described.

In this embodiment, an optical disc having a land portion and a groove portion is used. If the land portion or the groove portion is being traced, the inclination detection signal can be obtained without timing. In the following description, an example in which a light spot traces a land portion will be described.

FIG. 11 is a diagram showing spots tracing the land portion of the optical disk. In the figure, 3
5 is a spot, 27 is a land, and 28 is a groove.

According to the circuit shown in FIG. 4, each push-pull signal is PP1 = (Sa + Sb)-(Sc + Sd) PP2 = (Se-Sf).

When the optical disc 5 is tilted, as described above, the push-pull signal mainly including the central portion of the superposition is caused by the non-uniform behavior in the superposition portion of the diffracted 0th order light and the diffracted 1st order light. The push-pull signal PP1 which does not include the central portion of the overlap with PP2 exhibits different behavior.

FIG. 12 shows the PP when the optical disc is tilted.
It is the graph which plotted 1 and PP2. The conditions are that the light source wavelength is 660 nm and the numerical aperture (NA) of the objective lens is 0.
6. The track pitch is 1.08 μm, the groove width is 0.4 μm in full width at half maximum, and the depth is about 50 nm. In the graph, black plots (■, ●) are designed when the objective lens 4 is at the design center in the optical disc radial direction, and white plots (□, ○) are designed in which the objective lens 4 is designed in the optical disc radial direction. 200 μm from the center to the outer circumference of the disc
It shows when it is shifting. Square mark (■, □) is P
P1 and circles (●, ◯) indicate PP2.

Therefore, also in this embodiment, a difference is taken between PP1 and PP2 so as to cancel the offset amount due to the objective lens shift.

Referring to FIG. 12, when there is no disc tilt, that is, when each signal value is 0 mradian, Se-Sf + 200 = -0.032 (Sa + Sb)-(Sc + Sd) + 200 = -0.08
4 Se-Sf = 0 (Sa + Sb)-(Sc + Sd) = 0 Therefore, the offset amount at PP1 = -0.032 The offset amount at PP2 = -0.084 From the above, the offset amount at PP1 and the offset at PP2 The quantity ratio (= k) is about 2.6.

As described above, also in the present embodiment, the value of k is determined by measuring each signal value when there is no objective lens shift and when there is a predetermined amount of shift.

Therefore, k = 2.6 times as much PP2 as PP1.
Make a signal minus. This is the tilt detection signal according to this embodiment.

According to the circuit of FIG. 4, TILT = (Sa + Sb)-(Sc + Sd) -k (Se
-Sf).

FIG. 13 is a graph in which a value obtained by normalizing the tilt detection signal thus created by the sum Itop at the land portion is plotted against the tilt of the optical disk. In the graph, the black plot indicates that the objective lens 4 is at the design center in the radial direction of the optical disc, and the white plot indicates that the objective lens 4 is shifted by 200 μm from the design center in the radial direction of the optical disc toward the disc outer peripheral direction. It shows the time. Here, the total sum Itop in the land portion is Sa + Sb + Sc + Sd + k (Se + Sf) 2 in the land portion.

From the graph, it is almost the same when the objective lens 4 is at the design center in the radial direction of the optical disc and when the objective lens 4 is shifted by 200 μm from the design center in the radial direction of the optical disc to the outer peripheral direction of the disc. It can be seen that the signal is a signal that changes monotonously with a change in the tilt of the optical disc.

Needless to say, in the case of the present embodiment, the condition is that the push-pull signal as a tracking error can be detected. That is, the condition is that the track pitch (land pitch or groove pitch) is larger than the spot diameter (half-value width).

As described above, according to this embodiment,
It is possible to realize an optical disc tilt detection device that can detect tilt with high accuracy without timing in parts other than the pre-pit portion and that is not easily affected by movement of the objective lens.

[0076]

As described above, according to the present invention,
In any optical disc, it is possible to generate a tilt detection signal with high sensitivity and small influence of the objective lens shift.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an optical head according to the present invention.

FIG. 2 is a diagram showing a light receiving area of a light receiving unit 7 and a state of a spot on the light receiving unit.

FIG. 3 is a diagram showing a prepit portion of an optical disc, a state when a spot traces the prepit portion, and a state of a sum signal corresponding to the total received light amount obtained from the light receiving means 7 at that time.

FIG. 4 is a block diagram showing a circuit configuration of a tilt detecting means 7.

FIG. 5 is a graph in which push-pull signals PP1 and PP2 when the optical disc is tilted are plotted.

FIG. 6 is a graph in which a value obtained by dividing a tilt detection signal by a total sum Io in a mirror unit is plotted with respect to a tilt of an optical disc.

FIG. 7 is a diagram showing a prepit portion of an optical disc according to the second embodiment, a state when a spot traces the prepit portion, and a state of a sum signal corresponding to the total received light amount obtained from the light receiving means 7 at that time. Is.

FIG. 8 shows the difference signals (SA + S) when the optical disc is tilted.
It is a graph which plotted B)-(SC + SD) and SE-SF.

FIG. 9 is a graph in which a value obtained by dividing a tilt detection signal by a total sum Io in a mirror unit is plotted against the tilt of an optical disk according to the second embodiment.

FIG. 10 is a block diagram showing a circuit configuration according to a second embodiment.

FIG. 11 is a diagram showing spots tracing a groove area and a land portion of an optical disc.

FIG. 12 is a graph plotting PP1 and PP2 when an optical disc is tilted according to the third embodiment.

FIG. 13 is a graph in which a value obtained by dividing the tilt detection signal by the total sum Itop in the land portion is plotted against the tilt of the optical disk according to the third embodiment.

[Explanation of symbols]

1 light source 2 Optical system optical axis 3 beam splitter 4 Objective lens 5 Optical disc 6 Light receiving optical system 7 Light receiving means 8 Tilt detection means 9 Difference signal generating means 10, 20 Amplification means 11 Differential signal generating means in inclination detecting means

Continued front page    (72) Inventor Akihiro Arai             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Toru Nakamura             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Takao Hayashi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 5D118 AA13 CB03 CC12 CD04 CF03

Claims (3)

[Claims] 1. A light flux from a light source is condensed on an optical disc by an objective lens, light from the optical disc is guided to a light receiving means, and an optical axis of the objective lens is detected by an inclination detecting means based on an output from the light receiving means. In the optical disc tilt detection device for detecting the tilt with respect to the optical disc, the optical disc has pre-pits, and the light receiving means includes a first region for receiving at least a central portion of a light beam in a track direction of the optical disc and a peripheral region sandwiching the first region. A second area for receiving light from the optical disc, and a split sensor for receiving a light beam so as to divide each area into two equal parts in the radial direction of the optical disc. The first difference signal,
A second difference signal is generated in the second area, and at the position of the prepit, either one of the first and second difference signals is multiplied by a predetermined value, and then one of the two is multiplied by the predetermined value. An optical disk tilt detecting device, which is means for obtaining a difference between a difference signal and the other difference signal. 2. A light beam from a light source is condensed on an optical disk by an objective lens, light from the optical disk is guided to a light receiving means, and an optical axis of the objective lens is detected by an inclination detecting means based on an output from the light receiving means. In the optical disc tilt detection device for detecting the tilt with respect to the optical disc, the optical disc has a sample servo pre-pit pair, and the light receiving means includes a first region for receiving at least a central portion of a light beam in a track direction of the optical disc. And a second area for receiving a peripheral portion sandwiching the area, and a split sensor for receiving a light beam so as to divide each area into two equal parts in the radial direction of the optical disc, and the tilt detecting means includes: The first difference signal in the region of 1,
A second difference signal is generated in the second area, and at the position of the prepit pair, either one of the first and second difference signals is multiplied by a predetermined value, and then the predetermined value is multiplied. Means for obtaining the difference between the difference signal and the other difference signal, the output from the inclination detecting means at the first prepit of the prepit pair, and the output at the second prepit of the prepit pair. An optical disk tilt detecting device comprising means for taking a sum with an output from the tilt detecting means. 3. A light beam from a light source is condensed on an optical disk by an objective lens, the light from the optical disk is guided to a light receiving means, and an inclination detecting means detects an optical axis of the objective lens based on an output from the light receiving means. In the optical disc tilt detecting device for detecting the tilt with respect to the optical disc, the optical disc has a groove for tracking guide, and the light receiving means has a first region for receiving at least a central portion of a light beam in the track direction of the optical disc and the first region. A second area for receiving light in a peripheral portion sandwiching the area, and a split sensor for receiving a light flux so as to divide each area into two equal parts in the radial direction of the optical disc. The first difference signal in the region of
A second difference signal is generated in the second area, and in the area having the tracking guide groove, either one of the first and second difference signals is multiplied by a predetermined value, and then the predetermined value is set. An optical disc tilt detecting device, which is means for obtaining a difference between one of the multiplied difference signals and the other difference signal.