JP4342513B2 - Optical pickup device and layout setting method thereof - Google Patents

Description

  The present invention relates to an optical pickup device and a layout setting method for setting the layout of an optical system thereof, and particularly suitable for use in a compatible optical pickup device capable of emitting laser light of a plurality of wavelengths and a layout setting method thereof. .

  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. 10 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. 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. 11, 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. Configurations 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 four-divided sensor is arranged so as to be suitable for detection of astigmatism, the track direction on the sensor is further inclined with respect to the dividing line of the four-divided sensor.
WO97 / 42631

  As described above, the present invention smoothes both the focus error signal and the tracking error signal even when the track direction on the photodetector is not 45 ° with respect to the deformation direction of the beam spot due to astigmatism. It is an object of the present invention to provide an optical pickup device that can be generated.

  In the present invention, when the track direction on the photodetector is not 45 ° with respect to the deformation direction of the beam spot due to astigmatism, the dividing line of the 4-split sensor is It is closer to the direction of 45 ° with respect to the deformation direction of the spot. According to the method of the present invention, both a focus error signal and a tracking error signal (push-pull signal) can be generated smoothly.

  According to a first aspect of the present invention, a semiconductor laser, an objective lens that converges laser light from the semiconductor laser onto a disk, and two split lines that receive the laser light reflected from the disk and are orthogonal to each other. A photodetector having a sensor pattern divided into four regions, and the laser beam emitted from the semiconductor laser is reflected and guided to the objective lens side, and the laser beam reflected from the disk is transmitted. And a flat optical member guided to the optical detector side, wherein the objective lens is a flat surface of the disc with respect to a diameter L of the disc parallel to the moving direction of the optical pickup device. The track direction of the disk on the photodetector is caused by the astigmatism action of the optical member. If the angle is not 45 ° with respect to the beam spot deformation direction, one of the two dividing lines of the sensor pattern moves the optical pickup device between the innermost and outermost positions of the disk. Of the first direction, which is the center direction of the displacement range in the track direction on the photodetector, and the second direction at an angle of 45 ° with respect to the deformation direction of the beam spot, the first direction The sensor pattern is arranged so as to be closer to the direction of 2.

  According to a second aspect of the present invention, in the optical pickup device according to the first aspect, the sensor pattern is arranged so that one of the two dividing lines of the sensor pattern coincides with the second direction. It is characterized by that.

  The third aspect of the present invention is divided into four regions by two orthogonal dividing lines as a configuration for generating a focus error signal based on the astigmatism method and a tracking error signal based on the push-pull method. Layout setting method of an optical pickup device comprising a photodetector having a sensor pattern, wherein the recording medium is a disk having spiral or concentric tracks, and an objective lens mounted on the optical pickup device Is arranged at a position separated by a distance Z in the plane direction of the disc with respect to the diameter L of the disc parallel to the moving direction of the optical pickup device, and the track direction of the recording medium projected onto the photodetector If the angle does not become 45 ° with respect to the deformation direction of the beam spot due to the action of astigmatism, two of the sensor patterns One of the dividing lines is a first direction that is the center direction of the displacement range in the track direction on the photodetector when the optical pickup device moves between the innermost and outermost positions of the disk. The arrangement of the sensor pattern is set so as to be closer to the direction of the second direction of the direction and the second direction having an angle of 45 ° with respect to the deformation direction of the beam spot. To do.

  According to a fourth aspect of the present invention, in the layout setting method according to the fourth aspect, the arrangement of the sensor pattern is set so that one of the two dividing lines of the sensor pattern matches the second direction. It is characterized by that.

  When the direction of the track projected onto the photodetector is tilted with respect to the dividing line of the quadrant sensor, the signal amplitude of the tracking error signal (push-pull signal) is degraded. On the other hand, when the direction that gives an angle of 45 ° with respect to the deformation direction of the beam spot caused by the astigmatism action is inclined with respect to the dividing line of the four-divided sensor, the signal amplitude of the focus error signal is degraded. When the present inventor examined which of the two signal amplitudes is more prominent, it was confirmed that the deterioration of the focus error signal was more prominent.

  Therefore, as in the present invention, one of the two dividing lines of the sensor pattern is arranged in the first direction that coincides with the track direction and in the second direction that forms an angle of 45 ° with respect to the deformation direction of the beam spot. Of these, the closer to the second direction, the degradation of the focus error signal and the tracking error signal can be effectively suppressed, and both error signals can be generated smoothly.

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 parallel to the disk surface due to astigmatism by the HD half mirror 12. And 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. .

  When the angle φ changes in the range of φmin ≦ φ ≦ φmax, if the dividing line of the four-divided sensor is made to coincide with φmin, the track direction is separated from this dividing line when the HD objective lens 15 is at the outermost peripheral position of the disk. It will be greatly inclined. On the other hand, when the dividing line of the four-divided sensor coincides with φmax, the track direction is greatly inclined from the dividing line when the HD objective lens 15 is at the innermost circumferential position of the disk.

In this case, an intermediate angle φave between φmin and φmax, that is, φave = α− (θ1max + θ1min) / 2 (3)
Can be matched with one dividing line of the four-divided sensor, the inclination of the track direction with respect to the dividing line can be suppressed.

  As described above, in order to optimize the tracking error signal, it is necessary to adjust one dividing line of the four-divided sensor along the direction of φave.

  However, as described above, in order to optimize the focus error signal, it is necessary to adjust one dividing line of the four-divided sensor to a position of ψ = 45 ° as shown in FIG. In this case, if the deflection angle α is 45 ° and there is no normal deviation of the HD objective lens 15 (θ1max = θ1min = 0), φave according to the above equation (3) can be made equal to ψ = 45 °. Therefore, one dividing line of the four-divided sensor can be adjusted to a position where both the focus error signal and the tracking error signal are optimized.

  However, when the deflection angle α is not 45 ° as in the present embodiment, or the normal deviation occurs in the HD objective lens 15, φave according to the equation (3) is set to ψ = 45 °. Cannot match. Therefore, one dividing line of the four-divided sensor cannot be adjusted to a position where both the focus error signal and the tracking error signal are optimized.

  In this case, the dividing line of the four-divided sensor can be normally adjusted in a range from the position of ψ = 45 ° to the position of φave. At this time, as the dividing line approaches the position of ψ = 45 °, the focus error signal is optimized, but the tracking error signal is deteriorated. On the other hand, as the dividing line approaches the position of φave, the tracking error signal is optimized, but the focus error signal is deteriorated.

  The inventor of this application appropriately sets the dividing line of the four-divided sensor in the range from the position of ψ = 45 ° to the position of φave when ψ = 45 ° and φave do not match. We examined whether. At this time, the deterioration of the focus error signal and the tracking error signal when the dividing line of the four-divided sensor deviates from the position of ψ = 45 ° or φave was considered as follows.

  As shown in FIG. 3A, when astigmatism is introduced into the laser beam, the beam spot on the photodetector is deformed in two directions orthogonal to each other. Therefore, when the quadrant sensor is rotated about a straight line passing through the center of the beam spot, the amplitude (Peak-to-Peak) of the focus error signal (astigmatism method) changes at a rotation period of 90 °.

  On the other hand, when the tracking error signal is generated according to the push-pull method, the tracking error signal amplitude (Peak-to-Peak) is obtained by rotating the quadrant sensor around the straight line passing through the center of the beam spot as described above. Changes at a rotation period of 180 °. That is, the amplitude period of the tracking error signal is twice the amplitude period of the focus error signal.

  Therefore, the degree of signal degradation when the dividing line of the four-divided sensor deviates from the optimal position is several steps greater in the focus error signal than in the tracking error signal. Therefore, when ψ = 45 ° and φave do not match, the dividing line of the four-divided sensor is more deteriorated in the focus error signal and tracking error signal when it is closer to the position of ψ = 45 ° than the position of φave. , Can be more effectively suppressed.

In the following, a specific adjustment example of the four-divided sensor in the case where the deflection angle α and the track angles θ1max and θ1min (normal deviation Z) are set to predetermined values in the optical system of FIG.

  In this embodiment, when the normal deviation Z of the HD objective lens 15 is set to Z = 5 mm and the deflection angle α is set to α = + 35 ° in the optical system of FIG. The arrangement of the divided sensors is adjusted to an appropriate value.

When the normal deviation Z of the HD objective lens 15 is 5 mm, referring to FIG. 3B, 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 values and the deflection angle α = + 35 ° into the above formulas (1) and (2), φmax and φmin shown in FIGS. 3B and 3C are obtained as follows.
φmax = 35 °-5 ° = 30 °
φmin = 35 ° -13 ° = 22 °

Further, from these φmax and φmin and the above equation (3), φave is obtained as follows.
φave = (30 ° + 22 °) / 2 = 26 °

  Therefore, from the above consideration, the dividing line of the four-divided sensor is set in the range of ψ = 45 ° and φave = 26 °, and closer to the position of ψ = 45 ° than the position of φave = 26 °. Just do it. More specifically, since the intermediate angle between φave = 26 ° and ψ = 45 ° is about 35 °, for example, the photodetector for HD so that the dividing line of the four-divided sensor is positioned at about 40 °. Sixteen sensor patterns may be arranged.

  In the above, the arrangement of the dividing lines of the four-divided sensor is adjusted on the basis of ψ = 45 ° and φave = 26 °. However, of φmax and φmin, there is a deviation from ψ = 45 °. You may make it adjust arrangement | positioning of the dividing line of a 4-part dividing sensor based on the larger one and (psi) = 45 degrees.

  That is, in the above example, of φmax = 30 ° and φmin = 22 °, the difference between φmin = 22 ° and ψ = 45 °, which is larger than ψ = 45 °, is divided into four-divided sensors. Adjust the line arrangement. In this way, compared with the above case, the deterioration of the tracking error signal is somewhat suppressed, while the deterioration of the focus error signal is somewhat increased.

  In this case, the dividing line of the four-divided sensor may be set in a range of ψ = 45 ° and φmin = 22 °, and closer to the position of ψ = 45 ° than the position of φmin = 22 °. More specifically, since the intermediate angle between φmin = 22 ° and ψ = 45 ° is about 33 °, for example, the position of the dividing line of the quadrant sensor is slightly smaller than 40 ° (for example, about 38 °). ) So that the sensor pattern of the photodetector 16 for HD may be arranged.

<Verification example>
Next, a verification example (simulation) of a focus error signal and a tracking error signal generated when the normal deviation Z of the HD objective lens 15 is Z = 5 mm and the deflection angle α is α = + 35 ° will be described. Show.

  Setting conditions (parameter setting values) in this verification example are as follows.

  4A and 4B show the parameter value of the disk 100 and the parameter value of the HD sensor 16 in this verification.

  FIG. 5A-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. 5A-2 is generated.

  FIG. 5B-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. 5B-2 is generated.

  6A and 6B 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. 8 shows the verification result (simulation).

  The verification result shown in the figure shows that the PP dividing line shown in FIG. 5 among the dividing lines of the four-divided sensor is shown in FIG. 3A with ψ = 45 ° as the reference position (angle = 0 °). This is a simulation of 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 direction toward and away from the disk plane direction.

  The vertical axis in the figure represents the standardized signal amplitudes of FIGS. 5 (a-2) and (b-2). The horizontal axis is the reference position (angle = 0 °) when the PP dividing line shown in FIG. 5 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. .

  In the drawing, 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). 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.

  As explained in the above consideration, the signal amplitude characteristic of the focus error signal is considerably sharper than the amplitude characteristic of the tracking error signal. From the figure, it can be seen that the signal amplitude of the focus error signal greatly deteriorates when the PP dividing line of the four-divided sensor deviates from the position of ψ = 45 °. On the other hand, the signal amplitude of the tracking error signal does not deteriorate so much even if the PP dividing line of the four-divided sensor deviates from the position of φave = 26 ° (the position of 19 ° in the lower part of FIG. 8). Therefore, it can be seen that the signal amplitude of the tracking error signal does not deteriorate so much even if the PP dividing line of the four-divided sensor is brought closer to the position of ψ = 45 °.

  When the PP dividing line of the four-divided sensor is aligned with the position of φ ave, the signal amplitude of the focus error signal deteriorates to about 82% of the maximum value (see “B” in the figure). Further, when the PP dividing line of the four-divided sensor is aligned with the position of φmin, the signal amplitude of the focus error signal is degraded to about 70% of the maximum value (see “C” in the figure). On the other hand, even if the PP dividing line of the four-divided sensor is aligned with the position of ψ = 45 °, the signal amplitude of the tracking error signal is maintained at about 95% of the maximum value (see “A” in the figure). . Accordingly, even when the PP dividing line of the four-divided sensor is aligned with the position of ψ = 45 °, a tracking error signal of an appropriate level can be generated. At this time, since the focus error signal is at the optimum level, the tracking error signal is set to the appropriate level while maintaining the focus error signal at the optimum level by aligning the PP dividing line of the four-divided sensor with the position of ψ = 45 °. It can be.

  As described above, according to the present embodiment, the PP dividing line of the HD sensor 16 is set to be closer to the position of ψ = 45 ° than the intermediate position between the position of ψ = 45 ° and the position of φave. As a result, both the focus error signal and the tracking error signal can be optimized without deterioration. At this time, even if the track angle θ1 changes as the HD objective lens 15 moves, the amplitude of the tracking error signal can be maintained at an appropriate level. Therefore, according to the present embodiment, stable focus servo and tracking servo can be realized.

Further, as verified in the present embodiment, even if the PP dividing line of the HD sensor 16 is set at the position of ψ = 45 °, a tracking error signal with little deterioration can be obtained. Accordingly, the PP dividing line of the HD sensor 16 may be set at a position of ψ = 45 °. In this way, the focus error signal can be maintained at the optimum level while suppressing the deterioration of the tracking error signal.

  In the first embodiment, the case where the deflection angle α is set in the plus direction (counterclockwise) as shown in FIG. 9A is shown, but the deflection angle α is in the minus direction as shown in FIG. 9B. (Clockwise) is set, φmax, φmin, and φave are obtained by substituting negative values for the deflection angle α in the above formulas (1), (2), and (3), and ψ = − The position of the dividing line of the four-divided sensor may be set based on 45 °.

For example, in FIG. 9B, when the normal deviation Z is Z = 5 mm (θ1max = 13 °, θ1min = 5 °) and the deflection angle α is α = −20 °, φmax, φmin and φave are It is determined as follows.
φmax = −20 ° − 5 ° = −25 °
φmin = −20 ° −13 ° = −33 °
φave = −20 ° − (13 ° + 5 °) / 2 = −29 °

  In this case, the dividing line of the four-divided sensor is set in the range of ψ = −45 ° and φave = −29 °, and closer to the position of ψ = −45 ° than the position of φave = −29 °. Just do it. More specifically, since the intermediate angle between φave = −29 ° and ψ = −45 ° is about −37 °, for example, the dividing line of the four-divided sensor is −40 ° or an angle slightly smaller than this. What is necessary is just to arrange | position the sensor pattern of the photodetector 16 for HD so that it may become a position (for example, about -42 degrees).

  Further, of φmax = −25 ° and φmin = −33 °, the difference between φmax = −25 ° and ψ = −45 °, which is larger than ψ = −45 °, is divided into four-divided sensors. The arrangement of the lines may be adjusted. In this way, as compared with the case where φave = −29 ° and ψ = −45 ° as described above, the deterioration of the tracking error signal is somewhat suppressed, while the deterioration of the focus error signal is somewhat increased.

  In this case, the dividing line of the four-divided sensor is set in the range of ψ = −45 ° and φmax = −25 °, and closer to the position of ψ = −45 ° than the position of φmax = −25 °. Just do it. More specifically, since the intermediate angle between φmax = −25 ° and ψ = −45 ° is about −35 °, for example, the division line of the four-divided sensor is positioned at a position of about −40 °. The sensor pattern of the optical detector 16 may be arranged.

In this case as well, similar to the verification in the first embodiment, even if the PP dividing line of the HD sensor 16 is set at a position of ψ = −45 °, a tracking error signal that does not deteriorate so much can be obtained. It is assumed. Therefore, the PP dividing line of the HD sensor 16 may be set at a position of ψ = −45 °. In this way, the focus error signal can be maintained at the optimum level while suppressing the deterioration of the tracking error signal. .

  Further, as shown in FIG. 9C, when the HD objective lens 15 is arranged on the left side of the DVD objective lens 26 and the normal deviation occurs in the minus direction, the above formula (1) ( 2) Substituting a negative value into the normal deviation Z in (3) to obtain φmax, φmin, and φave, and setting the position of the dividing line of the four-divided sensor based on these and ψ = 45 ° .

For example, in FIG. 9B, when the normal deviation Z is Z = −5 mm (θ1max = −5 °, θ1min = −13 °) and the deflection angle α is α = 20 °, φmax, φmin and φave are It is obtained as follows.
φmax = 20 ° − (− 13) ° = 33 °
φmin = 20 ° − (− 5) ° = 25 °
φave = 20 ° − (− 13 ° −5 °) / 2 = 29 °

  In this case, the dividing line of the four-divided sensor may be set in the range of ψ = 45 ° and φave = 29 °, and at a position closer to the position of ψ = 45 ° than the position of φave = 29 °. More specifically, since the intermediate angle between φave = 29 ° and ψ = 45 ° is about 37 °, for example, the dividing line of the four-divided sensor is 40 ° or a position slightly larger than this (for example, What is necessary is just to arrange | position the sensor pattern of the photodetector 16 for HD so that it may become about 42 degrees.

  Also, among φmax = 33 ° and φmin = 25 °, the arrangement of the dividing lines of the four-divided sensor is adjusted based on φmin = 25 ° and ψ = 45 °, which are more shifted from ψ = 45 °. You may make it do. In this way, as compared with the case where φave = 29 ° and ψ = 45 ° as described above, the deterioration of the tracking error signal is somewhat suppressed, while the deterioration of the focus error signal is somewhat increased.

  In this case, the dividing line of the four-divided sensor may be set in the range of ψ = 45 ° and φmin = 25 °, and at a position closer to the position of ψ = 45 ° than the position of φmin = 25 °. More specifically, since the intermediate angle between φmin = 25 ° and ψ = 45 ° is about 35 °, for example, the photodetector for HD so that the dividing line of the four-divided sensor is positioned at about 40 °. Sixteen sensor patterns may be arranged.

  In this case as well, similar to the verification in the first embodiment, even if the PP dividing line of the HD sensor 16 is set at a position of ψ = 45 °, a tracking error signal with little deterioration can be obtained. is assumed. Accordingly, the PP dividing line of the HD sensor 16 may be set at a position of ψ = 45 °. In this way, the focus error signal can be maintained at the optimum level while suppressing the deterioration of the tracking error signal.

  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.

  Conversely, the present invention can also be applied to the case where no normal deviation occurs in the objective lens and only the deflection angle α is an angle different from ± 45. In this case, θ1max = θ1min = 0 is substituted into the above equations (1), (2), and (3). At this time, φave = φmin = φmax = α. Therefore, the position of the dividing line of the four-divided sensor is adjusted according to the same method as described above based on ψ = 45 ° (or −45 °) and φave = φmin = φmax = α.

  Further, although the shake angle α is α = ± 45, the present invention can be applied in the same manner as in the first, second, and third embodiments even when the normal deviation occurs in the objective lens.

  Further, in the above embodiment, the HD half mirror 12 is used, but 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 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 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 in Example 1 FIG. 5 is a diagram illustrating an optical system of an optical pickup according to Examples 2 and 3. 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

11 HD Laser 12 HD Half Mirror 15 HD Objective Lens 16 HD Sensor

Claims (4)

A semiconductor laser, an objective lens for converging laser light from the semiconductor laser on the disk, and a sensor that receives the laser light reflected from the disk and is divided into four regions by two orthogonal dividing lines A photodetector having a pattern, and the laser beam emitted from the semiconductor laser is reflected and guided to the objective lens side, and the laser beam reflected from the disk is transmitted to the photodetector side In a pickup device including a flat plate-shaped optical member for guiding ,
The objective lens is disposed at a position separated by a distance Z in the plane direction of the disc with respect to the diameter L of the disc parallel to the moving direction of the optical pickup device,
If the track direction of the disk on the photodetector does not form an angle of 45 ° with respect to the deformation direction of the beam spot caused by the astigmatism of the optical member, one of the two dividing lines of the sensor pattern A first direction which is a center direction of a displacement range in the track direction on the photodetector when the optical pickup device moves between the innermost peripheral position and the outermost peripheral position of the disk, and the beam The sensor pattern is arranged so as to be closer to the second direction out of the second direction having an angle of 45 ° with respect to the deformation direction of the spot.
An optical pickup device characterized by that. In claim 1,
The sensor pattern is arranged so that one of the two dividing lines of the sensor pattern coincides with the second direction.
An optical pickup device characterized by that. As a configuration for generating a focus error signal based on the astigmatism method and a tracking error signal based on the push-pull method, a photodetector having a sensor pattern divided into four regions by two orthogonal dividing lines A layout setting method for an optical pickup device comprising:
The recording medium is a disk having a spiral or concentric track, and the objective lens mounted on the optical pickup device has a diameter L of the disk parallel to the moving direction of the optical pickup device. Arranged at a position separated by a distance Z in the plane direction of
When the track direction of the recording medium projected onto the photodetector does not form an angle of 45 ° with respect to the deformation direction of the beam spot caused by astigmatism, one of the two dividing lines of the sensor pattern is A first direction which is a center direction of a displacement range in the track direction on the photodetector when the optical pickup device moves between the innermost and outermost positions of the disk; and the beam spot The arrangement of the sensor pattern is set so as to be closer to the second direction out of the second direction having an angle of 45 ° with respect to the deformation direction of
A layout setting method for an optical pickup device. In claim 3 ,
Setting the arrangement of the sensor pattern so that one of the two dividing lines of the sensor pattern matches the second direction;
A layout setting method for an optical pickup device.

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