JP4460416B2 - Information processing apparatus and information recording medium - Google Patents

Description

  The present invention relates to an optical disc apparatus that optically records or reproduces information on an information recording medium such as an optical disc, and more particularly to tilt detection of an optical disc.

  In recent years, the recording density of optical discs has increased, and an objective lens having a large numerical aperture (NA) has been used to reduce the light spot of a light beam used for recording and reproduction. As a result, the distance between the information recording surface of the optical disc and the objective lens is shortened, and the influence of coma aberration that occurs when the optical disc is tilted due to warpage or the like cannot be ignored, and correct recording and reproduction cannot be performed. In order to prevent such aberrations from occurring, the inclination of the information recording surface of the optical disc and the optical axis of the objective lens is detected, and correction is made so that the optical axis of the objective lens is perpendicular to the information recording surface of the optical disc. It is necessary to provide the optical disk apparatus with a mechanism for correcting aberrations by performing the above.

  FIG. 15 is a schematic diagram for explaining the configuration of a conventional optical disc apparatus described in Patent Document 1. In FIG. The conventional optical disk apparatus of FIG. 15 includes a light source 101, a beam splitter 103, an objective lens 104, a detection optical system 106, a light receiving unit 107, and a tilt detection unit 108. The inclination detection unit 108 includes a signal calculation unit 109, an amplification amplifier 110, and a differential amplifier 111.

  Light emitted from the light source 101 and having the optical axis 102 passes through the beam splitter 103 and is condensed on the information recording surface of the optical disk by the objective lens 104. The light reflected by the optical disk 105 passes through the objective lens 104, is reflected by the beam splitter 103, and is guided to the detection optical system 106. The light transmitted through the detection optical system 106 enters the light receiving unit 107.

  FIG. 16 is a schematic diagram showing a light receiving region of the light receiving unit 107 and a state of an incident light beam. The light receiving unit 107 includes light receiving areas 107a to 107f, and the light flux 112 obtained from the optical disc 105 is irradiated onto the light receiving areas 107a to 107f. The light beam 112 includes a region 112a including only the 0th-order component of the diffracted light diffracted by the groove of the track of the optical disc 105 on the light receiving unit 107, a region 112b where the 0th-order component and the + 1st-order component overlap, a 0th-order component, And a region 112c where the first-order components overlap.

  As shown in FIG. 16, the light beam 112 is detected by being divided into six by the light receiving regions 107a to 107f. Signals respectively obtained from the light receiving regions 107a to 107f are input to the signal calculation unit 109, and difference signals PP1 and PP2 are generated based on the following calculation. Here, signals obtained from the light receiving regions 107a to 107f are represented by respective reference numerals.

PP1 = 107a + 107b- (107c + 107d)
PP2 = 107e-107f

  In the inclination detecting unit 108, the amplification amplifier 110 multiplies the signal PP1 by k. The differential amplifier 111 calculates a difference between the signal PP2 and the signal PR1 multiplied by k, and outputs the difference as a tilt error signal TILT. The tilt error signal TILT is expressed by the following equation.

  TILT = PP2-k * PP1

  Here, the mark * represents a multiplication symbol. Since the constant k is determined so that the offset of the signal PP2 caused by the positional deviation between the optical axis of the objective lens 104 and the optical axis 102 of the optical system is corrected by the signal PP1, the tilt error signal TILT is the position of the objective lens 104. An offset caused by the deviation is a corrected signal.

When the optical disc 105 is tilted in the radial direction with respect to the optical axis 102 of the optical system, coma aberration generated when light passes through the transparent substrate of the optical disc is the 0th order component and ± 1st order of the diffracted light from the track. The wavefronts of the regions 112b and 112c where the components overlap are mainly deformed. Since the wavefront deformation differs depending on the light receiving areas 107a to 107f, the signals PP1 and PP2 are affected by different modulations. The modulation difference is influenced by the tilt of the optical disc and appears in the tilt error signal TILT. Therefore, by detecting the tilt error signal TILT when the light spot is tracing the track, it is possible to detect the tilt of the optical disk that is not easily affected by the positional deviation of the objective lens.
JP 2003-45058 A

  However, when the inventor of the present application has detected the inclination of an optical disc in which the reflectance of a track recorded by using the technique disclosed in Patent Document 1 is different from that of an unrecorded track, the recorded track is recorded. It was found that the optical disk tilt detection signal is easily affected by a shift in the light-condensing state on the optical disk (also referred to as defocusing) in a portion adjacent to a non-track. This problem is described in more detail below.

  FIG. 17A is a cross-sectional view of a track formed on the information recording surface of the optical disc. Of the three tracks, information is recorded only on the left hatched track. The recorded track has a lower reflectance than the unrecorded track. FIG. 17B shows a simulation of the waveform of the tilt error signal TILT generated when the light spot crosses the track when every three recorded tracks are arranged as shown in FIG. It is the result. The conditions used for the calculation are as follows.

(Condition 1)
Wavelength of light source: 405 nm
Objective lens NA: 0.85
Thickness of transparent substrate of optical disk: 100μm
Track pitch: 0.32 μm
Track groove width: 0.18um
Track depth: 1/12 wavelength Reflected track reflectance: 0.5
Reflectivity of unrecorded tracks: 1
Optical disc tilt: None

  The width of the light receiving areas 107e and 107f for detecting the signal PP2 in the direction parallel to the track direction is 0.35 of the beam diameter, and the value of the constant k is 0.75. This value is a value for correcting the offset caused by the positional deviation of the objective lens as described above.

  As shown in FIG. 17A, the horizontal axis of FIG. 17B indicates the light spot position along the radial direction of the optical disc with the center of the center track as the origin. The centers of the three tracks shown in FIG. 17A are at 0 and ± 0.32 μm on the horizontal axis. The three graph curves in FIG. 17B show a state in which the light beam is correctly focused on the track (DF without defocus = 0 μm) and the focus position is shifted by ± 0.2 μm (DF = ± 0). .2 μm) shows the waveform of the tilt error signal TILT. As shown in FIG. 17B, at the −0.32 μm position, the signal level is the same regardless of the focus state. However, at the origin and +0.32 μm position, the signal level depends on the focus state. Is different. In the result of FIG. 17B, the level of the tilt error signal TILT differs depending on the focus state, although the state where the disc is not tilted is simulated. Accordingly, the level of the conventional tilt error signal TILT detected when the light spot is tracing the center and right tracks of the three tracks in FIG. 17A changes depending on the presence of defocus. However, an error occurs as if the tilt of the optical disk was measured.

  The present invention solves such a conventional problem, and can detect an inclination of an optical disc correctly, regardless of a focus state of a light beam irradiated to the optical disc, even in a place where the reflectance of adjacent tracks is different. It is another object of the present invention to provide an optical disk device.

  The tilt detection apparatus of the present invention condenses light emitted from a light source toward an information recording surface of an optical disc by an objective lens, and uses a plurality of diffracted light beams from tracks provided on the information recording surface to An inclination detecting device for detecting the inclination of the light beam, wherein the light receiving surface is provided, the light beam is divided into a plurality of regions and received, and a plurality of light receiving signals are received based on the intensity of the light received in each region. And a tilt detector that generates a tilt error signal including information corresponding to the tilt of the optical disk based on the plurality of received light signals, and the light flux is on the light receiving surface of the light receiver. + 1st order light region in which the 0th order light and + 1st order light of the diffracted light from the track overlap, a −1st order light region in which 0th order light and −1st order light overlap, and the + 1st order light region and − Sandwiched between primary light areas And a zero-order light region that does not include the + 1st-order light and the −1st-order light but includes the 0th-order light, and the light receiving unit is a light in a light-shielding region provided in at least a part of the 0th-order light region. The plurality of received light signals are generated.

  In a preferred embodiment, the light receiving surface of the light receiving unit includes a first region that receives a central portion of the + 1st order light region and a −1st order light region, and a pair of second regions that sandwich the first region. The first region and the second region are divided so as to separately detect the + 1st order light region and the −1st order light region of the light flux.

  In a preferred embodiment, the light receiving surface of the light receiving unit is divided into a pair of sub-regions by a line that symmetrically bisects the light beam across the −1st order light region and the + 1st order light region of the light beam, One of the pair of sub-regions includes a first region that receives light in the vicinity of the central portion of the + 1st order light region and the −1st order light region, and a second region that is a remaining region excluding the first region. The first region and the second region are respectively divided so as to separately detect the + 1st order light region and the −1st order light region of the luminous flux.

  In a preferred embodiment, the inclination detecting unit generates a push-pull signal from each of the first region and the second region of the divided light receiving unit, and the level of a modulation waveform by a track of the two push-pull signals. Detect phase difference.

  In a preferred embodiment, the tilt detection unit detects the level of the two push-pull signals when the light collected by the objective lens traces a track, and compares the levels to thereby detect the phase difference. Is detected.

  In a preferred embodiment, the tilt detection unit multiplies one of the two push-pull signals by a predetermined coefficient, generates a difference signal therebetween, and the light collected by the objective lens is tracked. When the signal is traced, the level of the difference signal is detected.

  In a preferred embodiment, the light receiving surface of the light receiving unit sandwiches the first region with a first region that receives a central portion of the + 1st order light region and a −1st order light region, and the + 1st order light region. A pair of second regions that receive the light region and the −1st order light region, and a pair of third regions that sandwich the pair of second regions and receive only the 0th order light region, The first, second and third regions detect the light beam separately in a region divided by a dividing line located between the + 1st order light region and the −1st order light region of the light beam.

  In a preferred embodiment, the light receiving surface of the light receiving unit is divided into a pair of sub-regions by a line that symmetrically bisects the light beam across the −1st order light region and the + 1st order light region of the light beam, One of the pair of sub-regions includes a first region that receives light in the vicinity of a central portion of the + 1st order light region b and a −1st order light region, and a first region that is adjacent to the first region, A second region that receives the remaining area of the −1st order light region, and a third region that is adjacent to the second region and receives only the 0th order light region, the first, second and The third region separately detects the light beam in a region divided by a dividing line located between the + 1st order light region and the −1st order light region of the light beam.

  In a preferred embodiment, the tilt detection unit generates a push-pull signal from each of the first, second, and third regions of the divided light receiving unit, and the push-pull signal obtained from the first region. And the push-pull signal obtained from the third region is multiplied by a predetermined first value, and then a first difference signal that is the difference between them is generated and detected from the second region And multiplying one of the generated push-pull signal and the push-pull signal detected from the third region by a predetermined second value, and then generating a second difference signal that is the difference between them. The phase difference of the modulation waveform by the track of the difference signal of 1 and the second difference signal is detected.

  In a preferred embodiment, the tilt detection unit detects and compares the first and second difference signal levels when the light collected by the objective lens is tracing the track. , Detecting the phase difference.

  In a preferred embodiment, the light shielding region blocks a light beam incident only on the first and second regions.

  In a preferred embodiment, the optical disc has different reflectivities between recorded tracks and unrecorded tracks.

  In a preferred embodiment, the light shielding region is positioned symmetrically with respect to a line dividing at least the first region.

  In a preferred embodiment, the light receiving unit includes a light detection element having the light receiving surface on which the light flux is irradiated, and the first and second regions are provided on the light receiving surface.

  In a preferred embodiment, the light detection element includes a light shielding film provided on the light receiving surface so as not to detect light in the light shielding region.

  In a preferred embodiment, the light detection element includes a detection region that detects light in the light shielding region, and a signal obtained from the detection region is not used to generate the tilt error signal in the tilt detection unit. .

  In a preferred embodiment, the light receiving unit includes the light receiving surface on which the light flux is irradiated, the hologram element provided with the first and second regions, and the first and second of the hologram element. And a light detecting element for receiving the light in each region.

  In a preferred embodiment, the hologram element diffracts the light beam in the light shielding region so that the light detection element does not receive the light beam.

  In a preferred embodiment, the light receiving unit includes a light detection element having the light receiving surface irradiated with the light flux, and the first, second, and third regions are provided on the light receiving surface.

  In a preferred embodiment, the light detection element includes a light shielding film provided on the light receiving surface so as not to detect light in the light shielding region.

  In a preferred embodiment, the light detection element includes a detection region that detects light in the light shielding region, and a signal obtained from the detection region is not used to generate the tilt error signal in the tilt detection unit. .

  In a preferred embodiment, the light receiving unit includes the light receiving surface on which the light beam is irradiated, the hologram element provided with the first, second, and third regions, and the first of the hologram elements. And a light detecting element for receiving the light in the second and third regions, respectively.

  In a preferred embodiment, the hologram element diffracts the light beam in the light shielding region so that the light detection element does not receive the light beam.

  An optical disc apparatus according to the present invention includes a drive unit for rotationally driving an optical disc having an information recording surface, a light source, an objective lens for condensing light emitted from the light source toward the information recording surface of the optical disc, and the information recording surface An optical head having a tilt correction unit that corrects an aberration caused by tilting the optical axis of the condensed light with respect to the vertical direction, and that records and reproduces information with respect to the information recording surface. A tilt detection device that is defined; and a drive signal generation unit that receives a tilt error signal of the detection device and drives the tilt correction unit.

  In a preferred embodiment, the tilt correction unit is an objective lens driving unit that tilts the objective lens at least in a radial direction of the optical disc.

  According to the present invention, the influence of the non-pairing of the light intensity in the 0th-order light region due to the difference in reflectance between adjacent tracks is reduced, regardless of the focus state of the light beam irradiated on the optical disc, A tilt error signal with high accuracy can be generated. Therefore, even if the optical disk is warped, data can be recorded with high density, and information recorded with high density on the optical disk can be correctly reproduced.

  The inventor of the present application has studied in detail the cause of the tilt error signal of the optical disc depending on the focus state of the light beam applied to the optical disc at a location where the reflectance of adjacent tracks is different. As a result, as shown in FIG. 17A, when the recorded track and the unrecorded track are adjacent to the central track, the light applied to the optical disc is added to the diffracted light based on each track. Thus, it has been found that diffracted light is generated by a structure in which the reflectance changes at a cycle three times the track pitch. Further, as shown in FIG. 16, this diffracted light appears in the region 112a including only the zeroth-order component of the light beam 112 obtained from the optical disk, and changes depending on the focus state of the light condensed toward the optical disk. It was. For this reason, it is considered that the tilt error signal changes depending on the focus state of the light condensed toward the optical disc, and an erroneous tilt error signal is generated.

  FIGS. 1A to 1C are graphs showing the intensity distribution of the light beam reflected from the optical disk. The intensity distribution is a direction orthogonal to the track (radial direction of the optical disk) and indicates a cross section passing through the center of the light beam. The intensity distributions in FIGS. 1A to 1C were obtained by calculation using the above-described condition 1. FIG. 1A shows an intensity distribution in a state where a light beam is irradiated to the center of the center track shown in FIG. FIG. 1B shows an intensity distribution in a state where a light beam is irradiated to the center of the center track and the focus position is shifted by 0.2 μm. FIG. 1C shows an intensity distribution in a state in which the left track center shown in FIG. 17A is irradiated with a light beam and the focus position is shifted by 0.2 μm. The horizontal axis of each graph represents the external ratio with the light beam radius being 1, and the vertical axis represents the light intensity. The region within ± 0.5 of the horizontal axis is a region where only the 0th order component of the diffracted light is approximately, and the region outside the region is an area where the 0th order component and the 1st order component of the diffracted light overlap. As can be seen from FIG. 1 (a), on the tracks where the reflectivity of adjacent tracks is different, the reflectivity is asymmetric with respect to the track irradiated with the light beam, so that the focus of the light beam matches. Even so, the light intensity distribution is asymmetric. As shown in FIG. 1B, the asymmetry of the light intensity distribution becomes large when the focus is not matched. Further, as shown in FIG. 1C, the light intensity distribution shows symmetry even if the focus is not matched on the track where the reflectance of the adjacent tracks on both sides is equal. Thus, in the region of only the 0th-order component, the symmetry of the intensity distribution changes depending on the position of the light beam or the focus state of the light beam. This is because, when the reflectances of the tracks on both sides are different, the light intensity distribution becomes asymmetric due to the interference between the diffracted light and the zero-order component due to the structure in which the reflectance changes at a period three times the track pitch, and the interference state is This is considered to change according to the focus state of the light beam.

  On the other hand, as shown in FIGS. 1A to 1C, in the region where the zero-order component and the first-order component overlap, the intensity distribution is approximately symmetric regardless of the position of the light beam and the focus state. In other words, the intensity of light in the region where the zero-order component and the first-order component overlap is less affected by the position of the light beam and the focus state in the optical disc having different reflectivities between the recorded track and the unrecorded track.

  From these facts, when detecting the tilt of an optical disc having different reflectivities between a recorded track and an unrecorded track, the light in the region of only the zero-order component of the light beam reflected from the optical disc is used to generate a tilt error signal. Not to be. As a result, the tilt error signal can be reduced from being affected by the focus state. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 2 is a block diagram showing a first embodiment of an optical disc apparatus according to the present invention. In the present embodiment, a read-only optical disk device is illustrated, but the present invention can be applied to a recording-only or an optical disk device that performs recording and reproduction. The optical disc apparatus 201 includes a rotation drive unit 202, an optical head 203, a control system 204, a reproduction signal processing system 205, and a controller 208.

  The rotation driving unit 202 has a turntable for placing the optical disc 5 thereon, and the optical disc 5 is placed on the turntable and is driven to rotate.

  The optical head 203 condenses the light on the information recording surface 5a of the optical disc 5, and records the data on the information recording surface 5a using the condensed light, or reproduces the data recorded on the information recording surface 5a. Or The optical head 203 includes a light source 1 used for recording and / or reproduction, a beam splitter 3, an objective lens 4, and an objective lens driving unit 206.

  The light emitted from the light source 1 passes through the beam splitter 3 and is condensed toward the information recording surface 5 a by the objective lens 4 through the transparent substrate of the optical disk 5. The light beam reflected by the information recording surface 5a enters the beam splitter 3 again through the objective lens 4. The beam splitter 3 reflects the reflected light beam toward the light receiving unit 30 described in detail below.

  An objective lens driving unit 206 is connected to the objective lens 4. The objective lens drive unit 206 functions as a focus correction unit and a tracking correction unit that move the objective lens 4 in a direction (also referred to as a focus direction) 231 and a direction (also referred to as a tracking direction) 232 perpendicular to the information recording surface 5a. . Also, it functions as a tilt correction unit that moves in the tilt direction 233 so that the radial tilt angle of the optical disc 5 changes. A traverse drive unit 207 is connected to the optical head 203 and moves the entire optical head 203 in the radial direction of the optical disc 5. The objective lens driving unit 206 may employ a known driving mechanism that drives the objective lens of the optical disk device. For example, a structure in which an objective lens is driven or displaced by electromagnetic force using a coil and a magnet may be employed.

  The control system 204 controls the rotation of the optical disc 5 and the condensing state and condensing position of the light condensed on the information recording surface 5a of the optical disc 5. Specifically, the rotation drive unit 202, traverse drive unit 207, and objective lens drive unit 206 are controlled. For this purpose, the control system 204 includes the light receiving unit 30, the focus error signal generation unit 211, the tracking error signal generation unit 212, the inclination detection unit 213, the phase compensation units 214 to 216, and the drive signal generation unit 218. With. The light receiving unit 30 divides and receives the light beam reflected from the information recording surface 5a, and generates a plurality of signals according to the intensity.

  The focus error signal generation unit 211 receives a plurality of signals from the light receiving unit 30, and generates a focus error signal indicating how much the light collection state of the light collected on the information recording surface 5a is deviated from a predetermined state. . The phase compensation unit 214 compensates the phase of the focus error signal and outputs it as a focus control signal to the drive signal generation unit 218. The drive signal generator 218 receives the focus control signal and outputs a focus drive signal for moving the objective lens 4 in the direction 231 perpendicular to the information recording surface 5a to the objective lens driver 206. Thereby, the light condensed on the information recording surface 5a is controlled so as to maintain a constant light collection state.

  The tracking error signal generation unit 212 receives a plurality of signals from the light receiving unit 30, and generates a tracking error signal indicating how much the light collected on the information recording surface 5a is deviated from the track. The phase compensation unit 215 compensates the phase of the tracking error signal and outputs the tracking error signal to the drive signal generation unit 218 as a tracking control signal. The drive signal generation unit 218 receives the tracking control signal and outputs a tracking drive signal for moving the objective lens 4 in the radial direction 232 parallel to the information recording surface 5a to the objective lens driving unit 206. As a result, the light focused on the information recording surface 5a is controlled so as to always trace the track.

  The light receiving unit 30 and the inclination detecting unit 213 constitute an inclination detecting device 241 as described in detail below. The tilt detection device 241 receives a plurality of signals from the light receiving unit 30 and outputs a tilt error signal indicating how much the information recording surface 5 a is tilted in the radial direction of the optical disc 5 with respect to the optical axis of the light emitted from the light source 1. Generate. The phase compensation unit 216 compensates the phase of the tilt error signal and outputs the tilt error signal to the drive signal generation unit 218 as a tilt control signal. The drive signal generation unit 218 receives the tilt control signal and outputs a tilt drive signal for moving the objective lens 4 in the tilt direction 233 to the objective lens drive unit 206. Thereby, the optical axis of the light condensed on the information recording surface 5a is controlled to be perpendicular to the information recording surface 5a.

  In this embodiment, the objective lens driving unit 206 functions as a focus correction unit, a tracking correction unit, and a tilt correction unit. However, the objective lens driving unit has functions as a focus correction unit and a tracking correction unit, and the tilt correction unit. May be provided separately from the objective lens driving unit. For example, a liquid crystal element may be provided between the objective lens 4 and the beam splitter 3 to correct the wavefront aberration of the passing light by changing the refractive index based on the tilt control signal.

  The focus error signal generation unit 211, the tracking error signal generation unit 212, the phase compensation units 214 to 216, and the drive signal generation unit 218 have a known configuration used in a conventional optical disc apparatus. The focus error signal can be generated by a known method such as an astigmatism method. The tracking error signal can be generated by a phase difference method, a push-pull method, a three beam method, or the like. The light receiving unit 30 may include detection elements that are commonly used to generate a focus error signal, a tracking error signal, and a tilt error signal, or may include separate detection elements. The light receiving unit 30 is usually provided in the optical head 203.

  In addition, the control system 204 includes a drive signal generation unit 224 for driving the traverse drive unit 207 and a drive signal generation unit 224 for driving the rotation drive unit 202. The drive signal generation unit 224 jumps the light spot to a predetermined track position on the information recording surface 5a based on the operation state of the optical disc apparatus 201, or the light spot continuously tracks the track with the recording or reproduction operation. A command is received from the controller 208 for tracing. Based on a command from the controller 208, the drive signal generation unit 224 generates a drive signal for driving the traverse drive unit 207 and moves the optical head 203. The drive signal generation unit 204 receives a command from the controller 208 and generates a drive signal for driving the rotation drive unit 202 so as to rotate the optical disc 5 at a predetermined rotation speed.

  The reproduction signal processing system 205 includes a waveform equalization unit 220, a PLL unit 221 and a decoder 222, reproduces information recorded on the information recording surface 5a of the optical disc 5, and generates a reproduction signal. The waveform equalization unit 220 receives a signal including information recorded on the information recording surface 5a from the light receiving unit 30, amplifies the signal in a predetermined frequency band, and outputs an RF signal. The PLL unit 221 receives the RF signal and generates a clock signal synchronized with the RF signal. The decoder 222 decodes the RF signal using the clock signal and outputs the information recorded on the information recording surface 5a.

  Next, the inclination detecting device 241 will be described in detail. As illustrated in FIG. 3, the tilt detection device 241 includes a light receiving unit 30 and a tilt detection unit 213. In addition, the inclination detection unit 213 includes a signal calculation unit 8 and a phase difference detection unit 9. Light emitted from the light source 1 along the optical axis 2 and condensed by the objective lens 4 is condensed toward the information recording surface 5a. The condensed light is reflected by the information recording surface 5a and returns to the objective lens 4 again. On the information recording surface 5a, tracks are formed spirally or concentrically at a predetermined pitch. For this reason, the light reflected from the information recording surface 5a includes a plurality of diffracted lights of different orders diffracted based on the periodically arranged tracks. The light beam 10 that has passed through the objective lens 4 is reflected by the beam splitter 3 and enters the light receiving unit 30.

  The light receiving unit 30 divides the light beam 10 into a plurality of regions and receives the light, and outputs a plurality of light reception signals based on the intensity of light received in each region. FIG. 4 schematically shows the light receiving surface 6 of the light receiving unit 30 for receiving the light beam 10 by dividing it into a plurality of regions. As shown in FIG. 5A, the light receiving unit 30 includes a hologram element 32 and one or more detection elements 33, the hologram element 32 divides the light beam 10, and guides the divided light to the detection element 33. A structure may be adopted. In this case, the surface of the hologram element 30 on which the light beam 10 is incident is the light receiving surface 6. As shown in FIG. 5B, when the light receiving unit 30 includes a light detecting element 34 that directly receives the light beam 10 and converts it into an electrical signal, the light receiving surface 6 is a detection surface of the light detecting element 34. .

  As shown in FIG. 4, the light beam 10 includes a 0th-order light region 10 a, a + 1st-order light region 10 b, and a −1st-order light region 10 c on the light receiving surface 6. In the + 1st order light region 10b, the 0th order light and the + 1st order light from the track overlap. Similarly, in the −1st order light region 10c, the 0th order light and the −1st order light overlap. The 0th-order light region 10a is sandwiched between the + 1st-order light region 10b and the -1st-order light region 10c, and does not include the + 1st-order light and the −1st-order light but includes the 0th-order light.

  The light receiving surface 6 includes a first region 31A that receives the central portions of the + 1st order light region 10b and the −1st order light region 10c, and a pair of second regions 31B that sandwich the first region 31A. . The first region 31A and the second region 31B are divided so as to detect the + 1st order light region 10b and the −1st order light region 10c separately. Specifically, the first region 31A is divided into regions 6e and 6f by a boundary C1 located between the + 1st order light region 10b and the −1st order light region 10c of the light beam 10. The second region 31B is divided into a region 6a and a region 6d, and a region 6b and a region 6c. As shown in FIG. 4, the boundary C <b> 1 is approximately parallel to the track extending direction in the light beam 10. In addition, the boundary between the first region 31A and the second region 31B is approximately perpendicular to the direction in which the track of the light beam 10 extends.

  In the inclination detection device 241 of the present embodiment, the light receiving unit 30 detects the light beam 10 in each of the regions 6a to 6f, excluding at least a part of the 0th-order light region 10a of the light beam 10, and in each of the regions 6a to 6f. A plurality of received light signals are output based on the light intensity. For this reason, the light receiving surface 6 has a light shielding region 11 in the 0th-order light region 10a of the light beam 10, and has a structure in which light incident on the light shielding region 11 does not contribute to a light reception signal. For example, as shown in FIG. 6A, a light shielding film 33 that prevents the light beam 10 from passing through may be formed in a region corresponding to the light shielding region 11 on the light receiving surface 6. More specifically, a light shielding film 33 may be provided on the light receiving surface 6 of the hologram element 32 and the light receiving surface 6 of the light detecting element 34 shown in FIGS.

Further, as shown in FIG. 6B, in each of the regions 6 a to 6 f of the light receiving surface 6, the regions 6 a _{2 to} 6 f ₂ that overlap the light shielding region 11 and the regions 6 a _{1 to} 6 f ₁ that do not overlap the light shielding region 11 are separated. However, the light received in the regions 6a _{2 to} 6f ₂ may not be used. For example, the light receiving surface 6 of the hologram element shown in FIG. 5A is divided as shown in FIG. 6B so that the light received in the regions 6a _{2 to} 6f ₂ does not enter the light detecting element 33. It may be led (diffracted) to a region other than the light detection element 33. Alternatively, the light-receiving signal generated by dividing the light-receiving surface 6 of the detection element 34 shown in FIG. 5B as shown in FIG. 6B and receiving light in the regions 6a _{2 to} 6f ₂ is the inclination detecting unit 213. Should not be output to.

  As shown in FIGS. 1A and 1B, the intensity distribution of light in the zero-order light region 10a is different between a positive region and a negative region with the center of the light beam 10 as the origin. For this reason, in order to reduce the influence of the asymmetry of the light intensity distribution, the light shielding region 11 is preferably provided symmetrically with respect to the boundary C1. A larger length L1 along the tracking direction of the light shielding region 11 is preferable because a signal component due to light received in the 0th-order light region 10a can be reduced and a change in signal intensity depending on a focus state can be suppressed.

  The width W1 along the direction perpendicular to the track direction of the light shielding region 11 is preferably narrower than the interval W2 between the + 1st order light region 10b and the −1st order light region 10c. This is because when the light shielding region 11 overlaps the + 1st order light region 10b or the −1st order light region 10c, the amplitude of the push-pull signal described below is lowered, and the detection sensitivity of the tilt error signal is lowered. Further, when the optical axis of the objective lens 4 is displaced with respect to the optical axis of the light emitted from the light source, the position of the light beam 10 is shifted, and the light shielding region 11 is changed to the + 1st order light region 10b or the −1st order light. There is a possibility of overlapping with the region 10c. In this case, as described above, the detection sensitivity of the tilt error signal is lowered. For this reason, when it is necessary to consider the positional deviation of the objective lens 4, the width W1 of the light shielding area does not overlap with the + 1st order light area 10b or the −1st order light area 10c even if the positional deviation due to the objective lens 4 occurs. It is preferable to provide a margin for the interval W2 between the + 1st order light region 10b and the −1st order light region 10c. Considering these points, when the diameter of the light beam 10 is 1, and the condition 1 is as described above, the outer shape of the light shielding region 11 is 0.5 <L1 <1 and 0.3 <W1 <0.45. It is preferable to satisfy.

  As shown in FIG. 3, the light reception signals S6a to S6f obtained from the regions 6a to 6f of the light receiving surface 6 are output to the signal calculation unit 8 of the inclination detection unit 213. The signal calculation unit 8 generates push-pull signals detected in the first region 31A and the second region 31B based on the light reception signals S6a to S6f. Specifically, when the push-pull signals detected in the first area 31A and the second area 31B are P1 and P2, respectively, the following expressions are used.

P1 = S6e-S6f
P2 = S6a + S6b- (S6c + S6d)

  FIGS. 7A to 7C are graphs showing the results of calculating one period of the modulation waveform by the track of the push-pull signals P1 and P2. The condition used for the calculation is the same as Condition 1 described above. 7A to 7C show the calculation results in the case where the radial inclination θ of the optical disc is different and θ = −0.6 °, θ = 0 °, and θ = + 0.6 °, respectively. Show. 7A and 7C, the inclination of the optical disk is reversed. As shown in these figures, the phase difference of the signal P2 changes according to the inclination of the optical disk. The direction in which the phase shifts in accordance with the direction of the optical disc tilt is also reversed. On the other hand, the phase of the signal P1 does not change much regardless of the tilt of the optical disk.

  Therefore, the optical disk tilt can be detected by detecting the value and direction of the phase difference. A general method can be employed for detecting the phase difference. For example, the phase difference detection unit 9 shown in FIG. 3 receives the signal P1 and the signal P2 from the signal calculation unit 8, passes them through a low-pass filter, and removes the DC component. After that, the level of the signal P2 is detected at the timing when the amplitude of the signal P1 changes from positive to negative or from negative to positive (zero crossing timing), and is output as a tilt error signal TL.

  The phase difference detection unit 9 may generate a tilt error signal TL that corrects an offset that occurs when the optical axis of the objective lens 4 is shifted with respect to the optical axis 2 of the optical system including the light source 1. . Specifically, the phase difference detection unit 9 sets a predetermined constant k and performs the following calculation.

  TL = P1-k * P2

  The tilt detection device 241 can detect the tilt of the optical disc by detecting the level of the tilt error signal TL when the light beam collected by the objective lens 4 is tracing the track.

  FIG. 8 is a graph showing a result of calculating the waveform of the tilt error detection signal TL generated by the tilt detection device 241 while changing the defocus amount. The tilt error detection signal TL is obtained from the relationship of TL = P1-k * P2 so that it can be easily compared with the conventional example. As the calculation condition, the above-mentioned condition 1 was used. The constant k was 0.8, and the width in the direction perpendicular to the track of the light shielding portion 11 was 0.35 of the beam diameter. FIG. 8 is a graph when the light beam is correctly focused on the track (no defocus, DF = 0 μm) and when the focus position is shifted by ± 0.2 μm (DF = ± 0.2 μm). Show. As is apparent from FIG. 8, when the light beam is located at -0.32 μm, 0 μm, and +0.32 μm, which are the center positions of the three tracks, the signal level is almost zero regardless of the defocus amount. Alternatively, the zero cross points of the three graphs are almost the same regardless of the defocus amount. This indicates that the tilt error signal is not affected by the condensing state of the light beam condensed on the optical disk.

  As described above, according to the present embodiment, at least part of the light in the 0th-order light region of the light beam reflected from the optical disc is not used for generating the tilt error signal. As a result, the influence of the non-pairing of the light intensity in the 0th-order light region caused by the difference in reflectance between adjacent tracks is reduced, and the accuracy is high regardless of the focus state of the light beam irradiated on the optical disk. A tilt error signal can be generated. Therefore, even if the optical disk is warped, data can be recorded with high density, and information recorded with high density on the optical disk can be correctly reproduced.

  In the present embodiment, the light shielding area of the light receiving surface 6 is formed in a belt-like rectangle, but the light shielding area may have other shapes. For example, an elliptical light shielding region 36 may be provided on the light receiving surface 6 as shown in FIG. In addition, the light shielding area may be constituted by a plurality of divided areas. As shown in FIG. 9B, a light shielding area 37 in which a plurality of rectangular areas are arranged in the tracking direction may be provided on the light receiving surface 6. Further, as shown in FIG. 9C, a light shielding area 38 in which a plurality of elongated areas extending in the tracking direction are arranged in a direction perpendicular to the tracking direction may be provided on the light receiving surface 6.

(Second Embodiment)
FIG. 10 is a block diagram showing an inclination detecting device 242 used in the second embodiment of the optical disc apparatus according to the present invention. The structure of the optical disk apparatus of the present embodiment is the same as that of the optical disk apparatus shown in FIG.

  The inclination detection device 242 includes a light receiving unit 40 and an inclination detection unit 214. The inclination detection unit 214 includes a signal calculation unit 14, amplification amplifiers 15 and 17, differential amplifiers 16 and 18, and a phase difference detection unit 19.

  Similar to the first embodiment, the light receiving unit 40 receives the light beam 10 by dividing it into a plurality of regions, and outputs a plurality of light reception signals based on the intensity of light received in each region. FIG. 11 schematically shows the light receiving surface 12 of the light receiving unit 40 for receiving the light beam 10 by dividing it into a plurality of regions. As described in the first embodiment, the light receiving surface 12 may be a light receiving surface of a hologram element or a light receiving surface of a detection element.

  The light receiving surface 12 sandwiches the first region 41A and the first region 41A that receive the central portions of the + 1st order light region 10b and the −1st order light region 10c, and the + 1st order light region 10b and the −1st order light. It includes a pair of second regions 41B that receive the region 10c and a pair of third regions 41C that sandwich the pair of second regions 41B and receive only the 0th-order light region. The first region 41A, the second region 41B, and the third region 41C respectively transmit the light of the luminous flux in the region divided by the dividing line C1 located between the + 1st order light region 10b and the −1st order light region 10c. It is divided so that it can be detected separately. Specifically, the first area 41A is divided into areas 12e and 12f. The second region 41B is divided into a region 12a and a region 12d, and a region 12b and a region 12c. The third region 41C is divided into a region 12g and a region 12j, and a region 12h and a region 12i.

  As in the first embodiment, the light receiving unit 40 detects the light beam 10 in each of the regions 12a to 12j, excluding at least part of the 0th-order light region 10a of the light beam 10, and transmits the light in each of the regions 12a to 12j. A plurality of received light signals are output based on the intensity. For this reason, the light receiving surface 12 has a light shielding region 21 in the 0th-order light region 10a of the light beam 10, and has a structure in which light incident on the light shielding region 21 does not contribute to a light reception signal. The specific structure of the light shielding region 21 is the same as that of the first embodiment. The light shielding region 21 is preferably provided only in the first region 41A and the second region 41B of the light receiving surface 12. Moreover, it is preferable that the light shielding region 21 is disposed symmetrically with respect to the boundary C1. When the length of the light shielding region 21 in the track direction is L1, the length of the first region 41A and the second region 41B in the tracking direction is L3, the diameter of the light beam 10 is 1, and the above condition 1 Therefore, it is preferable that the outer shape of the light shielding region 11 satisfies 0.5 <L1 <L3 and 0.3 <W1 <0.45.

  As shown in FIG. 10, the light reception signals S12a to S12j obtained from the regions 12a to 12j of the light receiving surface 21 are output to the signal calculation unit 14 of the inclination detection unit 214. The signal calculation unit 8 generates push-pull signals detected in the first region 41A, the second region 41B, and the third region 41C based on the light reception signals S12a to S12j. Specifically, when the push-pull signals detected in the first area 41A, the second area 41B, and the third area 41C are P1, P2, and P3, respectively, the following expressions are used.

P1 = S12e-S12f
P2 = S12a + S12b- (S12c + S12d)
P3 = S12g + S12h- (S12i + S12j)

  Since the signal P1 and the signal P2 are based on the light applied to the + 1st order light region 10b and the −1st order light region 10c, they are modulated by the track. On the other hand, since the signal P3 is based on the light irradiated to the 0th-order light region 10a, the signal P3 is not subjected to modulation by the track, and corresponds to the position of the light beam on the light receiving surface 12 that moves according to the positional deviation of the objective lens 4. Contains information. The tilt detection unit 214 corrects an offset generated in the signal P1 and the signal P2 due to the positional deviation of the objective lens 4 using the signal P3, and generates a tilt error signal. Specifically, as shown in FIG. 10, the signal P3 output from the signal calculation unit 14 is multiplied by K1 and K2 by the amplification amplifiers 15 and 17, respectively. The differential amplifier 16 subtracts the signal P3 multiplied by K1 from the signal P1 to generate a corrected signal CP1. The differential amplifier 18 subtracts the signal P3 multiplied by K2 from the signal P2 to generate a corrected signal CP2. Here, the constants K1 and K2 are determined so that the offset generated by the positional deviation of the objective lens of the signals P1 and P2 is corrected. That is, the signals CP1 and CP2 are expressed by the following equations.

CP1 = P1-K1 * P3
CP2 = P2-K1 * P3

  When there is an inclination of the optical disc 5, a phase difference corresponding to the inclination of the optical disc is generated in the waveforms of the signals CP1 and CP2 as in the waveforms of the signals P1 and P2 shown in FIG. Therefore, the tilt error signal TL corresponding to the tilt of the optical disc is detected by detecting the phase difference with the phase difference detector 19 in the same manner as in the first embodiment.

  FIGS. 12A and 12B are graphs showing the results of calculating the waveforms of the signals CP1 and CP2 modulated on tracks having different reflectivities. In each figure, the focus position was set to −0.2 μm, 0 μm, and +0.2 μm, and the calculation was performed using the above-mentioned condition 1. The widths in the track direction of the first region 41A and the second region 41B were 0.35 and 0.65, respectively, with respect to the beam diameter, and the constants K1 and K2 were 1.4 and 1.0, respectively. The width of the light shielding portion 21 in the direction orthogonal to the track was set to 0.35 with respect to the beam diameter.

  As shown in FIGS. 12A and 12B, the zero-cross points of the three waveforms of the signals CP1 and CP2 are the same regardless of the focus state. This indicates that the signal CP1 and the signal CP2 are not easily affected by the defocus due to the effect of the light shielding unit 21. Since the tilt error signal is generated based on the signals CP1 and CP2, according to the present embodiment, it is possible to realize an optical disc apparatus including a tilt detection apparatus that generates a tilt error signal that is not easily affected by defocusing. it can.

  Further, as can be seen from the waveforms in FIGS. 7A to 7C, the zero-cross point of the waveform of the signal P1 hardly deviates from the track center even if there is an inclination of the optical disk. Therefore, it can be said that the signal CP1 generated from the signal P1 is a stable signal in which the zero cross point of the waveform does not shift due to the positional deviation of the objective lens or the inclination of the optical disc. Therefore, the phase difference detection unit 19 can also detect the phase difference between the signal CP1 and the signal CP2 by measuring the level of the signal CP2 at the zero cross point of the signal CP1, and can generate a tilt error signal. .

  Further, the above-described stability of the signal CP1 indicates that the signal CP1 can be suitably used as a tracking control signal. For example, tracking control is performed using the signal CP1, and the tilt error signal is generated by measuring the level of the signal CP2 by the phase difference detection unit 19 while the light spot is tracing on the track, that is, It is possible to detect the tilt of the optical disc.

  In the first and second embodiments, the tilt error signal is generated using the entire light beam irradiated on the light receiving surface. However, as is apparent from FIGS. 4 and 6, the 0th-order light region, the −1st-order light region, and the + 1st-order light region of the light flux have a symmetrical shape in the track direction. For this reason, the light beam is bisected by a center line that passes through the center of the light beam and is perpendicular to the track direction, and when the center line is viewed in the left-right direction, the light in the upper half or lower half is divided into tilt error signals (and Tracking error signal) may be used for generation. In this case, the remaining half of the light that is not used for generating the tilt error signal may be used for generating the focus error signal.

  FIG. 13 shows a modification in which the upper half of the light beam 10 is used to generate a tilt error signal in the first embodiment. As shown in FIG. 13, the light-receiving surface 46 of the light-receiving unit has a pair of sub-regions 46a by a center line C2 that symmetrically bisects the light beam 10 across the + 1st-order light region 10b and the -1st-order light region 10c of the light beam 10. And is divided into sub-regions 46b. The sub-region 46a is a second region 31B ′ that is a remaining region excluding the first region 31A ′ and the first region 31A ′ that receives the vicinity of the central portion of the + 1st order light region 10b and the −1st order light region 10c. Including. The first region 31A ′ and the second region 31B ′ are divided into a region 6e ′, a region 6f ′, and a region 6a by the center line C1 so that the + 1st order light region 10b and the −1st order light region 10c of the light beam are separately detected. Further divided into 'and region 6d'. The light shielding area 11 ′ has the same structure as that of the first embodiment except that the light shielding area 11 ′ is provided only in the sub area 46 a of the light receiving surface 46.

  FIG. 14 shows a modification in which the upper half of the light beam 10 is used to generate a tilt error signal in the second embodiment. As shown in FIG. 14, the light-receiving surface 52 of the light-receiving unit has a sub-region 52a and a sub-region 52 formed by a center line C2 that symmetrically bisects the light beam 10 across the + 1st-order light region 10b and the −1st-order light region 10c. It is divided into regions 52b. The sub-region 52a is adjacent to the first region 41A ′ and the first region 41A ′ that receive the vicinity of the central portions of the + 1st order light region 10b and the −1st order light region 10c, and the first order light regions 10b and −1. It includes a second region 41B ′ that receives the remaining region of the secondary light region 10c, and a third region 41C ′ that receives only the zeroth-order light region adjacent to the second region 41B ′.

  The first region 41A ′, the second region 41B ′, and the third region 41C ′ are divided into a region 12e ′ and a region by a dividing line C1 positioned between the + 1st order light region 10b and the −1st order light region 10c, respectively. 12f ′, region 12a ′ and region 12d ′, and region 12g ′ and region 12j ′. The light shielding area 21 ′ has the same structure as that of the second embodiment except that the light shielding area 21 ′ is provided only in the sub area 52 a of the light receiving surface 52.

  By using such a light receiving surface, it is not necessary to provide a light shielding region in the sub region 46b (FIG. 13) or the sub region 52b (FIG. 14) that is not used for generating the tilt error signal. Therefore, when these lower regions are used for generating a focus error signal, the light beam obtained from the optical disk can be used more effectively.

  The present invention is preferably used for an optical disc apparatus that records or reproduces information on an information recording medium having a reflectivity different between recorded, unrecorded, and erased tracks, such as a phase change optical disc. it can. In particular, it can be suitably used for an optical disc drive having a mechanism for adjusting the tilt of the optical disc and an optical disc apparatus having a function of correcting coma aberration generated by the tilt of the optical disc by tilting the objective lens.

(A) and (b) are cases where the reflectances of adjacent tracks are different, and the light intensity distribution of the light beam obtained from the optical disc in a state where the focus is matched and a state where the focus is not matched (C) is a diagram showing the light intensity distribution of the light beam obtained from the optical disc in the case where the reflectances of the adjacent tracks are the same and the focus is not the same. It is. 1 is a block diagram showing a first embodiment of an optical disc apparatus of the present invention. It is a block diagram which shows the inclination detection apparatus used for the optical disk apparatus of FIG. It is a figure explaining the light-receiving surface of the light-receiving part used for the inclination detection apparatus of FIG. (A) And (b) is a schematic diagram explaining the specific structure of the light-receiving part used for the inclination detection apparatus of FIG. (A) And (b) is a schematic diagram explaining the specific structure of the light-receiving surface of the inclination detection apparatus of FIG. (A) to (c) are graphs showing the waveforms of push-pull signals S1 and S2 obtained from optical discs having different inclinations by the inclination detection device of FIG. 4 is a graph showing a waveform of a tilt error signal obtained from optical discs having different tilts by the tilt detection device of FIG. 3. (A)-(c) is a figure which shows the other example of the light-shielding area | region provided in a light-receiving surface. It is a block diagram which shows the inclination detection apparatus used for 2nd implementation of the optical disk apparatus of this invention. It is a figure explaining the light-receiving surface of the light-receiving part used for the inclination detection apparatus of FIG. (A) And (b) is a graph which respectively shows the waveform of signal CP1 and CP2 obtained from the optical disk from which inclination differs by the inclination detection apparatus of FIG. It is a figure explaining the light-receiving surface of the light-receiving part used for the modification of 1st Embodiment. It is a figure explaining the light-receiving surface of the light-receiving part used for the modification of 2nd Embodiment. It is a block diagram which shows the structure of the conventional optical disk apparatus. It is a figure explaining the light-receiving surface in the conventional optical disk apparatus. (A) is a figure which shows the structure of an optical disk typically, (b) is a graph which shows the tilt error signal obtained from the optical disk from which inclination differs in the conventional optical disk apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Light source 2,102 Optical axis of optical system 3,103 Beam splitter 4,104 Objective lens 5,105 Optical disk 6,12 Light receiving surface 7,13,108 Inclination detection unit 8,14,109 Signal calculation unit 9,19 Phase difference detection unit 10 Light beam 11, 21 Light blocking unit 15, 17, 110 Amplifying amplifier 16, 18, 111 Differential amplifier 30, 40 Light receiving unit 201 Optical disc device 202 Rotation driving unit 203 Optical head 204 Control system 205 Reproduction signal processing system 206 Objective lens driver 208 Controller 211 Focus error signal generator 212 Tracking error signal generator 213 Tilt detector 214, 215, 216 Phase compensator 218, 224, 225 Drive 241, 242 Tilt detector

Claims (23)

An inclination detection device that collects light emitted from a light source toward an information recording surface of an optical disk by an objective lens and detects the inclination of the optical disk using a plurality of light beams of diffracted light from tracks provided on the information recording surface Because
A light receiving unit that receives a light by dividing the light flux into a plurality of regions and outputs a plurality of light reception signals based on the intensity of light received in each region;
A tilt detection unit that generates a tilt error signal including information according to the tilt of the optical disc based on the plurality of received light signals;
With
On the light receiving surface of the light receiving unit, the luminous flux includes a + 1st order light region where 0th order light and + 1st order light of the diffracted light from the track overlaps, and a −1st order where 0th order light and −1st order light overlap. An optical region, and a zero-order light region that is sandwiched between the + 1st-order light region and the −1st-order light region, does not include the + 1st-order light and −1st-order light, and includes 0th-order light,
The light receiving surface of the light receiving unit includes a first region that receives a central portion of the + 1st order light region and a −1st order light region, and a pair of second regions that sandwich the first region. And the second region are divided so as to separately detect the + 1st order light region and the −1st order light region of the luminous flux,
The light-receiving unit generates the plurality of light-receiving signals by excluding light from a light-shielding region provided in at least a part of the zero-order light region ;
The inclination detecting unit, the divided to generate a push-pull signal from each of the first and second regions of the light receiving portion, inclination detection for detecting a phase difference of the modulated waveform by the track of the two push-pull signal apparatus. An inclination detection device that collects light emitted from a light source toward an information recording surface of an optical disk by an objective lens and detects the inclination of the optical disk using a plurality of light beams of diffracted light from tracks provided on the information recording surface Because
A light receiving unit that receives a light by dividing the light flux into a plurality of regions and outputs a plurality of light reception signals based on the intensity of light received in each region;
A tilt detection unit that generates a tilt error signal including information according to the tilt of the optical disc based on the plurality of received light signals;
With
On the light receiving surface of the light receiving unit, the luminous flux includes a + 1st order light region where 0th order light and + 1st order light of the diffracted light from the track overlaps, and a −1st order where 0th order light and −1st order light overlap. An optical region, and a zero-order light region that is sandwiched between the + 1st-order light region and the −1st-order light region, does not include the + 1st-order light and −1st-order light, and includes 0th-order light,
The light receiving surface of the light receiving unit is divided into a pair of sub-regions by a line that symmetrically bisects the light beam across the −1st order light region and the + 1st order light region of the light beam. One includes a first region that receives the vicinity of the central portion of the + 1st order light region and the −1st order light region, and a second region that is the remaining region excluding the first region,
The first region and the second region are respectively divided so as to separately detect a + 1st order light region and a −1st order light region of the light flux ,
The light-receiving unit generates the plurality of light-receiving signals by excluding light from a light-shielding region provided in at least a part of the zero-order light region;
The tilt detection unit generates a push-pull signal from each of the first region and the second region of the divided light receiving unit, and detects a phase difference between modulation waveforms by tracks of the two push-pull signals. apparatus. The inclination detecting unit, by the light condensed by the objective lens to detect the level of the two push-pull signal while tracing the track, compare, claim 1 for detecting the phase difference Or the inclination detection apparatus of 2. The inclination detector generates a difference signal after multiplying one of the two push-pull signals by a predetermined coefficient, and the light collected by the objective lens traces the track. inclination detecting apparatus according to claim 1 or 2 for detecting the level of said difference signal. Receiving surface of the light receiving portion,
A first region that receives the central part of the + 1st order light region and the −1st order light region ;
A pair of second regions sandwiching the first region and receiving the + 1st order light region and the −1st order light region ;
And across the pair of second regions include <br/> a pair of third regions for receiving only the 0-order light region,
The first, second and third regions detect the light beam separately in a region divided by a dividing line located between the + 1st order light region and the −1st order light region of the light beam. The described tilt detection device. The light receiving surface of the light receiving unit is divided into a pair of sub-regions by a line that symmetrically bisects the light beam across the −1st order light region and the + 1st order light region of the light beam. One is a first region that receives the vicinity of the central portion of the + 1st order light region b and the −1st order light region, and the first region is adjacent to the first region, and the first order light region and the −1st order light region. A second region that receives the remaining region; and a third region that is adjacent to the second region and receives only the zero-order light region;
It said first, second and third regions, to claim 2 for detecting separately the light beams in the region is divided by a dividing line located between the +1 order light region and -1 order light region of the light beam The described tilt detection device. The tilt detection unit generates a push-pull signal from each of the first, second, and third regions of the divided light receiving unit, and the push-pull signal obtained from the first region and the third region After multiplying either one of the push-pull signals obtained from a predetermined first value, a first difference signal that is the difference between them is generated,
After multiplying one of the push-pull signal detected from the second region and the push-pull signal detected from the third region by a predetermined second value, a second difference that is the difference between them is multiplied. generates a signal, the tilt detecting device according to claim 5 or 6 detects the phase difference of the modulated waveform by the track of the first difference signal and the second difference signal. The tilt detection unit detects the phase difference by detecting and comparing the first and second difference signal levels when the light collected by the objective lens is tracing the track. inclination detecting apparatus according to claim 5 or 6. The inclination detecting device according to claim 5 or 6 , wherein the light shielding region blocks a light beam incident only on the first and second regions. The optical disk inclination detecting apparatus according to any one of recorded tracks and claim 1, the reflectance is different between the unrecorded track 9. The light blocking region, at least the inclination detecting apparatus according to any one of the first region claim 1 which is located symmetrically with respect to a line dividing the 9. The light receiving unit may include a light detecting element having a light receiving surface of the light flux is irradiated, the first and second regions, according to any of claims 1 to 4 which is provided on the light receiving surface Tilt detection device. The inclination detection device according to claim 12 , wherein the light detection element includes a light shielding film provided on the light receiving surface so as not to detect light in the light shielding region. The light detecting element includes a detection area for detecting light in said light blocking region, a signal obtained from the detection region of claim 12 which is not used for generating the tilt error signal in the tilt detection unit Tilt detection device. The light receiving unit includes the light receiving surface on which the light flux is irradiated, and the hologram element provided with the first and second regions, and the light in the first and second regions of the hologram element, respectively. inclination detecting apparatus according to claim 1 comprising a light-detecting element for receiving 4. The tilt detection apparatus according to claim 15 , wherein the hologram element diffracts the light beam in the light shielding region so that the light detection element does not receive the light beam. The light receiving unit may include a light detecting element having a light receiving surface of the light flux is irradiated, the first, second and third regions, one of claims 5 provided on the light receiving surface 9 of the An inclination detecting device according to claim 1. The inclination detection device according to claim 17 , wherein the light detection element includes a light shielding film provided on the light receiving surface so as not to detect light in the light shielding region. 18. The light detection element according to claim 17 , wherein the light detection element includes a detection region for detecting light in the light shielding region, and a signal obtained from the detection region is not used for generating the tilt error signal in the tilt detection unit. Tilt detection device. The light receiving unit includes the light receiving surface on which the light flux is irradiated, the hologram element provided with the first, second, and third regions, and the first, second, and third of the hologram element. inclination detecting apparatus according to any one of the light in the region from claim 5 respectively and an optical detector element for receiving 9. 21. The tilt detection apparatus according to claim 20 , wherein the hologram element diffracts the light beam in the light shielding region so that the light detection element does not receive the light beam. A drive unit for rotationally driving an optical disc having an information recording surface;
A light source, an objective lens that condenses the light emitted from the light source toward the information recording surface of the optical disc, and a tilt that corrects aberrations caused by the tilt of the optical axis of the light condensed on the information recording surface from the vertical direction An optical head having a correction unit for recording and reproducing information on the information recording surface;
An inclination detection device as defined in any one of claims 1 to 21 ,
A drive signal generation unit for receiving a tilt error signal of the detection device and driving the tilt correction unit;
An optical disc device comprising: The tilt correction portion, an optical disk apparatus according to claim 22 is an objective lens driving unit for tilting in a radial direction of at least the optical disc the objective lens.

Images