JPH0817064A - Optical disk device - Google Patents

Abstract

PURPOSE:To efficiently detect an tilt error(TLE) signal and a focus error(FE) signal of an optical pickup by utilizing a two-beam system as to the optical disk device which records and reproduces pieces of information of two systems by the two-beam system. CONSTITUTION:The reflected lights of two converged light spots B1 and B2 irradiating an optical disk 10 are guided to photodetectors 16 and 17 independently of each other, and two FE signals (E13 and E23) regarding the converged light spots B1 and B2 are obtained from the output signals of the photodetectors 16 and 17 through summing ampliflers 21 and 22, and 31 and 32 and differential amplifiers 23 and 33. Then a differential amplifier 24 finds the difference signal between the FE signals (E13 and E23) as the TLE signal and a summing amplifier 24 finds the sum signal of the FE signals (E13 and E23) as the FE signal of the optical pickup, thereby performing tilt and focus servocontrol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device,
Especially in an optical disc device for recording / reproducing information of two systems by a two-beam system for optical discs such as magneto-optical discs and phase change discs, the tilt error (TLE) signal and focus error (FE) signal of the optical pickup can be efficiently used. For improvements to detect.

[0002]

2. Description of the Related Art CD (Compact Disc) and LD (Laser Disc)
In an optical disc device intended for a disc, an MD (Mini Disc), etc., when the disc surface is inclined with respect to the optical axis of the irradiation light of the optical pickup, coma aberration occurs and jitter or crosstalk increases, resulting in Is known to cause deterioration of recording / reproducing characteristics [eg, "Jitter analysis of eye pattern in optical disc", Shigeo Kubota, Optics, 12 (1983), pp4.
37-]. To prevent this problem, a tilt servo control method has been proposed in which the optical pickup is tiltably supported and the tilt angle of the optical pickup is adaptively controlled by following the tilt of the optical disk. This product is actually implemented.

The following tilt servo control methods have been proposed at present. It has the configuration shown in FIG. 7 and is used in a disk device or the like for LD as the most general method. In addition to the optical system for reading information, the optical pickup 50 is provided with a light emitting diode 51 which is a light source and photodetectors 52 and 53 on both sides of the light emitting diode 51. The photoelectric conversion outputs of the photodetectors 52 and 53 are provided. Is obtained by the differential amplifier 54, and the difference signal is used as the TLE signal. And T
The tilt motor 55 is controlled based on the LE signal, and one end of the guide rail 56 is vertically displaced to keep the optical pickup 50 parallel to the disc 57 [for example, "Laser Disc Technical Book", supervised by Pioneer Corporation. , ASCII Publishing, 1986, pp97-].

This is the system disclosed in Japanese Patent Laid-Open No. 3-37837, and its configuration is shown in FIG. Optical pickup 61
The laser light for reading information is also used for TLE detection, and the 0th and ± 1st order tilt diffracted light is obtained from the laser light that has passed through the diffraction grating 62, and the half mirror, the objective lens, or the like is used. The disc 64 is irradiated through the projection optical system 63. Then, the tilted diffracted light reflected by the disk 64 goes backward through the projection optical system 63, is reflected by the half mirror, and is incident on g and h of the 8-division photodetector 65. Here, when the disc 64 is tilted, the 0th and + 1st order tilt diffracted lights and the 0th and −1st order tilt diffracted lights are different at the entrance pupil of the objective lens of the projection optical system 63. Therefore, the amount of tilt diffracted light incident on the detectors h and g of the photodetector 65 is biased, and the differential signal of the photoelectric conversion output of each photodetector h and g is output to the differential amplifier 66. By finding T
The LE signal is obtained. Further, if the outputs of the detection units e and f of the 8-division type photodetector 65 are obtained by the differential amplifier 67,
Two-axis tilt servo control is also possible.

Previous application of the applicant (Japanese Patent Application No. 4-79381
No.), and its configuration is shown in FIG. The reflected light of the disk 75 obtained by the projection optical system 72, 73, 74 of the optical pickup 71 is made incident on the photodetector 77 from the half mirror 73 through the detection lens 76, and the information is read. The irradiation light from the optical systems 72, 73, 74 is split by the half mirror 73 and guided to the tilt detecting optical systems 78, 79. Then, the reflected light from the disk 75 obtained through the detection half mirror 79 of the tilt detection optical systems 78 and 79 is guided to the two-division type photodetector 81 through the aperture 80, and the difference between the respective photoelectric conversion outputs. The TLE signal is obtained by obtaining the signal with the differential amplifier 82. In this method, the objective lens 74 of the projection optical system and the detecting half mirror 79 of the tilt detecting optical system are integrally formed in the tilt movable portion 71b independent of the optical pickup body 71a. Since the relative tilt relationship between 79 and the disk 75 becomes the relative relationship between the objective lens 74 and the disk 75, the influence of the tilt of the optical axis in the optical pickup main body 71a and the position fluctuation of the objective lens 74 due to focus / tracking control is affected. Only the relative tilt error between the objective lens 74 and the optical disk 75 can be satisfactorily detected without being received. Further, since the tilt movable section 71b is independent of the optical pickup body 71b, it is possible to perform tilt servo control at high speed.

On the other hand, as a recent attempt for high density recording on an optical disk, land / groove recording, that is, a method of recording on both the land and the groove has been proposed (Ohno et al .: “Land & Phase in Phase Change Optical Disk”). Examination of groove recording ", '93 Spring Applied Physics Society, Proceedings 29a-B-9), as a suggestion of the possibility of high-density recording without shortening the wavelength of the light source and improving the NA (Numerical Aperture) of the objective lens. Attention has been paid.

For the purpose of obtaining a strong tracking error signal and accurate address information, "only one side wall 1a of the groove 1 meanders as shown in FIG. 10, and the average width of the groove 1 is the groove. An optical disc characterized by being set to be equal to the average value of the lands 2 between 1 (Japanese Patent Laid-Open No. 5-314538) has been proposed. As a 2-beam system, highly accurate tracking error (TE) signal, wobbling carrier (WobC) signal, time / address (AD)
D) An optical disk device capable of obtaining a signal is proposed [Patent application filed on the same date as the present application (January 28, 1995) (reference number: 406001022)].

The optical disk device according to the above proposal is shown in FIG.
Each control signal is obtained by the circuit configuration shown in FIG. First,
The reflected light from each of the condensing spots B1 and B2 formed on the optical disc 10 is independently guided to the two-division type photodetectors 91 and 92 through the optical system, and the photoelectric conversion outputs of the respective detection units are respectively. The differential signals are input to the differential amplifiers 93 and 94 and the respective difference signals are obtained.
Then, each difference signal is input to each BPF 95, 96 whose pass band width is set to the wobbling frequency of the side wall 1a, and each BP is input.
Each wobbling modulation signal obtained from F95, 96
The amplitude component of the wobbling modulation signal is input to the V (envelope) detection circuits 97 and 98, and each ENV is further extracted.
The differential amplifier 9 outputs each amplitude signal output from the detection circuits 97 and 98.
9 and inputs the difference signal of the respective amplitude signals, which is the output of the differential amplifier 99, to the TE signal. In addition, a delay circuit 100 that delays the wobbling modulation signal corresponding to the focused spot B1 by a time τ is provided to match the phase of the wobbling modulated signal on the focused spot B2 side, and each wobbling modulated signal with the matched phase. It is input to the summing amplifier 101, and a WobC signal having a large amplitude is obtained from the output of the summing amplifier 101. Further, for the ADD signal, the output signal of the summing amplifier 101 is demodulated by the FM demodulator 102, and the demodulated signal is decoded by the decoder 103.
It is obtained by decoding with. The reproduction signals RF1 and RF2 of the two systems read from the disk 10 are photoelectric conversion outputs of the detectors of the photodetectors 91 and 92, respectively.
It is obtained by adding 4,105.

[0009]

However, even when recording / reproducing information of two systems at each converging spot B1, B2 while detecting a control signal by the two-beam method as described above, the NA is large. When an objective lens is used, tilt servo control of the optical pickup is required.
In that case, it is possible to apply each of the above-mentioned tilt servo control methods ~, but in the method of (1), an optical system for TLE signal and a detection system are provided to the optical pickup in addition to the optical system for information reading / recording. This method requires a diffraction grating 62 and a special 8-division type photodetector 65, and uses the "vignetting" phenomenon that occurs at the entrance pupil of the objective lens of the projection optical system 63. In addition, it is difficult to obtain high detection accuracy at the practical stage. In the method (1), the tilt movable section 71b is provided independently of the optical pickup main body 71a, and high-speed control is possible, but an optical system for TLE detection is required and the optical pickup mechanism is complicated. Size and size.

On the other hand, the purpose of the tilt servo control is to detect the tilt of the disc and adaptively follow the tilting angle of the optical pickup. In principle, the disc and the optical pickup face each other at two positions separated from each other. If the distance information is detected, it is possible to obtain relative tilt angle information regarding the direction connecting the two points. When performing recording / reproducing by the above-mentioned two-beam method, since two focused spots are irradiated from the optical pickup side to different positions on the disc, it is necessary to obtain TLE information based on the above-mentioned principle. convenient.

Therefore, according to the present invention, recording / recording is performed by the two-beam method.
Created for the purpose of providing an optical disc device capable of performing highly accurate tilt servo control by using reflected light from each condensing spot on the disc in an optical disc device for reproduction and capable of performing stable focus servo control. Was done.

[0012]

According to a first aspect of the present invention, a light irradiating means for irradiating an optical disc with two light-converging spots spaced apart from each other by a constant distance, and the above-mentioned light-converging spots are used. In an optical disk device equipped with two light detecting means for independently detecting and photoelectrically converting the reflected light of 2), two FE signals for each condensing spot portion are obtained based on the output signals of the respective light detecting means. An optical disc characterized in that one signal detecting means and a first calculating means for obtaining a difference signal between two FE signals by the respective signal detecting means are provided, and the difference signal obtained by the first calculating means is used as a TLE signal. Related to the device.

According to a second aspect of the present invention, in the case where the optical disk device of the first aspect of the present invention has a focus control means, a second arithmetic means for obtaining a sum signal of two FE signals by each signal detection means is provided, and The optical disc device is such that the focus control unit controls the focus of the optical pickup by using the sum signal obtained by the second calculation unit as the FE signal of the optical pickup.

[0014]

[Action]

Regarding the first invention: In this invention, two light-converging spots are irradiated from different positions on the optical disc from the light irradiation means of the optical pickup, and the photoelectric conversion of each light detection means corresponding to the two signal detection means. Two FE signals for each condensing spot portion are obtained based on the signal. Therefore, the first
The difference signal of each FE signal obtained by the calculation means shows the magnitude and polarity corresponding to the TLE state between the optical disc and the optical pickup, and the tilt servo control can be executed by using the difference and the polarity as the TLE signal.

Regarding the second invention: In the first invention, the TLE state between the optical disk and the optical pickup is
It is nothing but the fact that the focus state related to each focused spot changes with the opposite tendency. According to the present invention, since the second arithmetic means obtains the sum signal of the respective light detecting means and executes the focus control, the focus information in the middle of the focus state relating to each converging spot is obtained, and the TLE control according to the first invention. Together with this, it enables stable focus control at all times. Further, the FE signal obtained from the second calculation means of the present invention is
Since it is the sum signal of the FE signals detected at the positions separated by the distance between the two focused spots, the detection sensitivity higher than that of the FE signal obtained by the single focused spot can be obtained.

[0016]

Embodiments of the optical disk device of the present invention will be described in detail below with reference to FIGS. In the present embodiment, an optical disk device will be described as an example in which information of two systems is recorded / reproduced for the groove 1 and the land 2 of the optical disk shown in FIG. First, Fig. 1
Indicates a detection system of the TLE signal and the FE signal in this optical disc device, 10 is an optical disc, and 11 is an optical pickup. Here, the optical pickup 11 includes a semiconductor laser unit 12 including two laser beam emitting units 12a and 12b,
Equipped with a beam splitter 13, an objective lens 14, a cylindrical lens 15, two 4-split photodetectors 16 and 17, and a focus actuator 18, and emits from each laser beam emitting unit 12a and 12b. The respective laser beams thus transmitted pass through a beam splitter 13 and are then converged by an objective lens 14 to form focused spots B1 and B2 on the groove 1 and the land 2 of the optical disk 10, respectively.
The reflected light at B2 is converged by the objective lens 14, and each reflected light reflected by the mirror surface of the beam splitter 13 is made incident on each photodetector 16, 17 through the cylindrical lens 15. . In the case of the present embodiment, the laser beam emitting portions 12a and 12b are arranged on the straight line of the semiconductor laser unit 12 at regular intervals, and the direction of the straight line corresponds to the linear velocity direction of the optical disk 10. The above-mentioned optical relationship is obtained by mounting the semiconductor laser unit 12 so as to be inclined so as to have a predetermined angle with respect to.

The photoelectric conversion outputs of the photodetectors 16 and 17 are input to the arithmetic circuit 19, and the TLE signal and the FE signal obtained by the arithmetic circuit 19 are used to make an optical pickup.
The tilt servo control of the whole 11 and the focus servo control by driving the objective lens 14 are executed. That is, the optical pickup 11 is movable in the direction perpendicular to the track by the guide rail whose one end is rotatably supported, and the tilt actuator 20 provided at the other end of the guide rail is set to the TLE signal. Tilt servo control is performed by operating with a drive signal with phase compensation. Also,
For focus servo control, the focus actuator 18 is driven by the drive signal that is the phase compensation of the FE signal.
Operates the objective lens 14 to control the focused state of each of the focused spots B1 and B2.

By the way, the arithmetic circuit 19 has a circuit configuration as shown in FIG. First, the outputs of the detectors at the diagonal position in the photodetector 16 are added by the addition amplifiers 21 and 22, the addition outputs E11 and E12 are input to the differential amplifiers 23, and the difference signal E13 (= E12) of each output is added. -E11) is calculated. Also a photo detector
Similarly on the 17 side, the outputs of the diagonal position detectors are added by the addition amplifiers 31 and 32, and the addition outputs E21 and E22 are input to the differential amplifier 33 to output the difference signal E23 (= E22- E21) is required. Then, the difference signal (E13-E23) of the difference signals E13 and E23 is obtained by the differential amplifier 24 of the output stage, and the difference signal (E13-E23) is obtained.
13-E23) as the TLE signal, and the addition amplifier 3 in the output stage
In step 4, the sum signal (E13 + E23) of the difference signals E13 and E23 is obtained, and the sum signal (E13 + E23) is used as the FE signal.

Next, in the above configuration, TLE and F
The relationship between the generation state of E and the output states of the TLE signal and the FE signal corresponding thereto will be sequentially described. (1) Standard state [Refer to FIG. 2] In FIG. 1, the two laser irradiation light beams form focused spots B1 and B2 on the optical disc 10 through the objective lens 14, but in this state, both focused spots are formed. In B1 and B2, the irradiation light is in focus, and the disc is not tilted, which corresponds to a state in which optimum recording / reproduction is possible. In that case, in the present embodiment, since each reflected light is detected by each photodetector 16, 17 based on the astigmatism method using the cylindrical lens 15, both photodetectors 16, 17 are detected.
A circular converging spot is formed on the.

Therefore, the outputs E11 and E12 of the summing amplifiers 21 and 22 are equal, and the outputs E21 and E22 of the summing amplifiers 31 and 32 are also equal, so that the differential amplifiers 23 and 33 are equal. The outputs E13 (= E12-E11) and E23 (= E22)
-E21) becomes 0 level. As a result, the TLE signal which is the output of the differential amplifier 24 and the FE signal which is the output of the summing amplifier 34.
Both signals are 0 level.

(2) State of FE generation (disk out of focus)
In the state where no TLE occurs [see FIG. 3] In this state, the optical disc 10 is too far from the optical pickup 11 as shown in FIG.
It does not tilt itself, which means that the parallel relationship between the two is maintained. In this case, the focused spots B1 and B2 related to the laser beams of the two systems are larger than the standard state, and the respective reflected lights thereof are the photodetectors 16 and 17 due to the astigmatism phenomenon in the cylindrical lens 15. Each of the elliptical focused spots [see FIG. 3 (B)] that are inclined to the right side is formed. Further, since the optical disc 10 and the optical pickup 11 are excessively separated from each other by the same distance from the standard state, each of the elliptical focused spots has the same shape and is inclined in the same direction.

Therefore, the output E11 of the summing amplifier 21 becomes larger than the output E12 of the summing amplifier 22, and the output E13 of the differential amplifier 23 becomes a negative level. Similarly, the output E21 of the adding amplifier 31 becomes larger than the output E22 of the adding amplifier 32, and the output E23 of the differential amplifier 33 also becomes a negative level. Since the shape of each elliptical focused spot on each photodetector 16 and 17 is the same, the relationship of E13 = E23 is established. As a result, the TLE signal output from the differential amplifier 24 becomes 0 level, and the FE signal output from the summing amplifier 34 becomes negative level.

(3) FE generation state (disk is in focus)
In this state, TLE is not generated [see FIG. 4] In this state, the optical disc 10 is too close to the optical pickup 11 as shown in FIG. It corresponds to the state of being kept. In this case, as in the case of (2) above, the condensing spots B1 and B2 related to the laser beams of the two systems are larger than in the standard state, and the photodetectors 16 and 17 are opposite to the case of (2) above. Each of the elliptical focused spots inclined to the side [see FIG. 4 (B)] is formed. Further, the respective elliptical focused spots have the same shape and are inclined in the same direction.

Therefore, the output E11 of the summing amplifier 21 becomes smaller than the output E12 of the summing amplifier 22, and the output E13 of the differential amplifier 23 becomes a positive level. Similarly, the output E21 of the adding amplifier 31 becomes smaller than the output E22 of the adding amplifier 32, and the output E23 of the differential amplifier 33 also becomes a positive level. Since the elliptical focused spots on the photodetectors 16 and 17 have the same shape, the relationship of E13 = E23 is established as in the case of the above (2). As a result, the output of the differential amplifier 24, T
The LE signal becomes 0 level, and the FE signal output from the summing amplifier 34 becomes positive level.

(4) TLE occurrence state in average focus state
[Refer to FIG. 5] In this state, as shown in FIG.
The intermediate position between 1 and B2 is at the focusing distance by the objective lens 14, and the focused spot B1 is formed inside the focusing distance.
This corresponds to the case where the focused spot B2 is formed outside the focusing distance, and naturally the optical disc 10 is tilted so that T
It is also the state of occurrence of LE. In this case, the condensing spots B1 and B2 relating to the two systems of laser light are larger than the standard state due to the optically opposite relationship, and the respective reflected lights thereof are different due to the astigmatism phenomenon due to the cylindrical lens 15. Photo detector 1
Elliptical focused spots tilted on the opposite side to 6,17
[See FIG. 5B]. Also, each focused spot B1,
Since the approximate middle position of B2 is at the focusing distance, the elliptical condensing spots have almost the same shape only with the opposite inclinations.

Therefore, the output E11 of the summing amplifier 21 becomes smaller than the output E12 of the summing amplifier 22, and the output E13 of the differential amplifier 23 becomes a positive level. On the other hand, the output E21 of the summing amplifier 31
Is greater than the output E22 of the summing amplifier 32, and the differential amplifier
The output E23 of 33 goes to a negative level. And each photo detector 1
Since the shapes of the elliptical condensing spots at 6 and 17 have the above-described symmetrical relationship, the relationship | E13 | = | E23 | is established. As a result, the TLE output from the differential amplifier 24
The signal goes to a positive level and the output of the summing amplifier 34, FE
The signal becomes 0 level.

In the case of FIG. 5, the focused spot B1 is formed inside the focusing distance and the focused spot B2 is formed outside the focusing distance. In the case where there is an inverse relationship between inside and outside of the distance, that is, FIG. 5 (A)
If the optical disk 10 is tilted to the opposite side in
As a result, the TLE signal becomes a negative level, and the FE signal is 0 level as in the case of FIG.

(5) TLE generation state with only one focused spot focused [see FIG. 6] In this state, only one focused spot B2 is focused, as shown in FIG. 6 (A). Which corresponds to the case where the other condensing spot B1 is formed outside the focusing distance by the objective lens 14, and because the optical disc 10 is tilted as a matter of course, T
It is also the state of occurrence of LE. In this case, the focused spot B1
Is larger than that in the standard state, and the focused spot B2 has the same small diameter as in the standard state because it is in focus [see FIG. 6 (B) and FIG. 2]. Then, each of the reflected lights forms an inclined elliptical focused spot on the photodetector 16 side corresponding to the focused spot B1 due to the astigmatism phenomenon in the cylindrical lens 15, and the focused spot On the side of the photodetector 16 corresponding to B2, a circular focused spot similar to that in the standard state is formed [see FIG. 6 (B) and FIG. 2].

Therefore, the output E11 of the summing amplifier 21 becomes larger than the output E12 of the summing amplifier 22, and the output E13 of the differential amplifier 23 becomes a negative level. On the other hand, the outputs E21 and E22 of the summing amplifiers 31 and 32 are at 0 level, and the output E2 of the differential amplifier 33 is
3 also becomes 0 level. As a result, the TLE signal which is the output of the differential amplifier 24 becomes a negative level, and the FE signal which is the output of the adding amplifier 34 also becomes a negative level.

In the case of FIG. 6, the focused spot B1 is formed outside the focusing distance, and the focused spot B2 is in the focused state, but in the opposite case, that is, in FIG.
In the case where the optical disk 10 is tilted to the opposite side in (A), the focused spot B1 is in focus, and the focused spot B2 is formed outside the focusing distance, the summing amplifier 34 The FE signal, which is the output of, becomes a negative level as in the case of FIG. 6, but the TLE signal, which is the output of the differential amplifier 24, becomes a positive level.

As described above, according to the configuration of this embodiment,
Different output states of the TLE signal and the FE signal are obtained according to the generation states of TLE and FE. In each state of (2) to (5), the polarity and the amount of change of the TLE signal and the FE signal with respect to the 0 level can be obtained. Using the tilt actuator 20 and the focus actuator 18, the optical pickup 11
Is controlled to return to the standard state of (1).

The configuration of this embodiment can be added to the detection circuit for the read signals R1 and R2 and various control signals shown in FIG. That is, each two-division type photodetector of FIG.
It is easy to configure an equivalent detection circuit by appropriately dividing the 91 and 92 into four and adding a summing amplifier. The arithmetic circuit 19 of the present embodiment is connected to each photodetector of the four divisions. It is possible to detect the TLE signal and the FE signal only by doing this.

[0033]

The optical disk device of the present invention has the following effects due to the above configuration. The invention according to claim 1 uses reflected light from two converging spots in an optical disc device for recording / reproducing information of two systems by a two-beam system for an optical disc such as a magneto-optical disc or a phase change disc. TL with simple circuit configuration
Detecting E signal enables high-precision tilt servo control of the optical pickup. The invention of claim 2 enables highly accurate focus servo control together with the tilt control. And, each invention is a land using two beams which is attracting attention as a means for achieving high density recording on an optical disc.
It is most suitable for groove recording / playback system and can be easily combined with other control signal detection circuits.
Achieve efficient signal detection. Further, when the tilt servo control or the focus servo control is executed by the single beam method, the TLE signal and the FE signal are greatly affected directly by the defect of the disk, the variation of the irradiation intensity of the beam, and the like. Since the TLE signal and the FE signal are detected by using the reflected light from the focused spot, there is an advantage that the influence can be reduced to half.

[Brief description of drawings]

FIG. 1 is a TLE according to an embodiment of an optical disk device of the present invention.
It is a figure which shows the detection system of a signal and an FE signal.

FIG. 2 is a diagram showing a shape of each converging spot formed on an optical disc and each photodetector in a standard state, and a circuit diagram of an arithmetic circuit. (In the figure, the output state of each summing amplifier and each differential amplifier is also shown.)

FIG. 3 is a diagram illustrating an incident state (A) of irradiation light with respect to an optical disc in a state in which FE is generated (a disc is out of focus) and a state in which TLE is not generated, and each collection formed on the optical disc and each photodetector in that state. Shape of light spot and circuit diagram of arithmetic circuit
It is a figure which shows (B). (In the figure, the output state of each summing amplifier and each differential amplifier is also shown.)

FIG. 4 is a diagram illustrating an incident state (A) of irradiation light with respect to an optical disc in a state in which FE is generated (a disc is in a focus) and a state in which TLE is not generated, and each collection formed on the optical disc and each photodetector in that state. Shape of light spot and circuit diagram of arithmetic circuit
It is a figure which shows (B). (In the figure, the output state of each summing amplifier and each differential amplifier is also shown.)

FIG. 5 is a diagram illustrating an incident mode (A) of irradiation light with respect to an optical disc in a state where TLE is generated in an average focus state, shapes of respective focused spots formed on the optical disc and each photodetector in that state, and It is a figure which shows the circuit diagram (B) of an arithmetic circuit.
(In the figure, the output state of each summing amplifier and each differential amplifier is also shown.)

FIG. 6 is a state of incidence of irradiation light on an optical disc in a state where TLE is generated with only one focused spot being focused.
(A), the shape of each focused spot formed on the optical disc and each photodetector in that state, and the circuit diagram of the arithmetic circuit
It is a figure which shows (B). (In the figure, the output state of each summing amplifier and each differential amplifier is also shown.)

FIG. 7 is a diagram showing a tilt servo control method of a conventional technique.

FIG. 8 is a diagram showing a conventional TLE signal detection system.

FIG. 9 is a diagram showing a conventional TLE signal detection system.

FIG. 10: One-sided wobbling type optical disc
-314538) configuration diagram [(A) is an enlarged plan view of the disk,
(B) is a sectional view taken along line XX of (A).

FIG. 11: One-sided wobbling type optical disc
No. 314538) is a circuit diagram when a read signal and various control signals are detected by a two-beam method.

[Explanation of symbols]

1 ... Groove, 1a ... Side wall, 2 ... Land, 10, 57, 64, 75 ... Optical disc, 11, 50, 61, 71 ... Optical pickup, 12 ... Semiconductor laser unit, 12a, 12b ... Laser beam emitting section, 13 ...
Beam splitter, 14 ... Objective lens, 15 ... Cylindrical lens, 16,17,52,53,65,77,81,91,92 ... Photodetector, 1
8 ... Focus actuator, 19 ... Arithmetic circuit, 20 ... Tilt actuator, 21, 22, 31, 32, 34, 101, 104, 105 ...
Summing amplifier (21, 22, 31, 32; signal detecting means, 34; second computing means), 23, 24, 33, 54, 66, 67, 82, 93, 94, 99 ... Differential amplifier (23,
33; signal detecting means, 24; first computing means), 51 ... light emitting diode, 55 ... tilt motor, 56 ... guide rail, 62 ... diffraction grating, 63, (72, 73, 74) ... projection optical system, 71a … Optical pickup body, 71b… Tilt movable part, 73, 79… Half mirror, 74…
Objective lens, 76 ... Detection lens, (78, 79) ... Tilt detection optical system, 80 ... Aperture, 95, 96 ... BPF, 97, 98 ... EN
V detection circuit, 100 ... Delay circuit, 102 ... FM demodulator, 103 ...
Decoder, B1, B2 ... Focus spot, E11, E12, E13, E
21, E22, E23 ... Output voltage.

Claims (2)

[Claims] 1. An optical pickup which irradiates two focused spots on an optical disc in a state of being separated from each other by a constant interval, and a reflected light from each of the focused spots is independently detected and photoelectrically converted. In an optical disc device including two light detecting means for converting, two signal detecting means for obtaining two focus error signals for each condensing spot portion based on the output signal of each light detecting means, An optical disk device, characterized in that a first calculating means for obtaining a difference signal between two focus error signals by each signal detecting means is provided and the difference signal obtained by the first calculating means is used as a tilt error signal. 2. The optical disk device according to claim 1, further comprising a focus control means, wherein a second arithmetic means for obtaining a sum signal of two focus error signals by each signal detecting means is provided, and the sum obtained by the second arithmetic means. An optical disc device in which a focus control unit controls a focus of an optical pickup by using a signal as a focus error signal of the optical pickup.