JP2008102995A - Optical pickup device and optical disk device - Google Patents

Abstract

【Task】
SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup and an optical disc apparatus capable of simultaneously suppressing displacement of an objective lens and non-recording and a tracking error signal offset occurring at a boundary portion of a recording area.
[Solution]
The light beam reflected from the disk is divided and detected. The detector has a light receiving portion having regions 1, 2, 3, and 4, and regions 1 and 3 and regions 2 and 4 are axisymmetric with respect to the central axis of the light receiving portion. Regions 1 and 2 are shaped so that the width in the dividing line direction becomes narrower as they move away from the central axis of the light receiving portion in a substantially vertical direction. A tracking error signal is detected by four signals obtained from such a detector.
[Selection] Figure 3

Description

  The present invention relates to an optical pickup device and an optical disc device.

As background art in this technical field, there is, for example, Japanese Patent Laid-Open No. 9-223321. In this publication, there is a problem of "an optical information reproducing apparatus capable of reducing the number of optical components and simplifying the apparatus, and an optical information reproducing apparatus capable of adjusting a tracking error signal according to the characteristics of an optical desk". The optical information reproducing apparatus corresponds to a track with an optical pickup having an objective lens for irradiating light on the optical disk and a light spot of light emitted from the optical disk. A first dividing unit that divides the light spot into an end region and a middle region with respect to the center of the light spot, and the light spots in the end region and the middle region further correspond to the track of the optical disc. And a plurality of light receiving cells that receive the light divided by the first dividing means and the second dividing means. A light spot deviation signal detecting means for calculating a relative displacement of a light spot on the light receiving element by calculating the outputs of the light receiving cells that receive the light of the end region divided by the second dividing means And a tracking error generating means for calculating the relative displacement between the track and the objective lens by calculating the outputs of the light receiving cells for receiving the light in the middle area divided by the second dividing means, and detecting the light spot deviation signal Offset correction means for correcting the offset of the tracking error signal by calculation of the output signal of the means and the output signal of the tracking error generation means, an objective lens driving device for driving the objective lens in a direction across the track of the optical disk, and objective lens drive The tracking control means for controlling the drive of the device and the input of the tracking control means at the time of access to the light spot shift The output of No. detection means, at the time of reproduction information of the optical disc to enter the tracking control means, and a switching means for switching the output of the tracking error generating means via the offset correcting means "to be described.

Japanese Patent Laid-Open No. 9-223321

  In general, an optical pickup device irradiates a spot correctly on a predetermined recording track in an optical disc, so that the objective lens is displaced in the focus direction by detecting the focus error signal, and the adjustment is performed in the focus direction. Is detected, and the objective lens is displaced in the radial direction of the disk-shaped recording medium to perform tracking adjustment. The position of the objective lens is controlled by these signals.

  Among these, the push-pull method is known as a tracking error signal detection method, but there is a problem that a large direct current fluctuation (hereinafter referred to as a DC offset) is likely to occur due to the displacement of the objective lens in the tracking direction. Therefore, a differential push-pull method that can reduce the DC offset is widely used.

  The differential push-pull method (DPP: Differential Push Pull method) divides a light beam into a main light beam and a sub light beam by a diffraction grating, and reduces the DC offset by using the main light beam spot and the sub light beam spot in the radial direction. Yes.

  However, since a plurality of spots are formed on the optical disc, the light utilization efficiency of the main light beam is reduced. This main luminous flux not only generates a focus error signal and a tracking error signal, but also has a role of generating a recording mark on the recording optical disk. When recording on a recording optical disk, the recording speed increases as the amount of the main light beam on the disk increases. Therefore, using a diffraction grating in the forward optical system is disadvantageous from the viewpoint of recording speed.

Therefore, in Patent Document 1, a single spot is formed on the disk, and the reflected light is divided into a plurality of regions, thereby detecting a stable tracking error signal without a DC offset even when the objective lens is displaced in the tracking direction. . With such a configuration, there is an advantage that the light use efficiency is not lowered and the recording speed can be increased. (Hereafter referred to as 1 beam system)
However, if the detectors are divided into regions as in Patent Document 1, a problem occurs in a recordable optical disc such as BD-RE and BD-R. In the case of a recordable optical disc, there are an unrecorded area (hereinafter referred to as an unrecorded area) and an already recorded area (hereinafter referred to as a recorded area). In the area division as in Patent Document 1, the offset of the tracking error signal generated at the boundary between the unrecorded area and the recorded area on the disk cannot be reduced, which is a problem.

  As described above, the present invention improves the offset of the tracking error signal generated at the boundary between the unrecorded area and the recorded area, which is a problem in the one-beam system. Specifically, an optical pickup apparatus or an optical information reproducing apparatus using a new tracking error signal detecting means capable of detecting a stable tracking error signal even on an optical disk having a boundary between an unrecorded area and a recorded area. An optical information recording / reproducing apparatus is provided.

  An object of the present invention is to provide an optical pickup device and an optical information recording / reproducing device capable of detecting a stable tracking error signal.

  The above object can be achieved by the configuration described in the claims as an example.

  According to the present invention, it is possible to provide an optical pickup device and an optical information recording / reproducing device capable of detecting a stable tracking error signal.

  FIG. 1 is a schematic configuration diagram showing an example of an optical pickup device according to a first embodiment of the present invention.

  The optical pickup device 1 is configured to be driven in the radial direction of the optical disc 100 by the drive mechanism 7 as shown in FIG. An objective lens 2 is mounted on the actuator 5 on the optical pickup device, and light is irradiated from the objective lens 2 onto the optical disk. The light emitted from the objective lens 2 forms a spot on the disk and reflects the disk. By detecting the reflected light, a focus error signal and a tracking error signal are generated.

  In the optical pickup device as described above, FIG. 2 shows an optical system. Here, BD will be described, but HD DVD or other recording methods may be used.

  From the semiconductor laser 50, a light beam having a wavelength of about 405 nm is emitted as divergent light. The light beam emitted from the semiconductor laser 50 is converted into a substantially parallel light beam by the collimator lens 51. The light beam that has passed through the collimating lens 51 reflects the beam splitter 52. Part of the light beam passes through the beam splitter 52 and enters the front monitor 53. In general, when recording information on a recording type optical disc such as a BD-RE or BD-R, it is necessary to control the light amount of the semiconductor laser with high accuracy in order to irradiate the recording surface of the optical disc with a predetermined light amount. is there. Therefore, the front monitor 53 detects a change in the light amount of the semiconductor laser 50 when recording a signal on the recordable optical disk, and feeds it back to a drive circuit (not shown) of the semiconductor laser 50. As a result, the amount of light on the optical disk can be monitored.

  The light beam reflected by the beam splitter 52 enters the beam expander 54. The beam expander 54 is used to compensate for spherical aberration due to the thickness error of the cover layer of the optical disc 100 by changing the divergence / convergence state of the light beam. The light beam emitted from the beam expander 54 is reflected by the rising mirror 55, transmitted through the quarter-wave plate 56, and then condensed on the optical disk 100 by the objective lens 2 mounted on the actuator 5.

  The light beam reflected by the optical disk 100 passes through the objective lens 2, the quarter-wave plate 56, the rising mirror 55, the beam expander 54, and the beam splitter 52. The light beam that has passed through the beam splitter 52 is branched into a light beam that passes through the beam splitter 57 and a light beam that reflects.

  A focus error signal is detected from the light beam reflected by the beam splitter 57 by the knife edge method. Although the knife edge method is used here as the focus detection method, the present invention is not limited to this. Further, since the knife edge method is known, the description thereof is omitted. The light beam that has passed through the beam splitter 56 enters the detector 10. The detector 10 detects a signal on the disk and a tracking error signal.

  FIG. 3 shows a light receiving portion pattern of the present invention. The light receiving unit 10 has four regions, region I (region 1), region J (region 2), region G (region 3), and region H (region 4). Region I (region 1) and region G (region) 3), the region J (region 2) and the region H (region 4) are symmetrical with respect to the center line of the light receiving unit. Further, the region I (region 1) and the region J (region 2) are characterized in that the width in the direction of the central axis 500 becomes narrower as they are separated from the central axis (or the central line) 500 in a substantially vertical direction.

  Here, the principle of detecting a tracking error signal of the one beam system will be described with reference to FIG. On the detector surface, an area where the 0th-order diffracted light diffracted by the disk and ± 1st-order diffracted light interfere is generated. Since the state of interference in this region differs depending on the spot position on the track, the spot can be arranged at a desired track position using this. In practice, a push-pull signal is generated by calculating the difference between the signal obtained in the interference region Z1 of the 0th-order diffracted light and the + 1st-order diffracted light and the signal obtained in the interference region Z2 of the 0th-order diffracted light and the −1st-order diffracted light. . Further, the area other than the interference area hardly changes depending on the spot position on the track. The 1-beam method uses this characteristic.

This will be described in detail below. The light beam is displaced in the direction of the arrow in FIG. 3 with the displacement of the objective lens on the light receiving unit. At the same time, the intensity distribution center is displaced in the same direction. Due to these two effects, a DC offset occurs in the signal (I−J). In addition, a DC offset also occurs in the (GH) signal. FIG. 4 shows the offset amounts of the (I-J) signal and the (GH) signal with respect to the objective lens displacement amount. From this figure, it can be seen that the offset amount of the (I-J) signal and the (GH) signal has a substantially linear DC offset with respect to the displacement of the objective lens. Therefore, it can be seen that a tracking error signal with a suppressed DC offset can be detected by performing the following calculation.

ここでｋは、（Ｉ−Ｊ）の信号にＤＣオフセットと（Ｇ−Ｈ）信号のＤＣオフセットを補正する係数である。このようにして１ビーム方式はオフセットを抑制したトラッキング誤差信号を検出可能となる。

Here, k is a coefficient for correcting the DC offset of the (I−J) signal and the DC offset of the (GH) signal. In this way, the one-beam method can detect a tracking error signal with suppressed offset.

  Next, the offset of the tracking error signal generated at the boundary between the unrecorded area and the recorded area on the disc will be described. FIG. 5 is a diagram schematically showing a tracking error signal waveform of the one-beam method at the boundary between the unrecorded area and the recorded area. FIG. 5 (1) shows a case where the offset cannot be suppressed, and FIG. 5 (2) shows a case where the offset occurs on the reverse side due to overcorrection. FIG. 5 (3) shows a tracking error signal in which the offset is suppressed.

  In the tracking error signal waveforms as shown in FIGS. 5A and 5B, there is a high possibility that the tracking error signal does not cross the origin position due to variations or the like. If the tracking error signal does not cross, there will be a problem in servo control. (For tracking control, servo control is performed at this origin position.) For this reason, it is clear that a waveform as shown in FIG.

Here, the bottom ratio and the top ratio are considered as an index of the tracking error signal offset. The ratio of the bottom is (ac) / (c + d) shown in FIG. This is the difference between the bottom value of the tracking error signal in the recording area and the bottom value of the tracking error signal at the boundary between the unrecorded area and the recording area, and divided by the tracking error signal amplitude of the recording area. It shows how far the bottom is when compared to the tracking error signal amplitude.
On the other hand, the ratio of the top is (b−d) / (c + d). This is the difference between the tracking error signal top value in the recording area and the tracking error signal top value at the boundary between the unrecorded area and the recording area, and divided by the tracking error signal amplitude in the recording area. It shows how much the top is on the upper side when compared with the tracking error signal amplitude of the region.

If these two indexes are positive values, the servo error can be stabilized because the tracking error signal amplitude gradually changes as the spot moves from the unrecorded area to the recorded area as shown in FIG. 5 (3). Recognize. However, if the two indexes have a relationship between a positive value and a negative value, there is a problem because the offset cannot be suppressed.
Further, the offset of the tracking error signal also occurs when the objective lens is displaced in the tracking direction. For this reason, the offset due to the unrecorded area, the boundary of the recorded area and the displacement of the objective lens needs to be suppressed simultaneously.

Hereinafter, based on such an index, the offset of the tracking error signal generated at the boundary between the unrecorded area and the recorded area when the objective lens is displaced is evaluated. Here, the calculation conditions in the simulation are as follows.

Wavelength: 405nm
Objective lens NA: 0.85
Track pitch: 0.32 μm
Objective lens focal length: 1.41 mm

FIG. 6A shows the ratio of the top when the objective lens is displaced in the tracking direction using the light receiving unit of the present invention and Patent Document 1, and FIG. 6B shows the ratio of the bottom. As a condition of the light receiving unit of the present invention, the ratio t1 of the interval between the region I (region 1) and the region J (region 2) with respect to the diameter of the light beam incident on the detector is t1 = d2 / d1 = 0.19. The ratio t2 of the maximum width in the central axis direction of the region I (region 1) and the region J (region 2) with respect to the incident beam diameter is t2 = d3 / d1 = 0.5, the region I (region 1) and the region J ( The inclination angle θ of the outer shape of the region with respect to the direction perpendicular to the central axis of region 2) was set to θ = 10 deg.

  From FIG. 6, Patent Document 1 shows a negative value for most objective lens displacement amounts at the top ratio. The bottom ratio is a positive value, indicating that an offset has occurred.

  On the other hand, the ratio of the top and the ratio of the bottom of the present invention is positive in almost the range of displacement of the objective lens, and it can be seen that the offset of the boundary between the unrecorded area and the recorded area can be suppressed.

  Next, the effect of tilting the dividing lines of the region I and the region J will be described. FIGS. 7A and 7B show the results of simulation for the case of not tilting and the case of tilting. FIG. 7A shows the ratio of the top and FIG. 7B shows the ratio of the bottom. The conditions of the light receiving section are t1 = 0.19, t2 = 0.5, θ = 10 deg and t1 = 0.19, t2 = 0.5, and θ = 0 deg.

  The ratio of the top is a positive value in most areas where the objective lens is displaced, and the ratio of the bottom is greatly improved in the area where the displacement of the objective lens is negative. As described above, when the dividing line is inclined, the offset of the boundary between the unrecorded area and the recorded area can be suppressed. In particular, θ is 0 ° <θ <15 °, and t1 and t2 are DC under the conditions of 0 <t1 <0.35 and 0 <t2 <0.70 with respect to the beam diameter incident on the light receiving portion of the detector 10. A great improvement effect can be obtained in offset and offset suppression at the boundary between the unrecorded area and the recorded area.

  Considering simply, if the width in the direction of the central axis 500 becomes narrower as the regions I and J are separated from the central axis 500 in a substantially vertical direction as shown in FIG. 3, the objective lens is displaced, whereas the objective lens is displaced. It seems that the tracking error signal amplitude is extremely reduced because the area of the interference region (interference region Z1 or interference region Z2) detected by the light receiving portion region (region I or region J) in the direction to be detected decreases. In practice, however, the intensity distribution of the luminous flux is displaced by twice the amount of displacement of the objective lens in the objective lens displacement direction at the same time as the objective lens is displaced. For this reason, on the light receiving part region (region I or region J) in the direction in which the objective lens is displaced, the area is reduced but the strength is increased. In addition, on the light receiving region (region J or region I) opposite to the direction in which the objective lens is displaced, the intensity decreases but the area increases. Therefore, the tracking error signal amplitude is difficult to decrease and the DC offset correction is also easy. Further, since the offset at the boundary between the unrecorded area and the recorded area is prominently generated in the vicinity of the interference area (interference area Z1 or interference area Z2), the outside of the interference area on the DC offset detection side with respect to the displacement of the objective lens. Making the light incident on the light receiving portion is effective in suppressing the offset between the unrecorded area and the recorded area.

In FIG. 3, the dividing line inside the detector is shown as a straight line that is substantially parallel to the track and a straight line having a different angle from the straight line. However, as shown in FIG. There may be no problem even if it is a straight line as shown in FIG.
Although the light receiving portion pattern is shown here, the diffraction grating 101 having the same pattern as the light receiving portion pattern is arranged as in the optical system of FIG. 9, and detection is performed by changing the diffraction direction and angle in each region. It goes without saying that the same effect can be obtained even if signals are detected by a plurality of light receiving sections on the vessel.

FIG. 10 shows a light receiving portion pattern different from that of the first embodiment according to the second embodiment of the present invention. A difference from the first embodiment is that a central region Y (region 5) is provided. In the central region, the ratio of the length in the central axis direction to the diameter of the light beam incident on the light receiving portion of the detector 10 is t3, and the ratio of the length in the direction perpendicular to the central axis is t4. The light receiving unit can generate a tracking error signal by performing the following calculation.

図１１（１）は、本発明と特許文献１の受光部を用いて対物レンズがトラッキング方向に変位した時のトップの割合、図１１（２）はボトムの割合を示したものである。本発明の受光部の条件としてはｔ１＝０．１９、ｔ２＝０．５４、ｔ３＝０．１９、ｔ４＝０．１９、θ＝１０ｄｅｇとして計算を行った。

FIG. 11 (1) shows the ratio of the top when the objective lens is displaced in the tracking direction using the light receiving unit of the present invention and Patent Document 1, and FIG. 11 (2) shows the ratio of the bottom. As the conditions of the light receiving portion of the present invention, the calculation was performed with t1 = 0.19, t2 = 0.54, t3 = 0.19, t4 = 0.19, and θ = 10 deg.

  As shown in FIG. 11, in the tracking error signal of Patent Document 1, the characteristic of the boundary between the unrecorded area and the recorded area changes greatly with the displacement of the objective lens. On the other hand, the tracking error signal of the present invention does not depend on the displacement amount of the objective lens. For this reason, no special control is required for the displacement of the lens. In addition, it can be seen that the displacement of the objective lens is positive in most of the range, and the offset of the boundary between the unrecorded area and the recorded area can be suppressed.

  Thus, by using the detector pattern as in the present invention, stable tracking control can be performed even if the objective lens is displaced. In particular, θ is 0 degree <θ <15 degrees, t1, t2, t3, and t4 are 0 <t1, 0.35, and 0 <t2 <0.70 with respect to the diameter of the light beam incident on the light receiving portion of the detector 10. In the conditions of 0 <t3 <0.35 and 0 <t4 <0.35, a great improvement effect can be obtained in suppressing the DC offset and the offset between the unrecorded area and the recorded area.

  As described in the first embodiment, the offset at the boundary between the unrecorded area and the recorded area is remarkably generated in the vicinity of the interference area (interference area Z1 or interference area Z2), so that the central portion of the detection surface is hardly affected. Further, the coefficient k can be set to an appropriate value by not detecting this area as a tracking error signal. As a result, the effect of suppressing the offset between the unrecorded area and the recorded area can be improved.

  In FIG. 10, the dividing line inside the detector is shown as a straight line substantially parallel to the track and a straight line having a different angle therefrom, but the dividing line inside the light receiving unit is an arc as shown in FIG. There may be no problem even if it is a straight line as shown in FIG.

  Although the light receiving unit pattern is shown here, the diffraction grating 101 having the same pattern as the light receiving unit pattern is arranged as in the first embodiment, and signals are detected by a plurality of light receiving units on the detector. Needless to say, it is effective.

  FIG. 13 shows an optical system of an optical pickup device according to the third embodiment of the present invention. The same optical parts as those of the first embodiment shown in FIG. Here, BD will be described, but HD DVD or other recording methods may be used.

  From the semiconductor laser 50, a light beam having a wavelength of about 405 nm is emitted as divergent light. The light beam emitted from the semiconductor laser 50 reflects the beam splitter 52. Part of the light beam passes through the beam splitter 52 and enters the front monitor 53. The light beam reflected by the beam splitter 52 is converted into a substantially parallel light beam by the collimator lens 51. The light beam that has passed through the collimating lens 51 enters the beam expander 54. The light beam emitted from the beam expander 54 is reflected on the rising mirror 55, passes through the quarter-wave plate 56, and then condensed on the optical disk 100 by the objective lens 2 mounted on the actuator 5.

  The light beam reflected by the optical disk 100 passes through the objective lens 2, the quarter-wave plate 56, the rising mirror 55, the beam expander 54, the collimator lens 51, and the beam splitter 52.

The light beam that has passed through the beam splitter 52 is split by the diffraction grating 11 into a light beam that generates a focus error signal (0th order diffracted light) and a light beam that generates a tracking error signal (+ 1st order diffracted light or −1st order light). Here, the description will be made with reference to the diffraction grating of FIG. 3 of the first embodiment, but FIG. 8 (1) or FIG. 8 (2) of the first embodiment or FIG. 10 or FIG. 12 (1) or FIG. Even if it is the diffraction grating of 2), there is no problem.
The light beam branched by the diffraction grating 11 enters the detection lens. The detection lens is given predetermined astigmatism when the light beam is transmitted, and is used for focus error signal detection. In addition, since the light beam that generates the tracking error signal is given astigmatism and spherical aberration when diffracting the diffraction grating 11, the light beam that has passed through the detection lens 59 is condensed on the light receiving portion.

  FIG. 14 shows the detector 12 and the detected light flux. The detector 12 is divided into focus detection areas 40 to 43 and tracking error signal areas 44 to 47. Since the focus error signal is known, a description thereof will be omitted. Since the light beams diffracted by the diffraction grating 11 have different diffraction directions in the respective regions, the light beam diffracted in the region G in FIG. 1 is the region 45 in FIG. 14, the light beam diffracted in the region H is in the region 46, and the region I. The diffracted light beam enters the region 44 and the light beam diffracted by the region J enters the region 47, respectively. Thereby, a tracking error signal is generated. Here, the RF signal can be detected by taking the sum of the focus error signal, the sum of the tracking error signal, or the sum of the focus error signal and the tracking error signal. A tracking error signal detection method DPD (Differential Phase Detection) employed in DVD-ROMs and the like can also be handled by using detection signals in the focus error areas 40 to 43.

  With such an optical system configuration, not only the tracking error signal but also other signals can be obtained. Although the diffraction grating 11 is arranged on the detection side here, there is no problem even if it is arranged near the objective lens using the polarizing diffraction grating 13 as shown in FIG.

  FIG. 16 shows an optical system of an optical pickup device according to the fourth embodiment of the present invention. The same optical parts as those of the first embodiment shown in FIG. Here, BD will be described, but HD DVD or other recording methods may be used.

  The semiconductor laser 90 emits a P-polarized light beam as a divergent light beam having a wavelength of about 405 nm. The light beam emitted from the semiconductor laser 90 is transmitted through the beam splitter 91 and reflected from the mirror 92. A part of the light beam outside the effective diameter is incident on the front monitor 93. The light beam reflected by the mirror 92 enters the auxiliary lens 94 and the collimating lens 95. Since the collimator lens 95 can be driven in the direction of the optical axis by a driving device (not shown), spherical aberration due to the thickness error of the cover layer of the optical disc 100 is compensated by changing the divergence / convergence state of the light beam. can do.

  The P-polarized light beam transmitted through the collimating lens 95 is incident on the polarizing diffraction grating 14 of the present invention. The P-polarized light beam incident on the polarizing diffraction grating 14 is transmitted as it is, reflected by the rising mirror 96, transmitted through the quarter-wave plate 97, and then becomes circularly polarized light. The circularly polarized light beam is condensed on the optical disk 100 by the objective lens 2 mounted on the actuator 5.

  The light beam reflected by the optical disk 100 passes through the objective lens 2 and the quarter wavelength plate 97. The circularly polarized light beam becomes S-polarized light by the quarter wavelength plate 97. The S-polarized light beam reflects from the rising mirror 96 and enters the polarizing diffraction grating 14. The incident S-polarized light is divided into a plurality of light beams by the polarizing diffraction grating 14. The light beam that has passed through the polarizing diffraction grating 14 passes through the collimator lens 95, the auxiliary lens 94, and the mirror 92, is reflected by the beam splitter 91, and enters the detector 15.

  FIGS. 17 and 18 show the pattern of the polarizing diffraction grating 14 (FIG. 17) and the detector 15 (FIG. 18) considering not only the tracking error signal but also the focus error signal. The polarizing diffraction grating 14 is a diffraction grating in which only ± first-order light is diffracted, and the diffracted light beam has a different diffraction direction and diffraction angle in each region. For the sake of simplicity, in FIG. 18, the light beams diffracted from the respective regions of the polarizing diffraction grating shown in FIG. In addition, the subscript of the letter indicates + 1st order diffracted light if +, and -1st order diffracted light if −. For example, the + 1st order diffracted light in the region L of the polarizing diffraction grating 14 in FIG. 17 is incident on the region 74 of the detector 21 in FIG.

The focus error signal detection method is a knife edge method, and detection is performed using first-order diffracted light diffracted by the regions N, P, Q, and O of the polarization diffraction grating 17. Since the knife edge method is well-known, description is abbreviate | omitted. The tracking error signal detection is obtained by performing the following calculation using the detection signals in the regions 70 to 79 and the regions 81 to 84.

偏光性回折格子１４はフォーカス検出等のために複数の領域に分割されているが、トラッキング誤差信号の観点から言えば実施例２の図１０と同様の検出方式である。
さらにＲＦ信号検出は、領域７０〜７９の検出信号を用いて以下の演算を行うことで得られる。

The polarizing diffraction grating 14 is divided into a plurality of regions for focus detection and the like, but from the viewpoint of the tracking error signal, the detection method is the same as in FIG. 10 of the second embodiment.
Further, the RF signal detection can be obtained by performing the following calculation using the detection signals in the regions 70 to 79.

またＤＰＤ信号検出は、領域７０〜７７の検出信号を用いて以下の演算を行うことで得られる。

The DPD signal detection is obtained by performing the following calculation using the detection signals in the regions 70 to 77.

このような光学系構成とすることでトラッキング誤差信号だけでなく他の信号も得ることが可能となる。

With such an optical system configuration, not only the tracking error signal but also other signals can be obtained.

  In Example 5, an optical reproducing apparatus equipped with the optical pickup device 1 will be described. FIG. 19 shows a schematic configuration of the optical reproducing apparatus. The optical pickup device 1 is provided with a mechanism that can be driven along the radial direction of the optical disc 100, and is position-controlled in accordance with an access control signal from the access control circuit 172.

  A predetermined laser driving current is supplied from the laser lighting circuit 177 to the semiconductor laser in the optical pickup device 1, and laser light is emitted from the semiconductor laser with a predetermined amount of light according to reproduction. The laser lighting circuit 177 can be incorporated in the optical pickup device 1.

  The signal output from the photodetector in the optical pickup device 1 is sent to the servo signal generation circuit 174 and the information signal reproduction circuit 175. The servo signal generation circuit 174 generates a servo signal such as a focus error signal, a tracking error signal, and a tilt control signal based on the signal from the photodetector, and based on the servo signal generation circuit 174, the actuator drive circuit 173 passes through the servo signal generation circuit 174. The position of the objective lens is controlled by driving the actuator.

The information signal reproduction circuit 175 reproduces the information signal recorded on the optical disc 100 based on the signal from the photodetector.
Part of the signals obtained by the servo signal generation circuit 174 and the information signal reproduction circuit 175 are sent to the control circuit 176. The control circuit 176 is connected to a spindle motor drive circuit 171, an access control circuit 172, a servo signal generation circuit 174, a laser lighting circuit 177, a spherical aberration correction element drive circuit 179, and the like, and the rotation of the spindle motor 180 that rotates the optical disc 100. Control, access direction and access position control, servo control of the objective lens, control of the amount of light emitted from the semiconductor laser in the optical pickup device 1, correction of spherical aberration due to the difference in disk substrate thickness, and the like are performed.

  In Example 6, an optical recording / reproducing apparatus equipped with the optical pickup device 1 will be described. FIG. 20 is a schematic configuration of an optical recording / reproducing apparatus. This apparatus is different from the optical information recording / reproducing apparatus shown in FIG. 19 in that an information signal recording circuit 178 is provided between the control circuit 176 and the laser lighting circuit 177, and a recording control signal from the information signal recording circuit 178 is provided. Based on the above, the lighting control of the laser lighting circuit 177 is performed, and a function of writing desired information to the optical disc 100 is added.

FIG. 3 is a diagram illustrating the arrangement of an optical pickup device and an optical disc in Embodiment 1. 1 is a diagram illustrating an optical pickup device using a one-beam system in Embodiment 1. FIG. 3 is a diagram illustrating a light receiving unit or a diffraction grating surface of the present invention in Example 1. FIG. It is a figure explaining DC offset when the objective lens of FIG. 1 is displaced to inner and outer periphery. FIG. 6 is a diagram schematically illustrating an offset generated at a boundary between an unrecorded area and a recorded area in the one-beam method in the first embodiment. FIG. 6 is a diagram comparing characteristics of an unrecorded area and a recorded area in Example 1 with Patent Document 1. FIG. 6 is a diagram for explaining the effect of the present invention due to the difference in the method of dividing the light receiving unit or the diffraction grating surface in Example 1. It is a figure which shows the light-receiving parts other than FIG. 3 in Example 1, or a diffraction grating surface. 1 is a diagram illustrating an optical pickup device using a one-beam system in Embodiment 1. FIG. 6 is a diagram illustrating a light receiving unit or a diffraction grating surface in Example 2. FIG. 6 is a diagram comparing characteristics of an unrecorded area and a recorded area in Example 2 with Patent Document 1. FIG. FIG. 9 is a diagram illustrating a light receiving unit or a diffraction grating surface other than that in FIG. 8 in Example 2. FIG. 6 is a diagram illustrating an optical pickup device that uses a one-beam system according to a third embodiment. It is a figure explaining the light-receiving part in Example 3. FIG. It is a figure explaining the optical pick-up apparatus using 1 beam systems other than FIG. 13 in Example 3. FIG. FIG. 10 is a diagram for explaining an optical pickup device using a one-beam system in Example 4. 6 is a diagram illustrating a diffraction grating surface in Example 4. FIG. It is a figure explaining the light-receiving part in Example 4. FIG. FIG. 10 is a diagram illustrating an optical reproducing device according to a fifth embodiment. FIG. 10 is a diagram for explaining an optical recording / reproducing apparatus in Example 6.

Explanation of symbols

1: optical pickup device, 2: objective lens, 5: actuator, 7: drive mechanism, 10: detector, 11: diffraction grating, 12: detector, 13: diffraction grating, 14: diffraction grating, 15, detector, 19: detector, 40 to 47: light receiving area, 50: semiconductor laser, 51: collimating lens, 52: beam splitter, 53: front monitor, 54: beam expander, 55: rising mirror, 70 to 84: Region of light receiving unit, 101: diffraction grating, 56: 1/4 wavelength plate, 57: beam splitter, 58: focus detector, 59: detection lens,
90: Semiconductor laser, 91: Beam splitter, 92: Mirror, 93: Front monitor, 94: Auxiliary lens, 95: Collimating lens, 96: Raising mirror, 97: 1/4 wavelength plate, 171: Spindle motor, 172: Access control, 173: Actuator drive circuit, 174: Servo signal generation circuit, 175: Information signal reproduction circuit, 176: Control circuit, 177: Laser lighting circuit, 178: Information recording circuit, 179: Spherical aberration correction element drive circuit, 180 : Spindle motor, 500: Diffraction grating center axis

Claims (8)

A semiconductor laser that emits laser light;
An objective lens for irradiating an optical disk with a light beam emitted from the semiconductor laser;
A photodetector for receiving the light beam reflected from the optical disc;
An optical pickup device comprising:
The photodetector has a light receiving unit having four regions of region 1, region 2, region 3, and region 4,
Regions 1 and 3 and regions 2 and 4 of the light receiving portion are line symmetric with respect to the center line of the light receiving portion,
The area 1 and the area 2 of the light receiving portion become narrower as they move away from the center line,
Outputting signals detected in the area 1, area 2, area 3, and area 4 of the light receiving unit;
Optical pickup device. A semiconductor laser that emits laser light;
An objective lens for irradiating an optical disk with a light beam emitted from the semiconductor laser;
A diffraction grating for branching the light beam reflected from the optical disc;
A photodetector for receiving a light beam branched by the diffraction grating;
An optical pickup device comprising:
The diffraction grating has four regions of region 1, region 2, region 3, and region 4,
Regions 1 and 3 and regions 2 and 4 of the diffraction grating are line symmetric with respect to the center line of the diffraction grating,
Regions 1 and 2 of the diffraction grating become narrower with distance from the center line,
Outputting a signal detected from the diffracted light of region 1, region 2, region 3 and region 4 of the diffraction grating;
Optical pickup device. A semiconductor laser that emits laser light;
An objective lens for irradiating an optical disk with a light beam emitted from the semiconductor laser;
A photodetector for receiving the light beam reflected from the optical disc;
An optical pickup device comprising:
The photodetector has a light receiving section having five areas of area 1, area 2, area 3, area 4, and area 5,
Regions 1 and 3 and regions 2 and 4 of the light receiving portion are line symmetric with respect to the center line of the light receiving portion,
The region 5 of the light receiving part is formed symmetrically with respect to the center line and on the center line.
The area 1 and the area 2 of the light receiving portion become narrower as they move away from the center line,
Outputting signals detected in the area 1, area 2, area 3, and area 4 of the light receiving unit;
Optical pickup device. A semiconductor laser that emits laser light;
An objective lens for irradiating an optical disk with a light beam emitted from the semiconductor laser;
A diffraction grating for branching the light beam reflected from the optical disc;
A photodetector for receiving a light beam branched by the diffraction grating;
An optical pickup device comprising:
The diffraction grating has five regions of region 1, region 2, region 3, region 4, and region 5,
Regions 1 and 3 and regions 2 and 4 of the diffraction grating are line symmetric with respect to the center line of the diffraction grating,
The region 5 of the diffraction grating is formed in line symmetry with respect to the center line and on the center line,
Regions 1 and 2 of the diffraction grating become narrower with distance from the center line,
Outputting a signal detected from the diffracted light of region 1, region 2, region 3 and region 4 of the diffraction grating;
Optical pickup device. A semiconductor laser that emits laser light;
An objective lens for irradiating an optical disk with a light beam emitted from the semiconductor laser;
A photodetector for receiving the light beam reflected from the optical disc;
An optical pickup device comprising:
The photodetector has a light receiving section having a region 1, a region 2, a region 3, a region 4, a region 5, a region 6, and a region 7.
Region 1 and region 3 and region 6 and region 2 and region 4 and region 7 of the light receiving unit are line symmetric with respect to the center line of the light receiving unit,
The region 5 of the light receiving section is further subdivided into four regions of region 8, region 9, region 10 and region 11, and the regions 8 and 10 and regions 9 and 11 are line symmetric with respect to the center line. Is formed,
The region 1 and the region 2 of the light receiving portion become narrower as they move away from the center line, and the region 1 and the region 2 are further divided into two in a direction perpendicular to the center line,
Outputting signals detected in region 1, region 2, region 3, region 4, region 5, region 6, and region 7 of the light receiving unit;
Optical pickup device. A semiconductor laser that emits laser light;
An objective lens for irradiating an optical disk with a light beam emitted from the semiconductor laser;
A diffraction grating for branching the light beam reflected from the optical disc;
A photodetector for receiving a light beam branched by the diffraction grating;
An optical pickup device comprising:
The diffraction grating has a region 1, a region 2, a region 3, a region 4, a region 5, a region 6, and a region 7.
Region 1 and region 3 and region 6 and region 2 and region 4 and region 7 of the diffraction grating are line-symmetric with respect to the center line of the diffraction grating,
The region 5 of the diffraction grating is further subdivided into four regions of region 8, region 9, region 10, and region 11, and the regions 8, 10 and 9 and 11 are symmetrical with respect to the center line. Is formed,
Regions 1 and 2 of the diffraction grating become narrower as they move away from the center line, and regions 1 and 2 are further divided into two in a direction perpendicular to the center line,
Outputting a signal detected from the diffracted light of region 1, region 2, region 3, region 4, region 5, region 6, and region 7 of the diffraction grating;
Optical pickup device. The optical pickup device according to any one of claims 1 to 6,
The region 1 and the region 2 have sides having an inclination angle θ with respect to a direction perpendicular to the center line,
The tilt angle θ is 0 degree <θ <15 degrees.
Optical pickup device. An optical pickup device according to any one of claims 1 to 6,
A servo signal generation circuit that generates a tracking error signal using a signal output from the optical pickup device;
An optical disc device having
The servo signal generation circuit includes:
A signal A1 incident on the region 1 and detected by the detector;
A signal A2 incident on the region 2 and detected by the detector;
A signal A3 incident on the region 3 and detected by the detector;
A signal A4 incident on the region 4 and detected by the detector;
By the coefficient k for correcting the light quantity of the region 1, the region 2, the region 3, and the region 4,
A tracking error signal is generated by Expression (A1-A2) -k × (A3-A4).
Optical disk device.

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