Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
  • G11B7/123—Integrated head arrangements, e.g. with source and detectors mounted on the same substrate
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
  • G11B20/10—Digital recording or reproducing
  • G11B20/10009—Improvement or modification of read or write signals
  • G11B20/10305—Improvement or modification of read or write signals signal quality assessment
  • G11B20/10388—Improvement or modification of read or write signals signal quality assessment control of the read or write heads, e.g. tracking errors, defocus or tilt compensation
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
  • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
  • G11B7/0901—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following only
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
  • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
  • G11B7/0925—Electromechanical actuators for lens positioning
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
  • G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
  • G11B7/127—Lasers; Multiple laser arrays
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
  • G11B7/13—Optical detectors therefor
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
  • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
  • G11B7/1372—Lenses
  • G11B7/1374—Objective lenses
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
  • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
  • G11B7/095—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble
  • G11B7/0956—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble to compensate for tilt, skew, warp or inclination of the disc, i.e. maintain the optical axis at right angles to the disc

Definitions

• the present invention relates to an optical pickup and an optical reproducing apparatus that irradiate an optical recording medium such as an optical disk with light from, for example, a light emitting unit and receive and detect return light due to reflection from the optical recording medium.
• the present invention relates to an optical pickup and an optical reproducing apparatus which are suitably applied when detecting a tracking error signal for an optical disc having an arbitrary bit depth.
• optical pickups optical disk drives for so-called compact disk (CD) players, etc.
• optical pickups for magneto-optical disk drives use the entire system to individually assemble each optical component, such as gratings and beam splitters.
• the configuration of the device has become complicated and large, and strict alignment accuracy has been required when optically setting the position when assembling in a hybrid manner on a substrate.
• Fig. 8 shows a configuration diagram of an example of a conventional optical disc dedicated to reproduction of a compact disc (CD).
• the optical pickup 81 includes a semiconductor laser 82, a diffraction grating 83, a beam splitter plate 84, an objective lens 85, and a light receiving element 86 including a photo diode.
• the laser beam L from the semiconductor laser 82 is reflected by the beam splitter plate 84, converged by the objective lens 85, irradiated on the optical disk 90, and returned by the optical disk 90. Is transmitted through the beam splitter plate 84 and is detected by the light receiving element 86.
• such an optical pickup 81 has a large number of parts and is not only very large, but also requires high precision in its arrangement, and as a result, productivity is low.
• a tracking sensor method in an optical device such as an optical pickup, a push-pull method, a three-beam method, a heterodyne method, and the like are usually used.
• 9A and 9B show schematic configuration diagrams of a tracking servo using the push-pull method.
• a mark or space is recorded by unevenness due to a pit on the surface of the disk 52.
• the pit is irradiated with light, the light is diffracted by the unevenness and is split into a 0th-order diffracted light (main beam B) and a first-order soil diffracted light (sub-beam B ').
• S! Indicates irradiation spots of the 0th-order diffracted light and ⁇ 1st-order diffracted light, respectively.
• the circle of S0 is due to the aperture of the objective lens.
• a diagram bisected nonwoven Todaio de PD R by the light receiving portion, PDL is disposed formed.
• TE (PDL-PDR) does not become 0 and shows a positive or negative value depending on the direction of the shift. As a result, the direction and amount of deviation from the track can be detected.
• a tracking servo using the push-pull method can be realized with a two-part photodiode, and can be configured at low cost.
• the spot of the received light is shifted as shown by a broken line, and tracking is performed at the true position of the track.
• FIG. 11 shows the effect of the lens shift on the tracking error signal in the case of the conventional push-pull signal as described above.
• the vertical axis is represented by a relative value.
• Discs have a group pitch
• the calculation was performed with a disk of 1.6 ⁇ m, a depth of group Z 8, and a duty (duty: ratio of group to track width) of 65%.
• the laser wavelength is 0.78 // m. Was.
• the tracking error signal in the conventional push-pull signal is offset by the shift of the objective lens.
• the depth of the pit of the disk 52 is ⁇ Z4n.
• the signal becomes 0 due to the interference between the 0th-order diffracted light and the ⁇ 1st-order folded light, so that a tracking error signal cannot be detected in principle. Therefore, it cannot be used for a disc 52 having a pit depth of IZ4n.
• the push-pull method cannot be applied to DVD (Digital Versatile Disk) -ROM.DVD-Video because the depth of this pit is near ⁇ / 4 ⁇ .
• light is split by a diffraction grating to form a main beam and two sub-beams on both sides of the main beam.
• Figure 12 shows the spot position on the disk surface in the three-beam method.
• the reflected light of the two sub-beams is detected, a difference signal is obtained, and a tracking servo is performed using the difference signal.
• the reflected light by the spots S i and S 2 of the sub-beams is not symmetrical, and the tracking error signal due to the difference signal fluctuates from zero.
• the amount of fluctuation of this tracking error signal is the spot S of the main beam. Since it changes according to the amount of deviation from the track center, tracking servo can be performed.
• the reflected light of the main beam is used to detect a disc recording signal. In this case, it is possible to cope with the objective lens shift described above without causing an offset.
• the phase difference detection method is particularly effective for tracking servos of discs with a standard pit depth of ⁇ / 4n.
• the phase difference detection method is based on a method of heterodyne detection using the diffraction spectrum of a two-dimensional pit as an RF (harmonic) signal as a reference, and a method of digitally processing each signal detected on a photodetector. It is better realized.
• a tangential direction T which is, for example, a pit row direction of an irradiating portion of an optical disc with respect to an optical axis
• Photodiodes PD a, PD b, PD c, and PD d are formed in the vertical and horizontal directions in the direction perpendicular to the direction T, and placed in the far-field region. Then, the return light from the optical disk is detected by the four-division photodiodes PDa to PDd.
• the center circle corresponds to the pupil of the lens and corresponds to the spot of the 0th-order diffracted light.
• the other eight circles correspond to spots of the first-order diffracted light.
• the dotted line in the center is an image corresponding to the disc pit P.
• signal processing is performed on the configuration of the four-division photodiodes PDa to PDd, for example, as follows.
• An RF signal (PDa + PDb + PDc + PDd), which is the sum of detection signals of each photodiode, and a signal obtained by calculating a detection signal of each photodiode (eg, PDa + PDc— Heterodyne detection of PD b — PD d) with phase taken into account.
• Operation signal (PDa + PDc)-(PDb + PDd)
• V p period of pit sequence
• ⁇ angular velocity of optical disc
• Equation 1 the part of C sin (27 ⁇ V t / v p ) in Equation 1 is the RF signal (PD a + PD b + PD c + PD d) power and 'cos (2 ⁇ a ⁇ tvp). Taking this into consideration, this is the reference signal that is obtained when heterodyne detection of the operation signal is performed. This was a signal Karade tracks the amount v t obtained by heterodyne down detection can determined Mel things.
• the offset of the tracking error signal due to the lens shift hardly occurs, and the method is effective for a disc having a pit depth of I / 4n.
• CLC Confocal Laser Power Bra
• a light emitting unit is arranged at a confocal position of a converging means such as a lens and a light receiving unit is formed in the vicinity of the confocal position where the light emitting unit is located.
• the applicant has arranged a split photodiode that forms the light receiving section at the confocal position described above.
• An optical device that performs a tracking servo by using a push-pull method or the like by using these divided photodiodes was proposed earlier (see “Optical Device” in Japanese Patent Application No. Hei 7-355528).
• the tracking error signal is detected by the push-pull method (CPP method) using the light receiving unit near the confocal position, it is possible to prevent lens offset and disk warpage. Also, stable tracking error signals can be detected, and alignment during assembly is greatly simplified. Further, since the light emitting section and the light receiving section are formed on the same substrate, the number of components can be reduced, and the manufacturing cost can be reduced and the reliability can be improved.
• CPP method push-pull method
• FIG. 14 shows an example.
• FIG. 14 is an example of a numerical calculation result showing a relationship between a tracking error signal and a detrack amount by the CPP method when defocus occurs.
• the disk is Fig. 11
• the model has the same shape as that used in the calculation of
• the spot force method, the astigmatism method, the Nifeg method, and the like are used to control the amount of defocus force to a level less than the focal depth of the objective lens.
• the defocus amount is not always set to 0 ⁇ m, and a delicate variation within the depth of focus is constantly occurring.
• the present invention enables an optical device such as an optical pickup to reduce the number of optical components and simplify alignment at the time of optical arrangement setting.
• tracking error signals can be obtained stably for optical recording media of all pit depths, and can be easily manufactured by a semiconductor process. is there.
• the invention of the present application provides a semiconductor laser, reflecting means for guiding the emitted light emitted from the semiconductor laser to an optical disc, and condensing the emitted light reflected by the reflecting means on the optical disc.
• An objective lens a light receiving means disposed within a range substantially within a convergence limit of return light from the optical disc, and at least one of marks or spaces on the optical disc detected by the light receiving means. It is an object of the present invention to provide an optical pickup comprising: a tracking error signal generating means for generating a tracking error signal based on light reflected from an end.
• the objective lens when reproducing an optical disc medium having a mark or space formed on the medium, the objective lens is tracked based on the tracking error signal generated by the tracking error signal generating means. It is an object of the present invention to provide an optical reproducing apparatus provided with a driving means for driving in a direction.
• the photodetector is arranged at a position within the convergence limit of the return light near the confocal position, the return light that can be received is band-limited, and extra diffracted light is And the offset due to lens shift can be reduced.
• FIG. 1 is a schematic configuration diagram (perspective view) of an optical device according to an embodiment of the present invention
• FIG. 2 is an enlarged view of a main part of the optical device in FIG. 1
• FIG. 4 is a plan view of a main part of the optical device of FIG. 1
• FIGS. 4A and 4B are schematic diagrams of a pit edge for explaining detection at a pit edge.
• FIG. 5 is a diagram showing the characteristics of the tracking error signal when the disc pit depth is I / 4n.
• Fig. 5A shows the tracking error due to the lens shift in the radial direction.
• FIG. 5B is a diagram showing a change in a signal
• FIG. 5B is a diagram showing a change in a tracking error signal due to a focus
• FIG. 5C is a diagram showing a change in a tracking error signal due to a disc duty.
• FIG. Fig. 6 shows the characteristics of the tracking error signal when the disc pit depth is s / 6n.
• Fig. 6A shows the tracking error signal due to the lens shift in the radial direction.
• FIG. 6B is a diagram showing a change in the tracking error signal due to the focus, and FIG.
• FIG. C is a diagram showing a change in a tracking error signal due to a disc duty.
• Fig. 7 is a diagram showing the characteristics of the tracking error signal when the disk pitch is IZ 8 n. Of these, Fig. 7A shows the tracking error due to the lens shift in the radial direction.
• FIG. 7B is a diagram showing a change in a signal
• FIG. 7B is a diagram showing a change in a tracking error signal due to a focus
• FIG. 7C is a diagram showing a change in a tracking error signal due to a disc duty. It is.
• FIG. 8 is a schematic configuration diagram of a conventional optical device
• FIGS. 9A and 9B are diagrams illustrating a tracking servo by a push-pull method.
• FIG. 10 is a diagram for explaining a problem in the push-pull method.
• FIG. 10A is a diagram showing an offset when the lens is shifted
• FIG. FIG. 4 is a diagram showing an offset when a lens is tilted.
• FIG. 11 FIG. 12 is a diagram showing the influence of lens shift on a tracking error signal by the conventional push-pull method.
• FIG. 12 is a diagram for explaining a tracking servo by the 3-spot method.
• FIG. 3 is a diagram for explaining a tracking servo by the phase difference detection method
• FIG. 14 is a diagram showing a relationship between a tracking error signal and a defocus amount by the CPP method.
• the present invention relates to a light emitting unit including a semiconductor laser and a reflecting surface for reflecting light emitted from the semiconductor laser, and a light receiving unit including a photodetector.
• Converging means for converging and irradiating the light emitted from the light emitting section to the optical recording medium and converging the return light reflected from the optical recording medium, wherein the light emitting section and the light receiving section are formed on the same semiconductor substrate.
• the confocal point of the convergence means is set on the semiconductor substrate, and the photodetector is arranged and formed near the confocal position by the return light convergence means and within the convergence limit of the return light, thereby recording information on the optical recording medium.
• An optical device that detects a tracking error signal by detecting and detecting the return light generated by the pit or the end of the area where the light is emitted by the photodetector.
• this optical device 10 is an optical disk 2 having, for example, a recording pit as an optical recording medium of an irradiated portion, and irradiates the optical disk 2 with a laser beam. This is the case where the present invention is applied to an optical pickup for reading a record.
• FIG. 2 is an enlarged perspective view of the optical device
• FIG. 3 is a plan view thereof.
• the optical device 10 includes an optical semiconductor element 7 on which a semiconductor laser LD is formed, and an output light L F of the semiconductor laser LD. Is provided with an objective lens 3 as a converging means for converging and irradiating the light onto an optical disc 2 as an irradiated portion.
• the objective lens 3, the emitted light LF is configured to converge illumination returned light L R reflected by the optical disk 2 to the optical semiconductor element 7.
• the optical device 10 includes a so-called CLC (conformer) in which a light emitting unit is disposed at a confocal position of a converging unit such as a lens, and convergently irradiates return light reflected from an irradiated portion near a confocal position where the light emitting unit is located.
• CLC converging unit
• the return light L R is what is converged by the objective lens 3 to the vicinity (the diffraction limit of the immediate Chi lens) light diffraction limit, the light diffraction limit, the outgoing light L F from the semiconductor laser LD
• the wavelength is I and the numerical aperture of the objective lens 3 is NA, 1.22 ⁇ ⁇ .
• the optical semiconductor element 7 has a resonator length on the semiconductor substrate 1 in the direction along the substrate surface as a light emitting portion and, for example, parallel to the tangential direction T of the optical disk 2.
• the semiconductor laser LD having a direction, and the semiconductor laser reflecting surface M that reflects light emitted L F from the provided and one oblique surface which faces the emission end face of the semiconductor laser LD of the LD is formed, and a light receiving portion
• a photodetector composed of PD2 is formed.
• the area of the optical diffraction limit of the return light L R, 2 Tsunofu constitutes the light receiving portion of the above-described O Todaio de PD 1, PD 2 is formed.
• These photodiodes PD 1 and PD 2 are divided into two by a dividing line in the tangential direction T.
• the optical semiconductor element 7 is arranged in the direction of the pit row of the optical disc 2, that is, The tangential direction T of the disk and the direction of the drive of the semiconductor laser LD are arranged so as to coincide with each other.
• the semiconductor substrate 1 is formed of GaAs. If the reflection surface M is formed by ⁇ 1 1 1 ⁇ crystal plane,
• This optical semiconductor element 7 can be manufactured in a series of semiconductor manufacturing steps by a so-called wafer batch process in which a plurality of optical semiconductor elements 7 are simultaneously formed on a wafer.
• an optical device 10 such as an optical pickup that makes use of the advantages of the confocal optical system with simple adjustment and little change over time is configured. be able to.
• the reflection surface M can be easily formed because the reflection surface M can be formed in a planar state.
• the emitted light L F reflected by the reflecting surface M is converging and irradiating the optical disc 2 by the objective lens 3
• the outgoing light L F is reflected by the optical disc 2
• the return light L R is converged again by the objective lens 3 and travels to the optical semiconductor element 7.
• the return light L R focuses (confocal) around the reflection surface M of the optical semiconductor element 7 and the two photodiodes PD formed near this confocal point. 1, light reception detection at PD 2
• the two follower Todaio de PD 1, PD 2 is formed in the return light L optical diffraction within the limit of R, spatially bandlimited added.
• Forming the two photodiodes PD 1 and PD 2 within the optical diffraction limit described above is, specifically, the area of the two photodiodes. This is achieved by making the range fall within a circle corresponding to the approximate disk size.
• the early disc size is the size of the return light corresponding to the circle of diameter ⁇ on the optical disc expressed by the following equation.
• This spatial band limitation uniquely identifies the adverse effect on the signal due to the fact that the 0th-order diffracted light is extremely reduced compared to the 1st-order diffracted light in the region outside the optical diffraction limit and high wavelength components are generated. This function is particularly effective when lens shift occurs.
• the push-pull signals, ie, the CPP signals, of the half-division photodiodes PD 1 and PD 2 arranged near the confocal position are different in the focus direction within the depth of focus and the pit depth. It has the disadvantage of being susceptible to the disk parameters all night long.
• the push-pull detected on the two-division photodiodes PD 1 and PD 2 placed near the confocal position from the pit formed as a recording signal on the optical disc 2 or something similar thereto Consider a signal.
• the basic signal detection mechanism is based on the optical device proposed above.
• a semiconductor structure is arranged at a confocal position, and the semiconductor structure reflects return light to a photo diode at a distance of about H m from the confocal position to about 100 m. Propagation was performed to detect light reception.
• the confocal position The return light LR is received and detected by a 2-division photo diode placed in the vicinity.
• the difference signal component obtained by subtracting the detection signal between the two-part photodiodes PD1 and PD2 is almost the same in both the present embodiment and the configuration of the optical device proposed earlier. And the amplitudes are only slightly different.
• the size of the two-part photodiodes PD 1 and PD 2 is spatially limited within the light diffraction limit by, for example, the above-described method, and so on. Remove unnecessary signals.
• Et al is, in the optical device 1 0 of the present embodiment will be receiving and detecting the tiger Kkinguera first signal using a return light L R in the pit Bok edge of the optical disk 2.
• the pit edge is a transition point from a mark to a space or from a space to a mark when a binary digital signal is recorded as a mark or a space on an optical recording medium.
• the follower by Todaio de PD 1, PD 2 in the return light L R is irradiated, by performing a calculation as described below for these follower Todaio de PD 1, the signal obtained from the PD 2, tigers Tsukin Guera Various signals such as signals and RF (harmonic) signals are generated respectively.
• the generation of the tracking error signal in the optical device 10 is based on the following equation, where the tracking error signal is STE, and the light receiving amounts of the photodiodes PD 1 and PD 2 are IPD 1 and IPD 2, respectively. This is achieved by (2).
• STE (IPD 1 — IPD 2) edgel (or * edge 2) (2)
• Equation (2) * edge1 and * edge2 indicate the detection at the rising and falling pit wedges, respectively.
• a good tracking error signal can be obtained by using the detection at either the rising edge or the falling edge.
• FIG. 4A shows the detection position at the rising pit edge (1)
• FIG. 48 shows the detection position at the falling pit edge (2).
• the upper and lower arrows indicate the moving direction of the recording medium
• the horizontal arrows indicate the detecting direction.
• the tracking error signal STE has a sufficient margin for the lens shift in the radial direction R.
• the RF signal can be detected by the sum signal of the two photodiodes PD 1 and PD 2.
• the focus error signal can be detected using a known detection method, for example, by separating the return light LR in the middle and detecting the received light.
• a conventionally used method such as a phase difference detection method can be used. Since the two-division photodiodes PD 1 and PD 2 are spatially limited, no extraordinary diffracted light is received as described above, so that the tracking error signal has a falling or rising peak. A good tracking error signal can be obtained only by detecting the return light at the edge.
• PD 2 is formed on the diffraction limit in the region of the returning light L R, the diffraction limit region
• the offset of the tracking error signal when the lens shift appears outside (pit depth: generated at a value other than 1 / 4n) is removed, and the effect of the lens shift on the tracking error signal is greatly reduced. Can be made smaller.
• the tracking error signal is detected by receiving the return light L R due to the pit edge of the optical disk 2, the tracking error signal is detected.
• the effect of emphasizing the signal itself is obtained, so that the effect of the force force within the depth of focus on the CPP signal can be relatively reduced.
• the influence of defocus (see Fig. 13) seen in the CPP signal can be reduced.
• a better tracking error signal can be obtained.
• the tracking error signal binarizes the RF signal, which is the sum signal of the PD1 signal and the PD signal, and then generates the PD signal at the rising edge or the falling edge. It is obtained by sampling the difference signal between the 1 signal and the PD 2 signal. Further, the tracking error signal obtained in this way is applied to the above-mentioned actuating coil via a power amplifier for driving the actuating coil, and is applied to the tracking direction. By performing the servo, a reproducing apparatus for an optical recording medium can be realized.
• the power amplifier may be provided with a phase compensation circuit according to the characteristics of the factor.
• a tracking error signal is calculated taking into account the lens shift characteristics in the radial direction, the force-dependent, and the duty-dependent characteristics.
• Figure 5 shows the results.
• FIG. 5 ⁇ shows the change of the tracking error signal due to the lens shift LS in the radial direction R of the disc
• Fig. 5B shows the focus when the duty of the disc pit is 65%
• FIG. 5C shows a change in the tracking error signal due to a focus shift within the depth (hereinafter referred to as “defocus”)
• FIG. 5C shows a change in the tracking error signal due to a change in the duty of the disc pit. Shown.
• FIGS 5A to 5C are all calculated when the modulation is detected at the position where the modulation degree is the best around the rising edge. The results are shown.
• the tracking error signal is less affected, regardless of the optical disc of any pit depth and the lens shift in the radial direction of the disc. It can be seen that an S-shaped tracking error signal can be obtained.
• the slope of the tracking error signal is affected by the sign of the defocus, and the slope of the tracking error signal becomes larger as the force becomes more positive.
• a tracking error signal can be detected corresponding to a disc having any pit depth
• the same optical system is applied to an optical device using a red material for a semiconductor laser LD. Then, for example, it can be used as an optical pickup device common to DVD-R0M and DVD-RAM.
• optical device 10 of the present embodiment the following advantages are obtained by having a feature in detecting a tracking error signal.
• Tracking servo can be applied to optical discs of all pit depths or group depths.
• the tracking error signal can be changed to lens shift and parameter changes of the optical system for optical disks of all pit depths or group depths. Become stronger.
• a simple optical system with a reduced number of components can be configured. Therefore, the assembly process and the adjustment process can be simplified.
• the optical recording medium is described as the optical disc 2 having a pit.
• the present invention is applied to an optical apparatus using an optical recording medium having a recording area equivalent to other pits. Can also be applied.
• optical device of the present invention is not limited to the above-described embodiment. Instead, various other configurations can be adopted without departing from the gist of the present invention. Industrial applicability
• the photodetector since the photodetector is arranged at a position within the convergence limit of the return light near the confocal position, the return light that can be received is band-limited. Since the extra diffracted light generated by the lens shift or the like is not received, the influence of the fluctuation of the convergence means such as the objective lens on the tracking error signal can be reduced.
• the manufacturing cost of the optical device can be reduced, and the power consumption of the optical device can be reduced.
• the light emitting section and the photodetector are formed on the same semiconductor substrate, so that the number of components can be reduced and the optical device can be reduced in size and weight.
• the response speed is also improved, and the change over time after assembling the optical device can be reduced.
• a confocal optical system it can be formed in a semiconductor process, so that reproducibility is high and manufacturing can be performed with high yield.

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Citations (6)

• 1999
  • 1999-10-27 WO PCT/JP1999/005930 patent/WO2000025310A1/ja not_active Application Discontinuation
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