JP5014041B2 - Information recording / reproducing device - Google Patents

Description

  The present invention relates to an information recording / reproducing apparatus for optically recording or reproducing information on an information recording medium such as an optical disk.

  Conventionally, a disk-shaped medium such as an optical disk (hereinafter referred to as a disk) has been developed as the main axis of information storage media due to the portability of the medium, ease of handling, superiority of high-speed and random access response, and the like. . In recent years, along with the progress of high-density disks and high transfer rates, small-diameter and large-capacity disks have been adopted in mobile video devices such as high-definition digital cameras and video cameras, and the market has been further expanded.

  In particular, as a product group that supports high-definition video HD (High Definition), small-sized and light-weight HD cameras and HD displays have rapidly emerged. Or the “watching” environment is expanding. Against this background, in order to meet the need to record HD images for a long time, the capacity of the disc is being increased.

  As a promising technology for realizing a large disk capacity, there is a “multilayering” technique in which a plurality of recording / reproducing layers are stacked on a single disk. For example, in a DVD (Digital Versatile Disc), a double-layer disc is standardized, and a cover layer, a first layer, and a second layer are formed from the light beam incident side that is responsible for recording and reproducing information. A reflective film is formed on the second layer, and an intermediate layer is formed between the first layer and the second layer. The amount of reflected light from the first layer and the second layer is designed to be substantially the same.

  2. Description of the Related Art Conventionally, an optical head (hereinafter referred to as an optical pickup) that carries out irradiation of a light beam is mounted on an optical disc apparatus when information is recorded on or reproduced from a disc. The optical pickup includes a laser light source, an optical lens group including an objective lens for condensing a light beam on a disk surface, an actuator for driving the objective lens, and the like.

  The optical disc apparatus has a focus servo and tracking servo function for causing a light beam spot to follow a target track on the disc surface in order to drive and control the optical pickup to record or reproduce information on the disc. The tracking servo generates a track error signal by detecting reflected light from the disk with an optical sensor and performing arithmetic processing. Then, the position of the objective lens is controlled in the radial direction of the disk medium in accordance with the polarity and level of the error signal.

  At this time, a sled mechanism is provided for moving the entire optical pickup in the disc radial direction so that the objective lens is movable in the vicinity of the optical axis center of the optical pickup. Then, it is possible to control access to a desired track from the inner periphery to the outer periphery of the disk, such as an address seek operation, a track trace operation, and a track jump operation.

  By the way, various problems have become apparent in the optical disk apparatus corresponding to the multilayer disk. In particular, a wavefront aberration occurs due to a thickness error between layers from the light incident surface to the disk to each recording / reproducing layer. The light beam spot quality is directly related to information recording and reproduction. When the wavefront aberration increases, the recording or reproduction quality deteriorates, that is, the recording / reproduction margin decreases.

  In addition, the problem of leakage of reflected light from another layer different from the servo access layer (hereinafter referred to as crosstalk) becomes a noise component and causes a decrease in the recording / reproducing margin is also a problem inherent to the multilayer disc.

  With respect to such problems, techniques disclosed in Japanese Patent Application Laid-Open No. 10-106010 (Patent Document 1), Japanese Patent Application Laid-Open No. 08-212611 (Patent Document 2), Japanese Patent Application Laid-Open No. 11-016200 (Patent Document 3), etc. It has been known.

  Japanese Patent Application Laid-Open No. 10-106012 discloses a technique for eliminating spherical aberration caused by a disc thickness error by driving means for moving an optical element constituting an optical pickup in the optical axis direction. Japanese Patent Application Laid-Open No. 08-212611 discloses a technique in which a liquid crystal element is disposed in an optical path of an optical pickup, and a voltage corresponding to spherical aberration is applied to the liquid crystal element to give a phase difference to the light beam and correct the aberration. Is disclosed.

Furthermore, Japanese Patent Application Laid-Open No. 11-016200 discloses that a plurality of return light beams are extracted by providing an optical pickup with a plurality of branched optical members. In the same publication, these are subjected to arithmetic processing to reduce leakage of reflected light from other layers and secure a recording / reproducing margin.
JP 10-106012 A Japanese Patent Laid-Open No. 08-212611 JP-A-11-016200

  FIG. 14 is a diagram qualitatively showing how spherical aberration, which is the most dominant aberration, increases as the number of disk media increases. In the figure, the vertical axis represents the amount of spherical aberration generated, and the horizontal axis represents the number of layers of the medium. As is well known, since the spherical aberration increases in proportion to the medium substrate thickness error, the amount of spherical aberration increases according to the number of recording layers constituting the single-layer disc, double-layer disc and medium, and the quality of the light beam spot. Decreases. It is known that this spherical aberration increases as the objective lens numerical aperture (NA) of the optical pickup increases and the wavelength of the laser becomes shorter. In particular, due to the multi-layered medium, the layers farther from the light incident side are more susceptible to the substrate thickness error of the intermediate layer, and various margins tend to be severe.

  Further, with the increase in the number of recording media, the increase in NA, and the shortening of the wavelength, coma aberration occurs due to tilt (tilt), so that the tilt margin becomes more severe in the back layer. Thus, in a desirable form of a recording / reproducing drive corresponding to a multilayer medium, various recording / reproducing margins tend to be severer from the light incident side to the back layer.

  The techniques of Patent Documents 1 to 3 attempt to secure a recording / reproducing margin by providing a correction mechanism for such an increase in spherical aberration.

  Specifically, the one in Patent Document 1 is equipped with a mechanism for moving an optical element in an optical pickup that is responsible for recording or reproducing information on a disk, the one in Patent Document 2 is equipped with a liquid crystal element, and the one in Patent Document 3 Is to add an element for branching and extracting a plurality of reflected lights. As described above, the techniques described in Patent Documents 1 to 3 deal with the increasing aberration by providing a dedicated correction mechanism.

  However, the optical disk apparatus for mobile use is assumed to be field-operated that a user can hold with one hand, and further downsizing is promoted for each component of the optical pickup in order to reduce the size of the housing. In addition, due to market needs for recording as high-quality video as possible for a long time, it is essential to deal with large-capacity multi-layer discs, and it is urgent to secure a recording / reproduction margin required for optical disc apparatuses.

  Under such circumstances, the prior art described above has caused an increase in the size and weight of the optical pickup, an increase in the number of control signal lines, and the like, and has not been able to cope with the reduction in size and weight of the optical disc apparatus and further in the cost reduction.

  An object of the present invention is to provide an information recording / reproducing apparatus capable of ensuring a recording / reproducing margin with a simple configuration without adding a new mechanism or member.

When the present invention is an optical disc where the information recording medium is either single-layer recording medium having a single recording layer, it is detected whether or not the multi-layer recording medium having a plurality of recording layers, and detects a multilayer recording medium, AT The movable range of the objective lens in the radial direction of the optical disc with respect to the actuator is set narrower than in the case of a single-layer recording medium.

  According to the present invention, a recording / reproducing margin in a multilayer recording medium can be secured with a simple configuration. That is, by setting the movable range of the objective lens to be narrower in the multilayer recording medium than in the single-layer recording medium, it is possible to suppress an effective light amount reduction and aberration generation. Further, by setting the control range of the objective lens for each recording layer, a more detailed recording / reproducing margin increasing effect can be obtained. Furthermore, when recording / reproducing a multi-layer recording medium, by setting the movable range of the objective lens in accordance with the recording / non-recording state of each recording layer, the effect of expanding the recording / reproducing margin according to the use situation unique to the multi-layer recording medium is obtained. It is done.

  Next, the best mode for carrying out the invention will be described in detail with reference to the drawings.

(First embodiment)
<Overall Configuration and Series of Operations of this Embodiment>
FIG. 1 is a block diagram showing a first embodiment of the information recording / reproducing apparatus of the present invention. In the figure, 201 is an optical disc (hereinafter referred to as a disc) which is an information recording medium. In this embodiment, the disc 201 is a single-layer recording medium having one recording layer or a two-layer recording medium having two recording layers, and information can be recorded or reproduced on any disc. A disk having two or more recording layers is called a multilayer recording medium.

  Reference numeral 202 denotes an optical pickup (OPU) for irradiating a light beam to the disk 201 to record or reproduce information, 205 denotes a spindle motor (SPM) that drives the disk 201 to rotate, and 206 denotes a spindle driver that drives the spindle motor 205. . Reference numeral 209 denotes an AT (Auto Tracking) / AF (Auto Focusing) driver that drives an AT / AF actuator (not shown) in the optical pickup 202.

  Reference numeral 203 denotes a thread feeding mechanism that moves the optical pickup 202 in the radial direction of the disk 210, and reference numeral 204 denotes a thread (SLED) driver that drives the thread feeding mechanism 203. A servo processor 210 performs servo control such as spindle control, focus control, tracking control, and thread control.

  Reference numeral 207 denotes a reproduction signal processing unit that performs reproduction signal processing, 211 denotes a recording data processing unit that performs recording data processing, and 208 denotes a matrix calculation unit 208 that generates a servo-related signal such as a focus error signal, tracking error signal, or lens position signal. is there. A system controller 212 controls the entire apparatus.

  The basic operation of FIG. 1 will be described. The system controller 212 has a central processing function (CPU), and controls the entire operation of the optical disc apparatus by executing a higher-level designation command or a predetermined program from an operation system (not shown).

  The disk 201 is, for example, a phase change type disk recording medium, and the recording layer is made of a phase change material such as Ge—Sb—Te. When the light intensity is modulated and irradiated from the optical pickup 202 while rotating the disk 201, the amorphous state and the crystalline state change reversibly. In order to change the recording layer from the crystalline state to the amorphous state, the light beam is irradiated onto the pulse, once melted, and then rapidly cooled.

  On the other hand, in order to change the crystalline state from the amorphous state, annealing is performed at a temperature equal to or higher than the crystallization temperature by irradiation with a light beam having a relatively weak light intensity. Using such a phase change characteristic, information 1 or 0 can be stored by changing the state of the medium.

  The optical pickup 202 includes an optical coupling group, a laser light source (semiconductor laser), a laser driver for driving the laser light source, an objective lens for condensing a light beam from the laser light source on a recording layer of the optical disk, and the like. . Further, it is composed of an actuator for driving the objective lens in the focus direction and the tracking direction, a light receiving element for detecting reflected light from the disk, or the like.

  The optical pickup 202 performs light beam (laser light) irradiation to the disk 201, position control of the light beam (light beam spot), and detection of reflected light from the disk. The servo processor 210 controls the entire servo control.

  The servo processor 210 performs rotational drive control of the spindle motor 205 via the spindle driver 206. The rotation control of the spindle motor 205 employs a so-called CLV (Constant Linear Velocity) method. The disk 201 has meandering sidewalls called wobbles along the track grooves. The servo processor 210 controls the disk rotation speed so that the frequency of the wobble becomes a target value.

  The optical pickup 202 is provided with an AT / AF actuator for driving the objective lens in the tracking direction and the focus direction. The AT / AF driver 209 is controlled based on a tracking error signal and a focus error signal obtained by detecting and calculating reflected light from the disk 201. The objective lens is controlled in the tracking direction and the focus direction by driving the AT / AF actuator.

  Thus, focus control for maintaining the focus of the light beam spot on the target track of the rotating disk 201 or tracking control for tracking the light beam spot in the groove direction with respect to the information track is performed. Further, the thread feeding mechanism 203 is driven by the thread driver 204 to control the relative position between the optical pickup 202 and the objective lens. The position control of the objective lens is controlled by fine adjustment by an actuator and rough adjustment by a thread feed mechanism.

  FIG. 2 is a diagram showing an outline of lens position control (fine adjustment) by an actuator. In FIG. 2, 701 is a disk surface, 702 and 703 are objective lens positions, and 704 is a light beam. At the objective lens position 702, the objective lens center and the optical axis coincide with each other, and tracking tracking to the disk surface 701 is performed.

  Further, recording or reproduction is performed while shifting the objective lens to the position of 703 (only the lens position signal ΔLP) by the actuator and tracing the light beam spot on the target track. That is, while the objective lens is in the movable range of the actuator, the thread feeding mechanism 203 is stopped and the objective lens is shifted in the disk radial direction only by the actuator control to perform tracking tracking.

  At this time, when it is detected by the lens position signal LP that the objective lens position is located at the movable range end of the actuator, the servo processor 210 operates the thread feeding mechanism 203 to move the entire optical pickup 202 in the disk radial direction. (Coarse tone). In this way, the fine adjustment by the actuator and the rough adjustment by the thread feeding mechanism 203 are combined to control the objective lens to follow a predetermined track of the disk. The lens position signal LP is obtained from the sensor output in the optical pickup 202 as will be described later.

  Next, the sensor signal obtained from the optical pickup 202 is sent to the reproduction signal processing unit 207. The reproduction signal processing unit 207 performs gain control (Auto Gain Control), filtering (Pre Filter), and digitization (Analog / Digital Converter). Further, a clock generated in synchronization with the edge of the reproduction signal is generated from the digitized reproduction signal by a PLL (Phase Locked Loop) of the reproduction signal processing unit 207. It also performs waveform equalization using an equalizer, data detection using PRML (Partial-Response Maximum-Likelihood), demodulation processing, ECC (Error Correction Code), and the like.

  Subsequently, a data recording operation on the disc of the information recording medium will be described. The recording data to the disc 201 is subjected to predetermined modulation processing and data conversion in accordance with the disc recording format in the recording data processing unit 211. A laser driver (not shown) is built in the optical pickup 202, performs a well-known write strategy process, and controls a laser lighting cycle according to a recording data pattern.

<Generate lens position signal LP from sensor output>
Next, a method for generating a lens position signal (LP) will be described with reference to FIG. FIG. 3 shows a light spot arrangement, a sensor configuration, and a matrix portion on a track of a DPP method using three beams. The sensor unit in FIG. 3 corresponds to the light receiving element in the optical pickup 202, and the matrix unit corresponds to the matrix calculation unit 208 in FIG.

  As shown in FIG. 3, the position of the main beam Main is controlled at the center of the track. The positions of the sub beams SUB1 and SUB2 are shifted in the 1/2 track radial direction with respect to the main beam Main. The sensor unit corresponds to three beams, and a four-divided sensor (A to D) is arranged in the main beam Main, and a two-divided sensor (E to F, G to H) is arranged in the sub beams SUB1 and SUB2.

  The matrix section shows functional blocks that perform arithmetic processing on each sensor output signal. Reference numerals 601 to 604 denote calculators, 605 to 606 denote adders, and 607 denotes a coefficient calculator. The reflected light of the main beam Main is received by the four-divided sensors A to D.

  Of the sensor signals of the four-divided sensor, (A + D) and (B + C) are input to the calculator 602, and (A + D)-(B + C) is calculated and output. The reflected light of the sub beam SUB1 is received by the two-divided sensors E and F. The sensor signal of the two-divided sensor is input to the calculator 601 and an (EF) signal is output.

  On the other hand, the reflected light of the sub beam SUB2 is received by the two-divided sensors G and H. The output signal of the two-divided sensor is input to the calculator 603, and a (GH) signal is output. Further, the (EF) signal and the (GH) signal are input to the adder 605, and the (E + G)-(F + H) signal is output. Subsequently, the coefficient calculator 607 multiplies the predetermined coefficient k and outputs k {(E + G) − (F + H)}.

  On the other hand, the track error signal TE is obtained by the calculation of the calculator 604.

TE = (A + D)-(B + C) -k {(E + G)-(F + H)}
The push-pull signal of the main beam is obtained as the output signal (A + D) − (B + C) of the calculator 602, and includes an offset due to the objective lens shift in the disc radial direction. Therefore, after the push-pull component (E + G) − (F + H) of the sub beam is multiplied by a predetermined coefficient k, a difference calculation is performed to generate a track error signal TE in which the offset component is canceled.

  Here, the lens position signal LP is obtained by the calculation of the adder 606.

LP = (A + D)-(B + C) + k {(E + G)-(F + H)}
The lens position signal LP is extracted as a lens shift component in the disc radial direction by the sum of the main push-pull signal and the sub push-pull signal. The lens position signal LP is used for setting the control range of the objective lens as will be described later.

<Functional Configuration of System Controller 212 of Present Embodiment>
FIG. 4 is a functional block diagram relating to lens position control of the system controller 212. Reference numeral 501 denotes a disc determination unit, 502 a lens position control mode setting unit, and 503 a sled servo.

  The operation of the disc discrimination unit 501 will be described with reference to FIG. FIG. 5A shows a focus error signal, and FIG. 5B shows a disk layer detection pulse. Now, it is assumed that the disk surface is irradiated with laser light from the laser light source in the optical pickup 202 and the objective lens is brought closer to the disk surface.

  Then, focusing is performed at the lens position 801 (disk surface), and the focus error signal changes to an S shape. When the objective lens approaches the disc surface, the lens is focused at the lens position 802 (first layer), and the focus error signal becomes S-shape again.

  When the objective lens further approaches the disk surface, focusing is performed at the lens position 803 (second layer), and the focus error signal becomes S-shaped. The disc layer detection pulse shown in FIG. 5B is generated from the S-shaped zero cross signal. Therefore, the recording layer of the disc can be determined by counting the number of disc detection pulses during the movement period of the objective lens. That is, the number of disk layers N [layers] = disk layer detection pulse-1. It can also be determined whether the disc is a single-layer recording medium or a multi-layer recording medium.

  Next, operations of the lens position control mode setting unit 502 and the sled servo 503 will be described with reference to FIG. FIG. 6 is an explanatory diagram of the control of the sled servo 503. FIG. 6 (a) shows the operation in mode 1, and FIG. 6 (b) shows the operation in mode 2. The difference in the movable range of the objective lens is distinguished as modes 1 and 2.

  The vertical axis of FIG. 6A indicates the level of the lens position signal LP that represents the relative position of the objective lens with respect to the optical pickup 202. The lower limit of the vertical axis is the movable limit in the inner circumferential direction of the disk, and the upper limit is the movable limit on the outer circumferential side of the disk. The horizontal axis indicates time.

  In mode 1 in FIG. 6A, the lens position signal LP changes between the threshold values Th1 and Th2, and the position of the objective lens is controlled during this time. 6A shows a state in which the objective lens is traced on the track from the inner circumference of the disk toward the outer circumference by the tracing operation of the objective lens by the actuator.

  At the point B, when the lens position signal LP reaches the threshold Th1, the sled servo that controls the optical pickup 202 is operated to shift the lens position between B and C to Th2. The feed control stops at point C, and trace control of the light beam spot is performed again by controlling the objective lens by the actuator. Thereafter, between C and D; trace operation, between D and E;

  Next, the operation in mode 2 shown in FIG. The lens position signal LP changes between the threshold values Th3 and Th4, and the position of the objective lens is controlled during this time. Between a and b, the objective lens is traced by the actuator, and the objective lens is traced on the track from the inner circumference to the outer circumference of the disk.

  When the lens position signal LP reaches the threshold Th3 (Th3 <Th1) at the point b, the sled servo that feeds and controls the optical pickup 202 operates to move the lens position between b and c to Th4 (Th4 <Th2). shift. The feed control stops at the point c, and the light beam spot trace is controlled again by the objective lens control by the actuator.

  Thereafter, between c and d; trace operation, between d and e; The difference between the modes is the control range (movable range) of the objective lens, and the relationship of mode 1> mode 2 is established.

  FIG. 7 shows a graph of the amount of light (FIG. 7A) and the total wavefront circumferential difference (FIG. 7B) when the objective lens is shifted. In FIG. 7A, the horizontal axis indicates the objective lens position [μm], and the vertical axis indicates the objective lens output light amount. If the amount of light when the objective lens position is 0, that is, when the center of the objective lens coincides with the optical axis is 1, when the objective lens position is shifted by +300 [μm], the light amount becomes 0.8, which is about 20 % Reduction in light intensity is observed. Although the position of the objective lens is controlled by an actuator, the amount of relative positional deviation from the optical pickup is expected to be approximately ± 300 [μm].

  On the other hand, in FIG. 7B, the horizontal axis indicates the objective lens position [μm], and the vertical axis indicates the total wavefront aberration [mλrms] which is the optical spot quality on the disk surface. When the objective lens position is 0, that is, the aberration when the objective lens center and the optical axis coincide with each other is 30 [mλrms], the aberration is 50 [mλrms] when the objective lens position is shifted by +300 [μm]. It becomes.

<Description of Operation Flow of this Embodiment>
Next, the operation of this embodiment will be described using a flowchart. FIG. 8 shows an operation flow of this embodiment.

Step 101: Disc discrimination Disc discrimination is performed when a disc is inserted or when the power is turned on. If the disk 201 is a single-layer recording medium, the process proceeds to step 102, and if it is a two-layer (multi-layer recording medium), the process proceeds to step 103. Disc determination is performed using the method described with reference to FIG. 5. If the count value of the disc layer detection pulse in FIG. 5B is two, a single-layer disc (single-layer recording medium), and if three, a dual-layer disc ( Multi-layer recording medium). Hereinafter, the control range (movable range) of the objective lens is set according to the detection result.

Step 102: Lens position control mode 1 setting The system controller 212 sets the lens position control to mode 1. That is, when the disc detection result is a single-layer recording medium, the control range of mode 1 is set.

Step 103: Set to lens position control mode 2 The system controller 212 sets the lens position control range to mode 2. That is, when the disc detection result is a multilayer recording medium, the control range of mode 2 is set.

  FIG. 9 shows an example of mode 1 / mode 2 of lens position control. In mode 1, the control range of the objective lens is set to ± 300 [μm], and in mode 2, it is set to a narrow control range of ± 150 [μm], which is half of mode 1. The control range of the objective lens refers to a movable range with respect to the center position of the objective lens.

  When setting the movable range of the objective lens, the relationship between the lens position signal LP and the movement distance of the objective lens is examined in advance and stored in the memory. For example, as shown in FIG. 6, the servo processor 210 sets the movable limit when the objective lens reaches the lens position signal level corresponding to Th1, based on the recording or reproduction.

  As described above, in the present embodiment, the movable range of the objective lens is set narrower in the case of multi-layer recording medium shooting than in the case of a single-layer recording medium with respect to the reduction in recording / reproducing margin due to lens shift. By doing so, it is possible to suppress an effective decrease in light amount and occurrence of aberrations, and to obtain a recording or reproduction margin increase effect.

  In the present embodiment, the relative position of the objective lens with respect to the optical pickup is controlled using the lens position signal LP obtained from the sensor output, but is controlled using a sensor that detects the physical position of the objective lens. Also good. The same applies to the following embodiments.

  In addition, the control mode is changed by dividing the number of layers of the disc into a single layer and two layers. However, even if the number of layers of the disc is three or more, a plurality of modes can be set according to the number of layers. It is clear from the main point.

(Second Embodiment)
Next, a second embodiment of the information recording / reproducing apparatus of the present invention will be described. The functional configuration of the second embodiment is the same as that of FIG. 1, but the second embodiment is different in that the movable range of the objective lens is set for each recording layer when the disk is a multilayer recording medium.

<Description of Operation Flow of Second Embodiment>
FIG. 10 shows an operation flow of the second embodiment.

Step 901: Disc discrimination Disc discrimination is performed when a disc is inserted or when the power is turned on. If the recording medium is a single-layer recording medium, the process proceeds to step 902. If the recording medium is a multilayer recording medium, the process proceeds to step 903. The disc discrimination method is the same as in the first embodiment.

Step 902: Lens position control mode 1 setting The system controller 212 sets the lens position control to mode 1. That is, when the disc detection result is a single-layer recording medium, the mode 1 is set. Mode 1 is the same as lens position control mode 1 for the single-layer disc described in FIG.

Step 903: Servo access layer detection When the disc detection result is a multilayer recording medium, the system controller 212 detects the servo access layer (recording layer to be recorded or reproduced) of the disc. This is detected based on the count value of the disk layer detection pulse as described in FIG. If the count value of the disc layer detection pulse is two, the recording layer of the first layer (first layer from the light incident side) is discriminated to be the second recording layer if it is three.

Step 904: Objective Lens Control Range Table Setting The system controller 212 sets the movable range of the objective lens for each recording layer based on a table prepared in advance according to the servo access layer. FIG. 11 shows an example of a lens position control table.

  In FIG. 11, the movable range of the objective lens is set for each of the first layer (first layer from the light incident side) of the disk, and the second layer is set to mode 3, and the second layer is set to mode 4. In mode 4, the movable range of the objective lens is set to ± 150 [μm], and in mode 3, a wide movable range of ± 200 [μm] is set. Also in this embodiment, the setting of the movable range of the objective lens is performed in the same manner as described with reference to FIG.

  As described above, in this embodiment, the movable range of the objective lens is set for each recording layer of the disc. That is, in the case of a two-layer disc, the margin on signal quality is wider in the recording layer L0 (first layer) on the near side as viewed from the light incident side than in the recording layer L1 (second layer) on the back side.

  In this embodiment, by making the movable range of the objective lens different between the first layer and the second layer, it is possible to suppress the effective light amount reduction and the occurrence of aberration, and to contribute to securing the recording / reproduction margin of the second layer. Become.

  In this embodiment, the control mode is changed by dividing the number of layers of the disc into the first layer and the second layer. However, even if the number of recording layers of the disc is three or more, a plurality of modes are selected according to the recording layers. It is clear from the gist of the present invention that it can be set. That is, by setting the movable range of the objective lens to be narrower toward the recording layer farther from the light incident side of the multilayer recording medium, it is possible to contribute to securing a recording / reproducing margin.

  Further, from the viewpoint of the film material composition of the multilayer disk, the recording film on the light incident side is restricted in particular to use a material that increases the transmittance (for example, Ge—Sb—Te system). In addition, it is possible to provide a metal reflective film having a rapid cooling effect on the recording film on the back side, and it is easy to recrystallize after melting with a recording power, thereby improving the recording quality. That is, depending on the film material and film structure, there may be a recording / reproducing margin that is lower on the light incident side.

  Due to the difference in the characteristics of the medium, the margins of the first layer and the second and subsequent layers may be reversed. According to the present embodiment, the optimum control range can be set according to the margin for each recording layer, so that it is possible to cope with such a medium difference.

(Third embodiment)
Next, a third embodiment of the information recording / reproducing apparatus of the present invention will be described. The functional configuration of the third embodiment is the same as that of FIG. 1, but the third embodiment further determines whether the recording layer has been recorded or not recorded as compared to the second embodiment. And the point which sets the movable range of an objective lens for every recording layer differs according to the discrimination | determination result.

<Description of Operation Flow of Third Embodiment>
FIG. 12 shows an operation flow of this embodiment.

Step 1001: Disc discrimination Disc discrimination is performed when a disc is inserted or when the power is turned on. If the disc is a single-layer recording medium based on the detection result, the process proceeds to step 1002, and if the disk is a multi-layer recording medium, the process proceeds to step 1003. The disc discrimination method is the same as in FIGS.

Step 1002: Lens movable range mode 1 setting The system controller 212 sets the objective lens movable range to mode 1, and performs subsequent objective lens position control according to mode 1. Mode 1 is the lens position control mode of FIG. 9 as described above.

Step 1003: Discrimination of recording / unrecorded state of each recording layer The system controller 212 detects the recording state of each layer of the multilayer recording medium. That is, it is detected whether each recording layer of the disc has been recorded or not recorded. Whether the recording layer has been recorded or not recorded can be determined from, for example, disc management information. If any data is recorded on the recording layer of the disc, it is recorded.

Step 1004: Servo access layer detection The system controller 212 detects a layer for servo access. This is the same as FIG.

Step 1005: Lens position control table setting The system controller 212 sets the movable range of the objective lens based on a table prepared in advance according to the servo access layer. The movable range of the objective lens is set in the same manner as in FIGS. In the table, the movable range of the objective lens of the servo access layer is individually set according to the condition (recorded / unrecorded condition) of the recording layer adjacent to the servo access layer.

  FIG. 13 shows an example of the objective lens position control table. As shown in FIG. 13, the movable range of the objective lens is individually set according to the recording state of the servo access layer and the adjacent recording layer. For example, regarding the recording layer of the first layer (the first layer from the light incident side) of the disc, ± 150 [μm] is set if the adjacent second recording layer has been recorded, and the second layer is in an unrecorded state If so, ± 200 [μm] is set.

  For the second recording layer, ± 100 [μm] is set if the adjacent first recording layer has been recorded, and ± 150 [μm] is set if the first recording layer is unrecorded. Thus, by setting the movable range of the objective lens according to the recording state of the adjacent recording layer, it is possible to secure a margin according to the recording state of the disc.

  In this embodiment, the control mode is changed by dividing the number of layers of the disc into the first layer and the second layer. However, even if the number of layers of the disc is 3 or more, a plurality of modes can be set according to each layer. Is clear from the gist of the present invention.

1 is a block diagram of an information recording / reproducing apparatus according to the present invention. It is a figure explaining lens shift. It is a functional block diagram of a sensor part and a matrix calculating part. It is a functional block diagram of a system controller. It is a figure explaining disk discriminating operation. It is a figure explaining the objective-lens control range of this invention. It is a figure explaining the influence of a lens shift concretely. It is a flowchart which shows the operation | movement of the 1st Embodiment of this invention. It is a figure which shows the objective lens control range setting table used for the 1st Embodiment of this invention. It is a flowchart which shows the operation | movement of the 2nd Embodiment of this invention. It is a figure which shows the objective lens control range setting table used for the 2nd Embodiment of this invention. It is a flowchart which shows the operation | movement of the 3rd Embodiment of this invention. It is a figure which shows the objective lens control range setting table used for the 3rd Embodiment of this invention. It is a figure which shows the relationship between the number of recording layers of a multilayer disc, and spherical aberration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 201 Optical disk 202 Optical pick-up 203 Thread feed mechanism 204 Thread driver 205 Spindle motor 206 Spindle motor driver 207 Reproduction signal processing part 208 Matrix calculation part 209 AT / AF driver 210 Servo processor 211 Recording data processing part 212 System controller

Claims (4)

In an information recording / reproducing apparatus having an optical pickup including a laser light source, an objective lens for condensing a light beam from the laser light source on an optical disc, and an actuator for driving the objective lens in a tracking direction,
Means for detecting whether the optical disc is a single-layer recording medium having one recording layer or a multilayer recording medium having a plurality of recording layers;
Means for setting a movable range in the radial direction of the optical disk of the objective lens with respect to the actuator according to a detection result of the detection means;
An information recording / reproducing apparatus characterized in that when the optical disc is detected as a multilayer recording medium by the detecting means, the movable range of the objective lens is set narrower than in the case of the single-layer recording medium.   The said setting means sets the said movable range of the said objective lens for every recording layer of the said optical disk, when the said optical disk is detected by the said detection means as a multilayer recording medium. Information recording / reproducing apparatus.   A unit for detecting whether each recording layer of the optical disc is recorded or not recorded, and the setting unit sets the movable range of the objective lens for each recording layer of the optical disc. The information recording / reproducing apparatus according to claim 2, wherein the movable range of the objective lens is set according to a recording state.   When setting the movable range of the objective lens for each recording layer of the optical disc, the setting means sets the movable range of the objective lens narrower toward the recording layer farther from the incident side of the light beam of the optical disc. The information recording / reproducing apparatus according to claim 2.