JP2000339718A - Optical detector and signal processing circuit, and optical information reproducing device using them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable to cope with increment of speed by providing a light receiving surface quadri-divided in at least one light receiving region, and by irradiating simultaneously different record information trains of three or more lines on an optical information recording medium with light beams branched to three or more lines of at least one group converged to the optical information recording medium. SOLUTION: Each detected current photoelectric-converted and detected by each light receiving surface a-d is converted into voltage by current-voltage conversion amplifier 40-43 provided in the inside of a package of an optical detector 9, and sent to an output terminal of the optical detector 9. In the same way, each output line of light receiving surface e-l is connected to current- voltage conversion amplifiers 44-51 and each a-l is outputted to 12 output terminals of the optical detector 9 respectively. Operation is performed for output signals a-d out of these signals by adders 52, 53 and a subtracter 57, a tracking signal, a focus error signal, and the like are calculated and are made control information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information reproducing apparatus (hereinafter, referred to as an optical disk apparatus) used for reproducing an information signal recorded on an optical information recording medium (hereinafter, referred to as an optical disk).

[0002]

2. Description of the Related Art An optical disk apparatus is an information recording / reproducing apparatus characterized by a non-contact, large-capacity, high-speed access, and low-cost medium. By utilizing these characteristics, it can be used as a digital audio signal recording / reproducing apparatus or a computer. It is used as an external storage device.

[0003] With the expansion of use, the miniaturization and cost reduction of optical disk devices and the increase of data transfer rate are being promoted, and miniaturization and simplification of optical heads and high-speed reproduction technology are indispensable. As means effective for miniaturization and simplification of an optical head, many configurations in which a detection optical system is provided with a diffraction grating and a hologram element are disclosed. For example, in Japanese Patent Application Laid-Open No. 8-77578, a hologram element is arranged immediately below one objective lens, and a multi-segment photodetector is provided near a laser light source, so that a tracking offset due to the displacement of the objective lens is almost generated. A configuration effective to perform tracking error signal detection by the push-pull method without any problem and to reduce the size and simplify the optical head is disclosed.

On the other hand, the amount of data recorded on an optical disk has been increasing more and more in recent years, and with the increase in the amount of data, it has been required to increase the data transfer rate during reproduction of the optical disk. Therefore, a method for increasing the speed of data reproduction by increasing the number of rotations of the optical disk, and a method for increasing the data transfer rate by simultaneously reproducing data from a plurality of tracks by using a plurality of light beams. And so on. For example, Japanese Patent Application Laid-Open No. 61-117744 discloses such a device.

[0005] Currently used optical discs can be broadly classified into two types depending on the structure of recording tracks on which information is recorded. That is, a continuous guide groove is provided in advance on the information recording surface of the disk, and a recordable disk capable of recording or erasing an information signal along the guide groove, and concave and convex pits corresponding to the information signal. The columns are two types of read-only discs formed in advance on the disc. However, the push-pull method, which is the optimal tracking error signal detection method for a recordable disk having a guide groove, is not suitable for a read-only disk without a guide groove, and conversely, the tracking error signal of a read-only disk. As a detection method, a general three-spot method or a differential phase detection method (a phase difference detection method), which has recently attracted attention, cannot be applied to a recordable disc. It was difficult to support both recordable discs and read-only discs. further,
Apart from the difference in track structure, there are various types of optical disks depending on the difference in substrate thickness and the corresponding wavelength. For example, the thickness of a disk substrate such as a CD or CD-R
The optimum laser beam wavelength for recording and reproduction at 2 mm is 780 n
DVD-ROM standardized recently in spite of m band
Alternatively, for a DVD-RAM or the like, the disk substrate thickness is 0.6
mm and the corresponding wavelength is in the 650 nm band. Therefore, D
It is practically difficult to record / reproduce data on / from a CD disk with the same optical system using an objective lens optimally designed for a VD disk due to aberrations such as spherical aberration caused by differences in disk substrate thickness and the like. .

[0006]

As described above, at present, the most appropriate tracking error signal detection method is completely different depending on the type of the optical disk. However, these optical disks are already widespread or will surely spread in the near future. Therefore, as an optical disk device, it is naturally desirable that a single device can satisfactorily cope with all of these plural types of optical disks. However, as described above, at present, there is no focus error detecting means which can obtain a good focus error signal which has a simple configuration and is free from the influence of disturbance, and a plurality of tracking error detecting means are required to cope with various optical discs. It is necessary to incorporate the optical head into one optical disk device, which is disadvantageous for downsizing the optical head itself.

On the other hand, if it is attempted to use a plurality of simultaneous data reproductions using a plurality of light beams for the purpose of speeding up the data transfer rate, the number of light spots used for signal reproduction increases, so The problem that the internal configuration of the detector and the configuration of the optical head itself are extremely large and complicated is inevitable.

In view of the above situation, the problem to be solved by the present invention is to use a simple detection optical system and a simple configuration of a photodetector to cope with the reproduction of various optical discs, while using a plurality of light beams. It is an object of the present invention to provide an optical disk apparatus which can cope with an increase in data transfer rate by simultaneous reproduction using data.

[0009]

In order to solve the above-mentioned problems, the present invention provides a semiconductor laser light source and an optical branching element for splitting a light beam emitted from the semiconductor laser light source into three or more light beams. A condensing optical system for converging the three branched light beams and irradiating a predetermined position on the optical disk with an independent light spot, and a position where each of the three light beams reflected from the optical disk is irradiated A photodetector arranged so that three light receiving areas are arranged at the same time, and each light beam emitted from the semiconductor laser light source and reflected by the optical disk is independently received by the at least one of the three light receiving areas; By subjecting the photoelectric conversion signal obtained from the photodetector to a predetermined operation, a focus error signal and a tracking error signal of the light spot irradiated on the optical disk are obtained. In the optical disk apparatus having a signal processing circuit for reproducing an information signal which signal generation and recorded on the optical disc, at least of the optical detector 1
One light receiving area is provided with a light receiving surface divided into four in a cross shape,
At least one set of the three branched light beams condensed on the optical disk is simultaneously irradiated on three different recording tracks on the optical disk.

Further, in the present invention, the signal processing circuit is provided with a tracking error detection method comprising a differential phase detection method and a focus error detection method comprising an astigmatism method.

Further, in the present invention, the signal processing circuit includes a first tracking error detection method comprising a differential phase detection method and a second tracking error detection method comprising a three spot method, and the signal processing circuit is used for the optical disk apparatus. The tracking error detection method is selected depending on the type of the optical disk to be used.

Further, in the present invention, at least two of the three light receiving regions of the photodetector have light receiving surfaces divided into four in a cross shape, and the output of each of the four light receiving surfaces is In addition, a focus error detection method including an astigmatism method is provided.

Further, in the present invention, the zero-order light, the + 1-order light, and the -1 order light of the light beam after branching in the optical branching device are provided.
The light intensity ratio of the next light is set to 1: 1 to 1: 1.

In the present invention, the detection range of the focus error signal is set between 4 μm and 7 μm.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration and operation of an optical head according to a first embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 are schematic front views of an optical head according to a first embodiment of the present invention, showing a state where different types of optical disks 7 and 14 are being reproduced. In FIG. 1, a laser light source 1 is, for example, a semiconductor laser oscillating at a wavelength of 650 nm. The emitted light beam is converted into a parallel light beam by the collimating lens 8 and reaches the diffraction grating 4. The transmitted outgoing luminous flux by the diffraction grating 4 and the 0th-order light transmitted as it is at a predetermined diffraction angle are equal to 0.
In this configuration, at least three luminous fluxes of approximately the same light amount of the + 1st-order diffracted light and the -1st-order diffracted light that separate from the next-order light are formed. These three light beams are incident on a dichroic half mirror 3 having wavelength selectivity, and after about half the amount of light is reflected on the surface, they pass through a cubic type beam splitter 5 and an objective lens 6 and, for example, a DVD-RAM disk or
The light is condensed on the recording surface of an optical disk 7 such as a VD-ROM disk to form three light spots (not shown). Further, after the light is reflected from the optical disk 7, the light reaches the dichroic half mirror 3 via the objective lens 6 and the beam splitter 5 by following the same optical path as the outward light in reverse. In the dichroic half mirror 3, about half of the returning light amount is transmitted and collected on a predetermined light receiving surface of the photodetector 9.

In FIG. 2, a light beam emitted from a laser light source 11 which is a semiconductor laser oscillating at a wavelength of, for example, 780 nm is converted into a parallel light beam by a collimating lens 12 and reaches a diffraction grating 13. The outgoing light beam transmitted through the diffraction grating 13 is separated from the 0th-order light transmitted as it is by a predetermined diffraction angle.
The light is separated into at least three luminous fluxes of approximately the same light amount of the + 1st-order diffracted light and the -1st-order diffracted light that are separated from the next light. After these three light beams enter the beam splitter 5 and are reflected therefrom, they pass through an objective lens 15 and are passed through an optical disk 1 such as a CD-ROM disk or a CD-R disk.
The light is condensed on the recording surface No. 4 to form three light spots. Further, the three light spots reflected from the optical disk 14 follow the same optical path as the forward light, and
The light is condensed on a predetermined light receiving surface of the photodetector 9 through the beam splitter 5, the dichroic half mirror 3, and the like. Here, the dichroic half mirror 3 transmits almost 100% of the 780 nm laser light.

Here, the photodetector 9 has a configuration in which at least one light receiving region composed of four light receiving surfaces is formed in a cross shape as described later. Each of the 0th-order light, the + 1st-order diffracted light, and the -1st-order diffracted light reflected from the optical disc 7 or the optical disc 14 is substantially at the center of each light receiving area, that is, at the point where the vertical and horizontal division lines in the light receiving area cross each other. And the light beam are condensed at a position where the center of intensity of the light beam substantially coincides. At this time, since each light beam is given a predetermined astigmatism when passing through the dichroic half mirror 3 which is arranged inclined with respect to the optical path, as described later, a cross-shaped light receiving area , The focus error signal is detected by the astigmatism method. Similarly, by using an output signal composed of four light receiving surfaces, it is possible to detect a tracking error signal by a push-pull method or a differential phase detection method.
Here, the astigmatism method, the push-pull method, and the differential phase detection method itself are already known, and therefore detailed description is omitted.

The objective lens 6 and the objective lens 15 are integrally held by an actuator 16, and both can be driven two-dimensionally by energizing the coil 10 from the outside. Further, an optimum objective lens can be selected according to the type of the optical disc to be reproduced.
Therefore, regardless of the type of the optical disc, the light spot can always be controlled to a desired position based on the focus error signal and the tracking error signal obtained from the photodetector 9.

Next, the light spot on the optical disk 7 will be described with reference to FIG. In this embodiment, the light spots 100 and 101 and 10
The irradiation position interval in the disk radial direction of No. 2 is DVD
-It is set so as to substantially coincide with the guide groove pitch of the DAM disk. That is, for example, the DV shown in FIG.
Three light spots 100, 10 on the D-RAM disk
When the light spot 100 of the 0th-order light is located directly above the space 301 between the guide grooves of the disk as shown in FIG.
The light spots 102 of the 1st and −1st order diffracted lights are respectively located directly above the adjacent guide grooves 300. And guide groove 3
3A or 3C is always maintained between the light spots 100, 101, and 102 even when the light spot irradiation position is relatively shifted from the light spot 100. Dripping. On the other hand, the light beam reflected by the optical disk is
Under the influence of the diffraction by the guide groove 300, a specific intensity distribution pattern that periodically changes in accordance with a relative change in the irradiation position of the light spot and the guide groove of the disk is obtained. FIG. 3A and FIG. 3C show the intensity distributions of the reflected light flux of the light spot 100 of the 0th-order light and the reflected light fluxes of the light spot 101 of the + 1st-order diffracted light and the light spot 102 of the -1st-order diffracted light. As shown in the figure, the change is such that the left and right are completely inverted.

By the way, when a focus error signal by the astigmatism method is detected from these reflected light beams, there is a problem that a large disturbance is easily generated in the focus error signal detected as described above. The main factors are the periodic change of the intensity distribution pattern of the reflected light beam due to the influence of the diffraction in the groove 300 and the disturbance of the push-pull signal caused by the periodic change. Therefore, as shown in FIGS. 4A and 4B, when comparing the focus error signal obtained from the reflected light beam of the light spot 100 with the focus error signal obtained from the reflected light beam of the light spot 101 and the light spot 102, While the waveform of the focus error signal itself is almost the same, the phase of the disturbance component generated in the signal is almost completely inverted. Therefore, the focus error signal obtained from the reflected light flux of the light spot 100 and the light spot 101
Alternatively, when the focus error signal obtained from the reflected light beam of the light spot 102 or the sum signal of the both is added, the focus error itself is doubled while the disturbance component is almost completely canceled as shown in FIG. The obtained good focus error signal can be obtained.

The above phenomenon also applies to the detection of a tracking error signal by the push-pull method. That is, generally, when a tracking error signal is detected by the push-pull method, when the objective lens is displaced in the tracking direction, the light spot irradiated on the light receiving surface of the photodetector 9 is displaced accordingly, and FIG.
As shown in (a) and (b), a large offset occurs in the detected tracking error signal. This offset is applied to the light spot 10 as shown in FIGS. 5 (a) and 5 (b).
The tracking signal detected from the reflected light beam of 0 and the tracking error signal detected from the reflected light beams of the light spot 101 and the light spot 102 are generated in substantially the same direction in the same direction. On the other hand, the tracking error signal itself is detected from the phase of the signal detected from the light beam reflected from the light spot 100 and from the reflected light beam from the light spots 101 and 102 for exactly the same reason as described in the above description of the focus error signal. The signal phase is almost completely inverted. Therefore, by subtracting the tracking error signal detected from the disk reflected light of each light spot, only the offset component is cancelled, and the offset as shown in FIG. 5C is greatly reduced. Tracking error signal can be obtained.

In the embodiment according to the present invention, a good focus error signal and tracking error signal are detected by utilizing the above-described principle.

FIG. 6 is a plan view and a block diagram showing a first embodiment of the photodetector and the signal processing circuit according to the present invention. As shown in the figure, the photodetector 9 has four divided light-receiving surfaces in the shape of a cross indicated by symbols a, b, c, and d.
A divided light receiving area 200 is disposed, and a quadrant light receiving area 201 having divided light receiving surfaces represented by symbols e, f, g, and h, and symbols i, j, and
A quadrant light receiving area 202 represented by k and l is arranged. On the light receiving area 200, the disk reflected light of the on-disk light spot 100 is condensed to form a detection light spot 110. Similarly, the light reflected from the light spot 101 on the disc is reflected on the light receiving area 201, and the light reflected from the light spot 102 on the disk is reflected on the light receiving area 202. I have.

Each of the detection currents detected by photoelectric conversion on each of the light receiving surfaces a, b, c, and d is converted into a current-voltage conversion amplifier 40, 41, 4 provided inside the package of the photodetector 9.
Are converted into voltages by the light detectors 9 and 2, respectively.
Output terminal. Similarly, the light receiving surfaces e, f, g, h,
The output lines of i, j, k, l are current-voltage conversion amplifiers 44,
45, 46, 47, 48, 49, 50, 51. (Hereinafter, for the sake of simplicity, these voltage-converted detection signals are denoted by the same symbols as the light-receiving surfaces on which the detection signals are detected.) After all, the twelve output terminals of the photodetector 9 Contains a, b, c, d,
e, f, g, h, i, j, k, l are output.

Next, the arithmetic circuit will be described. Of the 12 detection signals output from the output terminal of the photodetector 9,
From the output signals a, b, c, and d, signals (a + c)-(b + d) are output by adders 52 and 53 and a subtractor 54, and signals (a +) are output by adders 55 and 56 and a subtractor 57.
d)-(b + c) is output. Here, the signal (a +
c)-(b + c) corresponds to a focus error signal of the light spot 100 on the disk detected by the so-called astigmatism method. (A + d) and (b + c) correspond to the detected light amounts in each area when the detection light spot 110 is divided into two in the disk tracking direction (radial direction), and a difference signal (a + d) between these two signals -(B
+ C) corresponds to a tracking error signal of the optical spot 100 on the disk detected by the so-called push-pull method.

Further, a phase difference detection circuit 80 is connected to the output signals a, b, c and d, and this circuit uses a so-called phase difference detection method (differential phase detection circuit).
Light spot 10 on disk by detection method)
A tracking error signal of 0 is also detected. Since the phase difference detection method is a known technique, a detailed description is omitted here.

The output signals a, b,
By generating the sum signal RF2 of c and d, the information signal recorded on the optical disk can be reproduced by a predetermined signal reproducing circuit. Although not shown in this embodiment, the adder 81 is stored in the package of the photodetector 9 and the sum signal (a + b +
A configuration in which an output terminal of (c + d) is added is also possible.

Similarly, the adders 82 and 83 generate the sum signals RF1 and RF3 of the output signals e, f, g, h and i, j, k, l, so that the information signal recorded on the optical disc is converted. Reproduction can be performed by a predetermined signal reproduction circuit, so that information signals can be reproduced simultaneously in all three detection areas. Although not shown in the present embodiment, the adders 82 and 83 are stored in the package of the photodetector 9 and the sum signals (e + f + g + h) and (i + j + k +) are applied to the signal output terminal of the photodetector 9.
Needless to say, a configuration in which the output terminal of l) is added is also possible.

Further, from the output signals e, f, g, h,
The signal (e + g) is output by the adders 58 and 59 and the subtractor 60.
− (F + h) is output, and the adders 61 and 62 and the subtractor 6
3, the signal (e + h)-(f + g) is output. Similarly, from the output signals i, j, k, l, the adder 6
4, 65, the signal (i + k)-(j +
1) is output, and a signal (i + 1)-(j + k) is output by the adders 67 and 68 and the subtractor 69.

The signals (e + g)-(f + h) and (i +
k)-(j + 1) is added to the signal (e + g +
i + k)-(f + h + j + 1)
Further, the signal is amplified by the amplifier 71 at a predetermined amplification factor K1. The amplification factor K1 of the amplifier 71 is equal to the signal (e + g + i
+ K)-(f + h + j + 1) is the signal (a + c)-(b +
The signal amplitude is determined to be substantially the same as that of d). This signal (e + g + i + k)-(f + h + j
+ L) corresponds to the sum signal of the focus error signals of the light spots 101 and 102 on the disk detected by the so-called astigmatism method.

On the other hand, (e + h)-(f + g) and (i +
l)-(j + k) is added to the signal (e + h) by the adder 73.
+ I + l)-(f + g + j + k), which is further amplified by the amplifier 74 at a predetermined amplification factor K2.
The amplification factor K2 of the amplifier 74 is the signal (e + h + i + 1)
− (F + g + j + k) is determined to have substantially the same signal amplitude as the signal (a + d) − (b + c). still,
This signal (e + h + i + 1)-(f + g + j + k) is
When the detection light spots 111 and 112 are divided into two in the disk tracking direction (radial direction), this corresponds to the difference in the total detected light amount in each area, and tracking of spots 101 and 102 on the disk detected by a so-called push-pull method. This is equivalent to the sum of the error signals. The signal output from the subtractor 75 is {(a + d) − (b + c)} − K2 · {(e + h + i +
l)-(f + g + j + k)}. This signal is obtained from the tracking error signal of the spot 100 on the disk obtained from the light receiving area 200.
This corresponds to a signal obtained by subtracting the tracking error signals of the spots 101 and 102 on the disc obtained from the light receiving areas 201 and 202.

The focus error signal output terminal and the tracking error signal output terminal of the signal processing circuit are provided with switches 90 and 91, respectively. This is provided to appropriately switch between a focus error signal and a tracking error signal used for controlling the actuator 16 according to the type of the disk as described below. That is, for example, D
When playing back an optical disk such as a VD-RAM disk having a continuous guide groove on the recording surface of the disk, first, as shown in FIG. a + c)-(b
+ D) and the signal K1 ｛(e +
i + g + k)-(h + l + f + j)} through adder 72. Signal {(a + c)-(b + d)} + K1 · {(e + i + g +
k)-(h + l + f + j)} is output as a focus error signal. As described above, this signal is a focus error signal of the light spot 100 on the optical disk by the astigmatism method and the light spot 101.
And 102 are equivalent to a signal obtained by adding the sum signal of the focus error signals of No. and No. 102 with the signal amplitude adjusted. Therefore, this signal is a good focus error signal in which the leakage of the focus error signal due to the diffraction in the guide groove is largely eliminated as described above.

Next, regarding the tracking error signal,
The changeover switch 91 is switched, and the signal {(a + d) − (b + c)} − K2 · {(e + h + i +
l)-(f + g + j + k)}. This is a signal obtained by subtracting the sum signal of the tracking error signals of the spots 101 and 102 on the disks obtained from the light receiving areas 201 and 202 from the tracking error signal of the spot 100 on the disk obtained from the light receiving area 200 as described above. Equivalent to. Therefore, this signal is a good tracking error signal in which the offset due to the displacement of the objective lens has been largely eliminated despite being detected by the push-pull method.

Here, when the relative irradiation position intervals of the light spots 100, 101, and 102 irradiated to the DVD-RAM disk are as shown in FIG. The interval is the track pitch Tp
Consider the case where the value is set to 1/2 of 1. DV
Since the D-RAM disk is a so-called land-groove recording, information signals are recorded on the guide grooves 300 (grooves) and between adjacent guide grooves 301 (lands) on both sides thereof. Therefore, the information signal recorded on the predetermined guide groove 300 and the information signal recorded on the adjacent guide groove 301 on both sides thereof (or conversely, the predetermined guide groove 301
The information signal recorded above and the guide groove 3 adjacent on both sides thereof
00 is recorded on three light spots 10
0, 101 and 102 can be played back simultaneously. As shown in FIG. 8B, three light spots 1
00, 101, and 102 are not necessarily adjacent to each other, and the light spot 100 is located between the guide grooves.
If there is a relationship of 02 on the guide groove (or the light spot 100 is on the guide groove and the light spots 101 and 102 are between the guide grooves), as shown in FIG.
The information signals from 0, 101 and 102 are output to three output RF
1, RF2, and RF3, and it is needless to say that the recorded information on the DVD-RAM disk can be reproduced at the same time.
The same result can be obtained regardless of the number of recording tracks between 102.

On the other hand, DVD-ROM disks and CD-R
When reproducing a read-only disc such as an OM disc in which phase pits corresponding to a recording signal are provided on the disc, even if a signal based on an ordinary astigmatism method is used as a focus error signal, the influence of disturbance will not occur. Absent. Further, a tracking error signal based on a phase difference detection method output from the phase difference detection circuit 80 can be used as the tracking error signal. Therefore, as shown in FIG. 9, the changeover switches 90 and 91 are switched to output (a + c)-(b + d) as the focus error signal and the tracking error signal output from the position difference detection circuit 80 as the tracking error signal. Thus, a desired error signal suitable for a read-only disc can be obtained.

Here, as shown in FIG.
Guide groove interval (recording track pitch) in M disk
Tp2 is １ ／ of the recording track pitch Tp1 in the DVD-RAM disk. (DVD-R
The recording track pitch of the OM disk is 0.74 μm,
The guide groove interval of the DVD-RAM disk is 1.48 μm. Therefore, if the relative irradiation position intervals of the light spots 100, 101, and 102 applied to the DVD-RAM disk are as shown in FIG. 3 or FIG. 8A, the same optical head is used. When a DVD-ROM disk is reproduced, three light spots are inevitably irradiated on three recording tracks 400 adjacent to each other, as shown in FIG. Moreover, in the present invention, three light spots 100, 10
In this configuration, the disc reflected lights of the discs 1 and 102 are incident on independent light receiving areas 200, 201 and 202, respectively. Therefore, it is possible to simultaneously and independently reproduce information signals recorded on separate recording tracks of a DVD-ROM disc using each of these three light spots. As shown in FIG. 10B or 10C, three light spots 100, 10
10 and 10 are not necessarily on adjacent recording tracks (FIG. 10B shows a state where there is a gap for one recording track, and FIG. 10C shows a state where there is a gap for two tracks).
, Three light spots 10 on the recording track
If there are 0, 101 and 102, the sum signal RF of each light receiving area
It is needless to say that three recording tracks of a DVD-ROM can be reproduced simultaneously by means of 1, RF2 and RF3. Further, as described above, if the arrangement of the optical spots on the DVD-RAM disk enables simultaneous reproduction of three recording tracks, the positional relationship of the optical spots on the DVD-ROM disk is as shown in FIG. As shown in c), the arrangement is made with an even number of recording tracks including zero inserted, and the sum signals RF1, RF2, RF3 of each light receiving area can be reproduced simultaneously by three light spots.

When playing back a CD-ROM / CD-R,
By rotating and adjusting the diffraction direction of the light beam in the diffraction grating 13 shown in FIGS. 1 and 2, it is possible to arrange as shown in FIG. 11 (a) or (b).
In the figure, a recording track 500 of a CD-ROM or a CD-R has an interval of Tp3 and has three light spots 1.
Each of 00, 101, and 102 is arranged on the recording track 500. FIG. 11A shows a state where the light spot is located on an adjacent track, and FIG.
This shows a state in which there is a gap corresponding to the number of recording tracks of a book.
In any state, as in the signal reproduction method using the DVD-ROM shown in FIG. 9, the focus error signal uses the astigmatism method, and the tracking error signal uses the phase difference detection method.
201, 202 have three light spots 110, 111, 1
12 and three information signals RF1, RF2, RF3
At the same time, and the recorded information on the disc can be reproduced. There is no particular limitation on the number of recording tracks into which the light spots are inserted, and a configuration in which all the light spots are arranged on the recording tracks is the same as in the case of the DVD-ROM. .

Next, a second embodiment of the photodetector and the signal processing circuit according to the present invention will be described with reference to FIG. The same symbols used in the drawings are the same as those used in the description so far. The difference from the configuration of FIG. 6 is that one of the three light receiving areas 202
Are constituted by one light receiving surface. Also in this case, for an optical disk with a guide groove such as a DVD-RAM disk, by using the astigmatism detection method and the push-pull method obtained from two light-receiving areas having four-divided light-receiving surfaces, good results can be obtained. At the same time that the focus error signal and the tracking error signal can be detected,
From all three light spots, disc recording information RF1,
RF2 and RF3 can be reproduced.

FIG. 13 shows a third embodiment according to the present invention. Three light receiving areas 200, 201, 2
02, only one light receiving area 200 is formed of four divided light receiving surfaces, and only one light spot 110 can detect a focus error signal by an astigmatism method and a tracking error signal by a phase difference detection method. It is. Therefore, it is difficult to satisfactorily reproduce a disk with a guide groove such as a DVD-RAM disk. However, for a DVD-ROM disc or a CD-ROM disc, for example, a good focus error signal and a good tracking error signal from the light spot 110 are detected, and at the same time, information signals from three different recording tracks are RF1, RF2 and RF2. Reproduction is possible at the same time as RF3.

FIG. 14 shows a fourth embodiment according to the present invention. Three light receiving areas 200, 201, 2
02, only one light receiving area 200 is formed of four divided light receiving surfaces, which is the same as FIG. The difference from FIG. 13 is that outputs from two light detection areas 201 and 202 each formed of one light receiving surface are detected as a difference signal by a subtractor 85. Thereby, as shown in FIG. 15, for example, the interval between the light spots 100, 101, and 103 on the CD-ROM disk is set to be approximately 略 of the recording track Tp3 (= 1.6 μm). Thus, good tracking error detection by the so-called three spot method is possible. When the three-spot method is used, three tracks cannot be reproduced simultaneously on a CD-ROM. However, as shown in FIGS. 1 and 2, a plurality of diffraction gratings for splitting a light beam are used. In a certain optical system, for example, by using one of the systems, it is possible to perform focus error signal detection by the astigmatism method and tracking error signal detection by the phase difference detection method on the light spot 110 of the DVD-ROM disc. At the same time, the DVD-ROM can simultaneously reproduce information signals RF1, RF2, and RF3 from three recording tracks.

FIG. 16 shows a fifth embodiment according to the present invention. Three light receiving areas 200, 201, 2
6 is the same as FIG. 6, but is different from FIG. 6 in that two light receiving regions 203 and 204 are further provided. That is, in the present embodiment, there are five independent light receiving areas, and the information signals RF1 to RF5 can be output. This allows
As shown in FIG. 17, for example, light spots 100, 101, 102, 103, and 104 on a total of five discs of zero-order light, ± first-order light, and ± second-order light on a DVD-ROM disc
Are arranged on five different recording tracks, so that the information signals RF1, RF2, RF3, RF4, and RF5 from the respective recording tracks in the five light receiving regions in FIG.
Can be reproduced simultaneously. As for the generation of the focus error signal and the tracking error signal, an optimum configuration may be selected in each device. Therefore, in the configuration described in the second to fourth embodiments,
The same effect can be obtained with a configuration in which two light receiving regions are added on the outside. It goes without saying that the light receiving area for generating the focus error signal and the tracking error signal may be set to any of the five light receiving areas.

FIG. 18 shows a sixth embodiment according to the present invention. Three light receiving areas 200, 201, 2
13 is the same as FIG. 13 except that four light receiving regions 203, 204, 205, and 206 are further provided. That is, it has seven independent light receiving areas, and can output seven information signals RF1 to RF7 obtained from the light receiving areas. Thereby, as shown in FIG. 19, for example, the 0th order light, ± 1st order light, ± 1st order light on the DVD-ROM disk
Light spots 100, 101, 102, 103, 104, 105, 1 on a total of seven disks of secondary light and ± tertiary light
06 is arranged on seven different recording tracks, seven information signals RF from each recording track are provided.
1, RF2, RF3, RF4, RF5, RF6, RF7
Can be reproduced simultaneously. For the generation of the focus error signal and the tracking error signal, an optimum configuration may be selected in each device. In the configuration described in the first, second, and fourth embodiments, four light receiving elements are provided on the outside. A similar effect can be obtained with a configuration in which an area is added. It goes without saying that the light receiving area for generating the focus error signal and the tracking error signal may be set to any of the seven light receiving areas. Further, it is needless to say that by adding a high-order diffracted light and a considerable number of light receiving areas, it is possible to simultaneously reproduce more track record information.

In the optical system shown in this embodiment, for example, an objective lens optimally designed for reproducing a DVD disk and an objective lens optimally designed for reproducing a CD disk are mounted together in the same optical head. However, the configuration has been described in which switching is performed according to the type of disc to be reproduced. However, according to the present invention, the wavelength 650 nm
Function of condensing the light beam on the recording surface of a DVD disk having a disk substrate thickness of 0.6 mm;
A lens having both a function of condensing a light beam of nm on a recording surface of a CD disk having a disk substrate thickness of 1.2 mm and a thickness of 1.2 mm may be used. Also,
For example, in the case of an optical system configuration such as a DVD-ROM or a DVD-RAM disk having only the same laser wavelength, the present invention can be realized even with an optical system configuration including one objective lens 6 and one diffraction grating 4 as shown in FIG. It goes without saying that you can do it.

FIG. 21 shows a seventh embodiment according to the present invention. For example, a state is shown in which a disc such as a DVD-R disc whose recording track pitch is slightly different from that of a DVD-ROM is being reproduced. DVD-R
The recording track Tp4 (= 0.8 μm) of the disc is D
Recording track Tp2 of VD-ROM (= 0.74 μm)
Is slightly larger than that of DV, as shown in FIG.
Of the light spots 100, 101 and 102 set at the interval of the recording track Tp2 of the D-ROM, the light spots 101 and 102 corresponding to the ± first order light are the light spots 1
In the state where 00 is on the recording track, it is arranged at a shifted position. In such a case, the first
, The information can be reproduced by the light spot 100, that is, the zero-order light. In addition, when the recording track deviation is so small, the information can be reproduced with practically no problem with respect to ± primary light, and the number of recording tracks from which information is reproduced at the same time can be appropriately selected.

FIG. 22 shows an eighth embodiment of the present invention, and is a schematic diagram of a focus error signal. As shown in the first to seventh embodiments, in the simultaneous reproduction of information signals by using a plurality of light beams, the smaller the arrangement interval of each light receiving area is, the more the light enters the other light receiving area. Even when the outer peripheral light of the light beam is defocused, the light is easily leaked. Further, for example, in the above-described special objective lens corresponding to the two-wavelength laser, since the outer peripheral light of the light beam tends to be relatively larger than that of the normal objective lens, the leakage into other light receiving regions is large. Prone. In the present invention, by setting the detection range H of the focus error signal between 4 μm and 7 μm, the detection range H is within the range of the focus shift where the influence of the leak from the other light beam is small and the disturbance to the apparatus is caused. Even when an impact occurs, it is possible to detect a focus error in which the focus servo is hard to come off.

It should be noted that which one of the first to eighth embodiments is selected may be appropriately selected according to the type of the optical disk device to which the optical disk device is compatible, and a plurality of embodiments may be used in combination. It does not matter.

[0048]

As described above, according to the present invention, 1
Using an optical head with a simple configuration equipped with a plurality of photodetectors, it is possible to reproduce high-density discs such as DVD-RAM and DVD-ROM discs, as well as existing optical discs such as CD, CD-ROM and CD-R. And an optical disc device capable of simultaneously reproducing three recording tracks with three light spots effective for increasing the data transfer rate, and a necessary and sufficient light detection system configuration according to the type of the optical disc. It is possible to construct

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram of an optical head according to the first embodiment of the present invention, showing a state where a second optical disc is being reproduced.

FIG. 3 is a diagram schematically showing a positional relationship between light spots applied to a DVD-RAM disk and a state of a reflected light beam according to the present invention.

FIG. 4 is a diagram for explaining the effect of reducing disturbance of a focus error signal according to the present invention.

FIG. 5 is a diagram for explaining an effect of reducing an offset of a tracking error signal according to the present invention.

FIG. 6 is a first diagram illustrating a photodetector and a signal processing circuit according to the present invention.
FIG. 3 is a schematic plan view and a block diagram showing the embodiment.

FIG. 7 is a first diagram related to the photodetector and the signal processing circuit of the present invention.
FIG. 3 is a schematic plan view and a block diagram shown for explaining a first function of the embodiment.

FIG. 8 is a schematic plan view showing a positional relationship between light spots applied to a DVD-RAM disk according to the present invention.

FIG. 9 is a first diagram illustrating the photodetector and the signal processing circuit according to the present invention.
FIG. 9 is a schematic plan view and a block diagram shown for explaining a second function of the embodiment.

FIG. 10 is a schematic plan view showing a positional relationship between light spots applied to a DVD-ROM disk according to the present invention.

FIG. 11 is a schematic plan view showing the positional relationship between light spots applied to a CD-ROM disk according to the present invention.

FIG. 12 is a schematic plan view and a block diagram showing a second embodiment relating to a photodetector and a signal processing circuit of the present invention.

FIG. 13 is a schematic plan view and a block diagram showing a third embodiment relating to a photodetector and a signal processing circuit of the present invention.

FIG. 14 is a schematic plan view and a block diagram showing a fourth embodiment relating to a photodetector and a signal processing circuit of the present invention.

FIG. 15 is a schematic plan view showing the positional relationship of light spots in a three-spot system applied to a CD-ROM disk according to the present invention.

FIG. 16 is a schematic plan view and a block diagram showing a fifth embodiment relating to a photodetector and a signal processing circuit of the present invention.

FIG. 17 is a schematic plan view showing a positional relationship between five light spots applied to a DVD-ROM disk according to the present invention.

FIG. 18 is a schematic plan view and a block diagram showing a sixth embodiment relating to the photodetector and the signal processing circuit of the present invention.

FIG. 19 is a schematic plan view showing a positional relationship between seven light spots applied to a DVD-ROM disk according to the present invention.

FIG. 20 is a schematic front view showing a configuration of an optical head used in an embodiment of the present invention.

FIG. 21 is a schematic plan view showing a positional relationship between light spots applied to a DVD-R disc according to a seventh embodiment of the present invention.

FIG. 22 is a schematic diagram illustrating a detection range of a focus error signal according to an eighth embodiment of the present invention.

[Explanation of symbols]

1, 11 semiconductor laser light source, 4, 13 diffraction grating, 6, 15 objective lens, 7, 14 optical disk, 9 photodetector, 100 to 106 optical spot on disk, 110 to 116: light spot on light receiving surface, 200 to 206: light receiving area

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme Court ゛ (Reference) G11B 7/14 G11B 7/14 (72) Inventor Masayuki Inoue 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Stock Company. 5D118 AA11 AA24 AA26 BA01 BB02 CA23 CA24 CD02 CD03 CD08 CF06 CF16 CG04 CG05 DA02 DA08 DC03 5D119 AA10 AA41 BA01 DA01 DA05 EC44 EC45 FA05 FA08 JA11 JA22 JA43 KA08 KA02

Claims (6)

[Claims] 1. One or more semiconductor laser light sources,
A light splitting element for splitting at least one light beam among the light beams emitted from the semiconductor laser light source into three or more light beams, and all light beams including the three or more light beams A condensing optical system that condenses and irradiates a predetermined position on the optical information recording medium with an independent light spot, and a converging optical system that irradiates three or more light beams reflected by the optical information recording medium with each other. At least the first, second, and third light receiving regions are arranged, and at the same time, each light beam emitted from the semiconductor laser light source and reflected by the optical information recording medium is at least one of the first, second, and third light beams. A photodetector arranged so as to be independently received in a light receiving region, and a light spot irradiated on the optical information recording medium by performing a predetermined operation on a photoelectric conversion signal obtained from the photodetector. An optical information reproducing apparatus having a signal processing circuit for generating a focus error signal and a tracking error signal of the optical information recording medium and reproducing an information signal recorded on the optical information recording medium; The region has a light receiving surface divided into four sides in a cross shape, and at least one set of the three or more branched light beams condensed on the optical information recording medium is different on the optical information recording medium. An optical information reproducing apparatus, wherein three or more recording information sequences are irradiated simultaneously. 2. The optical information according to claim 1, wherein said signal processing circuit has a tracking error detection method comprising a differential phase detection method and a focus error detection method comprising an astigmatism method. Playback device. 3. The signal processing circuit according to claim 1, further comprising a first tracking error detection system comprising a differential phase detection system and a second tracking error detection system comprising a three-spot system. 3. The optical information reproducing apparatus according to claim 1, wherein a tracking error detection method is selected depending on a type of the information recording medium. 4. At least two light receiving regions among the three light receiving regions of the photodetector are provided with light receiving surfaces divided into four in a cross shape, and the output of each of the four light receiving surfaces is an astigmatism method. 4. The optical information reproducing apparatus according to claim 1, further comprising a focus error detection method comprising: 5. The light beam splitter according to claim 1, wherein the light intensity ratio of the zero-order light, the + 1st-order light, and the -1st-order light of the light beam after splitting in the light splitting element is set to 1: 1, approximately 1: 1, respectively. An optical information reproducing apparatus according to any one of claims 1 to 4. 6. The detection range of the focus error signal is 4
The optical information reproducing apparatus according to claim 1, wherein the optical information reproducing apparatus is set between μm and 7 μm.