JP4390769B2 - Optical pickup device - Google Patents

Description

  The present invention relates to an optical pickup device, and is particularly suitable for use in a compatible optical pickup device capable of emitting laser light having a plurality of wavelengths.

  Development of HD DVD (High Definition Digital Versatile Disc) using a laser beam of blue wavelength is in progress with the increase in capacity of optical discs. Currently, a compatible optical pickup applicable to both the HDDVD and the existing DVD is being developed.

  In this type of compatible optical pickup, a configuration in which an objective lens is separately provided for each of the HDDVD laser beam and the DVD laser beam can be employed (Patent Document 1). Here, the two objective lenses can be arranged side by side in a direction orthogonal to the disk diameter. In this case, if one objective lens moves on the disk diameter, the other objective lens moves parallel to this diameter at a position away from this diameter by a certain distance. However, when this is done, the relationship between the other objective lens and the track direction changes in accordance with the movement of the objective lens as follows.

  FIG. 13 shows the angle in the track direction at each moving position when the two objective lenses move in the disc radial direction.

  In FIG. 5A, one of the two objective lenses moves on the OY line (normal deviation = 0), and the other is positioned at a distance Z from the OY line by the OY line. (Normal deviation = Z). At this time, assuming that the angle in the track direction is θ2 (angle formed by a line parallel to the track tangent and the OX line) in FIG. 10A, the distance between the displacement of the objective lens and the track angle is shown in FIG. There is a relationship as shown in FIG. 4B shows the case where the normal deviation is 5 mm.

  As shown in the figure, when there is no normal deviation of the objective lens, the track angle θ2 is always zero regardless of the movement position of the objective lens. On the other hand, when the normal deviation occurs in the objective lens, the track angle θ2 changes as the objective lens moves as shown in the figure. When the track angle θ2 changes in this way, the track direction on the photodetector also changes. This causes a problem that the track direction rotates with respect to the dividing line of the sensor pattern and an appropriate push-pull signal cannot be generated.

  In the figure, the track angle θ2 satisfies the relationship θ2 = θ1. That is, the track angle can also be expressed as θ1.

  By the way, in this type of optical pickup device, as shown in FIG. 14, a flat half mirror is inserted into an optical system having a swing angle α, and astigmatism is introduced into the laser light by the refraction action of the half mirror. The structure which carries out can be taken. In this way, the optical system can be accommodated in a compact manner and the number of parts can be reduced.

  However, in this case, the swing angle α may not be set to ± 45 ° because of the layout of the optical components. In this case, the track direction on the photodetector is not 45 ° with respect to the beam spot deformation direction due to astigmatism. For this reason, there arises a problem that the quadrant sensor cannot be arranged at a position where both the focus error signal and the tracking error signal (push-pull signal) are appropriate.

  That is, if the four-divided sensor is arranged so that the dividing line is 45 ° with respect to the beam spot deformation direction, the track direction on the sensor is inclined with respect to the dividing line. On the other hand, when the four-divided sensor is arranged so that the dividing line is along the track direction, the dividing line of the four-divided sensor does not become 45 ° with respect to the deformation direction of the beam spot.

Furthermore, as described above, when the normal deviation occurs in the objective lens, the relationship between the deformation direction of the beam spot due to astigmatism and the track direction may be further deteriorated depending on the direction or size of the normal deviation. In this case, if the dividing line of the sensor pattern is adjusted so as to be suitable for detection of astigmatism, a proper push-pull signal cannot be generated and tracking control cannot be performed smoothly.
WO97 / 42631

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup device that can suppress a shift between a dividing line direction and a track direction of a sensor pattern to a minimum even when a normal deviation occurs in an objective lens as described above.

  The present invention provides a method for setting appropriate values for the direction or size of the normal deviation Z and the swing angle α. According to the method of the present invention, it is possible to effectively suppress the deviation between the dividing line direction of the sensor pattern and the track direction.

   An optical pickup device according to a first aspect of the present invention converges a semiconductor laser and a laser beam emitted from the semiconductor laser onto the disc and has a diameter L of the disc parallel to the moving direction of the optical pickup device. On the other hand, the first objective lens disposed at a position separated by a distance Z in the plane direction of the disk and the laser light reflected from the disk are received and divided into four regions by two orthogonal dividing lines. A photodetector having a divided sensor pattern; and the laser beam emitted from the semiconductor laser is reflected and guided to the first objective lens side, and the laser beam reflected from the disk is transmitted. The laser is provided with a flat optical member that leads to the photodetector side, and is reflected by the optical member and guided to the first objective lens side Is tilted in the plane direction of the disk by a swing angle α with respect to a straight line perpendicular to the diameter L of the disk and parallel to the plane direction of the disk, the swing angle α and the distance Z Is adjusted so that the track direction of the disk on the photodetector is approximately 45 ° with respect to the direction of astigmatism introduced by the optical member, and two dividing lines of the sensor pattern are adjusted. One of them is matched with a straight line having an angle of about 45 ° with respect to the astigmatism introduction direction.

According to a second aspect of the present invention, in the optical pickup device according to the first aspect, an angle formed by a straight line connecting the center of the disk and the access position of the first objective lens and the diameter L is a track angle θ1. When the track angle θ1 when the first objective lens is at the innermost circumferential position of the disk is θ1max, and the track angle θ1 when the first objective lens is at the outermost circumferential position of the disk is θ1min,
α− (θ1max + θ1min) / 2 = ± 45 °
The swing angle α and the distance Z are set so as to satisfy the above condition.

  According to a third aspect of the present invention, in the optical pickup device according to the first or second aspect, the optical pickup device further includes a second objective lens different from the first objective lens, wherein the second objective lens is It is arranged at a position along the diameter L of the disk.

  According to a fourth aspect of the present invention, in the optical pickup device according to the third aspect, the actuator has an actuator that drives an objective lens, and the first objective lens and the second objective lens are the same actuator movable part. It is equipped with.

  According to a fifth aspect of the present invention, in the optical pickup device according to the third or fourth aspect, the laser light is guided to the second objective lens and the laser light reflected by the disk is received. An optical system is arranged as a second optical system different from the first optical system having the semiconductor laser, the photodetector, and the optical member.

  According to a sixth aspect of the present invention, in the optical pickup device according to the fifth aspect, the first optical system and the second optical system guide laser beams of different wavelengths to the corresponding disks, respectively. And

  According to the present invention, it is possible to provide an optical pickup device that can suppress a deviation between a dividing line direction and a track direction of a sensor pattern to a minimum even when a normal line deviation occurs in an objective lens.

The significance or effect of the present invention will become more apparent from the following description of embodiments. However, the following embodiment is merely an example for embodying the present invention, and the meaning of the term of the present invention or each constituent element is limited to that described in the following embodiment. Is not to be done.

  Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to a compatible optical pickup device for HDDVD and DVD.

  First, FIG. 1 shows the basic configuration of the optical system. In the figure, the spindle motor 200 is also shown for convenience. This optical system is divided into an optical system (HD optical system) for irradiating HDDVD with laser light and an optical system (DVD optical system) for irradiating DVD with laser light.

  The HD optical system includes an HD laser 11, an HD half mirror 12, an HD rising mirror 13, an HD collimator lens 14, an HD objective lens 15, and an HD sensor 16.

  The HD laser 11 emits a blue wavelength laser beam having a wavelength of about 400 nm. The HD half mirror 12 reflects a part of the laser light emitted from the HD laser 11 to the HD rising mirror 13 side and reflects a part of the laser light incident from the HD rising mirror 13. The light is transmitted and guided to the HD sensor 16.

  Here, the HD half mirror 12 is formed of a flat glass material having a constant thickness, and the plane facing the HD laser 11 and the HD rising mirror 13 out of two parallel planes. Further, a half mirror surface is formed. The HD half mirror 12 is disposed so as to be inclined in parallel to the disk surface by a certain angle with respect to the optical axis of the laser light incident from the HD rising mirror 13. For this reason, astigmatism is introduced into the laser light transmitted through the HD half mirror 12 among the laser light from the HD rising mirror 13 due to refraction when the light passes through the HD half mirror 12. In the present embodiment, a focus error signal for HDDVD is generated based on the astigmatism method.

  The HD rising mirror 13 reflects the laser light reflected by the HD half mirror 12 in the direction of the HD collimator lens 14. The HD collimator lens 14 converts the laser light reflected by the HD rising mirror 13 into parallel light. The HD objective lens 15 converges the laser light from the HD collimator lens 14 on the disk 100.

  The HD sensor 16 receives laser light (reflected light from the disk 100) that has passed through the HD half mirror 12. The HD sensor 16 is divided into four regions by two orthogonal dividing lines so that a focus error signal can be generated by the astigmatism method and a tracking error signal can be generated by the one-beam push-pull method. Divided sensor patterns (four-divided sensors) are arranged.

  The DVD optical system includes a DVD laser 21, a DVD diffraction grating 22, a DVD half mirror 23, a DVD startup mirror 24, a DVD collimator lens 25, a DVD objective lens 26, It is composed of a DVD sensor 27.

  The DVD laser 21 emits red wavelength laser light having a wavelength of about 650 nm. The DVD diffraction grating 22 divides the laser beam from the DVD laser 21 into three beams. The DVD half mirror 23 reflects a part of the laser light incident from the DVD diffraction grating 22 toward the DVD rising mirror 24 and a part of the laser light incident from the DVD rising mirror 24. Is transmitted to the DVD sensor 27.

  Here, the DVD half mirror 23 is formed of a flat glass material having a constant thickness, and the DVD half mirror 23 on the side facing the DVD diffraction grating 22 and the DVD rising mirror 24 out of two parallel planes. A half mirror surface is formed on the plane. The DVD half mirror 23 is disposed so as to be inclined in parallel to the disk surface by a certain angle with respect to the optical axis of the laser beam incident from the DVD rising mirror 24. For this reason, of the laser light from the DVD startup mirror 24, the laser light that passes through the DVD half mirror 23 and travels toward the DVD sensor 27 is not reflected by the refraction action when passing through the DVD half mirror 23. Point aberration is introduced. In the present embodiment, a DVD focus error signal is generated based on the astigmatism method.

  The DVD raising mirror 24 reflects the laser light reflected by the DVD half mirror 23 toward the DVD collimator lens 25. The DVD collimator lens 25 converts the laser light reflected by the DVD startup mirror 24 into parallel light. The DVD objective lens 26 converges the laser light from the DVD collimator lens 25 onto the disk 100.

  The DVD sensor 27 receives laser light (reflected light from the disk 100) that has passed through the DVD half mirror 23. The DVD sensor 27 is provided with a sensor pattern capable of generating a focus error signal by the astigmatism method and generating a tracking error signal by the differential push-pull method. That is, in order to receive the main beam, a sensor pattern (four-divided sensor) divided into four regions by two orthogonal dividing lines is arranged, and further divided into two to receive two sub beams. Two pairs of sensor patterns are arranged.

  The HD objective lens 15 and the DVD objective lens 26 are mounted on a common actuator movable portion 30. Here, these two objective lenses are mounted on the actuator movable portion 30 so as to be arranged in a direction perpendicular to the disc diameter at a certain distance from each other. The actuator movable unit 30 is driven by the objective lens actuator 31 in the tracking direction and the focus direction. Accordingly, when focus servo and tracking servo are applied to one of the HD objective lens 15 and the DVD objective lens 26 via the objective lens actuator 31, the other objective lens also moves in the focus direction along with the objective lens to be controlled. And driven in the tracking direction. The objective lens actuator 31 can have a known configuration.

  FIG. 2 shows the relationship between the objective lens and the disk. As described above, in the present embodiment, of the two objective lenses, the DVD objective lens 26 is arranged so as to move on the disc diameter (indicated by a one-dot chain line L1 in the figure). Therefore, the HD objective lens 15 moves on a straight line (indicated by a one-dot chain line L2 in the figure) that is shifted from the disk diameter L1 by a certain distance.

  FIG. 3 is a diagram showing the state of the beam spot on the HD sensor 16.

  Referring to FIG. 5A, when a focus error occurs in the HD objective lens 15, the beam spot on the HD sensor 16 is moved in a direction parallel to the disk surface by the astigmatism effect of the HD half mirror 12. Deforms in a direction perpendicular to this. Accordingly, if the angle ψ between one dividing line of the four-divided sensor arranged in the HD sensor 16 and the disk plane direction is set to ψ = 45 ° as shown in the figure, the focus error based on the astigmatism method Detection can be performed properly.

Referring to FIG. 2B, the angle φ between the track direction projected on the beam spot on the HD sensor 16 and the disk plane direction is when the track angle θ1 shown in FIG. 2 is minimum (θ1min). That is, the maximum value is obtained when the HD objective lens 15 is at the outermost peripheral position of the disk. If the angle φ at this time is φmax, φmax is given by the following equation.
φmax = α−θ1min (1)

Similarly, as shown in FIG. 2C, the angle φ is minimum when the track angle θ1 is maximum (θ1max), that is, when the HD objective lens 15 is at the innermost circumferential position of the disk. If the angle φ at this time is φmin, φmin is given by the following equation.
φmin = α−θ1max (2)

  As described above, the angle φ between the track direction and the disc plane direction changes in the range of φmin ≦ φ ≦ φmax until the HD objective lens 15 moves from the disc innermost circumference position to the outermost circumference position. .

  In order to properly generate the tracking error signal (push-pull signal), the track direction may be made to coincide with one dividing line direction of the four-divided sensor. Accordingly, as shown in FIG. 5A, in order to properly detect the focus error, when the angle ψ between one dividing line of the four-divided sensor and the disk plane direction is set to ψ = 45 °. Can appropriately generate a tracking error signal (push-pull signal) by setting the angle φ between the track direction and the disk plane direction to φ = ± 45 °.

  However, as described above, the angle φ changes in the range of φmin ≦ φ ≦ φmax as the HD objective lens 15 moves. Therefore, the angle φ cannot be set to φ = ± 45 ° at any objective lens position.

  In this case, if φmin = ± 45 °, when the HD objective lens 15 is moved to the outermost peripheral position, the deviation angle in the track direction with respect to the dividing line of the four-divided sensor is increased, and the tracking servo characteristics are deteriorated. On the contrary, if φmax = ± 45 °, when the HD objective lens 15 moves to the innermost peripheral position, the angle of deviation in the track direction with respect to the dividing line of the four-divided sensor increases, and the tracking servo characteristics deteriorate.

On the other hand, an intermediate angle φave between φmin and φmax, that is, φave = α− (θ1max + θ1min) / 2 (3)
Is equal to ψ = 45 °, the deviation angle in the track direction with respect to the dividing line of the four-divided sensor when the HD objective lens 15 is moved to the innermost circumferential position or the outermost circumferential position is compared with the above case. Is suppressed. Therefore, by setting φave = ± 45 °, it is possible to suppress the deterioration of the tracking servo characteristics.

As described above, by setting φave = ± 45 °, focus error detection based on the astigmatism method and tracking error detection based on the one-beam push-pull method can be performed smoothly. That is, the optical system shown in FIG. 1 can lead to an appropriate focus error signal and tracking error signal when the following conditions are satisfied.
φave = α− (θ1max + θ1min) / 2 = ± 45 ° (4)

Therefore, by setting the deflection angle α and the track angles θ1max and θ1min so as to satisfy the above formula (4), it is possible to obtain an optical system that can derive an appropriate focus error signal and tracking error signal. Here, the track angles θ1max and θ1min can be adjusted by the size of the normal deviation Z of the HD objective lens 15. Accordingly, if the arrangement of the HD optical system is adjusted so that the deflection angle α and the normal deviation amount Z satisfy Expression (4), it is possible to derive appropriate focus error signals and tracking error signals.

A specific configuration example when setting the deflection angle α and the track angles θ1max and θ1min (normal deviation Z) in the optical system of FIG. 1 will be described below.

  In this embodiment, when the normal deviation Z of the HD objective lens 15 is fixed at Z = 5 mm in the optical system of FIG. 1, an appropriate value of the deflection angle α is obtained, and the HD optical system This is to set the arrangement. In this embodiment, the HD objective lens 15 is arranged on the right side of the DVD objective lens 26 as in the optical system shown in FIG.

  When the normal deviation Z of the HD objective lens 15 is 5 mm, referring to FIG. 13B, the maximum value θ1max and the minimum value θ1min of the track angle θ1 are the maximum value θ1max = 13 ° and the minimum value θ1min, respectively. = 5 °. By substituting these into the above equation (4), the deflection angle α becomes α = + 54 ° and −36 °.

  Therefore, in the present embodiment, in FIG. 2, the HD laser 11, the half mirror 12, and the HD sensor 16 are arranged so that the deflection angle α is + 54 ° or −36 °. Further, the sensor surface of the HD sensor 16 is adjusted so that an angle ψ between one dividing line of the four-divided sensor arranged in the HD sensor 16 and the disk plane direction is ψ = 45 °.

  When the deflection angle α is limited to a range of −45 ° ≦ α ≦ + 45 ° in order to reduce the size of the optical system, the deflection angle α is set to −36 °. In this case, the optical system is configured as shown in FIG.

  A verification example (simulation) of the focus error signal and tracking error signal generated when the deflection angle α is −36 ° will be described below.

  First, setting conditions (parameter setting values) in this verification example will be described.

  5A and 5B show the parameter value of the disk 100 and the parameter value of the HD sensor 16 in this verification.

  FIG. 6A-1 shows a tracking error signal (push-pull signal) generation circuit in this verification. In this configuration, when the tracking servo is turned off while rotating the disk, a push-pull signal shown in FIG. 6A-2 is generated.

  FIG. 6B-1 shows a circuit for generating a focus error signal (push-pull signal) in this verification. In this configuration, when the HD objective lens 15 is displaced in the focus direction, a focus error signal shown in FIG. 6B-2 is generated.

  7A and 7B show various parameters of the optical system for HD in this verification. In this verification, the various parameters in the figure are set to the values shown in FIG.

  FIG. 9 is a diagram showing an optical system for HD, which is a comparative example in this verification, and a simulation result thereof. In this comparative example, the swing angle α is set to + 35 °. In the comparative example, the normal deviation Z of the HD objective lens 15 is set to 5 mm as in this embodiment. Further, the verification result shown in the lower part shows that the PP dividing line shown in FIG. 6 among the dividing lines of the four-divided sensor approaches the disk plane direction in FIG. 3A with ψ = 45 ° as the reference position. In addition, the signal amplitude (FE amplitude) of the focus error signal and the signal amplitude (TE amplitude) of the tracking error signal (push-pull signal) when rotated in the separating direction are simulated.

  The vertical axis in the lower part of FIG. 9 is a standardized representation of the signal amplitudes of FIGS. 6 (a-2) and (b-2). The horizontal axis is the reference position (angle = 0 °) when the PP dividing line shown in FIG. 6 is at the position of ψ = 45 ° in FIG. 3A, and the PP dividing line is defined from this reference position. The rotation angle when the PP dividing line is rotated is represented by positive when rotating in the direction approaching the disk plane direction in the figure and negative when rotating in the direction approaching the disk plane direction. .

  9, the TE amplitude indicated by a broken line is the TE amplitude when the track angle θ1 of the HD objective lens 15 is the minimum value θ1min = 5 ° (when the HD objective lens 15 is at the outermost peripheral position). The amplitude is shown. The TE amplitude indicated by the solid line indicates the TE amplitude when the track angle θ1 of the HD objective lens 15 is the maximum value θ1max = 13 ° (when the HD objective lens 15 is at the innermost peripheral position). Yes.

  From this simulation result, when the PP dividing line of the HD sensor 16 is set at the position of ψ = 45 ° so that the focus error signal is the best, the TE amplitude when the track angle θ1 is the maximum value θ1max = 13 °. It can be seen that (see B in the figure) deteriorates. That is, it can be seen that the tracking error signal deteriorates when the HD objective lens 15 is in the vicinity of the innermost circumferential position.

  Further, when the PP dividing line of the HD sensor 16 is set at the position of ψ = 45 ° so that the focus error signal is the best, the track angle θ1 changes from the minimum value θ1min = 5 ° to the maximum value θ1max = 13 °. Accordingly, it can be seen that the TE amplitude varies in the range from A to B in FIG. That is, it can be seen that the amplitude of the tracking error signal varies greatly when the HD objective lens 15 moves from the outermost position to the innermost position. Thus, when the TE amplitude fluctuates greatly according to the position of the HD objective lens 15, stable tracking servo is hindered.

  FIG. 10 is a diagram showing a verification result in this example. In this embodiment, the swing angle α is set to −36 ° as described above. The normal deviation Z of the HD objective lens 15 is 5 mm. The vertical axis and the horizontal axis of the verification result shown in the lower stage are as described in the comparative example.

  From this simulation result, when the PP dividing line of the HD sensor 16 is set at the position of ψ = 45 ° so that the focus error signal is the best, the minimum value is obtained even when the track angle θ1 is at the maximum value θ1max = 13 °. It can be seen that even when the value is θ1 min, the substantially best TE amplitude can be obtained uniformly. That is, it can be seen that the best tracking error signal can be obtained regardless of the position of the HD objective lens 15 from the innermost position to the outermost position.

  In this case, even if the track angle θ1 changes in the range of the minimum value θ1min = 5 ° to the maximum value θ1max = 13 °, the TE amplitude does not change significantly as in the comparative example. According to the present embodiment, even when the HD objective lens 15 moves from the outermost position to the innermost position, a tracking error signal without amplitude fluctuation can be generated. Therefore, according to the present embodiment, stable tracking servo can be realized.

As described above, according to the present embodiment, by setting the PP dividing line of the HD sensor 16 at the position of ψ = 45 °, both the focus error signal and the tracking error signal are optimized without deterioration. be able to. Even if the track angle θ1 changes as the HD objective lens 15 moves, the amplitude of the tracking error signal can be held near the maximum amplitude with almost no change. Therefore, according to the present embodiment, stable focus servo and tracking servo can be realized.

  In this embodiment, when the deflection angle α is fixed at + 35 ° in the optical system of FIG. 1, an appropriate value of the normal deviation Z of the HD objective lens 15 is obtained, and the arrangement of the HD optical system is determined. It is to set. In this embodiment, unlike the optical system shown in FIG. 1, the HD objective lens 15 is disposed on the left side of the DVD objective lens 26.

When the deflection angle α of the HD objective lens 15 is + 35 °, the maximum value θ1max and the minimum value θ1min of the track angle θ1 must satisfy the following relationship from the equation (4).
(Θ1max + θ1min) / 2 = −10 °, + 80 ° (5)

Here, since (θ1max + θ1min) / 2 = + 80 ° cannot exist, the relationship between the maximum value θ1max and the minimum value θ1min is defined as follows.
(Θ1max + θ1min) / 2 = −10 ° (6)

Referring to FIG. 13, since θ = Sin ⁻¹ (Z / r) (r: distance from the disc center to the radial position of the HD objective lens), θ1max corresponding to rmin = 21.9 mm, rmax Θ1min corresponding to 58.0 mm is θ1min = −14.3 ° and θ1max = −5.5 °, respectively, when the normal deviation Z = 5.6 mm. At this time,
(Θ1max + θ1min) /2=−9.9° (7)
Thus, the relationship of the above formula (6) is substantially satisfied.

  Therefore, in the present embodiment, the HD objective lens 15 is arranged on the left side of the DVD objective lens 26 so that the normal deviation Z = 5.6 mm. In this case, the optical system is configured as shown in FIG.

  FIG. 12 shows a verification example (simulation) of the focus error signal and tracking error signal generated when the optical system is configured according to this embodiment. The vertical axis and the horizontal axis of the verification condition and the verification result shown in the lower part of FIG. 12 are the same as those in the verification example of the first embodiment.

  From the simulation results shown in the lower part of FIG. 12, when the PP dividing line of the HD sensor 16 is set at the position of ψ = 45 ° so that the focus error signal is the best, the track angle θ1 is the maximum value θ1max. It can be seen that even when the value is at the minimum value θ1 min, the substantially best TE amplitude can be obtained uniformly. That is, it can be seen that the best tracking error signal can be obtained regardless of the position of the HD objective lens 15 from the innermost position to the outermost position.

  In this case, even if the track angle θ1 changes in the range from the maximum value θ1max = −5.5 ° to the minimum value θ1min = 1−14.3 °, the TE amplitude is large as in the comparative example in the first embodiment. There is no change. According to the present embodiment, even when the HD objective lens 15 moves from the outermost position to the innermost position, a tracking error signal without amplitude fluctuation can be generated. Therefore, according to the present embodiment, stable tracking servo can be realized.

  Thus, according to the present embodiment, as in the first embodiment, by setting the PP dividing line of the HD sensor 16 at a position of ψ = 45 °, both the focus error signal and the tracking error signal can be obtained. It can be the best without deterioration. Even if the track angle θ1 changes as the HD objective lens 15 moves, the amplitude of the tracking error signal can be held near the maximum amplitude with almost no change. Therefore, according to the present embodiment, as in the first embodiment, stable focus servo and tracking servo can be realized.

  While the embodiments and examples according to the present invention have been described above, the present invention is not limited to the above-described embodiments and examples, and various other modifications are possible.

  For example, in the above-described embodiment, the case where the normal deviation occurs in the HD objective lens is shown, but the present invention is similarly applied to the case where the normal deviation occurs in the DVD objective lens. Can do. Furthermore, the present invention can also be applied to the case where normal deviation occurs in both the HD objective lens and the DVD objective lens.

  In the above embodiment, the HD half mirror 12 is used. However, instead of this, a flat polarizing mirror can be used. In this case, a polarizing film is formed on the surface on which the laser beam from the HD laser 11 is incident, out of the two surfaces of the polarizing mirror. A λ / 4 plate is disposed in the optical path from the polarizing mirror to the HD objective lens 15.

  In the above embodiment, the collimator lens is arranged in the optical system. However, when the laser light is incident on the objective lens in a finite system, the collimator lens can be omitted.

  In addition, in the above-described embodiment, an HDDVD and DVD compatible pickup and an optical disk device are illustrated, but the present invention can be similarly applied to compatible pickups and optical disks for other disks.

The embodiments of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims.

The figure which shows the optical system of the optical pick-up which concerns on embodiment The figure which shows the relationship between the objective lens and disk which concern on embodiment The figure which shows the state of the beam spot on the sensor for HD which concerns on embodiment 1 is a diagram illustrating an optical system of an optical pickup according to a first embodiment. The figure explaining the verification conditions in Example 1 The figure explaining the verification conditions in Example 1 The figure explaining the verification conditions in Example 1 The figure explaining the verification conditions in Example 1 The figure which shows the verification result of the comparative example in Example 1 The figure which shows the verification result in Example 1 FIG. 5 is a diagram illustrating an optical system of an optical pickup according to the second embodiment. The figure which shows the verification result in Example 2 The figure explaining the problem when the normal deviation arises in the objective lens The figure which shows the structural example of the optical system of an optical pick-up

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 HD laser 12 HD half mirror 14 HD collimator lens 15 HD objective lens 16 HD sensor 21 DVD laser 23 HD half mirror 25 HD collimator lens 26 HD objective lens 27 HD sensor 30 Actuator movable part 31 Objective lens actuator

Claims (5)

A semiconductor laser;
The laser beam emitted from the semiconductor laser is converged on the disk, and is arranged at a position separated by a distance Z in the plane direction of the disk with respect to the diameter L of the disk parallel to the moving direction of the optical pickup device. A first objective lens;
A photodetector having a sensor pattern that receives the laser light reflected from the disk and is divided into four regions by two perpendicular dividing lines;
Reflecting the laser light emitted from the semiconductor laser and guiding it to the first objective lens side, transmitting the laser light reflected from the disk and guiding it to the photodetector side, and A flat optical member that gives astigmatism to the reflected laser light;
The optical axis of the laser beam reflected by the optical member and guided to the first objective lens side is perpendicular to the diameter L of the disk and parallel to the plane direction of the disk. Is tilted by the swing angle α in the plane direction of the track angle θ1 and the distance Z is an angle formed by the diameter L and a straight line connecting the center of the disk and the access position of the first objective lens. The track angle θ1 when the first objective lens is at the innermost circumferential position of the disk is θ1max, and the track angle θ1 when the first objective lens is at the outermost circumferential position of the disk is θ1min. When
α− (θ1max + θ1min) / 2 = ± 45 °
And one of the two dividing lines of the sensor pattern is aligned with a straight line having an angle of approximately 45 ° with respect to the astigmatism introduction direction provided by the optical member. An optical pickup device in which a photodetector is disposed . In claim 1,
A second objective lens different from the first objective lens, and the second objective lens is disposed at a position along the diameter L of the disc;
An optical pickup device characterized by that. In claim 2,
An actuator for driving the objective lens, wherein the first objective lens and the second objective lens are mounted on the same actuator movable portion;
An optical pickup device characterized by that. In claim 2 or 3,
An optical system for guiding laser light to the second objective lens and receiving the laser light reflected by the disk is a first optical system having the semiconductor laser, a photodetector, and an optical member. Arranged as a different second optical system,
An optical pickup device characterized by that. In claim 4,
The first optical system and the second optical system guide laser beams of different wavelengths to the corresponding discs,
An optical pickup device characterized by that.

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