JP2011159353A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To protect recorded data from unpredictable radiation of reproduction power and to improve disk discrimination reliability, in an optical disk recording/reproducing device that records and reproduces data to/from single-layer and multilayer disks. <P>SOLUTION: An optical pickup includes an optical modulation means divided into a plurality of sections by an elliptical- or circular-shaped division line. In normal recording and reproducing, a light spot having a normal NA is used while inactivating the optical modulation means. On the other hand, during idle or standby where recording and reproducing are not performed or when a disk is discriminated, a large light spot (small NA) is used by activating the optical modulation means, and the disk is irradiated with predetermined power lager than reproducing power. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical disc, and more particularly, to an optical disc recording / reproducing apparatus having a plurality of information recording layers.

  As a technique for effectively changing the numerical aperture NA in accordance with the operation mode and irradiating the optical spot with a light spot having a different shape, there is, for example, Japanese Patent Application Laid-Open No. 6-290485.

  Patent Document 1 states that “the light transmittance of the central portion 112 and the light transmittance of the side portions 113 and 113 can be controlled by a signal from the control means 110. Thereby, the second embodiment is compared with the first embodiment. In addition, by setting the light transmittance of the central portion 112 to 1 and the light transmittance of the side portions 113 and 113 to 0, it is possible to obtain a condensing spot having a diameter larger in one direction than a normal condensing spot. Has been.

  Further, Patent Document 1 states that “the modulation means 111 is modulated by a method as shown in the fifteenth embodiment so that a tracking servo signal optimum for seeking, that is, a converging spot width for obtaining a track crossing signal can be obtained. In addition, at the time of reproduction, the modulation amount of the modulation means 111 is set by the method as described in the sixteenth embodiment or the like so as to obtain the condensing spot length and width at which an optimum reproduction signal can be obtained. It is described.

  Further, in Patent Document 1, “the focus spot diameter is set to be enlarged in both the vertical and horizontal directions before the start of focus pull-in (step 402) (step 419), and the focus pull-in is completed in that state. According to Examples 14 to 16, a condensing spot is set (step 420). "

JP-A-6-290485

  In recent years, in order to further increase the capacity of an optical disc, studies have been made on laminating a plurality of information recording layers on one optical disc. In order to realize the recording / reproduction of the innermost layer, it is necessary to set the reflectance of each layer before that to be low according to the number of stacked layers. As an example, a conventional Blu-ray Disc (hereinafter abbreviated as BD) is required. In the case of a recordable single-layer disc, the reflectivity in the unrecorded state is around 18%, and in the recordable double-layer disc, it is around 6%. Therefore, the reflectance of each layer needs to be around 3%.

  Since the decrease in reflectance is accompanied by a decrease in the signal noise ratio (hereinafter abbreviated as SNR) of the reproduction signal, it is necessary to increase the reproduction power in accordance with the decrease in the reflectance in order to secure the SNR. In the example of the BD, the reproduction power needs to be increased to about 1.2 mW for the multi-layer disc, whereas the reproduction power is about 0.3 mW for the single-layer disc and about 0.7 mW for the double-layer disc.

  On the other hand, recording-type optical discs based on the recording principle of recording film state changes caused by heating with a focused beam are sensitive to thermal energy, and thus continue to be irradiated for a long time even at a reproduction power level. As a result, there may be a phenomenon that the recorded data deteriorates. Hereinafter, the resistance against such a deterioration phenomenon is referred to as a reproduction light resistance as a concept, but it is necessary to suppress the reproduction power in order to ensure the reproduction light resistance.

  In order to achieve both SNR ensuring and trade-off light strength ensuring which are in a trade-off relationship, it is considered that the reproducing power is individually set for each layer in the multilayer disk. For example, the reproduction power may be 1.2 mW in the first layer, 1.4 mW in the second layer, and 1.6 mW in the third layer.

  However, when the reproduction power of each layer is different, there is a possibility that the recorded data may be deteriorated if there is a focus jump failure or a focus error. For example, in the above example, if it is accidentally drawn into the first layer with the intention of being drawn into the third layer, the reproduction power of 1.6 mW is applied to the first layer which should be 1.2 mW of reproduction power. As a result, there is a problem that the recorded data is deteriorated.

  Further, as described above, when the reproduction power is different by about 4 times between the single-layer disc and the multilayer disc, the reproduction power in disc discrimination (disc layer count) when the disc is loaded becomes important. That is, when disc discrimination is performed with the reproduction power of a multi-layer disc, there is a problem that the recorded data is deteriorated when the loaded disc is a single-layer disc or a double-layer disc. Conversely, when disc discrimination is performed using the playback power of a single-layer disc, in addition to the low reflectivity of each layer in a multi-layer disc, the focus error signal etc. due to the influence of spherical aberration caused by the difference in distance from the disc surface to each layer Therefore, there is a problem that an appropriate signal cannot be acquired and there is a high possibility of erroneous determination.

  The present invention has been made in view of the above, and an object of the present invention is to protect recorded data from unexpected reproduction power irradiation in an optical disk recording / reproducing apparatus capable of recording and reproducing single-layer and multi-layer disks. It is. Another object of the present invention is to improve the reliability of disc discrimination.

  In order to solve the above-described problems, the present invention uses the configuration described in the claims as an example.

  According to the present invention, recording data can be protected from unexpected reproduction power irradiation. Further, the reliability of disc discrimination is improved.

Flowchart of playback preparation operation in the first embodiment Configuration of optical pickup in the first embodiment The top view of the light modulation means in 1st Example Block diagram of the optical disk recording / reproducing apparatus in the first embodiment Flowchart of recording preparation operation in the first embodiment The top view of the light modulation means in 2nd Example Flowchart of disk discrimination operation in the second embodiment

  In describing the details of the present invention, for the sake of convenience, a BD is taken as an example of a conventional optical disc having a single layer or two information recording layers in the present invention. In addition, for the sake of convenience, an optical disc having three or four information recording layers in the present invention will be described assuming a next-generation BD that uses a BD optical system and signal format. However, the essence of the present invention is not limited to the BD and the next-generation BD, and can be applied to an optical recording medium or an optical disk in which ensuring of SNR and ensuring of reproduction light resistance are in a trade-off relationship with respect to reproduction power. .

  Embodiments of an optical disc apparatus and an optical disc recording / reproducing method according to the present invention will be described below in detail with reference to the drawings. According to the optical disk apparatus shown in the following embodiments, it is possible to protect recorded data from unexpected reproduction power irradiation, and to ensure reliability of disk determination, particularly for an optical disk having a plurality of information recording layers. improves.

  The configuration and operation of the optical disc recording / reproducing apparatus as the first embodiment of the present invention will be described with reference to the drawings.

  FIG. 2 is a configuration diagram of the optical pickup in the present embodiment. The optical pickup according to the present embodiment converts a laser light source 11 in a 405 nm band that is a wavelength corresponding to BD, a laser drive circuit 12 that drives the laser light source 11, and a light beam emitted from the laser light source 11 into a parallel light beam. The collimating lens 13, the light modulating means 14 capable of modulating the amplitude of a part of the light beam when the parallel light beam is transmitted, and substantially 100% of the predetermined linearly polarized light, and the linearly polarized light orthogonal to the linearly polarized light is transmitted. A polarizing beam splitter 15 that reflects approximately 100%, a quarter-wave plate 16 that converts linearly polarized light into circularly polarized light, and circularly polarized light into linearly polarized light, and a two-lens combination lens with a variable distance between lenses. The spherical aberration correcting means 17 for adjusting the spherical aberration of the parallel light beam according to the cover layer thickness of the optical disk 30 mounted in this manner, and the predetermined information recording on the optical disk 30 with the parallel light beam. It provided on an objective lens 18 forming a light spot follows a predetermined NA and a predetermined amount of aberration, the objective lens actuator 19 for displacing the objective lens 18 in the focusing direction and the tracking direction. In addition, a front monitor 20 that receives a part of the light beam emitted from the laser light source 11 and converts it into an electrical signal, a detection lens 21 that converts a reflected light beam from the disk into a predetermined convergent light beam, and receives the converged light beam. And a photodetector 22 that converts the signal into an electrical signal.

  The linearly polarized light beam emitted from the laser light source 11 is converted into a parallel light beam by the collimator lens 13 and enters the light modulation means 14.

  The light modulation means 14 of this embodiment includes a liquid crystal element divided into at least two regions, a polarizing element that transmits substantially 100% of predetermined linearly polarized light, and reflects substantially 100% of linearly polarized light that is orthogonal to the linearly polarized light. It consists of. FIG. 3 is a plan view of the light modulation means 14 of the present embodiment, and shows an example of a division pattern of the liquid crystal element. In the present embodiment, the central region 14a through which the principal ray of the light beam passes is elliptical, the direction corresponding to the disk radial direction is the major axis direction, and the major axis is equivalent to 0.7 in terms of NA of the objective lens 18. The direction corresponding to the disk tangential direction is the minor axis direction, and the minor axis corresponds to 0.5 in terms of the NA of the objective lens 18. The peripheral region 14b can be controlled in optical rotation by being electrically operated through the light modulation means control circuit 42. In the operating state, the transmitted light beam is rotated by 90 ° with respect to the incident light beam, and is not operated. It does not rotate in the state. On the other hand, the linearly polarized light incident on the central region 14a is transmitted without changing the polarization direction. The polarizing element is arranged so that the linearly polarized light transmitted through the central region 14a and the linearly polarized light transmitted through the peripheral region 14b in a non-operating state are transmitted approximately 100%.

  The light beam that has passed through the light modulating means 14 is a predetermined linearly polarized light regardless of whether the light modulating means 14 is in an operating state or a non-operating state, and enters a polarizing beam splitter 15 disposed in a direction that transmits approximately 100% of the linearly polarized light. Incident. The light beam that has passed through the polarizing beam splitter 15 is then converted into circularly polarized light by the quarter-wave plate 16, given a predetermined spherical aberration by the spherical aberration correcting means 17, and then guided to the objective lens 18. The objective lens 18 condenses the incident light beam on the information recording layer of the optical disc 30 to form a light spot.

  When the light modulation means 14 is in a non-operating state, the light beam passes through the central area 14a and the peripheral area 14b of the light modulation means 14 as described above, and is equivalent to NA 0.85 due to the aperture restriction provided in the objective lens actuator 19. The optical disc 30 is irradiated as a general light spot in BD.

  On the other hand, when the light modulation means 14 is in an operating state, the light beam passes through only the central region 14a, so that the disk radial direction is narrowed to NA 0.7 and the disk tangential direction is narrowed to NA 0.5. That is, by causing the light modulation means 14 to function as an aperture limit, an elliptical light spot whose major axis is the disk tangential direction that is larger than a general light spot in BD is formed.

  Here, the reason why the shape of the central region 14a of the light modulation means 14 is an elliptical shape having different NAs in the disk tangential direction and the disk radial direction will be described.

First, with regard to the disk radial direction, the generation of push-pull signals was considered. The push-pull signal is used not only as a tracking error signal but also for reproducing address information and the like from a wobble signal superimposed on the push-pull signal.
The push-pull signal is generated using a diffraction phenomenon due to the groove structure of the disk, and it is ensured that the 0th-order diffracted light and the ± 1st-order diffracted light overlap, in other words, ± 1st-order diffracted light is incident on the pupil of the objective lens. This is a necessary condition for detecting a sufficient push-pull signal. Under the condition where the track pitch is 0.32 μm and the wavelength is 405 nm, when the NA is 0.63 or less, the ± first-order diffracted light is not incident on the pupil of the objective lens, and the push-pull signal is hardly detected. Therefore, in this embodiment, NA 0.7 is set so that a push-pull signal can be detected.

  Further, regarding the disk tangential direction, the energy density of the light spot was considered. For the same amount of incident light, the energy density of the light spot is generally determined by the area of the light spot. In the case of a circular shape, if treated as being inversely proportional to the square of NA, NA 0.7 as in the disk radial direction In this case, the energy density of the light spot is 0.68 times that of the NA 0.85 light spot. Furthermore, the energy density can be reduced by lowering the NA in the disk tangential direction to make it elliptical. . However, the smaller the NA, the greater the influence of the relative displacement between the dividing line of the light receiving surface of the light detector 22 and the light spot on the light receiving surface on the deterioration of the focus error signal, leading to a decrease in focus error detection accuracy. There is a fear. Therefore, in this embodiment, NA is set to 0.5 as an example. In this case, the energy density is about 0.48 times the half of the light spot with NA of 0.85.

  FIG. 4 is a block diagram of the optical disk recording / reproducing apparatus of the present embodiment. The optical disk recording / reproducing apparatus of this embodiment includes an optical pickup 10, a spindle motor 31, a slider mechanism 32, a system control circuit 40, a servo control circuit 41, an optical modulation means control circuit 42, and a servo signal generation circuit 43. The reproduction signal generation circuit 44, the reproduction signal binarization circuit 45, the encoder 46, the decoder 47, the light modulator driving setting and the light spot power setting value for each operating condition (or the light emission of the laser light source 11). A light spot condition storage means 48 for storing the power setting value). Although not shown, an interface is provided to communicate with the host device.

  The configuration and operation of the optical pickup 10 are as described above.

  The system control circuit 40 has a function of controlling the operation of the entire optical disc recording / reproducing apparatus of this embodiment. In other words, rotation control of the optical disk 30 mounted on the spindle motor 31 is performed via the servo control circuit 41, and seek control and feed control for driving the slider mechanism 32 to displace the optical pickup 10 in the radial direction of the optical disk 30 are performed. Then, the objective lens actuator 19 mounted on the optical pickup 10 is driven to perform focus control and tracking control of the objective lens 18, and the spherical aberration correcting means 17 also mounted on the optical pickup is driven to reduce the spherical aberration. to correct. Further, the light spot condition storage means 48 is referred to, and the operation state and non-operation state of the light modulation means 14 are switched via the light modulation means control circuit 42 as described above according to the reference result.

  Further, the system control circuit 40 performs laser based on the output of the front monitor 20 mounted on the optical pickup 10 so that the emitted light amount of the laser light source 11 becomes a predetermined light amount based on the reference result of the light spot condition storage means 48. The laser light source 11 is driven via the drive circuit 12. The laser drive circuit 12 has a function of superposing a high frequency of a predetermined frequency on the drive current, and causes the laser light source 11 to emit light with a predetermined pulse waveform during reproduction. At the time of recording, the recording data signal is converted into an NRZI signal by predetermined modulation recording by the encoder 46 and supplied to the system control circuit 40. The system control circuit 40 converts the recording data signal into a recording strategy (light emission pulse train) corresponding to the NRZI signal, The laser light source 11 is caused to emit light with a predetermined light intensity and pulse width via the laser drive circuit 12.

  The reflected light beam from the optical disk 30 is received by the photodetector 22 and converted into an electrical signal, which is sent to the servo signal generation circuit 43 and the reproduction signal generation circuit 44. The servo signal generation circuit 43 selects and generates various servo signals by a detection method suitable for the mounted optical disk 30 and supplies the selected servo signal to the system control circuit 40. The servo signal includes at least a focus error signal and a tracking error signal. Based on these servo signals, the system control circuit 40 drives the objective lens actuator 19 via the servo control circuit as described above to operate the focus servo and tracking servo. Further, the spherical aberration correcting means 17 is driven via the servo control circuit 41 based on the amplitude of the push-pull signal generated by the servo signal generation circuit 43 and the amplitude of the reproduction signal supplied via the reproduction signal generation circuit 44. Then, the spherical aberration is corrected in accordance with the cover layer thickness of the optical disc 30.

  The reproduction signal generation circuit 44 includes a waveform equalization circuit and an A / D converter. The analog reproduction signal supplied from the optical pickup 10 is subjected to sampling and quantum after a predetermined waveform equalization process. Is converted into a digital signal and supplied to the reproduction signal binarization circuit 45.

  The reproduction signal binarization circuit 45 includes a transversal filter, a Viterbi decoding circuit, and a PRML reproduction system parameter setting circuit. The digital signal supplied from the reproduction signal generation circuit 44 is equalized to a predetermined PR class by a transversal filter. The Viterbi decoding circuit performs maximum likelihood decoding and converts this equalized waveform into an NRZI signal based on a predetermined modulation rule. The PRML playback system parameter setting circuit has a function of evaluating an error in the NRZI signal generated by the Viterbi decoding circuit. Further, a target waveform after PR equalization by the transversal filter corresponding to the PR class and the signal level supplied from the reproduction waveform generation circuit 44 is determined, and based on the target waveform and the error evaluation result, the transversal filter is determined. The tap coefficient and the discrimination point level in the Viterbi decoding circuit are set. The NRZI signal generated by the reproduction signal binarization circuit 45 is converted into a reproduction data signal by the decoder 47.

  FIG. 1 is a flowchart of the reproduction preparation operation of this embodiment. The operation procedure until the optical disc recording / reproducing apparatus of the present embodiment starts reproduction in response to a reproduction command from the host apparatus is shown.

  First, in order to set the optical pickup 10 to the idle mode, the current operation mode is confirmed as step 100, and the process branches according to the result. Here, the idle mode is a standby state in which the optical disc apparatus is operating but data is not being reproduced or recorded on the optical disc 30 loaded.

If it is not the idle mode, the set value of the idle mode is read from the light spot condition storage means 48 as step 101. In the present embodiment, the state of the light modulation means is the operation state regardless of the type of the optical disk 30 loaded.
On the other hand, the power of the light spot is set to a different setting value depending on whether the optical disc 30 is a single-layer disc, a two-layer disc, or a three-layer or four-layer disc. (Unlike the light spot power in the reproduction mode, which will be described later, in the three-layer or four-layer disc, all the information recording layers have the same setting value.) In this embodiment, the energy density of the light spot is taken into consideration. Here, the value of the reproduction power at the standard speed of each disk is set to be 1 to 2 times, and as an example, the power of the light spot is 0.5 mW for a single-layer disk, 1.0 mW for a double-layer disk, 3 layers or 4 layers The disk is 2.0 mW. Note that different setting values can be used depending on whether the optical disc 30 is a write-once disc or a rewritable disc.

  Further, the setting of high frequency superposition by the laser driving circuit 12 is off. In general, laser noise can be reduced by high-frequency superposition, but on the other hand, reproduction light resistance is reduced. In the idle mode, it is possible to further secure the reproduction light resistance by turning off the high frequency superimposition. Alternatively, it is possible to increase the power of the light spot as the reproduction light resistance improves.

Next, in step 102, the light modulation means 14 is set to an operating state, and light is emitted with a set value corresponding to the optical disk 30 on which the laser light source 11 is mounted.
As described above, by setting the light modulation means 14 to the operating state, the aperture of the light beam is restricted to NA 0.5 in the disk tangential direction and NA 0.7 in the disk radial direction, which is larger than the normal light spot of NA 0.85. An enlarged elliptical light spot is formed. In addition, the power of the light spot is made higher than the normal reproduction power at NA 0.85, and the energy density of the light spot is made lower than the energy density of the normal light spot at NA 0.85.

As a result, in the idle mode, it is possible to improve the light intensity received by the photodetector 22 and ensure the reproduction light resistance while ensuring the SNR of the servo signal and the like.
If the idle mode is already set at step 100, the above steps 101 and 102 are skipped.

  Next, in step 103, an access operation is performed. That is, according to the reproduction start address, the optical pickup 10 is driven in the disk radial direction by the slider mechanism 32 to perform a seek operation, the objective lens actuator 19 is driven to perform a focus jump to the target information recording layer, and further tracking An operation is performed to obtain an address from the wobble signal, and the track is moved to position the light spot on the track having the reproduction start address.

  By the way, it is known that spherical aberration proportional to the fourth power of NA occurs with respect to the thickness error of the cover layer. However, if there is spherical aberration, the waveform of the focus error signal is distorted and the focus jump fails. Cause. In the present embodiment, since the light spot is NA 0.7 in the disk radial direction and NA 0.5 in the disk tangential direction at the time of focus jump, distortion of the focus error signal is suppressed and stable focus jump is possible.

  In step 104, the reproduction mode setting value is read from the light spot condition storage means 48. The setting value of the reproduction mode is recorded in advance in the light spot condition storage means 48 as each setting value corresponding to the type of the mounted optical disk 30 and each information recording layer. In the present embodiment, the state of the light modulation means 14 is a non-operating state regardless of the type of the mounted optical disk 30.

  On the other hand, the power of the light spot is a set value that differs depending on whether the optical disc 30 is a single-layer disc, a two-layer disc, a three-layer or a four-layer disc (and for each information recording layer in a three-layer or four-layer disc). As an example, the power of the light spot at the standard playback speed is 0.3 mW for a single-layer disc, 0.6 mW for a dual-layer disc, 1.2 mW for the first layer of a three-layer disc, and 1 for the second layer of a three-layer disc. .1 mW The third layer of a three-layer disc is 1.0 mW. The first and second layers of the four-layer disc are 1.2 mW, the third layer is 1.1 mW, and the fourth layer is 1.0 mW. Note that different setting values can be used depending on whether the optical disc 30 is a write-once disc or a rewritable disc.

  A set value is previously stored in the light spot condition storage means 48 for each condition so that different reproduction powers can be set depending on the reproduction speed. When the reproduction power differs depending on the reproduction speed, a situation may occur in which the conditions corresponding to the reproduction speed are not directly recorded in the light spot condition storage unit 48. For example, it is desired to perform reproduction at 5 × speed, but the conditions under which the set value is recorded are the standard speed, 2 × speed, 4 × speed, and 6 × speed. In this case, each set value of 4 × speed and 6 × speed is read, and a set value of 5 × speed is calculated by linear interpolation or the like.

  The setting of high frequency superimposition of the laser drive circuit 12 is on.

  In step 105, the light modulation means 14 is set in a non-operating state, and irradiation is performed as a normal light spot with NA of 0.85. Further, the laser light source 11 is caused to emit light based on the type of the loaded optical disk 30 and the power of the light spot corresponding to the information recording layer read in step 104. That is, a standard light spot suitable for reproduction of BD and next generation BD is formed. Then, the spherical aberration and the focus offset are adjusted as necessary.

  The reproduction preparation is completed by the above procedure, and reproduction is started.

FIG. 5 is a flowchart of the recording preparation operation of this embodiment. The operation procedure until the optical disc recording / reproducing apparatus of the present embodiment starts recording in response to a recording command from the host apparatus is shown.
The operations of Step 100, Step 101, and Step 102 are the same as the above-described reproduction preparation operation, and the light spot is set to the idle mode.
In step 106, an access operation is performed to position the light spot on the track having the recording start address.
In step 107, the recording mode setting value is read from the light spot condition storage means 48. The setting value of the recording mode is recorded in advance in the light spot condition storage means 48 as each setting value corresponding to the type of the mounted optical disk 30 and each information recording layer. Each setting value of the recording strategy including the power information and the pulse correction information determined by the preliminary test writing is also read at this step as a part of the recording mode setting value.

  In this embodiment, as in the reproduction mode, the state of the light modulation means 14 is a non-operating state regardless of the type of the optical disk 30 loaded.

  On the other hand, the power of the light spot is set to the bias power (or cooling power) of the recording strategy. In general, the recording power and the erasing power of the recording strategy vary from disk to disk, but the bias power can be shared between the disks. In this embodiment, the same value as the power of the light spot in the above-described reproduction mode is used. As an example, the power of the light spot at the standard recording speed is 0.3 mW for a single-layer disc, 0.6 mW for a dual-layer disc, 1.2 mW for the first layer of a three-layer disc, and 1 for the second layer of a three-layer disc. .1 mW The third layer of a three-layer disc is 1.0 mW. The first and second layers of the four-layer disc are 1.2 mW, the third layer is 1.1 mW, and the fourth layer is 1.0 mW.

  When the bias power of the recording strategy varies depending on the recording double speed, the set value that is not directly recorded in the light spot condition storage means is calculated by linear interpolation or the like as in the reproduction mode.

  Further, the setting of high frequency superimposition of the laser driving circuit 12 is off.

  In step 108, the light modulation means 14 is set in a non-operating state, and irradiation is performed as a normal light spot with NA of 0.85. Further, the laser light source 11 is caused to emit light based on the type of the loaded optical disc 30 and the power of the light spot corresponding to the information recording layer read in step 107. That is, a standard light spot suitable for BD and next-generation BD recording is formed. Then, the spherical aberration and the focus offset are adjusted as necessary.

  The recording preparation is completed by the above procedure, and recording is started.

  As described above, in this embodiment, in particular, the power setting of the light spot in the idle mode is set to the same value for all information recording layers in a three-layer or four-layer disc, and different reproduction speeds are set. By setting the same value for the recording double speed, it is possible to prevent the information recording layer from being irradiated with a light spot with higher power than expected even if there is a focus jump failure or seek failure during the access operation. Recording data can be protected.

  The configuration and operation of an optical disc recording / reproducing apparatus as the second embodiment of the present invention will be described with reference to the drawings.

  The configuration of the optical disk recording / reproducing apparatus in the present embodiment is the same as that of the first embodiment except for the optical modulation means 14 in the optical pickup 10 to be described later, and the operation of each component is similar to that of the first embodiment. Therefore, explanation is omitted.

  FIG. 6 is a plan view of the light modulation means 14 of the present embodiment and shows an example of a division pattern of the liquid crystal element. The elliptical central region 14a in the first embodiment is converted into a circular central region 14c corresponding to 0.5 in terms of the NA of the objective lens and crescent-shaped central side regions 14d and 14e on both sides. The area is divided into four areas and includes four areas including the peripheral area 14b.

  The peripheral region 14b and the central side regions 14d and 14e can be controlled in optical rotation by being electrically operated via the light modulation means control circuit 42. Rotates 90 ° and does not rotate in the non-operating state. Further, the linearly polarized light incident on the central region 14c is transmitted without changing the polarization direction.

  When the light modulation means 14 is not in operation, the light beam passes through the central area 14c, the central side areas 14d and 14e, and the peripheral area 14b of the light modulation means 14 as described above, and the aperture provided in the objective lens actuator 19 The optical disc 30 is irradiated as a general light spot on a BD, with a restriction of NA 0.85.

  As the first operation state of the light modulation means 14, only the peripheral region 14b is set in the operation state, and the central side regions 14d and 14e are set in the non-operation state. That is, it is the same as the operation state of the light modulation means 14 in the first embodiment, and the aperture of the light beam is limited to NA 0.5 equivalent in the disk tangential direction and NA 0.7 equivalent in the disk radial direction, and the normal NA 0.85 is obtained. An elliptical light spot that is larger than the light spot is formed.

  Further, as the second operation state of the light modulation means 14, the peripheral region 14b and the central side regions 14d and 14e are both in the operation state. In this case, the aperture of the light beam is restricted to NA 0.5 or equivalent to form a circular light spot that is larger in the disk radial direction than the elliptical light spot in the first embodiment.

  The first operation state is for forming a light spot in the idle mode as in the first embodiment, while the second operation state is for forming a light spot in a disc discrimination mode to be described later. is there. When disc is discriminated, no tracking operation is required, and there is no need to generate a push-pull signal. In this embodiment, therefore, the aperture is limited to NA 0.5 equivalent in the disk radial direction as well as the disk tangential direction. In this case, the energy density is 0.35 times the light spot with NA of 0.85.

FIG. 7 is a flowchart of the disc discrimination operation of this embodiment.
In step 111, the slider mechanism 32 is driven to displace the optical pickup 10 in the radial direction of the disk so that the disk is discriminated at a radial position. As an example, it is positioned at the innermost circumferential position where the influence of the disc runout is small.
In step 112, the spindle motor 31 is driven to rotate the optical disc 30 in order to prevent the information recording surface from being damaged by energy injection during focusing in a focus sweep described later.
In step 113, the disc discrimination mode setting value is read from the light spot condition storage means 48. As described above, the operation state of the light modulation means 14 in the disc discrimination mode is the second operation state, and the light spot irradiated on the optical disc 30 corresponds to NA 0.5. The set value of the light spot power takes into consideration the protection of the information recording surface of a single-layer disc having the smallest reproduction power and the securing of the amount of reflected light for a three-layer or four-layer disc. In this embodiment, the energy density of the light spot corresponding to NA 0.5 is 0.35 times that of the light spot of NA 0.85 at the time of reproduction, so the value is 2.8 times or less of the reproduction power. The power of the light spot is 0.8 mW. However, the power of the light spot can be further increased by turning off the high frequency superimposition.
In step 114, the light modulation means 14 is set to the second operation state, and the laser light source 11 emits light so that the power of the light spot is 0.8 mW. High frequency superimposition is turned off.
In step 115, the objective lens actuator 19 is driven to displace the objective lens 18 in the focus direction, a focus sweep operation is executed, and a focus error signal is detected.
In step 116, a predetermined calculation process is performed on the detected focus error signal. For example, the type and the number of layers of the mounted optical disc 30 are determined from the focus error signal amplitude and the number of zero crossings.

  By the way, it is known that spherical aberration proportional to the fourth power of NA occurs with respect to the thickness error of the cover layer. However, if there is spherical aberration, the waveform of the focus error signal is distorted and three or four layers are generated. This is a cause of misclassification of the number of layers with respect to the layer disc. In this embodiment, the amount of spherical aberration generated by a light spot corresponding to NA 0.5 is 0.12 times the amount of spherical aberration generated by a light spot of NA 0.85 with respect to the thickness error of the same cover layer. Therefore, it is possible to obtain a focus error signal that can be suppressed to a small level and has almost no distortion. Therefore, the number of layers can be determined stably, and the initial setting of the spherical aberration correcting means 17 can be omitted.

  In step 117, the validity of the disc discrimination result is determined including the validity of the acquired focus error signal. If the determination result is valid, the disk determination process is terminated with the disk determination result in step 116. Further, as an inappropriate case, for example, a case where a disc different from the BD or the next generation BD, such as a CD (compact disc) or a DVD, is mounted. In that case, the optical pickup 10 or the like is changed to a setting suitable for CD or DVD, and the description is omitted, but the operation shifts to a disc discrimination operation different from the present embodiment. Alternatively, the disc determination process is terminated as an error determination.

  In this embodiment, in particular, a light spot having a smaller NA than that in the idle mode is used to suppress the generation of spherical aberration and to enable irradiation with a light spot having a higher power than in the reproduction mode. The disc can be discriminated by measuring the number of information recording layers stably for any of the disc, the three-layer disc or the four-layer disc.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of each embodiment.

  In addition, each of the above-described configurations may be configured such that some or all of them are configured by hardware, or are implemented by executing a program by a processor. Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

DESCRIPTION OF SYMBOLS 10 ... Optical pick-up, 11 ... Laser light source, 13 ... Collimating lens, 14 ... Light modulation means, 15 ... Polarizing beam splitter, 16 ... 1/4 wavelength plate, 17 ... Spherical aberration correction means, 18 ... objective lens, 19 ... objective lens actuator, 20 ... front monitor, 21 ... detection lens, 22 ... photodetector, 30 ... optical disc, 31 ... Spindle motor, 32 ... Slider mechanism

Claims (17)

An optical disk playback device,
A light source, an objective lens that collects a light beam emitted from the light source to form a light spot on the information recording surface of the optical disk, and a shape of the light spot by modulating a predetermined region among a plurality of divided regions An optical pickup comprising a light modulation means for changing
A control unit for controlling the optical pickup,
The controller is
A first light spot is formed by setting the light modulation means in a first operation state, the light source is caused to emit light at a first light emission power, and the optical pickup and the objective lens are displaced so that the first light spot is formed. Positioned on a predetermined track of the optical disc,
Forming the second light spot smaller than the first light spot with the light modulation means in the second operation state, causing the light source to emit light with a second light emission power smaller than the first light emission power, and Control to play the optical disc,
An optical disk reproducing apparatus characterized by the above. The light modulating means includes
The elliptical dividing line having a major axis in the direction corresponding to the radial direction of the optical disc is divided into inner and outer regions, and the elliptical dividing line is a circular shape corresponding to the aperture limit of the objective lens in the light modulator The optical disk reproducing apparatus according to claim 1, wherein the optical disk reproducing apparatus is smaller than a cross section of the light flux. A storage unit for storing the operation state of the light modulator and the light emission power of the light source as set values;
The optical disk according to claim 1, wherein the control unit refers to the storage unit and controls an operation state of the light modulation unit and a light emission power of the light source based on a reference result. Playback device. An optical disk recording device,
A light source, an objective lens that collects a light beam emitted from the light source to form a light spot on the information recording surface of the optical disk, and a shape of the light spot by modulating a predetermined region among a plurality of divided regions An optical pickup comprising a light modulation means for changing
A control unit for controlling the optical pickup,
The controller is
A first light spot is formed by setting the light modulation means in a first operation state, the light source is caused to emit light at a first light emission power, and the optical pickup and the objective lens are displaced so that the first light spot is formed. Positioned on a predetermined track of the optical disc,
The light modulation means is in the second operation state to form a second light spot smaller than the first light spot, and the light source emits light including a second light emission power smaller than at least the first light emission power. Control to emit light with a pulse train and record on the optical disc,
An optical disk recording apparatus characterized by the above. The light modulating means includes
The elliptical dividing line having a major axis in the direction corresponding to the radial direction of the optical disc is divided into inner and outer regions, and the elliptical dividing line is a circular shape corresponding to the aperture limit of the objective lens in the light modulator The optical disk recording apparatus according to claim 4, wherein the optical disk recording apparatus is smaller than a cross section of the light flux. A storage unit for storing the operation state of the light modulator and the light emission power of the light source as set values;
6. The optical disc according to claim 4, wherein the control unit refers to the storage unit and controls an operation state of the light modulation unit and a light emission power of the light source based on a reference result. Recording device. An optical disk device for reproducing an optical disk,
A light source, an objective lens that collects a light beam emitted from the light source to form a light spot on the information recording surface of the optical disk, and a shape of the light spot by modulating a predetermined region among a plurality of divided regions An optical pickup comprising a light modulation means for changing
A control unit for controlling the optical pickup,
The control unit forms a first light spot with the light modulation unit in a first operation state and reproduces the light source with a first light emission power during reproduction of an optical disc having one information recording layer. Then, the optical recording unit is controlled so as to reproduce an optical disc having one information recording layer, and when the number of layers on the information recording surface of the optical disc is determined, the light modulation means is set to the second operating state to set the first operating state. A second light spot larger than the first light spot is formed, the light source emits light with a second light emission power larger than the first light emission power, and the objective lens is displaced in the focus direction of the optical disc for focusing. An optical disc apparatus, wherein an error signal is obtained and control is performed so as to determine the number of layers of the information recording surface of the optical disc based on the focus error signal. The light modulating means includes
Divided into inner and outer regions by a circular or elliptical dividing line, the circular or elliptical dividing line being smaller than a circular light beam cross section corresponding to the aperture limit of the objective lens in the light modulation means; The optical disk apparatus according to claim 7. A storage unit for storing the operation state of the light modulator and the light emission power of the light source as set values;
9. The optical disc apparatus according to claim 7, wherein the control unit refers to the storage unit and controls an operation state of the light modulation unit and a light emission power of the light source based on a reference result. . An optical disc reproducing method in an optical disc apparatus,
The optical disk device includes a light source, an objective lens that collects a light beam emitted from the light source to form a light spot on an information recording surface of the optical disk, and modulates a predetermined area among a plurality of divided areas. An optical pickup comprising a light modulation means for changing the shape of the light spot,
A first light spot is formed by setting the light modulation means in a first operation state, the light source is caused to emit light at a first light emission power, and the optical pickup and the objective lens are displaced so that the first light spot is formed. Positioning on a predetermined track of the optical disc;
Forming the second light spot smaller than the first light spot with the light modulation means in the second operation state, causing the light source to emit light with a second light emission power smaller than the first light emission power, and And a step of reproducing the optical disc.   11. The optical disk reproducing method according to claim 10, wherein the first light spot has an elliptical shape having a major axis in a tangential direction of the optical disk.   Referring to a storage unit that stores the operation state of the light modulation unit and the light emission power of the light source as set values, and controlling the operation state of the light modulation unit and the light emission power of the light source based on a reference result; 12. The optical disk reproducing method according to claim 10 or 11, wherein the optical disk reproducing method is characterized in that: An optical disc recording method in an optical disc apparatus,
The optical disk device includes a light source, an objective lens that collects a light beam emitted from the light source to form a light spot on an information recording surface of the optical disk, and modulates a predetermined area among a plurality of divided areas. An optical pickup comprising a light modulation means for changing the shape of the light spot,
A first light spot is formed by setting the light modulation means in a first operation state, the light source is caused to emit light at a first light emission power, and the optical pickup and the objective lens are displaced so that the first light spot is formed. Positioning on a predetermined track of the optical disc;
The light modulation means is in the second operation state to form a second light spot smaller than the first light spot, and the light source emits light including a second light emission power smaller than at least the first light emission power. And an optical disc recording method comprising: emitting light by a pulse train and recording the optical disc.   The optical disk recording method according to claim 13, wherein the first light spot has an elliptical shape with a major axis in a tangential direction of the optical disk.   Referring to a storage unit that stores the operation state of the light modulation unit and the light emission power of the light source as set values, and controlling the operation state of the light modulation unit and the light emission power of the light source based on a reference result; The optical disk recording method according to claim 13 or 14, A method of discriminating the number of optical disc layers in an optical disc device,
The optical disk device includes a light source, an objective lens that collects a light beam emitted from the light source to form a light spot on an information recording surface of the optical disk, and modulates a predetermined area among a plurality of divided areas. An optical pickup having a light modulation means for changing the shape of the light spot, and when reproducing an optical disc having a single information recording layer, the light modulation means is set to a first operation state as a first operation state. A light spot is formed, the light source is caused to emit light with a first light emission power, and the optical disk having one information recording layer is reproduced.
When determining the number of optical disc layers,
Forming a second light spot larger than the first light spot with the light modulation means in a second operating state;
Causing the light source to emit light at a second light emission power greater than the first light emission power;
Displace the objective lens in the focus direction of the optical disc to obtain a focus error signal,
A method for discriminating the number of layers of an optical disc, comprising discriminating the number of layers on the information recording surface of the optical disc based on the focus error signal.   Referring to a storage unit that stores the operation state of the light modulation unit and the light emission power of the light source as set values, and controlling the operation state of the light modulation unit and the light emission power of the light source based on a reference result; The method for discriminating the number of optical disc layers according to claim 16, wherein:

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