JP2007234083A - Optical pickup device and tilt detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a conventional optical pickup device installed with a tilt sensor causes the cost increase and upsizing of the optical pickup device due to the attachment of the tilt sensor, and a circuit system is complicated since an inspection for tilt detection beforehand is required and many various operations are required even during the tilt detection further in another conventional optical pickup device not loaded with a tilt sensor. <P>SOLUTION: The optical pickup device comprises: a light source for irradiating an optical storage medium with a light beam; a separation means for separating the light beam into one main beam and two sub beams; a light receiving part for radiating the one main beam and the two sub beams so as to be arranged in a direction orthogonal to an information recording track that an optical recording medium has and respectively independently receiving the reflected light; and a calculation means for calculating the difference of output signals outputted from the light receiving part corresponding to the received light quantities of the reflected light of the two sub beams and detecting the tilt of the optical recording medium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical pickup device, and more particularly to an optical pickup device having a function of detecting a tilt amount and a tilt detection method.

  In recent years, there has been a strong demand for further increase in capacity of optical discs as information recording media. In order to increase the capacity, it is effective to increase the density of information recorded on the optical disk, and the track pitch and pit pitch, which are physical intervals of information recorded on the optical disk, have been reduced. Yes. In order to cope with the increase in the density of the disk, it is necessary to further reduce the spot size of laser light as a light source mounted on an optical pickup device that is a key part of the optical disk device. Studies such as using a semiconductor laser with a short wavelength and raising the numerical aperture (NA) of an objective lens of an optical pickup device are being promoted.

  On the other hand, when the density of an optical disk is increased, the problem of poor reading of information recorded on the optical disk or poor writing of information on the optical disk due to the occurrence of tilt becomes obvious. The tilt means an angular deviation between the optical axis of the laser beam and the perpendicular of the recording surface of the optical disc, that is, an inclination deviation of the recording surface of the optical disc with respect to the laser beam. The causes of this are as follows: (1) When the optical disk is held by the spindle motor, the optical disk is held in a tilted state. (2) The optical disk itself is distorted during manufacturing of the optical disk. (3) An inclination shift occurs between the axis of the spindle motor and the optical axis of the lens of the optical pickup device due to a change with time of the optical disk device.

  Conventionally, as long as the optical axis is adjusted at the time of manufacturing the optical disk device, even if the tilt amount increases due to the above-described reasons, there has been no significant influence on signal reading. As the density of optical discs increases, slight optical axis misalignment has become a problem.

In the optical disc apparatus, the relationship between the wavelength λ of the laser beam, the numerical aperture NA, and the allowable tilt value T is
T = λ / (NA) ³ (1)
When the wavelength λ of the laser beam is shortened and the numerical aperture NA is increased, the allowable value T of the tilt amount decreases. If the tilt amount exceeds the allowable value, the spot quality of the laser beam condensed on the optical disk is greatly deteriorated due to the occurrence of coma, and there arises a problem that accurate signal reading or writing becomes difficult.
As a solution to this problem, a method of eliminating the occurrence of tilt, that is, a method of using an optical disk with a small amount of deformation or a material of an optical disk device using a material with little temporal change, can be considered. Both of these are not realistic because they lead to a significant increase in manufacturing costs. For this reason, as a solution to the above problem, a method of mounting a tilt sensor for detecting a tilt deviation of the optical disc on an optical pickup device has been implemented.

FIG. 12 shows a configuration example of the tilt sensor. The tilt sensor 110 includes a light emitting element 111 such as a light emitting diode, a two-divided light receiving element 112, a lens 113, and a case 114 that holds each of the components as main components.
13 and 14 show the principle of tilt detection by the tilt sensor 110. FIG. First, since the light emitting element 111 is disposed on the center line X of the lens 113, the light emitted from the light emitting element 111 is a light beam that is symmetrical with respect to the center line X as shown in FIG. Irradiate the object 1 to be detected. At this time, if the detected object 1 is not tilted with respect to the light emitted from the light emitting element 111, the reflected light reflected by the detected object 1 is also symmetric with respect to the center line X. Is held. Therefore, the outputs from the respective parts of the two-divided light receiving element 112 arranged symmetrically with respect to the center line X are the same.

  In addition, as shown in FIG. 14, when the right side of the detected object 1 is raised with respect to the center line X, that is, when the detected object 1 is tilted, it is reflected by the detected object 1. The reflected light is shifted without being maintained in the condition of being symmetrical with respect to the center line X. As a result, of the outputs from the two-divided light receiving element 112, the output from the right half 112a of the two-divided light receiving element becomes larger than the output from the left half 112b of the two-divided light receiving element according to the tilt amount. Accordingly, from this unbalanced output state, both the tilt direction indicating which side the tilt of the detected object 1 is tilted with respect to the center line X and the tilt amount which is the magnitude of the tilt are obtained. Can be detected.

  If the direction and amount of tilt can be detected, this tilt problem can be solved by providing a mechanism for correcting these. For example, a mechanism portion that can tilt the optical pickup device is provided in the optical disk device. Then, tilt control of the optical pickup device may be performed using the mechanism portion so as to correct the tilt direction and amount obtained from the tilt sensor.

In addition, a method of detecting a tilt by calculating a signal used for an existing servo operation without mounting a tilt sensor has been proposed (for example, Patent Document 1). Specifically describing this document, as described in paragraph numbers (0052) to (0064) of the publication, for example, the asymmetry of the groove crossing signal with respect to the tilt and the asymmetry of the groove crossing signal with respect to the lens shift are used. Thus, an output corresponding to the amount of tilt is obtained by performing arithmetic processing.
JP 2001-344790 A

  However, the method of mounting the tilt sensor on the optical pickup device has the following problems. First, when the tilt sensor is mounted on the optical pickup device, it is necessary to adjust the mounting angle with respect to the optical pickup device, which leads to an increase in the number of manufacturing steps and time of the optical pickup device. This hinders price reduction. Moreover, since the number of parts increases, it is disadvantageous not only in cost but also in downsizing the optical pickup device. Furthermore, since the tilt sensor cannot be mounted at the same position as the objective lens of the optical pickup device, the tilt sensor is mounted at a position different from the objective lens. This means that the position where the tilt sensor is mounted, that is, the position where the tilt sensor detects tilt and the position where light is collected by the objective lens and reproduction recording is performed are different on the same optical disk. Therefore, there is a problem that an error occurs between the tilt state at the position where correction is to be performed and the tilt detection signal obtained from the tilt sensor.

Further, the method of Patent Document 1 has the following problems. For example, as described in the paragraph numbers (0061) and (0069) of the publication, in order to detect the tilt, it is necessary to perform various inspections in advance, and further, the data acquired by the inspection is stored. The storage means is necessary for the optical disc apparatus. In addition, since various kinds of calculations are required during tilt detection, the circuit system becomes complicated in combination with the storage means. Furthermore, as described in the paragraph number (0051) of the publication, since the tilt detection signal uses a signal when the tracking servo is OFF, tilt detection cannot be performed in real time while the tracking servo is ON. .
Therefore, the object of the present invention is to add a special part that causes an increase in cost and size of the optical pickup device, and further reduces the prior inspection for detecting the tilt and various complicated arithmetic processes, thereby simplifying the operation. It is an object of the present invention to provide an optical disc apparatus capable of performing tilt detection with high reliability in real time while performing simple calculation.

  In order to achieve such an object, the present invention includes a light source for irradiating an optical storage medium with a light beam, separation means for separating the light beam into one main beam and two sub beams, the one main beam and two The sub-beams are irradiated so as to be arranged in a direction orthogonal to the information recording track of the optical recording medium, and the reflected light is independently received, and the received light quantity of the reflected light of the two sub-beams. Correspondingly, there is provided an optical pickup device comprising a calculating means for calculating a difference between output signals output from the light receiving section and detecting a tilt of the optical recording medium.

  The two sub-beams are sub-beam S1 and sub-beam S2, and each light-receiving unit that receives the reflected light of sub-beam S1 and sub-beam S2 receives the reflected light by dividing it in the track direction of the optical information recording medium. S11, S12, S21, and S22 are output signals output from the light receiving unit corresponding to the amount of light received in the light receiving region, and (S11−S12) + (S21−S22). It is desirable to calculate and detect the tilt of the optical storage medium.

  Alternatively, the two sub-beams are sub-beam S1 and sub-beam S2, and each light-receiving unit that receives the reflected light of sub-beam S1 and sub-beam S2 receives the reflected light by dividing it in the track direction of the optical information recording medium. If the output signals output from the light receiving unit corresponding to the amount of light received in the light receiving region are S11, S12, S21, and S22, (S11 + S12) − (S21 + S22) is calculated. It is desirable to detect the tilt of the optical storage medium.

  Alternatively, the two sub-beams are sub-beam S1 and sub-beam S2, and each light-receiving unit that receives the reflected light of sub-beam S1 and sub-beam S2 receives the reflected light by dividing it in the track direction of the optical information recording medium. Assuming that the output signals output from the light receiving unit corresponding to the amount of light received in the light receiving region are S11, S12, S21, and S22, (S11−S12) / (S11 + S12) + (S21 It is desirable to calculate −S22) / (S21 + S22) and detect the tilt of the optical storage medium.

Alternatively, the two sub-beams are sub-beam S1 and sub-beam S2, and each light-receiving unit that receives the reflected light of sub-beam S1 and sub-beam S2 receives the reflected light by dividing it in the track direction of the optical information recording medium. An output signal output from the light receiving unit corresponding to the amount of received light received in the light receiving region is S11, S12, S21, and S22, the one main beam is a main beam M1, and the main If the output signal corresponding to the received light quantity of the reflected light of the main beam M1 from the light receiving section that receives the reflected light of the beam M1 is TOTAL, {(S11 + S12) − (S21 + S22)} / TOTAL
Alternatively, it is desirable to calculate {(S11−S12) + (S21−S22)} / TOTAL and detect the tilt of the optical storage medium.

  Further, detecting the tilt of the optical storage medium means that a constant or 0 which is a calculation result in a state without tilt, or at least a tilt direction or amount by comparing a calculation result in a state with tilt and 0. It is desirable that one of them can be calculated.

  Further, the main beam and the sub beam are separated so that a phase difference can be given to a part of the sub beam so that the track cross signal component in the reflected light of the sub beam is substantially zero due to reflection on the optical recording medium. Preferably generated by means.

  Alternatively, a light source, a light receiving element, a light guiding unit, a separating unit, and a quarter wavelength plate, which are main components of the optical pickup device, are mounted on a casing, and these are configured as one component. It is desirable that

  Furthermore, it is desirable that the separating means is configured using a polarization diffraction element having polarization characteristics.

  Further, according to the present invention, the light beam emitted from the light source is separated into one main beam and two sub beams by the separating means, and the one main beam and the two sub beams are separated into an information recording track included in the optical recording medium. Irradiated so as to be aligned in a direction orthogonal to each other, the reflected light of the two sub-beams reflected from the optical storage medium is received by the light-receiving unit that receives each independently, and the received light amount of the reflected light of the two sub-beams Correspondingly, the tilt of the optical storage medium is detected by calculating the difference between the output signals output from the light receiving section, thereby detecting the tilt of the optical storage medium.

  As described above, the reliability of the optical pickup device is reduced by adding no special parts that increase the cost and size of the optical pickup device, and reduce the pre-inspection for detecting the tilt and various complicated calculation processes. High tilt detection can be performed in real time.

Example 1
Embodiment 1 of the present invention will be described below with reference to the drawings. 1 to 6 are views showing Embodiment 1 of the present invention.

  As shown in FIG. 1, an optical disc device 70 includes a spindle motor 2 that holds and rotates an optical disc 1, and an optical pickup device 3A for reading information recorded on the optical disc 1 or writing information to the optical disc 1. And a driving device 4 for roughly moving the optical pickup device 3A in the radial direction of the optical disc 1 (hereinafter referred to as a radial direction). The rotation control system 5 is configured to control the rotation speed of the spindle motor 2 based on position information in the radial direction of the optical disc 1 among the information read by the optical pickup device 3A.

  In the present embodiment, the optical disk 1 is an information recording medium from which information recorded on itself can be read by irradiation with laser light or the like. Further, the information recording medium may be such that information can be additionally written, erased or overwritten by changing the irradiation power of the laser beam or the like.

  The optical pickup device 3A includes a semiconductor laser for generating a laser beam, a collimating lens for converting the laser beam from diverging light to parallel light, a beam splitter for branching or changing the optical path of the laser beam, and a laser beam. For example, a light receiving element such as a photodiode for detection, an objective lens for driving a laser beam to a desired position on the optical disc 1, a drive system, and the like are provided. The drive system is configured such that the objective lens can be finely moved in the focus direction and the tracking direction. The drive system finely moves the objective lens, and guides the laser beam spot focused by the objective lens to a desired position on the optical disc 1.

  Next, a specific optical system configuration of the optical pickup device 3A is shown in FIG. In FIG. 2, the laser beam emitted from the semiconductor laser 6 is divergent light, but is converted into parallel light when passing through the collimating lens 7. Then, after passing through the half-wave plate 50, the polarization direction is aligned, and then enters the shaping prism 8. The shaping prism 8 has a function of shaping the beam cross-sectional shape of the laser beam converted into parallel light by the collimating lens 7. Therefore, the laser beam incident on the shaping prism 8 is shaped so that the light intensity distribution is uniform and is emitted from the shaping prism 8.

  Thereafter, the light beam is separated into three light beams (hereinafter referred to as three beams) by the diffraction effect of the phase shift grating 9 described later, and all of these are incident on the polarization beam splitter (PBS) 10. The PBS 10 has a boundary surface having a reflection or transmission action, and a part of the laser beam passes through the boundary surface and enters an APC (Auto Power Control) photodetector 17. The output of the semiconductor laser is automatically controlled according to the amount of light incident on the APC photodetector 17.

  On the other hand, most of the laser beam is reflected by the boundary surface of the PBS 10, passes through the quarter-wave plate 60, and then enters the beam expander unit 11. The beam expander unit 11 includes a concave lens 11a and a convex lens 11b. When spherical aberration due to a thickness error of the optical disk 1 occurs, the beam expander unit 11 has a function of correcting the aberration by driving the concave lens 11a in the optical axis direction. Have.

  The laser beam that has passed through the beam expander 11 is reflected by the 45 ° mirror 12 to be guided in the direction of the optical disc 1 and is focused on the optical disc 1 by the objective lens 13. Then, the reflected light from the optical disk 1 (hereinafter referred to as return light) passes through the objective lens 13, the 45 ° mirror 12, the beam expander 11, and the quarter wavelength plate 60 and then enters the PBS 10, and the boundary surface of the PBS 10. Transparent. Thereafter, the light is condensed on the light receiving element 16 by the condenser lens 14 and the cylindrical lens 15.

  Next, the phase shift grating 9 and the three beams separated and generated by the diffraction effect of the phase shift grating 9 will be described in detail. First, the three beams separated and generated by the phase shift grating 9 are composed of one main beam and two sub beams. Since the sub beam is mainly used as a part of a tracking servo signal, the output may be sufficiently smaller than the main beam, and may be, for example, about one tenth of the main beam output. The positional relationship of these three beams is separated and generated so as to be arranged in three directions orthogonal to the groove direction of the grating of the phase shift grating 9, with the central portion being the main beam and both ends being the sub beams.

  Further, in this embodiment, when the three beams are collected on the optical disc 1, the three beams are set so as to be aligned in a direction orthogonal to the track direction of the optical disc 1. Therefore, when the phase shift grating 9 is mounted on the optical pickup device 3A, the grating groove direction of the phase shift grating 9 is disposed so as to satisfy the positional relationship between the three beams and the track direction of the optical disc 1. Mount.

  FIG. 6 is a schematic diagram showing the characteristics (grating pattern) of the grating formed in the phase shift grating 9. The grating pattern is preferably a pattern for detecting a tracking error signal using the phase shift DPP method disclosed in Japanese Patent Laid-Open No. 2001-250250, and an example thereof is shown. Hereinafter, the grating pattern will be described.

  The grating pattern in FIG. 6 is composed of two regions, region 31a and region 31b. For reference, a region through which a laser beam passes is schematically indicated by a dotted circle in the drawing. FIG. 6 shows a three-dimensional coordinate system based on the X, Y, and Z axes. An example of the positional relationship between the region 31a and the region 31b will be described using this coordinate system as follows. That is, assuming that the center point of the dotted circle in the figure is the origin of the three-dimensional coordinate system and the optical axis direction of the laser beam is the Z-axis direction, the grating pattern surface is configured on the XY plane as shown in the figure. The And only the 4th quadrant area | region on the said XY plane is comprised by the area | region 31b, and the other area | region is comprised by the area | region 31a. The difference between the region 31a and the region 31b is that the phase is 180 degrees different in the periodic structure of the grating. By adopting such a configuration, the push-pull signal output, which is the track cross signal component in the return light of the sub beam due to reflection on the optical disc 1, becomes almost zero, and thus has the following advantages. That is, in the manufacture of the optical pickup device, the adjustment process of the positional relationship between the track of the optical disk and the three beams, which is necessary when using the conventional grating pattern, is not required.

  Of course, the grating pattern in the present embodiment is merely an example, and any other grating pattern may be used as long as it is disclosed in Japanese Patent Laid-Open No. 2001-250250. Needless to say.

  Furthermore, in the present embodiment, the grating that separates and generates the three beams is not limited to the phase shift grating. The effect of the present invention can be obtained even with the conventional grating pattern, that is, a so-called general grating grating. In that case, as described above, in the manufacture of the optical pickup device, an adjustment process of the positional relationship between the track of the optical disk and the three beams is required.

  The contents of the adjustment process will be described as follows. That is, of the three beams separated and generated by the grating, when one main beam irradiates the disk groove portion on the optical disc, two sub beams irradiate the disc land portion. In the case where the main beam irradiates the disk land portion, the two sub beams are steps for adjusting the groove direction of the grating so as to irradiate the disk groove portion. As a specific method, for example, the grating groove direction can be adjusted by rotating the grating along a plane perpendicular to the optical axis.

  Next, a specific method for performing tilt detection will be described. FIG. 3 shows the shape of the light receiving portion of the light receiving element 16 which is a component of the optical pickup device 3A. Since there are three light beams reflected from the optical disk 1 by the three beams, the light receiving unit is also composed of three regions for receiving each light. Further, each of the three areas is divided as follows.

  First, a region located in the center of the three regions is divided into four, and the divided light receiving units are referred to as a light receiving unit A, a light receiving unit B, a light receiving unit C, and a light receiving unit D. Further, the two regions located on both sides so as to sandwich the central region are both divided into two, and each of the divided light receiving portions is a light receiving portion E, a light receiving portion F, a light receiving portion G, and a light receiving portion H. . Of the reflected light from the optical disk 1 by three beams, the reflected light by the main beam is received by the light receiving part A, the light receiving part B, the light receiving part C, and the light receiving part D, and the reflected light by the sub beam is received by the light receiving part E and the light receiving part F. , And the light receiving part G and the light receiving part H.

  Reflected light from the optical disk contains various information on the optical disk, and appears as changes in the brightness, size, and shape of the spot on the light receiving element. Therefore, a plurality of light receiving portions of the light receiving element are arranged by division or the like so that each change can be acquired. The various types of information can be obtained by performing arithmetic processing on a plurality of signals obtained by the above configuration.

  Among the information obtained by the arithmetic processing, there is a push-pull (or tracking push-pull) signal that is well known as indicating the track related information of the optical disc. The push-pull signal is obtained by differentially processing each output from the light receiving unit arranged so as to divide the spot on the light receiving element into two. Here, the dividing direction for dividing the spot on the light receiving element into two is as follows. Since the spot on the light receiving element is reflected light from the optical disc, it reflects characteristics such as the direction of the spot converged on the optical disc. Therefore, the spot on the light receiving element is divided into two in a direction equivalent to the direction in which the spot converged on the optical disk is divided into two along the track of the optical disk.

In the push-pull signal, a push-pull signal obtained by three main beams is MPP (Main Push-Pull), and a push-pull signal obtained by sub-beams is SPP (Sub Push-Pull). In order to focus on a desired track on the optical disc, the objective lens is controlled to follow in the radial direction. The tracking error signal TES (Tracking Error Signal) for this purpose is TES = MPP-α (SPP) α: constant (2)
Is generated by

In this embodiment, the cylindrical lens 15 rotates the direction of the spot on the light receiving element, that is, the beam pattern of the reflected light from the optical disc 1 projected onto the light receiving element by 90 °. This state is schematically shown in FIG. 4 used for explaining the principle of tilt detection described later. Therefore, when the output signals of the light receiving portions A to H are Sa to Sh,
MPP = (Sa + Sd) − (Sb + Sc) (3)
SPP = (Se−Sf) + (Sg−Sh) (4)
It can be expressed as.

Further, in order to focus on a desired position in the thickness direction on the optical disk, that is, the recording surface position, the objective lens is controlled to follow in the focus direction. The focus error signal FES (Focus Error Signal) for that purpose is determined by the astigmatism method.
FES = (Sa + Sc) − (Sb + Sd) (5)
Further, the information signal generated by the arithmetic expression and recorded on the optical disc is the sum signal (TOTAL) of the main beam,
TOTAL = Sa + Sb + Sc + Sd (6)
It is generated by the arithmetic expression.

The tilt signal (TILT) for tilt detection in this embodiment is
TILT = (Se + Sf) − (Sg + Sh) (7)
Or TILT = (Se−Sf) + (Sg−Sh) (8)
It is generated by the arithmetic expression.

  Note that, as a specific example of the calculation means for performing the calculations of the expressions (7) and (8), a configuration using a combination of operational amplifiers is simple and desirable. 7 (a) and 7 (b) show the calculations of equations (7) and (8) using the output signals Sa to Sh of the light receiving portions A to H. FIG. FIG. 7A shows an example of the arithmetic configuration of the formula (7), and FIG. 7B shows an example of the arithmetic configuration of the formula (8).

  4 and 5 are diagrams for explaining a tilt detection method using a tilt signal (TILT) according to the present embodiment. First, the sub-beams S1 and S2 directed from the objective lens 13 toward the disk 1 irradiate the optical disk 1 as light beams that are symmetrical with respect to the optical axis L as shown in FIG.

At this time, if the optical disc 1 is not tilted, the reflected sub-beam light reflected by the optical disc 1 returns at an angle that is symmetrical with respect to the optical axis L. However, since vignetting (a part of the light beam is blocked) by the objective lens 13 occurs, the area near the main beam is slightly reduced in each sub beam. In addition, each beam pattern on the light receiving element including the main beam is rotated by 90 ° by the cylindrical lens 15 described above. However, since the sub-beam areas for irradiating the light receiving portions E, H and F, G are the same, from the equation (7),
TILT = (Se + Sf) − (Sg + Sh) = 0 (9)
Or from equation (8):
TILT = (Se−Sf) + (Sg−Sh) = 0 (10)
It becomes.

Here, as shown in FIG. 5A, when the optical disk 1 is tilted, for example, the right side of the drawing is raised, the vignetting of the reflected light by the sub-beam S2 out of the reflected light by the sub-beam increases, and the other sub-beam S1 causes the vignetting. The vignetting of the reflected light is reduced.
Therefore, TILT = (Se + Sf) − (Sg + Sh)> 0 (11)
Or TILT = (Se−Sf) + (Sg−Sh)> 0 (12)
Next, as shown in FIG. 5B, when the optical disc 1 is tilted up, for example, the left side of the drawing, the vignetting of the reflected light by the sub-beam S1 among the reflected light by the sub-beams is increased. The vignetting of the reflected light due to S2 is reduced.
Therefore, TILT = (Se + Sf) − (Sg + Sh) <0 (13)
Or TILT = (Se−Sf) + (Sg−Sh) <0 (14)
From the above, from the signal obtained by the TILT arithmetic expression, both the tilt direction as to which side the optical disc 1 is tilted with respect to the optical axis L and the tilt amount, which is the magnitude of the tilt, are generated. Can be obtained.

In general, the optical pickup device switches the amount of laser beam applied to the optical disc during recording and during reproduction. In order to prevent the TILT from being affected by such a change in the amount of irradiation light, it is desirable to normalize the TILT with an output corresponding to the amount of irradiation light. Furthermore, it is simple and desirable to use an output based on the return light from the optical disc, instead of directly detecting the amount of irradiation and obtaining an output. Also, by normalizing using the output from the return light, it is possible to avoid the influence on the TILT output due to the difference in reflectance between optical disks, and even the difference in reflectance between the recorded part and the unrecorded part even in the same optical disk.
Specifically, for example, using equation (7),
TILT = {(Se + Sf)-(Sg + Sh)}
/ (Sa + Sb + Sc + Sd) (15)
Alternatively, using equation (8)
TILT = (Se−Sf) / (Se + Sf)
+ (Sg-Sh) / (Sg + Sh) (16)
Alternatively, using equation (8)
TILT = {(Se−Sf) + (Sg−Sh)}
/ (Sa + Sb + Sc + Sd) (17)
It is normalized by the arithmetic expression.

  The TILT described above can detect in real time the disc surface tilt in the vicinity of the recording or reproducing area while performing the focusing and tracking and recording or reproducing the data. Therefore, by using this signal, tilt correction can be performed more accurately than in the conventional method. For example, recording / reproduction performance as an optical disk device can be achieved even for a bad disk having a large tilt where the optical disk itself is distorted. Will not deteriorate.

  The tilt correction method can be realized by, for example, a method of tilting the entire optical pickup device 3A so as to correct the tilt direction and amount obtained from TILT, or a method of tilting only the objective lens 13. .

  As described above, three beams of one main beam and two sub-beams obtained by separating the laser light emitted from the semiconductor laser 6 that is the light source of the optical pickup device 3A are arranged in the track direction of the optical disc 1. Irradiate so as to be aligned in a direction perpendicular to the direction. Of the return lights of the two beams, the return lights of the two sub beams are received by the light receiving unit E, the light receiving unit F, the light receiving unit G, and the light receiving unit H that receive the light beams independently. By obtaining a tilt signal proportional to the tilt of the optical disc 1 by the differential calculation (7) or (8) of the output signal obtained from each light receiving section, the following operations and effects are obtained.

  That is, it is not necessary to add special parts such as a tilt sensor that increase the cost and increase the size of the optical pickup device. Further, it is possible to detect a tilt with high reliability in real time without stopping the focus and tracking servo operations without requiring a prior inspection or complicated arithmetic processing to detect the tilt.

  Further, from the equations (2) to (4), each output Se from the light receiving unit E, the light receiving unit F, the light receiving unit G, and the light receiving unit H used for obtaining the tilt signal is also used for generating the tracking error signal. , Sf and Sg, Sh are used, and the following operations and effects are achieved. That is, according to the present invention, the light receiving unit for tracking error signal and the light detecting unit for tilt detection and the output signal can be used together, and therefore no light receiving unit or light receiving element dedicated to tilt signal detection is required.

  Furthermore, the push-pull component of each sub-beam is normalized by the output based on the respective return light amounts with respect to the expression (8) that is the tilt signal generation expression, and the expression (16) is obtained as follows. There are effects and effects. That is, the optical disc 1 is an accurate tilt signal that is not affected by the difference in reflectivity even when the recorded portion and the unrecorded portion are mixed and the reflectivity varies depending on the disc position where each sub beam is irradiated. Can be generated.

  In addition, the equations (7) and (8), which are the tilt signal generation equations, are normalized by the sum signal output based on the return light amount of the main beam, and the equations (15) and (17) are obtained, respectively. Produces the following actions and effects. In other words, the amount of laser beam irradiation on the optical disk is switched between recording and playback. Even when the amount of sub-beam changes due to such a change in the amount of irradiation, an accurate tilt signal that is not affected by the difference in the amount of light is obtained. Can be generated.

  Further, the use of the phase shift grating 9 for the diffractive element for generating the main beam and the sub beam provides the following operations and effects. In other words, in the manufacture of the optical pickup device, the adjustment process of the positional relationship between the track of the optical disk and the three beams, which is necessary when using the conventional grating pattern, is not required, and the grating placement accuracy is greatly eased. Can do.

(Example 2)
Example 2 of the present invention will be described below. As shown in FIG. 8, the optical pickup device 3 </ b> B includes an optical integrated unit 19, a collimator lens 7, and an objective lens 13. A laser beam emitted from a semiconductor laser 41, which is a light source mounted on the optical integrated unit 19, is collimated by the collimator lens 7 and then condensed on the optical disk 1 through the objective lens 13. Then, the light reflected from the optical disc 1 (hereinafter referred to as return light as in the first embodiment) passes through the objective lens 13 and the collimator lens 7 again, and is a light receiving element mounted on the optical integrated unit 19. The light is received on 38.

  The optical disc 1 includes a substrate 1a, a cover layer 1b through which a laser beam is transmitted, and a recording layer 1c formed at the boundary between the substrate 1a and the cover layer 1b. The objective lens 13 can be driven in a focus direction (Z-axis direction) and a tracking direction (X-axis direction) by an objective lens driving mechanism (not shown), and even if the optical disc 1 has surface deflection or eccentricity. The condensing spot of the laser beam can follow the predetermined position of the recording layer 1c.

  In this embodiment, a case will be described in which the optical integrated unit 19 is provided with a short wavelength light source having a wavelength of about 405 nm, and the objective lens 3 is provided with a high NA objective lens having an NA of about 0.85. The present invention is not limited to this, but by providing the short wavelength light source and the high NA objective lens, high-density recording / reproduction becomes possible.

  FIG. 9 is an enlarged view of the optical integrated unit 19 shown in FIG. As shown in FIG. 9, the optical integrated unit 19 includes a semiconductor laser 41 as a light source, a light receiving element 38, a polarization beam splitter (PBS) 34 as a laser beam guiding unit, and a laser beam separating unit. A polarization diffraction element 35 and a quarter-wave plate 36 are provided, and these are mounted on a holder 37 as a casing to constitute a single component. The holder 37 is formed with a window portion 37d for allowing light to pass therethrough.

  For convenience of explanation, the surface on which the laser beam (light beam 20) emitted from the semiconductor laser 41 is incident on the PBS 34 is the light beam 20 incident surface of the PBS 34, and the surface on which the return light is incident on the PBS 34 is the return light of the PBS 34. The incident surface. The surface on which the light beam 20 enters the polarization diffraction element 35 is defined as the light beam 20 incidence surface of the polarization diffraction element 35, and the surface on which return light is incident on the polarization diffraction element 35 is defined as the return light incidence surface of the polarization diffraction element 35. And Here, the polarization diffraction element 35 is disposed so that the light beam 20 incident surface of the polarization diffraction element 35 faces the return light incident surface of the PBS 34 and the optical axis of the light beam 20 passes. .

  As described above, in the present embodiment, the semiconductor laser 41 emits the light beam 20 having a short wavelength of about λ = 405 nm. ) Is linearly polarized light having a polarization vibration plane in the X-axis direction, that is, P-polarized light. The light beam 20 emitted from the semiconductor laser 41 enters the PBS 34.

  The PBS 34 has two boundary surfaces, that is, a polarization beam splitter (PBS) surface 34a and a reflection mirror surface (reflection surface) 34b. In this embodiment, the PBS surface 34a transmits linearly polarized light having a polarization vibration surface in the X-axis direction with respect to the illustrated optical axis direction (Z-axis direction), that is, P-polarized light, and polarization vibration perpendicular to the polarization vibration surface. It has a characteristic of reflecting linearly polarized light having a polarization vibration surface in the Y-axis direction, that is, S-polarized light with respect to the surface, that is, the optical axis direction (Z-axis direction) shown in the figure. The PBS surface 34a is disposed so that the optical axis of the light beam 20 passes and the light beam 20 having P-polarized light is transmitted. The reflection mirror surface 34b is disposed so as to face the PBS surface 34a and have an angle of 90 degrees with the PBS surface 34a.

  The P-polarized light beam 20 incident on the PBS surface 34a passes through the PBS surface 34a as it is. The light beam 20 that has passed through the PBS surface 34 a then enters the polarization diffraction element 35.

  Next, the polarization diffraction element 35 will be described in detail. The polarization diffraction element 35 is composed of a first polarization hologram element 31 and a second polarization hologram element 32. Both the first polarization hologram element 31 and the second polarization hologram element 32 are arranged so that the optical axis of the light beam 20 passes through, and the first polarization hologram element 31 is a second polarization hologram element. It is arranged closer to the semiconductor laser 41 than 32.

  The first polarization hologram element 31 has a characteristic of diffracting P-polarized light and transmitting S-polarized light. Conversely, the second polarization hologram element 32 has a characteristic of diffracting polarized light and transmitting P-polarized light. The diffraction of these polarized light is performed by the groove structure (grating) formed in each polarization hologram element, and the diffraction angle is defined by the pitch of the grating (hereinafter referred to as the grating pitch).

  The first polarization hologram element 31 is formed with a hologram pattern which is a grating pattern for generating three beams for detecting a tracking error signal (TES). That is, when the P-polarized light beam 20 transmitted through the PBS surface 34a is incident on the first polarization hologram element 31 constituting the polarization diffraction element 35, it is diffracted and three beams (one main beam for detecting TES) are detected. Beam and two sub-beams) and exits from the first polarization hologram element 31. The detailed hologram pattern of the first polarization hologram element 31 will be described later. As a TES detection method using three beams, a three-beam method, a differential push-pull (DPP) method, a phase shift DPP method, or the like is generally known.

  As described above, the second polarization hologram element 32 diffracts the S-polarized light and transmits the P-polarized light as it is. That is, since the light beam 20 that has passed through the first polarization hologram element 31 and becomes three beams is P-polarized light, it passes through the second polarization hologram element 32 as it is. A detailed hologram pattern of the second polarization hologram element 32 will also be described later.

  The quarter-wave plate 36 can be converted into circularly polarized light when linearly polarized light is incident and emitted. Accordingly, the P-polarized light beam 20, which is linearly polarized light incident on the quarter-wave plate 36, is converted into a circularly-polarized light beam and emitted from the optical integrated unit 19.

  As shown in FIG. 8, the circularly polarized light beam emitted from the optical integrated unit 19 is collimated by the collimator lens 7 and then condensed on the optical disc 1 through the objective lens 13. Then, the light beam reflected by the optical disk 1, that is, the return light, passes through the objective lens 13 and the collimator lens 7 again, and is incident on the quarter-wave plate 36 disposed in the optical integrated unit 19 again.

  The return light incident on the quarter-wave plate 36 of the optical integrated unit 19 is circularly polarized light, and this quarter-wave plate 36 causes the Y-axis direction with respect to the illustrated optical axis direction (Z-axis direction). It is converted into linearly polarized light having a polarization oscillation surface of S, that is, S-polarized light. The return light converted to S-polarized light is incident on the second polarization hologram element 32.

  The return light converted to S-polarized light that has entered the second polarization hologram element 32 is diffracted into zero-order diffracted light (non-diffracted light) 22 and + 1st-order diffracted light (diffracted light) 23, thereby producing a second polarization hologram. The light is emitted from the element 32. Return light (0th-order diffracted light and + 1st-order diffracted light) that is diffracted S-polarized light is incident on the first polarization hologram element 31 and is transmitted as it is. The return light, which is S-polarized light, enters the PBS 34, is reflected by the PBS surface 34a, is further reflected by the reflecting mirror 34b, and then exits the PBS 34. The return light emitted from the PBS 34 is received by the light receiving element 38. The light receiving portion pattern of the light receiving element 38 will be described later.

  Next, the hologram pattern formed on the first polarization hologram element 31 shown in FIG. 6 will be described. The grating pitch in the first polarization hologram element 31 is designed so that the three beams are sufficiently separated on the light receiving element 38.

  As one specific example, the distance between the semiconductor laser 41 and the first polarization hologram element 31 is about 5 mm in terms of the optical path length in the air, and the distance between the main beam and the sub beam on the light receiving element 38 is about 150 μm. To. Further, the interval between the main beam and the sub beam on the optical disc 1 is set to about 16 μm. In that case, the grating pitch in the first polarization hologram element 31 is preferably about 14 μm. The grating groove direction is arranged in a direction parallel to the track of the optical disc 1 so that the main beam and the sub beam on the optical disc 1 are aligned in a direction perpendicular to the track direction of the optical disc 1.

  As a hologram pattern formed on the first polarization hologram element 31, detection of a tracking error signal using the phase shift DPP method disclosed in Japanese Patent Laid-Open No. 2001-250250 described in the first embodiment is performed. It is desirable to have a lattice pattern for FIG. 6 shows a schematic diagram of the lattice pattern, but since specific description and effects have already been described in Example 1, they are omitted here.

  Next, the hologram pattern formed on the second polarization hologram element 32 will be described. FIG. 10 is a schematic diagram showing a hologram pattern formed on the second polarization hologram element 32. The hologram pattern of the second polarization hologram element 32 includes three regions 32a, 32b, and 32c. Specifically, one semicircular region 32c divided into two by an X-axis direction boundary line 32x corresponding to the radial direction, and an inner peripheral region 32a in which the other semicircular region is further divided by an arc-shaped boundary line. And an outer peripheral region 32b. For reference, a region through which return light passes is schematically shown by a dotted circle in the drawing.

  The grating pitch in each of the regions of the second polarization hologram element 32 is the smallest in the region 32b (maximum diffraction angle), the largest in the region 32c (minimum diffraction angle), and the region 32a is a numerical value between these values. It has become. The spherical aberration error signal (SAES) used to correct the spherical aberration can be detected using the + 1st order diffracted light from the region 32a and the region 32b. The FES used for correcting the focal position deviation is a single knife edge method using + 1st order diffracted light from the region 32c, or a double knife using + 1st order diffracted light from the regions 32a, 32b and 32c. Detection is possible by the edge method. Furthermore, in the present invention, the 0th-order diffracted light is used by detecting the main beam of the 0th-order diffracted light for detection of high-speed signals such as RF signals (information signals recorded on the optical disk) and TES using the phase difference detection (DPD) method. These main beams and sub beams are used for TES detection using the phase shift DPP method.

  Next, the relationship between the division pattern of the second polarization hologram element 32 and the light receiving portion pattern of the light receiving element 38 will be described with reference to FIGS.

  First, the optical state of FIG. 11A will be described as follows. That is, with respect to the thickness of the cover layer 1b of the optical disc 1 in FIG. 8, the position of the collimating lens 7 in the optical axis direction is adjusted so that spherical aberration does not occur in the focused beam by the objective lens 13. . In the state where the adjustment is made, the light beam 20 is focused on the recording layer 1c in a focused state. FIG. 11A shows the spot of the return light on the light receiving element 38 in this case. Further, FIG. 11A also shows the relationship between the three regions 32a to 32c of the second polarization hologram element 32 described in FIG. 10 and the traveling direction of the + 1st order diffracted light. The center position of the second polarization hologram element 32 is set at a position corresponding to the center position of the light receiving portions 38a to 38d. However, for convenience of explanation, the center position of the second polarization hologram element 32 is shifted from the actual position in the X-axis and Y-axis directions. Show.

  As shown to Fig.11 (a), the light receiving element 38 is comprised by 14 light-receiving parts of 38a-38n. In the forward optical system (the optical system until the light beam 20 emitted from the semiconductor laser 41 reaches the optical disk 1), the three beams formed by the first polarization hologram element 31 are reflected by the optical disk 1 and returned light. Then, in the return path optical system (the optical system until the return light reflected by the optical disk 1 reaches the light receiving element 38), it is further separated by the second polarization hologram element 32, and three non-diffracted lights (0th order diffracted light) ) 22 and nine diffracted lights (+ 1st order diffracted lights) 23, a total of 12 beams are formed. The light receiving element 38 includes a light receiving portion for receiving a light beam necessary for detecting the servo signal including the RF signal and the tilt signal among the non-diffracted light 22 and the diffracted light 23.

  Next, the optical state of FIG. 11B will be described as follows. That is, the spot of the return light on the light receiving element 38 when the objective lens 13 in FIG. 8 approaches the optical disc 1 from the state of FIG. As the objective lens 13 approaches the optical disc 1, the beam diameter of the return light increases, so that the size of the spot on the light receiving element 38 also increases. However, it is assumed that no light beam protrudes from the light receiving unit yet in this state.

  Next, the servo signal generation operation will be described. Here, the output signals of the light receiving portions 38a to 38n are represented as Sa to Sn.

The RF signal (RF) is an information signal recorded on the optical disc as described above, and is detected using the main beam of 0th-order diffracted light. Therefore, RF is the same as in equation (6).
RF = Sa + Sb + Sc + Sd (18)
It is generated by the arithmetic expression.

  The tracking error signal (TES1) by the DPD method is detected by performing a phase comparison of Sa to Sd. The DPD method is a detection method effective for an optical disc on which information pits have already been recorded, such as a read-only optical disc, and uses the following principle.

  For example, when the pit row formed on the recording layer 1c of the optical disc 1 shown in FIG. 8 is scanned by the light beam condensed by the objective lens 13, the pit row is reflected from the optical disc 1 depending on the positional relationship between the pit row and the light beam. The intensity distribution pattern of the return light, which is the reflected light, changes. In order to detect the change of the intensity distribution pattern, attention is paid to two output changes of (Sa + Sc) and (Sb + Sd). That is, when the light beam scans the center of the pit row, the two output changes (Sa + Sc) and (Sb + Sd) are in phase, whereas the light beam is shifted from the center of the pit row. When the position is scanned, a phase difference occurs between the two output changes. Further, the direction of the phase difference, that is, the phase advance and the phase delay are reversed depending on the direction of deviation from the center of the pit row, that is, whether the optical disc 1 is displaced toward the inner circumference side or the outer circumference side. . Therefore, by using this principle, a tracking error signal can be obtained.

The tracking error signal (TES2) by the phase shift DPP method is
TES2 = {(Sa + Sb)-(Sc + Sd)}
−α {(Se−Sf) + (Sg−Sh)} (19)
Given in. Here, α is a constant, and is set to an optimum value for canceling the offset output generated in the TES2 output due to objective lens shift or the like.

The focus error signal (FES) is detected using a double knife edge method. That is, FES is
FES = (Sm−Sn) − {(Si + Sk) − (Sj + Sl)} (20)
Given in.

Further, the tilt signal (TILT) for detecting the tilt of the present invention is similar to the calculation of the expression (7) or (8) in the first embodiment.
TILT = (Se + Sf) − (Sg + Sh) (21)
Or TILT = (Se−Sf) + (Sg−Sh) (22)
It is generated by the arithmetic expression.

  Also, as a specific example of the calculation means for performing the calculations of the equations (21) and (22), a configuration using a combination of operational amplifiers is simple and desirable as in the first embodiment.

  The present embodiment is greatly different from the first embodiment in that an optical integrated unit 19 is provided. The optical integrated unit 19 includes a semiconductor laser 41, which is a main component of the optical pickup device 3B, a light receiving element 38, a polarization beam splitter (PBS) 34 as a laser beam guiding unit, and a laser beam separating unit. The polarization diffraction element 35 and the quarter wavelength plate 36 are mounted on a holder 37 which is a casing, and these are configured as one component. By having the optical integrated unit 19, the following operations and effects not found in the first embodiment are achieved. That is, since the main components of the optical pickup device 3B are integrated, it is possible to suppress deterioration of characteristics due to temperature changes and external impacts, and it is possible to provide a highly reliable optical pickup device.

  Further, although the polarization diffraction element 35 is used as the laser beam separating means in the optical pickup device 3B, this also has the following operations and effects not found in the first embodiment. That is, by using a diffraction element having polarization characteristics, it is possible to suppress a light amount loss during diffraction. Then, the output of the semiconductor laser can be reduced by the amount of light quantity loss suppressed. This is particularly effective when a large amount of laser beam is required, such as when recording on the optical disc 1. That is, recording with a smaller semiconductor laser output than before is possible, and as a result, the life of the semiconductor laser is extended. Furthermore, since excessive heat generation is also reduced, a highly reliable optical pickup device capable of stable operation over a long period of time can be provided.

  In other respects, since the tilt detection method and detection formula are the same as in the first embodiment, the same operations and effects as in the first embodiment are achieved.

It is a figure for demonstrating the structure of the optical disk apparatus which has the optical pick-up apparatus of Example 1 of this invention. It is a figure for demonstrating the structure of the optical system of the optical pick-up apparatus of Example 1 of this invention. It is a figure of the light receiving element for demonstrating the tilt detection of Example 1 of this invention. It is a figure for demonstrating a state when the optical disk is not tilted. It is a figure for demonstrating a state when the optical disk is tilting. It is a figure for demonstrating the phase shift grading of Example 1 of this invention. It is a figure for demonstrating the circuit structure as a calculating means of Example 1 of this invention. It is the figure which showed the structure of the optical pick-up apparatus of Example 2 of this invention. It is the figure which expanded and showed the structure of the optical integrated unit of the optical pick-up apparatus of Example 2 of this invention. It is a figure which shows an example of the structure of the grating | lattice pattern in the 2nd polarization hologram element 32 of Example 2 of this invention. It is a figure explaining the light-receiving part pattern of the light receiving element used for the optical integrated unit of Example 2 of this invention, (a) is the light-receiving state of the light beam in case the spherical aberration does not generate | occur | produce in the said light-receiving part pattern (B) is the figure which showed the light-receiving state of the light beam in case the objective lens approaches the optical disk from the state of (a). It is a figure which shows the structural example of the tilt sensor mounted in the conventional optical pick-up apparatus. It is the figure which showed the detection principle of the tilt by the tilt sensor mounted in the conventional optical pick-up apparatus. It is another figure which showed the detection principle of the tilt by the tilt sensor mounted in the conventional optical pick-up apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Spindle motor 3A, 3B Optical pick-up apparatus 4 Drive apparatus 5 Rotation control system 6,41 Semiconductor laser 7 Collimating lens 8 Shaping prism 9 Phase shift grating 10,34 Polarization beam splitter (PBS)
DESCRIPTION OF SYMBOLS 11 Beam expander unit 12 45 degree mirror 13 Objective lens 14 Condensing lens 15 Cylindrical lens 16,38 Light receiving element 17 Photo detector for APC 19 Optical integrated unit 35 Polarization diffraction element 36,60 1/4 wavelength plate 37 Holder 37d Window 50 50 half-wave plate 70 optical disk device 110 tilt sensor 111 light emitting element 112 two-divided light receiving element 112a two-divided light receiving element right half 112b two-divided light receiving element left half 113 lens 114 case

Claims (10)

A light source for irradiating the optical storage medium with a light beam; separation means for separating the light beam into one main beam and two sub beams; and the one main beam and two sub beams on an information recording track of the optical recording medium. The difference between the output signal output from the light receiving unit corresponding to the received light quantity of the reflected light of the two sub beams and the light receiving unit that irradiates the light so as to be arranged in a direction orthogonal to each other and receives the reflected light independently of each other And an arithmetic means for detecting the tilt of the optical recording medium. The two sub-beams are sub-beam S1 and sub-beam S2,
Each light receiving unit that receives the reflected light of the sub beam S1 and the sub beam S2 has a light receiving region that receives the reflected light by dividing the reflected light into two in the track direction of the optical information recording medium,
When the output signals output from the light receiving unit corresponding to the amount of received light received in the light receiving region are S11, S12 and S21, S22,
2. The optical pickup device according to claim 1, wherein (S11-S12) + (S21-S22) is calculated to detect a tilt of the optical storage medium. The two sub-beams are sub-beam S1 and sub-beam S2,
Each light receiving unit that receives the reflected light of the sub beam S1 and the sub beam S2 has a light receiving region that receives the reflected light by dividing the reflected light into two in the track direction of the optical information recording medium,
When the output signals output from the light receiving unit corresponding to the amount of received light received in the light receiving region are S11, S12 and S21, S22,
2. The optical pickup device according to claim 1, wherein (S11 + S12)-(S21 + S22) is calculated to detect a tilt of the optical storage medium. The two sub-beams are sub-beam S1 and sub-beam S2,
Each light receiving portion that receives the reflected light of the sub beam S1 and the sub beam S2 has a light receiving region that receives the reflected light by dividing the reflected light into two in the track direction of the optical information recording medium,
When the output signals output from the light receiving unit corresponding to the amount of received light received in the light receiving region are S11, S12 and S21, S22,
2. The optical pickup device according to claim 1, wherein a tilt of the optical storage medium is detected by calculating (S11-S12) / (S11 + S12) + (S21-S22) / (S21 + S22). The two sub-beams are sub-beam S1 and sub-beam S2,
Each light receiving unit that receives the reflected light of the sub beam S1 and the sub beam S2 has a light receiving region that receives the reflected light by dividing the reflected light into two in the track direction of the optical information recording medium,
The output signals output from the light receiving unit corresponding to the amount of received light received in the light receiving region are S11, S12 and S21, S22,
The one main beam is a main beam M1,
When an output signal corresponding to the amount of light received from the main beam M1 reflected from the light receiving unit that receives the reflected light from the main beam M1 is TOTAL,
{(S11 + S12)-(S21 + S22)} / TOTAL
2. The optical pickup device according to claim 1, wherein {(S11-S12) + (S21-S22)} / TOTAL is calculated to detect a tilt of the optical storage medium. Detecting the tilt of the optical storage medium means
6. The tilt direction or amount can be calculated by comparing a constant or 0 as a calculation result in a state without tilt and a calculation result in a state with tilt. The optical pickup device according to any one of the above.   The main beam and the sub beam give a phase difference to a part of the sub beam so that a push-pull signal output which is a track cross signal component in the reflected light of the sub beam due to reflection on the optical recording medium becomes almost zero. The optical pickup device according to claim 1, wherein the optical pickup device is generated by a separating means capable of   A light source, a light receiving element, a light guiding unit, a separating unit, and a quarter-wave plate, which are main components of the optical pickup device, are mounted on a casing, and these are configured as one component. The optical pickup device according to claim 1, wherein the optical pickup device is an optical pickup device.   9. The optical pickup device according to claim 8, wherein the separating unit is configured using a polarization diffraction element having polarization characteristics. The light beam emitted from the light source is separated into one main beam and two sub beams by the separating means,
Irradiating the one main beam and the two sub beams so as to be aligned in a direction orthogonal to the information recording track of the optical recording medium,
The reflected light of the two sub-beams reflected from the optical storage medium is received by a light receiving unit that independently receives each of the reflected light,
A tilt of the optical storage medium, wherein the tilt of the optical storage medium is detected by calculating a difference between output signals output from the light receiving unit corresponding to the received light quantity of the reflected light of the two sub beams. Detection method.

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