JPH06236567A - Tracking error detector and optical disk device equipped with the same - Google Patents

Abstract

PURPOSE:To provide an optical disk device capable of generating satisfactory tracking error signals for each of plural disks that have different track intervals from each other as the tracking error detector in an optical disk device. CONSTITUTION:A main spot as well as two sets of side spots are irradiated on an optical disk by a diffraction grating more than two surfaces. From four light receiving regions 1a to 1e, on which reflected lights of the side spots are made incident, two kinds of tracking error signals are generated by employing two sets of differential detection systems 2 and 3. At that time, the distance between the respective sets of side spots is optimally set against each of the two kinds of track intervals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc device for reproducing a signal from an optical disc on which a signal is recorded in a pit format or the like, and an optical spot for signal reproduction is correctly positioned on an information track formed on the optical disc surface. The present invention relates to a tracking error detection device that generates a tracking error signal that indicates whether or not a track error signal is generated, and in particular, the same tracking error detection device can be used for a plurality of types of optical disks with different track intervals of information tracks formed on the disk surface. The present invention relates to a tracking error detection device capable of generating good tracking error signals, and an optical disk device including the tracking error detection device.

[0002]

2. Description of the Related Art Conventionally, as a method for detecting a tracking error and generating a tracking error signal in an optical disk device such as a compact disk or a video disk,
The 3-spot method is well known. The three-spot method will be described below with reference to FIGS. 2 and 3.

FIG. 2 is an explanatory view showing a positional relationship between a light spot irradiated on the optical disc and an information track formed on the optical disc, and FIG. 3 shows a tracking error and detects a tracking error signal. It is explanatory drawing which shows the tracking error detection part which produces | generates and outputs.

In these figures, 201 is a pit and 2 is
02 to 204 are information tracks (hereinafter simply referred to as "tracks") formed as a pit string consisting of pits.
2a, 102b, 102c are light spots, 10
Reference numerals 2x, 102y, and 102z denote reflected light (reflected light from the disk surface of the light spot), 4a, 4b, and 4c, respectively, light-receiving regions that configure a photodetector, and 5 denotes a differential amplifier.

In the three-spot method, the three light spots obtained by dividing the laser light into three by the diffraction grating are arranged relative to the tracks on the optical disk as shown in FIG. Irradiation is performed as 102b and 102c.

At this time, the central light spot (hereinafter,
Main spot) 102b and main spot 1
Two light spots (hereinafter, referred to as side spots) 102a and 102c at symmetrical positions with respect to 02b.
If the distance S1 separated along the disk radial direction between each of the above and the above is set to the relationship of S1 = (T1) / 4 (Equation 1) with respect to the track interval T1, the best tracking error signal is obtained. can get.

Light spots 102a, 1 from the optical disk
02b, 102c reflected light 102x, 102y, 102
z is, as shown in FIG. 3, three light receiving regions 4a, 4b,
4c respectively. The difference between the outputs of the light receiving regions 4a and 4c is taken by the differential amplifier 5, and this becomes a tracking error signal. Further, the focus error signal and the reproduction signal are derived from the output of the light receiving region 4b (these are well-known matters, and therefore a detailed description thereof will be omitted). For example, in the case of a compact disc and its reproducing apparatus, the track interval T1 = 1.
6 μm, distance S1 = 0.4 μm.

On the other hand, as the wavelength of the laser diode has been shortened in recent years, it has become possible to narrow the light spot to a smaller diameter. As a result, reproduction of a high-density optical disc in which finer pits are formed is reproduced. Is becoming possible. Even in the tracking error detection for such a high density optical disc, if the above-mentioned distances related to the three light spots are designed and adjusted so as to satisfy the equation (1), the conventional three-spot method can be used. Can be applied.

[0009]

In the above-mentioned prior art, the track spacing T1 and the distance S1 are designed and adjusted so as to satisfy the above equation (1) for optical discs of different types having different track spacings. If so, no particular problem occurs. However, whether or not a good tracking error signal can be generated each time by using one error detecting device and applying it to optical discs of different types having greatly different track intervals without adjusting each time. For example,
There is a problem that you can't do such economic and convenient things.

FIG. 4 shows the light spot 102 shown in FIG.
a, 102b, 102c are track intervals T2 (> T1)
FIG. 6 is an explanatory diagram showing a positional relationship between a track and a light spot when the optical disc of FIG. FIG. 5 is a waveform diagram showing the outputs of the light receiving regions 4a and 4c and the differential amplifier 5 (FIG. 3) when the light spots 102a, 102b and 102c of FIG. 4 are crossed with respect to the track.

In FIG. 5, r1 to r6 indicate the positions of the main spot 102b in FIG. 4 in the disk radial direction (direction crossing the track), for example, the position r2.
Is track 205, position r5 is track 206, position r
6 corresponds to each position of the track 207. In this case, the output waveforms of the light receiving regions 4a and 4c in FIG. 3 do not have sinusoidal waveforms as shown in FIG.
When 2 is significantly wider than T1, the waveform has a flat portion.

The phase difference between the outputs of the light receiving regions 4a and 4c is not 180 ° but 180 ° or less. Therefore, the tracking error signal output from the differential amplifier 5 becomes zero at the positions r3 to r4 as shown in FIG. 5, and a normal tracking error signal cannot be obtained.

FIG. 6 shows the light spot 102 shown in FIG.
a, 102b, 102c are track intervals T3 (<T1)
FIG. 6 is an explanatory diagram showing a positional relationship between a track and a light spot when the optical disc of FIG. FIG. 7 is a waveform diagram showing the outputs of the light receiving regions 4a and 4c and the differential amplifier 5 (FIG. 3) when the light spots 102a, 102b and 102c of FIG. 6 are crossed with respect to the track.

In FIG. 7, r7 to r9 indicate the positions of the main spot 102b in the disk radial direction in FIG. 6, for example, the position r7 is the track 208 and the position r.
8 corresponds to each position of the track 209, and position r6 corresponds to each position of the track 210. The output waveforms of the light receiving regions 4a and 4c in FIG. 3 are sinusoidal waveforms as shown in FIG. 7 in this case, but the amplitude G2 of the obtained signal is smaller than the amplitude G1 in FIG. Become.

Further, as shown in FIG. 7, the phase difference between the outputs of the light receiving regions 4a and 4c is not 180 ° but 180 ° or more. Therefore, the tracking error signal which is the output of the differential amplifier 5 has a very small amplitude as shown in FIG. 7, and the amplitude becomes almost zero at S1 = (T3) / 2 (Equation 2).

Therefore, assuming a tracking error detection device designed and adjusted to generate a good tracking error signal with respect to the track interval T1, in that device, an optical disc whose track interval is significantly different from T1 is used. It will be appreciated that, on the other hand, a good tracking error signal cannot be generated.

An object of the present invention is to solve the above problems and to apply it to a plurality of types of optical discs having different track intervals by two times or more with one tracking error detecting device and without adjusting each time. Another object of the present invention is to provide an economical tracking error detection device which can generate good tracking error signals.

[0018]

In order to achieve the above object, a tracking error detecting apparatus according to the present invention comprises a light source such as a laser diode, a collimating lens, a diffraction grating having two or more surfaces, or ± 2nd order with one surface. In addition to the diffraction grating that generates higher-order diffracted light of a higher light intensity with a predetermined light intensity, the beam splitter, the objective lens, the detection lens, and the light-receiving area where the main spot reflected light is incident, side spot reflected light is also generated. The photodetector has at least four incident light-receiving regions, and at least two differential amplifiers that take two of the light-receiving regions as a set and take a difference signal.

[0019]

[Operation] The laser light emitted from the laser diode is
The light is incident on a diffraction grating having two or more surfaces or a diffraction grating that generates high-order diffracted light of ± second-order light or more with a predetermined light intensity through a collimator lens, and becomes parallel light in at least five directions. By passing the collimated light through the beam splitter and the objective lens, at least one main spot and two side spots separated by a first distance from the main spot as one set (pair) are formed on the optical disc. At least five light spots are irradiated, one side spot and a second side spot that is a pair (pair) of two side spots that are similarly separated by the second distance.

The reflected light from the optical disk is an objective lens,
The light is incident on a photodetector having a light-receiving region through which the main spot reflected light is incident and at least four light-receiving regions through which the side spot reflected light is incident through the beam splitter and the detection lens. The two light-receiving region outputs on which the first side spot reflected light is incident are input to the first differential amplifier as a set, and the first tracking error signal which is the difference signal is obtained.

Similarly, two light receiving region outputs on which the second side spot reflected light is incident are input to the second differential amplifier as a set, and a second tracking error signal which is a difference signal is obtained. . This results in at least two tracking error signals from at least four side spots.

As described above, the first distance between the main spot and the side spot is optimized for the first track spacing, and the second distance is set for the second track spacing. By setting it to be optimal,
Even if the first and second track intervals are significantly different, it is possible to generate good tracking error signals. Further, by using the third and subsequent side spots in the same manner, it is possible to generate good tracking error signals even when the track intervals differ by three or more types.

[0023]

Embodiments of the tracking error detecting device according to the present invention will be described below. FIG. 1 is a schematic diagram showing a detection unit of a tracking error detection device as a first embodiment of the present invention, and FIG. 8 is a schematic diagram showing an optical unit of the tracking error detection device.

In these figures, 101v, 101
w, 101x, 101y and 101z are reflected lights of light spots from the optical disk, 1a, 1b, 1c and 1 respectively.
d, 1e are light-receiving regions, 2, respectively, which constitute a photodetector.
Reference numeral 3 is a differential amplifier, 10 is a light source such as a laser diode, 11 is a collimating lens, 13 and 14 are diffraction gratings, 15 is a beam splitter, 17 is an objective lens, 200 is an optical disk on which pits are formed, and 18 is The detection lens 1 is a photodetector having the light receiving regions 1a to 1e.

Further, FIGS. 9A and 9B respectively show
FIG. 10 is an explanatory diagram showing a positional relationship between a light spot irradiated on an optical disc and a track in the embodiment of the present invention.
Reference numerals 1a, 101b, 101c, 101d and 101e are light spots.

First, in FIG. 8, the emitted light emitted from the light source 10 becomes parallel light 103 by the collimator lens 11 and enters the diffraction gratings 13 and 14. Here, the diffraction gratings 13 and 14 are designed so as to suppress the generation of high-order diffracted light of ± 2nd-order light or higher. Further, for example, the ratio of the diffraction angles of the diffraction gratings 13 and 14 is designed to be 2: 3 so that the diffracted parallel light beams do not overlap. As a result, the light that has passed through the diffraction grating 13 is split into parallel light in three directions, and the subsequent diffraction grating 14 splits the light in three directions to split a total of nine directions. The collimated light is beam splitter 15, objective lens 1
It is irradiated onto the optical disc 200 as a light spot 101 via the beam line 7.

The light spot 101 applied to the optical disk 200 has a spot arrangement as shown in FIG. 9A or 9B when viewed in detail. The above-mentioned diffraction grating 13,
Of the total nine light spots obtained by 14, the four light spots corresponding to the parallel light in which the ± first-order light of the diffraction grating 13 is diffracted by the diffraction grating 14 in the ± 1st order are
Since it is not directly related to the operation of this embodiment, illustration thereof is omitted,
Only five light spots that are directly related are shown in FIG. 9 (a) or (b).

Further, in FIG. 9 (a) or (b),
A distance P along the disc circumferential direction between the main spot 101c and the side spot 101b (or 101d).
3, main spot 101c and side spot 101
The ratio of a (or 101e) to the distance P4 along the disc circumferential direction is approximately 2: 3, which is the same as the diffraction angle ratio of the diffraction gratings 13 and 14.

Here, the distance S1 between the main spot 101c and the side spot 101d (or 101b) separated along the disc radial direction, and the main spot 10
1c and the side spot 101e (or 101a) are separated by a distance S2 along the disc radial direction with respect to the track spacing T1 shown in FIG. 9A and the track spacing T2 shown in FIG. 9B. Then, the diffraction gratings 13 and 14 are designed and adjusted so that S1 = (T1) / 4 (Equation 3) and S2 = (T2) / 4 (Equation 4), respectively.

As a result, the side spots 101b, 1
01d can be optimally arranged with respect to the track interval T1 shown in FIG. 9A, and the side spots 101a and 101e can be optimally arranged with respect to the track interval T2 shown in FIG. 9B. Each light spot 101a, 101b,
101c, 101d, and 101e are reflected light 10 on the light receiving areas 1a, 1b, 1c, 1d, and 1e shown in FIG. 1, respectively.
1v, 101w, 101x, 101y, 101z are introduced.

In FIG. 1, the distance P1 between the light receiving areas 1b and 1c and the distance P between the light receiving areas 1a and 1c.
The ratio of 2 is the ratio of diffraction angles of the diffraction gratings 13 and 2: 2: 3.
Is almost equal to. Of the light receiving areas corresponding to the side spots, the outputs of the light receiving areas 1b and 1d are input to the differential amplifier 2, and the first tracking error signal 1 is obtained as a difference signal of (1b output)-(1d output). Light receiving area 1
The outputs of a and 1e are input to the differential amplifier 3, and the second tracking error signal 2 is obtained as a difference signal of (1e output)-(1a output). A focus error signal and a reproduction signal are derived from the output of the light receiving area 1c.

As described above, for the optical disc having the track interval T1, the tracking error signal 1 is transmitted to the track interval T1.
Tracking error signal 2 for 2 optical discs,
By switching and outputting by a switching means (not shown), a good tracking error signal can be generated for both optical disks.

FIG. 10 is an explanatory view showing another example (different from that of FIG. 9) of the positional relationship between the light spot irradiated on the optical disk and the track as a main part of another embodiment of the present invention. Is. Only parts different from those shown in FIG. 9 will be described below.

In FIG. 9, in both (a) and (b), the track 203 (2) on which the main spot 101c is irradiated.
06), a virtual line connecting the side spots 101b and 101d (passes the main spot 101c)
And the virtual line connecting the side spots 101a and 101e (passing the main spot 101c), the side spots 101a to 101e
Was placed.

On the other hand, in the example of FIG. 10, in both (a) and (b), the side spot 1 is applied to the track 203 (206) irradiated with the main spot 101c.
Virtual line connecting 01b and 101d (main spot 1
01c)) and side spots 101a and 10
The side spots 101a to 101e are arranged so that an imaginary line connecting 1e (passing through the main spot 101c) is inclined in the same direction.

As shown in FIG. 10, in this case also, the main spot 101c and the side spot 101d (or 101)
b) the distance S1 along the radial direction of the disc
And main spot 101c and side spot 101e
(Or 101a), the distance S2 separated along the disk radial direction is the track spacing T shown in (a) of FIG.
1, with respect to the track interval T2 shown in FIG.
The diffraction gratings 13 and 14 (FIG. 8) are designed and adjusted so as to satisfy the equations (3) and (4), respectively.

FIG. 11 is a schematic diagram showing the structure of the detection unit of the tracking error detection device suitable for the light spot arrangement shown in FIG. 11, the same functional parts as those in FIG. 1 are designated by the same reference numerals.

Here, the side spots 101b and 10b
A virtual line connecting 1d and side spots 101a and 1a
The virtual line connecting 01e is the main spot 101c.
Since the side spots 101a to 101e are arranged so as to be inclined in the same direction with respect to the track irradiated with, the polarity of the signal input of the differential amplifier is as shown in FIG.
Unlike that shown in, it becomes as follows.

That is, in FIG. 11, the outputs of the light-receiving regions 1b and 1d of the light-receiving regions corresponding to the side spots are input to the differential amplifier 2 and are (1b output)-(1d output).
As the difference signal, the first tracking error signal 1 is obtained. The outputs of the light receiving areas 1a and 1e are input to the differential amplifier 3, and the second tracking error signal 2 is obtained as a difference signal of (1a output)-(1e output) (this is shown in FIG.
That is different from (1e output)-(1a output), which means that the polarities of signal inputs are reversed.

In the embodiment described above, FIG.
Although the diffraction gratings 13 and 14 shown in (1) are treated as two independent diffraction gratings, this embodiment can also be realized by using a diffraction grating in which a grating groove for two surfaces is formed in one diffraction grating. For example, a diffraction grating with grating grooves formed on both sides of one substrate,
Alternatively, even if a diffraction grating constituted by a series of parallelogram grids on one surface of one substrate is used, the diffraction grating shown in FIG.
A light spot having the arrangement shown in is obtained.

However, in these cases, when designing the diffraction grating, it is necessary to determine in advance the angle between the grating grooves or the internal angle of the parallelogram according to the ratio of the track intervals T1 and T2. , The distances S1 and S
Independent adjustment of 2 is not possible. However, on the contrary, there is also an advantage that only one of the distances S1 and S2 needs to be adjusted at the time of adjusting the diffraction grating.

FIG. 12 is a schematic view showing a cross section of a diffraction grating used in the second embodiment of the present invention. The diffraction gratings 13 and 14 in the first embodiment are designed so that the generation of high-order diffracted light of ± 2nd order light or more is suppressed to a low level. However, the present diffraction grating 19 shown in FIG. ± 2
Design to generate diffracted light up to the next light.

In FIG. 12, groove width D2 and groove pitch D3
Is, for example, D2 / D3 = 0.33 (Equation 5), the ± first-order light 105 diffracted by the diffraction grating 19
The ratio of the light intensities of b and 105d and the ± secondary lights 105a and 105e is 4: 1. Further, the ratio of the 0th order light 105c and the ± 1st order lights 105b and 105d is set to a desired value according to the groove depth D1.

As a result, the light that has passed through the diffraction grating 19 is split into parallel light in at least five directions, the angles of which differ by θ. Although the description has been given here by taking the diffraction grating having a rectangular groove as an example, the shape of the grating is not particularly limited, and may be a trapezoidal groove or a triangular groove.

FIG. 13 is a schematic view showing an optical portion of a tracking error detecting device according to the second embodiment of the present invention, and FIG.
The same functional parts as those in FIG. In FIG. 13, 19 is the diffraction grating shown in FIG. 12, and 20 is a photodetector. The diffraction grating 19 is provided between the collimator lens 11 and the beam splitter 15 instead of the diffraction gratings 13 and 14 (FIG. 8). Diffraction grating 1
The light that has passed through 9 is split into parallel light in at least five directions, and is irradiated onto the optical disc 200 as a light spot 106 via the objective lens 17.

The light spots applied to the optical disc 200 are arranged as shown in FIG. 14 (a) or (b). Note that, in FIG. 14, among the light spots obtained by the diffraction grating 19, the spots due to the diffracted light of higher orders of ± 3rd order or more are omitted. A distance P5 along the disc circumferential direction between the main spot 106c and the side spot 106b (or 106d) and a distance P6 along the disc circumferential direction between the main spot 106c and the side spot 106a (or 106e). The ratio of and is the diffraction grating 1
The angles of the parallel light in the five directions obtained in 9 are equal to θ, so that the ratio is 1: 2.

The distance S1 between the main spot 106c and the side spot 106d (or 106b) along the disc radial direction, and the main spot 106
Similarly, the ratio between c and the side spot 106e (or 106a) and the distance S2 separated along the disc radial direction is also 1: 2.

Therefore, if the track interval T1 shown in FIG. 14A and the track interval T2 shown in FIG. 14B are T1 = (T2) / 2 (Equation 6), the distance S1 is obtained. By adjusting the diffraction grating 19 so as to satisfy the above equation (3) or S2 above the equation (4), respectively.
b and 106d are track intervals T1 shown in FIG.
In contrast, the side spots 106a and 106e are shown in FIG.
The optimum arrangement can be made with respect to the track interval T2 shown in (b).

FIG. 15 is a schematic diagram showing a detection unit of a tracking error detection device according to the second embodiment of the present invention. Each light spot 106a, 106b, 106c, 10
6d and 106e are light receiving regions 20a, 20b, and
Reflected light 106v, 106 on 20c, 20d, 20e
It is derived as w, 106x, 106y, and 106z.

In FIG. 15, light receiving regions 20b and 20c
The ratio of the distance P7 between the light receiving areas 20a and 20c and the distance P7 between the light receiving areas 20a and 20c is 1: 2. Of the light receiving areas corresponding to the side spots, the outputs of the light receiving areas 20b and 20d are input to the differential amplifier 2, and the first tracking error signal 1 is obtained as a difference signal of (20b output)-(20d output). The outputs of the light receiving regions 20a and 20e are input to the differential amplifier 3, and the second tracking error signal 2 is obtained as a difference signal of (20a output)-(20e output).

As described above, the present embodiment can be applied when the track interval T1 and the track interval T2 satisfy the relationship of the equation (6). According to this embodiment, one of the two diffraction gratings can be omitted, and only one of the distances S1 and S2 needs to be adjusted when adjusting the diffraction grating. Further, since it is possible to irradiate the five optical spots on the optical disc and the photodetector at equal intervals, the absolute value of the distance P8 in the disc circumferential direction between the main spot and the side spots is determined by the diffraction of two surfaces. It can be made smaller than the absolute value of P4 when a grid is used.

As a result, for example, there is an advantage that the tolerance value such as accuracy with respect to the deviation from the radius when the tracking error detecting device is moved in the radial direction of the optical disc is increased.

By the way, when the tracking error signal is generated by the difference signal of the side spots in the detecting section of the tracking error detecting device, there is actually a sensitivity variation in each light receiving area. Therefore, balance adjustment for correcting this is performed. Also, a gain adjustment is required to make the amplitudes of the first tracking error signal 1 and the second tracking error signal 2 substantially match.

FIG. 16 is a block diagram showing the configuration of the differential amplifiers 2 and 3 taking these factors into consideration. In the figure, 301, 302, 307 and 308 are IV converters 303 and 30 for converting an input current into a voltage, respectively.
4, 306, 309, 310, and 312 are amplifiers with gains K1, K2, K3, K4, K5, and K6, respectively.
Reference numerals 5 and 311 are subtractors.

Hereinafter, the case where the differential amplifiers 2 and 3 shown in FIG. 16 are applied as the differential amplifiers 2 and 3 shown in FIG. 15 will be described as an example. In the differential amplifier 2, the IV converters 301 and 302 have the light receiving regions 20b and 20 respectively.
Input the current from d and convert it to voltage. The outputs of the I-V converters 301 and 302 are input to amplifiers 303 and 304, respectively, multiplied by K1 and K2, and then subtracted by a subtractor 305.
And it becomes a difference signal.

Here, K1 and K2 are replaced by amplifiers 303 and 30.
The balance of both side spots is adjusted by setting the amplitudes of the four outputs to match. The amplifier 3
One of the gains 03 and 304 may be set to 1 and may be omitted. The output of the subtractor 305 is K3 in the amplifier 306.
It is amplified twice and becomes the first tracking error signal 1.

Similarly, in the differential amplifier 3, the light receiving region 2
The currents from 0a and 20d are I-V converters 307 and 30.
8, the amplifiers 309 and 310, and the subtracter 311 to input to the amplifier 312, which is amplified by K6 times to become the second tracking error signal 2. Where the side spot 1
06b, 106d and side spots 106a, 106e
If the light intensity ratio of 4 is, for example, 4: 1, the amplitudes of the tracking error signals 1 and 2 can be made substantially equal by setting the ratio of the gain K3 of the amplifier 306 and the gain K6 of the amplifier 312 to 1: 4. it can.

Although the IV converter, the amplifier, and the subtractor are described as independent functional blocks, it goes without saying that the circuit can have a structure in which the respective functions are combined. Absent.

FIG. 17 shows a case where the light spot 106 (106a to 106e) in FIG. 14A is entirely displaced in the disk radial direction by a distance (T1) / 2 relative to the track. Light spot 106
It is explanatory drawing which shows the relative positional relationship with respect to the track of (106a-106e).

In FIG. 17, each distance S1, S2, T1
Satisfies the relationship described above with reference to FIG. At this time, the side spots 106a and 10
Since the distance 6e separated along the radial direction of the disk corresponds to the track interval T1, the side spot 106
a and 106e are, for example, tracks 203 and 20 respectively.
4 is illuminated.

Therefore, the side spots 106a,
If 106e is used as a light spot for signal reproduction, 2
Tracks can be played back simultaneously. At this time, as the tracking error signal, the one obtained from the side spots 106b and 106d is used.
06c runs between tracks 203 and 204, and is functionally a play.

FIG. 18 is a schematic diagram showing the structure of the detection unit of the tracking error detection apparatus suitable for the light spot arrangement shown in FIG. 18, the same functional units as those in FIG. 15 are designated by the same reference numerals, and the description thereof will be omitted.

Referring to FIG. 17 and FIG. A tracking error signal is generated by the side spots 106b and 106d, but since the optical spot arrangement is shifted by (T1) / 2 in the disk radial direction (compared to that of FIG. 14A), the differential amplifier The input signal polarity of 2 is shown in FIG.
Switch to the opposite of the case.

That is, the outputs of the light receiving regions 20b and 20d are input to the differential amplifier 2, and the first tracking error signal 1 is obtained as a difference signal of (20d output)-(20b output). Further, the outputs of the light receiving regions 20a and 20e are the second
In addition to being input to the differential amplifier 3 to obtain the tracking error signal 2 of the above, the first reproduction signal 2a and the second reproduction signal 2b are respectively output from the outputs of the light receiving regions 20a and 20e.
Derive. With such a configuration, the first tracking error signal 1 and the first and second reproduction signals 2a and 2b can be obtained for the optical disc having the track interval T1.

In each of the embodiments described above, the number of light spots irradiated on the optical disc 200 is set to five.
Although described as spots, the present invention can be similarly applied when the number of light spots is five or more. In this case, by adding a diffraction grating, or by designing a diffraction grating of one surface to generate high-order diffracted light of ± 3rd order light or more with a predetermined light intensity or more, Add a number. Then, by adding the light receiving area and the differential amplifier corresponding to the added side spot,
A third or higher tracking error signal is obtained.

In the description of the optical section of the tracking error detecting device, the diffraction grating is arranged between the collimating lens 11 and the beam splitter 15, but this is used as the light source 10.
It may be arranged between the collimator lens 11 and the collimator lens 11. Further, in the optical section, the collimator lens 11 and the detection lens 18 are not essential as the constituent elements of the present invention and can be omitted.

FIG. 19 is a block diagram showing a configuration when the tracking error detecting device according to the present invention is mounted on an optical disk device and used. In the figure, 401 is a spindle motor for rotating the optical disc, 402 is an objective lens actuator for displacing the objective lens in two axial directions, and 403 is a light provided with the optical section of the tracking error detection device shown in FIG. 8 or 13. The head.

In addition, 404 is a changeover switch, 4
Reference numeral 05 is a tracking control circuit for controlling the position of the light spot in the tracking direction, 406 is an IV converter for converting the input current into voltage, 407 is a focus control circuit for controlling the position of the light spot in the focus direction, and 408 is switching. A controller that controls switching of the switch 404.

The reproduction signal and the focus error signal output from the optical head 403 are input to the IV converter 406 and the focus control circuit 407, and the objective lens actuator 402 is driven by the output of the focus control circuit. . The tracking error signal 1 and the tracking error signal 2, which are other outputs of the optical head 403, are input to the input terminal a and the input terminal b of the changeover switch 404, respectively.

The output terminal c of the changeover switch 404 is connected to the terminal a side or the terminal b side by the control signal 410. The output of the changeover switch 404 is input to the tracking control circuit 405, and the objective lens actuator 402 is driven by the output of the tracking control circuit. The reproduced signal is obtained as the output of the IV converter 406.

On the other hand, the controller 408 inputs the discrimination signal 409 for discriminating the track interval of the optical disk 200 mounted on the spindle motor 401, and the changeover switch 404 for the optical disk having the track interval T1.
Is connected to the terminal a side, and for an optical disc having a track interval of T2, a control signal 410 for connecting the changeover switch 404 to the terminal b side is output.

As a result, when the optical disk having the track interval T1 is reproduced, the tracking error signal 1 and the track interval T
Tracking control can be performed using the tracking error signal 2 when reproducing the second optical disk, and stable tracking control operation can be expected for both disks.

Here, as a method of obtaining the discrimination signal 409, (a) information indicating the track interval is recorded at a predetermined track interval in a predetermined area of the disc, and detected from the reproduction signal. In the case of a disc with a built-in cartridge, a method of providing an identification hole or the like for identifying the track interval in the cartridge and detecting this with a sensor can be considered.

[0074]

According to the tracking error detecting device of the present invention, a diffraction grating having two or more surfaces or a diffraction grating for generating high-order diffracted light of ± second order light or more with a predetermined light intensity on one surface is used. As a result, one or more main spots and four or more side spots, that is, a total of five or more light spots, can be irradiated to generate two or more types of tracking error signals from two or more sets of side spots. By setting the spot-to-spot distance of each side spot in the radial direction of the disc for each track interval, a good tracking error signal can be obtained for each of multiple types of discs whose track intervals are significantly different. Can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a detection unit of a tracking error detection device that is a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a positional relationship between a light spot and a track according to a conventional technique.

FIG. 3 is a schematic diagram showing a configuration of a tracking error detection unit according to a conventional technique.

FIG. 4 is an explanatory diagram showing another example of the positional relationship between a light spot and a track in the case of a conventional technique.

FIG. 5 is a waveform diagram showing output waveforms of a photodetector and a differential amplifier in the case of a conventional technique.

FIG. 6 is an explanatory diagram showing another example of the positional relationship between the light spot and the track in the case of the conventional technique.

FIG. 7 is a waveform diagram showing output waveforms of a photodetector and a differential amplifier in the case of a conventional technique.

FIG. 8 is a schematic diagram showing a configuration of an optical unit of the tracking error detection device according to the first embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a positional relationship between a light spot and a track according to the present invention.

FIG. 10 is an explanatory diagram showing another example of the positional relationship between the light spot and the track in the case of the present invention.

FIG. 11 is a schematic diagram illustrating another configuration example of the detection unit of the tracking error detection device that is the first embodiment of the present invention.

FIG. 12 is a schematic view showing a cross section of a diffraction grating.

FIG. 13 is a schematic diagram showing a configuration of an optical unit of a tracking error detection device that is a second embodiment of the present invention.

FIG. 14 is an explanatory diagram showing a positional relationship between a light spot and a track according to the present invention.

FIG. 15 is a schematic diagram showing a configuration of a detection unit of a tracking error detection device that is a second embodiment of the present invention.

FIG. 16 is a block diagram showing a configuration of a differential amplifier.

FIG. 17 is an explanatory diagram showing another example of the positional relationship between the light spot and the track according to the present invention.

FIG. 18 is a schematic diagram showing another configuration example of the detection unit of the tracking error detection device according to the second embodiment of the present invention.

FIG. 19 is a block diagram showing a configuration example when a tracking error detection device according to the present invention is applied to an optical disc device.

[Explanation of symbols]

1, 20 ... Photodetector, 2, 3 ... Differential amplifier, 10 ... Laser diode, 11 ... Collimating lens, 13, 14,
19 ... Diffraction grating, 15 ... Beam splitter, 17 ... Objective lens, 18 ... Detection lens, 301, 302, 307,
308 ... IV converter, 303, 304, 306, 30
9, 310, 312 ... Amplifier, 305, 311 ... Subtractor, 402 ... Objective lens actuator, 404 ... Changeover switch, 405 ... Tracking control circuit, 407
... Focus control circuit, 408 ... Controller

Front Page Continuation (72) Inventor Kuniichi Onishi, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Visual Media Research Laboratories

Claims (10)

[Claims] 1. A track formed on a disk surface is irradiated with a main spot and a pair of side spots symmetrically positioned with respect to the main spot, and an optical system including an irradiation source of the spot is used for the track. In a tracking error detection device that generates a tracking error signal that represents a deviation from a track when traveling above, from the detection output of the reflected light from the disk surface of the side spot, the side that is symmetrically positioned with respect to the main spot. A tracking error detection device characterized in that there are a plurality of pairs of spots. 2. The tracking error detection device according to claim 1, wherein only one set among a plurality of sets of tracking error signals generated from detection outputs of reflected light from the disk surface of the plurality of pairs of side spots is used. A tracking error detection device characterized in that it is selectively switched and taken out and used for tracking control. 3. A laser light source, an objective lens that receives laser light emitted from the laser light source and focuses it on a track on the optical disk surface, and a laser light focused on the track on the optical disk surface from the disk. And a separation means for separating and extracting the reflected light from the optical path at a position between the objective lens and the laser light source while the reflected light of the optical path reverses the same optical path as when it is incident and returns. In the optical system consisting of a detecting means for receiving and detecting the reflected light taken out by the above, by disposing at least two diffraction gratings in the optical path between the laser light source and the separating means, At least two pairs of a main spot and a pair of side spots symmetrically positioned with respect to the main spot are formed as the laser light focused on the track of the optical disc surface. The detection means has a light receiving area corresponding to each of the main spot and at least two pairs of side spots, and a detection output from each light receiving area of the pair of side spots corresponding to each spot. A differential amplifying means, which outputs the difference as a tracking error signal indicating a deviation from the track when the optical system travels on the track of the disk surface, is provided for each pair of the side spots. A tracking error detection device comprising at least two. 4. The tracking error detecting device according to claim 3, wherein at least ± second-order light is formed on one surface instead of the diffraction grating on at least two surfaces provided in the optical path between the laser light source and the separating means. The tracking error detecting device is provided with a diffraction grating that can generate even higher-order diffracted light. 5. The tracking error detecting device according to claim 3, wherein a main spot formed as a laser beam focused on a track of the optical disc surface and a pair of symmetrically located main spots are formed. At least two pairs of each side spot are 1
A line segment that connects two side spots that are located on a straight line or that are symmetrically located around the main spot has the same direction with respect to the track direction for the side spots that belong to any pair. A tracking error detection device characterized by being inclined. 6. The tracking error detecting device according to claim 3 or 4, wherein at least two pairs of side spots that are symmetrically positioned with respect to the main spot belong to one of the pair of side spots. The distance from each of the side spots to the position corresponding to the main spot along the radial direction of the disc is ½ of the track interval.
And the respective distances from each of the remaining two side spots belonging to the pair to the position corresponding to the main spot in the radial direction of the disc are formed on a second disc different from the disc. A tracking error detection device characterized by being equal to 1/2 of the interval. 7. The tracking error detecting device according to claim 4, wherein the diffraction grating capable of generating at least a high-order diffracted light of ± second-order light on one surface is a concave portion and a convex portion that form a grating groove. A tracking error detection device characterized in that the tracking error detection device is a diffraction grating having different widths. 8. The tracking error detecting device according to claim 3 or 4, wherein each of the differential amplifying means comprises balance adjusting means for matching respective amplitude values of detection outputs from two input light receiving regions. A tracking error detection device characterized by being provided. 9. The tracking error detection device according to claim 3, wherein at least two pairs of side spots forming a pair symmetrically to each other with respect to the main spot are provided with a first pair. The first distance, which is the distance from each of the two side spots belonging to the group to the position corresponding to the main spot along the radial direction of the disc, and each of the remaining two side spots belonging to the second pair. To a main spot equivalent position along the disk radial direction with a second distance, which is 1: 2, the differential corresponding to the first pair of side spots. The polarity of the two inputs in the amplifying means is compared with the polarity of the two inputs in the differential amplifying means corresponding to the second pair of side spots, and the tracker is inverted for tracking. By using it as an error signal, the second pair of side spots can be made to travel on different tracks corresponding to the respective side spots as reproduction spots, and reproduction signals can be obtained from both tracks. A tracking error detection device characterized by: 10. An optical disk device comprising the tracking error detection device according to any one of claims 1 to 9.