JP2008305459A - Optical pickup and optical information recording/reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup for easily obtaining an optimal servo signal output according to the type of an optical information recording medium, and stably controlling recording/reproducing characteristics. <P>SOLUTION: This device is provided with: a light source 1; a first diffraction element 3 for dividing an optical beam emitted from the light source 1 into zeroth order diffracted optical beam and ±first-order diffracted optical beams; a condenser lens 9 for condensing the zeroth order diffracted optical beam and ±first-order diffracted optical beams on the information recording layer of an optical information recording medium to form three optical beam spots on the information recording layer; a second diffraction element 12 for further dividing the zeroth order diffracted optical beam reflected on the information recording layer into a plurality of diffracted optical beams; and a light receiving element 14 with a plurality of light receiving parts arranged for receiving the zeroth order diffracted optical beam and the ±first-order diffracted optical beams reflected on the information recording layer, and the plurality of diffracted optical beams divided by the second diffraction element to convert them into electric signals. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical pickup that optically records information or data on an optical information recording medium such as an optical disk, or optically reads information or data recorded on the optical information recording medium. The present invention also relates to an optical information recording / reproducing apparatus such as an optical disk drive or an optical disk recorder provided with such an optical pickup.

  Data recorded on the optical disk is reproduced by irradiating the rotating optical disk with a relatively weak light beam of a constant light quantity and detecting reflected light modulated by the optical disk.

  In a reproduction-only optical disc, information by pits is previously recorded in a spiral shape at the manufacturing stage of the optical disc. On the other hand, in a rewritable optical disk, a recording material film capable of optically recording / reproducing data is deposited on the surface of a substrate on which a track having spiral lands or grooves is formed by a method such as vapor deposition. Has been. When data is recorded on a rewritable optical disc, the optical disc is irradiated with a light beam whose amount of light is modulated in accordance with the data to be recorded, thereby changing the characteristics of the recording material film locally to write the data. Do.

  The pit depth, track depth, and recording material film thickness are smaller than the thickness of the optical disk substrate. For this reason, the portion of the optical disc where data is recorded constitutes a two-dimensional surface and may be referred to as a “recording surface”. In this specification, in consideration of the fact that such a recording surface also has a physical size in the depth direction, the phrase “information recording layer” is used instead of the phrase “recording surface”. We will use it. A general optical disc has at least one such information recording layer. One information recording layer may actually include a plurality of layers such as a phase change material layer and a reflective layer.

  When data is recorded on a recordable optical disk or when data recorded on such an optical disk is reproduced, the light beam must always be in a predetermined focused state on the target track in the information recording layer. For this purpose, “focus control” and “tracking control” are required. “Focus control” is to control the position of the objective lens in the normal direction of the information recording surface so that the focal position of the light beam is always located on the information recording layer. On the other hand, the tracking control is to control the position of the objective lens in the radial direction of the optical disc (hereinafter referred to as “disc radial direction”) so that the spot of the light beam is located on a predetermined track.

  Conventionally, optical disks such as DVD (Digital Versatile Disc) -ROM, DVD-RAM, DVD-RW, DVD-R, DVD + RW, and DVD + R have been put to practical use as high-density and large-capacity optical disks. Also, CD (Compact Disc) is still popular. Currently, development and commercialization of next-generation optical discs such as Blu-ray Disc (BD), which has higher density and larger capacity than those optical discs, are being promoted.

  These optical discs have various physical structures that differ depending on the type. For example, the physical structure of the track, the track pitch, the depth of the information recording layer (the distance from the light incident side surface of the optical disc to the information recording layer), and the like are different. In order to appropriately read or write data from a plurality of types of optical discs having different physical structures in this way, an appropriate wavelength is used by using an optical system having a numerical aperture (NA) corresponding to the type of the optical disc. It is necessary to irradiate the information recording layer of the optical disc with the light beam.

  An optical pickup is an apparatus that is incorporated in an optical information recording / reproducing apparatus and records or reproduces information by irradiating an optical information recording medium with a laser beam.

  As described above, the standards of optical information recording media are diversified. When reproducing and recording recorded information, one optical information recording / reproducing apparatus needs to support optical information recording media of various standards. There is. Therefore, the optical pickup mounted in the optical information recording / reproducing apparatus has a center wavelength of 790 nanometers (hereinafter, the unit “nanometer” may be expressed as [nm]) for a CD and a DVD. On the other hand, a semiconductor laser having a center wavelength of 660 [nm] and 405 [nm] for BD is mounted.

  In a conventional optical pickup, a focus error is detected by a spot size method, and a tracking error is detected by a three-beam method, a push-pull method, or a differential push-pull method (see, for example, Patent Document 1).

  FIG. 8 is a diagram schematically showing a conventional optical pickup described in Patent Document 1. In FIG. 8 includes a light source 122, a collimating lens 123 that converts a light beam emitted from the light source 122 into substantially parallel light, a diffracting unit 124 that forms diffracted light, a forward light beam, and a return light beam. Splitter 125 for reflecting light, objective lens 126 for condensing the light beam on optical information recording medium 102, collimator lens 127 for collimating the reflected light from optical information recording medium 102, and splitting the reflected light beam into a plurality of light beams. A hologram element 108, a cylindrical lens 109, and a light detection element 110 are provided.

  FIG. 9 is a plan view showing an arrangement configuration of the light receiving portions in the light detection element 110 used in the optical pickup 101 of FIG. The light detection element 110 in FIG. 9 is provided with light receiving portions 151 and 152 for detecting focus error signals and light receiving portions 153, 154 and 155 for detecting tracking error signals. Based on the outputs of these light receiving portions, the focus error signal detection is formed using the spot size method, and the tracking error signal is formed using the three beam method.

A direction corresponding to a direction crossing the track rather than a direction along the track on the optical information recording medium 102 with respect to a part or all of the spot group formed on the light detection element 110 by the reflected light from the optical information recording medium 102 The spot diameter increases. This is realized by the cylindrical lens 109 exhibiting a function of correcting the shape of a light spot on the light detection element 110 (light spot by reflected light). If the manufacturing accuracy and assembly accuracy of the components vary, a positional deviation between the light receiving portions 151 to 154 and the light spot occurs on the light detection element 110. In the optical pickup having the configuration shown in FIGS. 8 and 9, even when such a positional deviation occurs, the occurrence of an offset in the push-pull signal is suppressed.
JP 2002-92932 A (paragraph numbers 0026 to 0032, FIGS. 2 and 3)

  However, the optical pickup disclosed in Patent Document 1 has a problem that stable control cannot be performed on an optical disc in which the reflectance of a recording mark increases after recording.

  In general, in a phase change type optical disc, the reflectance of a recording mark becomes low after recording. Such an optical disc is referred to as a High-to-Low type optical disc. On the other hand, an optical disc in which the reflectance of a recording mark becomes high after recording is called a low-to-high type optical disc, and an organic dye-containing material is used for the information recording layer, and the optical disc is manufactured at a low cost.

  In the above optical pickup, since the spot size method is adopted for forming the focus error signal, when the light spot formed on the low-to-high type optical disk crosses the track, the reflected light intensity becomes high. Therefore, noise (groove crossing noise) due to the tracking error signal is easily superimposed on the focus error signal. In the optical pickup having the above configuration, it is considered that servo control becomes unstable due to such groove crossing noise.

  Further, when tracking error signal detection is performed by the three-beam method, there is a problem that it is difficult to stably control an optical disc having a two-layer structure such as a DVD-R or a DVD-RW. Hereinafter, the reason will be described.

  FIG. 10 (a) schematically shows a cross section of the optical disc when a light spot is formed on the L0 layer of the DVD for recording or reproduction. On the other hand, FIG. 10B schematically shows a cross section of the optical disc when a light spot is formed on the L1 layer of the BD for recording or reproduction.

  As shown in FIG. 10A, when a light spot is formed on the LO layer of the DVD, the L1 layer is also irradiated with a part of the light beam, so that interference occurs, and as a result, in the L1 layer. The reflected light becomes a stray light component and enters the light detection element. Since the light receiving units 153 and 155 shown in FIG. 9 receive the reflected light of the sub beam, the amount of incident light is low. When stray light is incident, the light receiving units 153 and 155 are greatly affected even by a small amount of light. This problem is particularly noticeable with BD. In BD, since the distance from the optical disk surface to the information recording layer (light transmission cover thickness) is as small as 0.1 mm, in the case of a two-layer structure, stronger stray light is likely to be formed as shown in FIG. It is.

  The present invention has been made to solve the above problems, and an optical pickup and an optical pickup capable of easily obtaining an optimum servo signal according to the type of the optical information recording medium and stably controlling the recording / reproducing characteristics. An object is to provide an information recording / reproducing apparatus.

  The optical pickup of the present invention includes a light source, a first diffractive element that divides the light beam emitted from the light source into a 0th-order diffracted light beam and a ± 1st-order diffracted light beam, and the 0th-order diffracted light beam and the ± 1st-order diffracted light beam. Are condensed on the information recording layer of the optical information recording medium, a condensing lens for forming three light beam spots on the information recording layer, and the 0th-order diffracted light beam reflected by the information recording layer A second diffractive element that is divided into a plurality of diffracted light beams; the 0th-order diffracted light beam and the ± 1st-order folded light beam reflected by the information recording layer; And a light receiving element in which a plurality of light receiving portions that receive the diffracted light beam and convert it into an electrical signal are arranged.

  In a preferred embodiment, the light receiving element includes a first light receiving section group that receives the 0th-order diffracted light beam and the ± 1st-order folded light beams reflected by the information recording layer and converts them into electrical signals; And a second light receiving unit group that receives at least a part of the plurality of diffracted light beams divided by the diffraction element and converts them into electric signals.

  In a preferred embodiment, a switching circuit is provided that switches between the first light receiving unit group and the second light receiving unit group in accordance with the optical characteristics of the information recording layer of the optical information recording medium.

  In a preferred embodiment, a beam splitter for changing an optical path of the reflected light beam is further provided in an optical path of the light beam between the light source and the condenser lens, and the first diffractive element includes the beam splitter and the beam splitter. The second diffractive element is disposed between the beam splitter and the light receiving element.

  In a preferred embodiment, the optical characteristics of the information recording layer are low-to-high type in which the reflectance of the recording portion is higher than the reflectance of the unrecorded portion and the reflectance of the recording portion than the reflectance of the unrecorded portion The high-to-low type is reduced.

  An information recording / reproducing apparatus of the present invention includes any one of the above optical pickups, a preprocessing circuit capable of generating a plurality of types of servo signals based on an electric signal output from the light receiving element, and the optical information recording medium. Control means for determining optical characteristics of the information recording layer and selecting a servo signal used for controlling the optical pickup from the plurality of types of servo signals according to the determination result.

  In a preferred embodiment, the light receiving element included in the optical pickup includes a first light receiving section group that receives the 0th-order diffracted light beam and the ± 1st-order folded light beams reflected by the information recording layer and converts them into electrical signals. And a second light receiving unit group that receives at least a part of the plurality of diffracted light beams divided by the second diffractive element and converts them into electrical signals.

  In a preferred embodiment, a switching circuit is provided that switches between the first light receiving unit group and the second light receiving unit group in accordance with the optical characteristics of the information recording layer of the optical information recording medium.

  In a preferred embodiment, a beam splitter for changing an optical path of the reflected light beam is further provided in an optical path of the light beam between the light source and the condenser lens, and the first diffractive element includes the beam splitter and the beam splitter. The second diffractive element is disposed between the beam splitter and the light receiving element.

  In a preferred embodiment, the optical characteristics of the information recording layer are low-to-high type in which the reflectance of the recording portion is higher than the reflectance of the unrecorded portion and the reflectance of the recording portion than the reflectance of the unrecorded portion. The high-to-low type is reduced.

  In a preferred embodiment, when the optical characteristic of the information recording layer is a high-to-low type, the control unit performs a tracking control signal using an output from the second light receiving unit group.

  In a preferred embodiment, the control means also determines whether the number of information recording layers provided in the optical information recording medium is singular or plural.

  A semiconductor device according to the present invention is a semiconductor device provided in the information recording / reproducing apparatus, wherein the optical pickup included in the information recording / reproducing apparatus is operated to determine the type of the optical information recording medium, and the optical information A program for selecting the focus control and tracking control method according to the type of the recording medium and executing the focus control and tracking control of the optical information recording medium is executed in the optical information recording / reproducing apparatus. Semiconductor device.

  According to the present invention, an optimum servo signal can be selectively used according to various optical information recording media with a simple configuration, and stable control can be performed for various optical information recording media. Realize.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
First, a first embodiment of an optical pickup according to the present invention will be described with reference to FIG.

  The optical pickup 30 of the present embodiment includes each component described below.

  A light source 1 shown in FIG. 1 is a semiconductor laser that emits a light beam having an oval light intensity distribution on a plane perpendicular to the optical axis. When recording / reproducing data on / from an optical disc such as a BD or HD-DVD, a semiconductor laser that emits blue-violet light having a center wavelength of 405 [nm] is preferably used.

  The optical information recording medium 15 is an optical disc such as a BD-ROM, a BD-R (single layer or a plurality of layers), or a BD-RE (single layer or a plurality of layers), and the reflectivity of a recording mark becomes low after recording. Either a high-to-low phase change optical disk or a low-to-high dye optical disk in which the reflectivity of a recording mark is high after recording may be used.

  The beam shaping element 2 is an element that performs beam shaping on the light beam emitted from the light source 1. Astigmatism can be adjusted to a predetermined value by moving the beam shaping element 1 in the optical axis direction.

  The diffractive element 3 divides the light beam emitted from the light source 1 into three light spots of zero-order light and ± first-order light. By providing the diffraction element 3, it becomes possible to detect a tracking error signal using the DPD method or the DPP method.

  The beam splitter 4 reflects and changes the direction of the light beam emitted from the light source 1. The light beam emitted from the light source 1 is substantially linearly polarized, and the beam splitter 4 is designed to reflect the light beam emitted from the light source 1 (outgoing light). As will be described later, the polarization direction differs by about 90 ° between the light beam emitted from the light source 1 (forward light) and the reflected light from the optical information recording medium 15 (return light). The beam splitter 4 used in the present embodiment has a property that reflection / transmission characteristics differ depending on the direction of the polarization main axis of incident light, and is designed so that forward light is reflected and return light is transmitted.

  The collimating lens 5 makes the light beam reflected by the beam splitter 4 substantially parallel light. The mirror 6 deflects the light beam that has been made substantially parallel light by the collimating lens 5.

  The light reflected by the mirror 6 passes through the λ / 4 plate 7 and is converted from linearly polarized light to circular or elliptically polarized light, and then enters the diffraction lens 8. The diffractive lens 8 corrects chromatic aberration that occurs when the recording and reproducing operations are switched.

  The condensing lens 9 condenses the light beam to form a light spot on the information recording layer of the optical information recording medium 15. Reflected light from the optical information recording medium 15 enters the beam splitter 4 through the condenser lens 9, the λ / 4 plate 7, the mirror 6, and the collimator lens 5. The reflected light is converted from circularly or elliptically polarized light into linearly polarized light when passing through the λ / 4 plate 7. The direction of the polarization main axis (electric field vector direction) of the reflected light transmitted through the λ / 4 plate 7 is orthogonal to the direction of the polarization main axis of the light beam emitted from the light source 1. For this reason, when entering the beam splitter 4, the direction of the polarization main axis of the reflected light from the optical information recording medium 15 is parallel to the direction in which the light can pass through the beam splitter 4. The reflected light from the optical information recording medium 15 passes through the beam splitter 4 and enters the optical element 12.

  The optical element 12 has a function of diffracting the 0th-order reflected light and dividing it into a plurality of diffracted light beams. For example, 80% of the light beam incident on the optical element 12 is transmitted as it is as zero-order light, and the remaining 20% is divided into two as ± first-order light and emitted.

  The detection lens 13 is a lens having a cylindrical surface. The detection lens 13 generates astigmatism in the reflected light from the optical information recording medium 15, and can detect the focus error signal by the astigmatism method or the differential astigmatism method.

  The light receiving element 14 receives reflected light (detection light) from the detection lens 13 and converts it into various servo signals.

  FIG. 2 is a diagram illustrating an arrangement of a plurality of light receiving portions in the light receiving element 14. The light receiving portions 14a, 14b, and 14c are collectively referred to as “first light receiving portion group 14aa”, and the light receiving portions 14d, 14e, 14f, and 14g are collectively referred to as “second light receiving portion group 14bb”.

  The light receiving unit 14a is composed of four divided regions A, B, C, and D. Similarly, the light receiving unit 14b includes four divided regions I, J, K, and L, and the light receiving unit 14c includes four divided regions E, F, G, and H. Each of the areas A to L is a photoelectric conversion element such as a photodiode that outputs an electric signal having a magnitude corresponding to the amount (intensity) of incident light. Hereinafter, for the sake of simplicity, the magnitude of the electrical signal output from each area is represented by the reference numeral of that area. For example, the magnitude of the electrical signal output from the region A is represented by “A”.

  The light receiving portions 14d, 14e, 14f, and 14g are configured by regions B5, B6, B1, and B3, respectively. Each of these regions B5, B6, B1, and B3 is also a photoelectric conversion element such as a photodiode that outputs an electric signal having a magnitude corresponding to the amount (intensity) of incident light. For these areas as well, the magnitude of the electrical signal output from each area is represented by the reference numerals of the areas. For example, the magnitude of the electrical signal output from the region B6 is represented by “B6”.

Of the 0th order light and ± 1st order light formed by the diffractive element 3, the 0th order light is reflected by the optical information recording medium 15 and finally enters the light receiving portion 14 a. On the other hand, after the ± first-order light is reflected by the optical information recording medium 15, it finally enters the light receiving portions 14b and 14c. The tracking error signal can be expressed by the following formula.
DPD method: (B + D), (A + C) (1)
DPP method: (C + D)-(A + B) -k [(G + H)-(E + F)] (2)

  Here, k is a coefficient. The coefficient k is also used in many expressions shown below, but the coefficient k in each expression can take a different value for each expression.

The focus error signal can be expressed by the following formula.
Astigmatism method: (B + D)-(A + C) (3)
Differential astigmatism method: (B + D)-(A + C) + k [(F + H)-(E + G)] (4)

  As described above, when DPD or DPP is used for detecting the tracking error and the astigmatism method or the differential astigmatism method is used for detecting the focus error, the output from the first light receiving unit group 14aa of the light receiving element 14 is used. The output of the second light receiving unit group 14bb is not necessary. In the present embodiment, the light receiving element 14 is provided with a second light receiving unit group 14bb separately from the first light receiving unit group 14aa, and the servo signal is generated even using the output of the second light receiving unit group 14bb. Is possible. The “servo signal” in this specification is a signal such as a tracking error signal and a focus error signal, and is used for servo control.

  In the present embodiment, the optical element 12 is used to form a light beam incident on the second light receiving unit group 14bb. As described above, the optical element 12 is an element that diffracts the zero-order light of the reflected light beam to form ± first-order light, and can be suitably configured from a diffraction element such as a hologram.

  FIG. 3 is a plan view showing an example of the divisional arrangement of the diffraction regions of the optical element 12. A circle shown in FIG. 3 corresponds to a cross section of a light beam (0th-order reflected light beam) incident on the optical element 12. The inside of the circle shown in FIG. 3 is divided into a plurality of parts B1, B3, B5, and B6, and each part has different diffraction characteristics. For this reason, the light beam (0th-order reflected light beam) incident on the optical element 12 is diffracted in different directions depending on the incident position. More precisely, the 0th-order light that is not diffracted out of the light beam incident on the optical element 12 is incident on the light receiving portion 14a of FIG. On the other hand, of the light beam incident on the optical element 12, the light diffracted as the + 1st order light is incident on the light receiving portions 14d, 14e, 14f, and 14g in FIG. Specifically, the + 1st order light incident on and diffracted in the portion B1 in FIG. 3 enters the light receiving unit 14f (region B1) in FIG. That is, the area B1 in FIG. 3 corresponds to the area B1 in FIG. Similarly, the areas B3, B5, and B6 in FIG. 3 correspond to the areas B3, B5, and B6 in FIG.

According to the optical element 12 having the configuration shown in FIG. 3, it is possible to detect a tracking error performed using the second light receiving unit group 14bb in FIG. In the present specification, such a tracking error detection method is referred to as an APP (Advanced Push Pull) method. A signal used in the APP method can be expressed by the following equation.
APP method: (B3-B1) -k (B6-B5) (5)

  Since all signals necessary for the APP method can be obtained using the + 1st order light from the optical element 12, a light receiving unit for receiving the −1st order light from the optical element 12 is not necessary.

  In this embodiment, the diffraction element 3 and the optical element 12 described above are used, and the light receiving element 14 provided with the first light receiving part group 14aa and the second light receiving part group 14bb is used, so that one optical configuration is used. Realization by switching between two types of focus error signal detection: astigmatism method and differential astigmatism method, and switching between three types of tracking error signal detection: DPD method, DPP method, and APP method Is possible.

  When the optical information recording medium 15 is a single-layer disk such as BD-R or BD-RE, as shown in Table 1 below, focus error signal detection is performed by the astigmatism method, and tracking error signal detection is performed by the APP method. If done, stable control is possible.

  Further, when the optical information recording medium 15 is a double-layer disc such as a BD-R or a BD-RE, for example, as shown in Table 2 below, the focus error signal is detected by the astigmatism method. May be performed by the APP method.

  FIG. 4 is a diagram schematically illustrating the stray light incidence region in the light receiving element 14. As is apparent from FIG. 4, in the present embodiment, the second light receiving unit group 14bb is separated from the stray light incident area around the first light receiving unit group 14aa. Therefore, stable control is possible without being adversely affected by stray light as described with reference to FIG.

  When the optical information recording medium 15 is an optical disc (for example, a low-to-high type organic dye-based optical disc) in which the reflectance of the recording mark after recording is high, as shown in Table 3 below, the focus error Signal detection is performed by the differential astigmatism method, and tracking error signal detection is performed by the DPP method.

  According to the DPP method, signal leakage (groove crossing noise) of a tracking error signal generated when one light spot crosses a track is canceled by forming three light spots. Therefore, stable control is possible even with the Low-to-High type.

  As described above, in this embodiment, the focus signal detection method and the tracking error signal detection method can be switched as appropriate according to the type (optical characteristics) of the optical disc, so that it is stable for various types of optical information recording media. Control becomes possible, and the recording / reproducing characteristics are improved. In addition, since an optimum servo signal can be selectively generated from a plurality of types of servo signals with a simple configuration, the optical pickup can be further reduced in size and weight. The relationship between optical disc type and error signal detection is summarized in Table 4 below.

  Next, an embodiment of an optical information recording / reproducing apparatus according to the present invention will be described with reference to FIG.

  The optical information recording / reproducing apparatus of the present embodiment is an optical disc apparatus 50 including an optical pickup 30 according to the present invention.

  The optical disk device 50 of this embodiment includes an optical pickup 30, a spindle motor 43 that rotates the optical information recording medium 15, a transfer motor 42 that controls the position of the optical pickup 30, and a control means that controls these operations. I have. The optical pickup 30 is electrically connected to a pre-processing circuit 36 that is a signal processing means, and a drive circuit 41 that controls the operation of the condenser lens 9 and the light source (not shown) of the optical pickup 30, and between them. Send and receive electrical signals.

  Data optically read from the optical information recording medium 15 is converted into an electrical signal by the light receiving element 14 (FIG. 1) of the optical pickup 30. This electrical signal is input to the preprocessing circuit 36 via a signal connection means (not shown). The pre-processing circuit 36 generates a servo signal including a focus error signal and a tracking error signal based on the electrical signal obtained from the optical pickup 30, and also provides an analog signal such as a waveform equivalent of a reproduction signal, a binary slice, and synchronization data. Process. In particular, the preprocessing circuit 36 in the present embodiment is configured to generate various servo signals by various methods based on a plurality of electrical signals obtained from the light receiving element 14 of the optical pickup 30, and will be described later. Thus, it is possible to selectively output a servo signal according to the type (optical characteristic) of the optical information recording medium 15 loaded in the apparatus.

  The servo signal generated by the preprocessing circuit 36 is input to the control circuit 37. The control circuit 37 causes the optical spot of the optical pickup 30 to follow the optical information recording medium 15 via the drive circuit 41. The drive circuit 41 is connected to the optical pickup 30, the transfer motor 42, and the spindle motor 43. The drive circuit 41 realizes a series of controls such as focus control and tracking control of the condenser lens 9, transfer control, spindle motor control, and the like with a digital servo. In addition to driving an actuator (not shown) of the condenser lens 9 by the action of the drive circuit 41, driving of a transfer motor 42 for transferring the optical pickup 30 to the inner periphery and outer periphery of the optical information recording medium 15, and optical information recording The spindle motor 43 that rotates the medium 15 is appropriately driven.

  The synchronization data generated by the preprocessing circuit 36 is subjected to digital signal processing by the system controller 40, and the recording / reproducing data is transferred to the host via an interface circuit (not shown). The preprocessing unit 36, the control circuit 37, and the system controller 40 are connected to the central processing unit 38 and operate according to instructions from the central processing unit 38. A program that defines a series of operations including a control operation of rotating the optical information recording medium 15, transporting the optical pickup 30 to a target position, forming a light spot on the target track of the optical information recording medium 15, and following it. Is stored in advance in a semiconductor device such as the nonvolatile memory 39 as firmware. Such firmware is read from the non-volatile memory 39 by the central processing means 38 in accordance with the required operation mode.

  In the present specification, the preprocessing circuit 36, the control circuit 37, the center line arithmetic processing means, the nonvolatile memory 39, and the system controller 40 are collectively referred to as “control means”.

  In a typical optical disc of the optical information recording medium 15, disc information called TOC is recorded on the inner periphery thereof. The type of the optical disk can be determined by discriminating the difference in the signal amplitude caused by the difference in the reflectance of the information recording layer by reproducing this TOC (disc discrimination). The focus error signal detection and tracking error signal detection to be used are determined according to the discriminated type of the optical information recording medium 15.

  The relationship between the disc discrimination result and the focus error signal detection and tracking error signal detection methods used is as shown in Table 4, for example. The relationship between the type of the optical information recording medium 15 and the focus error signal detection and tracking error signal detection in the present embodiment is stored in advance in the nonvolatile memory 39 as firmware. The optical disc apparatus of the present embodiment has a function of selecting optimum focus signal detection and tracking error signal detection according to the disc discrimination result, and stable control can be performed for various types of optical information recording media. It becomes possible.

  According to the present embodiment, stable control can be performed on various types of optical information recording media by switching focus signal detection and tracking error signal detection according to the type of the discriminated optical information recording medium. .

  In the present embodiment, the control means in the information recording / reproducing apparatus has a configuration that can generate a plurality of servo signals based on the electrical signal output from the optical pickup 30. It is not limited to. The optical pickup 30 itself may include a “switching circuit” for outputting a servo signal selected according to the type of the optical information recording medium. Discrimination of the type of optical information recording medium (disc discrimination) is performed by the control means of the information recording / reproducing apparatus. This control means provides a switching signal to the switching circuit of the optical pickup 30 to optimize the disc according to the disc discrimination result. It is also possible to selectively output a servo signal from the optical pickup.

  FIG. 11 is a flowchart showing an example of the procedure of the optimum servo signal selection operation by the program built in the nonvolatile memory 39.

  First, after the apparatus is activated, the program operates the optical pickup 30 according to a command from the central processing means 38 to irradiate the optical information recording medium 15 with laser light (step S1). Then, the data recorded in the optical pickup 30 is acquired and detected by the preprocessing circuit 36 from the reflected light (step S2: signal detection). Through this operation, the type of the optical information recording medium 15 can be determined (step S3: disc determination). Disc discrimination can be performed by obtaining disc information from a disc information area located in the inner periphery of the optical information recording medium 15. In addition, the type of the optical disk can be determined based on the magnitude of the output signal amplitude.

  In step S4, control formulas (1), (2), (3), (4), (5), (6), (7), ( 8) is selected, and in step S5, servo control (focus control and tracking control) of the optical disk is started using an optimal servo signal. Since the subsequent processing is the same as a known procedure, description thereof is omitted here.

(Embodiment 2)
Next, a second embodiment of the optical pickup according to the present invention will be described with reference to FIG.

  FIG. 6 is a schematic diagram illustrating the configuration of the optical pickup according to the present embodiment. Components corresponding to the components of the optical pickup according to the first embodiment are denoted by the same reference numerals. Of the configuration of the optical pickup device of the present embodiment, the description of the parts common to the optical pickup of the first embodiment will not be repeated.

  The optical pickup shown in FIG. 6 includes a second light source 10 having a semiconductor laser package that emits a red light beam having a center wavelength of 660 [nm] and an infrared light beam having a center wavelength of 790 [nm]. . The second light source 10 has a monolithic semiconductor laser chip, and the red light emitting points and the infrared light emitting point positions are arranged at a predetermined interval, for example, 110 microns.

  The diffraction element 16 for CD / DVD divides the light beam radiated from the second light source 10 into three light spots of the 0th order light and the ± 1st order light with the center wavelength being red and infrared. The prism 11 deflects the light beam emitted from the second light source 10. The second mirror 17 vertically deflects the light beam from the second light source 10. The first mirror 6 is designed to totally reflect light whose center wavelength is in the blue wavelength band and transmit light in the center wavelength of red and infrared.

  The light that has passed through the first mirror 6 is reflected by the second mirror 17, then passes through the second λ / 4 plate 18 and the second condenser lens 19, and information on the optical information recording medium 15. Condensed on the recording layer. The light reflected by the information recording layer of the optical information recording medium 15 is guided to the light receiving element 14 as described for the optical pickup 30 of the first embodiment.

  FIG. 7 shows an arrangement of a plurality of light receiving portions in the light receiving element 14 preferably used in the present embodiment. The light receiving units 14a, 14b, and 14c as a whole are referred to as a “first light receiving unit group 14aa”, and the light receiving units 14d, 14e, 14f, and 14g as a whole are referred to as a “second light receiving unit group 14bb” and the light receiving units 14h, 14i, and 14j as a whole. As a whole, it will be referred to as a “third light receiving unit group 14 cc”.

  Of the red light beam emitted from the second light source 10, the 0th-order light formed by the CD / DVD diffraction element 16 is incident on the light-receiving unit 14a, and the ± first-order light is received by the light-receiving units 14b and 14c. Is incident on. The error signal in the red wavelength band can be expressed by equations (1), (2), (3), (4), and (5).

As described above, the emission point of the infrared light beam emitted from the second light source 10 is separated from the emission point of the red light beam by a predetermined distance. Therefore, by arranging the third light receiving unit group 14cc at a predetermined distance from the first light receiving unit group 14aa, the reflected light of the infrared color can be received by one light receiving element. The tracking error signal in the infrared wavelength band can be expressed by the following equation.
DPD method: (b + d), (a + c) (6)
DPP method: (c + d)-(a + b) -k (ge) (7)

The focus error signal can be expressed by the following formula.
Astigmatism method: (b + d)-(a + c) (8)

  A CD / DVD diffraction element 16 and an optical element 12 are used, and a light receiving element 14 including a first light receiving part group 14aa, a second light receiving part group 14bb, and a third light receiving part group 14cc is used as a light receiving part. Accordingly, it is possible to select optimum focus error signal detection and tracking error detection according to the type of the optical information recording medium with one optical configuration.

  Also in this embodiment, focus signal detection and tracking error signal detection can be easily switched, and stable control can be performed for various optical information recording media including BD, DVD, and CD. In addition, since the servo signal can be optimally selected with a simple configuration, it is possible to provide an optical pickup that can be easily reduced in size and weight.

  In this embodiment, instead of the condensing lens 9 shown in FIG. 6, if a condensing lens capable of condensing all the light beams in the blue, red, and infrared wavelength bands is used, This eliminates the need for providing the mirror 17, the second λ / 4 plate 18, and the second condensing lens 19, thereby enabling downsizing.

  The optical pickup of the present embodiment can be used for the information recording / reproducing apparatus shown in FIG. Further, the present invention can be applied to a known optical disc apparatus other than the apparatus shown in FIG.

  Note that in order to determine the type of the optical information recording medium, test recording may be performed in the inner circumference or outer circumference area of the optical information recording medium. In that case, the reflected light from the part where the test recording was performed is measured, and the type of the optical information recording medium is determined depending on whether the reflected light intensity of the recorded part is higher or lower than the reflected light intensity of the unrecorded part. can do.

  The optical information recording medium applicable to the present invention is not limited to the BD, but may be an HD-DVD type optical disc.

  The optical pickup and the optical information recording / reproducing apparatus of the present invention are useful as an optical pickup and an optical information recording / reproducing apparatus capable of recording / reproducing data with respect to a plurality of types of optical information recording media such as a BD.

1 is a schematic diagram illustrating a configuration of an optical pickup in Embodiment 1. FIG. FIG. 3 is a plan view illustrating an example of arrangement of light receiving portions of the light receiving element according to the first embodiment. FIG. 3 is a diagram illustrating a reflected light division region of an optical element of the optical pickup according to the first embodiment. FIG. 3 is a plan view schematically showing a stray light irradiation region on the light receiving element in the first embodiment. 1 is a schematic diagram showing a configuration of an optical information recording / reproducing apparatus in Embodiment 1. FIG. 6 is a schematic diagram illustrating a configuration of an optical pickup according to Embodiment 2. FIG. 6 is a plan view showing an example of arrangement of light receiving portions of a light receiving element in Embodiment 2. FIG. It is a schematic diagram which shows the structure of the conventional optical pick-up. It is a schematic diagram of arrangement | positioning of the light-receiving part of the light receiving element of the conventional optical pick-up. (A) is a schematic configuration diagram of a DVD double-layer disc, and (b) is a schematic configuration diagram of a BD dual-layer disc. 5 is a flowchart showing a procedure of an operation program in the first and second embodiments.

Explanation of symbols

1 Light Source 3 Diffraction Element (First Diffraction Element)
4 Beam splitter (Polarized beam splitter)
5 Collimating lens 6 Mirror 7 λ / 4 plate 9 Condensing lens 12 Optical element (second diffractive element)
13 detection lens 14 light receiving element 14aa first light receiving portion group 14bb second light receiving portion group 15 optical information recording medium 30 optical pickup 50 information recording / reproducing apparatus

Claims (13)

A light source;
A first diffractive element that splits a light beam emitted from the light source into a zero-order diffracted light beam and a ± first-order diffracted light beam;
A condensing lens for condensing each of the zero-order diffracted light beam and the ± first-order diffracted light beam on an information recording layer of an optical information recording medium, and forming three light beam spots on the information recording layer;
A second diffractive element for further dividing the zero-order diffracted light beam reflected by the information recording layer into a plurality of diffracted light beams;
A plurality of light beams that are irradiated with the 0th-order diffracted light beam and the ± 1st-order folded light beam reflected by the information recording layer, and the plurality of diffracted light beams divided by the second diffractive element, and converted into electrical signals A light receiving element in which a plurality of light receiving portions are arranged;
Optical pickup with The light receiving element is
A first light receiving unit group that receives the 0th-order diffracted light beam and the ± 1st-order folded light beam reflected by the information recording layer and converts them into electrical signals;
A second light receiving unit group that receives at least a part of the plurality of diffracted light beams divided by the second diffractive element and converts them into electrical signals;
With an optical pickup.   The optical pickup according to claim 2, further comprising a switching circuit that switches between the first light receiving unit group and the second light receiving unit group in accordance with optical characteristics of an information recording layer of the optical information recording medium. A beam splitter for changing the optical path of the reflected light beam in the optical path of the light beam between the light source and the condenser lens;
The first diffraction element is disposed between the beam splitter and the information medium;
The optical pickup according to claim 1, wherein the second diffraction element is disposed between the beam splitter and the light receiving element.   The optical characteristics of the information recording layer are Low-to-High type in which the reflectance of the recording portion is higher than the reflectance of the unrecorded portion, and High- in which the reflectance of the recording portion is lower than the reflectance of the unrecorded portion. The optical pickup according to any one of claims 1 to 4, wherein the optical pickup is distinguished by one of a to-low type. An optical pickup according to claim 1,
A preprocessing circuit capable of generating a plurality of types of servo signals based on the electrical signal output from the light receiving element;
Control means for determining optical characteristics of the information recording layer of the optical information recording medium, and selecting a servo signal used for controlling the optical pickup from the plurality of types of servo signals according to the determination result;
An information recording / reproducing apparatus. The light receiving element included in the optical pickup is:
A first light receiving unit group that receives the 0th-order diffracted light beam and the ± 1st-order folded light beam reflected by the information recording layer and converts them into electrical signals;
A second light receiving unit group that receives at least a part of the plurality of diffracted light beams divided by the second diffractive element and converts them into electrical signals;
The information recording / reproducing apparatus according to claim 6, comprising:   The information recording / reproducing apparatus according to claim 6, further comprising a switching circuit that switches between the first light receiving unit group and the second light receiving unit group in accordance with optical characteristics of an information recording layer of the optical information recording medium. . A beam splitter for changing the optical path of the reflected light beam in the optical path of the light beam between the light source and the condenser lens;
The first diffraction element is disposed between the beam splitter and the information medium;
The information recording / reproducing apparatus according to claim 6, wherein the second diffraction element is disposed between the beam splitter and the light receiving element.   The optical characteristics of the information recording layer are Low-to-High type in which the reflectance of the recording portion is higher than the reflectance of the unrecorded portion, and High- in which the reflectance of the recording portion is lower than the reflectance of the unrecorded portion. The information recording / reproducing apparatus according to claim 6, wherein the information recording / reproducing apparatus is distinguished by one of a to-low type.   The information recording / reproducing apparatus according to claim 10, wherein when the optical characteristic of the information recording layer is a high-to-low type, the control unit performs a tracking control signal using an output from the second light receiving unit group. .   12. The information recording / reproducing apparatus according to claim 6, wherein the control unit also determines whether the number of information recording layers provided in the optical information recording medium is singular or plural. A semiconductor device provided in the information recording / reproducing apparatus according to claim 6,
Operating an optical pickup included in the information recording / reproducing apparatus and determining a type of the optical information recording medium;
Selecting a focus control and tracking control method according to the type of the optical information recording medium, and executing the focus control and tracking control of the optical information recording medium;
A semiconductor device incorporating a program for causing the optical information recording / reproducing apparatus to execute the program.

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